The solar magnetism is generated and sustained through an internal dynamo. This process is driven by the combined action of two main mechanisms: turbulent convective motions and large-scale differential rotation (DR). The subsequent magnetic-field build-up can lead to intense surface eruptive events, but also sustain longer-term magnetic cyclic variabilities, such as the Sun's 11-year cycle....
Helioseismology has revealed that the Sun’s differential rotation profile substantially deviates from the well-known Taylor-Proudman theorem. It has been postulated that this deviation arises because the poles are warmer than the equator by a few degrees. Recently, global inertial modes of oscillation have been observed and identified on the Sun, including high-latitude modes with m=1,2,3....
Abstract: The role of convection in forming active regions is controversial. In the thin-flux-tube model, the properties of the active regions are set by the flows in the flux tube during its rise: in the mean-field framework the properties are set by the interaction of the magnetic field with the surrounding turbulent convective motions. Recent observational results point to convection...
There is a pressing need to model XUV solar irradiances, given the scarcity of current measurements. One of the measurable effects of a solar cycle is the significant (more than one order of magnitude) variation in XUV irradiance. XUV radiation drives the ionosphere and the thermosphere. As a first step in the modelling, we present EUV irradiances in a sample of strong spectral lines formed in...
In this presentation, we will explore the fundamental properties of magnetic reconnection, with a particular emphasis on the complexities of three-dimensional (3D) reconnection and the differences with two-dimensional (2D) scenarios. We will present recent state-of-the-art numerical simulations that show how 3D reconnection is key to understanding a variety of phenomena such as braiding,...
Understanding the interplay between magnetic reconnection and turbulence is an important challenge in solar physics, which must be solved to address the fundamental processes and properties of solar flares and other coronal energy releases. In the last few years, exciting advances in this area have been enabled by 3D direct numerical simulations that capture the generation of turbulence inside...
MHD waves are recognized as significant contributors to the energy budget of the solar atmosphere, the acceleration of the solar wind and the composition of coronal plasma. Recent advancements in instrumentation, techniques, and processing methods have unlocked new diagnostic capabilities for exploring the excitation and propagation of MHD waves within various magnetic structures in the solar...
Solar eruptive events such as coronal mass ejections (CMEs), along with the associated solar energetic particles (SEPs), pose serious threats to spacecraft and astronauts. The growing impact of these harsh space weather events on modern societies has driven the development of numerical models capable of enhancing our understanding of the underlying physics and reliably forecasting these...
Cool plasma condensations in the corona manifest themselves as various types of
prominences, loop structures, flare loops, coronal rain etc. They can be highly
dynamical, exhibiting fine structures down to resolution of current instruments.
Nowadays they are modeled using multidimensional MHD simulations. But to compare
with observations, a non-LTE radiative-transfer spectral synthesis is...
Reconnection events in coronal loops are singularly too small and fast to be detected (nanoflares), whereas their collective action could be sufficient to sustain the million degrees corona against thermal conduction and radiative losses. Recent studies have observed and modelled the dynamic counter part of nanoflares, i.e. the nanojets, which are a byproduct of the magnetic reconnection and...
Quantifying the energy content of accelerated electron beams during solar eruptive events is a key outstanding objective that must be constrained to refine particle acceleration models and understand the electron component of space weather. Previous estimations have used in situ measurements near the Earth, and consequently suffer from electron beam propagation effects. In this study, we...
Radio photons interact with anisotropic density fluctuations in the heliosphere which can alter their trajectory and distort the properties that are deduced from observations. This is particularly evident in solar radio observations, where anisotropic scattering leads to highly-directional radio emissions, meaning that observers at varying locations will measure different radio-source...
Observation and simulation studies suggest that particles can be accelerated in the current sheet and above the loop-top during solar flares. Considering the flare process is a turbulent 3D phenomenon in reality, 3D models are crucial for understanding and interpreting particle acceleration in flares. Using the Stochastic Differential Equations (SDE) method to solve the Parker Transport...
Plasma flows in the near-surface region are thought to play an important role in replenishing the quiet Sun magnetic field. The interaction of magnetic fields with the complex flow structure causes these fields to reorganize at sub-granular scales. Horizontally aligned vortex flows near the edge of solar granules can grab magnetic fields from beneath and bring them to the visible surface....
Vortex flows are structures associated with the rotation of the plasma and/or the magnetic field that are present throughout the solar atmosphere, which have been detected in both numerical simulations and observations. In recent years, their study has become increasingly important, as they are present on a wide variety of temporal and spatial scales and can connect several layers of the solar...
Flux emergence in the solar atmosphere is a complex process that causes release of magnetic energy as heat and acceleration of solar plasma. We analyse imaging spectropolarimetric data taken in the He I 1083 nm line at a spatial resolution of 0.26", a time cadence of 2.8 s, and a spectral range of 150 km s$^{−1}$ around the line. This data is complemented by imaging spectropolarimetric data in...
The mechanism behind the formation of the solar penumbra remains a topic of debate, with the magnetic field configuration above the photosphere not yet thoroughly explored. In this study, we examine the formation of sunspot penumbra through a novel approach using the analysis of magnetic fields derived from Non-Linear Force-Free Field (NLFFF) extrapolations. We perform NLFFF extrapolations on...
Ellerman bombs are sites of magnetic reconnection in the deep solar atmosphere. They can be observed as strong enhancements of the hydrogen Balmer lines and display rapid variability on small spatial and temporal scales. They are typically found in young active regions with vigorous emergence of magnetic fields. High-spatial resolution observations with the Swedish 1-m Solar Telescope in La...
Small scales EUV brightening in the solar atmosphere are observed everywhere and they have been classified following a variety of observational properties. For instance, they resemble small jets, bright dots or tiny loops. X-ray and EUV observations from the existing imagers, have been used to infer, for instance, the energy budget needed to heat the solar corona, as we expect the heating...
Dark halos (DHs) are regions of reduced emission compared to the quiet Sun that are observed around active regions (ARs) at various wavelengths and wavebands, corresponding to chromosphere, transition region (TR) and corona. While in the chromosphere DHs are associated with the H$\alpha$ fibril vortex around the AR cores, in the upper atmospheric layers the origin of their dark emission is...
We present the results of coordinated observations of the Swedish 1-m Solar Telescope with Solar Orbiter that took place from October 12th to 26th 2023. The campaign resulted in 7 datasets of various quality. The observational programs were adjusted to the seeing conditions. The observations cover two active regions, a sunspot and a coronal hole. We focus on the morphology and evolution of...
At Solar Orbiter’s perihelion, the FSI telescope of the EUI instrument images the EUV corona up to 1 Rsun above the limb with a plate-scale better than 1000 km on the Sun. Here we report on exceptional FSI image sequences in the 17.4nm bandpass with deep exposures and a 30s cadence during the so-called “Density Fluctuations” and “Probe Quadrature” Solar Orbiter Observing Plans...
The radio Sun in the centimetric range (18-26 GHz) is dominated by the quiet-Sun emission, which covers the entire surface of the solar disk as a mostly uniform background. The quiet-Sun is mostly characterised by bremsstrahlung (free-free) emission at local thermal equilibrium. The solar disk at these frequencies shows dynamical chromospheric structures and phenomena -- such as Active...
Thermal non-equilibrium (TNE) is a thermodynamical state set by a stratified (mainly at the footpoints) and quasi-steady heating. It is believed to play a major role in producing a variety of very common solar phenomena, in particular: prominences, coronal rain, and long-period EUV pulsations. These two later phenomena are the two faces of the same coin: the EUV pulsations results of the...
Solar prominences are the birthplaces of coronal mass ejections, making studies of their pre-eruptive dynamics crucial for space weather. In this talk, I will review our most recent numerical studies of prominence dynamics with MPI-AMRVAC code.
Our investigation extends to the eruption evolution and the generation of coronal waves, which propagate over considerable distances through a...
It is generally believed that the chromosphere is heated by the dissipation of acoustic waves or predominantly acoustic slow modes. Here we propose that some of these essentially acoustic waves have a magnetic origin in that they are generated by torsional Alfénic pulses propagating along small-scale magnetic flux concentrations that root in the photosphere. But how do these torsional Alfvén...
Radio signals propagating via the solar corona and solar wind are significantly affected by compressive waves, impacting solar burst properties as well as sources viewed through the turbulent atmosphere. While static fluctuations scatter radio waves elastically, moving, turbulent or oscillating density irregularities act to broaden the frequency of the scattered waves. Using a new anisotropic...
In recent years, the so-called AWSOM models are a new generation of solar atmospheric models, which incorporate the heating and forces of Alfvén waves on top of more classical effects. They are outperforming older models capturing most aspects of the solar corona, but are still lacking in open field regions because of the lack of reflections and turbulence development.
In this contribution, I...
Switchbacks are large Alfvénic deflections , or even reversals, of the magnetic field in the solar wind. Many authors have suggested that switchbacks are linked to interchange reconnection in the solar corona, but the manner of this connection remains unclear. In our previous work we have shown that both the interchange reconnection process itself (Wyper et al. 22) as well as coronal jets and...
Sustained kink oscillations in coronal loops have long been observed in TRACE, SDO/AIA, and more recently in SolO/EUI images. Although their properties are quite well-known now, their driver and excitation mechanism remain under active debate. In this contribution I give an overview over recent publications and discuss how the different proposed ideas/theories for photospheric driving can be...
The mass cycle of solar prominences or filaments is still not completely understood. Researchers agree that these dense structures form by coronal in-situ condensations and plasma siphoning from the underlying chromosphere. In the evaporation-condensation model siphoning arises due to evaporation of chromospheric plasma from localised footpoint heating but this is challenging to justify...
Solar prominences are cool and dense plasma clouds suspended in the hot solar corona, supported by the magnetic field. They are common features in the solar atmosphere, but their exact formation mechanism is still unclear. We use the radiative magnetohydrodynamic code MURaM to simulate the formation and dynamics of a prominence in the solar atmosphere. MURaM includes the relevant physical...
Coronal mass ejections (CMEs) are huge eruptions of magnetized plasma from the Sun that travel into interplanetary space. These energetic and complex phenomena, when they interact with Earth's magnetic field, can cause significant disruptions. Due to their potential impact, there has been a strong focus on studying CMEs to predict them well in advance of their arrival at our planet. In my...
Our study aims to advance our understanding of the complex interactions between Coronal Mass Ejections (CMEs) and the solar wind/interplanetary magnetic field (IMF) system. We introduce a novel flux-rope semi-analytical MHD model that incorporates a comprehensive approach to understanding the impact of magnetic erosion and virtual mass on the propagation of CMEs. This model explores the...
Coronal dimmings are sudden decreases of the solar EUV and soft X-ray emission caused by coronal mass ejection (CMEs). From the solar observations, we know that dimming regions map to the bipolar ends of closed magnetic field lines that become stretched or temporarily opened during an eruption, and the decrease in the emission is a result of the depletion of coronal plasma caused by the...
We present a rare case of a three-part solar coronal mass ejection (CME) observed in the low corona on March 28, 2022. We observe a bright core/prominence, dark cavity, and a bright CME leading edge in SolO/EUI and STEREO-A/EUVI. We perform 3D reconstructions of the filament eruption from three vantage points: SolO, STEREO-A, and SDO. The filament height increased from 28 to 616 Mm over 30...
Parker Solar Probe (PSP) and Solar Orbiter (SO) observe the Sun from unprecedented close-in orbits out of the Sun-Earth line. Due to the highly elliptical orbits of the respective S/C, they cover varying heliocentric distances during their encounters around the Sun. They both provide high-resolution observations of the heliosphere through their white light heliospheric imagers: PSP/WISPR and...
Coronal pseudostreamer flux systems have a specific magnetic configuration that influences the morphology and evolution of coronal mass ejections from these regions. Here we present the analysis of a recent, high-resolution magnetohydrodynamic simulation of a CME eruption from an idealized pseudostreamer configuration through the construction of synthetic remote sensing and in-situ...
We present observations of a solar eruption captured by Metis onboard Solar Orbiter on October 12, 2022, during its perihelion passage. Using total brightness data, we observed the outward propagation of helical structures for more than three hours, extending up to 3 solar radii following a polar crown prominence eruption. These structures exhibited a notable trend: their inclination decreased...
Observations have shown a clear association of filament/prominence eruptions with the emergence of magnetic flux in or near filament channels. Magnetohydrodynamic (MHD) simulations have been employed to systematically study the conditions under which such eruptions occur. These simulations to date have modeled filament channels as two-dimensional (2D) flux ropes or 3D uniformly sheared...
Magnetic flux rope (MFR) is generally considered the core structure of coronal mass ejections (CMEs). However, how an MFR forms and develops into a CME has been elusive. Through a series of observational studies, we found that a coherent magnetic flux rope may originate from a ‘seed’ MFR that is formed through magnetic reconnection in a current layer underneath a sheared magnetic arcade, as a...
The study of coronal mass ejection triggering and early evolution necessitates numerical modelling, as measuring the coronal magnetic field is challenging. A key ingredient of the modelling efforts is to reliably identify and track the underlying magnetic structure of the eruption, the magnetic flux rope (MFR), in the simulation data. To achieve this, we developed an extraction and tracking...
The properties of pre-eruptive structures of coronal mass ejections (CMEs) are important for forecasting solar eruptions, the former of which are usually quantified by measuring the properties of their footpoints in observations. However, the matter of how to identify the footpoints of pre-eruptive structures and how to do so with the use of ground-based instruments still remains elusive. In...
The 3D coronal magnetic field is the decisive component to understand the formation and eruption of flux ropes in the solar corona. Non-linear force-free magnetic field extrapolations are a frequently applied method to provide a realistic estimate of the coronal magnetic field from photospheric vector magnetograms but are typically limited to small simulation volumes.
We present a novel...
Solar flare prediction has often been studied with data from the Solar Dynamics Observatory (SDO), which provides images of the full solar disk in different wavelength bands, probing different heights of the solar atmosphere, including the photospheric magnetic field. Recent studies have shown that spectroscopic data such as observations with the Interface Region Imaging Spectrograph (IRIS)...
The three-dimensional magnetic reconnection geometries have recently been shown to be present in solar flares, providing explanations for various observed phenomena, including evolution of sigmoids, drift of the erupting flux rope legs, and the shape of solar flare arcades. We review the observational evidence for these processes and their consequences for space weather. Particular emphasis is...
X-ray observations provide insight into the energy release in solar flares - the heated material and accelerated particles detectable via thermal and non-thermal bremsstrahlung emission respectively. We present observations of small active regions flares and even smaller quite Sun “flares” observed with the Nuclear Spectroscopic Telescope Array (NuSTAR), a highly sensitive telescope providing...
The mechanism of energy release from solar flares are still not fully understood and the study of small-scale features is an important aspect toward this understanding. Flare ribbons act as the footpoints of a flare and are crucial to know the process of flare reconnection. We present here a study about the fine structures of flare ribbons using a high resolution observations using the Swedish...
The gradual phase is a relatively quiet stage in the evolution of a flare, encompassing most of its duration. During this phase, the hot and dense flare loops, formed by reconnection and chromospheric evaporation in the impulsive phase, gradually cool down and decrease in density. We propose and demonstrate with 3D simulation that the seemingly calm gradual-phase flare loops are filled with...
Recent exploitation of spectropolarimetric data has significantly enhanced our understanding of the dynamical and magnetic responses of the photospheric and chromospheric layers during the rapid energy release that occurs in solar flares. In this context, we utilized high-resolution observations from 22nd October 2014, captured during an X1.6 confined flare by the Interferometric Bidimensional...
During the impulsive phase of the flare, beams of non-thermal electrons move from the magnetic reconnection site towards the chromosphere, where the density increases rapidly. Therefore, we can estimate the plasma density distribution along the non-thermal electrons path directly from the observations of the energy-altitude relation obtained for the HXR footpoint sources. Its shape is...
The quest for ever higher spatial and temporal resolution in solar physics can sometimes be thwarted by photon flux. However, in solar flares the greatly increased output across most of the electromagnetic spectrum means that we can often take advantage of high spatial and temporal resolution simultaneously. The rapid evolutionary timescales of flares certainly merit this effort. This talk...
Observations of greater than 100 MeV gamma-ray emission from solar flares from active regions located behind the visible solar disk pose interesting questions regarding the acceleration sites and mechanism, the transport and interaction points of the accelerated particles during these events. Two of the most popular scenarios to explain these observations are (a) acceleration at the coronal...
The Solar Orbiter's Major Flare SOOP (Solar Orbiter Observing Plan) campaign successfully captured several M- and C-class flares as the spacecraft approached perihelion in Spring of this year (March and April). This campaign provided unprecedented observations of solar flare dynamics through high-resolution extreme ultraviolet (EUV) observations using the High Resolution Imager (HRIEUV) of the...
Monster active regions 13663 and 13664 produced not less than 18 X-class solar flares between May 3 and May 15, before rotating out of view from Earth. Despite this, AR 13664 continued to exhibit significant activity, generating numerous events observed by instruments onboard the Solar Orbiter mission. This extraordinary sequence of strong flares not only delighted sky watchers with remarkable...
For the first time we present comparison of advanced FLARIX NLTE time-dependent numerical simulations of flaring emission with spectral observations of a compact C1.6 GOES-class flare recorded with MSDP (Multichannel Subtractive Double Pass) imaging spectrograph installed at the Białków Observatory. The high time resolution (50 ms) MSDP spectral data, enabled comprehensive analysis of H-alpha...
Over the past few decades, advancements in solar instrumentation, both ground- and space-based, have resulted in a large amount of high-quality spectral and spectro-polarimetric data. It is of great importance for the solar community to reliably extract the physical information encoded in these observations. The inversion of this type of data has been established as the most precise method to...
Determination of solar magnetic fields with a spatial resolution set by the diffraction limit of a telescope is difficult because the time required to measure the Stokes vector with sufficient signal-to-noise ratio is long compared to the solar evolution timescale. This difficulty becomes greater with increasing telescope size as the photon flux per diffraction-limited resolution element...
A primary goal in today's solar physics research is to develop remote sensing methods for measuring the elusive magnetic fields of the chromosphere and transition region. A very promising strategy is to exploit the fingerprints that the magnetic field leaves in the polarization of strong resonance lines through the joint action of the Zeeman, Hanle, and magneto-optical (MO) effects....
Contemporary solar physics deals with the increasing amount of high-dimensional data, making it an excellent case for the application of machine learning (ML) algorithms. Synoptic full-disk observations with the Solar Dynamics Observatory (SDO) are one example, allowing us to follow the solar magnetic activity over more than one solar activity cycle and to study its local and global facets....
Thermal conductivity provides important contributions to the energy evolution of the upper solar atmosphere, behaving as a non-linear concentration-dependent diffusion equation. Computational discretisation limits the operation of solving such terms due to numerical instabilities and other error build-up. Recently, different methods have been offered as best-fit solutions to these problems in...
Please find the detailed program here:
https://indico.ict.inaf.it/event/2971/timetable/#20240912
Spectropolarimetric observations provide valuable information about the physical conditions in the solar atmosphere, particularly the magnetic field. However, traditional pixel-by-pixel inversion techniques fail to capture the inherent spatial and temporal coherence of the solar atmosphere. To address this limitation, we propose a novel approach that utilizes neural fields (NFs) to perform...
One crucial objective of Solar Orbiter is to explore the connection between the solar surface and the heliosphere. Since March 2022, several Solar Orbiter Observing Plans (SOOP) have been run to address this goal, ranging from Connection Mosaic to Slow Solar Wind. None of these SOOPs gave a global view of the Sun.
A dedicated SOOP, led by the Extreme Ultraviolet Imager, has been designed to...
The Corona, the outermost layer of the Sun, is a region of intense activity and showcases various solar phenomena that affects the thermal distribution of its constituting plasma. The study of the temperature distribution across the corona is essential in understanding different heating mechanisms that lead to the strikingly high temperatures reached by the corona. This distribution can be...
The European Solar Telescope (EST) will be equipped with a comprehensive suite of state-of-the-art intruments designed to observe the solar atmosphere at high spatial and temporal resolution and with high polarimetric sensitivity. Among them are three Tunable-Imaging Spectropolarimeters and Fixed-Band Imagers (TIS/FBIs) that will provide diffraction-limited measurements of photospheric and...
Intense space weather storms are caused dominantly by coronal mass ejections (CMEs). Their ability to drive significant disturbances in the near-space environments at the Earth and other planets of the solar system is owed to their strong magnetic fields, sustained southward field direction and high solar wind speeds. The magnetic field in CMEs is however difficult to estimate in advance due...
Its magnetic field turns the Sun from a dull, middle-aged star into a lively, variable, energetic and attractive subject of study. The field relieves our star from the monotony of a placid, somewhat boring existence, providing it instead with a restless and engaging magnetic personality. This is seen in the play of its ever-changing magnetic features such as mighty sunspots and faculae at the...
The Solar Influences Data Analysis Center (SIDC) at the Royal Observatory of Belgium (ROB) is well known for its advanced solar data analysis methods and comprehensive data catalogues, including CACTUS for automatic CME detection, Solar Demon for EUV flare and dimming detection, SPoCA-suite for the extraction of active regions and coronal holes, etc. Beyond its research initiatives and data...
This review talk covers the solar-terrestrial connection, especially from the perspective of space weather modelling and forecasting.
Firstly, we give an overview of the effects of space weather and provide examples of their economic, political, and societal costs. This is followed up by a review of the current state-of-the-art operational space weather forecasting and nowcasting tools,...
The EUropean Heliospheric FORecasting Information Asset (EUHFORIA, Pomoell and Poedts, 2018), a physics-based and data-driven heliospheric and CME propagation model, can predict the solar wind plasma and magnetic field conditions at Earth. It contains several flux-rope CME models, such as the simple spheromak and more advanced FRi3D and toroidal CME models. This enables the prediction of the...
With March 2022 we entered a new era of complex solar eruptions in the wake of solar cycle 25. Several of these so-called Big Solar Storms were observed in the past years in remote sensing image data and measured in-situ. Some of them even caused aurorae in low latitudes, repeatedly confirming that the interaction between multiple CMEs, as well as CIRs, lead to extreme conditions in near-Earth...
The open flux problem is currently an unsolved mystery, representing a 2-3 factor mismatch between the open flux measured at 1 AU and that via remote sensing of the solar atmosphere and extrapolated to 1 AU. One explanation is that the open flux at the photosphere is underestimated, in particular in the polar regions. Until now it was impossible to test this with observations: the Polarimetric...
One of the main goals of heliospheric physics is to gain a complete picture of the dynamic processes occurring in the solar atmosphere and how these influence the inner heliosphere. Missions such as ESA/NASA’s Solar Orbiter, which couples unprecedented, close-up views of the solar atmosphere to solar wind measurements in the inner heliosphere, provide invaluable insights into the sources,...
The solar wind streams from compact sources at or near the Sun, accelerates across the low solar corona, and expands into the whole interplanetary space. The physical properties of any wind streams thus reflect the characteristics of their source regions and those of the extended zones of the corona they cross, and are affected by the time-varying strength and geometry of the global background...
Shocks driven by coronal mass ejections (CMEs) are the most relevant accelerators of solar energetic particles (SEPs) in the inner heliosphere. SEPs are of great scientific interest because they represent a natural hazard in the near-Earth environment, from the instruments on board spacecraft to the electricity networks and astronauts' lives. In this study, we aim at analyzing CME-driven...
A large discrepancy between modelling results and in-situ observations by Parker Solar Probe (PSP) was observed while modelling of solar wind using the 3D MHD model EUHFORIA (Pomoell & Poedts, 2018) at near the Sun distances. The default coronal model used in EUHFORIA consists of potential field source surface extrapolation (PFSS), Schatten current sheet (SCS) model and semi-empirical WSA...
Global models of the solar coronal magnetic field are an essential tool for assessing the global-scale magnetic environment of the corona and its connectivity to the heliosphere. In particular, the Potential Field Source Surface (PFSS) model continues to be a frequently and widely adopted tool in the community despite several well-known deficiencies of the model. For instance, regions of open...
The modelling of cool coronal loops can aid our understanding of processes in the upper solar atmosphere, and better understand their dynamics and evolution.
In this study, we explored the structure, and principal Lyman, Balmer, and MgII h&k emission of cool loops. This was achieved through the use of a 2D NLTE (i.e. departures from local thermodynamic equilibrium) cylindrical radiative...
On October 3, 2023, around 12:45 UT, a prominence erupted from the active region located at 18°N, 20°W, as observed by the Full Sun Imager/Extreme Ultraviolet Imager (FSI/EUI) on board the Solar Orbiter. This eruption was followed by a partial halo coronal mass ejection (CME) and a CME-driven shock, confirmed by the detection of a Type II radio burst by . In order to estimate the CME plasma...
What physical mechanisms heat the outer solar or stellar atmosphere to million-kelvin temperatures is a fundamental but long-standing open question. In particular, the solar corona in active-region cores contains an even hotter component reaching 10 MK, manifesting as persistent coronal loops in extreme ultraviolet and soft X-ray images, which imposes a stringent energy budget. Here, based on...
The solar flare event of 1 July 2012 13:08 UTC was observed in both the Hα 6563 Å and Fe I 6302 Å lines by the CRisp Imaging SpectroPolarimeter (CRISP) instrument at the Swedish 1-m Solar Telescope (SST), providing information about the connectivity and dynamics of the photosphere, chromosphere and corona. This study focuses on the changes in the sheared photospheric flow pre and post flare....
Sunspot formation is the primary manifestation of magnetic flux emerging from the convection zone into the solar atmosphere. Among the various features of sunspots, the penumbra is particularly intriguing due to several unresolved issues, such as the interpretation of its formation and decay processes and understanding its bolometric brightness.
Recent high-resolution spectropolarimetric...
One of the intriguing mechanism of the Sun is the formation of concentrated magnetic regions of opposite polarities on the surface called bipolar magnetic regions (BMRs). Such regions generally appear tilted with respect to the equatorial line. The thin flux tube model, employing the rising of magnetically buoyant flux loops twisted by the Coriolis force, is a popular paradigm to explain the...
Solar Orbiter's observations, during Remote Science Windows, a period of ~30 days happening twice per year, are organized into Solar Orbiter Observing Plans (SOOPs). Each SOOP consists of a coordinated set of operations involving multiple instruments to address mission objectives. The Eruption Watch SOOP is a high-resolution plan designed to capture eruptive events, engaging all remote...
Radio signals propagating via solar corona and solar wind are significantly affected by density fluctuations, impacting solar radio burst properties as well as the observations of sources viewed through the turbulent atmosphere. Using large-scale simulations of radio-wave transport, the radial profile of anisotropic density turbulence from the low corona to 1 au is explored. For the first...
Solar flares invariably begin with "hot onset" soft X-ray emission. This produces an initial horizontal branch in an [EM,T] diagnostic diagram (Jakimiec), a phase characterized by hot (5-20 MK) soft X-ray emission with continously growing emission measure. As detected by GOES, the hot onset may begin over up to 30 minutes
prior to the flare impulsive phase. This universal property has the...
Along with the increase in high-performance computing resources, the ability to conduct 3D simulations has made a difference to unveiling the topology of the magnetic structures during the eruption. Flux emergence has been proposed as a main trigger mechanism of CMEs Feynman & Martin(1995). The emergence of magnetic flux can reconnect with an existing, current-carrying flux rope and lead to an...
Sympathetic eruptions of solar prominences have been studied for decades, yet identifying their causal relationships remains challenging. Here, we analyze a failed prominence eruption and subsequent mass drainage from a neighboring prominence, and investigate their potential connections. Leveraging stereoscopic observations from instruments such as LST, CHASE, and EUI, we observe that the...
The standard flare model is in generally depicted and studied in 2D simulations with an anti-symmetrical magnetic field configuration, symmetrical in magnitude, either side of the polarity inversion line. However, flare observations confirm that most flare have a significantly asymmetrical values of the magnetic field strength.
Here we present the first multi-dimensional...
Solar flares have long puzzled physicists due to their complex and multiscale nature and significant impact on Earth. The prediction of solar flares is challenging because the underlying physical processes are not yet fully understood and cannot yet be observationally resolved. Recent advances have been made using powerful numerical tools such as magnetohydrodynamic (MHD) simulations, though...
The Ca II 8542 line forms in the lower to middle solar chromosphere. Its sensitivity to magnetic fields as well as the accessibility to ground-based telescopes make it a preferred line for chromospheric diagnostics. The spatially averaged spectra of this line show a red-asymmetry in the line core which is often indicated by a line bisector that has an "inverse C-shape". Leenaarts et al. (2014)...
The polar magnetic field in the Sun is an important aspect of the solar dynamo process for predicting future solar cycles. However, systematic measurements of this polar field have only been available since 1976 at the Wilcox Solar Observatory (WSO). Prior to 1976, there was a lack of direct information on polar magnetic fields, leading people to utilize various proxies such as polar faculae...
A detailed understanding the structure and dynamics of the chromosphere is important to understand the heating of the solar atmosphere. The local magnetic field couples the turbulent convection zone to the atmosphere and provides the energy flux which heats the atmosphere. The study of the chromosphere is complicated by it's highly dynamic nature, additionally the radiative processes must be...
Lim et al. (2023) have recently proposed that the slope ($\delta$) of the power law distribution between the energy flux and oscillation frequency could determine whether high-frequency transverse oscillations give a dominant contribution to the heating ($\delta$<1). Using the meta-analysis of decayless transverse oscillations, it has been found that high-frequency oscillations could play a...
We present results of the behaviour of the solar differential rotation during solar cycle No. 24 derived from the Kanzelhöhe data set (Kanzelhöhe Observatory for Solar and Environmental Research, University of Graz, Austria). Sunspot groups and their properties (umbra, penumbra, size, and position) were identified by morphological image processing of Kanzelhöhe white light images for the time...
Various dynamical processes occur in the solar atmosphere, significantly contributing to its thermal balance. Observations and simulations have particularly highlighted the importance of waves and magnetic reconnection in the chromosphere, which provide the necessary energy to counterbalance radiative cooling. However, the relative contributions of different processes in various solar regions...
Using a simplified kinetic plasma model, we show that a transition region and a million-Kelvin corona can form thanks to fast, short-lived temperature fluctuations in the chromosphere. The proposed mechanism works if such activity occurs on sub-second timescales, which however are unresolved in current observations.
We briefly outline the model and then discuss two scenarios in which...
In a quiet region, a variety of convection (granulation)-driven phenomena at a tiny spatial scale are observed. For their understanding, it is important to derive the vector of the velocity and magnetic field. One of the effective approaches to study the phenomena is to take advantage of the stereoscopic configuration between Solar Orbiter (SO)/ Polarimetric Helioseismic Imager (PHI) and...
Understanding the mechanism behind coronal heating remains a fundamental challenge in solar physics. Above small-scale bipolar regions we observe Coronal Bright Points (CBPs) in extreme-UV coronal emission. We analyze 346 CBPs track their lifetimes, shapes, polarities, merging behavior, etc. to select a typical CBP for a 3D MHD simulation.
Most CBPs show magnetic some flux cancellation. The...
Close-to-limb magnetic field observations face challenges due to foreshortening, reduced light levels, the influence of the observation angle on the radiative transfer, among other effects. These factors contribute to increased uncertainty in the inferred magnetic field, impacting studies involving magnetograms.
To address these limitations, we can leverage data from a second vantage...
Since its launch in February 2020, Solar Orbiter (SO) has been providing high-quality data from the many layers of the solar atmosphere. The Polarimetric and Helioseismic Imager onboard SO (SO/PHI) is a spectropolarimeter scanning the Fe I line at 617 nm, the same line sampled by SDO/HMI and many other on-ground instruments providing data of the solar photosphere. A first comparison of the...
We present the study of the flare and coronal mass ejection (CME) event observed on 2 November 2021. The double-peak M1.7 GOES X-class flare originated from active region AR 12891 with has beta configuration of its photospheric magnetic field. The CME propagated strongly southward from the Sun-earth line. The CME-flare event was associated with a complex radio event consisting of multiple lane...
The eleven-year solar activity cycle is known to affect solar acoustic oscillations; higher activity is correlated with an increase in mode frequencies and a decrease in their lifetimes. Activity related frequency shifts have also been observed in other stars, but are difficult to measure mode by mode. Measurements seismic travel times provide an alternate method which is robust to noise ...
During the first half of May 2024, Active Region 13664 was the source of 11 X class flares, over 50 M class flares as well as numerous coronal mass ejections (CMEs). The high number of CMEs launched in quick succession caused the largest geomagnetic storm since two decades. The most distinct phenomena in the low corona associated with CMEs and strong flares are coronal dimmings, which are...
We presents a comparison of plasma dynamics in Coronal Holes (CHs) and Quiet Sun (QS) through observations and 2.5D MHD flux emergence simulations. We observe these regions in chromospheric and transition region lines of IRIS as a function of the underlying photospheric magnetic field (|B|). We find excess intensity (blue, redshifts) in QS(CH) with |B|. We observe persistent upflows,...
Closed magnetic loops make up a large part of the magnetically closed corona of the Sun and other stars.
Coronal loops come in different shapes and sizes.
Loop length, magnetoconvection at the footpoints and numerical resolution influence loop properties such as temperature, density and velocities.
These parameters in turn influence observable quantities such as emission intensity and the...
The solar corona is hypothesized to be heated via small-scale random impulsive events, i.e., nanoflares. Recent DEM analysis results indicate that nanoflare generation frequency may be noticeably higher than the characteristic cooling rate of coronal plasma. Hence, individual nanoflare lightcurves are hardly distinguishable from the seemingly uniform background, complicating standard...
Flares and jets are explosive phenomena driven by magnetic reconnection in the solar atmosphere. We present a comprehensive study combining observational analysis and numerical simulations to elucidate the intricate structures and processes underlying these events. Utilizing SDO/HMI vector magnetogram data, we performed a data-constrained simulation of a C1.3 class flare observed in an active...
Solar flares are large eruptions of electromagnetic radiation from the Sun which can affect the Earth's atmosphere and the radio communications. Since the delay between the flare event and their near-Earth effects is only 8 minutes, it is essential we can forecast these events in advance. This work aims to train a Deep Learning model to predict flares within a forecasting window. We use images...
Coronal rain can be a key indicator of coronal heating taking place. To resolve
the coronal heating problem it behoves us to fully investigate this link across
the full disk of the Sun. There is no lack of observational data, but currently
this data is inadequate for a complete analysis of the phenomenon to be carried
out. The AIA 304 channel provides the best dataset for coronal rain...
The relationship between the total magnetic flux of active regions (ARs) and the area of their enclosed sunspots serves as a fundamental property of ARs. Notably, deducing the historical magnetic flux of the brightening magnetic features on the Sun, i.e., faculae and networks, is compelling for understanding the long-term variations of the solar surface magnetic flux. It is also significant...
Coronal mass ejections (CMEs) are powerful solar events involving the expulsion of plasma and magnetic fields, significantly impacting Space Weather. Traditional coronagraphs face challenges in accurately measuring the early evolution of Earth-directed CMEs due to projection effects. Coronal dimmings, characterized by localized reductions in extreme-ultraviolet (EUV) and soft X-ray emissions,...
In this work we take advantage of the unique orbit of the Solar Orbiter spacecraft which enables us to study flares from multi-viewpoints away from the Sun-Earth line. A dataset of flares for which the chromospheric footpoint emission is occulted from Solar Orbiter’s point of view and the total flare emission is observed by Earth based observatories (i.e. Fermi/GBM) are identified. This allows...
Converging flows are visible around Bipolar magnetic regions (BMRs) on the solar surface, according to observations. Average flows are created by these inflows combined, and the strength of these flows depends on the amount of flux present during the solar cycle. In models of the solar cycle, this average flow can be depicted as perturbations to the meridional flow. Here, we study the effects...
The data transmitted by Parker Solar Probe (PSP) from the young solar wind build on the puzzle of electron properties with many important pieces. Of particular interest are the suprathermal populations responsible for the transport of heat flux in the solar wind. We refer to both suprathermal components, the so-called halo and the strahl or beam component, whose trends suggested by previous...
Small-scale magnetic reconnection events have a fundamental role in the dynamics and evolution of active regions and flux emergence. To detect them, we can use Ellerman Bombs (EBs), events found across the photosphere of emerging active regions produced by the reconnection of strong field concentrations of opposite polarity. Their main characteristic is the enhancement of the wings of the...
Energetic electrons from solar flares can move downward to produce X-rays in the chromosphere and upward to generate type III radio bursts in space. Previous studies found a good temporal correlation but a weak intensity correlation between both emissions due to different emission mechanisms. Theoretically, a link between the speed of outward electron beams (from radio) and the energy density...
The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter is composed of three telescopes, the Full Sun Imager (FSI), and two High Resolution Imagers observing in EUV (HRIEUV) and Lyman-alpha (HRILYA). EUI observes the Sun from the smallest features at the base of the corona and in the chromosphere up to the largest scales in the extended corona.
EUI observations are indispensable for...
High-frequency radio observations with large single-dish radio telescopes of the INAF network, in the context of the SunDish project, provided ∼450 solar images since 2018, useful to monitor the vertical structure and physical conditions of the solar chromosphere both for quiet and active regions, during their evolution at different phases of the solar cycle.
Solar radio mapping in K-band...
The extreme-ultraviolet (EUV) brightenings identified by Solar Orbiter (SolO), commonly known as campfires, are the smallest detected, to date, transient brightenings or bursts observed in the non-active regions of the lower solar corona. Our understanding about the role of campfires in the coronal heating stands elusive due to the absence of extensive statistical studies. We perform...
Mass drainage is frequently observed in solar filaments. During filament eruptions, falling material most likely flows along magnetic field lines, which may provide important clues for the magnetic structures of filaments. Here we study three filament eruptions exhibiting significant mass draining, often manifested as falling threads at a constant speed ranging between 50--300 km s$^{-1}$. We...
Solar filaments can undergo eruptions and result in the formation of coronal mass ejections (CMEs), which could significantly impact planetary space environments. Observations of eruptions involving polar crown filaments, situated in the polar regions of the Sun, are limited due to their remarkable stability. In this study, we report a polar crown filament eruption, characterized by fast...
Magnetic reconnection is the key mechanism for various explosive phenomena in astrophysical plasmas, such as jets, flares, and coronal mass ejections (CMEs), yet many details remain elusive. An important piece of the puzzle is whether shock waves, a major particle accelerator in the universe, can be excited directly through flaring reconnections rather than driven by the jet/CME piston. Here,...
On March 26, 2022 the ESA Solar Orbiter mission observed the early evolution of a Coronal Mass Ejection (CME). On that day the spacecraft was at a heliocentric distance of 0.32 AU, and a longitude separation from Earth of 74.5 degrees. The CME source region shows no pre-existing filament or flux-rope. The event was first observed in the inner corona by the EUI telescope, showing the initial...
Stiefel et al. (2023) reported on a first observation in hard X-rays of nonthermal emission coming from the anchor points of an erupting filament. We concluded that flare accelerated electrons must have entered the flux rope and precipitated along the erupting filament into the chromosphere producing Bremsstrahlung in the hard X-ray range.
The detection of such events is challenging for...
Flare-accelerated energetic electrons play a critical role in the magnetic energy release and transport during solar flares. X-ray diagnostics provide crucial insights into the acceleration and propagation of energetic electrons. A deeper understanding of the dynamics of energetic electrons after injection is required to improve the X-ray spectral analysis. Previous studies have shown that the...
Magnetic reconnection is a leading candidate for the heating of the non-flaring solar corona. Specifically, heating might stem from numerous, localized and impulsive episodes of magnetic energy release. Though potentially intense, those fleeting “Nanoflares” are generally difficult to observe in the corona as the highly efficient thermal conduction and the low emission measure wash out their...
The expanding solar wind plasma ubiquitously exhibits anisotropic non-thermal particle velocity distributions. Typically, proton Velocity Distribution Functions (VDFs) show the presence of a core and a field-aligned beam. Novel observations made by Parker Solar Probe (PSP) in the innermost heliosphere have revealed new complex features in the proton VDFs, namely anisotropic beams that...
The hard X-ray imaging spectrometer STIX onboard Solar Orbiter has been operating continuously for 3.5 years recording over 50’000 solar flares. This poster will present science highlights including results from the Solar Orbiter Flare Watch from Spring 2024.
The heat-flow fluctuations along the quiet Sun convective pattern are studied in data provided by high-resolution observations and simulations. Using the methods of stochastic thermodynamics it is shown that heating and cooling of the photospheric flows obey a remarkable thermal relaxation asymmetry which was recently discovered in laboratory experiments.
We investigate several mechanisms that may produce abundance variations in the solar atmosphere, called as the First Ionization Potential (FIP) effect. We develop and exploit a multi-specie 1-D model of the solar atmosphere (called IRAP’s Solar Atmospheric Model: ISAM) that solves, along a given magnetic field line, the transport of neutrals, electrons and charged particles from the...
Coronal hole plumes, largely radial ray-like structures located in coronal holes, are often the targets of studies of magnetohydrodynamic waves and of solar wind origins in the corona. The plume bases seem to be very active with many small-scale transients observed, which are likely important to the formation and evolution of plumes and could contribute to the solar wind. We study three plumes...
The origin of the slow solar wind remains an open issue. One proposed explanation is that upflows at the border of active regions can be a source of the slow solar wind. The processes generating these upflows are not fully understood. Three potential mechanisms have been proposed: (I) reconnection between closed coronal loop and open magnetic field lines in the lower corona, (II) reconnection...
The Solar Atmosphere is subject to a number of oscillatory motions. Magnetic flux tubes acts as wave guides from the lower atmosphere to the upper. In a uniform plasma, there are three distinct magnetohydrodynamic (MHD) wave modes: Alfvén and fast and slow magnetoacoustics waves. In a non-uniform plasma, like the solar atmosphere, these wave modes no longer decouple. It follows that...
The influence of solar flares on the dynamics of lower atmospheric plasma is not yet fully understood. We performed full-Stokes spectropolarimetric observations of active region NOAA 3363 on GREGOR Infrared Spectrograph (GRIS) during consecutive C class flares on July 16, 2023. The near-infrared spectral interval covered photospheric Si I 10827 ̊A and Ca I 10839 ̊A lines and chromospheric He...
Twisted magnetic fields in the solar chromosphere are thought to give rise to a plethora of MHD waves and flows, enabling mass and energy channelling from the photosphere to the corona. Here we report on the statistical properties of observations of waves and flows in an apparently stable but relatively large-scale spiral structure (herein referred to as a “giant spiral”), close to disk...
The origin and formation of the slow solar wind remain an open question in solar physics. One possible scenario is that the slow solar wind may arise from coronal hole boundaries (CHBs) via interchange reconnection. This process also dominates the small-scale evolution of coronal hole boundaries. In this study, we investigate the small-scale evolution of magnetic field and plasma properties at...
Type II solar radio bursts are regarded as signatures of shock-accelerated electrons in the solar corona. They show emission lanes drifting slowly from higher to lower frequencies at the fundamental and/or harmonic of the local plasma frequency. Occasionally, these lanes can be further split into two components. This phenomenon is known as band-splitting, and its origin is still under debate....
This study, focused on exploring the properties of Bright Points (BPs) in different regions of the Sun, with a particular emphasis on their oscillatory behavior. They developed a machine learning model to identify and analyze BPs in solar images, achieving a 78% accuracy in BP identification, then used wavelet and Fourier analysis to investigate the oscillatory behavior of the identified...
Understanding the mechanisms of high-energy particle production and propagation from the Sun is crucial for advancing solar physics and enhancing space weather prediction. This work aims to elucidate electron acceleration processes within the solar atmosphere and their journey into the heliosphere. We use data from advanced radio telescopes, such as the Low-Frequency Array and Nançay...
A key problem faced by global models of the solar corona is a consistent underestimation of the amount of Open Flux. Recent studies have shown that introducing bipole twist or helicity condensation to non-potential global models can partially resolve this disagreement between simulated and measured values of the Solar Open flux. Here, we disentangle these effects to focus entirely on the...
Non-thermal particle acceleration in the solar corona is evident from both remote hard X-ray (HXR) sources in the chromosphere and direct in-situ detection in the heliosphere. Correlation of spectral indices between remote and in-situ energy spectra presents the possibility of a common source acceleration region within the corona, however the properties and location of this region are not well...
The elusive solar corona, when observed in white light, presents contributions from two main components of scattered photospheric light: the K-corona, due to electrons, and the F-corona, due to dust. While the K-corona corresponds to the "true corona" and displays structuring in the form of helmet streamers, pseudostreamers, coronal holes, and plumes, the diffuse F-corona dominates the...
Our Sun is a dynamic star, home to a wide range of activities, from subtle, short-duration events to large coronal mass ejections (CMEs) and strong flares. CMEs and flares can overlap; distinguishing between “eruptive” and “confined” flare magnetic configurations is essential. Understanding the intricacies of these solar eruptions and their connections to preceding activity is crucial in...
Small-scale solar events, such as microflares and mini-filament eruptions, are prevalent in the solar atmosphere. However, their eruption mechanisms are still not understood thoroughly. With a combination of 174 Å images of high spatio-temporal resolution taken by the Extreme Ultraviolet Imager on board Solar Orbiter and images of the Atmospheric Imaging Assembly on board Solar Dynamics...
We report the first stereoscopic observations of HXR emission sources registered by STIX onboard Solar Orbiter and HXI on ASO-S. This is a case study of a two-stage failed eruption. First, it was slowed down due to a helical kink. However, the legs of the kinked structure started to reconnect and the second stage of eruption started. This eruption failed a few minutes later due to reconnection...
We report the simultaneous observations of quasi-periodic pulsations
(QPPs) in wavelengths of hard X-ray (HXR), microwave, Ly$\alpha$,
and ultraviolet (UV) emissions during the impulsive phase of an X6.4
flare on 2024 February 22 (SOL2024-02-22T22:08). The X6.4 flare
shows three repetitive and successive pulsations in HXR and
microwave wavebands, and they have an extremely-large...
Solar flares are driven by the release of free magnetic energy and are often associated with restructurization of the magnetic field topology. Observations of the evolving magnetic field in the flaring volume are limited to only one case, the X8.2 limb flare on 2017-09-10, where a coherent decay of the magnetic field in the corona was detected cospatial with efficient particle acceleration...
The objective of this work is to identify various periods of magnetic helicity and detect the long-periods plasma oscillations in an Active Region NOAA12353 prior to a series of C-class flares in the lower solar atmosphere.
To analyse the magnetic helicity flux in the lower solar atmosphere, linear force-free field extrapolation was used to construct a model of the magnetic field structure of...
Using photospheric vector magnetograms obtained by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory (SDO) and a magnetic connectivity-based method, we compute the magnetic helicity and free magnetic energy budgets of a simple bipolar solar active region (AR) during its magnetic flux emergence phase which lasted $\sim$47 hrs. The AR did not produce any coronal mass...
Solar active regions (ARs), which are formed by flux emergence, serve as the primary sources of solar eruptions. However, the specific physical mechanism that governs the emergence process and its relationship with flare productivity remains to be thoroughly understood. In this study, we examined 136 emerging ARs, focusing on the evolution of their magnetic helicity and magnetic energy during...
The equilibrium of coronal structures like loops in active regions is determined by a balance between the inward magnetic tension and the outward magnetic pressure gradient forces. The dissipation of the magnetic energy from the volume below the loops after a flare causes the lack of magnetic support, hence a contraction or implosion of the coronal loops. Such a contraction is also observed...
At low coronal temperatures of approximately 1 MK, distinct regions show emission at a level significantly below the quiet Sun. Prominent examples are coronal voids in the quiet Sun and dark halos (also referred to as canopies or moats) surrounding active regions. Several models have been proposed, yet the mechanism behind the formation of dark halos remains not fully understood.
Solar...
The Metis Coronagraph onboard the Solar Orbiter (SolO) mission is a powerful
instrument capable of observing the solar corona simultaneously in the Visible (VL) broad-band light (580-640 nm) and in the Ultraviolet (UV) narrow spectral range centered on the Lyman α line of Hydrogen at 121.6 nm. This multiwavelength approach allows a comprehensive analysis of various eruptive solar events....
The derivation of the coronal proton bulk speed is one of the main goals of the Metis coronagraph on board the Solar Orbiter S/C. Metis is capable of acquiring both visible-light (VL) broadband (580-640 nm) polarized brightness (pB) images and ultraviolet (UV) HI Lyman-alpha (121.6 nm) images simultaneously with high temporal (up to 1 s for the UV and 60 s for VL/pB) and spatial (down to 4500...
Solar flares can release coronal magnetic energy explosively and may impact the safety of near-Earth space environments. Their structures and properties on the macroscale have been interpreted successfully by the generally accepted 2D standard model, invoking magnetic reconnection theory as the key energy conversion mechanism. Nevertheless, some momentous dynamical features discovered by...
Magnetohydrodynamic waves are ubiquitously detected in the highly structured solar atmosphere. At the same time, the solar atmosphere is also a highly dynamic plasma environment, giving rise to flows of various magnitudes, which can lead to instability of the waveguides. Recent studies have not only introduced waveguide asymmetry to generalize “classical” symmetric modelling of the fine...
We model Si IV emission originating at footpoints of loops heated by an electron beam. Time dependent plasma parameters (temperature, density, non-Maxwellian beam electron distribution function...) in the transition region are modeled using radiation-hydrodynamical simulations via the FLARIX code for a wide range of the beam parameters. The ionization stages of Si are shown to be out of...
Oscillations around the X-points play an important role in corona plasma heating. In this paper we investigate resonance absorption around X points. We have found analytical solutions for the Alfven continuum mode in the presence of a guide field. We also drive a jump conditions in the flux coordinates. Using these conditions, we obtain the dispersion relation and solve it numerically to find...
Coronal Mass Ejections (CMEs) are large-scale eruptive events originating from the magnetically complex regions of the Sun, and also the most energetic phenomenon in the heliosphere. Even though CMEs have been largely studied in the last several decades, and despite significant advances in our knowledge about them, a lot remains unknown about their internal structure, dynamics, and how they...
Reduced order modelling (ROM) plays an important role in the descriptions of different plasma environments such as heliosphere, solar wind and beyond. ROMs can be obtained via analytical closures; however, such approaches are limited when distribution functions are far from Maxwellian and/or in weaker guide fields. To push the envelope of ROMs in plasmas we apply machine learning frameworks...
Magnetohydrodynamic (MHD) waves have been utilised for decades for probing plasmas and increasing understanding of dynamic processes within the solar atmosphere, a technique called MHD seismology. Propagating slow magnetoacoustic (MA) waves are particularly valuable for MHD seismology due to their persistence, propagation along magnetic field lines, and their links to the coronal heating...
A prominence eruption associated with a limb CME was observed on April 12, 2023 by the multi-channel Metis Coronagraph on board the Solar Orbiter mission. The prominence, seen in the Metis UV Lyman-alpha images as a very bright and elongated arch propagating southward, is instead much weaker in Metis visible light (VL) images. In our work, we studied the 3D position of the prominence to...
We present comprehensive tables of Net Radiative Cooling Rates (NRCR) in cool solar plasma with prominence-like properties. These NRCR are based on the 1D non-LTE radiative transfer modelling of prominences in the transitions of 5-level plus continuum hydrogen, Mg II and Ca II ions. These atomic transitions are the dominant contributors to the radiative energy budget of prominence-like...
An accurate determination of the trajectory of Coronal Mass Ejections (CMEs) is crucial for space weather forecasting and assessing whether or not they will impact Earth. Deviation of CME trajectory from a radial propagation is often observed as a consequence of gradients in the local magnetic pressure or due to CME-CME interactions visible within the coronagraphs' field of view. The...
Coronal loops are the basic structures of the solar corona resulting from the confinement of the multi-thermal coronal plasma in magnetic flux tubes.
Improving their modeling could help in understanding the physical processes involved in the formation and evolution of loops, and the mechanisms of energy transfer in the solar atmosphere.
In this work we performed several direct numerical...
Magnetic loops are widely observed structures in the solar transition region and corona. As closed magnetic flux tubes, they can act as important wave guides for MHD waves, particularly transverse waves/oscillations. In recent coronal observations, transverse oscillations in small magnetic loops have been frequently studied, uncovering two different types of decayless kink oscillations. The...
Solar flares can induce many changes in the Sun’s atmosphere, primarily due to the energy deposited in the lower atmosphere by particles accelerated from a magnetic reconnection site in the corona. The majority of this energy is deposited in the chromosphere, although the method of this energy transport is not yet agreed on. Radiation hydrodynamics models predict that an electron beam via the...
Apparent slipping motions of reconnecting field lines are a prime signature of three-dimensional magnetic reconnection, the process powering flares and eruptions. The existence of slipping motions in the super-Alfvénic regime is a key prediction of 3D magnetohydrodynamic extensions to the standard flare model. Validating these predictions proved challenging as the detection of slipping...
Magnetic reconnection is a fundamental physical process that converts magnetic energy into plasma energy and particle energy in various astrophysical phenomena. In this talk, I will show a unique dataset of a solar flare where a continually stretched current sheet formed various plasmoids. EUV images captured reconnection inflows, outflows, and particularly the recurring plasma blobs...
The solar corona is extremely hot with temperatures above 1 MK. In the decades after this discovery, many different heating methods have been developed to explain the high temperatures. A prominent category of these heating models is direct current (DC) heating, where the dissipation of strong currents, created by the tangling and braiding of magnetic field due to the convective motions in the...
The buildup of the pre-eruptive coronal structure and the eruption onset mechanism are the two most critical yet poorly understood problems. Coronal structures like sigmoids and filaments have been identified as pre-eruptive structures; their associated pre-flare motions as well as pre-flare brightenings have been identified as precursor signatures, yet none of these definitively leads to...
Active region moss forms at the footpoints of 3--10 MK hot loops. Observations with the High-resolution Coronal Imager (Hi-C) revealed some moss regions exhibiting temporal variability on timescales of 30s. This rapid moss variability is hypothesized to be an indirect evidence for the nanoflare heating model of coronal loops. However, since Hi-C was a sounding rocket mission, the observations...
Solar flares are intense localized eruption of electromagnetic radiation over a wide range of energies in the solar atmosphere. A primary characteristics of solar flares is the acceleration of electrons to higher energies and X-Ray observation serves as the key diagnostic to study them in details. In this study, we are investigating the time evolution of solar flares using the warm-target...
Bipolar light bridges (BLBs) are bright features in sunspots located between two umbrae with opposite magnetic polarity. Recent observations revealed intriguing cases of BLBs with very strong magnetic fields of the order of 8.2 kG, which is at least twice the typical values measured in sunspot umbrae. Since these observations were only a few, it is a question of whether BLBs with...
Sun-as-a-star (SAAS) observations provide a valuable link between resolved solar observations and disk-integrated stellar observations, as it gives a unique insight into how well-defined solar activity affects the average spectrum. This activity can affect the integrated spectrum in complex ways, and therefore the values of for example reference spectra and exoplanet characterizations. It is...
Spicules are the thin, hair/grass-like structures prominently observed at the chromospheric solar limb. It is believed that fibrils and Rapid Blue and Red Excursions (RBEs and RREs; collectively referred to as REs) correspond to on-disk counterparts of type I spicules & type II spicules, respectively. Our investigation focuses on observing the response of these REs alongside similar spectral...
Abstract: Recurrent jets are regarded as one of the crucial processes for the periodic release of magnetic free energy through intermittent magnetic reconnections. In this talk, we will present a detailed analysis of the dynamic, thermal, and magnetic characteristics and evolution of a typical anemone jet amid a series of recurrent eruptions at the edge of the active region 13102. This jet...
The formation of penumbrae has been studied by many authors and, yet, many questions remain to be answered. Penumbra formation is a target of opportunity that, due to its relatively fast development, is not common to observe with very high spatial resolution. In this work we present ground-based spectropolarimetric observations of a forming sunspot on the NOAA 11024 recorded with the...
Oscillatory Reconnection is a fundamental relaxation mechanism, characterised by changes in magnetic connectivity, the oscillatory nature of which requires no external periodic driving force to be sustained. This process has been one of the proposed mechanisms behind phenomena, such as quasi-periodic pulsations (QPPs). Its manifestation through the interaction of the ubiquitous waves with null...
Reconnection is a fundamental process that is at the heart of dynamic events such as solar flares. Despite these phenomena being time-dependent, they are often explained using steady-state theoretical reconnection models such as Sweet-Parker and Petschek. In this presentation I will compare the steady-state models of reconnection with a high-resolution simulation of oscillatory reconnection; a...
The recent discovery of ubiquitous switchbacks, localized magnetic deflections in the nascent solar wind, by the Parker Solar Probe (PSP) has sparked interest in uncovering their origins. A prominent theory suggests these switchbacks originate in the lower corona through magnetic reconnection processes, closely linked to solar jet phenomena. Jets are impulsive phenomena, observed at various...
Knowing how much of a particular magnetic system will erupt is, naturally, fundamental to predicting a CME event and the hazard it presents. Usually, we speak about full eruptions when most of the magnetic structure escapes from the Sun, producing a CME; and about failed/confined eruptions, when the eruptive process, including flares and filament activation, is halted in the low corona, with...
Alfvénic waves are one of the most promising candidates for heating the solar corona and accelerating the solar wind in polar coronal holes. These are observed as the transverse motion of spicules (jets elongated along the magnetic field lines) in the chromosphere. However, whether sufficient wave energy is carried to the corona remains unclear because the waves in the chromosphere suffer from...
We analyzed the properties of the magnetic field of a solar sunspot, which was closely associated with a solar eruption in active region AR 13079 observed on August 13, 2022, using modern computational techniques. Spektropolarimetric observations were obtained using the infrared spectrograph GREGOR (GRIS) on the 1.5-meter GREGOR Telescope. Our goal was to examine the magnetic and dynamic...
Magnetic flux rope eruptions are one of the primary mechanisms behind large coronal mass ejections. Flux ropes are twisted bundles of magnetic flux in the lower solar corona, which can store vast amounts of magnetic energy and remain in quasi-equilibrium for some time. If the conditions are correct, these ropes can violently erupt – but it is also equally possible for them to diffuse away into...
The solar chromosphere consists of poorly understood, dynamic fine structures. In this work we use the MURaM code, which has recently been updated to include the NLTE physics required to treat the chromosphere. Our flux emergence simulations of an enhanced network element show finely structured chromospheric features, akin to the rapid red and blue shifted excursions (RREs and RBEs) observed...
Solar flares are among the most spectacular and energetic phenomena in the solar system, and understanding their driving mechanisms is of paramount importance in solar physics. It is widely accepted that magnetic reconnection is the primary mechanism behind solar flares; allowing for the conversion of magnetic energy into plasma energy, resulting in the acceleration of particles such as...
Spacecrafts such as Parker Solar Probe (PSP) and Solar Orbiter (SolO) study the solar atmosphere by making in-situ and remote observations at an unprecedented spatial and temporal resolution, shedding light on coronal heating and solar wind acceleration mechanisms. Alfvenic fluctuations such as switchbacks and pure Alfven waves are some of major carriers of magnetic energy, but the energy...
Quasi-periodic oscillations (QPOs) observed in the solar chromosphere and transition region during flares offer valuable insights into the atmospheric response to sudden energy releases and the evolution of the magnetic field. We have analyzed an M-6.5 class flare observed by the Interface Region Imaging Spectrograph (IRIS) with emphasis on the QPOs in the Doppler velocity measured in the Si...
In the solar atmosphere, radiation plays an important role in the energy balance. Extinctions or emissions of photons from transitions between atomic energy levels can either heat or cool the local atmosphere, and their contributions are expressed as the radiative flux divergence, referred to as the radiative losses. Detailed calculations could be computationally expensive, especially in the...
Flares and CMEs are different manifestations of the same energy release process, during which flux ropes act as the key magnetic structure. However, due to the lack of in-situ observation, it is still difficult to capture the dynamic evolution of flux rope in detail. Here, we analyze the forces that control the dynamic evolution of a flux rope in a 3D RMHD simulation conducted with the MURaM...
We present indications of reconnection within the erupting flux rope which occurred during the impulsive phase of the Apr 2, 2022 flare. Combining data from ground-based radiospectrometers, EUV and X-ray data from different vantage points (STEREO, AIA/SDO, EUI/Solar Orbiter, STIX/Solar Orbiter, Fermi), we show that rare and unique radio bursts in the GHz frequency range are co-temporal with...
The emergence and evolution of solar granulation provide important insights into photospheric plasma dynamics. We investigate the temporal evolution of convective cells both in quiet and magnetised regions, tracking their evolution over periods of approximately 30 minutes.
We employed a pattern-recognition algorithm based on multiple intensity thresholds for solar granulation segmentation,...
Many studies of quasi-periodic pulsations in solar flares have identified characteristic periods in the 5 – 300s range. These phenomena are crucial to understand as they relate to fundamental energy release on the Sun. Due to observational constraints it is unclear whether the periods of quasi-periodic pulsations extend down into the < 5s period regime. The Fermi Gamma-ray Burst Monitor...
In solar flares, magnetic reconnection is key to restructuring the coronal magnetic fields and converting magnetic free energy into other forms of energies. The footpoints of newly reconnected magnetic flux tubes are mapped by chromospheric flare ribbons. The ribbons hence provide clues for structures of, and reconnection processes in, the coronal current sheet, which are still poorly...
During its first close encounter of 2023, the Solar Orbiter spacecraft was magnetically connected to different areas within an active region-coronal hole (AR-CH) complex. As the spacecraft was close to the Earth-Sun line at the time, IRIS and Hinode EIS were able to provide coordinated observations of the AR-CH complex. These complementary datasets provide the perfect opportunity to...
The presence of energetic electrons in the heliosphere is associated with solar eruptions, but details of the acceleration and transport mechanisms are still unknown. We explore how electrons interact with shock waves under the assumptions of stochastic shock drift acceleration (SSDA). Consideration of the shock wave parameter space, such as shock speed, shock obliquity, shock thickness, and...
Solar flares are accompanied by many types of radio bursts. In decimetric range the most frequent types are type III and IV (continua) bursts. The slowly positively drifting bursts (SPDBs) we study are rarely observed in decimetric radio emission of solar flares. To understand with what flare process this kind of radio burst is associated and how these bursts can be generated, we studied the...
We present a detailed analysis of solar flares observed on 30 September 2022 using high-resolution spectroscopic data from the X-ray Spectrometer (XSM) onboard Chandrayaan-2 and the Spectrometer/Telescope for Imaging X-rays (STIX). By leveraging XSM's broad-band spectral sensitivity and STIX’s spectra in the softer energy range, we explore the intricate dynamics of solar flare emissions.
We...
It is widely accepted that eruptive phenomena on the Sun are related to the solar magnetic field, which is closely tied to the observed magnetic concentrations (MCs). Therefore, studying MCs is critical in order to understand the origin and evolution of all forms of solar activity. In this paper, we investigate the statistics of characteristic physical parameters of MCs during a whole solar...
We use statistical tools to analyse data from the Solar Dynamics Observatory Helioseismic and Magnetic Imager to determine the distribution of the magnetic flux of photospheric magnetic features and its variation over a full solar cycle.
We use statistical figures of merit to test how well different types of probability distribution function represent the magnetic flux distribution...
Kanzelhöhe Observatory for Solar and Environmental Research (KSO) provides daily multispectral synoptic observations of the Sun. The synoptic observations allow us to study the subsurface dynamics of the Sun, such as the profile of solar differential rotation, meridional and zonal flows, and their variability, which are crucial for understanding the solar dynamo. Our goal is to extend the...
Solar flares and accompanying coronal mass ejections are drivers of intense space weather, which can have major impacts on e.g., satellite communication, navigation, and power-grid integrity. To this day, precise predictions of solar flare events remain challenging, due to the complexity of the underlying physical processes.
This study aims to improve solar flare forecasting through the...
This contribution will review recent science highlights of the ESA/NASA Solar Orbiter mission, with a focus on high-resolution observations of the mission’s remote-sensing instruments. Solar Orbiter’s science return is significantly enhanced by coordinated observations with other space missions, including Parker Solar Probe, SDO, SOHO, STEREO, Hinode and IRIS, as well as new ground-based...
The Radio Neutrino Observatory Greenland (RNO-G) hunts for neutrinos at the highest energies interacting in the deep glacial ice. Seven of its 35 stations (24 antennas/station) have been taking data since 2022. RNO-G is sensitive in the 80-750 MHz region and records snapshots of time-domain waveforms of with GSa/s sampling rate whenever signals above the thermal noise floor trigger a station....
We analyze series of Dopplergrams from MWO (1967-2012), GONG (2001-2022), and SDO/HMI (2010-2022) to characterize the temporal variations of the high-latitude solar inertial mode with azimuthal order $m=1$. This mode has an amplitude of 10-20 m/s, making it the strongest among all the observed modes in the inertial frequency range. We will present measurements of the mode's power and...
We present unique results of a recent study of bright eruptive prominence embedded in the core of a CME observed by the Metis coronagraph on board the Solar Orbiter on April 25-26, 2021. Metis provides simultaneous imaging in the hydrogen Lyman alpha line and in the VL. Triangulation is used to estimate the de-projected height and velocity of the structure. Based on previous studies of the...
The ultraviolet Lyman-alpha line of neutral hydrogen is the brightest emission line in the quiescent solar spectrum and is a significant radiator of flare energy. The study of spectrally resolved Lyman-alpha flare observations may provide a valuable diagnostic of where flare heating occurs in the solar atmosphere. Despite this potential diagnostic use, most contemporary flare observations in...
Flat fielding spectro-polarimetric data with one spatial and one spectral dimension is inherently difficult and therefore its potential is often not fully exploited. Flat fielding approaches for spectrographs are rarely described in detail, approaches for polarimeters have not been described at all so far. Moreover, the tools needed to calibrate data of a similar type are usually re-invented...
This study aims to reveal the heating mechanism in coronal loops by observationally deriving the relation among the heating flux $F_\rm{H}$, the magnetic field $B_\rm{base}$, and the loop half-length $L_\rm{half}$. While the previous studies investigated the heating mechanism assuming some parameters (e.g., heating scale height), this study directly derives the parameters from the...
So-called White Light Flares (WLFs) show enhancements in the visible spectrum with respect to the solar black-body curve. The Interface Region Imaging Spectrograph (IRIS) has found enhancements in the NUV spectral region, indicating an enhanced Balmer continuum. Statistical studies using imaging instruments have shown such enhancements to occur commonly, but what causes these enhancements is...
As seen in most textbooks of astrophysics, most astronomical bodies such as main sequence stars have been investigated only by Newtonian gravity. This is presumably based on a belief that Newtonian physics could be sufficient to extract important physics of most astronomical bodies except compact stars and General Relativity would be too precise to be suitable.
In this talk, I will...
Solar radio spikes observed as narrow-bandwidth, sub-second bursts are indicative of rapid, small-scale energy release in the corona, yet localising the site of electron acceleration is a significant challenge. Using millisecond imaging from the LOw Frequency ARray (LOFAR) between 30-45 MHz, we present a statistical analysis of solar radio spikes associated with a coronal mass ejection (CME)....
Context. Stellar flares has an impact on habitable planets. To study the flares by observations with no spatial resolution, Sun-as-a-star analyses are developed. With the data of Sun-as-a-star observations, a simulation of solar flares is required to provide a systemic clue to the Sun-as-a-star study.
Aims. We aim to develop a model of solar flares and study the relationship between the...
The solar chromosphere and transition region (TR) play an important role in coupling the dense, 6000K photosphere to the tenuous, million degree corona. As the plasma beta changes dramatically over these layers, ascertaining the processes that maintain their thermal structure remains a fundamental problem in solar physics. By combining observations from the 50-cm Multi-Application Solar...
SOLAR-C and MUSE are among the next generation solar missions, with launch dates in 2028 and 2027 respectively. Those mission will carry two complementary instruments providing each high resolution spectroscopy in the UV and EUV.
The EUV High-throughput Spectroscopic Telescope (EUVST) onboard SOLAR-C will obtain high temporal, spectral, and spatial resolution spectra of the Sun over a wide...
Non-LTE radiative transfer in 2D was performed for the hydrogen plasma of a loop-like structure within eruptive prominence obtained by 3D MHD simulation. The simulation made by Fan & Liu (2019) shows evolution of a prominence from quasi-equilibrium to the onset of eruption of a twisted, prominence forming coronal magnetic flux rope which underlays a coronal streamer. The 180th time step of the...
Coronal bright points are systems of loops that connect small bipoles in the magnetic network of the quiet Sun.
While a bright point as a whole might persist for several hours, individual loops within it evolve on timescales of minutes.
Capturing their atmospheric signatures, that span from the ultraviolet to X-rays, requires simultaneous observations over a broad range of plasma...
In this contribution we use millimeter wavelength diagnostic to test a new model of the solar chromosphere resembling an enhanced network region. The model is based on the recently developed chromospheric extension of the non-equilibrium version of the radiative-MHD code MURaM. We synthesized radio brightness at the operational wavelengths of the Atacama Large Millimeter/Submillimeter Array...
Coronal loops, the arching structures filled with magnetically confined million Kelvin hot plasma, are the prominent features of the solar atmosphere. These loops are best observed in the extreme ultraviolet (EUV) and X-ray wavelengths. Coronal loop emission generally traces the magnetic field lines in the upper solar atmosphere. Thus probing their spatial morphology and evolution will help us...
Sunspots are intense regions of magnetic flux that are rooted deep below the photosphere. It is well established that sunspots host magnetohydrodynamic waves, with numerous observations showing a connection to the internal acoustic or p-modes of the Sun. The p-modes are fast waves below the equipartition layer and are thought to undergo a double mode conversion as they propagate upwards into...
Coronal loops are known to host Alfvén waves propagating in the corona from the lower layers of the solar atmosphere and because of their internal structure, phase-mixing is likely to occur. The structure of the coronal loop could be significantly affected by the thermodynamic feedback of the heating generated by phase-mixing. However, this phenomenon can be sensitive to the period of the...
Active region NOAA 13664 has been so far the most flare-prolific active region of the present solar cycle, producing eight X- and several M- and C-class flares, causing the strongest geomagnetic storm since 2003. In this study, the evolution of the non-neutralized (net) electric currents is examined, along with that of the emerging flux. The net currents were calculated using a method based on...
The feasibility of restoration of spectrograph data was first demonstrated by Keller and Johannesson [1995] based on a speckle-based method. In van Noort [2017] this method was revisited using an MFBD based approach on data acquired with the SST. This new approach allows for the restoration of spectro-polarimetric data over large FOVs with a spatial resolution that can compete with that of...
In this talk, I will show the method to confirm the existence of the nonthermal component down to 6.5 keV in the observed X-ray spectrum of a microflare first reported by Glesener et al., 2020. We report the first imaging evidence for low-energy cutoff of energetic electrons in EM maps of >10 MK plasma, which first appeared as two coronal sources significantly above the chromospheric...
The SPICE instrument on board Solar Orbiter observes in the (extreme-)UV, including the Lyβ and Lyγ lines. Forming in the upper chromosphere, they are very sensitive to energy input and the ionisation stratification, offering important diagnostic information of solar flare energetics. We report here on the first high-cadence (5s) flare observations from SPICE, presenting an overview of the...
We analyzed a rapid filament restructuring during a confined C2 flare that led to an eruptive M4 flare 1.5 h later. During the C2 flare, the filament's southern half disappeared, and the remaining plasma flowed into a new, longer channel, similar to an EUV hot channel seen during the flare.
We took advantage of the quasi-quadrature position (84°) between SDO and Solar Orbiter, during its...
Bright heads of penumbral filaments, penumbral grains (PGs), show apparent horizontal motions inward, toward the umbra, or outward, away from the umbra. Using high-resolution spectropolarimetric observations and numerical simulations of sunspot penumbrae, we aim to prove whether the direction of these motions is related to the inclination of the penumbral magnetic field.
Magnetic-field...
The changing magnetic field in solar flares has a complex association with the UV emissions of the flare ribbons. These ribbons appear as visual markers indicating the sites where magnetic field lines go through a coronal reconnection processes, which has been determined to be the driving process of flare formation. However, this process is not entirely clear. We aimed to investigate the...
Solar flares are complex multiscale phenomena that demand modeling strategies capable of precisely capturing processes at both the microscale and macroscale. At the microscale, kinetic models such as the Particle-In-Cell (PIC) method are crucial for an accurate depiction of physical phenomena, especially particle acceleration near reconnection sites. However, the extensive computational...
The origin of the sudden deflections of the magnetic field, known as magnetic switchbacks, is still hotly debated. These structures, which are omnipresent in the in situ observations made by Parker Solar Probe (PSP), are likely to have their seed in the lower corona. There is an increasing consensus that small-scale energetic magnetic field reconnection plays a crucial role in establishing the...
On October 28, 2021 the first X-class solar flare of Solar Cycle 25 occurred in active region NOAA AR 12887. It produced the rare event of ground-level enhancement of the solar relativistic proton flux and a global extreme ultraviolet (EUV) wave, along with a fast halo coronal mass ejection (CME) as seen from Earth's perspective. A few hours before the flare, a slower CME had erupted from a...
Coronal mass ejections (CMEs) and solar flares are the most energetic explosive phenomena in our solar system and are able to release a large quantity of plasma and magnetic flux into the interplanetary space, probably affecting the safety of human high-tech activities in the outer space. To predict CME/flares caused space weather effects, we need to elucidate some fundamental but still...
It is well known that the dominant frequency of oscillations in the solar photosphere is at $\approx$3 mHz, which is the result of global resonant modes pertaining to the whole stellar structure. However, analyses of the horizontal motions of nearly $1$ million photospheric magnetic elements spanning the entirety of solar cycle 24 has revealed an unexpected dominant frequency $\approx$5 mHz,...
The Hα line is widely used to study solar chromosphere, but polarimetric studies to infer magnetic fields are scarce. This is partly due to no polarimetric studies of Hα line utilizing 3-D radiative transfer, and earlier 1-D radiative transfer studies suggested a significant contribution of the photospheric fields. By analyzing spectropolarimetric data of a small pore simultaneously recorded...
This study investigates the damping characteristics of Doppler velocity oscillations in solar bright points (BPs) using spectral analysis and deep learning techniques.
This study analyzed Doppler shifts in the solar spectrum captured by the Interface Region Imaging Spectrograph (IRIS), focusing on periodic oscillations within BPs. The damping of red and blue Doppler shifts and employed deep...
Recent high-resolution solar observations have unveiled the presence of small-scale loop-like structures in the lower solar atmosphere, often referred to as unresolved fine structures, low-lying loops, and miniature hot loops. These structures undergo rapid changes within minutes, and their formation mechanism has remained elusive. In this study, we conducted a comprehensive analysis utilizing...
Solar jets, characterized by small-scale plasma ejections along open magnetic field lines or the limbs of large-scale coronal loops, play a crucial role in the dynamics of the solar atmosphere. They are often associated with other solar activities, including campfires, filament eruptions, coronal bright points, flares, and coronal mass ejections. Although spectral and EUV images have been...
Plasma upflows with a Doppler shift exceeding 20 km/s at active region (AR) boundaries are considered potential sources of nascent slow solar wind. These upflows are often located at the footpoints of large-scale fan-like loops, showing temperature-dependent Doppler shifts from the transition region to the lower corona. In this study, we identified two upflow regions in the vicinity of an...
Magnetic bright points on the solar photosphere mark the footpoints of kilogauss magnetic flux tubes extending toward the corona. Convective buffeting of these tubes is believed to excite magnetohydrodynamic waves, which can propagate to the corona and there deposit heat. Measuring wave excitation via bright-point motion can thus constrain coronal and heliospheric models, and this has been...
Solar atmospheric heating inferred from observations is known to be higher than the equilibrium rate of a static atmosphere, but it is unclear how the heating is supplied. Two leading theories are standing out as the most likely candidates to balance the high radiative losses of the solar atmosphere: heating by waves (AC heating), and magnetic reconnection (DC heating). Understanding AC...
We present observations of small- to intermediate-scale energy release events occurring in the solar atmosphere, investigated using multiwavelength, multi-instrument high-resolution data. Ultraviolet (UV) observations acquired by satellites, along with complementary simultaneous spectro-polarimetric measurements by ground-based telescopes, allow us to shed light on the dynamic interplay...
Vortex flows in the solar photosphere are ubiquitous and are thought to inject energy into the upper solar atmosphere in the form of Poynting flux. However, observing photospheric intensity vortices is challenging due to their small size and the fact that the flow field is primarily parallel to the plane-of-sky. Despite this, a large number of photospheric intensity vortices have been observed...
The solar chromosphere is a highly dynamic layer governed by magnetic forces. Models and observations alike have difficulties in their analysis and interpretation. For instance, what mechanism is responsible for heating the chromosphere needs yet to be determined. Chromospheric plasma contains a significant amount of neutral particles. For phenomena operating at timescales significantly larger...
The chemical properties of the solar plasma remain unchanged as it travels unadulterated along open fields from the chromosphere/corona into the heliosphere and can be used as a tracer for the sources of the solar wind.
The solar corona should have the same chemical composition as the solar photosphere. However, It has been found that in the corona, some solar regions exhibit a different...
One of the most stunning discoveries of the Parker Solar Probe mission is the wealth of kinetic scale processes occurring in the low solar atmosphere (Bale et al. 2019). In this work (Afify et al. 2024), we investigate, with a combination of theoretical and numerical tools, the ion-acoustic waves observed by the Parker Solar Probe near the Sun (Mozer et al. 2021, 2023; Kellogg et al. 2024)....
Context. Much of a solar flare's energy is thought to be released in the continuum. The optical continuum ("white-light") is of special interest due to the ability of observing it from the ground.
Aims. We aim to investigate the prevalence of white-light emissions in solar flares, what influences them, and what causes them to begin with. We furthermore seek to understand the response of the...
Solar coronal waves frequently appear as bright disturbances that propagate globally from the eruption center in the solar atmosphere, just like the tsunamis in the ocean on Earth. Theoretically, coronal waves can sweep over the underlying chromosphere and leave an imprint in the form of Moreton wave, due to the enhanced pressure beneath their coronal wave front. Despite the frequent...
Traditional approaches to tracking solar outflows for space weather forecasting rely primarily on coronagraph images, which generally observe the solar corona above a minimum height of about 2.5 solar radii. Extreme ultraviolet (EUV) imagers have been widely used to characterize features on the solar disk, but their limited fields of view have prevented their use for tracking outflows through...
