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...
An accurate assessment of our current space weather modeling is necessary due to progress in space weather research. Any validation framework needs suitable qualitative data for consistent validation procedures. The qualitative data also contributes to the refinement of the model and hence better forecasting ability. In alignment with this objective specifically for CME events, we present a...
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....
Solar energetic particles (SEPs) are highly energetic charged particles that have their origin of acceleration in strong space-weather driving phenomena that the Sun produces, e.g., solar flares and coronal mass ejections. These particles pose a radiation hazard to both technological equipment and living organisms in space, which is why the nature of these events is an important subject of...
It is well accepted that the physical properties obtained from the solar magnetic field observations of active regions (ARs) are related to solar eruptions. These properties consist of temporal features that might reflect the evolution process of ARs, and spatial features that might reflect the graphic properties of ARs. In this study, we generated video data sets with timescales of 1 day and...
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...
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...
Numerical models of the solar atmosphere are an important tool in solar physics. Both, models and spectro-polarimetric inversion techniques require stratifications for the plasma temperature and density. For the case of explicit numerical schemes with high-order derivatives we require an isotropic diffusion equation for numerical stability. Otherwise, wiggles and inaccuracies can occur at...
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...
Numerical simulations have proven invaluable in understanding the physics of the Sun. With increasing computing power available, we launch increasingly complicated multi-physics simulations. Every single physics module requires validation and we must understand the role of each of these physical processes. This work presents an analytical solution for non-linear diffusivity in 1D, 2D, and 3D....
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...
Solar observations have often served as benchmarks of stellar conditions. A particularly illustrative example of the above link is given by the observations in the Ca II H and K lines at 396.847 nm and 393.367 nm, respectively, which are the two deepest and broadest absorption lines in the visible spectrum of the Sun. Although widely observed over the years, several aspects of the emission of...
CHIANTI is the most widely-used database in solar physics, and in some cases is the reference dataset for other databases in astrophysics. We present here a significant update to the modelling. CHIANTI has, up until now, used the coronal approximation to calculate ion balances. This is only suitable in the more tenuous, high temperature solar corona. New effects have been added to the models...
The near-ultraviolet (NUV) part of the solar spectrum contains a dense haze of spectral lines. Some of the Fe I lines in this region show very broad profiles typical of chromospheric lines which contrast the well-studied photospheric Fe I lines in the visible part of the spectrum. The diagnostic potential of these spectral lines is largely unexplored due to a lack of high-resolution...
Investigating the solar wind is important for our understanding of the dynamics of plasma in the solar system environment. At 1 AU, where the solar wind interacts with the Earth's magnetosphere, we can also identify different transient processes, such as Interplanetary Coronal Mass Ejections (ICMEs) and Corotating Interaction Regions (CIRs), which may result in the occurrence of magnetic...
We are proposing a visualization of vector magnetograms whereby the three components of the photospheric magnetic field vector are combined into RGB colored maps, creating color-coded magnetograms (COCOMAGs). Ιn this configuration the primary and secondary colors represent magnetic field with different orientation. The areas occupied by different color hues are extracted, creating appropriate...
When reconstructing the coronal magnetic field topology, which is an essential input to heliospheric space weather forecasting models, one can chose among many coronal models. These range from simple empirical to state-of-the-art magnetohydrodynamic (MHD) models. In this study we try to address how well coronal models agree well with each other regardless of their complexity and simulation set...
Active regions (ARs) are the photospheric manifestation of the emergence of magnetic flux ropes (FRs) formed within the solar interior. A key parameter of their evolution is the inclination of the AR polarity axis with respect to the equatorial direction, known as the tilt angle, which is fundamental in semi-empirical flux transport models proposed to explain the transference from toroidal to...
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...
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...
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...
Understanding the relationship between solar activity and solar wind is crucial for exploring the interactions among different solar atmospheric layers and the dynamics within the heliosphere. In this work, we used data from five solar cycles to examine the phase relationship between a proxy of solar activity, namely the Ca II K index, and solar wind parameters at 1 AU, such as dynamic...
Coronal Mass Ejections (CMEs) are the main drivers of the disturbances in interplanetary space. Then, understanding CMEs is crucial for advancing space weather studies. Assessing the numerical heliospheric model capabilities is crucial, as understanding the nature and extent of the limitations can be used for improving space weather predictions. In a statistics study it was shown that among...
To study and resolve small-scale features in the solar atmosphere, ever larger telescopes are built, such as the European Solar Telescope (EST) or the Daniel K. Inouye Solar Telescope (DKIST). However, diffraction-limited observations are not feasible for large aperture telescopes because the Earth's turbulent atmosphere distorts the raw observations. Therefore, post-image reconstruction...
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...
Helioseismology can detect active regions on the Sun’s far side days before they rotate to the Earth’s side, using solar acoustic oscillations. These far-side maps provide an important input for space weather models. Recent advances in theoretical and computational helioseismology have improved far-side imaging, which enables high-confidence detection and daily tracking of medium-size active...
The solar/stellar wide-spectral coverage polarimeter, SOWISP, is a dedicated instrument for investigating time-dependent energetics of solar flares. With four-state polarisation measurements and a field-of-view the size of an average sunspot, the instrument, currently in the R&D phase, will allow to probe changes in the magnetic structure with a spatial resolution of below 20 arcsec. Unique...
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,...
We present a method for a direct measurement of the height variations in the solar photosphere based on stereoscopy. Our method calculates differences in altitude of the solar surface by shifting and correlating two images, mapped from the same surface feature observed from two different vantage points. We apply this method to simultaneous continuum intensity observations from Solar Orbiter’s...
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...
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...
During inter-planetary coronal mass ejections we expect faster solar wind to push into slower ambient wind, leading to the formation of super-sonic shocks. This may trigger turbulence to amplify magnetic fields stronger than expected by pure compressional effects, known as turbulent dynamo action. The turbulent nature of iCME fronts can be uncovered by computing the electromotive force. Peaks...
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...
The Hanle effect refers to the modification of degree of linear polarization and rotation of the plane of polarization of the scattered radiation in the presence of an external magnetic field. In a recent publication, we reported spectral lines in the extreme-ultraviolet (EUV) range that exhibit sensitivity to the unsaturated Hanle effect and are, therefore, inherently sensitive to the vector...
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...
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,...
Magnetic reconnection preferentially takes place at the intersection of two separatrices or two quasi-separatrix layers, which can be quantified by the squashing factor Q, whose calculation is computationally expensive due to the need to trace as many field lines as possible. FastQSL is developed for obtaining Q and the twist number, with the performance of millions of Q values per second....
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...
EUHFORIA is a space weather forecasting tool used to predict the geo-effectiveness of coronal mass ejection (CME) impacts. In this 3D MHD simulation, magnetic structures evolve in the heliosphere after being injected into the domain at 0.1 AU. The accuracy of EUHFORIA's predictions strongly depends on the coronal model used to initiate the solar wind and the properties of the CME model...
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...
Full-disk spectroscopic observations of the solar corona are highly desired to forecast solar eruptions and their impact on planets and to uncover the origin of solar wind. In this paper, we introduce a new multislit design (five slits) to obtain extreme-ultraviolet (EUV) spectra simultaneously. The selected spectrometer wavelength range (184–197 Å) contains several bright EUV lines that can be...
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 Heliospheric Space Weather Centre (HSWC) is an ALTEC, INAF – OATo, and UniGe joint project aimed at providing and supporting services related to the heliosphere. It currently hosts two tools developed by ALTEC and INAF: the Geo Magnetic Effectiveness (H103d) and the CME propagation prediction (H103e). The tools are part of the SWESNET project, within the ESA Space Weather programme. The...
Coronal mass ejections (CMEs) are giant expulsions of magnetized plasma from the Sun that manifest flux rope structures. Flux rope CME models such as the spheromak model with spherical geometry and the ‘Flux Rope in 3D’ (FRi3D) model with a global twisted magnetic flux tube geometry are already widely used in studying CME evolution and propagation in the heliosphere within the EUropean...
Many spectral lines used for solar observations have poorly determined atomic parameters, such as the transition probability or the central wavelength. Using poor atomic line parameters in spectropolarimetric inversions produces erroneous results for inferred atmospheric parameters. Therefore, we applied a newly developed coupled inversion method to infer the transition probability and...
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...
We perform a data-constrained simulation with the zero-beta assumption to study the mechanisms of rotation and failed eruption of a filament in active region 11474 on 2012 May 5. Our simulation reproduces most observational features very well, e.g., the large-angle rotation, the confined eruption and flare ribbons. We discover two flux ropes in the sigmoid system, an upper flux rope (MFR1) and...
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....
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...
Our understanding of the physics behind the origin and the evolution of the solar wind in the low/middle corona depends on our capability of gathering information on the characteristics of the solar wind and on its interaction with the magnetic field within this region. Despite the possibility of acquiring in situ measurements closer to the Sun provided by the Parker Solar Probe and the Solar...
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...
The calculation of the emerging radiation from a model atmosphere requires knowledge of the emissivity and absorption
coefficients, which are proportional to the atomic level population densities of the levels involved in each transition. Due to the
intricate interdependency of the radiation field and the physical state of the atoms, iterative methods are required in order to calculate
the...
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...
In-situ measurements of kinetic-scale collisionless current sheets in the solar wind have shown that such current sheets are often approximately force-free despite having a plasma beta of the order of one. Statistical analyses have found that the plasma density and temperature can vary across a current sheet in an anti-correlated manner such that the plasma pressure remains essentially uniform...
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...
Associations between space weather and events on Earth, e.g., geomagnetic perturbations affecting power grids, are well-known. Effects on human health and physiology are less well investigated, and current evidence, suggesting, e.g., less frequent cardiovascular events during phases of high geomagnetic disturbance, builds on small patient cohorts and a wide array of statistical tests....
With current observational methods it is not possible to directly measure the magnetic field in the solar corona with great accuracy. Therefore, coronal magnetic field models have to rely on extrapolation methods using photospheric magnetograms as boundary conditions. In recent years, due to the increased resolution of observations and the need to resolve non-force-free lower regions of the...
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...
This work dealt with the numerical simulation of the magnetic Rayleigh Taylor instability (IMRT) in a magnetic tube suspended in the chromosphere/photosphere conditions. We solved the compressible nonlinear MHD equations using the 2.5D open-source MPI-AMRVAC numerical code. Therefore we were interested in studying the effect of the horizontal magnetic tension on the development of the IMRT and...
Interplanetary coronal mass ejections (ICMEs) are known to drive the most intense geomagnetic storms. The fastest ICMEs can travel from the Sun to 1 AU in less than 24 hours. In order to have fast and reliable time-of-arrival predictions, it is crucial to develop models that are both physically accurate and computationally efficient. A paramount example is the drag-based model (DBM), which...
Solar flares significantly ionize the neutral atmosphere, leading to increases in the electron density of the ionosphere. This ionospheric disruption impacts the Earth-Ionosphere waveguide, affecting electromagnetic signal propagation between transmitters and receivers. Such ionization-induced perturbations can be observed as fluctuations in the signal amplitude and phase, and thus can be used...
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...
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...
We present the study of several halo CMEs that propagated non-radially and as a result, they impacted Earth as flank-encounters. We utilized the default-setup of EUHFORIA and the Cone model for the CMEs, in order to model the selected events. For the modeling input parameters we used a) the DONKI database and b) the GCS technique (Thernisien et. al 2006, 2009) for reconstructing the CMEs. Our...
Coronal mass ejections (CMEs) are rapid eruptions of magnetized plasma that occur on the Sun. They are known to be the main drivers of adverse space weather. The accurate tracking of their evolution in the heliosphere in numerical models is of the utmost importance for space weather forecasting. We implement the RBSL flux rope model in COCONUT, a new global coronal MHD modeling, to simulate...
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...
METIS is the coronagraph of the scientific payload of Solar Orbiter, a joint ESA-NASA mission aiming at studying the Sun poles and the circumsolar region. METIS operations are handled via the Metis Operations Facility (MOF), which is built, run, and maintained by ALTEC in close collaboration with INAF. MOF empowers the scientific analysis and exploitation of data acquired by METIS in different...
In the frame of single-dish radio monitoring of the solar atmosphere with INAF radio telescopes we are developing and exploiting innovative single-dish radio imaging techniques at high-frequencies up to 100 GHz. Since 2018, we have been monitoring the solar atmosphere in the 18-26 GHz frequency range providing weekly images, in perspective covering the entire current solar cycle ([SunDish...
Kappa-distributions are particle distributions with a Maxwellian core and high-energy tail. They have strong theoretical support and can originate in the in the solar corona and transition region as a result of heating processes. Distributions with high-energy tail influence individual ionization, recombination and collisional excitation rates what affects the ionization equilibrium,...
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...
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...
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...
The behavior of energetic electrons from solar flares traveling through interplanetary space is crucial for understanding space environment and its impact on Earth. This transport is effectively influenced by the pitch-angle scattering due to the broad existence of interplanetary magnetic turbulence. However, how does the strength of pitch-angle scattering change over the electron energy and...
In this contribution we investigated the impact of a powerful gamma ray burst (GRB) that
occurred on October 9 2022, on the Earth's environment using a very low frequency
receiver (VLF) to probe the lower ionospheric region (the D region). In addition to the
VLF data analysis, we employed numerical simulation through the Long Wavelength
Propagation Capability code (LWPC) to derive 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...
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...
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...
Coronal holes are known to be the main source of open magnetic flux (OMF) in the heliosphere. However, there's a notable difference between OMF measured in-situ and the flux estimated from solar observations. This study looks at OMF changes and their link to solar coronal holes and active regions, focusing on a significant OMF increase in September-October 2014.
Firstly, we establish a...
An observation of a prominence on the solar limb took place on April 15, 2023, by several instruments including the Spectral Imaging of the Coronal Environment (SPICE) and the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. We aim to create parameter maps on the prominence region, including temperature, pressure, and column mass, by studying the integrated intensity of the Lyman-beta...
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...
The solar atmosphere hosts various physical phenomena driven by strong magnetic fields, but accurate and efficient MHD numerical modelling of such phenomena is challenging. Specifically, high accuracy typically requires low numerical dissipation, which may come with high computational costs and is prone to numerical oscillations. Conversely, efficiency demands sufficient robustness, which...
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...
Predicting solar flares is crucial for communications and satellite operations. Previous Machine Learning (ML) work focused on classifying flares with labels such as M and X, overlooking the continuous nature of X-ray flux. Our approach uses Convolutional Neural Networks (CNNs) to predict X-ray flux from Helioseismic and Magnetic Imager (HMI) and Extreme Ultraviolet (EUV) images of the Sun,...
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...
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...
The extreme ultraviolet High-Resolution Imager (HRI) of the EUI telescope onboard Solar Orbiter observes the solar corona in a ~5 $\mathring {\textrm A}$ passband near 174 $\mathring {\textrm A}$ with unprecedented high spatial resolution. We perform radiometric cross-calibration of the HRI and the EUV channels of the Atmospheric Imaging Assembly (AIA) telescope of the SDO in order to allow...
We present a method and application of data-driven simulations with the MURaM radiative MHD code. Combined with a bottom boundary driver that reproduces the evolution of observed magnetic field, the sophisticated energy equation accounts for thermal conduction along magnetic fields, optically-thin radiative loss, and heating of coronal plasma by viscous and resistive dissipation, which allows...
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...
In May 2024, a G5-class geomagnetic storm, the most intense since the Halloween solar storms of 2003, hit Earth. Over a dozen X-class flares were observed by GOES, and several Coronal Mass Ejections were launched towards Earth. These events caused significant disturbances in the Earth’s upper atmosphere, impacting satellite orbits and causing auroras to be visible at mid-latitudes globally....
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...
The Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50m single-dish millimetre telescope, could lead to new discoveries in the field of solar millimetre astronomy. With AtLAST’s proposed frequency range from ∼30 GHz to 1 THz, it would observe the solar continuum radiation originating in the chromosphere. However, the chromosphere’s highly dynamic nature prohibits meaningful...
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...
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...
The Atacama Large Aperture Submillimeter Telescope (AtLAST) is a proposed single-dish full-steerable 50m telescope that would be located at 5100m altitude in the Chilean Andes near ALMA. Among a large range of scientific topics, AtLAST would be able to observe the Sun, probing the thermal and magnetic structure of the solar chromosphere, chromospheric heating, flares, prominences, 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....
The recently available observations of the solar wind by Parker Solar Probe (PSP) at close to the Sun distances show large variations. Majority of attempts to model solar wind with EUHFORIA (European heliospheric forecasting information asset, Pomoell & Poedts, 2018), along the PSP trajectory, provided not very accurate modelling results. In attempt to understand the source of this inaccuracy,...
In most cases, the best spectral diagnostics to measure electron densities / temperatures, chemical composition and non-equilibrium effects in coronal plasma have not been explored at all or only partially (with e.g. little spatial/temporal information).
A few examples, from the X-rays to the infrared are provided, with suggestions for future instruments.
New EUV diagnostics for the outer...
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...
Observations in the Extreme Ultraviolet (EUV) are crucial for understanding the dynamics of the solar corona. The current EUV observing method utilises an entrance slit and scans over a field of view to build up 2D imaging spectroscopy. This scanning results in low-cadence images on the order of minutes which misses fundamental processes that occur on faster timescales. The application of...
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...
The SunsCube One (SEE) mission, currently in the early design stages, is being built by a team led by the University of Roma Tor Vergata. This mission is one of several small satellites planned by the Italian Space Agency (ASI) under ALCOR program. SEE proposes a 12U CubeSat to investigate gamma-ray, X-ray, and ultraviolet (UV) solar emissions. SEE aims to improve our understanding of space...
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 evolution of the solar magnetic field is the key factor governing space weather drivers. Accurate forecasting of space weather requires precise modelling of the magnetic field's evolution on the solar surface using methods like Surface flux transport (SFT). Conventionally used SFT modelling techniques involve grid-based numerical schemes, making them computationally expensive. In this...
The prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure) has been recently developed and validated by the CAESAR (Comprehensive Space Weather Studies for the ASPIS prototype Realization) project.
The ASPIS prototype unifies multiple Space Weather (SWE) resources (data and models) through a flexible and...
This work presents the outcome of the CAESAR (Comprehensive spAce wEather Studies for the ASPIS prototype Realization) project, which was supported by ASI and INAF from 21 December 2021 to 24 May 2024 (ASI-INAF n.2020-35-HH.0 agreement). CAESAR was devoted to study the relevant aspects of Space Weather (SWE) science and realize the prototype of the scientific data centre for Space Weather of...
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 Polarimetric and Helioseismic Imager onboard the Solar Orbiter
spacecraft (SO/PHI) has the unique opportunity to scan the entire
solar disk within approximately 4 hours with its High Resolution
Telescope (HRT). Such a so-called "full-disk mosaic" was produced on
March 22, 2023 at a solar distance of 0.495 AU where the SO/PHI-HRT
platescale of 0.5" covered a...
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...
Open problems in solar and heliospheric physics are (i) how charged particles are accelerated up to high energies and (ii) how they are transported in the inner heliosphere. Among candidates for particle acceleration there are shocks driven by coronal mass ejections (CMEs). We started a new research project (*) whose main methods are remote observations, numerical simulations, and in situ...
Predicting future solar activity cycles is a complex task that requires the incorporation of machine learning techniques. The aim of this study is to apply neural network techniques to the prediction of the 25th period of the solar cycle series. We consider two methods for the prediction models, namely the Nonlinear AutoRegressive eXogenous (NARX) and the Voting Regressor (VR) (with...
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...
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...
Understanding the magnetic field evolution of Coronal Mass Ejections (CMEs) is crucial for space weather research. We examined the 10 March 2022 CME, focusing on its magnetic field evolution from the near-Sun space to L1. The Solar Orbiter's in-situ measurements, 7.8 degrees east of the Sun-Earth line at 0.43 AU, provided a unique vantage point, along with the WIND measurements at L1.
We...
The data-driven time-dependent magnetofrictional method (TMFM) has proven to be a powerful tool for studying solar coronal eruptive events. Coupling data-driven TMFM with magnetohydrodynamic (MHD) simulations potentially provides a robust and efficient approach to study such events in more detail.
As has been shown by a number of studies, TMFM is capable of incorporating observational data...
We present our new approach to characterize
solar-like stars and their interaction with hosted exoplanets in analogy to the Sun-Earth system. Our investigation allows us to obtain not only a highly accurate characterization of the mother star, but also to study the impact of the star's rotational and activity history on the evolution of its exoplanets.
This information, coupled with
the...
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...
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...
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...
