In this talk I will review recent progress and the remaining challenges in both modelling and analysing observed magnetohydrodynamic (MHD) waves in the lower solar atmosphere. To model waves in sunspot umbrae, we have had to go beyond the standard cylindrical flux tube model due to the irregular shapes of the MHD waveguides. For sunspots the umbra/penumbra boundary shape is reasonably static...
We theoretically investigate the interplay between magnetohydrodynamic (MHD) waves and shear flows in a partially ionized solar plasma, focusing on the energy exchange mediated by the flow and the transformation between wave modes. We consider a simple model composed of a uniform partially ionized plasma with a straight magnetic field. A shear flow is present in the direction of the magnetic...
Mode conversion of magnetohydrodynamic (MHD) waves at coronal magnetic null points is of intense interest due to its potential roles in coronal heating and oscillatory reconnection. Recently, the first direct imaging of MHD wave conversion was reported in a complex pseudostreamer magnetic topology, accompanied by transverse oscillations. In this study, we perform 2.5D MHD simulations using the...
The nature of MHD waves within inhomogeneous media is fundamental to understanding and interpreting wave behaviour in the solar atmosphere. We investigate fast magnetoacoustic wave behaviour within magnetically-inhomogenous, gravitationally-stratified media, by studying various magnetic environments, including a simple X-type null point and also a topology created by two dipoles. We find that...
Prominences are cold and dense structures in the hot and tenuous solar corona and are ubiquitous on the Sun. They possess thermodynamic conditions that vary from chromospheric internally to those of the corona that surrounds them. Even though predominantly in the corona, they connect all the layers in the solar atmosphere and play an important role in the energy transfer between the different...
We performed numerical simulations to study mechanisms of solar prominence formation triggered by a single heating event. In the widely accepted “chromospheric-evaporation condensation” model, localized heating at footpoints of a coronal loop drives plasma evaporation and eventually triggers condensation through the development of thermal instability. The occurrence of condensation is strongly...
Under coronal conditions, especially in flaring loops, the mean-free-path of electrons can no longer be assumed to be small in comparison to the temperature length scales. In this case, the thermal transport is non-local, and the classical Spitzer–Härm (SH) approximation is violated. Here, we consider two scenarios in which the effects of non-local thermal transport are important. The first...
The coronal heating problem and the generation of the solar wind remain central challenges in solar physics, both of which require a detailed understanding of wave-based heating mechanisms. In this study, we investigate the turbulent cascade of kink and Alfv\'en wave energy and its role in heating the solar atmosphere and driving the solar wind, through a newly implemented physics module in...
Solar prominences are composed of thin threads that outline particular magnetic field lines of the prominence structure. Observations have shown the presence of Alfvénic waves in threads, which are probably driven at the photosphere. Wave dissipation could be a relevant heating mechanism in prominences. In this work, we construct 1D equilibrium models of partially ionized prominence threads...
Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere and are key in many models for seismological or energy conversion processes. With the help of modern coronagraphs on board missions such as Solar Orbiter, Aditya-L1 and PROBA-3, it is now possible to study wave dynamics in the extended solar atmosphere in unprecedented detail. In our work, we aim to provide context to such...
Understanding the formation and dynamics of cool solar loops is essential for unraveling the complex energy transport mechanisms in the solar atmosphere. In this talk, we will focus on the formation of cool loops driven by Alfvén pulses under ideal and non-ideal magnetohydrodynamic (MHD) regimes. Using 2.5D MHD simulations in a gravitationally stratified model solar atmosphere, we demonstrate...
In this talk, we present results from 2.5D MHD simulations of a solar eruption, the propagation of coronal waves through a non-uniformly magnetized solar corona, and their interaction with remote flux rope prominences, leading to induced prominence dynamics. The initial atmosphere is a non-adiabatic, gravitationally stratified corona permeated by a magnetic field composed of two main...
Helioseismology has revolutionised our understanding of the Sun’s
internal structure and dynamics, offering unparalleled insights into
processes hidden beneath the solar surface. In this review, I will
summarise key developments in global and local helioseismology,
including recent advances in determining large-scale flows in the solar
interior. I will highlight the current status of...
Coronal waves have been intensively studied due to their potential role in coronal heating and their application in plasma diagnostics. One particularly promising candidate is the recently discovered low-amplitude decayless kink oscillations, which are ubiquitous in the solar corona. Their undamped nature suggests the presence of a continuous energy input counteracts dissipation, although the...
Acoustic waves below the cut-off frequency reflect at the photosphere, forming standing p-modes in sub-photospheric cavities. Above the cut-off, waves propagate as pseudomodes. Recent observations show pseudomode frequencies vary in anti-phase with the 11-year solar cycle, which is not yet fully explained. Using the Klein-Gordon equation with a piecewise acoustic potential, we study the...
Atmospheric gravity waves (AGWs) are low-frequency, buoyancy-driven waves generated by turbulent convection in the lower solar atmosphere. In addition to their role as energy agents and coupling atmospheric layers, simulations showcase their sensitivity to the average magnetic field topology. Using multi-height IBIS/DST and HMI/SDO velocity and magnetic field observations, we investigate the...
Gravity waves are generated by turbulent subsurface convection overshooting or penetrating locally into a stably stratified medium. While propagating energy upwards, their characteristic negative phase shift over height is a well-recognized observational signature. Since their first detailed observational detection and estimates of energy content, a number of studies have explored their...
The nonlinear evolution of Alfvénic modes (torsional, kink, or fluting modes) in magnetic flux tubes is strongly affected by the Kelvin-Helmholtz (KH) instability, which arises from shear flows at the tube boundary. In this study, we show that baroclinic instabilities of Rayleigh-Taylor (RT) type can also emerge at locations in the boundary where the plasma acceleration is directed normal to...
Solar prominences, composed of ribbon-like structures with fine thread-like substructures, are widely believed to form via thermal instability (TI) leading to the cooling and condensation of hot coronal plasma. Motivated by the ubiquitous presence of sub-Alfvenic counter-streaming flows along magnetic field lines in prominences, we revisit TI in magnetized plasmas under the influence of shear...
Despite its extremely high temperature, the Solar corona features many cooler structures, like prominences and coronal rain. The root cause of the formation of cool and dense plasma is a thermal runaway effect, in which the plasma density increases in response to a decrease in temperature due to radiative cooling, in turn enhancing the radiative cooling effect again. This thermal instability...
Abstract: Cool (≈10^4 K), dense material permeates the hot (≈10^6 K), tenuous solar corona in form of coronal condensations, for example prominences and coronal rain. As the solar atmosphere evolves, turbulence can drive mixing between the condensations and the surrounding corona. Whilst both the corona and the condensations are relatively thermally stable, in the sense that radiative losses...
The state of coronal loops essentially depends on the complex interplay between plasma flows, gravity, heating, radiative cooling and conduction. Numerical simulations show that, under the influence of a steady or quasi-steady footpoint heating, coronal loops can be in a state of thermal non-equilibrium (TNE), characterised by a localised thermal runaway that leads to the formation of cold and...
Forced magnetic reconnection is triggered by external perturbations, which plays a crucial role in the energy release during solar transient events, that are often associated with the disintigration of electric current sheets (CSs) through tearing instability. The instability in the CS is triggered by imposing impulsive velocity perturbations concentrated at different locations in the upper...
The magnetic field in the Sun’s corona stores energy that can be released to heat plasma and drive solar eruptions. Measurements of the global coronal magnetic field have been limited to several snapshots. In this work, we present observations, using the Upgraded Coronal Multi-channel Polarimeter, that provide 114 magnetograms of the global corona above the solar limb spanning ~8 months. We...
Coronal fan loops rooted in sunspot umbra constantly show 3-min period propagating slow magnetoacoustic waves (SMAWs) in the corona. However, the origin of these waves in the lower solar atmosphere is still unclear. Here, we present the results of our study of these waves along a clean fan loop system using multi-wavelength imaging observations from IRIS and SDO. We demonstrate a novel...
Within the last decade, solar physics has moved into a golden era of discovery. A diverse assortment of ground- and space-based facilities have helped make rapid progress in the detection, identification, characterisation and understanding of dynamic oscillatory motions spanning the entire solar atmosphere. Combined modelling efforts have resulted in a number of outstanding science questions...
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...
Magnetic pores act as conduits for magnetohydrodynamic (MHD) waves, facilitating energy transport through the solar atmosphere. While Grant et al. (2015) identified upwardly propagating sausage-mode oscillations, and Albidah et al. (2020,2023) and Jafarzadeh et al. (2024) demonstrated the power of Proper Orthogonal Decomposition (POD) in analysing wave dynamics, a detailed breakdown of wave...
The general understanding of oscillations in the Sun's atmosphere is that the photosphere is dominated by the global resonant modes of the entire stellar structure at 3mHz, while, moving upwards to the chromosphere, the dominant period shifts to 5mHz. However, the availability of stable and seeing-free coverage of the Sun for more than 15 years thanks to NASA’s Solar Dynamics Observatory (SDO)...
In the ever-evolving field of instrumentation for solar physics, the need for high cadence simultaneous observations at high resolutions in both the spatial and spectral domains is undeniable. To successfully achieve such measurements requires the implementation of contemporary technology, with integral field units (IFUs) offering a clear path. Here, we present a novel fibre-fed variation of...
The plages are strong magnetic field regions, and they frequently appear as bright intensity patches (in the chromosphere) around sunspots. The high-resolution spectroscopic observations are used from the Interface Region Imaging Spectrograph (IRIS), and magnetic field observations from Helioseismic and Magnetic Imager (HMI) are used to diagnose the waves in an active-region (AR) plage. We...
Propagating slow magnetoacoustic waves, observed as intensity disturbances in coronal extreme ultraviolet (EUV) emission, are powerful tools for magnetohydrodynamic (MHD) seismology. Their dispersive properties, phase speeds, and damping behaviour enable diagnostics of coronal plasma conditions, including magnetic field geometry. Using quasi-stereoscopic data from the Atmospheric Imaging...
Solar vortex flows are rotating plasma structures widely detected in direct solar observations as well as comprehensive numerical simulations. We investigate and compare vortex dynamics in three magnetic regions, viz., Quiet Sun, Weak Plage, and Strong Plage, using realistic three-dimensional simulations from a comprehensive radiation-magnetohydrodynamics (MHD) code, MURaM. We find that the...
The solar atmosphere is a dynamically turbulent and magnetically organised environment, where waves and flows are central to energy transport. Among the features shaping this complexity are solar vortices—localised, rotating structures that span multiple spatial and temporal scales. This talk focuses on how vortices influence wave propagation and energy redistribution, particularly in the...
Vortex flows in the solar photosphere are ubiquitous and are thought to channel energy into the upper solar atmosphere in the form of Poynting flux and excitation of Alfv\'{e}n waves. 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...
The outermost layer of the solar atmosphere is referred to as corona, of which temperature is hundred times hotter than the surface while the ultimate heat source locates at the inner core. The solar coronal heating problem is one of the most critical challenges in solar physics. Recent advancements in observational accuracy have revealed numerous facts that cannot be explained by the...
Magnetic null points are natural ‘weaknesses’ in the magnetic topology of the solar atmosphere. When perturbed, they facilitate time-dependent magnetic reconnection, leading to the reconfiguration of magnetic field lines and plasma heating. This work employs advanced three-dimensional, nonlinear magnetohydrodynamic (MHD) simulations to investigate wave-generating, time-dependent reconnection...
Decades-long studies of asymmetric spectral lines observed in the solar corona and the transition region point to mass and energy transport from the lower layers of the solar atmosphere to the corona. Slow magnetoacoustic waves and jets (plasma upflows) are considered to be the two possible drivers for these spectral line asymmetries. However, due to insufficient multiwavelength observations...
Spectral (periodogram) analysis has proved effective for identifying oscillatory behavior in Hα solar filament observations. In this preliminary study, we apply recent periodogram‐based frameworks—those of Luna et al. (2022) and Castelló et al. (2025)—to extreme-ultraviolet (EUV) image sequences from the Solar Orbiter mission. Adopting a Bayesian inference approach with a red-noise background...
The launch of Solar Orbiter in 2020 made a multi-view observation of the Sun possible. Since the start of the nominal mission phase, at the end of 2021, the SO/PHI instrument has provided the magnetic field vector and LoS velocity of the solar photosphere. The data taken while Solar Orbiter was in inferior conjunction showed an excellent agreement between magnetic and, more recently, velocity...
Over the past few years, multi-line spectropolarimetry has revolutionized diagnostic capabilities, enabling the accurate identification of MHD modes in diverse structures and assessing their contributions to the energy budget of the solar atmosphere. In this presentation, I will illustrate the potential of these diagnostic techniques through the analysis of several illustrative cases....
The Metis coronagraph on board Solar Orbiter allows observations of the middle solar corona at spatial resolutions that can rival or surpass those attained by other operating coronagraphs over a field of view going from 1.6 to 3.4 degrees, corresponding to the range 1.7 - 3.6 solar radii at perihelion. The instrument is also capable to observe the corona at high temporal cadences - down to 20...
Transverse kink oscillations have long been observed in the corona and in closed magnetic loops especially. Although their properties are quite well-known now it is still rather unclear how they manage to sustain themselves over quite a long duration, with open questions regarding their driver and excitation mechanism. In this talk I will give an overview over the different ideas/theories that...
Understanding the polarisation state of coronal waves is key to constraining wave displacement and velocity amplitude, improving estimates of wave energy flux and deposition. We present a novel method to infer the polarisation of a standing kink oscillation in a coronal loop from a single viewpoint, using combined spectral and imaging data from the Coronal Multi-channel Polarimeter (CoMP)....
We investigate the propagation of Alfven waves in the solar chromosphere, distinguishing between upward and downward propagating waves. We find clear evidence for the reflection of waves in the chromosphere and differences in propagation between waves interpreted to be resonant or nonresonant with the overlying coronal structures. This establishes the wave connection to coronal element...
The evolution of Alfvén waves in coronal loops can be affected by phase mixing and turbulent cascade. Both processes contribute to the dissipation of the bulk energy of the waves through the generation of small spatial scales. Different regimes can be envisaged according to how timescales of the two processes are related and to the typical dissipative timescale. We investigate the interplay of...
The 2024 total solar eclipse over North America provided a multi-perspective view of the Sun and solar wind through combined ground (DKIST, Mauna Loa Solar Observatory UCoMP and K-Cor) and space (Parker Solar Probe, Solar Orbiter, LASCO/C2, Hinode/EIS) -based remote and in situ observations. Through a multi-mission coordinated effort, we examine near-contemporaneous and multi-wavelength...
Solar active regions are rich in dynamic phenomena driven by wave propagation. Among the most striking are umbral flashes, sudden brightenings observed in the chromospheric core of some spectral lines. Traditionally attributed to upward-propagating shock waves, this interpretation has been recently questioned by observations of downflowing umbral flashes and the identification of resonant...
IBIS2.0 is the updated edition of the Interferometric BIdimensional Spectrometer( operated at the Dunn Solar Telescope of the National Solar Observatory from 2003 to 2019). The enhancements include a new optomechanical design, an upgraded polarimetric unit, and a new array of high-performance cameras, all aimed at improving the instrument's capability to capture high-resolution...
On 26 September 2022, a quiescent solar prominence was observed using Hα imaging spectroscopy with SDDI on SMART. Previous studies found 4- and 15-minute oscillations with limited spatial coverage. We extend this to the full prominence using 3D wavelet analysis, comparing with SDO/AIA, STEREO-A/EUVI, and Solar Orbiter/EUI data for a tomographic view.
We examine oscillatory power from 3 to 64...
On 26 September 2022, a quiescent solar prominence was observed using Hα imaging spectroscopy with SDDI on SMART. Previous studies found 4- and 15-minute oscillations with limited spatial coverage. We extend this to the full prominence using 3D wavelet analysis, comparing with SDO/AIA, STEREO-A/EUVI, and Solar Orbiter/EUI data for a tomographic view.
We examine oscillatory power from 3 to 64...
Coronal fan loops rooted in sunspot umbra constantly show a 3-min period propagating slow magnetoacoustic waves (SMAWs) in the corona (upper solar atmosphere). Using the recently devised technique of Rawat & Gupta (2023), we trace these loops along with their cross-sectional area with height from the photosphere to the corona via the transition region and chromosphere (lower solar atmosphere)....
RTV scaling laws and their generalisations have proven to be valuable in inferring some of the key properties of coronal loops, such as the heating rate, from more easily observable temperature and loop length. Over the years, many heating mechanisms have been tested against the resulting predictions in a search for the dominant one(s) in the solar corona, so far without conclusive results. On...
Vortices are ubiquitous in the turbulent upper solar atmosphere, acting as key drivers of energy, mass, and momentum transport from the photosphere through the chromosphere and into the corona. By examining how vortices influence each other rather than treating them as isolated phenomena, we find that highly interconnected “vortex communities” can arise. With their degree of interconnectedness...
Abstract
The evolution of the magneto-Rayleigh-Taylor instability (MRTI) in a slab model of an isolated horizontal magnetic flux sheet embedded in a two-layer atmosphere with different densities and temperatures is investigated using the 2.5D magneto-hydrodynamic (MHD) code AMRVAC.
In the solar context, this two-layer model serves as a simplified representation of the...
Atmospheric gravity waves (AGWs) are buoyancy-driven waves generated by overshooting turbulent convection in the vertically stratified solar atmosphere. These waves are of particular interest due to their potential role in mediating the energy balance of the chromosphere. AGWs are typically analyzed through k-ω diagnostic diagrams, which are interpreted by comparison with theoretical models...
This work investigates wave activity on the Solar Photosphere in the presence
of active regions, aiming to explore a possible connection with a phenomenon
observed in the Solar Corona: the First Ionization Potential (FIP) effect. This
effect refers to a chemical inhomogeneity in the solar atmosphere, where ele-
ments with low first ionization potential are preferentially transported to...
We can deduce the activity and dynamic status of the Sun and its possible dependence on the magnetic cycle using continuous, multi-height observations of the solar atmosphere. Furthermore, multi-height observations allow us to probe the propagation of magneto-acoustic-gravity waves through the solar atmosphere, potentially providing insight into other solar phenomena, such as the heating of...
We performed full Stokes spectropolarimetric observations of loop footpoints in the active region NOAA 13363 during a C-class flare with the GREGOR Infrared Spectrograph (GRIS) on 2023 July 16. The observed spectral region included the photospheric Si I 10 827 A and Ca I 10 839 A lines and the chromospheric He I 10 830 A triplet. Simultaneously, high-cadence and high-resolution imaging...
We analyze the stability of chromospheric jets by investigating the Kelvin-Helmholtz Instability (KHI) in partially ionized plasma. Emphasizing the role of ambipolar diffusion, we explore how stability varies with the degree of ionization and compute KHI growth times for various conditions. A magnetic slab model with linear perturbation theory for incompressible, single-fluid MHD is used to...
We present a method combining ideas from the theory of vector-valued
kernels with delay-coordinate embedding techniques in dynamical systems
capable of identifying spatiotemporal patterns, without prior knowledge of the
state space or the dynamical laws of the system generating the data. The
approach is particularly powerful for systems in which characteristic patterns
cannot be readily...
The Els ̈asser variables have been widely used in magnetohydrodynamics (MHD) to describe Alfv ́en waves. However, Els ̈asser variables are less suited for other wave modes, such as fast and slow magnetosonic waves, which require mixed components. To address this limitation, Q-variables were introduced as a generalisation of the Els ̈asser formalism, which allows for tracking waves with phase...
Observations of the Sun reveal a rich array of dynamics throughout all levels of the solar atmosphere. In many cases. the observed dynamic motions are driven by the magnetic field. However, the lower solar atmosphere, i.e. the photosphere and chromosphere, is a partially ionised plasma, with most of the species being neutral. This means that the driver of the fluid motions cannot directly...
The explosive increase in observational data from ground- and space-based instruments highlights the need for automated detection techniques capable of detecting the phenomena of interest in a large amount of data for a reasonable time. Nowadays, Artificial Neural Networks (ANN) demonstrate such a capability. In this study, we demonstrate how artificial neural networks can be used to detect...
Solar pores unlike Sunspots are difficult to analyse, due to being much smaller in size, the absence of a penumbra and its shape evolution appearing more unstable, giving no fixed boundary of the pore. By using shape analysis tool Deformetrica created by Bone et al (2018), we can fix grid points over the shape of the pore and track the changes as it evolves over time. By doing this, we can...
Wave phenomena are key to diagnosing the solar atmosphere, from chromospheric magnetoacoustic oscillations to Alfvénic waves in the corona. Yet, interpreting these complex signals depends critically on choosing the right analysis methods — a non-trivial task given the multi-dimensional, non-stationary nature of solar data and the diversity of available techniques. In this presentation, we...
