Abstracts

Accepted Abstracts.

• Author: Joel Allred ¶

  When: Monday - 14:35

  Coauthors: Graham Kerr, Joel Dahlin, Silvina Guidoni, Marc Swisdak, Judy Karpen

  Title: Flare Modeling with RADYN Arcade

  Abstract Dominant processes occurring during solar flares range from global scale restructuring of magnetic field to particle acceleration and transport at the kinetic scale, some ten orders of magnitude smaller. Currently no single model can resolve such disparate scales. Instead, distinct models have been developed, each tackling only some aspects of a complete solar flare. Here we report on progress in developing a new composite flare model, which chains outputs from several well-tested codes. These were chosen to cover the range of physical processes dominating flares. The ARMS MHD code predicts the evolution of the global magnetic field and arcade structure and provides the conditions in which particles are accelerated. The hybrid fluid/particle kglobal code is used to simulate self-consistently the dynamic interplay between the MHD fluid and the accelerated nonthermal particles. We trace field lines in the ARMS arcade simulation and inject accelerated particles at looptops. Particle transport and the radiative-hydrodynamic response to these are modeled using the RADYN+FP code. We show the radiation predicted by our composite simulation with particular emphasis on the IRIS and MUSE responses

• Author: Patrick Antolin ¶

  When: Tuesday - 14:00

  Coauthors: Samuel Hor, Jamal Wachira

  Title: Coronal rain as a proxy for coronal heating

  Abstract The solar corona can host large amounts of cool material in the form of prominences and coronal rain. The presence of this cool phenomena is intimately linked to the spatial and temporal properties of how the enigmatic coronal heating and flaring mechanisms operate. Numerical modelling indicates that electron beam heating alone from flare reconnection cannot explain the usually observed coronal rain during the flare gradual phase, suggesting that significant secondary heating sources must exist associated with the flaring. Similarly, the models indicate that the quiescent coronal rain produced by coronal heating is the product of specific spatial localisation and temporal occurrence frequency of the unknown heating events. In this talk I will discuss the results of a parameter space investigation with HYDRAD where we explore the spatial and temporal properties that secondary heating sources in flares must have to generate coronal rain. I will also present new Solar Orbiter-AIA-IRIS observations that show that coronal rain can carry a large amount of kinetic energy that can be used as proxy for the total integrated coronal heating at the origin of it, supported by numerical modelling. Most of the rain’s energy is radiated away upon impact, but 20% goes into the generation of hot upflows that reheat and replete the hosting coronal structures leading to a feedback effect. We discuss how MUSE will be able to test the predicted heating in flares and quiescent regions, and further constrain the theoretical understanding of thermal non-equilibrium processes.

• Author: Souvik Bose ¶

  When: Wednesday - 10:10

  Coauthors: Bart De Pontieu, Viggo Hansteen and Alberto Sainz-Dalda

  Title: Active region heating in the chromosphere and the corona: insights from high resolution observations and simulations

  Abstract At the interface between the Sun’s million-degree corona and its surface lies the chromosphere. At roughly 10,000 K it is much cooler than the corona, but also several orders of magnitude denser. Understanding what heats the corona is indirectly related to understanding the heating mechanisms in the chromosphere since it processes all the magnetoconvective energy that ultimately drives the heating of the corona. Yet many questions pertaining to the coupling of these layers remains a topic of significant research. In this talk, I will focus on recent progresses in high-resolution ground and space-based observations and state-of-the-art numerical simulations of the dynamic solar atmosphere, in particular of the active regions, in an attempt to understand how the atmosphere above the active regions is heated from tens of thousands to millions of degrees. Moreover, this talk will also highlight how the synergy between observations and modeling is key to make advances in our understanding of the chromosphere.

• Author: Stephen Bradshaw ¶

  When: Wednesday - 11:20

  Coauthors: None

  Title: Application of a multi-species NLTE modeling framework to a solar flare and interpreting emission spectra.

  Abstract Conventional approaches to constructing numerical models of the solar atmosphere assume a fully equilibrated plasma, wherein all species are in collisional thermal equilibrium amongst themselves and each other. This yields single fluid formulations of the governing evolution equations, such as ideal MHD, or, at best, a treatment that accommodates different electron and ionized hydrogen and helium temperatures. In reality, a comparison between the timescales of observed solar activity and inter-species collisional timescales demonstrates that the former can be significantly shorter than the latter. There are important consequences for the model predicted spectra that are frequently used to deduce the presence of physical processes from observed spectral signatures. For example, the true thermal width of an emission line can be very different to the width predicted by setting the ion temperature equal to the electron temperature (or to the formation temperature of the ion in equilibrium), leading to very misleading interpretations concerning the preferential energization of particular species and the presence of excess broadening due to (e.g.) turbulence. We will present a new multi-species modeling framework to accommodate the NLTE coupling between arbitrary species, including the strongly charged ion populations of relevance to the solar atmosphere, and some recent results from its application to solar flares.

• Author: Mats Carlsson ¶

  When: Thursday - 09:00

  Coauthors: None

  Title: Chromospheric modelling

  Abstract Models of the Solar chromosphere have progressed due to increased computing capacity, as well as an enhanced understanding of the physics of the chromosphere, and thanks to new observations with high spatial and temporal resolution. Models based on reproducing observations have advanced from 1D semi-empirical models aiming at reproducing a temporal average to spatially resolved inversions of large fields of view. Numerical simulations are now conducted in 3D and can incorporate scattering, approximations to full non-LTE radiative transfer, out-of-equilibrium ionization, and ion-neutral effects. Synthetic observables can be produced with full 3D radiative transfer, including partial redistribution for realistic, multi-level model atoms. We will discuss here the strengths and weaknesses of various chromospheric modelling schemes, and what discrepancies between synthetic observables and real observations can tell us about what is missing and what should be addressed in the next two years.

• Author: Mark Cheung ¶

  When: Monday - 09:25

  Coauthors: Juan Martínez-Sykora, Amy Winebarger, Vishal Upendran, Carlos José Diaz Baso, David Fouhey, Kyuhyuon Cho, Bart De Pontieu, Paola Testa, Adrian Daw, Gabriele Cozzo

  Title: Multi-slit disambiguation and High-level Science Data Products for MUSE

  Abstract We provide an update on the development of algorithms, software and pipeline for resolving multi-slit disambiguation for MUSE spectra. The principles beyond this development effort are first introduced, and then we dive deep into the performance / quality / speed of the candidate techniques, which includes conventional Gaussian fitting, singular value decomposition, compressed sensing, and deep neural networks. The outputs from these codes are intended to be high-level data products which provide zeroth, first and second moment raster maps in the various spectral lines.

• Author: Georgios Chintzoglou ¶

  When: Tuesday - 11:10

  Coauthors: None

  Title: MUSE Observations as Discriminants of Solar Eruption Models in δ-spot ARs

  Abstract Solar eruptions in active regions reflect the coupled processes of magnetic energy storage and release. In δ-spot regions, recent observations and radiative-MHD simulations show that collisional shearing - the collision of non-conjugate bipoles - drives rapid photospheric flux cancellation at compact PILs. This process builds seed magnetic flux ropes that accumulate flux until reaching the torus-instability threshold, which then triggers eruption. In this framework, cancellation provides the storage “engine,” while instability defines the onset. Classical tether-cutting (TC; runaway reconnection at the PIL) and breakout (BO; null-point reconnection in multipolar topologies) remain alternative pathways, but require observational discriminants.

  The Multi-slit Solar Explorer (MUSE) will deliver precisely such diagnostics: high-cadence Doppler and line-width imaging can reveal whether persistent activity concentrates above cPILs (favoring cancellation/TC) or at remote nulls (favoring BO). MUSE’s ability to capture filament slow-rise velocities on-disk, coupled with vector magnetography (e.g., from the Helioseismic and Magnetic Imager or from Ground Based Observatories, such as the Swedish Solar Telescope and the Daniel K. Inouye Solar Telescope) and advanced data-driven non-linear force-free field or MHD 3D modeling, offers a direct test of torus-instability onset and a pathway to predictive capability for Earth-directed eruptions.

• Author: Kyuhyoun Cho ¶

  When: Monday - 10:05

  Coauthors: Juan Martinez-Sykora, Adrian Daw, Bart De Pontieu

  Title: Removal of Diffraction in Multi-slit Spectrograph

  Abstract A multi-slit spectrograph is a crucial technique for acquiring observational data with wide field-of-view coverage in a short time cadence. However, space telescopes typically use mesh-type grids in their filters for structural reinforcement, which introduces diffraction patterns. Eliminating these diffraction patterns in a multi-slit spectrograph is a challenging task, primarily due to the overlapping spectra within a single exposure. In this study, we propose three distinct methods—yx removal, monochromatic removal, and iterative removal—to address this issue. Using 3D radiative MHD simulations, we synthesize the Multi-slit Solar Explorer (MUSE) spectrograph with diffraction and evaluate the performance of each method. We conclude with a discussion of the advantages and limitations of the proposed approaches.

• Author: Gabriele Cozzo ¶

  When: Tuesday - 15:30

  Coauthors: G. Cozzo, P. Testa, J. Martinez-Sykora, F. Reale, P. Pagano, F. Rappazzo, V. Hansteen, and B. De Pontieu

  Title: Pinpointing nanoflare‑scale coronal heating through reconnection-outflows spectroscopy

  Abstract Magnetic reconnection is widely regarded as a key process for coronal heating, powering phenomena that range from rare, energetic flares to the numerous micro‑ and nanoflares. The observed self‑similar scaling of these events implies that the corona is pervasively heated by rapid, small‑scale energy bursts. Yet the corona’s faint, optically thin, highly conductive plasma has long hidden clear evidence of the low‑energy tail of these events. High‑resolution IRIS observations have recently uncovered small (a few Mm), rapid (a few hundred km/s), short‑lived (tens of seconds), jet‑like bursts, called "nanojets", that expand perpendicular to the guide field of coronal loops. Current models indicate that these impulsive outflows result from the release of magnetic tension when misaligned coronal loop strands reconnect at small angles. Viewed as the dynamic counterpart of nanoflares, nanojets show that the kinetic signatures of magnetic reconnection can pinpoint sites of localised energy release and reveal how braided‑field reconnection transforms magnetic energy into nanoflare‑scale heating. Although detection remains challenging and their ubiquity is not yet proven, observations and modelling of nanojets suggest that coronal‑loop plasma is frequently accelerated by the “bow‑shot” release of magnetic tension within braided fields through component 3D reconnection. Forthcoming high‑resolution EUV spectroscopy from MUSE will extend such diagnostics to hotter plasma, unveiling the small-scale dynamics of coronal heating processes and ultimately establishing the role of reconnection outflows in the solar corona. In the talk, we will focus on reconnection outflows produced by widespread heating episodes in full 3D MHD simulations of coronal heating by magnetic braiding. We will discuss their possible detection and diagnostics with UV and EUV high resolution spectroscopy, taking as a reference the state-of-art spectral capabilities of IRIS and the opportunities that spectra and images from MUSE will open up.

• Author: Lars Daldorff ¶

  When: Tuesday - 13:40

  Coauthors: Craig D. Johnston (GMU/NASA), James A. Klimcuk (NASA), Shanwlee Sow Mondal (CUA/NASA), Will T. Barnes (AU/NASA), James A. Leake (NASA), Jack Reid (St. Andrews/UK), Jacob D. Parker (NASA)

  Title: Nanoflares and Coronal Heating: The Role of Fine-Scale Magnetic Reconnection

  Abstract Understanding the evolution of active regions requires quantifying their temporal variability, with coronal heating playing an important role in governing the energetics and dynamics of the solar atmosphere. We present ongoing efforts at NASA GSFC to model self-consistent coronal heating mechanisms. Through LaRe3D MHD simulations of Parker-type coronal loop configurations, we reproduce multi-thermal loop systems that offer insight into key observables - such as quasi-circular cross-sections and “apparent” motions in the corona - and allows us to link these features back to the underlying heating processes. While the primary objective of the simulations was to investigate the evolution and heating dynamics of the corona, we have also examined the interaction between the chromosphere and transition region to better understand chromospheric events and how their observables both influence and respond to coronal conditions.

• Author: Adrian Daw ¶

  When: Monday - 10:55

  Coauthors: None

  Title: Atomic physics (and uncertainties) in support of MUSE approach towards multi-slit disambiguation and cross-calibration

  Abstract A method is presented to disambiguate MUSE spectrograph (SG) data by simultaneously fitting multiple Gaussians to each “y” location along the 35 slits and leveraging known atomic physics of the contributing ions. The band passes of the 3 spectrograph channels are designed to target the ‘main’ lines of Fe IX, XV and XIX, but in extreme cases such as flares, there will be contributions to the SG data from a number of other species as well, leading to potential blends of ‘minor’ lines from neighboring slits with the main lines. Known wavelength separations and branching ratios are employed to limit the number of free parameters and obtain convergence. Information from the minor lines can be employed in cross-calibration of the SG channels as well as diagnostics of the solar plasma. Progress on automation of the procedure will be presented using simulated solar data, and significant ‘minor’ ions will be discussed. Regarding the atomic physics, in a related effort, the Smithsonian Astrophysical Observatory (SAO) electron beam ion trap (EBIT) is now operational and observing the 50-200 A wavelength range to address atomic data needs of MUSE and other solar missions.

• Author: Ineke De Moortel ¶

  When: Tuesday - 14:40

  Coauthors: C.A. Breu, T.A. Howson

  Title: Observational signatures of elementary heating mechanisms

  Abstract Key to making progress on the long-standing coronal heating problem is the identification of distinguishing observational signatures. To complement large-scale, self-consistent MHD models, we focus on 3D simulations of specific heating mechanisms to study heating in coronal loops. We use both boundary-driven and magneto convection-driven simulations to look at MHD waves, reconnection and small-scale motions such as vortices driven by rotational flows. Differences in the plasma response (e.g. temperature, density, flows) could potentially be observable, helping constrain the significance of the different heating mechanisms. Using synthetic observables derived from the numerical experiments, we consider the signatures of the different heating mechanisms, focusing in particular on the observational capabilities of the upcoming MUSE mission.

• Author: Bart De Pontieu ¶

  When: Monday - 09:10

  Coauthors: The IRIS and MUSE Teams

  Title: IRIS and MUSE status

  Abstract I will provide an overview of current operations and capabilities of IRIS, as well as a progress report of the development of the MUSE spacecraft and instrument, and plans for operations, data pipeline, and science analysis.

• Author: Carlos Diaz Baso ¶

  When: Thursday - 15:30

  Coauthors: TBD

  Title: How machine learning and inversion techniques can advance our understanding of the low solar atmosphere?

  Abstract In the last decade, machine learning and neural networks have emerged as powerful tools for extracting and analyzing relevant information from huge collections. They have demonstrated their versatility in data preprocessing, automatic segmentation of solar features, image deconvolution and reconstruction, acceleration of spectropolarimetric inversion techniques and prediction of explosive phenomena. This contribution will focus on how these advanced techniques, can be leveraged to maximize the scientific return from missions like MUSE and IRIS. We will review pioneering applications that directly support the operations and enhance the data products of these missions. We will describe the methodologies, discuss current challenges, and offer a perspective for future research that integrates these powerful tools with ongoing and future observational capabilities.

• Author: Cooper Downs ¶

  When: Thursday - 11:40

  Coauthors: Tibor Török, Viacheslav S. Titov, Jon A. Linker

  Title: Studying Solar Eruptions Through the Lens of Global Coronal Modeling and Observations

  Abstract Understanding the energy storage and release processes of solar eruptions, also known as Coronal Mass Ejections (CMEs), remains a key science driver in solar and heliospheric physics. Through its unique high-resolution spectroscopic capabilities and tightly integrated modeling support, the MUSE mission is poised to provide unprecedented insight into these processes within coronal source regions. However, this just the beginning of a CMEs journey through the heliosphere, which often involves a coupled non-linear interaction with the global background through which it erupts. In this talk, we provide a brief overview of the large-scale coronal context of solar eruptions through the lens of data-constrained global coronal modeling. With MUSE & IRIS in mind, we focus particularly on how the global state of corona may (1) magnetically influence the local forces or connectivity a source region prior to eruption; and/or (2) observationally inform our understanding of a CME’s subsequent evolution (coronal dimming, EUV waves, shocks, etc.). We also touch on possible ways in which global coronal modeling might help complement MUSE & IRIS data analysis and high-resolution modeling efforts for CME source regions.

• Author: Christopher Entzel ¶

  When: Monday - 11:35

  Coauthors: Charles Kankelborg

  Title: The Active Sun Irradiance Observer (ASIO)

  Abstract Solar flares are the most energetic events in the solar system, and while they are well-studied, the behavior of flaring plasmas on shorter time scales remains poorly understood. Limitations in current instrument cadences prevent experimentalists from observing the more dynamic properties of solar flares. ASIO, the Active Sun Irradiance Observer, will sample at an unprecedented cadence of 100 Hz, offering unique observational opportunities. ASIO is a radiometer measuring short-wavelength irradiance in its three spectral passbands of 0.5-4 Å, 1-8 Å, and 2-16 Å. It also uses a quadrant photodiode configuration to give ASIO direction sensitivity with a modeled precision greater than 40″ for each 0.01s measurement, or greater than 4″ for second averages. This instrument will investigate the existence of short-wavelength, sub-second quasi-periodic pulsations (QPPs) and attempt to observe associated rapid oscillations in SXR bright points. The engineering model has been tested, and the flight model is in production. ASIO is scheduled for delivery to the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL) in Spring 2026 and will be launched as a part of the Multi-slit Solar Explorer (MUSE) mission in 2027.

• Author: Yuhong Fan ¶

  When: Monday - 13:25

  Coauthors: Maria Kazachenko (CU/LASP), Andrei Afanasev (CU/LASP), and George Fisher (SSL/UC Berkeley)

  Title: Data-driven MHD models of Flares and Eruptions

  Abstract We present data-driven magneto-hydrodynamic (MHD) simulations of the 2011-02-15 coronal mass ejection (CME) event of Active Region (AR) NOAA 11158, driven with a lower boundary electric field derived based on the normal magnetic field and the vertical electric current measured from the HMI vector magnetograms. The simulation shows the build-up of a pre-eruption coronal magnetic field close to that obtained from the nonlinear force-free field extrapolation, and it subsequently develops multiple eruptions. We find that the pre-eruption sigmoidal fields are strongly sheared fields with no dipped field lines, until the onset of the eruption where an erupting magnetic flux rope containing dipped field lines forms because of the tether-cutting reconnection in the current sheet that forms in the sheared field. The erupting magnetic field develops a complex structure containing two distinct flux ropes. We compare the forward modeled synthetic EUV emissions from the simulations with the observations by the SDO/AIA and STEREO/EUVI. We also examine the magnetic field evolution in comparison with the observed development of the coronal dimmings. The qualitative agreement between the modeled evolution and the observations suggest that the derived electric field is a promising way to drive MHD simulations to model the realistic complex magnetic field evolution in eruptive flare events in solar active regions.

• Author: Fabiana Ferrente ¶

  When: Tuesday - 11:30

  Coauthors: Salvatore Luigi Gugliemino, Daniele Spadaro, Paolo Romano

  Title: Spectropolarimetric Diagnostics of Solar Flares: Observations and Constraints for Numerical Modeling

  Abstract We review our recent work on high-resolution spectropolarimetric observations of solar flares and discuss how these measurements provide constraints for numerical modeling. In particular, we focus on the confined X1.6-class flare that occurred on 22 October 2014 in active region AR 12192, observed with the Interferometric BIdimensional Spectropolarimeter (IBIS) at the Dunn Solar Telescope. Full Stokes profiles were acquired in both the photospheric Fe I 617.3 nm and chromospheric Ca II 854.2 nm lines. We also present preliminary results from spectropolarimetric data obtained during a summer 2023 observing campaign at the GREGOR telescope, targeting smaller-scale flaring events observed in the He I 1083.0 nm spectral window and coordinated with IRIS satellite observations. The datasets were analyzed using different inversion codes, including STiC, DeSIRe, and HAZEL. Our results provide important constraints on flare models, which must reproduce intense, localized chromospheric heating, chromospheric evaporation and condensation, as well as dynamic magnetic field reconfigurations in the lower atmosphere. Additionally, we show that flare activity enhances the sensitivity of the Ca II 854.2 nm line to deeper atmospheric layers, highlighting the necessity for realistic radiative transfer treatments in numerical simulations. These findings emphasize the diagnostic power of chromospheric spectropolarimetry in validating and refining MHD models of solar flares, and underscore the importance of coordinated observational and theoretical efforts to improve our understanding of flare-driven energy transport and magnetic restructuring.

• Author: Lyndsay Fletcher ¶

  When: Tuesday - 09:00

  Coauthors: None

  Title: Constraining Solar Flare Models with Observations of Flare Ribbons

  Abstract For flares that take place on the solar disk, our main insights into their energy release phase come from observations of flare ribbons - the typically elongated, multi-wavelength brightenings in the lower atmosphere which, according to our understanding, map out the footprint of the magnetic field involved in coronal energy release. Ribbon temporal and spatial evolution, including recently at very high resolutions, inform us about the flare overall topology, and properties of the coronal instability and reconnection process. Spectroscopy can be used to derive local ribbon plasma properties that change in response to the flare energy input, permitting detailed model-data comparisons that are as useful in demonstrating where current models and observations do not agree as where they do. This talk will focus on aspects of model constraints from flare ribbons, emphasising the new capabilities that MUSE will bring to observations of both the ribbon structure and evolution, and the evolving plasma properties.

• Author: Lindsay Glesener ¶

  When: Thursday - 14:20

  Coauthors: None

  Title: Complementing IRIS and MUSE with coordinated hard X-ray observations – how to achieve additional constraints on numerical models

  Abstract Over the past decade, IRIS has made large strides in studying the detailed interactions between the chromosphere and the corona via the transition region. And once in operation, the MUSE spacecraft will provide us with novel and scientifically important views of the energization of the solar corona, the solar wind, and solar eruptive events. All of these endeavors are broadly enhanced by a rich multiwavelength set of solar observations, and hard X-ray studies are an important component of this set.

  Hard X-rays (HXRs) are one of the most direct probes available for accelerated electrons on the Sun. They can be used to measure non-thermal electron distributions, including their total energy content, average energies, and how low in energy the distribution extends. HXRs can also measure thermal plasma of the solar corona, with particular sensitivity to flare-temperature plasma of several to tens of millions of degrees. The combination of high-energy X-ray measurements with detailed temperature and velocity measurements from the UV and EUV enables an integrated understanding of flares and plasma heating on the Sun. For example, HXR measurements of accelerated electrons provide the input to numerical studies of flare heating, explaining results observed by IRIS and eventually by MUSE. Bremsstrahlung HXRs are fairly insensitive to ionization states and thus, when combined with EUV line emission, can be used to study the ionization of high-temperature plasma on the Sun whenever it is heated. X-ray studies of transients are particularly sensitive to hot and non-thermal components. When combined with wavelengths sensitive to cooler plasma, an entire energy budget of active regions and transients can be produced.

  This talk will discuss the science that IRIS and MUSE can achieve with the aid of HXR studies, including currently available and future instruments.

• Author: Milan Gosic ¶

  When: Thursday - 10:10

  Coauthors: Viggo H. Hansteen, Alberto Sainz Dalda, Bart De Pontieu, Luc Rouppe van der Voort

  Title: Validating Bifrost models using existing photospheric and chromospheric observations

  Abstract Solar magnetic fields have long been recognized as the main drivers of various solar phenomena that greatly impact our space environment. These fields are organized across a broad range of spatial and temporal scales, from large-scale active regions to those that collectively form what is known as the quiet Sun (QS): ephemeral, network, and small-scale internetwork magnetic fields. Numerous studies have demonstrated that QS magnetic fields play a crucial role in maintaining solar magnetism. Understanding the origins of QS magnetic fields, their subsequent spatio-temporal evolution, and their contribution to the energetics and dynamics of the solar atmosphere is therefore of paramount importance. Various theoretical models have been proposed to explain the origins and properties of QS fields. However, the properties and, particularly, the origins of these fields remain a topic of ongoing debate among researchers. In this work, we will compare two Bifrost models of quiet Sun-like magnetic fields with observations from the Swedish 1-meter Solar Telescope (SST) and the Interface Region Imaging Spectrograph (IRIS). We will describe the characteristics of the magnetic fields identified in both the models and the observed data. Finally, we will discuss our current understanding of the topology of QS magnetic fields, noting discrepancies between observed data and Bifrost models, but also between other numerical models in general.

• Author: Salvo Guglielmino ¶

  When: Thursday - 11:20

  Coauthors: Fabiana Ferrente, Daniele Spadaro, Paolo Romano

  Title: Multi-wavelength Observational Constraints of Energy Release from the Photosphere to the Corona

  Abstract Recent advances in multi-wavelength solar observations have led us into a transformative era for understanding the connection between magnetic field and energy release in the solar atmosphere. Building upon the contributions of missions such as Hinode, SDO, and IRIS, we combine data relevant to the upper layers of the atmosphere with spectro-polarimetric measurements, acquired by both ground-based and space-borne facilities. This coordinated approach enables us to track the evolution of magnetic fields in the photosphere and to analyse their impact up to the corona, investigating energetic events at different spatial scales. Here, we explore events such as UV bursts, as observed by IRIS, that caused an increase in Si IV and O IV line intensity (by factors of 100-1000) and significant line broadening (up to ± 150 km/s), indicating bi-directional plasma flows from magnetic reconnection. These events are usually associated with surges. SDO/AIA imaging often reveals bright counterparts across all channels, suggesting a significant involvement of the upper atmospheric layers. Underlying these events, high-resolution spectro-polarimetry in the photosphere and chromosphere details the magnetic configuration during flux emergence and decay. Our observations of the low atmospheric magnetic field provide the necessary boundary conditions for realistic simulations, while the UV diagnostics offer a precise ground truth for the predicted upper atmospheric response by numerical models. Forcing models to replicate the observed rapid heating, specific line intensities, and high-velocity reconnection jets is essential for advancing our fundamental understanding of how magnetic energy is stored, released, and propagated through the stratified plasma of the solar atmosphere. Our findings demonstrate the vital role of multi-instrument campaigns in addressing key challenges in solar physics, paving the way for future studies with advanced spectro-polarimetric instruments and the MUSE satellite.

• Author: Viggo Hansteen ¶

  When: Monday - 09:45

  Coauthors: TBD

  Title: Overview of your recent efforts on validation of numerical models of flares, quiet Sun, and active regions through comparison with observations

  Abstract MUSE observations will offer unprecedented large fields of view and high temporal cadences. However, this comes at a cost of possible confusion: The four main lines targeted by MUSE are accompanied by a large set of weaker lines that potentially can make deriving intensities, velocities and line widths complicated. In order to resolve possible ambiguities we have constructed a number of numerical models of solar scenes including synthetic observables from MUSE as well as from SDO/AIA and SDO/HMI, Hinode/EIS and IRIS. While the MUSE observables are used to test disambiguation strategies, the latter observables are used to validate the numerical models themselves. Do the numerical experiments reproduce solar observables well enough to be used as a guide for constructing the MUSE data reduction pipeline?

• Author: Shinsuke Imada ¶

  When: Tuesday - 15:50

  Coauthors: SOLAR-C International Team

  Title: Overview of coronal modeling in support of the EUVST project

  Abstract SOLAR-C is a next-generation solar mission designed to unravel how mass and energy are transferred through the solar atmosphere, ultimately addressing how the plasma universe is created and how the Sun influences the Earth and other planets. A key objective is to understand how magnetic fields and plasma interactions drive solar activity, such as flares and coronal mass ejections (CMEs).

  The mission has two primary scientific goals:

  1. To understand the fundamental processes responsible for the formation of the solar atmosphere and the solar wind
  2. To understand how the solar atmosphere becomes unstable and releases energy in the form of flares and eruptions

  To achieve these, SOLAR-C will adopt the following unique approaches:

  1. Simultaneous observations across all temperature regimes from the chromosphere to the corona
  2. High-cadence tracking of fine-scale atmospheric structures
  3. Spectroscopic diagnostics of dynamic elementary processes

  Magnetic reconnection is one of the central mechanisms for converting magnetic energy into plasma kinetic and thermal energy. SOLAR-C will observe reconnection-driven dynamics at high resolution and test competing models (e.g., Sweet-Parker, Petschek, plasmoid instability) by measuring velocity, density, temperature, ionization rate, and associated structures like shocks and magnetic islands. It will also clarify the role of fast reconnection in partially ionized chromospheric plasma.

  In addition to observations, this mission will actively incorporate numerical modeling to interpret data and simulate the time-dependent evolution of plasma parameters, helping to bridge theory and observation and further deepen our understanding of magnetic energy release in the solar atmosphere.

• Author: Sarah Jaeggli ¶

  When: Thursday - 15:10

  Coauthors: Alexandra Tritschler, Friedrich Woeger, David Boboltz, and the DKIST Science Operations Team

  Title: Current and Future Capabilities of DKIST, and the Potential for DKIST/IRIS/MUSE Observations

  Abstract The Daniel K. Inouye Solar Telescope (DKIST) is the U.S. National Science Foundation’s flagship facility for solar observations, offering diffraction-limited 20 km resolution at 500 nm enabled by the 4-meter primary mirror of the telescope and a high-order adaptive optics system. DKIST instruments provide access to a wide variety of wavelengths throughout the visible and infrared spectrum, targeting polarized diagnostics for characterizing the magnetized solar plasma, both in the lower solar atmosphere and above the solar limb in the corona. DKIST is currently conducting science observations and progressively ramping up observing modes offered to the community, including opportunities for coordinated observations with the Interface Region Imaging Spectrograph (IRIS). The next generation of high resolution EUV spectrographs, including the Multi-Slit Solar Explorer (MUSE), will be launching in the next few years and provide an exciting opportunity for complementary observations. Using the dynamic capabilities of MUSE and the magnetic characterization from DKIST, we will be able to gain knowledge of how mass, radiation, and magnetic fields interact, from the lower solar atmosphere to the corona and address many outstanding questions in solar physics.

• Author: Meng Jin ¶

  When: Thursday - 13:40

  Coauthors: None

  Title: Recent Advances and Ongoing Challenges in Global MHD Modeling of Coronal Mass Ejections and Their Space Weather Impacts

  Abstract Coronal mass ejections (CMEs) are large-scale explosive events on the Sun that not only disturb the solar atmosphere but also drive hazardous space weather events as they propagate through the heliosphere. Given their critical role in space weather, substantial efforts have been devoted to developing physics-based global MHD models of CMEs. In this talk, I will briefly summarize recent advances and ongoing challenges in the CME modeling. In particular, I will highlight how the unique capabilities of MUSE -- its large field of view and high temporal and spatial resolution -- can significantly enhance data-constrained CME modeling, ultimately improving our ability to forecast space weather. I will also present preliminary results of synthetic MUSE observables derived from global CME simulations, including CME-associated phenomena such as EUV waves and coronal dimmings. These results illustrate how MUSE observations can offer new insights into the fundamental physical processes governing CME propagation, and its interaction with the global solar corona.

• Author: Jayant Joshi ¶

  When: Thursday - 11:00

  Coauthors: None

  Title: Quiet-Sun Ellerman Bombs and Their Impact on the Upper Solar Atmosphere

  Abstract Recent high-resolution observations have shown that quiet-Sun Ellerman bombs (QSEBs), thought to be driven by magnetic reconnection in the deep solar atmosphere, are more prevalent than previously known, with about 750,000 present across the quiet Sun at any given time. Analysing Hβ and Hε observations from the Swedish 1-m Solar Telescope, we detected ubiquitous QSEBs characterised by rapid variability and flame-like morphologies. While a subset of these events showed localised heating in the transition region, indicated by UV brightenings in Si IV observations from the Interface Region Imaging Spectrograph, only a small fraction of QSEBs contributed to such heating. Additionally, we found cases where QSEBs were linked to the formation of type II spicules, suggesting that magnetic reconnection could be a driving mechanism for spicules. However, these associations account for only a small portion of the total number of QSEBs and spicules, indicating that QSEBs likely play a limited role in global upper-atmosphere heating and spicule formation.

• Author: Maria Kazachenko ¶

  When: Monday - 16:05

  Coauthors: None

  Title: Review of Confined vs Eruptive Flares: Observations and Models

  Abstract What distinguishes confined solar flares from eruptive ones in terms of their underlying physical properties? In this talk, I will review our current understanding of this question from the perspectives of theory, numerical simulations, and multi-wavelength observations. I will highlight key differences in magnetic topology, energy release, and dynamics between these two classes of flares. Additionally, I will discuss how upcoming observations from the MUSE mission can advance our understanding of the physical mechanisms driving both eruptive and confined flares.

• Author: Graham Kerr ¶

  When: Monday - 13:45

  Coauthors: None

  Title: Energy transport during solar flares: Disentangling different mechanisms via model-data comparisons

  Abstract Solar flares release a tremendous amount of energy, that ultimately produces a broadband enhancement to the Sun’s radiative output. Detailed study of solar flare ribbons and footpoints has revealed much about the plasma response to energy injection, as well as how that energy propagates from the corona to lower atmosphere. However, model-data discrepancies have demonstrated that we are missing key ingredients. Our picture of flare energetics, considering both the magnitude of energy and its spatiotemporal distribution through the Sun’s atmosphere, is incomplete. I will present an overview of some key model-data discrepancies, as well as recent examples of how high-resolution observations, and attempts to model them, have revealed key insights to flare energy transport. Those observations include high-cadence IRIS datasets, and Solar Orbiter’s Major Flare Campaign datasets. I will conclude with some comments on how MUSE will make substantial progress in furthering our understanding of the various means by which flare energy is transported.

• Author: Elena Khomenko ¶

  When: Wednesday - 14:30

  Coauthors: E. Khomenko, A. Navarro, N. Vitas, M. Collados, D. Martínez-Gómez, B. Popescu Braileanu, M. Modestov, S. J. Gonzalez Manrique, M. Koll Pistarini, M. M. Gómez Míguez, I. Bonilla Mariana

  Title: Modeling and observing ion-neutral interaction in the solar atmosphere

  Abstract In this talk I will describe our group's current effort for modeling the partially ionized solar plasma based on the single-fluid and two-fluid multi-species formalism, and our initial steps for the detection of multi-fluid effects in observations. Scientific questions include clarifying chromospheric wave-based heating mechanisms, creating multi-dimensional realistic models of the solar chromosphere and low corona incorporating ion-neutral effects, and understanding neutrals' role in prominence and sunspot dynamics. Among the main conclusions, our research shows that: (i) multi-fluid effects become apparent for waves with frequencies lower than typical inter-particle collisional frequencies, unlike suggested in homogeneous plasmas; (ii) ambipolar heating is most significant in the quietest regions, characterized by small-scale dynamo fields, in which our best resolution simulations numerically resolve ambipolar heating in at most of 25% of simulation volume; (iii) multi-fluid effects show up within transition layers between cool and hot materials, such as the solar transition region and prominence-corona interface. Multi-fluid effects operate at scales beyond the resolution capabilities of even the most advanced instrumentation, necessitating specialized observational initiatives. I will describe our attempts for the detection of subtle differences in velocities between ions and neutrals in solar prominences and sunspots, and how future observations may help in detecting multi-fluid effects.

• Author: James Klimchuk ¶

  When: Tuesday - 13:10

  Coauthors: None

  Title: Coronal Models of Quiescent Active Regions

  Abstract I will review existing and planned coronal models of non-flaring active regions, highlighting their differences, and suggesting ways in which MUSE might discriminate among them.

• Author: Adam Kowalski ¶

  When: Tuesday - 09:40

  Coauthors: None

  Title: First Steps Toward 3D RMHD Simulations of Flare Beam Generated Chromospheric Condensations

  Abstract I present the first steps taken toward 3D radiative magnetohydrodynamic simulations of the response of the solar chromosphere to nonthermal electron beams. This new modeling approach is motivated by outstanding discrepancies between IRIS spectra of solar flares and 1D radiative hydrodynamic models with the RADYN code. I summarize the challenges from FUV/NUV continuum ratios and red-wing asymmetries that are indicative of dense, beam-heated chromospheric condensations. The new models have a long way to go to include all critical ingredients identified over the last several decades, which I highlight.

• Author: Jorrit Leenaarts ¶

  When: Thursday - 09:30

  Coauthors: None

  Title: Current understanding of He II 304 line formation and the role of non-equilibrium ionization.

  Abstract MUSE will be equipped with a context imager that observers the He II 304 Å line. The line is sensitive to temperatures around 100 kK. Unlike lines that form at higher temperatures in the corona, the 304 line cannot be accurately modelled assuming optically thin line formation. Instead it requires taking into account optically thick non-LTE line formation and non-equilibrium ionisation of helium. In this talk I will review our current understanding of He II 304 Å line formation and discuss how it could help interpreting IRIS observations.

• Author: Wei Liu ¶

  When: Tuesday - 10:50

  Coauthors: Patrick Antolin (Northumbria Univ.), Xudong Sun and Soumyaranjan Dash (Univ. Hawaii), Sijie Yu (NJIT), Manuel Luna Bennasar (Universidad de Las Islas Baleares), Cooper Downs and Viacheslav S. Titov (PSI)

  Title: Coronal Cooling and Condensation near Magnetic Null Points: Feeding the Return Flow of the Chromosphere-Corona Mass Cycle

  Abstract Coronal heating and cooling are the two sides of the same coin, which are equally important to the fundamental process of mass transport in the solar atmosphere and the chromosphere-corona mass cycle. The cool, dense chromosphere is the source of mass that is heated and transported upward to the hot, tenuous corona. Meanwhile, the corona, under favorable conditions, can undergo a process called thermal non-equilibrium via radiative cooling and condense into cold material in the forms of coronal rain and prominences, which, if not ejected with solar eruptions, generally return to the chromosphere eventually. Where, when, and how such cooling condensations take place is not well understood. We report imaging and spectroscopic observations from SDO/AIA/HMI and IRIS that can shed light on this question. It is well known that coronal rain is common in AR loops because of strong heating, high densities, and thus strong radiative cooling there. However, on the quiet Sun away from active regions, such condensations do not appear randomly, but follow a pattern to preferentially occur at the dips of coronal loops or funnels. They are located at/near magnetic "topological singularities", such as null points and quasi-separatrix layers (QSLs), which are regions characterized by high values of the squashing factor. Some of such structures appear at high latitudes and are long-lived (~ 1 year) during certain phases of the solar cycle. We identified evidence of magnetic reconnection at such locations, which can produce favorable conditions, e.g., density enhancement by compression and/or mass trapping in plasmoids, that can trigger run-away radiative cooling. We present MHD simulations that demonstrate the role of reconnection in transporting cooled mass from overlying, long loops to underlying, short loops where it slides down as coronal rain. We discuss what observations MUSE can potentially provide to advance our understanding of this phenomenon.

• Author: Dana Longcope ¶

  When: Monday - 14:05

  Coauthors: Jiong Qiu

  Title: Using MUSE and IRIS to address questions raised by recent flare model/observation comparisons

  Abstract Recent multi-wavelength flare observations have driven models to draw several conclusions that pose new questions for future observations to address. It is now evident that flare reconnection releases magnetic energy into a sequence of distinct loops, which relax to form the flare arcade. This finding has enabled the modeling of flares using one-dimensional loop models. Observations are empirically matched only when energy is input impulsively, but in sequence of events persisting well into what has been called the gradual phase. It is also found that energy release must consist of a brief burst followed by an extended tail, which maintains each post-reconnection loop at elevated temperature for half an hour or more. At least one model has included a population of Alfven waves to power the tail. High resolution, and high cadence spectroscopic observations, such as from MUSE, will allow us to uncover the true nature of the long-tail energy dissipation. Fidelity to observations also requires that each loop start, prior to its reconnection, at a density higher than one expects in a quiescent active region. This appears to require energy released from prior events, on other field lines, somehow drive evaporation in the loop before reconnection occurs. IRIS observations in conjunction with IRIS will reveal how pre-reconnection evaporation in the loops created by flare reconnection.

• Author: Juraj Lorincik ¶

  When: Tuesday - 09:20

  Coauthors: Vanessa Polito, Jaroslav Dudik, Graham Kerr, Alberto Sainz Dalda, Guillaume Aulanier, Bart De Pontieu, Laura Hayes

  Title: High-Cadence IRIS Observations: Validating Flare Models

  Abstract High-cadence flare observing programs of the Interface Region Imaging Spectrograph (IRIS) opened new windows into the study of flares as inherently transient phenomena at unprecedented sub-second time resolution. We focused on dynamics and spectra of a flare ribbon formed during an inconspicuous flare from 2022 September 25. Imaging observations from the Slit Jaw Imager (SJI), for the first time, revealed flare ribbon kernels exhibiting motions at speeds reaching thousands of kilometers per second, direct observational evidence of slip-running reconnection predicted nearly two decades ago. A computer vision-aided comparison between kernel dynamics determined from SJI data and SDO/AIA confirmed that the high (< 2 s) SJI cadence was indispensable for this discovery, now validated by several follow-up studies. Studying spectra formed in these kernels was the objective of our subsequent analysis on the emission response to energy deposition. Intensities of prominent IRIS lines (Mg II, C II, and Si IV), formed in the chromosphere and the transition region, exhibited enhancements whose peak times varied across the ions, with the Si IV emission typically preceding Mg II by up to a few seconds. To our knowledge, such short-time delays between emission originating in different regions within the lower atmosphere have not yet been reported. To understand the nature of these delays, we analyzed a grid of RADYN flare simulations subjected to electron beam, thermal conduction, and Alfvén wave heating. Electron beam parameters were constrained by Fermi/GBM hard X-ray data. Models heated by high-flux electron beams or Alfvén waves reproduced the observed delays, while thermal conduction failed to do so. Our results provide vital observational support for long-standing theoretical predictions and challenge the current generation of flare models. The upcoming MUSE mission is well poised to advance our understanding of flare dynamics and spectra, and therefore build upon these findings.

• Author: Juan Martínez-Sykora ¶

  When: Wednesday - 15:40

  Coauthors: Sam Evans, Meers Oppenheimer, Yakov Dimant, Bart De Pontieu, Mats Carlsson

  Title: Probing the Thermal Farley–Buneman Instability in the Chromosphere: New Insights, Limits on Single Fluid Assumptions, Constraints, and Broader Implications.

  Abstract Understanding the chromospheric energy balance is critical, as it forms the interface between the cooler solar surface and the multi-million-degree corona. However, radiative MHD models often fail to reproduce key chromospheric observables—especially in active regions like plage—pointing to missing physics. One compelling candidate is the Thermal Farley–Buneman Instability (TFBI). Recent advances in linear theory reveal where large-scale 3D MHD models break down, particularly where the single-fluid approximation no longer holds. This theory shows that TFBI can grow under typical chromospheric conditions—across realistic ranges of density, temperature, magnetic field, and ionization fraction. We validate this instability using a suite of models, including multi-fluid 2D, kinetic 2D, and 3D simulations. Our preliminary analysis, combining our results with IRIS observations, reveals strong non-thermal broadening in the optically thin O I line between flux concentrations in plage, which is consistent with TFBI. Together, these results indicate that TFBI can drive meter-scale turbulence in the chromosphere, leading to localized heating and electric field restructuring—providing a promising path to understanding chromospheric turbulence and heating.

• Author: Biswajit Mondal ¶

  When: Tuesday - 11:50

  Coauthors: Amy R. Winebarger

  Title: Does the Flaring Mechanism Drive Elemental Abundance Redistribution?

  Abstract X-ray and EUV spectroscopy have revealed a long-standing puzzle in solar physics: the First Ionization Potential (FIP) effect, in which the abundances of certain elements in the corona differ from their photospheric values. These differences are not uniform across coronal structures and exhibit significant fluctuations during flares, yet their connection to the flaring process remains unclear. Here, we discuss a recent study that demonstrates a clear correlation between temperature-sensitive flaring plasma emission and element-specific abundance changes during a solar flare. These findings suggest that energy deposition in the chromosphere drives plasma evaporation from different chromospheric heights, thereby modulating elemental abundances. We also discuss how existing IRIS observations and the upcoming MUSE mission could provide important clues for understanding how flaring mechanisms may be responsible for abundance redistribution.

• Author: Fernando Moreno-Insertis ¶

  When: Tuesday - 14:20

  Coauthors: Viggo H Hansteen, Daniel Nóbrega-Siverio

  Title: Exploring magnetic flux cancellation from the solar photosphere to the corona

  Abstract Magnetic flux cancellation is often understood as the direct meeting at low atmospheric levels of magnetic patches with opposite polarity, accompanied by a simultaneous reduction in their magnetic flux — and, in some cases, the complete disappearance of one or both of them from magnetograms. Observational studies of this process over the past decades have primarily relied on magnetograms and Doppler maps derived from photospheric or chromospheric spectral lines. A smaller number of studies have employed spectropolarimetric data inversions. In parallel, theoretical investigations have been conducted using either analytical approaches or idealized, purely coronal MHD numerical models. Radiation-MHD models that incorporate self-consistent sub photospheric convection have also been explored; however, these typically extend only up to the low chromosphere and assume geometrically simple initial magnetic field configurations. In this lecture, I will present recent results from a radiation-MHD simulation performed with the Bifrost code. This model spans from the uppermost layers of the solar interior to the corona; in it multiple episodes of magnetic flux emergence and cancellation take place. We analyze the temporal evolution of a few cancellation events, compute observational proxies, and investigate the fascinating magnetic topology at and around the cancellation site. Our study provides a three-dimensional picture of the events taking place above a cancellation site, and offer a perspective beyond the traditional dichotomy of Ω-loop retraction versus U-loop rise often used to interpret observations.

• Author: Åke Nordlund ¶

  When: Thursday - 12:00

  Coauthors: Andrius Popovas, Mikolaj Szydlarski

  Title: Overview of Whole-Sun modeling project, including DISPATCH

  Abstract I will give an overview of the ongoing modeling efforts in the ERC/SYG Whole Sun project, focusing mainly on the DYABLO and DISPATCH code developments, which aim to indeed model the whole Sun. The DISPATCH development has reached a state where it is possible to model the entire solar convection zone, going arbitrarily close to the surface -- and indeed optionally include photospheric, chromospheric, and coronal physics. The strategy and intent is to apply a "zoom in" methodology, where one starts with a large extent in model space time, with necessarily limited spatial resolution, and then zooms in to specific spatial and temporal regions of interest, allowing the modeling there to be based on initial and boundary conditions available from the larger extent model. One could then, for example, model the dynamics of flux emergence on the scale of a solar active region, and focus on how the emerging flux interacts with the surface layers, without being forced to adapt arbitrary and parameterized initial and boundary conditions. As part of the zoom-in modeling one can choose to include more physical detail, for example physics modules that were previously developed in the context of the BIFROST code. A particle-in-cell solver that connects smoothly to an MHD solver in which it is embedded has also been developed, allowing studies of non-thermal particle acceleration in realistic settings. As part of the Whole Sun team efforts, a benchmark setup that contains the main ingredients and challenges of the sharp transition at the solar continuum surface was also developed. This may be of interest to other modelers as well, who are welcome to a copy of the generic benchmark setup and procedures.

• Author: Daniel Nóbrega-Siverio ¶

  When: Wednesday - 09:50

  Coauthors: TBD

  Title: Deciphering solar coronal heating: 3D reconnection in Coronal Bright Points.

  Abstract Coronal Bright Points (CBPs) are fundamental building blocks of the solar atmosphere. These ubiquitous brightenings, typically spanning 5–40 Mm, consist of compact, hot loops that shine in X-rays and EUV for hours to days. CBPs are also known sources of dynamic events such as coronal jets and small-scale filament eruptions. In this talk, we present a novel 3D radiative-MHD model that successfully reproduces the main observational characteristics of CBPs, including their sustained heating. We perform an in-depth analysis of three-dimensional magnetic reconnection processes within the CBP, focusing on braiding-induced reconnection at loop footpoints, interchange reconnection associated with the null point, and slipping reconnection along quasi-separatrix layers. In addition, we link these reconnection modes with their expected observational signatures, providing synthetic EUV diagnostics to facilitate direct comparisons with instruments such as SDO/AIA, Solar Orbiter/EUI, and the upcoming MUSE and Solar-C missions.

• Author: Joten Okamoto ¶

  When: Wednesday - 14:10

  Coauthors: None

  Title: Findings on the magnetic field structure of the chromosphere obtained from the CLASP missions and future research

  Abstract The CLASP (Chromospheric Lyman-Alpha/LAyer Spectro-Polarimeter) missions are sounding-rocket observation experiments to demonstrate the measurement of polarized spectroscopic data in the ultraviolet wavelength range to reveal the solar chromopheric magnetism. We have conducted three flights targeting Lyman-alpha and magnesium lines. The observation in the Lyman-alpha line has confirmed the scattering polarization due to differences in solar latitude, while also indicating that the influence of local structural irregularities on polarization cannot be ignored. The observations in the magnesium lines (and, by chance, manganese lines) detected differences in magnetic field strength due to variations in the height of the chromosphere, and for the first time, the expansion of magnetic flux tubes from the photosphere to the chromosphere was shown observationally. In addition, meaningful information on the three-dimensional structure of the magnetic field above a sunspot was obtained. Research is also underway to investigate the relationship between the structures estimated from physical information such as temperature and electron density derived from inversion and atmospheric heating in the chromosphere.

• Author: Vanessa Polito ¶

  When: Monday - 15:25

  Coauthors: None

  Title: Disentangling Solar Flare mechanisms: Insights from IRIS and Future Perspective with MUSE

  Abstract Since its launch in 2013, the Interface Region Imaging Spectrograph (IRIS) has offered an unprecedented view into solar flares — the most energetic explosions in the solar system. Understanding flares and solar eruptions remains a central challenge in solar physics and is critical for advancing space weather forecasting. Despite substantial progress, many of the physical processes driving these events are still not fully understood. In this talk, I will highlight recent key findings that combine IRIS spectroscopic observations with state-of-the-art flare simulations. These results open promising pathways for distinguishing between competing models of flare energy release and transport. I will also discuss how upcoming observations with the Multi-slit Solar Explorer (MUSE) will be instrumental in probing physical mechanisms that remain out of reach with current single-slit spectrograph instruments, offering a major leap forward in our ability to study flare dynamics.

• Author: Damien Przybylski ¶

  When: Wednesday - 13:50

  Coauthors: None

  Title: Simulations of the chromosphere with the MURaM code

  Abstract We introduce simulations of the solar atmosphere, utilizing the MURaM code. These simulation now include a set of NLTE physics required to accurately treat the solar chromosphere, similar to those in the Bifrost code. A number of diagnostics have now been computed from the models, spanning from the photosphere to the upper chromosphere. The diagnostics show a close match to average line profiles and qualitatively reproduce a number of observed phenomena. Using these initial simulations we investigate the dynamics and energy transfer into the solar chromosphere. Finally, we discuss the limitations of the work, and plans for future improvement of the models.

• Author: Fabio Reale ¶

  When: Wednesday - 09:30

  Coauthors: F. Reale, G. Cozzo, P. Testa, A.F. Rappazzo, P. Pagano

  Title: MUSE and magnetic reconnection in coronal loops

  Abstract Magnetic reconnection remains a key issue in plasma and coronal physics. I will review and discuss possible key signatures in coherent and chaotic scenario of coronal closed structured, that derive from past experience in data analysis and forward modeling, and in the light of MUSE future achievements.

• Author: Kathy Reeves ¶

  When: Monday - 11:55

  Coauthors: Xiaocan Li, Chengcai Shen, Xiaoyan Xie

  Title: How can MUSE and IRIS observations of solar flares be used to constrain models?

  Abstract In this talk, we examine some state-of-the-art flare models and determine how MUSE and IRIS can be used to determine the physical mechanisms of observed flare phenomena. The region above the flare loops is particularly interesting for understanding the details of reconnection. We will examine signatures of turbulence and supra-arcade downflows in this region as they would be observed by MUSE and IRIS. We will also examine footpoint signatures to determine if signatures of accelerated particles or current sheet dynamics can be gleaned from the observations.

• Author: Matthias Rempel ¶

  When: Wednesday - 09:00

  Coauthors: None

  Title: 3D radiation MHD models of quiescent active regions

  Abstract In this talk I provide an overview of 3D radiation MHD models of quiescent active regions. These models span in vertical extent from upper convection zone into the lower corona. Resolved magneto-convection in the photosphere self-consistently creates the Poynting flux that transports energy into the corona, however, the heating itself is entirely due to numerical dissipation (either explicit or implicit). While various types of waves are present in these models, heating appears to be dominated by braiding. Currently these models come in two flavors: simulations of entire active regions with moderate resolution and “straightened loop” models that focus on a small non-expanding loop with much higher resolution. Interestingly both types of setups do maintain a corona, suggesting that both macro (scales large than granulation) and micro (scale of granulation and smaller) braiding can provide a sufficient energy flux, ultimately models that combine the full range of scale are needed to address how the energy input into the corona is distributed over the full range of scales. Models of entire active regions do systematically underestimate non-thermal line widths, likely due to lack of sufficient resolution. There are moderate trends that show an increase in the non-thermal linewidth with resolution or reduced viscosity, suggesting that grid spacings of less than 10km would be required. This is supported by loop models that show with 12km grid spacing non-thermal line widths almost compatible with observational constraints. Full active region models with a sufficient resolution (<10km) and a range of scales (sub granular to super granular) to capture the energy transport and associated velocity dynamics should be achievable (although still expensive) within the coming decade.

• Author: Matthias Rempel ¶

  When: Wednesday - 09:00

  Coauthors: J. Martinez-Sykora, A. Winebarger, M.C.M. Cheung, P. Testa, B. De Pontieu, V. Hansteen, C. Johnston, V. Polito, C. Cozzo & V. Upendran

  Title: 3D simulations of solar flares with improved treatment of the transition region

  Abstract We compared existing MURaM M and X-flare simulations to large database of flares observed with AIA. It was found that the flare simulations systematically overestimate AIA counts for the cooler channels (171) forming in the transition region by 2-3 orders of magnitude, while the hotter emission (94) was less affected. The root cause for this discrepancy was an overestimation of the transition region width due to insufficient resolution, therefore leading to a larger emitting volume and too high synthetic counts for transition region emission. We implemented an adaption of the TRAC method (Johnston et al. 2021) to rescale the optically thin radiative loss and the emission measure in the transition region to compensate for the numerical broadening. The resulting corrected emission counts generally fall within the observed range, although they remain near the upper end of the observed range. The use of the TRAC method does increase chromospheric evaporation during flares, which results in increased GOES X-ray emission. Specifically for stronger flares (M-X) this requires accounting for non-thermal plasma to avoid unrealistically high GOES emission. I discuss recent attempts to address this issue.

• Author: Rebecca Robinson ¶

  When: Monday - 11:15

  Coauthors: None

  Title: A mission-embedded outreach program for NASA’s Multi-slit Solar Explorer (MUSE) mission: Inspiring future generations of solar explorers beyond boundaries and backgrounds

  Abstract In the wake of the Decadal Survey for Solar and Space Physics, it has become abundantly clear that general knowledge of these subjects in the US is absent in comparison to other subfields of astrophysics. This is an alarming deficiency because we rely on the Sun to survive, and understanding our immediate space environment is crucial for understanding our relationship with the Sun. With that, it is our responsibility as scientists and educators to advocate for and share the knowledge of our Sun and space environments as accessible as possible. One way to do so is by developing mission-specific outreach programs that tackle fundamental science questions and topics that are relevant to the Sun-Earth system. As a new and budding example, we introduce the new outreach program for NASA's Multi-slit Solar Explorer (MUSE) mission. This program officially began on December 1, 2024 and includes three main local partners: California Academy of Sciences, Chabot Space and Science Center, and the Boys & Girls Club of the Peninsula. Each partner's scope of work is shaped by their resources and expertise, and each remains committed to creating reusable and versatile outreach products. This talk will summarize the scientific goals of the MUSE mission, detail the MUSE outreach program, highlight our collaborations with other heliophysics missions (e.g. PUNCH), and provide a preliminary assessment of our contribution to the future of heliophysics outreach.

• Author: Luc Rouppe van der Voort ¶

  When: Thursday - 09:50

  Coauthors: None

  Title: Recent insights from chromospheric observations

  Abstract The Swedish 1-m Solar Telescope (SST) on La Palma is capable of achieving high resolution observations of the photosphere and chromosphere over extended periods of time (sometimes longer than an hour). The CRISP and CHROMIS instruments can achieve diffraction limited spatial resolution (down to 0.1 arcsec for CHROMIS) and typically sample spectral lines over multiple positions in less than 10 seconds. With recent and upcoming instrument upgrades, the field of view is large enough to cover complete active regions (~2 arcmin diameter for CRISP2). In this talk, I give an overview of some of the results from observing campaigns from the past few seasons. In particular, I present results from studies on Ellerman bombs and their connection with spicules.

• Author: Alberto Sainz Dalda ¶

  When: Wednesday - 15:20

  Coauthors: Jaime de la Cruz Rodríguez, Viggo Hansteen, Bart De Pontieu, and Milan Gosic

  Title: The thermodynamics and radiative losses derived from IRIS observation inversions.

  Abstract IRIS's multiline spectral capabilities have been used to build the most comprehensive database of model atmospheres spanning from the mid-photosphere to the upper chromosphere. We introduce the inversion tool developed to extract thermodynamic properties and radiative losses in the lower solar atmosphere from this database. This tool, called IRIS^2+, can analyze a large variety of IRIS observations and invert up to six chromospheric and six photospheric lines observed simultaneously. As a result, the atmospheric conditions along the optical depth are more accurately constrained than previous results that only used one or two lines during inversion. Additionally, IRIS^2+ provides radiative losses integrated over the high-, mid-, and low-chromosphere. Understanding thermodynamics and radiative losses is crucial for comprehending energy transfer from the lower atmosphere to the corona. Consequently, these measurements serve as valuable observational constraints for both coronal models and results derived from MUSE observations.

• Author: Tong Shi ¶

  When: Thursday - 14:00

  Coauthors: Meng Jin, Juan Martinez Sykora

  Title: MUSE synthesis with AWSoM global CME simulations

  Abstract Understanding initiation, evolution, and large-scale impact of CMEs remains a critical challenge for solar physics and space-weather forecasting. MUSE delivers high-resolution, high-cadence EUV spectroscopy over a wide FOV, uniquely suited to capture CME dynamics through the lower corona. Localized codes (MURaM, Bifrost, PLUTO) excel at small-scale heating and turbulence but cannot simulate global coronal reconfiguration during eruptions. In contrast, AWSoM provides a global MHD description with physics-based Alfven wave heating, ideal for modeling sympathetic CME events across multiple active regions. Here, we develop a data-processing and synthesis code that converts AWSoM outputs into VDEMs for the MUSE pipeline. By accounting for spherical geometry, stretched radial grids, AMRs, and off-axis lines of sight, our tool ensures fidelity across MUSE's expansive FOV. Applied to AWSoM CME simulations, it generates synthetic MUSE rasters at target spatial and temporal resolutions. Preliminary comparisons with Hinode/EIS-style spectra show that MUSE's combination of high cadence and wide coverage enhances tracking of global magnetic restructuring and understanding of sympathetic eruptions. These results underscore MUSE's transformative potential for unraveling multi-scale CME physics and should help inform optimized observing strategies.

• Author: Abhishekh Kumar Srivastava ¶

  When: Wednesday - 11:40

  Coauthors: Eric R. Priest, Sripan Mondal, David I. Pontin

  Title: Overview of the Symbiosis of Waves and Reconnection as a Source for Coronal Heating

  Abstract “Symbiosis of Waves and Reconnection" (SWAR) refers to the interconnection of waves and magnetic reconnection processes whereby each can mutually trigger each other. External wave-like perturbations can trigger or facilitate reconnection, whereas, on the other hand, reconnection can also generate waves. This interplay can lead to localized heating and dynamics in the solar atmosphere, such as coronal heating and the generation of the solar wind. We will review and present some of our MHD models to describe the physics of this process, and its significance. Some preliminary observations will also be presented. In particular, MUSE will be invaluable in highlighting the observational effects of this combination of waves and reconnection. Furthermore, these fundamental physical processes are likely to occur over a wide range of spatial and temporal scales, thus indicating the broader applicability of dynamics and heating in a wide range of plasma environments.

• Author: Paola Testa ¶

  When: Wednesday - 11:00

  Coauthors: None

  Title: Heating of active region cores: observational constraints on nanoflare heating models

  Abstract Recent high resolution observations of various layers of the solar atmosphere, from the chromosphere to transition region and corona, demonstrate the diagnostic power of spectroscopic data for investigating the mechanisms responsible for heating the solar corona. I will discuss how new MUSE diagnostics will significantly improve on current observations to understand the heating of active regions, in particular focusing on the hotter AR cores.

• Author: Shin Toriumi ¶

  When: Tuesday - 10:00

  Coauthors: None

  Title: The current status of R2D2 flux emergence simulations and how MUSE and IRIS can constrain them

  Abstract Magnetic flux generated by the dynamo mechanism in the convection zone emerges to the surface and forms an active region, which sometimes produces solar flares. Understanding how the magnetic flux is generated, transported, and released is important for comprehending the MHD processes that are universal to the Sun and other stars. Recently, the radiative MHD code R2D2 has enabled more realistic reproductions of active regions through flux emergence simulations that include the deep convection zone. Representative results demonstrate that large-scale convection cells facilitate flux emergence and that the interaction between convection and magnetic flux can lead to the formation of complex active regions with sheared arcades and flux ropes. Additionally, turbulent convection was found to inject magnetic helicity, which may contribute to flare production. While Hinode and other observations suggested the formation of flux ropes and system destabilization due to flare-triggering reconnection, these phenomena are highly dynamic and the details remained unclear. Therefore, IRIS and, in particular, MUSE are expected to contribute to elucidating these processes due to their high-speed imaging spectroscopy capabilities. At the same time, in the current version of R2D2, the upper boundary is located just above the photosphere, so it is not clear how the active region forms the magnetic field in the upper atmospheres. Thus, the plan is to improve the simulations by, e.g., using R2D2 as a bottom boundary condition for data-driven models.

• Author: Durgesh Tripathi ¶

  When: Wednesday - 12:00

  Coauthors: A. N. Ramaprakash, Sreejith, P. and SUIT Team

  Title: Bridging Layers of the Sun: Coordinated Observations with SUIT and MUSE

  Abstract The Solar Ultraviolet Imaging Telescope (SUIT), one of the seven payloads aboard India's Aditya-L1 mission, provides continuous full-disk and region-of-interest imaging of the Sun’s photosphere and chromosphere in the near and mid ultraviolet. With a pixel size of 0.7 arcseconds and a temporal cadence ranging from 6 seconds to about a minute—depending on filter selection—SUIT captures the dynamics in the lower solar atmosphere in great detail. It utilises 8 narrow-band filters, including key diagnostics such as Mg II h & k and Ca II h, along with 3 broadband filters, enabling a rich exploration of various features in the solar atmosphere. When combined with the forthcoming observations from NASA’s Multi-slit Solar Explorer (MUSE)—which will probe the transition region and corona with high-resolution spectroscopy—this coordinated approach offers seamless multi-layer coverage of the solar atmosphere. Together, SUIT and MUSE will enable unprecedented studies of the dynamic coupling across the solar atmosphere, from the photosphere to the corona. This talk will showcase SUIT’s key capabilities and present early results from its initial operations. We will also highlight the immense scientific potential of SUIT-MUSE synergy.

• Author: Vishal Upendran ¶

  When: Thursday - 13:20

  Coauthors: None

  Title: Constraining solar wind sources with AI

  Abstract Solar wind is a stream of particles starting from the Sun and filling up the interplanetary medium. The interaction of solar wind with Earth's magnetosphere gives rise to near-Earth space weather. It is hence imperative to both forecast, and constrain the sources of solar wind. Typically, velocities, magnetic field configuration, and abundances (if available) are mapped to in-situ measured wind speeds. In this work, we present an alternative approach to constraining solar wind sources using AI. We demonstrate that AI models are able to learn the association between solar wind sources and in-situ measured modalities. We also present evaluation criteria for these estimated sources, which let's us understand the working of such ML models.

• Author: Jaime de la Cruz Rodriguez ¶

  When: Wednesday - 13:20

  Coauthors: J. Leenaarts, A. Pastor Yabar, A. Sukhorukov

  Title: Setting constraints on Chromospheric heating through NLTE inversions of observations

  Abstract Inversion methods allow inferring the physical parameters of a model atmosphere by reconstructing spectropolarimetric observations. The resulting models can be very useful to study chromospheric heating because they can be used to a) study correlations between different physical parameters as a function of space and time and b) to estimate the radiative losses, which must be compensated by heating mechanisms at any time.

  In recent years, many improvements in the microphysics and a better modeling of the instrumental degradation in the inversion process have allowed us to simultaneously interpret more chromospheric diagnostics. As a result, modern inversion techniques allow for higher fidelity models, with sensitivity to a wider range of temperatures and densities.

  In this talk I will present my view on how inversion codes can help us to quantify/constrain the role of several heating mechanisms from observations as well as how can we use them to help validating numerical models.