Amir Caspi

Solar plasma composition differs between the photosphere and corona over a range of timescales, with preferential enhancement of elements with low first ionization potential (FIP). However, the physical origin of the FIP fractionation remains incompletely understood. Furthermore, during flares, the FIP bias also exhibits rapid changes, associated with fast transport of material with different FIP biases. We present novel observations from the Solar Orbiter SPICE and Extreme Ultraviolet Imager (EUI), Hinode Extreme Ultraviolet Imaging Spectrometer (EIS), and Chandrayaan-2 Solar X-ray Monitor (XSM) instruments, finding rapid abundance changes in the emitting plasma, on timescales of minutes, during the eruptive M7.6-class solar flare observed on 2024 September 30. These instruments have wide temperature coverage and find contrasting abundance evolution patterns between the hotter and cooler plasma components. 3D reconstruction of the active region and additional observations from the Solar Orbiter STIX X-ray telescope show how the hot and cool plasma components, emitting in different spectral regions and observed with the various instruments, sample the plasma composition evolution in distinct locations within the observed flaring plasma. The bright postflare looptops observed by SPICE show coronal FIP bias, while the hot plasma observed with XSM exhibits FIP bias decreasing from coronal to photospheric during the impulsive phase. We interpret these observations as evidence of the X-ray diagnostics seeing hot coronal reconnection outflows mixing with chromospheric plasma as flare loops sequentially energize and relax, explaining why the FIP bias decreases from coronal to a hybrid; and the cool looptops seen with SPICE show coronal abundances due to coronal material deposited near the looptops.

The 2024 total solar eclipse over North America enabled an unprecedented multi-perspective view of the solar atmosphere through coordinated ground- and space-based observations. Here we use these near-contemporaneous, multi-wavelength datasets to derive the plasma conditions and magnetic environment of an equatorial coronal hole. By connecting remote observations of the nascent solar wind to \emph{in situ} measurements, we trace the energy budget of a single solar wind stream from the subsonic corona across the Alfv\'en surface. Our results demonstrate that enthalpy and Alfv\'en wave energy fluxes dominate the low-coronal budget, with nearly all energy converted to ion heating and acceleration within the Alfv\'en surface. The stream’s evolution is well-described as a thermal-pressure driven wind with additional energy deposited by Alfv\'enic fluctuations. The observed evolution of these Alfv\'enic fluctuations deviate from a dissipation-free curve throughout, indicating significant and persistent dissipation before reaching the Alfv\'en surface.

MEGA-H is a multi-detector, wide-field telescope system that produces ultra-high-resolution, seamless images. The optical path employs pickoff mirrors that partition the image field onto three individual detectors. The detectors can be located conveniently apart from each other while preserving the whole FOV and producing a recombined image without any gaps. This architecture enables a scientist to choose the best detector for the task, which may have the good detection properties but insufficient number of pixels, and combine multiple detectors to achieve the desired pixel count. This camera system will initially be mounted behind a wide FOV white light imager and be capable of both wide FOV (10 degrees on diagonal) and high instantaneous field of view (iFOV) (

We present an extension of the Coronal Reconstruction Onto B-Aligned Regions (CROBAR) method to Linear Force Free Field (LFFF) extrapolations, and apply it to the reconstruction of a set of Atmospheric Imaging Assembly, Michelson Doppler Imager, and STEREO EUVI data. The results demonstrate that CROBAR is not only capable of reconstructing coronal emission structures, but also the previously made claim that it can constrain coronal field extrapolations, in this case the LFFF’s α parameter. They also provide a real-world example of how CROBAR can easily incorporate information from multiple perspectives to improve its reconstructions, and we also use the additional perspectives to help validate the reconstructions. We furthermore touch on the use of real-world emission passbands rather than idealized power-law type ones using differential emission measures (DEMs). We conclude with a comparison of CROBAR-generated emission to observed emission and those produced with idealized DEM based power laws. These results further illustrate the promise of CROBAR for real-world applications, and we make available a preliminary release of the software available for download.

The Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is a NASA Small Explorer to determine the cross-scale processes that unify the solar corona and heliosphere. PUNCH has two science objectives: (1) understand how coronal structures become the ambient solar wind, and (2) understand the dynamic evolution of transient structures, such as coronal mass ejections, in the young solar wind. To address these objectives, PUNCH uses a constellation of four small spacecraft in Sun-synchronous low Earth orbit, to collect linearly polarized images of the K corona and young solar wind. The four spacecraft each carry one visible-light imager in a 1 + 3 configuration: a single Narrow Field Imager solar coronagraph captures images of the outer corona at all position angles, and at solar elongations from 1.5° (6 R _⊙ ) to 8° (32 R _⊙ ); and three separate Wide Field Imager heliospheric imagers together capture views of the entire inner solar system, at solar elongations from 3° (12 R _⊙ ) to 45° (180 R _⊙ ) from the Sun. PUNCH images include linear-polarization data, to enable inferring the three-dimensional structure of visible features without stereoscopy. The instruments are matched in wavelength passband, support overlapping instantaneous fields of view, and are operated synchronously, to act as a single “virtual instrument” with a 90 ^∘ wide field of view, centered on the Sun. PUNCH launched in March of 2025 and began science operations in June of 2025. PUNCH has an open data policy with no proprietary period, and PUNCH Science Team Meetings are open to all.

We detect rapid downflows of 150–217 km s ⁻¹ in Infrared Interferometer in Space (or IRIS) Si iv 1402.77 nm measurements of an X9-class solar flare on 2024 October 3. The fast redshift values persist for over 15 minutes from flare onset, and can be split into two distinct stages of behavior, suggesting that multiple mechanisms are responsible for the downwards acceleration of flare ribbon plasma. The first stage of rapid downflows is synchronized with peaks in emission from the Advanced Space-based Solar Observatory Hard X-ray Imager (or ASO-S HXI) and Large Yield Radiometer (or LYRA) Ly α measurements, indicating that the chromospheric downflows (with a maximum redshift of 176 km s ⁻¹ ) result from chromospheric condensations associated with impulsive energy release in the solar flare. Later in the event, strong Si iv flare ribbon downflows persist (to a maximum value of 217 km s ⁻¹ ), despite the magnetic flux rate falling to zero and high-energy hard X-ray (HXR) and Ly α measurements returning to background levels. This is reflective of downflows in the flare ribbon footpoints of flare-induced coronal rain. HXR spectral analysis supports this scenario, revealing strong nonthermal emission during the initial downflow stage, falling near background levels by the second stage. Despite these distinct and contrasting stages of ribbon behavior, Si iv Doppler velocities exhibit quasiperiodic pulsations with a constant ∼50 s period across the 15 minutes of flare evolution (independent of loop length). We deduce that these pulsations are likely caused by MHD oscillations in the magnetic arcade. Finally, we utilize machine learning K -means clustering methods to quantify line profile variations during the stages of rapid downflows.

We present observations of an eruptive solar flare on 2016 January 6 that occurred behind the solar limb from the perspective of the Earth, but was well observed by the Solar-Terrestrial Relations Observatory (or STEREO) and the Solar Extreme Ultraviolet Monitor on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Light curves showing the evolution of the flare’s irradiance as a function of time taken by MAVEN are well correlated with the brightness evolution of fan structures observed in the Project for On-Board Autonomy 2's Sun Watcher with Active Pixels and Image Processing (SWAP) 174 Å passband, suggesting that the radiance of structures near the flare site was influenced by emission from the flare. Because SWAP did not directly observe the flare itself, this event represents a rare opportunity to study the evolution of emission near a flare without the risk of instrumental scattered light contaminating the observations. We analyze this evolution and implement a simple model to explore the possibility that resonant excitation (RE, also known as resonant scattering) plays an important role in driving coronal extreme-ultraviolet (EUV) emission during flaring events. Our modeling shows that for a large flare, RE could increase emission from nearby structures by about 45%, consistent with our findings that the involved structures observed by SWAP increased in brightness by about 60% during the flare. We conclude that RE may play an important role in driving coronal EUV emission under certain circumstances and should be accounted for in models and emission-based analysis tools.

We present observations of an eruptive solar flare on 2016 January 6 that occurred behind the solar limb from the perspective of the Earth, but was well observed by STEREO and the Solar Extreme Ultraviolet Monitor on the Mars Atmosphere and {Volatile} EvolutioN (MAVEN) mission. Light curves showing the evolution of the flare's irradiance as a function of time taken by MAVEN are well correlated with the brightness evolution of fan structures observed in the PROBA2 SWAP 174 Å passband, suggesting that the radiance of structures near the flare site was influenced by emission from the flare. Because SWAP did not directly observe the flare itself, this event represents a rare opportunity to study the evolution of emission near a flare without the risk of instrumental scattered light contaminating the observations. We analyze this evolution and implement a simple model to explore the possibility that resonant excitation (or resonant scattering) plays an important role in driving coronal EUV emission during flaring events. Our modeling shows that for a large flare, resonant excitation could increase emission from nearby structures by about 45%, consistent with our findings that the involved structures observed by SWAP increased in brightness by about 60% during the flare. We conclude that resonant excitation may play an important role in driving coronal EUV emission under certain circumstances and should be accounted for in models and emission-based analysis tools.