Including ST Division Outstanding ECS Award Lecture
Orals: Tue, 5 May, 16:15–08:40 | Room E2
Radio emissions excited by semi-relativistic electrons that are accelerated into the heliosphere by solar flares and CME-driven shocks are abundant, intense, and observed across various solar longitudes. We have shown that radio photons are highly-susceptible to anisotropic scattering off small-scale heliospheric density fluctuations. While such influence on the emitted radio photons significantly complicates their analysis, interpretation, and ability to extract the true physical properties from the observations, it also makes radio emissions a powerful and unique diagnostic of the heliospheric environment. This talk will showcase some of the fascinating diagnostic capabilities of solar radio bursts that make them beneficial to various heliosphysics disciplines. Such bursts have historically been used to obtain information on the exciters of the associated electrons and the acceleration mechanisms. However, recent studies demonstrated that solar radio bursts can also be used to diagnose the level and anisotropy of heliospheric density fluctuations, trace the configuration of the magnetic field, and even reveal the presence of magnetic switchbacks. They also constitute an asset in forecasting solar energetic particles (SEPs) and are thus an integral part of several space weather models.
How to cite: Chrysaphi, N.: The diagnostic power of heliospheric radio emissions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22046, https://doi.org/10.5194/egusphere-egu26-22046, 2026.
In my ERC-AdG project ‘Open SESAME’ (project No 101141362), we aim to develop a time-evolving model for the entire solar atmosphere, including the chromosphere and transition region, based on a multifluid description. Currently, models are primarily steady, rely on a single-fluid description and include only the corona due to computational challenges. We plan to use time-evolving ion-neutral and ion-neutral-electron models. The multifluid approach will enable us to describe the intricate physics in the partially ionised chromosphere and quantify the transfer of momentum and energy between the atmospheric layers. The questions of where the solar wind originates and how solar flares and coronal mass ejections are driven have fundamental scientific importance and substantial socio-economic impact.
This goal is now achievable by combining our implicit numerical solver with a high-order flux reconstruction (FR) method. The implicit solver enables larger time steps, avoiding the numerical instabilities that lead to strict time-step limitations in explicit schemes. The high-order FR method enables high-fidelity simulations on very coarse grids, even in zones of high gradients. We will introduce three critical innovations. First, we will combine high-order FR with physics-based r-adaptive (moving) unstructured grids, redistributing grid points toward regions with high gradients while preserving the HPC cluster's load-balancing. Second, we will implement CPU-GPU algorithms for the new heterogeneous supercomputers advanced by HPC-Europa. Third, we will implement AI-generated magnetograms to enable the model to respond to the time-varying photospheric magnetic field, which is crucial for understanding key properties of the solar plasma and processes.
Thus, we will develop a first-in-its-kind high-order GPU-enabled 3D time-accurate solver for multifluid plasmas. If successful, we will implement the most advanced data-driven solar atmosphere model in an operational environment. The project commenced on September 1, 2024, and we have already obtained interesting results in time-dependent full-MHD corona modelling, inclusion of the TR, AI-generated magnetograms (for the far side of the Sun), and high-order flux reconstruction simulations.
How to cite: Poedts, S. and the Open SESAME: Including the transition region and chromosphere in a global model for the solar atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3309, https://doi.org/10.5194/egusphere-egu26-3309, 2026.
We present a first record of significantly enhanced occurrences of magnetic reconnection exhausts as measured by the Wind satellite across a stream interaction region (SIR) at 1 AU from 10:11:20 UT on 4 Jan 2019 to 09:58:00 UT on 5 Jan 2019. The activity is clustered in a slow wind compression regime ahead of the SIR interface with a deflected, compressed fast wind. The 43 exhausts of this 1-day SIR dominate a distribution of 71 exhausts as obtained by a multi-window sliding technique application to the 8-day period on 1-9 Jan 2019. Active current sheets inside the SIR are associated with normal directions mostly near the ecliptic plane and a more azimuthal-than-Parker magnetic field direction at 1 AU. We find that exhausts wider than 500 ion inertial lengths are typically present just upstream and inside this SIR rather than within unperturbed slow and fast winds beyond a shocked solar wind. The observations suggest that plasma and field compressions may be crucial elements in driving a break-up of large-scale current sheets embedded in SIRs into smaller, multi-layered current sheet segments through magnetic reconnection.
How to cite: Eriksson, S., Chasapis, A., Mallet, A., and Swisdak, M.: Ubiquitous Occurrences of Multi-scale Layers of Magnetic Reconnection across a Solar Wind Stream Interaction Region at 1 AU, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-68, https://doi.org/10.5194/egusphere-egu26-68, 2026.
While quasi- perpendicular shocks are commonly associated with an ordered downstream magnetic field and quasi-parallel shocks with strong turbulence, recent observations reveal a more nuanced picture. Some quasi-parallel shocks exhibit downstream rms magnetic fields that significantly exceed the mean field. These enhanced fluctuations are dominated by coherent rotations of the magnetic field vector, whose amplitude is much larger than that of the mean field. The rotations are well organized, forming distinct regions of strong and weak rotational activity. This demonstrates that downstream magnetic field fluctuations in quasi-parallel shocks need not be random and may instead reflect an underlying ordered structure.
How to cite: Golan, M. and Gedalin, M.: The rotational structure of downstream magnetic field in quasi-parallel shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4444, https://doi.org/10.5194/egusphere-egu26-4444, 2026.
Fast and slow solar wind exhibit distinct kinetic, compositional, and bulk properties that are related to their solar sources. In recent years, the Alfvénic slow wind has emerged as a third class of solar wind, characterized by speeds typical of nominal slow wind but by several properties commonly associated with fast wind. These include similarities in the solar source, often identified with regions of strongly diverging open magnetic field, challenging the traditional solar wind classification based solely on bulk speed.
The Solar Wind Analyzer (SWA) plasma suite onboard Solar Orbiter provides unique capabilities to investigate how Alfvénic slow wind differs from the fast wind and to relate these differences to their solar sources.
In this study, we present selected examples of Alfvénic solar wind streams observed by SWA. Combined observations from all SWA sensors, together with magnetic field measurements from the Magnetometer (MAG), are used to characterize plasma properties and solar wind fluctuations through spectral analysis. The magnetic connectivity of each stream to its solar source is investigated using Potential Field Source Surface (PFSS) extrapolations combined with ballistic backmapping from the spacecraft and supported by remote-sensing observations.
Our results show that proton velocity distribution functions exhibit anisotropies and field-aligned beams characteristic of Alfvénic streams, while electron pitch-angle distributions display clear strahl populations. Oxygen and carbon charge-state ratios are low in fast wind, while they are higher in Alfvénic slow wind, approaching values typical of standard slow wind. Magnetic connectivity indicates that fast wind originates from a large coronal hole, while Alfvénic slow wind intervals are connected to pseudostreamers with high expansion factors or to coronal holes whose field lines cross pseudostreamer regions that later dissipate.
These findings support the idea that a simple fast/slow wind classification is insufficient to link in situ solar wind properties to their solar sources, and suggest that Alfvénicity is closely related to source-region magnetic topology. In particular, super-radial expansion may play a role in reducing the wind speed while preserving Alfvénic characteristics, setting the conditions for the origin of the Alfvénic slow wind. These results also have implications for the energy balance of solar wind fluctuations observed in situ.
How to cite: D Amicis, R. and the List of authors: Characterization of Alfvénic Solar Wind Intervals Observed by SWA onboard Solar Orbiter, with Insights into Their Solar Sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9184, https://doi.org/10.5194/egusphere-egu26-9184, 2026.
SUNSTORM 1 was a 2-unit CubeSat that observed hundreds of solar flares from low Earth orbit during its three-year operation between August 2021 and September 2024. Its payload was the X-ray Flux Monitor for CubeSats (XFM-CS), a non-imaging X-ray spectrometer capable of observing flares from A to X level in the 1–30 keV range with high precision. First results have demonstrated the instrument’s suitability for studies of larger solar eruption events.
We construct an overview of M and X class flares observed by SUNSTORM 1/XFM-CS during the mission. The soft X-ray flare spectra are fitted with a thermal model to obtain the peak flux, peak count, emission measure and flare temperature. For eruptive events, flare characteristics are connected to properties of the accompanying coronal mass ejections, and links between key parameters are discussed in relation to the underlying mechanisms. Our study highlights the scientific output of the SUNSTORM 1 mission and provides spectroscopic results of some of the biggest flares observed during the rise phase of Solar Cycle 25.
How to cite: Takala, S., Lehtolainen, A., Kilpua, E., Palmroth, M., and Huovelin, J.: Spectroscopic analysis of M and X class flares observed by SUNSTORM 1 XFM-CS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9341, https://doi.org/10.5194/egusphere-egu26-9341, 2026.
Empirical relations are used to link modelled coronal magnetic field structure — particularly flux-tube expansion and distance to coronal hole boundary — to solar-wind speed. There is a lot of uncertainty embedded within these relations, particularly when used as an interface for heliospheric models. Hence, augmenting these relations could provide a powerful way to sample model uncertainty using ensemble techniques. We present a simplified empirical solar-wind speed equation that can be readily optimised for different configurations of an open-source Potential Field Source Surface and Schatten Current Sheet (PFSS+SCS) coronal model, in-lieu of the full Wang–Sheeley–Arge (WSA) equation. Optimisation is performed using a 10-year reanalysis dataset of in-situ solar-wind speed observations, reconstructed at 21.5 rS across longitudes at the sub-Earth point via a combined corotation and backmapping technique. We trial several functional forms for the simplified equation and explore three linear-regression techniques, highlighting the challenges of fitting empirical relations to noisy data. To minimise overfitting, we select a regression approach that fits directly to the distribution of reconstructed observations. We find an equation candidate that successfully reproduces the distribution of observed solar-wind speeds and performs comparably to WSA when coupled with the Heliospheric Upwind eXtrapolation with Time-dependence (HUXt) model to generate hindcasts at 1 AU. The new equation is not intended to replace WSA; the internal complexity remains a key element for WSA. Due to its simplicity, our equation produces less variability than WSA on average. The trade-off in complexity is balanced by usability within ensemble/multi-model frameworks. The equation can be easily perturbed to quantify uncertainty in windspeed magnitude and easily re-optimised for PFSS+SCS models with different source-surface and outer-boundary heights.
How to cite: Edward-Inatimi, N., Owens, M., Barnard, L., Lang, M., Turner, H., Gonzi, S., Marsh, M., and Yeates, A.: Adapted empirical modelling of near-Sun solar-wind speeds for use in ensemble forecasts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12367, https://doi.org/10.5194/egusphere-egu26-12367, 2026.
Aims
We aim to investigate how the combined effects of spatial sparsity and temporal intermittency of stochastic heating events shape the stationary density and temperature profiles of the coronal plasma. We also aim to establish a theoretical kinetic framework capable of linking coronal heating with EUV observations.
Methods
We extend the kinetic model of Barbieri et al. (2025) by introducing a time-dependent stochastic boundary condition that accounts for intermittent heating at the chromospheric base. A surface coarse-graining procedure is applied to derive Vlasov-type equations for the averaged distribution functions. Analytical expressions are obtained for the corresponding density, temperature, and Differential Emission Measure (DEM) profiles, valid in the regime where the heating time scales are much shorter than the electron crossing time.
Results
We show that the temperature inversion and the coronal temperature plateau arise naturally when the combined parameter A = A_S × A_t is much smaller than unity, where A_S is the surface filling factor of heating events and A_t is their temporal duty cycle. Spatial and temporal intermittency are found to contribute in the same way to shaping the density and temperature profiles. The computed DEM exhibits a monotonic decrease with temperature up to 10⁶ K, followed by a peak marking the transition to the low corona, and shows good agreement with the observational results reported by Dolliou et al. (2024).
Conclusions
The present model unifies previous spatial and temporal kinetic descriptions of coronal heating within a single analytical framework. It provides a direct connection between the microscopic dynamics of stochastic heating and observable quantities such as the DEM.
How to cite: Barbieri, L. and Demoulin, P.: Coronal heating driven by spatially sparse and temporalintermittent energy release: a kinetic approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13483, https://doi.org/10.5194/egusphere-egu26-13483, 2026.
The energy source for major solar eruptions, such as flares and coronal mass ejections (CMEs), is recognized to be the free magnetic energy (energy above the potential field state) stored in the solar magnetic field prior to eruption. A key question for both predicting future eruptions and estimating their possible magnitude is, what is the bound to this energy?
The Aly-Sturrock theorem states that the energy of a fully force-free field cannot exceed the energy of the so-called open field. If the theorem holds, this places an upper limit on the amount of free energy that can be stored. This is not a practical limit, as even the largest CMEs open only a portion of the coronal magnetic field. The energy of a closely related field, the partially open field (POF), is believed to provide the corresponding limit for a localized region, such as an active region. We have developed practical methods for estimating the POF energy (POFE). The estimates are based on potential-field like solves that can be computed rapidly. We test our estimation methods by comparing them with the maximum energy storage achieved in MHD simulations of three solar eruptions: July 14, 2000, October 1, 2011, and March 7, 2012. We discuss the practicality of applying POFE estimates routinely to solar active regions.
Research supported by NASA and NSF.
How to cite: Linker, J. A., Downs, C., Torok, T., Titov, V., and Caplan, R.: Energy Storage for Extreme Solar Eruptions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15303, https://doi.org/10.5194/egusphere-egu26-15303, 2026.
The presented work revisits the Statistical Injection of Condensed Helicity (STITCH) model by Antiochos et al. 2013; Mackay et al. 2014; Dahlin et al. 2022. The model includes a statistical description of the small-scale circulation motions in the solar photosphere and accounts for their effect on the magnetic helicity in the solar corona.
The statistical effect of small-scale circulation motions may be quantified following well-known analogy between the density of the magnetic moment of microscopic currents in magnetic media, on one hand, and the angular momentum density, on the other hand. Within the framework of magnetostatics the magnetic moment density of the microscopic currents (referred to as magnetization) is a statistical quantity characterizing the magnetized medium. Its gradient in non-uniform medium results in macroscopic magnetization current. Similarly, the angular momentum density may be involved as the statistical characteristic of the small-scale horizontal motions in the photosphere. In this application only the vertical component of the angular momentum density, ζ, matters, which is ideologically close to the parameter used in the STITCH model.
Analogously to the magnetization current in magnetostatics, the horizontal gradient in ζ would result in large-scale horizontal motion. Indeed, for a uniform isotropic turbulence, the chaotic small-scale and high-frequency velocity would cancel in average. However, with any horizontal gradient in ζ the larger rotational velocity of a stronger nearby vortex is not fully balanced by the opposite rotation of a smaller vortex, thus resulting in the averaged larger-scale velocity.
This velocity is perpendicular to the horizontal gradient of vertical magnetic field, BR or, equivalently, it is aligned with the level contours, BR=const, of the vertical field. Such motion drags the footpoints of the field lines of the coronal magnetic field, thus resulting in generation and accumulation of the magnetic helicity. The average velocity field parameterized in terms of gradients in ζ may be used as the boundary condition for an analytical or numerical model of the solar corona. Particularly, it is implemented in the SWMF code of the University of Michigan and used to pump helicity and the magnetic free energy of the active region to bring it to the threshold of eruption
Assuming that the sign of ζ is the same as that of projection of the solar angular velocity vector on the radial direction, it should be mostly positive in the northern hemisphere and mostly negative in the southern hemisphere. The rate of magnetic helicity production appears to be proportional to the negative of ζ. Hence, the described mechanism may result in the magnetic helicity in the solar corona such that the negative magnetic helicity dominates in the northern hemisphere and the positive magnetic helicity dominates in the southern hemisphere. The latter conclusion agrees with the so called “hemisphere rule” as confirmed by statistical analysis of observations.
How to cite: Sokolov, I., Liu, X., Antiochos, S., and Gombosi, T.: Non-Vanishing Angular Momentum Density in the Photospheric Horizontal Motions Induces Magnetic Helicity in the Solar Corona in Agreement with the “Hemisphere Rule”, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15456, https://doi.org/10.5194/egusphere-egu26-15456, 2026.
Orals: Wed, 6 May, 08:30–10:10 | Room M1
Rotation is an intrinsic property of stars and provides essential constraints on their structure, formation, evolution and interaction with the interplanetary environment. The Sun provides a unique opportunity to explore stellar rotation from the interior to its atmosphere in great detail. We know that the Sun rotates faster at the equator than at the poles, but how this differential rotation behaves at different atmospheric layers within it is not yet clear. Here we extract the rotation curves of different layers of the solar photosphere and chromosphere by using whole-disk Dopplergrams obtained by the Chinese Hα Solar Explorer (CHASE) for the wavebands Si I (6,560.58 Å), Hα (6,562.81 Å) and Fe I (6,569.21 Å) with a spectral resolution of 0.024 Å. We find that the Sun rotates progressively faster from the photosphere to the chromosphere. For example, at the equator, it increases from 2.81 ± 0.02 μrad s−1 at the bottom of the photosphere to 3.08 ± 0.05 μrad s−1 in the chromosphere. The ubiquitous small-scale magnetic fields and the height-dependent degree of their frozen-in effect with the solar atmosphere are plausible causes of the height-dependent rotation rate. The results have important implications for understanding solar subsurface processes and solar atmospheric dynamics.
How to cite: Rao, S.: Height-dependent differential rotation of the solar atmosphere detected by CHASE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17757, https://doi.org/10.5194/egusphere-egu26-17757, 2026.
Compared to energetic electrons in solar flares, which can be readily observed in hard X-rays and radio, our understanding of energetic ions is severely deficient. Our main diagnostics for ions are gamma-ray observations, which remain challenging. A particularly intriguing case are behind-the-limb (BTL) gamma-ray flares, where the flare is occulted as seen from Earth, but nevertheless gamma-ray emission is detected by near-Earth spacecraft. Here, we investigate the relationship between the gamma-ray emission measured with Fermi-LAT, hard X-ray observations from STIX on Solar Orbiter, and ground-based radio observations, for a small sample of BTL gamma-ray flares. In all events, type II radio bursts were present that were synchronized in time with the gamma-ray emission. Conversely, we find a significant delay between the impulsive phase of the flare as recorded by STIX and the gamma-ray emission. These findings support the notion that the highly relativistic ions that produce the gamma-rays in BTL flares are accelerated at CME-driven propagating coronal shock waves rather than in large-scale flare loops.
How to cite: Warmuth, A.: New constraints on ion acceleration in behind-the-limb gamma-ray flares from Fermi-LAT, SolO/STIX, and ground-based radio observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19231, https://doi.org/10.5194/egusphere-egu26-19231, 2026.
Coronal dimmings are observed as sudden and localized reductions in EUV and X-ray emission of the solar corona. Traditionally, significant dimmings at 1-2MK are regarded as robust indicators of coronal mass ejections (CMEs), reflecting the density depletion caused by plasma escaping into interplanetary space. Here we present a peculiar high-temperature dimming observed on 2012 July 5. Using Sun-as-a-star observations from SDO/EVE and GOES, we identified significant intensity drop in the Fe XVIII (6.5 MK) and Fe XX (9.3 MK) hot lines, with a maximum depth of over 20% observed in the GOES soft X-ray (SXR) flux. Spatially resolved analysis from SDO/AIA reveals that this signature originated from a failed eruption where the bulk of the plasma was constrained by the overlying magnetic loop system. This case demonstrates that deep coronal dimmings in hot lines can occur without actual mass loss, providing a critical caveat for the interpretation of stellar coronal dimmings used to find stellar CMEs.
How to cite: Wang, X., Chen, H., Veronig, A., and Tian, H.: A Long-term Coronal Dimming in High-Temperature Spectral Lines During an M-class Confined Flare, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19388, https://doi.org/10.5194/egusphere-egu26-19388, 2026.
Since December 2024, Parker Solar Probe has reached the mission's closest perihelion distance of 9.8 solar radii six times. Data from each orbit has shown the spacecraft has been diving deep below the Sun's Alfvén surface with each pass, and covering nearly half the Sun at the same time. These measurements may therefore be interpreted as some of the most unambiguous direct sampling of a star's corona to date in regions which could previously only be probed with remote sensing techniques. In this talk we will review some recent insights into the large scale structure of the solar maximum corona and the Alfvén surface revealed by these new data, as well as our recent work studying the properties of polar-like fast solar wind in its early life and its subsequent evolution. We will close with a brief discussion on what we stand to learn with Parker continuing these deep dives as the Sun retreats into its next solar minimum.
How to cite: Badman, S.: The outer reaches of the Solar Corona as measured by Parker Solar Probe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12552, https://doi.org/10.5194/egusphere-egu26-12552, 2026.
The properties of the solar wind, as measured in situ throughout the heliosphere, depend both on the characteristics of its coronal source and on the intrinsic processes governing its interplanetary evolution. Recently, radial and Parker spiral alignment techniques have been applied to Parker Solar Probe (PSP) and Solar Orbiter (SO) observations to investigate the radial evolution of the same solar wind parcel. These studies have shown that the solar wind can undergo significant acceleration even beyond its primary acceleration region (i.e., above 15 solar radii). However, such radial and Parker spiral alignments are rare in practice, which limits the statistical significance and general applicability of the results.We introduce a new source alignment technique designed to overcome these limitations. Using magnetic backmapping, we associate similar solar wind streams observed by the two spacecraft based on the proximity of their photospheric footpoints, combined with additional in situ stream similarity criteria. Applying the source alignment method to PSP and SO observations, we identify a total of 560 alignment intervals, each lasting 30 minutes. By constructing statistics over all alignments, we find that the solar wind speed increases by an average of 43\% (approximately 143 km/s) between the two probes. This result demonstrates that solar wind acceleration in the inner heliosphere remains significant compared to that occurring below 15 solar radii. Among the different energetic contributions, the radial evolution of the electron thermal energy shows the strongest correlation with the increase in kinetic energy.
How to cite: Dakeyo, J.-B., Ervin, T., Bale, S., Démoulin, P., Sioulas, N., Réville, V., Liu, M., Rouillard, A., Maksimovic, M., Larson, D., Romeo, O., Louarn, P., and Livi, R.: On the Radial Evolution of the Solar Wind : The Source Alignment Method Applied to Parker Solar Probe and Solar Orbiter Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21926, https://doi.org/10.5194/egusphere-egu26-21926, 2026.
Solar energetic particles (SEPs) accelerated by distant interplanetary (IP) shocks driven by coronal mass ejections (CMEs) are different from energetic storm particles (ESPs), which are generally followed by geomagnetic storms. ESPs are believed to be accelerated by near-Earth IP shocks and often reach their peak intensities at the arrival times of these shocks at the Earth’s location or at the Sun–Earth L1 point. These energetic particles predominantly propagate along interplanetary magnetic field (IMF) lines. However, to the best our knowledge, the influence of IMF fluctuations on the directional anisotropy of energetic particle fluxes has not been investigated. In this study, we address this open question using directionally resolved energetic particle observations from the SupraThermal and Energetic Particle Spectrometer (STEPS) of the Aditya Solar wind Particle EXperiment (ASPEX) payload onboard Aditya-L1 mission. Following its launch on 02 September 2023, Aditya-L1 completed several Earth-bound orbits. During this phase, two of the six ASPEX-STEPS detector units were kept operational. We analyze energetic ion fluxes below 1.3 MeV obtained by these two detectors during a pair of SEP-ESP events observed by ASPEX-STEPS. Our results reveal that the temporal evolution of directional anisotropy in ion differential directional fluxes differs significantly between the SEP and ESP events. Furthermore, fluctuations in the directional anisotropy exhibit periodicities similar to those observed in IMF fluctuations, indicating a strong causal relationship. Number of common periodicities also differs between the SEP and ESP events. These findings are important to understand the transport of energetic particles and space weather impacts. The details of this study will be discussed.
How to cite: Dalal, B. and the ASPEX-Aditya L1 team: Directional anisotropy in solar energetic particle and energetic storm particle fluxes as measured by ASPEX-STEPS and the role of IMF fluctuations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16251, https://doi.org/10.5194/egusphere-egu26-16251, 2026.
Solar corona fills the whole solar system with the stream of ionized particles – solar wind. Its basic parameters and their evolution with the distance from the Sun were predicted by the Eugene Parker’s hydrodynamic theory in the middle of the last century but the latest observations covering the range from 0.09 to 100 AU give us the possibility to check and modify this crude simplification.
Two essential features distinguish the solar wind from a classical hydrodynamic flow - its weakly collisional nature and the presence of a magnetic field. The absence of frequent collisions allows a motion of different ion populations with various velocities and thus one should ask what a “real” solar wind velocity is. The magnetic field is not just passively frozen in the solar wind plasma as is often assumed, but its force action plays an important role in the release of the solar wind from the corona. Moreover, the magnetic field facilitates excitation and propagation of a variety of waves. The wave interactions lead to turbulence and form interplanetary shocks but their role in the solar-wind acceleration and heating is still not fully understood.
The lecture synthesizes multi-decade observations from numerous spacecraft to address these issues and to discuss their implications for solar-wind formation and evolution through heliosphere. Recent studies have revealed significant changes in the radial trends of plasma and magnetic-field parameters, including ion velocity (Nemecek et al. 2020), plasma beta (Safrankova et al. 2023), interplanetary shock properties and occurrence rates (Kruparova et al. 2025; Park et al. 2023), velocity-temperature relations (Durovcova et al. 2026), and the cross helicity of fluctuations (Park et al. 2025) in the region near Mercury’s orbit. We focus on the physical processes shaping this region and discuss possible interpretations of the observed phenomena. While solar-wind formation and evolution are currently the subject of intense investigation enabled by new observational capabilities, this lecture emphasizes our group's contributions to present knowledge.
How to cite: Nemecek, Z. and Safrankova, J.: Solar wind on the path from the Sun to Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7940, https://doi.org/10.5194/egusphere-egu26-7940, 2026.
Because of the lack of white light coronagraph observations in the low solar corona (1-1.5 solar radius), total solar eclipses are a standard way of assessing coronal structures and testing coronal models. Total solar eclipses constrain the validation period of coronal modelling, as they occur rarely. However, currently, it is the only way to distinguish features in the low corona near the solar surface. Soon, the PROBA 3 mission will provide continuous observations of the low corona. Total solar eclipses provide a single snapshot of the solar corona, whereas time-dependent simulations require continuous white-light observations.
COCONUT was utilised to predict the previous total solar eclipse in April 2024 (Baratashvili et al. 2025, A&A, in press). In the setup demonstrated in the manuscript, a low-resolution, simplified approach is used. However, multiple developments in the COCONUT model since the previous total solar eclipse allow the continuous time-dependent and high resolution simulations (Wang et al, 2025, in press) for the predictions on the upcoming total solar eclipse on August 12, 2026, at 18:27 UT. Additionally, we plan a network of observations in Spain with multiple sites (Santiago Compostela, Teruel, Villadolid, Riga) to obtain the best coverage of the total solar eclipse and obtain high-quality images to use them for validating the predictions performed by the COCONUT model. Synthetic white-light images will be generated from the COCONUT simulations to compare to the observed images directly.
This way we can use the total solar eclipse on August 12, 2026, to validate the COCONUT model, and identify its strengths and weaknesses.
How to cite: Schmieder, B., Baratashvili, T., Poedts, S., Lani, A., Wang, H., Foing, B., Sansari, S., Zeegers, S., Pascual, J., Nahum, R., Nagainis, K., Gomez de Castro, A. I., and Heras, A.: Total Eclipse on August 12, 2026: observations in Spain and prediction with COCONUT, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1542, https://doi.org/10.5194/egusphere-egu26-1542, 2026.
Many spacecraft observations made near Earth revealed a clear correlation between the solar wind temperature, T and the bulk speed, V. This relationship is also used to estimate the expected proton temperature at a given solar wind speed. However, the mechanisms leading to this correlation are not yet fully understood. We use measurements made by the Solar Probe Cup (SPC) instrument onboard Parker Solar Probe and show that the proton temperature follows a power-law dependence on the proton bulk speed even at small radial distances from the Sun around 0.1 AU. The median T-V relationship becomes steeper with increasing heliocentric distance, and the exponent of the T-V dependence is significantly smaller closer to the Sun than near Earth. We derive the radial dependence of this exponent and compare it with predictions from the spherically symmetric 1D time-stationary solar wind expansion models (Shi et al., 2022). We identify a model that includes an external force as the most successful in reproducing the observed radial dependence. Due to the limited number of SPC observations near the Sun capturing high-speed solar winds, the radial profile of the measured proton temperature for fast solar winds has a high uncertainty. Thus, we use the observed radial dependence of the T-V relationship to compute the radial profiles of the expected solar wind temperature for different solar wind speeds. Our findings suggest that slow solar wind streams cool significantly faster with heliocentric distance than the high-speed streams.
How to cite: Durovcova, T., Satyasmita, S., Safrankova, J., and Nemecek, Z.: Study of the temperature-speed relationship from 0.1 to 1 AU and estimation of the expected temperature radial profiles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5360, https://doi.org/10.5194/egusphere-egu26-5360, 2026.
Under ideal conditions, open magnetic field lines originating from the Sun follow the Parker Spiral topology. In reality, conditions are often not ideal and deflections in field lines from this path are observed. A class of these deflections, known as magnetic switchbacks, are accompanied by correlated velocity enhancements, revealing a highly Alfvénic behavior. Even though this phenomenon was previously identified in in-situ data at distances between 0.3-3 au from missions such as Helios and Ulysses in 1990s, the interest in the scientific community increased when Parker Solar Probe (PSP) revealed the unexpectedly frequent nature of these structures at closer distances to the Sun. In light of this discovery, the formulation of a solid definition and the development of robust detection methods became crucial for further analysis, as this interest brought along various views on the definition and the properties of switchbacks. So far, the research has relied mainly on manual or semi-automatic detection methods which are both time consuming with the increasing amount of data and prone to subjective interpretation that might result in significant differences across studies. To address this issue, we have developed a fully automated detection algorithm to minimize the subjectivity and the time required to analyze the data. The algorithm relies on the two fundamental characteristics of switchbacks: the deflection angle from the Parker spiral and the degree of Alfvénicity. Using these properties, we apply multiple detection criteria with varying thresholds to reveal how switchback properties depend on the chosen definitions. We will present our preliminary results focusing on the occurrence rate and duration of the switchbacks at different heliodistances during the first 21 PSP encounters.
How to cite: Gülay, E., Asvestari, E., Good, S., and Kilpua, E.: Preliminary Statistical Analysis of Magnetic Switchbacks with an Automated Algorithm during Parker Solar Probe Encounters , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5732, https://doi.org/10.5194/egusphere-egu26-5732, 2026.
Sunspots are the longest continuously observed manifestations of solar activity and form the basis of modern indices of solar variability. Systematic sunspot catalogues, beginning with the Greenwich Photoheliographic Results and later continued by the Debrecen Observatory, provide a unique long-term record of solar activity. Space-based full-disk observations now allow these records to be extended using data from modern instruments.
We present a work-in-progress methodology for the construction of a sunspot database based on observations from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), covering the period from 2010 onward. The database is developed within an ongoing project running until 2028 and is intended to be continuously extended rather than finalized at a single endpoint. The current implementation uses one flattened SDO/HMI intensitygram per day, prioritizing long-term homogeneity over high temporal cadence.
Sunspot detection is performed using a threshold-based method applied to flattened HMI intensity images. Umbrae and penumbrae are detected and treated as separate features. The detection approach can be extended to non-flattened full-disk images through the optional application of limb-darkening compensation, enabling future use with other instruments/observations. For each detected sunspot, the current database structure includes observation time, positional information in both image-plane (x–y) and heliographic coordinates, area measurements, and a provisional identification number. The database format itself remains under active development.
The assignment of persistent identification numbers across consecutive observations is under development and is based on the near preservation of relative distances and angular relationships between sunspots on the solar sphere (pattern preservation). The association of individual sunspots with sunspot groups and active regions is planned as a subsequent step.
This contribution focuses on the detection methodology, evolving database design, and tracking concept, and presents the current status of the pipeline. The resulting database is intended as a community resource for future studies of sunspot evolution, long-term solar activity, and solar rotation.
How to cite: Sudar, D.: A Sunspot Database from SDO/HMI Observations: Methodology and Current Status, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5989, https://doi.org/10.5194/egusphere-egu26-5989, 2026.
Large-scale solar eruptions, which are observed as flares, erupting prominences/filaments, and coronal mass ejections (CMEs), are powered by the free (excess) magnetic energy that is stored prior to eruption in current-carrying (sheared/twisted) magnetic fields. During an eruption, some of this magnetic energy is released and converted into kinetic energy in the form of thermal/non-thermal particle energy and bulk flow energy. It is well established that magnetic reconnection is the key driver of this energy release and conversion. However, the detailed physical conditions that determine the partitioning and distribution of the released energy are not yet well understood. Following the seminal work by Birn et al. (2009), we employ magnetohydrodynamic (MHD) simulations to study the energy conversion and transport due to reconnection in a flare current sheet, using an adiabatic energy equation. We extend the work by Birn et al. in three different ways. First, we consider a model in which the flare current layer is self-consistently formed by the eruption of a magnetic flux rope that evolves into a CME. Second, we incorporate the effect of reconnection between the legs of the flux rope. Third, we extend the analysis of the energy transport (and plasma heating) to the CME. In this presentation we summarize our main results and briefly discuss the next step, which will be the extension of our model to thermodynamic MHD.
How to cite: Torok, T., Mason, E., and Ben-Nun, M.: Energy Conversion and Transport During Flare Reconnection in a CME Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8261, https://doi.org/10.5194/egusphere-egu26-8261, 2026.
The background solar wind is one of the most crucial aspects in space weather forecasting. It is the environment through which coronal mass ejections propagate, impacting their geo-effectiveness. Due to the solar rotation and the slow evolution of solar sources of the solar wind, solar wind parameters exhibit an autocorrelation with a period of roughly 27 days. We make use of this property and produce a solar wind persistence model with input from multiple spacecraft (Solar Orbiter, Parker Solar Probe, STEREO-A and OMNI) projected onto the ecliptic. We present the statistical performance of the persistence model. The model propagates in-situ data from the position of their measurement radially away from the Sun, as well as longitudinally with the solar rotation rate. We combine measurements from different spacecraft into one solar wind forecast at Earth using error estimates from a statistical evaluation of solar wind persistence across radial, longitudinal, and latitudinal separation. Due to the long persistence of the solar wind, the model does not rely heavily on real-time measurements but rather can use weeks-old in-situ measurements from all the spacecraft. The source code and model output will be made publicly available.
How to cite: Milošić, D., Temmer, M., Heinemann, S., Hofmeister, S., and Owens, M.: P2D – A two-dimensional solar wind persistence model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10346, https://doi.org/10.5194/egusphere-egu26-10346, 2026.
Proton measurements of the Energetic and Relativistic Nuclei and electron Experiment (ERNE) aboard the Solar and Heliospheric Observatory (SOHO) reach up to ∼50 MeV in the currently available scientific data product. However, the instrument has some channels that primarily respond to high-energy protons (hundreds of MeV) that have not yet been calibrated or released. Within the EU Horizon Europe project SPEARHEAD (SPEcification, Analysis & Re-calibration of High Energy pArticle Data), the Geant4 model of the instrument has been reconstructed by scratch, and its response functions have been recalculated.
Penetrating particles in the detector are identified by detecting a signal in the plastic scintillator anti-coincidence (AC) detector at the bottom of the detector stack. The anti-coincidence detector is read out by photodiodes, which introduce some detection inefficiency. As there is no pulse-height data available from the AC scintillator, and the detection threshold was not calibrated prior to the launch, the response of the ERNE AC counters is not well known. Without knowledge of the AC response, the physical quantities cannot be obtained from the ERNE observations. To address this gap, an in-flight calibration of the detection threshold has been attempted. We take advantage of the fact that the Electron Proton Helium INstrument (EPHIN), another detector aboard SOHO, provides reliable observations of protons in a similar energy range. With a subsequent bow-tie analysis, the effective energy (~130 MeV) and differential geometric factor (~878 cm2) of this previously unused instrument channel have been determined. Here, we provide an overview of the work done so far and outline the ongoing efforts expected to yield a new dataset of ~130 MeV proton observations over the entire SOHO mission period of 30 years.
SPEARHEAD has received funding from the European Union’s Horizon Europe programme under grant agreement No 101135044. The work reflects only the authors’ view, and the European Commission is not responsible for any use that may be made of the information it contains.
How to cite: Gieseler, J., Fedeli, A., Hamza, S., Heber, B., Hörlöck, M., Ngom, C., Oleynik, P., Palmroos, C., and Vainio, R.: Extending SOHO/ERNE proton measurements beyond 100 MeV, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12287, https://doi.org/10.5194/egusphere-egu26-12287, 2026.
The propagation of Galactic Cosmic Rays (GCRs) within the heliosphere is modeled by the Parker Transport Equation (PTE), which can be numerically solved using a Stochastic Differential Equation (SDE)–Monte Carlo approach. While this method is computationally intensive, the rapid growth of available high-performance computing (HPC) resources now enables its efficient implementation.
To fully exploit these advancements, we developed COSMICA, a novel GPU-accelerated code that implements a three-dimensional SDE solver in CUDA/C++, optimized for multi-GPU execution. This allows the simulation of billions of quasi-particle trajectories with unprecedented computational efficiency.
In this work, we present COSMICA’s validation against a benchmark heliospheric model, demonstrating runtime reductions exceeding an order of magnitude compared to the benchmark model, while maintaining full consistency with reference flux predictions.
How to cite: Della Torre, S., Bacciu, L., Grazioso, M., Gervasi, M., La Vacca, G., Rossi, S., and Nobile, M. S.: Why Performance Matters: Accelerating Solar Modulation of Galactic Cosmic Rays with High-Performance Computing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13075, https://doi.org/10.5194/egusphere-egu26-13075, 2026.
Reliable measurements of Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) require
well-calibrated spaceborne particle instruments. This study presents a cross-calibration of the
Electron, Proton and Helium Instrument (EPHIN) aboard SOHO with high-precision proton and helium
measurements from PAMELA and AMS-02. The analysis extends the established $\Delta E$--$\Delta E$
technique to later mission phases, accounting for detector aging and changes in instrument response
after 2017.
A GEANT4-based model of EPHIN, including a simplified representation of the SOHO spacecraft, is used
to derive energy response functions for penetrating protons and helium nuclei. Simulated detector
responses based on force-field–modulated GCR spectra reproduce the observed EPHIN energy-loss
distributions within about 30\%. Effective energies and fluxes are obtained using a bow-tie inversion
method and compared with AMS-02 and PAMELA observations during quiet solar conditions. The results
show agreement within the combined systematic uncertainties, demonstrating that SOHO/EPHIN
continues to provide valuable and reliable energetic particle measurements for long-term
heliospheric studies.
The EPHIN is supported under Grant 50~OC~2302 by the German Bundesministerium für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR). We acknowledge partial support from the Horizon Europe Program project SPEARHEAD (GA 101135044).
How to cite: Heber, B., Hörlöck, M., Köberle, M., Kühl, P., Romaneehsen, L., and Papaioannou, A.: Cross calibration of SOHO ~1 GV proton and helium fluxes with PAMELA and AMS-02, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14443, https://doi.org/10.5194/egusphere-egu26-14443, 2026.
We present long-baseline Very Low Frequency (VLF) observations of solar flare-induced ionospheric disturbances obtained at the Bulgarian Polar Astronomical Observatory (St. Kliment Ohridski Base) on Livingston island, Antarctica, representing the first such measurements from this high-latitude Southern Hemisphere location. Using continuous VLF transmissions at 21.4 kHz (NPM, Hawaii) and 24.0 kHz (NAA, Maine), propagating over trans-hemispheric paths exceeding 11,000 km, we investigate the response of the ionospheric D-region to solar flares during the period 24 January–8 February 2025. After removing the strong diurnal signal via superposed epoch analysis, we analyse the flare-related perturbations in VLF amplitude and their correlation with GOES soft X-ray flux for 41 flares of class C7.0 and above. The long propagation paths provide enhanced sensitivity to flare-driven changes in D-region ionization. The observations reveal clear, frequency-dependent responses and measurable time delays between X-ray and VLF peaks. These delays, including cases of near-zero or negative lag for stronger events, highlight the role of flare spectral characteristics and D-region recombination processes. Our results demonstrate the scientific value of Antarctic VLF observations for probing solar-terrestrial processes coupling, and establish a new node in the global VLF monitoring network, with direct relevance for space weather research.
How to cite: Kozarev, K., Petkov, P., Nachev, I., Radeva, V., Dechev, M., Atanasov, A., and Borisov, G.: Long-Baseline VLF Observations of Solar Flares from Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17608, https://doi.org/10.5194/egusphere-egu26-17608, 2026.
The JUpiter ICy moons Explorer (JUICE) mission, launched on 14 April 2023, is currently in its interplanetary cruise phase and is expected to arrive at Jupiter in July 2031. Throughout its eight-year journey to the Jovian system, the spacecraft is exposed to a highly variable radiation environment dominated by galactic cosmic rays (GCRs) and episodic solar energetic particle (SEP) events. Upon arrival at Jupiter, JUICE will encounter one of the most intense radiation environments in the Solar System, characterized by powerful radiation belts populated primarily by highly energetic electrons. Monitoring and characterizing this radiation environment is therefore essential both for scientific return and for spacecraft and instrument safety.
To address these challenges, JUICE carries the RADiation-hard Electron Monitor (RADEM). RADEM was designed to measure high-energy protons (5-250 MeV), electrons (0.3-40 MeV), and to some extent ions (Z>=2). Since launch, RADEM has been operating continuously during the cruise phase, providing uninterrupted measurements of the energetic particle environment in interplanetary space.
After nearly three years of operations, RADEM has already recorded tens of SEP events associated with solar activity. These observations provide valuable insight into the spatiotemporal evolution, intensity, and spectral characteristics of energetic particles. In this work, we present an overview of RADEM’s in-flight performance and scientific observations to date. We also discuss updates and optimizations to the instrument’s operational settings implemented during cruise, aimed at improving the quality of its measurements.
How to cite: Pinto, M., Gomes, A., Rodríguez-García, L., Mewes, M., Parente, R., and Rodrigues, A.: Three-Years of RADEM aboard the JUICE mission: Observations, Updates and Future Perspectives, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21750, https://doi.org/10.5194/egusphere-egu26-21750, 2026.
The Energetic Solar Eruptions: Data and Analysis Tools (SOLER) project presents a wide array of software tools to help in the analysis of solar energetic particle (SEP) events. The current heliospheric fleet of spacecraft, which has expanded significantly in recent years, offers an unprecedented number of simultaneous vantage points and, as such, uniquely extensive data on solar eruptions and their effects throughout the heliosphere. In an effort to utilize this data to its full potential, SOLER provides software tools in the form of easy-to-use open-source Python Jupyter Notebooks. The tools are designed such that even users with limited programming experience can get the most out of them, allowing one to focus on what matters most: the science. They are available online and require no installation by the user.
The tools cover a wide range of functionalities. They include automatized data loaders that handle downloading from the web and enable visualization of SEP intensity-time profiles and other in-situ measurements made by various instruments aboard the heliospheric fleet. Additional tools assist in determining the Pitch-Angle Distributions (PAD) and capabilities for background-subtraction of SEPs and first-order anisotropies, their energy spectra, including the ability to fit the spectra using a variety of mathematical models. The final set of tools is dedicated to the determination of SEP event onset times and related analysis. These tools offer a linear regression method designed to identify the times at which SEP intensities change rapidly as well as a novel combination of a modified Poisson-CUSUM scheme, statistical bootstrapping, and methodological time-averaging to estimate the most probable onset time along with the associated confidence intervals.
This project has received funding from the European Union's Horizon Europe research and innovation programme under grant agreement No 101134999 (SOLER). Views and opinions expressed are those of the authors only and do not necessarily reflect those of the European Union or HaDEA. Neither the European Union nor the granting authority can be held responsible for them.
How to cite: Palmroos, C., Gieseler, J., Dresing, N., Fedeli, A., Lang, J., Jebaraj, I., Kanto, S., Santala, O., Price, D., Vuorinen, L., and Vainio, R.: SOLER Open-Source Python Tools for the Analysis of Energetic Solar Eruptions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21849, https://doi.org/10.5194/egusphere-egu26-21849, 2026.
Large-scale coronal waves are large-amplitude or shocked fast magnetosonic waves, most probably caused by the rapid lateral expansion of the flanks of a coronal mass ejection (CME). These waves can be observed in soft X-ray and EUV images as bright fronts crossing large areas of the solar disk, with the strongest signals observed in filters that image the solar corona at temperatures of around 1-2 MK. While some large-scale coronal waves are observed to be quasi-circular, most exhibit non-isotropic propagation in terms of direction and speed. As expected of magnetosonic (shock) waves, they exhibit wavelike behavior, such as reflection, refraction, and transmission, in regions with different magnetosonic speeds, such as coronal holes and active regions, due to variations in magnetic flux density and plasma density. However, the resulting non-isotropic wavefront behavior is rarely investigated in detail.
Here, we investigate the two-dimensional velocity field of the fast and complex large-scale coronal wave observed on September 6, 2011. We use the newly developed multi-sector method of the SOLERwave tool, using a Huygens-plotting-based approach. The multi-sector method utilizes perturbation profiles derived in multiple directions (sectors) to determine the location of the wavefront at a given time. The two-dimensional velocity vector at each point along the wavefront is derived by identifying the point closest to it along the wavefront observed one time step earlier and dividing the distance between the two points along the solar surface by the time difference between the observations. For the event under study the resulting two-dimensional velocity field shows a significant difference between the northward traveling and the northwest ward traveling part of the wave front of over 40%, in the range of 750 to 1500 km/s. To determine the cause of this difference in speed, we investigate the coronal structures and the photospheric magnetic field distribution along different propagation directions of the wave, and set the findings in context with alternative interpretations like potential misidentification of the expansion/opening of CME loops as wave front.
This project has received funding from the European Union's Horizon Europe research and innovation program under grant agreement No 101134999.
How to cite: Baumgartner-Steinleitner, M., Veronig, A., and Dissauer, K.: Investigation of the two-dimensional velocity field of the fast large-scale coronal wave observed on September 6, 2011, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7369, https://doi.org/10.5194/egusphere-egu26-7369, 2026.
We present the analysis of high-resolution Hα observations of fan-shaped jets above a penumbral light bridge (LB) subject to external disturbance through fast down-flows in active region (AR) 12683 using data from the Goode Solar Telescope (GST) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Jets are observed with an occurrence rate of 5-6 min, reaching heights of 7-14 Mm above the LB with ascent speeds of 70 km/s and nearly parabolic trajectories. Associated bright fronts are seen as evidence of shock wave heating. We report the discovery of linear dark condensations of 0.45 Mm thickness that propagate ahead of the jet and shock, suggesting matter is being compressed in front of the shock. Fast down-flows of 40-80 km/s reach the South end of the LB with the same periodicity as the jets. The jets and associated small-scale linear structures exhibit horizontal motion, differential with height, along the LB axis at speeds of 35-55 km/s away from the interaction site. This speed is consistent with a magnetic field of 40-100 G. We propose that the fast down-flows triggers magnetic reconnection at the footpoint of the LB, which in turn drives the jets and the horizontal dynamics along the LB. We suggest that the linear fine-structure is the result of a fast magnetoacoustic wave propagating away from the reconnection site.
How to cite: Brocklebank, K., Verwichte, E., and Shetye, J.: Interactions between fast Down-flows and Fan-shaped Jets above a Penumbral Light Bridge using the Goode Solar Telescope, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14689, https://doi.org/10.5194/egusphere-egu26-14689, 2026.
The Chromospheric Magnetism Explorer (CMEx) mission is under development to make measurements of the Sun’s magnetic field between the photosphere and corona. This mission contributes to the critical problems documented in the 2013 U.S. National Academies Solar and Space Physics Decadal Survey, namely “Determine How Magnetic Energy is Stored and Explosively Released.” CMEx does so by returning magnetic field strength and direction information of active regions prior to, and following eruptions. CMEx is also poised to provide insight into heliospheric magnetic fluxes, adding unique observational data to answer the so-called “open flux problem.” The CMEx mission collects spectropolarimetry data and generates magnetic field information utilizing inversion codes and other techniques that interpret Zeeman- and Hanle-effect changes to spectral lines. The CMEx instrument consists of a two-band ultraviolet spectropolarimeter with a single band ultraviolet imager. The instrument performs repeated raster scans of prominences, filaments, and coronal holes at a cadence allowing direct observation of evolving and changing solar magnetic structures. Launched into a 6 A.M. sun-synchronous orbit, CMEx will have continuous visibility of the sun outside of its 3-month eclipse season, allowing near constant monitoring of solar features of interest. Image stacking and subsequent spectrum demodulation onboard the observatory provides for downlink of full Stokes vector information for the observed spectral lines. CMEx also utilizes the instrument raster scan mirror to provide line-of-sight stability by compensating for spacecraft motion and attenuating system jitter. Observation plans developed by the Science Operations Center (SOC) are transferred to the Mission Operations Center (MOC) for conversion into command sequences subsequently uplinked to the observatory via KSAT ground stations. After launch, CMEx will complete a two-year science mission following a month of combined on-orbit spacecraft and instrument commissioning. CMEx provides a high-performance space observatory by combining heritage instrument and spacecraft element designs, as well as commercial-off-the-shelf (COTS) technologies into a low-cost solution appropriate for a cost-capped small explorer class NASA mission. In December 2025, the CMEx project was selected to receive an extended Phase A study.
CMEx is a NASA Heliophysics Small Explorer (SMEX) mission led by the Principal Investigator, Dr. Holly Gilbert, at the High Altitude Observatory (HAO) at the National Science Foundation National Center for Atmospheric Research (NSF NCAR). The CMEx mission partners include BAE Systems, Inc., Space and Mission Systems (BAE Systems, SMS), and the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder (CU/LASP).
How to cite: Kalinowski, B.: The Chromospheric Magnetism Explorer (CMEx) Mission System Concept, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15801, https://doi.org/10.5194/egusphere-egu26-15801, 2026.
