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 influence of dissipating solar diurnal tides in driving the mean zonal wind in the upper mesosphere and lower thermosphere (UMLT) is investigated using the zonal and meridional winds observed by the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument onboard the Ionospheric Connection Explorer (ICON) satellite over the region of interest having a latitudinal and longitudinal extent of 5° N - 15°N and 67.5°E - 90°E, respectively, for the years 2020, 2021 and 2022. The mean zonal wind exhibits consistent seasonal variation with large westward winds at 91-103 km during January-March and September-December, however with varying intensity (20-40 m/s) in all the three years. The diurnal tidal amplitude in meridional wind (DTV) also displays similar seasonal variation with maximum amplitudes reaching ~80–100 m/s. The seasonal variation of westward acceleration due to diurnal tide momentum deposition is found to be maximum during January-March (18-43 m/s/day) and September-December (40-55 m/s/day) and reveals similar seasonal variation and intensity of the mean westward winds. This clearly indicates that the potential role of diurnal tide in driving the mean zonal flow.  The westward acceleration induced by the vertical gradient of meridional flux of zonal momentum (F_meridional) due to diurnal tide exceeds the convergence of vertical flux of zonal momentum (F_zonal) due to diurnal tide during January-March, while the westward acceleration induced by both F_zonal and F_meridional are larger and comparable during September-December.

How to cite: Basu, S. and Sundararajan, Dr. S.: Influence of diurnal tide on the low-latitude UMLT mean zonal wind: Evidence from momentum flux estimation using ICON-MIGHTI winds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2435, https://doi.org/10.5194/egusphere-egu26-2435, 2026.

We performed a one-year long simulation using the upper-atmosphere configuration of the Icosahedral Nonhydrostatic model (UA-ICON). The simulation has a horizontal resolution of 20 km and 180 vertical levels between the ground and 150 km. At 110 km height and every hour we extracted the gravity wave vectors and amplitudes with the small-volume few-wave decomposition method S3D, which is part of the software package JUWAVE. We focus on low-latitudes, i.e. +/- 40 degrees. The model simulates clear signatures of gravity wave activity above convective hotspots over summer continents. Ray tracing shows that the largest perturbations in the thermosphere are likely primary waves from developing convection. These signatures are most prominent in waves with short horizontal scales and long vertical wavelengths. In turn, horizontally short waves with smaller vertical wavelengths cannot be traced down to the lower stratosphere. For horizontally long waves, we find a clear diurnal/longitudinal pattern in the gravity wave activity, which results from interactions with tides. The study has broad implications of how whole-atmosphere high-resolution models may help forecast thermospheric density and ionospheric perturbations, both from the numerical weather prediction perspective, as well as empirically based on known patterns of lower-atmospheric variability.

How to cite: Stephan, C.: Tracing low-latitude thermospheric gravity waves in a whole-atmosphere simulation to their sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2620, https://doi.org/10.5194/egusphere-egu26-2620, 2026.

Prior studies identified a fine structure in the middle latitude ionosphere known as the strip-like plasma density bulge. These bulges emerge during geomagnetic storms, exhibiting a broad longitudinal span of over 150° and a narrow latitudinal extent of 1°~5°. The observations from the DMSP and ICON satellites reveal stronger equatorward ion drifts and neutral winds on the poleward side of bulges compared to the equatorward side. Using the Sami2 is Another Model of the Ionosphere (SAMI2), the bulge feature was reproduced for the storm of 4~6 November 2021 by amplifying the default meridional winds. Numerical simulations indicate that global wind disturbances establish a sharp meridional wind gradient within the lower mid-latitude region. This gradient, in turn, drives a divergence in ion transport parallel and perpendicular to the magnetic field lines, which ultimately results in the localized accumulation of plasma. The phenomenon is most pronounced in the vicinity of ±30° quasi-dipole latitude. This region is characterized by a magnetic inclination angle of approximately 45°, a configuration where the meridional wind component acts most efficiently to elevate ions vertically.

How to cite: Du, W., Zhong, J., and Wan, X.: Storm-Time Strip-Like Plasma Density Bulges at Middle Latitudes Shaped by Meridional Wind Gradients, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3064, https://doi.org/10.5194/egusphere-egu26-3064, 2026.

In Fujisawa et al. (2022) [1], we previously produced an objective analysis of the Venusian atmosphere by assimilating horizontal winds derived from cloud tracking of the UVI camera onboard the Venus orbiter Akatsuki. To produce objective analysis, we used the Venus atmospheric data assimilation system ALEDAS-V (Sugimoto et al., 2017) [2], which is based on the Venus general circulation model AFES-Venus (Sugimoto et al., 2014) [3]. This dataset appropriately corrects both the phase bias of thermal tides and the super-rotation speed in AFES-Venus to be closer to those observed in the real Venusian atmosphere. The dataset was produced by assimilating observations from September to December 2018, a period that includes an intensive observation period of Akatsuki.

Akatsuki has accumulated observational data over a long period from 2015 to 2024, and it has been revealed that the super-rotation speed exhibits both faster and slower periods (Horinouchi et al., 2024) [4]. In this study, we selected five epochs during the Akatsuki observation period that exhibit characteristic super-rotation speeds and performed data assimilation for each epoch. As a result, we confirmed that distinct super-rotation speeds corresponding to each epoch, including their meridional asymmetry, are reproduced. In the presentation, we will show the relationship between the reproduced super-rotation speeds and the structure of the atmospheric circulation.

• [1] Fujisawa, Y., et al. (2022) Sci. Rep. 12, 14577.
• [2] Sugimoto, N., et al. (2017) Sci. Rep. 7(1), 9321.
• [3] Sugimoto, N., et al. (2014) J. Geophys. Res. Planets 119, 1950–1968.
• [4] Horinouchi, T., et al. (2024) J. Geophys. Res. Planets 129, e2023JE008221.

How to cite: Fujisawa, Y., Sugimoto, N., Komori, N., Murakami, S., Ando, H., Takagi, M., Imamura, T., Horinouchi, T., Hashimoto, G. L., Ishiwatari, M., Enomoto, T., Miyoshi, T., Kashimura, H., and Hayashi, Y.-Y.: Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data Assimilation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3726, https://doi.org/10.5194/egusphere-egu26-3726, 2026.

Jupiter’s magnetosphere features internal mass loading from its innermost moon Io. The neutral gases from Io’s escaping atmosphere are ionized to become the plasma torus, which mainly consists of sulfur and oxygen ions. Under centrifugal force, plasma in the torus is transported outward and forms a thin plasma disk near the equator, while the transport mechanism and timescale remain unclear. Since 2016, the plasma disk between 10 and 50 RJ has been continuously observed by the Juno mission. Using multi-year thermal plasma measurements from the JADE ion detector, we perform an analysis that reveals significant temporal variation of plasma disk from a long-term perspective. For different Juno orbits, the plasma disk observations are categorized as either enhanced or depleted based on plasma density. Extreme cases indicate vastly different states of the plasma disk, with variations exceeding one order of magnitude. Further analysis of multiple plasma disk crossings by Juno reveals correlations between density enhancements and fluctuations in plasma density and magnetic field profiles, which are typical features of flux tube interchange. This suggests that flux tube interchange is triggered by an increase in the plasma source and is considered the primary mechanism for outward plasma transport. Finally, Juno’s in-situ measurements also show a correlation with remotely sensed Io’s torus ribbon brightness from the ground-based IoIO observatory, lagged by about 30 to 50 days. This suggests that the temporal variation of the plasma disk is modulated by changes in Io’s torus and that the average plasma transport time from the torus to the plasma disk is around 40 days. 

How to cite: Bagenal, F. and Wang, J.-Z.: Temporal Variations of Jupiter’s Plasma Disk Observed by Juno , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4537, https://doi.org/10.5194/egusphere-egu26-4537, 2026.

Jupiter’s moon Io is the most volcanically active body in the Solar System, powered by intense internal heating due to tidal dissipation. Although tidal friction is widely accepted as the main energy source, how this heat is distributed within Io and how it shapes the moon’s internal structure remain open questions. In this study, we use Io’s tidal response, quantified through the degree-2 Love number (k₂)_, to constrain its interior, using recent estimates derived from Juno observations (Park et al., 2025).

We model Io with a three-layer structure consisting of a fluid core, a viscoelastic mantle, and a crust, using an adapted version of the California Planetary Geophysics Code (CPGC). Tidal dissipation is self-consistently coupled to mantle rheology through an Andrade model, with viscosity and shear modulus updated as functions of the local melt fraction. We explore two end-member scenarios that differ in the treatment of the Andrade parameter β: in the first, β is held constant, representing a uniform dissipation regime dominated by deep-mantle heating; in the second, β varies with depth, allowing dissipation to be preferentially localized in the upper mantle. In both scenarios, viscosity and shear modulus evolve with melt fraction.

Our results identify several partially molten mantle configurations whose real part of k₂ is consistent with Juno constraints. In all acceptable models, melt fractions remain below the threshold required to form a global magma layer. To test the physical viability of these states, we compare thermodynamic melt production with the capacity for melt migration. We find that melt transport is efficient enough to prevent long-term melt accumulation, favoring a stable, partially molten “magma sponge” rather than a global magma ocean. These results provide new constraints on Io’s thermal state and are consistent with independent estimates of its global volcanic output.

How to cite: Paris, M., Mura, A., Zambon, F., Genova, A., Tosi, F., Piccioni, G., Consorzi, A., Mitri, G., Sordini, R., Noschese, R., Cicchetti, A., Plainaki, C., Bolton, S., and Sindoni, G.: Juno Constraints on Io’s Interior: Tidal Response and Melt Stability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5870, https://doi.org/10.5194/egusphere-egu26-5870, 2026.

Terrestrial exploration with the help of rovers typically employs traditional stereo cameras, relying on binocular optical designs with large, bulky, and often moving parts. The stereo camera design concept presented in this study was developed and built using commercial off-the-shelf (COTS) components, allowing for rapid-prototyping, cost-effective testing, and performance evaluation under simulated mission conditions. An innovative use of four-mirror optical configuration and a monochrome CMOS sensor introduces a novel approach to achieve high resolution stereo imaging, while maintaining low power consumption and space requirements suitable for compact lander missions. By utilizing a single-detector stereo vision, the camera system can effectively create 3D reconstructions of observed objects with a spatial resolution of 54 μm per pixel, and depth resolution of <1 mm per pixel with the stereo baseline length of 116 mm, an instantaneous field of view of 601 μrad per pixel. The optical performance was validated with experiments such as the resolution and shape measurement test. The scientific applicability was demonstrated by extracting the static angle of repose of regolith simulants EAC-1A and NU-LHT-2M, as well as the relative surface albedo through a photometric stereo method, providing deeper understanding into the physical and optical properties of lunar regolith analogues. The presented camera design offers a balance between performance with compactness, addressing challenges faced by conventional stereo cameras such as baseline constraints, environmental exposure, and computational efficiency. Further design limitations and stereo matching inaccuracies were identified during testing and characterisation. The stereo camera developed in this study demonstrates capabilities for high-resolution, in-situ lunar surface analysis based on regolith characterization and contributes to an in-depth understanding of lunar regolith properties by close-range scientific analysis of its geo-mechanical behaviour.

How to cite: Chauhan, S. C., Jaumann, R., Grott, M., and Althaus, C.: Prototype Design for a Lunar Lander High Resolution Stereo Camera, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7948, https://doi.org/10.5194/egusphere-egu26-7948, 2026.

Auroras are the result of charged particles interacting with a planetary atmosphere, driving several processes involving the excitation and ionization of molecules and atoms, leading to spectacular emissions. This study investigates Martian auroral emissions using observations from the Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope Probe. The analysis focuses on the oxygen emission lines at 130.4 nm and 135.6 nm, which are key diagnostics of electron precipitation. EMUS emission images are processed to compute brightness maps and intensity ratios, identify energetic regions using thresholding techniques, and generate histograms that characterize the spatial distribution and statistical properties of auroral energy across different regions of Mars.

In addition, data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, particularly magnetic field measurements from the MAG instrument, are used to correlate auroral observations with the Martian crustal magnetic field. By combining EMM ultraviolet observations with MAVEN magnetic field measurements, the study explores the relationship between auroral morphology, energy deposition, and underlying magnetic field topology.The goal is to assess how magnetic field geometry influences the localization and structure of auroral emissions and to better constrain the coupling between the solar wind, the Martian magnetosphere, and the upper atmosphere.

The combined analysis demonstates the potential of how combined EMM and MAVEN observations improves our understaing of of auroral processes on Mars and their implications for planetary atmosphere studies and space weather interactions.

How to cite: Alblooki, S. and Atri, D.: Exploring Martian Auroras Using EMM/EMUS and MAVEN/MAG: Insights into Ultraviolet Emissions and Crustal Magnetic Field Interactions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8953, https://doi.org/10.5194/egusphere-egu26-8953, 2026.

Viscosity is a fundamental physical parameter governing the generation, transport, and eruption of geological melts, dictating magma ascent rates, eruption styles, and the kinetics of physicochemical processes. On Earth, melts viscosities have been widely measured from various rock samples through high T-P (temperature & pressure) experiments, and a continuous viscosity-temperature-pressure (V-T-P) dependence can be obtained by different melt viscosity models. However, due to significant compositional differences, particularly in iron and titanium oxides between lunar and terrestrial basalts, no existing model can be simply used to predict magma viscosity on the Moon.

In this study, we have collected and trained on a comprehensive dataset of 28898 hand-curated melt measurements (compositions, pressure, temperatures and viscosity), including typical lunar melt types of ferrobasaltic melts, Apollo 15C green glass, Apollo 17 orange glass, Apollo 14 black glass, as well as synthetic high-titanium mare basalts and KREEP basalts. We have employed Kolmogorov-Arnold Networks (KANs) to construct a deep learning model and established a relationship between lunar melt viscosity and its temperature, pressure, and composition (V-T-P-C). Unlike traditional Multi-Layer Perceptrons (MLPs), KANs utilize learnable spline functions rather than fixed activation functions. This architecture offers superior interpretability and generalization capabilities, making it particularly suitable for predicting viscosity under complex thermodynamic conditions.

The predicted rheological behavior of KREEP lunar silicate melts (Apollo samples) from KANs are well consistent with experimental measurements. Taking into account the compositions of basalts obtained from Chang’e 5 and 6 sampling, model suggests that the viscosity values ( Pa·s ) of young basalts (~2.0 Ga for Chang’e 5 and ~2.8 Ga for Chang’e 6) are ~2.5 orders of magnitude lower than that of relatively older Apollo-type basalts (>3.0 Ga) under the same T-P conditions.

How to cite: Chen, Y. and Huang, Q.: Investigating Lunar Melt Viscosity via Deep Learning: A Kolmogorov-Arnold Networks (KANs) Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9039, https://doi.org/10.5194/egusphere-egu26-9039, 2026.

This contribution presents a petrographic, microstructural, and micro-analytical approach developed for the comprehensive study of ordinary chondrites, as part of a master’s thesis aimed at defining an analytical protocol for the petrological and minerochemical characterization of extraterrestrial materials. The ultimate goal is the establishment of a dedicated laboratory for the petrological study of meteorites, exploiting available instrumentation and acquired micro-analytical expertise to achieve both a complete classification of chondrites and a deeper understanding of the processes governing their genesis and evolution.

The study was carried out in collaboration with the Italian Museum of Planetary Sciences, where an internship allowed the examination of a reference collection of classified meteorite thin sections commonly used for educational purposes. Subsequently, three ordinary unclassified chondrites, provided by the “Museo del Cielo e della Terra” (San Giovanni in Persiceto, Bologna, Italy) and by a private collection, were investigated.

The analytical workflow includes: (i) macroscopic measurements and photographic documentation; (ii) petrographic analysis by transmitted and reflected light optical microscopy for microstructural and mineralogical characterization; (iii) SEM-EDS X-ray compositional mapping on the whole petrographic thin section as well as on selected chondrules and microstructural sites; (iv) SEM-EDS quantitative microanalyses of mineral phases; and (v) micro-Raman spectroscopy.

Preliminary results indicate that, from a chemical perspective, two of the unclassified samples can be assigned to the H group and one to the L group of ordinary chondrites. Petrographic observations classify the investigated meteorites as petrologic types 4 to 6. The most common chondrule textures observed include porphyritic and barred olivine, porphyritic olivine–pyroxene, granular olivine–pyroxene, radial pyroxene, and complex chondrules.

SEM-EDS compositional maps of entire thin sections and selected microstructural domains enable visualization of textural relationships, estimation of modal mineral abundances relative to metallic phases, and the development of a comparative framework among ordinary chondrites. Mineral chemistry data are compared with literature values to refine classification criteria. Micro-Raman spectroscopy is performed on opaque phases or on selected minerals for the correct identification of the polymorphic phase which constrains proper ranges of P-T conditions. Moreover, micro-Raman analyses are employed to characterize solid and fluid/melt inclusions within primary minerals, assess surface alteration features, and investigate dust extracted from fractures, providing insights into secondary processes related to atmospheric entry and post-impact evolution.

How to cite: Borghetti, S., Di Martino, M., Ferrando, S., Faggi, D., Ghignone, S., Morelli, M., Serra, R., and Vaggelli, G.: A Petrographic and Micro-Analytical Framework for the Study and Classification of Meteorites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11477, https://doi.org/10.5194/egusphere-egu26-11477, 2026.

The recent Martian exploration mission has provided substantial evidence for the presence of hydrous sulphate minerals, especially in the Gale Crater and Meridiani Planum. These findings are crucial for understanding the past climate, water activity, and geological history of early Mars. Studying the sulphate formation process, particularly jarosite, has become increasingly important. In this context, terrestrial analog sites with similar mineral deposits can serve as effective models for exploring and analyzing sulphate deposits in detail. The Matanomadh and Harudi formations of Kachchh, Gujarat, India, were chosen as Martian analog sites because they expose well-preserved, clay-rich jarosite layers that may help better understand paleo-environmental conditions during Martian alteration. Here, jarosite is found alongside grey carbonaceous shale, weathered basalt, and gypsum, typically appearing as lenses of variable width, interconnected veins, or veinlets. Pure jarosite samples were collected after detailed field studies from the Matanomadh and Harudi formations of Kachchh. Powdered samples were characterized using X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HR-TEM), Field Emission Scanning Electron Microscopy (FE-SEM), X-Ray Photoelectron Spectroscopy (XPS), and Elemental Analyzer-Isotope Ratio Mass Spectrometry (EA-IRMS) for sulfur isotope analysis. All XRD patterns were analyzed with the FullProf program using Rietveld refinement, employing the R-3m space group. The average a- and c-cell dimensions for jarosite were calculated as a = 7.3028 Å and c = 16.6376 Å. The XRD diffractogram displays a distinct peak at (006) at 2θ = 32.29°. FE-SEM images show that jarosite crystals have well-formed pseudohexagonal shapes with defined faces and edges. HR-TEM analysis indicates the dominance of sodium (Na), and elemental mapping confirms homogeneous grains. XPS analysis of jarosite revealed prominent peaks for Fe2p_3/2 and S2p at approximately 713.4 eV and 169.9 eV, respectively. S2p peaks were also observed in the host shale rock. δ³⁴S values for jarosite (-8.4 to -16‰) are close to values typical of supergene or steam-heated hydrous sulphates derived from pyrite or H₂S oxidation. The cell dimensions obtained from XRD data agree with literature values, confirming the mineral as Natrojarosite. The peak position of the (006) reflection in natrojarosite differs from that of jarosite. In this sample group, iron (Fe) exists in the +3 oxidation state, as confirmed by XPS. Based on the presence of sulfur (S -1) peaks in the associated shale, it is inferred that shale may serve as a sulfur source for natrojarosite formation in the current study area under acidic, oxidizing conditions.

How to cite: Saha, N. and Majumdar, A. S.: Integrated Micro to Nano-Scale Characterization of Hydrous Sulphate Mineral-Jarosite in Kachchh, Gujarat, India: Implication for Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12992, https://doi.org/10.5194/egusphere-egu26-12992, 2026.

We report on observations of negative carbon and oxygen pickup ions (PUIs) originating from dust orbiting Jupiter. The PUIs are observed at altitudes of a few thousand kilometers (~4,800 – 10,200 km) above the 1-bar level of Jupiter’s atmosphere and up to ~11,000 – 15,000 km from the equatorial plane, thus providing constraints on the location of the dust population and its composition. The Jovian Auroral Distributions Experiment – Electron sensors on Juno detect these PUIs because of the combination of a fast-moving spacecraft and the large Keplerian orbital speed of the dust near Jupiter. We demonstrate that this scenario is consistent with the observations. We find a PUI C/O ratio of 10 ± 5 and a PUI energy release of ~11 ± 9 eV. Electron stimulated desorption is a likely process forcreating these PUIs. The dust is well inside the halo population and likely carbonaceous.

How to cite: Allegrini, F., Szalay, J., McComas, D., Ebert, R., Bolton, S., Clark, G., Connerney, J., Kurth, W., Louarn, P., Mauk, B., Pontoni, A., Saur, J., Valek, P., Wang, J.-Z., and Wilson, R.: Detection of negative carbon and oxygen pickup ions from dust orbiting Jupiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14123, https://doi.org/10.5194/egusphere-egu26-14123, 2026.

The radical terraforming of Mars was proposed in 2025 (LPSC2025, 1558.pdf) envisions bringing volatiles with a total mass of approximately 10¹⁹ kg from the Kuiper Belt to Mars. This would amount to approximately 1000 asteroids. Upon reaching Mars, these bodies will have velocities ranging from a few to a dozen or so km/s relative to the planet. The impact sites and their parameters will be controlled to some extent. This would be a unique opportunity to use these bodies to modify the surface of Mars. The goal of radical terraforming is also to create open water reservoirs and rivers. The planet's current topography makes these plans very difficult. Large elevation differences would lead to rapid concentration of water in a few low-lying areas. We show examples of possible stable zones that would provide habitable conditions for ecosystems from Earth. Another possibility of using impacts is the targeted transformation of minerals. Asteroids themselves contain not only water and volatile substances but also other compounds. Placing them in appropriate places can make the economy easier for future residents.

How to cite: Czechowski, L.: Radical Terraforming of Mars and Planetary Engineering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14494, https://doi.org/10.5194/egusphere-egu26-14494, 2026.

In this project, we are exploring a few aspects of low frequency and wavenumber magnetic field energy spectra in the context of space physics, following observations of 1/f behavior (e.g. [1]-[4]). The origin of this phenomena is still debated;  however studies have suggested that these processes could be generated from scale-invariant processes in the corona or further within the dynamo of the Sun. One of the paradigms that has been discussed ([5],[6]) for achieving scale invariant structure is the merger of two dimensional or quasi-two dimensional magnetic flux tubes or flux ropes. This may be particularly relevant in the corona. To further explore this connection, it becomes necessary to understand the distributions of size and magnetic flux content, as well as the morphology of magnetic structures/”islands” in two dimensional turbulence representations. These features of the magnetic field will be explored using methods described herein [7]. These will be implemented using magnetic fields obtained from synthetic construction and 2D simulation. 

[1]Burlaga, L. F., & Ness, N. F. 1998, JGR, 103, 29 719

[2]Matthaeus, W. H., & Goldstein, M. L. 1986, PhRvL, 57, 495

[3]Wang, J., Matthaeus, W. H., Chhiber, R., et al. 2024, SoPh, 299, 169

[4]Pradata, R. A., Roy, S., Matthaeus, W. H., et al. 2025, ApJL, 984, L23

[5]Matthaeus, W. H., & Goldstein, M. L. 1982, JGR, 87, 6011

[6]Mullan, D.J.: 1990, Astron. Astrophys. 232, 520.

[7]Servidio, S., Matthaeus, W., Shay, M., et al. 2010, Physics of Plasmas, 17

How to cite: Pradata, R., Khan, M. B., Pecora, F., Matthaeus, W., Roy, S., and Adhikari, S.: Exploring Magnetic Island Morphology through 2D MHD and Synthetic Fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14898, https://doi.org/10.5194/egusphere-egu26-14898, 2026.

The Juno spacecraft made close flybys of Io on Dec. 2023 (PJ57) and Feb 2024 (PJ58) above respectively the northern/southern hemisphere with an altitude at closest approach (CA) of ~1,500 km.

On PJ57, Juno went through the Alfven wing and both the Juno/Waves and Radio-occultation measurements showed a surprising large electron density n_el ~ 28,000 near closest approach. On PJ58, Juno flew slightly behind the Alfven wing and the instruments measured a plasma density consistent with the background plasma torus density.

We run numerical simulations of the plasma/atmosphere interaction along teh PJ57 and PJ58 flyby to constrain IO’s polar atmosphere. Our numerical simulations are based on (1) A prescribed atmospheric composition and distribution of S, O, SO₂ and SO; (2) A MHD code to calculate the plasma flow into Io’s atmosphere; (3) A multi-species physical chemistry code to compute the change of the plasma properties (ion densities, composition and temperature) during the plasma/atmosphere interaction (4) a formulation of the ionization by the field-aligned electron beams used for auroral electrons on Earth.

We compute the multi-charged ion composition of the plasma along each flyby and compare to the Juno/JADE measurements to infer the atmosphere composition (O, S, SO2, SO) and density at polar latitudes. 

How to cite: Dols, V. and Bagenal, F.: The Juno PJ57 and PJ58 flybys of Io: Multi-species physical chemistry simulations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14914, https://doi.org/10.5194/egusphere-egu26-14914, 2026.

Participatory science, also called citizen science, connects scientists with the public to enable discovery by engaging broad audiences across the world. In aurora science, direct collaborations, crowdsourced efforts, and community engagement bridge aurora chasers with scientists to do research. These efforts have been fueled by recent large geomagnetic storms, evolving consumer camera technologies, social media, and dedicated citizen science projects. In this presentation, we highlight recent, cutting-edge participatory science efforts with a primary focus on the Aurorasaurus project and how it can be used to study major storm-time auroral activity.

Aurorasaurus is an award-winning citizen science platform that has been operating for over a decade. Aurora observers submit visibility reports and photos, which are filtered and cleaned to generate science-quality datasets. We highlight Aurorasaurus data from recent major geomagnetic storms in 2024 and 2025, emphasizing how rapid, widespread reporting during extreme events enables mapping of storm-time auroral extent and tracking changes in the auroral oval boundary at low latitudes. During the May 10-11, 2024 geomagnetic storm, Aurorasaurus compiled more than 5,000 vetted reports from 50+ countries, allowing for unique data-model comparisons and tracking of the extent of auroral visibility.

We also address the efficacy of using citizen science photos for research. We discuss how submitted images not only provide additional perspectives and validation of reported auroral forms, but can also constitute unique scientific datasets beyond the capabilities of traditional instrument networks. For example, modern consumer cameras can capture high spatial resolution views of fine-scale auroral structure, and photos from multiple observers can be combined to enable stereoscopic and tomographic reconstructions of auroral morphology and its evolution.

Finally, we briefly note complementary campaign-style participatory science efforts, including the AurorEye project’s low-cost deployable all-sky timelapse units, the SolarMaX mission in coordination with SpaceX’s Fram2 launch, and collaborations between aurora chasers and the SuperDARN team to supplement radar measurements with optical aurora data. With the ongoing solar maximum, it is important to harness the excitement and enthusiasm surrounding the aurora and space weather. Participatory science efforts build important relationships between public communities and scientists and unlock unique research benefits.

How to cite: Ledvina, V., MacDonald, E., Edson, L., and Natsheh, F.: Cutting-Edge Projects in Aurora Participatory Science, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16003, https://doi.org/10.5194/egusphere-egu26-16003, 2026.

The integration of gravity and topography data is a primary approach for investigating the crustal properties of terrestrial planets. While previous studies have extensively employed admittance analysis and gravity field models to estimate parameters like effective elastic thickness () and load density—particularly for Martian volcanic provinces—these methods often fail to resolve the detailed 3D distribution of subsurface structures.

Three-dimensional gravity inversion offers a powerful alternative for characterizing volcanic plumbing systems. However, existing applications often neglect the significant gravitational contribution of the crust-mantle interface (Moho relief) to Bouguer anomalies. Furthermore, as the spatial scale of investigation increases, the curvature of the planetary surface must be rigorously accounted for to avoid modeling errors.

To address these challenges, this study proposes an advanced 3D gravity inversion framework. We integrate the high-resolution MRO120F gravity model with recent crustal thickness models to isolate "residual" Bouguer anomalies that specifically reflect intra-crustal density variations. By incorporating spherical coordinate corrections and stripping the gravitational effects of the Moho, we reconstruct the 3D subsurface geological structure of a representative Martian volcanic region. Our results demonstrate that this refined inversion strategy significantly improves the resolution of magmatic features, providing new insights into the magmatic origins and evolutionary mechanisms of planetary volcanoes. In the future, we plan to apply this method to the geological structure analysis of the Tianwen landing area, providing a reference for subsequent Mars research plans. In the future, we plan to apply this method to the geological structure analysis of the Tianwen landing area, providing a reference for subsequent Mars research plans.

How to cite: He, Z., Cai, H., Huang, Q., and Hu, X.: A Gravity Inversion Strategy for Accurate Resolution of Intra-Crustal Structures Accounting for Moho Relief, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19711, https://doi.org/10.5194/egusphere-egu26-19711, 2026.

Organic compounds are a ubiquitous component of cosmic dust and provide insight into the origin of planetary systems, the availability of carbon for life in the solar system and beyond, and the distribution of potential biosignatures in the universe. Compositional and dynamical analysis of such dust grains can shed insight into their origin. The Destiny Dust Analyzer (DDA) onboard JAXA’s interplanetary space mission DESTINY+ will detect and analyse the composition of (sub-)micron sized dust ejecta during flybys of asteroids Apophis and Phaethon [1,2]. DDA will characterise both interplanetary and interstellar dust grains during the mission’s lifetime [3]. DDA is an impact ionisation time-of-flight mass spectrometer, whereby dust particles incident onto the instrument’s target at hypervelocity (≥ 2 km s^-1) vaporise and partially fragment into various constituent ions and neutrals. Here, we investigate the capability of DDA to detect a mixture of complex organic compounds in single cosmic dust particles. An organic cosmic dust analogue is prepared by coating polycyclic aromatic hydrocarbon, perylene (C₂₀H₁₂), microparticles with an ultrathin overlayer of a conductive polymer, polypyrrole H(C₄H₂NH)_nH, to enable acceleration up to hypervelocities with a high-voltage van de Graaff instrument. Time-of-flight mass spectra obtained at impact speeds ~3-20 km/s are recorded in this calibration campaign. The characteristic parent molecular ion for perylene, [C₂₀H₁₂ (+H)]⁺, is observed at m/z 251 ± 1 in mass spectra arising from impacts between 3 and 8 km s^-1. However, between 8 and 18 km s^-1, no such parent ion is observed. Instead, impact ionisation mass spectra exhibit a characteristic series of homologous [C_nH_m]⁺ fragments originating from both polypyrrole and perylene, alongside some non-sequential ions which may be diagnostic for distinguishing between different organic components in cosmic dust. The contributions of each species to fragmentation patterns in the mass spectra is coupled with the impact velocity. Our results are in agreement with Mikula et al. (2024), who investigated impact ionisation of polypyyrole-coated anthracene particles for the Interstellar Dust EXperiment (IDEX) onboard NASA's Interstellar Mapping and Acceleration Probe (IMAP), and observed a similar relationship between fragmentation pattern and velocity [4].

Additional experiments with a range of PAHs, heterocycles, and lower mass organics at various velocities, will yield further insight into the detection and characterisation of heterogeneous dust likely to be encountered by DDA. Similarly, theoretical chemical calculations could assist in deciphering the contribution of different species to mass spectral features via the analysis of dissociation thermodynamics and kinetics.

[1] Ozaki et al. (2022) https://doi.org/10.1016/j.actaastro.2022.03.029

[2] Simolka et al. (2024) https://doi.org/10.1098/rsta.2023.0199

[3] Krüger et al. (2024) https://doi.org/10.1016/j.pss.2024.106010

[4] Mikula et al. (2024) https://doi.org/10.1021/acsearthspacechem.3c00353

How to cite: Khawaja, N., Srama, R., Chan, D. H. H., Simolka, J., Armes, S. P., Mikula, R., Hirai, T., Li, Y., Strack, H., O'Sullivan, T. R., Bera, P. P., Mocker, A., Trieloff, M., Postberg, F., Hillier, J. K., Kempf, S., Sternovsky, Z., Yabuta, H., and Krüger, H.: Deciphering mixtures of complex organic compounds in cosmic dust particles using JAXA's Destiny+ Dust Analyzer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21015, https://doi.org/10.5194/egusphere-egu26-21015, 2026.

How to cite: Encrenaz, T., Greathouse, T., Marcq, E., Shao, W., Lefèvre, F., Giles, R., Lefèvre, M., Widemann, T., Bézard, B., and Sagawa, H.: Simultaneous mapping of CO, SO2 and HDO on the night side of Venus , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22816, https://doi.org/10.5194/egusphere-egu26-22816, 2026.

Multi-ring impact basins represent some of the oldest and most degraded large-scale structures on terrestrial planetary bodies, making their identification and characterization particularly challenging. Only a few well-preserved examples are known, such as the Orientale basin on the Moon, commonly regarded as the archetype of multi-ring basins. On Mercury, several multi-ring basins were initially proposed based on Mariner 10 imagery (Spudis & Guest, 1988); however, most of these candidates were not confirmed by subsequent analyses using MESSENGER data (e.g., Fassett et al., 2012; Orgel et al., 2020), highlighting the difficulty of recognizing ancient, highly modified basin architectures. Here we present a semi-automatic workflow aimed at the systematic characterization of multi-ring basins on Mercury. The workflow combines manual structural mapping with quantitative, data-driven analyses and consists of four main steps: (1) construction of a structural map of tectonic features; (2) determination of the basin center using concentric deviation analysis (Karagoz et al., 2024); (3) estimation of the multi-ring geometry through a newly developed tool that analyzes the radial distribution of mapped structures using one-dimensional kernel density estimation (KDE). In this step, dominant concentric rings are identified as statistically robust density maxima obtained with a Gaussian kernel and an objectively defined Silverman bandwidth, while ring uncertainty is quantified through the interquartile range (IQR) of associated structures; and (4) comparison of the inferred ring geometry with the basin’s median radial topographic profile, derived from 360 azimuthally distributed radial profiles, to assess geometric and morphological consistency. We apply this workflow to two basins of different confidence levels. For the Orientale basin on the Moon, the method identifies three concentric rings corresponding to the Inner Rook Ring, Outer Rook Ring, and Cordillera Ring, consistent with previous studies (Spudis et al., 2013). For the Andal–Coleridge basin on Mercury, a probable multi-ring basin, the workflow retrieves a four-ring geometry that broadly coincides with rings II–V proposed by Spudis & Guest (1988). These results demonstrate that the combined use of structural mapping, KDE-based ring detection, and radial profile analysis provides a robust and reproducible framework for investigating degraded multi-ring basins. Future work will apply this workflow to additional candidate basins on Mercury to reassess their multi-ring nature and improve constraints on the planet’s early impact and tectonic history.

Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2024-18-HH.0.

How to cite: Sepe, A., Ferranti, L., Galluzzi, V., Schmidt, G. W., and Palumbo, P.: A data-driven approach to multi-ring basin identification on Mercury, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23072, https://doi.org/10.5194/egusphere-egu26-23072, 2026.

How to cite: Liu, W.: An important medium for ion energization and non-thermal ions' energy release in the near-Sun solar wind: ion-scale waves , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-266, https://doi.org/10.5194/egusphere-egu26-266, 2026.

The plasma wave instruments on both Voyager spacecraft have observed electron plasma oscillations in the very local interstellar medium (VLISM).  The generally accepted explanation of these events is that the electron foreshock of shocks in the VLISM comprise electron beams in the range of 10 to 100 eV that are unstable to Langmuir waves, or electron plasma oscillations.  Further, at least some of these events have been tied to solar transients departing the Sun more than a year earlier that evolve as they propagate outward.  These disturbances are led by shocks and the impulse of these on the heliospause results in some of the shock impulse continuing into the VLISM.  Previously, Voyager 1 had detected the most distant evidence of these transients at about 145 AU.  In August 2025 Voyager 2 detected electron plasma oscillations near 140 AU. A simple model of the propagation of this disturbance suggests a transient from the Sun in 2022 as its source, near the beginning of the current solar maximum.  New Horizons observed a series of shocks in 2022 – 2023 at heliocentric distances near 55 AU that could be related to the Voyager 2 event. Given these events occur early in solar cycle 25, it is possible additional shocks will be detected by Voyager and enable us to extend the distance over which these disturbances can travel in the VLISM.

We further relate some of the transients observed by the Voyager plasma wave instruments to global models of the VLISM density and magnetic field (Fraternale et al., 2026).  For example, these models show the increased density and magnetic field associated with the so-called pf2 (pressure front 2) described by Burlaga et al. (2021).  We can now show that the 2-3 kHz radio emissions observed by the Voyagers in the early 1980’s, 1990’s, and 2000’s are related to density structures just beyond the heliopause presumed to be associated with global merged interaction regions stemming from very active solar conditions.

How to cite: Kurth, W., Jaynes, A., Fraternale, F., Kim, T., and Pogorelov, N.: Effects of solar transients observed in the VLISM , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4233, https://doi.org/10.5194/egusphere-egu26-4233, 2026.

Interpreting the response of the magnetosphere to solar wind driving is being historically limited by the sparse measurements of upstream conditions. Recent investigations, using multiple upstream monitors, revealed that properties of the solar wind are often non uniform on spatial scales comparable to the size of the Earth’s magnetosphere. This aspect remarks the limitation of the common assumption of the impact of a uniform solar wind front based on single probe observations. Here, we perform a critical investigation of a case study in which a particular solar wind mesoscale structure, in the form of a periodic density structure (PDS), shows coherence on a limited extent of the Earth’s upstream region. First, we examine the possible reasons behind discrepancies in the measurements among different solar wind monitors. Then, we discuss the response of the magnetosphere in terms of Ultra-Low-Frequency (ULF) waves based on properties of the solar wind driver including the periodicities of the PDSs, the extent of their spatial coherence, and the associated interplanetary magnetic field properties.

How to cite: Di Matteo, S., Recchiuti, D., and Villante, U.: Magnetosphere response to a spatially non-uniform solar wind stream, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15149, https://doi.org/10.5194/egusphere-egu26-15149, 2026.

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) (<1.5”) to observe the Sun’s corona.

We describe our progress in assembling and testing the instrument, which is built around COTS telescope optics and camera heads.  Alignment features facilitate fine positioning of the two pickoff mirrors and three camera heads.  Stray light control features prevent ‘sneak path’ rays from falling on the wrong detector. The instrument is designed to work in an airborne environment.  A thermal control subsystem incorporates four thermal zones, to maintain tight focus and alignment under dynamic environmental conditions, while a focus mechanism compensates for large changes in temperature.  The data path is sized to store full-resolution data from three 127 Mpixel cameras, at a rate of 10 GB/s. A real time viewer produces fused images from the three cameras for monitoring of the image acquisition process. 

MEGA-H is sponsored by HESTO,  NASA’s Heliophysics Science and Technology Office.

How to cite: Eskin, J., Caspi, A., DeForest, C., Oakley, P., Brown, B., Finch, T., Frye, J., Lage, J., Sharma, J., Speck, R., Spuhler, P., and Turner, R.: Status of MEGA-H: An Ultra-Wide-Field Camera for Heliophysics Applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15364, https://doi.org/10.5194/egusphere-egu26-15364, 2026.

Understanding star and planet formation in extreme environments is crucial for uncovering the origins of our solar system. While most knowledge comes from nearby, isolated regions such as Taurus and Lupus, over half of all stars and planetary systems form in environments exposed to strong far-ultraviolet (FUV) radiation emitted by massive OB stars, with energies below the Lyman limit (E <13.6 eV).

NGC 6357—a young (~1–1.6 Myr), massive star-forming complex located 1690 pc away and hosting over 20 O-type stars—provides a unique opportunity to study the effects of FUV radiation on protoplanetary disks. This is the focus of the XUE (eXtreme UV Environments) collaboration.

Here, we present results from XUE2, a disk in the Pismis 24 cluster, based on spectra from JWST/MIRI and VLT/FORS2, complemented by photometric data. We first characterize the central star through spectrophotometric fitting, a fundamental step since protoplanetary disks are shaped by their host stars.

To evaluate the potential for rocky planet formation, we conduct a molecular and mineralogical analysis of the disk. We identify CO and CO₂ and report a tentative detection of CH₃⁺, key molecules for organic chemistry. Additionally, we identify predominantly amorphous silicates, as well as crystalline species such as enstatite and forsterite—molecules and minerals also observed in disks exposed to lower irradiation levels.

These findings offer new insights into the composition of inner disk regions under strong FUV irradiation, helping to constrain the formation conditions of rocky planets in massive clusters—an essential contribution to understanding the origins of the diverse exoplanets observed today.

How to cite: Lemus Nemocon, M. A., Ramírez-Tannus, M. C., and Higuera Garzón, M. A.: Molecular and Crystalline Structures in a Highly Irradiated Protoplanetary Disk in NGC 6357, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21494, https://doi.org/10.5194/egusphere-egu26-21494, 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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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.

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 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.

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.

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 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 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, B_R or, equivalently, it is aligned with the level contours, B_R=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.

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.

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.

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.

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.

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.

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.

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.

     High-energy electrons in the heliosphere are significantly influenced by irregularities in the solar wind and interplanetary magnetic field. One of the most powerful and actively studied irregularities are interplanetary (IP) shocks. We used data from Solar Orbiter’s Solar Wind Analyser (SWA) and magnetometer (MAG), and the method developed by Yakovlev et al. (2025) to determine the relevant shock parameters. We identified 69 IP shocks which occurred at varying distances from the Sun.

      To demonstrate the variability in acceleration, dissipation, and absence of response of high-energy electrons across selected narrow energy bands, we analyzed data derived from the Suprathermal Telescope of Electrons and Protons (STEP), the Electron and Proton Telescope (EPT, Sun direction), and the High Energy Telescope (HET, Sun direction) of the Energetic Particle Detector (EPD) suite onboard Solar Orbiter. For a quick-look analysis, we demonstrate light curves of particle fluxes in a few energy ranges in the upstream/foreshock and downstream/aftershock regions.

     We also present selected parameters of the IP shock wave, including IP shock types (FF, SR, SF, FR), magnetic and gas compression factors, plasma beta parameters, shock angles, Alfvenic and magnetosonic Mach numbers, as well as Alfvenic and shock speeds.

     This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences, carried out in collaboration with the U.S. National Academy of Sciences, with the financial support of external partners”.

1. O. Yakovlev, O. Dudnik, A. Wawrzaszek. Statistical analysis of interplanetary shock waves measured by a Solar Wind Analyzer and a magnetometer onboard the Solar Orbiter Mission in 2023. Journal of Space Weather and Space Climate. 2025, 15, 32. https://doi.org/10.1051/swsc/2025027

How to cite: Dudnik, O., Yakovlev, O., Dudnik, B., Mason, G., Warmuth, A., Schuller, F., and Wimmer-Schweingruber, R. F.: Responses of energetic electrons to the interplanetary shock waves detected in 2024 with Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-363, https://doi.org/10.5194/egusphere-egu26-363, 2026.

     Interplanetary (IP) shock waves are one of the direct manifestations of solar activity impacting the normal state of the solar wind as it moves through the heliosphere. In the heliosphere, shocks can occur individually or in linked pairs. Linked shock pairs manifest as two successive compression fronts in the plasma, typically travelling in the same direction, but originating from different sources. One such source of paired shocks are corotating interaction regions (CIRs), where the fast solar wind from the coronal hole overtakes the slower solar wind. When that happens, the interaction creates compression regions at the boundaries of the solar wind flux, leading to sudden changes in its parameters and resulting in the formation of forward and reverse shocks.

     Another source of the formation of paired shock waves are coronal mass ejections (CMEs) that occur in various active regions (ARs), or sequential CMEs from the same ARs. Paired shock waves are an effective accelerator of energetic charged particles, which are fundamental to heliospheric dynamics. They also play a key role in modulating cosmic rays and triggering geomagnetic disturbances in the near-Earth space.

     Our study examines the main characteristics of the forward and reverse shock pair detected on May 21, 2024, when Solar Orbiter flew at a distance of 0.79 AU from the Sun, and about 170 degrees west of the Earth-Sun line. We discuss CMEs as sources of the shock pair, and present the main parameters of the forward and reverse shocks in the interaction region. The study is based on experimental data regarding the kinetic parameters of the solar wind and characteristics of the interplanetary magnetic field, as derived from instruments on the Solar Orbiter mission. We also discuss an abrupt increase in energetic ion fluxes within the interaction region of both shocks, as recorded by the Energetic Particle Detector (EPD) onboard the Solar Orbiter mission.

     This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.

How to cite: Yakovlev, O., Dudnik, O., Mason, G., Dudnik, B., Warmuth, A., Schuller, F., and Wimmer-Schweingruber, R. F.: Case study of the forward-reverse interplanetary shock wave pair in May 2024, detected by Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-435, https://doi.org/10.5194/egusphere-egu26-435, 2026.

The BepiColombo Environmental Radiation Monitor (BERM), currently travelling toward Mercury, and the Energetic Particle Detector (EPD) aboard Solar Orbiter are both monitoring the radiation environment in the inner heliosphere. Three Solar Energetic Particle (SEP) events, 2021-07-15, 2022-07-23 and 2023-03-13 were detected simultaneously by the two missions during intervals of favourable magnetic connectivity, providing valuable cases for comparative analysis and instrument intercalibration.

We investigated the interplanetary conditions of each event using solar wind plasma and magnetic field observations. Proton anisotropy measurements from Solar Orbiter enabled the identification of isotropic periods during the decay phase of the SEP events, from which representative proton spectra were derived. These spectra were then fitted and compared with BERM observations to obtain intercalibration factors.

Our results confirm a high level of agreement between the instruments. For the 2.15 MeV and 6.85 MeV proton channels, we obtained calibration factors of 0.95±0.10 and 1.02±0.30, corresponding to deviations of only 5% and 2%. These findings demonstrate the consistency of SEP measurements by BERM and EPD and highlight the valuable role that planetary missions can play in heliophysics research.

How to cite: Gomes, A., Rodríguez-García, L., Pinto, M., Gómez-Herrero, R., Rodríguez-Pacheco, J., Wimmer-Schweingruber, R., Jones, G., Besse, S., and Gonçalves, P.: Intercalibration between energetic particle instruments BERM onboard BepiColombo and EPD aboard Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-723, https://doi.org/10.5194/egusphere-egu26-723, 2026.

The Sun is the most efficient particle accelerator in the solar system, capable of accelerating particles such as electrons and protons to relativistic energies. Solar Energetic Particles (SEPs) are known to be accelerated both at solar flare reconnection sites and by shocks driven by coronal mass ejections. One way to distinguish between these two SEP acceleration mechanisms is through their energy spectra, either fluence or peak intensity.
While the spectral breaks commonly observed in solar energetic electron (SEE) spectra may represent signatures of the acceleration process, several transport-related effects have also been proposed as their origin. In this study, we analyse the energy spectra of intense SEE events measured by Solar Orbiter’s Energetic Particle Detector (EPD) between December 2020 and December 2022. EPD’s unprecedented energy resolution enables us to identify spectral features with greater detail than previously possible.
We investigate the shape of SEE spectra by fitting them with a range of mathematical models. Our results are compared with previous studies, and we explore possible connections to transport-related effects. In addition, we examine potential correlations between spectral features and parameters such as radial distance or properties of the associated solar events.
Our analysis reveals four distinct spectral shapes: single power-law, double power-law, and two types of triple power-law spectra, namely knee–knee (KK) and ankle–knee (AK) forms. No significant correlations with radial distance are found. However, the observed spectral shapes exhibit an ordering with respect to the longitudinal separation between the spacecraft and the associated solar flare.
We conclude that multiple processes likely contribute to shaping SEE spectra. Our results suggest that the two breaks observed in KK triple power-law spectra arise from distinct physical effects, namely Langmuir-wave generation and pitch-angle scattering. Furthermore, the break in double power-law spectra may represent a merger of the first and second breaks seen in KK triple power-law spectra.

How to cite: Fedeli, A., Dresing, N., Gieseler, J., Warmuth, A., Schuller, F., Gómez-Herrero, R., Jebaraj, I. C., Espinosa, F., and Vainio, R.: Peak-intensity energy spectra of intense solar energetic electron events measured with Solar Orbiter in 2020-2022, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6758, https://doi.org/10.5194/egusphere-egu26-6758, 2026.

In this work we incorporate Solar Orbiter’s Polarimetric and Helioseismic Imager (PHI) Full Disc Telescope (FDT) observations into the Air Force Data Assimilative Photospheric flux Transport (ADAPT) model to construct more complete global solar photospheric maps. We feed these maps into the Wang-Sheeley-Arge (WSA) model to reconstruct the solar corona and perform solar wind simulations for a period of two months in 2024 at multi-spacecraft locations (Solar Orbiter, PSP, ACE, STEREO-A). We assess the quality of our predictions, and compare our results when no FDT data have been employed in order to understand how the addition of far side information affects the open magnetic field topologies on the Sun, their connectivity with various spacecraft of interest, the shape and structure of the heliospheric current sheet, as well as the solar wind predictions at different points in the interplanetary space. Our results demonstrate the value of incorporating far-side information in improving the heliospheric modeling and forecasting globally, as well as the significance of 4pi continuous monitoring of the Sun for more reliable space weather predictions overall.

How to cite: Samara, E., Arge, C. N., Schonfeld, S., Farrish, A., Henney, C., Nieves-Chinchilla, T., and Wallace, S.: The influence of Solar Orbiter/PHI far-side information on coronal holes and solar wind predictions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7556, https://doi.org/10.5194/egusphere-egu26-7556, 2026.

Solar Orbiter is able to cover the far-side of the Sun for almost 6 months every year. This allows us to detect far-side flux emergence or disappearance events that remain undetected at Earth for several days. We showed in a previous study that these events, although located on the other side of the Sun, can affect the modeling of the Sun-Earth chain and change space weather previsions (Perri et al. 2024).

Our aim is to scan Solar Orbiter/PHI data in order to provide a catalogue of the major far-side events undetected at Earth.

We scan data for the period 2022-2024, and for each year we look at the data between March and September where the far-side coverage is the best. We combine SO/PHI maps with SDO/HMI, and compare them with GONG-ADAPT synoptic maps used in space weather forecasts. We use a specific post-processing in order to make the data comparable, and find criteria and thresholds to help us detect major differences between day-side and far-side magnetic fields.

We find a list of 27 true flux-emergence events, and an additional list of 3 events where a decaying active region actually regained an intense magnetic field. The delay between the far-side and the Earth field of view detection ranges from 2 to 15 days, with a peak at 12. All these far-side emergence events take place at low latitudes (between -25 and 30) due to the fact that we are at the beginning of solar cycle 25. However, they appear at all longitudes (no active longitude for this kind of events). They all show a similar size (about 10 degrees in both latitudinal and longitudinal extent). We compare these observations with far-side maps from both GONG and HMI websites, and find an average delay of 4 days for the detection for HMI, and 7 days for GONG.

This catalogue can be used to improve space weather forecasts, and shows the need for synchronic views of the Sun.

How to cite: Perri, B., Legrand, H., Brun, A. S., Finley, A., and Strugarek, A.: Far-side active region emergence catalogue from Solar Orbiter/PHI, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7581, https://doi.org/10.5194/egusphere-egu26-7581, 2026.

Stream interaction regions (SIRs) are formed where high-speed streams from coronal holes expand into slower preceding solar wind. Simulations have long shown significant latitudinal structuring to SIRs and their associated energetic populations, which have been additionally suggested from high-latitude Ulysses observations. However, multi-point observations of SIRs from observers at different latitudes are needed to constrain this variability. This includes better understanding the role of coronal hole properties and impacts of latitudinal variability in the preceding slow solar wind streams on the evolution of SIR structures. In this presentation, we focus on recent off-ecliptic Solar Orbiter observations in comparison with observations at ACE and STEREO-A to further explore the importance of latitudinal structuring of SIRs and associated energetic particles. 

How to cite: Allen, R., Ho, G., Mason, G., Walker, M., Davis, S., Wimmer-Schweingruber, R., Rodriguez-Pacheco, J., Vines, S., Li, G., Filwett, R., and Dayeh, M.: Latitudinal Variability of Stream Interactions Regions: Multi-spacecraft Comparisons with Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12435, https://doi.org/10.5194/egusphere-egu26-12435, 2026.

Since April 2023, solar flares have been simultaneously observed by the Spectrometer/Telescope for Imaging X-ray (STIX) onboard ESA’s Solar Orbiter and by the Hard X-ray Imager (HXI) onboard the Chinese ASO-S mission. The two telescopes independently measure 2D Fourier components (visibilities) of the flaring X-ray radiation from different vantage points. However, by combining their datasets, it is possible to obtain a sampling of the 3D Fourier transform of thermal hard X-ray sources in solar flares. This combined dataset allows reconstructing the 3D morphology of the flaring sources by solving an inverse imaging problem.

In this presentation, we describe the methodology we developed for 3D reconstruction of thermal hard X-ray sources in solar flares from combined STIX/HXI data. We present the results obtained in the case of the X9.1 GOES class event which occurred on October 3, 2024. During this event, the two instruments were in an ideal configuration, where the separation angle between them and the flaring site was approximately 90 degrees. We validate the 3D reconstruction by comparing them with the 2D images independently reconstructed from STIX and HXI data. Finally, we determine the altitude of the reconstructed X-ray source above the solar surface as a function of time, and we derive estimates of its radial velocity. 

How to cite: Palumbo, B., Massa, P., Stiefel, M., Ryan, D., Collier, H., Su, Y., Piana, M., and Krucker, S.: 3D reconstruction of thermal hard X-ray sources in solar flares from combined STIX and HXI visibilities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12658, https://doi.org/10.5194/egusphere-egu26-12658, 2026.

Particles in the solar wind show a variety of deviations from thermodynamic equilibrium. These non-thermal features include secondary particle beams drifting relative to the main core population. Several mechanisms have been proposed to explain the formation of such beams, but the topic remains debated.
Recently, thanks to the excellent energy resolution of the Proton Alpha Sensor (PAS) on board Solar Orbiter, the technique described in De Marco et al. (A&A, 2023) has made it possible, in many cases, to clearly identify, not only proton beam, but also the more elusive alpha-particle beam. In this preliminary work, we present observations in which the proton velocity distribution function, instead of following a simple core+beam scenario, displays a more complex structure, exhibiting modulations consistent with the superposition of several sub-populations. Such multi-beam configurations are typically short-lived, representing transient stages in the evolution of proton beams. These observations indicate that proton populations may be continuously reshaped by local kinetic processes, providing an observational basis for future studies on the formation and evolution of multiple proton populations. Furthermore, these complex distributions can offer valuable insight into wave–particle interactions in the solar wind, helping to connect kinetic-scale structures with plasma turbulence and instabilities.

How to cite: De Marco, R., Dhamane, O. S., D'Amicis, R., Benella, S., Perrone, D., and Bruno, R.: Observations of multiple ion populations in solar wind velocity distributions with Solar Orbiter-PAS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13538, https://doi.org/10.5194/egusphere-egu26-13538, 2026.

Solar flares and associated eruptions are a known source of solar energetic particles (SEPs), but it is often challenging to establish a precise link between individual flares and SEP events measured in-situ throughout the heliosphere. The Solar Orbiter mission, with its Spectrometer/Telescope for Imaging X-rays (STIX) and Energetic Particle Detector (EPD), provides excellent measurements for systematic studies of these phenomena. Based on these data, we developed an algorithm that automatically links solar flares to SEP electron events using a STIX flare list, SEP electron measurements from EPD, and considering model predictions of magnetic connectivity between the Sun and the spacecraft. As a result, the method identifies several hundred flares to be connected to SEP events - out of more than 25000 flares detected with STIX between 2021 and 2025.  The precise linkage criteria can be set by the user - including the accepted distance between flare and modelled magnetic footpoint and the length of the accepted time window for SEP arrival.  A first comparison of the automatic method with the CoSEE-Cat electron event catalogue for the time period 2021 - 2022 shows, that about 50% of the links found by the algorithm are actual physical links. The method is already available as quick-look online tool for flare-SEP linkage.

How to cite: Janitzek, N., Jentgens, H., Kistler, F., Bischof, L., Stiefel, M., Barczynski, K., Zhu, Y., Harra, L., Gomez-Herrero, R., Warmuth, A., Rouillard, A., Wimmer-Schweingruber, R., Rodriguez-Pacheco, J., and Krucker, S.: An automated approach to link solar flares and energetic particle events measured with Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16991, https://doi.org/10.5194/egusphere-egu26-16991, 2026.

The transport of solar energetic particles (SEPs) through the heliosphere is governed by the interplanetary magnetic field (IMF) embedded in the solar wind plasma. Large-scale fluctuations in the IMF give rise to the transient variation in SEP intensities. Here, we present Solar Orbiter (SolO) observations of a distinct class of SEP flux variations: short-timescale (~1 hr) directional flux reversals (DFRs). Data from the Energetic Particle Detector (EPD) reveal that these reversals are a common feature in SEP events, occurring simultaneously across a wide energy range (keV to tens of MeV) and exhibiting steep intensity gradients. Unlike classic 'dropout' events—where intensity decreases isotropically—DFRs display a asymmetric signature where a intensity drop in one direction coincides with a spike in another. These intermittent variations are associated with flux-rope magnetic structures and distinct solar wind properties, which serves as direct evidence that the spacecraft has encountered a new solar wind stream with a different magnetic field connectivity. These observations demonstrate that SEPs act as an effective probe of solar wind structures, providing new insights into their nature.

How to cite: Chen, X. and Li, G.: Probing Solar Wind Structures with Solar Energetic Particle Observations from Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17968, https://doi.org/10.5194/egusphere-egu26-17968, 2026.

Forbush decreases (FDs) are one of the very common in-situ signatures of interplanetary coronal mass ejections (ICMEs) throughout the heliosphere. These short-term reductions in the galactic cosmic ray flux are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). We recently developed an analytical model to explain CME-related FDs using an expansion-diffusion approach and utilized it to develop a best-fit procedure (ForbMod, Dumbovic et al., 2024). According to the model, the amplitude of the depression at a given point in the heliosphere depends on the initial CME properties as well as its evolutionary properties.

We develop a scheme that will allow us to analyze CME evolution using a set of CME-ICME-FD observations, as well as in situ measurements only, and design a graphical user interface to perform ICME and FD analysis throughout the heliosphere. We measure, catalogue and analyse ICMEs and related FDs using Helios, Ulysess, SOHO and Solar Orbiter spacecraft, as well as ground-based measurements from the South Pole neutron monitor at Earth and MSL/RAD at Mars. This research was partly funded by the European Space Agency (projects ForbMod and ForbMod2) and partly by European Union (project SPEARHEAD, No 101135044). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency (HaDEA). Neither the European Union nor the granting authority can be held responsible for them.

How to cite: Dumbovic, M., Bernd, H., Malte, H., Marlon, K., Athanasios, P., Alexander, M., Ilya, U., Jan, G., Erika, P., Akhay Kumar, R., Galina, C., and Anamarija, K.: Measuring Forbush decreases and probing CME evolution throughout the heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18496, https://doi.org/10.5194/egusphere-egu26-18496, 2026.

This presentation will provide a status update of the ESA/NASA Solar Orbiter mission and summarise recent science highlights.

Solar Orbiter has been acquiring unique data from as close as 0.29 au solar distance since 2022, combining in situ measurements close to the Sun with simultaneous high-resolution solar imaging and spectroscopic observations. These multi-instrument data have enabled the science community to address fundamental solar physics questions, including determining the linkage between observed solar wind streams and their source regions on the Sun. Solar Orbiter’s science return is significantly enhanced by coordinated observations with other space missions, as well as ground-based telescopes.

In 2025, Solar Orbiter’s out-of-ecliptic mission phase started, acquiring first detailed observations of the Sun’s unexplored polar regions from 17° heliolatitude. During its proposed mission extension, Solar Orbiter will successively increase its maximal inclination to 24° in January 2027, 30° in April 2028 and 33° from July 2029 onwards. This phase is opening a new frontier in solar physics, with the prospect of revolutionising our understanding of magnetic flux transport and the solar dynamo.

How to cite: Müller, D., Janvier, M., De Groof, A., Williams, D., Walsh, A., Fischer, C., Osuna, P., Nieves, T., and Lario, D.: Solar Orbiter: Mission status and science highlights, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18646, https://doi.org/10.5194/egusphere-egu26-18646, 2026.

The extreme-ultraviolet (EUV) brightenings identified by Solar Orbiter, commonly known as “campfires”, are one of the fine-scale transient brightenings detected in the solar corona. Using closest-perihelion observations of Extreme-Ultraviolet Imager (EUI) onboard Solar Orbiter, recently we have reported the presence of smallest and shortest-lived EUV brightenings in the quiet-sun to date. We will present the spatio-temporal distribution of EUV brightenings over different magnetic environments of the solar atmosphere and discuss their role in coronal heating. By using various sets of quiet-sun and coronal-hole observations from HRIEUV/EUI we will present a comparative analysis of morphological and photometrical properties of EUV brightenings. We will discuss the interlinks of EUV brightenings to the photospheric dynamics and magnetic field distribution using HRT/PHI observations. Further their potential coupling through the solar atmosphere will be addressed using SPICE and IRIS observations.

How to cite: Narang, N., Verbeeck, C., Berghmans, D., Mierla, M., Parenti, S., Auchere, F., Chitta, P., and Calchetti, D.: Influence of magnetic-field distribution on the spatio-temporal properties of EUV brightenings in the solar atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19475, https://doi.org/10.5194/egusphere-egu26-19475, 2026.

We present a comprehensive catalogue of 212 Solar Energetic Particle (SEP) events observed by the High Energy Telescope (HET) of the Energetic Particle Detector (EPD) onboard Solar Orbiter during the ascending and maximum phases of Solar Cycle 25 (2020–2025). The survey is based on combined measurements of approximately 1 MeV electrons and 8 MeV protons, and includes a substantial subset of events with proton energies exceeding 25 MeV and 50 MeV, providing broad coverage of energetic particle conditions in the inner heliosphere. SEP events were identified through statistically significant enhancements above background levels. For each event we derived key parameters, including onset and peak times, peak intensities, fluences, and electron-to-proton (e/p) ratios. Particle release times at the Sun were estimated using both time-shifting and velocity-dispersion analysis (VDA) techniques. These release times were compared with observations of solar flares and associated coronal mass ejections (CMEs) in order to identify the most probable parent solar sources and to investigate the relationship between SEP characteristics and eruption properties. In situ measurements of the solar wind plasma and interplanetary magnetic field were further employed to characterize the heliospheric environment of each event and to compute magnetic connection angles, enabling an assessment of the role of magnetic connectivity in SEP onset and intensity. We also examine the diagnostic value of e/p ratios and elemental abundance signatures for distinguishing between impulsive and gradual SEP events. As part of this work, we developed two open-source tools—SEP-PACT for catalogue construction and VDA for release-time analysis—available via the SPEARHEAD GitHub repository (https://github.com/spearhead-he). The complete catalogue will be released through Zenodo and the SPEARHEAD web interface (https://spearhead-he.eu), providing a valuable resource for future studies of SEP acceleration and transport in the inner heliosphere. 

Acknowledgement: The is work has received funding from the European Union’s Horizon Europe programme under grant agreement No 101135044 (SPEARHEAD).

How to cite: Papaioannou, A. and the SPEARHEAD Collaborative Network: Solar Energetic Particle Events in the Inner Heliosphere: Observations from Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19554, https://doi.org/10.5194/egusphere-egu26-19554, 2026.

Magnetic switchbacks, often observed in the near-Sun solar wind, have received increased interest in recent years due to their potential role in mediating the heating and acceleration of the solar wind, but their origin remains debated. In this work, we present a coordinated observation of a switchbacks cluster by BepiColombo (0.35 au) and Solar Orbiter (0.67 au), obtained during the alignment between 6-8th October 2021, which enabled the direct investigation of switchbacks evolution across heliocentric distances. In particular, the stream observed by the spacecraft can be tracked back to the boundary of an equatorial coronal hole. Plasma and magnetic field data measured in-situ exhibit remarkable similarities at both locations. In particular, larger-scale switchbacks exhibit strong sub-linear expansion, thus appearing almost unevolved in morphology during the propagation when the spacecraft cutting-angle effect is taken into account. The stable magnetic configuration of the analyzed switchbacks suggests that they can be identified as small-scale flux ropes. Indeed, for shear-driven instabilities triggered by stream interaction with the background slow wind, short-living (one eddy turnover time, $\tau \sim 1$ hr) switchbacks would be expected compared to the travel time from BepiColombo to Solar Orbiter ($\sim 38$ hr). These findings provide critical insights on switchbacks origin and evolution, potentially constraining future phenomenologies on their formation. A useful consequence of our observations is that statistical analyses on switchbacks evolution should always account for the cutting-angle effect.

How to cite: Stumpo, M., Benella, S., Di Bartolomeo, P. P., Milillo, A., Heyner, D., Nicolaou, G., Varsani, A., Larosa, A., Pezzi, O., Trotta, D., Laurenza, M., D'Amicis, R., Laky, G., and Jeszenszky, H. and the BepiColombo/MPO-MAG TEAM: Long-lived magnetic switchbacks tracked across 0.32 au through BepiColombo-Solar Orbiter radial alignment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21309, https://doi.org/10.5194/egusphere-egu26-21309, 2026.

The Proton Alpha Sensor (PAS), part of the Solar Wind Analyzer (SWA) onboard Solar Orbiter, has been designed to measure the full 3D ion velocity distribution function (VDF) at time cadence larger than one sample per second, thus, faster than the typical proton cyclotron period (Burst mode). Unfortunately, due to software difficulties, this capability to explore ion kinetic processes has been only activated during the first months of operation (2020-mid 2021) so that the ‘normal mode’ cadence (1 VDF each 4 s) was systematically used from 2021 to 2024. After in-depth analysis, a new software version has finally been implemented at the end of 2024, restoring in part the PAS burst mode capability. As a result, an impressive set of continuous full 3D VDF measurements at 1 s cadence has been obtained in 2025. More recently, we have fully restored the PAS burst mode. Since December 2025, PAS is then operated at a continuous 1 s cadence, with 8 bursts of 5 minutes per day during which full 3D measurements at 2 or 4 Hz, thus below the proton cyclotron period, are performed. As illustrated by examples (waves, sharp gradients, turbulence, shocks), this obviously re-opens a window to study various dynamical plasma phenomena at ion kinetic scales.

How to cite: Louarn, P., Fedorov, A., Barthe, A., Penou, E., Génot, V., Fargette, N., Kieokaew, R., Plotnikov, I., Réville, V., Rouillard, A., Lavraud, B., Prech, L., D'Amicis, R., Raines, J. M., Lewis, G., and Owen, C. J.: The Solar Wind at ‘short scales’: Observations at second and sub-second cadences with PAS/SWA. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21760, https://doi.org/10.5194/egusphere-egu26-21760, 2026.

Abundance ratios of heavy ions in the solar wind can be used to probe the low solar corona through the freeze-in and First Ionization Potential (FIP) effects, while their speeds and temperatures can probe both collisionless and collisional processes in the solar wind. We present results demonstrating how heavy ion properties act as diagnostics for phenomena spanning different regimes within the heliosphere. Through a cross-correlation analysis between heavy ion density ratios and proton specific entropy from 1998-2011, we find that the variability in solar wind fluid entropy freezes-in between approximately 1.4-1.8 solar radii in heliocentric distance, constraining time-dependent processes in solar wind formation. Additionally, by incorporating proton temperature anisotropies to compare with heavy ion temperatures, we observe that certain heavy ion species are less subject to the CGL conditions in the highly collisionless solar wind than protons are, placing constraints on inter-species energy partitioning. These analyses, based on measurements of heavy ions at 1 AU, can be extended to data collected by the Heavy Ion Sensor onboard Solar Orbiter. Through the incorporation of proton anisotropies and heavy ion measurements across variable heliocentric distances, these extended analyses will further probe the thermodynamic evolution of the solar wind.

How to cite: Nakhleh, A., Viall, N., Lepri, S., and Raines, J.: Heavy Ion Properties as Diagnostics of Solar Wind Thermodynamic Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22023, https://doi.org/10.5194/egusphere-egu26-22023, 2026.

We present an analysis of internal oscillations observed in a solar prominence located at the eastern limb on 26 September 2022. The prominence axis is oriented nearly parallel to the line of sight (approximately perpendicular to the limb), providing a particularly favorable geometry for the simultaneous detection of intensity variations and Doppler-shift signatures. Wavelet analysis was performed on ground-based H-α observations from the Solar Dynamics Doppler Imager (SDDI), complemented by space-based data from the SDO/AIA 304 Å and STEREO-A 304 Å channels. These chromospheric diagnostics of cool prominence plasma were further supplemented by coronal observations from UCoMP. The primary aim of this study is to compare oscillation periods detected within the prominence body with those present in the surrounding coronal environment, allowing us to investigate the coupling between cool chromospheric material and the overlying hot coronal plasma. The prominence is embedded within a well-developed coronal cavity, indicative of strong magnetic structure and a significant decrease of ambient coronal density.

How to cite: Wiśniewska, A., Koza, J., Muro, G., and Ichimoto, K.: Multi-Diagnostic Investigation of Solar Prominence Oscillations from the Chromosphere to the Corona, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2447, https://doi.org/10.5194/egusphere-egu26-2447, 2026.

Recent advances in space-based solar instrumentation, from missions such as Parker Solar Probe, Solar Orbiter, Proba3, Aditya, and PUNCH, have significantly expanded our ability to observe the solar corona across a wide range of wavelengths, spatial scales, and observational geometries. By combining EUV imaging with white-light coronagraphic and heliospheric observations, both static and dynamic coronal structures can now be investigated in unprecedented detail. Recent advances in coronal polarimetry provide new opportunities to probe the coronal magnetic field, offering additional constraints on the 3D geometry of coronal mass ejections (CMEs) and on the dynamics of the expanding corona. Special focus lies on the onset of CMEs, which can be tracked continuously from their low-coronal onset through the early stages of their outward propagation. This contribution highlights the synergy between these complementary observations, demonstrating how multi-passband and multi-vantage-point measurements provide new insights into CME initiation, further evolution, and coronal structuring.

How to cite: Temmer, M.: Tracing CME Initiation from the Low Corona to the Inner Heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3392, https://doi.org/10.5194/egusphere-egu26-3392, 2026.

Magnetic reconnection at the near-Sun heliospheric current sheet (HCS) dissipates the Parker spiral and converts magnetic energy into kinetic energy of the plasma constituents. Observations at a radial distance of ~16.25 Rs by Parker Solar Probe associated with the encounter 14 (E14)  HCS crossing have shown that reconnection-driven particle acceleration mechanisms, likely facilitated by the merging of large-scale flux tubes, are able to accelerate protons up to ~400 keV, which is ≈1000 times greater than the available magnetic energy per particle during this crossing (Desai et al. 2025; Phan et al. 2024). In this paper, we present a detailed analysis of the pitch-angle distributions, differential energy spectra, and maximum energies and spectra of protons and heavy ions (He, O, and Fe) in conjunction with observations of local wave activity during the E14 HCS crossing. Our results show the following: 1) First direct observations of the energization of protons and heavy ions during reconnection. 2) First direct observations that the power-law spectral slopes of heavy ions differ from that of protons, which contradicts previous simulation results where the spectral indices of all ion species are essentially identical. 3) First demonstration that the anisotropies and beams of ions produced during reconnection drive waves in the ion cyclotron range of frequencies. 4) First evidence that the pitch angle scattering of protons is stronger than that of the other ion species and that this might be responsible for the harder spectral slopes of the heavy ions compared with protons.  In summary, PSP observations during the E14 HCS crossing provide strong evidence for in-situ reconnection-driven acceleration of protons and heavy ions at the near-Sun HCS that will need to be fully accounted for by contemporary reconnection-driven energization models.

How to cite: Desai, M., Drake, J., Swisdak, M., Fitzmaurice, A., McComas, D., Bale, S., Phan, T., Berland, G., Mitchell, D., Cohen, C., Hill, M., Christian, E., Schwadron, N., McNutt, R., Matthaeus, W., Rahmati, A., Whittlesey, P., Livi, R., and Larson, D.: Proton and Heavy Ion Acceleration by Magnetic Reconnection at the near-Sun Heliospheric Current Sheet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3589, https://doi.org/10.5194/egusphere-egu26-3589, 2026.

The origin of the proton beam, a secondary proton population observed in the solar wind, remains unclear. Measurements made by the Solar Probe Cup (SPC) instrument onboard Parker Solar Probe (PSP), together with earlier observations from the Helios mission, suggest that the relative proton beam abundance increases from the Sun to Earth. In addition to the SPC, the PSP is equipped with the SPAN-I instrument which measures ion velocity distribution functions (VDFs) during the PSP’s perihelia that are not covered by the SPC instrument. However, the limited field of view of the SPAN-I instrument prevents direct observation of the full ion VDFs. We apply the Gyrotropic Slepian Reconstruction method (Das and Terres, 2025b) to recover the full ion VDFs and perform bi-Maxwellian fitting to derive the parameters of the proton core and beam populations. We observe that the drift velocity of the proton beam remains close to the local Alfvén speed, even at small heliocentric distances. This finding suggests that the proton beam formation may be related to the reconnection processes near the Sun. Thus, we focus on variations of the proton beam parameters across switchbacks. In addition, we investigate the radial evolution of the proton beam parameters using combined observations from PSP and Solar Orbiter.

How to cite: Satyasmita, S., Durovcova, T., Das, S. B., Terres, M., Nemecek, Z., and Safrankova, J.:  Processing of ion VDFs from the SPAN-I measurement onboard Parker Solar Probe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5277, https://doi.org/10.5194/egusphere-egu26-5277, 2026.

Parker Solar Probe and Solar Orbiter are revolutionising our understanding of the Sun’s corona and wind by providing an unprecedented multi-scale view of the inner heliosphere. The Fast Wind Connection Science Solar Orbiter Observing Plan (Fast Wind SOOP) in Spring 2025 highlighted the complementary nature of these missions. Following a Venus gravity assist in February 2025, Solar Orbiter increased its orbital inclination to begin investigating the Sun’s polar regions. In March 2025, with the Sun near activity maximum, Parker Solar Probe, Solar Orbiter, and near-Earth satellites intercepted fast solar wind (600-800 km/s) originating from a large trans-equatorial coronal hole within a few days of one another. Parker Solar Probe’s 24th perihelion sampled pristine, sub-Alfvénic solar wind around 10 solar radii, while Solar Orbiter conducted a latitudinal scan at 60–70 solar radii. The variation in radial distance and latitude between the two spacecraft provided valuable insight into the structuring of the solar wind at large scales. While Solar Orbiter targeted high resolution imaging and spectroscopy of the solar wind source regions, supported by observations from Hinode and IRIS. These coordinated campaigns are allowing us to investigate the physical process that heat, accelerate and structure the solar wind at both large and small scales.

How to cite: Finley, A.: Results from the Spring 2025 Fast Wind Connection Science Campaign: Coordinated Sub-Alfvénic and Out-of-Ecliptic Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5633, https://doi.org/10.5194/egusphere-egu26-5633, 2026.

Parker Solar Probe (PSP) has observed strong perpendicularly diffused proton beams in velocity distribution functions. These were first reported by Verniero et al 2022 and termed as so-called hammerhead VDFs. Attempts to numerically simulate the formation of hammerheads have yet to produce results in alignment with spacecraft observations. This necessitates detailed statistical studies of the occurrence conditions and the associated plasma processes in order to better guide simulations. We developed a Python-based, open-source and fast hammerhead detector called hampy and investigated 20+ recent encounters of PSP data starting from E04. We also carry out detailed field-of-view (FOV) analysis to disqualify the hammerhead detection being a consequence of FOV-biased detection. Our results show that hammerheads dominantly occur around the heliospheric current sheet (HCS). As the HCS goes from being flat to vertical over the solar cycle (going from early to later PSP encounters), the occurrence of hammerheads are seen to pile up in narrow bounds around the HCS with progressively later encounters. We also characterize the hammerhead populations across encounters and heliospheric distance to study trends in the anisotropy of the proton beam and its connection to the density of proton beams as well as the drift speed of the beam to the core.

How to cite: Das, S. B., Verniero, J., Badman, S., Alexander, R., Terres, M., Paulson, K., Shankarappa, N., Fraschetti, F., Rivera, Y., Carcaboso, F., Larson, D., Livi, R., Rahmati, A., and Stevens, M.: Dominant occurrence of hammerhead velocity distributions close to the heliospheric current sheet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8461, https://doi.org/10.5194/egusphere-egu26-8461, 2026.

Understanding how erupting prominences evolve while propagating into the middle corona is essential for constraining the early phase of coronal mass ejections (CMEs).
This study aims to investigate the evolution of erupting prominences across the transition from the inner to the middle corona by Solar Orbiter EUI/FSI EUV observations with Metis coronagraph images. The unique characteristics of these instruments—notably the large field of view of the FSI imager, the overlap between their FOVs together with the high-cadence sequences acquired during Remote Sensing Windows—enable the construction of continuous mosaics. These mosaics trace prominence dynamics and morphology seamlessly from their onset in the low corona up to several solar radii. As part of this project, we are developing EUIMET, a dedicated tool that generates EUI/ FSI - Metis mosaics from calibrated data and provides configurable enhancement techniques and opacity level options to optimize the visibility of faint key coronal features.

We apply this method to the spectacular polar crown eruption of 20 October 2023, jointly observed by both instruments, and perform an in-depth morphological and kinematic characterization using triangulation and time–distance analyses. This case study serves as a proof of concept for future systematic investigations of eruptive prominences observed simultaneously in EUV, UV, and with-light regimes.

By providing a unified view of prominence evolution across the middle corona, this work aims to improve our understanding of CME initiation and propagation processes. The developed mosaic tool and data products will be made publicly available to support the solar physics community.

How to cite: De Leo, Y., Di Lorenzo, L., Jerse, G., Zhuang, B., Cremades, H., Temmer, M., and Romoli, M.: Investigating the evolution of erupting prominences seamlessly using mosaics of EUI/FSI and Metis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9643, https://doi.org/10.5194/egusphere-egu26-9643, 2026.

Understanding how energy is transferred in the solar wind is a fundamental problem in heliophysics. A primary source of energy in the solar corona and solar wind is the ubiquitous presence of both coherent and incoherent waves. In particular, recent observations from the Parker Solar Probe (PSP) have provided compelling evidence for the role these waves play in transferring energy to the plasma, offering new insights into the microphysical processes governing solar wind dynamics. Here, we propose a new method to identify coherent and incoherent waves using measurements from PSP. Using the resulting datasets, we investigate the distribution of magnetic helicity in two-dimensional wavenumber space and examine the evolution of turbulence imbalance at sub-ion scales. These results provide new observational constraints on the formation and evolution of turbulence in the near-Sun solar wind.

How to cite: Zhao, J.: Observations of Coherent and Incoherent Waves in the Near-Sun Solar Wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10907, https://doi.org/10.5194/egusphere-egu26-10907, 2026.

The solar wind shows different electrons populations, namely, the core, a thermalized isotropic component, and the suprathermals, at energies larger than a few kT, which exhibit non-gaussian energy tails. The latter is divided among an isotropic halo and the strahl population which we can describe as an excess of electrons aligned with the magnetic field line direction.

For this study, we aim at characterizing the strahl electrons distributions and their radial evolution in the close neighborhood of the Sun. For this purpose we study their pitch angle width (PAW) and look for correlations between this quantity and other local plasma or magnetic field parameters. Using the data of the 17th first encounters from Parker Solar Probe plasma analyzers (SPAN-e and SPAN-i) and magnetometers (FIELDS-MAG).

We explore the repartition of the SPAW in a parameter space including distance to the Sun, plasma moments (n, T, v, ...) and magnetic fluctuations properties (alfvenicity, intensity of fluctuations, etc.). 
First, we show that Coulomb collisions are the main scattering process closer than 35 solar radii, a region where the SPAW decreases with distance to the Sun - this is a first unambiguous and quantitative observation of the effect of coulomb collisions on suprathermals.
Further away from the Sun, we identify two solar wind type of streams : one in which SPAW are very small, and one characterized by large SPAW. The characteristics of magnetic fluctuations and background plasma properties in these two type of streams are identified, and we discuss the possible reasons of the existence of these low and high scattering regimes.

How to cite: Cherier, E. and Zaslavsky, A.: Scattering of the suprathermal electrons in the solar wind : diagnostic with Parker Solar Probe data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10954, https://doi.org/10.5194/egusphere-egu26-10954, 2026.

The WISPR instrument onboard Parker Solar Probe (PSP) has provided unprecedented observations of the solar corona, revealing fine-scale structures with exceptional spatial and temporal resolution. Among the most prominent features observed are circle or oval shaped transient density enhancements, commonly referred to as blobs. WISPR images are densely populated with these bright, quasi-circular features. We apply a machine learning (ML)–based approach for automatic blob detection, to handle variations in blob size, brightness, and image background complexity. When applied to multiple PSP encounters (E1-E24), this method reveals a clear increase in the number of detected blobs with decreasing heliocentric distance, in agreement with expectations from coronal dynamics and density dropoff. In addition, we find a significantly higher number of blobs in the aftermath of coronal mass ejections (CMEs). The structures can originate from different physical processes including tearing instabilities at the post–coronal mass ejection (CME) current sheets, interchange reconnection in the corona and magnetic reconnection between flux ropes and the ambient solar wind. This ML-based approach enables robust blob detection across varying observational conditions and provides new insights into the spatial distribution and evolution of coronal density structures in the near-Sun environment.

How to cite: Cappello, G., Temmer, M., Li, Y., Jarolim, R., Liewer, P. C., and Bothmer, V.: Automatic Detection of Blobs in WISPR/Parker Solar Probe Data Using a Machine Learning Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11653, https://doi.org/10.5194/egusphere-egu26-11653, 2026.

For the first time in the history of solar physics,  the solar corona can be observed in its entirety radial extent . This achievement is made possible by the combined capabilities of a new generation of spaceborne coronagraphs—ASPIICS/PROBA‑3 probing the inner corona, Metis aboard Solar Orbiter covering the mid‑corona, and LASCO on SoHO together with CCOR aboard GOES19  and PUNCH extending the view outward. Together, these instruments provide unprecedented multi‑passband coverage from approximately 1.1 up to 30 solar radii.

Within this emerging observational framework, Metis plays a pivotal role. Its simultaneous visible‑light and ultraviolet HI Lyman‑α imaging, when integrated with complementary measurements from other missions, enables detailed diagnostics of key coronal plasma properties and large‑scale dynamics across the 1.7–9 solar radii range. In this review, it will be outlined the major advances achieved to date, including constraints on solar wind outflows (2D maps and fluctuations) and the characterization of density fluctuations associated with waves and dynamic phenomena such as eruptive prominences, CMEs, and CME‑driven shocks.

How to cite: Frassati, F.: Observing the Solar Corona: How Metis advances our understanding of solar wind, waves, CMEs, and shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12665, https://doi.org/10.5194/egusphere-egu26-12665, 2026.

The 2024 total solar eclipse over North America provided a multi-perspective view of the Sun and solar wind through combined ground (DKIST, Mauna Loa Solar Observatory UCoMP and K-Cor) and space (Parker Solar Probe, Solar Orbiter, LASCO, Hinode) -based remote and in situ observations. Through a multi-mission coordinated effort, we examine near-contemporaneous and multi-wavelength observations of the corona to derive detailed plasma conditions and magnetic field properties used to compute an energy budget of an equatorial coronal hole. The remote properties of nascent coronal hole wind are connected to its heliospheric counterpart sampled by Parker Solar Probe and Solar Orbiter during a fortuitous spacecraft alignment. Together, the Alfvén wave, enthalpy, kinetic, and gravitational energy fluxes of a single solar wind stream can be traced from deep in the corona (subsonic regime), across the Alfvén surface and beyond, providing critical constraints to the mass and energy flow in the atmosphere of our star.  Our main results show that a hydrodynamic framework with added Alfvén wave forcing accurately describes radial solar wind observations. Comparisons between measured magnetic and velocity fluctuations and the radial scaling of the WKB approximation indicate significant dissipation below the Alfvén surface. 

How to cite: Rivera, Y. and the 2024 Solar Eclipse Coordination Team: Measured energy exchange in coronal hole solar wind from its solar origins to the heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12938, https://doi.org/10.5194/egusphere-egu26-12938, 2026.

In order to investigate the sources and the physical mechanisms for the propagation of the Slow Solar Wind (SSW), it is essential to analyze and modeling solar data in the middle corona which determines the large scale structure and also the origin of the SSW (from 1.5 up to 6 solar radii). 

We have analysed high temporal frequency visible light observations acquired by Metis coronagraph on Solar Orbiter during the perihelia on October 2022, April 2023 and September 2024.

In particular, we focused on series of total and polarized Brightness observations lasting for 40 min up to few hours, acquired with a cadence of 20 s and 60 s. The field of view of the observations ranges from 1.7 to 3.5 solar radii.

We have found in these data sets several examples of inflows detected as collapsing loops and density inhomogeneities. We have noticed that this kind of features are observed mainly along the streamer axis and they are not observed in pseudo-streamers.

Similar features have been detected by ASPIICS on PROBA3 from the limb to few solar radia, allowing the study of the dynamics of the corona with a continuous coverage of the field of view.

How to cite: Abbo, L., Andretta, V., Zhukov, A., Mierla, M., Fineschi, S., Romoli, M., Spadaro, D., and Susino, R.: Detection of downflows with Metis and ASPIICS observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13364, https://doi.org/10.5194/egusphere-egu26-13364, 2026.

The Dynamic Eclipse Broadcast (DEB) Initiative team developed projects for the 2023 annular and 2024 total solar eclipses, building on the group's success from the 2017 Citizen CATE Experiment. The DEB Initiative instrument captured the inner white-light corona at a roughly 5 second cadence and had slight overlap with the SOHO LASCO field-of-view. The DEB Initiative data imaged the inner 90 arcsec of the corona which is not visible with the new Proba-3 ASPIICS instrument. During the 08 Apr 2024 total solar eclipse, DEB citizen science teams operated 80 telescopes at sites both inside and outside the path of totality. Within the path of totality, more than 30 teams collected approximately 500 Gbytes of imagery at locations from Mazatlan, Mexico, to Moncton, Canada. Team positioning provided over 90 minutes in coverage from the first image to the last image, but cloudy weather, combined with geographical spacing, resulted in gaps with no data during about 37 minutes of that time. We discuss the image processing from single exposures to spatially-filtered HDR summed frames using several of the types of analysis produced by Druckmuller and co-workers with some changes for our particular instruments.  We also discuss spatial and intensity calibration among several of the telescopes which collected scientific data.

How to cite: Brevik, C., Penn, M., Baer, R., Mandrell, C., and Henson, H.: Ground-based, white-light imaging of the solar corona by the Dynamic Eclipse Broadcast (DEB) Initiative during the 2024 Total Solar Eclipse, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15657, https://doi.org/10.5194/egusphere-egu26-15657, 2026.

Proba-3 is a mission dedicated to the in-flight demonstration of precise formation flying techniques and technologies, launched on 5 December 2024. The Proba-3 mission consists of two small satellites in a highly elliptical orbit around the Earth. During observation campaigns around the orbit apogee, the two satellites fly in a precise formation, producing a very long baseline solar coronagraph called ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). One spacecraft carries the optical telescope, and the second spacecraft carries the external occulter of the coronagraph. The inter-satellite distance of around 144 m allows observing the inner corona in eclipse-like conditions, i.e. close to the solar limb and with very low straylight, in different channels: white light (total brightness), Fe XIV (530.45 nm), He I (587.72 nm) and polarisation. The first results of ASPIICS will be presented, and synergies with other missions observing the corona will be discussed.

How to cite: Dolla, L.: Observing the solar corona with the PROBA-3/ASPIICS coronagraph from 1.1 to 3 solar radii, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17258, https://doi.org/10.5194/egusphere-egu26-17258, 2026.

Starting from encounter 22, Parker Solar Probe is on orbits having the closest approach to the sun (perihelion of 9.9 Rs). We examine the encounter 22, the period from 22nd to 27th December 2024, during which there is roughly three continuous days of sub-alfvenic solar wind. Two heliospheric current sheet crossings are identified. A particular region of interest is also the region of strong fluctuations in the plasma parameters on the 24th of December, when the spacecraft is close to the perihelion. We study the dynamics of the solar wind and the formation of localized structures, such as switchbacks, current sheets, and magnetic flux ropes. We compare these to similar structures that form during periods of Aflvenic solar wind. This allows us to conclude on potential generation mechanisms of different localized structures. 

How to cite: Abdulmajed, R., Vaivads, A., Karlsson, T., Sorriso-Valvo, L., and D. Bale, S.: Small-scale localized structures in sub-alfvenic regions of solar wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19918, https://doi.org/10.5194/egusphere-egu26-19918, 2026.

The Quasi-Thermal Noise (QTN) spectroscopy is an efficient tool to study, in the radio frequency domaine, the electrostatic fluctuations due to the thermal motion of the charged particles in a plasma that surrounds a passive antenna. This noise is ubiquitous, and most of the time, is dominant around the electronic plasma frequency.

The voltage power spectrum of the electrostatic fluctuations depends on the velocity distribution of the electrons f_e(v), in addition to the antenna response function. The shape of the QTN in a weakly magnetized plasma allows one to yield an accurate diagnostic of the electron properties such as the total electron density n_e and core temperature T_c, which allows one to analyze the electronic populations in the solar wind with great precision.
We present a semi-automatic method to determine the density of the electrons.

It has been applied on the Parker Solar Probe (PSP) and on the WIND spacecraft, between late 2018 and early 2025.
Yielding a large-scale structure of the solar wind density, down to 10 Solar Radii, we discuss on its radial and temporal variations with the solar cycle.Finally, based on the above method, we discuss on the implementation of a full fitting to deduce a precise diagnostic of the thermal and non-thermal populations of the electrons, both in the solar wind and in the hermean magnetosphere, when the BepiColombo data will be available in early 2027.

How to cite: Verkampt, B., Issautier, K., Griton, L., and Meyer-Vernet, N.: Quasi-Thermal Noise Spectroscopy, a powerful tool for understanding the plasma in the Heliosphere., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20801, https://doi.org/10.5194/egusphere-egu26-20801, 2026.

Parker Solar Probe (PSP) is the first spacecraft deeply diving into the solar corona. By the EGU 2026, PSP will have completed 27 orbits, including 6 perihelia as close as 9.86 solar radii. PSP reached the ultimate perihelion of 9.86 solar radii first on 24 December 2024, and every 88 days afterwards. This presentation presents a summary of the white-light, plasma and magnetic field properties of magnetic flux rope CMEs and ICMEs observed remotely and in-situ within the solar corona by the WISPR camera and the SWEAP and FIELDS plasma and magnetic field instruments. The study includes events als observed by the imagers of the PUNCH mission. 

How to cite: Bothmer, V., Bale, S., Cappello, G., Chifu, I., Deforest, C., Gibson, S., Hess, P., Linton, M., Müller, E., Palmerio, E., Pulupa, M., Shaik, S., Stenborg, G., Stevens, M., Temmer, M., Team, P., and Team, P.: Parker Solar Probe observations of magnetic flux ropes from within the solar corona, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22305, https://doi.org/10.5194/egusphere-egu26-22305, 2026.

Coronal mass ejections are the main drivers of extreme space weather events, so it is essential to model these transients accurately and with enough lead time to be able to forecast severe geomagnetic storms. Many different analytic and numerical models are currently employed with different structures, from analytic flux ropes with drag based propagation and hydrodynamic pulses in 3D MHD, to magnetised flux ropes and spheromaks. Tools such as the CCMC CME scoreboard are currently used to compare space weather forecasts, however this only compares a few parameters and a more detailed evaluation of when different models replicate CME structures accurately is important to further our understanding. We compare the structure and in-situ signatures of 3 different magnetised CME models: the 3DCORE analytic flux rope, Spheromak and Gibson-Low flux rope models. There is a large amount of uncertainty when extrapolating from single point measurements to infer 3D structure, so we also explore whether galactic cosmic ray (GCR) particles could be used as another in situ measurement for determining the structure of a CME. GCRs show transient decreases in flux due to the passage of CMEs, and we model this using test particle simulations in conjunction with the CME models, reproducing GCR modulations known as a Forbush decreases, and explore how the Forbush decrease signature varies with CME model and parameters. Through these simulations, we aim to gain a greater understanding of what a CME `looks like’ and how to more accurately reproduce geoeffective CME structure using magnetised models.

How to cite: Norman, H., Desai, R., Arber, T., Bennet, K., Rüdisser, H., and Davies, E.: Comparing CME models to increase our understanding of 3D CME structure, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1156, https://doi.org/10.5194/egusphere-egu26-1156, 2026.

Coronal mass ejections (CMEs), powerful solar eruptions with massive plasma ejected into the interplanetary space, are caused by the release of the magnetic free enengy stored in coronal electric currents. Photospheric current helicity, defined as the integral of the product of vertical electric current density and vertical magnetic field ($H_c=\int j_zB_z\ dS$), serves as a key parameter in understanding the eruptions. Using a 3D magnetohydrodynamic model, we identify a current helicity reversal pattern associated with the eruption: a pre-eruption decrease and a post-eruption increase. This helicity reversal is attributed to the redistribution of electric currents: before the eruption, currents concentrate toward the polarity inversion line (PIL); after the eruption they move away from the PIL, consistent with the flare ribbon separation, which is caused by the upward progression reconnection site. To validate this pattern, we conducted an observational analysis of 50 $\geq$M5.0 eruptive flares. The results reveal that 58\% of cases exhibited a pre-eruption decrease and 92\% showed the post-eruption increase in current helicity. Detailed analysis of two cases with this reversal suggests that they share the same current redistribution pattern, consistent with the mechanism identified in the simulations. Moreover, the pre-eruption decrease could be observed clearly even in the long-term evolution of the two cases. Current helicity can serve as an indicator of when electric currents are built up for the subsequent eruption, and it has the potential to predict CMEs to some extent.

How to cite: Sun, Z., Li, T., Tian, H., Bian, X., and Kontogiannis, I.: Current Helicity Reversal during Coronal Mass Ejections, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1903, https://doi.org/10.5194/egusphere-egu26-1903, 2026.

Coronal mass ejections (CMEs) are explosive releases of large volumes of magnetized coronal plasma into interplanetary space, and they are a significant cause of space weather disturbances, such as geomagnetic storms. Therefore, predicting CME occurrence is a considerable challenge; however, due to limited understanding of their generation mechanisms, accurate predictions have not been achieved. Meanwhile, various studies have explored the magnetic characteristics of active regions that determine whether solar flares can erupt or not into CMEs. In particular, Muhamad and Kusano (2025) recently found that a new parameter, consisting of the critical height (h_c) at which torus instability can grow and the ratio of the direct to return electric currents, can effectively distinguish the source active regions where solar flares erupt and do not erupt to CMEs, with unprecedented accuracy. Based on these results, we propose a new CME generation mechanism, a "two-stage instability model," and verify it using 3D MHD simulations. The two-stage instability model suggests that, in the first stage, small-scale magnetic reconnection triggers the growth of a double-arc instability (Ishiguro and Kusano, 2017), which raises the twisted magnetic flux to the critical height (h_c). In the second stage, the torus instability grows and drives CMEs. Simulations using a shear-arcade magnetic field as the initial condition clearly demonstrate the validity of this model. Furthermore, the simulation results suggest that (1) the two-stage instability model can explain the cause of the slow-rise phase, which is considered a precursor to CMEs, and (2) the dependence of the torus instability on the initial magnetic field distribution can provide insight into the physics that determines the duration and spatial extent of solar flares. Based on these results, we propose a new method for predicting CME occurrence from magnetic field data in active regions and discuss its forecasting capability.

How to cite: Kusano, K.: Two-stage Instability Model for Explaining and Predicting the Generation of Coronal Mass Ejections, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2109, https://doi.org/10.5194/egusphere-egu26-2109, 2026.

CMEs often exhibit the archetypical three-part structure in coronagraphs, including the bright core, dark cavity, and bright front. In the popular explanation, the bright core corresponds to the cold and dense filament, which locates at the dip of MFR. The dark cavity is the MFR with relatively lower density due to the enhanced magnetic pressure. The bright front originates from the pileup of background plasma along the MFR boundary. For many years, there has been no controversy over this traditional opinion. Based on a series of studies (Song et al. 2017, 2019a, 2019b, 2022, 2023a, 2023b, 2025a, 2025b), we completed a new explanation on the nature of the three-part structure of CMEs. The new explanation suggests that the MFR is responsible for the bright core, the plasma pileup along the overlying coronal loops corresponds to the bright front, and the low-density zone between them appears as the dark cavity in the early eruption stage. The new explanation predicts that almost 100% of normal CMEs have the three-part structure in the inner corona, which has been proved by observations (Song et al. 2023b, ApJL).

How to cite: Song, H.: A New Explanation on the Nature of Three-part Structure of CMEs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2791, https://doi.org/10.5194/egusphere-egu26-2791, 2026.

We investigate combined remote-sensing and in-situ data for a case study on a coronal mass ejection (CME) interacting with the nearby located heliospheric current sheet (HCS). The CME is related to the largest directly observed flare (X9.0) of solar cycle 25 on October 3, 2024. We find the CME source region to be a so-called nested active region, hence, persisting over several solar rotations. The active region and its evolution is therefore significantly linked to the structure of the global magnetic field. In-situ measurements indicate that a combined system of HCS and CME structures is propagating outward and generating a weak shock front ahead of it. The CME itself is highly interrupted by clear HCS-related structures, i.e., the heliospheric plasma sheet. The interaction process might have caused the CME-related shock-sheath region to be separated from the magnetic ejecta part by almost 40 hours. This event shows the intrinsic relation between solar surface structures, global magnetic field and the evolution of complex eruptive events.

How to cite: Temmer, M., Heinemann, S., Dresing, N., Dumbovic, M., and Asvestari, E.: Disruption of the October 3, 2024 CME by the Heliospheric Current Sheet – A Sun-to-Earth Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3021, https://doi.org/10.5194/egusphere-egu26-3021, 2026.

There is current renewed interest in using distant retrograde orbits (DRO) for a space weather forecasting mission, which would temporarily place spacecraft at a position near the Sun--Earth line, but closer to the Sun than the L1 point. For a continuous coverage, several spacecraft would be needed at such sub-L1 distances. With in situ observations of the magnetic field, the southward Bz < 0 field of solar coronal mass ejections (CMEs), which is not accessible remotely, could be measured hours in advance. This Bz < 0 field is a decisive factor for forecasting geomagnetic storm intensity. Here, we analyse DROs at different distances for their efficacy for a space weather forecasting mission. First, we present a simple open-source numerical framework to generate DRO trajectories, based on equations for the constrained three-body problem. This makes them easily accessible for their introduction into numerical or empirical simulations of the solar wind or CMEs. Secondly, we analyze their general characteristics, such as relationships between their minimum distance to the Sun along the Sun-Earth line and their widest longitudinal extent. Third, we combine recent progress on our understanding of the magnetic structure of CMEs with the DRO characteristics and the possible number of spacecraft, to find clues on an optimal mission configuration, at distances between 0.8 and 0.9 au from the Sun. We also identify knowledge gaps and open challenges. ESA HENON (launch 2026) and ESA SHIELD (planned for the 2030s) are bound to be the first missions to realize space weather forecasts with sub-L1 data on DROs. We here provide a baseline for future studies by combining DRO calculations with the current state of knowledge on CMEs, for space weather forecasts with strongly enhanced lead times. 

How to cite: Möstl, C., Weiler, E., Davies, E. E., Rüdisser, H. T., Amerstorfer, U. V., Camattari, F., Lugaz, N., and Palmerio, E.: Calculation of distant retrograde orbits and their use for space weather forecasting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4993, https://doi.org/10.5194/egusphere-egu26-4993, 2026.

Coronal dimmings are regions of transiently reduced extreme ultraviolet (EUV) and soft X-ray (SXR) emission caused by plasma evacuation during the liftoff of coronal mass ejections (CMEs). As such, they serve as powerful diagnostics of CME initiation and early evolution. In May 2024, active region (AR) 13664 was among the most flare productive regions in recent decades, producing 54 M-class and 12 X-class flares. The rapid sequence of Earth-directed CMEs from AR13664 triggered the most intense geomagnetic storm in two decades. We present a two-part analysis of the coronal dimmings from AR 13664 associated with the May 2024 storms.

First, we systematically identify and analyse 22 dimming events (16 on-disc and 6 off-limb) and their characteristic parameters using SDO/AIA observations. We find that the dimming area, growth rate, and magnetic flux strongly correlate with GOES flare peak flux, fluence, and flare reconnection flux. These correlations are stronger than those found in previous statistical studies, highlighting the tight coupling between flares and dimmings. However, we find no correlation between dimming properties and CME maximum speed derived from SOHO/LASCO coronagraph measurements, suggesting that dimmings are more closely linked to the early-stage CME evolution rather than their later propagation. 

Second, we investigate the morphology and spatial evolution of the 16 on-disc dimmings in relation to flare ribbon location and coronal magnetic field structures. We employ high resolution PFSS and NLFF extrapolations alongside the dimming morphology to identify which magnetic structures are involved in the eruptions and how they participate in them. By considering the dimming expansion direction and the flare ribbon location, we identify two distinct magnetic domains associated with different polarity inversion lines. We also relate the dimming expansion, together with the orientation of the flare ribbons along the PILs, to the different geoeffectiveness of the associated CMEs.

These results underscore the extensive potential of coronal dimmings to characterise solar eruptions and understand the physical processes behind them.

How to cite: Razquin, A., Veronig, A. M., Dissauer, K., Barnes, G., Podladchikova, T., and Jain, S.: Coronal dimmings as diagnostics of the May 2024 solar energetic events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5329, https://doi.org/10.5194/egusphere-egu26-5329, 2026.

How to cite: Hu, H., Chen, C., Jiao, Y., Zhu, B., Wang, R., Zhao, X., and Yang, L.: Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5427, https://doi.org/10.5194/egusphere-egu26-5427, 2026.

Studying the structure of solar active regions through magnetic field modelling and observations strengthens our understanding of eruptive phenomena in the solar atmosphere. AR12975 featured an interesting event, where a significant restructuring of a pre-existing filament occurs approximately 1.5 hours before fully erupting. This event also shows clear signatures of coronal dimmings, which refer to a decrease in brightness in EUV and SXR observations of the Sun. They are interpreted as the density depletion caused by a coronal mass ejetion (CME) liftoff. As such, they are one of the most prominent low-corona signatures of CMEs and serve as important diagnostics for CME initiation and magnetic field reconfiguration after an eruption. Core dimmings, also known as flux rope dimmings, mark the footpoints of the erupting CME flux rope. To study them more in-depth we perform a time-dependent data-driven magnetofrictional simulation of AR12975. In particular, we focus on its magnetic structure and how the footpoints of the magnetic flux rope relate to the core dimming signatures observed in different EUV wavelenghts. To identify the magnetic flux rope from the model we use the Graphical User Interface for Tracking and Analysing flux Ropes (GUITAR). GUITAR uses a set of MFR proxies (here: combined maps of the twist parameter as well as the logarithm of the squashing factor) in combination with mathematical morphology operations to locate the MFR cross-section in a 2D plane. We also use GUITAR to disentangle the two flux systems that take part in the eruption. 

How to cite: Wagner, A., Razquin, A., Veronig, A., Dissauer, K., Pomoell, J., and Kilpua, E.: Studying the connection between coronal dimmings and flux rope footpoints using data-driven modelling and observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5621, https://doi.org/10.5194/egusphere-egu26-5621, 2026.

Recent multi-spacecraft observations show the complex structure of Interplanetary Coronal Mass Ejections (ICMEs) as they propagate through interplanetary space. These observations allow us to monitor magnetic-field-related parameters systematically across vast spatial domains. Among the measurable quantities, magnetic helicity is of particular interest as it is quasi-conserved even in resistive MHD. It serves as a robust measure of the magnetic field complexity and, consequently, provides a physically grounded tracer for linking the magnetic topology of the ICME’s source region in the low solar atmosphere to the large-scale magnetic configuration in interplanetary space.

We present the analysis of a flare/CME event (SOL2024-03-23T X1.1) paired with a study of the ICME’s flux rope global structure that presumably impacted Solar Orbiter (at a heliocentric distance of 0.39 AU), BepiColombo (0.58 AU), STEREO-A (0.96 AU), as well as Wind (0.99 AU).

To model the three-dimensional coronal magnetic field of the solar source active region (NOAA 13614), we employ a non-linear force-free (NLFF) extrapolation based on the recently developed machine-learning approach. To infer the properties of the associated CME at the different locations in interplanetary space, we apply the semi-empirical 3DCORE model to the individual in-situ spacecraft data. Based on the modeling of the underlying magnetic field structure, we are able to compute the magnetic helicity in the solar source region (using a finite-volume method) as well as in interplanetary space, the latter using a linear force-free ("Lundquist") and a nonlinear force-free ("Gold-Hoyle") approach. This approach allows us to trace its evolution continuously from the low corona to near-Earth space. Our broader objective is to establish consistent and physically meaningful helicity estimates across coronal and Heliospheric domains.

How to cite: Moulin, A., Thalmann, J., Veronig, A., Dumbović, M., Rüdisser, H., Möstl, C., Amerstorfer, U., and Davies, E.: Tracing Magnetic Helicity from the Solar Source Region to Interplanetary Space: A Multi-Spacecraft Analysis of the March 23, 2024 ICME, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6837, https://doi.org/10.5194/egusphere-egu26-6837, 2026.

How to cite: Davies, E., Möstl, C., and Weiler, E.: Investigating the local and global expansion of ICMEs using multi-spacecraft observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7391, https://doi.org/10.5194/egusphere-egu26-7391, 2026.

We have developed and implemented a new data-driven method to initiate a coronal mass ejection (CME) in the Alfven Wave Solar atmosphere Model (AWSoM). Our new approach uses an HMI vector magnetogram observed prior to the CME eruption. First we obtain an approximate non-linear force free (NLFF) magnetic field in the vicinity of the active region with a magnetofriction code. Next, this magnetic field is inserted into the AWSoM steady state solution in place of the original potential field to obtain an approximate steady state with the full physics of AWSoM. At this point the currents present in the NLFF field are ignored. Finally, we return to using the potential field as the background so that the difference of the NLFF and potential fields becomes the initial magnetic field structure of the CME. Solving in time-accurate mode with the NLFF field currents fully included results in an eruption. We report on the results obtained with this new CME initiation method for several events.

How to cite: An, Y., Toth, G., and Popescu Braileanu, B.: Initiating coronal mass ejection based on vector magnetograms in the Alfven Wave Solar atmosphere Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7878, https://doi.org/10.5194/egusphere-egu26-7878, 2026.

It is generally accepted that magnetic flux ropes (MFRs) are a critical component of many coronal mass ejections. However, the nature of the pre-eruptive magnetic configuration of CMEs is still under debate. A more crucial question is how the pre-eruptive magnetic configuration forms in the Sun and further evolves toward eruptions. In our previous statistical studies, we investigated pre-eruptive magnetic properties of 80 erupting MFRs whose feet are well identified by conjugate coronal dimmings. An interesting finding from our previous study is that 17 out of 80 MFRs carried significant non-neutralized electric currents prior to their eruption.  Here we investigate the entire evolution of these MFRs from birth to eruption. Impressively, the significant non-neutralized electric current appeared several hours ahead of the formation of coronal MFRs. The buildup of coronal MFRs were simultaneous with evolution of the non-neutralized electric current in the photosphere. The preflare brightening with two ribbon-like structures always observed among the coronal MFRs. Quantitative measurements indicate that the significant non-neutralized electric current also flows through the footpoints of the erupting MFRs. The asymmetric distributions of electric current and magnetic twist were found in these MFRs. The evolution of the photospheric non-neutralized electric current is demonstrated to signal the buildup of the pre-eruptive structure and the imminent eruption.

How to cite: Wang, W., Liu, R., Qiu, J., Guo, J., and Wang, Y.: Evolution of Solar Magnetic Flux Ropes with Significant Non-neutralized Electric Current toward Eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9648, https://doi.org/10.5194/egusphere-egu26-9648, 2026.

We present a comprehensive multi-instrument analysis of a sequence of eruptive prominences observed on 21 September 2025, associated with clearly detected coronal mass ejections (CMEs). These events were simultaneously observed by PROBA-3/ASPIICS (in both He I D3 and Fe XIV), SDO/AIA, PROBA-2/SWAP 174 Å, Solar Orbiter/FSI 304 and 174 Å, and Metis in both visible light and UV Lyα, as well as from a separated viewpoint by STEREO-A/EUVI and COR1/COR2, and LASCO C2/C3 in the outer corona. The well-suited constellation of spacecraft, separated by approximately 45° each, together with the range of available instruments, provides unprecedented coverage of the eruptive structures from the solar surface through the low corona and into the outer corona, enabling the tracking of prominences across multiple temperature regimes and perspectives. The multi-wavelength and multi-viewpoint analysis of these eruptive prominences allows investigation of how prominence plasma evolves and interacts with the surrounding corona, and explores the contribution to the early CMEs development.

How to cite: Liberatore, A., Patel, B., Mierla, M., Susino, R., Frassati, F., Romoli, M., and Zhukov, A.: The Role of Eruptive Prominences in early CME Evolution: Investigation from Coordinated Multi-instrument Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13526, https://doi.org/10.5194/egusphere-egu26-13526, 2026.

How to cite: Liu, X., Antiochos, S., Sokolov, I., Gombosi, T., Sachdeva, N., and Zhao, L.: MHD Simulations of CMEs with Energy Conservation: Reconnection Thermodynamics as a Critical Aspect of CME Dynamics , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14296, https://doi.org/10.5194/egusphere-egu26-14296, 2026.

Being one of the major drivers of space weather, coronal mass ejections (CMEs) have been in the spotlight of space physics research for many years. As a result, we now have a larger variety of analytical and numerical models at our disposal to describe CMEs as magnetised as well as non-magnetised structures. By applying these models to reconstruct past CME events, we can assess their performance and accuracy and whether they can be used for improving our forecasting capabilities. Such studies also help to identify all physical processes that are relevant to adequately describe CME evolution in the interplanetary space and avoid oversimplified model assumptions. But CME model applications do not stop there. Sculpting the interplanetary space, CMEs play a crucial role in particle transport both of solar and galactic origin. And current CME models can help not only to study the transport of solar energetic particles from a fundamental point of view but also offer the possibility to explain specific particle events observed by spaceborne instruments or ground-based detectors.

Despite such advancements, CME models suffer both from numerical and observational limitations. From artifacts introduced by numerical implementation schemes to difficulties in constraining observationally the numerous parameters involved in CME modelling, these issues introduce an element of uncertainty in our reconstructions. Of particular interest is the understanding of how observed parameters translate into model input. Especially when considering that the CME configurations we use have smooth, uniform, and often symmetric shapes during insertion which do not reflect the complex structures observed in remote sensing observations.

In this presentation, we will explore the state-of-the-art in CME modelling including current advancements in flux rope numerical implementation that has great potential in boosting CME studies. We will revisit how CME modelling contributed to a better understanding of the physical process that impact flux rope evolution and discuss some of the many applications of CME modelling in particle research. Finally, we address the limitations we are facing and the future needs and aspects of CME modelling.

How to cite: Asvestari, E.: Exploring current advancements, applications, limitations, and future aspects of modelling coronal mass ejections, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14598, https://doi.org/10.5194/egusphere-egu26-14598, 2026.

On March 15, 2015 a Coronal Mass Ejection (CME) associated with a C9.1 class flare caused the biggest geomagnetic storm of solar cycle 24. We present a numerical modeling study of the pre-eruption energetic phase, onset and evolution of this CME in the solar corona and the inner heliosphere. The CME initiation is modeled using the STITCH (STatisTical Injection of Condensed Helicity) methodology with the extended 3D global magnetohydrodynamic (MHD) model of the solar corona, Alfven Wave Solar atmosphere Model (AWSoM). STITCH is a statistical approximation of the hard to capture (numerically) small scale photospheric motions, by injecting a net helicity and forming sheared filament channels over polarity inversion lines (PILs). This emulates the energy build-up due to the small-scale convective motions and magnetic reconnection on the solar surface. In comparison to analytical flux-rope models, this method provides a realistic way to investigate the onset and eruption of a CME from the solar surface utilizing observations of the photospheric magnetic field. The shearing of the PIL of the erupting active region energizes the filament channel leading to flare reconnection and eruption of the CME flux-rope structure. We describe the magnetic and plasma properties of the pre-eruption and post eruption phase of the CME and its evolution characteristics.

How to cite: Sachdeva, N., Antiochos, S., and van der Holst, B.: Data-Driven Numerical Modeling of CME Onset and Eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15438, https://doi.org/10.5194/egusphere-egu26-15438, 2026.

Interaction of Coronal Mass Ejection (CMEs) with Solar High-Speed Streams (HSSs) could alter their plasma and magnetic field properties. The properties of such an interaction should be encoded in the in-situ plasma and magnetic field observations. To characterise the properties of such interaction, we analyse the in-situ signatures of 28 interplanetary coronal mass ejections (ICMEs)b interacting with high-speed streams (HSS) at 1AU between 2010 and 2018. We analyse the ICME velocity profiles, duration of the sheath and magnetic obstacle (MO), and distortion of the MO, as well as search for the signatures of the reconnection exhausts. We find 20 events where ICME is in front of the HSS and 8 events where it is behind the HSS. Statistical analysis is performed for these two classes of interaction separately. We find that ICMEs interacting with HSS generally show distinct speed profiles for cases where HSS is in front or behind. We find that HSS catching up to ICMEs tends to accelerate them from the back, whereas HSS in front of ICMEs do not significantly alter the typical speed expansion profiles but tends to inhibit the formation of sheath. We find that 70 precent of such events does not show discernible sheath region. We find that the average magnetic field magnitude tends to be higher for cases where the ICME is in front of the HSS compared to when it is behind. Although we find reconnection exhaust signatures in about 30% events, we do not find significant evidence of the distortion of the internal magnetic structure. Our results indicate that interaction with HSS does not significantly influence the ICME internal magnetic structure, however, it may significantly influence its kinematics.

How to cite: Remeshan, A. K., Dumbović, M., Fargette, N., and Temmer, M.: Characterisation of in situ signatures of coronal mass ejections interacting with high-speed streams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17902, https://doi.org/10.5194/egusphere-egu26-17902, 2026.

To enable timely action in mitigating damage from severe space weather events, there is an urgent need for advanced Sun-to-Earth MHD models capable of delivering timely, high-fidelity, and comprehensive space weather forecasts. Recently, the numerical stability of the time-evolving coronal MHD models COCONUT and SIP-IFVM have been significantly improved by the energy decomposition strategy and the extended magnetic field decomposition methods, respectively. The implicit temporal integrations, with Newton iterations or pseudo–time marching method performed within each time step, enables high computational efficiency with desired temporal accuracy. Several observation-based coronal evolution and CME propagation simulations further demonstrate that these methods collaboratively achieve an effective balance between high computational efficiency, numerical stability, and modeling accuracy. Currently, we further go to the planetary space by directly extending our coronal models to 1 AU or coupling the coronal model with an inner heliosphere model. Based on the faster-than-real-time time-evolving solar-terrestrial MHD model, we are performing CME propagation simulations in the time-evolving solar-terrestrial plasma background, rather than the usually adopted quasi-static background. We will report on the algorithm innovations we recently made for improving the performance of MHD coronal models and CME simulations. We will also discuss the impact of temporal variations in the coronal and solar wind background on CME propagation, as well as the effects of the interface introduced by coupling separately run coronal and inner heliosphere models, a common practice adopted to simplify parameter adjustment and reduce computational cost. These algorithmic innovations and resulting findings provide an opportunity to develop more reliable Sun-to-Earth MHD models suitable for practical CME simulations.

How to cite: Wang, H., Stefaan Poedts, S., Lani, A., Linan, L., Baratashvili, T., Zhou, Y., Guo, J., Dhib, R., Jeong, H.-J., Noraz, Q., Wu, H., Zhuo, R., Liu, J., Dong, L., Najafi-Ziyazi, M., Zhukov, J. M., and Schmieder, B.: HERMES: Highly Efficient and quasi-Realistic Modeling of coronal mass Ejections in a time-evolving Solar-terrestrial background, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19280, https://doi.org/10.5194/egusphere-egu26-19280, 2026.

Interplanetary coronal mass ejections (ICMEs) carry magnetic clouds, multi-scale structures which span a considerable fraction of an astronomical unit and display a rich dynamics at many spatial scales, including turbulence. Spacecraft that encounter an ICME can measure smoothly rotating "magnetic cloud" (MC) intervals or less organised "magnetic obstacle" (MO) ones.

We aim to understand to what extent the interplay of expansion, turbulence, and internal cloud dynamics affects the magnetic cloud properties, which then translate to signatures measured by spacecraft. We perform 2.5D MHD simulations of a magnetic flux rope embedded in the turbulent expanding solar wind, using the expanding box model, which decouples large and small scales and provides high resolution. We employ virtual spacecraft to probe the local plasma properties.

The flux rope exhibits a coherent large-scale expansion, and clear and stable MC signatures are always found by spacecraft intercepting the flux rope core. Disordered MO signatures appear at the flux rope edges, due to both expansion and turbulent transport. The strength of the expanding flow controls the angular extent of coherent signatures, whereas the intensity of turbulence controls the variability between different spacecraft encounters and the amount of distortion and deflection that the cloud experiences. Our results support the idea that the MC/MO dualism is a consequence of the impact geometry. The presence of MO signatures at the edges is instead controlled by the initial confinement of the axial flux rope field by magnetic tension: disordered signatures disappear for narrow flux ropes.

How to cite: Sangalli, M., Kilpua, E., Good, S., Landi, S., Pomoell, J., and Verdini, A.: Evolution of magnetic cloud signatures in the turbulent solar wind: virtual spacecraft analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19705, https://doi.org/10.5194/egusphere-egu26-19705, 2026.

Coronal mass ejections (CME)-driven shocks are the most efficient accelerators of gradual solar energetic particles (SEPs), which pose risks to technological infrastructure and human activity in space. Knowing the physical properties of expanding shocks is critical in order to prevent SEPs hazard and to understand their impact to the near-Earth environment. However, a thorough picture on how the properties of shocks evolve from the corona to the heliosphere remains poorly constrained.  We present a study of a unique event, a shock driven by a circumsolar CME on 2023 March 13, observed from multiple spacecraft, using both remote sensing observations from STEREO-A/COR2 and in-situ data from Parker Solar Probe (PSP), Solar Orbiter (SolO), and Wind. We focused on the determination of some key parameters, such as the density compression ratio and the Alfvénic Mach number. The analysis of remote-sensing data has required advanced modelling of the 3D geometry of the observed shock complemented by raytracing simulation of the Thomson scattered emission, which was compared with the brightness measured from STEREO-A/COR2.
Following the evolution of the parameters, we have found that closer to the Sun, both the density compression ratio and the Alfvénic Mach number remain almost constant, while they increase at larger radial distances. These results highlight a non-trivial evolution of the properties of the shock during its journey throughout the interplanetary medium, with implications for SEP acceleration and space-weather forecasting.

This study was carried out within the "Data-based predictions of solar energetic particle arrival to the Earth: ensuring space data and technology integrity from hazardous solar activity events" (CUP H53D23011020001) funded by Next Generation EU’ PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR), and the Space It Up! project, funded by the Italian Space Agency (ASI) and the Ministry of University and Research (MUR), under Contract Grant Nos. 2024-5-E.0-CUP n.I53D24000060005.

How to cite: Nisticò, G., Chiappetta, F., Chimenti, M., Larosa, A., Malara, F., Pucci, F., Sorriso-Valvo, L., Zimbardo, G., and Perri, S.: Evolution of interplanetary CME-driven shocks from remote-sensing and in-situ observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20092, https://doi.org/10.5194/egusphere-egu26-20092, 2026.

One of the major challenges in space weather forecasting is the reliable prediction of the magnetic structure of interplanetary coronal mass ejections (ICMEs) in near-Earth space. This challenge becomes even more pronounced when a CME interacts with high-speed streams (HSSs) or other CMEs during its interplanetary evolution. Within the framework of global MHD modeling, several efforts have been made to simulate the CME magnetic field from the Sun to Earth. However, it remains difficult to deduce a flux-rope solution that can robustly reproduce the magnetic structure of CMEs. Moreover, a comprehensive understanding of how CME–HSS interactions lead to enhanced space weather impacts of CMEs and their associated sheath regions is still lacking.

In this work, we implement a new flux-rope model in the European Heliospheric Forecast Information Asset (EUHFORIA), featuring an initially force-free toroidal flux rope embedded in the low-coronal magnetic field. The novel embedding technique self-consistently generates a draping field around the flux rope, preserving the normal component of the magnetic field at the flux-rope boundary. The flux-rope dynamics in the low and middle corona are solved using a non-uniform advection constrained by the observed kinematics of the CME. This produces a global, non-toroidal, stretched loop-like magnetic structure, in which the lower half of the torus remains below the inner boundary of the heliospheric model. At heliospheric distances, the subsequent evolution is modeled as an MHD process using EUHFORIA, yielding a classical flux-rope geometry consistent with observations of bi-directional electrons.

We further investigate CME–HSS interactions using this modeling framework by constructing synthetic high-speed streams and studying their interaction with CMEs of varying kinematics. Our results show that CME–HSS interactions lead to significant deformation of the CME magnetic structure. We find that the relative speed between the CME and the HSS plays a decisive role in determining the degree of ICME compression and the resulting enhancement of its space weather impact.

How to cite: Sarkar, R., Pomoell, J., Kilpua, E., and Asvestari, E.: Modelling CME–High-Speed Stream Interactions Using a Novel Flux-Rope Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21712, https://doi.org/10.5194/egusphere-egu26-21712, 2026.

Ultralow frequency (ULF) waves in the Hermean foreshock are believed to be driven by the interaction of solar wind ions reflected from the bow shock with the original solar wind beam. The direction of the interplanetary magnetic field (IMF) determines what regions are accessible to the reflected ions, and where therefore ULF waves are growing to an observable amplitude. Short Large-Amplitude Magnetic Structures (SLAMS) have been suggested to form when the growth of the ULF waves enter a non-linear, explosive stage. We use observations of foreshock ULF waves and SLAMS based on MESSENGER magnetic field data to investigate the relation between the two types of phenomena. We study the spatial extent of both SLAMS and ULF waves for different IMF directions, and relate them to the angle q_Bn between the IMF and the bow shock normal. At Earth, a majority of SLAMS have an elliptical polarization in the opposite sense to the ULF waves. We investigate whether this is the case also at Mercury, and also check if there is a continuous change of distribution of polarization organized by amplitude of SLAMS and structures with an amplitude intermediate between ULF waves and SLAMS, sometimes known as ‘shocklets’. The results are discussed in terms of possible similarities between terrestrial and Hermean SLAMS formation mechanisms, with a particular focus on possible extensions of these studies to be performed by the upcoming BepiColombo mission.

How to cite: Karlsson, T., Bergman, S., and Wong Chan, T. K.: The relation between Ultralow Frequency (ULF) waves and Short Large Amplitude Magnetic Structures (SLAMS) in the Mercury foreshock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1541, https://doi.org/10.5194/egusphere-egu26-1541, 2026.

The foreshock is a large region of space upstream of a collisionless shock characterised by the presence of particles of solar wind origin that have been reflected at the shock. The interaction between these particles and the pristine solar wind can also generate ultra-low frequency (ULF) waves that are advected toward the quasi-parallel bow shock, that is, the part of the bow shock where the interplanetary magnetic field (IMF) and shock normal are almost parallel. The interaction between the ULF waves and the shock cause the quasi-parallel bow shock and the magnetosheath downstream of it to become turbulent and dynamic, which in turn can lead to the formation of transient structures such as magnetosheath jets. During intervals of quasi-radial IMF at Earth, the quasi-parallel bow shock is upstream of the dayside magnetosheath, and the dynamics of the quasi-parallel bow shock and magnetosheath have larger potential to have geoeffective consequences. Understanding the properties of the foreshock is therefore important, but studying the overall structure of this extended region using point measurements by spacecraft is difficult.

In this study, we present the first ever global 6D (3D+3V) hybrid-Vlasov simulation of near-Earth space with quasi-radial IMF conditions, featuring a high-resolution foreshock. We introduce the new criterion that was used to identify the foreshock for the purpose of applying adaptive mesh refinement, and elaborate on some of the technical challenges that needed to be overcome to make the simulation possible. We investigate the effects of ULF waves on the velocity distributions in different parts of the foreshock. Finally, we probe the velocity distributions inside magnetosheath jets in order to study their kinetic nature.

How to cite: Suni, J., Palmroth, M., Turc, L., Ojuva, M., Kotipalo, L., Alho, M., and Ganse, U.: 6D hybrid-Vlasov simulation of a high-resolution foreshock during quasi-radial IMF: First Vlasiator results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1794, https://doi.org/10.5194/egusphere-egu26-1794, 2026.

Collisionless low Mach number shocks are abundant in astrophysical and space plasma environments, exhibiting complex wave activity and wave-particle interactions. In this paper, we present 2D Particle-in-Cell (PIC)  simulations of quasi-perpendicular nonrelativistic low Mach number shocks, with a specific focus on studying electrostatic waves in the shock ramp and the precursor regions. In these shocks, an ion-scale oblique whistler wave creates a configuration with two hot counter-streaming electron beams, which drive unstable electron acoustic waves (EAWs) that can turn into electrostatic solitary waves (ESWs) at the late stage of their evolution. By conducting simulations with periodic boundaries, we show that EAW properties agree with linear dispersion analysis. The characteristics of ESWs in shock simulations, including their wavelength and amplitude, depend on the shock velocity. When extrapolated to shocks with realistic velocities, the ESW wavelength is reduced to one tenth of the electron skin depth and the ESW amplitude is anticipated to surpass that of the quasi-static electric field by more than a factor of 100. These theoretical predictions may explain a discrepancy, between PIC and satellite measurements, in the relative amplitude of high- and low-frequency electric field fluctuations. 

How to cite: Bohdan, A., Tran, A., Sironi, L., and Wilson, L. B.: Electrostatic Waves and Electron Holes in Simulations of Low-Mach Quasi-perpendicular Shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2987, https://doi.org/10.5194/egusphere-egu26-2987, 2026.

Short Large-Amplitude Magnetic Structures (SLAMS) are isolated non-linear magnetic field signatures frequently observed in the foreshock of quasi-parallel shocks. They are believed to form due to a non-linear growth of ultra-low frequency (ULF) waves, but the detailed formation mechanisms are still highly uncertain. SLAMS have been suggested to be important for the formation of the quasi-parallel shock, and understanding the nature of these structures is hence important in order to fully understand the physics of collisionless shocks.

The majority of SLAMS (about 80%) are right-hand polarized in the spacecraft frame, corresponding to a left-hand polarization in the plasma frame. This polarization is opposite from that of the ULF waves from which they are believed to grow. The reason for this polarization change is unknown. Not all SLAMS are however right-hand polarized in the spacecraft frame. About 20% are left-hand polarized, and the reason for these two different groups of SLAMS and their underlying formation mechanisms are also unknown.

In this work, we make a statistical analysis of the polarization properties of SLAMS in the foreshock of Earth using data from the Cluster mission. The aim is to investigate the difference between right-hand and left-hand polarized SLAMS, studying differences in the ion distribution and the general properties of the plasma environment. This can give clues about the underlying formation mechanisms. We also study the evolution of the polarization as the ULF waves grow into SLAMS.

How to cite: Bergman, S., Karlsson, T., and Wong Chan, T. K.: The polarization of Short Large-Amplitude Magnetic Structures (SLAMS) in the foreshock of Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3425, https://doi.org/10.5194/egusphere-egu26-3425, 2026.

Collisionless shocks play a key role in space and astrophysical plasmas, enabling the conversion of large-scale kinetic energy into heat and non-thermal particle populations without relying on binary Coulomb collisions. Instead, these shocks are sustained by collective effects such as wave-particle interactions that are inherently kinetic and often nonlinear. Despite significant observational and theoretical efforts, the precise mechanisms and spatial localization of energy dissipation in collisionless shocks remain debated. While it is widely accepted that dissipation occurs within the shock ramp, simulations and observations have shown that energy conversion may also extend upstream and downstream, involving shock structures such as the foot and overshoot. Observational studies using Magnetospheric Multiscale (MMS) have further highlighted that ion heating are often concentrated in the ramp and foot, while electron heating may remain nearly constant or increase only under specific conditions such as enhanced wave activity in the transition region.

We analyze high-resolution measurements from the MMS mission across multiple quasi-perpendicular bow shock crossings. We quantify energy contribution of different particle species within a vicinity of the shock ramp to analyze energy transfer among electrons, ions and electromagnetic fields within collisionless shocks. By correcting the measured ion and electron distribution functions for instrumental effects, we isolate the energy contributions of each species and examine how they vary throughout the shock structure. We calculate the theoretically expected values for thermal energy from mass conservation principles and Rankine-Hugoniot conditions to analyze the observed deviation from adiabatic behavior in collisionless shocks. Finally, we discuss how energy transfer between species depends on various shock parameters.

How to cite: Villaflor, V., Bohdan, A., and Jenko, F.: Energy dissipation in collisionless shocks: MMS observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3632, https://doi.org/10.5194/egusphere-egu26-3632, 2026.

Understanding ion energization during the interaction between an Interplanetary (IP) shock and a Bow shock remains an important and intriguing problem in space plasma physics. In this context, we present hybrid particle-in-cell simulations using the 2D EPOCH code to investigate particle acceleration during supercritical collisionless shocks interactions. In order to estimate the level of particle energization in two shocks interaction, we consider two cases. First, we present an example of particle acceleration induced by an isolated bow shock resulting from the solar wind-Earth’s magnetosphere interaction. Second, we present a case study of a Coronal Mass Ejection (CME)–driven IP shock interaction with the Earth’s bow shock for both quasi-parallel and quasi-perpendicular geometries. During the interaction of two shocks, ions undergo multiple reflections between the converging magnetic fields, enabling efficient energy gain through Fermi acceleration. By modelling the system using hybrid simulations, we can further observe how this acceleration is modified and enhanced in the presence of ion-kinetic scale structures and non-stationary developed self-consistently at both shocks. As expected, the shock–shock configuration produces substantially stronger ion energization than a single isolated collisionless shock. Our simulations show that as the two shocks approach and overlap, their highly structured magnetic ramps, reflected-ion populations, and upstream waves interfere, producing time-dependent variations in shock thickness, amplitude, and position. By analyzing ion velocity distributions, bulk flow, temperature, and electromagnetic fields, we characterize key features of the interaction region, including shock evolution, reformation, ion reflection, and particle energization. These results provide new insight into how shock–shock interactions influence the turbulent shock transition and enhance ion acceleration compared with a single shock.

How to cite: Imtiaz, N., Gingell, I., and Steinvall, K.: Kinetic Simulations of Particle Acceleration in Collisionless Supercritical Shock-Shock Interaction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4068, https://doi.org/10.5194/egusphere-egu26-4068, 2026.

Interplanetary shocks are ubiquitous in the heliosphere in relation or not with solar events such as Stream Interaction Regions and Coronal Mass Ejections. However, their interactions with planetary environments remain poorly understood. 

In this study, we performed hybrid-PIC simulations of the interaction between interplanetary shocks and a realistic near-Earth environment system. We firstly focused on two aspects: (i) the self-consistent generation of a realistic bow shock–magnetosheath–magnetopause system, and (ii) a stand-alone analysis of the self-consistent evolution of a high-speed stream throughout an interplanetary medium in different scenarios. The latter included quasi-perpendicular, quasi-parallel, and Parker spiral-based scenarios, in order to highlight their profoundly diverse dynamics, as well as the possible formation of large upstream instabilities, such as foreshocks.

Finally, we present preliminary findings on the interaction between the realistic near-Earth environment and an interplanetary shock-front and shock-sheath in a quasi-perpendicular scenario.

How to cite: Cazzola, E., Fontaine, D., and Savoini, P.:  3D hybrid simulations of self-consistent IP shocks and their interaction with Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5366, https://doi.org/10.5194/egusphere-egu26-5366, 2026.

The properties of the region upstream of planetary bow shocks depend strongly on the direction of the interplanetary magnetic field. For the quasi-parallel bow shock, part of the solar wind ions is reflected back upstream from the shock and this reflected ion population triggers instabilities resulting in a turbulent region. Within this region, Short Large-Amplitude Magnetic Structures (SLAMS) can frequently be found, which are suggested to play a pivotal role in the formation of planetary bow shocks. Yet many properties of SLAMS are not well known at Earth and even less so at other planets.

SLAMS are identified by three criteria. First, a magnetic field amplitude twice the background magnetic field is required. Second, SLAMS should exhibit an elliptic polarization so that it can be differentiated from a shock oscillation. Last, it takes place upstream of the bow shock. 

Here we present results on the occurrence and other properties of SLAMS at different planetary foreshocks including Mars, Saturn and Mercury using different space missions. The results presented here can also offer comparative insights with SLAMS found at Earth for exploring potential dependencies on system size, and other magnetospheric and solar wind parameters.

How to cite: Wong Chan, (. T. K., Karlsson, T., and Bergman, S.: Statistical study of SLAMS at different planetary foreshocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7354, https://doi.org/10.5194/egusphere-egu26-7354, 2026.

Despite decades of study, questions about particle acceleration and energy cascades within the heliosphere remain open. Understanding these turbulent processes is key to understanding solar wind plasma dynamics. Interplanetary shocks provide a natural laboratory for investigating turbulent properties across the shock in upstream and downstream regions. However, conventional single-point spacecraft observations make it difficult to distinguish spatial from temporal variations, limiting direct comparisons with theoretical models.

We used the Wind, ACE, and DSCOVR missions, which are located at the L1 Lagrange point, to study turbulent scales perpendicular and parallel to the interplanetary (IP) shock normal. We estimate correlation lengths and effective Reynold numbers from the autocorrelation functions (ACFs). We show that these turbulent parameters decrease from upstream to downstream. However, an extended statistical analysis of tens of IP shocks showed little or no systematic decrease in correlation length across shocks. This can be related to the limitations of single-point measurements and to the small upstream and downstream intervals for the estimation of ACFs. To partially overcome these limitations, we identified cases in which the same turbulent structures were first observed upstream by Wind and then downstream by MMS near the subsolar point. This enabled us to better compare the properties of turbulence across the Earth’s bow shock. This multi-spacecraft configuration improves constraint on the spatial evolution of turbulence across shocks, allowing for more reliable estimates of correlation scales.

How to cite: Abushzada, I., Pitna, A., Nemecek, Z., and Safrankova, J.: Evolution of Solar-Wind Turbulence Correlation Lengths Across Interplanetary Shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8041, https://doi.org/10.5194/egusphere-egu26-8041, 2026.

Past kinetic simulations and spacecraft observations have shown that traveling foreshocks (TFs) are bounded by either foreshock compressional boundaries (FCBs) or foreshock bubbles (FBs). Here we present four TFs with a different kind of structure appearing at one of their edges. Two of them, observed by the Cluster mission, are bounded by a hot flow anomaly (HFA). In one case, the HFA was observed only by the spacecraft closest to the bow shock, while the other three probes observed an FCB. In addition, two other TFs were observed by the MMS spacecraft to be delimited by a structure that we call HFA-like FCB. In the spacecraft data, these structures present signatures similar to those of HFAs: dips in magnetic field magnitude and solar wind density, decelerated and deflected plasma flow and increased temperature. However, a detailed inspection of these events reveals the absence of heating of the SW beam. Instead, the beam almost disappears inside these events and the plasma moments are strongly influenced by the suprathermal particles. We suggest that HFA-like FCBs are related to the evolution and structure of the directional discontinuities of the interplanetary magnetic field whose thickness is larger than the gyroradious of suprathermal ions. We also show that individual TFs may appear together with several different types of transient upstream mesoscale structures, which brings up a question about their combined effect on regions downstream of the bow shock.

How to cite: Kajdič, P., Blanco Cano, X., Rojas Castillo, D., and Omidi, N.: Different Transient Phenomena at the Edges of Traveling Foreshocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8229, https://doi.org/10.5194/egusphere-egu26-8229, 2026.

Shocklets are nonlinear compressive magnetosonic structures formed by the steepening of ultra-low-frequency (ULF) waves due to dispersive effects in collisionless foreshocks. At Earth, they are characterized by sharp upstream edges, moderate magnetic compression, and frequent whistler wave precursors.

We investigate shocklet-like structures in Mercury’s foreshock using 20 Hz magnetic field observations from the MESSENGER mission. The analysis targets upstream intervals with broadband ULF activity at frequencies of 2 Hz and below, including both low-frequency (≲0.3 Hz) and higher-frequency (~1–2 Hz) fluctuations analogous to waves known to evolve into shocklets at Earth.

More than 200 candidate events are identified and classified into two main categories based on waveform morphology and polarization. The first consists of Earth-like shocklets, exhibiting sharp leading edges, clear magnetic compression, linear or elliptical polarization, and frequent whistler precursors. The second, more prevalent category comprises ULF magnetosonic waves with superposed higher-frequency fluctuations, displaying weaker steepening and less clear polarization. 

These observations indicate that similar wave-steepening processes operate at Mercury and Earth. However, Mercury’s weaker bow shock and therefore a reduced foreshock turbulence could favor multiscale wave coexistence and a broader diversity of shocklet-like structures.

How to cite: Rojas Castillo, D., Vaquero Bautista, C., Blanco Cano, X., Plashcke, F., Pump, K., Kajdic, P., and Heyner, D.: Shocklet-like Structures in Mercury’s Foreshock: New Evidence from MESSENGER, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8322, https://doi.org/10.5194/egusphere-egu26-8322, 2026.

Collisionless shocks are often modelled as smooth, planar surfaces - but many show organized corrugations that steer how particles get accelerated and how they radiate. We present a simple, linear magnetohydrodynamic (MHD) model that treats the shock as an evolving interface. This lets us separate two things: (1) the shock’s own properties and geometry, and (2) the statistics of the upstream turbulence that hits it. With this separation, we obtain a
direct map from incoming fluctuations to the corrugation patterns they create, including their drift speed and coherence. In our model, the interface acts like an “impedance” that focuses broad-band turbulent power into fast-mode waves that skim along the shock. The shock responds most strongly when the wave’s normal group speed is small (a sharp, single-peaked response). Corrugation strength increases with compression, while the shock geometry and plasma beta control how long these patterns persist. The framework makes testable predictions linking upstream turbulence and shock shape to fine
structure in electromagnetic signals from heliospheric and supernova-remnant shocks.

How to cite: Jebaraj, I. C., Malkov, M., Wijsen, N., Pomoell, J., Krasnoselskikh, V., Dresing, N., and Vainio, R.: Turbulence-driven corrugation of fast-mode shock waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8354, https://doi.org/10.5194/egusphere-egu26-8354, 2026.

Foreshock transients are formed when a solar wind directional discontinuity interacts with the reflected solar wind particles upstream of Earth's bow shock. Their sizes can be multiple Earth radii, and they can drive significant wave activity and accelerate particles in Earth's magnetosphere. In this study, we aim to determine which solar wind context hosts the most discontinuities and is the most favorable for foreshock transient formation. We consider quiet solar wind and large-scale structures like coronal mass ejections and high speed streams. To identify discontinuities in the solar wind, we use 1-second resolution magnetic field data from the Advanced Composition Explorer (ACE) spacecraft. We also use solar wind measurements from ACE to study properties around the discontinuities like direction of the convective electric field and solar wind cone angle, that can reveal whether a discontinuity is more likely to form a foreshock transient once it reaches the near-Earth space. In this work we use the definition "wave storm" to describe multi-hour intervals when ultra-low frequency wave activity on Earth is continuously increased. We will assess whether the occurrence rate of discontinuities and favorable conditions for foreshock transient formation in these large-scale structures are connected to wave storm occurrence and intensity. 

How to cite: Lipsanen, V., Turc, L., Ojuva, M., Hoilijoki, S., Dahani, S., Tao, S., Kalliokoski, M., and Kilpua, E.: Statistical study of directional discontinuities: solar wind context and relevant properties for foreshock transient formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11231, https://doi.org/10.5194/egusphere-egu26-11231, 2026.

The interaction of solar wind directional discontinuities with a shock can give rise to large-scale transient structures such as hot flow anomalies and foreshock bubbles. These transients play an important role in particle acceleration, and, when they are formed at Earth's bow shock, can have a global impact on near-Earth space. The properties of foreshock transients upstream of the shock have been extensively studied, and a number of recent studies have started taking a closer look at their signatures in the magnetosheath. There however often remain ambiguities as to whether a structure is observed upstream or downstream of the shock, which cannot be resolved with single-point or closely-spaced multi-spacecraft observations. Foreshock transient properties strongly depart from typical solar wind values, and vary widely from one event to another. It can therefore be difficult to conclude with certainty on which side of the shock a set of observations is made without having reference upstream measurements. To complicate matters further, the bow shock moves in response to the foreshock transient’s varying properties, which can lead to boundary crossings embedded within the transient's observations. In this work, we leverage 2D global numerical simulations performed with the hybrid-Vlasov Vlasiator model to get a global view of the interaction of foreshock transients with Earth's bow shock and compare their properties upstream and downstream of the shock. We investigate how foreshock transient signatures change as they are processed through the shock and compare ion energy spectrograms and velocity distribution functions on both sides of the shock. We aim to identify signatures which could be then used to distinguish between upstream and downstream observations. We test our findings on events previously reported in the literature. Determining whether a foreshock transient is observed before or after its interaction with the shock is crucial to evaluate its impact on the magnetosphere, as a change in e.g. dynamic pressure variations can lead to a different amplitude in the response of the magnetopause.

How to cite: Turc, L., Dahani, S., Suni, J., Tao, S., Kalliokoski, M., Lipsanen, V., Ojuva, M., and Palmroth, M.: Foreshock transient signatures upstream and downstream of the shock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11250, https://doi.org/10.5194/egusphere-egu26-11250, 2026.

In the transition region of a collisionless shock, the magnetic field strength generally reaches a larger value than the eventual downstream one. The formation of this magnetic overshoot plays an important role in, e.g., regulating the ion reflection. The magnitude of the overshoot varies spatially and temporarily along the shock front, necessitating several measurements to quantify it.

Catalogues of in situ shock crossing observations are now readily available from across the whole heliosphere, enabling large statistical studies. Here we combine measurements from Earth, Mars, Saturn as well as interplanetary shocks in the inner heliosphere, to investigate how the magnitude of the overshoot depends on the upstream parameters.

Consistent with previous studies, we find that there is a clear relationship with the upstream Alfvén Mach number and the magnitude of the overshoot relative to the upstream field strength. In the low Mach number (< 4) range, however, there appears to be an intriguing difference between planetary and interplanetary shocks. In contrast to past studies, we find that the overshoot does not depend on the upstream plasma beta for a given Alfvén Mach number.

How to cite: Hietala, H., Hoang, A., Lindberg, M., Sattiraju, T., Koller, F., and Vuorinen, L.: Magnetic overshoots at heliospheric shocks: parameter studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11398, https://doi.org/10.5194/egusphere-egu26-11398, 2026.

Collisionless shocks, such as planetary bow shocks and interplanetary shocks, can cause a wide range of ion kinetic instabilities in their downstream region. These phenomena (in particular mirror mode, ion cyclotron, and firehose instabilities) are sensitive to upstream solar-wind conditions. Changing the Mach number, from low to high, is expected to modify the balance between wave activity, transient structures, and turbulent fluctuations. However, a systematic comparative picture across Mach number regimes is still lacking.

We investigate the emergence and behaviour of ion kinetic instabilities across shock crossings spanning a broad range of Alfvénic and magnetosonic Mach numbers under selected solar wind conditions. We focus on the role of upstream parameters such as plasma beta, alpha-to-proton abundance ratio, or upstream interplanetary magnetic field fluctuations in shaping downstream instability behaviour. The analysis is based on MMS terrestrial bow shock crossings and cross-checked against interplanetary shocks by Wind and Solar Orbiter, enabling us to disentangle local planetary bow shock effects from more universal shock-driven processes. This study aims to clarify which instabilities dominate under different upstream conditions and how they contribute to plasma variability and energy redistribution downstream of collisionless shocks.

How to cite: Koller, F., Hietala, H., Vuorinen, L., and Lindberg, M.: Ion Plasma Stability Downstream of Collisionless Shocks Across the Mach Number Regimes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12052, https://doi.org/10.5194/egusphere-egu26-12052, 2026.

Interplanetary (IP) shocks are driven by solar activity and provide a unique in situ laboratory for studying particle acceleration. With its high-resolution measurements in the suprathermal range (above ~10 keV), Solar Orbiter opens a new window on how particles are energized out of the thermal population.

We focus on energetic proton production at IP shocks observed by Solar Orbiter, presenting results from a systematic calculation of proton acceleration efficiency and discussing its variability across 150 events observed since launch. We then highlight a subset of particularly strong shocks where the energetic particle pressure exceeds the combined magnetic and thermal pressure, a regime with direct relevance to cosmic-ray shocks in astrophysical environments. For these shocks, we examine the details of the local plasma and magnetic field conditions, with focus on upstream fluctuations and their role in particle acceleration. Together, these results provide new insight into how shocks accelerate particles across both heliospheric and broader astrophysical environments.

How to cite: Trotta, D., Giacalone, J., Lario, D., Raptis, S., Turner, D. L., Mostafavi, P., Hietala, H., Reville, B., Pezzi, O., and Wimmer-Schweingruber, R.: Energetic Protons at Solar Orbiter Shocks: Efficiency, Variability, and Energetic Particle Pressure-Dominated Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13398, https://doi.org/10.5194/egusphere-egu26-13398, 2026.

The ion foreshock is the region of space where solar wind ions interacting with Earth’s bowshock can reach after being reflected in the bowshock instead of penetrating into the megnetosheath. The foreshock forms wherever the interplanetary magnetic field is quasit parallel to the bowshock’s normal and connected to it. In the foreshock, the ions reflected at the bowshock form a population that propagates in the upstream direction and make the Velocity Distribution Function (VDF) unstable, giving rise to Ultra Low Frequency (ULF) waves.

The Magnetospheric Multiscale Mission (MMS) in it orbit around the earth periodically probes the ion foreshock. The on-board Fast Plasma Investigation (FPI) instrument provides full ion VDFs of this region, a velocity distribution function comprised of the contributions of all ion populations present, including different ion species and the back-streaming protons characteristic of the ion foreshock. Here we present a method based on Gaussian Mixture Models (GMM) that we use to decompose full ion VDF into partial VDFS corresponding to the different ion populations. In this way, we can isolate the VDF of only the back-propagating foreshock protons, that can be used to study how they contribute to the instability of the full VDF and the excitation of propagation of ULF waves throughout the foreshock.

We demonstrate the ability of this method to find separate population-specific VDFs and apply it to a case study where ULF waves are observed in association to a diffuse back-streaming proton distribution function.

How to cite: Albert, I. F., Toledo-Redondo, S., Graham, D., Khotyaintsev, Y., Norgren, C., Montagud-Camps, V., and Castilla-Tevar, A.: Characterization of back-streaming proton VDFs in the Earth's bowshock using a Gaussian Mixture Model., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13565, https://doi.org/10.5194/egusphere-egu26-13565, 2026.

The solar wind interaction with Mercury’s magnetic field generates a bow shock in front of the planet. As at Earth, the region upstream of the shock that is magnetically connected to it, and known as foreshock, is permeated by a variety of waves. The characteristic frequencies and wave properties so far reported are (i) high frequency 2 Hz whistler waves (similar to the 1 Hz waves at Earth), (ii) intermediate frequency of 0.8 Hz, whose properties and formation mechanism remains unknown and (iii) lower frequency compressive waves in the 0.3 Hz range (corresponding to the large amplitude 30-s waves observed at Earth’s foreshock). The existence of ultra-low frequency waves indicates that backstreaming ions are able to drive instabilities as in the terrestrial case. However, simultaneous occurrence of different modes at Earth is not often observed.  In this work we use Messenger magnetic field data to study some examples of extended regions at Mercury’s foreshock where multiple wave modes at frequencies 2, 0.8 and 0.3 Hz co-exist. The waves can maintain coherence over long intervals of time which may be related to the fact that the shock is weaker with Mach numbers in the range 2-5, and so that less backstreaming ions and density gradients are expected. Future work using plasma data from the BepiColombo mission are needed to understand in more detail wave generation and evolution in Mercury’s environment.

How to cite: Blanco-Cano, X., Plaschke, F., Kajdic, P., Rojas-Castillo, D., Pump, K., Heyner, D., Vaquero-Bautista, C. A., Erinfolami, F., Poh, G., Karlsson, T., and Le, G.: Multi-mode wave observations at Mercury’s Foreshock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13602, https://doi.org/10.5194/egusphere-egu26-13602, 2026.

Diffusive shock acceleration is widely accepted as the primary mechanism to generate high-energy particles in supernova remnant shocks but faces challenges with efficiently accelerating low-energy particles, known as the injection problem. Shock stochastic drift acceleration presents a promising pre-acceleration mechanism, in which the whistler waves in shock transition region can be essential in scattering and energizing low-energy electrons, aligning well with observations (Amano et al., 2022). However, the physical origin of these waves within the shock transition layer has not been fully understood.

In our study, we investigate the generation of whistler-mode waves by shock-reflected electrons at quasi-perpendicular collisionless shocks. Using Liouville mapping, we construct the electron velocity distribution function in the shock, which allows us to explicitly capture the phase-space features of mirror-reflected electrons near the upstream edge of the shock transition region. Based on the constructed distribution, we perform a linear instability analysis using a semi-analytical method (Kennel & Wong, 1967) to examine the whistler wave generation by the mirror-reflected electrons.

We find that the reflected electrons can excite two distinct instabilities with different propagation directions when both the upstream electron beta β_e and Alfvén Mach number in the de Hoffmann-Teller frame M_A/cosθ_Bn are sufficiently large, where M_A is Alfvén Mach number and θ_Bn is the angle between the upstream magnetic field and the shock normal. In the parameter regime of Earth's bow shock, the instability threshold is approximately M_A/cosθ_Bn>∼50. Since such shocks are super-critical with respect to the whistler critical Mach number, the excited waves cannot propagate upstream and instead accumulate within the shock transition layer.

Furthermore, we find that the pitch-angle scattering by the generated waves may trigger secondary instabilities on the same branch. We suggest that the sequence of instabilities likely happening within the shock transition layer can efficiently scatter the reflected electrons over a broad range of pitch angles. We propose that this sequence of self-generated instabilities enables the confinement of the reflected electrons within the shock transition region. Such self-confinement provides the key ingredient of stochastic shock drift acceleration, which then offers a plausible mechanism for the electron injection into diffusive shock acceleration.

How to cite: Wang, R. and Amano, T.: Generation of Whistler Waves by Reflected Electrons and Their Self-Confinement at Quasi-Perpendicular Shocks , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15879, https://doi.org/10.5194/egusphere-egu26-15879, 2026.

We investigate the diffusive shock acceleration of partially ionized ions by introducing helium-, carbon-, and iron-like ions at solar abundances into two-dimensional hybrid (kinetic ions/fluid electrons) simulations of nonrelativistic collisionless shocks. We find that heavy ions are preferentially accelerated, with energy transfer to helium comparable to or exceeding that of hydrogen, enhancing shock acceleration efficiency. Moreover, accelerated helium ions play a role in magnetic field amplification and in controlling the ensuing spectra of accelerated particles. We also show how efficient particle acceleration modifies the shock compression ratio, which has implications for the predicted arrival times of coronal mass ejections at Earth. 

How to cite: Caprioli, D., Orusa, L., Cernetic, M., Haggerty, C. C., and Ostler, B.: Acceleration of He and heavy ions at collisionless shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22242, https://doi.org/10.5194/egusphere-egu26-22242, 2026.

We investigate two adjacent solar energetic electron (SEE) events measured by Solar Orbiter/EPD at 0.93 au with a separation of ~30 minutes on December 24, 2022. STEREO-A (Wind) with a longitudinal separation of ~5°(19°) from Solar Orbiter shows no clear observations of SEEs, indicating the presence of a <20° longitudinal distribution for these two events. In addition, the nearly symmetric peaks in temporal profiles and strongly beamed pitch angle distributions in both events suggest that most of these SEEs undergo essentially scatter-free propagation in the interplanetary medium. Utilizing the pan-spectrum fitting method, we self-consistently determine the spectral shape of background-subtracted electron peak flux vs energy. Event #1 is fitted to a triple power-law spectrum with two spectral breaks at ~22 and 290 keV. Event #2 shows a double power-law spectrum with a spectral break around 25 keV. For both events, the power-law spectrum extends down to below 10 keV, implying that these SEEs could originate high in the corona. We further derive the electron injection profiles at sun by forward fitting in-situ temporal profiles, for the two events. According to the characteristics of injection timing and spectral shape, Event #1 consists of three SEE populations, respectively, at energies below ~22 keV, between ~22 keV and ~290 keV, and above ~290 keV, while Event #2 consists of two populations, respectively, at energies below and above ~25 keV. The low-energy population likely provides seed populations for further acceleration process (processes) to form the high-energy population (populations).

How to cite: Wang, L., Li, Y., Wimmer-Schweingruber, R., Su, Y., and Krucker, S.: Solar Energetic Electron Events on 2022 December 24, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1917, https://doi.org/10.5194/egusphere-egu26-1917, 2026.

The Chinese Tianwen1 mission arrived at Mars since 2021 and the Mars Energetic Particle Analyzer (MEPA) instrument has been monitoring the energetic particle fluxes at the orbit of Mars, measuring protons in the energy range up to 100 MeV. It has captured a series of Solar Energetic Particle (SEP) events at Mars and we have anlayzed the energy spectra and time evolution and each event and derived their statistical properties which show different characteristics from SEP events detected elsewhere. We will give a brief summary of the MEPA observed SEP events at Mars in comparison to other events observed at Earth and other locations. 

How to cite: Guo, J. and Cao, Y.: SEP events observed at Mars by the Chinese Tianwen1 mission over the past years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2738, https://doi.org/10.5194/egusphere-egu26-2738, 2026.

Local particle acceleration in the shock sheath region formed during the interaction between multiple coronal mass ejections (CMEs) is a complicated process that is still under investigation. On March 23, 2024, the successive eruption of two magnetic flux ropes (MFRs) from the solar active region 3614 produced twin CMEs, as identified in coronagraph images. By analyzing in-situ data from Solar Orbiter and Wind, it is found that the primary ICME-driven shock overtook the preceding ICME, trapping it in the sheath between the shock and the primary ICME, forming the ICME-in-sheath (IIS) structure. Using Solar Orbiter observations, we show that both electrons and ions are accelerated within the IIS. A clear enhancement of suprathermal electrons was observed at the IIS boundary, where strong flow shear and large magnetic field variation suggest possible local electron acceleration. Electrons (> 38 keV) exhibit a long-lasting enhancement in the IIS with a spectral index of ~2.2, similar to that in the shock sheath and the primary ICME, indicating a similar solar origin. Inside both the sheath and IIS, spectra of proton and ⁴He are generally consistent with the prediction of the diffusive shock acceleration, whereas Fe and O present a double power-law shape. Additionally, the Fe/O ratio in the IIS is higher than that in the sheath, and more close to the abundance of the flare-related particles, suggesting the remnant particles of flare confined in the IIS.

How to cite: Chen, X., Li, C., Xu, Z., Nicolaou, G., Kollhoff, A., Ho, G. C., Wimmer-Schweingruber, R. F., and Owen, C. J.: Local Particle Acceleration in an ICME-in-Sheath Structure Observed by Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4238, https://doi.org/10.5194/egusphere-egu26-4238, 2026.

Solar energetic particles (SEPs), which originate from the eruptive activities of the solar corona, are accompanied by a significant amount of high-energy charged particles, can cause damage to spacecraft systems and affect human activities in space.

Describing the propagation of SEPs in interplanetary space constitutes an indispensable component in the construction of SEP physical model. In this work, we developed a coupled Physics-based model composed of a data-driven analytical background model and a particle transport model represented by the focused transport equation (FTE). By using the coupled model, we try to simulate the energetic particle propagation in different interplanetary structures, such as the stream interaction region (SIR) and the coronal mass ejection (CME), with specific cases observed by WIND, STEREO A/B and SOHO, and to explore the physical nature behind the spacecraft observations.

How to cite: Shen, F., Tao, X., Luo, X., and Feng, X.: Modelling Solar Energetic particle (SEP) Transport Related with Stream Interaction Regions and CME Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4592, https://doi.org/10.5194/egusphere-egu26-4592, 2026.

The composition of solar energetic particle (SEP) events varies significantly from event to event and with energy within individual events.  For example, although the ‘typical’ Fe/O ratio is considered to be 0.134, it is observed to vary from <0.01 to >1 and often shows strong dependence on energy.  Several processes and conditions may contribute to this variability, including the dominant acceleration process (e.g., diffusive shock acceleration versus magnetic reconnection), the properties of the seed population being accelerated, the conditions of the interplanetary medium  as the particles travel from the acceleration region to the observer.  Here we examine the composition variability as measured by older missions such as ACE and STEREO, but also include more recent observations from Parker Solar Probe, Solar Orbiter and the newly launch Interstellar Mapping and Acceleration Probe (IMAP).  The combination of these measurements also provides the capability of examining the composition of individual events as a function of radius and longitude.

How to cite: Cohen, C.: Composition variations and their implications for SEP acceleration and transport processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5099, https://doi.org/10.5194/egusphere-egu26-5099, 2026.

The spatial size of collisionless shock waves is suggested to play an important role in determining the maximum energy gain of particles accelerated at heliospheric and astrophysical shocks. In addition, shocks energize particles with different starting/upstream energies differently. This study aims to investigate the maximum energy gain at heliospheric shocks at various sizes and seed conditions. In our comparison, we focus on the Martian, Venusian, terrestrial, and Jovian bow shocks, as well as interplanetary shocks, using spacecraft data from the MAVEN, Venus Express, Magnetospheric Multi-Scale (MMS), Juno, Parker Solar Probe, and Solar Orbiter spacecraft missions, respectively. These shock systems are chosen because of their vast physical size difference and therefore constitute perfect laboratories for the intended comparison study. We explore the maximum energy dependence on the shock obliquity and shock Mach number measured for each shock crossing. In addition to the maximum energy, we also compare the suprathermal electron spectral index for the different sets of shocks and its dependence on the shock obliquity.

How to cite: Lindberg, M., Hietala, H., Koller, F., and Vuorinen, L.: Comparison of Particle Acceleration at Planetary Bow Shocks and Interplanetary Shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5421, https://doi.org/10.5194/egusphere-egu26-5421, 2026.

The joint ESA/NASA Solar Orbiter mission has observed suprathermal and energetic particles throughout much of Solar Cycle 25, spanning the period from 2020 to 2025, providing unprecedented coverage of the inner heliosphere. Measurements of protons, and heavy ions show substantial temporal variability in particle intensities over the solar cycle. In particular, the Suprathermal Ion Spectrograph (SIS) of the Solar Orbiter Energetic Particle Detector (EPD) measures suprathermal ion abundances from hydrogen through iron with high precision. Previous studies have shown that the suprathermal ion population in the heliosphere arises from multiple source populations. In this work, we focus on the composition and origin of the quiet-time suprathermal population, using Solar Orbiter/SIS composition measurements to examine how source contributions vary with solar activity level and heliocentric distance. We find that during periods of low solar activity and relatively stable particle intensities, the suprathermal heavy-ion composition closely resembles that of the ambient solar wind and/or corotating interaction regions, indicating that these sources make a dominant contribution under quiet conditions. Impulsive material, such as ³He-rich ions, becomes more prominent during more active intervals but represents a reduced fraction of the suprathermal pool during quiet times. These observations demonstrate that the quiet-time suprathermal population in the inner heliosphere is largely controlled by solar-related sources, providing important constraints on the seed population available for subsequent energetic particle acceleration.

How to cite: Ho, G., Mason, G., Allen, R., Hart, S., Kouloumvakos, A., Wimmer-Schweingruber, R., Rodríguez-Pacheco, J., and Gómez-Herrero, R.: Quiet-time Suprathermal Intensities and Composition Observed by Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5904, https://doi.org/10.5194/egusphere-egu26-5904, 2026.

With its inclined orbit, Solar Orbiter now reaches higher heliocentric latitudes than are accessible from the ecliptic. We will investigate small, dispersive solar particle events and compare their onset times with X-ray measurements. Using the first particles to arrive, we determine the path lengths along which they traveled and compare these with the expected values. This exploratory work could help elucidate the global configuration of the coronal and interplanetary magnetic field and discern between traditional models and, e.g., the Fisk model. We find that at the heliographic latitudes attained by Solar Orbiter, small, dispersve events do not appear different form in-ecliptic solar particle events.

How to cite: Wimmer-Schweingruber, R. F., Rodriguez-Pacheco, J., Ho, G. C., Warmuth, A., Berger, L., Mason, G. M., Ding, Z., Gomez-Herrero, R., Krucker, S., Kollhoff, A., Espinosa, F., Kühl, P., Allen, R. C., Cernuda, I., Gunaseelan, S., Jentsch, E., Kartavykh, Y., Fleth, S., and Eldrum, S.: Dispersive  out-of-ecliptic solar particle events observed by EPD on Solar Orbiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6620, https://doi.org/10.5194/egusphere-egu26-6620, 2026.

How to cite: Han, C., Wimmer-Schweingruber, R., Kühl, P., Berger, L., Ding, Z., Kollhoff, A., Shi, Q., Xu, Z., and Qin, M.: Modulation of the Heliospheric Current Sheet in the Propagation of Solar Energetic Electrons: an Investigation Based on CoSEE-Cat, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6684, https://doi.org/10.5194/egusphere-egu26-6684, 2026.

The significance of ³He-rich solar energetic particle (SEP) events, though often overlooked, is threefold: (1) they trace small-scale sites that may serve as precursors to larger eruptive activity, (2) they probe the structure of magnetic connectivity that help refine solar wind and coronal magnetic field models, and (3) they provide constraints on waveparticle interactions and turbulence that influence the acceleration of heavy ions. These ³He-rich events are typically short-lived, exhibit low total particle intensity, and are associated with active region jets and Type III radio bursts. This study presents results from a ³He/⁴He ratio survey using Parker Solar Probe’s IS⊙IS/EPI-Hi instrument from its launch through 2025. We investigate the occurrence, energy spectra, and spatial distribution of ³He-rich SEP events across radial distances. By analyzing the radial distribution of ³He-rich events, we aim to determine whether their characteristic enhancements persist over heliocentric distance or degrade due to transport effects, complementing prior studies focused primarily on longitudinal connectivity. Emphasis is placed on identifying correlations between ³He enrichment and solar source properties, including the differential emission measure (DEM) of active regions and the presence of jets. DEM maps constrain low coronal temperature and density structure, enabling identification of plasma environments where ion cyclotron waves may resonate with ions of specific charge-to-mass ratios, such as the case in which ³He is selectively energized, thus linking in-situ ³He-rich SEP composition via wave-particle processes. We further compare PSP observations with those from other spacecraft (IMAP, ACE, STEREO, Solar Orbiter) during periods of apparent Parker spiral field line alignment to study transport and re-acceleration effects.

How to cite: Muro, G., Cohen, C., Leske, R., and Xu, Z.: 3He-Rich SEPs throughout the inner heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8158, https://doi.org/10.5194/egusphere-egu26-8158, 2026.

Enhancements in ³He abundance, a characteristic feature of impulsive solar energetic particle events, are also frequently observed in gradual solar energetic particle events, but the origin of the ³He-rich contribution to the seed population (remnant material versus fresh injection from the parent active region) remains unresolved. We investigate the origin of ³He enrichment in high-energy (25–50 MeV) solar proton events observed by the Solar and Heliospheric Observatory, selecting events that coincide with <1 MeV/nuc ³He-rich periods detected by the Advanced Composition Explorer from 1997 to 2021. Extreme-ultraviolet imaging from the Solar Dynamics Observatory and STEREO reveals narrow, jetlike eruptions in the parent active regions of about 60% of the events. Notably, the highest ³He/⁴He ratios occur when coronal jets are present, consistent with fresh, jet-driven injection of suprathermal ³He that is subsequently reaccelerated during the event. Correspondingly, jet-associated events show fewer pre-event (residual) ³He counts, indicating that enrichment in these cases does not primarily come from remnant material. We find a positive correlation between ³He/⁴He and Fe/O, strongest in jet-associated events, consistent with a common jet-supplied seed population reaccelerated by the coronal mass ejection shock. We also find that a substantial fraction of apparent ³He enrichments arise from overlap with independent impulsive SEP activity, highlighting the need to separate superpositions from true reacceleration signatures.

How to cite: Bucik, R., Hart, S., Dayeh, M., Desai, M., Mason, G., and Wiedenbeck, M.: Helium-3 Enrichment in Gradual Solar Energetic Particle Events: Evidence for a Jet-supplied Seed Population, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8583, https://doi.org/10.5194/egusphere-egu26-8583, 2026.

We present observations of impulsive solar energetic particle events on 2025 March 20 observed at high heliolatitude by Solar Orbiter and compare them with near-ecliptic observations by the Wind spacecraft. Solar Orbiter, located at 0.38 au, a Carrington longitude of 139.7◦ and a latitude of −16.6◦, detected two ion events at ∼0.1-6 MeV and two electron events at ∼40-200 keV. These events exhibit clear velocity dispersion and strong field-aligned anisotropy. Velocity dispersion analysis of both ion and electron events yields path lengths consistent with the nominal Parker spiral length. Furthermore, the first electron event exhibits a double-power-law spectrum with an index of 2.3 ± 0.3 below a break energy of 58 ± 4 keV and an index of 4.0±0.2 at energies above, while the second electron event exhibits a single-power-law spectrum with an index of 4.6 ± 0.2. In contrast, the Wind spacecraft, located at 1 au, a Carrington longitude of 120.0◦, and a latitude of −7.1◦, observed only one electron event, which shows insignificant velocity dispersion and arrives ∼20 min later than expected. The Parker spiral footpoints of the two spacecraft were separated by ∼15◦ in longitude and ∼10◦ in latitude, providing a lower limit on the angular extent of impulsive electron events. The delayed arrival at Wind may be attributed to the electron diffusion in the solar source region.

How to cite: Yang, L., Ding, Z., Wang, W., Heidrich-Meisner, V., Wimmer-Schweingruber, R., Wang, L., Pisa, D., Zhu, Y., Battaglia, A., Kollhoff, A., Rodríguez-Pacheco, J., and Ho, G.: Impulsive Solar Energetic Particle Events at High Heliolatitude, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8925, https://doi.org/10.5194/egusphere-egu26-8925, 2026.

Solar energetic particle (SEP) events provide key constraints on particle acceleration and transport in the heliosphere. While most events are dominated by outward streaming particles along open magnetic field lines, rare bidirectional events showing concurrent sunward and anti-sunward flows, offer a unique probe of magnetic connectivity and the coupling of multiple acceleration sources. Here we analyze two uncommon bidirectional anisotropic SEP events observed by Solar Orbiter, focusing on their association with magnetic flux ropes. Both events exhibit two distinct velocity-dispersion signatures during the onset phase, accompanied by opposite anisotropies. The sunward-streaming protons show a delayed apparent release, a harder spectrum, and higher intensities, consistent with acceleration at a CME-driven shock and subsequent transport within transient magnetic structures. In contrast, the promptly released anti-sunward protons are more consistent with flare-related acceleration. These observations demonstrate the diagnostic power of jointly using anisotropy, inferred release times, source spectra, and in situ magnetic structure signatures to disentangle SEP transport in complex large-scale transients, and they pose new constraints for current SEP transport models.

How to cite: Ding, Z., Wimmer-Schweingruber, R., Yang, L., Kollhoff, A., Kühl, P., Berger, L., Ho, G., and Mason, G.: The impact of large-scale transient structures on solar energetic particle transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9709, https://doi.org/10.5194/egusphere-egu26-9709, 2026.

On 9 October 2024, a major Solar Energetic Particle (SEP) event was detected simultaneously across a wide range of heliolongitudes and heliocentric distances. Signatures were observed by Solar Orbiter, Parker Solar Probe (PSP), STEREO-A, near-Earth spacecraft (SOHO, GOES, ACE), and surface instruments on Mars (MSL/RAD). The event originated from an X1.8 solar flare in Active Region (AR) 3848, which produced a fast, Earth-directed full-halo coronal mass ejection (CME). This study aims to characterize the acceleration and heliospheric distribution of SEPs during this event and to evaluate its implications for space weather forecasting and radiation risks for future human exploration of Mars. We combined imaging and in situ particle observations from multiple spacecraft positioned at different longitudes and heliocentric distances. Analyses included flare and CME timing, SEP fluxes, onset times, and energy spectra at each vantage point. Multi-point comparisons allowed us to assess how CME-driven shocks accelerate and transport SEPs, and how cross-field propagation and interplanetary scattering shaped the observed particle distributions, particularly at Mars.

The X1.8 flare began at 01:25 UTC, peaked at 01:56 UTC, and ended at 02:43 UTC. The associated full-halo CME was first detected by LASCO at 02:12 UTC from ~N13 W08, with speeds estimated at ~1,500 km/s (leading edge) and ~2,100 km/s (shock front). The CME arrived at Earth around 10 October 14:45 UTC. Solar proton intensities began rising at 02:40 UTC and reached S2 (moderate) radiation storm levels by 07:30 UTC. Widespread SEP detections, including at Mars, demonstrate efficient particle acceleration over an exceptionally broad spatial domain and highlight the role of extended shock fronts, cross-field diffusion, and interplanetary turbulence in shaping SEP propagation. These results provide critical constraints for SEP transport models and underline the value of multi-point observations for advancing forecasting capabilities and mitigating radiation hazards in deep space missions.

How to cite: Khaksari, S., Wimmer-Schweingruber, R. F., Löwe, J. L., Guo, J., Pacheco, D., Heber, B., Dröge, H., J. Lillis, R., Ding, Z., Ehresmann, B., M. Hassler, D., Löffler, S., Zeitlin, C., and Matthiä, D.: Requirements for Solar Energetic Particle Forecasting at Mars: Lessons from Multi-Point Observations of the 9 October 2024 CME-Driven Shock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10464, https://doi.org/10.5194/egusphere-egu26-10464, 2026.

The HENON CubeSat mission is designed to fly on a distant retrograde orbit (DRO) around the Earth at about 0.1 Earth radii, for advance time space weather monitoring. The mission has a set of instruments which include an energetic particle detector measuring protons from a few MeV to hundreds of MeV. In this work, we investigate under what conditions energetic particles can be accelerated at interplanetary shocks above the detection threshold of about 2 MeV of the HENON instrument.
We set up a test particle numerical simulation in which protons move in the drift approximation around a shock transition, and are accelerated each time they cross the shock. Protons are injected at the shock with an energy of few tens of keV and are scattered in pitch angle by a collision operator. In the simulation, we vary the pitch-angle scattering time, the shock compression ratio, and the type of transport, which can be either normal diffusion or superdiffusion. In the superdiffusive case, a power-law distribution of scattering times is generated in order to reproduce a Levy walk. The proton energy spectra are obtained as a function of the elapsed time, keeping in mind that for strong heliospheric shocks associated to fast coronal mass ejections, the shock lifetime is of the order of one or two days. Several runs are carried out in order to determine (i) the parameter domain which leads to efficient acceleration and (ii) which runs lead to the highest energies. For typical parameters, superdiffusive acceleration turns out to be faster in accelerating protons. Simulation results will be presented for a wide parameter range, and we find that energies in the range of 2-10 MeV can be reached in a number of cases. 
This work was funded by the Italian Space Agency (ASI) through the Argotec contracts, numbers ARG-IT-CON-P-HEN-220002 and ARG-IT-CON-P-HEN-250003. GZ, SP, and GP acknowledge partial support by the Italian PRIN 2022, project 2022294WNB entitled "Heliospheric shocks and space weather: from multispacecraft observations to numerical modelling” (CUP H53D23000900006).

How to cite: Zimbardo, G., Scarivaglione, L., Prete, G., Perri, S., Marcucci, M. F., Laurenza, M., Landi, S., Greco, A., Malara, F., and Servidio, S.: Numerical study of proton acceleration at interplanetary shocks for the interpretation of the HENON CubeSat mission measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12945, https://doi.org/10.5194/egusphere-egu26-12945, 2026.

Impulsive solar energetic particle (SEP) events are characterized by compositional anomalies, the highly elevated ³He/⁴He ratio in particular. They also tend to be abundant in heavy elements and electrons.  It is still not clear how impulsive SEP (ISEP) events are produced, largely because of the difficulty of finding their solar sources.  It is true that they are often identified as coronal jets, energetically much less pronounced than solar flares, which are found around the times of type III radio bursts in the decametric-hectometric wavelength range. But in a small number of ISEPs observed by Solar Orbiter, search of the solar source seems to be not hopeful.  In this work we try to find the solar sources of the ISEPs with high ³He flux as  published by Kouloumvakos et al. (2025). We first concentrate on those events that occurred while Solar Orbiter was magnetically connected to the part of the Sun visible from Earth so that we can make use of multi-channel SDO/AIA data. To explore the effect of spatial resolution on the detectability of the source region, we study ISEPs that were observed when Solar Orbiter was close to the Sun and the likely source regions happened to be in the field of view of EUI/HRI. Lastly we investigate the relation of dropouts in ions and electrons with the properties of the source regions.

How to cite: Nitta, N., Bucik, R., Mason, G., Ho, G., Rodríguez-Pacheco, J., Wimmer-Schweingruber, R., Allen, R., Kouloumvakos, A., Gomez-Herrero, R., and Krupar, V.: Solar sources of impulsive solar energetic particle events with high 3He content , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16510, https://doi.org/10.5194/egusphere-egu26-16510, 2026.

Macro-modeling of the solar corona and solar wind seeks to describe the physical mechanisms that accelerate plasma particles to supersonic speeds and to explain their properties at various heliographic coordinates, increasingly sampled by space missions. Recent observational evidence provided by Parker Solar Probe on suprathermal electrons with Kappa-type velocity distributions at the origins of the solar wind has revived interest in deciphering kinetic effects and their consequences. We present new results from two complementary approaches of the solar wind, namely the kinetic-exospheric models and the HD/MHD fluid models with kinetic components. In this case, both approaches capture and quantify the effects of suprathermal electrons modeled with Kappa distributions, standard and regularized Kappa models. The latter have been introduced more recently for a physically and statistically consistent characterization of suprathermal populations and their consequences. Overestimations of the energy transferred directly or indirectly (e.g., through the ambipolar field created in the acceleration regions) to the solar wind by suprathermal electrons are thus prevented. One can consider for the first time those more energetic electrons, with strong suprathermal tails and associated with the source of energetic solar outflows, such as coronal mass ejections and bursts. Furthermore, such conditions cannot be ruled out as being conducive to the shaping of stellar winds in the astrospheres of stars with coronas much hotter than those of the solar corona.

How to cite: Lazar, M., Vinogradov, A., Poedts, S., and Fichtner, H.: The impact of suprathermal electrons in solar wind macromodeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17669, https://doi.org/10.5194/egusphere-egu26-17669, 2026.

Radiation environments driven by solar energetic particle (SEP) events are a key risk for deep-space missions, and robust flux retrievals are essential for both operations and long-term environment models. We present an end-to-end proton flux inversion pipeline for the Radiation-Hard Electron Monitor (RADEM) on ESA’s JUICE mission, focusing on the proton detector channels in the nominal configuration. We apply a normalization that converts Geant4 simulation counts into calibrated response-matrix elements, consistent with the General Particle Source (GPS) setup (surface source on a sphere) and a cosine-weighted angular distribution within a finite cone. The response matrix is then used with multiple inversion approaches and time-averaging schemes to retrieve proton intensities in predefined energy bands.

To validate absolute scaling and spectral behavior, we compare RADEM-derived proton time series for selected SEP events with contemporaneous IREM (INTEGRAL Radiation Environment Monitor) Level-2 proton differential fluxes integrated over matching energy bands. The comparison includes quiet-time intervals before and after each event and focuses on periods when JUICE and IREM were in close spatial proximity. We discuss practical sensitivities across the tested inversion approaches and outline next steps. This work provides a reproducible foundation for SEP analyses with RADEM and supports broader heliospheric energetic particle studies across missions.

How to cite: Kilic, C., Galli, A., Hajdas, W., Grzanka, L., Adamus, G., Kozimor, D., and Swakoń, J.: Deriving SEP Proton Fluxes with the JUICE Radiation Environment Monitor: Response-Matrix Inversion and Near-Conjunction Validation with IREM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19322, https://doi.org/10.5194/egusphere-egu26-19322, 2026.

We investigate the impact of a Coronal Mass Ejection (CME) on the transport and acceleration of relativistic protons in the solar wind using a coupled 3D Magnetohydrodynamics (MHD) simulation and test-particle approach. The CME is modelled as a spheromak propagating through a Parker-like solar wind and the trajectories of 5 GeV protons are integrated in the guiding-centre approximation limit. Our results show that the CME can significantly accelerate the protons up to tens of GeV.
Particles gain energy through an adiabatic heating mechanism as they access to regions of compressed plasma downstream of the CME-driven shock. In our configuration, the maximum energy gain, which is about 50 % per crossing, occurs when the perturbation reaches about 0.3 AU, which corresponds to ~9 hours after the spheromak is injected.
The parallel diffusion plays an important role by confining the particles within the simulation domain long enough for them to encounter the disturbance multiple times and gain energy at each interaction. Particles' energy spectra at 1 AU shows the energy gain depends on the longitude of the magnetic field line on which the particle is located. They also show that the spectra are harder for smaller values of the parallel mean free path λ. 

How to cite: Houeibib, A., Pantellini, F., and Griton, L.: Acceleration of relativistic protons in a CME-perturbed solar wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19733, https://doi.org/10.5194/egusphere-egu26-19733, 2026.

On 21 November 2024, a strong solar energetic particle (SEP) event implying protons of 100 MeV near Earth was associated with an eruption located on the far side of the Sun as viewed from Earth.
The source region was identified using EUV observations from the Solar-Terrestrial Relations Observatory (STEREO) as NOAA AR 13892, located around (lon, lat) = (355°, -20°) in Carrington coordinates at around 00:45 UT. Due to its location, the associated flare produced only weak soft X-ray signatures in Earth-based observations. The Spectrometer/Telescope for Imaging X-rays (STIX) instrument on-board Solar Orbiter, which was also positioned on the far side relative to the parent active region, recorded an increase in the 15-25 keV range.
The flare was followed by a coronal mass ejection (CME) of speed 1436 km/s, propagating on the solar limb and driving a shock wave at its front. The 3D geometry of the CME-driven shock was reconstructed using white-light remote-sensing observations from STEREO-A and SOHO. This was then combined with global magneto-hydrodynamic (MHD) simulations from Predictive Science Inc. (PSI), to derive the MHD properties of the shock surface, as well as the magnetic field lines connecting the spacecraft to the Sun’s surface.
This enables the study of MHD shock parameters evolution along field lines regarding the SEP profile and characteristics measured at the corresponding spacecraft. We therefore investigated acceleration scenarios for the energetic particles that reached Earth, STEREO-A and Solar Orbiter, which are magnetically connected to different regions of the evolving shock.

How to cite: Jarry, M., Papaioannou, A., Talebpour Sheshvan, N., Rouillard, A. P., Lavasa, E., Vasalos, G., and Anastasiadis, A.: Proton acceleration by CME-driven shock during the 21 November 2024 (GLE76) event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19845, https://doi.org/10.5194/egusphere-egu26-19845, 2026.

It is well established that solar energetic particles events typically show normal velocity dispersion (VD), where the release of particles is independent of energy, producing anpattern with an earlier onset at higher energies. Recent measurements by NASA’s Parker Solar Probe (PSP) and ESA’s Solar Orbiter(SolO), however, reveal events with a mixed dispersion behaviour: VD at lower energies, but an inverse velocity dispersion (IVD) at higher energies, in which higher-energy particles arrive later than lower-energy ones. Building on our earlier SolOsurvey of 10 IVD proton events and its interpretation in terms of time-dependent shock diffusive acceleration, we extend the method to multi-point IVD observations by SolO, STEREO-A (STA), and PSP. For events observed at multiple longitudes, we apply consistent VDA/IVD fitting to infer release heights and radial mean free paths at each spacecraft and quantify their variability with magnetic connection. Observers with larger connection angles systematically show delayed VDA release times; we compare these delays with EUV-wave arrival at the magnetic footpoint or with fitted CME connection times. We further investigate inter-spacecraft SEP properties, such as time-integrated spectra, spectral breaks, and pitch-angle anisotropies.

How to cite: Li, Y., Guo, J., Pacheco, D., Ding, Z., Temmer, M., and Wimmer-Schweingruber, R. F.: Inverse velocity dispersion events in multi-spacecraft analyses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20100, https://doi.org/10.5194/egusphere-egu26-20100, 2026.

We investigate the transport of solar energetic particles (SEPs) during the relativistic and longitudinally widespread event of 28 October 2021 - GLE73, with the aim of quantifying the roles of parallel and perpendicular diffusion and constraining the spatial extent of the injection region. Inverse modeling is performed using numerical simulations of focused particle transport that include cross-field diffusion, in order to reproduce multi-spacecraft observations from STEREO-A, Solar Orbiter, and near-Earth missions over a wide range of electron and proton energies. Simulated intensity and anisotropy time profiles are compared across multiple helio-longitudes to derive consistent transport parameters. The results yield parallel mean free paths compatible with predictions from dynamical turbulence models for pitch-angle scattering. The inferred perpendicular mean free paths constitute a significant fraction of the parallel values, amounting to approximately 1–3% for electrons and 5–10% for protons, with a tendency to increase with particle rigidity. The injection region is found to be relatively narrow (≤20°) and to decrease with increasing rigidity. These findings indicate that a localized injection combined with efficient perpendicular diffusion can account for the observed widespread SEP signatures.

Acknowledgement
This research was supported by the European Union’s Horizon Europe programme under grant agreement No. 101135044 (SPEARHEAD; https://spearhead-he.eu/).

How to cite: Lavasa, E., Lang, J. T., Papaioannou, A., Strauss, D. T., Mallios, S., Hillaris, A., Kouloumvakos, A., Anastasiadis, A., and Daglis, I. A.: Transport of relativistic solar energetic particles during GLE73, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20416, https://doi.org/10.5194/egusphere-egu26-20416, 2026.

A significant fraction of the energy of extreme solar eruptive events is channeled into the energetic particles associated with gradual solar energetic particle (SEP) events, posing a significant radiation hazard to humans and technological assets in space.  The high-energy particles in gradual SEP events are known to be accelerated by coronal-mass-ejection-driven shocks, but how the resulting SEP energy spectra for different elements depend on the fundamental parameters that characterize the shock and ambient upstream medium remains an open question.  Here we present the predicted properties of SEP energy spectra using a Liouville mapping technique applied to the electromagnetic field structure of the shock transition generated by a suite of hybrid kinetic ion and fluid electron simulations of quasiperpendicular shocks.  We focus on how the predicted SEP energy spectra depend on the Mach number and shock-normal angle of a collisionless shock in the planar limit and on the suprathermal velocity distributions of protons and heavier elements in the upstream interplanetary medium.  For example, we find accelerated SEP energy spectra peak at higher energies for higher shock-normal angles, in qualitative agreement with previous numerical and observational findings.  We summarize our findings with a comparison of the fundamental parameter dependencies revealed here to those found in observations of CME shocks in the inner heliosphere.

How to cite: Howes, G., Lnu, Y., Felix, A., and Riggs, J. D.: Dependence of Solar Energetic Particle Energy Spectra on the Fundamental Parameters of CME Shocks., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22688, https://doi.org/10.5194/egusphere-egu26-22688, 2026.

The heliosphere can be considered as a plasma bubble formed by the solar wind as it flows outward from the Sun, carving through the local interstellar medium. Due to the relative motion of the heliosphere against the local interstellar medium, a continuous stream of interstellar neutrals (ISNs) enters the heliosphere with a defined speed and direction. Upon entering the heliosphere, ISNs are subjected to ionization processes, which further leads to the creation of interstellar pickup ions (PUIs). PUIs are continuously injected into the solar wind. In the velocity space, their velocity distribution (VDF) initially forms a torus-like shape.

The energies of interstellar pickup helium fall within the measurement range of the SupraThermal Electrons and Protons (STEP) sensor of the Energetic Particle Detector (EPD) onboard Solar Orbiter. By sacrificing mass information, STEP achieves a temporal resolution of up to 1 second. This work presents observations from STEP/EPD. We report several clear torus-shaped velocity distributions of interstellar pickup He⁺ observed at unprecedented temporal resolution.

How to cite: Gu, C., Berger, L., Wimmer-Schweingruber, R. F., Heidrich-Meisner, V., Seimetz, L., Jentsch, E., and Hecht, M.: Torus-shaped velocity distribution of interstellar pickup He+ observed at unprecedented resolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2590, https://doi.org/10.5194/egusphere-egu26-2590, 2026.

NASA’s Interstellar Mapping and Acceleration Probe (IMAP) mission launched on 24 September 2025, inserted into L1 orbit on 8 January 2026, and began routine science operations on 1 February 2026. The spacecraft and all ten instruments are fully commissioned and operating well, which allows IMAP to provide its planned extensive and well-coordinated new observations of the inner and outer heliosphere and scientific closure on two of the most important topics in Heliophysics: 1) the acceleration of charged particles and 2) the interaction of the solar wind with the local interstellar medium. IMAP’s ten instruments provide complete and synergistic observations that examine particle energization processes at 1 au while simultaneously probing the global heliospheric interaction with the very local interstellar medium (VLISM). The in situ observations include solar wind electrons and ions from solar wind up through suprathermal ions, pickup ion, and energetic ions, as well as the interplanetary magnetic field. IMAP provides Energetic Neutral Atom (ENA) global imaging of the outer heliosphere via ENAs from 10s of eV up through 100s of keV, as well as observations of interstellar neutral atoms traversing the heliosphere. IMAP also directly measures interstellar dust that enters the heliosphere and the solar-wind-modulated ultraviolet glow. The IMAP mission also provides extensive new real-time measurements critical to Space Weather observations and predictions, and much more. This paper provides a brief mission overview, as well as some first light and early science observations.

How to cite: McComas, D. and the IMAP Mission team: The Interstellar Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3610, https://doi.org/10.5194/egusphere-egu26-3610, 2026.

The Low Energy Charged Particle (LECP; Krimigis et al. 1977) detector on Voyager is capable of measuring both the intensities and directions of energetic ions inside the heliosphere, providing direct sampling of their anisotropies at seven positions separated by 45 deg within its scan plane (one sector is blocked and is used for calibration purposes). When expressed in terms of roughly parallel (azimuthal; T) and perpendicular (Radial; R) components to the magnetic field direction, these anisotropies can provide important insights on the ion flow properties in and beyond the heliosheath. The analysis of 40-139 keV ions obtained by the LECP on Voyager 1 (V1) have shown that the azimuthal ion anisotropy turns to -T inside the heliosheath and revealed (a) the existence of a region of ~9-10 au before the HP, consistent with an inward radial flow of suprathermal ions into the heliosheath, and (b) a region of ~30 au beyond the heliopause (HP), consistent with a radial outflow of suprathermal ions leaking from the HS into interstellar space (Dialynas et al. 2021; 2024). Beyond this point, both the azimuthal and radial anisotropies are nearly zero, which roughly coincides with an abrupt and prolonged increase in both the magnetic field intensity (Burlaga et al. 2023) and electron densities (Kurth, 2024), known as “second pressure front” (pf2). The confluence of these observations indicate that V1 may have entered a new region in the VLISM beyond ~152 au, progressively developing characteristics akin to the pristine IS medium. Recent magnetic field observations (Burlaga et al. 2024a) have shown that the magnetic field parameters are consistent with a clear separation of two regions in space beyond ~155 au, exhibiting different magnetic field properties. Burlaga et al. (2024b), argued that this is a solar cycle effect in the VLISM, most likely a manifestation of a prolonged compression/shock of solar origin (e.g. Gurnett et al. 2021), whereas Fisk & Gloeckler (2022) argue that the Voyager measurements before the “pf2” are indicative of the flow of ions through the so-called “heliocliff”. We will present an update on the Voyager 1 measurements and preliminary results from the analysis of the >28 keV ion anisotropies from Voyager 2.

References

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How to cite: Dialynas, K., Krimigis, S., Decker, R., Hill, M., Nikoukar, R., Opher, M., and Liokati, E.: Properties of suprathermal ion anisotropies from LECP on the Voyager inside the heliosheath and beyond the heliopause, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8009, https://doi.org/10.5194/egusphere-egu26-8009, 2026.

Research on the interstellar medium and its interaction with the solar system constitutes a significant topic in planetary and heliospheric physics. As the Sun traverses the local interstellar cloud, interstellar neutrals penetrate the heliosphere, forming the interstellar wind and scattering solar extreme ultraviolet (EUV) emission lines. The intensity of this scattered radiation serves as a key diagnostic for the characteristic parameters of the interstellar wind, which are crucial for characterizing the structure of the heliosphere and the properties of the very local interstellar medium (VLISM). Meanwhile, EUV emission is a powerful tool for studying stellar and heliospheric evolution. Due to strong absorption by the interstellar medium at EUV wavelengths, accurate modeling is essential for interpreting observations and understanding these interactions. In this study, we review classical modeling methods for the density distribution of interstellar helium atoms in the heliosphere and the corresponding intensity of the resonantly scattered 58.4 nm radiation. We establish distinct density and intensity models for different orbital positions of Earth. Our results show that when Earth enters the helium focusing cone in the downwind region, both the helium density and the 58.4 nm radiation intensity increase rapidly, with the temperature effect playing a particularly important role. The radiation intensity in the downwind direction can reach up to 170 times that in the upwind direction. For simplicity, some secondary factors such as solar line width and Doppler shift effects were omitted. This modeling work provides valuable insights into the heliosphere-VLISM interaction and large-scale heliospheric structure, and can aid in the analysis of current and future measurements of the outer heliosphere and interstellar boundary. 

How to cite: Lyu, J., Yuan, C., He, F., and Ying, B.: The density distribution and 58.4 nm radiation intensity of interstellar helium in the heliosphere: a model simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9134, https://doi.org/10.5194/egusphere-egu26-9134, 2026.

The Interstellar Mapping and Acceleration Probe (IMAP) is a heliophysics NASA mission to study the acceleration of charged particles and the interaction of the solar wind with the local interstellar medium. IMAP combines images of the plasma boundary regions of the heliosphere by means of Energetic Neutral Atoms (ENAs) with in-situ measurements of the interstellar neutrals flowing into the heliosphere and of the local plasma and dust environment in the solar wind. IMAP was launched in September 2025 and begins its nominal science phase in February 2026. At the same time, the Interstellar Boundary Explorer (IBEX, launched in 2008, IMAP's predecessor in terms of ENA imaging) is still active and continues its observations of heliospheric ENAs. IBEX covers an energy range of roughly 10 eV to 6 keV whereas IMAP covers a wider energy range from roughly 10 eV to 300 keV with three different types of ENA instruments.

In this presentation, we concentrate on the energy spectrum of heliospheric ENAs measured at solar wind energies all the way down to the lowest energy bins of IMAP and IBEX. This energy spectrum is crucial to understand the plasma pressure balance of the heliosphere with respect to the surrounding Very Local Interstellar Medium and to understand the various plasma populations and acceleration mechanisms in the heliosphere. IBEX observations indicate ENA intensities 1-2 orders of magnitude higher than most heliospheric ENA model predictions at energies between 50 eV and 500 eV. The spectrum seems to drop below a power law and start rolling over near 100 eV, but a definite answer is thwarted by the large error bars below 100 eV. Before the advent of IMAP, three explanations have been investigated to explain the discrepancy between ENA measurements with IBEX and model predictions: Additional ENA sources from beyond the heliopause, heliosheath turbulence unaccounted for in models, and/or local foreground near IBEX or in the inner solar system. IMAP will help resolve these outstanding questions thanks to the improved geometric factors of its ENA instruments and the lower background levels expected for the IMAP location at L1 compared with IBEX in Earth orbit.

Based on the knowledge from the first few months of IMAP science observations, we show the first raw data of the ENA spectral intensities measured with IMAP between roughly 100 eV and 1 keV, and we discuss the necessary analysis steps to compare these data with the energy spectra measured with IBEX and those predicted by models. These steps include the correction for the spacecraft motion with respect to the Sun and the correction for ionization losses. Both corrections become more important at lower ENA energies: the typical ENA speed is no longer much faster than the speed of the spacecraft  relative to the Sun, and an increasing fraction of ENAs does not reach IMAP or IBEX because they are ionized by charge-exchange, photo-ionization, or electron impact ionization on their years-long travel from the edge of the heliosphere toward the inner solar system. 

How to cite: Galli, A. and the Interstellar Mapping and Acceleration Probe team for low energy ENAs: The Interstellar Mapping and Acceleration Probe: A glimpse at the first heliospheric ENA energy spectra measured below solar wind energy , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9945, https://doi.org/10.5194/egusphere-egu26-9945, 2026.

The variability of solar wind properties directly impacts the outer heliosphere, which is expected to exhibit a time-dependent structure, driving a significant impact on the solar modulation of galactic cosmic rays. In addition to the Voyager probes that provided in-situ measurements of the outer heliosphere's properties, the New Horizons mission is currently offering valuable experimental data as it approaches the termination shock. Moreover, remote sensing observations of the outer heliosphere via energetic neutral atom (ENA) fluxes from the Interstellar Boundary Explorer (IBEX) clearly indicate long-term variations in the heliospheric boundaries. Soon, the Interstellar Mapping and Acceleration Probe (IMAP) will also contribute high-accuracy ENA flux observations. By employing a semi-analytical approach to solve the solar wind dynamics throughout the heliosphere, we have developed a data-driven model that leverages available in-situ and remote sensing data from the outer heliosphere to estimate the long-term, time-dependent distance of the termination shock from the Sun and the width of the heliosheath. Our predictions align closely with Voyager observations, differing by only a few astronomical units (AU). This will enhance our understanding of cosmic ray modulation in the heliosphere.

How to cite: La Vacca, G., Della Torre, S., and Gervasi, M.: A Data-Driven Model for the Long-Term Variations of the Heliospheric Boundaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12257, https://doi.org/10.5194/egusphere-egu26-12257, 2026.

The Interstellar Dust Experiment (IDEX) is a dust impact ionization Time-of-Flight (ToF) mass spectrometer launched onboard the Interstellar Mapping and Acceleration Probe (IMAP) on September 24, 2025. IMAP is in nominal science operations at the Sun-Earth Lagrange Point L1, with IDEX passively collecting cosmic dust grains at a cadence of roughly one interplanetary particle per week. IDEX will detect and analyze both Interstellar Dust Grains (ISDs) from the Local Interstellar Medium (LISM) as well as Interplanetary Dust grains (IDPs). ISD collection will begin in April 2026 as we enter the interstellar dust focusing season. IDEX will collect a variety of ISDs and IDPs over its lifetime, ranging from pristine to heavily processed particles that are a mixture of mineral and organic material.

We investigate how IDEX can be used to determine the degree of processing dust grains have undergone. These studies inform the analysis of IDEX flight data representative of organic and mineralogical cosmic dust grains. Assessments of aromaticity and the presence of functional groups can be used to determine the processing of organic species. Polycyclic aromatic hydrocarbons (PAHs) are the most pristine organic compounds. PAH destruction and processing lead to the production of heterocyclic compounds and decreasing aromaticity in organic species. Minerals can be appraised via the degree of serpentinization and conversion from crystalline to amorphous silicates. IDEX's large effective area combined with high mass resolution (m/dm > 200) and dynamic range make it well suited to assess minute variations in mass spectra pointing to pristine versus processed materials. Various campaigns from the last two years build and support the techniques presented here to analyze IDEX flight data.

How to cite: Mikula, R., Sternovsky, Z., Horyani, M., Armes, S., Ayari, E., Bouwman, J., Hillier, J., Khawaja, N., Postberg, F., Kempf, S., and Srama, R.: Measuring the processing of organic and mineral cosmic dust grains with the Interstellar Dust Experiment (IDEX) instrument, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14550, https://doi.org/10.5194/egusphere-egu26-14550, 2026.

In the coming years, New Horizons (NH) is expected to exit the heliosphere by crossing the solar wind termination shock (TS) and make the first measurements of pick-up ions (PUIs) across the TS boundary. To date, the only working spacecraft to have crossed the TS are Voyager 1 and 2, with Voyager 1 encountering the TS on day of year (DOY) 351, 2004 at ~94 AU, and Voyager 2 undergoing multiple crossings between DOY 243 and 344, 2007 at ~83.6 AU. Although NH is approximately aligned in heliolongitude with Voyager 2, its trajectory lies near the heliographic equator, in contrast to the higher northern and southern heliolatitudes of Voyager 1 and 2, respectively.

In this work, we analyze energetic particle observations (∼40–200 keV) from the Voyager Low Energy Charged Particle (LECP) instruments and the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) onboard NH to characterize radial intensity variations in the outer heliosphere. Voyager 1 and 2 observations show a systematic decrease in energetic particle intensities with increasing heliocentric distance, followed by a recovery prior to their respective TS crossings, forming a heliospheric energetic particle “valley.” NH/PEPSSI observations from 5 to 60 AU exhibit a comparable radial decline but have yet to show the expected increase on the march toward the TS crossing.

To mitigate temporal variability associated with solar cycle effects, all observations are normalized using near-Earth energetic particle measurements from IMP-8/EPE and ACE/EPAM. The combined radial profiles from Voyager and NH are well described by a double power-law with a break at~33 AU. The combined radial profiles from Voyager and NH are well described by a power-law dependence with a distinct break beyond ~33 AU. This break likely reflects a transition in the dominant transport and/or acceleration mechanisms operating in the inner and outer regions separated by this radial distance. The presence of this break across multiple heliolatitudes suggests a global heliospheric feature, potentially reflecting changes in particle transport, acceleration, or local plasma conditions in the outer heliosphere. By scaling the Voyager observations to the NH measurements, we estimate a NH TS crossing between 2027 (~68 AU) and 2034 (~83 AU).

How to cite: Nikoukar, R., Hill, M. E., Dialynas, K., Krimigis, S. M., Brown, L., Kollmann, P., Decker, R. B., Manweiler, J. W., Reeve, W. S., Florinski, V., Zhang, M., Richardson, J., Opher, M., Giacalone, J., Adhikari, L., Brandt, P. C., carcaboso, F., Cooper, J. F., Elliott, H. A., and Gold, R. and the Romina Nikoukar: An Energetic Particle Valley in the Outer Heliosphere: Insights from Voyager and New Horizons and Implications for New Horizons’ Termination Shock Encounter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15428, https://doi.org/10.5194/egusphere-egu26-15428, 2026.

Voyager 1 observed a shock-like discontinuity in the magnetic field strength and proton density at 2020.4, where the compression ratio was 1.35 and 1.36, respectively, and there was no change in the magnetic field direction [Burlaga et al., 2023]. After the jump, the magnetic field strength remained at a higher level until recently, creating a magnetic hump or pileup region. A magnetic pileup boundary or ion composition boundary has been routinely observed between the cometary bow shock and the comet’s ionopause. Solar wind protons are reflected from and heavy cometary pickup ions (mainly water group ions) are transmitted through this boundary, also known as protonopause.  A similar ion composition boundary is expected in the inner heliosheath. As the solar wind approaches the very local interstellar medium (VLISM), the density of interstellar pickup protons and pickup He⁺ is gradually increasing. At the ion composition boundary, solar wind protons are reflected from the potential barrier. However, heavier pickup He⁺ ions with higher kinetic energy are able to cross this boundary, separating solar wind protons from heavier interstellar pickup ions. The electrons carry the magnetic field across the ion composition boundary without change in the magnetic field direction. To maintain pressure balance, the transmitted pickup ions and the magnetic field are compressed, creating a magnetic pileup region. Such an ion composition boundary or magnetic pileup boundary was first suggested by Sauer et al. [1995] in the magnetosheath of comets, Mars, and Venus. We suggest that the magnetic pileup boundary observed by Voyager 1 in 2020 is associated with an ion composition boundary in the solar wind. We present multi-fluid simulations of the ion composition boundary in the inner heliosheath. We show that an ion composition boundary is formed when the generalized sonic Mach number has reached 1 from below. The generalized sonic Mach number can be increased by either accelerating the plasma or reducing the sonic speed. As the solar wind approaches the heliopause, interstellar He⁺ pickup ions gradually reduce the sonic speed until the generalized sonic Mach number reaches 1 and a new type of plasma boundary, the ion composition boundary is formed. Our results imply that Voyager 1 is still in the inner heliosheath, has not crossed the heliopause, and has not entered the VLISM yet. We predict that Voyager 1 will continue to observe a stronger magnetic field until the heliopause is reached, which is expected to be a tangential discontinuity with a rotation in the magnetic field. The heliospheric ion composition boundary could be verified by New Horizons or other interstellar missions in the future, such as Interstellar Probe.

How to cite: Zieger, B. and Opher, M.: The Ion Composition Boundary: A New Type of Plasma Boundary in the Inner Heliosheath, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15488, https://doi.org/10.5194/egusphere-egu26-15488, 2026.

Launched in September 2025, NASA’s Interstellar Mapping and Acceleration Probe (IMAP) now operates at the Sun–Earth L1 Lagrange point to investigate the interaction between the heliosphere and its interstellar environment. Among its ten-instrument payload is the Interstellar Dust Experiment (IDEX), which is designed to measure the flux, size distribution, and chemical, elemental, and isotopic composition of dust particles entering the solar system.

IDEX directly samples interstellar dust (ISD) originating in the local interstellar medium (LISM), providing unique insight into the composition of contemporary interstellar solid matter. A key scientific objective is to assess whether the present-day LISM dust population is compositionally consistent with the primordial material from which the solar system formed. In addition to ISD, IDEX measures interplanetary dust particles (IDPs) of cometary and asteroidal origin, including grains that may preserve pre-solar molecular cloud material as well as particles altered by solar system processing. These observations enable comparisons between interstellar, cometary, and asteroidal dust and help constrain the origins and evolutionary histories of organic-rich materials.

IDEX measurements of the directional and size distributions of ISD provide critical constraints on models of dust transport through the heliosphere, including the filtering effects of heliospheric magnetic fields and solar activity on small, charged grains. These data contribute to improved understanding of the heliospheric boundary and the processes governing the penetration of dust into the inner heliosphere.

IDEX is an impact-ionization time-of-flight mass spectrometer that analyzes ions generated by high-velocity dust impacts on a target surface. This presentation provides an overview of IDEX’s scientific objectives and measurement capabilities and reports on early in-flight performance and initial results, demonstrating IDEX’s role in linking interstellar and solar system material populations.

How to cite: Horanyi, M., Tucker, S., Sternovsky, Z., Knappmiller, S., Ayari, E., Mikula, R., Kempf, S., and Szalay, J.:  First results of the Interplanetary Dust Experiment (IDEX) onboard the Interplanetary Mapping and Acceleration Probe (IMAP) Mission., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15635, https://doi.org/10.5194/egusphere-egu26-15635, 2026.

The IMAP-Hi Imager is one of three advanced imagers on the Interstellar Mapping and Acceleration Probe (IMAP) designed to remotely measure and detect energetic neutral atoms (ENAs) from the outer heliosphere. These ENAs are formed by charge exchange of ions in a hot plasma with cold ambient neutral atoms, travel in ballistic trajectories from the source plasma, and thus carry crucial information about their source plasma population, enabling observation of the global structure and dynamics of plasma domains across the outer heliosphere and beyond. IMAP-Hi was optimized to measure neutral Hydrogen over the energy range (500 eV – 15 keV) of core and suprathermal solar wind ion populations. IMAP-Hi is significantly more capable than its predecessor IBEX-Hi, with substantially improved energy range, energy resolution, imaging resolution, sensitivity, and background rejection. IMAP-Hi is comprised of two identical ENA imagers, enabling larger combined geometric factor, enhanced viewing near the ecliptic plane (heliospheric nose, tail, low-latitude ribbon, and flanks), and higher temporal cadence of viewing. Hi45 observes a 45° half-angle cone centered on the spin axis in an antisunward direction, whereas Hi90 views perpendicular to the spin axis. Observations from IMAP-Hi, IMAP-Lo and IMAP-Ultra will allow for a transformational advance in our understanding of the interaction between the heliosphere and the local interstellar medium (LISM), and the particle processes occurring in these regions.  We give an overview of IMAP-Hi performance status on early flight operations of IMAP-Hi and present an initial look at the first IMAP-Hi ENA sky maps.  

How to cite: Reisenfeld, D., Funsten, H., and Allegrini, F. and the IMAP-Hi Team: First Light from the IMAP-Hi Energetic Neutral Atom (ENA) Imager on the IMAP Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15922, https://doi.org/10.5194/egusphere-egu26-15922, 2026.

NASA’s Interstellar Mapping and Acceleration Probe (IMAP) mission is providing comprehensive observations of both the in situ magnetic field and charged particle environment as well as remotely exploring energetic neutral atoms (ENAs), dust particles, and ultraviolet photons that originate from the outer heliosphere and beyond. Collectively, these measurements will advance our understanding of particle acceleration throughout the solar system and how the solar wind and interstellar medium interacts with the boundary of our heliosphere. Here, we focus on heliospheric observations from the IMAP-Ultra (Ultra) instrument, which is one of three ENA imagers on IMAP. Ultra measures ~3 – 100 keV neutral atoms over its large ~96° × 120° field of view (FoV), achieving angular resolutions ≤ 6° above 10 keV for H. Since IMAP’s launch on September 24, 2025, both Ultra sensors have been fully commissioned and are collecting new and exciting observations of the heliosphere. In this presentation, we highlight the global heliospheric configuration of > 3.7 keV H ENAs with detailed investigations into its spectral variations, evolving heliotail structure as a function of energy, and high angular resolution structures (up to 2° for energies > 30 keV).

How to cite: Clark, G., Gkioulidou, M., Mitchell, D., Dutton, N., DeMajistre, R., Provornikova, E., Walia, N., McComas, D., Reisenfeld, D., Funsten, H., Schwadron, N., Allegrini, F., Möbius, E., Bzowski, M., Turner, D., and Christian, E.: IMAP-Ultra Observations of Heliospheric Energetic Neutral Atoms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16060, https://doi.org/10.5194/egusphere-egu26-16060, 2026.

The Interstellar Dust Experiment (IDEX) is an impact-ionization time-of-flight mass spectrometer aboard NASA’s Interstellar Mapping and Acceleration Probe (IMAP), launched in September 2025 and operating at the Sun–Earth L1 Lagrange point. IDEX combines a large sensitive area (>600 cm²), high mass resolution (m/Δm > 200 at m = 100 u), and a wide dynamic range to measure the mass, flux, dynamics, and elemental and chemical composition of interstellar and interplanetary dust particles. The instrument’s performance has been validated through extensive laboratory calibration using iron, platinum-coated olivine, and aluminum particles with masses from approximately 3 × 10⁻¹⁸ to 10⁻¹⁴ kg and impact velocities of 4–50 km s⁻¹. In flight, IDEX operates in the ambient space environment, where it is exposed to interplanetary Lyman-α radiation and galactic cosmic rays. Many of the dust particles detected by IDEX in space are substantially larger than those achievable in laboratory accelerators and therefore generate significantly larger impact charges. This presentation provides an overview of the in-flight performance of IDEX, focusing on key instrument parameters and their comparison with laboratory calibration results.

How to cite: Sternovsky, Z., Horanyi, M., Tucker, S., Ayari, E., Hillier, J., Kempf, S., Knappmiller, S., Mikula, R., and Szalay, J. R.:  Calibration and performance of the Interstellar Dust Experiment (IDEX) onboard the Interplanetary Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16857, https://doi.org/10.5194/egusphere-egu26-16857, 2026.

Solar wind features a latitudinal structure that evolves during the solar activity cycle. The only in-situ measurements of the solar wind speed and density available so far were performed by Ulysses at the turn of the 20th and 21st centuries. They showed the general behavior of the solar wind speed and density. However, details of possible asymmetries and regular structure evolution at shorter time scales could not be established because the measurements were performed in-situ along a highly elliptical orbit with a period of the order of half of the solar cycle.

Complementary methods of monitoring the solar wind latitudinal profiles include remote-sensing observations such as hydrogen Lyman-α backscatter glow observations. Helioglow maps observed by SOHO/SWAN suggested that the solar wind flux temporarily features flux maxima at mid-latitudes.

Insight from Ulysses resulted in a hypothesis that the energy flux of solar wind is latitudinally invariant, which cannot be verified without additional observations. A confirmation of this invariance would be an important milestone in the understanding of the solar wind emission mechanism and would provide a handy tool supporting the retrieval of the solar wind structure from observations of the helioglow.

GLObal solar Wind Structure (GLOWS) is a Lyman-α photometer onboard Interstellar Mapping and Acceleration Probe (IMAP), dedicated to helioglow observations optimized for the retrieval of the solar wind structure. We present how GLOWS observations will be used to infer the structure of the solar wind and to verify the hypothesis of latitudinal invariance of the solar wind energy flux.

How to cite: Kowalska-Leszczynska, I., Bzowski, M., Porowski, C., Strumik, M., and Kubiak, M. A.: From Hydrogen backscatter glow to solar wind structure – how we do it with IMAP/GLOWS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17718, https://doi.org/10.5194/egusphere-egu26-17718, 2026.

Since Voyager 2 crossed the termination shock in 2007 and the heliopause in 2018, the radial flow speed in the heliosheath () has remained uncertain due to persistent discrepancies between measurements from the Plasma Science (PLS) instrument and values inferred from energetic particle observations using the Compton–Getting (CG) effect. These differences are critical because they directly impact our understanding of heliosheath structure and dynamics and play a central role in validating global magnetohydrodynamic (MHD) models. In this work, we revisit the estimation of heliosheath flow speeds from Low-Energy Charged Particle (LECP) data by expanding the legacy CG-based method to account for anisotropic particle distributions in the plasma frame and by combining measurements from multiple energy channels. These refinements provide a more physically realistic interpretation of particle anisotropies and CG-derived flow speeds and offer a pathway toward reconciling plasma and particle measurements of heliosheath flows.

How to cite: Nikoukar, R., Hill, M. E., Dialynas, K., Krimigis, S. M., Richardson, J., and Opher, M.: Revisiting Heliosheath Flows from Voyager Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20521, https://doi.org/10.5194/egusphere-egu26-20521, 2026.

Space Research Centre, Polish Academy of Sciences, Warsaw, Poland GLOWS (GLObal solar Wind Structure) is one of the experiments on a NASA mission IMAP (Interstellar Mapping and Acceleration Probe). The objective of GLOWS is to investigate the global heliolatitude structure of the solar wind and its evolution during the solar cycle. Additionally, GLOWS investigates the distribution of interstellar neutral hydrogen (ISN H) and the solar radiation pressure acting on ISN H. The objectives of GLOWS are accomplished by observation of the heliospheric hydrogen backscatter glow (the helioglow). The helioglow is created by resonant excitation of ISN H atoms within several au from the Sun by the intense solar electromagnetic radiation in the Lyman-α waveband 121.567 nm. The H atoms move in this region collisionless, and thus immediately after excitation of the photons from the Sun, they re-emit them in random directions. Those re-emitted photons form the helioglow. The intensity of the helioglow observed at ∼1 au varies across the sky, dependent on the location of the observer; it is on the order of 300–1000 Rayleigh. We present an update on the GLOWS instrument observations, carried on since November 2025, and the first latitudinal profiles solar wind speed and density obtained on the orbit.

How to cite: Kubiak, M., Bzowski, M., Porowski, C., Strumik, M., and Kowalska-Leszczynska, I.: Solar wind structure seen by IMAP/GLOWS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21088, https://doi.org/10.5194/egusphere-egu26-21088, 2026.

We present new, multipoint observations of interplanetary shocks observed by six observatories around the first Sun-Earth Lagrange (L1) point. With IMAP, SWFO-L1, ACE, Wind, DSCOVR, and Aditya-L1, we investigate multiple interplanetary shocks associated with the passage of two coronal mass ejections (CMEs) on 11-12 November 2025. Inter-spacecraft separations range from 10s of Earth radii (Re) to ~200 Re, offering a number of different baselines and geometries for multipoint analysis. We analyze shock orientations and speeds and diagnose the interaction between the two CMEs. The 6-point observatories showcase how the CME shocks and sheaths are structured and allow for analysis of the interface between ejecta and ambient solar wind plasmas. We also show that spatial gradients of the structures can be resolved by combining different sets of tetrahedra within the constellation and discuss options for full volume reconstruction of the time-dependent plasma dynamics.

How to cite: Turner, D., Raptis, S., Horbury, T., Rankin, J., Cohen, C., Wilson, L., Christian, E., Szabo, A., Sankarasubramanian, K. S., Vassiliadis, D., Gkioulidou, M., and McComas, D.: Multipoint analysis of interplanetary shocks with 6-point observatories around Sun-Earth L1, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21785, https://doi.org/10.5194/egusphere-egu26-21785, 2026.

Impact-ionization time-of-flight mass spectrometry (II-TOF-MS) is a primary technique for in-situ compositional analysis of interplanetary and interstellar dust. However, quantitative elemental and isotopic interpretation requires laboratory validation against well-characterized standards across realistic encounter speeds.

We present hypervelocity dust-accelerator measurements of platinum-coated San Carlos olivine (Fo≈92) using the high-resolution reflectron-style Hyperdust II-TOF-MS. The olivine starting material was independently characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX), providing ground-truth Mg, Si, and Fe abundances and confirming low grain-to-grain compositional variability. More than 500 individual olivine projectiles were accelerated to encounter speeds spanning the regime relevant to modern spaceborne dust analyzers (≈10–25 km s⁻¹).

Time-domain spectra were analyzed by identifying major multiplets and fitting isotopic peaks with exponentially modified Gaussian line shapes to obtain integrated peak areas. Isotopic multiplets for Mg, Si, and Fe are resolved, and accepted spectra reproduce terrestrial isotope ratios within a defined tolerance, enabling robust peak deconvolution and contamination control. Using EDX-normalized relative sensitivity factors (RSFs), we convert ion intensities to elemental ratios and compare single-impact and ensemble results to the EDX composition.

At higher encounter speeds (≈19–25 km s⁻¹), RSF-corrected Mg/Si and Fe/Si ratios agree with the EDX values within uncertainties and cluster along the olivine compositional trend, with dispersion smaller than the separation between olivine and pyroxene in Mg–Fe–Si space. Ratios involving Si show stronger speed dependence at lower velocities, consistent with ionization effects and potential isobaric contributions near the Si region, while Mg/Fe remains comparatively stable.

These results provide a quantitative calibration benchmark demonstrating that high-resolution II-TOF-MS can recover elemental and isotopic information for silicate dust and can discriminate mineral families at encounter speeds typical of upcoming and current missions, including IDEX (IMAP), SUDA (Europa Clipper), and DDA (DESTINY+).

How to cite: Ayari, E., Horanyi, M., Sternovsky, Z., Szalay, J., and Mikula, R.: Quantitative olivine elemental and isotopic ratios from hypervelocity impact ionization TOF mass spectrometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21860, https://doi.org/10.5194/egusphere-egu26-21860, 2026.

Saturn kilometric radiation (SKR) is mostly a fully circularly polarized radio emission from Saturn's auroral region. However, Fischer et al. (2009, doi:10.1029/2009JA014176) found that SKR can show a linear component and be elliptically polarized, and this SKR property is typically found above observational latitudes of about 30 degrees (in both hemispheres). Using all available RPWS (Radio and Plasma Wave Science) data throughout the Cassini mission, we calculated mean polarization properties (linear, circular, total) of SKR for each hour in the frequency range from 100 to 1200 kHz. This revealed transitional latitudes from 20 to 40 degrees in which the linear polarization degree of SKR rises from around 0.1 (which is the usual error for the polarization measurement) up to 0.6. Furthermore, we found that SKR shows a lower total polarization degree at the transitional latitudes. 
We will try to give a reason for this unexpected behavior. We will also show comprehensive meridional plots of SKR circular, linear, and total polarization to understand the polarization properties of this important Saturnian radio emission.

How to cite: Fischer, G., Jost, D., Taubenschuss, U., Pisa, D., Cecconi, B., Lamy, L., and Kurth, W.: Analysis of elliptical polarization of Saturn kilometric radiation throughout the Cassini mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6325, https://doi.org/10.5194/egusphere-egu26-6325, 2026.

An one-dimensional fluid model is presented which describes the generation of  type III radiation as an antenna problem at which the triggering current pulse imitates the temporal evolution of the beam instability. The mechanism works without the involvement of the classical plasma emission via the parametric processes and the coalescence of waves. After linearization of the Maxwell-fluid equations and Fourier transform in space, the system of nine differential equations describing the temporal evolution of the fluid and electromagnetic quantities is solved numerically. It is shown that the commonly observed beating structure of the electromagnetic radiation in form of a double-peak in their spectra, commonly explained by parametric decay of the beam-excited Langmuir wave, is caused by the superposition of two wave modes of mixed polarisation (Langmuir/z wave) which belong the wave number of optimum mode coupling. Within in the same formalism the generation of the second harmonic of the electromagnetic radiation is calculated by taking into account the nonlinear currents as product of the first-order terms. Satellite observations of beam-excited Langmuir waves and solar type III radiation are discussed in the light of the presented antenna model.

How to cite: Sauer, K. and Liu, K.: Solar type III radiation as antenna problem - Electromagnetic wave generation by the beam-driven electron current, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13785, https://doi.org/10.5194/egusphere-egu26-13785, 2026.

The study presented here is a continuation of a series of works where the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field B and its gradient ∇B in the source region is investigated, using the recent magnetic field model for Jupiter, based on Juno’s first 33 polar orbits observations, Jupiter Refence Model JRM33, proposed by Connerney et al. [Journal of Geophysical Research: Planets, 127, 1-15, 2022]. Our results are compared to those obtained earlier using the JRM09 model derived from the first nine orbits of the Juno spacecraft by Connerney et al. [Geophysical Research Letters, 45, 2590-2596, 2018]. The JRM33 model confirms the former findings where the radio emission is beamed in a hollow cone exhibiting a flattening in a specific direction. The Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI). We interpret this flattening by the fact that the magnetic field in the radio source does not have any axial symmetry because B and ∇B are not parallel. This assumption is confirmed by the amplitude of the flattening of the cone which appears to be more important for the northern emission (31.8%) than for the southern one (11.4%) probably due to the fact that the angle between the directions of B and ∇B is greater in the North (~10°) than in the South (~5°). We propose a theoretical study of the propagation and amplification of the waves by the CMI in the radio source in the plane (B, ∇B) as well as in the perpendicular plane aiming to evaluate the emergence angle of the radiation.

How to cite: Galopeau, P. and Boudjada, M.: Contribution of JRM33 model to the study of emission cone of Jovian decameter radiation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13922, https://doi.org/10.5194/egusphere-egu26-13922, 2026.

We present a study of fine time–frequency structures and their complex temporal evolution in the narrowband (NB) and wideband (WB) components of Jupiter’s sporadic decametric (DAM) emission, including cases where both components appear simultaneously in dynamic spectra. High-resolution observations of a Jovian radio storm on 26 November 2009, featuring emission from Io-C and Io-A″ sources, were recorded with the UTR-2 telescope (8–32 MHz) using a baseband digital receiver, enabling waveform acquisition suitable for offline multi-scale analysis. Spectral images were produced with a custom multi-scale algorithm incorporating high-pass filtering to suppress narrowband radio frequency interference (RFI) while preserving intrinsic Jovian signals. Windowed Fourier transforms traced the formation, temporal evolution, and internal structure of NB events and their relation to classical S- and L-bursts. Some NB events exhibit complex patterns requiring interpretations beyond standard classifications. Combined with spacecraft observations from Juno and the forthcoming JUICE mission, these data allow disentangling intrinsic emission physics from propagation effects. In particular, the analysis demonstrates the potential to study emissions arriving simultaneously from two spatially separated sources with different polarization. Future studies, combining high-resolution spectra from UTR-2, GURT, LOFAR, NenuFAR, NDA, LWA, and other instruments with spacecraft measurements, will further enable identification and characterization of modulation patterns in Jupiter’s DAM waves. These results provide constraints for DAM generation models, emphasize the value of polarization-resolved, high-resolution studies, and support the identification of emission sources and plasma media along the propagation path.

How to cite: Litvinenko, G., Ryabov, V., Rothkaehl, H., and Zakharenko, V.: Study of the Jovian Decameter Narrow- and Wideband Emission: Fine Time–Frequency Structures and Temporal Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17286, https://doi.org/10.5194/egusphere-egu26-17286, 2026.

The Solar Radio Monitoring website (secchirh.obspm.fr) serves as a hub for the combined visualisation of solar radio data, specifically designed to support multi-wavelength analysis of solar activity and its complex solar-terrestrial relationships. Through the integration of high-resolution ground-based observations from the Nançay Radio Heliograph (NRH) with dynamic spectra from a wide range of instruments operating across the globe (ORFEES, NDA, HUMAIN, Gauribidanur, Culgoora, learmonth, Yunan and Arthemis), as well as hectometric and kilometric measurements from space missions such as WIND, and STEREO, the website provides a continuous and global view of the solar environment, from the low corona to the interplanetary medium. This multi-instrument synergy is further strengthened by the integration of Solar Orbiter’s instruments. In particular, STIX delivers quantitative X-ray measurements that trace accelerated electrons in active regions, EPD characterizes ions and suprathermal particles up to several hundred MeV per nucleon, while RPW (Radio & Plasma Waves) provides measurements of the surrounding radio and plasma wave environment. These measurements enable researchers to track the propagation of these particles through the solar corona and interplanetary space. By integrating these diverse datasets, the website facilitates fast visualization of particle acceleration and transport processes and provides indispensable tools to both experts and the broader scientific community for fundamental heliophysics research and the improvement of space weather forecasting models. This contribution presents the latest developments of the Solar Radio Monitoring website, with a particular focus on recent enhancements in multi-instrument data integration and visualization tools.

How to cite: Hamini, A. and Romagnan, R.: Radio Monitoring and Solar Radio Orbiter Instruments: tools for fast access to space and ground-based radio observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19375, https://doi.org/10.5194/egusphere-egu26-19375, 2026.

We investigate Type III solar radio bursts observed by the radio and plasma wave experiment (RPWS) onboard Cassini spacecraft (Galopeau et al., 2007) in the period from January 2004 to September 2017. In this time interval of about thirteen years an important number of solar Type III bursts has been recorded. We consider in this work the remote sensing of the Saturn’s magnetosphere environment using the daily RPWS dynamic spectra in the frequency range from 1 Hz to 16 MHz. In spite of the enormous distance between the Sun and Saturn, in the order of ~ 1.5 109 km, this instrument detected Type III bursts superposed to magnetospheric auroral activity emitted by Saturn (Boudjada et al., 2023). We underline in this analysis on particular solar radio bursts which exhibit saturated intensity levels, like the Saturnian kilometric radiation (SKR). We attempt to discuss the origin of the saturated and boosted Type III bursts, drifting rapidly from high to low frequencies, and considered to be generated in the solar corona following Archimedean spiral linked to the solar magnetic field expansion in the interplanetary medium.

References:
Boudjada et al., Statistical analysis of Solar Type III radio bursts observed by RPWS experiment in 2004-2017 during the Solar cycles 23-24. In Proceedings Kleinheubach Conference, Ed. U.R.S.I. Landesausschuss in Deutschland e.V., IEEE, Miltenberg, 2023. 

Galopeau et al., Spectral features of SKR observed by Cassini/RPWS: Frequency bandwidth, flux density and  polarization. Journal of Geophysical Research, 112, A11, 2007.

How to cite: Boudjada, M. Y., Galopeau, P. H. M., Lammer, H., Lecacheux, A., and Rucker, H.: Solar activity at Saturn’s magnetosphere environment: Case study of Type III radio bursts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20595, https://doi.org/10.5194/egusphere-egu26-20595, 2026.

As a universal nonlinear structure in space plasma, electron phase space holes, also named as electrostatic solitary waves (ESWs), have a 60-year research history. An important challenge has been to reveal the microscopic evolutionary process of ESWs. Previous simulations have shown that collision coalescences determine whether several weak ESWs can evolve into a strong one. However, the simulated collision coalescence has not yet been demonstrated in observations. Here, we employ coordinated observations from the MMS multi-satellite mission to unveil two distinct evolutionary processes: collision coalescence and mutual penetration of ESWs in space plasmas. Subsequently, collision simulations reveal that the conditions for coalescence are closely linked to the ratio of the maximum capture velocity of the trapped electrons to the hole velocity, consistent with the findings of energy balance analysis based on the virial theorem and successfully explaining the observed collision coalescence and mutual penetration of ESWs. Therefore, we provide a direct observational evidence to collision coalescence and mutual penetration of ESWs for the first time.

How to cite: Dong, Y. and Yuan, Z.: Collision coalescence and mutual penetration of electron phase space holes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2476, https://doi.org/10.5194/egusphere-egu26-2476, 2026.

Alpha particles constitute the most energetic ion population in the solar wind and play an important role in turbulent energy conversion and ion-scale heating. Yet, the physical processes governing their temperature evolution, anisotropy development, and differential streaming remain incompletely understood. Using Parker Solar Probe observations and 2.5D particle-in-cell simulations, we investigate how the alpha–proton temperature ratio regulates the subsequent alpha heating efficiency and associated kinetic signatures. The observations reveal that alpha heating and anisotropy are strongly modulated by the local value of temperature ratio. The simulations reproduce these trends, showing that increasing temperature ratio lowers the growth of alpha thermal energy, anisotropy, and differential drift. These results demonstrate that the alpha heating pathway could be self-regulated by its initial thermodynamic state, with hotter alphas remaining farther from the instability threshold and experiencing less resonant energization. Our findings provide new constraints on ion-scale dissipation in the near-Sun solar wind and offer a unified interpretation of alpha-proton heating.

How to cite: Xiong, Q. and Huang, S.: Alpha Particle Heating and Anisotropy in the Solar Wind Turbulence: Insights from PSP Observations and PIC Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4789, https://doi.org/10.5194/egusphere-egu26-4789, 2026.

Collisionless shock waves and plasma turbulence play fundamental roles in particle acceleration and energy dissipation in space plasmas. In the heliosphere, the inherently turbulent solar wind continuously interacts with planetary bow shocks and interplanetary shocks. Such pre-existing turbulence can modulate the shock front, influence particle acceleration and transport, and modify the plasma conditions and plasma stability in the vicinity of the shock. We present a novel modelling setup in which we use MHD simulations to generate turbulent fields that are dynamically input to our hybrid shock simulations. This allows us to study the interaction between realistic plasma turbulence and a shock wave. Here we report results on the influence of upstream turbulence on plasma stability against ion kinetic instabilities downstream of a perpendicular shock. We find that while turbulence can locally drive plasma towards an unstable configuration, it generally makes the downstream plasma more stable against proton cyclotron and mirror mode instabilities. We also find that a sharp low limit in β_parallel–T_perp/T_parallel “Brazil plots”, sometimes also seen in observations, can be caused by tracks representing adiabatic evolution of plasma in magnetic islands.

How to cite: Vuorinen, L., Burgess, D., Trotta, D., and Koller, F.: Influence of upstream turbulence on plasma stability at a perpendicular shock: hybrid simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7356, https://doi.org/10.5194/egusphere-egu26-7356, 2026.

In solar wind turbulence, the energy transfer/dissipation rate is typically estimated using MHD third-order structure functions calculated using spacecraft observations. However, the inherent anisotropy of solar wind turbulence leads to significant variations in structure functions along different observational directions, thereby affecting the accuracy of energy-dissipation rate estimation. An unresolved issue is how to optimise the selection of observation angles under limited directional sampling to improve estimation precision. We conduct a series of MHD turbulence simulations with different mean magnetic field strengths, B₀. Our analysis of the third-order structure functions reveals that the global energy dissipation rate estimated around a polar angle of θ = 60^◦ agrees reasonably with the exact one. The speciality of 60^◦ polar angle can be understood by the Mean Value Theorem of Integrals, since the spherical integral of the polar-angle component of the divergence of Yaglom flux is zero, and this polar-angle component changes sign around 60^◦. Existing theory on the energy flux vector as a function of the polar angle is assessed, and supports the speciality of 60^◦ polar angle. The angular dependence of the third-order structure functions is further assessed with virtual spacecraft data analysis. The present results can be applied to measure the turbulent dissipation rates of energy in the solar wind, which are of potential importance to other areas in which turbulence takes place, such as laboratory plasmas and astrophysics.

How to cite: Yang, Y., Jiang, B., Gao, Z., Pecora, F., Gao, K., Li, C., Oughton, S., Matthaeus, W., and Wan, M.: Angular dependence of third-order law in anisotropic MHD , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7873, https://doi.org/10.5194/egusphere-egu26-7873, 2026.

The current sheet stress balance conditions describe the equilibrium between magnetic stresses and plasma pressure across a thin current sheet. We build upon existing work developed in the context of magnetotail reconnection to derive a set of stress balance conditions for reconnection outflows in the solar wind, which are typically characterised by a bifurcated reconnection current sheet (RCS). Applying our framework to a symmetric bifurcated RCS model, we determine the outflow region opening angle and beam population properties, obtaining values consistent with observations of reconnection in the solar wind. We then validate our framework against observations of solar wind reconnection outflows from Solar Orbiter, highlighting one event with properties compatible with our simple symmetric model. For this event, we estimate an outflow region opening angle ranging from 3.4°-8.2°, in line with values reported in previous studies. We also reconstruct the outflow beam distribution functions and find that the predicted beam velocities and temperatures match observations well, although the densities are underestimated. Overall, our stress balance framework captures some of the key features of solar wind reconnection outflow, including current sheet bifurcation and counter-streaming beams. Future work will extend the framework to asymmetric reconnection geometries.

How to cite: Suen, G. H. H., Owen, C., and Verscharen, D.: Current sheet stress balance models of bifurcated current sheet reconnection in the solar wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7974, https://doi.org/10.5194/egusphere-egu26-7974, 2026.

Electron-scale instabilities at collisionless shocks are central to plasma dissipation and particle energization, yet their physical origin and nonlinear consequences remain poorly constrained. In this presentation, we investigate the development and impact of electron Kelvin–Helmholtz instability (EKHI) at quasi-perpendicular shocks, which reveals a new pathway for electron acceleration and electron-scale structure formation.

High-resolution particle-in-cell simulations show that intense electron velocity shear naturally forms along the shock surface due to drift motion. When the shear layer thickness approaches electron kinetic scales, it becomes unstable to EKHI. This instability is localized within the shock transition, evolves on electron timescales, and is fundamentally distinct from ion-scale KH modes commonly observed at planetary boundaries.

In the nonlinear stage, the EKHI generates coherent electron vortices embedded within the shock ramp. These vortices are accompanied by strong bipolar parallel electric fields and pronounced charge separation, which effectively generate field-aligned electron beams therein. Interestingly, we further demonstrate that EKHI between the reforming shock fronts can produce electron vortex magnetic holes, which are electron-scale coherent structures frequently observed in turbulent plasma. This indicates a possible generation mechanism for electron-scale magnetic holes in Earth's magnetosheath.

These results identify EKHI as a key mechanism linking shock-surface shear flows, electron vortices, magnetic holes, and electron energization at quasi-perpendicular shocks. This process provides a viable pre-acceleration channel for electrons and has broad implications for kinetic-scale energy conversion at collisionless shocks.

How to cite: Guo, A., Lu, Q., Lu, S., Yao, S., Yang, Z., and Gao, X.: Electron Kelvin-Helmholtz Instability at Quasi-perpendicular Shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8006, https://doi.org/10.5194/egusphere-egu26-8006, 2026.

The transport of energetic particles is intimately related to the properties of plasma turbulence, a ubiquitous dynamical process that transfers energy across a broad range of spatial and temporal scales. However, the mechanisms governing the interactions between plasma turbulence and energetic particles remain incompletely understood. Here we present comprehensive observations from the upstream region of a quasi-perpendicular interplanetary (IP) shock on 2004 January 22, using data from four Cluster spacecraft to investigate the interplay between turbulence dynamics and energetic particle transport. Our observations reveal a transition in energetic proton fluxes from exponential to power-law decay with increasing distance from the IP shock. This result provides possible observational evidence of a shift in transport behavior from normal diffusion to superdiffusion. This transition correlates with an increase in the time ratio from $\tau_s/\tau_{c}<1$ to $\tau_s/\tau_{c}\gg1$, where $\tau_s$ is the proton isotropization time, and $\tau_{c}$ is the turbulence correlation time. Additionally, the frequency-wavenumber distributions of magnetic energy in the power-law decay zone indicate that energetic particles excite linear Alfvén-like harmonic waves through gyroresonance, thereby modulating the original turbulence structure. These findings provide valuable insights for future studies on the propagation and acceleration of energetic particles in turbulent astrophysical and space plasma systems.

How to cite: Zhao, S., Yan, H., and Liu, T. Z.: Observations of Turbulence and Particle Transport at Interplanetary Shocks: Transition of Transport Regimes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11082, https://doi.org/10.5194/egusphere-egu26-11082, 2026.

As the solar wind propagates through interplanetary space, adiabatic expansion preferentially cools the plasma in the direction perpendicular to the mean magnetic field, while leaving the temperature parallel to the field largely unaffected. The combined effect of the growing temperature anisotropy and the more rapid decrease of magnetic energy relative to the parallel pressure naturally drives the plasma toward the firehose instability threshold. Concurrently, the turbulent cascade from large to small scales leads to kinetic-scale dissipation, resulting in plasma heating and the potential development of suprathermal tails in velocity distribution functions. A central open question is how turbulence-driven heating competes with expansion-induced temperature anisotropies to regulate the onset and nonlinear evolution of kinetic instabilities. In this work, we present the first fully kinetic three-dimensional particle-in-cell (PIC) simulations of an expanding-box system that includes large-scale turbulent forcing, mimicking Alfvénic fluctuations. Our simulations reveal the emergence of suprathermal tails in the electron velocity distribution functions driven by expansion, suggesting an origin in the interplay between turbulence and the firehose instability. This work aims to bridge solar wind observations and theoretical models by providing a unified, fully kinetic framework that captures the coupled effects of expansion, turbulence-driven heating, and kinetic instabilities at electron scales.

How to cite: Péters de Bonhome, M., Bacchini, F., and Pierrard, V.: Formation of Suprathermal Electron Tails in an Expanding, Turbulent Solar Wind: Insights from Fully Kinetic Particle-in-Cell Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11350, https://doi.org/10.5194/egusphere-egu26-11350, 2026.

 In recent years, significant progress has been made in the velocity-moment-based quasilinear (QL) theory of waves and instabilities in plasmas with non-equilibrium velocity distributions (VDs) of the Kappa (or κ-) type. However, the temporal variation of the parameter κ, which quantifies the presence of suprathermal particles, is not fully captured by such a QL analysis, and typically κ remains constant during plasma dynamics. We propose a new QL modeling that goes beyond the limits of a previous approach (Moya et al. 2021), realistically assuming that the quasithermal core cannot evolve independently of energetic suprathermals. The case study is done on the electron-cyclotron (EMEC) instability generated by anisotropic bi-Kappa electrons with A = T⊥/T∥ > 1 (∥, ⊥ denoting directions with respect to the background magnetic field). The parameter κ self-consistently varies through the QL equation of kurtosis (fourth-order moment) coupled with temporal variations of the temperature components, relaxing the constraint on the independence of the low-energy (core) electrons and suprathermal high-energy tails of VDs. The results refine and extend previous approaches. A clear distinction is made between regimes that lead to a decrease or an increase in the κ parameter with saturation of the instability. What predominates is a decrease in κ, i.e., an excess of suprathermalization, which energizes suprathermal electrons due to self-generated wave fluctuations. Additionally, we found that VDs can evolve towards a quasi-Maxwellian shape (as κ increases) primarily in regimes with low beta and initial kappa values ≳ 5. The relaxation of bi-Kappa electron VDs under the action of instability is only partial by reducing the temperature anisotropy, whereas the contribution of wave fluctuations generally enhances suprathermal electrons. The present results show preliminary agreement with in-situ observations in the solar wind, suggesting that the new QL model could provide a sufficiently explanatory theoretical basis for the kinetic instabilities in natural plasmas with Kappa-like distributions.

How to cite: Moya, P. S., Navarro, R., Lazar, M., Yoon, P., López, R., and Poedts, S.: Quasilinear approach of bi-Kappa distributed electrons with dynamic κ parameter. EMEC instability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11406, https://doi.org/10.5194/egusphere-egu26-11406, 2026.

In collisionless plasmas, turbulence generates intermittent small-scale structures such as intense, thin current sheets, within which magnetic reconnection can occur. These structures, and reconnection in particular, are thought to play a key role in turbulence dynamics, energy dissipation, and particle energisation. The Earth’s magnetosheath, a highly turbulent region downstream of the bow shock, provides a natural laboratory for studying these nonlinear plasma processes. The Magnetospheric MultiScale (MMS) mission offers high-resolution, multi-point observations that are ideally suited to resolving small-scale structures in this environment. However, identifying and characterising such structures in spacecraft observations remains challenging due to their localised nature, complex magnetic topology, and the wide range scales involved.

We propose an unsupervised machine learning approach to systematically identify and characterise these structures, with specific emphasis on magnetic reconnection sites within turbulent plasma observations. Our method uses the Toeplitz Inverse-Covariance Clustering (TICC) algorithm, which models each cluster as a time-invariant correlation network, enabling the detection of complex patterns in turbulence. We evaluate TICC’s ability to identify reconnection events against existing datasets and interpret its clusters using the network-based feature scores. Finally, we assess the turbulence properties associated with the identified structures and the prevalence of magnetic reconnection across multiple intervals. This study aims to provide key insight into how the role of turbulent plasmas may vary across different turbulent environments.

How to cite: Quijia Pilapaña, P., Stawarz, J., and Smith, A.: Characterising Small-Scale Structures in the Turbulent Magnetosheath Using Unsupervised Machine Learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11844, https://doi.org/10.5194/egusphere-egu26-11844, 2026.

Modelling turbulence kinetically in space remains challenging due to the multiscale nature of plasma. An alternative approach is to adopt a fluid model hierarchy and close it using a phenomenological expression or law derived from local kinetic simulations. We address this challenge by examining decaying turbulence in the near-Earth magnetosheath using fully kinetic particle-in-cell (PIC) simulations [1]. We apply machine learning techniques to extract a non-local five-moment electron-pressure-tensor closure trained on these simulations. The data are carefully split across simulations initialized with different initial conditions, while maintaining the same turbulence and temperature levels. We evaluate the learned “equation of state” using energy-channel diagnostics, with emphasis on the pressure–strain interaction (a key mediator of turbulence heating). The new global closure outperforms common local approaches (e.g., double-adiabatic [2] and MLP-type closures [3]) in reconstructing key statistics. An equation of state trained on simulations with fewer particles per cell generalises to more accurate simulations with a higher number of particles per cell and different turbulent initialisations, while using the same physical parameters. Off-diagonal terms are more challenging to predict, but performance improves with the quantity of training data.

Finally, we couple this data-driven electron closure with kinetic ion dynamics, advancing toward hybrid kinetic simulations in which electrons are represented by a neural network-based equation of state. This hybrid physics-informed machine learning framework offers a pathway to computationally efficient models with improved physical realism, potentially enabling both predictive simulations and parameter inference in heliospheric and magnetospheric applications.

How to cite: Miloshevich, G., Vranckx, L., de Oliveira Lopes, F. N., Dazzi, P., Arrò, G., and Henri, P.: Electron Neural Closure for Turbulent Magnetosheath Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12428, https://doi.org/10.5194/egusphere-egu26-12428, 2026.

We present a particle-in-cell (PIC) simulation of decaying turbulence with initial conditions representative of the solar wind, in which magnetic depressions form during the nonlinear phase. We analyse the statistical properties of these structures, including size and intensity. We analyse a few of them in detail, looking at the properties of ions and electrons inside and outside them. Using virtual spacecraft, we simulate how these structures would be observed in situ by real spacecraft. We also analyse the trajectories of a few macroparticles entering these structures and undergoing trapping. We compare our simulation results with recent Solar Orbiter observations in the solar wind.

How to cite: Pucci, F., Karlsson, T., Arrò, G., Simon-Wedlund, C., Preisser, L., Ballerini, G., Henri, P., Califano, F., and Volwerk, M.: Magnetic depressions in a kinetic turbulence simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12574, https://doi.org/10.5194/egusphere-egu26-12574, 2026.

One of the key questions about magnetic reconnection is to understand how energy is partitioned between ions and electrons, especially inside the EDR and in the outflow regions. This requires studying the energy transport terms corresponding to kinetic, thermal and electromagnetic energies respectively, along with the energy conversion terms. Previous studies have shown that ion energy flux dominates close to the EDR in magnetopause reconnection, while the electron energy flux is dominant inside it. However, one must be careful while computing the energy transport terms using MMS data, since the results can be dominated by uncertainty. This is particularly true for magnetotail reconnection, where the plasma is tenuous. Here, we present a detailed analysis of the errors in these energy transport terms, and perform a comparative study between reconnection events observed in the magnetopause, magnetosheath and magnetotail regions.

How to cite: Roy, S., Vörös, Z., Settino, A., Nakamura, R., Roberts, O., Yang, Y., Bandyopadhyay, R., and Matthaeus, W. H.: Estimating errors in energy transport terms during magnetic reconnection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14700, https://doi.org/10.5194/egusphere-egu26-14700, 2026.

How to cite: Lübke, J., Effenberger, F., Wilbert, M., Fichtner, H., and Grauer, R.: Magnetic mirroring and curvature scattering cause anomalous cosmic-ray transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15269, https://doi.org/10.5194/egusphere-egu26-15269, 2026.

In plasma physics, one of the main obstacles to unravelling the mechanisms responsible for energy transfer between electromagnetic fields and plasma particles is the multiscale nature of plasma phenomena. In this context, plasma turbulence plays a fundamental role because it transports energy across spatial scales from the energy injection scales (large-scales) down to small-scales at which energy is dissipated. One of the key open challenges in plasma turbulence research is understanding how the small-scale turbulent dynamics couple into and influences the large-scale behaviour of the system and how that influences the energy budget and energy transport at system scales. One approach to address this challenge is to employ so-called Large Eddy Simulations, where the large scales of the system are directly simulated, and the small-scale anomalous dynamics are parameterized using Sub-Grid-Scale (SGS) models for the anomalous contributions. However, the appropriate SGS models for describing collisionless plasma systems with large scale separations remain poorly constrained.

In this work, we employ a series of Vlasov-Hybrid simulations modelling conditions similar to turbulence in Earth’s magnetosheath to characterize the anomalous contributions to the total electric field from each term in the generalized Ohm’s law for different plasma conditions. We discuss the role of anomalous (turbulent) resistivity and anomalous viscosity on the total electric field, and we show that the most relevant anomalous contribution comes from the Hall term for plasmas with low plasma beta. We provide insight on how to model SGS terms in collisionless plasmas at scales within the kinetic range where terms associated with sub-ion physics are not necessarily negligible. To do this we establish the dependence of the anomalous terms on resolved quantities such as the magnetic field, electric current density and plasma vorticity and we evaluate their contribution to the magnetic field generation. Since electric fields strongly contribute to plasma particle energization, our results are relevant for better understanding the cross-scale energy transfer and the anomalous contribution to the energy budget.

How to cite: Agudelo Rueda, J. A., Stawarz, J. E., Franci, L., Granier, C., and Yokoi, N.: On the Anomalous Contribution to the Electric Field in Turbulent Collisionless Plasmas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19281, https://doi.org/10.5194/egusphere-egu26-19281, 2026.

We present a model of the heliospheric magnetic field that combines a large-scale Parker Spiral component with a small-scale turbulent contribution generated using a wavelet-based approach. The turbulent fluctuations are constructed to reproduce key properties of magnetic turbulence observed in the expanding solar wind, including a radially decreasing amplitude and a spatially varying correlation length. The wavelet-based method is adapted from a previously developed Cartesian model through the introduction of a new coordinate system, which ensures the correct radial scaling of the turbulence correlation length. This approach allows us to model a wider spectral range of fluctuations than is typically achievable with magnetohydrodynamic simulations, a crucial requirement for accurately describing gyroresonant scattering of energetic particles. The model is designed for future applications in studies of energetic particle transport in the heliosphere.

How to cite: Malara, F., Larosa, A., Pucci, F., Pezzi, O., Sorriso-Valvo, L., Chiappetta, F., Chimenti, M., Nisticò, G., Perri, S., and Zimbardo, G.: Modelling the heliospheric magnetic field through wavelet-based synthetic turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20991, https://doi.org/10.5194/egusphere-egu26-20991, 2026.

Understanding and modelling turbulence in space plasmas requires capturing kinetic effects that go beyond standard fluid closures. In the present work, we present a data-driven framework that combines unsupervised clustering and sparse equation discovery to identify effective closures in turbulent plasmas. Our primary focus is on solar-wind observations, but with possible applications to magnetospheric environments.

We use unsupervised clustering methods, more specifically k-means, to identify dynamically similar regions in both in situ spacecraft data and numerical simulations. The first part of the project is focused on numerical simulations. Clustering is performed on multidimensional feature spaces constructed from plasma moments, fields, and other pressure-tensor-related quantities, applied to either 3D or 2D simulations. The resulting clusters define coherent regions characterized by comparable kinetic activity, anisotropy, and turbulence properties.

These clustered regions serve as domains for sparse identification of nonlinear dynamics (SINDy). Particular emphasis is placed on exploring data-driven closures involving the pressure tensor, including anisotropic and nongyrotropic contributions, and understanding their role in momentum and other dynamical equations.

The framework is designed to function consistently across both in situ measurements, such as Magnetospheric Multiscale (MMS) observations, and PIC simulations, enabling direct validation and comparison. This combined approach provides a structured method for discovering interpretable, region-specific closures in turbulent space plasmas and supports the development of reduced models directly informed by observations.

How to cite: de Oliveira Lopes, F. N., Dazzi, P., Miloshevich, G., and Keppens, R.: Data-Driven Identification of Region-Dependent Pressure Tensor Closures in Turbulent Space Plasmas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21072, https://doi.org/10.5194/egusphere-egu26-21072, 2026.

Jupiter has the most powerful aurora in the solar system, which is currently studied by NASA's Juno spacecraft. Observations above Jupiter's poles have shown that electrons accelerated toward Jupiter, which contribute to auroral emissions, are frequently accompanied by electrons accelerated in the opposite direction, deep into Jupiter's large magnetosphere. These energetic, bidirectional electrons often exhibit broadband energy distributions consistent with a stochastic particle acceleration mechanism. Alfvén waves, which are observed as magnetic field fluctuations, are being discussed to play an important role in the acceleration process. These waves are belived to be generated by the discontinuous radial plasma transport from Jupiter's plasma source Io to the outer magnetosphere.  We investigate magnetic field and plasma measurements in Jupiter's middle magnetosphere, where Alfvénic fluctuations have been observed, to analyze if a correlation between magnetic field fluctuations and plasma velocity fluctuations can be observed.

How to cite: Piasecki, J., Saur, J., Szalay, J., and Clark, G.: Magnetic field fluctuations in Jupiter's middle magnetosphere on auroral field lines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21383, https://doi.org/10.5194/egusphere-egu26-21383, 2026.

Magnetic reconnection plays an important role in the turbulent relaxation of space and astrophysical plasmas, such as the solar corona, solar wind, and Earth’s magnetosheath. Recent studies have shed light on the role of magnetic reconnection as an efficient energy dissipation mechanism in these large-scale turbulent systems. However, the relative role of magnetic reconnection in dissipating turbulent energy in these macroscopic systems is still not fully understood. To investigate these issues, we simulate a turbulent plasma system using magnetohydrodynamic (MHD) simulations. A large number of reconnection sites are found, and their statistical properties are quantified. The study reveals, for the first time, that the distribution of upstream reconnecting fields is strongly correlated with the distribution of global fields at the energy-containing scales. To further explore these relations in weakly collisional systems, we perform a similar analysis on kinetic Particle-in-Cell (PIC) simulations of plasma turbulence and on in situ observations of the terrestrial magnetosheath using the Magnetospheric Multiscale Mission (MMS). Notably, the key conclusions drawn from MHD simulations remain valid in both the kinetic simulations and MMS observations. These findings are expected to significantly refine theoretical estimates of reconnection rates and heating rates resulting from magnetic reconnection.

How to cite: Khan, M. B., Shay, M. A., Oughton, S., Matthaeus, W. H., Haggerty, C., Adhikari, S., Cassak, P. A., Yang, Y., Bandyopadhyay, R., Roy, S., O’Donnell, D., and Fordin, S.: Turbulent fluctuations at the Correlation Scale as the Driver of Magnetic Reconnection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22923, https://doi.org/10.5194/egusphere-egu26-22923, 2026.

Relativistically hot plasmas are well known astrophysical sources of synchrotron emission, and the degree of linear polarization is affected by the level of turbulence in the source. Here we show, by means of a series of 3D numerical simulations, how the properties of decaying turbulence in hot plasmas depend on the magnetization of both the initial guide field and fluctuations, and how the turbulent Kolmogorov-type cascade proceeds in time. Dissipation occurs in thin, intermittent current sheets, variance anysotropy and non-Gaussian deviations appear at small scales. The computed synthetic polarization maps and degree depend on the plasma dynamics and on the angle of the line-of-sight direction with respect to the guide field. We describe how observations of these quantities may be used to infer the turbulence properties in the source.

How to cite: Del Zanna, L., Landi, S., and Bucciantini, N.: Relativistic MHD turbulence in hot plasmas and synchrotron polarization properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2463, https://doi.org/10.5194/egusphere-egu26-2463, 2026.

We statistically study the power spectral density (PSD) of the magnetic field turbulence in the upstream solar wind of the Martian bow shock by investigating the data from Tianwen-1 and MAVEN during November 13 and December 31 in 2021. Their spectral indices and break frequencies are automatically identified. According to the profiles of the PSDs, we find that they could be divided into three types A, B and C. Only less than a quarter of the events exhibit characteristics similar to the 1 AU PSDs (Type A). We observe the energy injection in more than one-third of the events (Type B), and find the disappearance of the dissipation range in over one third of the PSDs (Type C), which is likely due to the dissipation occurring at higher frequencies rather than proton cyclotron resonant frequencies.

We present an in-depth study of energy injection processes associated with Type-B spectra. Singular Value Decomposition analysis reveals that the gain regions are predominantly composed of compressive wave modes. Notably, a subset of these modes is identified as relatively pure, broadband ion cyclotron waves, a feature not recognized in prior statistical surveys of proton cyclotron waves. Statistical analysis of Type-B events observed by two spacecraft reveals spatial differences: events detected by MAVEN at the quasi-parallel bow shock nose are strongly influenced by the foreshock and correlate with reflected pickup ions. In contrast, concurrent events observed by Tianwen-1 on the flank show no clear connection to the foreshock or the ambient electric field direction, suggesting a potential link to upstream processes in the southern hemisphere.

The statistical study demonstrates the complicated turbulent environment of the solar wind upstream of the Martian bow shock.

How to cite: Zou, Z., Wang, Y., Wu, Z., Su, Z., and Huang, Z.: Solar Wind Turbulence Spectra and Energy Injection Upstream of Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3454, https://doi.org/10.5194/egusphere-egu26-3454, 2026.

Spatiotemporal correlation of magnetic field fluctuations is investigated using the
Magnetospheric Multiscale mission in the terrestrial magnetosheath. The first observation of
the turbulence propagator emerges through analysis of more than a thousand intervals.
Results show clear features of spatial and spectral anisotropy, leading to a distinct behavior of
relaxation times in the directions parallel and perpendicular to the mean field.
The full space-time investigation of the Taylor hypothesis presents a scale-dependent
anisotropy of the magnetosheath when compared to characteristic flow propagation time and
with Eulerian estimates.
The turbulence propagator reveals that the amplitudes of the perpendicular modes decorrelate
according to sweeping or Alfvénic mechanisms. The decorrelation time of parallel modes
instead does not depend on the parallel wavenumber which could be due to resonant
interactions.
This study provides unprecedented observations into the space-time structure of turbulent
space plasmas, also giving critical constraints for theoretical and numerical models.

How to cite: Pecora, F., Matthaeus, W. H., Greco, A., Dmitruk, P., Yang, Y., Carbone, V., and Servidio, S.: Turbulence in the terrestrial magnetosheath: space-time correlation using MMS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3808, https://doi.org/10.5194/egusphere-egu26-3808, 2026.

Turbulence plays an important role in the processes responsible for solar wind heating and acceleration by transferring energy to small scales where it is ultimately dissipated. Understanding turbulence dynamics at kinetic scales is therefore essential for determining how heating occurs in a weakly-collisional plasma. While much progress has been made at magnetohydrodynamic and ion scales, sub-electron scale turbulence remains poorly understood due to limited measurements beyond magnetic field fluctuations. However, Parker Solar Probe (PSP), equipped with its high-resolution instruments and unique near-Sun orbit, provides an excellent opportunity to study turbulence at such scales. In addition to the magnetic field (B), we obtain for the first time, the density (n) spectra (using spacecraft potential measurements) extending to scales smaller than the electron gyro-radius (ρ_e). At scales larger than ρ_e, n and B spectra exhibit similar slopes (-2.62, -2.56), indicative of Kinetic Alfvén turbulence. Below ρ_e, both spectra steepen, with B steepening more than n (-3.84 vs -3.28). This difference between the slopes of the two fields is consistent with turbulence becoming electrostatic in nature and the presence of an electron entropy cascade. While the n spectra has a slope close to the -10/3 prediction, the B spectra is much shallower than the expected -16/3 slope of entropy cascade. We speculate that this apparent shallowing may be due to the finite frequency resolution of the instrument and the presence of weakly damped electromagnetic fluctuations near ρ_e.

How to cite: Mondal, S., Chen, C., and Manzini, D.: The Nature of Turbulence at Sub-Electron Scales in the Solar Wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3865, https://doi.org/10.5194/egusphere-egu26-3865, 2026.

We study Cluster Guest Investigator data when 2 satellites were at 7 km distance, that corresponds to few electron Larmor radius. We find a typical spectral shape within the kinetic range and signatures of intermittency up to electron scales. Local analysis of magnetic fluctuations at electron scales indicates presence of vortex-like coherent structures. We show that these electron scale events are embedded in coherent structures at ion and fluid scales. The results at 1 au are compared with spectral properties and coherent structures at kinetic scales observed by Parker Solar Probe at 11.4 solar radii distance from the Sun during Encounter 19.

How to cite: Alexandrova, O., Fournier, A., Hellinger, P., Maksimovic, M., Mangeney, A., and Bale, S.: Solar wind turbulence from fluid to kinetic scales: observations at 0.053 and 1 au. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3992, https://doi.org/10.5194/egusphere-egu26-3992, 2026.

The heating of corona and solar wind remains a fundamental but unresolved problem in space and astrophysical plasma physics. Ion cyclotron waves (ICWs) have long been proposed as a potential mechanism, energizing solar wind ions through cyclotron resonance. The wave-particle energy transfer is typically evaluated using quasilinear diffusion theory, which assumes gyrotropic ion distributions and may underestimate the actual efficiency. Therefore, high-resolution measurements of three-dimensional ion velocity distribution functions are essential to capture agyrotropic signatures arising from kinetic or nonlinear effects. Here, we report Solar Orbiter observations showing that falling-tone ICWs can efficiently energize agyrotropic protons via nonlinear cyclotron resonance. These phase-bunched ions generate resonant currents that mediate substantial energy transfer, with efficiencies up to two orders of magnitude higher than previous quasilinear estimates. These findings highlight the critical role of nonlinear wave–particle interactions in solar wind heating and acceleration, which may operate more broadly across diverse plasma environments.

How to cite: Li, J., Khotyaintsev, Y. V., Graham, D. B., and Louarn, P.: Direct Observations of Solar Wind Proton Energization via Nonlinear Cyclotron Resonance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4983, https://doi.org/10.5194/egusphere-egu26-4983, 2026.

Coronal mass ejections (CMEs) are one of the main drivers of strong space weather disturbances. The interaction between CMEs and the Earth’s magnetic field can cause a wide range of phenomena and the magnetic configuration and orientation are key factors in determining the geo-effectiveness of this type of events. Modeling these events accurately is an ongoing challenge, and data-driven simulations are a valuable operational and research tool, widely used by the community.

Using the 3D data-driven MagnetoHydroDynamical (MHD) heliospheric solar wind and CME evolution model EUHFORIA (European Heliospheric FORecasting Information Asset), our aim is to model CME events that can impact the Earth. Forthcoming missions, developed by ASI (Italian Space Agency), aims to improve space weather forecasting capabilities, particularly for CMEs, solar energetic particles (SEPs), and other interplanetary disturbances.

In particular SEPs events are of huge importance for Space Weather risks. It is well established that particle acceleration at shocks is linked to the turbulence characterizing the environment in which particles are propagating. Consequently, understanding the role of turbulence is of fundamental importance for the propagation, acceleration and characterization of SEP events. To account for these processes, we aim to integrate the effects of both large-scale structures and turbulence in the simulations, either by using 3D EUHFORIA outputs or thorough 2.5 MHD simulation performed with MPI-ArmVAC, thereby enhancing the diagnostic capabilities of virtual spacecraft.

As a case study, we analyse the event of 3 November 2021, observed by both ACE and Solar Orbiter (SolO), which were nearly co-located in latitude and longitude, with a radial separation of ~22 million km. Comparing EUHFORIA simulations with in situ data from both spacecraft provides valuable insight into the new mission’s potential performance once operational.     

This study was carried out within the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under Contract Grant Nos. 2024-5-E.0-CUP and I53D24000060005.                                                                                                                          

How to cite: Prete, G., Stefaan, P., Gatetano, Z., and Sergio, S.: From Large-Scale Structures to Turbulence: Advancing Virtual Spacecraft Diagnostics for Space Weather Forecasting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5000, https://doi.org/10.5194/egusphere-egu26-5000, 2026.

The power spectral densities (PSDs) of solar wind ion moments and magnetic field turbulence in the MHD range of frequencies can be fitted by a power law with the index of -5/3 and with the power index ranging from 2 to 4 at frequencies exceeding the proton gyroscale. However, this general statement has many exceptions. As examples, (i) the density spectra exhibit a clear flattening at the high-frequency part in the MHD range but a similar effect was not reported for any other quantity, (ii) the -5/3 index is a good approximation for the magnetic field at the Earth orbit but -3/2 fits the velocity spectra better, (iii) the magnetic field spectral index evolves trough the inner heliosphere, reaching -5/3 value at 0.3 AU.  

For this reason, the paper analyzes the power spectra of solar wind and magnetic field fluctuations computed in the frequency range around the break between MHD and kinetic scales. We use Spektr-R proton moments and Wind magnetic field at 1 AU, combine them with Parker Solar Probe and Solar Orbiter observations in the inner heliosphere and concentrate on the overall PSD profiles of the density, thermal speed, parallel and perpendicular components of magnetic field and velocity fluctuations and investigate statistically the role of parameters like the fluctuation amplitude, collisional age, temperature anisotropy, ion and/or electron beta and cross-helicity.

How to cite: Safrankova, J., Nemecek, Z., Nemec, F., and Durovcova, T.: Relation of the magnetic field spectral indices with plasma properties within the heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5056, https://doi.org/10.5194/egusphere-egu26-5056, 2026.

Turbulent small‑scale dynamo action, magnetic reconnection, and kinetic instabilities in fully three‑dimensional magnetosheath turbulence must be investigated together to understand how energy is exchanged, redistributed, and dissipated in a collisionless plasma. Clarifying how these processes coexist and how they may sequence in time is essential for understanding turbulent energy transfer at sub‑ion scales. Using high‑resolution tetrahedral MMS observations in the magnetosheath, we compute a suite of diagnostics that characterize the dynamical role of velocity‑gradient structures, including field‑aligned stretching of the magnetic field, compressive motions, pressure–strain interactions, field–particle energy conversions, and pressure‑anisotropy instability measures. All quantities are derived directly from MMS time series. The measurements errors in the considered quantities are evaluated through Monte‑Carlo–based uncertainty analysis. As a working hypothesis, we examine whether regions with strong field‑aligned stretching or compression tend to coincide with magnetic‑field amplification associated with pressure‑anisotropy instabilities, conditions that may be favorable for turbulent dynamo‑like behavior. Conversely, we test whether intervals containing potentially reconnecting thin current sheets exhibit enhanced current density, elevated field particle and pressure-strain interactions and anisotropy relaxation. To explore the temporal relationships between these processes, we apply cross‑correlation analysis to the above diagnostic measures. This approach allows us to assess whether dynamo‑like amplification statistically precedes current‑sheet formation and dissipation, or whether these processes tend to overlap. Early results suggest that both ordered sequences and simultaneous occurrences are possible, reflecting the intermittent and multi‑scale nature of collisionless turbulence. The combined diagnostic and uncertainty‑quantification framework offers a possibility to evaluate the occurrence rates of magnetic‑field amplification, reconnection, and dissipation processes in collisionless space plasmas.

How to cite: Vörös, Z., Roberts, O. W., Yordanova, E., Settino, A., Upadhyay, A., Roy, S., Nakamura, R., Schmid, D., Volwerk, M., and Narita, Y.: Sub‑ion‑scale energy‑conversion pathways in magnetosheath turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7595, https://doi.org/10.5194/egusphere-egu26-7595, 2026.

Solar Orbiter observations of homogeneous turbulence at various solar wind conditions are used to estimate the power that is carried by coherent structures above a threshold across the turbulent cascade [1]. Turbulence is a potential mechanism heating the solar wind. Both wave-wave interactions and coherent structures are mechanisms that may mediate the turbulent cascade. Coherent structures have been found to be sites of dissipation.

Following the method first proposed by Bendt & Chapman (2025) [2] a threshold is determined above which fluctuations may be coherent structures. We find that the percentage of power carried by coherent structures (LIM-P) is significant, increasing with increasing frequency and maximising at ~50% just below the scale break where the inertial range transitions to the kinetic range. At distances <0.4 AU the increase of this percentage follows a roughly linear trend. Beyond 0.4 AU, there are two subranges in the inertial range. In the kinetic range, the LIM-P decreases approximately linearly with increasing frequency. We generally find more power in coherent structures in parallel than perpendicular fluctuations. Within 0.4 AU this degree of anisotropy does not vary across inertial and kinetic ranges. Beyond 0.4 AU, there is successively more power in coherent structures perpendicular than parallel fluctuations.

If coherent structures do indeed dissipate to heat the solar wind, our results, that there is significant power in coherent structures support the idea that coherent structures are important for dissipating energy of the turbulent cascade and thus solar wind heating. The trend of the LIM-P across frequencies suggests that wave-wave interactions at larger scales are systematically supplanted by coherent structures on smaller scales.

[1] Bendt & Chapman (submitted to ApJLett) Fraction of energy carried by coherent structures in the turbulent cascade in the solar wind.

[2] Bendt & Chapman (2025) Ubiquitous threshold for coherent structures in solar wind turbulence. Phys. Rev. Research doi:10.1103/PhysRevResearch.7.023176

How to cite: Bendt, A. and Chapman, S.: Evolution of power in coherent structures across scales and heliocentric distance in solar wind turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7619, https://doi.org/10.5194/egusphere-egu26-7619, 2026.

Turbulence in the terrestrial magnetosheath drives rapid energy exchanges between electromagnetic fields and flows through strong intermittent compressions, shear layers, and velocity gradient structures. These concurrent and competing processes can generate temperature anisotropies and drive plasma instabilities. Yet the dynamical pathways linking velocity-gradient processes to anisotropy evolution in compressible collisionless plasmas remain poorly understood. We combine high cadence multi-point MMS measurements to quantify the pressure–strain interaction Π: ∇u (decomposed into compressible and incompressible parts), the non-ideal work J·E′, and the electron heat flux q (and ∇·q, where the signal-to-noise ratio is sufficiently large) for selected turbulent magnetosheath intervals. Physically motivated thresholds (percentile-based and background relative) identify episodes of enhanced Π: ∇u, J·E′, and heat flux activity. Then, the electron temperature anisotropy Te_⊥/Te, versus parallel electron plasma β_e(“Brazil”) plots are obtained from the time series under investigation, with added theoretical thresholds corresponding to whistler and firehose instabilities. In this parameter space, the trajectories of the plasma, associated with the various enhanced energy conversion and transport terms, are visualized. Case studies and ensemble statistics reveal that a dominance of different channels occurs in overlapping but non-identical regions: Π: ∇u peaks are associated with rapid anisotropy excursions and compressive structures, J·E′, with localized current and electromagnetic activity, and heat flux events with directed heat-transport toward whistler and firehose thresholds. This approach offers a practical pathway to quantify how turbulence and localized structures push plasma toward or beyond linear instability thresholds, with implications for modeling dissipation and wave generation in collisionless plasmas.

How to cite: Upadhyay, A., Vörös, Z., Roy, S., Svenningsson, I., Settino, A., Roberts, O. W., Yordanova, E., and Nakamura, R.: Multi-channel energy conversions and heat flux transport associated with pressure-anisotropy driven instabilities for electrons in magnetosheath turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7817, https://doi.org/10.5194/egusphere-egu26-7817, 2026.

The Pressure--Strain interaction,  - (P_α • ∇ )•u_α , is a fundamental diagnostic for energy conversion in collisionless space plasmas, facilitating the exchange between bulk kinetic and internal energy for both electrons (α=e) and ions (α=i) without collisional dissipation. This interaction is traditionally decomposed into two distinct physical processes: the isotropic component pθ, associated with dilatation, and the anisotropic component Pi-D, related to deviatoric deformation.

In this study, we perform a synchronized statistical analysis of these components by integrating Particle-In-Cell (PIC) simulations with in-situ observations from the Magnetospheric Multiscale (MMS) mission. By examining probability distribution functions (PDFs) and employing coarse-graining techniques, we identify contrasting statistical signatures for pθ and Pi-D. Our results indicate that  pθ exhibits nearly Gaussian PDFs with kurtosis values close to a normal distribution, suggesting relatively homogeneous fluctuations across the plasma. In contrast, Pi-D displays sharply peaked, heavy-tailed PDFs, with these tails persisting even at large scales. Notably, the extreme events within the Pi-D tails are spatially correlated with coherent structures, such as current sheets and vortices.

Furthermore, scale-dependent filtering reveals that both pθ and Pi-D are highly sensitive to the analysis scale. However, a significant divergence is observed between PIC simulations and MMS data regarding their scale-dependent behaviors, highlighting potential differences between numerical modeling and high-resolution observations. We conclude that  pθ serves as a distributed background channel for energy exchange, while Pi-D acts as a localized, intermittent channel. These findings clarify the statistical nature of the Pressure--Strain interaction and offer critical insights into the dissipation pathways and heating mechanisms within turbulent space environments.

How to cite: Ye, Y., Yang, Y., Wang, S., Parashar, T., Wang, Y., Wan, M., and Shi, Y.: Pressure–Strain Interaction in Collisionless Plasma Turbulence: Statistics and Scale Dependence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7850, https://doi.org/10.5194/egusphere-egu26-7850, 2026.

The difference in energy between velocity and magnetic field fluctuations in a plasma is quantified by the residual energy.  In the solar wind, residual energy is typically negative at magnetohydrodynamic (MHD) inertial scales, indicating an excess of magnetic fluctuation energy that arises from the presence of magnetically dominated structures and a turbulent cascade.  Recent observations have shown that fast-mode shock waves, in contrast, have a conspicuous positive signature – i.e. an excess of velocity fluctuation energy – in spectrograms of residual energy.  We show how the positive residual energy of super-Alfvénic (i.e. fast-mode) MHD shocks is a natural consequence of the Rankine-Hugoniot jump conditions.  The jump conditions have been used to derive an equation for the residual energy in terms of the shock angle, density compression ratio and upstream Alfvén Mach number.  Values obtained from this equation agree well with the observed residual energies of 141 interplanetary shocks.  The potential use of positive residual energy as a fast-mode shock identification signature in spacecraft data is considered, and the significance of these findings for understanding compressive fluctuations more generally in the solar wind is briefly discussed.

How to cite: Good, S., Palmunen, K., Chen, C., Kilpua, E., Mäkelä, T., Ruohotie, J., Sishtla, C., and Soljento, J.: Positive residual energy of magnetohydrodynamic fast-mode shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7861, https://doi.org/10.5194/egusphere-egu26-7861, 2026.

Magnetic- and density-field fluctuations in the solar wind extend over a broad range of spatial and temporal scales. At inertial (MHD) scales, magnetic-field fluctuations are dominated by Alfvénic and/or 2D turbulence, while compressive magnetic fluctuations are associated with slow and fast MHD modes. Density fluctuations at these scales arise primarily from a mixture of entropic, slow-mode, and fast-mode contributions in the transition range near ion characteristic scales, the nature of these fluctuations changes as MHD descriptions break down and kinetic effects become important. At sub-ion scales, both magnetic-field and density fluctuations are governed by fully kinetic processes. Their coupling reflects the dominance of kinetic Alfvén wave like fluctuations, leading to enhanced compressibility and altered phase relationships between density and magnetic fields. Across all these regimes, density fluctuations—tightly linked to magnetic-field variability—play a key role in the scattering of radio waves from astrophysical sources both within and beyond the heliosphere, providing a powerful diagnostic of solar-wind turbulence across scales.

In this paper, we describe observations from two long solar wind intervals measured by the BMSW instrument onboard the Spektr-R spacecraft, which provides ion density measurements at a cadence of 32 ms. Because the Spektr-R magnetometer was not operational, we analyze magnetic-field measurements from the THEMIS-C and Wind spacecraft. The analysis of density fluctuations shows that at large (inertial) scales the fluctuations are nearly isotropic, while in the kinetic range they become strongly anisotropic. In contrast, magnetic-field fluctuations display pronounced anisotropy in both the inertial and kinetic ranges. We discuss the differing anisotropic properties of density and magnetic-field fluctuations and the complications they introduce in interpreting multi-spacecraft measurements.

How to cite: Pitna, A., Nemecek, Z., Safrankova, J., Zank, G., Kontar, E., Strauss, D. T., and Roberts, O. W.: Anisotropies of density and magnetic field fluctuations from inertial to kinetic scales in solar wind turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8023, https://doi.org/10.5194/egusphere-egu26-8023, 2026.

Magnetic switchbacks are large-amplitude magnetic field deflections of Alfvénic nature that are characterized by a high degree of correlation between the velocity and the magnetic fields. They are routinely detected in the inner heliosphere and are characterized by timescales that vary from hundreds of seconds up to a few hours. By means of high cadence Solar Orbiter measurements for the magnetic field vector from the fluxgate magnetometer MAG and for the reprocessed ion data sampled  from the Proton and Alpha particle sensor (PAS) of the Solar Wind Analyser (SWA) suite, we have investigated their turbulent properties in terms of Alfvénicity, structure functions, and intermittency, but also how their presence affect ion kinetic features. In particular, the analysis of a case-study switchback has shown that proton and alpha particle densities increase within it, suggesting ongoing wave activity. Very interestingly, we observe a clear correlation between the magnetic deflection and alpha particle temperature, while no correlation has been found with proton temperature. This is an indication of a possible role played by switchbacks in preferentially heating heavy ions. The shapes of the proton and alphas velocity distribution functions around switchbacks will also be presented and discussed.

How to cite: Perri, S., Perrone, D., Settino, A., Chiappetta, F., D'Amicis, R., De Marco, R., Pecora, F., and Bruno, R.: Turbulence and kinetic signatures around switchbacks in the inner heliosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9415, https://doi.org/10.5194/egusphere-egu26-9415, 2026.

Interplanetary coronal mass ejections (ICMEs) and their sheath regions represent large-scale solar wind transients with distinct plasma properties compared to the solar wind. ICMEs are characterized by the presence of a large-scale flux rope, while sheaths are known for their turbulent and variable nature. At small scales, however, ICMEs, their sheaths, and the solar wind all show signs of magnetohydrodynamic turbulence. As a common property of turbulence, intermittency has been studied extensively in the solar wind and more recently also in ICMEs and their sheaths. Since intermittency manifests as non-Gaussian distributions of fluctuations, scale-dependent kurtosis is a commonly used measure for intermittency. Kurtosis is applied in different ways, with some studies using absolute or mean values of kurtosis to quantify the non-Gaussianity of the distributions at certain scales, while others use the slope of kurtosis to characterize how distributions evolve across scales. However, the interpretation of results can depend on the chosen kurtosis measure. We use data from the Wind spacecraft to study intermittency in the slow and fast solar wind, ICMEs, and ICME sheath regions. Kurtosis is computed from the local intermittency measure through wavelet analysis. Intermittency is measured both with mean values and slopes of kurtosis in the inertial range. Both measures indicate the least amount of intermittency in the fast solar wind, while some variation is observed in the case of the most intermittent plasma environment. In addition, we examine relationships between both intermittency measures and common plasma and turbulence properties.

How to cite: Ruohotie, J., Good, S., and Kilpua, E.: Comparison of intermittency in the solar wind, interplanetary coronal mass ejections and their sheath regions at 1 au, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9840, https://doi.org/10.5194/egusphere-egu26-9840, 2026.

Alfvénic fluctuations are a ubiquitous, particularly in fast streams, whereas the slow wind is typically characterized by reduced Alfvénicity and enhanced variability. However, the slow wind can display strongly Alfvénic behavior as well, with fluctuation properties comparable to those of fast streams, challenging the traditional fast–slow wind dichotomy.

In this study, we perform a comparative analysis of fast solar wind and Alfvénic slow wind during the October 2022 perihelion. In particular, we investigate the solar source and the turbulent properties of the different solar wind regimes, using plasma and magnetic field measurements from the Solar Wind Analyser (SWA) and Magnetometer (MAG) instruments onboard Solar Orbiter. We further investigate possible connections between large-scale turbulence properties and small-scale dissipation by examining the relationship between inertial-range fluctuations and magnetic-field polarization at ion scales across the spectral break. By combining in situ observations with remote-sensing data and two-step ballistic backmapping, we show that Solar Orbiter was magnetically connected to the coronal hole has a bright structure within it, indicating that the observed solar wind variability is driven by spatio-temporal changes in magnetic connectivity to coronal source. Our results show that Alfvénic slow-wind interval preserve a high degree of Alfvénicity, as evidenced by large normalized cross helicity, near kinetic–magnetic energy equipartition, low magnetic compressibility, and large-amplitude magnetic and velocity fluctuations comparable to those observed in fast Alfvénic streams, despite their lower bulk speeds and higher Coulomb collisional age. These findings pose significant challenges for solar-wind models, which must account for the persistence of strong Alfvénic turbulence in slow wind originating from nearby and evolving coronal source regions while exhibiting markedly different bulk plasma properties.

How to cite: Dhamane, O. S., D'amicis, R., Benella, S., Yardley, S., De marco, R., Bruno, R., Sorriso-Valvo, L., Telloni, D., Perrone, D., Owen, C., Louarn, P., Livi, S., Raghav, A., Kumbhar, K., Sharma, U., Kadam, S., and naik, U.: Characterization of Multiple Alfvénic Solar Wind Regimes Observed by Solar Orbiter at the October 2022 Perihelion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11085, https://doi.org/10.5194/egusphere-egu26-11085, 2026.

Magnetohydrodynamic (MHD) turbulence is a fundamental process in astrophysical plasmas and plays a central role in energy dissipation and particle acceleration. In this work, we use high-resolution three-dimensional MHD simulations to investigate the relationship between turbulent cascade processes and the underlying structure of the magnetic and velocity fields. We determine whether regions of enhanced energy transfer and/or dissipation correlate with regions of enhanced strain- or rotation-dominated velocity and magnetic fields.

First, we apply the filtering approach [1] to coarse-grain simulation snapshots on a given scale, obtaining spatial fields of energy transfer and dissipation. We then characterise each field as strain- or rotation-dominated using the coarse-grained tensor invariants [2,3,4], with velocity and magnetic fields treated separately. Regions of intense dissipation and energy transfer are then characterised as either strain- or rotation-dominated.  This analysis is repeated across scales from the inertial range to dissipation scales to explore the relative importance of strain- and rotation-dominated features in the turbulent cascade.

The results provide insight into the phenomenology of MHD turbulence, which will be discussed in the context of recent in situ observations.

[1] M. Germano, Turbulence: the filtering approach. Journal of Fluid Mechanics. (1992) doi:10.1017/S0022112092001733

[2] V. Quattrociocchi, G. Consolini, M. F. Marcucci, and M. Materassi, On geometrical invariants of the magnetic field gradient tensor in turbulent space plasmas: Scale variability in the inertial range, Astrophys. J. (2019) doi: 10.3847/1538-4357/ab1e47

[3] B, Hnat, S. C. Chapman, C. M. Liptrott, N. W. Watkins, Solar wind magnetohydrodynamic turbulence energy transfer rate ordered by magnetic field topology Phys. Rev. Res. (2025) doi:10.1103/9wb2-r437

[4] B, Hnat, S. C. Chapman, C. M. Liptrott, N. W. Watkins, Magnetic Topology of Actively Evolving and Passively Convecting Structures in the Turbulent Solar Wind Phys. Rev. Lett. (2021) doi:10.1103/PhysRevLett.126.125101

How to cite: Liptrott, C., Chapman, S., Hnat, B., and Watkins, N.: Correlation Between Field Rotation–Strain Balance and Turbulent Cascade Processes in 3D MHD Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11490, https://doi.org/10.5194/egusphere-egu26-11490, 2026.

Collisions are nearly negligible in many space and astrophysical plasmas, allowing charged-particle velocity distribution functions (VDFs) to depart from local thermodynamic equilibrium (LTE). How collisionless plasmas relax these non-LTE distributions and convert turbulent energy into particle heating remains an open question. We investigate deviations from LTE in ion velocity distribution functions (iVDFs) within collisionless plasma turbulence using high-resolution measurements from the Magnetospheric Multiscale (MMS) mission. We find that the iVDFs' non-bi-Maxwellian features are widespread and can be significant. Their complexity increases with ion plasma beta and turbulence intensity, with pronounced high-order non-LTE features emerging during intervals of large-amplitude magnetic field fluctuations. In addition, we show that turbulence-induced magnetic curvature plays a significant role in ion scattering and contributes to the isotropization of the iVDF. These results highlight the complex interaction between turbulence and the velocity distribution of charged particles, providing new insight into the kinetic processes responsible for energy conversion in collisionless plasmas.

How to cite: Richard, L., Servidio, S., Svenningsson, I., Artemyev, A. V., Klein, K. G., Yordanova, E., Chasapis, A., Pezzi, O., and Khotyaintsev, Y. V.: Non-Maxwellianity of ion velocity distributions in the Earth's magnetosheath, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12070, https://doi.org/10.5194/egusphere-egu26-12070, 2026.

A natural laboratory for studying turbulence in space plasmas is the Solar Wind. The existence of intermittency in the inertial range, where the plasma dynamics can be explained within the framework of the magnetohydrodynamic model, is one of the primary characteristics of the observed turbulence. The emergence of anomalous scaling characteristics and multifractality for both magnetic and velocity field variations is the evidence of intermittency. Here, we examine the multifractal nature of the Elsasser variables demonstrating the various intermittent degrees of z± variations using data from Solar Orbiter.  Additionally, by examining the joint-multi fractal spectrum, we investigate the relationship between the singularity spectra of z± fluctuations. In relation to the asymmetry of the observed singularity spectra, the significance of stochastic energy redistribution throughout the inertial cascade is also discussed.

This research is supported by the Space It Up! project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0—CUP n. I53D24000060005.

How to cite: Consolini, G., Belardinelli, D., Benella, S., and D'Amicis, R.: Intermittency and Multifractality of Elsasser Variables in Turbulent Solar Wind, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13035, https://doi.org/10.5194/egusphere-egu26-13035, 2026.

In space plasmas, turbulent relaxation processes lead to the spontaneous formation of long-lived, coherent structures. By combining solar wind observations, theoretical models, and numerical simulations, we demonstrate how the plasma locally evolves toward metastable, force-free equilibria. These persistent vortices, observed within the turbulent inertial range, act as sites for particle energization and trapping, directly influencing transport and acceleration — especially in reconnection regions between interacting magnetic islands. Recent high-resolution Magnetospheric Multiscale (MMS) measurements in the magnetosheath provide direct observational evidence of such structures, confirming their central role in mediating the turbulent cascade and dissipation. This study was carried out within the Space It Up project, funded by the Italian Space Agency (ASI) and the Ministry of University and Research (MUR), under Contract Grant Nos. 2024-5-E.0-CUP and I53D24000060005.

How to cite: Servidio, S., Pecora, F., Fortugno, E. M., Greco, A., Imbrogno, M., and Matthaeus, W. H.: Relaxation and Coherent Structures in Space Plasma Turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13144, https://doi.org/10.5194/egusphere-egu26-13144, 2026.

In weakly collisional plasmas, a complete understanding of the turbulent cascade at kinetic scales remains a fundamental and elusive problem. In this regime, spatial and velocity-space fluctuations are inherently coupled, giving rise to complex patterns in which electrostatic waves continuously interact with a network of nonlinear coherent structures. This complex interplay, potentially ubiquitous across turbulent plasma environments, is thought to play a central role in controlling energy transport and dissipation. In this research, we report the first direct investigation of the nonlinear interaction between electrostatic waves and density holes at Debye and sub-Debye scales, using high-resolution Vlasov–Poisson simulations to model the dynamics of a four-dimensional (2D–2V) plasma distribution. In particular, we construct an inhomogeneous equilibrium embedded in a proton background, consisting of a periodic lattice of electron density gaps, and perturb it with nonlinear plasma oscillations in the form of turbulent electron acoustic waves. The resulting dynamics reveal a distinctive regime in which wave–hole interaction redirects the originally one-directional, wave-driven cascade into the full phase space, uncovering a previously unexplored pathway for the emergence of phase-space structures and the transfer of energy across kinetic scales.

How to cite: Celebre, G., Imbrogno, M., Servidio, S., and Valentini, F.: Phase-Space Dynamics of Electron Acoustic Turbulence in 2D-2V Inhomogeneous Plasmas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13712, https://doi.org/10.5194/egusphere-egu26-13712, 2026.

The energy spectrum of magnetic field fluctuations in fast and alfvénic slow solar winds generally presents a spectral break at low frequencies that separates two distinct regions. In the high-frequency side of the break, the spectrum follows a power-law in frequency with exponents that vary about -3/2 and -5/3. In the lower-frequency side of the spectral break, corresponding to the largest physical scales, the spectrum is less steep and presents a power law as the inverse of the frequency. In the same range of scales, plasma fluctuations in the heliosphere are affected by deformations of the flow due to the expansion of the solar wind and velocity shear caused by wind stream interaction. We investigate the impact of these large-scale deformations of the plasma flow on turbulence properties, with our main focus being the rate at which energy of the fluctuations is transferred from large to small scales. In our study, the energy transfer rate is estimated from a Karman-Howarth-Monin (KHM) equation, a scale-dependent energy budget equation that allows to quantify the contributions of different terms to the energy transfer. We have derived a KHM equation that accounts for the combined contribution of expansion and shear in two particular cases: when the planes affected by Shear and Expansion are Aligned or Transverse (SEAT) to each other. We will present the plasma SEAT equations that model the large-scale deformation of the plasma flow, the KHM equations derived from it and preliminary numerical results from 3D single-fluid simulations that will show how both large-scale deformation of the flow intervene in the cross-scale energy transfer and affect turbulence properties.

How to cite: Montagud-Camps, V., Verdini, A., Hellinger, P., and Terradas, J.: Expansion and shear effects on cross-scale energy transfer rate: the SEAT model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14375, https://doi.org/10.5194/egusphere-egu26-14375, 2026.

Energy transfer across scales is essential for understanding the dissipation and heating of plasma turbulence. In the energy cascade scenario, the energy transfer rate is generally quantified by the dissipation rate in the small dissipation range, along with the third-order law in the inertial range. To investigate the local properties of the energy transfer process, here we employ three main diagnostics: the locally averaged dissipation rate  ε_r at different scales r, the local energy transfer (LET) rate, and the scale-filtered energy flux. The direct numerical simulation of three-dimensional incompressible magnetohydrodynamic (MHD) turbulence is conducted. Preliminary results include: (i) the spatial distributions of these energy transfer diagnostics show scale dependence, which also suggests that these diagnostics dominate at different scales; and (ii) even though these diagnostics could not be pointwise correlated, they exhibit similar patterns. To further quantify their correlation, we calculated the correlation functions, which show that the energy dissipation rate, the LET, and the scale-filtered energy flux have regional correlation, that is, they occur in close proximity to each other. Further analyses shall be conducted from several aspects: (i) taking into account the anisotropic effect on the energy transfer process, and (ii) extending into kinetic systems, wherein kinetic particle-in-cell (PIC) simulations shall be used, and the energy conversion channels, such as pressure-strain interaction and electromagnetic work, will be employed. 

How to cite: Cheng, Z. and Yang, Y.: Statistics of Locally Averaged Energy Transfer Rate in Plasma Turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14395, https://doi.org/10.5194/egusphere-egu26-14395, 2026.

Energetic particles in astrophysical plasmas, both in the heliosphere and in a variety of cosmic environments, interact with turbulence that is magnetised, intermittent, and inherently multiscale. Understanding how these turbulent structures govern particle transport and acceleration is key to interpreting cosmic ray propagation, space weather phenomena, and high-energy radiation signatures. Here, I report on intial results of our ISSI Team #24-608 that brings together experts in space plasma turbulence, particle transport modeling, and spacecraft data analysis to develop the next generation of physically realistic test-particle simulations. These models incorporate turbulence features constrained by heliospheric in-situ observations from Parker Solar Probe and Solar Orbiter, as well as numerical simulations resolving coherent structures like current sheets and flux ropes across broad dynamical ranges. We investigate the role of such intermittency and structure in modifying classical diffusion coefficients and enabling anomalous transport regimes. Our approach aims to move beyond idealised turbulence assumptions, providing testable predictions for particle fluxes and anisotropies in the heliosphere and beyond. These developments offer new perspectives on energetic particle dynamics across cosmic environments, with implications for galaxy-scale feedback processes and magnetised turbulence from star-forming regions to the intergalactic medium.

How to cite: Effenberger, F., Lübke, J., Fichtner, H., and Grauer, R.: Energetic Particle Transport in Structured and Multiscale Plasma Turbulence: Bridging Observations, Theory, and Simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14406, https://doi.org/10.5194/egusphere-egu26-14406, 2026.

We verify the level of multifractality of the solar wind magnetic field fluctuations (energy density and components) measured by the Parker Solar Probe (PSP) during its first perihelion (01-09.11.2018), recently reported in literature. Two different complementary fractal approaches, namely the Rank Ordered Multifractal Analysis (ROMA, Chang and Wu 2008) and the Partition Function Multifractal Analysis (PFMA, Halsey et al. 1986) are applied, for the first time, on the same data set. ROMA considers the raw fluctuations at all scales, grouped according to their rank; PFMA provides a multifractal spectrum from a measure extracted from data and assumed to be the result of a multiplicative process. The methodology provides new insights on the multifractality close to the Sun (at 0.17-0.23 au), and complements other studies of the same dataset, at close distances from the Sun, and at solar minimum.

At 0.17 au, a cross-over is identified at a narrow range of scales centered on ~4 s (corresponding to a spatial scale of ~1400 km) separating two sub-ranges of inertial scales, with different statistical and fractal properties. The cross-over is detected by four different approaches (1) flatness behavior, (2) structure functions power law scaling, (3) change of turbulence regime across the inertial range, (4) change of the ROMA spectra over the two inertial scale-ranges. Left-skewed asymmetry of PFMA multifractal spectra further supports the complexity of the underlying dynamics dominated by large fluctuations. Conversely, the lack of right-skewed multifractal spectra at 0.17 au, as detected in the outer heliosphere, underline the different state of fluctuations near the Sun. The results have been recently accepted for publication in the Astrophysical Journal (Teodorescu et al., 2026).

Chang, T., & Wu , C.C. 2008, PhRvE, 77, 045401. doi:10.1103/PhysRevE.77.045401

Halsey, T. C., Jensen, M. H., Kadanoff, L. P. et al. 1986, PhRvA, 33, 1141–1151. doi:10.1103/PhysRevA.33.1141

Teodorescu, E., Wawrzaszek, E., Echim, M., 2026, ApJ, DOI: 10.3847/1538-4357/ae3185

How to cite: Teodorescu, E., Wawrzaszek, A., and Echim, M.: Bifractality and Cross-over Behavior Observed in Solar Wind Intermittency by Parker Solar Probe: Rank Ordered Analysis and Partition Function Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14470, https://doi.org/10.5194/egusphere-egu26-14470, 2026.

In the MHD inertial range (scales larger than ion-kinetic scales) turbulent fluctuations in the solar wind are often Alfvénic in character, meaning that their magnetic and flow velocity fluctuations are proportional to each other and predominantly perpendicular to the background magnetic field. However, observations of the solar wind have shown that there is a significant difference in the energy in velocity fluctuations and normalized magnetic fluctuations. This difference, called the residual energy, should be zero for linear Alfvén waves, but is consistently observed to be negative in the solar wind, with magnetic fluctuations dominating. This work investigates the energy partition in strong three-wave interactions through an experimental campaign on the LArge Plasma Device (LAPD) in an MHD-like regime. Primary (driven) modes are launched from antennas, and secondary modes generated by the strong three-wave interaction are observed. The primary modes are shown to have no residual energy, while the secondary modes have significant residual energy - negative in the “sum” mode and positive in the “difference” mode. These results constitute the first laboratory demonstration that residual energy can indeed be generated by nonlinear mode coupling.

How to cite: Abler, M., Dorfman, S., and Chen, C. H.: First Laboratory Observations of Residual Energy Generation in Strong Alfvén Wave Interactions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16141, https://doi.org/10.5194/egusphere-egu26-16141, 2026.

The velocity distribution functions (VDFs) of space plasma typically present non-Maxwellian shapes due to the very low level of collisisionality. The small scale gradients of the VDFs could be the key feature to explain heating and dissipation, inibiting the revesibility of the energy exchange between fields and particles once a significant level of complexity is achieved.
In this work, we investigate the solar wind protons VDFs fine features and their relation to different measures of the real space turbulent cascade. We explore different solar wind regimes and heliocentrice distances by using both Parker Solar Probe and Solar Orbiter data.
These results, suggestive of the presence of a dual velocity-real space cascade, contribute to a better understanding of turbulence in space plasmas.

How to cite: Larosa, A., Pezzi, O., Trotta, D., Ran, H., and Sorriso-Valvo, L.: Phase space cascade in the inner Heliosphere , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19459, https://doi.org/10.5194/egusphere-egu26-19459, 2026.

The interplay between turbulence and magnetic reconnection in collisionless plasmas is of great interest in many different space and astrophysical environments. Turbulence generates ion-scale current sheets (CSs) which reconnect, driving a turbulent cascade at sub-ion scales and thus providing a channel for energy dissipation. We present a collection of high-resolution 2D and 3D hybrid (kinetic ions, fluid electrons) simulations of plasma turbulence with different physical parameters to investigate how the macroscopic properties of the turbulent plasma background affect the dynamics and statistics of magnetic reconnection. We focus our analysis on the impact of two key parameters: the energy injection scale (i.e., the turbulence correlation length) and the amplitude of the initial fluctuations with respect to the ambient magnetic field (i.e., the turbulence strength). These two, combined, also determine the nonlinear time associated with the turbulent cascade. We first compare the similarity and differences in the properties and dynamics of the turbulence itself (shape and size of coherent structures in real space, spectral properties of the turbulent fluctuations, energy transfer rate) and then the changes in the properties and dynamics of the CSs undergoing reconnection (CS thickness and aspect ratio, reconnection rate). We discuss how the above properties rescale with respect to the two key parameters in the context of existing theories and models for turbulence and magnetic reconnection and the physical implications of our findings.

How to cite: Franci, L., Papini, E., Del Sario, D., Dhole, D., Hellinger, P., Landi, S., Verdini, A., and Matteini, L.: Effect of Turbulence Amplitude and Correlation Length on Magnetic Reconnection Dynamics in Hybrid Simulations of Collisionless Plasmas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20512, https://doi.org/10.5194/egusphere-egu26-20512, 2026.

Magnetic reconnection is a fundamental energy conversion process in plasmas. While

changes in the topology of the magnetic field take place inside a small region, acceleration  and heating of the plasma are distributed over larger scales. Acceleration and heating drive plasma transport and lead to explosive magnetic energy release likewise on large scales during phenomena such as substorms, solar flares, and  possibly gamma ray bursts. With modern space  technology, geospace is an ideal plasma laboratory for studying how collisionless magnetic reconnection operates in nature since plasmas and fields in action can be directly measured at high cadence. With the advanced in-situ measurement capability to resolve electron-scale physics, the four Magnetospheric Multiscale (MMS) spacecraft  have significantly advanced the study of magnetic reconnection and relevant plasma processes.  In this presentation we highlight unsolved problems of magnetic reconnection in collisionless plasma. Advanced in-situ plasma measurements and simulations have enabled scientists to gain a novel understanding of magnetic reconnection. Nevertheless, outstanding questions remain concerning the complex dynamics and structures in the diffusion region, cross-scale and regional couplings, the onset of magnetic reconnection, and the details of particle energization. We discuss future directions for magnetic reconnection research, including new  observations, new simulations, and interdisciplinary approaches.

How to cite: Nakamura, R. and Burch, J. L. and the Outstanding Questions of Magnetic Reconnection Team: Outstanding Questions and Future Research on Magnetic Reconnection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4296, https://doi.org/10.5194/egusphere-egu26-4296, 2026.

Plasma structures with enhanced dynamic pressure, density or speed are often observed in Earth’s magnetosheath. These structures, known as jets and fast plasmoids, can be registered in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks Using measurements by the Magnetospheric Multiscale (MMS) spacecraft, Goncharov et al., (2020) showed similarities in the plasma properties of the jets and fast plasmoids. On the other hand, they pointed out that the different magnetic fields inside the structures suggest that the formation mechanisms are not the same. Previous studies established that foreshock structures can be a source of the jets (Raptis et al., 2022). Xirogiannopoulou et al. (2024) found that the subsolar foreshock contains several types of structures with enhanced density or/and magnetic field magnitude, like plasmoids, SLAMS and mixed structures. Following these results, we use multi-spacecraft data collected by THEMIS, Cluster, Magnetospheric Multiscale Spacecraft (MMS) and OMNI missions, and present analytical multi-spacecraft statistical and case studies on the connection between the activity around the bow shock. Based on our comparative analysis, we discuss features of jet-like structures, and their relation to the different phenomena in the foreshock.

How to cite: Goncharov, O., Xirogiannopoulou, N., Balot, P., Grygorov, K., Safrankova, J., Nemecek, Z., and Hajos, M.: Connection of the magnetosheath jet-like structures with foreshock activities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4405, https://doi.org/10.5194/egusphere-egu26-4405, 2026.

Long-lasting quasi-radial interplanetary magnetic field (IMF) events represent a distinct class of solar wind conditions characterized by an unusual magnetic field orientation. Unlike typical solar wind intervals, these events deviate significantly from the nominal Parker spiral configuration, leading to altered large-scale spatial correlations of the IMF. In this study, we investigate the spatial correlation characteristics of long-lasting quasi-radial IMF events and compare them with those observed during normal Parker spiral conditions. Quasi-radial IMF events are identified using the criterion Bx / B >0.9 sustained for more than 4 hours, following a definition similar to that adopted in previous studies. Applying this criterion to Wind magnetic field observations from 2001 to 2024, we identify a total of 753 long-lasting quasi-radial IMF events. We calculate correlation coefficients between Wind and ACE magnetic field measurements without applying a time shift, thereby focusing on the intrinsic spatial correlation rather than propagation effects. The correlation analysis is performed for multiple magnetic field parameters, with particular emphasis on the magnetic field magnitude. Our results indicate that, during quasi-radial IMF conditions, the correlation coefficient of the magnetic field magnitude exceeds that of typical Parker spiral intervals when the spacecraft separation distance is greater than approximately 30 Re. However, within the intermediate separation range of roughly 30–150 Re, the correlation values are generally lower than those observed during Parker spiral conditions, suggesting a scale-dependent modification of IMF coherence under quasi-radial configurations. These findings imply that long-lasting quasi-radial IMF events exhibit distinct spatial correlation behaviors compared to nominal solar wind conditions, potentially reflecting differences in solar wind structure, turbulence properties, or magnetic field topology.

How to cite: Pi, G., Nemecek, Z., and Safrankova, J.: Correlation coefficient of long-lasting quasi-radial IMF events , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5423, https://doi.org/10.5194/egusphere-egu26-5423, 2026.

Plasma waves play a central role in the solar wind–magnetosphere interaction, especially in the foreshock and magnetosheath, where reflected particles, shock processes, and turbulence shape their properties. While these regions have been widely studied, the way foreshock waves evolve as they encounter the bow shock and how their downstream signatures relate to the upstream conditions remain poorly understood. Using multi-spacecraft observations from the MMS and/or THEMIS missions, we examine wave activity in the foreshock and characterize their key properties and put our findings in context with previous statistical results. We also present a statistical analysis of wave activity in the magnetosheath and compare it with the simultaneous measurements in both regions to explore how wave signatures change across the bow shock. This approach provides a more complete picture of how plasma waves vary across regions and offers new insight into their evolution in the near-Earth environment.

How to cite: Balot, P., Goncharov, O., Safrankova, J., Nemecek, Z., Xirogiannopoulou, N., and Grygorov, K.: Statistical study of wave activity in the foreshock and magnetosheath regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5486, https://doi.org/10.5194/egusphere-egu26-5486, 2026.

The May 2024 geomagnetic superstorm was one of the most extreme space weather events of the past two decades. Starting from the Sun, a group of sunspots had grown significantly, producing a substantial solar flare and launching six coronal mass ejections (CMEs) and reaching the Earth, they significantly affected the Earth's magnetosphere. The Shue et al. (1998) model predicts the magnetopause position at a minimum distance of ~4 Re during the main phase of a storm, while the MHD (SWMF) model predicts a minimum at ~3.3 Re. To validate these models, we manually identified the magnetopause crossings observed by THEMIS, GOES, and MMS during the storm period. The crossings are identified by examining the multispacecraft data, and the impact of extreme conditions on the magnetopause location is determined. The observation and the Shue et al. (1998) model suggest that the magnetopause is compressed from 10 Re to 4 Re in a period of no more than 20 minutes. The manual identification from the multi-spacecraft data assumes that the magnetopause location is approximately 5 Re, and this result is consistent with predictions using various models. Moreover, the normal of each magnetopause crossing and its difference between the predicted normal from the Shue et al. (1998) model were calculated. The results can provide key insights into the dynamic magnetopause under extreme conditions.

How to cite: Ghosh, M., Wang, D., Haas, B., Lyu, X., Pi, G., Nemecek, Z., and Safrankova, J.: Validation of magnetopause positions predicted by models against multi-mission magnetopause crossings for the May 2024 superstorm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5547, https://doi.org/10.5194/egusphere-egu26-5547, 2026.

ESCAPADE is a twin-spacecraft low-cost Mars mission that will revolutionize our understanding of how space weather conditions drive magnetic structure and flows of energy and momentum throughout Mars’ unique hybrid magnetosphere, and how this interaction drives both ion escape and sputtering escape.  ESCAPADE will measure magnetic field strength and topology, suprathermal ion distributions and electron flows, and thermal electron and ion densities, as well as possibly image visible aurora. Our 2-part scientific campaign of temporally and spatially-separated multipoint measurements in different regions of Mars’ diverse plasma environment, will allow us to untangle spatial from temporal variability, characterize short-term variability, and unravel the cause-and-effect of solar wind control of magnetospheric structure and ion and sputtering escape for the first time.

ESCAPADE launched on November 13, 2025.  Though it is a Mars mission, ESCAPADE’s journey begins with a 12 month “loiter” phase within ~2.5 million km of earth, primarily on the anti-sunward side, looping around the L2 Lagrange point and passing twice through the Earth’s magnetotail, at ~320 and again at ~80 earth radii.  Instruments are due to be turned on in late February 2026, just prior to this first tail passage. ESCAPADE will provide the first two-point measurements of heliospheric conditions in these regions of space, addressing questions of solar wind and space weather structure on ~10⁵ km scales and investigating distant magnetotail features, including spatial extent, dependence on solar wind conditions, and the existence of reconnection in the distant magnetotail.  In November 2026, ESCAPADE will execute Oberth maneuvers at a ~500 km perigee to start their interplanetary journey, arriving at Mars in September 2027 and beginning their science mission in spring 2028. This presentation will focus on first results from the plasma instruments in the near-Earth heliospheric environment.