The radiation belts of the Earth and magnetised planets include high energy electrons reaching energies of up to 50 MeV.  Observations at the Earth show that the electron flux is highly variable, and that acceleration must take place inside the planetary magnetic field.   Soon after the radiation belts were discovered it was thought that inward radial diffusion was the main process responsible for the acceleration, but it was difficult to reproduce the timescale for some of the observed variations in the electron flux.  Local electron acceleration via Doppler shifted cyclotron resonance with chorus waves was proposed as an alternative mechanism and has been shown to play a major role in forming the outer electron belt at the Earth reaching energies of several MeV.  Here we review some of the evidence for local acceleration and describe the process of chorus wave acceleration at the Earth.  We review other types of plasma waves, such as magnetosonic waves, that could contribute to electron acceleration and describe the conditions necessary to reach electron energies of several MeV.  We show examples of chorus and other types of plasma waves at Jupiter and Saturn and show how they play an important role in accelerating electrons to form the radiation belts at those planets.  We suggest that wave acceleration is the missing link in a set of process that starts with volcanic gasses from the moon Io and results in the emission of synchrotron radiation from Jupiter.  We suggest that wave acceleration is a universal process operating at the magnetised planets.  Finally, we show how wave acceleration is included into space weather forecasting models to help ensure the safe and reliable operation of satellites on orbit around the Earth.

How to cite: Horne, R.: Electron Acceleration by Wave-Particle Interactions at the Earth and Magnetised Planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11783, https://doi.org/10.5194/egusphere-egu25-11783, 2025.

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from the Sun's lower atmosphere, significantly influencing space weather and planetary environments. To improve predictions of CME arrival and their impacts on Earth and its surroundings, a deeper understanding of their origins, initiation, and complex early evolution is crucial. While coronagraphic observations have been essential for studying the dynamics of CMEs, they cannot capture the initial, critical phase of CME development. Consequently, investigating indirect phenomena in the lower solar atmosphere has become essential. One of the most prominent indirect indicators associated with CMEs is coronal dimming. These are localized, sudden decreases in coronal emission observed at extreme ultraviolet and soft X-ray wavelengths, which evolve rapidly during the lift-off and early expansion phases of CMEs. Coronal dimmings have been interpreted both as “footprints” of the erupting magnetic structure and as indicators of coronal mass loss in the lower corona.

I will review recent advancements in using coronal dimmings to diagnose CMEs. Topics covered will include statistical studies linking dimming characteristics to CME mass and speed, the use of dimmings as early indicators of CME propagation direction, and insights into the magnetic topology and reconfiguration of the early CME stages based on dimming locations and fine structure. Additionally, the potential role of dimmings in the pre-event phase preceding CME onset will be discussed. Finally, I will highlight future research directions and underexplored areas in CME science, emphasizing the untapped potential of coronal dimmings in advancing our understanding of these dynamic solar events.

How to cite: Dissauer, K.: Footprints of Giants – Exploring Early Diagnostics of Coronal Mass Ejections Through Coronal Dimmings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17289, https://doi.org/10.5194/egusphere-egu25-17289, 2025.

The ionosphere, a natural plasma, plays a significant role in planetary satellite and communication systems and is affected by space weather events. Strong solar activities have sudden and long-term effects on the ionosphere. Ionospheric disturbances caused by these activities are considered to be one of the biggest sources of errors in satellite navigation systems and satellite communications. Both the ionosphere and magnetosphere of Mars and Earth are easily influenced by space weather conditions. Solar winds and Coronal Mass Ejections (CMEs) are among the major events influencing space weather. The ionosphere, which is highly sensitive to the effects of space weather, is much thinner and patchier on Mars compared to Earth. The rapid and intense increase in Mars missions in recent years has made today’s research more critical for future missions. In our study, we selected an August 2018 CME and examined its effects on Mars's ionosphere using the instruments on the MAVEN satellite. In addition to the SWEA, SWIA, STATIC values from the MAVEN satellite data, the height change of the relevant solar wind in the Martian ionosphere will be investigated. Investigating ionospheric disturbances with satellites like MAVEN is essential for analyzing the much thinner Martian ionosphere compared to Earth's and contributing to future Mars missions. Understanding space weather is crucial for tracking the evolution of both Earth's and the Red Planet's ionospheric structures and the long-term impact of solar flares on planetary magnetospheres.

How to cite: Dokur, A. and Can, Z.: Effects of the August , 2018 CME on Mars Ionosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1031, https://doi.org/10.5194/egusphere-egu25-1031, 2025.

On 13 June, day 165 of 2024, Juno passed through Io's main Alfvén wing at a distance of some 23 Io radii (R_I) below the moon during perijove (PJ) 62.  Evidence for this passage was clearly seen in the Juno plasma wave, magnetometer, and ion plasma data. The plasma wave signature was an intensification of quasi-electrostatic waves below about 1 kHz with a weaker magnetic component, all lasting for about 90 seconds.  A strong modification of the magnetic field was observed primarily in the co-rotation direction but with a significant component in the direction away from Jupiter. Ions in the range below about 1 keV/q were slowed within the Alfvén wing. The Juno mission has afforded multiple opportunities to examine the Io-Jupiter interaction near the planet and two close flybys through the Alfvén wing during perijoves 57 and 58.  Hence, PJ62 provided observations of the Io-magnetosphere interaction at an intermediate distance.  The broadband electromagnetic emission below 1 kHz was observed during PJs 57 and 58, however, the magnetic component is markedly reduced from those. An estimate of the power in the interaction obtained by scaling the Poynting flux and integrating over the cross section of the flux tube is ~500x10⁹ W.  And modeling of the current suggests filamentation of the Alfvén waves as observed in other Io Alfvén wings.

How to cite: Kurth, W., Sulaiman, A. H., Connerney, J. E. P., Allegrini, F., Valek, P., Ebert, R. W., Paranicas, C., Clark, G., Kruegler, N., Hospodarsky, G. B., Piker, C. W., Kotsiaros, S., Imai, M., and Bolton, S. J.: Juno Observations of Io's Alfvén Wing from 23 Io Radii , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3870, https://doi.org/10.5194/egusphere-egu25-3870, 2025.

Motivated by the need for more accurate radiation environment modelling, this study focuses on identifying and analyzing the drivers behind the sub-relativistic electron flux variations in the inner magnetosphere. We utilize electron flux data between 1 and 500 keV from the Hope and MagEIS instruments on board the RBSP satellites, as well as from the FEEPS instruments on board the MMS spacecrafts, along with solar wind parameters and geomagnetic indices obtained from the OmniWeb2 and SuperMag data services. We calculate the correlation coefficients between these parameters and electron flux. Our analysis shows that substorm activity is a crucial driver of the source electron population (10 - 100 keV), while also showing that seed electrons (100 - 400 keV) are not purely driven by substorm events, but also from enhanced convection/inward diffusion. By introducing time lags, we observed a delayed response of electron flux to changes in geospace conditions, and we identified specific time lag periods where the correlation is maximum. This work contributes to our broader understanding of the outer belt sub-relativistic electron dynamics, and forms the basis for future research.

How to cite: Christodoulou, E., Katsavrias, C., Kordakis, P., and Daglis, I.: Influence of solar wind driving and geomagnetic activity on the variability of sub-relativistic electrons in the inner magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4720, https://doi.org/10.5194/egusphere-egu25-4720, 2025.

This study investigated high-frequency gravity waves (HFGWs) observed by the Zhurong/Tianwen-1 and Perseverance/Mars 2020 rovers between 09:00 and 11:00 local time, from Ls 140° to 165° in Mars Year 36. By analyzing the eccentricity of hodographs for monochromatic wind perturbations obtained from the horizontal wind perturbation, HFGWs were identified via their predominantly linear characteristics.The propagation directions of these waves were determined using polarization relationships from the linear theory of HFGWs. The stability of the background atmosphere was estimated from the Dynamic Meteorology Laboratory general circulation model simulation. The frequency of HFGWs doubled following the onset of a regional dust storm (RDS) in the Utopia Planitia region, where the Zhurong rover landed. The HFGWs observed by Zhurong predominantly propagated in a north-south direction before the RDS and then in an east-west direction afterward. The changes in propagation direction were likely related to atmospheric instability and the background wind changes before and after the storm.

How to cite: Yang, C., Sun, C., Ban, C., Lai, D., Wu, Z., Fang, X., and Li, T.: Observed Martian High-frequency gravity waves by Zhurong and Perseverance rovers before / after a regional dust storm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5310, https://doi.org/10.5194/egusphere-egu25-5310, 2025.

A typical long-duration positive ionospheric storm (LDPS) developed in the midlatitude ionosphere in the European sector in response to a strong geomagnetic storm of February 26-27, 2023 (Kp = 7-, minimum SYM-H = -161 nT). To advance the current understanding of storm-time midlatitude ionosphere, we investigated the drivers of this LDPS using combination of multi-instrument observations and modeling, with focus on magnetically conjugate locations. Simulations with the field line interhemispheric plasma (FLIP) model constrained by the observed F2-layer peak height (h_mF₂) and density (N_mF₂) data at Kharkiv (50^oN, 36^oE) and Grahamstown (33.3^oS, 26.5^oE) were validated with the O/N₂ ratio data from the Global Ultraviolet Imager (GUVI). Our results indicate that neither the F2-layer peak uplift nor the O/N₂ ratio increase can be considered exclusive drivers of an LDPS. Each driver can be dominant depending on conditions. An LDPS can develop even when the h_mF₂ decreases and sometimes, a small h_mF₂ increase of ~10-20 km can cause a strong LDPS. Similarly, an O/N₂ increase is not a primary or necessary condition for an LDPS to develop but a small O/N₂ increase of ~20-30% can cause a prominent LDPS. Finally, the formation of a positive or negative storm can be inhibited if the raising/lowering of h_mF₂ is counterbalanced by a decrease/increase in the O/N₂ ratio.

How to cite: Reznychenko, M., Kotov, D., Richards, P. G., Bogomaz, O., Goncharenko, L., Paxton, L. J., Hernandez-Pajares, M., Reznychenko, A., Shkonda, D., Barabash, V., and Domnin, I.: Investigation of the Drivers of Long-Duration Positive Ionospheric Storms During the Geomagnetic Storm on February 26-27, 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5836, https://doi.org/10.5194/egusphere-egu25-5836, 2025.

Heavy ion composition and charge-state distributions provide valuable information about the source region of the solar wind due to the 'freeze-in' effect, making them valuable diagnostics for understanding the conditions of their source regions. Small-scale flux ropes (SFRs) have been studied for decades, but their source regions and formation mechanisms are still under debate. While heavy ion signatures in relatively large-scale flux rope structures, known as magnetic clouds (MCs), have been well studied, those signatures are still unclear in SFRs that last only couple of minutes. More importantly, heavy ions do not necessarily travel at the same speed as protons in the solar wind. A potential ion-proton differential velocity could cause a temporal lag between the heavy ion signal and the boundaries of SFRs, which introduces deviations when heavy ion signatures in SFRs are investigated.

In this study, we review ten years of in-situ solar wind heavy ion data obtained from the Solar Wind Ion Composition Spectrometer (SWICS) on board the Advanced Composition Explorer (ACE). The data set is derived from the Pulse Height Analysis (PHA) data, at 12-min resolution. By investigating every energy per charge step of each SWICS measurement interval, more SFRs with short duration, even shorter than 12 minutes, are included. We conduct a statistical study on the ion-proton differential streaming in over 6300 SFRs that are heavy ion abundant, as well as in the surrounding solar wind.

Positive ion-proton differential streaming is found common in SFRs but less common in SFRs that are located in recorded Interplanetary Coronal Mass Ejections (ICMEs) . About 50% heavy-ion-dense SFRs show ion-proton differential velocity larger than 0.2 times the local Alfvén speed. Positive ion-proton differential streaming has also been observed in the background solar wind near SFRs. However, some cases show strong positive ion-proton differential streaming exclusively within SFRs. Ion-proton differential streaming is crucial for understanding heavy-ion signatures in small-scale structures, with their acceleration mechanisms being of particular interest. A further study shows that SFRs detected at 1 AU are unlikely to be the interplanetary manifestations of nanoflare- or microflare-associated small CMEs, or at least not solely so.

How to cite: Gu, C., Heidrich-Meisner, V., and Wimmer-Schweingruber, R. F.: The ion-proton differential streaming observed in Small-scale Flux Ropes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6031, https://doi.org/10.5194/egusphere-egu25-6031, 2025.

The Comet Interceptor mission will attempt to fly by a yet undetermined target comet. The conditions of this flyby will remain largely unknown up to the selection of target and possibly even the moment of encounter. A detailed trajectory design phase, which includes verification of the technical limitations implied by the flyby geometry, precedes target comet selection, so the flyby velocity and the details of the geometry are known in advance. Solar irradiance and the neutral gas expansion speed can be estimated reasonably well. However, the comet outgassing rate, the dust production rate, and the solar wind conditions are only known within broader uncertainty margins. The present contribution aims to optimally choose the distance of closest approach based on a simplified formalism that expresses, on one hand, the science return to be expected as a function of the closest approach distance, and, on the other hand, the risks implied by a close approach. This is done by performing Monte Carlo simulations over a large sample of possible flyby configurations, based on the expected probability distributions of the gas and dust production rates and the solar wind conditions, and for different closest approach distances. For small flyby distances, a spacecraft can study the nucleus, the neutral gas coma, and the induced magnetosphere from up close, benefiting the science return. There is a trade-off to be made against the cometary dust collision risk, which becomes larger close to the nucleus. The change of the optimal flyby distance with gas and dust production rate, solar EUV flux, and flyby speed is discussed. The conclusion is that the Comet Interceptor main spacecraft and its two daughter probes – within the limitations of the approximations made – would benefit from a target comet with a gas production rate of 10²⁸-10²⁹ molecules·s^-1, a low dust-to-gas ratio, a high solar EUV flux, and a slow flyby speed (De Keyser et al., 2024, https://doi.org/10.1016/j.pss.2024.106032), for which the optimal closest approach distance (somewhere between 300 to 2000 km for the mother spacecraft) would yield a good science return at a limited risk.

How to cite: De Keyser, J., Edberg, N. J. T., Henri, P., Rothkaehl, H., Della Corte, V., Rubin, M., Funase, R., Kasahara, S., and Snodgrass, C.: Finding the optimal flyby distance for the Comet Interceptor comet mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6228, https://doi.org/10.5194/egusphere-egu25-6228, 2025.

Recently, a model of the vertical profiles of shell currents and the magnetic field in the ionosphere has been developed (Romashets and Vandas, 2024). The distribution was determined for polar and equatorial regions. A global three-dimensional pattern of the shell-currents flow and its interconnections with the field aligned current (FAC) can be reconstructed. The magnetic field induced by the shell currents can produce at some locations a geomagnetic effect comparable to that of the ring current. The Biot-Savart integration over the entire ionosphere to derive the shell-currents induced magnetic field could be a challenging task. Here, we present an alternative method which utilizes spherical harmonics of different types for the inner and outer problems. The magnetic field inside the ionosphere is known, and outside of it is current-free and is represented as a gradient of a scalar potential, a sum of spherical harmonic functions with their coefficients. For the inner problem, only terms with (r/r0)^-n-1 are present in the sum, while the outer scalar potential contains only terms with (r/r0)ⁿ. Here 0<n<N, N=13, and r0 is the average distance from the Earth’s center to the ionosphere. Both the inner and outer problems for finding the induced magnetic field have only one condition: the magnetic field calculated with the scalar potential must be equal to the known magnetic field in the ionosphere. This research was supported by the NSF 2230363 and AVCR RVO:67985815 grants.

References.

• Romashets, M, Vandas, Determination of Vertical Profiles of Shell
  Currents in the Ionosphere, Annales Geophysicae, submitted, 2024.

How to cite: Romashets, E. and Vandas, M.: Magnetic field induced by the ionospheric shell currents., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6829, https://doi.org/10.5194/egusphere-egu25-6829, 2025.

The Parker Solar Probe (PSP) has provided unprecedented detailed in-situ measurements of proton velocity distributions (VDs) in the young solar wind, unveiling striking hammerhead features. The first interpretations and analyses, including PIC simulations of these unexpected shapes, suggested the involvement of more complex processes, especially kinetic instabilities. Recently, in A&A, 692, L6 (2024), we have identified a self-generated instability triggered by proton beams, whose back-reaction on the proton VDs can form the hammerhead proton population. An effective and numerically less-expensive quasi-linear approach enabled us to explore how this plasma micro-instability reshapes proton distribution, reducing beam drift and inducing a strong perpendicular temperature anisotropy, the main feature of the hammerhead structure. Our results align with PSP's in situ data and provide a fresh perspective on these distributions' dynamic and transient nature. These findings offer new insights into the role of kinetic instabilities in shaping space plasma dynamics.

How to cite: Shaaban, S. M., Lazar, M., López, R. A., Yoon, P. H., and Poedts, S.: Plasma Mechanisms Behind Hammerhead Proton Populations Observed by Parker Solar Probe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8215, https://doi.org/10.5194/egusphere-egu25-8215, 2025.

The Chang’e-6 (CE-6) mission, part of China's lunar exploration program, marked a significant milestone as the first mission to return samples from the far side of the Moon. One of the highlights of CE-6 mission is that it piggybacked four international payloads, including the INstrument for landing-Roving Laser Retroreflector Investigations (INRRI), developed through a collaboration between the Italian National Institute for Nuclear Physics — Frascati National Labs (INFN-LNF) and the Aerospace Information Research Institute, Chinese Academy of Sciences (AIRCAS).

INRRI is a lightweight, passive optical instrument composed of eight cube corner retroreflectors made from fused silica, offering a wide 120° field of view. This robust and miniaturized design has a high level of maturity and inheritance from previous missions such as NASA’s Mars InSight and Perseverance, where similar retroreflectors had been successfully deployed. For CE-6 mission particularly, INRRI was mounted on a specialized bracket to minimize interference from ascender plume effects during liftoff. CE-6 INRRI underwent rigorous qualification tests, including mechanical (acceleration, shock, sinusoidal and random vibrations) and thermal vacuum tests, to validate its structural integrity. After integrated with the lander, CE-6 INRRI underwent the whole spacecraft random and sinusoidal vibration tests and successfully passed all evaluations.

The CE-6 INRRI serves as a high-precision absolute control point, crucial for improving lunar surface mapping especially for the lunar far side. Initial validation of INRRI’s operational status has been achieved through observations by the Lunar Orbiter Laser Altimeter (LOLA) onboard NASA’s Lunar Reconnaissance Orbiter (LRO). Future observations by laser ranging from lunar orbiters will refine its position, and will contribute to improving the accuracy of orbit determination for lunar orbiters, advancing studies of lunar geodesy, Earth-Moon dynamics and lunar physics.

Building on this success, the Italian-Chinese collaboration team are working on the piggybacking of Chang’e-7 LAser Retroreflector Arrays (CLARA), including MoonLIGHT (Moon Laser Instrumentation for Geodesy, Geophysics and General relativity High accuracy Tests) and INRRI. Currently INRRI for CE-7 has just completed its mechanical tests and is in the process of arranging the subsequent experiments.

How to cite: Wang, Y., Dell'Agnello, S., Di, K., Muccino, M., Cao, H., Porcelli, L., Deng, X., Salvatori, L., Ping, J., Tibuzzi, M., Li, Y., Filomena, L., Kang, Z., Montanari, M., Meng, Z., Mauro, L., Xie, B., and Maiello, M.: The First Lunar Far-Side Laser Retroreflector Deployed on Chang’e-6 Lander and Prospect for Chang’e-7 Mission , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8557, https://doi.org/10.5194/egusphere-egu25-8557, 2025.

With the growth of industry, transportation and machinery the issue of studying and damping vibrations and acoustic oscillations has become critical. Up to 4,000 earthquakes occur on Earth each year. Structures such as skyscrapers and bridges must be designed to withstand ground vibrations without damage. Machinery and tools operate with components that torsion and vibrate in the form of structural nodes. These nodes are connected by specific links to form complex multi-mass mechanical systems. Preventing vibration damage to multi-mass structures remains a pressing problem today. Therefore, the development of methods to calculate the amplitude, frequency and phase of the generated vibrations is a relevant task. Currently known methods of dynamic calculations are the use of analytical techniques for determining the intrinsic frequency of transverse and longitudinal oscillations of shells, rods and rotating machine parts (L.D. Landau, E.M. Lifshitz, V.I. Mossakovskiy, K.V. Frolov). Each task solved with these methods must strictly define the initial and boundary conditions of the oscillatory process. The application of these computational methods to multi-mass systems is very labor-intensive because, in addition to the calculation of amplitude, frequency, and phase, it is necessary to take into account the mode of oscillation. The study of free oscillations in multi-mass systems requires the formation of a system of linear differential equations and the use of cyclic frequency equations for multi-mass systems. Currently, simpler engineering methods such as electromechanical analogies were widely adopted in engineering practice. This period also saw the beginning of research into the resonant frequencies of living organisms to ensure the safety of vehicles subjected to vibration loads. This research was particularly important to the aerospace industry. When launching rockets carrying astronauts, spacecraft experience tremendous vibration shocks. In order to avoid harmful resonance effects, the natural frequencies of the astronaut's body and its organs must be determined. We have used a method based on electromechanical analogies to calculate the resonance frequencies. This method is based on the model of the astronaut's body as a vibrating system proposed by Prof. I. K. Kosko. The computational scheme of this model was developed for the first time. The astronaut's body was modeled as a lumped mass system connected by elastic links, the stiffness of which was determined according to the series and parallel rules. The study used data on the elastic modulus and mass of each part of the astronaut's body. The intrinsic frequency of the astronaut's body was calculated to be 1.702 Hz. The results highlight the importance of taking these data into account when designing the damping system for the astronaut's seat in order to prevent the vibration frequency of the rocket from coinciding with the resonance frequency of the astronaut's body. This approach allows the identification of frequencies that must be avoided to minimize the risk of damage caused by vibration loads. This work demonstrates the application of electromechanical analogies as a simplified engineering method for determining the natural frequencies of complex multi-mass systems such as the human body.

How to cite: Sokol, G., Snobko, D., Kadilnikova, T., and Dalik, M.: Method of electromechanical analogies in calculations of natural frequencies of multi-mass mechanical and biological systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10294, https://doi.org/10.5194/egusphere-egu25-10294, 2025.

Space weather causes geomagnetic disturbances that can affect critical infrastructure. Understanding the dynamic response of the coupled solar wind-magnetosphere-ionosphere system to severe space weather is essential for mitigation purposes. This paper reports on a detailed analysis of the most recently observed May 10, 2024, storm. We demonstrate that the global response to the storm dynamics was strikingly different in various sectors and at various latitudes. Results in the American and European sectors show that the most extreme mid-latitude response was associated to substorm related activity. However, no adverse impact of the storm on bulk power systems was report in North America or other parts of the world.

How to cite: Ngwira, C. and Weygand, J.: Global Geomagnetic Response and Impact During the 10 May 2024 Gannon Storm – Observations and Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12754, https://doi.org/10.5194/egusphere-egu25-12754, 2025.

During the May 2024 space weather event, Kiruna magnetometer (KIR) registered historically large positive deviation of the northward geomagnetic disturbance (dX = +1300 nT) at around 12 UT (14 MLT, i.e., postnoon).  The large dX is observed entire Scandinavia, giving AU = 1431 nT at 12:11 UT, but not in the Atlantic or North American sectors (although we do not know the disturbance at 15-23 ML because no data at > 55° Mlat is available).  

Such large positive dX of dayside stations is not very rare, most of them are observed in the North American continent.  Out of total 21 AU peaks of > +1300 nT separated by more than 1 hour (12 magnetic storms) during 1978-2019, 2 events are peaked at 09-15 UT, 8 events at 15-21 UT, 6 events at 21-03 UT, and 5 events at 03-09 UT.

For the European sector, dX value in the May 2024 event is the second largest after the 24 November 2001 event in both AU statistics (1978-2019) and Kiruna magnetometer (1962-2024).  The same uncommon nature is even seen in Kp=9 that was registered at 09-12 UT.  During 1932-2024, Kp=9 was observed only during 4 events at 09-15 UT, whereas Kp=9 was observed during 10 events at 15-21 UT, 8 events at 21-03 UT, and 5 events at 03-09 UT.

Although these UT anomaly is within the statistical fluctuation, we attribute this to the geomagnetic tilt toward the North American sector.  This makes stations at the same geomagnetic latitudes (e.g., AE stations and Kp stations) located at lower geographic latitudes (i.e., under higher ionospheric conductivity) in the North American sector than the other longitudes when the stations are located near noon (09-15 MLT).  Accordingly, the dayside dX and local K tends to register higher in the North American sector than the other longitudes.  Since extremely large AU (> 1300 nT) tends to occur near noon (this is the case with the 12 storms mentioned above), we expect more frequent large dX when the North America is near noon (15-24 UT).  For Kp, large Kp requires K=9 at Kp station even in the dayside where the disturbance is normally smaller than the nightside.  Then the North America may easier to register large K even during daytime due to higher conductivity.  If the rareness of high AU and Kp during 09-15 UT has such solid reason, the May 2024 space weather event was actually very unusual. 

Finally, there is one more peculiar feature of the large dayside AU for the May 2024 event is that it is preceded only by normal substorm (AL ≈ -600 nT) and followed by a strong negative excursion in the Alaska-Pacific sector instead.  This is quite different from ordinary dayside positive dX that is normally preceded by substorm of large AL (which is the case for the 24 November 2001 event with AL < -1300 nT).

Acknowledgment: We used provisional AE, SuperMAG, INTERMAGNET and Kp.  We thank all contributing observatories and institutions for these datasets.  

How to cite: Yamauchi, M., Nanjo, S., Kotani, T., and Matzka, J.: Unusually large positive geomagnetic variation (AU) near noon on 11 May, 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12948, https://doi.org/10.5194/egusphere-egu25-12948, 2025.

After its arrival at Jupiter in July 2016, Juno conducted a global survey of Jupiter's magnetosphere with its highly eccentric polar orbit. Since then, the JADE instrument has accumulated a large amount of plasma measurements. Using a developed forward modeling method and a supercomputer cluster, we fit all ion measurements between 10 and 50 R_J from PJ5 to PJ56, obtaining a dataset with 70,487 good fits that consists of the following set of plasma parameters: abundances of different heavy ions, density, temperature, and 3‐D bulk flow velocity of heavy ions. This dataset has applications in the research on large-scale structures and small-scale dynamics in Jupiter’s magnetosphere, particularly the equatorial plasma disk region. Potential applications of this dataset include, but are not limited to, the following topics: 1) How is plasma distributed radially and vertically within the plasma disk? 2) What drives the local time asymmetry of plasma flow? 3) What are the consequences of centrifugal instabilities? 4) How is mass and energy transported in the magnetosphere? 4) How is force balance achieved and maintained? An overview of the dataset and some example applications will be presented in this talk.

How to cite: Wang, J., Bagenal, F., Wilson, R., Valek, P., Ebert, R., and Allegrini, F.: Ion Parameters Dataset from Juno/JADE Observations and Its Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14033, https://doi.org/10.5194/egusphere-egu25-14033, 2025.

Introduction: The Outer Planet Atmospheres Legacy (OPAL) program began in 2014 as part of the Hubble 2020 legacy initiative (Simon et al. 2015; DOI: 10.1088/0004-637X/812/1/55). These observations were meant to cement long-term legacy of the Hubble Space Telescope (HST) by ensuring a regular cadence of giant planet observations to fill temporal gaps between individual programs. The giant planets have highly dynamic atmospheres, so long-term trends tied to seasonal or other evolutionary cycles require regular data collected using the same instruments and filters.

In addition to building up a long data base of consistent observations on an annual cadence, serendipitous discoveries have been made along the way. Filters extend from the near-UV (F225W at 225 nm) to the near-IR (FQ889N at 889 nm), and each planet is imaged to cover all longitudes over a period of two planetary rotations. All raw data are immediately available to the public, and the team also hosts high level science products in the form of global maps at the MAST Archive (Simon 2015; DOI: 10.17909/T9G593).

OPAL at Jupiter: Hubble’s exquisite spatial resolution and OPAL’s global and temporal coverage allow detailed study of Jupiter’s long-lived vortices, high speed narrow wind jets, and alternating, variable, bands of colored clouds. OPAL results have included studies of vortices including the Great Red Spot (GRS), zonal wind speeds, small atmospheric waves, long-term color trends, and UV-dark ovals in the polar hoods.

Space missions: OPAL data have extended the science return of several space missions, with Jupiter observations commencing one year before Juno arrived at Jupiter. OPAL wind and cloud structure measurements have been used in diverse analyses of phenomena from the gravitational anomaly of the GRS, to deep zonal atmospheric structure revealed by microwave emission, to convective cycles in cyclonic vortices. Wave, jet, and vortex features previously observed by Voyager and Cassini have also been studied in greater detail with the long-term OPAL program.

Earth-based observatories: High-resolution visible-wavelength observations from OPAL target the planets near solar opposition to maximize spatial resolution, as do many Earth-based programs. Multi-observatory studies include correlations between cloud color from OPAL and microwave brightness from the VLA, comparisons between Doppler velocimetry from the ground and time-series imaging from OPAL, calibration, validation, and context for spectroscopic measurements, and deep context for stratospheric aerosol anomalies.

Conclusion: The results cited here are a small subset of the Jupiter results achieved with the OPAL monitoring of the outer planets, with additional discoveries at Saturn, Uranus, and Neptune. As of January 2025, 62 papers have cited OPAL data. With more than 10 years of data in hand, and continuing for the life of Hubble, we expect the scientific return to increase exponentially. OPAL serves as a model for future long-term programs at other observatories.

Acknowledgments: This research is based on HST observations (with NASA support; see Simon et al. 2015). GSO was additionally supported by NASA through contract 80NM0018D0004 to JPL.

How to cite: Wong, M. H., Simon, A. A., and Orton, G. S.: The Hubble OPAL Program: 10 years of time-variable phenomena on Jupiter and the other giant planets (invited), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14713, https://doi.org/10.5194/egusphere-egu25-14713, 2025.

During the active phase of solar cycle 25, the Parker Solar Probe (PSP) spacecraft frequently observes circularly polarized Type III radio storms. The most intense and longest duration event occurred following a large coronal mass ejection (CME) on 5 September 2022. For several days following the CME, PSP observed a storm of Type III radio bursts. The polarization of the storm started as left hand circularly polarized (LHC) and switched to right hand circularly polarized (RHC) at the crossing of the heliospheric current sheet.

We analyze properties of this Type III storm. The drift rate of the Type IIIs indicates a constant beam speed of ~0.1c, typical for Type III-producing electron beams. The sense of polarization is consistent with fundamental emission generated primarily in the o-mode.

In addition to this prototypical event, we present a survey of radio observations throughout the PSP mission, demonstrating that the majority of encounters contain Type III storms, that the storms are typically strongly (but not completely) circularly polarized, and that the sense of polarization and the sign of the radial magnetic field are consistent with o-mode emission.

How to cite: Pulupa, M., Bale, S., Jebaraj, I., Romeo, O., and Krucker, S.: Circularly Polarized Type III Storms Observed with PSP, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14886, https://doi.org/10.5194/egusphere-egu25-14886, 2025.

Modeling the formation conditions of the Galilean moons remains a significant challenge. While it is widely assumed that the moons formed within a circumplanetary disk (CPD) that surrounded Jupiter during the final stages of its growth, the physical properties and composition of this disk remain poorly constrained in theoretical models.

One approach to infer the properties and composition of the CPD is to use the bulk composition of the Galilean moons as a reference to extract compositional trends for the disk. A notable example is the gradient in water content with distance from Jupiter: from completely dry Io to a 1:1 water to rock ratio on Ganymede and Callisto. This gradient strongly suggests that the CPD exhibited a corresponding water abundance gradient during its formation.

With the JUICE and Europa Clipper missions currently cruising to the Jovian system, the coming decade will provide an unprecedented opportunity to study Europa, Ganymede, and Callisto. These missions are expected to refine our understanding of the bulk composition of the moons and provide new constraints for CPD models.

In this context, we aim to model the midplane volatile species composition of the CPD using a 2-dimensional proprietary framework. The model assumes a quasi-stationary disk heated by viscous stress, infalling gas, and the young, hot Jupiter. A key feature of the model is the presence of shadow regions that can be up to 100 K cooler than their surroundings and persist for up to 100 kyr.

Our results indicate that the profile of volatile species in the midplane shows enrichment peaks during the early evolution of the disk. However, maintaining these enrichments requires an accretion rate to the CPD of about 10^-7 M_jup/yr for at least 1 Myr. If the accretion rate decreases too rapidly, the ice abundances rapidly decrease.

In addition, we show that shadows within the CPD can significantly influence its volatile composition on short timescales of less than 100 kyr. These shadowed regions may trap ice of volatile species that would otherwise remain in the vapor phase, thereby altering the overall composition of the CPD.

How to cite: Schneeberger, A., Bennacer, Y., and Mousis, O.: Impact of self-shadowing on the Jovian Circumplanetary disk ice composition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15614, https://doi.org/10.5194/egusphere-egu25-15614, 2025.

Some problems of gravity assist and terraforming of Mars

Introduction

Here we consider versions of terraforming that would allow colonists to live without pressure suits. The current mass of the Martian atmosphere is 2.5x10¹⁶ kg [1]. We consider 4 variants of terraforming. C indicates how many times we need to increase the mass of the atmosphere. For version v1 we assume a pressure of 10 kPa at the bottom of Hellas Planitia, C= 8.6, for v2 we use 10 kPa at the reference level for Mars and C=16.4, for v3 we use 101.3 kPa at the bottom of Hellas Planitia, C= 87.3, and for v4 we use 101.3 kPa at the reference level for Mars, C= 166.1.

For variant v4, 1 body with a radius of ~100 km (and density of 1000 kg m^-3) would be sufficient.

Possible sources

Celestial bodies orbiting far from the Sun contain large amounts of water, CO₂, nitrogen, etc. There are two places where there are enough bodies useful to our problem: the Kuiper Belt (KB) and the Oort Cloud (OC) [2]. The Kuiper Belt (KB) contains over 70,000 objects with diameters larger than 100 km. The mass of the KB is large enough [2, 3]. The total mass of the OC is ~3×10²⁵ kg [4]. The problem is the large distance from the Sun, so we consider only the KB as the source.

Transporting bodies

Initially ion engines change orbit of the chosen body, in order to later use the effect of gravity assist. This requires precise maneuvering. Since there are many bodies in the KB whose size is sufficient for gravity assist, we assume that a change in velocity of ~50 m/s  (using the engine) is sufficient. However, in our case, gravity assist is fraught with significant danger. KB bodies are unstable when volatiles escape. To calculate possible tidal effects, we use the methods developed in [5].

The gravity assist may be used to reduce the relative velocity of Mars and the impactor. This is important because strong heating of the atmosphere will lead to the escape of gases [6].

[1] Mars Fact Sheet. NASA.

[2] Hargitai, H. and Kereszturi, A., 2015, ISBN 978-1-4614-3133-6.

[3] Lorenzo I. 2007. Monthly Notices RAS. 4 (375), 1311–1314.

[4] Weissman, P. R. 1983. Astronomy and Astrophysics. 118 (1): 90–94.

[5] Czechowski, L., 1991. Earth, Moon and Planets, 52, 2, 113-130 DOI: 10.1007/BF00054178

[6] Czechowski, L., et al., 2023. Icarus, doi.org/10.1016/j.icarus. 2023.115473.

How to cite: Czechowski, L.: Some problems of gravity assist and terraforming of Mars, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16329, https://doi.org/10.5194/egusphere-egu25-16329, 2025.

The formation of the ice giants Uranus and Neptune remains poorly understood, with several competing hypotheses attempting to explain their observed compositions. In particular, the carbon enrichment and nitrogen depletion observed in these planets challenge traditional models of planet formation. However, the measurement of the deuterium-to-hydrogen (D/H) ratio in Uranus by the Herschel Space Telescope provides a critical constraint on its bulk composition, including the CO/H2O ratio, providing valuable insights into the planet's formation and evolution.

D/H measurements in comets and planets are crucial for understanding their formation history. In the protosolar nebula, water ice is enriched in deuterium in the colder, outer regions and depleted in the warmer, inner regions relative to protosolar hydrogen. For example, D/H measurements from gas giants, which are predominantly composed of hydrogen, typically reflect or closely resemble the protosolar hydrogen D/H ratio. In contrast, D/H measurements from ice giants like Uranus and Neptune show supersolar D/H ratios in their atmospheres. The leading hypothesis to explain this is that their envelopes formed through the mixing of protosolar hydrogen with deuterium--rich primordial ices that they accreted during their formation. 

Under this assumption, the atmospheric D/H ratio of Uranus can be directly linked to the D/H ratio of its building block ices, depending on models of its internal structure. Assuming a cometary D/H ratio for the primordial ices accreted by Uranus enables the estimation of the planet's bulk composition, particularly its CO/H2O ratio. The objective of this study is to compare the inferred CO/H2O ratio of Uranus, derived from D/H remote sensing measurements, with values predicted for the protosolar nebula using a protoplanetary disk model. These findings provide critical constraints on the timing and location of Uranus's formation within the early Solar System and offer valuable insights into the processes that shaped its evolution.

How to cite: Benest Couzinou, T. and Mousis, O.: Constraints on Uranus formation from its D/H ratio, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16970, https://doi.org/10.5194/egusphere-egu25-16970, 2025.

The observing time of the cutting-edge radio interferometers tends to be heavily oversubscribed. This, coupled with the fact that solar activity is inherently unpredictable leads to limited observing time being granted for solar observations. There are, of course, dedicated solar monitoring radio telescopes, but their data quality, and hence the resulting science, pales in comparison with what is possible with the best-in-class instruments. A robust and reliable automated near-real time observing trigger for cutting-edge radio interferometers derived from dedicated solar monitoring telescopes can improve this situation dramatically. By enabling one to use precious observing time only when some solar activity is known to have just taken place, such a system can vastly increase the efficiency of limited available observing time to capture instances of solar activity. With observatories like the Square Kilometre Array Observatory (SKAO) on the horizon, the need for such a system is even more imperative. We present such a system developed by us for the SKAO-low precursor, the Murchison Widefield Array (MWA) based on near-real time data from the Yamagawa spectrograph which observes the Sun daily from rise to set in the band from 70 MHz to 9 GHz and is located at similar longitude as the MWA.  Generating an observing trigger poses an interesting and challenging problem. Not only does one have to reliably detect and reject any radio frequency interference (RFI) which is inevitably present, to be successful, a trigger needs to be raised as early after the start of the event as feasible. We have devised, implemented and tested algorithms to identify and remove the RFI and do an effective ‘de-noising’ of the data to improve the contrast with which features of interest can be detected. We note that much of the event data lost due to the latency from Yamagawa can be recovered using the data buffer available at the MWA, which was designed exactly to meet such needs. These triggers have been tested and tuned using the archival Yamagawa data, end-to-end tests of triggered observations have successfully been carried out at the MWA. Very recently this real time triggering has been operationalized at the MWA, a very timely development in view of the approaching solar maxima.

How to cite: Patra, D., Kansabanik, D., Oberoi, D., Kubo, Y., Williams, A., Meyers, B., and Nishizuka, N.: A Real-time Automated Triggering Framework for Solar Radio Burst Detection using Yamagawa Spectrograph for the Murchison Widefield Array, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18086, https://doi.org/10.5194/egusphere-egu25-18086, 2025.

With the rapid advancements in computer graphics, rendering technologies, and artificial intelligence, 3D visualization of deep-space environments has become a transformative approach to improving teleoperation systems. Traditional Lunar-to-Earth teleoperation faces challenges such as low bandwidth, high latency, and limited situational awareness, which hinder intuitive and efficient remote operations. To address these issues, we propose a novel framework that integrates AI-driven 3D reconstruction algorithms and cutting-edge rendering techniques to reconstruct and visualize deep-space environments with exceptional precision and clarity. By processing sparse telemetry data into high-fidelity 3D models and leveraging photorealistic rendering, our system enhances spatial awareness, reduces cognitive load, and improves decision-making efficiency for ground-based operators. Furthermore, the framework is designed to overcome deep-space constraints, such as limited computational resources and communication delays, ensuring its robustness in real-world missions. This approach not only advances the efficiency of telemetry and teleoperations but also bridges the gap between remote sensing data and actionable insights, paving the way for more autonomous, immersive, and scientifically impactful deep-space exploration.

How to cite: Li, Y., Yang, S., Lu, J., Chen, J., Xu, T., Xing, Z., Chen, L., and Zhang, Z.: Immersive 3D Visualization for Enhanced Lunar Teleoperation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18510, https://doi.org/10.5194/egusphere-egu25-18510, 2025.

The ESA-PROBA3 spacecraft was successfully launched aboard a four-stage PSLV-XL rocket from the Satish Dhawan Space Centre in Sriharikota, India, on Thursday, December 5th, at 11:34 CET (10:34 GMT, 16:04 local time).  Formation flying a pair of spacecraft will form an artificial solar eclipse in space, casting a precisely-controlled shadow from the Occulter platform to the  Coronograph spacecraft to open up sustained views of the Sun's faint surrounding corona. The payload on the ESA-PROBA3 Occulter spacecraft includes the Digital Absolute Radiometer (DARA) from the Physikalisch Meteorologisches Observatorium, Davos and World Radiation Center (PMOD/WRC). It aims at measuring the Total Solar Irradiance (TSI) in orbit. The destination of the spacecraft is a highly elliptical orbit (600 x 60530 km at around 59 degree inclination). We will present the initial results from this new experiment since its launch.

How to cite: Montillet, J.-P., Finsterle, W., Haberreiter, M., Schmutz, W., Pfiffner, D., Koller, S., and Gander, M.: Initial Results of Total Solar Irradiance Measurements by DARA-PROBA3, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18737, https://doi.org/10.5194/egusphere-egu25-18737, 2025.

Aromatic compounds, with their stable cyclic structure and [4n+2]π electrons, are resistant to chemical attack and degradation. This stability makes them prevalent in celestial bodies and valuable in designing polymers that withstand harsh space conditions [1-4].
In interstellar space, aromatic molecules make up ~20% of atomic carbon and are key to forming complex organic molecules [1]. Cyanopyrene, cyanonaphthalene, and indene have been identified in the TMC-1 molecular cloud [5]. Aromatic molecules are also found in Solar System objects, including Martian soil from Gale Crater mudstones [7-10].
Thiophene, an aromatic molecule, was detected by NASA’s Curiosity rover in the Glen Torridon clay unit, where high-temperature pyrolysis (~850°C) revealed sulfur-bearing organics, including alkyl derivatives, likely from Martian organic materials [9]. Atomic oxygen (O) in its ground state (³P) is a strong oxidant that degrades aromatic compounds like benzene and pyridine, releasing CO [10-13]. Recent models show O(³P) is present in small amounts on Mars’s surface and abundant in low orbit [13]. This presents a dual challenge: degrading thiophene-based polymers used in spacecraft and explaining Mars's organic scarcity [16].
Using quantum chemistry methods, we examined thiophene fragmentation from O(³P) interactions. Our results matched experimental data from the crossed molecular beam (CMB) scattering technique [10], showing that the reaction forms thioacrolein and CO, attacking the sulfur atom and breaking the aromatic ring. This ISC-enhanced mechanism may destabilize sulfur-containing polymers and contribute to organic compound loss on Mars.

Additionally, the photodissociation of O₃ on Mars generates highly reactive atomic oxygen in the excited ¹D state, which likely accelerates organic degradation [13]. While photodissociation degrades complex organics, residual organic matter remains unless converted to volatile species. These findings are pivotal for developing space-resilient materials and understanding atomic oxygen's role in Mars's chemical evolution. Furthermore, the degradation products, including released carbon, may contribute to forming prebiotic molecules, enriching the diversity of planetary systems and interstellar chemistry.

References
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[2] D.A.F.T.W. Strganac, et al., J. Spacecr. Rocket 1995, 32,502–506


[3] K.K. De Groh, et al., High Perform. Polym. 2008, 20, 388–409


[4] T. K. Minton, et al., ACS Appl. Mater. Interfaces 2012, 4, 492−502


[5] G. Wenzel, et al., Science, 2024, 386,810-813.


[6] M.A. Sephton, Nat. Prod. Rep., 2002,19, 292-311


[7] C. Sagan, et al., Astrophys. J., 414, 1, 399-405

[8] J. L. Eigenbrode, et al., Science, 2018, 360, 1096–1101


[9] M. Millan, et al., J. Geophys. Res. Planets, 2022, 127, e2021JE007107


[10] Vanuzzo G., et al., J.  Phys. Chem. A, 2021, 125, 8434–8453


[11] Recio P., et al., Nat. Chem., 2022, 14, 1405–1412


[12] J. Lasne, et al., Astrobiology, 2016, 16, 977


[13] G. M. Paternò, et al., Scientific Reports, 2017, 7, 41013


[14] S. A. Benner, et al., PNAS, 2000, 97, 6, 2425–2430


How to cite: Campisi, D., Parriani, M., Pannacci, G., Vanuzzo, G., Casavecchia, P., Rosi, M., and Balucani, N.: Reaction of Atomic Oxygen with Thiophene: Implications for Satellite Polymers in Low Mars Orbit and Chemistry of Mars, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20186, https://doi.org/10.5194/egusphere-egu25-20186, 2025.

The Sun is currently traversing the local interstellar medium at a relative velocity of approximately 26 km s⁻¹. Due to the Sun’s motion, interstellar dust grains from the interstellar medium are transported trough the heliosphere’s boundary, from the upwind direction.

Dust grains in a space environment are subject to a variety of charging mechanisms, which result in an overall equilibrium charge on their surface. In the interstellar medium and in the solar wind, the primary charging mechanisms are plasma collection, secondary electron emission, and photoelectric emission. The charge acquired by a dust grain depends on a number of factors, including the size, composition, and structure of the dust grain itself, as well as on the characteristics of the surrounding environment.

The magnetic field that the dust grains encounter when approaching the heliosphere, starts to change into the heliospheric magnetic field. Hence, the motion of individual grains near the heliospheric interface changes due to the influence of the Lorentz forces. The amount of trajectory deflection depends on the charge-to-mass ratio of a grain. Consequently, not all interstellar dust grains enter the solar system.

We discuss the dust charging with a particular focus on the influence of the space environment conditions that are expected at different locations throughout the heliosphere, including its boundary regions and including short-term and long-term variations of space environment conditions due to solar activity. These are necessary to calculate the dust trajectories in particular at the heliospheric interface. The results will help to explain the physical processes occurring at the boundary of the heliosphere.

How to cite: Arnet, T. and Sterken, V. J.: Charging and Dynamics of Interstellar Dust at the Heliospheric Interface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-923, https://doi.org/10.5194/egusphere-egu25-923, 2025.

The Parker Solar Probe mission has been revolutionizing our understanding of the Sun for nearly half a solar cycle, providing unprecedented insights into its dynamic atmosphere. Having completed 22 of its planned 24 orbits during the mission's prime science phase, the spacecraft continues to deliver data of unmatched quality, captivating both the global scientific community and the public. Parker Solar Probe has already yielded paradigm-shifting discoveries, cementing its status as one of the most successful heliophysics missions to date. With the spacecraft and its instruments performing exceptionally well, the mission's future beyond the prime science phase looks exceedingly promising. I will provide an overview the mission's remarkable achievements and explore its potential as we move into the declining phase of solar cycle 25 and beyond.

How to cite: Raouafi, N. E.: Parker Solar Probe: From Exploration to Paradigm-Shifting Discoveries, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1180, https://doi.org/10.5194/egusphere-egu25-1180, 2025.

In  standard  2D eruption models, the eruption of a magnetic flux rope is associated with magnetic reconnection occurring beneath it. However, in a 3D context, additional reconnection possibilities arise, particularly involving interactions between the flux rope and the overlying arcades. This process results in the drifting of the legs of the erupting flux rope.

We show examples of such magnetic reconnections between erupting filaments interacting with coronal arcades, called ar-rf (arcade + rope – rope + flare loop), using AIA/SDO and IRIS data.

To understand the physical processes behind observations, we perform data-inspired MHD numerical simulations, which reproduce such magnetic reconnection between flux rope and overlying magnetic fields. Our model clearly exhibits the slippage of flux-rope field lines and the remote heating and flare ribbons due to such external reconnection.

How to cite: Schmieder, B., Guo, J., Joshi, R., Dudik, J., and Poedts, S.: 3D Magnetic reconnection in solar eruptions: observations and MHD numerical simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1796, https://doi.org/10.5194/egusphere-egu25-1796, 2025.

The remote observations of braided solar coronal magnetic fields, together with in situ interplanetary measurements of (a) intermittent fluxes of energetic solar particles due to a large scale flaring magnetic field as well as (b) sustained small-scale magnetic fields reversals in the solar wind opens a new venue for interpretation of a wide range of heliospheric phenomena. The standard description of magnetic fields as a set of simple, (distorted) field lines is generalized to strongly structured topological features. Combining mathematical considerations, remote images and in situ satellite observations, we construct new characteristics of those topological magnetic structures, applying Braid and Knot Theory to physical configurations, deducing their topological invariants and constraining their evolution and stability, delineating the relaxation path to magnetized equilibria. The 3-dimensional interconnection between the mathematical braids and knots are applied to the topologically non-trivial magnetized structures from solar corona to the interplanetary medium. The analysis results in conjectures regarding (i) braids’ stability under oscillations and successive appearance and decay of magnetic loops, (ii) reconfiguration of braided structures into magnetic knotted configurations, (iii) their large-scale expansion into the solar wind resulting in the intermittent observation of the solar flare ions and (iv) emission of small-scale compound magnetic knots by solar wind resulting in switchback structures.  Future high-quality missions are expected to delineate in higher resolution the structure and evolution of all these topological forms together with the required constrains for their appearance.

How to cite: Roth, I.: Topological features of the heliospheric magnetic fields., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2064, https://doi.org/10.5194/egusphere-egu25-2064, 2025.

We report observations of time-intensity profiles,pitch-angle distributions, spectral forms, and maximum energies of <500 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with eleven separate crossings of the heliospheric current sheet (HCS) that occurred near perhelia during Parker Solar Probe (PSP) encounters E07-E21. We find that the ST ion observations fall into three categories, namely: 1) the E07 observations posed serious challenges for existing models of ST ion production in the inner heliosphere; 2) ST observations during 8 HCS crossings are consistent with a scenario in which the accelerated ions escape out of sunward-located reconnection exhausts; and 3) two HCS crossings (E14 & E20) when PSP traversed regions close to the reconnection exhaust and observed ST protons up to ~500 keV and >150 keV in energy. During the latter two crossings, PSP detected sunward-directed reconnection-generated plasma jets and sunward propagating energetic protons up to ~400 keV within the exhaust, thereby unambiguously establishing their origin from HCS-associated X-line located anti-sunward of PSP. We present detailed analysis of the evolution of the pitch-angle distributions and spectral properties during this crossing which have revealed, for the first time, important clues about the nature of ion acceleration via reconnection-driven mechanisms at the near-Sun HCS.

How to cite: Desai, M. and the Parker Solar Probe ISOIS, SWEAP, and FIELDS Science Teams: Ion Acceleration at the Near-Sun Heliospheric Current Sheet Crossings observed by Parker Solar Probe During Encounters 7-22, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2951, https://doi.org/10.5194/egusphere-egu25-2951, 2025.

Our heliosphere is surrounded by the Local Interstellar Medium. Their interactions lead to a range of observable phenomena such as energetic neutral atoms from the outer regions of the heliosphere and the influx of some interstellar neutrals into the inner solar system. Hydrogen is the dominant neutral species in the Local Interstellar Medium, but due to ionization and radiation pressure only a fraction of the interstellar neutral hydrogen atoms reach the inner solar system. Observing this signal therefore offers a reality check for our assumptions on the Local Interstellar Medium and on solar-activity dependent loss processes inside the heliosphere. So far, the IBEX-Lo instrument onboard the Interstellar Boundary Explorer in Earth orbit has been the only instrument to directly measure interstellar neutral hydrogen atoms.

This presentation shows the maps of 15 years of IBEX-Lo observations of the interstellar neutral hydrogen signal, covering more than one solar cycle and including two solar minima where the signal in IBEX-Lo is strongest. Despite the very intense interstellar neutral helium signal, the hydrogen signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. As expected, the retrieved interstellar neutral hydrogen signal is anti-correlated with solar activity. On the other hand, the discrepancy, known from earlier studies, between observed and predicted energy of the interstellar hydrogen atoms persists.

How to cite: Galli, A., Swaczyna, P., Bzowski, M., Kubiak, M. A., Kowalska-Leszczynska, I., Wurz, P., Rahmanifard, F., Schwadron, N. A., Möbius, E., Fuselier, S. A., Sokol, J. M., Gasser, J., Heerikhuisen, J., and McComas, D. J.: 15 years of interstellar neutral hydrogen observed with the Interstellar Boundary Explorer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3201, https://doi.org/10.5194/egusphere-egu25-3201, 2025.

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 that when the solar activity is low, the wind is fast and rare, with an equatorial band filled with a slower but denser outflow. During epochs of high activity, the band of slow wind expands to all latitudes. However, details of possible north/south 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 interplanetary scintillations (IPS) and hydrogen Lyman-α backscatter glow observations. Existing analyses of IPS and helioglow observations returned somewhat conflicting conclusions. Helioglow maps observed by SOHO/SWAN suggested that the solar wind flux temporarily features flux maxima at mid-latitudes. Analysis of IPS observations for equivalent times did not reveal such maxima in the solar wind speed.

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 provide a handy tool supporting retrieval of the solar wind structure from observations of either IPS or the helioglow.

GLObal solar Wind Structure (GLOWS) is a Lyman-α photometer onboard Interstellar Mapping and Acceleration Probe (IMAP), dedicated to helioglow observations aimed at retrieval of the solar wind structure. We present how GLOWS observations can be interpreted to resolve the helioglow/IPS solar wind structure dilemma 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.: How GLOWS will reveal the latitudinal structure of the solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3612, https://doi.org/10.5194/egusphere-egu25-3612, 2025.

Many proxies for assessing the eruptive activity of solar active regions (ARs) have been suggested, mostly based on measurements of the photospheric magnetic field. Here we test the usefulness of DC/RC (ratio of photospheric direct to return current) for assessing the ability of ARs to produce CMEs, and compare it with the amount of shear along the eruptive section of the polarity inversion line (PIL). We find that all source regions of eruptive flares have DC/RC > 1.63 and PIL shear > 45° (3.2 and 68° on average), tending to be larger for stronger events. Both quantities are on average smaller for source regions of confined flares (2.2 and 46°), albeit with substantial overlap. Many source regions, especially those of eruptive X-class flares, exhibit elongated direct currents (EDCs) bracketing the eruptive PIL segment, typically coinciding with areas of continuous PIL shear > 45°. However, a small subset of confined flares have DC/RC close to unity, very low PIL shear (< 38°), and no clear EDC signatures, rendering such regions less likely to produce a CME. A simple quantitative analysis reveals that DC/RC and PIL shear are almost equally good proxies for assessing CME-productivity, and comparable to other proxies suggested in the literature. We also demonstrate that an inadequate selection of the current-integration area typically yields a substantial underestimation of DC/RC.

How to cite: Torok, T., Liu, Y., Titov, V. S., Leake, J. E., Sun, X., and Jin, M.: Non-Neutralized Electric Currents and Eruptive Activity in Solar Active Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4170, https://doi.org/10.5194/egusphere-egu25-4170, 2025.

The IDEX instrument onboard the Interstellar Mapping and Acceleration Probe (IMAP) will detect and analyze interplanetary dust particles (IDPs) and interstellar dust (ISD) particles near 1 AU. The ISD particles originate from our Local Interstellar Cloud. These particles are a source of pickup ions within the heliosphere and are mass-filtered at the heliospheric boundary and thus their detection and analysis aids our understanding of the connection and interaction between the heliosphere and the Local Interstellar Cloud. In preparation for the IMAP mission, the dust accelerator operated at the University of Colorado is used to conduct an experimental campaign that will aid the interpretation of future measurements by IDEX.  More specifically, the laboratory version of IDEX is used to collect calibration data on dust samples of known size and chemical composition. Such data are required to characterize – and hence assign - impinging dust particles. Recently, comprehensive studies were undertaken to assess the impact ionization properties of (i) a model polycyclic aromatic hydrocarbon (anthracene) and (ii) various rocky minerals. Time-of-flight mass spectra obtained from individual microparticles were recorded over a wide impact velocity range (2 - 35 km s^-1) to evaluate the strong variation of the impact spectra with their kinetic energy. 

How to cite: Sternovsky, Z., Mikula, B., Armes, S. P., Ayari, E., Bouwman, J., Hillier, J., Horanyi, M., Kempf, S., Postberg, F., and Srama, R.: Measuring the composition of interstellar dust particles with the Interstellar Dust Experiment (IDEX) instrument, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4599, https://doi.org/10.5194/egusphere-egu25-4599, 2025.

Previous statistical studies revealed that the tangential component of the solar wind velocity is positive (co-rotating) in the vicinity of the Sun but it turns its sign at about 0.2 AU. After it, this negative value increases toward 0.3 AU and gradually relaxes to zero at distances in excess of 10 AU. Since the intervals of a large negative tangential velocity component exhibit also enhanced cross-helicity, outward propagating Alfven waves generated in the outer corona were suggested as the most probable source of the observed deviation. However, the weak point of this conclusion is that the waves would deviate the solar wind velocity in all directions with the same probability. For explanation of this caveat, we use all available data gathered by PSP and analyze factors that can affect the velocity direction like waves, stream interactions or magnetic reconnection. As a result, we suggest interchange reconnection of closed lines of coronal loops with the open lines from nearby coronal hole as a most probable driver of the observed velocity reversal.  However, this type of reconnection is expected at the source regions of the slow wind whereas the negative tangential velocity component was observed in the fast wind and we discuss a scenario that can explain this objection.   

How to cite: Nemecek, Z., Durovcova, T., and Safrankova, J.: Evolution of solar wind velocity direction in the inner heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4774, https://doi.org/10.5194/egusphere-egu25-4774, 2025.

Direct observations in the inner heliosphere have been limited due to the large gravitational potential differences, leaving many aspects of the physical processes governing the propagation of interplanetary coronal mass ejections (ICMEs) and solar energetic particles (SEPs) unresolved. Recent multi-point observations by spacecraft such as BepiColombo (Benkhoff et al., 2021; Murakami et al., 2020), Parker Solar probe (Fox et al., 2016) and Solar Orbiter (Müller et al., 2020) offer unique opportunities to explore the radial and longitudinal evolution of solar ejecta in unprecedented detail (e.g. Hadid et al., 2021; Mangano et al., 2021).

In this study, we utilized the Solar Particle Monitor (SPM) aboard BepiColombo/Mio, a non-scientific housekeeping radiation monitor for scientific observations. SPM’s ability to measure higher energetic particles makes it particularly effective for studying phenomena such as SEPs and galactic cosmic rays. We developed a novel inversion method based on response functions derived from Geant4 (Allison et al., 2016) radiation simulations, and reconstructed the primary energy and flux of incident particles from SPM data (Kinoshita et al., 2025, JGR).

This method was applied to an SEP event observed in March 2022, when BepiColombo and STEREO-A were aligned along the same Parker spiral magnetic field line. The energy spectra from BepiColombo/SPM, BERM (Pinto et al., 2022) and STEREO-A/HET (Von Rosenvinge et al., 2008) showed remarkable similarity, suggesting a common origin. Additionally, SPM detected a Forbush Decrease (FD) event following the SEP, marking the arrival of an ICME. This ICME also reached Earth, where FD signatures were recorded by ground neutron monitors. A comparison of FD profiles such as shapes and depth between BepiColombo and the Earth provided insights into the spatio-temporal evolution of the ICME as it propagated in the inner heliosphere.

Our findings contribute to a deeper understanding of SEP acceleration mechanisms and ICME dynamics in the inner heliosphere. Moreover, they demonstrate the potential of repurposing housekeeping instruments for scientific applications, paving the way for expanding solar observation networks with ongoing and future missions.

How to cite: Kinoshita, G., Ueno, H., Murakami, G., Pinto, M., Yoshioka, K., Miyoshi, Y., and Saito, Y.: Unveiling SEP Acceleration and ICME Evolution in the Inner Heliosphere using Housekeeping Radiation Data Acquired by BepiColombo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4776, https://doi.org/10.5194/egusphere-egu25-4776, 2025.

Understanding the mechanisms that generate information flow in dynamical systems is crucial for advancing causal inference and dependency characterization in natural and engineered systems. Information flow is defined as the exchange of predictive or uncertainty-reducing knowledge between variables in a coupled system, arising when fluctuations in one component influence the variability in another. This study establishes that information flow emerges as a direct result of trajectory divergence in phase-space, an effect encoded in the generalized dynamics of probability density functions. We show that when the divergence of flow fields in phase-space is non-zero, it induces temporal changes in the entropic structure of the system. This expands the traditional Liouville equation to non-conservative systems. This divergence creates, rather than merely propagates, informational dependencies among system components, highlighting the dynamic nature of mutual and multivariate information in such systems.

Our results reveal that in conservative systems, where phase-space volume is preserved, the system entropy remains invariant, and informational dependencies are determined solely by initial conditions. In contrast, dissipative systems—exemplified by the damped harmonic oscillator and the Lorenz system—exhibit significant entropic and informational evolution driven by non-zero divergence. The mathematical framework presented quantifies the role of divergence in shaping joint, marginal, and conditional entropy, as well as bivariate and higher-order mutual information. This approach provides a comprehensive understanding of how phase-space dynamics underpin the flow and transformation of information.

The findings have profound implications across multiple domains, including environmental science, climate dynamics, and engineered systems, where causal relationships often arise from interactions between variables in complex networks. By bridging physical principles with information theory, the work offers a new lens for exploring the dynamics of natural and artificial systems, with potential applications in predictive modeling, data assimilation, and the design of resilient systems under uncertainty.

This investigation not only addresses a longstanding question about the origin of information flow in coupled systems but also lays the groundwork for future studies incorporating time-lagged dependencies and higher-order interactions in both theoretical and applied contexts. The framework proposed herein enables a more refined analysis of information flow in complex systems, advancing our ability to interpret, predict, and engineer their behavior.

How to cite: Kumar, P.: Phase-Space Divergence as the Driver of Information Flow in Dynamical Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5249, https://doi.org/10.5194/egusphere-egu25-5249, 2025.

The existing fleet of spacecraft at 1 AU represents an important opportunity for multi-mission, multi-spacecraft direct investigations of heliospheric plasmas.

In this work, we focus on a strong interplanetary (IP) shock which crossed Wind, ACE, DSCOVR, THEMIS B and THEMIS C on 3 Nov 2021. Further, the shock was observed by well radially aligned Solar Orbiter at 0.8 AU. Such spacecraft configuration was used in a previous study to constrain the extent of the shock upstream populated by compressive structures (shocklets).

Here, we study the acceleration of protons up to 5 MeV energies and focus on the variability of energetic particle production. By cross-correlating energetic particle fluxes for the different vantage points, we find that the production of low energy (up to 100 keV) protons is strongly influenced by the local shock conditions, while high energy ones (up to 1 MeV) respond to the average shock conditions. At higher energies, we find that the energetic particle fluxes are modulated by large-scale structuring in the shock surroundings.

This study is relevant for IMAP, which will soon join such spacecraft fleet, and yield novel measurements of energetic particles at Lagrange point L1.

How to cite: Trotta, D., Horbury, T. S., and Giacalone, J.: Multi-spacecraft observations of particle acceleration in the near-Earth environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5514, https://doi.org/10.5194/egusphere-egu25-5514, 2025.

Small-scale solar wind structures, consistently impacting Earth, provide a fundamental energy transfer from the Sun to the Geospace. However, what we measure at L1 might not be consistent with structures arriving at Earth. We explore how well OMNI data resemble direct near-Earth measurements using THEMIS. We focus on variations in large-scale solar wind structures such as coronal mass ejections (CMEs) and stream interaction regions (SIR) with their distinct substructures. Our study is based on existing CME/SIR lists of events defined by Koller et al. [2022] in OMNI data. For the given time ranges, we compare the timing and appearance of the structures in the solar wind plasma and magnetic field parameters as probed by OMNI and THEMIS. We find that, on average, correlations between the structures measured at OMNI and THEMIS increase with the length of the measured structure. In addition, we find shifts between the structure measurements of a few minutes. Moreover, for CMEs that could form a sheath, we found an above-average coverage in the THEMIS measurements. By providing a more comprehensive understanding of solar wind dynamics and the relationships between their substructures measured at different locations, this research will significantly contribute to the field of space weather and heliospheric physics.

How to cite: Blüthner, G., Stadlober-Temmer, M., Koller, F., and Volwerk, M.: Solar wind structures – correlation between OMNI and THEMIS data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5604, https://doi.org/10.5194/egusphere-egu25-5604, 2025.

One of the commonly observed features of the solar wind is the simultaneous streaming of two different proton populations, one of which is the dominant denser core, and the other is the less dense and faster-propagating, minor population called the beam. The proton beam relative abundance is typically 10-20%, and the proton beam moves relative to the core along the interplanetary magnetic field at about 1.2 local Alfven speed. The origin and evolution of the proton beam is not yet fully understood.  A previous study based on data from the Helios mission suggests that the seed of the proton beam forms close to the Sun, leading to the observed correlation between the relative abundance of the proton beam and alpha particles. The Parker Solar Probe (PSP) mission, which has already achieved its closest approach to the Sun, gives us an opportunity to study the proton beam parameters near the solar wind source regions. We focus on the non-thermal features of the ion velocity distribution functions (VDFs) observed near the Sun by PSP. We investigate the mechanisms that change the proton beam parameters both in the initial phase of the solar wind expansion and on its way towards the Earth.

How to cite: Satyasmita, S., Durovcova, T., Nemecek, Z., and Safrankova, J.: Study of the Proton Beam Parameters near the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6362, https://doi.org/10.5194/egusphere-egu25-6362, 2025.

JUICE was launched in April 2023, and it is now in its cruise phase to Jupiter, where it is scheduled to arrive in July 2031. JUICE carries a radiation monitor, namely the RADiation hard Electron Monitor (RADEM) to measure protons, electrons, and ions, detecting particles coming from the anti-Sun direction. On 2024 May 13, a large solar energetic particle (SEP) event took place in association with an eruption close to the western limb of the Sun as seen from Earth. Providentially, at that time JUICE was very closely located to STEREO-A, namely the difference in location was 0.13 au in radial distance, 0.3° in latitude, and 1.6° in longitude.

We analysed the interplanetary context through which the particles propagated using the ENLIL model combined with in-situ plasma measurements. We studied the proton anisotropies measured by near-Earth spacecraft and STEREO-A and focused on an isotropic period during the decay phase of the SEP event to compute the proton energy spectrum. We fit the STEREO-A spectrum and compared it to that measured by JUICE to estimate energy-dependent intercalibration factors.

The proton spectral indices measured by JUICE and STEREO-A were similar. The proton fluxes measured at the effective energy channels of 6.8 MeV, 22.2 MeV, and 31.6 MeV by the radiation monitor onboard JUICE agree within 15% with the STEREO-A measurements. The differences were slightly higher for the 14.0 MeV channel, which agrees within 30%.

How to cite: Rodríguez-García, L., Palmerio, E., Pinto, M., Dresing, N., Cohen, C., Gómez-Herrero, R., Gieseler, J., Santos, F., Espinosa Lara, F., Cernuda, I., Witasse, O., and Altobelli, N.: Comparing observations of the closely located JUICE and STEREO-A spacecraft during the widespread solar energetic particle event of 2024 May 13, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6498, https://doi.org/10.5194/egusphere-egu25-6498, 2025.

In a weakly magnetized and randomly inhomogeneous solar wind plasma where upper-hybrid wave turbulence is generated, electromagnetic radiation at plasma frequency is modeled theoretically and numerically. Owing to three independent approaches which lead to the same results (Particle-In-Cell simulations, theoretical and numerical modeling, as well as analytical calculations performed in the framework of weak turbulence theory extended to randomly inhomogeneous plasmas), electromagnetic emissions in the O-, X- and Z-modes, as well as their corresponding radiation rates, are calculated as a function of the ratio of the cyclotron to the plasma frequency ω_c/ω_p and the average level of random density fluctuations ΔN. These emissions are due to electrostatic waves transformations and mode conversion on random density fluctuations. In this view, the condition for appearance or absence of some modes, are discussed for the case of type III solar radio bursts.

How to cite: Krafft, C., Volokitin, A., Polanco-Rodriguez, F. J., and Savoini, P.: Electromagnetic wave radiation in turbulent magnetized and inhomogeneous plasmas : theory and simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6681, https://doi.org/10.5194/egusphere-egu25-6681, 2025.

Nonlinear wave interactions as well as wave transformation processes on random plasma density inhomogeneities are thought to play a central role in electromagnetic wave radiation during type III solar radio bursts, in particular by generating radio waves at both the plasma frequency ω_p and its harmonic 2ω_p. Large-scale and long-term 2D Particle-In-Cell (PIC) simulations involving an electron beam generating upper-hybrid wave turbulence have been shown (e.g. Krafft et al. 2024 ApJL 967 L20) to be an efficient tool to study mechanisms as electrostatic decay, electromagnetic decay, wave coalescence, or conversion of modes at constant frequency.  Here a local and a global approach are combined to evidence such mechanisms in weakly magnetized solar wind plasmas, and to study their properties as a function of plasma parameters as the cyclotron frequency ω_c, the average level of random density fluctuations ΔN, and the ion-to-electron temperature ratio T_i/T_e.

How to cite: Polanco-Rodriguez, F. J., Krafft, C., and Savoini, P.: Wave processes during type III solar radio burts : 2D PIC simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6736, https://doi.org/10.5194/egusphere-egu25-6736, 2025.

Coronal magnetic field models have to rely on extrapolation methods using photospheric magnetograms as boundary conditions. In recent years, due to the increased resolution of observations and the need to resolve non-force free lower regions of the solar atmosphere, there have been increased efforts to use magnetohydrostatic (MHS) field models instead of force-free extrapolation methods. Although numerical methods to calculate MHS solutions can deal with non-linear problems and hence provide more accurate models, analytical three-dimensional MHS equilibria can also be used as a numerically relatively “cheap” complementary method.

We discuss an extrapolation method based on a family of analytical MHS equilibria that allows for a transition from a non-force-free region to a force-free region. The solution involves hypergeometric functions and while routines for the calculation of these are available, this can affect both the speed and the accuracy of the calculations. We have looked into the asymptotic behaviour of this solution to approximate it by exponential functions which improves the numerical efficiency. We present results with boundary conditions based on artificial magnetograms to test the method, and also the application of the model to observational data.

How to cite: Nadol, L. and Neukirch, T.: Three-Dimensional Solar Magnetic Field Extrapolation Using Analytical Magnetohydrostatic Equilibrium Solutions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6910, https://doi.org/10.5194/egusphere-egu25-6910, 2025.

Observational analyses of the evolution and dynamics of coronal mass ejection (CME) case study events tend to employ a holistic approach that takes advantage of multi-point and multi-regime measurements. Ideally, well-observed CMEs can be followed from their eruption off the solar disc via multi-wavelength remote-sensing data, through their coronal and heliospheric evolution via white-light imagery, and up to their arrival at a spacecraft of interest via in-situ measurements at one or more locations. In practice, events that can be tracked consistently through multiple regimes and from multiple viewpoints are understandably rare, and most CME detections are characterised by some “missing pieces in the puzzle” and/or limited observational perspectives. In this presentation, we shall focus on an event that was imaged remarkably well in white light (by both coronagraphs and heliospheric imagers) but had its source region and eruption dynamics completely hidden from view.

On March 13, 2023 an exceptionally fast and energetic CME was released from the solar far side as seen from Earth. Alas, the two other spacecraft equipped with disc cameras—STEREO-A and Solar Orbiter—were also imaging mostly the Earth-facing Sun, leaving a critical observational gap into the source, topology, and onset of the eruption. On the other hand, the coronal and heliospheric evolution of the CME were well observed from these three viewpoints as well as by Parker Solar Probe, which was located closer in longitude to the eruption’s source region. We present a synthesis of available (off-limb) EUV and white-light remote-sensing observations that aims to infer the complex eruption and early evolution of the event as well as to contextualise in-situ measurements at Parker Solar Probe, which was impacted by the CME at a heliocentric distance of ~0.25 au. Finally, we highlight the importance of observing the far side of the Sun, which, among other advantages, can fill a crucial observational gap required for multi-viewpoint measurements of every CME.

How to cite: Palmerio, E., Hess, P., Bothmer, V., Jebaraj, I., Dresing, N., and Wijsen, N.: When Most of the Action is Hidden from View: A Synthesis of Observations of the Fast March 13, 2023 CME, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7400, https://doi.org/10.5194/egusphere-egu25-7400, 2025.

Type III solar radio emissions are intense wave phenomena originating from eruptive events in the solar corona. These emissions are produced by energetic electron beams traveling outward from the Sun along the magnetic Parker spiral. As these beams propagate, they generate intense electrostatic Langmuir waves, which are subsequently converted into freely propagating radio waves. These radio waves, characterized by their distinct dispersed signatures in the time-frequency domain, can be detected throughout the solar system.

However, their propagation is not straightforward. Local density variations in the solar wind plasma cause refraction and, in some cases, reflection of the waves. Such density variations between the source and the observer can obscure low frequency part of the emissions, limiting their propagation to frequencies above the local L-O cutoff frequency. Multi-point observations reveal that the spatial and temporal coincidence of type III emission sources and solar wind density structures modifies the lower-frequency boundary of the detected emissions.

Additionally, some emissions display stripe-like patterns, which are also attributed to local plasma density variations at their source. The fine structures of these low-frequency (<100 kHz) emissions can be resolved with the very high time-frequency resolution of the Radio and Plasma Wave (RPW) instrument onboard the Solar Orbiter. These observations provide valuable insights into the interaction between solar radio emissions and the solar wind plasma environment.

How to cite: Pisa, D., Souček, J., Santolík, O., Formánek, T., Taubenschuss, U., Maksimovic, M., Khotyaintsev, Y., and Boldu, J.: Fine structures of solar type III radio bursts observed in the inner heliosphere by Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8710, https://doi.org/10.5194/egusphere-egu25-8710, 2025.

Type III solar radio emissions originate from a mode conversion of electrostatic Langmuir waves generated by an energetic electron beam. This electron beam creates a bump-on-tail instability in the electron velocity distribution function, generating Langmuir waves as the electrons propagate along the magnetic field lines in the solar wind. The Solar Orbiter spacecraft enables us to study Type III radio emissions and the Langmuir waves locally generated in the solar wind with a very high temporal resolution. Using electron velocity distribution measurements obtained by the Solar Wind Analyser (SWA) and Energetic Particle Detector (EPD) instruments, we model the plasma environment and numerically solve the dispersion relation. After deriving the dispersion relation for the generalized Langmuir/Z-mode, we successfully match the waveform data observed by the Radio and Plasma Waves (RPW) instrument with the theoretical prediction. Furthermore, we analyse the wave polarization properties, including a coherent high frequency magnetic component. Combining the solution of the dispersion relation and observations, we constrain the wave vector and provide valuable insights into the wave polarisation properties.

How to cite: Formanek, T., Santolik, O., Soucek, J., Pisa, D., Zaslavsky, A., Maksimovic, M., Kretzschmar, M., Owen, C., and Rodriguez-Pacheco, J.: Polarisation Analysis of in-situ observations of Langmuir/Z-Mode Waves by Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8896, https://doi.org/10.5194/egusphere-egu25-8896, 2025.

The rapid rotation of sunspots is considered as one possible mechanism for triggering solar eruptions. The sunspot rotation may also contribute to the accumulation of magnetic helicity in solar active regions. Studying the sunspot rotation and the underlying mechanisms behind this motion is crucial for enhancing our understanding of solar eruptions. We aim to investigate the relationships between rotational sunspots and solar eruptions, including solar flares and coronal mass ejections (CMEs), in a larger sample. In this study, we have examined the full-disk HMI vector magnetograms with temporal resolution of one day from 2011 to 2019 and found 163 active regions that exhibit a near-bipolar configuration with single or pair of sunspots. To determine the sunspot rotation, we first employed the Differential Affine Velocity Estimator for vector magnetograms (DAVE4VM) to the HMI vector magnetogram to calculate the photospheric velocity field. We then applied the Automated Swirl Detection Algorithms (ASDA;Liu et al. 2019) to the velocity field to verify the presence of sunspot rotation. All 163 active regions were analyzed for five-days evolution to detect rotational sunspots. Some previous studies have doubted whether sunspot rotation represents an actual motion. Therefore, in this study, we only focus on the long-time rotation lasting for at least 10 hours. The results indicate that only 38 active regions are associated with rotational sunspots. We subsequently estimated the duration of rotation and the average rotational velocity for each sunspot. The rotational durations range from 16 hours to 100 hours and the average rotational velocities range from 1.00 to 4.73 deg per hour. Interestingly, not all rotational sunspots are associated with CMEs. About 16 active regions with rotational sunspots produced eruptive flares. The average rotation duration of sunspots with CMEs is approximately 10 hours longer than the sunspot without CMEs, while the average rotational velocities remain similar. 

How to cite: Wang, W., Liu, R., Liu, J., and Wang, Y.: A statistical study of rotational sunspots in solar cycle 24: Comparing with solar flares and CMEs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9297, https://doi.org/10.5194/egusphere-egu25-9297, 2025.

Energetic particles in the heliosphere are produced by flaring processes on the Sun or shocks driven by coronal mass ejections. These particles can be detected remotely through the electromagnetic radiation they generate (X-rays or radio emission) or in situ by spacecraft monitoring the Sun and the heliosphere. Here, we investigate the acceleration location, escape, and propagation directions of electron beams producing radio bursts observed with the Low Frequency Array (LOFAR), Parker Solar Probe (PSP) and Solar Orbiter (SolO) and compare it to hard X-ray (HXR) emission and in situ electrons observed at SolO. These observations are combined with a three-dimensional (3D) representation of the electron acceleration locations and results from a magneto-hydrodynamic (MHD) model of the solar corona in order to determine the connectivity to Solar Orbiter and relate the electrons observed remotely to in situ electrons. We observed a long-duration metric-decametric type II radio burst with good connectivity to Solar Orbiter, which also observed a significant in situ electron event. The injections times of the in situ electrons are simultaneous with the onset of the type II radio burst. The properties of the SolO electrons also indicate that shock acceleration is likely the main contributor to the observed fluxes, with a possible smaller contribution coming from the flare, given the presence of HXRs and type III radio bursts.

How to cite: Morosan, D., Dresing, N., Palmroos, C., Gieseler, J., Jebaraj, I., Pomoel, J., and Zucca, P.: Determining the possible acceleration regions of in situ electrons using space- and ground-based radio observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9971, https://doi.org/10.5194/egusphere-egu25-9971, 2025.

Analyzing multi-instrument, multi-mission in-situ space physics data presents significant challenges, hindering scientific progress. The SCIentific Qt application for Learning from Observations of Plasmas (SciQLop) addresses these challenges by providing a comprehensive tool suite  for simplified data discovery, retrieval, visualization, and analysis. SciQLop facilitates access to data from remote servers like CDAWeb and AMDA via tools like Speasy. Crucially, SciQLop integrates with event catalogs through TSCat and its associated GUI, allowing users to define and search for specific events and then seamlessly access the corresponding data across multiple instruments and missions. This poster demonstrates how SciQLop facilitates massive in-situ data analysis and event-based studies, empowering researchers to focus on scientific interpretation and accelerate discovery in space physics.

How to cite: Jeandet, A., Renard, B., Aunai, N., Ghisalberti, A., Génot, V., André, N., and Bouchemit, M.: SciQLop: A Tool Suite for Multi-Mission High-Resolution In-Situ Data Analysis in the Heliophysics Community, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10101, https://doi.org/10.5194/egusphere-egu25-10101, 2025.

The solar wind is permeated by Alfvénic fluctuations across a broad range of scales, with fluctuations that have an anti-sunward sense of propagation typically dominating.  Recent studies have shown that cross helicity, which can be used to measure the difference between the sunward and anti-sunward fluctuation power, is more balanced inside interplanetary coronal mass ejections (ICMEs) than in the solar wind generally.  A possible cause of balanced cross helicity in ICMEs is their closed magnetic field structure, with a closed loop connected at both ends to the Sun being able to support a more balanced population of Alfvénic fluctuations.  To test this hypothesis, we have performed a statistical study that compares cross helicity with electron strahl signatures for a large number of ICMEs at 1 au.  Bidirectional electrons are a well-established signature of closed magnetic field structures in ICMEs.  A moderate correlation between bidirectional electrons and balanced cross helicity has been identified, supporting the closed-field hypothesis as an origin of the balanced cross helicity found in ICMEs.

How to cite: Good, S., Franc, A., Pal, S., and Kilpua, E.: Cross helicity and electron strahl signatures in interplanetary coronal mass ejections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10642, https://doi.org/10.5194/egusphere-egu25-10642, 2025.

Solar type III radio bursts are common radio emissions generated by energetic electron beams traveling through the solar corona. These serve as important remote sensing tools for studying plasma and electron beams in the solar wind. In this work, we aim to combine observations from both the Parker Solar Probe (PSP) and Solar Orbiter (SolO) spacecrafts in order to study solar type III radio bursts from different point of view and distances. In particular, we investigate observed differences in the fine structures, such as striae, as well as in the radio spectrum fluctuations to gain a deeper understanding of the physical mechanisms influencing the propagation of electrons beams.

How to cite: Thepthong, P., Kretzschmar, M., Maksimovic, M., and Pesini, A.: Joint Analysis of Solar Type III Radio bursts with Parker Solar Probe and Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10692, https://doi.org/10.5194/egusphere-egu25-10692, 2025.

Magnetic ejecta (ME) characterized by large-scale smoothly-rotating magnetic field lines inside interplanetary coronal mass ejections (ICMEs) may erode while interacting with the surrounding ambient solar wind plasma in the heliosphere. Erosion may occur while ICME-surrounding solar wind structures are in favorable conditions leading to magnetic reconnection with MEs. Erosion may peel off the outer layers of ME eventually leading to changes in their structures and magnetic properties. In this study, we analyze the erosion of three ICME events observed by very rare radial alignments of multiple spacecraft, where the spacecraft were within 3.5 degrees of angular separations. The three events were observed by pairs of spacecraft: (1) Parker Solar Probe (0.53 au) and Wind (0.997 au) on September 2023, (2) Solar Orbiter (0.85 au) and Wind (0.98 au) on November 2021, and (3) STEREO-A (0.95 au) and Wind (1.005 au) on August 2023. Analyzing the radial evolution of the magnetic, ion and supra-thermal electron properties and Alfvenicity inside the MEs, and reconnection exhausts at their boundaries, we assess the impact of erosion on the structures of ME and their geo-effectiveness. Thus, taking the opportunity of such rare spacecraft alignments, we comment on how erosion may impact ICME radial evolution and may lead space weather prediction operations to be more challenging in the heliosphere.

How to cite: Pal, S., Good, S., Jian, L., Nieves-Chinchilla, T., and Nicolaou, G.: Radial Evolution of Interplanetary Coronal Mass Ejections and Change of Their Geo-effectiveness Due to Erosion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11303, https://doi.org/10.5194/egusphere-egu25-11303, 2025.

In this presentation we update the community on the current status of the Interstellar Mapping and Acceleration Probe (IMAP), the latest mission in the Solar Terrestrial Probes (STP) program of NASA’s Science Mission Directorate Heliophysics Division, which is slated to launch in September of 2025. With ten instruments, IMAP provides the complete set of observations to investigate two intimately coupled and vitally important research areas of Heliophysics: 1) the acceleration of energetic particles expelled from the Sun and 2) the interaction of the solar wind and energetic particles with the local interstellar medium. IMAP simultaneously examines particle injection and acceleration processes at 1 AU, while remotely imaging the global heliospheric interaction and its response to particle populations generated earlier through the aforementioned acceleration processes. That remote imaging is possible via the detection of Energetic Neutral Atoms (ENAs) that are being emitted when the charged particles expelled from the sun, and after they have been accelerated, interact with interstellar neutrals when they reach the heliospheric boundary. In addition to in-situ acceleration and remote ENA observations, IMAP instruments directly sample both interstellar neutral atoms and interstellar dust drifting into the heliosphere; interstellar pickup ions; solar wind ions, electrons, and magnetic field; and the Sun’s three-dimensional hydrogen “helioglow.” In addition to periodically downlinking the full science data, a subset of real time space weather data is continuously broadcast back to Earth from L1. For more information about IMAP and the great contributions from all of our 25 institutions, see https://imap.princeton.edu/. Please also Follow, Like, and Share us on Facebook.com/IMAPMission and Instagram@IMAPSpaceMission.

How to cite: Gkioulidou, M., McComas, D., Schwadron, N., and Christian, E.: IMAP Mission in the Runup to Launch , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12678, https://doi.org/10.5194/egusphere-egu25-12678, 2025.

The self-consistent generation of type III radio emissions and their morphological features has been an open problem since the 1950s. Using data from the Parker Solar Probe, namely the radio frequency spectrometer (RFS) to analyze type III fine structures (striae) and link them to the statistical properties of density fluctuations from 13 to 60 solar radii obtained using the floating potential technique. We find that the average level of density fluctuations decreases with distance from the Sun, while the intermittency is high at the characteristic scales of the striae. Our findings demonstrate that the probabilistic model of beam-plasma interaction describes, step by step, the self-consistent generation of type III radio bursts, from the excitation of Langmuir waves to electromagnetic wave emission.

How to cite: Jebaraj, I. C., Voshchepynets, A., Krasnoselskikh, V., De Wit, T. D., Sioulas, N., Larosa, A., Colomban, L., Agapitov, O., Chen, C., Hlebena, M., Balikhin, M., and Bale, S.: Evolution of Randomly Inhomogeneous and Intermittent Plasma: Effects on Langmuir Wave Generation and Type III Radio Emission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13125, https://doi.org/10.5194/egusphere-egu25-13125, 2025.

The Parker Solar Probe (PSP), launched in 2018, has already accumulated seven years of observations with the Wide-Field Imager for Solar Probe (WISPR), offering numerous opportunities to study different coronal structures in visible light, such as streamers, dynamic outflows of blobs, and expanding coronal mass ejections (CMEs). Their brightness profiles are of interest because they depend on the position of these coronal structures with respect to the Thomson Sphere (TS), defined as the sphere with a radius equal to the distance between the Sun and the observer (i.e., PSP). The same feature moving in the observer's line of sight will appear brighter when it is in the vicinity of the TS because it is closer to the Sun, hence its density and brightness are higher. A study by Nisticò et al. (2020) demonstrated how the brightness profiles of ray tracing simulated blobs in WISPR change depending on their position relative to the TS and their speed. We apply the same theoretical approach to simulated and actual observations of coronal streamers in WISPR. Their brightness variations help us to infer the dynamics, scattering angle, velocity, extension, and electron density of these structures. To validate our results, we use multiple approaches, including MHD modeling and triangulation techniques to determine the location and dynamics of coronal structures.

How to cite: Cappello, G., Temmer, M., Linton, M., Nisticò, G., Palmerio, E., Lienhart, A., Howard, R., Stenborg, G., Voulidas, A., Bothmer, V., and Liewer, P.: Investigating the Brightness of Coronal Rays with the Parker Solar Probe/WISPR Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13180, https://doi.org/10.5194/egusphere-egu25-13180, 2025.

In preparation for the PUNCH mission which is planned to be launched in 2025, we construct synthetic white light (WL) images of the inner heliosphere based on GAMERA 3D MHD output. GAMERA is a 3D MHD code whose capabilities have been extended to perform time-dependent solar wind simulations by frequently updating the input magnetograms and thus the boundary conditions at the inner boundary of the code, offering a much more realistic reconstruction of the solar wind propagation and evolution. By employing this capability, we explain the phenomena and structures of the solar wind we see in the synthetic WL images from multiple view points (ACE, STEREO, PUNCH) and compare with the traditional steady state MHD approach.

How to cite: Samara, E., Malanushenko, A., Provornikova, E., Arge, C. N., and Merkin, V.: The importance of time-dependent MHD solar wind simulations in the frame of the PUNCH mission , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13918, https://doi.org/10.5194/egusphere-egu25-13918, 2025.

Last December the Parker Solar Probe attained the lowest perihelion distance of 9.8 solar radii for the mission.  The Integrated Science Investigation of the Sun (ISʘIS), and the other instruments onboard, reported healthy status after the encounter and will transmit the collected data in February and March.  ISʘIS measures energetic ions from ~20 keV to >100 MeV/nucand electrons from ~30 keV to 6 MeV and has provided unprecedented observations of solar energetic particle (SEP) events close to the Sun.  Here we review the latest data and present some of the more striking results that have been obtained as solar cycle 25 approaches its maximum.

How to cite: Cohen, C.: Recent Results from the Integrated Science Investigation of the Sun on Parker Solar Probe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14351, https://doi.org/10.5194/egusphere-egu25-14351, 2025.

The Dynamic Eclipse Broadcast (DEB) Initiative is a network of volunteer citizen science telescope-observing teams that was initiated to observe the Annular Solar Eclipse of October 2023 and the Total Solar Eclipse of April 2024.  82 teams composed of amateur astronomers, university students, high school students, and astronomy enthusiasts were formed across North America.  Teams participated in training events and practice sessions to be ready for the 2023 and 2024 solar eclipses.  Weather permitting, each team collected a series of science and calibration images before, during, and after the eclipses with identical portable solar telescopes. The data collected by those teams during the 2024 Total Solar Eclipse is being processed to observe changes in the inner solar corona that occurred during the time that the Moon’s shadow moved across North America.

The project is now moving into a new phase, with teams using their equipment to observe and record white light high energy X-class solar flares. The high levels of activity on the Sun during solar maximum and the large geographic area covered by this telescope network have allowed the team to collect sub-second cadence data on four X-flares to date with preliminary analysis showing a white light flare signature in the highest energy X4.5 flare.

The DEB Initiative plans to continue its work, broadening its network across the planet by recruiting teams from around the world.  Continued efforts are planned to observe solar flares as well as to collect another series of white light coronal images during the August 2, 2027, Total Solar Eclipse which will sweep across North Africa.

How to cite: Brevik, C., Baer, R., Penn, M., Mandrell, C., Henson, H., and Simões, P.: The Dynamic Eclipse Broadcast (DEB) Initiative:  A network of volunteer citizen scientists observing the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14720, https://doi.org/10.5194/egusphere-egu25-14720, 2025.

Parker Solar Probe (Parker) is capable of making observations of type III radio bursts in their generation region. PSP recorded a type III radio burst with frequency decay down to the local Langmuir frequency and simultaneously slow electrostatic plasma waves near the Langmuir frequency, which often harmonics. From the electric field fluctuations, the k-value of the Langmuir wave is estimated to be 0.14 and kλd = 0.4 and the phase velocity of the Langmuir wave was <10000km/s. The oscillations on the main frequency and the first harmonics were also detected in magnetic field perturbations. We demonstrated the presence of the second rapid Langmuir wave seen in the observations as the addition of two waves, one of which has small frequency variations that arise because the wave travels through density irregularities. This wave-wave interaction guided by a dense electron beam in the presence plasma density irregularities leads to the generation of the electromagnetic waves observed as type III radio burst

How to cite: Agapitov, O., Mozer, F., Sauer, K., and Voshchepinets, A.: Generation of the Type III Radio Bursts: Comparison of the Model Results and Parker Solar Probe Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15565, https://doi.org/10.5194/egusphere-egu25-15565, 2025.

The heliospheric current sheet (HCS) is observed as a sector boundary in the ecliptic plane, and its orientation and structure have been intensely studied. It divides the heliosphere into regions with opposite magnetic polarities. Analysis of its local structure at 1 AU let to study the HCS as a magnetic directional discontinuity supported by a current sheet (CS).

HYTARO+ is an analytical model development to evaluate the influence of the solar magnetic dipole in the topology of the local structure of the HCS. Using multipole expansion, HYTARO+ analyzes the contribution of the dipolar and quadrupolar magnetic field in the HCS. HYTARO+ deepens the study of the background magnetic field present in the analyzed current sheet crossings.

A preliminary analysis, evaluating the influence of the solar magnetic dipole in the topology of the local structure of the HCS, is summarized. The data provided by the Parker Solar Probe (PSP) and Solar Orbiter (SolO) instrumentation have allowed us to advance in the analysis of the multipole components of the IMF by performing location-dependent studies.

How to cite: Arrazola Pérez, D., Blanco Ávalos, J. J., Hidalgo Moreno, M. Á., and Jiménez, J. J.: Influence of the solar magnetic dipole in the topology of the local structure of the HCS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16148, https://doi.org/10.5194/egusphere-egu25-16148, 2025.

Large-scale coronal waves, also called EIT waves (named after the Extreme Ultraviolet Imaging Telescope on the SOHO satellite they were first observed with), or extreme ultra violet (EUV) waves are fast magnetosonic magnetohydrodynamic waves caused by the fast lateral expansion of coronal mass ejections (CMEs).  They may detach from their driver and are observed as bright fronts crossing large areas of the solar disk. As their initial speed can exceed the local magnetosonic speed, they can develop into large-amplitude waves or even shock fronts, which may be responsible for accelerating solar energetic particle (SEPs).

The EU Horizon project SOLER investigates energetic solar eruptions starting from three perspectives: fast CMEs, strong flares, and large SEP events to improve our understanding on how the eruptive phenomena are linked, how they interact with each other, and how they result in acceleration of high energy particles and their release from the solar corona into interplanetary space.  In this study we present a tool for the analysis of large-scale coronal waves, and demonstrate its outcomes for several events during the May 2024 high activity period.

The Python tool automatically derives the speed and the amplitude evolution of the waves based on perturbation profiles. In order to analyze the imprints of large-scale coronal waves on the lower atmosphere layers, we need to extract the distance of the wave front from its origin for each time step. To do so, the solar full-disk image is split it equidistant circles on the spherical surface around the center of the wave. As estimate of the wave center, we use the position of the associated flare following previous studies. Since large-scale coronal waves usually reveal a non-isotropic propagation, these rings are split up further along the azimuthal direction into different sectors. The analysis is performed on base ratio images (where each image is divided by the same pre-event image), and for each segment the mean intensity value of the pixels is calculated. The segments along each considered propagation direction are combined into intensity profiles along great circles which originate at the flare position, so-called perturbation profiles. A peak finding algorithm marks the peaks and fronts of these perturbation profiles for the wave tracing algorithm. The wave tracing algorithm checks for continuously moving peaks, and applies linear fits to the obtained time-distance profiles to derive the wave speed.

We present the results for multiple waves that were associated with eruptive X- class flares that occurred between the 9^th of May and the 15^th of May 2024, observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory. The average wave propagation speeds obtained are in the range from 300 – 800 km/s, with the peaks of the perturbation amplitudes up to 1.4 in the AIA 211 Å filter.

This project has received funding from the European Union's Horizon Europe research and innovation program under grant agreement No 101134999. As part of the grant agreement the tool will be made public.

How to cite: Baumgartner-Steinleitner, M., Veronig, A., and Dissauer, K.: Demonstration of a new python tool for semiautomatic tracing of large-scale coronal waves on the events between May 9th and May 15th 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17300, https://doi.org/10.5194/egusphere-egu25-17300, 2025.

The physical role played by small-scale activity that occurs before the sudden onset of solar energetic events (SEEs, i.e., solar flares and coronal mass ejections) remains in question, in particular as related to SEE initiation and early evolution.  It is still unclear whether such precursor activity, often interpreted as plasma heating, particle acceleration, or early filament activation, is indicative of a pre-event phase or simply on-going background activity.

In this contribution we investigate the uniqueness and causal connection between precursors and SEEs using paired activity-quiet epochs. We focus on transient brightenings (TBs) and present analysis regimes to study their role as precursors, including imaging of the solar atmosphere, magnetic field, and topology analysis using archive data from the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory. Applying these methods qualitatively to three cases, we find that prior to solar flares, TBs 1) tend to occur in one large cluster close to the future flare location and below the separatrix surface of a coronal null point, 2) are co-spatial with reconnection signatures in the lower solar atmosphere, such as bald patches and null point fan traces and 3) cluster in the vicinity of strong-gradient polarity inversion lines and regions of increased excess magnetic energy density. TBs are also observed during quiet epochs (i.e., no SEE activity) of the same active regions, but they appear in smaller clusters not following a clear spatial pattern, although sometimes associated with short, spatially-intermittent bald patches and fan traces, but predominantly away from strong gradient polarity inversion lines in areas with little excess energy density.

How to cite: Dissauer, K., Barnes, G., Leka, K., and Wagner, E.: Investigating the Uniqueness and Causal Relationship of Precursor Activity to Solar Energetic Events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17740, https://doi.org/10.5194/egusphere-egu25-17740, 2025.

The Parker Solar Probe and Solar Orbiter missions are uniquely equipped to study Type III solar radio bursts. Both spacecraft measure two components of the radio-frequency electric field with unprecedented time and frequency resolution. In addition, for the first time, both spacecraft are equipped with high-frequency magnetic sensors (up to 1 MHz), allowing direct measurements of the magnetic component of both Z-mode (slow extraordinary) and ordinary electromagnetic wave modes.

PSP repeatedly came closer to the source region than any other satellite before. This unique combination of capabilities provided exceptional data. The analysis of these wave data provided unambiguous evidence of the basic elements of the wave generation mechanisms: the initial generation of Langmuir or slow extraordinary waves, and the transformation of the primary waves into electromagnetic waves, producing fundamental and harmonic electromagnetic waves.

A major discovery is the determination of the polarization properties of these emissions: the fundamental emission is produced as a highly polarized ordinary wave, while the harmonic emission is produced as a much more diffuse, weakly polarized combination of ordinary and extraordinary waves. This discovery can be used to distinguish between fundamental and harmonic emissions.

These experimental studies were accompanied by theoretical and computer simulation studies, which allowed to determine the main physical mechanism of fundamental emission generation as a direct transformation of electrostatic waves into electromagnetic waves, and to confirm the generation of harmonic emission as a result of coupling of primary and reflected quasi-electrostatic waves. 

The authors are greatful to ISSI for the support of the team "Beam Plasma Interaction and Type III Solar Radiobursts", and financial support by  
NASA Grants: 80NSSC20K0697 and 80NSSC21K1770, and CNES Grants: “Parker Solar Probe” and “Solar Orbiter”   

How to cite: Krasnosselskikh, V., Jebaral, I. C., Pulupa, M., Dudok de Wit, T., Voshchepynets, A., Larosa, A., Bale, S. D., Krafft, C., Volokitin, A., Agapitov, O., Cooper, T., Kretzschmar, M., and Balikhin, M.: Type III Solar Radio Bursts: recent progress due to PSP and Solar Orbiter measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18165, https://doi.org/10.5194/egusphere-egu25-18165, 2025.

Forecasting the arrival of Coronal Mass Ejections at Earth depends on accurate characterisation of their three-dimensional structure and kinematics. This is usually achieved via forward-modelling; applying an assumed model of the CME structure to white-light observations, which may be achieved using a small number of observing spacecraft. An alternative approach is inverse modelling, whereby white-light images are treated as two-dimensional projections of the Thomson-scattered light from the 3D plasma distribution. Inversion of images taken from multiple vantage points is purely mathematical and allows the three-dimensional CME density structure to be constrained. However, the method requires multiple observing spacecraft and, to-date, it has enjoyed limited success when applied to CMEs.

We establish the effectiveness of the tomographic inversion method using synthetic imagery produced by state-of-the-art magnetohydrodynamic simulations using the CORonal HELiospheric (CORHEL) model. This is performed for a fleet of spacecraft, such that various combinations can be combined and used to perform tomography on the synthetic imagery, with the goal of establishing the minimum requirements for successful 3D CME reconstruction. We demonstrate how the number of observing spacecraft influences the solution, how well the technique is augmented using polarised brightness measurements and the optimal orbital configuration, including out-of-ecliptic observers.

How to cite: Barnes, D., Palmerio, E., Amerstorfer, T., Asvestari, E., Barnard, L., Bauer, M., Čalogović, J., Hess, P., Kay, C., Kenny, K., and Cappello, G.: Tomographic Inversion of Synthetic White-Light Images: Observing Coronal Mass Ejections in 3D, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18793, https://doi.org/10.5194/egusphere-egu25-18793, 2025.

The Sun is a prominent source of radio emission due to its proximity and solar activity. The most violent solar eruptive events, solar flares and coronal mass ejections (CMEs), can accelerate electrons, producing radio emissions often observed as bursts classified into different types. In particular, type IV radio bursts, which are routinely observed by the Parker Solar Probe (PSP), are associated with CMEs and electrons trapped within strong coronal magnetic fields. The distinct spectral and temporal features exhibited by these bursts enable inferences about the dynamics of CMEs and properties of the energetic particles. While spacecraft such as PSP provide valuable in-situ data supporting analysis of remotely obtained radio spectra, physics-based numerical models play a crucial role in enhancing our understanding of the mechanisms driving radio emissions.

In this talk, we present a novel coupling of three numerical models to simulate gyrosynchrotron (GS) emission from energetic electrons deep in the solar corona. Using the data-driven magnetohydrodynamic (MHD) coronal model COCONUT, we solve the 3D ideal MHD equations to derive coronal background configurations from 1 to 21.5 solar radii, including a CME modelled as a Titov–Démoulin flux rope. Subsequently, we utilise the particle transport code PARADISE to propagate energetic electrons as test particles through the MHD snapshots by solving the focused transport equation stochastically, obtaining spatio-temporal electron intensities. Finally, we use the solar wind parameters from COCONUT and the electron energy and pitch angle distributions from PARADISE as input to the Ultimate Fast GS Code (Kuznetsov and Fleishman, 2021), which computes emission and absorption coefficients that can be integrated along a line of sight to obtain radio spectra directly comparable to spacecraft measurements. This coupled approach illustrates how varying electron injection spectra and CME properties affect the observed radio spectra, offering insights into the energetic particles and CMEs. Furthermore, we highlight the potential of our model in future studies incorporating observational data.

How to cite: Husidic, E., Wijsen, N., Jebaraj, I. C., Linan, L., Vainio, R., and Poedts, S.: Modelling Gyrosynchrotron Emission from Energetic Electrons in the Solar Corona, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18867, https://doi.org/10.5194/egusphere-egu25-18867, 2025.

The Sun manifests its activity across different temporal scales and via transient phenomena that start from solar flares and, through energetic particles, coronal mass ejections, and solar wind, impact the whole heliosphere. The understanding of the causality of this chain of events is hampered by the fact that several open issues still bother a full comprehension of the trigger of such chain, i.e., solar flares. The present talk aims to shed some light on two specific aspects of these elusive phenomena characterizing the active Sun: the determination of the volume of a thermal flaring emission, and the estimate of its effectiveness as particle accelerator. For the first problem, we will show that computer vision applied to hard X-ray observations provided by STIX on-board Solar Orbiter and HXI on-board ASO-S is able to provide the three-dimensional reconstruction of the solar flare thermal emission. For the second problem, the application of an inversion method to STIX visibilities will contribute to settle the long-standing issue concerning the determination of the acceleration rate associated with magnetic reconnection.

How to cite: piana, M., volpara, A., massa, P., palumbo, B., ryan, D., su, Y., emslie, G., massone, A. M., benvenuto, F., and krucker, S.: The elusive solar flares: characterizing the trigger of the Sun-heliosphere connection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19097, https://doi.org/10.5194/egusphere-egu25-19097, 2025.

Solar type III radio bursts are amongst the most intense emissions found within Solar System. The bursts are generated by the relativistic electron beams ejected from the Sun as they propagate through the corona and solar wind. One the key parameters that can control beam plasma interactions is level of the density fluctuations. The density fluctuations can change the local phase velocity of the Langmuir waves generated by the beam instability, resulting in changes of the resonant conditions of wave-particle interaction. Changes in the wave phase velocity during the wave propagation can be described in terms of probability distribution function determined by distribution of the density fluctuations. This enables an approach that describes beam-plasma interaction with a system of equations, similar to well known quasi-linear approximation, but with the conventional velocity diffusion coefficient and the wave growth rate are replaced by the averaged in the velocity space. This approach, known as probabilistic model, allows to describe generation of the Langmuir waves in randomly inhomogeneous solar wind in self-consistent manner. Although previous version of the probabilistic model could explain some of the observational features of the emission, it had significant limitation, as it did not include time of flight effects. Here we present results of the numerical simulation based on an updated set of equations that can describe generation of the Langmuir waves by the electron beam as it propagates from the source region up to 10 Solar radii.   

How to cite: Voshchepynets, A., Krasnoselskikh, V., and Jebaraj, I.: Simulation of the beam plasma interaction in randomly inhomogeneous solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19891, https://doi.org/10.5194/egusphere-egu25-19891, 2025.

This research will explore solar wind parameters and present evidences of additional acceleration of particles in 3D reconnecting current sheet formed in the interplanetary magnetic field. The observational results will be compared with simulations of particle acceleration in 3D reconnecting current sheet using particle-in-cell approach. We also show the variations of electron pitch-angle distribution (PAD) during spacecraft crossing reconnecting current sheets (RCSs) with magnetic islands. The energy gains and the PADs of particles would change depending on the specific topology of magnetic fields. Besides, the observed PADs also depend on the crossing paths of the spacecraft. When the guiding field is weak, the bi-directional electron beams (strahls) are mainly present inside the islands and located closely above/below the X-nullpoints in the inflow regions. The magnetic field relaxation near X-nullpoint converts the PADs towards 90◦. As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of RCSs. Mono-directional strahls are quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature drift acceleration.   Our results link the electron PADs to local magnetic structures and directions of spacecraft crossings derived from in-situ observations by WIND, ACE and Parker Probe.  

How to cite: Zharkova, V., Khabarova, O., and Malandraki, O.: Additional acceleration of solar wind particles in the heliosphere and diagnostics from space observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20306, https://doi.org/10.5194/egusphere-egu25-20306, 2025.

The Plasma Wave Subsystem (PWS) onboard the Voyager spacecraft have continuously recorded dust impacts over the past ~50 years, from the inner solar system to the very local interstellar medium. Not originally intended for this measurement, PWS detects a large surge in voltage when a dust particle impacts the spacecraft body, is vaporized and ionized, and becomes an expanding cloud of charge which is measured by the electric field antenna. While Voyager 2 lost the ability to measure dust impacts after it experienced a waveform receiver failure around 60 AU, Voyager 1 has recorded impacts along its entire trajectory. Dust impacts are very characteristic within the waveform data and can be automatically selected, although a human-in-the-loop method needs to be used to verify each dust impact signal. The rate of dust impacts has varied throughout the Voyager 1 flight. At a radial distance of 30 AU, Voyager 1 measured dust at a rate of 3 +/- 1 impacts per hour. At 70 AU, that increased to a peak of 6 +/- 3 impacts per hour, then started to fall off again after passing the Termination Shock and again after crossing the Heliopause. The last group of measurements showed impact rates of about 3 +/- 2 per hour. Converting to flux units gives values in the range of what Ulysses obtained for interstellar dust, indicating the Voyager impacts are of the same origin. We present the full set of dust impact measurements as well as compare with New Horizons measurements over radial distance and model simulations that utilize different dust grain size distributions to bring more insight to the Voyager dust data set.

How to cite: Jaynes, A., Kurth, W., Gurnett, D., and Granroth, L.: 50 years of Interstellar Dust Measurements from Voyager 1, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20516, https://doi.org/10.5194/egusphere-egu25-20516, 2025.

Energetic electrons accelerated by solar flares in the corona may propagate downward, produce X-rays in the chromosphere, and upward, producing coherent type III radio bursts in interplanetary space.  Previous statistical studies of radio and X-ray flare observations have found a good temporal link between the two wavelengths but only a weak correlation between the intensities, in part due to the different emission mechanisms.  Assuming both electron populations share properties from a common acceleration region, theory has predicted a link between the speed of the electron beams travelling outwards (deduced from radio) and the energy density of the electrons travelling downwards (deduced from X-rays). The Solar Orbiter mission is equipped with the STIX and RPW instruments, allowing for simultaneous observations of both X-ray and Radio emissions that can test this theory.   We present results derived from the comparison of 38 radio type III bursts detected by RPW (<10 MHz) associated in time with flares observed by STIX in the 4-150 keV range . From X-ray spectroscopy we obtained the electron spectral index and the electron number of the associated HXR peak, from which the power can be estimated. We derived the Type III exciter speed using the rise and peak times of the time-profiles (V_r and V_p , respectively) in the 0.4-4 MHz range.  We find the observed ratio V_r/V_p is 0.78 +- 0.07, complementing previous similar studies at higher frequencies (30 – 70 MHz) with a ratio of 0.8+-0.06. We report a correlation between the power of all electrons with energies above 30 keV and V_r  (cc=0.47), whilst none is obtained when comparing it with V_p. There is an anticorrelation of the velocities with the electron spectral index as expected, however the anticorrelation coefficients are weak. Relevant correlations are seen when comparing the peak Radio intensity with the electron spectral index (cc=-0.81) and power (E>30keV) (cc=0.59). The energy of the escaping electrons producing the type III radio emission and the ones producing non-thermal HXRs are also compared, showing a significant correlation (cc=0.57). Our results show a clear relation between the most energetic electrons in both populations of beams, supporting the scenario of a common acceleration region. The energy distribution of escaping and confined electrons for some events may depend on other parameters like the geometry of the reconnecting magnetic field.

How to cite: Paipa-Leon, D., Reid, H., Vilmer, N., and Maksimovic, M.: Diagnostics of flare-accelerated electron beams with X-ray and Radio data from Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-541, https://doi.org/10.5194/egusphere-egu25-541, 2025.

How to cite: Wang, R.: High-resolution Observations of Clustered Dynamic Extreme-Ultraviolet Bright Tadpoles (CEBTs) near the Footpoints of Corona Loops, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3015, https://doi.org/10.5194/egusphere-egu25-3015, 2025.

Nanojets are small-scale jets generated by component reconnection, characterized by their motion perpendicular to the reconnecting magnetic field lines. As an indicator of nanoflare events, they are believed to play a significant role in coronal heating. Using high-resolution EUV imaging observations from the Solar Orbiter/Extreme Ultraviolet Imager (EUI), we identified 27 nanojets during an M7.6 flare on September 30, 2024. Most nanojets exhibit velocities around 1000 km/s, comparable to the typical coronal Alfvén speed. To our knowledge, these speeds are the highest ever reported for small-scale jets. The average kinetic energy of the nanojets is estimated to be 2.3×10²⁵ erg, with events of higher speeds typically displaying greater kinetic energy and longer durations.

How to cite: Gao, Y., Tian, H., Van Doorsselaere, T., and Berghmans, D.: Solar Orbiter/EUI observation of nanojets during a flare with unprecedented high speeds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4897, https://doi.org/10.5194/egusphere-egu25-4897, 2025.

The ESAC Science Data Centre (ESDC) plays a crucial role in preserving and providing long-term access to data from all ESA space science missions. Recent enhancements to the Solar Orbiter Archive (SOAR) aim to provide researchers with more intuitive and powerful tools for data access. These updates include the ability to search data by solar distance and utilize Field of View (FoV) tables. The contents of the Solar Orbiter mission orbit file have been ingested and is available via our standard TAP interface. This allows users to search a rich set of metadata based on Distance and Latitude. Integration with commonly used tools like Python, TOPCAT, and SunPy has further streamlined data access and interoperability. Other upcoming features will be presented.

How to cite: Middleton, H., Masson, A., Cook, J., and Janitzek, N.: New Highlights from the Solar Orbiter Archive, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6493, https://doi.org/10.5194/egusphere-egu25-6493, 2025.

Interplanetary (IP) shocks are important sites of particle acceleration in the Heliosphere and can be observed in-situ utilizing spacecraft measurements. Solar Orbiter provides observations of interplanetary shocks at different locations in the inner heliosphere with unprecedented time and energy resolution in the suprathermal (usually above 50 keV) energy range, thus opening a new observational window to study particle acceleration.

We first discuss the behaviour of a strong IP shock observed as close as 0.07 AU by Parker Solar Probe and then by Solar Orbiter at 0.7, highlighting how the shock and energetic particle production change for different evolutionary stages/locations across the event.

Then, we discuss the case the strongest shock observed by Solar Orbiter so far, associated with efficient production of very high energy electrons (up to 18 MeV) and protons  (up to 30 MeV).

How to cite: Trotta, D. and the co-authors: Solar Orbiter observations of interplanetary shocks in the inner heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6668, https://doi.org/10.5194/egusphere-egu25-6668, 2025.

A very fast coronal mass ejection (CME) was ejected on September 5, 2022, which was measured in situ by Parker Solar Probe (PSP) and Solar Orbiter, and observed remotely by Stereo-A, SOHO and PSP. Here, we carry out the reconstruction of the CME in the corona by using SOHO/LASCO, STEREO-A/COR2, and PSP/WISPR data. The obtained CME parameters are used as input for an MHD simulation with the PLUTO code of an erupting flux rope propagating into the Parker spiral reconstructed with RIMAP, a method which reconstructs the heliosphere on the ecliptic plane from in situ measurements acquired by spacecraft with heliocentric orbits. Then we analyze in-situ Solar Orbiter measurements at 0.7 AU to check the results of the RIMAP simulation, to study the CME-driven shock properties and how they compare with the simulated ones. The level of magnetic turbulence around the shock and the transport of energetic particles are also considered: large fluxes of energetic particles accelerated in situ are measureded by Solar Orbiter/EPD instrument in the energy range 111 keV-3.7 MeV, causing an amplification of magnetic fluctuations. Analyzing the upstream energetic particle time profiles, the transport regime of accelerated particles is found to be normal, although non Gaussian features are also present. As a surprising results, we find that the energetic particles differential flux at Solar Orbiter has a spectral index harder than that predicted by diffusive shock acceleration for the measured compression ratio. The possible reasons for such a discrepancy are discussed. 

How to cite: Zimbardo, G., Bemporad, A., Biondo, R., Frassati, F., Mancuso, S., Nisticò, G., Pagano, P., Perri, S., Prete, G., Reale, F., and Susino, R.: Joint investigation of the September 5, 2022, coronal mass ejection event with remote observations, numerical simulations, and in situ measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7018, https://doi.org/10.5194/egusphere-egu25-7018, 2025.

We study tiny EUV jets jointly observed by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter and the high-resolution H-alpha images from the Visible Imaging Spectrometer (VIS) installed on the 1.6 m Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). The EUV jets repeatedly occurred on 2022-10-29 around 19:10 UT in a quiet sun region (201E, 356N). SDO and IRIS data are used to connect the GST images with the EUI images. A general agreement between the direction of the EUI jets and the alignment of the VIS spicules probably indicates the local magnetic structure. However, the EUI jets show an evolving helical structure, while the H-alpha spicules retain the linear shape. An obvious H-alpha counterpart to the EUI jets is the appearance of red shift concentrated under the EUI jets, while blue shift dominates elsewhere. We use the thin flux tube model to suggest that the morphology of the transient coronal brightening is a manifestation of Alfven wavefronts generated as a result of exchange reconnection, and the red-shifted H-alpha line structure is a downward reconnection outflow from the coronal X-point. The detection of such a sophisticated coronal evolution decoupled from chromospheric dynamics is made possible by the Solar Orbiter's high resolution and a distinctive viewing angle, furthering its goal of understanding how the Sun generates small-scale ejections in the chromosphere and corona. 

How to cite: Lee, J.: The First Joint Observation of EUV Jets and spicules with BBSO/GST and Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7244, https://doi.org/10.5194/egusphere-egu25-7244, 2025.

On October 28, 2021 the first X-class solar flare of Solar Cycle 25 occurred in active region NOAA AR 12887 with a peak at 15:35 UT. It produced the rare event of ground-level enhancement of the solar relativistic proton flux and a global extreme ultraviolet wave, along with a fast halo coronal mass ejection (CME) as seen from Earth's perspective. A few hours before the flare, a slower CME had erupted from a quiet Sun region just behind the northwestern solar limb. Solar Orbiter was almost aligned with the Sun-Earth line and, during a synoptic campaign, its coronagraph Metis detected the two CME events in both Visible Light (VL) and UltraViolet (UV) channels. The earlier CME took place in the northwest (NW) sector of Metis field of view, while several bright features of the flare-related event appeared mostly to the southeast (SE).

The NW and SE events have two distinct origins, but were both characterized by a very bright emission in HI Ly-alpha visible in the UV images of Metis up to 8 solar radii. This work is a follow-up study of two out of the six events analyzed by Russano et al. 2024 (A&A, 683, A191), aimed at investigating the evolution of these two almost co-temporal CMEs but originating in such distinct source regions. To that end, we extensively inspect data sets from numerous remote-sensing instruments observing the Sun in several spatial and spectral regimes. We characterize several aspects of these CMEs, including their three-dimensional properties, kinematics, mass, and temporal evolution of those quantities.

Results of this work point to notable differences between these two events showing significant UV emission in the corona.

How to cite: De Leo, Y., Cremades, H., Iglesias, F. A., Teriaca, L., Aznar Cuadrado, R., López, F. M., di Lorenzo, L., Temmer, M., Romoli, M., and Spadaro, D.: Two distinct eruptive events observed by Metis on October 28, 2021, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8631, https://doi.org/10.5194/egusphere-egu25-8631, 2025.

The wave-particle resonance is fundamental for mediating energy transfer, thereby facilitating particle heating and acceleration in the plasma universe. Cyclotron resonance between ion cyclotron waves and solar wind ions offers a compelling explanation for the long-standing solar wind heating problem.
Additionally, this resonance can drive wave excitation, although direct observational evidence remains limited. The Solar Orbiter spacecraft provides high-resolution three-dimensional ion velocity distributions, enabling detailed investigations of wave-particle interactions. Here, we present two events featuring counterpropagating ion cyclotron waves, in which the ion gyro-phase spectra exhibit phase-bunched signatures, providing solid evidence of cyclotron resonance. The anisotropic core and beam populations resonate with outward- and inward-propagating waves, respectively. The ion distributions denote pronounced agyrotropy, highlighting the pivotal role of nonlinear wave-particle resonances in driving wave excitation and particle energization in the solar wind.

How to cite: Li, J., Khotyaintsev, Y., and Graham, D.: Identifying the Ion Cyclotron Wave Excitation via Cyclotron Resonance in the Solar Wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9592, https://doi.org/10.5194/egusphere-egu25-9592, 2025.

Intermittency is a common feature of solar wind turbulence where it presents itself as non-Gaussian fluctuations and embedded coherent structures. Small-scale magnetic field fluctuations in interplanetary coronal mass ejections (ICMEs) have a behaviour matching the presence of intermittency but properties and significance of intermittency in ICMEs are not yet known. We use data from Solar Orbiter and Parker Solar Probe to study intermittency in 49 ICMEs and the related upstream and downstream solar wind periods and sheath regions at heliospheric distances of 0.25-1 au. For comparing the different plasma environments, the gradient of kurtosis is used to measure intermittency with larger values being an indication of faster increase of kurtosis towards smaller scales and thus higher level of intermittency. Kurtosis is seen to behave similarly in all studied plasma environments, but the largest gradients are seen in the upstream solar wind at the lower end of the inertial range. The downstream solar wind, sheaths and ICMEs show similar values and behaviour for the gradient. The connection between kurtosis and common plasma parameters is studied with some differences found in different intervals but with no strong correlations.

How to cite: Ruohotie, J., Good, S., Möstl, C., and Kilpua, E.: Statistical analysis of intermittency in solar wind transients: Solar Orbiter and Parker Solar Probe observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9722, https://doi.org/10.5194/egusphere-egu25-9722, 2025.

Ion beams are non Maxwellian features frequently observed in solar wind ion distribution functions. These beams appear as two distinct populations of ions with the same charge state but different bulk velocities. While various mechanisms – such as magnetic reconnection and resonant wave-particle interactions – have been proposed to explain their formation, their origin remains an open question and a subject of ongoing debate.

To better understand the kinetic processes driving particle acceleration, it is essential to identify and isolate the double streams in the particle measurements. To achieve this, we have developed a novel numerical method that leverages clustering techniques commonly used in machine learning. This approach enables the successful separation of up to four ion populations: the proton core and beam, as well as the alpha particle core and beam.

We present case studies in which proton and alpha beams were identified during specific events, such as magnetic switchbacks and interplanetary disturbances associated with solar eruptions. By isolating these beams, we examine their density, temperature, and velocity, and provide a detailed characterization of how the different distribution functions respond to such dynamic conditions.

These findings offer valuable insights into the intricate behavior of solar wind ions, shedding light on the underlying acceleration mechanisms and deepening our understanding of the complex processes shaping the solar wind.

How to cite: De Marco, R., Laurenza, M., D'Amicis, R., Bruno, R., Torda, T., Perrone, D., Marcucci, M. F., Owen, C. J., Louarn, P., and Fedorov, A.: Decoding Ion Beams in the Solar Wind: Insights into Kinetic Processes and Acceleration Mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10791, https://doi.org/10.5194/egusphere-egu25-10791, 2025.

The Energetic Solar Eruptions: Data and Analysis Tools (SOLER) project (2024–2027) will investigate the most energetic phenomena occurring at the Sun using the newly expanded unprecedented heliospheric spacecraft fleet including Solar Orbiter, Parker Solar Probe, BepiColombo, STEREO A, and near-Earth spacecraft. We investigate energetic solar eruptions starting from three perspectives: fast (speed > 1000 km/s) coronal mass ejections (CMEs), strong (GOES class > M5) X-ray flares, and large (detected at >25 MeV proton energies) solar energetic particle events. Key parameters of the various eruption phenomena will be determined and their interrelations examined to make significant leaps in our understanding on how the eruptive phenomena are linked to each other, how they interact with each other, and how they result in acceleration and release of high energy particles from the solar corona into interplanetary space. Because of their direct link to particle energisation, large-amplitude coronal waves and shocks related to these events will be in focus as well. Magnetic connections of sources with each other and with the in-situ observers will be determined. In addition to producing significant amounts of new scientific knowledge in the field, SOLER will provide the wider scientific community a wide array of advanced data products, and novel data analysis and visualisation tools that will be openly distributed.

This poster will present an overview of SOLER, its objectives and plans, and the first results of the project.

SOLER has received funding from the European Union's Horizon Europe research and innovation programme under grant agreement No 101134999.

How to cite: Vainio, R., Briand, C., Dresing, N., Kilpua, E., Morosan, D., Pomoell, J., Price, D., Veronig, A., and Warmuth, A.: The Horizon Europe SOLER project (2024-2027): project objectives and first results, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11202, https://doi.org/10.5194/egusphere-egu25-11202, 2025.

The Sun produces eruptive events that release energetic particles, such as protons and electrons, into the heliosphere. These solar energetic particles (SEPs) can reach exceptionally high energies and pose risks to satellite technology and astronauts in space, particularly those outside the protective shield of Earth’s magnetic field. Identifying the mechanisms that accelerate SEPs remains a significant challenge in current research, which hampers our ability to predict SEP events effectively. Even cutting-edge space missions such as Solar Orbiter and Parker Solar Probe often do not reach close enough distances to the Sun to make direct observations of the acceleration processes without interference from transport effects.

Analyzing the spectra of SEPs is essential for understanding the acceleration mechanisms involved, as different phenomena should exhibit unique spectral features. However, it is also recognized that transport effects can significantly alter these spectral shapes, and the intricacies of these processes are still not fully understood.

Our research targets a subset of SEPs, solar energetic electrons (SEEs). We utilize the advanced measurements obtained from the Energetic Particle Detector (EPD) onboard the Solar Orbiter spacecraft. EPD boasts unparalleled time and energy resolution, detecting energetic particles at a 1-second interval across energies ranging from suprathermal to relativistic. This data, combined with Solar Orbiter's varying proximity to the Sun, enables us to analyze SEE energy spectra with unprecedented detail and to better understand the transport effects involved.

In this study, we investigate the peak intensity spectra of the most intense SEE events recorded by Solar Orbiter/EPD at 43 keV from December 2020 to December 2022. The spectral characteristics are derived by fitting the spectra using various mathematical models. We will present the findings of our statistical analysis and compare them with previous research outcomes.

How to cite: Fedeli, A., Dresing, N., Vainio, R., Gieseler, J., Gómez Herrero, R., Espinosa Lara, F., Warmuth, A., and Schuller, F.: Spectral Analysis of the most intense Solar Energetic Electron Events Observed with Solar Orbiter from December 2020 to December 2022, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11505, https://doi.org/10.5194/egusphere-egu25-11505, 2025.

In this study, we determine the differential emission measures (DEMs) using Solar Orbiter/Extreme Ultraviolet Imager (EUI)/Full Sun Imager (FSI) and AI-generated EUV data. The FSI observes only two full-disk extreme UV (EUV) channels (174 and 304 Å), which poses a limitation for accurately determining DEMs. We address this problem using deep learning models based on Pix2PixCC, trained using the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) dataset. These models successfully generate five-channel (94, 131, 193, 211, and 335 Å) EUV data from 171 and 304 Å EUV observations with high correlation coefficients. We then apply the trained models to the Solar Orbiter/EUI/FSI dataset and generate the five-channel data that the FSI cannot observe. Here we use the regularized inversion method to compare the DEMs from the SDO/AIA dataset with those from the Solar Orbiter/EUI/FSI ones with AI-generated data. First, we demonstrate that, when SDO and Solar Orbiter are at inferior conjunction, the main peaks and widths of both DEMs are well consistent with each other at the same coronal structures. These results reveal that deep learning can make it possible to properly determine the DEMs using Solar Orbiter/EUI/FSI and AI-generated EUV data. Additionally, we determine the DEM when the two instruments are at various angular separations, such as when 60 degrees (L4 and L5) and 180 degrees apart. Our results suggest that the stereoscopic DEM analysis of coronal features using our methodology should be possible. 

How to cite: Youn, J., Lee, H., Jeong, H.-J., Lee, J.-Y., Park, E., and Moon, Y.-J.: Exploring the Potential of DEM Analysis Using Solar Orbiter/EUI and AI-Generated Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11786, https://doi.org/10.5194/egusphere-egu25-11786, 2025.

The Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter continuously measures the Sun in the energy range 4-150 keV. Due to the spacecraft’s peculiar orbit, around 50% of all STIX flares are backside flares and lack a corresponding GOES class. In Stiefel et al. (2025) we describe the correlation between the STIX background detector and GOES measurements where we found a power-law function between the two data sets. This function can be used to get a proxy of the GOES class for large backside flares.

Building up on the approach of using the background detector of STIX, we want to discuss how we can improve the spectral fitting of the thermal emission of large flares (> X1-class) observed by STIX and discuss the occurrence of “super-hot” components (e.g. Caspi et al. (2010)) in these flares. Using imaging and spectral analysis of STIX data, we want to understand the physical origin and the temporal evolution of the super-hot component. This talk will highlight the importance of understanding the thermal emission in solar flares and the richness of information we can gain regarding the thermal emission by combining spectral and spatial observations by various X-ray instruments.

How to cite: Stiefel, M. Z., Bajnoková, N., Massa, P., and Krucker, S.: X-ray diagnostics of thermal flare emissions by Solar Orbiter/STIX and GOES, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11967, https://doi.org/10.5194/egusphere-egu25-11967, 2025.

This talk will report on the mission status and highlight recent science results of the ESA/NASA Solar Orbiter mission. Solar Orbiter’s science return is significantly enhanced by coordinated observations with other space missions, including Parker Solar Probe, SDO, SOHO, STEREO, Hinode and IRIS, as well as ground-based telescopes like DKIST and SST. This talk with present examples of such collaborative efforts and outline future opportunities. Starting in February 2025, Solar Orbiter’s highly elliptical orbit will get progressively more inclined to the ecliptic plane, which will enable the first detailed observations of the Sun’s unexplored polar regions. I will summarise the observing plans for the first year of the high-latitude phase and describe opportunities for participation of the science community.

How to cite: De Groof, A., Mueller, D., Zouganelis, Y., Janvier, M., Walsh, A., Williams, D., Osuna, P., and Fischer, C.: Solar Orbiter: Mission Status, Science Highlights and Look-out for the High-Latitude Phase, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12901, https://doi.org/10.5194/egusphere-egu25-12901, 2025.

We examine 3He-rich solar energetic particles (SEPs) detected on 2023 October 24-25 by Solar Orbiter at 0.47 au. The measurements revealed heavy-ion enhancement not increasing smoothly with mass. C, and especially N, Si, and S, stand out in the enhancement pattern with large abundances. Except for 3He, heavy ion spectra can only be measured below 0.5 MeV/nucleon. At 0.386 MeV/nucleon, the event showed a huge 3He/4He ratio of 75.2±33.9, larger than ever previously observed. Solar Dynamics Observatory extreme ultraviolet data showed a mini filament eruption at the solar source of 3He-rich SEPs that triggered a straight tiny jet. Located at the boundary of a low-latitude coronal hole, the jet base is a bright, small-scale region with a supergranulation scale size. The emission measure provides relatively cold source temperatures of 1.5 to 1.7 MK between the filament eruption and nonthermal type III radio burst onset. The analysis suggests that the emission measure distribution of temperature in the solar source could be a factor that affects the preferential selection of heavy ions for heating or acceleration, thus shaping the observed enhancement pattern. Including previously reported similar events indicates that the cool material of the filament in the source is a common feature of events with heavy-ion enhancement not ordered by mass. Surprisingly, sources with weak magnetic fields showed extreme 3He enrichment in these events. Moreover, the energy attained by heavy ions seems to be influenced by the size and form of jets.

How to cite: Bucik, R., Mason, G., Mulay, S., Ho, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Origin of Unusual Composition of 3He-Rich Solar Energetic Particles , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13242, https://doi.org/10.5194/egusphere-egu25-13242, 2025.

The Electron Analyser System (EAS), a dual sensor system within the Solar Wind Analyser (SWA) suite, is capable of measuring a full 3D velocity distribution function (VDF) of solar wind electrons with energies of a few eV to ~5 keV in an accumulation time of 1 second.  At full energy and angular resolution, telemetry constraints limit the maximum EAS normal mode data return to 1 3D VDF every 10 seconds.  However, the SWA DPU includes a rolling buffer capable of storing 1-second full electron VDF data for a period of 5 minutes.  Over the last year, during periods in which the telemetry allocation is high, we have been able to freeze this buffer and return this data up to three times per hour, generating a large dataset of very high time resolution electron measurements.  Moreover, a trigger detection algorithm is at times operated by the Radio and Plasma Waves (RPW)  instrument, combining data from the magnetometer and the SWA Proton and Alpha Sensor in order to detect the passage of a shock passed the spacecraft.    Although the operation of the algorithm has suffered from a number of technical issues, receipt of a positive flag is used by SWA to freeze the EAS rolling buffer and add the resulting data to the telemetry stream.  This operation has again generated a significant dataset of high resolution electron data which is often associated with a solar wind transient, such as a shock or a current sheet.

In this presentation, we present case studies of periods in which SWA-EAS returned this high resolution data, bringing out new features of electron dynamics that are not captured by normal resolution instruments on Solar Orbiter or other missions.  For example, we examine the development of electron distributions across the shock, revealing how the ‘flat-top’ nature of the downstream distribution develops as a function of pitch angle.  Moreover, even the manually triggered events can be used to reveal how the electron distribution may vary with less dramatic, but more regular, variations in the solar wind, such as those driven by waves or instabilities.

How to cite: Owen, C. and the Solar Orbiter SWA, MAG and RPW teams: Solar wind electron dynamics revealed by high-time resolution observations of 3D electron velocity distribution functions captured by Solar Orbiter SWA., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13243, https://doi.org/10.5194/egusphere-egu25-13243, 2025.

We present a comprehensive catalogue of solar energetic electron (SEE) events, derived from joint observations by remote-sensing and in-situ instruments aboard the Solar Orbiter spacecraft. The Energetic Particle Detector (EPD) is used to characterise the properties of energetic electrons in situ and to estimate their injection times at the Sun. The timing, location, and intensity of associated X-ray flares is obtained using the Spectrometer/Telescope for Imaging X-rays (STIX), while the Extreme Ultraviolet Imager (EUI) provides complementary observations of the flare evolution and eruptive phenomena. The Solar Orbiter coronagraph (Metis) and heliospheric imager (SoloHI) are employed to characterise potential associated coronal mass ejections (CMEs). Type III radio bursts detected by the Radio and Plasma Waves (RPW) instrument are used to connect the eruptive solar events to the SEE events observed in situ. We present the catalogue's contents, and the methodology employed to determine key parameters. Finally, we discuss statistical results from the catalogue.

How to cite: Warmuth, A. and the STIX-EPD-RPW-EUI-Metis-SoloHI joint analysis team: Solar Orbiter's Comprehensive Solar Energetic Electron event Catalogue (CoSEE-Cat): a new resource for studying particle acceleration and transport in the heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13913, https://doi.org/10.5194/egusphere-egu25-13913, 2025.

Solar Orbiter's coordinated observations with space-based and ground-based instruments are game changers in studying the connection between the Sun and the heliosphere. Our aim is to present the results and challenges of coordinated observations obtained with the Solar Orbiter and other instruments and highlight the advantages of using coordinated observations obtained with the Solar Orbiter and various telescopes.

We received two groups of unique coordinated observations:

1) We successfully coordinated observation campaigns between Solar Orbiter and the Daniel K. Inouye Solar Telescope (DKIST) in October 2022 and October 2023. These two telescopes provide a stereoscopic view with unprecedented high resolution. The scientific aim of these observations was related to active region studies from different vantage points (four proposals) and polar magnetic field regions (one proposal). The next observation session is planned for April 2025 and will focus on the upflow regions at the borders of active regions.

2) In October 2024, we successfully coordinated observations between the Solar Orbiter, the Interface Region Imaging Spectrograph (IRIS), and Hinode. The uniqueness of the obtained observations lies in the highest temporal cadence, 1 sec, of a solar atmosphere image ever achieved. These images were recorded by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. These coordinated observations from October 2024 show an active region with flaring activity.

The presented data are publicly available, and their interpretation is provided among others under the ISSI Team titled: "Active Region Evolution Under the Spotlight, with Unprecedented Coordinated High-Resolution Stereoscopic Observations and Numerical Simulations.” In conclusion, the coordinated observations from two different vantage points with imaging, spectroscopy and magnetic field instrument opened a new era in investigating structures in the solar atmosphere.

How to cite: Barczynski, K., Janvier, M., Nelson, C., Lim, D., Tritschler, A., Schad, T., Harra, L., and Müller, D.: Coordinated observation with Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16849, https://doi.org/10.5194/egusphere-egu25-16849, 2025.

Plasma upflows with a Doppler shift exceeding 20 km/s at active region (AR) boundaries are considered potential sources of nascent slow solar wind.  These upflows are often located at the footpoints of large-scale fan-like loops, showing temperature-dependent Doppler shifts from the transition region to the lower corona. In this study, we identified two upflow regions in the vicinity of an active region by analyzing the blueshifts of the Fe XII 195 line observed by Hinode/EIS. Context images for the two regions were obtained by the High Resolution Imager (HRI) telescope of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter. The region to the west of the AR appears as typical fan-like loops, while the eastern upflow region is near AR moss, revealing moss-like features but with lower intensity from the upper transition region into the corona. Free from the potential contamination of fan-like loops, the east region provides unique insights into the flow properties from the chromosphere into the corona and the coupling between the atmospheric layers in the upflow region. Carefully addressing the point spread function issue with the SPectral Imaging of the Coronal Environment (SPICE), we derive the Doppler shifts of Ne VIII, emitted by cooler plasma compared to Fe XII, in these two regions. The fan-like loops in the west show downflows (redshifts) of approximately 20 km/s, whereas the eastern region shows upflows (blueshifts) from 20 to 30 km/s. This suggests the actual upflows might develop in the upper transition region (~0.6 MK), challenging the typical conclusion of a coronal upflow (> 1 MK), which is affected by downflows in fan-like loops.  Observations from the Interface Region Imaging Spectrograph (IRIS) satellite confirm the coronal upflows influence the velocity field in the lower transition region (Si IV). However, the critical transition temperature from a net redshift into a blueshift is still unclear due to the lack of temperature coverage. Combined with potential field extrapolations, we confirm the driver of the major upflow component might be persistent reconnections between over-pressure AR loops and ambient low-pressure field lines. However, the small-scale dynamics in upflows by observed HRIEUV, e.g., dynamic fibrils and jetlet, may still contribute passively to the upflow plasma in the coupled atmosphere. Preliminary differential emission measure (DEM) analysis reveals a photospheric abundance in both upflow regions, which is compared to the in-situ solar wind measurements when the Solar Orbiter was predicted to connect to the west upflow region by the Connectivity tool. 

How to cite: Zhu, Y., Harra, L., Barczynski, K., Janitzek, N., Plowman, J., Mzerguat, S., Auchère, F., Thompson, W., Parenti, S., Chitta, L. P., Peter, H., Fredvik, T., Grundy, T., Ni, Y.-W., and Chen, P.-F.: Upflows in a Decaying Active Region and its Potential Contribution to the Solar Wind , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18322, https://doi.org/10.5194/egusphere-egu25-18322, 2025.

Solar flares and associated eruptions are a known source of solar energetic particles (SEPs). Yet, 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) provide new measurements for a systematic investigation of these phenomena. Based on these data, we developed an algorithm that automatically links solar flares to SEP events using a STIX flare list, model prediction of magnetic connectivity between the Sun and the spacecraft, and SEP electron measurements from EPD. A first evaluation shows that 50% of the links produced by the algorithm are actual physical links, while inversely 26% of all manually identified physical links were detected by the algorithm for the two-years test period in 2021 and 2022. This can be considered as a modest success rate for a fully automatic linkage between solar and in-situ events, but it provides a very helpful pre-selection of about 100 SEP-related flares compared to more than 5000 flares detected with STIX.

How to cite: Janitzek, N., Kistler, F., Stiefel, M., Barczynski, K., Zhu, Y., Harra, L., Gomez-Herrero, R., Rodriguez-Pacheco, J., Roco-Moraleda, M., Battaglia, A., Collier, H., and Krucker, S.: An automated approach to link solar flares and energetic particle events based on measurements from Solar Orbiter and modelled magnetic connectivity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19476, https://doi.org/10.5194/egusphere-egu25-19476, 2025.

Solar flares are energetic and dynamic phenomena in the solar system emitting radiation impulsively, and solar energetic electrons (SEEs). Therefore, we investigate the high-energy X-ray emission and SEEs observed by STIX and EPD onboard the Solar Orbiter mission. During September 18-30, 2021, the Solar Orbiter mission - being closer to the Sun (~0.6 AU) and having a moderate separation angle (~30-40⁰) from the Sun-Earth line provided a unique opportunity for an exhaustive multi-wavelength investigation of several weak flares, associated nonthermal X-ray emission, and SEE’s characteristics. A multiwavelength investigation of spectral and imaging-mode observations of the 20 weak (~B-class), but hard X-ray (HXR)-rich flares, revealed a definitive role of pre-flare plasma density in the loops to be responsible for disparate thermal-nonthermal emission partition during flares. We further investigate remote and in-situ observations of three flares (two B-class, and a C1.6 -class) showing different thermal-nonthermal X-ray emission partitions, and associated SEEs. The timing and spatial correlation of the solar events at source and in-situ SEE enhancements revealed agreement in the 1) onset time of HXR emission and SEE enhancement, and 2) power-law spectral indices of HXR emission and SEEs. Interestingly, we find a very weak HXR burst (B3-class; nonthermal electron spectral index ~ 6) to cause a significant SEE enhancement despite an impulsive C3 flare that occurred a mere 15 minutes before it without any SEE enhancement signatures. Therefore, a comprehensive assessment of energy released during flares is only possible by characterising the observed nonthermal emission as well as particles.

How to cite: Awasthi, A. K., Warmuth, A., Mrozek, T., Sylwester, J., Sylwester, B., and Schuller, F.: Investigating weak flares energetics through nonthermal emission and solar energetic electrons: STIX and EPD observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20333, https://doi.org/10.5194/egusphere-egu25-20333, 2025.

We investigate the signatures of oscillatory motions in the solar transition region with data from the SPICE instrument on the Solar Orbiter spacecraft. The solar transition region is the thin interface between the cooler lower solar atmosphere and the million-degree corona, across which the energy (and mass) flux crucial for maintaining the solar corona and the solar wind are transported. The plasma temperature and density change a few orders of magnitudes across the transition region, creating a sharp discontinuity in the plasma parameters. This natural boundary is a theorized location for MHD wave mode conversion generating coronal Alfvenic waves, which are a leading candidate for heating the solar corona and powering the solar wind through their dissipation. The key objective of this study is to determine how the oscillatory behavior of plasma in different parts of the solar TR behaves with spectrographic observations from the SPICE spacecraft. We use sit-and-stare observations of atomic lines with formation temperatures between log(T)=4-5.7. In particular, we study the power spectra of the oscillatory motions and the coherency between the intensity and velocity perturbations as a signature of the MHD modes. To enhance the interpretation of the observational study, we use as a complementary tool the wave properties of synthetic observables from 3D rMHD MURaM models, which are ab initio MHD computations which extend from the convection zone to the corona.

How to cite: Molnar, M., Hassler, D., and Plowman, J.: Wave dynamics across the solar transition region with the SolO/SPICE instrument , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20356, https://doi.org/10.5194/egusphere-egu25-20356, 2025.

Proper characterization of particle energization in the solar wind requires observations from thermal through energetic particles of multiple elements. Observations of in situ particles in different energy ranges require different instruments that must be properly intercalibrated. Solar Orbiter’s Heavy Ion Sensor (HIS) is a time-of-flight ion mass spectrometer that observes the heavy ion composition of the thermal solar wind. Orbiter’s Suprathermal Ion Spectrograph (SIS) is an energy time-of-flight detector that observes particles from suprathermal energies to the lower range of energetic particles. We report on the intercalibration between these two instruments in six isotropic, quiet intervals when both instruments provide reliable, high-quality observations. These results will enable analysis of more complex events where transient processes locally modify the distributions.

How to cite: Alterman, B., Allen, R., Dewey, R., Livi, S., Raines, J., Lepri, S., Spitzer, S., Bert, C., Owen, C., Ho, G., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., Wurz, P., Philips, M., Damicis, R., Mason, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J. and the Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph team: Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21838, https://doi.org/10.5194/egusphere-egu25-21838, 2025.

Inverse velocity dispersion (IVD) in solar energetic particle (SEP) events, where higher-energy particles arrive later than lower-energy particles, is increasingly observed by spacecraft such as Parker Solar Probe (PSP) and Solar Orbiter (SolO). However, the underlying mechanisms driving IVD events are not well understood. This study examines the physical processes responsible for long-duration IVD events by analyzing the SEP event detected by SolO on June 7, 2022. The event displayed a clear and prolonged IVD signature across proton energies ranging from 1 to 20 MeV, with heavy ions exhibiting varying nose energies. Simulations indicate that evolving shock connectivity plays a crucial role in shaping the IVD signature, as SolO’s connection shifts from the shock flank to the nose over time, resulting in a gradual increase in the maximum particle energy along the field line. Furthermore, model results show that limited cross-field diffusion affects both the nose energy and the duration of the IVD event. This study highlights that long-lasting IVD events are primarily driven by evolving shock connectivity to the observer, with connections to more efficient acceleration sites at larger solar distances.

How to cite: Ding, Z. and Wimmer-Schweingruber, R.: Inverse Velocity Dispersion in Solar Energetic Particle Events Observed by Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2506, https://doi.org/10.5194/egusphere-egu25-2506, 2025.

As Solar Cycle #25 reaches its peak of activity, Solar Orbiter is observing a substantial increase in solar flares, coronal mass ejections (CMEs), and solar energetic particles (SEPs). Specifically, the Energetic Particle Detector (EPD) on board Solar Orbiter has been tracking and characterizing the rise in SEP activity over the past five years. This paper focuses on the intensities of suprathermal and energetic particles from 2020 through 2025. Both electrons, ions, and ³He particles show a notable increase, which aligns closely with other solar phenomena. We compare the SEP flux observed during this cycle with the measurements from Cycles #23 and #24, as recorded by ACE. The results reveal that the flux levels in Cycle #25 are significantly higher than those of Cycle #24, and comparable to those observed during Cycle #23. This surge in solar activity is filling the heliosphere with high-energy SEP particles, which are influencing the entire solar system, including Earth.

How to cite: Ho, G., Mason, G., Allen, R., Kouloumvakos, A., Wimmer-Schweingruber, R., Rodríguez-Pacheco, J., and Gómez-Herrero, R.: Solar Energetic Particles in Solar Cycle #25: Observations and Comparisons with Previous Cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2858, https://doi.org/10.5194/egusphere-egu25-2858, 2025.

The sources and origins of solar energetic particles (SEPs), especially for the GeV-level events, are the premise and fundamental issue for SEP-induced space-weather disasters. Observational evidence indicates that the anisotropy properties exist in the 3D large temporal-spatial turbulence magnetic reconnection(3D LTSTMR) in solar activities, which is essential to understanding the energy conversion between magnetic energy and acceleration energy (bulk kinetic energy) and heating energy (thermal kinetic energy) over different particle species (e.g., electron, ion, 3He/4He, and other heavier particles), and SEPs characteristics and acceleration propagation in non-ideal diffusion regions. In this work, on the supercomputer platform (GPU heterogeneous architecture & ARM architecture), a 3D spherical coordinates system () for flare loop 3D LTSTMR is applied to explore the helical turbulence-induced anisotropic characteristics (TAC, including turbulence anisotropy, TA; turbulence intensity, TI; and spectral anisotropy properties) through the improved relativistic hybrid particle-in-cell and lattice Boltzmann (RHPIC-LBM2) code. Firstly, we deduced the explicit expression of the turbulence-induced dissipation-diffusion (TIDD) terms under fully coupled hydro-dynamic-kinetic continuous scales by considering the turbulence-resistance-induced self-generated organization and the turbulence-viscosity-induced self-feeding-sustaining with filter theory. Then, we improved the input module and dissipation-diffusion module and added a new TIDD module in the original RHPIC-LBM model algorithm code. Finally, we analyze the TAC in the impulsive twisted multi-magnetic flux ropes (MFLs) & multi-current plasma flux ropes (CFLs) & multi-plasma flux ropes (PFLs). It is found that the magnetic strength (MFLs), current density (CFLs), and charged flow (PFLs, electron, ion, 3He/4He) anisotropy exist and vary in different evolution times (65.6000s to 74.3467s) in the different direction ( plane,  plane), in the different scale (R=24Mm) at B&U decoupled frozen-in condition broken region. The main findings of the present study are as follows: 1) The TAC in the radial direction is stronger than in the azimuthal direction ( plane) and in the polar direction ( plane); 2) The TAC of magnetic strength (MFLs), current density (CFLs), and charged flow (PFLs) do not overlap in the evolution process; 3) The TAC increases with the evolution time and reaches its maximum when the turbulence enters the fully developed stage; 4) The TAC decreases with the decreasing scale and exhibits weakness when entering the micro-kinetic scale. We anticipate these results to be a key point and give new insights for evaluation of the short-time real-time extremely GeV-SEPs prediction (GPU heterogeneous architecture) and the real-time long-time SEP monitor (ARM architecture), which serve for the 'China Science Development Strategy: Space Science (2020-2035)', and 'The Strategic Position of Space Astronomy: China's Space Science 2035 Development Strategy' in NSFC&CAS. and 'National Mid- and Long-term Plan for Space Science in China (2024-2050). 

URL: Share files：EGU2025_anis...ics[Folder]  Cloud disk link：https://pan.cstcloud.cn/s/Xt4ZjsrR3s

How to cite: Zhu, B.:  Investigation of the anisotropic characteristics in the flare loop turbulence magnetic reconnection through improved RHPIC-LBM on the supercomputer platform , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3936, https://doi.org/10.5194/egusphere-egu25-3936, 2025.

It was the best of times, it was the worst of times – for two traveling interplanetary shocks observed by Solar Orbiter on November 29 and 30 in 2023. We investigate these two very dissimilar shocks which were observed within less than 27 hours to elucidate obviously present non-equilibrium features and test the assumption of gyrotropy. We find very different behavior of particles at the two shocks which are – of course – due to differences in the two shocks.

The first of the two shocks was observed at 07:51:17 on Nov. 29, 2023, was quasi-parallel (θ_Bn ≈ 33°) and the weaker of the two shocks (fast magnetosonic (Alfvénic) Mach number of 2.4 (2.6)). It had no or only a minimal effect on the suprathermal (E less than ~1 MeV) particle population which was anisotropic and streaming away from the Sun. It was likely running into a small ICME and exhibited upstream wave activity with a dominant period just below one second.

The following shock on Nov 30, 2023 (10:47:26) was stronger (fast magnetosonic (Alfvénic) Mach number of 3.8 (4.5)) and quasi-perpendicular (θ_Bn ≈ 81°). Wave activity upstream of this shock was weaker than at the first and limited to the shock ramp, as expected for a quasi-perpendicular shock. Upstream protons and He2+ particles show clear core-beam velocity distribution functions. Suprathermal ions upstream of the second shock are more isotropic than around the first shock but nevertheless show a clear bump-on-tail distribution which lasts for approximately two gyroperiods. The level of fluctuations of the interplanetary magnetic field (IMF) is low which probably allows this “beam” to survive. The region downstream of this shock is rich in further unusual properties of the suprathermal ions. These exhibit strong non-equilibrium features in their differential intensities and anisotropic features which suggest non-gyrotropic behavior.

How to cite: Wimmer-Schweingruber, R. F., Yang, L., Kollhoff, A., Berger, L., Kühl, P., Böttcher, S. I., Trotta, D., Kieokaew, R., Louarn, P., Fedorov, A., Rodriguez-Pacheco, J., Gómez Herrero, R., Espinosa Lara, F., Ho, G. C., Allen, R. C., Mason, G. M., and Lario, D.: A Tale of Two Shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4447, https://doi.org/10.5194/egusphere-egu25-4447, 2025.

Investigations of Solar Energetic Particle (SEP) events have long utilized the dispersive nature of onset times, i.e., earlier arrival of higher energy particles compared to lower energy populations, to infer information such as path length to an acceleration site. However, recent observations by Solar Orbiter and Parker Solar Probe have begun to characterize SEP events with an apparent “inverse velocity dispersion” (IVD) at higher energies, above a critical energy separating the classic velocity dispersion signature. These “nose”-feature SEP events may provide new insight into the impacts of magnetic connectivity to locations along an expanding CME-driven shock wave, variations of acceleration along the shock surface, and transport effects in the inner heliosphere. This presentation focuses on a statistical analysis of the occurrence rate and characteristics of IVD events observed by Solar Orbiter relative to their footpoint locations with respect to the initial flare site. While SEP events without IVDs have a broad distribution in location relative to the flare site, IVD events show a clear bias in occurrence to events with footpoints westward of the associated flare location. Implications of this spatial biasing, and impacts on the characteristics, i.e., critical energy and dispersive slope of the IVD portion of the event, is discussed in relation to recent modeling work (Ding et al., 2025). Additionally, the IVD events observed by Solar Orbiter, captured over a wide range of radial distances, is compared to a published IVD event from Parker Solar Probe near the corona at 15 solar radii (e.g., Cohen et al., 2024). These results imply that magnetic connectivity plays an important role in IVD events, particularly for those observed at larger radial distances.

How to cite: Allen, R., Ho, G., Mason, G., Cohen, C., Xu, Z., Ding, Z., Kouloumvakos, A., Wimmer-Schweingruber, R., Rodriguez-Pacheco, J., Vines, S., Filwett, R., and Dayeh, M.: The relationship of inverse velocity dispersion SEP event characteristics with footpoint location: A survey of Solar Orbiter observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4503, https://doi.org/10.5194/egusphere-egu25-4503, 2025.

Populations of energetic particles, ranging from solar energetic particles to incredibly high-energy cosmic rays, are ubiquitous in space and astrophysical plasmas. Several intertwined phenomena, including shocks, magnetic reconnection, jets, and turbulence, are responsible for the efficient energization of particles and for determining their transport properties.

Plasma turbulence produces patchy coherent structures, such as reconnecting current sheets, plasmoids, and vortices across a vast range of spatial scales. Under some circumstances, these structures can entrap particles, thus providing fast energization through, for example, drift acceleration. I will review some of these mechanisms and outline recent numerical efforts aimed at investigating how coherent structures, such as large-scale eddies or flux ropes, impact particle transport and energization. I will also comment on the applicability of these results in space and astrophysical contexts.

How to cite: Pezzi, O., Trotta, D., Benella, S., Sorriso-Valvo, L., Malara, F., Pucci, F., Meringolo, C., Matthaeus, W. H., and Servidio, S.: The role of coherent turbulent structures in influencing particle transport and energization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4592, https://doi.org/10.5194/egusphere-egu25-4592, 2025.

We present a model of the magnetic field in the heliosphere. Our model's magnetic field is made of a large-scale component, modeled as the Parker Spiral, and a small-scale turbulence component, modeled through a wavelet-based method. The turbulent component is tailored to reproduce a few key properties of magnetic fluctuations in the Parker Spiral, such as a varying correlation length and a decreasing turbulence amplitude as a function of the radial distance from the Sun. The wavelet-based method is obtained from a previously developed Cartesian method by defining a new set of coordinates to ensure the correct scaling of the turbulence correlation length as a function of the radial distance. Our algorithm allows for reproducing a larger spectral range of fluctuations than magnetohydrodynamic simulations, which is needed to properly describe the gyroresonant scattering of energetic particles. In the future, the model will be used to study energetic particle propagation in the heliosphere.

How to cite: Pucci, F., Malara, F., Larosa, A., Pezzi, O., and Perri, S.: Wavelet-based modeling of the heliospheric turbulent magnetic field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4800, https://doi.org/10.5194/egusphere-egu25-4800, 2025.

Electrons are a subsonic plasma species in the solar wind. Their kinetic behaviour is - to a much greater extent than the proton behaviour - the result of an interplay between global properties of the heliosphere and local plasma processes. The global properties of the heliosphere include the interplanetary electrostatic potential, the large-scale interplanetary magnetic field, and the density profile of the plasma. The local plasma processes include collisions, wave-particle interactions, and turbulence. Through this interplay, the electron distribution function develops interesting kinetic features that are observable in situ. In addition to a quasi-Maxwellian core, the distribution exhibits suprathermal populations in the form of the strahl and halo components as well as cut-offs due to loss effects in the interplanetary potential.

We discuss the interaction of suprathermal electrons with local structures such as compressive waves and magnetic holes, and the impacts of these structures on the global electron transport in the heliosphere. The regulation of the electron heat flux is of particular interest in this context. We support these results with observations from Solar Orbiter and Parker Solar Probe. 

How to cite: Verscharen, D., Coburn, J., and Liu, J.: Modulation of suprathermal electrons and their heat flux in compressive plasma structures in the solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5198, https://doi.org/10.5194/egusphere-egu25-5198, 2025.

Context. The Energetic Particle Detector (EPD) suite onboard Solar Orbiter provides unprecedented high-resolution measurements
of suprathermal and energetic particles in interplanetary space. These data can resolve particle dynamics near interplanetary shocks,
offering new insights into particle acceleration and transport processes.
Aims. We present observations of energetic proton bursts downstream of an interplanetary shock and discuss possible acceleration
and formation processes.
Methods. We combined data from two sensors of EPD, the SupraThermal Electron Proton (STEP) sensor and the Electron-Proton
Telescope (EPT), to investigate the proton bursts across the full energy range. We examined the dynamic energy spectra, temporal
flux profiles, pitch-angle distributions, and spectral features of these proton bursts.
Results. We find that these proton bursts travel anti-parallel to the interplanetary magnetic field (IMF) in a region where the IMF
is pointing southward, substantially out of the ecliptic plane. These bursts typically last for ∼10-20 s and span a wide energy range
from ∼20 to ∼1000 keV. Their energy spectra typically show an evident bump in the ∼20-100 keV range, characterized by a valley at
∼20-30 keV, a peak at ∼40-50 keV, a full width at half maximum of ∼30 keV, and a positive spectral slope of ∼1 between the valley
and peak. These proton bursts exhibit no velocity dispersion feature and their occurrences do not coincide with significant changes in
the IMF direction or with enhancements in the 4-100 kHz electric potential oscillations or the 0.1-4 Hz magnetic field fluctuations.
Conclusions. These results suggest that the proton bursts could originate from a source below the ecliptic plane, probably the part
of the shock situated there. These protons could be accelerated through shock-drift acceleration or shock-surfing acceleration, with
varying efficiencies at different parts of the source. The observed spectral bumps likely result from transport effects affecting the
low-energy ∼10-50 keV protons.

How to cite: Yang, L., Li, X., Heidrich-Meisner, V., Wimmer-Schweingruber, R., Wang, L., Kollhoff, A., Zhu, X., Nicolaou, G., Ding, Z., Berger, L., Liu, H., Rodríguez-Pacheco, J., Mason, G., and Ho, G.: Energetic proton bursts downstream of an interplanetary shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5824, https://doi.org/10.5194/egusphere-egu25-5824, 2025.

Title: Investigating Solar Sources of  ³He-Rich and  ³He-Poor SEP Events in 2024 using

Solar Orbiter HET

Authors:

Sindhuja. G¹, Robert F. Schweingruber¹, Patrick Kühl¹, Alexander Kollhoff¹, Zheyi Ding¹, Sebastian

Fleth¹, Lars

Berger¹, Javier Rodriguez-Pacheco², George C. Ho³, Glenn M. Mason⁴, Raul Gomez-

Herrero², Francisco Espinosa Lara², Ignacio Cernuda², Stephan Böttcher¹, Sandra Eldrum¹, and

Robert C. Allen³,

1) Institute of Experimental and Applied Physics, Kiel University, Leibnizstaße 11, DE-24118

Kiel.

2) Universidad de Alcalá, Space Research Group, 28805 Alcalá de Henares, Spain

3) Southwest Research Institute, San Antonio, TX, USA

4) Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA

Abstract:

This study focuses on the solar sources of  ³He-rich and ³He-poor solar energetic particle

(SEP) events observed in 2024, utilizing data from the High-Energy Telescope (HET) onboard

the Solar Orbiter mission. The HET instrument, which measures the energy spectra of energetic

particles—including helium and protons—operates in the energy range of ~7–500 MeV/nucleon

and provides critical insights into particle acceleration in the inner heliosphere. The SEP

events were selected based on specific criteria: comparable ³He^/4He ratios in Suprathermal Ion

Spectrograph (SIS) and HET at 8.2 MeV data, a Type III radio burst association with the event,

and an increase in electron flux within the 10-100 MeV energy range. These events include both

³He-rich and  ³He-poor types, providing an opportunity to explore the differences in their

solar origins.

In particular, ³He-rich events are significant as they offer valuable insights into the mechanisms

of particle acceleration and transport associated with coronal mass ejections (CMEs). Our

analysis aims to compare the energy spectra and particle composition between ³He-rich and

³He-poor events, shedding light on the underlying physical processes that govern these

phenomena. By examining the solar sources of these distinct event types, we seek to uncover the

factors contributing to variations in helium content and acceleration mechanisms.

Furthermore, we present the kinematics of associated CMEs and flare properties, offering a comprehensive

view of the dynamics behind these SEP events. This study is expected to enhance our

understanding of the role of helium-rich events in the solar wind and their potential impacts on

Earth's magnetosphere, ultimately contributing to the broader comprehension of heliospheric dynamics

and solar particle acceleration processes.

How to cite: gunaseelan, S., F. Schweingruber, R., Kühl, P., Kollhoff, A., Ding, Z., Fleth, S., Berger, L., Pacheco, J. R., Ho, G. C., Mason, G. M., Herrero, R. G., Espinosa Lara, F., Cernuda, I., Böttcher, S., Eldrum, S., and Allen, R. C.: Investigating Solar Sources of Helium-Rich and Helium-Poor SEP Events in 2024 using Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6608, https://doi.org/10.5194/egusphere-egu25-6608, 2025.

This study examines the impact of non-local phenomena on the transport of energetic particles, which are frequently observed in interplanetary space near collisionless shocks. The prevailing theory of particle acceleration at shocks, known as diffusive shock acceleration (DSA), is based on the standard diffusion equation and predicts a specific density profile for energetic particles: upstream of the shock, the density is expected to exhibit exponential growth, while downstream, it should form a constant, flat profile. However, these predictions often conflict with observations around shocks in interplanetary space. In practice, data analysis and numerical simulations  indicate a long power-law-like upstream density profile, while the downstream region exhibits a decreasing, non-flat density profile. This discrepancy leads to consider of a modified version of the ordinary Fick's law relating the macroscopic diffusive flux of energetic particles with the number density. As described by Calvo et. al (2007), in this formulation the spatial derivative of the number density is replaced by an extended spatial integration of a function depending on the density profile multiplied by a statistical weight that decreases with increasing distance from the point where the flux is being evaluated, which yields a non-local diffusive flux. Such expression is called the Fractional Fick's Law as it involves fractional order derivatives. It can be shown that substituting this fractional flux into the continuity equation recovers the Fractional Diffusion Equation describing superdiffusion, that is, an anomalous diffusion regime in which the mean square displacement of particles grows super-linearly with time. We use a numerical Fortran 90 code for evaluating the fractional flux using the trapezoidal rule for integration. After verifying that the numerical method used is consistent and correct, this code is tested using the density profiles of accelerated particles at a numerically simulated shock in two scenarios: one involving normal diffusion and the other involving superdiffusion. Notably, in both cases, a downstream negative flux is observed, indicating the presence of uphill transport, i.e., transport in the same direction as the density gradient. Finally, the fractional flux is numerically evaluated using data from the ACE and Wind spacecrafts for two different shock crossings. In both events, uphill transport is observed, which is an intriguing and counterintuitive result that allows for the correct interpretation of satellite observations, as well as shedding light on the physical processes underlying the acceleration of energetic particles at space and astrophysical shocks.

How to cite: Simone, M., Zimbardo, G., Perri, S., and Prete, G.: Fractional Fick's Law and Anomalous Transport of Energetic Particles at Interplanetary Shocks., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6809, https://doi.org/10.5194/egusphere-egu25-6809, 2025.

Solar energetic electron (SEE) events are one of the most common solar particle acceleration phenomena in the interplanetary space. Here we present a comprehensive study of SEE events with a fast-rise, fast-decay temporal profile on 2022 March 6, observed both by SolO/EPD at 0.5 AU and by Wind/3DP at 1 AU with a longitudinal separation of ~1° between the two spacecraft. SolO/EPD detect three SEE events at ~4-100 keV during 08:00 UT- 09:15 UT, while Wind/3DP only measures one SEE event at 0.6-66 keV between 08:00 UT and 13:00 UT. According to the velocity dispersion analysis, the solar injection’s start-time (peak-time) of the EPD first (third) event agrees with the solar injection’s start-time (peak-time) of the Wind/3DP event within uncertainties. Three SEE events observed by EPD exhibit, respectively, a single-power-law (SPL) energy spectrum with a power-law spectral index of β=3.4±0.1, a double-power-law (DPL) spectrum with a spectral index of β₁=4.0±0.3 (β₂=5.7±1.5) at energies below (above) a break energy of E_b=23±10 keV, and a DPL spectrum with β₁=2.9±0.9 (β₂=5.5±2.4) at energies below (above) a break energy of E_b=9±3 keV. The 3DP SEE event shows an SPL energy spectrum with β=3.4±0.2. At ~7 keV, the electron pitch angle width at half maximum is about 13-20° during the event peak-time for the three EPD events, while at 4 keV it is about 47° for the 3DP event. On the other hand, the first and third EPD events are likely accompanied by two HXR microflares measured by SolO/STIX, while the third event are probably associated with three EUV jects measured by SDO/AIA; the 3DP event is associated with the two HXR microflares and three jects. All these microflares/jets, as well as the magnetic field lines connecting to SolO and Wind, originate from the same active region (AR12957). Therefore, we can construct a formation scenario of these SEEs: the three events detected by SolO likely arise from different sources/processes at the Sun; as the electrons propagate from 0.5 AU to 1 AU, the three events merged into one event detected by Wind.

How to cite: Wang, L., Li, W., Ma, Q., Wimmer-Schweingruber, R. F., Krucker, S., and Mason, G. M.: Solar Energetic Electron Events Observed by Solar Orbiter and Wind on 2022 March 6, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7591, https://doi.org/10.5194/egusphere-egu25-7591, 2025.

Detailed analysis of solar energetic particle (SEP) events sometimes strongly suggests that the energetic particles measured by well-connected spacecraft are mainly accelerated by a coronal mass ejection (CME)-driven shock, as for example, the SEP event on 2013 August 19 or on 2022 January 20.

In this study, we analyse the relations between the solar activity and the SEP peak intensities measured by MESSENGER, STEREO and ACE spacecraft during 2010-2015. We investigate the 3D kinematic profile of the CME and associated shock wave from 1 to 15 hours and determine their main morphological (size) and dynamic (propagation and expansion speeds, acceleration) properties. We study their relationship with the main characteristics of the SEP events (for protons and electrons), such as peak flux and timing measured in situ. A summary of the results, implications for the Space Weather research, and comparison with previous works is presented.

How to cite: Rodríguez-García, L.: Acceleration of SEPs in the inner heliosphere. What CME properties account for SEP events?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8043, https://doi.org/10.5194/egusphere-egu25-8043, 2025.

Multiple interplanetary coronal mass ejections (ICMEs) and the shocks they drive sometimes form shock-ICME interaction regions, where suprathermal electrons can undergo complex and not yet fully understood physical processes. To enhance our understanding of electron acceleration and transportation in these regions, we will present a comprehensive study of a shock-ICME interaction case based on multi-spacecraft observations. From November 29th to December 2nd, 2023, four ICMEs and three ICME-driven shocks were successively observed by SolO (0.84 AU), STEREO-A (0.97 AU), and Wind (0.99 AU), with a maximum longitudinal separation of ~17°. First, we will analyze the electron pitch angle distributions to constrain scattering and/or reflection effects at each location. Secondly, we will self-consistently characterize the energy spectral features of these suprathermal electrons using a recently proposed extended pan-spectrum fitting method (Li et al., 2025). These features will help reveal the origin, acceleration, and transportation processes of suprathermal electrons observed in shock-ICME interaction regions, particularly the different physical scenarios occurring at each interaction phase. Finally, we will compare these suprathermal electrons with those observed near typical interplanetary shocks, in order to assess whether shock-ICME interaction regions provide more efficient acceleration for suprathermal electrons.

How to cite: Ma, Q. and Wang, L.: Multi-spacecraft Observations of Interplanetary Suprathermal Electrons in a Shock-ICME Interaction Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8856, https://doi.org/10.5194/egusphere-egu25-8856, 2025.

The presence of energetic electrons in the heliosphere is associated with solar eruptions, but details of the acceleration and transport mechanisms are still unknown. We explore how electrons interact with shock waves under the assumptions of shock drift acceleration (SDA), diffusive shock acceleration (DSA), and stochastic shock drift acceleration (SSDA). Consideration of the shock wave parameter space, such as shock speed, shock obliquity, shock thickness, and plasma density upstream of the shock, helps determine electron spectra and their highest energies. With suitable simulation parameters, the model is able to accelerate thermal electrons to relativistic energies and, additionally, to produce an electron beam upstream of the shock wave, a requirement for the type II radio burst seen in radio observations associated with shock waves and particle acceleration.

This presentation delves into the results of the presented model in regards to electron acceleration and transport within shock waves, contributing to our understanding of solar and interplanetary phenomena and their practical applications in space weather forecasting.

Additionally, the model is developed to be an easy-to-use open source tool for understanding observations of high energy electron populations and the ensuing highly localized radio bursts, integration to other heliosphere plasma models through wrappers, and teaching modeling of particle acceleration in a high-performance computing setting.

This study has received funding from the European Union's Horizon Europe research and innovation programme under grant agreement No 101134999 (SOLER). The presentation 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: Nyberg, S., Afanasiev, A., Vainio, R., and Vuorinen, L.: Simulating electron acceleration in shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13267, https://doi.org/10.5194/egusphere-egu25-13267, 2025.

Solar energetic particle (SEP) events with compositional anomalies such as the highly elevated ³He/⁴He ratio have been known for more than half a century, but their origin is still not well-understood.  This is largely because of the difficulty of identifying their solar sources. In solar cycle 23, thanks to the availability of high-resolution coronal images from SOHO and other missions, coronal jets were found to be the typical solar manifestation of ³He-rich SEP events observed by ACE and Wind. They were often temporally correlated with type III radio bursts and electron events, which often gave the onset times with less uncertainties than the velocity dispersions of the ³He-rich SEP events themselves.  The widely used technique has been to search for jets and related phenomena around the times of the type III bursts that occur in the interval that is estimated from ion data.  However, data from Solar Orbiter in the present solar cycle have revealed ³He-rich SEP events whose solar sources are unidentifiable with this technique because unique jets are not found at the times of the type III bursts. In some cases, it is even hard to find a type III burst. In this work, we further investigate some of these difficult cases including the late October 2022 period, trying to find some clues in high-resolution and differently scaled EUV intensity and difference images. Other possibilities will also be pursued, including subtle changes in global magnetic field configurations (that may be related to observed dropouts) and acceleration above the low corona, etc.  We also discuss how these events may change our views of the solar sources of ³He-rich SEP events that are based on previous results.

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.: On the identification of the solar sources of 3He-rich solar energetic events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13835, https://doi.org/10.5194/egusphere-egu25-13835, 2025.

Velocity dispersion (VD) is a common feature of solar energetic particle (SEP) events, in which particles with higher kinetic energies (and thus higher speeds) arrive earlier than those with lower energies. However, recent observations by the Solar Orbiter (SolO) mission have identified a series of SEP events with a previously not reported feature in which particles with higher energies arrive later, apparently exhibiting inverse velocity dispersion (IVD). We analyse several such SEP events and suggest two explanations for this effect: 1) changes in magnetic connectivity between the observer and the outward-propagating shock which continuously accelerates particles; 2) the acceleration time for higher-energy particles is longer during the diffusive shock acceleration process so that they are released later. These observations provided a first opportunity to quantify the energy-dependent release process which greatly advances our understanding of the particle acceleration process.

How to cite: Li, Y., Guo, J., Pacheco, D., Wang, Y., Temmer, M., Ding, Z., and Wimmer-Schweingruber, R. F.: The first observation of later arrival of more energetic particles during solar eruptions observed by the Solar Orbiter mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14047, https://doi.org/10.5194/egusphere-egu25-14047, 2025.

At the CLEAR space weather center of excellence, we are building a comprehensive prediction framework for solar energetic particles (SEP) events by integrating physics-based simulations, machine learning techniques, and empirical methods. A cornerstone of this framework is the Solar Wind with Field Line and Energetic Particles (SOFIE) Model, a physics-based approach designed to predict the properties of SEP events, with a focus on the time-intensity profiles across energies ranging from 1 MeV to several hundred MeV, as well as the corresponding time-evolving energy spectra.

The SOFIE model incorporates all major factors influencing the generation and propagation of SEPs. These include: 4π maps of photospheric magnetic fields, corona (1 − 20Rs), inner and middle heliosphere (0.1 AU to Jupiter’s orbit) plasma environment, magnetic connectivity with respect to the solar source, CME initiation, SEP seed population, shock acceleration mechanisms, and energetic particle transport processes.

The background solar wind plasma in the solar corona and heliosphere is modeled by the Alfven Wave Solar-atmosphere Model(-Realtime) (AWSoM(-R)) driven by the magnetic field measurement of the Sun’s photosphere. The model's background solar wind solution is continuously updated using near-real-time, hourly GONG magnetograms. In the background solar wind, the CMEs are launched employing the Eruptive Event Generator using Gibson-Low configuration (EEGGL), by inserting a flux rope estimated from the free magnetic energy in the active region. The acceleration and transport processes are then modeled self-consistently by the multiple magnetic field line tracker (M-FLAMPA). In this work, we present the prototype of the SOFIE model, showcasing its capability to predict the time-intensity profiles and time-evolving energy spectra of SEP events, demonstrated through simulations of historical SEP events.

How to cite: Zhao, L. and Gombosi, T. and the CLEAR Team: Forecasting Time-Intensity profiles of Solar Energetic Particles using the Solar Wind with Field Lines and Energetic Particles (SOFIE) Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14356, https://doi.org/10.5194/egusphere-egu25-14356, 2025.

We report the energetic proton dynamics around an interplanetary shock driven by a coronal mass ejection (CME). We use the high-resolution EPT instrument onboard the Solar Orbiter to study the local acceleration process of energetic protons. The interplanary shock is observed by the Solar Orbiter on March 14th 2023 at 0.6 au. A magnetic structure is also present 7-minute upstream the shock. The magnetic structure manifests as a B_N reservsal and mangetic depression with asymmteric magnetic magnitude on each side. A detailed analysis suggests that the magnetic structure is possibly related to a magnetic reconnection. The magnetic reconnection region is partially crossed by the Solar Orbiter, which passes through the reconnection upstream, the diffusion region and an extended exhaust region in sequence. Upstream the structure, the proton differential flux anisotropy is constant which is dominated by the parallel-propagating energetic protons from the shock. Interestingly, a bipolar-like flux anisotropy is present between the magnetic structure and the shock, while B_R>0 is satisfied all the time. This suggests that some local physical processes may play a role in proton acceleration due to the presence of magnetic reconnection. We also compare the flux spectra upstream and downstream the structure, the spectral indices of which are very different. Our work highlights the importance of magnetic structures/reconnection in particle acceleration, even when the structure is close to the shock.

How to cite: Zhu, X. and Yang, L.: Proton acceleration during the interaction of magnetic structure with interplanery shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14525, https://doi.org/10.5194/egusphere-egu25-14525, 2025.

The primary source of suprathermal particles is in the solar corona. These particles are generally considered a seed population to be accelerated to solar energetic particles by coronal mass ejection shocks. Their distribution in the corona is vital for us to understand the production of solar energetic particles. During propagation through interplanetary space, the properties of suprathermal particles can change dramatically by various transport mechanisms, such as scattering, adiabatic cooling, and stochastic acceleration. To link observations made in the interplanetary space to particle distribution in the solar corona, we have developed a focused transport to calculate the propagation effect. This paper will present focused transport model calculations to show how particle scattering and acceleration can affect the evolution of the suprathermal particle spectrum and anisotropy in interplanetary space.

How to cite: Zhang, M.: A focused transport model of suprathermal particles in the interplanetary medium, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14948, https://doi.org/10.5194/egusphere-egu25-14948, 2025.

A sustained gamma-ray emission (SGRE) event from the Sun was observed on 2024 September 9 by the Large Area Telescope (LAT) on Fermi satellite at energies >100 MeV. SGRE requires the precipitation of >300 MeV protons deep into the photosphere. The SGRE event was associated with a shock-driving coronal mass ejection (CME) that originated ~40 degrees behind the east limb of the Sun. The event was observed by multiple spacecraft such as the Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO), Parker Solar Probe (PSP),  Solar Orbiter (SO), Solar Dynamics Observatory (SDO), Wind, and GOES, and by ground-based radio telescopes. Based on observations from SO’s Spectrometer Telescope for Imaging X-rays (STIX), we estimate that the eruption location to be S17E129. GOES observed a large solar energetic particle (SEP) event but only in the >10 MeV energy channel because of poor magnetic connectivity. However,  SO was well-connected to the eruption region and hence observed high-energy particles.  We infer that >300 MeV particles from the extended shock precipitated on the frontside of the Sun to produce the SGRE event. Forward modeling of the CME using SOHO and STEREO observations indicate that the CME flux rope had  high initial acceleration of the CME (`2.5 km s^-2), high speed (2500 km s^-1), and associated with type II bursts in the metric to decameter-hectometric (DH) wavelengths. All these properties are characteristic of frontside CMEs that are associated with SGRE events.  Furthermore, the durations of SGRE and type II burst are similar as in longer duration (>3 hours) SGRE events.

How to cite: Gopalswamy, N., Makela, P., Xie, H., Akiyama, S., Yashiro, S., Bale, S., Wimmer-Schweingruber, R., and Krucker, S.: Transport of high energy protons from a backside solar eruption to produce gamma-ray emission on the front side of the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16916, https://doi.org/10.5194/egusphere-egu25-16916, 2025.

The Sun constantly emits a stream of charged particles, e.g. electrons and protons which is called the solar wind. In addition to this low energetic background, Solar Energetic Particle (SEP) events occur and are observed by Solar Orbiter in the inner heliosphere. Here, we are interested in the electron component of SEP events. The Electron Analyzer System (EAS) and the SupraThermal Electron Proton (STEP) sensor on Solar Orbiter measure electrons in the energy range from 1 eV to 5 keV and 2 keV to 60 keV, respectively. The field of view of STEP overlaps with the field of view of the EAS 1 sensor head. SEP events are identified in the STEP data and compared with the electron signal in the EAS data. We utilize this overlap to evaluate the electron measurements in STEP and EAS for at least one selected SEP event. During electron SEP events and times where most of the higher energy bins in EAS 1 are populated, the one dimensional differential energy flux spectra show an overlap within the respective uncertainties. SEP events typically show a velocity dispersion. In a Velocity Dispersion Analysis (VDA), for each energy channel an onset time for the event is determined. Due to the reduced quantum efficiency in the highest energy channels of EAS, higher fluxes are required to detect an SEP event in EAS than in STEP. To increase the signal to noise ratio for the SEP events, EAS bins in all three measurement dimensions, i.e. azimuth, elevation and energy, are chosen depending on the pitch angle coverage of the event. Anisotropic SEP events cover fewer instrumental bins in EAS than isotropic events. To test the uncertainty of the onset times depending on the method several approaches are compared, including a manual identification and the Poisson CUSUM method on the EAS Level 1 count data. The selected event illustrates the importance of considering an energy dependent minimal detection threshold in VDA since VDA relies on the assumption that the earliest detected particles for each energy are indeed the first particles that reach the spacecraft. The VDA is then applied to the STEP data and the results are compared with the EAS results. The instrumental and quantum efficiency driven onset times influence the approximation of the release time of the accelerated particles at the acceleration time, i.e. in the solar corona while neglecting transport effects along the way to the spacecraft. All in all combining EAS and STEP gives us several advantages. (1) It allows us to evaluate the calibration of both instruments. (2) With EAS the VDA is extended to lower energies. (3) In addition the full 360° field of view of EAS helps us to evaluate the anisotropy of SEP events outside the field of view of STEP which are strong enough to produce a signal in the higher EAS energy bins.

How to cite: Jentsch, E., Heidrich-Meisner, V., and Wimmer-Schweingruber, R. F.: Investigating electrons in SEP events observed by Solar Orbiter/EPD/STEP and Solar Orbiter/SWA/EAS with Velocity Dispersion Analysis , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18931, https://doi.org/10.5194/egusphere-egu25-18931, 2025.

Solar energetic particles (SEPs) accelerated in coronal mass ejection (CME)-driven shocks are a critical factor in space weather hazards, yet significant gaps remain in understanding their acceleration mechanisms. While diffusive shock acceleration (DSA) is widely accepted as the primary process, the role of adiabatic focusing in spatially inhomogeneous magnetic fields is poorly understood within one-dimensional DSA theories. Using a Monte Carlo approach within a one-dimensional oblique shock framework, we investigated the effects of adiabatic focusing and particle escape of SEPs. Our model incorporates realistic magnetic field geometries and plasma parameters derived from the COolfluid COroNa UnsTructured (COCONUT) model. The results reveal that magnetic field inhomogeneities significantly influence particle acceleration efficiency and escape dynamics, highlighting the critical role of focusing effects. These findings provide new insights into SEP transport and acceleration, advancing our ability to accurately model particle behavior in CME-driven shocks.

How to cite: Annie John, L., Vainio, R., Afanasiev, A., and Poedts, S.: Modeling SEP Acceleration and Transport: A 1D Framework with COCONUT-Derived parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19421, https://doi.org/10.5194/egusphere-egu25-19421, 2025.

Data-driven simulations of the solar corona have gathered traction in recent years for modelling the destabilisation of magnetic flux ropes (MFRs). To correctly apply and interpret results from these modelling efforts, it is crucial to understand how MFRs behave in such simulations and why they exhibit certain behaviour. For example, one aspect is to understand what effect does the evolution of the photospheric magnetic field have on the MFR system once it has reached an already unstable state. To probe the effect of data-driving, we first run a fully data-driven time-dependent magnetofrictional (TMF) simulation. Subsequently, we systematically relax the model (i.e., turn off the photospheric driving) at different times and analyse the MFRs' behaviour. In addition to the magnetofrictional relaxation, we also employ a zero-beta magnetohydrodynamics (MHD) model for the relaxation part of the analysis and compare the differences. To extract the simulated MFRs we use our novel Graphical User Interface for Tracking and Analysing flux Ropes (GUITAR). We find that even for MFRs that have been found to be eruptive in the relaxation simulations, MFR properties can greatly vary depending on the time of relaxation. Furthermore, there are striking differences between magnetofrictional and MHD relaxation simulations; not all initial TMF states which are eruptive in MHD are eruptive in the magnetofrictional relaxation. Furthermore, not only do the MFR properties significantly vary, but also the interpretation of which instability is at play varies between the two modelling prescriptions. 

How to cite: Wagner, A., Price, D. J., Bourgeois, S., Daei, F., Pomoell, J., Poedts, S., Kumari, A., Barata, T., Erdélyi, R., and Kilpua, E. K. J.: Magnetic flux rope evolution and stability in data-driven coronal magnetic field simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1591, https://doi.org/10.5194/egusphere-egu25-1591, 2025.

In the present paper, to understand the role of solar winds in the origin of the coronal mass ejections (CMEs)  Phenomena we have studied the relationship between the Extreme Ultraviolet Imaging Telescope (EIT) waves phenomena with solar flares, coronal holes, solar winds, and CMEs events. The EIT/ SOHO instrument recorded 176 EIT events during the above period (March 25, 1997-June 17, 1998) and the EIT waves list was published by Thompson & Myers (2009). After temporal matching of EIT wave events with CME phenomena, we find that corresponding to 58 EIT wave events, no CME events were recorded and thus we excluded 58 EIT wave events from the present study. Out of 176 EIT wave events, only 106 are accompanied by CME phenomena. The correlation study of the speed of EIT wave events and CMEs events of 106  events shows poor correlation r= 0.32, indicating that the EIT waves and CMEs events do not have a common mechanism of origin and also indicate that some other factor is working in the formation of  CMEs from EIT waves. Further, we have also matched the spatial matching EIT wave sources as indicated by Thomson & Myers (2009) with CHs and flares and found that CMEs appear to be associated with EIT wave phenomena and CHs.  Earlier  Verma & Pande (1989) and  [3] Verma (1998) indicated that the CMEs may have been produced by some mechanism in which the mass ejected by solar flares or active prominences gets connected with the open magnetic lines of CHs (source of high-speed solar wind streams) and moves along them to appear as CMEs. Most recently Verma & Mittal (2019) proposed a methodology to understand the origin of CMEs through magnetic reconnection of   CHs open magnetic field and solar flares.  In the present paper, we proposed a scenario/ 2-dimensional model in which the origin of CMEs through reconnection of EIT waves and solar winds coming from the CHs and also found that the calculated CMEs velocity after reconnection of EIT waves and solar winds coming from the CHs are in very close to the observed CMEs linear velocity. We also calculated the value of the correlation coefficient between the observed linear velocity of CME events and the calculated value of CME velocity after reconnection and found the value as r=0.884. The value of correlation as r=0.884 is excellent and supports the proposed methodology.  Finally, we have also discussed the role of solar wind phenomena in the formation of CMEs phenomena with other solar phenomena, in the latest scenario of solar heliophysics phenomena.

REFERENCES

Thompson, B. J.  &  D. C.  Myers, D. C. (2009) Astrophys. J. Suppl. 183, 225.

 Verma, V. K.  &  Pande, M. C. (1989)  Proc. IAU Colloq. 104  (Poster Papers) , p.239.

 Verma, V. K. (1989)  J.  Geophys Indian Union, 2, 65

Verma, Virendra & Mittal, N.  (2019) Astronomy Letters, 45, 164-176.

How to cite: Verma, V.: Relationship among EIT Waves, Coronal Mass Ejections, Solar Flare, Coronal Holes, and Solar Wind Phenomena , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1798, https://doi.org/10.5194/egusphere-egu25-1798, 2025.

A new shock-capturing tool is introduced to study the coronal mass ejection-driven shock originating from the low solar corona. Multi-spacecraft observations, including SOHO, SDO, GOES, ACE near Earth, and STEREO-A/B, are used for model-data comparison and validation. We show the simulated observables, including extreme ultraviolet and white-light images, shock properties, as well as proton time-intensity profiles and energy spectra, and compare them to observations. Our simulation results demonstrate the efficient integration of the Poisson bracket scheme with a particle solver in the Space Weather Modeling Framework (SWMF) for simulating a practical SEP event, as well as the capability of capturing a time-evolving shock surface in the SWMF. 

How to cite: Liu, W., Gombosi, T., Sokolov, I., and Zhao, L. and the CLEAR Team: Not All Shocks Are Created Equal: Shock Acceleration During the 2013 April 11 Solar Energetic Particle Event, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3351, https://doi.org/10.5194/egusphere-egu25-3351, 2025.

Interplanetary coronal mass ejections often carry large-scale magnetic clouds, which display internal substructures and small-scale fluctuations. These complex multi-scale clouds represent the main drivers of geomagnetic storms at Earth, and the amplitude, coherence and variability of their magnetic field all contribute to their geoeffectivity.

We present high resolution simulations of a magnetic cloud interacting with turbulent fluctuations while propagating in the spherically expanding solar wind; we investigate the effects of turbulence on the internal dynamics and magnetic field variability. Our simulations employ the expanding box model, a semi-lagrangian numerical approach that allows to follow the evolution of a parcel of plasma in the spherical solar wind flow, decoupling the small-scale internal dynamics from the large-scale motion.

We recover observed features such as the radial expansion of the structure and the low-temperature and low-beta signatures of magnetic clouds, together with a quite rich internal dynamics. We also find that turbulent reconnection and field transport produce smaller secondary magnetic flux ropes, possibly enhancing the cloud's geoeffectivity; this behaviour might also account for the relatively small magnetic correlation lengths which have been estimated in interplanetary magnetic clouds.

How to cite: Sangalli, M., Verdini, A., Landi, S., and Papini, E.: The turbulent evolution of an interplanetary magnetic cloud in the expanding solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4434, https://doi.org/10.5194/egusphere-egu25-4434, 2025.

Coronal Mass Ejections (CMEs) are the major sources of severe space weather events, causing potential damages to orbital and ground assets including satellites, space stations and power grids. To avoid the huge economic losses, it is crucial to understand the propagation of CMEs and derive physical parameters especially in 3-dimension for better prediction of CME propagation. We have developed an algorithm to automatically reconstruct CME structure based on double view-point observations and machine learning technique. The algorithm consists of three steps: region acquirement, model construction, function optimization. First, we train two Convolutional Neural Networks (CNNs) to identify the CME in visual observations from the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) COR-2 Coronagraph onboard the Solar TErrestrial RElations Observatory (STEREO), respectively. The CME region information is then leveraged with the Principal Component Analysis algorithm and Otsu's method. Next, we establish the Graduated Cylindrical Shell (GCS) model and project it into the field of view of the coronagraphs. In the final step, we construct a function to measure the difference between the image of the GCS model and the CME region. Then the optimal 3D CME parameters can be obtained. Several CME events are chosen to show the accuracy and effectiveness of our method. We also conduct a statistical analysis on 127 CME events from 2007 to 2014 to investigate the 2D and 3D parameters of CMEs. Our method can be used to provide CME initial parameters in magnetohydrodymic simulations for accurate prediction and understanding of CME.

How to cite: Lin, R., Yang, Y., and Shen, F.: An algorithm to derive CME 3D parametersbased on machine learning and double view-point observation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4695, https://doi.org/10.5194/egusphere-egu25-4695, 2025.

  Magnetic helicity is an important concept in solar physics, with a number of theoretical statements pointing out the important role of magnetic helicity in solar flares and coronal mass ejections (CMEs). Here we construct a sample of 47 solar flares, which contains 18 no-CME-associated confined flares and 29 CME-associated eruptive flares. We calculate the change ratios of magnetic helicity and magnetic free energy before and after these 47 flares. Our calculations show that the change ratios of magnetic helicity and magnetic free energy show distinct different distributions in confined flares and eruptive flares. The median value of the change ratios of magnetic helicity in confined flares is -0.8%, while this number is -14.5% for eruptive flares. For the magnetic free energy, the median value of the change ratios is -4.3% for confined flares, whereas this number is -14.6% for eruptive flares. This statistical result, using observational data, is well consistent with the theoretical understandings that magnetic helicity is approximately conserved in the magnetic reconnection, as shown by confined flares, and the CMEs take away magnetic helicity and energy from the corona, as shown by eruptive flares. 

How to cite: Wang, Q., Zhang, M., Yang, S., Yang, X., and Zhu, X.: Change Ratios of Magnetic Helicity and Magnetic Free Energy During Major Solar Flares , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5088, https://doi.org/10.5194/egusphere-egu25-5088, 2025.

We conducted a comprehensive statistical analysis of the evolution of coronal mass ejections (CMEs) and their embedded magnetic obstacles with and without driving a sheath. Specifically, we explored the thermal and magnetic pressure within the different CME regions, alongside with the open solar flux (OSF) through various solar cycles. Preliminary results indicate significant differences in the fluctuations of the mean and standard deviation of the magnetic field between solar cycles 23 and 24. The analysis reveals that the sheath total pressure is higher than that of magnetic obstacles, with a notable decrease in pressure from solar cycle 23 to 24. Likewise, the OSF shows a decrease from solar cycle 23 to 24, correlating with the observed CME pressure trends. These findings suggest that the characteristics of ICME sheath regions and magnetic obstacles vary depending on the ambient solar wind conditions present during each individual cycle. This research represents an initial step towards a more comprehensive understanding of the dynamics and variability of ICME sheaths, with implications for space weather forecasting and modeling.

How to cite: Larrodera, C., Temmer, M., and Owens, M.: Investigating the Dynamics and Variability of ICME Sheaths and Magnetic Obstacles Across Solar Cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6729, https://doi.org/10.5194/egusphere-egu25-6729, 2025.

We investigate the effects of interplanetary coronal mass ejections (ICMEs) on the interplanetary (IP) medium, namely the solar wind (SW) and the interplanetary magnetic field (IMF). Our objective is to quantify how ICMEs alter the properties of the IP medium and to determine the degree of preconditioning. The latter occurs when ICMEs modify the IP medium in a way that enables subsequent ICMEs to propagate more efficiently, experience reduced deceleration, and retain higher energy over greater distances. This phenomenon has been proposed in the past to explain some of the shortest ICME travel times, the most intense geomagnetic storms, and the highest-energy ICME ever observed in situ.

Our analysis is based on a statistical study of a carefully curated sample of events. We examine the IP medium during 48-hour intervals before and after the passage of ICMEs. On average, the post-ICME solar wind exhibits reduced density and dynamic pressure, along with increased total velocity. Meanwhile, the trailing IMF becomes more intense and displays a stronger radial alignment. These findings indicate that even relatively moderate ICMEs can significantly precondition the IP medium, potentially influencing the behavior and impact of subsequent events.

How to cite: Kajdic, P., Temmer, M., and Blanco-Cano, X.: Statistical Analysis of Preconditioning in the Interplanetary MediumInduced by Isolated ICMEs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7448, https://doi.org/10.5194/egusphere-egu25-7448, 2025.

The connection between coronal mass ejections (CMEs) and solar flares has been studied statistically, but the details of this relationship remain largely unknown. Soft X-rays provide us a unique depiction of eruption dynamics due to the coronal first ionization potential (FIP) bias: abundances of low FIP elements are observed to peak at flare onset, and decrease abruptly towards photospheric values during the impulsive phase before recovery. Recovery times have been linked to the time when the plasma is trapped within the magnetic field, suggesting that CMEs delay abundance recovery. This provides a useful tool for studying the characteristics and dynamics of flares and CMEs and their effects on each other.

This study aims to connect flare characteristics to CME properties using soft X-ray spectroscopy and hard X-ray imaging. The temporal evolution of plasma parameters and elemental abundances during the eruption event are analyzed with soft X-ray data from the SUNSTORM 1 X-ray Flux Monitor for CubeSats (XFM-CS). Evolution of the X-ray loop emission source is investigated with a time-series analysis of image reconstructions utilizing The Spectrometer Telescope for Imaging X-rays (STIX) instrument on board Solar Orbiter. CME kinematics are analyzed with a variety of remote-sensing data. The resulting study shows that emission from a post-CME looptop source significantly affects eruption dynamics by slowing down abundance recovery, and relates this evolution to the flare profile. 

How to cite: Takala, S., Lehtolainen, A., Kilpua, E., Palmroth, M., Mitchell, J., Warmuth, A., and Huovelin, J.: Quantifying CME effects on plasma parameters and elemental abundance recovery during a flare event with X-ray spectroscopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8335, https://doi.org/10.5194/egusphere-egu25-8335, 2025.

Magnetic clouds (MCs) are closed magnetic structures embedded in interplanetary coronal mass ejections (ICMEs). They have physical interest by their own, and, more recently, by their Earth magnetosphere effects.

Data from the period 2008-2014 Stereo A and B (MAG, PLASTIC and SWEA PAD sensors) and from different ICME catalogues have been used to elaborate an exhaustive list of MCs.

To establish the boundaries of those  MCs we have used six criteria, like a low-beta plasma or higher magnetic field intensity than the values in calm solar wind conditions.

In this presentation we show the orientation of the axis (latitude and longitude) of all MCs in that period of time as determined by the well-known Hidalgo model for their magnetic topology.

How to cite: Jiménez Cuenca, J. J., Arrazola Pérez, D., Blanco Ávalos, J. J., and Hidalgo Moreno, M. Á.: Orientation of the axis of MCs observed by STEREOs in time period 2008-2014, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11530, https://doi.org/10.5194/egusphere-egu25-11530, 2025.

One of the major challenges in space weather forecasting is to reliably predict the magnetic structure of interplanetary coronal mass ejections (ICMEs) in the near-Earth space. In the framework of global MHD modelling, several efforts have been made to model the CME magnetic field from Sun to Earth. However, it remains challenging to deduce a flux-rope solution that can reliably model the magnetic structure of a CME. Aiming to improve the space-weather forecasting capability, we implement a new flux-rope model in “European heliospheric forecasting information asset” (EUHFORIA). Our flux-rope model includes an initially force-free toroidal flux-rope that is embedded in the low-coronal magnetic field. The embedding technique adds a significant novelty to the state-of-the-art as it preserves the continuity condition of the magnetic field at the flux-rope boundary and maintains the force-free solution of the flux rope. The dynamics of the flux rope in the low and middle corona are solved by a non-uniform advection constrained by the observed kinematics of the event. This results in a global non-toroidal loop-like magnetic structure that locally manifests as a cylindrical structure. At heliospheric distances, the evolution is modeled as a MHD process using EUHFORIA. We assess our model results on several ICMEs, including cases of interacting events. Comparing the model results with the in-situ magnetic field configuration of the ICME at 1 au, we find that the simulated magnetic field profiles of the flux-rope are in very good agreement with the in-situ observations. Therefore, the framework of toroidal model implementation as developed in this study could prove to be a major step-forward in forecasting the geo-effectiveness of CMEs.

How to cite: Sarkar, R., Pomoell, J., and Kilpua, E.: Modelling the Sun-to-Earth Propagation of CMEs Using a Novel Flux-Rope Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11725, https://doi.org/10.5194/egusphere-egu25-11725, 2025.

Solar Energetic Particles (SEPs) represent a natural hazard for the Earth environment, from the instruments on board spacecraft to the electricity networks and astronauts life. These events are produced by solar eruptions such as flares and Coronal Mass Ejections (CMEs) that spread into the interplanetary space. In this study, we analyze energetic particle fluxes at CME-driven shocks measured in-situ by multiple satellites at different radial distances and longitudes and derive the parameters of the shocks such as the compression ratio, the angle between the magnetic field and the normal to the shock, and the Mach numbers. When it is possible, we compare these quantities with the shock parameters computed at the coronal sources using remote-sensing observations. Following the evolution of the parameters characterizing the CMEs from the source to space will help space weather models to improve predictions on the arrival of SEPs at the Earth. Magnetic field turbulence is also investigated by calculating the power spectral density, the autocorrelation function, in order to derive the turbulence correlation length and the level of magnetic intermittency. This study is achieved in the context of the research project “Data-based predictions of solar energetic particle arrival to the Earth” funded by the Italian Ministry of Research under the grant scheme PRIN-2022-PNRR.

How to cite: Chiappetta, F., Perri, S., Nisticò, G., Pucci, F., Malara, F., Sorriso-Valvo, L., and Zimbardo, G.: Analysis of the CME-driven shocks detected through in-situ measurements and remote-sensing observations by multi-spacecraft , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12587, https://doi.org/10.5194/egusphere-egu25-12587, 2025.

CMEs interact with the solar wind and heliospheric magnetic field which influence their propagation, expansion as well as internal magnetic structure. We understand these processes on a global level, however we are still lacking a detailed qualitative and quantitative understanding of the CME evolution on a level that could result in a reliable forecast. Our limitations are influenced by uncertainties in measurements as well as uncertainties in associating remote-to-insitu events and observation-to-model comparison. These uncertainties affect not only inputs to our CME propagation models, but also evaluation of the outputs. As an example, we present the newly developed adaptation of the widely used drag-based model (DBM, Vrsnak et al., 2013) for 3D geometry, which should in theory provide more accurate forecast. However, we show that for an arbitrary evaluation sample it does not provide significantly different results from its 2D counterpart.

How to cite: Dumbovic, M.:  Why doesn’t model improvement result in better forecast: the 3D drag-based model for CME propagation example, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12767, https://doi.org/10.5194/egusphere-egu25-12767, 2025.

The Eruptive Event Generator – Gibson-Low (EEGGL) generates an unstable 3D flux rope from a given synoptic solar magnetogram that can be inserted into magnetohydrodynamic (MHD) coronal simulations for coronal mass ejection (CME) initiation. This model has been used extensively for CME simulation, both for studying the evolution of the CME itself and for generation of solar energetic particles that propagate throughout the heliosphere. EEGGL relies on empirical fitting of test events to find the relationship between the magnetogram, CME parameters, and flux rope geometry and strength. As part of the CLEAR NASA Center of Excellence at the University of Michigan, validation and enhancement of EEGGL is a key deliverable. In this presentation, we provide results from the updated EEGGL with improvements to enhance the robust nature of the code. A statistical validation is performed comparing synthetic white-light coronal images generated by the simulation to coronagraph observations, focusing on CME speed and strength. While past publications have occasionally optimized the flux rope based on a priori knowledge, we use larger statistics from agnostic runs to evaluate model performance. Such steps prepare the model for running in a fully-automated low-latency configuration.

How to cite: Keebler, T., Zhao, L., Jin, M., Sokolov, I., and Sachdeva, N.: Evaluation of the Gibson-Low flux rope generation method in coronal mass ejection simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13015, https://doi.org/10.5194/egusphere-egu25-13015, 2025.

Coronagraphic observations enable the monitoring of coronal mass ejections (CMEs) through scattered light from free electrons. These observations allow for the estimation of the density, velocity, and propagation direction of the ejected plasma, which is critical for space weather forecasting. However, determining the 3D plasma distribution from 2D imaging data is challenging due to the optically thin medium and the complex image formation processes based on scattered light.

We present a method for 3D tomographic reconstructions of the heliosphere using multi-viewpoint coronagraphic observations. Our method leverages Neural Radiance Fields (NeRFs) to estimate the electron density in the heliosphere through a ray-tracing approach. The model is optimized by iteratively fitting the time-dependent observational data, accounting for the underlying Thomson scattering of image formation.  Typically, tomographic reconstructions based on a limited number of viewpoints are insufficient to constrain the 3D plasma distribution. To address this, we introduce additional physical constraints, including continuity, solar wind speed, and propagation direction, to enable a physics-informed tomographic reconstruction.

We utilize synthetic observations of CMEs based on GAMERA simulations to evaluate the model's performance with respect to viewpoint positions, physics-based constraints, and CME configurations. The results demonstrate that our method can reliably estimate the CME propagation direction and velocity using two viewpoints. Furthermore, we show that additional viewpoints can be seamlessly integrated, enhancing the reconstruction of the plasma distribution in the heliosphere and improving CME forecasting capabilities. This research underscores the value of physics-informed methods for 3D CME tomography, paving the way for advanced space weather monitoring.

How to cite: Jarolim, R., Hung, C.-M., Lamdouar, H., Sanner, M., Stevenson, E., Veitch-Michaelis, J., Bouri, I., Malanushenko, A., Ruzicka, V., and Urbina-Ortega, C.: Tomographic Reconstructions of Coronal Mass Ejections with Physics-Informed Neural Radiance Fields, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13105, https://doi.org/10.5194/egusphere-egu25-13105, 2025.

Due to high solar activity, since the launch of Solar Orbiter about 5 years ago, at least 50 solar coronal mass ejection (CME) events have been observed at multiple spacecraft in situ, and more than 70 with at least one in situ and one imaging instrument. This type of measurement is of high importance for several reasons, which are relevant to improve both our basic understanding of the general nature of CMEs and to enhance our space weather forecasting capabilities. I will give an overview of the most important results so far using CME multipoint observations. They have been enabled by especially combining the in situ magnetic field observations made by Solar Orbiter, Parker Solar Probe, BepiColombo, near-Earth spacecraft at L1 and STEREO-A. We demonstrate how observations in the inner heliosphere allow us to create a power law for CME evolution seamlessly covering 0.07 to 5.4 au. We discuss results on flux rope coherence in interplanetary space, which is exceedingly relevant for understanding the 3D magnetic flux rope shape, and the applicability of upstream monitors for CME forecasting. Our living catalogs ICMECAT and LineupCAT for single and multipoint CME observations by various spacecraft are presented and are encouraged to be used by the research community. The most recent addition to the fleet of spacecraft enabling these groundbreaking observations is the PUNCH mission planned to be launched in February 2025, which enables polarized heliospheric imaging from Earth orbit. Here, new possibilities to derive the CME 3D structure in combination with in situ magnetic field observations of the same CME emerge. 

How to cite: Möstl, C., Weiler, E., Davies, E. E., Rüdisser, H. T., Amerstorfer, U. V., Amerstorfer, T., Le Louëdec, J., Bauer, M., Horbury, T. S., and Lugaz, N.: Multipoint coronal mass ejection events in solar cycle 25, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13215, https://doi.org/10.5194/egusphere-egu25-13215, 2025.

Numerical modeling of the solar wind and Coronal Mass Ejections (CMEs) is a vital tool for both space weather predictions as well as improving the understanding of CME evolution in the solar wind. We utilize the state-of-the-art 3D MHD model - Alfven Wave Solar atmosphere Model (AWSoM) and a self-consistent CME model - STITCH (Statistical Injection of Helicity Condensation) to simulate the global background solar wind plasma and initiate a CME eruption on the Sun. The STITCH method forms sheared arcades through helicity injection driven purely by photospheric magnetic field observations. These models are utilized to perform a detailed study of the structure and evolution of a CME propagating in the solar wind from the Sun to the Earth using 3D simulation results to probe multiple viewpoints in the corona and the inner heliosphere.

How to cite: Sachdeva, N., van der Holst, B., Antiochos, S., Manchester, W., Huang, Z., and Toth, G.: Evolution of Coronal Mass Ejections in the Solar Wind using Data-Driven Numerical Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13899, https://doi.org/10.5194/egusphere-egu25-13899, 2025.

Understanding mesoscale structures in the solar wind background and coronal mass ejections (CMEs) is one of the science objectives of the PUNCH mission to be launched in early 2025. We do not fully understand what processes form these structures and where as well as how they evolve from the outer solar corona through the heliosphere. In anticipation of the detailed high-sensitive large field-of-view PUNCH imaging, MHD simulations capable of modeling the global inner heliosphere while simultaneously resolving structures at mesoscales can help predict what structures we can expect to form in certain CME-solar wind interaction scenarios. We use an efficiently parallelized and scalable physics-based MHD model with numerical algorithms featuring high resolving power to perform global inner heliosphere simulations with CMEs with a high resolution. Using the GAMERA-Helio inner heliosphere model coupled with the Gibson-Low CME model, we model the evolution of a wide and fast CME flux rope through a realistic solar wind background. The simulation resolves spatial scales down to ~0.1 solar radii (~10 Earth radii), enabling, to study mesoscale structures that form in the CME-solar wind interaction in a global context. We discuss the development of ripples and irregularities at the CME shock, compressions, and magnetic field fluctuations in the CME-driven sheath, and connect these structures with the interaction between the CME and background solar wind flows. By computing the total and polarized white light brightness from high-resolution GAMERA MHD simulations, we show how mesoscale structures that form at the CME-solar wind interface appear in synthetic images in the FOV of the PUNCH mission.

How to cite: Provornikova, E., Merkin, V., Samara, E., Braga, C., Malanushenko, A., McCubbin, A., and Gibson, S.: High-Resolution Simulations of CME-Solar Wind Interaction in The Heliosphere: A Focus On Mesoscale Structures For PUNCH, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14092, https://doi.org/10.5194/egusphere-egu25-14092, 2025.

Coronal mass ejections (CMEs) are the leading driver of space weather and it is vital for space weather forecasting to benefit from a comprehensive understanding of the conditions in which CMEs are initiated. The rotation of sunspots around their umbral center has long been considered an important condition leading to CMEs. To unveil the underlying mechanisms, we carried out a data-driven MHD simulation for the event of a large sunspot with a rotation of days in a solar active region, NOAA 12158, which produced two homologous halo CMEs. Our simulation successfully follows the long-term quasi-static evolution of the active region and the eruptions, with magnetic field structure being highly consistent with the observed coronal emission. The onset time of the simulated eruption is a very good match to the observations. The simulation shows that through the successive rotation of the sunspot, the coronal magnetic field is sheared with a vertical current sheet created progressively. Once fast reconnection sets in at the current sheet, the eruption is instantly triggered, with a highly twisted flux rope originating from the eruption, forming the CME. This data-driven simulation stresses magnetic reconnection as the key mechanism in CMEs resulting from sunspot rotation.

How to cite: Jiang, C.: Data-driven MHD simulation of a sunspot-rotating active region leading to homologous CMEs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14094, https://doi.org/10.5194/egusphere-egu25-14094, 2025.

In this work, we use multispacecraft observations and a high-resolution numerical simulation to understand the CME event on 2021 December 4, with an emphatic investigation of its three-part structure and rotation. This event is observed as a partial halo CME from the back side of the Sun by coronagraphs and reaches the BepiColombo spacecraft and the MAVEN/Tianwen-1 as a magnetic flux-rope-like structure. It is disclosed that in the solar corona the CME, with no signatures of a prominence at the beginning, evolves into a three-part morphology. The moving and expanding CME produces the high-density front, and the CME’s differential expansion rates lead to the distinct rarefaction rates of the plasma, which results in the formation of the low-density cavity and the high-density core. It is also found that when CME arrives in the interplanetary space, the downside and the right flank of the CME moves with the fast solar wind, and the upside does in the slow-speed stream. The different parts of the CME with different speeds generate the nonidentical displacements of its magnetic structure, resulting in the rotation of the CME in the interplanetary space. These results provide new insight into interpreting CMEs ’ structures and dynamics during their traveling through the solar corona into the heliosphere.

How to cite: Yang, L., Ma, M., Shen, F., Feng, X., Shen, C., Chi, Y., Wang, Y., Xiong, M., Zhou, Y., Zhang, M., and Zhao, X.: Three-part Structure Formation & Interplanetary Rotation of Mars-Directed Coronal Mass Ejection on 2021 December 4, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14219, https://doi.org/10.5194/egusphere-egu25-14219, 2025.

Filament eruptions are one of the most e ective methods for generating coronal mass ejections (CMEs) and solar flares. Consequently, understanding their triggering mechanisms and eruption dynamics is a key focus in solar activity research. This study presents a statistical analysis of  filament eruption events and draws the following conclusions: 1) Quiescent filaments (QSFs) are rarely triggered by the reconnection process. When QSFs do experience reconnection, they are typically found in stronger magnetic environments. 2) Reconnection-triggered filaments produce faster CMEs compared to non-reconnection-triggered filaments, affecting both active region filaments (ARFs) and other filaments. Among these, reconnection-triggered intermediate filaments (IFs) exhibit the highest average CME velocity, surpassing ARFs. 3) Most QSFs undergo a prolonged slow rise phase without significant observable signals. The exact underlying mechanism remains unclear, but the helicity condensation theory is proposed as a possible explanation. 4) The average velocity of eruptive QSFs associated with detectable flares is higher than that of ARFs. This suggests that in weaker magnetic environments, reconnection can significantly enhance CME propagation, whereas in active regions, stronger reconnection is required to achieve similar effects.

How to cite: Zou, P.: A statistical study of solar  lament eruptions based on the kinetic evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14222, https://doi.org/10.5194/egusphere-egu25-14222, 2025.

Coronal mass ejections (CMEs) undergo multiple evolutionary processes during their propagation through the heliosphere, such us deformation, rotation, and erosion. These processes may result from interactions with the ambient solar wind or with other large-scale structures. However, due to the limitation of single-point measurements of solar wind plasma or interplanetary magnetic field (IMF) properties, it is extremely challenging to infer their topology or evolutionary processes that may have undergone.

Suprathermal electrons are continuously emerging from the solar corona along the IMF. They travel faster than the solar wind, and when comparing their intensity to the direction of the IMF (i.e. analysing their pitch-angle distributions, PADs), we can extract fundamental information about the IMF topology and the conditions of the solar wind plasma. Therefore, understanding the behaviour of suprathermal electron PADs during CME encounters sheds light on the IMF that these particles travelled through, which presumably corresponds to their global structure.

Extracting the information from long periods of observations of suprathermal electron PADs, however, can be challenging. Recently, Carcaboso et al. (2020) introduced a robust method to compute large number of suprathermal electron PADs from distinct missions and derive different properties from their shape. This method can, among others, characterise salient features, automatically identify various PAD types –such as bidirectional, isotropic, simple strahl, loss cone, and pancake–, and quantify the degree of anisotropy.

Recent missions like Parker Solar Probe or Solar Orbiter enable us to observe CMEs at varying heliocentric distances during the ongoing solar cycle (SC25), which is crucial to understand their evolution and topology from the initial stages to more advanced phases. This provides a unique opportunity for a thorough analysis of suprathermal electron PADs at different heliocentric distances, offering insights into how CMEs evolve and interact with the solar wind.

By applying the suprathermal electron PAD analysis method introduced by Carcaboso et al. (2020) to the unique data from the most recent heliospheric missions, this work aims to enhance our understanding of CME evolution and global topology.

Carcaboso, F., Gómez-Herrero, R., Lara, F. E., Hidalgo, M. A., Cernuda, I., & Rodríguez-Pacheco, J. (2020). Characterisation of suprathermal electron pitch-angle distributions-Bidirectional and isotropic periods in solar wind. Astronomy & Astrophysics, 635, A79

How to cite: Carcaboso, F., Verniero, J., Lario, D., Espinosa Lara, F., Szabo, A., and Gómez-Herrero, R.: What can suprathermal electron tell us about the topology and evolution of CMEs?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14429, https://doi.org/10.5194/egusphere-egu25-14429, 2025.

Coronal mass ejections (CMEs), originating from the sun's corona, are large-scale eruptions of plasma and magnetic flux that propagate into interplanetary space, and are capable of significantly influencing the dynamic environment of the inner solar system. Previous studies have established that CMEs exhibit turbulent behavior, characterized by energy cascades from larger to smaller scales through the formation of eddies. This study investigates the turbulence properties at different stages of a CME evolution. We divide the CME event into three intervals, characterised by the arrival of the CME shock and the magnetic cloud region. The magnetic field signal was decomposed using the method of empirical mode decomposition (EMD) into intrinsic mode functions (IMFs), which capture inherent oscillatory modes within the data. For each magnetic field component (Bx, By, Bz), we generated Fourier power spectra and Hilbert-Huang spectra, representing the power distribution across frequencies within the three intervals. These spectra can provide insights into the turbulent nature of the magnetic field during the different stages of CME evolution.

How to cite: Dagore, A., Prete, G., and Carbone, V.:  Analysing Turbulence in Coronal Mass Ejections Using Empirical Mode Decomposition , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15115, https://doi.org/10.5194/egusphere-egu25-15115, 2025.

Coronal mass ejections (CME) are one of the main drivers of space weather. However, quasi-realistic and efficient numerical modelling of the CME propagation and evolution process in the whole solar-terrestrial space, especially in the sub-Alfvénic corona, is still lacking. Recently, we have made some attempts to improve our ability to model CMEs. 1. We developed an efficient and quasi-realistic time-evolving MHD coronal model which can be used to provide inner-boundary conditions for the inner heliosphere models in practical space weather forecasting.  2. We developed an efficient and time-accurate MHD model of the solar corona and CME to timely and accurately simulate time-varying events in solar corona with low plasma β. 3. We developed an extended magnetic field decomposition strategy to improve the numerical stability of the time-evolving MHD coronal models in solving low-β issues. 4. We are conducting some faster-than-real-time CME simulations from the solar surface to 1 AU based on the work mentioned above. In this work, the solar-terrestrial space is covered by extending the coronal model to 1 AU or by coupling the coronal model with an inner heliosphere model. These MHD models are demonstrated to be very efficient and numerically stable and are promising to timely and accurately simulate time-varying events in solar-terrestrial space for practical space weather forecasting. I'd like to share our research work at EGU conference and call for more collaborations to perform more interesting research works.

How to cite: Wang, H., Poedts, S., Lani, A., Brchnelova, M., Linan, L., Baratashvili, T., Guo, J., Yang, L., Zhang, F., Zhou, Y., and Lin, R.: Efficient and Quasi-realistic Magnetohydrodynamic Modeling of Coronal Mass Ejection Propagation and Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15241, https://doi.org/10.5194/egusphere-egu25-15241, 2025.

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from the Sun's lower atmosphere, significantly influencing space weather and planetary environments. To improve predictions of CME arrival and their impacts on Earth and its surroundings, a deeper understanding of their origins, initiation, and complex early evolution is crucial. While coronagraphic observations have been essential for studying the dynamics of CMEs, they cannot capture the initial, critical phase of CME development. Consequently, investigating indirect phenomena in the lower solar atmosphere has become essential. One of the most prominent indirect indicators associated with CMEs is coronal dimming. These are localized, sudden decreases in coronal emission observed at extreme ultraviolet and soft X-ray wavelengths, which evolve rapidly during the lift-off and early expansion phases of CMEs. Coronal dimmings have been interpreted both as “footprints” of the erupting magnetic structure and as indicators of coronal mass loss in the lower corona.

I will review recent advancements in using coronal dimmings to diagnose CMEs. Topics covered will include statistical studies linking dimming characteristics to CME mass and speed, the use of dimmings as early indicators of CME propagation direction, and insights into the magnetic topology and reconfiguration of the early CME stages based on dimming locations and fine structure. Additionally, the potential role of dimmings in the pre-event phase preceding CME onset will be discussed. Finally, I will highlight future research directions and underexplored areas in CME science, emphasizing the untapped potential of coronal dimmings in advancing our understanding of these dynamic solar events.

How to cite: Dissauer, K.: Footprints of Giants – Exploring Early Diagnostics of Coronal Mass Ejections Through Coronal Dimmings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17289, https://doi.org/10.5194/egusphere-egu25-17289, 2025.

Predicting the geo-effectiveness of CMEs relies on accurate modeling of their propagation and interaction with the solar wind. EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is a state-of-the-art 3D magnetohydrodynamic (MHD) model designed to model the evolution of CMEs in the heliosphere. I will present the several advanced CME models implemented in EUHFORIA, including the spheromak model, Fri3D (Flux-Rope in 3D), spheromak, and two toroidal CME models (Soloviev and Miller-Turner based models). Additionally, a more recent deep learning-based model, PINN, has been developed and implemented in EUHFORIA to enable access to toroidal magnetic field distributions that are otherwise not analytically accessible or computationally expensive to obtain. 

I will also present the latest advancement in EUHFORIA: its coupling with the global MHD coronal model COCONUT (COolfluid COroNal UnsTructured). While EUHFORIA injects CME models at 0.1 AU, this approach omits critical interactions occurring near the Sun, where the CME engages with the structured solar wind. COCONUT addresses this limitation by simulating the solar corona, starting from the solar surface and extending to 0.1 AU, using observed magnetograms to produce a realistic solar wind environment. This coupling enables us to track the propagation of a CME from its launch at the Sun’s surface through the corona and into the heliosphere. By aligning the outer boundary of COCONUT with the inner boundary of EUHFORIA, we ensure a seamless transfer of CME properties, including its magnetic field structure and plasma characteristics.

I will present the first results of this coupling, showcasing how different flux-rope CME models (e.g., Titov-Démoulin and RBSL) propagate dynamically through the coupled domain. This innovative integration marks a significant step forward in our ability to predict CME impacts and understand the physics driving space weather events.

How to cite: Linan, L., Baratashvili, T., Maharana, A., Guo, J., Lani, A., Schmieder, B., and Poedts, S.: Advanced flux-rope CME models in EUHFORIA and coupling with COCONUT, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17746, https://doi.org/10.5194/egusphere-egu25-17746, 2025.

The prevailing view of coronal mass ejections (CMEs) has long been that their magnetic field structure is best described by a highly twisted, circular cross-section magnetic flux rope model. This concept, which emerged from studies in the 1970s and 1980s, has become the foundation for most common CME depictions and has inspired various fitting models developed in the 1990s and 2000s. These models aim to provide three-dimensional visualizations of data from remote sensing and in situ measurements.

However, the landscape of CME research has evolved significantly since this paradigm's inception. A wealth of new data has emerged, including multi-point measurements, remote heliospheric observations, advanced physical models, and sophisticated numerical simulations. Collectively, these advancements have revealed that while the traditional paradigm explains certain CME characteristics, it falls short in capturing the full complexity of magnetic field structures in many instances.

This work provides a comprehensive review of four decades of continuous observations and ongoing research since the introduction of the highly twisted circular cross-section flux rope model. It proposes a more nuanced and realistic representation that better reflects the true intricacy of magnetic ejecta within CMEs. It also propses a new method to visualizing and quantifying the magnetic confuguration through the extraction of the magnetic helicity of CMEs during their journey to 1 AU, utilizing 3-D magneto-hydrodynamical (MHD) simulations.

How to cite: Al-Haddad, N., Lugaz, N., Berger, M., and Farrugia, C.: On the Complex Magnetic Topology of Coronal Mass Ejections: An Enhanced Paradigm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19089, https://doi.org/10.5194/egusphere-egu25-19089, 2025.

We present a new free and open source (FOSS) simulation platform under development at the Finnish Meteorological Institute. Building on top of our existing space weather models for Earth, Mercury and other planets, the aim is to enable efficient global simulations of plasma interactions in the solar system and beyond, including unmagnetized and magnetized planetary bodies with and without atmospheres and ionospheres. Our development focuses on a flexible combination of magnetohydrodynamic (MHD), hybrid particle-in-cell (PIC) and full-kinetic methods. Fast time to solution is achieved via runtime adaptive mesh refinement (AMR), temporal substepping and massively parallel implementation using the message passing interface (MPI) and open multi-processing (OpenMP). We describe our approaches to combining different physical solutions within the same simulated volume and combining AMR with substepping. We verify the implementation against a plethora of test cases in one, two and three dimensions, and also discuss initial results from simulations of Mercury and BepiColombo flybys using particle and MHD approaches and highlight the largest differences.

How to cite: Honkonen, I., Jarvinen, R., and Phillips, D.: Platform of adaptive algorithms for global simulations of planetary space weather, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1388, https://doi.org/10.5194/egusphere-egu25-1388, 2025.

We present analyses of plasma wave modes in our global hybrid particle-in-cell simulation code, RHybrid, for flowing planetary plasma interactions. The model treats ions as macroscopic particle clouds moving under the Lorentz force while electrons are a charge-neutralising, massless fluid. Magnetic field is advanced by Faraday's law and coupled self-consistently with ion dynamics (ion charge density and ion electric current density) via non-radiative Maxwell's equations. We describe analyses of several test cases, like random initial conditions and backstreaming suprathermal populations, compared against known solutions, observations and previous results from local and global modeling, including Mercury-type solar wind and interplanetary magnetic field conditions. The results show dispersion relations, parameter correlations, polarisations and more. We discuss the accuracy of modelling of theoretical results, including properties of whistler, Alfvén and magnetosonic waves, and ion-ion streaming instabilities in RHybrid. With this work, we prepare for further development of the Finnish Meteorological Institute's free and open source space weather particle simulation platforms, and for the interpretation of upcoming observations from the BepiColombo mission.

How to cite: Phillips, D., Jarvinen, R., Honkonen, I., and Kallio, E.: Plasma waves in a global ion-kinetic hybrid simulation for Mercury's space weather, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1415, https://doi.org/10.5194/egusphere-egu25-1415, 2025.

Discoveries by Parker Solar Probe (PSP) highlight the significance of nonthermal distributions in triggering ion-scale instabilities (Verniero et al. 2020, 2022; An et al. 2024; Liu et al. 2024). In this study, we show how the electron nonthermal (kappa) distribution could change the onset threshold of the ion-acoustic instability (IAI) recently observed by PSP (Mozer et al. 2021, 2023; Kellogg et al. 2024) between 15 and 25 solar radii and modeled by Afify et al. (2024). We perform analytical studies and kinetic simulations using the Vlasov-Poisson code with a parameter regime relevant to PSP observations. A setup of kappa-distributed electrons and two counterstreaming Maxwellian ion distributions (a core and a beam) is shown to be unstable w.r.t. the IAI, however, the electron-to-core and beam-to-core temperature ratios are slightly different from those recorded by PSP. The simulated growth rates have been validated by the kinetic theory. In the saturation regime, we do observe the formation of ion holes in the beam phase-space density. With large kappa values, the ion-acoustic waves interacted substantially with the beam, for instance, κ = 20, and shifted away from the beam with lower kappa values, for instance,  κ = 5 and 7. Our findings confirm that protons exhibit reduced resonance in the presence of kappa electrons, and the electron heating observed by PSP during the presence of IAI is not replicated in our simulation (Mozer et al. 2022).

References

Afify, M. A., Dreher, J., Schoeffler, K., Micera, A., & Innocenti, M. E. 2024, APJ, 971, 93
An, X., Artemyev, A., Angelopoulos, V., et al. 2024, PRL, 133, 225201.
Kellogg, P. J., Mozer, F. S., Moncuquet, M., et al. 2024, ApJ 964, 68.
Liu, W., Jia, H., & Liu, S. 2024, AJL 963, L36.
Mozer, F., Bale, S., Kellogg, P., et al. 2023, Phys. Plasmas, 062111, 30
Mozer, F. S., Bale, S. D., Cattell, C. A., et al. 2022, AJL 927, L15.
Mozer, F. S., Vasko, I. Y., & Verniero, J. L. 2021, ApJL, 919, L2.
Verniero, J. L., Chandran, B. D. G., Larson, D. E., et al. 2022, ApJ, 924, 112
Verniero, J. L., Larson, D., Bowen, T. A., et al. 2020, ApJS, 248, 5

How to cite: Afify, M. S., Dreher, J., O'Neill, S., and Innocenti, M. E.: The role of nonthermal electron distribution in triggering electrostatic ion-acoustic instability near the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2097, https://doi.org/10.5194/egusphere-egu25-2097, 2025.

A flattop distribution is one of the most characteristic non-Maxwellian velocity distributions in space plasmas. It is often observed in collisionless shocks and reconnection sites in near-Earth space. In this contribution, we discuss a numerical approach to study a flattop plasma in particle-in-cell (PIC) simulations. Specifically, we propose two numerical methods for randomly generating flattop-distributed velocities: a piecewise rejection method and a transform method from a gamma-distributed random number. Their usability is briefly compared.
Gamma-distributed random numbers are useful for generating flattop and other distributions. However, random number generators (RNGs) for gamma distribution may not be always efficient. Here, we propose a novel RNG algorithm for gamma distribution with shape parameter less than unity, based on the generalized exponential distribution and the squeeze method [1]. Numerical tests show that the proposed method is one of the best two in this category.

[1] S. Zenitani, Economics Bulletin, 44, 1113-1122 (2024), arXiv:2411.01415

How to cite: Zenitani, S.: Random number generation in kinetic plasma simulation: flattop and gamma distributions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2192, https://doi.org/10.5194/egusphere-egu25-2192, 2025.

The magnetohydrodynamic model of the solar high-temperature atmosphere is an important plasma model, which can reproduce many important features in simulating solar coronal plasma and magnetic field processes. However, the assumption of the MHD model may fail during highly dynamic and transient events, such as magnetic reconnection, and plasma heating, and in partially ionised structures such as the chromosphere, sunspots, and coronal rain. Therefore, a two-fluid MHD model with ions and neutral components can simulate many new phenomena. This study considers the two- fluid effects of solar plasma, and investigates the modification to traditional MHD models by including neutral components. We simulated MHD waves, and loop top turbulences in partially ionised plasma in sunspots or chromospheric flows. We focus on the separation of ions and neutral components in energy transfer processes and the potential contribution of neutral components to the nascent solar wind. Our simulations show that two-fluid effects would contribute significantly to solar plasma heating by collisional friction, and lead to the leakage of neutral components across the magnetic field lines and escape to the corona, it completely revolutionised our understanding of the corona, in which the role of the neutral component was neglected.

How to cite: Yuan, D. and Kuzma, B.: Two-fluid magnetohydrodynamic effects in the high-temperature atmosphere of the sun and their new perspectives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2724, https://doi.org/10.5194/egusphere-egu25-2724, 2025.

Magnetohydrodynamic (MHD) waves interact with the solar magnetic structures and have the potential to heat solar plasma and be used as a tool for plasma diagnostics. Despite extensive research, the precise mechanisms by which waves contribute to energy transport and dissipation remain incompletely understood. Additionally, utilizing wave characteristics for accurate diagnostics of the coronal plasma structure presents a significant challenge. Here, we utilize the Goode Solar Telescope to demonstrate transverse oscillations of the dark fibrils within the umbra of a sunspot and investigate their role in plasma heating. Additionally, we use EUV observations to show a quasi-periodic fast-mode MHD wave passing through a coronal hole could serve as a tool for plasma diagnostics. Our study finds that transverse oscillations are prevalent in the umbra of sunspots and carry a wave energy flux that significantly exceeds the loss rate of the solar active regions. Furthermore, the discovery of the MHD wave lensing effect provides a new mechanism for coronal hole diagnostics, with potential application to polar regions. These findings confirm the crucial role of MHD waves in coronal heating and demonstrate their potential as diagnostic tools for coronal plasma parameters. The studies provide new perspectives for understanding the multi-scale energy conversion and wave-magnetic field interactions in the solar atmosphere.

How to cite: Fu, L., Yuan, D., Kuźma, B., and Shen, Y.: Magnetohydrodynamic wave as a tool for solar plasma diagnostics and heating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3036, https://doi.org/10.5194/egusphere-egu25-3036, 2025.

A series of numerical simulations of convective dynamo, with varying grid resolution, with or without explicit magnetic diffusivity and viscosity, are presented and analyzed. It is found that in the simulations, with the increase of Reynolds number, the magnitude of current helicity increases dramatically, whereas the variation of kinetic helicity is very moderate. The competition between the kinetic helicity term and the current helicity term of the alpha coefficient results in an interesting behavior of the large-scale magnetic fields that resembles the ``dynamo-disappear-and-recover" phenomena reported in Hotta et al. 2016 Science paper. Our simulation and analysis suggest that, the role of current helicity first functions to suppress the dynamo, as the convectional $\alpha$-quenching concept states, but then functions to drive the dynamo, instead of quenching it, after a critical Reynolds number is exceeded.

How to cite: Zhang, M. and Fan, Y.: The role of current helicity in driving solar dynamo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3046, https://doi.org/10.5194/egusphere-egu25-3046, 2025.

Understanding solar eruptive phenomena requires accurate information about the coronal magnetic field. However, due to current technological limitations, direct measurement of the coronal magnetic field in three dimensions remains nearly impossible. Consequently, it is often approximated as a force-free field (FFF) using vector magnetogram data, which provide the three components of the magnetic field on the two-dimensional photospheric surface as boundary conditions.

Previously, we introduced a novel method for reconstructing coronal magnetic fields based on the poloidal-toroidal (PT) representation, which led to the development of the NFPT (Nonvariational Force-Free Field Code in Poloidal-Toroidal Formulation) in Cartesian coordinates. However, this approach did not account for the spherical geometry of the Sun's surface.

In this study, we present an improved FFF code that operates in spherical coordinates, incorporating the PT representation. This approach facilitates straightforward implementation of photospheric boundary conditions, with vector magnetogram data used as input. In our code, the source-surface top boundary is set at 2.5 solar radii, where the source surface region is believed to exist. The new code has been validated against analytic models by Low and Lou (1990) and compared with other FFF codes. This spherical-coordinate-based code aims to improve the accuracy of magnetic field information in an equilibrium state, thereby bringing qualitative enhancements to the initial conditions for global heliospheric modeling.

How to cite: Yi, S., Choe, G.-S., Kim, S., and Lee, M.: A Novel Poloidal-Toroidal Approach for Spherical Force-Free Field Reconstruction of Coronal Magnetic Fields, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3962, https://doi.org/10.5194/egusphere-egu25-3962, 2025.

We explored the origin of quasi-periodic pulsations (QPPs) in multiple wavelengths of a white-light flare, which occurred at the edge of a sunspot group. A short period at about 3 minutes is simultaneously observed in wavebands of HXR, microwave, and Lyα during the flare impulsive phase. The onset of flare QPPs is almost simultaneous with the start of magnetic cancellation between positive and negative fields, indicating that it is most likely triggered by accelerated electrons that are associated with periodic magnetic reconnections. A long period at about 8 minutes is only detected in the white-light emission, suggesting the presence of cutoff frequency. The similar periods of 3 and 8 minutes are measured at the umbra and penumbra in the adjacent sunspot. Moreover, the NLFFF extrapolation results suggest that the flare area and sunspots are connected by the magnetic field lines. Our observations support the scenario that the short-period QPP is modulated by the slow magnetoacoustic wave originating from the sunspot umbra, while the long-period QPP is probably modulated by the slow-mode magnetoacoustic gravity wave leaking from the sunspot penumbra.

How to cite: Li, D.: Exploring the origin of quasi-periodic pulsations during a white-light flare, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3997, https://doi.org/10.5194/egusphere-egu25-3997, 2025.

Ion cyclotron waves (ICWs) are prevalent in the near-Sun solar wind and play a significant role in the nonadiabatic heating of plasma. Recent observations from the Parker Solar Probe (PSP) have revealed the simultaneous presence of anti-sunward and sunward ICWs in the vicinity of the Alfvén surface. However, single-satellite observations cannot effectively trace the generation and evolution of these observed waves. To address this limitation, we employ kinetic-hybrid simulations to replicate the generation and evolution of counter-propagating ICWs under typical plasma conditions in the near-Sun solar wind. Following the linear growth phase, the simulated waves exhibit amplitude and polarization characteristics that closely match the observations. Additionally, our simulation illustrates proton scattering and helium heating induced by the counter-propagating waves. These results underscore the significance of locally generated ICWs in influencing solar wind ion dynamics.

How to cite: Wu, Y., Shi, C., Zhao, J., and Tao, X.: Kinetic-Hybrid Simulations of Counter-Propagating Ion Cyclotron Waves and Proton Scattering in the Near-Sun Solar Wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4616, https://doi.org/10.5194/egusphere-egu25-4616, 2025.

We have used a particle-in-Cell (PIC) simulation combined with a global MHD simulation to investigate energy transport from reconnection in the magnetotail to the inner magnetosphere. Initially, we ran an MHD simulation driven by nominal solar wind parameters and southward IMF. After reconnection starts in the magnetotail, we loaded the PIC simulation with plasma based on the MHD parameters. The PIC simulation extended from the solar wind outside of the bow shock to beyond the reconnection region in the tail and was run for 1m 47s. During that time, particles from the reconnection region reached the inner magnetosphere. We evaluated the transport of energy by examining the ion and electron energy fluxes, the Poynting flux and the changes in the particle and electromagnetic power densities in the simulation box as functions of time. We evaluated the changes in the energy densities by examining the divergences of the ion and electron energy fluxes and the Poynting flux. The particles move earthward in narrow channels like bursty-bulk-flows (BBFs). The Poynting power density is smaller than the ion particle power density. The ion kinetic power density is larger than the thermal power density. The energy exchange between kinetic energy and thermal energy is determined by the off-diagonal terms in the pressure tensor.

How to cite: Walker, R. and Rusiatis, L.: A  Simulation of Energy Exchange from Magnetotail Reconnection to the Inner Magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5369, https://doi.org/10.5194/egusphere-egu25-5369, 2025.

Combined with data assimilation methods, a three-dimensional magnetohydrodynamic (MHD) numerical model is an effective tool to explore the mechanism of space weather. As a driver of space weather, the dynamic development of stream interaction regions (SIRs) near the orbit of Mars is an area of active research. In this study, we use the interplanetary total variation diminishing (TVD) MHD model to simulate solar wind parameters and
model SIRs near Mars from 2021 November 15 to 2021 December 31. In this model, the MHD equations are solved by the conservation TVD Lax–Friedrichs scheme in a rotating spherical coordinate system with six component meshes used on the spherical shell. Solar wind velocity, density, temperature, and magnetic field strength are given at the inner boundary due to the characteristic waves propagating outward. We compared modeled results with observations from Mars Atmospheric Volatile EvolutioN (MAVEN) and Tianwen-1 (China’s first Mars exploration mission). Statistical analysis shows that the simulated results can capture SIRs and are in good agreement with observations; moreover, the assimilated results based on the Kalman filter improve the accuracy of numerical prediction compared with simulated results. This paper is the first attempt to simulate SIR events combined with MAVEN and Tianwen-1 in situ observations. Our work demonstrates that using the MHD model with the Kalman filter to reconstruct solar wind parameters can help us study the characteristics of SIRs near Mars, improve the capabilities of space weather forecasting, and understand the background solar wind environment.

How to cite: Shen, F., Zhang, H., Yang, Y., Chi, Y., Shen, C., and Tao, X.: Three-Dimensional Magnetohydrodynamic (MHD) Modeling of Solar Wind Near Mars by Combinng with data assimilation method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5598, https://doi.org/10.5194/egusphere-egu25-5598, 2025.

Coherent radio emission mechanism of solar radio bursts is one of the most complicated and controversial topics in the solar physics. To clarify mechanism of different types of solar radio bursts, (radio) wave excitation by energetic electrons in homogeneous plasmas has been widely studied via particle-in-cell (PIC) code numerical simulations. In this study, we, however, investigate effects of inhomogeneity in plasmas of the solar coronal on wave excitation by ring-beam distributed energetic electrons utilizing 2.5-dimensional PIC simulations. Disequilibrium introduced by the inhomogeneous magnetic field is balanced by either inhomogeneous density or inhomogeneous temperature of the background plasma. Both the beam and electron cyclotron maser (ECM) instabilities could be triggered with the presence of the energetic ring-beam electrons. Onset of the ECM instability is, however, later than the beam instability to excite waves in this study. The resultant spectrum of the excited electromagnetic waves presents a zebra-stripe pattern in the frequency space. The inhomogeneous density or temperature in plasmas would, however, influence the frequency bandwidth, excitation location of these excited waves. This study will, hence, help diagnose the plasma properties at the generation sites of solar radio bursts. Applications of this study to solar radio bursts (e.g., solar type V, zebra-pattern radio burst) will be discussed.

How to cite: Zhou, X., Munoz, P., Benacek, J., Zhang, L., Wu, D., Chen, L., Ning, Z., and Buechner, J.: Coherent Wave Excitation by Energetic Ring-beam Electrons in Inhomogeneous Solar Corona, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6157, https://doi.org/10.5194/egusphere-egu25-6157, 2025.

Interplanetary shocks (IPs) are ubiquitous in the Heliosphere, and are particularly relevant when associated to Stream Interaction Regions and Coronal Mass Ejections due to their great geomagnetic effectiveness on Earth. As their evolution and propagation may vary based on the different interplanetary conditions, it is crucial to study the shocks characteristics under different scenarios to gain a better understanding of the different types of interactions with the near-Earth environment.  

In this work, we propose a systematic analysis of the evolution, propagation and characterization of self-consistently generated interplanetary shocks under different conditions, such as different interplanetary magnetic field intensity, direction and particles density, velocity, by means of hybrid computer simulations (fluid electrons, kinetic ions).  The use of a hybrid formalism allows us to simulate large domains necessary for the shocks to form and evolve, by still retaining the kinetic information, which is fundamental to consider important kinetic effects, e.g., in supercritical shock-fronts. 

In particular, upon setting up an initial steepening velocity profile between slower and faster velocities, we observe this profile to evolve in a two boundaries-structure, separated by a turbulent sheath.  We first qualify these boundaries relative to the structure expected from steady shocks, we estimate their respective velocity and their compression factor. We also analyse the main characteristics of the turbulent sheath, which propages at an intermediate velocity with a enhanced magnetic field and transverse components in the magnetic field and velocity. All these features are consistent with observations of SIRs at 1 AU (e.g., Jian+, 2006). Moreover, we also discuss the effects of different IMF orientations on the shock dynamics, as the different kinetic effects between a quasi-perpendicular and quasi-parallel configuration at the shock can bring to significant differences in the shock-front propagation and the related donwstream sheath turbulence.

How to cite: Cazzola, E., Fontaine, D., and Savoini, P.: Self-consistently generated, evolving and propagating interplanetary shocks with 3D hybrid simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6853, https://doi.org/10.5194/egusphere-egu25-6853, 2025.

The standard flare model is in generally depicted and studied in 2D simulations with an anti-symmetrical magnetic field configuration, symmetrical in magnitude, either side of the polarity inversion line. However, flare observations confirm that most flare have a significantly asymmetrical values of the magnetic field strength. 

Here we present the first multi-dimensional magnetohydrodynamic flare simulation featuring evaporation driven by energetic electron beams in an asymmetrical magnetic field configuration. The simulation conditions that we use are known to rely significantly on those beams of electrons to drive the evaporated plasma upwards from the lower atmosphere (Druett et al. 2023). We study the impact of an asymmetrical configuration on the evolution and geometry of the flare-loop system as well as the impacts on the beam-driven evaporation using the MPI-AMRVAC model.

This results in multiple Hard X-Rays deposition sites in the lower atmosphere, Hard X-Rays sources forming at the top of the flare loop, and a sustained rotating flux rope structure with associated footpoint electron deposition flux.

How to cite: Dubart, M., Druett, M., and Keppens, R.: Beam-driven evaporation in 2.5D flare simulations with an asymmetric magnetic field configuration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8769, https://doi.org/10.5194/egusphere-egu25-8769, 2025.

The next generation of numerical plasma models need to have the capacity to address multi-scale problems for which fluid-only codes miss physics and pure kinetic codes are too computationally heavy. The code PHARE, currently being developed, aims at enabling the evolution of complex plasma systems over a dynamic hierarchy of grids with different mesh resolutions and potentially different plasma formalisms as well. This Adaptive Mesh and Model Refinement (AM2R) will provide better resolution and better realism to the solution where and when assessed necessary. This work will present the ongoing progress on the project, regarding the AMR Hybrid-PIC and AMR Hall-MHD solvers.

How to cite: Caromel, U., Aunai, N., Smets, R., and Deegan, P.: Adaptive mesh and model refinement for numerical plasma models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11264, https://doi.org/10.5194/egusphere-egu25-11264, 2025.

Rotational discontinuities (RDs) are considered in magnetohydrodynamics (MHD) as a kind of stable, persistent structure. As recent observations have shown, RDs may effectively describe the boundaries of switchbacks in the solar wind, around / inside which the plasma is highly dynamic and with phase space density variations. Because of the low collisionality of the solar wind, it may be worthwhile to revisit RDs with a kinetic approach. We therefore model the the plasma in RDs representing switchbacks with the state-of-the-art full-particle simulation code ECSim, and discuss the kinetic effects occurring in RD plasmas, including proton heating, anisotropy alternation, and modification of a core-beam composition, as well as the potential implications for the nature of switchbacks.

How to cite: Lin, R., Bacchini, F., and He, J.: Kinetic Effects of Rotational Discontinuities on Maxwellian and Non-Maxwellian plasmas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13772, https://doi.org/10.5194/egusphere-egu25-13772, 2025.

In collisionless plasmas such as the solar wind, the particle velocity distributions can be shaped by various wave-particle interactions, which lead to effective energy transfer between electromagnetic fields and particles. The commonly-observed quasi-monochromic waves by in-situ satellites are widely believed to be generated by plasma instabilities via wave-particle interactions. Thus, how to quantify the role(s) of wave-particle interactions in plasma instabilities is a fundamental problem in the space plasma community. Recently, we developed a theoretical method quantifying both resonant and nonresonant wave-particle interactions, and we performed the comprehensive analyses on ion temperature anisotropy instabilities in the solar wind. This report will introduce new findings.

How to cite: Zhao, J.: Quantifying wave-particle interactions in ion temperature anisotropy instabilities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13988, https://doi.org/10.5194/egusphere-egu25-13988, 2025.

Modeling Solar magnetic field in the corona is very important to understand the solar eruption and heating mechanism. However, the direct measurements of solar magnetic field in the solar corona is still taking a great challenge not only in the high accurate measurements of solar polarization signal, but also in the inversion approach for the Optic-thin condition of corona atmosphere. Existence and uniqueness in the force-free/Non-force-free extrapolation in the solar corona is still unknown. Magnetic helicity, as a topological invariant, has become a key factor in exploring the generation of magnetic fields within the Sun, solar eruptions, and energy transfer processes in interplanetary. We firstly give a short review of modelling magnetic helicity in the solar corona from the observation to simulation. Then we introduce a new method by calculating the potential current in a magnetic-helicity-conservation-decomposed approach to derive the magnetic helicity/energy equivalence of three-dimension magnetic field only based on the photospheric vector magnetogram. We testify our method by using the given magnetic field of Low and Lou (1990) and the difference is very small. Even though, the Lorentz force caused from the calculated magnetic field well explained the strong shearing movements of polarity inversion line (PIL) in the newly emerging active region of NOAA11158. Finally, we apply our method to the observation data and it is also successfully found that the weak/strong loss ratio of magnetic helicity in the solar confined/eruptive solar events.

How to cite: Yang, S.: Modeling Solar Magnetic Field In The Solar Corona From The View Of Magnetic Helicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14276, https://doi.org/10.5194/egusphere-egu25-14276, 2025.

The ERC-AdG project Open SESAME (project No 101141362) aims 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 solar flares and coronal mass ejections are driven have fundamental scientific importance and substantial socio-economic impact. Indeed, the solar atmospheric model is the crucial missing link in the Sun-to-Earth model chain to predict the arrival and effects of CMEs on Earth.

This goal is now possible by combining our implicit numerical solver with a high-order flux-reconstruction (FR) method. The implicit solver avoids the numerical instabilities that lead to strict time-step limitations on explicit schemes. The high-order FR method enables high-fidelity simulations on very coarse grids, even in zones of high gradients. We started with this new development and will introduce three critical innovations. First, we will combine high-order FR with physics-based r-adaptive (moving) unstructured grids, redistributing grid points to regions with high gradients. Second, we will implement CPU-GPU algorithms for the new heterogeneous supercomputers advanced by HPC-Europa. Third, we will implement AI-generated magnetograms to make the model respond to the time-varying photospheric magnetic field, which is crucial for understanding important solar plasma properties 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 started on 1 September 2024, and we already have interesting results on time-dependent corona modelling and high-order flux-reconstruction simulations.

How to cite: Poedts, S. and the Open SESAME: Open SESAME: status and further plans, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16188, https://doi.org/10.5194/egusphere-egu25-16188, 2025.

We report an M9.3 flare and filaments activities from NOAA Active Region 11261 that are strongly modulated by the 3D magnetic skeleton. Magnetic field extrapolation from the vector magnetic field suggests complex magnetic connectivity and the existence of a high coronal null point southeast of the active region. A small filament over the  inversed V-shaped polarity inversion line erupted and resulted in the M9.3 flare associated with a weak hot mass ejection, CME-like features, and the formation and activity of a relatively large filament. The ejection features and the eruption of the large filament were toward the southeast. Comparative analyses have disclosed the following new facts: (1) the trajectory of looptop hard X-ray emission provides solid evidence that the magnetic reconnection site propagated up toward the coronal null point as the flare and filaments erupted. (2) the EVU observations show coronal mass ejection-like eruption features in the ejection region of the magnetic skeleton. (3) the closed fan confined the west end of the large filament and the corresponding flare ribbons. We demonstrate a spatiotemporal relationship between the magnetic skeleton and the flare filament activity. We conclude that the magnetic skeleton can modulate and determine almost all the characteristics of the studied activity in the corresponding scale.

How to cite: Guo, J.: The Role of Magnetic Skeleton in Solar Flare Filaments Activities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16745, https://doi.org/10.5194/egusphere-egu25-16745, 2025.

The solar wind is an accessible natural laboratory for investigating thermal and energetic particles in space plasmas. The particle dynamics in the solar wind has a highly multi-scale nature, covering 8 orders of magnitude of spatial scales, from the lengths characteristic of the electron gyromotion around magnetic field lines ( ~1 km) to those characteristic of particle transport from the Sun to the Earth ( ~ 1 au). Studying such dynamics is a difficult endeavour, especially due to the solar wind’s strongly turbulent nature. Current models of particle dynamics in turbulent plasmas suffer from one or more limitations, such as unrealistic plasma background (e.g., 2D modelling, lack of the correct statistical turbulent properties such as anisotropy and intermittency of structures) or limited accuracy (e.g., small computational grids, low resolution in phase space). Most importantly, they only employ one simulation at a time and thus they only model the turbulent energy cascade over three decades of scales at best. 
We present our innovative solution to overcome all those limitations: the multi-scale Box-in-Box (BIB) approach.  The first step is to model the turbulent energy cascade from very large to very small scales, using a portion of a large simulation as initial condition for another one with higher resolution and repeating this process multiple times in sequence while coupling different physical models, e.g., MHD at the largest scales, hybrid across the ion scales, and fully kinetic at electron ones. The second step is advancing test-particles trajectories using the turbulence simulations as an evolving background from small to large scales, starting from the fully kinetic simulation and then switching to the hybrid and finally to the MHD one as the energy (and thus the gyroradius) of the test particles increases. We will show and discuss the main technical challenges of this kind of approach, the required operations in the different steps of the procedure, and some successful results. Our innovative BIB approach makes it possible to model the large-scale propagation of energetic particles in the turbulent solar wind while retaining a realistic and self-consistent description of the microphysics responsible for particle energization. Our BIB simulations will be particularly useful for developing and testing new visualisation and analysis techniques for future multi-scale space missions such as HelioSwarm and Plasma Observatory.

How to cite: Franci, L., Papini, E., and Trotta, D.: Modelling the particle dynamics in turbulent plasmas using the innovative multi-scale Box-In-Box (BIB) approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19152, https://doi.org/10.5194/egusphere-egu25-19152, 2025.

Solar flares, eruptive prominences (EPs), and coronal mass ejections (CMEs) significantly impact Earth's environment and human habitability, as they are different manifestations of solar storms. Sometimes, solar energetic particle events (SEPs) are associated with interplanetary shocks driven by CMEs that propagate through the turbulent solar wind. We investigate the physical mechanisms of these phenomena in a more realistic gravitationally stratified solar atmosphere using 2.5D magnetohydrodynamics (MHD) and particle simulations. Our research covers three main topics:

(1) MHD simulations of solar flux rope eruptions and prominence formation: Starting from the standard solar eruption model, we employed 2.5D MHD simulations to investigate two scenarios of flux rope and prominence eruptions within a more realistic, gravitationally stratified solar atmosphere. We developed an enhanced levitation model for prominence formation and proposed a novel mechanism involving plasmoid-fed processes in the current sheet. The former is driven by photospheric converging motions, while the latter focuses on the catastrophe model of flux rope eruption and emphasizes the crucial role of magnetic reconnection in prominence formation. These models describe the formation of flux ropes during eruption and pre-existing flux ropes beforehand, respectively. Additionally, we explored "mesoscale" phenomena during flux rope eruption and their association with Quasi-Periodic Pulsations (QPPs), reproducing multi-wavelength observational images.

(2) Shock-turbulence interactions in interplanetary space: Solar wind turbulence is ubiquitous, and when CMEs propagate through the solar wind, they drive interplanetary shocks that interact with solar wind turbulence, which is one of the sources of SEPs. These interactions result in a turbulent downstream fluid. We found that after shocks propagate across turbulence, the downstream occurrence of plasmoids (i.e., small magnetic flux ropes in the solar wind) increases, saturates to a peak value for a certain interval, and then gradually decreases away from the shock. This behavior is consistent with in-situ measurements taken by the Magnetospheric Multiscale (MMS) mission at Earth's bow shocks. These plasmoid structures are important for plasma heating and particle acceleration.

(3) Particle accelerations during solar eruptions: We investigated particle acceleration during solar eruptions, focusing on: 1) test-particle modeling of non-adiabatic motion of particles in 2D magnetic islands and 2) a combined Particle-In-Cell (PIC) and MHD approach (PIC-MHD) to study particle acceleration at interplanetary shocks. In the PIC-MHD approach, the background thermal plasma is treated as a magnetofluid, while the motion of non-thermal particles is influenced by the Lorentz force. This method accounts for electromagnetic interactions between non-thermal particles and the background magnetofluid, potentially leading to upstream self-excited turbulence that enhances particle acceleration through various mechanisms.

Overall, our research focuses on various processes in solar storms. Understanding and even predicting these phenomena are crucial for studying their impact on human habitability.

How to cite: Zhao, X.: CMEs and Interplanetary Shocks: 2.5D Numerical Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21910, https://doi.org/10.5194/egusphere-egu25-21910, 2025.

Ellerman bombs (EBs) and ultraviolet (UV) bursts are two of the smallest observed solar activities triggered by magnetic reconnection in the lower solar atmosphere, typically associated with flux emergence regions. Joint observations from the Interface Region Imaging Spectrograph (IRIS) satellite and ground-based solar telescopes reveal that approximately 20% of hot UV bursts are temporally and spatially connected with the cooler EBs. Using 3D radiation magnetohydrodynamic (RMHD) simulations with the MURaM code, we investigated the spontaneous emergence of a magnetic flux sheet, leading to complex magnetic field structures and diverse high-temperature activities due to magnetic reconnection. The simulations show that opposite-polarity magnetic fields converge in the lower solar atmosphere, forming thin current sheets and triggering plasmoid instability, which results in small twisted magnetic flux ropes and highly nonuniform plasma density and temperature. Hot plasmas (>20,000 K) emitting strong UV radiation coexist with cooler plasmas (<10,000 K) showing Hα wing emissions, with the former located ~700 km above the solar surface and the latter above them. Synthesized images and spectral line profiles exhibit characteristics of both EBs and UV bursts, demonstrating that turbulent reconnection mediated by plasmoid instability can occur in small-scale reconnection events in the partially ionized lower solar atmosphere. This model explains the formation mechanisms of UV bursts connected with EBs and indicates that UV bursts can form in atmospheric layers extending from the lower chromosphere to the transition region.

How to cite: Cheng, G.: Turbulent Reconnection in the Lower Solar Atmosphere Triggers UV Bursts Connecting with Ellerman Bombs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21916, https://doi.org/10.5194/egusphere-egu25-21916, 2025.

Parker Solar Probe had its lowest-ever perihelion of 9.86 solar radii on December 24, 2024 ('Encounter 22') and another on March 22, 2025 (Encounter 23).  We will present data from these Encounters, focusing on magnetic field measurements,  solar connectivity, and Heliospheric Current Sheet (HCS) crossings as the spacecraft crossed nearly halfway around the Sun in just 4 days.  We also compare E22/E23 measurements of the radial magnetic field and field magnitude to trends from earlier Encounters showing increasing radially-normalized magnetic flux with altitude.  We will review highlights of previous PSP solar encounters and compare to the latest encounters at the lowest-ever perihelion.

How to cite: Bale, S., Badman, S., Ervin, T., Dudok de Wit, T., Goetz, K., Horbury, T., Larson, D., Malaspina, D., Pulupa, M., Rawafi, N., Stevens, M., and Velli, M.: Parker Solar Probe at 9.86 solar radii: magnetic field structure, trends, and connectivity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4601, https://doi.org/10.5194/egusphere-egu25-4601, 2025.

Many in-situ solar wind observations show a clear correlation between the proton temperature and the bulk speed. Different authors use various formulas to describe this behavior, but one relation over a speed range covering both the slow and fast solar winds is usually sufficient for measurements made at 1 AU. Moreover, the relationship is observed throughout the solar cycle and no significant variations were measured. Therefore, it is commonly used to predict the expected solar wind temperature for a given solar wind speed. The ratio between the expected and measured proton temperature also serves as one of the ICME identifiers since these often have unusually low temperatures. However, the mechanisms leading to the relationship between the proton temperature and speed are not fully understood. It may be the result of solar wind acceleration processes near the Sun, but it may also change during the solar wind propagation, for example due to the stream interactions and/or different ways of energy transfer in solar wind streams coming from distinct source regions. We use observations from the recent inner-heliosphere missions (Parker Solar Probe and Solar Orbiter) and combine them with the near-Earth measurements (WIND, ACE) to study the radial evolution of this relationship. We find that the character of the radial evolution changes significantly at about 0.4 AU from the Sun. We discuss the possibility that the solar wind reaches a nearly collisionless regime near this point, thus we also investigate the effect of the collisional age.

How to cite: Durovcova, T., Satyasmita, S., Safrankova, J., and Nemecek, Z.: Changes of the temperature-speed relationship through the inner-heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4812, https://doi.org/10.5194/egusphere-egu25-4812, 2025.

How to cite: Varesano, T., Hassler, D., and Zambrana-Prado, N.: Investigating the Origins of the Solar Wind: Understanding Plasma Composition and Fractionation with Solar Orbiter SPICE, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5841, https://doi.org/10.5194/egusphere-egu25-5841, 2025.

The analysis of directional discontinuities (DDs) in the solar wind provides insights for understanding its embedded structures, such as flux ropes and switchbacks (SBs).

We aim to investigate the occurrence and nature of DDs observed by BepiColombo (BC) close to Mercury’s orbit and to establish links between magnetic field measurements and plasma parameters. Specifically, we assess the potential of DDs as indicators of SBs and other solar wind structures.

We use the attitude gradient to detect discontinuities combined with minimum variance analysis to characterize their boundaries.

During the selected period between 5 and 16 October 2021, a total of 1136 DDs were identified, with 960 meeting the eigenvalue ratio criterion for classification. The majority (83%) were rotational discontinuities (RDs) or either discontinuities (EDs). Low compressibility (CB < 0.03) conditions yielded a higher proportion of RDs and EDs (94%). PICAM observations revealed significant ion energy enhancements and particle deflections correlated with magnetic field reversals, particularly during SBs structures with low compressibility.

The results confirm the suitability of attitude gradient-based methods for DD detection and the potential of CB and z as proxies for identifying quasi-Alfvénic structures. The combined analysis of magnetic and plasma data highlights the role of DDs as markers of SBs, advancing our understanding of their nature and prevalence in the solar wind at 0.34 AU.

How to cite: Di Bartolomeo, P. P., Stumpo, M., Benella, S., Alberti, T., Milillo, A., Varsani, A., Heyner, D., Aronica, A., Jeszenszky, H., Kazakov, A., Noschese, R., Gunter, L., Plainaki, C., Moroni, M., and Giovannelli, L.: Detecting in-situ directional discontinuities in the solar wind at Mercury's Orbit, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6400, https://doi.org/10.5194/egusphere-egu25-6400, 2025.

Low latitude coronal holes are known to be the source of fast solar wind streams which
can have a significant effect on geomagnetic activity, especially around solar minimum activity.
A large number of methods have been developed in the last years to automatically detect
coronal holes in solar EUV and X-ray images.

Using a set of 29 solar images we now have a database of coronal hole identifications
from 15 different detection methods (Reiss et al., 2024). In this paper we have
compared these results and evaluated how the properties of coronal holes change
depending on the detection scheme.  
The next step of this investigation is to include magnetic field and solar wind modeling.
In the current contribution we provide a comparison of the observed coronal holes
with coronal holes derived from magnetic field extrapolations.

How to cite: Muglach, K., Martin, R., Majumdar, S., and S2-01 ISWAT Team, T.: Comparing Automated Coronal Hole Detection Schemes with Coronal Magnetic Field Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7810, https://doi.org/10.5194/egusphere-egu25-7810, 2025.

Solar wind transients such as corotating interaction regions can cause geomagnetic storms. Understanding solar wind conditions throughout the inner heliosphere is crucial for forecasting space weather conditions at Earth and other planets. Recent missions, including Parker Solar Probe (PSP) and Solar Orbiter offer new possibilities for probing the evolution of solar wind properties due to their orbits at various solar distances. We investigate how persistent the solar wind plasma flow is over distance by correlating solar wind parameters measured by spacecraft located at different positions in the heliosphere (0.1AU – 1.5AU). For that, we introduce a new two-dimensional persistence model of the solar wind based on in-situ measurements. Assuming persistence, the measured in-situ parameters from inner spacecraft are being propagated outwards applying the process of inelastic collisions between the plasma parcels. The resulting time-dependent 3D map of solar wind parameters is compared to in-situ data from spacecraft located further away and at different longitudinal positions from the Sun. We present statistics on the comparison between modeled and measured in-situ solar wind plasma parameters across radial distances and temporal evolutions.

How to cite: Milošić, D., Temmer, M., Heinemann, S., Hofmeister, S., Guo, J., and Cao, Y.: Persistence of Solar Wind Characteristics through Radial and Temporal Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9744, https://doi.org/10.5194/egusphere-egu25-9744, 2025.

During its encounter, Parker Solar Probe can sample the plasma outflow from the Sun in periods of corotation, allowing us to follow the solar wind during its radial evolution. We analyze plasma and magnetic field properties in two periods of corotation when Alfvènic streams of the solar wind were sampled. These data are then compared with results of a solar wind model.

In particular, the numerical model is an updated version of VPE (Grappin et al. 2011 ApJ) that solves one one-dimensional MHD equations including radiation and conduction, with separate proton and electron temperatures. Integration starts from the chromosphere and reaches PSP orbit and beyond.  Magnetic and velocity fluctuations are also injected from the chromosphere and  can contribute to the heating of the solar wind via a phenomenological turbulent dissipation (VPEW model). 

We use measurements to constrain several free parameters of the model, namely the chromospheric density, the magnetic field intensity and expansion, the fluctuations amplitude, and the turbulent phenomenology, and discuss their implications for the plasma properties closer to the Sun and for the heating and acceleration of the solar wind.

How to cite: Verdini, A., Grappin, R., Landi, S., and Franci, L.: Constraints on the heating and acceleration of Alfvénic streams using Parker Solar Probe data and a two-temperature solar wind model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10252, https://doi.org/10.5194/egusphere-egu25-10252, 2025.

Localized deflections in the interplanetary magnetic field, often accompanied by enhancements in solar wind velocity and disrupt the idealized Parker spiral topology that is otherwise dictated by the speed of the solar wind plasma flow. Such events, historically referred to by terms such as jets, velocity spikes, or the most recent adopted name magnetic switchbacks, were first observed in 1995 with Ulysses at 2.4 au. The reanalysis of Helios (1976) in 2018 confirmed their presence at smaller heliospheric distances (0.3 au). Their infrequent occurrence at these distances initially led to the belief that they are rare. This perspective changed dramatically with Parker Solar Probe’s (PSP) approach to 0.16 au in 2018, shortly after its launch, revealing an abundance of these deflections within smaller heliodistances. This sparked a significant interest within the scientific community to investigate their properties, possible sources, and significant processes inside the solar corona. However, this new interest also brought forth challenges, as their properties, origin, and behaviour across different radial distances remain unclear, and the lack of a unified definition leaves the subject open to interpretation. For our analysis, after careful consideration of the different properties of switchbacks, literature review, and comparisons between different studies we have constructed a set of criteria based on which we collected a small catalogue of switchbacks. The data considered are from different PSP encounters spanning the minimum, ascending phase, and maximum of the current solar cycle. We present our preliminary analysis, focusing on characteristics such as the direction of the magnetic field vector, and its magnitude, the plasma speed, density, and temperature, and the strahl electron pitch angle distribution.

How to cite: Gülay, E. and Asvestari, E.: Preliminary Results of Switchback Analysis in Parker Solar Probe Observations near the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11776, https://doi.org/10.5194/egusphere-egu25-11776, 2025.

The solar magnetic field expands outward from the Sun with the solar wind and fills the heliosphere.  Understanding the structure, dynamics, and connectivity of this field underlies many unanswered questions in solar and heliospheric physics.  In the presence of ideal  flows and in the reference frame co-rotating with the Sun, the solar wind plasma flow is aligned with the magnetic field. In this approximation, tracing the magnetic connectivity of plasma parcels encountered in the heliosphere back to the Sun reveals their solar origin. The magnetic field is also important for the propagation of solar energetic particles (SEPs), guiding them along magnetic field lines from their generation near the Sun to locations in the heliosphere.  Models with varying degrees of complexity are used to estimate the magnetic field connectivity and interpret observations.  A standard approach is to use potential field models to describe the corona, and to ballistically map points in the heliosphere back to the corona with the in situ measured solar wind speed.  More advanced models couple the potential field corona with a heliospheric MHD model.  We test the strengths and limitations of these approaches by utilizing a data-driven time-evolving model of the corona and heliosphere, computed for a month of evolution surrounding the 2024 total solar eclipse.  The time-evolving model is highly dynamic, with many small-scale eruptions.  We treat the time-dependent model as the ``ground truth'' and investigate how well the standard approaches capture the time-varying magnetic connectivity.

Research Supported by NASA and NSF.  Computational resources provided by the NSF ACCESS program and the NASA Advanced Supercomputing division at Ames.

How to cite: Linker, J. A., Downs, C., Caplan, R., Lionello, R., Riley, P., Mason, E., and Palmerio, E.: Magnetic Connectivity in the Time-Evolving Heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12408, https://doi.org/10.5194/egusphere-egu25-12408, 2025.

As the solar wind expands in the inner heliosphere, the evolution and relaxation of the electron velocity distribution function (eVDF) is governed by a complex interplay of collisional and collisionless processes.
This study investigates with numerical simulations the competition between Coulomb collisions and the electron firehose instability (EFI) - a kinetic instability arising under anisotropic pressure conditions - during the isotropization of the electron VDF.
The goal is to gain deeper insights into how collisional and collisionless processes influence each other in this regime.
Fully kinetic simulations are run using the particle-in-cell (PIC) code OSIRIS, in the presence and absence of Coulomb collisions.
The plasma density  (and hence the collisional frequency) is progressively increased in the presence of collisions to investigate solar wind regions progressively closer to the Sun.

How to cite: Völp, J., Schoeffler, K., Tenerani, A., and Innocenti, M. E.: PIC simulation of the competition of collisional and collisionless processes in the relaxation of the electron velocity distribution function in the young solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12695, https://doi.org/10.5194/egusphere-egu25-12695, 2025.

We present the study of a radial alignment between Parker Solar Probe and Solar Orbiter occurring at the end of April 2021. The two spacecraft were respectively at ~0.075 and ~0.9 au from the Sun. With the help of a propagation method, we identified the same density structure crossing both spacecraft, with a time delay of ~138 h between the two. This density structure is part of the heliospheric plasma sheet. We found that for this event, in-situ density measurements were concordant with radial gradients, while the magnetic field measurements were more concordant with longitudinal gradients. The structure is moreover inferred to have been generated by interchange reconnection in the high corona (2-3 solar radii), as observations are not in agreement with a generation by reconnection of the solar wind open field lines.

How to cite: Demoulin, P., Berriot, E., Alexandrova, O., Zaslavsky, A., Maksimovic, M., and Nicolaou, G.: Parker Solar Probe - Solar Orbiter radial alignment study: evolution of the heliospheric current sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12793, https://doi.org/10.5194/egusphere-egu25-12793, 2025.

Findings from the Parker Solar Probe (PSP) mission uncover frequent occurrences of small-scale magnetic flux ropes (SMFRs) and switchbacks (SBs - sharp deflection of magnetic field direction with radial velocity spike inside) as structural components of the solar wind. These mesoscale structures are present at all heliocentric distances and are specifically active in the young solar wind. SMFRs exhibit fundamental physical traits akin to larger structures but are distinguished by their notably smaller scale, lasting from seconds to a couple of hours, spanning distances from a few thousand kilometers to several solar radii (Rs). Previous research has identified mesoscale features, including successive SMFRs, blobs, and SBs observed in the inner heliosphere. These observations were made during the PSP's co-rotational orbits with the Sun, aligned radially along a narrow longitudinal zone. By examining these sequential structures, we have determined SB structures at the boundaries of SMFRs. We showed that the cross-occurrence of SBs and SMFRs is significant and these SBs’ geometries are determined by the SMFR orientation. Our findings of switchbacks associated with SMFRs suggest that they are integral to understanding the magnetic topology and the evolution of SBs, influenced by surrounding structures during their propagation. Furthermore, stability assessments are conducted at the boundaries of SMFRs to derive the specific local origin of SBs and factors, which affect their parameters, providing insights into the dynamic processes shaping the young solar wind.

How to cite: Choi, K.-E., Agapitov, O., Lee, D.-Y., Mozer, F., and Huang, J.: Inter-relationships between Small-Scale Magnetic Flux Ropes and Switchbacks in the Young Solar Wind from Parker Solar Probe Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13228, https://doi.org/10.5194/egusphere-egu25-13228, 2025.

Previous studies on the interaction of Mars’ un-magnetized space environment with the solar wind have shown that the structural morphology of Mars’ hybrid magnetosphere and the plasma dynamical processes occurring within are strongly driven by its solar wind conditions. This unique interaction is highly complex during quiet solar wind periods, let alone extreme solar wind conditions such as the encounter of CMEs or other transient solar wind structures. This emphasizes the importance of accurate knowledge of the upstream solar wind conditions when any spacecraft is inside the hybrid magnetosphere. However, all planetary missions to Mars consist of only one spacecraft, which further highlights the need for a solar wind model to accurately predict the upstream solar wind conditions. Here, we aim to validate and assess the capability of the physics-based Alfvén Wave Solar atmosphere Model (AWSoM) developed at the University of Michigan in predicting the solar wind interplanetary magnetic field (i.e. B) and plasma conditions (i.e. velocity, temperature and density) by comparing its simulated outputs with the solar wind data from the MAVEN spacecraft; MAVEN has been in orbit around Mars since 2014. We surveyed and identified multiple Carrington rotations across 10 years of MAVEN solar wind observations whenever MAVEN is upstream of the martian bow shock, and compared them with the simulated outputs from AWSoM using the dynamic time warping technique as a metric tool. Preliminary results indicate that AWSoM was able to accurately predict the magnitude of each solar wind parameter but did not perform as well when predicting the time of occurrence for observed solar wind structures (i.e. time-shift between observed and simulated). We further investigated the quality of our data-model comparison between consecutive solar maximum of Solar Cycle 24 and current Solar Cycle 25, and the solar minimum in-between.  The data-model comparison methods and results presented in this study contribute to the overall space weather efforts to improve the accuracy and precision of the physics-based AWSoM solar wind predictions over large heliocentric distances, including Mercury and Earth.

How to cite: Poh, G., Gruesbeck, J., Sachdeva, N., Huang, Z., and DiBraccio, G.: Validation of the AWSoM Solar Wind Magnetic Field Model with Upstream Mars Solar Wind Conditions from MAVEN Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13763, https://doi.org/10.5194/egusphere-egu25-13763, 2025.

A faster than real time forecast system for solar wind and interplanetary magnetic field transients that is driven  by hourly updated solar magnetograms is proposed to provide a continuous nowcast of the solar corona (<0.1 AU) and 24-hours forecast of the solar wind at 1 AU by solving a full 3-D MHD model. This new model has been inspired by the concept of relativity of simultaneity used in the theory of special relativity. It is based on time transformation between two coordinate systems: the solar rest frame and a boosted system  in which the current observations of the solar magnetic field and tomorrow's measurement of the solar wind at 1 AU are simultaneous. In this paper we derive the modified governing equations for both hydrodynamics (HD) and magnetohydrodynamics (MHD) and present a new numerical algorithm that only modifies the conserved quantities but preserves the original HD/MHD numerical flux. The proposed method enables an efficient numerical implementation, and thus a significantly longer forecast time than the traditional method.  The detailed description of numerical algorithm may be found in https://doi.org/10.48550/arXiv.2501.07222.

How to cite: Sokolov, I. and Gombosi, T.: Physics-Based Forecasting of Tomorrow's Solar Wind at 1 AU, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14389, https://doi.org/10.5194/egusphere-egu25-14389, 2025.

How to cite: Wu, Z., He, J., and van Doorsselaere, T.: Multi-point observations and eigenmode instability analysis of tearing-induced reconnection in the heliospheric current sheet related to primary solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14938, https://doi.org/10.5194/egusphere-egu25-14938, 2025.

How to cite: Zhuo, R., Wu, Z., Ma, M., He, J., and Xiong, M.: Propagation of density fluctuations in the near-Sun environment inferred from radio sounding during Tianwen-1 solar conjunction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15009, https://doi.org/10.5194/egusphere-egu25-15009, 2025.

Recurring Coronal Holes (CHs) are long-lived structures in the solar corosna that survive over multiple solar rotations. They are sources of open magnetic field and fast solar wind streams filling the interplanetary space. Of the recurring CHs, those that can generate geomagnetic activity are particularly important due to the recurring impact they can have on the terrestrial environment. In this study we focus on reconstructing their vertical structure and assess how that changes with each rotation. To facilitate our study, we utilized the Potential Field Source Surface (PFSS) and the Schatten Current Sheet (SCS) model incorporated in the coronal modelling domain of EUHFORIA (European Heliospheric Forecasting Information Asset). We investigate the optimal parameter space for model initiation for each CH, compare the model output both to EUV and coronagraph white-light emissions, and assess the reconstructed heliospheric conditions using in situ measurements from different positions throughout the inner heliosphere.

How to cite: Asvestari, E., Heinemann, S., Temmer, M., Milošić, D., Gulay, E., and Pomoell, J.: Reconstructing the evolution of recurring coronal holes in space and time, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15393, https://doi.org/10.5194/egusphere-egu25-15393, 2025.

Strong perpendicular diffusion of the beam in ion VDFs have been detected in the solar wind using Parker Solar Probe's SPAN-i instrument and have been termed as the hammerhead distribution functions. There have been ongoing studies trying to simulate the formation of these hammerhead features, which have met with muted success. It has been hypothesized that these perpendicular scattering of ions can be attributed to resonant scattering of beam ions by parallel-propagating, right circularly polarized, fast magnetosonic/whistler waves (Verniero et al 2022). However, in order to extract definitive physical explanations and stipulate their occurrence rate as a function of plasma beta, closeness to the heliospheric current sheet and distance from change in magnetic topology, a statistical study and characterization is necessary of these hammerhead occurrences. In our study, we develop a super-fast Python-based repository to filter-out the hammerheads across all PSP data where the VDF is dominantly in the field-of-view of SPAN-i. Immediate future goals involve characterizing these hammerhead VDFs using more sophisticated fitting algorithms (sidestepping the bi-Maxwellian fits) to characterize various features of the distributions such as the distance between core and hammerhead, ratio of the parallel and perpendicular temperatures of the core and hammerhead, and other crucial features

How to cite: Das, S. B. and Verniero, J.: Hunting for hammerheads occurances using hammerhead finder software hampy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15609, https://doi.org/10.5194/egusphere-egu25-15609, 2025.

The solar wind expands outward from the solar corona, defining the interplanetary medium through which coronal mass ejections (CMEs) and solar energetic particles (SEPs) propagate. Accurate models of this ambient solar wind and its embedded magnetic fields are crucial for heliophysics and space weather research. Studies have highlighted the importance of ambient solar wind modeling for accurate CME arrival time predictions. However, comparisons of in situ spacecraft measurements to model solutions at L1 show that state-of-the-art models often perform comparably to a simplistic assumption that solar wind conditions at L1 repeat every 27 days. Here we study why state-of-the-art models often exhibit such surprisingly large errors. Going deeper than previous validation studies, we examine the physical reasons for erroneous predictions on an event-by-event basis by comparing imaging and in-situ observations with simulation results, and provide possible strategies to address these challenges. We study how magnetic structures at coronal hole boundaries, such as streamers and pseudo-streamers, affect model outcomes, among many other experiments. We also study how the choice of ADAPT maps could be crucial in the context of solar wind modelling. We demonstrate our recommendations for improving ambient solar wind modeling through the Wang-Sheeley-Arge (WSA) framework, as implemented by Reiss et al. (2019, 2020). Our findings highlight the different sources that could lead to erroneous predictions, how we can improve the predictions, and the critical need to better constrain magnetic models with observational data to enhance our ambient solar wind modeling capabilities. Moving forward, such improvements are vital for advancing the reliability of space weather forecasting, ultimately protecting astronauts and technological assets in space.

How to cite: Majumdar, S., Reiss, M., Muglach, K., and Arge, C. N.: Identifying and Correcting Errors in Ambient Solar Wind Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15901, https://doi.org/10.5194/egusphere-egu25-15901, 2025.

A global electric potential arises within the solar wind due to the mass disparity between electrons and protons, coupled with the constraints of charge quasi-neutrality and zero-current conditions on sufficiently large scales in the heliosphere. This so-called ambipolar electric potential may account for at least part of the solar wind acceleration. Recent findings from the Parker Solar Probe (PSP) reveal that the slow solar wind, with terminal velocities averaging around 250 km/s, could be entirely explained by the ambipolar electric potential. However, an additional, yet unidentified mechanism is required to explain the acceleration of the fast solar wind. 

Since the first in situ solar wind observations in 1959, neither magnetohydrodynamic nor kinetic models have been able to consistently account for the fast solar wind acceleration. Therefore, the processes responsible for this additional acceleration remain one of the most significant open questions in space physics. To address this challenge, we propose a pathway to account for the unexplained acceleration by incorporating velocity space diffusion of particles within the kinetic exospheric framework, which self-consistently determines the ambipolar electric potential. This was achieved for electrons by redistributing particles within regions of velocity space defined by the kinetic exospheric approach to account for a diffusion that would occur in the solar wind due to collisions or wave-particle interactions. These are therefore incorporated indirectly in the kinetic exospheric model through diffusion which inevitably fills regions of velocity space that would otherwise remain inaccessible and are thought to be the primary mechanisms behind the formation of the so-called halo population—higher-energy electrons that, unlike the strahl, are not predominantly directed an-sunward.

The recent discovery of the sunward deficit, predicted by the kinetic exospheric models, showed an anticorrelation between the electric potential and the solar wind terminal velocity, potentially implying that the electric potential is only a minor acceleration mechanism for the fast solar wind. We here find that even without the influence of velocity space diffusion, the same anticorrelation can be obtained by our kinetic exospheric model, from observationally derived input coronal temperatures, for a range of heliocentric distances typically sampled by PSP (above 13 Rs). This suggests that the electric potential might still be of major importance to explain the fast solar wind acceleration.

How to cite: Péters de Bonhome, M., Pierrrard, V., and Bacchini, F.: Solar Wind Acceleration Driven by Velocity Space Diffusion and the Ambipolar Electric Potential, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16263, https://doi.org/10.5194/egusphere-egu25-16263, 2025.

Solar wind modeling with the 3D MHD model EUHFORIA (EUropean Heliospheric FORecasting Information Asset; Pomoell & Poedts, 2018) revealed discrepancy with in situ observations by the Parker Solar Probe (PSP) at near-Sun distances . The default coronal model employed in EUHFORIA consists of the potential field source surface extrapolation (PFSS), Schatten current sheet (SCS) model and semi-empirical WSA model, which simulate the plasma and magnetic conditions at the inner boundary (0.1 AU). Parameters such as the PFSS source surface height (R_SS), which is the outer boundary of PFSS, and the inner boundary of SCS model influence the modelled coronal hole areas and the associated open flux areas. A default R_SS value of 2.6 R_⊙, as per McGregor et al. (2008), is used in EUHFORIA for solar wind simulations. Lowering the R_SS value has been reported to better capture coronal hole areas (Asvestari et al., 2019), improve the reconstruction of small-scale features (Badman et al., 2020), and more accurately reflect coronal magnetic field topologies during different phases of solar cycles (Lee et al., 2011; Arden et al., 2014).

In this parameter study we investigate the possible systematic effects of changing the outer boundary of the PFSS model and the inner boundary of the SCS model, while keeping default values for other parameters. The resulting solar wind simulations are compared to those obtained using all default parameters in the model, by evaluating their agreement with the in situ observations from PSP for its first ten perihelion encounters. Although we found improved modeling accuracy for several time intervals, first results do not show clear systematic improvements in the accuracy of the modeled solar wind.

How to cite: Valliappan, S. P. and Magdalenic, J.: Investigation of Source Surface Height Variations in EUHFORIA and Their Impact on Solar Wind Predictions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16626, https://doi.org/10.5194/egusphere-egu25-16626, 2025.

I analyse the spatial distribution of solar wind sources and relate them to the properties of the interplanetary wind by means of an extended time series of data-driven 3D simulations that cover more than two solar activity cycles. Magnetic connectivity jumps are related with solar wind plasma signatures and with topological features of the global magnetic field. The occurrence frequency and amplitudes if such connectivity jumps vary with the epoch of the solar cycle and on the distance to the ecliptic plane.
The same solar wind model (Multi-VP) constitutes the core of the SWiFT-FORECAST service, based on model pipeline initially developed in the scope of the H2020 SafeSpace project, and later integrated on ESA's SWESNET and on the Virtual Space Weather Modelling Centre.  Ensemble forecasts are produced at a daily cadence and with a lead time of a few days.  I will address some of the main challenges related to the implementation and validation of these models and pipelines, as well as the pernicious issues that stem from the lack of observables between the two boundaries of the Sun­–Earth system, and from the dependence of "point" forecasts on the global properties of the solar atmosphere.

How to cite: Pinto, R.: From multi-decadal solar wind modelling to real-time forecasting, and on moving away from the ecliptic plane, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17463, https://doi.org/10.5194/egusphere-egu25-17463, 2025.

Since Parker, the existence of the solar wind has been ascribed to the fact that the solar corona is not in hydrostatic equilibrium and thus is constantly expanding. However, the mechanism responsible for accelerating/heating the solar wind is widely debated, even though there is evidence that it is magnetic in nature. New space missions like Parker Solar Probe (PSP), Solar Orbiter (SolO) and BepiColombo (BC), being much closer to the Sun, allow observations of less evolved and less mixed solar wind. Thus, for example, the observed streams can be easily back-propagated to their source on the Sun, allowing generally more accurate characterizations. These new observations revealed that the measured magnetic field is highly structured close to the Sun, exhibiting patches of large and intermittent reversals associated with jets of plasma. Jetting activity reveals that the solar wind emission is discrete in nature rather than homogeneous, leading to intermittent/impulsive outflow from the corona driven by small-scale magnetic reconnection. In a recent work, it has been shown that super granulation structure at the coronal base remains imprinted in the near-Sun solar wind, resulting in the magnetic polarity inversions known as switchback. Farther from the Sun, however, switchbacks are less frequent, probably due to mixing and turbulent decay.

According to the Potential Field Source Surface extrapolation between 6th and 7th October 2021, BC and SolO were connected to the same region on the Sun. BC and SolO were located at 0.36 AU and 0.67 AU, respectively. Both spacecraft detected a patch of switchbacks, offering the opportunity to investigate their evolution with solar wind propagation. Our findings highlight the potential of BC for synergistic studies with PSP and SolO, despite its primary focus on Mercury’s environment.

How to cite: Stumpo, M., Di Bartolomeo, P. P., Benella, S., Larosa, A., Nicolaou, G., Pezzi, O., Trotta, D., Alberti, T., Milillo, A., Heyner, D., and D'Amicis, R.: Joint observations of magnetic switchbacks from BepiColombo and Solar Orbiter in the inner heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18403, https://doi.org/10.5194/egusphere-egu25-18403, 2025.

Mesoscale structures in the solar wind offer unique insights into its formation, retaining signatures of heating, release mechanisms, and acceleration processes. Plasma heavy ion composition and charge states are critical observables for studying these structures. These properties, established within about 5 solar radii, are preserved as the solar wind propagates, enabling the connection between in situ measurements and their solar sources. Elevated abundance ratios of low first ionization potential (FIP) elements (e.g., Fe/O) and higher charge states are indicative of solar wind originating from active regions and quiet Sun magnetic fields, in contrast to coronal holes. These properties are often structured on mesoscales and can exhibit quasi-periodic behavior, associated with interchange reconnection at the Sun’s open-closed magnetic boundary.

We investigate a multi-day interval from March 4–9, 2022, during which Solar Orbiter’s Heavy Ion Sensor (HIS) observed mesoscale solar wind structures at ~0.49 AU. These structures were confirmed to persist to L1 via ACE and Wind observations, with similar variability in Fe/O and O7+/O6+. Spectral analysis revealed quasi-periodic signals (~30-minute periodicities) in O7+/O6+ ratios during four of the six days analyzed. To link these observations to their solar origins, we used the Wang-Sheeley Arge (WSA) model driven by ADAPT synoptic maps. The model determined solar sources were characterized by parameters empirically related to solar wind formation, such as expansion and squashing factors.

A key feature of this interval was a small stream interaction region (SIR) observed at Solar Orbiter on March 8, coinciding with a connectivity change to a new open-field region bordering a compact active region. This event, confirmed through WSA modeling, corresponded to significant enhancements in Fe/O and O7+/O6+, providing evidence of mesoscale structures linked to active region dynamics. The FIP bias observed in situ (Fe/O) was compared to remote SPICE observations (S/O) at the modeled solar source locations, highlighting challenges in reconciling in situ and remote measurements due to differences in abundance ratio derivations.

Our results demonstrate that mesoscale structures form in active regions via interchange reconnection and survive through the heliosphere, maintaining their composition signatures. This study underscores the value of combining multi-messenger observations and physics-based modeling to trace solar wind origins and reveals the need for enhanced coordination in future heliophysics missions. These findings advance our understanding of solar wind structuring and dynamics, providing a framework for future studies of mesoscale phenomena.

How to cite: Zambrana Prado, N., Wallace, S., Gershkovich, I., Viall, N., Kucera, T., Young, P., Lepri, S., and Yardley, S.: Mesoscale Dynamics in the Solar Wind: Insights from Solar Orbiter and L1 Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18482, https://doi.org/10.5194/egusphere-egu25-18482, 2025.

This presentation outlines the Doppler dimming diagnostic method, the computational tools developed, and the solar wind speed maps derived from Metis data spanning a wide range of heliocentric distances, from approximately 1.5 to 10 solar radii, during the solar activity minimum.

The Doppler dimming diagnostic, which combine simultaneous Metis observations from its two channels, polarized broadband visible light and narrowband ultraviolet H I Lyα intensity, allows for the measurement of the expanding coronal plasma speed. The presented wind speed maps are obtained from Metis data sets collected during the cruise phase of the Solar Orbiter mission, shortly after its first perihelion at approximately 0.5 AU in June 2020, as well as before and after its second perihelion in January and February 2021. These observations provide critical insights into the solar corona above approximately 3.0 solar radii, while future Solar Orbiter perihelion passages will extend this analysis to distances as close as 1.7 solar radii.

The reliability of the derived wind speed values is evaluated, considering instrumental uncertainties, the inherent limitations of the diagnostic method, and key assumptions about solar corona model parameters, including electron and neutral atom kinetic temperatures and the 3D geometric configuration of the corona.

As expected at the minimum of the solar cycle, the obtained maps show a clear bipolar topology with a rapid transition to higher speeds in the interface zone between equatorial streamers and high-latitude regions. The equatorial regions, where intense and relatively stable streamer belt persists, do not exhibit speeds higher than 220 km/s up to the maximum observed distance, around 6 solar radii. In contrast, within the coronal holes, already just above the minimum observed heights, around 3.5 solar radii, the wind speed reaches the maximum values detectable using Doppler dimming diagnostics applied to the neutral hydrogen line, approximately 350 km/s.

The method and algorithms are further tested and applied to a sample of daily ultraviolet intensity images reconstructed from spectral data obtained by the UVCS instrument, in conjunction with visible light coronal observations performed by LASCO, both instruments onboard the SOHO mission during solar cycle 23. This extended analysis provides valuable insights into the solar wind acceleration region, covering distances between approximately 1.5 and 4.0 solar radii, encompassing nearly a full solar activity cycle, providing essential context to complement the present Solar Orbiter observations.

How to cite: Giordano, S. M., Spadaro, D., Susino, R., Ventura, R., Romoli, M., Fineschi, S., Zangrilli, L., and Telloni, D.: Solar Wind Speed Maps from the Metis coronagraph observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19935, https://doi.org/10.5194/egusphere-egu25-19935, 2025.

The solar wind and planetary magnetospheres provide excellent natural laboratories to study the basic physics of collisionless plasmas. In these systems, microscopic plasma physics often influences, or even controls, global plasma dynamics by controlling transport of energy and momentum. Electromagnetic fluctuations and the resulting wave-particle interactions are particularly omnipresent. Typical spectra of electromagnetic fluctuations in the solar wind are power laws in frequency, with multiple characteristic breaks signaling changes in the origin of fluctuating modes, as well as onset of dissipation. At frequencies above the electron cyclotron frequency, fluctuations become purely electrostatic, and a persistent level of broadband electrostatic noise is often observed.

High-resolution measurements reveal that these small-scale modes often contain highly coherent wave-packets and solitary structures, the latter likely being electron or ion phase space holes of a few tens of Debye length in size. These bipolar electric field structures can be weak double layers (WDLs), a localized and stable charge separation sustaining a net potential drop across. WDLs are often associated with particle acceleration and energy dissipation.

We present here a preliminary work in which we analyze data from various missions to search for and detect electrostatic solitary waves and WDLs in the inner heliosphere from the solar corona to 1 AU using electric field measurements from Parker Solar Probe, Solar Orbiter, MMS and Wind. Do WDLs observed in the near-Sun solar wind have finite potential drops oriented radially so as to slow escaping electrons and accelerate escaping ions?

How to cite: Salem, C., Bonnell, J., Pulupa, M., Chust, T., Le Contel, O., Jeandet, A., Malaspina, D., and Maksimovic, M.: Observations of Coherent Electrostatic Solitary Waves in the Inner Heliosphere , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20530, https://doi.org/10.5194/egusphere-egu25-20530, 2025.

How to cite: golan, M., gedalin, M., and Golan, M.: Observations of persistent downstream magnetic oscillations at the Earth bow shock , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16, https://doi.org/10.5194/egusphere-egu25-16, 2025.

In this study we investigate the formation of magnetosheath jets before, during, and after the interaction between Earth's bow shock and a solar wind rotational discontinuity in a 2D ecliptic simulation run of the global magnetospheric hybrid-Vlasov model Vlasiator. Magnetosheath jets are transient enhancements of dynamic pressure downstream of collisionless shocks, and they have been observed in Earth's magnetosheath, the magnetosheaths of other planets, as well as the sheaths of interplanetary shocks. Rotational discontinuities (RD) are boundaries where the components of the magnetic field and velocity tangential to the boundary change abruptly, and they have been observed by spacecraft in the solar wind and in Earth's magnetosheath. Both spacecraft observations and previous simulation studies have shown that RDs interacting with the bow shock can generate dynamic pressure pulses in the magnetosheath.

Studying magnetosheath jets is important because they have been shown to potentially have magnetospheric effects if impacting the magnetopause, and while travelling through the magnetosheath they can modify its properties. Statistical studies of simulations and spacecraft observations have shown that jets tend to form mainly at Earth's quasi-parallel bow shock, that is where the interplanetary magnetic field (IMF) direction is nearly parallel to the shock normal, but they have also been observed downstream of the quasi-perpendicular shock. By studying the formation and properties of jets at the quasi-parallel and quasi-perpendicular shock at different times in the simulation, we aim to shed light on the differences between jets forming at different parts of the shock, and during different stages of interaction between an RD and the bow shock.

How to cite: Suni, J., Palmroth, M., Turc, L., Battarbee, M., Pfau-Kempf, Y., and Ganse, U.: Rotational discontinuity-generated magnetosheath jets at Earth's quasi-perpendicular bow shock: Results from a hybrid-Vlasov simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1683, https://doi.org/10.5194/egusphere-egu25-1683, 2025.

It is common wisdom that collisionless shocks become nonplanar and nonstationary at sufficiently high Mach numbers. Whatever the shock structure, the upstream and downstream fluxes of the mass, momentum, and energy should be equal. These conservation laws are satisfied at low Mach numbers when the shock front is planar and stationary. When this becomes impossible, inhomogeneity and time dependence, presumably as rippling, develop. Using test particle analysis in a model shock profile, this study shows that the shock structure changes as a kind of "phase transition" when the Mach number is increased while the shock angle, the upstream beta, and the magnetic compression are kept constant.

How to cite: Gedalin, M.: A "phase transition" from a planar stationary profile to a rippled structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2077, https://doi.org/10.5194/egusphere-egu25-2077, 2025.

The size of collisionless shock waves is believed to play an important role in determining the maximum energy gain of particles accelerated at heliospheric and astrophysical shocks.
In this study, we use the Parker Solar Probe and Solar Orbiter gravity assists at Venus to investigate electron acceleration at the Venusian bow shock. 
The identified Venusian shock crossings are compared to terrestrial bow shock crossings with similar shock parameters using the Magnetospheric Multiscale (MMS) mission. The aim of the comparison is to uncover potential differences between the two different types of bow shocks and how the size of collisionless bow shocks affects electron acceleration. 
Preliminary results indicate a harder average spectral index (p ~ 3.5±0.6) for suprathermal electrons observed at Venus's bow shock than those found at Earth's bow shock (p ~ 4.9±0.8) for similar Mach number and shock angle.

How to cite: Lindberg, M. and Hietala, H.: Electron Acceleration Comparison of the Venusian and Terrestrial Bow Shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2626, https://doi.org/10.5194/egusphere-egu25-2626, 2025.

Collisionless shock waves are ubiquitous in astrophysical plasmas, from supernova remnants and planetary atmospheres to coronal mass ejections and laboratory experiments. These shocks are known to be efficient particle accelerators, crucial for understanding the origin of cosmic rays, including ultra-relativistic particles. This study presents a novel model of reinforced shock acceleration for electrons, integrating in-situ data from NASA's Magnetospheric Multiscale (MMS) and Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction (ARTEMIS) missions. Focusing on Earth's planetary environment, our analysis reveals a suprathermal electron injection threshold, demonstrating how a multiscale framework involving foreshock transient phenomena, a suprathermal seed population, and wave-particle interactions can systematically accelerate suprathermal electrons to relativistic energies. By merging theoretical advancements in astrophysical plasmas and shock physics with these multi-spacecraft observations, we address the persistent electron injection problem and explore the broader applicability of our model to other planetary environments within our solar system and beyond, including stellar and interstellar contexts.

How to cite: Raptis, S., Lalti, A., Lindberg, M., Turner, D., Caprioli, D., and Burch, J.: Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4552, https://doi.org/10.5194/egusphere-egu25-4552, 2025.

Recent studies suggest that magnetosheath jets can form at the boundaries of a hot flow anomaly (HFA) during shock-discontinuity interaction by solar wind's compression and less efficient deceleration from a curved bow shock. Here, based on Magnetospheric Multiscale (MMS) data and an 3D global hybrid simulation, we report two large-scale jets at the boundaries of an HFA that together with the HFA reached more than 20 Earth radii in width, thus representing a large-scale restructuring of the dayside magnetosheath. Since shock-discontinuity interaction is a universal process that can occur at all planets, we expect that magnetosheath restructuring under such mechanisms is also universal across the solar system.

How to cite: Zhou, Y., Guo, J., Raptis, S., Wang, S., Shue, J.-H., Wang, B., Lu, Q., Zhang, J., Shen, C., and Shao, P.: Magnetosheath Restructuring by Shock-Discontinuity Interaction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4963, https://doi.org/10.5194/egusphere-egu25-4963, 2025.

The bow shock at Earth is created when the super-Alfvénic solar wind interacts with Earth’s magnetosphere and is slowed to sub-Alfvénic velocities. Depending on the angle θ_Bn between the interplanetary magnetic field and the bow shock normal, the shock is defined to be either quasi-perpendicular (θ_Bn > 45°) or quasi-parallel (θ_Bn < 45°). In the quasi-parallel regime, the upstream region magnetically connected to the shock, called the foreshock, is highly dynamic and characterized by various plasma instabilities and wave activity. Short Large-Amplitude Magnetic Structures (SLAMS) are non-linear isolated magnetic field signatures commonly observed in this region. They are believed to grow from ultra-low frequency (ULF) waves which are common in the foreshock.

SLAMS are suggested to be important for the formation of the quasi-parallel shock. They are propagating upstream towards the sun, but generally with a propagation velocity smaller than the solar wind velocity. Consequently, they are convected downstream towards the shock. If they obtain high propagation velocities they should, however, be able to become stationary in the bow shock frame of reference and studies have suggested that the shock itself is composed of a patchwork of SLAMS.

In this work, we use multipoint measurements made by the Cluster mission to make a statistical analysis of the propagation velocity of SLAMS in the foreshock of Earth. We study the dependence on other properties of the SLAMS, such as their amplitude, and parameters related to the upstream environment. 

How to cite: Bergman, S., Karlsson, T., Wong Chan, T. K., and Trollvik, H.: Statistical Study of the Propagation Velocity of Short Large-Amplitude Magnetic Structures (SLAMS) in the Foreshock of Earth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5884, https://doi.org/10.5194/egusphere-egu25-5884, 2025.

The solar wind and interplanetary magnetic field parameters observed in situ by the SWA and MAG instruments onboard the Solar Orbiter mission provide a unique opportunity to identify interplanetary (IP) shock waves at various distances from the Sun on the rising phase of the 25^th solar activity cycle.

In the frame of this work, to recognize IP shocks, we applied a semi-automated method on the base of quality factors comprising the solar wind velocity, density characteristics, and total interplanetary magnetic field parameters. As an example, we identified a few tens of various IP shocks that occurred in the inner heliosphere, at radial distances of 0.29–0.95 AU from the Sun. Most of them were classified as FF-type shock waves, with only a few events identified as FR-, SF- and SR-type shock waves. The semi-automatic algorithm mentioned was used to determine the time of passage of the shock wave front through the spacecraft’s location.

Moreover, we calculated the typical kinetic and magnetohydrodynamic characteristics of each identified shock wave. In particular, the radial dependences of parameters such as the density ratio (r_N), magnetic field (r_B) ratio, plasma beta (β_us), Alfvén velocity (V_A), the angle between the shock normal and the interplanetary magnetic field (Q_Bn), shock wave front velocity (V_sh), sound speed (V_s) and magnetosonic speed (V_fms) were analyzed. Additionally Alfvén (M_A) and magnetosonic (M_fms) Mach numbers were studied. Finally, the dependence of the number of identified shock waves on radial distance was also examined and compared with solar flares activity.

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., and Wawrzaszek, A.: Interplanetary shock waves semi-automated identified as seen by Solar Orbiter., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6223, https://doi.org/10.5194/egusphere-egu25-6223, 2025.

Properties of the region upstream of planetary bow shock depend strongly on the direction of the interplanetary magnetic field. For quasi-parallel bow shock, part of the solar wind ions are reflected back upstream from the shock and this reflected ion population triggers instabilities resulting in a turbulent region. In the quasi-parallel case, reflected particles travel far upstream, creating an extended turbulent foreshock 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 shock. 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 foreshock including Mars, Mercury and Saturn using the respective 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., Bergman, S., and Trollvik, H.: Statistical study of SLAMS at different planetary foreshock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6562, https://doi.org/10.5194/egusphere-egu25-6562, 2025.

Shocklets are compressive, linearly polarized magnetosonic structures that have been widely observed in the Earth's foreshock. They form due to wave steepening and dispersive effects, often accompanied by whistler wave precursors. At Earth these structures are characterized by steepened upstream edges, magnetic compression below 2, and associations with hot diffuse ion distributions. Shocklets play a crucial role in energy transfer and wave-particle interactions in collisionless shocks. While most studies have focused on Earth's foreshock, some evidence suggests their presence at Venus, raising questions about their existence in other planetary foreshocks.

In this study, we investigate the presence of shocklets in Mercury's foreshock using data from the MESSENGER mission. The timescales of Hermean shocklet candidates range from 3 to 30 seconds. Our preliminary analysis reveals that shocklets at Mercury exhibit greater diversity compared to those observed at Earth. While some structures resemble typical Earth-like shocklets, characterized by a sharp leading edge with whistler wave precursors followed by a slower relaxation, we also identify ULF magnetosonic waves accompanied by high-frequency fluctuations that display initial signs of wave steepening which could correspond to an early stage of the Earth-like shocklet. Our findings highlight the complex and dynamic wave activity in Mercury's unique solar wind environment.

How to cite: Rojas-Castillo, D., Vaquero Bautista, C. A., Blanco-Cano, X., Plaschke, F., Kajdic, P., Pump, K., and Heyner, D.: Shocklets in the vicinity of Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7432, https://doi.org/10.5194/egusphere-egu25-7432, 2025.

Particle acceleration and radiation are fundamental cosmic processes that significantly contribute to the universe’s energy density, driven by phenomena ranging from solar flares to supernova explosions. Shock waves, prevalent across various spatial scales, play a key role in converting kinetic energy into plasma heating and particle acceleration. Recent advancements from missions such as the Parker Solar Probe (PSP) have provided unprecedented insights into the dynamics of shock waves within the heliosphere, thereby enhancing our understanding of these critical energy conversion mechanisms.

In this talk, I will present findings from two recent studies that leverage the PSP’s unique proximity to the Sun and its advanced, high-fidelity instrumentation. First, we analyzed one of the fastest shocks ever observed on March 13, 2023, revealing the efficient acceleration of electrons up to and exceeding 6 MeV and the collective acceleration of ions from the thermal solar wind. Second, we made the surprising discovery of synchrotron radiation emanating from ultra-relativistic electrons in both a quasi-parallel and a quasi-perpendicular shock, with the quasi-parallel shock exhibiting significantly higher radiation intensities due to more effective electron acceleration. These results are consistent not just with theoretical models of strong cosmic shocks, but also observations. This offers an unprecedented opportunity to bridge in situ heliospheric observations with remote observations of phenomena such as supernova remnants.

How to cite: Jebaraj, I. C., Agapitov, O., Gedalin, M., Krasnoselskikh, V., Vuorinen, L., Miceli, M., Dresing, N., Cohen, C., Balikhin, M., Kouloumvakos, A., Palmerio, E., Wijsen, N., Mitchell, J. G., McComas, D., Rawafi, N., Kilpua, E., Vainio, R., and Bale, S.: Scale-Invariant Particle Energization and Radiation – Foundations for Building a Cosmic Bridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10616, https://doi.org/10.5194/egusphere-egu25-10616, 2025.

Solar wind directional discontinuities can generate transient mesoscale structures such as foreshock bubbles and hot flow anomalies (HFAs) upstream of Earth's bow shock. These structures can have a global impact on the near-Earth environment, and understanding their formation conditions is crucial to evaluate their contribution to solar wind-magnetosphere coupling. Here we present the results of a global 2D hybrid-Vlasov simulation (with 3D electromagnetic fields) of the interaction of a rotational discontinuity with near-Earth space, performed with the Vlasiator model. The magnetic field rotates by 90 degrees from ortho-Parker spiral to Parker spiral orientation across the discontinuity. As the discontinuity enters the simulation domain, a foreshock bubble forms duskward of the Sun-Earth line, where the foreshock is initially located. Shortly after the discontinuity makes first contact with the bow shock at the subsolar point, we find that a structure with enhanced temperature and strongly deflected flows develops at the intersection of the discontinuity with the bow shock. This structure displays typical features of an HFA. However, HFA formation requires electric fields pointing towards the discontinuity on at least one side, a condition which is not initially met in our simulation. We demonstrate that the prior generation of the foreshock bubble provides the necessary conditions for HFA formation. We then investigate the evolution of both structures as the discontinuity travels antisunward, showing that the foreshock bubble signatures tend to weaken while the HFA grows. We also report a large-scale bow shock deformation, with the bow shock expanding several Earth radii outward of its initial position within the compressed edge of the foreshock bubble. Our results provide new clues regarding the formation and evolution of large-scale foreshock transients and their impact on the shock.

How to cite: Turc, L., Archer, M. O., Zhou, H., Pfau-Kempf, Y., Suni, J., Kajdic, P., Blanco-Cano, X., Dahani, S., Lipsanen, V., Tao, S., Battarbee, M., and Palmroth, M. and the ISSI team 555: Foreshock bubbles can modify their solar wind discontinuities enabling secondary transients to form, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10989, https://doi.org/10.5194/egusphere-egu25-10989, 2025.

Short large-amplitude magnetic structures (SLAMS) are seen as critical elements in collisionless shocks with quasi-parallel geometries.  They can pre-accelerate solar wind ions into suprathermal energy as an injection mechanism for Diffusive Shock Acceleration. To understand the details of the injection problem, we present direct observations of nonstationarity of a SLAMS, using Magnetosperic Multiscale (MMS) measurement in a sting-of-pearls configuration separated by several hundreds of kilometers. We find that the upstream edge of the SLAMS serves as a local quasi-perpendicular shock front to reflect and accelerate solar wind ions. Accumulation of reflected ions results in upstream expansion of the SLAMS ramp and the reflecting point may change their location. Whistlers grow quickly as the SLAMS ramp propagates towards upstream and distort the SLAMS in return.    

How to cite: Wang, M., Khotyaintsev, Y., and Graham, D.: Multipoint Observations of Nonstationarity of a Short Large-Amplitude Magnetic Structure (SLAMS), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11679, https://doi.org/10.5194/egusphere-egu25-11679, 2025.

Low Mach number, fast magnetosonic,  dispersive shocks are formed if the characteristic scale of the shock front exceeds the characteristic the spatial scale associated with resistive processes. In these cases, dispersion arrests the nonlinear steepening of the shock front. According to the established view,  a whistler wave precursor, whose wave vector is parallel to the shock normal, is formed in oblique dispersive shocks provided that the Mach number does not exceed the Whistler Critical Mach number Mw. Numerical simulations and data obtained by the MMS satellites are used to investigate the evolution of the properties of the upstream whistler precursor as the Mach number increases above  Mw.

How to cite: Balikhin, M., Agapitov, O., Krasnoselskikh, V., Roytershteyn, V., Walker, S., Gedalin, M., Jebaraj, I. C., and Colomban, L.: Whistler Critical Mach Number Concept Revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12010, https://doi.org/10.5194/egusphere-egu25-12010, 2025.

The bow shock of Mars provides a compelling example of a mass-loaded, supercritical shock. A key challenge in space plasma physics is understanding the mechanisms of particle acceleration that occur at collisionless shocks. Due to extensive studies, the terrestrial foreshock is often considered a benchmark for interactions between planetary magnetospheres and the solar wind. The MAVEN mission at Mars is offering a wealth of data, simultaneously opening a window to study the Martian foreshock in detail.

 In this context, we present new measurements of velocity distribution functions of suprathermal protons upstream of Mars' bow shock. We identify backstreaming beams aligned (FAB) and misaligned with the interplanetary magnetic field (IMF) direction for various shock geometries. FAB bulk velocities are found to be well-distributed in relation to the shock speed. Our analysis reveals that, compared to their terrestrial counterparts, Martian FABs exhibit slower sunward motion. Additionally, it appears that these FABs originate from a shock region where the IMF lines form an angle of 20-50 degrees with the shock normal— a smaller source region than that of Earth's bow shock.

 These findings rule out specular reflection as the mechanism behind beam production. Typically, terrestrial FABs are produced through a quasi-adiabatic process that preserves the first invariant to some extent. In contrast, the new Martian observations provide a valuable comparison between the foreshocks of Earth and Mars, shedding light on key differences and enhancing our understanding of these planetary phenomena.

How to cite: Meziane, K., Mazelle, C., Simon-Wedlund, C., Halekas, J., Hamza, A., Bertucci, C., Mitchell, D., and Espley, J.: Ion acceleration at Mars Bow Shock - Results from MAVEN, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12526, https://doi.org/10.5194/egusphere-egu25-12526, 2025.

Using Magnetospheric Multiscale (MMS) data from Earth orbit, an automated clustering algorithm has been employed to classify dayside MMS data into four distinct regions: magnetosphere, magnetosheath, solar wind, and ion foreshock, as detailed in Toy-Edens et al. [JGR 2024].  Applied to eight years of MMS data, over 25,000 bow shock crossings were identified from all four MMS spacecraft. Using that event database, we highlight a series of results including: new, 3-dimensional, parameterized boundary model fits for the bow shock; statistical characteristics of the quasi-parallel and quasi-perpendicular bow shock; and a new 4-point timing algorithm to systematically determine bow shock normal directions. We detail new results concerning the accuracy and performance of the shock normal results, showing that this new approach works remarkably well. We also highlight some new results of kinetic shock behavior and compare those directly to results from state-of-the-art simulations of and corresponding predictions for collisionless shocks. We end with a discussion of future work, in which we hope to train a parameterized generative model for collisionless shock crossing data as a function of upstream plasma characteristics. Our hope is to be able to apply that model to collisionless shocks beyond 1 au, validating its performance with shock observations from other systems (including Venus, Mars, Jupiter, etc.), and ultimately apply it to solar and other astrophysical shocks that are beyond our reach for in situ observations. 

How to cite: Turner, D., Toy-Edens, V., Mo, W., and Young, S.: Employing machine learning techniques for systematic and statistical studies of collisionless shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13753, https://doi.org/10.5194/egusphere-egu25-13753, 2025.

Earth’s magnetosheath, the region between Earth’ magnetic field and the bow shock, gives rise to a plethora of transients, waves, and instabilities. Each effect changes the plasma parameter distribution, impacting the behaviour of the plasma that finally hits our magnetic field. Turbulence plays a crucial role in how energy injected into the system by transients or instabilities is transported and dissipated from large to small scales. We are investigating the role magnetosheath pressure enhancements (or so-called jets) play in adding to the turbulence in the system. These jets often plough through the system with high velocity, interacting with the surrounding environment, and slow down the further they travel. The propagation of jets is still largely unexplored, in particular when considering plasma turbulence. We aim to quantify whether jets drive turbulence in the magnetosheath plasma, and whether turbulent plasma fluctuations impact the propagation of jets. Magnetic orientation and distance to the shock are considered in the analysis in order to disentangle their impact on the effects. We are using MMS spacecraft measurements for the analysis of individual jet cases, and THEMIS spacecraft for a statistical analysis at event times when several spacecraft were close to the flow of jet events.

How to cite: Koller, F., Chen, C., and Hietala, H.: Turbulence Surrounding Magnetosheath Jets: Are Pressure Enhancement Stirring the Magnetosheath?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14042, https://doi.org/10.5194/egusphere-egu25-14042, 2025.

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections, and by the interaction of fast solar wind with slow streams of plasma. These shocks can be preceded by extended wave and suprathermal ion foreshocks perturbing large extensions of the heliosphere. In a recent study (Trotta et al., 2024 it was shown that the interaction between two interplanetary coronal mass ejections (ICMEs) can drive a forward and a reverse shock with similarities to those bounding stream interaction regions (SIRs). In this work we analyse the microstructure of this event observed by Solar Orbiter on March 8th, 2022 at 0.5 AU. We find that wave characteristics change from one ICME to the other. Inside the first ICME waves have a broad band sprectrum. In contrast, there are regions in the second ICME with very monochromatic waves. In both cases, waves are associated with proton and alpha particle distributions that show a super-Alfvenic drift, suggesting local wave generation. Larger amplitude waves due to ion reflection are found upstream of the forward shock forming an extended foreshock. Although the shock was weak,  reflected populations include alpha particles, and O⁶⁺ ions. Of particular interest is the fact that monochromatic ion cyclotron waves associated with anisotropic (Tperp >Tpar) ion distributions are found in the region between the two ICMEs. Our results show how ICME-ICME interaction can result in regions with a variety of microstructure phenomena in the inner heliosphere.

How to cite: Blanco-Cano, X., Trotta, D., Kieokaew, R., Livi, S., Hietala, H., Kajdic, P., Rojas-Castillo, D., Dimmock, A., Larosa, A., Hornury, T., Vainio, R., and Jian, L.: Microstructure at a fully formed Forward-Reverse Shock pair due to the interaction between two Coronal Mass Ejections observed at 0.5 AU., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14236, https://doi.org/10.5194/egusphere-egu25-14236, 2025.

We examine the possibility of remotely sensing Earth’s bow shock location, orientation, and velocity, via gyrosensing the plasma ions reflected from the shock. In this work, we present a remote gyrosensing approach to quantifying the bow shock properties for various interplanetary magnetic field orientations by analyzing reflected particles with different gyrophases and pitch angles. Then we suggest an analytical formalism for predicting the bow shock characteristics based on the azimuthal and zenith look angles of the reflected ions as observed by ElectroStatic Analyzers (ESA) on a single probe near the bow shock. The proposed method will be tested and verified with FPI ion instrument measurements onboard Magnetospheric MultiScale (MMS) spacecraft.

How to cite: Barani, M., Sibeck, D., McFadden, J., Bonnell, J., Wilson, L., and Koval, A.: Remote Gyrosensing of the Earth's Bow Shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14505, https://doi.org/10.5194/egusphere-egu25-14505, 2025.

Localised dynamic pressure enhancements – jets – have been observed downstream of both planetary and more recently interplanetary shocks. At planetary environments, jets are known to drive enhanced particle acceleration, large-amplitude magnetic field variations and reconnecting current sheets.

The analysis of interplanetary jets observed by Wind spacecraft near the Earth showed that their properties are similar to those of magnetosheath jets. Furthermore, we found jets also at low beta, low Mach number interplanetary shocks, i.e., conditions that are rare for the Earth’s bow shock.

Following the jet identification approach we introduced for Wind data, here we now apply it to Solar Orbiter measurements made at various heliocentric distances.

How to cite: Hietala, H., Shirazul, K., Trotta, D., Webb, P., Vuorinen, L., and Koller, F.: Investigating jets downstream of interplanetary shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17988, https://doi.org/10.5194/egusphere-egu25-17988, 2025.

In this paper, we discuss the changes to the magnetosheath plasma due to interaction with a density structure within the magnetic cloud an interplanetary coronal mass ejection that impacted Earth and caused significant perturbations in plasma boundaries. The bow shock breathing motion is evident due to the changes in the upstream dynamic pressure. A solitary magnetic enhancement forms in the inner magnetosheath with characteristics of a fast magnetosonic shock wave, propagating earthward and perpendicular to the background magnetic field. We show that the magnetosheath plasma is heated twice, during the bow shock crossing and during the interaction with the fast magnetosonic shock inside the magnetosheath. Following these events, a sunward motion of the magnetosheath plasma is evident. Analysis of ion distributions indicates that the sunward flows are caused by the reflection of flux tubes within the fast magnetosonic shock near the magnetopause boundary.

How to cite: Madanian, H.: Solitary magnetic structure and sunward flows in the dayside magnetosheath, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20631, https://doi.org/10.5194/egusphere-egu25-20631, 2025.

Collisionless diffusive shock waves are the primary mechanism for the production of high energy particles in the Sun, with the solar flare terminal shock waves located in the lower solar atmosphere providing the seed particles for the generation of high energy particles. Whether flare terminal shocks can trigger ground-level enhancement events with energies reaching GeV remains a mystery. Solar cosmic ray particle streams play a crucial role in the space weather environment, and in the heliospheric plasma bubble, solar high energy particle events at lower energy ranges typically exhibit single power law spectra, while at higher energy ranges, solar high energy particle events often have multi-power-law spectral features with "knee" and "ankle" breaks. The intrinsic mechanism behind these significant spectral changes is not yet clear. Through simulation comparisons, it was found that the particle spectra produced by the termination shocks of double solar flares in the low-energy range are double power-law spectra that soften to harden, whereas the spectra produced by single flare shock are single power-law spectra. We believe this is due to the stronger acceleration capability caused by the superposition of double shocks. Thus, it reveals that multi-shock interactions can lead to changes in the particle spectra.

How to cite: Wang, X.: Compare the differences in the high-energy particle spectra accelerated by single and double flare shocks., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20995, https://doi.org/10.5194/egusphere-egu25-20995, 2025.

The solar wind plasma is observed to fluctuate over a broad range of space and time scales, extending from scales above the magnetic field correlation scale to below those associated with the particle gyration. At scales larger than the gyroscale, the fluctuations are typically categorised as 1) non-compressive fluctuations that have Alfvénic correlation, 2) compressive fluctuations that perturb the plasma density and pressure. While the amplitude of the compressive fluctuations are subdominant to the Alfvénic component, they have unique dynamics that drastically alter the plasma. For example, compressive fluctuations perturb the pressure anisotropy and beam drift speeds. This may drive the perturbed plasma unstable, generating microscale waves that scatter particles and alter the effective mean free path. In addition, compressive fluctuations perturb the magnetic field strength, leading to stochastic heating and transit time damping. Therefore, an understanding of compressive fluctuations is vital to a complete picture of the plasma thermodynamics. To build on our understanding of the solar wind in the inner heliosphere, we combine observations from Solar Orbiter, Parker Solar Probe, and the Wind spacecraft to study compressive fluctuations. We compare amplitude ratios and polarisations to numerical models to understand the efficiency of various generation mechanisms of compressive fluctuations and how they heat and modify the thermodynamics of the solar wind plasma.

How to cite: Coburn, J., Verscharen, D., Tenerani, A., and Owen, C.: The Thermodynamic Impact of Compressive Fluctuations on the Solar Wind in the Inner Heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3330, https://doi.org/10.5194/egusphere-egu25-3330, 2025.

Solar Orbiter observations provide an unprecedented opportunity to study plasma turbulence in the solar wind. On magnetohydrodynamic scales intermittent structures mediate the cascade, due to non-linear wave-wave interactions and coherent structures. Those coherent structures are often quantified and identified by the Partial Variance Increment (PVI).

We obtain magnetic field fluctuations from observations of homogeneous turbulence by wavelet decompositions which preferentially resolve either signatures of coherent structures or wave-packets. Comparing the PVI obtained from both wavelet decompositions, this provides a new, physics based method to determine the PVI threshold above which fluctuations may be coherent structures.

We find a single PVI threshold in each of the kinetic and inertial ranges above which coherent structures typically dominate. This threshold is insensitive to the plasma conditions or heliocentric distance. Therefore, it suggests a ubiquitous constraint on the turbulent phenomenology. This can inform estimates of the heating rates of the solar wind due to the turbulence.

How to cite: Bendt, A. and Chapman, S.: Ubiquitous threshold for coherent structures in the kinetic and inertial ranges of solar wind turbulence from Solar Orbiter observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3592, https://doi.org/10.5194/egusphere-egu25-3592, 2025.

Space plasma turbulence incorporates multi-scale coexisting occurrences of many physical phenomena such as waves, large amplitude field and plasma fluctuations, formation of coherent structures and the large variety of associated energy transfer, transport and conversion processes. For example, magnetic reconnection converts magnetic energy to kinetic and thermal energies and accelerates particles. Contrarily, dynamo action refers to energy conversion processes through which magnetic fields are generated or/and amplified at the expense of kinetic energy. Magnetic reconnection has been extensively studied on the basis of in-situ measurements at large-scale magnetospheric boundaries, in the turbulent magnetosheath and in the solar wind. Dynamo processes have been investigated mainly through numerical studies and in laboratory liquid metal and laser experiments. In-situ observations of dynamo processes require certain physical assumptions to calculate gradients from single-point data in the solar wind. Here we study for the first time the kinematic small-scale dynamo in the turbulent magnetosheath. In the kinematic approach the back reaction of the amplified magnetic field to plasma flows is neglected. Small-scale dynamos can generate or amplify magnetic fields at scales comparable to, or smaller than, the characteristic scales of flow gradients in 3D plasma turbulence. The flow gradients are estimated on the basis of in-situ multi-point MMS measurements. Theoretical predictions and numerical simulation results for the turbulent kinematic dynamo are tested. Specifically, the expected stretching of the magnetic field by velocity gradients, the effect of compressions and the concurrent occurrence of pressure anisotropy instabilities are investigated. The observations show that the magnetosheath data exhibit the expected turbulent dynamo signatures. Since the increase of magnetic field is associated with the loss of kinetic energy, the small-scale dynamo represents an inherent ingredient of plasma turbulence.

How to cite: Vörös, Z., Roberts, O. W., Narita, Y., Emiliya, Y., Nakamura, R., Schmid, D., Settino, A., Wolwerk, M., Wedlund, C. S., Varsani, A., Sorriso-Valvo, L., Bourdin, P. A., and Kis, Á.: Turbulent small-scale kinematic dynamo in the terrestrial magnetosheath, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3759, https://doi.org/10.5194/egusphere-egu25-3759, 2025.

The very first observations by Mariner 5 highlighted the presence of Alfvénic fluctuations in the solar wind identified as nearly incompressible fluctuations accompanied by large correlations between velocity and magnetic field components as predicted by the magnetohydrodynamics (MHD) theory. Since then, Alfvénic fluctuations have been observed to be ubiquitous especially in high-speed solar wind streams, but are also in some cases in slow wind streams, which may in turn exhibit a strong Alfvénic character. The so-called Alfvénic slow wind resembles the fast wind in many aspects, but may also differ from it. Indeed, recent observations performed by Solar Orbiter have shown that the fast wind may display a strong Alfvénic content of the fluctuations than the one observed in the Alfvénic slow wind, especially closer to the Sun.

In this context, Solar Orbiter offers a unique opportunity to study the origin and radial evolution of the Alfvénic solar wind. In this particular study, we present a comparative study between different Alfvénic streams, both fast and slow, at different heliocentric distances, focusing on the characterization of Alfvénicity of different streams with particular reference to the energy balance of the fluctuations.

The aim of this work is to deepen our understanding of what are the mechanisms responsible for the evolution of Alfvénicity in solar wind fluctuations and to understand better to what extent the two solar wind regimes show different Alfvénic content of the fluctuations and eventually evolve in a different way.

How to cite: D Amicis, R., Benella, S., Bruno, R., De Marco, R., Velli, M., Perrone, D., Sorriso Valvo, L., Alterman, B. L., Sioulas, N., Franci, L., Verdini, A., Matteini, L., Telloni, D., Owen, C. J., Louarn, P., and Livi, S.: What determines the departure from equipartition of energy in Alfvénic fluctuations in solar wind streams? Insights from Solar Orbiter observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4040, https://doi.org/10.5194/egusphere-egu25-4040, 2025.

Exploration of space plasmas is entering a new era of multi-satellite constellation measurements that will determine fundamental properties of turbulence, with unprecedented precision. Familiar but imprecise approximations must be abandoned and replaced with more advanced approaches. We present the novel multispacecraft technique LPDE (Lag-Polyhedra Derivative Ensemble) for evaluating third-order statistics, using simultaneous measurements at many points. The method differs from existing approaches in that (i) it is inherently three-dimensional; (ii) it provides a statistically significant number of estimates from a single data stream; and (iii) it allows for a direct visualization of energy flux in turbulent plasma. Implications for HelioSwarm and Plasma Observatory and comparison with single-spacecraft approaches are discussed.

How to cite: Pecora, F., Servidio, S., Greco, A., Yang, Y., Matthaeus, W. H., Chasapis, A., Primavera, L., Hellinger, P., Pucci, F., Oughton, S., Gershman, D. J., Giles, B. L., and Burch, J. L.: Measuring the turbulent energy cascade rate with multiple spacecraft, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4534, https://doi.org/10.5194/egusphere-egu25-4534, 2025.

The power spectral densities (PSDs) of ion moments and magnetic field turbulence in the solar wind can be fitted by a power law with the power index of -5/3 in the MHD range of frequencies and with the power index ranging from 2 to 4 at frequencies exceeding the proton gyroscale.  However, the density PSD often exhibits a significant flattening at the high-frequency part of the MHD range but a similar effect was not observed for any other quantity. 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 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 or ion beta. The statistics based on more than 10 thousand of 20-minute intervals shows that the compressive component of magnetic field fluctuations behaves like the density fluctuation in the old, low-beta solar wind. On the other hand, a similar profile was not observed for either bulk or thermal speeds. The dependence on the collisional age initiated the comparison with Solar Orbiter and PSP observations in the inner heliosphere that would shed light on the processes leading to a formation of these spectral features.

How to cite: Safrankova, J., Nemecek, Z., and Nemec, F.: Flattening of the magnetic field power spectral density profile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4798, https://doi.org/10.5194/egusphere-egu25-4798, 2025.

We investigate properties of ideal second-order magneto-hydrodynamic (MHD) and Hall MHD invariants  (kinetic+magnetic energy and different helicities) in a two-dimensional hybrid simulation of decaying plasma turbulence. The combined (kinetic+magnetic) energy decays at large scales, cascades (from large to small scales) via the MHD non-linearity at intermediate scales. This cascade partly continues via the Hall coupling to sub-ion scales. The cascading energy is transferred (dissipated) to the internal energy at small scales via the resistive  dissipation and the pressure-strain effect. The mixed (X) helicity, an ideal invariant of Hall MHD, exhibits a strange behaviour whereas the cross helicity (the ideal invariant in MHD but not in Hall MHD), in analogy to the energy, decays at large scales, cascades from large to small scales via the MHD+Hall non-linearities, and is dissipated at small scales via the resistive dissipation and an equivalent of the pressure-strain effect. In contrast, the magnetic helicity is very weakly generated through the resistive term and does not exhibit any cascade; furthermore, the magnetic and cross helicities are not coupled in the hybrid approximation, so that the corresponding helicity barrier does not exist.

How to cite: Hellinger, P. and Montagud Camps, V.: Rugged magnetohydrodynamic invariants in weakly collisional plasma turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5936, https://doi.org/10.5194/egusphere-egu25-5936, 2025.

Turbulent processes play a key role in the dynamics of solar wind plasma fluctuations, governing energy transfer within the heliosphere and driving particle acceleration. In this study, we aim to investigate the nature of large- and small-scale fluctuations in the upstream and downstream regions of interplanetary shocks. By analyzing magnetic field fluctuations using both traditional and recently developed methods, we examine changes in correlation length, Taylor scale, and Reynolds number from upstream to downstream regions. Plasma and magnetic field measurements from the ACE, WIND, and DSCOVR missions are utilized in this analysis. Correlation lengths are determined using autocorrelation and cross-correlation functions applied across data from the three spacecraft. When analyzing the Reynolds number, we observe a decrease in values when transitioning from upstream to downstream regions, suggesting turbulence resetting in the case under consideration. Building on the findings of a case study, we extend our investigation by performing a statistical analysis of these parameters across multiple shocks.

How to cite: Abushzada, I., Pitna, A., Nemecek, Z., and Safrankova, J.: Autocorrelation and Cross-Correlation of MHD Turbulence across IP Shock: Multispacecraft Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6875, https://doi.org/10.5194/egusphere-egu25-6875, 2025.

The evolving subset of turbulent structures facilitates the energy transfer from large to small spatial scales, on average. Currently, it is not known how the discontinuities that develop between these structures alter the energy transfer in the solar wind. Quantifying the energy transfer to small scales is essential to explain the apparent plasma heating during its advection through the heliosphere. We analyse the energy transfer rate conditioned on the magnetic field line topology of the associated structures in the solar wind. Magnetic field line topology is classified using invariants of the magnetic field gradient tensor constructed from the Cluster spacecraft configuration on scale of approximately 40 proton gyro-radii. Third order structure functions are estimated for five solar wind intervals and conditioned on the contemporaneous values of the topological invariants. We determine how the global mean energy transfer rates correlate with the topology of the turbulence.

How to cite: Hnat, B., Chapman, S., and Watkins, N.: Statistics of the turbulent energy transfer rate conditioned on magnetic field line topology in the solar wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6877, https://doi.org/10.5194/egusphere-egu25-6877, 2025.

How to cite: Jiang, W., Li, H., Verscharen, D., Zheng, J., Klein, K., Riquelme, M., Liu, J., and Wang, C.: Multi-scale Dynamics of Coherent Electron Trapping and Diffusion in Earth's Magnetosheath, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7618, https://doi.org/10.5194/egusphere-egu25-7618, 2025.

We have studied the decay of turbulence in the solar wind. Fluctuations carried by the expanding wind are naturally damped because of flux conservation, slowing down the development of a turbulent cascade. The latter also damps fluctuations but results in plasma heating. We analyzed time series of the velocity and magnetic field (v and B, respectively) obtained by the WIND spacecraft at 1 au. Fluctuations were recast in terms of the Elsasser variables, z± = v ± B/√4πρ, with ρ being the average density, and their second- and third-order structure functions were used to evaluate the Politano-Pouquet relation, modified to account for the effect of expansion.

We find that expansion plays a major role in the Alfvénic stream, those for which z+ ≫ z‑. In such a stream, expansion damping and turbulence damping act, respectively, on large and small scales for z+, and also balance each other. Instead, z‑ is only subject to a weak turbulent damping because expansion is a negligible loss at large scales and a weak source at inertial range scales.

These properties are in qualitative agreement with the observed evolution of energy spectra that is described by a double power law separated by a break that sweeps toward lower frequencies for increasing heliocentric distances. However, the data at 1 au indicate that injection by sweeping is not enough to sustain the turbulent cascade. We derived approximate decay laws of energy with distance that suggest possible solutions for the inconsistency: in our analysis, we either overestimated the cascade of z± or missed an additional injection mechanism; for example, velocity shear among streams.

How to cite: Verdini, A., Hellinger, P., Landi, S., Grappin, R., Montagud-Camps, V., and Papini, E.: Decay of magnetohydrodynamic turbulence in the expanding solar wind: WIND observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9622, https://doi.org/10.5194/egusphere-egu25-9622, 2025.

Magnetohydrodynamic (MHD) shocks are one of the key nonlinear phenomena which occur in plasmas and can influence a dynamical evolution of a system at wide range of spatial scales. In the vicinity of the shock fronts, a majority of the dissipation of the incident bulk energy takes place. Furthermore, the incident fluctuations have profound effect on the shock front itself and also on the respective evolution of the transmitted/generated modes. Recently, several approaches have been developed focusing on the evolution of various plasma wave modes across MHD shocks. In this work, we investigate the transmission of quasi-2D turbulent fluctuations across fast forward shocks in the framework of the Zank et al. (2021) model. We take advantage of concurrent measurements of upstream and downstream plasma of a terrestrial bow shock, employing observations of the Wind spacecraft and Magnetophere Multiscale Mission (MMS). This partially mitigates two main limitations of single spacecraft studies, (a) the variability of incident plasma and magnetic field fluctuations and (b) the effects that stem from the evolution of fluctuations as they propagate away from the shock front. Our results suggest that the Zank et al. (2021) model predicts the downstream levels of fluctuations excellently for the quasi-perpendicular regime of the bow shock. We discuss the deviations between the predicted and observed levels of downstream fluctuations, highlighting the influence of bow shock nonplanarity and variable obliquity.

How to cite: Pitna, A., Zank, G., Zhao, L., Nakanotani, M., Gautam, S. P., Silwal, A., Abushzada, I., Park, B., Safrankova, J., and Nemecek, Z.: Evolution of Turbulent Fluctuations across Terrestrial Bow Shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9809, https://doi.org/10.5194/egusphere-egu25-9809, 2025.

We present a comprehensive analysis of the evolution of the turbulent energy dissipation at interplanetary (IP) shocks observed by Parker Solar Probe (≈0.4 AU), Solar Orbiter (≈0.8 AU), and Wind (1 AU). Our previous study reveals the conservation of the energy dissipating mechanisms across different types of IP shocks except fast reverse. Motivated to investigate the thickness of the shock transition region in terms of the dissipation of magnetic field turbulent energy, we adopt pairs of quasi-perpendicular fast forward (FF) and reverse (FR) shocks observed at Parker Solar Probe, Solar Orbiter, and Wind. By comparing these pairs of shock, we anticipate examining (1) whether FF and FR shocks are systematically different, (2) the dependence of the shock transition thickness on critical Mach number, and (3) on heliocentric distance. We present several parameters, i.e., cross- and magnetic helicity, and the amplitude of magnetic field fluctuations for the estimation of their correlation with the spectral index evolving through shock. The abrupt changes of the plasma parameters along with the spectral index shorter than the temporal resolution of the plasma measurement are overall observed showing their minimal correlations. This suggests a role of IP shock as a thin boundary simply distinguishing two different plasmas. We will extend this hypothesis toward a statistical study including near-shock processes such as particle acceleration and wave activities.

How to cite: Park, B., Pitna, A., Safrankova, J., and Nemecek, Z.: Evolution of Turbulent Energy Dissipation at Quasi-perpendicular Fast Interplanetary Shocks: The thickness of shock transition region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10420, https://doi.org/10.5194/egusphere-egu25-10420, 2025.

The solar wind is highly turbulent, which results in power-law spectra and intermittency for magnetic and velocity fluctuations within the inertial range. 
Using fast solar wind intervals measured during solar minima between 0.3 au and 3.16 au, a clear break emerges within the traditional inertial range, with signatures of two inertial sub-ranges with f^-3/2 and f^-5/3 power laws in the magnetic power spectra. The intermittency, measured through the scaling law of the kurtosis of magnetic field fluctuations, further confirms the existence of two different power laws separated by a clear break. A systematic study on the evolution of the said sub-ranges as a function of heliospheric distance shows correlation of the break scale with both the turbulence outer scale and the typical ion scales. Finally, using Parker Solar Probe data measured closer to the Sun, we highlight the role of switchbacks and switchback patches in generating such scale breaks.

How to cite: Sorriso-Valvo, L., Mondal, S., Banerjee, S., Larosa, A., Wu, H., Sioulas, N., Telloni, D., D'Amicis, R., and Yordanova, E.: Emergence of a characteristic scale in the Alfvénic solar wind turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11551, https://doi.org/10.5194/egusphere-egu25-11551, 2025.

Electromagnetic fluctuations in the solar wind cover a wide range of scales, from sun-rotation period to sub-electron scales. 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, which can be interpreted in terms of electron scale Alfven vortices. We discuss a possible connection of these small-scale vortices with coherent structures at ion scales. The results at 1 au will be compared with spectral properties and coherent structures at kinetic scales observed by Parker Solar Probe closer to the Sun.

How to cite: Alexandrova, O., Jovanovic, D., Hellinger, P., Demoulin, P., Maksimovic, M., Bale, S., and Mangeney, A.: Solar wind turbulent fluctuations within the kinetic range of scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11571, https://doi.org/10.5194/egusphere-egu25-11571, 2025.

In the transition range of the solar wind turbulence, the magnetic spectrum has been observed to be strongly anisotropic with respect to local mean field. However, the generation mechanism of the anisotropy remains not well understood. There are two typical types of waves existing in the transition range, including ion cyclotron waves (ICWs) and kinetic Alfven waves (KAWs) propagating in the directions parallel and perpendicular to magnetic field, respectively. In this work, we perform a statistical study on the effects of the waves on the spectral anisotropy of the transition range. We select 31 intervals from the measurements of Parker Solar Probe between 2018 and 2021. The magnetic helicity (sigma_m) diagnosis is applied on the magnetic field data at the frequency domain [0.1 Hz, 10 Hz], and the wavelet coefficients with sigma_m < -0.5 and sigma_m > 0.4 are considered as signals of ICWs and KAWs, respectively. We then remove them and find that the spectral anisotropy in the transition range becomes significantly weaker. Specifically, the spectra in the quasi-parallel direction statistically get shallower, and the average spectral index changes from -5.68±0.74 to -4.72±0.56. By contrast, the spectra in the perpendicular direction get slightly steeper, and the index changes from -3.63±0.34 to -3.95±0.41. Moreover, the anisotropic scaling in the transition range is found to be k_⊥ ~ k_∥^1.55±0.33. The new results about the magnetic field spectra after the removal of ICW and KAW will help to further understand the possible mechanisms that cause the spectral anisotropy in the transition range.

How to cite: Wang, X. and Zhang, H.: Effects of Waves on the Spectral Anisotropy of Transition Range in the Solar Wind Turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14164, https://doi.org/10.5194/egusphere-egu25-14164, 2025.

Understanding the nature and importance of various proposed heating processes that result from turbulent dissipation is imperative in describing a range of collisionless systems. We highlight the importance of kinetic phase space signatures of heating as pivitol in providing necessary contraints on turbulent dissipation. Understanding mechanisms through diffusive approximation schemes is largely a tractable problem that can be studied with modern plasma instrumentation. We highlight recent progress in understanding signatures of kinetic dissipation and particle heating using the Parker Solar Probe (PSP) mission. Importantly, our observations reveal that a range of heating mechanisms (stochastic heating, cyclotron resonance, and Landau damping) are likely important in explaining observed phase-space plasma signatures. The use of non-parametric approximations to particle distribution functions (via Hermite polynomials and Radial Basis Functions) is pivotal in understanding and characterizing these heating mechanisms. While our observations are from PSP, we discuss furture implementation of these techniques on current and future plasma missions (MMS and Plasma Observatory).

How to cite: Bowen, T., Ervin, T., Chasapis, A., Pezzi, O., Larosa, A., Klein, K., Mallet, A., and Bale, S.: Identifying Kinetic Phase Space Signatures of Turbulent Dissipation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14248, https://doi.org/10.5194/egusphere-egu25-14248, 2025.

Solar wind provides a natural laboratory for the plasma turbulence. The core problem is the energy cascade process in the inertial range, which has been a long-standing fundamental question. Many efforts are put into the theoretical modellings to explain the observational features in the solar wind. However, there are always questions remained. Here we report a new scenario that the inertial regime of the solar wind turbulence consists of two subranges based on the observation. We perform multi-order structure function analyses for one high-latitude fast solar wind interval at 1.48 au measured by Ulysses and one slow solar wind at 0.17 au measured by Parker Solar Probe (PSP). We identify the existence of two subranges in the inertial range according to their distinct scaling features. Based on the observational features, we propose that the possible mechanisms that subrange 1 is Iroshnikov-Kraichnan-like turbulence and subrange 2 is the intermittency-dominated region. The scenario of two subranges and their scaling laws not only shed new lights for the plasma turbulence, but also unify previous results that cause debates, making the observed scaling laws prepared for further theoretical modeling. 

How to cite: Wu, H., Huang, S., He, J., Yang, L., Sorriso-Valvo, L., Wang, X., and Yuan, Z.: A new scenario with two subranges in the inertial regime of solar wind turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14782, https://doi.org/10.5194/egusphere-egu25-14782, 2025.

Properties of the solar wind in different types of plasma (e.g., heliospheric current sheet, coronal hole, ejecta, sub-Alfvénic) are known to exhibit distinct features. Based on Parker Solar Probe measurements of the solar wind in the inner heliosphere, we compare the similarities and differences between two streams originating from different sources at the same radial distance. Despite sharing similar properties, including cross helicity, residual energy, Elsasser ratio, and magnetic compressibility, notable differences are observed. For the solar wind associated with active regions, the turbulence exhibits lower magnetic field fluctuation amplitudes, shallower magnetic field spectrum, and stronger intermittency, whereas the turbulence associated with coronal holes displays opposite characteristics. The switchback properties of these two streams are also discussed. Our results further explore the variabilities of solar wind turbulence, which may have implications for solar wind heating and acceleration.

How to cite: Wang, T., Chen, W., Yang, L., He, J., and Fu, H.: Turbulence features of the solar wind from different source regions based on Parker Solar Probe observation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15511, https://doi.org/10.5194/egusphere-egu25-15511, 2025.

The phenomenon of energy cascade in Alfvénic solar wind turbulence has traditionally been studied assuming ideal plasmas, where viscosity (ν) and resistivity (η) are equal and very small. However, recent observations suggest that in the solar wind, viscous-like effects related to velocity act on much larger scales compared to magnetic dissipation. The main novelty of this study lies in assuming phenomenological distinctions among dissipation mechanisms and hence assuming different values for ν and η.

In this work, we investigate the third-order Yaglom law for magnetohydrodynamic (MHD) turbulence through a combination of theoretical analysis and simulations. Specifically, we study the energy budget law for visco-resistive MHD and explore how differing viscosities and resistivities affect the energy cascade. The Yaglom relation, rewritten in terms of Elsässer variables, deviates from the ideal case due to the assumption ν ≠ η. This relation, which involves a third-order moment calculated from velocity and magnetic fields, provides a direct measure of the energy transfer rate across scales.

Our preliminary results, supported by direct numerical simulations, indicate that these findings could enhance the interpretation of solar wind and magnetosheath observations. The third-order moment is indeed particularly relevant as it enables a detailed comparison of energy transfer mechanisms, highlighting the differences that arise when the dissipation processes in the velocity and the magnetic field are different.

How to cite: Fortugno, E. M., Scarivaglione, L., Servidio, S., and Carbone, V.: Third-Order Law for MHD Turbulence Varying the Dissipation Mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16301, https://doi.org/10.5194/egusphere-egu25-16301, 2025.