EGU General Assembly 2024  

The sun, solar wind and magnetospheres exhibit non-linear processes that can couple across a broad range of space and time scales. These multiscale processes can be central to the dynamics of far from equilibrium plasmas, where collisionless processes dominate. This talk offers highlights from two interconnected approaches to advancing our understanding of multi-scale processes in solar system plasmas.

From the plasma physics: If sufficient simplifications can be made, we can study the plasma dynamics from first principles. The non-linear scattering and acceleration of energetic particles in current sheets, by wave particle interactions, and in shocks, can be approached from non self-consistent single particle dynamics allowing the full non-linear physics, including low-dimensional chaos, to be considered. The physics of shocks, reconnection, and its interplay with turbulence can be approached by fully kinetic self-consistent simulations, albeit with restrictions on physical dimension and the range of scales resolved. If bursty energy and momentum transport is an emergent process, then it can be captured by reduced models.

From the data: The full dynamics is revealed in all its richness in observations. A wealth of in-situ and remote observations are available from the fastest physical timescales of interest to across multiple solar cycles. In principle, these afford the study of specific physical process such as reconnection and turbulence, and system-scale processes such as the dynamics of magnetospheres, all of which are fully multiscale and non-linear. In practice, determining the physics from observations relies upon establishing robust, reproducible patterns and relationships from multipoint data in these inhomogeneously sampled, non time-stationary systems. As well as providing fundamental physical insights, these can deliver quantitative estimates of space weather risk.

How to cite: Chapman, S.: Multiscale matters: when coupling across multiple scales drives the dynamics of solar system plasmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3620, https://doi.org/10.5194/egusphere-egu24-3620, 2024.

Coronal mass ejections (CMEs) are humongous structures that permeate the heliosphere as they travel away from the Sun. Beginning their journey from a more-or-less localised region in the solar atmosphere, they expand to many times the size of the Sun through the corona, measure about 0.3 au in radial extent by the time they reach 1 au, and interact with the structured solar wind and other transients to form so-called merged interaction regions in the outer heliosphere. One of the most prominent challenges in heliophysics is the achievement of a complete understanding of the intrinsic structure and evolution of CMEs, in particular of their spatiotemporal variability, which in turn would allow more precise forecasts of their arrival time and space weather effects throughout the heliosphere. The most common methods to detect and analyse these behemoths of the solar system consist of remote-sensing observations, i.e. 2D images at various wavelengths, and in-situ measurements, i.e. 1D spacecraft trajectories through the structure. These data, however, are often insufficient to provide a comprehensive picture of a given event, due to the scarcity of available measurement points and the enormous scales involved. Some ways to circumvent these issues consist of taking advantage of multi-spacecraft observations of the same CME (usually at different heliolongitudes and/or radial distances) and to use simulations to complement the available measurements and/or to investigate the 3D structure of CMEs without constraints on the number of synthetic observers.

In this presentation, we will first provide a review of the advantages of multi-spacecraft observations of CMEs and how they have helped us build the overall picture of CME structure and evolution that forms our current understanding. We will then showcase examples of detailed CME studies, both in the observational and modelling regimes, that have been made possible due to the availability of multi-point measurements. These will include events observed remotely and/or in situ by the latest generation of heliophysics missions, i.e. Parker Solar Probe and Solar Orbiter. Finally, we will speculate on possible future avenues that are worthy of exploring to reach a deeper understanding of CMEs from their eruption throughout their heliospheric journey, especially in terms of novel space missions that may improve not only our knowledge from a fundamental physics standpoint, but also our prediction and forecasting capabilities.

How to cite: Palmerio, E.: Analysing CME observations and simulations with multi-spacecraft techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13951, https://doi.org/10.5194/egusphere-egu24-13951, 2024.

Solar flares are efficient accelerators of energetic particles, mainly electrons, which transport energy from reconnection site to the chromosphere. Energetic electrons are thermalized in the chromosphere and produce hard X-ray emission (HXR) following the thick-target bremsstrahlung mechanism. The thick-target model predicts that altitude of the HXR sources in the footpoints of solar flare decreases with increasing energy. The relation was registered for the solar flares observed with Yohkoh/HXT and RHESSI. In our research, we investigated the energy-altitude relation in flare footpoints in a group of strong (M and X GOES class) events that showed emission up to 84 keV recorded by the Spectrometer/Telescope for Imaging X-rays (STIX) onboard the Solar Orbiter. Here we present the results of analysis of the relation, e.g. temporal evolution and density distributions on selected examples. One of the interesting effects visible in some cases is bump in higher energies, when the sources appeared roughly on higher altitudes, which was very rare observed by previous X-ray instruments, but in STIX observations it’s very common. Thanks to unprecedented high temporal and spatial resolutions of STIX data, we can trace changes of plasma dynamics in footpoints like never before. 

How to cite: Mikula, K. and Mrozek, T.: Statistical studies of the energy-altitude relation in the footpoints of solar flares observed by STIX, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5659, https://doi.org/10.5194/egusphere-egu24-5659, 2024.

The interaction between waves and particles plays a pivotal role in particle acceleration near interplanetary shocks. Previously, detailed investigations about these processes were limited due to data availability and coarse time resolution from interplanetary missions. However, recent observations from the Solar Orbiter mission, with its high-resolution capabilities, have shed new light on this topic. In this work, we conduct a comprehensive study of wave-particle interactions near interplanetary shocks, using four years of data obtained by the Energetic Particle Detector (EPD), Magnetometer (MAG), Radio and Plasma Wave Analyzer (RPW) and Solar Wind Analyzer (SWA) onboard the Solar Orbiter. We analyze the propagation and polarization properties of waves associated with shocks through wavelet analysis. In addition, we reconstruct the pitch angle distributions and gyrophase distributions of particles in the solar wind frame of reference. These reconstructions help us identify wave-particle interactions in the data and investigate the energy transport during these events. We report on results from this ongoing analysis. Our results advance the understanding of particle acceleration induced by waves near interplanetary shocks, highlighting the role of wave-particle interactions in dynamic processes occurring in the inner heliosphere.

How to cite: Li, X., Heidrich-Meisner, V., Wimmer-Schweingruber, R., Zong, Q.-G., Wang, L.-H., Yang, L., and Berger, L.: Wave-Particle Interactions near Interplanetary Shocks: Solar Orbiter Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6035, https://doi.org/10.5194/egusphere-egu24-6035, 2024.

Modern astronomical instruments and devices in space provide scientists with a wealth of scientific and technical information. Scientists and developers are confronted with the question of how to gather, process, and store data that defines a particular phenomenon while developing artificial intelligence systems. An extensive array of data processing techniques is also employed in X-ray astronomy; however, the efficacy of these techniques is not universally reliable, which has consequential implications for the overall functionality of artificial intelligence systems and the likelihood of accurate classification. Automation and manual processes constitute the two broad categories into which these methods can be categorized. Each of these categories possesses distinct merits and demerits. Simplyified metric selection and precise definition are factors that contribute to such errors. This study examines the process of determining temporal metrics for the automated creation of a data set using the light curves of solar X-ray flares. The acquired data is designed for eventual utilization in machine learning systems. In order to determine the temporal characteristics of a solar X-ray flare, the flare's initiation, maximum, and termination points are postulated. The provided quantity of data points is adequate for ascertaining the X-ray burst's total duration, rise time, and decay time. Using an iterative algorithm, the authors suggest making it possible to automatically figure out the metrics related to the start, peak, and end of an X-ray flare. Researchers are testing the iterative algorithm on fake data made by the damped oscillations function, on fake periodograms that make the light curve more accurate, and on real data from solar X-ray bursts. This approach enables the automated extraction of temporal attributes of a solar X-ray burst for subsequent storage and aggregation as a database. It also facilitates further processing and utilization in the training of artificial intelligence systems.

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: Bilokon, O., Dudnik, O., Chechotkin, D., and Denkov, I.: An iterative algorithm for determining the temporal characteristics of solar X-ray flares for the automated formation of a data set in machine learning systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6670, https://doi.org/10.5194/egusphere-egu24-6670, 2024.

Ever since the first ³He-enhanced solar energetic particle (SEP) event was reported in the literature in 1970, the exact mechanism by which the isotope is enhanced orders of magnitude higher than its solar wind value remains unknown.  But the source, acceleration, and transport of SEP events can only be studied by multi-point simultaneous in-situ measurement within the heliosphere.  However, multi-spacecraft observations of ³He-rich solar energetic particle (SEP) event are scarce.  Further observations are much needed in order to understand and properly constrain the source and transport of the remarkable enriched ³He SEP event. In this paper, we report six ³He-rich SEP events that were detected by ACE, STEREO and Solar Orbiter near 1 au during Solar Orbiter’s aphelion pass at the end of 2022 and early 2023.  Many of these events were detected simultaneously by at least two or three spacecraft at up to ~40° longitudal separation, while some events were detected by only a single spacecraft even though an adjacent spacecraft was less than 20° away. These fortuitous multi-spacecraft observations of ³He-rich SEP events thus provide us observational constraint on the acceleration and propagation of this special class of SEP events. In addition, we will show in this paper how multi-spacecraft measurements could also be used to constraint the solar source region of ³He-rich SEP event.

How to cite: Ho, G., Mason, G., Kouloumvakes, A., Allen, R., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Longitudinal Extent of 3He-rich Solar Energetic Particle Events near 1 AU, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6724, https://doi.org/10.5194/egusphere-egu24-6724, 2024.

This contribution will summarise recent science highlights of the ESA/NASA Solar Orbiter mission and provide a mission status update. Solar Orbiter started its nominal mission phase in December 2021, with perihelia around 0.29 au occurring every six months. The ten instruments onboard provide high-resolution imaging and spectroscopy of the Sun and corona, as well as detailed in-situ measurements of the surrounding heliosphere. Together, these observations enable us to comprehensively study the Sun in unprecedented detail and determine the linkage between observed solar wind streams and their source regions on the Sun. Solar Orbiter’s science return is significantly enhanced by coordinated observations with other space missions, including Parker Solar Probe, SDO, SOHO, STEREO, Hinode and IRIS, as well as new ground-based telescopes like DKIST. Starting in 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.

How to cite: Mueller, D., Zouganelis, Y., De Groof, A., Williams, D., Walsh, A., Janvier, M., Nieves-Chinchilla, T., and Lario, D.: Solar Orbiter: Recent science highlights and mission status , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7975, https://doi.org/10.5194/egusphere-egu24-7975, 2024.

Interplanetary coronal mass ejections (ICMEs) transport magnetized plasma from the Sun. Magnetic clouds (MC) are closed structures immersed within ICMEs and form large-scale magnetic flux ropes. Their evolution in the solar wind is linked to the interaction with the surrounding solar wind and the magnetic force. In addition, these structures play a fundamental role in the propagation of solar energetic particles and cosmic rays observed by analyzing the flux variations of these particle populations. On November 3, 2021, one of these structures was observed at different solar distances by instruments aboard Solar Orbiter (SO) and instruments in Earth orbit.

Magnetic clouds are closed structures immersed within interplanetary coronal mass ejections. These structures have an important effect on the propagation of solar energetic particles and cosmic rays that is observed as variations in the flux of these particle populations. The evolution of a MC observed on November 3, 2021, is analyzed using in situ observations made by Solar Orbiter (SO), at 0.84 AU, and ACE, at 1 AU, spacecrafts when they were aligned with the Sun. The magnetic configuration of the MC is described using a magnetic model by observing its evolution at both heliodistances and the effect on solar energetic particles and cosmic rays.

How to cite: Arrazola Pérez, D., Blanco Ávalos, J. J., and Hidalgo Moreno, M. Á.: Study of the Interplanetary Coronal Mass Ejection of November 3, 2021, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8177, https://doi.org/10.5194/egusphere-egu24-8177, 2024.

The shock waves, spatial regions with magnetic field perturbations and irregularities, and other phenomena characterizing the environment in the heliosphere can occur during enhanced solar activity. Clarifying the reasons for these events allows us to better understand the interconnection between processes on the Sun and interplanetary space.

In our study, which is based on the data processing from both SWA-PAS and MAG instruments we examine variations of the different parameters of the solar wind and interplanetary magnetic field derived as a result of in-situ measurements aboard the Solar Orbiter in the first half of 2023.

In the period selected both instruments detected the events with significant variations of the key parameters of the solar wind befriended by specific changes in the magnetic field components. We demonstrate the most outstanding examples of the SWA-PAS and MAG data analysis allowing the identification of the ICME, shock waves, CIR, magnetic clouds, magnetic flux ropes, magnetic holes, and other Heliospheric phenomena with confidence. The particular interest is in the selected simultaneous or serial registration events of the two or more mentioned phenomena presented.

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. and Dudnik, O.: Recognition of the solar activity manifestation in the interplanetary space at joint data analysis from SWA-PAS and MAG instruments of the Solar Orbiter mission., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8270, https://doi.org/10.5194/egusphere-egu24-8270, 2024.

The emission of radiation associated with the release of energy in solar flares is in many cases modulated according to a quasi-oscillatory pattern. This behavior is known as Quasi-Periodic Pulsations (QPPs). STIX instrument on board  Solar Orbiter offers new opportunities to study these types of phenomena. We reviewed Quick-Look light curves of the STIX instrument recorded from the beginning of the mission (April 14, 2020) to the end of March 202. 129 flares with the clearest pulses were selected, for which the periodicity analysis was carried out using the Lomb-Scargle periodogram and the autocorrelation method. It was found that 70% of those flares showed statistically significant oscillations. The observed periods ranged from 43 to 1355 s. It was found that longer periods occur less frequently than shorter ones. It has also been shown that there is a relationship between the period and the time interval in which the oscillations were observed.

How to cite: Szaforz, Ż., Mrozek, T., and Tomczak, M.: Investigation of solar flares showing quasi-periodicity based on STIX Quick-Look light curves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8631, https://doi.org/10.5194/egusphere-egu24-8631, 2024.

The ESA mission Solar Orbiter is providing, besides other observations, in-situ measurements of the solar wind plasma. The boom mounted electron analyser (SWA-EAS) acquires ambient as well as spacecraft produced (photo-, secondary-) electrons. To correctly interpret and derive the solar wind electron population, we need to understand the artificial populations, their production rate, energy distribution, and directional dependence on the ambient conditions for the given spacecraft geometry. In order to investigate the various electron populations in the spacecraft vicinity, we incorporate a numerical model of the Solar Orbiter spacecraft into the Spacecraft Plasma Interaction Software (SPIS). Hereby, we present preliminary results and challenges of such simulations and their interpretations. 

How to cite: Herčík, D., Stverak, S., Hellinger, P., Gethyn, L., Nicolaou, G., and Owen, C. J.: Solar Orbiter charging effects on electron measurements via SPIS simulation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9679, https://doi.org/10.5194/egusphere-egu24-9679, 2024.

Solar Energetic Particles (SEPs), accelerated during solar eruptions, are observed using instruments onboard spacecraft in interplanetary space, at a large distance from their source. As SEPs propagate in the solar wind, they are guided by the interplanetary magnetic field (IMF), which consists of a large-scale Parker spiral magnetic field superposed by turbulent fluctuations. The turbulence causes the SEPs to scatter along the magnetic field lines, resulting in some cases in delayed arrival of SEPs to spacecraft in interplanetary space. It also gives rise to meandering of field lines, which helps to spread SEPs across heliolongitudes, and eventually results in diffusive cross-field propagation of the particles. To investigate how turbulence affects SEP propagation and arrival to observing spacecraft in different locations in the heliosphere, we have developed a novel analytical model of the IMF, where the Parker spiral is superposed with Fourier modes that represent the turbulence. Unlike any previous models, our description reproduces the observed geometry for the main mode of turbulence, the so-called 2D mode, with both the magnetic field disturbance vector and the wavenumber vector normal to the background Parker spiral field. We use 3D test particle simulations to study the propagation of energetic protons in our new turbulent IMF description. Particles are injected close to the Sun and observables derived at different radial distances and heliolongitudes, representing the locations of near-Earth spacecraft as well as locations accessible to Solar Orbiter and Parker Solar Probe. We compare the SEP onset times obtained from our simulations to those obtained with a 1D focused transport model. We find that the turbulence prolongs the field lines, and thus when particle are simulated in our new IMF model, the SEP intensity onsets are delayed compared to those obtained by using a 1D focused transport model. Further, we find that onset delay depends on the longitudinal separation of the SEP source and the heliolongitude of the location where the observables are derived. We discuss the implications of our findings on current understanding of the sources and transport of SEPs.

How to cite: Laitinen, T. and Dalla, S.: Modelling Solar Energetic Particle event onsets in the turbulent heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11192, https://doi.org/10.5194/egusphere-egu24-11192, 2024.

ESA’s Solar Orbiter mission, launched in February 2020, is designed to investigate how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To achieve its objectives, Solar Orbiter is equipped with a comprehensive suite of remote sensing and in situ instruments that work in concert to connect coronal structures and phenomena to their heliospheric counterparts. It aims to advance our understanding of the solar dynamo, responsible for the Sun’s magnetic cycle, by venturing out of the ecliptic plane to directly observe the Sun’s polar regions, providing an unprecedented view of our star. Since its launch, Solar Orbiter has completed 5 perihelion passes below the orbit of Mercury where it has taken the most detailed images of the Sun to date. The high resolution images have revealed previously unresolved coronal features that deepen our knowledge of how the corona is heated and the solar wind is formed, as well as how eruptions are triggered and release energy. As we now enter farther into solar maximum, the mission is perfectly placed to gain fresh insight to how transients drive heliospheric variability and impact local space weather. As such, the talk will present a brief overview of the overarching Solar Orbiter science objectives, discuss recent discoveries by the mission, and outlook for future observations and its exciting journey out of the ecliptic plane.

How to cite: Rivera, Y.: Solar Orbiter: Mission Goals, Recent Discoveries, and Future Outlook, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11461, https://doi.org/10.5194/egusphere-egu24-11461, 2024.

Impulsive solar energetic particle (SEP) events are typically associated with solar flares but the related particle injection and acceleration processes are still not well understood. We use in-situ and remote-sensing data from Solar Orbiter to establish a plausible link between a series of eruptions in a flaring region and a sequence of four SEP events measured at 0.5 AU between 5 and 6 March 2022. The direct comparison between these four events from the same source region allows to study the variability of the injected SEPs during an extended period of magnetic connectivity between Solar Orbiter and the flaring active region. In this study we analyze energetic electron, proton, and heavy ion data provided by the Energetic Particle Detector (EPD) suite onboard Solar Orbiter. Via a velocity dispersion analysis (VDA) of all measured particle species we estimate the solar event onset times which coincide with a series of solar eruptions that is observed by the Extreme Ultraviolet Imager (EUI) and the Spectrometer Telescope for Imaging X-rays (STIX) onboard Solar Orbiter. Further high-time-resolution EUV images and photospheric magnetic field information of the related active region is given by the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory. Solar Orbiter and Earth were nearly perfectly radially aligned at this time which enabled this additional remote sensing by SDO. We find that the energy spectra of the heavy ion in-situ measurements show significant differences between the four investigated SEP events in terms of overall particle intensity, spectral slope, and ³He / ⁴He abundances. By comparison with the remote-sensing observations we find that the two stronger SEP events (with higher ³He / ⁴He ratios) are related to solar eruptions with a more complex eruption pattern leading to extended brightening and restructuring of coronal loop structures. These new detailed observations can be used as starting point for quantitative modelling of flare-associated energetic particle acceleration and release in active regions.

This work has been funded by the Spanish Ministerio de Ciencia, Innovación y Universidades project PID2019-104863RBI00/AEI/10.13039/501100011033.

How to cite: Roco, M., P. Janitzek, N., Berger, L., Kühl, P., Heidrich-Meisner, V., Pacheco, D., Kollhoff, A., M. Mason, G., C. Ho, G., Rodríguez-Pacheco, J., Gómez-Herrero, R., Rodríguez-García, L., Harra, L., Barczynski, K., P. Walsh, A., Zouganelis, Y., Berghmans, D., Krucker, S., Francesco Battaglia, A., and F. Wimmer-Schweingruber, R.: Linking Solar Flare Observations to a Series of Impulsive Solar Energetic Particle Events Measured with Solar Orbiter at 0.5 AU, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11872, https://doi.org/10.5194/egusphere-egu24-11872, 2024.

Magnetic field reversals, where the radial component of the heliospheric magnetic field changes direction, are frequently observed in the near-Sun region. Theory and numerical simulations regarding these reversals suggest that possible generation mechanisms include interchange reconnection in the solar corona, or solar wind expansion and turbulence. Magnetic field reversals thus provide information about both the solar corona and solar wind acceleration and propagation. Previous observations, including magnetic field structure, He²⁺- abundance, and the so-called patchy-ness are not conclusive in revealing their origin. In this presentation we discuss in situ observations of protons, electrons, He²⁺, and heavy ions from Solar Orbiter's Solar Wind Analyser instrument , together with the magnetic field from the MAG instrument, during a long-duration magnetic field reversal. We identify the origin of the reversal using the in situ heavy ion data, magnetic connectivity tools, and plasma emission measurements from the Solar Dynamic Observatory. In addition, we study kinetic properties of the electrons, protons and heavy ions, in order to provide readily employable observational tests to help discern the origin of the magnetic field reversals.

How to cite: Coburn, J., Yardley, S., Dewey, R., Ngampoopun, N., Suen, G., Verscharen, D., Owen, C., Trotta, D., Nicolaou, G., Rivera, Y., Livi, S., Lepri, S., Raines, J., De Marco, R., and Ioannou, C.: Identifying the origins of magnetic field reversals: in-situ measurements from Solar Orbiter and connection to remote-sensing observations from SDO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11967, https://doi.org/10.5194/egusphere-egu24-11967, 2024.

The distribution of charged particles in the heliosphere covers more than 16 orders of magnitude in particle flux and more than 6 orders of magnitude in energy. While the majority of these particles are ionized hydrogen (protons) and fully ionized helium (alpha particles), heavier ions are also present. Because of the large parameter space that must be covered, different instruments are required and these instruments must be optimized to specific energy and particle flux ranges. They must also be designed to target specific ion species. To properly characterize the means by which different energy ranges are populated, the observations from these different instruments must be intercalibrated.

We present initial progress intercalibrating observations from Solar Orbiter’s Heavy Ion Sensor (HIS) and Suprathermal Ion Spectrograph (SIS). HIS is a heavy ion composition experiment that targets the solar wind through the low energy range of suprathermal energies with mass and charge state resolution. SIS covers the suprathermal and low range energetic particles with high mass resolution but without charge state resolution. Together, these two sensors cover heavy ion composition from solar wind to suprathermal energies. During advantageous conditions, proton distributions across both instruments are also available. Properly intercalibrated observations across these instruments enable studies of charged particle energization across the energy ranges, which is essential for characterizing a wide range of phenomena in heliosphere.

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., D'Amicis, R., Mason, G., Wimmer-Schweingruber, R. F., and Rodriquez-Pacheco, J.: Inter-Calibration of Solar Orbiter’s Heavy Ion Sensor and Suprathermal Ion Spectrograph, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13328, https://doi.org/10.5194/egusphere-egu24-13328, 2024.

This talk shows that imaging-spectroscopy analyses from data recorded by the Spectrometer/Telescope for Imaging X-rays (STIX) on-board Solar Orbiter allow to disentangle the two factors that determine the observed hard X-ray spectrum of a solar flare, i.e., the density of the accelerated electrons and the ambient target density. More specifically, we show, for the first time in a quantitative way, that in the case of some peculiar events characterized by a significant coronal emission, the number of non-thermal electrons accelerated by the flare is relatively small and that a high rate of such electrons is stopped before they can reach the chromosphere

How to cite: piana, M., volpara, A., massa, P., emslie, G., krucker, S., and massone, A. M.:  STIX electron flux maps allow the quantitative determination of the number of accelerated electrons in solar flares, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15888, https://doi.org/10.5194/egusphere-egu24-15888, 2024.

Ion velocity distribution functions in solar wind are often found to be non-Maxwellian. Streams of accelerated particles and temperature anisotropies are typical non-thermal features, whose origin is debated since the early years of in situ measurements. In order to disentangle the kinetic processes which may play a role in the generation of such distortions, particle double streams need to be identified and isolated. To this purpose, we have developed a numerical approach that leverages the clustering technique employed in machine learning. Here, we present the results obtained applying our technique to the ion distribution functions of a typical fast Alfvénic wind stream observed by Solar Orbiter-PAS in mid-September 2022, at a heliocentric distance of about 0.58 au. We could separate up to four ion families, namely proton core and beam and alpha core and beam. This allows us to characterize and compare their features, like the relative densities and temperatures. Differently from the better-known proton beam, alpha beam represents a relevant fraction of the alpha population, around 40%. Separating such a massive beam may shed new light on alpha kinetic features like the anomalous overheating mechanism. Moreover, the study of the velocity drift of the various ion populations indicates that both the alpha core and the alpha beam are sensitive to the Alfvénic fluctuations, and the surfing effect found in literature can be recovered only when considering the core and the beam as a single population.

The similarities between proton and alpha beams would suggest a common generation mechanism, apparently due to local physical conditions in the plasma.

How to cite: De Marco, R., Bruno, R., D'Amicis, R., Perrone, D., Marcucci, M. F., Telloni, D., Marino, R., Sorriso-Valvo, L., Fortunato, V., Mele, G., Monti, F., Fedorov, A., Louarn, P., Owen, C. J., and Livi, S.: Kinetic properties of proton and alpha beams in the Alfvénic wind observed by Solar Orbiter-PAS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16212, https://doi.org/10.5194/egusphere-egu24-16212, 2024.

Understanding the general properties of the various solar winds requires an understanding of the phenomena at their source. The properties of the solar wind are influenced by the exchange of energy at the base of the solar corona. For example, the speed of the solar wind is strongly influenced by the level of heating below the sonic point. The heating that occurs in the collisional part of the atmosphere modifies the ionisation level of the heavy elements and therefore their charge state. This is why the charge state ratios of heavy ions measured in the solar wind are good parameters for distinguishing between fast and slow solar winds. In this study, we use the new Irap solar atmospheric model (ISAM) to study the level of ionisation of heavy ions transported in fast and slow solar winds. ISAM is a 16-moment multi-species model that self-consistently couples the transport equations for neutral and ionised particles (H, p, e, He, O and Mg) from the lower chromosphere through the solar corona to the solar wind. The lower corona is a region that is strongly coupled to the transition region by the downward heat flux.

By solving first for H, p and e, we recover the results of previous modelling showing that variations in the source temperature modify the pressure of the transition region which, in turn, modulates the mass flux of the solar wind. Using an ad-hoc heating function characterised by a scale height inversely proportional to the expansion factor of the magnetic field lines channelling the solar wind, we first recover the general properties of the fast and slow solar winds, as well as the known observation that the source temperature of the slow wind is higher than that of the fast wind. We then solve explicitly the ionisation processes and the coupled transport of oxygen with the major species (H, p, e) in order to isolate the different processes that contribute to the ionisation level of the heavy ions. We compare the results of our modelling with spectroscopic and in situ data. This work was funded by the ERC SLOW SOURCE - DLV - 819189.

How to cite: Lomazzi, P., Thomas, S., Rouillard, A., Poirier, N., Réville, V., Lavarra, M., and Blelly, P.-L.: Modeling the source temperature of fast and slow winds using a 16 moments multi-species model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16348, https://doi.org/10.5194/egusphere-egu24-16348, 2024.

Solar Orbiter (SO) observations provide an unprecedented opportunity to study the evolution of solar energetic particle (SEP) events from different locations within the heliosphere. In this work, we have compiled a catalogue of SEP events based on observations of both electrons and protons from the High Energy Telescope (HET) of the Energetic Particle Detector (EPD) that occurred in 2020 to 2023 during the ascending phase of Solar Cycle 25. A scan of simultaneous So/HET intensity-time observations for ~10 MeV protons and near relativistic (~1 MeV) electrons has been performed. We have identified all enhancements observed above the background levels of these particular channels and surveyed available solar wind data by the SO/ Solar Wind Analyzer (SWA) and the SO/Magnetometer (MAG) during the identified events. Moreover, we employed Velocity Dispersion Analysis (VDA) for protons and electrons and Time-shifting Analysis (TSA) for electrons, alone, with the aim to infer the SEP release times at the Sun. Our resulting catalogue includes 75 SEP events. For each of these events (and for each species), we provide the onset and peak time, the peak flux value and fluence. We also identify the solar associations/sources for the SEP events, by comparing the inferred release times of the SEPs to the related light curves from the SO/Spectrometer/Telescope for Imaging X-rays (STIX), the standard flare list obtained from the GOES X-ray Sensor and their associated coronal mass ejections (CMEs). We find that a significant portion of all SEP events in our sample (48%; 36/75) reached 50 MeV for protons and thus are Space Weather relevant. Finally, a statistical analysis of our observations is presented. We have investigated correlations between peak particle fluxes (for protons and electrons) and event fluences, as well as peak particle fluxes (event fluences), flare magnitude and CME speed. We also calculate the connection angle to the apparent source and identify a subsample of the events that are better connected to the solar event. In addition, the e/p ratio is calculated and a division of the sample based on Fe-rich and ³He-rich events is discussed. 

Acknowledgement: Research leading to these results has received funding from the Horizon Europe programme project No 101135044 (SPEARHEAD).

How to cite: Papaioannou, A., Rodríguez-García, L., Gomez Herrero, R., Lavasa, E., Kouloumvakos, A., Vasalos, G., Warmuth, A., Richardson, I. G., Lario, D., Zouganelis, I., Espinosa Lara, F., Cernuda Cangas, I., Kuel, P., Schuller, F., Barczynski, K., Fleth, S., Anastasiadis, A., Walsh, A., Mueller, D., and Rodriguez-Pacheco, J. and the A Solar Orbiter Team: A catalogue of large solar energetic particle events observed by Solar Orbiter for the first ~ four years of measurements (2020–2023), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17889, https://doi.org/10.5194/egusphere-egu24-17889, 2024.

On November 27, 2021, Solar Orbiter has performed a gravity assist maneuver at the Earth and in December 2022 Solar Orbiter and STEREO-A were separated by less than 0.2 au. The periods around these two events provide unique opportunities to compare Solar Energetic Particle (SEP) observations from Solar Orbiter with corresponding observations from near-Earth missions and STEREO-A. The proximity of the different spacecraft offers a useful opportunity to compare the calibrations of the various particle instruments of the different spacecraft. Furthermore, the unique constellations can be used to study small-scale changes in the density distributions of the SEPs.

We will present observations of near-relativistic electrons with energies from 50 keV to 400 keV as well as observations of protons with energies from 50 keV to 50 MeV. In particular, we use the period around the Earth gravity assist maneuver for a comparison of measurements from the Electron Proton Telescope (EPT) and the High Energy Telescope (HET) aboard Solar Orbiter with measurements from the Electron Proton and Alpha Monitor aboard the Advanced Composition Explorer (ACE), the 3DP instrument aboard Wind and the Electron Proton Helium Instrument (EPHIN) aboard SOHO. The period around the close encounter with STEREO-A is used for a comparison of EPT and HET observations with measurements from the High Energy Telescope (STA/HET) and the Solar Electron and Proton Telescope (SEPT) aboard the STEREO-A spacecraft. For both periods we discuss the instrument calibrations and possible physical explanations for differences in particle observations.

Funding: This work was supported by the German Space Agency (Deutsches Zentrum für Luft- und Raumfahrt, e.V., (DLR)) under grant number 50OT2002 and has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004159 (SERPENTINE).

How to cite: Kollhoff, A., Jense, S., Dröge, H., Kühl, P., Gómez Herrero, R., R.-Pacheco, J., Wimmer-Schweingruber, R. F., and Heber, B.: Comparison of solar energetic particle observations from Solar Orbiter, near-Earth spacecraft and STEREO-A during Solar Orbiter's Earth gravity assist maneuver in November 2021 and its close encounter with STEREO-A in December 2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18758, https://doi.org/10.5194/egusphere-egu24-18758, 2024.

We propose a family of numerical solvers for the nonrelativistic Newton-Lorentz equation in particle-in-cell (PIC) simulation. The new solvers extend a popular 4-step procedure, which has second-order accuracy in time, in several ways. First, we repeat the 4-step procedure n cycles, using an n-times smaller timestep (Delta_t/n). To speed up the calculation, we derive a polynomial formula for an arbitrary cycling number n, based on our earlier work (Zenitani & Kato 2020, Comput. Phys. Commun.). Second, prior to the 4-step procedure, we apply Boris-type gyrophase corrections to the electromagnetic field. In addition to the magnetic field, we amplify the electric field in an anisotropic manner to achieve higher-order (N=2,4,6... th order) accuracy. Finally, we construct a hybrid solver of the n-cycle solver and the Nth-order solver. We call it the hyper Boris solver. The (n,N) hyper Boris solver gives a numerical error of ~ (Delta_t/n)^N at affordable computational cost.

How to cite: Zenitani, S. and Kato, T. N.: Hyper Boris integrators for particle-in-cell simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2175, https://doi.org/10.5194/egusphere-egu24-2175, 2024.

Context. The heating of the solar chromosphere, the associated plasma outflows, and the origin of the solar wind are key issues in heliophysics. In this paper, we provide a new perspective on their connection to the propagation and dissipation of waves generated by solar granulation.

Aims. The primary objective of this paper is to conduct 2.5-D numerical simulations of the partially ionized lower solar atmosphere, investigating the propagation and dissipation of granulation-generated waves in the context of plasma outflows and the related heating of the chromosphere, which is due to ion-neutral collisions.

Methods. We use the JOint ANalytical and Numerical Approach (JOANNA) code to solve the two-fluid model equations. We take into account partially ionized hydrogen plasma composed of ions (protons) and neutrals (H atoms), which are coupled via ion-neutral collisions. We focus on a quiet region of the solar chromosphere which is gravitationally stratified and magnetically constrained by an initially set magnetic Plasma flows and solar chromosphere heating arcade. Solar convection situated beneath the photosphere is the main source of these waves that are propagating through the simulated solar atmosphere.

Results. The numerical results obtained in our study reveal an important process in the lower solar atmosphere. The naturally evolving convection generates waves and a portion of the wave energy is dissipated due to ion-neutral collisions in the solar chromosphere. This dissipation of waves, in turn, leads to the release of thermal energy, resulting in the heating of the solar atmosphere. This phenomenon is also associated with upward-directed plasma flows, which may play a role in the formation of the solar wind. Furthermore, our analysis of the dominant wave periods in the various layers
of the solar atmosphere closely aligns with observational data from Wiśniewska et al. (2016) and Kayshap et al. (2018). This alignment underscores the crucial role ion-neutral collisions play in facilitating the energy release process, shedding light on the intricate dynamics of the solar atmosphere.

Conclusions. Based on our numerical simulations, we can draw the following conclusions: The dissipation of waves in the two-fluid plasma caused by ion-neutral collisions in the two-fluid plasma model leads to plasma outflows and increased heating in the chromosphere. These plasma outflows may play a role in the generation of the solar wind and the accompanying heating.

How to cite: Kumar, M., Murawski, K., Kuźma, B., Kadowaki, L., Kilpua, E., Poedts, S., and Erdelyi, R.: Solar granulation-generated chromospheric heating and plasma outflows in two-fluid magnetic arcade, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2303, https://doi.org/10.5194/egusphere-egu24-2303, 2024.

Modeling the three-dimensional (3D) magnetic fields of the solar active region in multiple layers is very important. The main approach is to extrapolate the magnetic field from magnetograms measured in the photosphere. A basic assumption of the modeling in the past several decades was to completely neglect all plasma effects and to perform the so-called force-free field (FFF) extrapolations. While the force-free assumption is well justified in the solar corona, it is not the case in the photosphere and chromosphere. A magneto-hydro-static (MHS) equilibrium which takes into account plasma forces, such as pressure gradient and gravitational force, is considered to be more appropriate to describe the lower atmosphere and has been developing rapidly during the past several years. In this talk, I am going to review various MHS modeling methods, including tests of these methods with known reference models and applications to real data. Recent developments of the MHS modeling will also be presented.

How to cite: Zhu, X.: On the current state of the development of the magneto-hydro-static extrapolation method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2367, https://doi.org/10.5194/egusphere-egu24-2367, 2024.

It is generally accepted that solar prominences, also known as filaments, are formed through thermal condensation instability from hot coronal plasmas. Within solar prominences (filaments), counter-streaming subscale flows are frequently observed. It is quite surprising that thermal instability in magnetized plasmas with such shear flows has never been earnestly studied despite extensive research on thermal instability in various astrophysical contexts. In this paper, we have investigated this unexplored territory of thermal instability and have unexpectedly gained hints on why solar filaments are filamentary.

We have performed linear stability analysis of magnetized plasmas with shear flows within the framework of magnetohydrodynamics (MHD), incorporating radiative cooling, phenomenological plasma heating, and anisotropic thermal conduction. Our approach formulates an eigenvalue problem, which we solve numerically to derive eigenfrequencies and eigenfunctions.

Our findings reveal that, for shear speeds less than the Alfven speed of the background plasma, the dominant mode corresponds to an isobaric thermal condensation mode. Most remarkably, the eigenfunctions associated with this mode display a distinctive, discrete structure resembling delta functions, especially when the shear velocity in the k-direction exceeds 10⁻⁵ of the Alfven speed. We identify that these delta function-like spikes coincide with the zeroes of the coefficients of the second-order derivative terms in the differential equation of the eigenvalue problem.

In contrast, for shear speeds exceeding the Alfven speed (a rare occurrence in reality), we observe an isentropic Kelvin-Helmholtz instability, incompatible with thermal condensation.

Our investigation underscores that any non-uniform velocity field with a magnitude surpassing 10⁻⁵ of the Alfven speed triggers the discrete eigenfunction characteristic of the condensation mode. Consequently, filamentary condensation at discrete layers or threads, emerges as a natural and universal process whenever thermal condensation instability arises in magnetized plasmas with shear flows.

How to cite: Choe, G., Lee, M., and Yi, S.: A Clue to the Filamentary Nature of Solar Filaments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3315, https://doi.org/10.5194/egusphere-egu24-3315, 2024.

Alfven waves contribute significantly to the solar coronal heating, the solar wind acceleration, as well as Alfv\'enic turbulence formation. As a universal process, magnetic reconnection has long been credited as a potentially crucial source of Alfven waves, but how magnetic reconnection trigger Alfven waves remains elusive. Here, with simulations of three-dimensional bursty interchange magnetic reconnection in the solar corona, for the first time, we find that Alfven waves are spontaneously excited in the reconnection sheet and propagate bi-directionally even along the unreconnected magnetic fields. The enhanced total pressure inherently carried by flux ropes gives kicks to the magnetic fields, and the nearly same propagation speed of the flux ropes and the kicks makes the kicks growing into the observed Alfven waves, which have large amplitudes and high frequencies, carrying substantial energy for heating the quiet corona and accelerating the solar wind. Our findings demonstrate that Alfven waves are natural products of three-dimensional intermittent magnetic reconnection, bringing its fundamental significance for energy release, transport, and conversion occurring in the plasma system.

How to cite: Yang, L., He, J., Feng, X., Li, H., Guo, F., Tian, H., and Shen, F.: Spontaneous Generation of Alfven Waves by Bursty Interchange Magnetic Reconnection in the Solar Corona, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4321, https://doi.org/10.5194/egusphere-egu24-4321, 2024.

Multiscale modeling of expanding plasmas is crucial for understanding the dynamics and evolution of various astrophysical plasma systems. In this context, the Expanding Box Model (EBM) was used to add the expansion into the kinetic equations, allowing us to describe plasma physics in a new system of reference non-expanding and co-moving with the plasma. This system allows us to maintain a constant volume through non-inertial forces, and its interpretation is fundamental to describing plasma physics.

We have employed the EBM formalism to incorporate the expanding properties of the system into the plasma dynamics, which mainly affects transverse coordinates (i.e., y y/o z). Coordinate transformations were introduced within the co-moving frame system to obtain the modified Vlasov equation. Our main goal is to develop a plasma physics theory through a novel first principle description in the expanding frame, which is fundamentally based on the (collisionless) Vlasov equation for the evolution of the velocity distribution functions. Based on this, the expanding moments, such as the continuity, momentum, and energy equations, can then be derived, and an MHD model of the plasma expansion can be developed. Finally, coupling the obtained moments and Maxwell equations, a CGL-like plasma description is developed in the EB frame to study the evolution of macroscopic quantities (temperature, magnetic field, parallel beta, and anisotropy).

Our results show the expansion affecting the kinetic and fluid equations through non-inertial and fictitious forces in the transverse directions, which contain all the information related to the expansion. These are thus reflected by the equations derived for the expanding moments of the distribution function, including density, bulk (drift) velocity, and pressure (or temperature). Furthermore, we developed an ideal expanding-MHD model based on these modified moments, providing a new interpretation and comparison with the existing results when expansion is considered. The EBM modifies the conservative form of the two adiabatic invariants in the CGL approximation. Equations are solved for radially decreasing magnetic fields and density profiles to study the relations between plasma parallel beta and anisotropy within the expansion. 

How to cite: Echeverria Veas, S., Moya, P., Lazar, M., Poedts, S., and Asenjo, F.: First Principle Description of Plasma Expansion using the Expanding Box Model. Implications for CGL Theory in the Solar Wind., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6152, https://doi.org/10.5194/egusphere-egu24-6152, 2024.

Linear theory is a well-established theoretical framework proven to accurately characterize instabilities in the solar wind weakly collisional plasma. We aim to describe the statistical properties of linear ion-driven instabilities between 0.3 and 1 au. We analyzed ∼1.5M proton and alpha particle Velocity Distribution Functions (VDFs) observed by Helios I & II, and ~5M VDFs observed by Wind, using Plasma in a Linear Uniform Magnetized Environment (PLUME) dispersion solver to calculate growth rate, frequency, wavevector, and the power emitted or absorbed by each VDF component. The descriptive statistical analysis shows that the stability of the solar wind is primarily determined by the collisional processing, rather than the distance from the Sun. We use this data set to train Stability Analysis Vitalizing Instability Classification (SAVIC) Machine Learning algorithm capable to classify the predicted unstable modes into physically meaningful “textbook” types. This method enables us to map the instability properties in multi-dimensional phase space. The proton-core-induced Ion Cyclotron (IC) mode dominates the collisionally young solar wind, while the alpha population plays more important role in the wave energy dynamics of the older wind. We also demonstrate that the proton beam population is not affected by the collisions and has the core-beam drift as the main source of free energy that determines its overall behavior in the solar wind. SAVIC code used here is publicly available for the community.

How to cite: Martinović, M. and Klein, K.: Overview of Ion-Driven Instabilities in the Inner Heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6557, https://doi.org/10.5194/egusphere-egu24-6557, 2024.

Imbalanced Alfvénic turbulence is a universal process playing a crucial role in energy transfer in space, astrophysical, and laboratory plasmas. A funda-
mental and long-lasting question about the imbalanced Alfvénic turbulence is how and through which mechanism the energy transfers between scales. Here, we show that the energy transfer of imbalanced Alfvénic turbulence is completed by coherent interactions between Alfvén waves and co-propagating anomalous fluctuations. These anomalous fluctuations are generated by nonlinear couplings instead of linear reflection. We also reveal that the energy transfer of the waves and the anomalous fluctuations is carried out mainly through local-scale and large-scale nonlinear interactions, respectively, responsible for their bifurcated power-law spectra. This work unveils the energy transfer physics of imbalanced Alfvénic turbulence, and advances the understanding of imbalanced Alfvénic turbulence observed by Parker Solar Probe in the inner heliosphere.

How to cite: Yang, L., He, J., Verscharen, D., Li, H., Bowen, T. A., Bale, S. D., Wu, H., Li, W., Wang, Y., Zhang, L., Feng, X., and Wu, Z.: Energy transfer of imbalanced Alfvénic turbulence in the heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6886, https://doi.org/10.5194/egusphere-egu24-6886, 2024.

One of the most important diamagnetic current driven instability transverse to the magnetic field is lower hybrid drift instability (LHDI) which excites lower hybrid drift waves (LHDW). LHDI gives rise to anomalous resistivity which further leads to onset of magnetic reconnection. Because of its high anomalous collision frequency, LHDI enhances the rate of transverse diffusion. The lower hybrid frequency (LHF) ranges between electron and ion cyclotron frequency which is a natural resonance. LHDW is generally observed in transition layer regions and magnetic reconnection sites, where the gradient in density occurs. We are presenting electromagnetic kinetic model including gradients in density and magnetic field, finite parallel wavenumber and non-thermal particle distribution function or kappa velocity distribution function.  The effect of the aforementioned factors on the growth rate of LHDI in different plasma beta circumstances has been thoroughly investigated and will be discussed. Space observation of drift driven wave using MMS spacecraft will also be discussed.

How to cite: Arya, N. and Kakad, A.: Observational and Theoretical Study of Lower Hybrid Drift Waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7061, https://doi.org/10.5194/egusphere-egu24-7061, 2024.

It is believed that the suprathermal populations of electrons and protons in the solar wind and terrestrial magnetosphere (with energies exceeding those of the bulk population up to several keV) can offer key answers to many major problems, such as the origin of energetic solar particles from interplanetary shocks, particle acceleration by the energy dissipation of the small-scale wave fluctuations, but also a certain level of kinetic turbulence which can explain the non-equilibrium quasi-stable states of space plasmas. Due to their low density and relatively high energy, these populations are collisionless, which means that their dynamics is governed by wave-particle interactions, especially resonant Landau or cyclotron interactions. We present here a series of recent results that demonstrate that the suprathermal populations, whether in the form of a less-drifting halo or the field-aligned beams/strahls, are mainly responsible for the resonant excitation of kinetic wave instabilities. The in-situ observations confirm both the electromagnetic fluctuations triggered by temperature anisotropy and the predominantly electrostatic excitations induced for instance by electron beams.

How to cite: Hamd, S. M. S., López, R. A., Lazar, M., and Poedts, S.: Resonant Wave Excitations of Suprathermal Populations in the Solar Wind and Terrestrial Magnetosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7217, https://doi.org/10.5194/egusphere-egu24-7217, 2024.

The space plasma environment, extending from the Sun to the Earth, includes regions of frozen conditions, zones of anomalous resistance caused by electromagnetic turbulence, interconnected regions characterized by weakly ionized gas systems in strong magnetic fields, coupled neutral-atmosphere chemical processes, and pure neutral-atmosphere collision systems. Owing to their complex interactions, an inclusive understanding and forecasting of the space environment remains an elusive goal, even with the advancements in high-performance instrumentation and in-situ observation of satellites. Therefore, it is imperative to develop space plasma simulations capable of providing comprehensive insights, ranging from local spatial domains to the global schematic.

Historically, the development of space plasma simulations has been constrained by computational time, memory capacity, and data storage limitations, resolving complex phenomena with restricted physics at local space scales.

Recently, as quantum computing hardware has advanced, quantum algorithms have proven to benefit exponential speedups. There has been a focus on the practical applications of quantum computing in finance, chemistry, fluids, and a variety of fields (e.g., Bouland et al.,[2020], Cao et al.,[2019], Egger et al.,[2020] and Budinski, [2022]). Then a quantum algorithm for the collisionless Boltzmann equation using the discrete velocity method was developed by (Todorova and Steijl, [2020]).

We have developed a quantum algorithm for the six-dimensional Boltzmann-Maxwell equations for collisionless plasmas with reference to (Higuchi, et al.,[2023]). We applied this methodology to propose a quantum approach that predicts kinetic and multiscale plasma dynamics.

In this presentation, we will introduce a quantum algorithm for performing super large- scale plasma simulations in a quantum computer and estimate the performance required by this task for future quantum error tolerant large-scale quantum computers. We will also discuss the prospects for applications that can be expected in our field, based on trends in the development of quantum computer hardware and software.

How to cite: Higuchi, H., Pedersen, J., and Yoshikawa, A.: Quantum Computing for Future Super Large-Scale Plasma Simulations: A Novel Approach for Simulating the Vlasov-Maxwell System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7222, https://doi.org/10.5194/egusphere-egu24-7222, 2024.

The electrons in the solar wind often exhibit non-equilibrium velocity distribution functions. Observed non-equilibrium electron features in the inner heliosphere include a field-aligned beam (called "strahl"), a suprathermal halo population, a sunward deficit in the distribution, and temperature anisotropy. These features are the result of a complex interplay between global expansion effects, collisions, and local interactions between the particles and the electromagnetic fields. Global effects create, for example, the strahl via the mirror force in the decreasing magnetic field and the sunward deficit via reflection effects in the interplanetary electrostatic potential. Local wave-particle interactions such as instabilities and wave damping change the shape of these signatures and thus the overall properties and moments of the electron distribution.

We discuss the formation of the relevant features in the electron distribution and analyse their impact on the linear stability of whistler waves in the inner heliosphere. We then present results from our numerical ALPS code that is capable of evaluating the linear stability of plasma with arbitrary background distributions. With results from our ALPS code, we show that the strahl-core-deficit configuration near the Sun drives oblique whistler waves unstable. However, it leads to enhanced damping of parallel whistler waves compared to a Maxwellian configuration. As the distribution evolves, the sunward deficit fills with electrons, at which point the plasma becomes unstable and drives parallel whistler waves. Our results highlight the need to treat electrons statistically as a globally inhomogeneous plasma component and to account for the detailed shape of their distribution in the evaluation of the plasma's linear stability.

How to cite: Verscharen, D., Micera, A., Innocenti, M. E., Coburn, J., Boella, E., Pierrard, V., Liu, J., Owen, C. J., Nicolaou, G., and Klein, K. G.: Statistical mechanics of the electrons in the solar wind: stability and instability of whistler waves in the inner heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8120, https://doi.org/10.5194/egusphere-egu24-8120, 2024.

A special observational signature in ICMEs that has puzzled researchers for a long time are so-called ”back regions” or ”magnetic-cloud-like (MCL)” parts of ICMEs which follow after the main flux rope rotation has passed the observer. These regions, occurring after the main flux rope rotation, display a peculiar behaviour where the magnetic field remains elevated with minimal rotation. Two proposed explanations involve magnetic reconnection during CME propagation or a purely geometric effect as the observer traverses the flux rope . 

We investigate in detail whether MCLs can be explained by an effect of the trajectory of an observer through a 3D expanding magnetic flux rope, without invoking magnetic reconnection as an explanation for those signatures. To this end, we employ the 3D coronal rope ejection (3DCORE) model, which has proven its ability to fit in situ magnetic fields of CME flux ropes. 

The model assumes an empirically motivated torus-like flux rope structure that expands self-similarly within the heliosphere, is influenced by a simplified interaction with the solar wind environment, and carries along an embedded analytical magnetic field. Developed for fitting, generating synthetic signatures, comparing models to observations, and analysing results, 3DCOREweb accelerates the determination of physical parameters, fostering research on the global magnetic structure of CMEs. Additionally, the interface aids in advancing our understanding of magnetic flux rope signatures arising from diverse 3D trajectories through CMEs.

How to cite: Rüdisser, H. T., Weiss, A. J., Möstl, C., Amerstorfer, U. V., Davies, E. E., and Weiler, E.: Understanding the effects of spacecraft trajectories through solar coronal mass ejection flux ropes using 3DCOREweb, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8372, https://doi.org/10.5194/egusphere-egu24-8372, 2024.

The kinetic Alfvén wave (KAW) is an extension of the Alfvén mode to the kinetic scales that propagates at quasi-perpendicular angles with respect to the background magnetic field in a magnetized plasma. The KAW is characterized by a right-handed polarization in the plane orthogonal to the background magnetic field. This allows the KAW to resonate with electrons, as contrary to the electromagnetic ion-cyclotron (EMIC) wave, which resonates with positive ions due to it’s its left-handed polarization. The EMIC mode is also a kinetic extension of the classical Alfvén wave, and propagates at quasi-parallel wavenormal angles. Due to the relevance and overall presence of both of these modes in space plasmas, understanding the nature of the transition from the EMIC mode to the KAW is a matter of great interest for the study of the micro-scale physics of these systems.

The transition from left-hand to right-hand polarized Alfvén waves depends on the wavenumber, plasma beta, temperature anisotropy, and ion composition of the plasma. Along with the temperature anisotropy, the electron-to-proton temperature ratio T_e/T_p is of great relevance for the characterization of the thermal properties of a plasma. This ratio varies significantly between different space plasma environments. Thus, studying how variations on this ratio affect the polarization properties of electromagnetic waves becomes of high relevance highly relevant
for our understanding of the dynamics of space plasmas.

In this work, we present an extensive study on the effect of the thermal properties of electrons on the behaviour and characteristics of Alfvénic waves in fully kinetic linear theory, as well as on the transition from EMIC to KAW. We show that the temperature ratio T_e/T_p has strong and non-trivial effects on the polarization of the Alfvénic modes, especially at kinetic scales (k_┴ρ_L>1, where k_┴=k sinθ and ρ_L= cs/Ω_p, with c_s the plasma sound speed and Ωp the proton’s gyrofrequency) and β_e+β_p>0.5, where β_s=8πnkT_s/B² is the ratio between thermal and magnetic pressure. We conclude that electron inertia plays an important role in the kinetic scale physics of the KAW in the warm plasma regime, and thus cannot be excluded in hybrid models for computer simulations.

How to cite: Sepúlveda, N. F., Moya, P. S., López, R. A., and Verscharen, D.: The effect of the thermal properties of electrons on the dispersion of kinetic Alfvén waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8536, https://doi.org/10.5194/egusphere-egu24-8536, 2024.

Recent observations of the interplanetary magnetic field have enlarged the magnetic field topology family in the inner heliosphere, and raises interest in the relationship between those topologies and the evolution of solar wind. For example, switchbacks that are kinks of magnetic field lines accompanied by velocity spikes and enhancement of the proton parallel temperature, have free energy both of the field and of the particles, and thus have potential for a series of plasma instabilities. It is favorable to extract elementary topologies from complicated structures like switchbacks before we look further in. Based on Particle-in-Cell simulations, we discuss from elementary topologies on the effect they have on kinetic processes of the solar wind plasma.

How to cite: Lin, R., Lapenta, G., and He, J.: How will interplanetary magnetic field topology modify solar wind kinetics?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11114, https://doi.org/10.5194/egusphere-egu24-11114, 2024.

We present a multi-ion generalization of the AWSoM model, a 3D global magnetohydrodynamic (MHD) solar corona and inner heliosphere model with incompressible turbulence. The AWSoM model with charge states is further extended to include temperatures for the various heavy ion species. The coronal heating is addressed via outward propagating low-frequency Alfven waves that are partially reflected by Alfven speed gradients. The nonlinear interaction of these counter-propagating waves results in turbulent energy cascade. To apportion the cascaded turbulent energies to the electron and ion temperatures, we employ the results of the theories of linear wave damping and nonlinear stochastic heating. This heat partitioning results in a mass proportional heating among ions.

How to cite: van der Holst, B., Landi, E., and Gombosi, T.: AWSoM solar wind model with charge states and ion temperatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11324, https://doi.org/10.5194/egusphere-egu24-11324, 2024.

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 from the corona, as shown by eruptive flares.

How to cite: Wang, Q., Yang, S., Zhang, M., Yang, X., and Zhu, X.:  Change Ratios of Magnetic Helicity and Magnetic Free Energy During MajorSolar Flares , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13542, https://doi.org/10.5194/egusphere-egu24-13542, 2024.

The exact coronal heating mechanism remains a riddle, but magnetically active regions are known to host coronal loops with extreme-UV emission. But also at much smaller sizes, up to 10 Mm, there are bipolar regions that can be associated with UV emission in coronal bright points (CBPs). We study the statistical properties of CBPs with continuous data from the SDO spacecraft to track the lifetime of CBPs. We use their tracking data to verify that the lower corona co-rotates with the photosphere. In a next step, we aim to reproduce an isolated CBP in a 3D magneto-hydrodynamic (MHD) simulation. To this end, we need observational data to drive the simulation from both, SDO/HMI and Hinode/NFI. As these instruments feature different resolutions and field-of-views, they also detect different levels of small-scale and large-scale magnetic structures in the photosphere. As we know, these magnetic patches are advected from photospheric horizontal motions and create the necessary Poynting flux at the base of the corona. Combining these data from two very different instruments is a task that needs careful overlaying, so that not artificial effects would appear in the MHD simulation. We use a multi-scale overlaying method to enlarge the field-of-view of Hinode with SDO data, to drive the simulation with consistent photospheric magnetic fields. The bottom and top boundaries are fully closed for any mass and heat flows. The output of the simulation will allow us to compute synthetic UV emission maps that we may compare directly to SDO and Hinode observations. With our model we test if the field-line braiding mechanism is sufficient to heat a CPB to the required temperature. We find that loop-like CBPs usually originate from bipolar regions. Weaker magnetic polarities produce fainter and hence cooler CBPs. And the same time, we find that lifetimes of typical CPBs are easily more than 6 hours. This supports the theory that the heating of CBP is mainly based on magnetic energy dissipation through a relatively steady and slow magnetic reconnection process.

How to cite: Kraus, I. and Bourdin, P.: Coronal Bright Points observed in the corona and photosphere with SDO and Hinode, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15727, https://doi.org/10.5194/egusphere-egu24-15727, 2024.

Coronal Mass Ejections (CMEs), huge magnetized plasma erupting from the Sun, pose potential risks to space weather and space-based infrastructure. While extensive research has focused on examining the kinematics of CMEs, there has been limited study of their thermodynamic evolution, particularly at specific heliocentric distances closer to the Sun. Acknowledging that variations in internal plasma properties can impact the overall evolution of CMEs and vice versa is crucial. This study investigates diverse kinematic profiles and associated thermodynamic changes in nine fast CMEs at coronal heights where measuring thermodynamics is challenging. We estimated the distance-dependent evolution of various internal parameters, including polytropic index, temperature, heating rate, pressure, and internal forces driving CME expansion by leveraging the improved Flux Rope Internal State (FRIS) model. The FRIS model utilizes the 3D kinematics derived from the Graduated Cylindrical Shell (GCS) model as input. Our findings reveal that CMEs can maintain their temperature above the adiabatic cooling threshold despite expansion, progressing towards an isothermal state during later propagation phases. The fast CMEs maintaining higher expansion speeds exhibit less pronounced temperature decreases. We found that CME's expansion speed and acceleration correlate well with its maximum temperature drop to reach the isothermal state. Multi-wavelength observations of flux ropes at the source region support the FRIS model-derived results at lower coronal heights. Our analysis elucidates that the primary forces influencing CME radial expansion are the centrifugal and thermal pressure forces, while the Lorentz force acts as a constraining factor. Notably, the thermal pressure force governs expansion at higher heights and is solely responsible for radial expansion. This study enhances our comprehension of the thermodynamic properties of fast CMEs, offering valuable insights for refining assumptions of the polytropic index value in different magnetohydrodynamics (MHD) models to improve the prediction of CME properties at 1 AU.

How to cite: Khuntia, S. and Mishra, W.: Understanding the Thermal Properties of Fast CMEs by Integrating White-light Observations and Analytical Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16790, https://doi.org/10.5194/egusphere-egu24-16790, 2024.

We simulate the propagation of relativistic test particles within the field of a 3D MHD simulation of the solar wind. The adiabatic ideal MHD equations are integrated numerically using the MPI-AMRVAC code. Test particles are initialized within the MHD simulation grid and advanced in time according to the guiding center equations, we employ a third-order accurate time prediction-correction method from Mignone et al. 2023 for integration. We also include possibility of diffusion in velocity space based on a particle-turbulence mean free path λ∥ along the magnetic field line. One of the first results where we consider 81 keV electrons injected at 0.139 AU heliocentric distance and mean free path λ∥ = 0.5 AU is in good qualitative agreement with measurements at 1 AU.

How to cite: Houeibib, A., Pantellini, F., and Griton, L.: Exploring Solar Energetic Particles Transport in the Inner Heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17085, https://doi.org/10.5194/egusphere-egu24-17085, 2024.

How the solar wind heat flux is constrained and how strahl electrons are scattered are two fundamental problems in the study of the electron dynamics in the solar wind. Recently, much attention has been paid to the role of the electron heat flux instability on these two problems. We have performed the instability analyses for the electron heat flux instability in the near-Sun solar wind where the plasma beta is much lower than one. We found that lower-hybrid waves and oblique Alfvén waves can be primarily triggered by the electron heat flux in the low-beta plasma environment, and we also explored the wave-particle interactions in each type instability through the energy transfer rate method. Moreover, using PSP observations, we will show the possible observation signature for the lower-hybrid waves in the near-Sun solar wind.

How to cite: Zhao, J.: Electron heat flux instability in the near-Sun solar wind, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17196, https://doi.org/10.5194/egusphere-egu24-17196, 2024.

Langmuir waves are frequently detected in the solar wind and affect the energetics of the plasma electrons. Previous observational studies have found Langmuir waves associated with magnetic holes in the solar wind. In our work, we aim to understand the connection between magnetic holes and these waves.

The Langmuir instability is a well-known consequence of electron beams in plasmas. We use particle-in-cell (PIC) simulations of a collisionless electron-ion plasma in a magnetic hole structure. We study the triggering of Langmuir waves by inhomogeneous beam instabilities in this configuration.

Our simulations reveal patterns that suggest that injecting a beam into the magnetic hole has the potential to create spatially inhomogeneous Langmuir wave packets by instability. We support our PIC simulations with linear stability calculations and discuss the conditions required for magnetic holes to emit Langmuir waves through our proposed mechanism. Our simulation results will be used in comparative studies with observational data of Langmuir-wave emitting magnetic holes.

How to cite: Liu, J., Verscharen, D., Coburn, J., Agudelo, J., Germaschewski, K., Reid, H., Nicolaou, G., and Owen, C.: Simulations of Langmuir-wave emission by magnetic holes in the solar wind, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18011, https://doi.org/10.5194/egusphere-egu24-18011, 2024.

Our research delves into solar wind's mesoscale features known as microstreams—periods of heightened speed and temperature lasting hours. Initially observed in Helios and Ulysses data, they're now prevalent in the 'young' solar wind by Parker Solar Probe and Solar Orbiter. Recent findings unveil microstreams' carriage of abundant Alfvénic perturbations—velocity spikes and magnetic switchbacks.

Employing a high-resolution 2.5 MHD model, we scrutinize the genesis of microstreams from emerging bipoles interacting with the ambient corona. Our simulations reveal the tearing-mode instability, forming plasmoids released into the solar wind. Our domain spans the lower corona to 20 Rs, enabling observation of plasmoid formation and their evolution into Alfvénic spikes (Gannouni et al. 2023). The magnetic emergence rate modulates microstream characteristics.

Additionally, 3D MHD simulations explore intermittent interchange reconnection in a 24x24x30Mm domain with a flux emergence rate of 1.38G/s. Reconnection spawns plasma jets and twisted magnetic field bundles, releasing hot plasma into the solar wind, inducing propagating waves and twists along magnetic field lines.

How to cite: Gannouni, B., Réville, V., and Rouillard, A.: Modelling the formation and  evolution of solar wind microstreams:from coronal plumes to propagating Alfvénic velocity spikes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18200, https://doi.org/10.5194/egusphere-egu24-18200, 2024.

    Solar and interplanetary radio bursts are important phenomena to reflect the electron acceleration and kinetic process in the corona and space plasmas. The near-Sun radio observation by Parker Solar Probe (PSP) provides an good chance to make the approach and in situ measurements for the emission source of radio bursts. According to the radio dynamic spectrum, we found that a large number of weak radio bursts with higher cutoff frequency f_lo can only be detected by PSP. These bursts have several obvious characteristics: (1) short duration (1-5 min); (2) narrow frequency band (0.5-15 MHz); (3) weak peak intensity (~ 10^-15 V²/Hz). Their relative frequency drift rate decreases from > 0.01 s^-1 to < 0.01 s^-1 implies that they are not the typical type III and II radio bursts. Based on the plasma empirical models and the data from in situ detection by PSP, the fitted models indicate that the radiation of these bursts might be generated by the electron cyclotron maser emission in the acceleration region of solar wind (1.1-10 R_S). The spectral characteristics of these bursts manifest that these bursts come from small-scale emission source, which have experienced strong kinetic evolution. We propose that these weak bursts are possibly the solitary wave radiation (SWR) generated from electron cyclotron maser instability with the energetic electrons trapped and accelerated by solitary kinetic Alfvén wave (SKAW) in the close magnetic structure. The decay of SKAW can well explain the deceleration of the emitting sources and the short duration.

How to cite: Ma, B., Chen, L., and Wu, D.-J.: Emission Mechanism of radio bursts from the Solar Wind Acceleration Region observed by Parker Solar Probe in near-Sun plasmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18356, https://doi.org/10.5194/egusphere-egu24-18356, 2024.

A nonlinear force-free field is solely determined by the normal components of magnetic field and current density on the entire boundary of the domain. Methods using three components of magnetic field suffer from either overspecification of boundary conditions and/or a nonzero divergence B problem. A vector potential formulation eliminates the latter issue, yet poses difficulties in imposing normal components of both magnetic field and current density on the boundary. This challenge arises due to the inability to fix all three components of the vector potential at the boundary while the vector potential within the interior domain undergoes iterative changes.

This paper explores four distinct boundary treatment approaches within the vector potential formulation. In two methods, the normal component of the vector potential is adjusted to satisfy the prescribed boundary-normal component of current density at each iteration, while the tangential components remain fixed throughout. In the other two methods, the tangential components of the vector potential are modified at each iteration, while the normal component remains fixed. Each group comprises both first-order and second-order boundary treatments. We conduct a comparative analysis of these methods against our established poloidal-toroidal formulation code and the optimization code in Solar Software.

While none of the four methods outperform our poloidal-toroidal formulation code, they demonstrate comparable or superior performance compared to the latter. This research is regarded to provide insights into optimizing boundary conditions for data-driven simulations using vector potentials. 

How to cite: Lee, M., Choe, G., and Yi, S.: Implementation of Boundary Conditions for Nonlinear Force-Free Field Computations Using Vector Potentials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18387, https://doi.org/10.5194/egusphere-egu24-18387, 2024.

The temperature of the solar atmosphere increases from thousands to millions of degrees moving from the lower layer (chromosphere) to the outermost one (corona), while the density drops accordingly. The mechanism behind this phenomenon, known as a temperature inversion, is still unknown. In this work, we model a coronal loop as a collisionless plasma confined in a semicircular tube that is subject to the Sun's gravity and in thermal contact with a fully collisional chromosphere behaving as a thermostat at the loop's feet. By using kinetic N-particle simulations and analytical calculations, we show that rapid, intermittent, and short-lived heating events in the chromosphere drive the coronal plasma towards a non-equilibrium stationary state. The latter is characterized by suprathermal tails in the particles velocity distribution functions, exhibiting temperature and density profiles strikingly similar to those observed in the atmosphere of the Sun. These results suggest that a million-Kelvin solar corona can be produced without the local deposition of heat in the upper layer of the atmosphere that is typically assumed by standard approaches. We find that suprathermal distribution functions in the corona are self-consistently produced instead of postulated a priori, in contrast to classical kinetic models based on a velocity filtration mechanism.

How to cite: Barbieri, L., Casetti, L., Verdini, A., Landi, S., Papini, E., and Di Cintio, P.: Temperature inversion in a gravitationally bound plasma: Case of the solar corona, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20270, https://doi.org/10.5194/egusphere-egu24-20270, 2024.

Solar energetic particle (SEP) events, particularly those of significant magnitude, are commonly associated with fast and wide coronal mass ejections (CMEs). These CMEs generate and drive shock waves in the solar corona, proving to be highly efficient in particle acceleration to high energies. Understanding the intricate connections between shock wave properties and SEP characteristics is crucial for advancing Space Weather forecasting.
To achieve this objective, we employ a methodology to analyze a SEP event involving a coronal shock wave, observed by several spacecraft well distributed around the Sun. Initially, we reconstruct the 3D ellipsoidal shape of the expanding shock, enabling the extraction of its geometry and kinematic properties. Using magneto-hydrodynamics (MHD) cubes, we then reconstruct the magnetic connectivity of spacecrafts and retrieve the MHD properties of the shock wave at the intersections with these magnetic field lines. The temporal correlations between the shock properties and the SEPs recorded by individual spacecraft can finally be compared.
Through the application of this methodology, we identify enhanced correlation coefficients between SEPs and shock parameters, such as speed, Alfvénic Mach Number, and theta_BN (the angle between the shock's normal and the magnetic field line). 
This work is funded by the H2020 SERPENTINE project.

How to cite: Jarry, M., Dresing, N., Vainio, R., Rouillard, A., Plotnikov, I., and Kouloumvakos, A.: Connecting the early temporal evolution of solar energetic particles to the properties of coronal shock waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-417, https://doi.org/10.5194/egusphere-egu24-417, 2024.

A methodological study of relativistic solar energetic particles provides the necessary basis to reveal the nature of various processes, such as the production and acceleration of energetic particles at the Sun, their transport in the interplanetary medium, interactions of energetic particles with magnetic fields in the heliosphere, the induced corresponding terrestrial and space weather effects. Following solar eruptive processes, such as solar flares and/or coronal mass ejections solar ions are accelerated to a high-energy range. When the energy of the accelerated solar proton reaches the GeV/n range, it is enough high, so that solar ions generate an atmospheric cascade in the Earth’s atmosphere, whose secondary particles reach the ground, eventually registered by ground-based detectors, such as neutron monitors (NMs). This particular class of events is known as ground-level enhancements (GLEs).

Over several decades, NMs provided the main records allowing analysis of GLEs, namely their spectral and anisotropy characteristics, a procedure requiring complicated modeling and several NM stations (records starting from GLE #5, 23-Feb-1956). However, the first four GLEs were recorded mostly by ionization chambers (ICs), devices with a weaker responses and greater energy threshold compared to NMs. Here, we analyzed several GLEs on the basis of historical records, where data of NMs and IC are both available. As a first step, we derived the GLE protons spectra employing a method verified by space-borne measurements. Secondly, employing a forward modeling, we rescaled the response of the available ICs, that is, we assessed the response function of selected ICs. Finally, employing a procedure similar to GLE analysis using NMs, but here using ICs records, we derived for the first time the spectra of e.g. GLE # 4. We compared the derived spectra with GLE #5 and discussed the obtained results.

How to cite: Mishev, A., Hayakawa, H., Koldobskiy, S., Poluianov, S., and Usoskin, I.: Study of major historical GLEs on the basis of historical records , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1309, https://doi.org/10.5194/egusphere-egu24-1309, 2024.

Solar energetic particles (SEPs) are bound to the interplanetary magnetic field (IMF) by the Lorentz force. The expansion of the IMF close to the Sun focuses the particle pitch-angle distribution, and scattering counteracts this focusing. Solar Orbiter observed an unusual solar particle event on 9 April 2022 when it was at 0.43 astronomical units (au) from the Sun. The inferred IMF along which the SEPs traveled was about three times longer than the nominal length of the Parker spiral.

Nevertheless, the pitch-angle distribution of the particles of this event is highly anisotropic, and the electrons and ions appear to be streaming along the same IMF structures. The angular width of the streaming population is estimated to be approximately 30 degrees. The highly anisotropic ion beam was observed for more than 12 h. This may be due to the low level of fluctuations in the IMF, which in turn is very probably due to this event being inside an interplanetary coronal mass ejection. The slow and small rotation in the IMF suggests a flux-rope structure. Small flux dropouts are associated with very small changes in pitch angle, which may be explained by different flux tubes connecting to different locations in the flare region. The unusually long path length along which the electrons and ions have propagated virtually scatter-free together with the short-term flux dropouts offer excellent opportunities to study the transport of SEPs within interplanetary structures. The 9 April 2022 solar particle event offers an especially rich number of unique observations that can be used to limit SEP transport models.

How to cite: Wimmer-Schweingruber, R. F., Yang, L., Kollhoff, A., Gomez-Herrero, R., Rodriguez-Pacheco, J., Espinosa, F., Cernuda, I., Ho, G. C., Mason, G. M., Warmuth, A., Owen, C. J., Rodriguez, L., Shukhobodskaia, D., Berger, L., Kühl, P., Heber, B., Wang, L., Bucik, R., and Malandraki, O.: Unusually long path length for a nearly scatter-free solar particle event observed by Solar Orbiter at 0.43 au, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2823, https://doi.org/10.5194/egusphere-egu24-2823, 2024.

A major impact on human and robotic space exploration activities is the sudden and prompt occurrence of solar energetic ion events. In 2023 and 2024,  {STEREO} is approaching the Earth from a behind position, soon passing Earth inside its orbit and thereafter moving ahead of Earth.  {STEREO} thus offers several unique opportunities during this passage. In the period from June 1 to November 1, 2023, 5 {SEP} events have been measured that cause proton fluxes of above 25~MeV to rise above 0.1 /(cm$^2$\; s\; sr\; MeV). Taking into account systematic and statistical uncertainties of the particle measurements we find a good agreement between both spacecraft.

The SOHO/EPHIN and STEREO/SEPTproject is supported under Grant 50~OC~2102 by the German Bundesministerium für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR). This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE).

How to cite: Heber, B., Banys, D., Berdermann, J., Dröge, H., Hörlöck, M., Kollhoff, A., Kühl, P., Malandraki, O., Martens, J., Posner, A., and Sierks, H.: The alignment of  STEREO-A and Earth: A unique opportunity to investigate Solar Energetic Particle events., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2836, https://doi.org/10.5194/egusphere-egu24-2836, 2024.

Solar eruptions can accelerate solar energetic particles (SEPs) to high energies which can, if they have sufficient energy, penetrate the Earth’s magnetic environment leading to numerous space weather hazards that can affect infrastructure and human health. Strong SEP events can be detected by ground-based neutron monitors (NMs) and registered at the Earth’s surface as ground-level enhancements (GLEs) if several NMs detect a significant increase in cosmic-ray count rates caused by arriving SEPs. The increase in the flux of high-energy particles entering the atmosphere during GLEs enhances the complex radiation environment at high altitudes which can pose a serious risk to airplane crew and passengers. As such there is a strong desire to develop nowcasting models that can quickly estimate the impact of GLEs on human health to help mitigate the threat GLEs pose. One avenue of approaching this issue is the development and application of proxies that allow for quick conservative estimates of the hazards. In this work, 21 of the 73 currently recorded GLEs have been analysed using the same verified method revealing the SEP characteristics during the events. These characteristics are used as inputs into a newly developed CRAC:DOMO radiation model to compute the radiation dose experienced at aviation altitudes. A comparison was then done with the real-time NM data during the GLE events to establish a relationship between the modelled dose and empirical NM data through a large statistical analysis. This was successful, with a very strong relationship being shown between the two variables. This result provides scientific support for using real-time NM data as a potential proxy in future nowcasting models aimed at estimating and mitigating the impacts of GLEs on humans and the aviation industry.

How to cite: Larsen, N. and Mishev, A.: Investigating the Potential for Using Real-Time Neutron Monitor Data as a Proxy for Estimating the Impact of Ground-Level Enhancements on Radiation Doses at Aviation Altitudes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3470, https://doi.org/10.5194/egusphere-egu24-3470, 2024.

Localised dynamic pressure enhancements—jets—are regularly observed downstream of the Earth’s bow shock. They drive enhanced particle acceleration, larger amplitude magnetic field variations and reconnecting current sheets. Various shock simulations have also exhibited jets, suggesting that they are not unique to the bow shock.

Here, we report the first observations of jet-like structures downstream of interplanetary shocks. We introduce an analysis approach suitable for such conditions and apply it to Wind spacecraft data using tools developed in the EU-project SERPENTINE. We first demonstrate the methods on a particularly high Mach number interplanetary shock that has properties comparable to the Earth’s bow shock. To further our understanding, we also investigate two low beta, low Mach number interplanetary shocks, i.e., conditions that are rare for the bow shock.

The jet-like structures we find are tens of ion inertial lengths in size, and some are observed further away from the shock than in a limited magnetosheath. We find that their properties are similar to those of magnetosheath jets: in the frame of the shock these structures are fast, cold, and most have no strong magnetic field variations. All three interplanetary shocks feature foreshock activity, but no strongly compressive waves. We discuss the implications these findings have for the proposed jet formation mechanisms. The prospects of observing downstream jets in further detail with future missions look promising.

How to cite: Hietala, H., Trotta, D., Fedeli, A., Wilson III, L. B., Vuorinen, L., LaMoury, A. T., and Coburn, J. T.: Downstream jets at interplanetary shocks: first observations and comparison with the magnetosheath, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3846, https://doi.org/10.5194/egusphere-egu24-3846, 2024.

It is shown that the first order Fermi acceleration of cosmic rays, based on a concept of ions reflected by shocks, is equivalent to the ballistic surfing acceleration (BSA) by the convection electric field. Despite big differences in the physics of the processes involved, both models lead to the same expression for the energy gain of a particle after one encounter with the shock, and consequently to the same power-law distribution of the cosmic ray energy spectrum after many encounters. BSA accelerates ions continuously from superthermal energies of 100eV up to very high energies observed in the cosmic ray spectrum. It is shown that the ‘knee’ observed in the spectrum at energy of 5×10¹⁵ eV could correspond to ions with gyroradius comparable to the size of shocks in supernova remnants.
It has been established that thermalization, heating, and energization of ions and electrons in collisionless shocks are related to the following plasma processes:

BSA – ballistic surfing acceleration
SWE –  stochastic wave energization
TTT – transit time thermalization
QAH – quasi adiabatic heating

References:
[1] K. Stasiewicz, MNRAS. 527, L71 (2023), Origin of flat-top electron distributions at the Earth’s bow shock, https://doi.org/10.1093/mnrasl/slad146
[2] K. Stasiewicz, MNRAS. 524, L50 (2023), Transit time  thermalization  and the stochastic wave energization of ions  in quasi-perpendicular shocks,  https://doi.org/10.1093/mnrasl/slad071
[3] K. Stasiewicz, B. Eliasson, MNRAS 520, 3238 (2023), Electron heating mechanisms at the bow shock - revisited with Magnetospheric Multiscale measurements, https://doi.org/10.1093/mnras/stad361

How to cite: Stasiewicz, K.: Reinterpretation of the Fermi acceleration of cosmic rays in terms of the ballistic surfing acceleration in shocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4672, https://doi.org/10.5194/egusphere-egu24-4672, 2024.

Human beings are considering going back to the Moon and eventually to Mars within the next decades. However, we are still facing one major hurdle ``space radiation'' which is a significant and unavoidable risk for crews' health, especially for long-term stays at future lunar or martian stations. In particular, sporadic solar energetic particles (SEPs) generated via extreme solar eruptions may enhance the lunar or martian surface radiation levels to potentially hazardous values. Recent lunar and martian surface and orbital radiation detectors have advanced our understanding of the radiation environment of both planetary bodies. We have used the state-of-the-art modeling appoaches to study the radiation environment of the Moon and Mars. In particular, we study and compare the potential radiation effects of historically large SEP events on the surface and subsurface of the Moon and Mars.

How to cite: Guo, J., Zhang, J., Liu, B., and Dobynde, M.: A comparison study of the impact of large Solar Energetic Particle events on the Moon and Mars , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4847, https://doi.org/10.5194/egusphere-egu24-4847, 2024.

Using magnetically well-connected solar energetic particle (SEP) observations, we derive the electron and proton parallel mean-free-paths (MFPs) by comparing in-situ observations to one-dimensional simulation results. These inferred MFPs are compared to theoretical estimates which have been constrained by solar wind turbulence observations. We show that these derived and theoretical values are mostly consistent for both protons and electrons, but do show significant inter-event variations which can be explained by changing solar wind turbulence conditions. To illustrate the influence of these changing scattering conditions on particle transport, we simulate SEP time profiles for magnetically connected and unconnected observers for different transport and/or acceleration parameters. We show that this can explain the observer inter-event variations observed for SEP events. Additionally, we show that such an ensemble modeling approach can be used to quantify the uncertainty in the underlying model assumptions and can, in principle, be used in physics-based SEP predictive models to produce SEP predictions that include an uncertainty band.

How to cite: Strauss, D. T., Lang, J., Engelbrecht, E., and van den Berg, J.: Quantifying the uncertainty associated with solar energetic particle transport models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5389, https://doi.org/10.5194/egusphere-egu24-5389, 2024.

Energetic particle populations are ubiquitous throughout the Universe and often found to be accelerated by astrophysical shocks. One of the most prominent sources for energetic particles in our solar system are huge eruptions of magnetized plasma from the Sun called coronal mass ejections (CMEs), which usually drive shocks that accelerate charged particles up to relativistic energies. Accelerated electrons can be observed remotely as low-frequency radio bursts or in situ at spacecraft. However, it is currently unknown where electrons accelerated in the early phases of such eruptions propagate and when they escape the solar atmosphere to eventually reach spacecraft. Here, we present a new study that uses a three-dimensional representation of radio emission locations in relation to the overlying coronal magnetic field, shock wave propagation, magneto-hydrodynamic (MHD) models of the solar corona, and radio imaging observations from ground-based observatories. These solar observations are also combined with in situ electron data at spacecraft.  Our results indicate that if the in situ electrons are shock-accelerated, their most likely origin is at or near the acceleration site of electrons beams producing herringbone radio bursts. This is the only region during the early evolution of the CME where there is clear evidence of electron shock acceleration and intersection of the CME shock with open field lines that can connect to the observing spacecraft.

How to cite: Morosan, D., Pomoell, J., Palmroos, C., Dresing, N., Asvestari, E., Gieseler, J., Kumari, A., and Jebaraj, I.: Connecting remote and in situ observations of shock-accelerated electrons associated with a coronal mass ejection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5558, https://doi.org/10.5194/egusphere-egu24-5558, 2024.

The activity of the Sun modulates the fluxes of galactic cosmic rays arriving at Earth. This heliospheric modulation of cosmic rays is often quantified by the modulation potential, which describes the average energy loss of particles during their transport in the heliosphere. The modulation potential is a useful parameter not only for understanding the behaviour of energetic particles in the heliosphere, but also as a measure of solar activity. However, the validity of the modulation potential, which utilizes the force-field methodology, is uncertain for shorter timescales, and often the estimates are only monthly or yearly.

Recently, an updated estimation of the modulation potential was done at a daily time resolution by utilizing neutron monitor (NM) measurements from 10 stations. We have now analysed the daily version and compared it (via a LIS model) to the variation of the daily GCR energy spectrum (for rigidities 1 to 100 GV) measured by the AMS-02 instrument in the ISS. We find that overall, the daily modulation potential works well for estimating daily count rates at different energies. The correspondence is lowest for the low energy bins, where we see an excess of particles, which seems to follow the solar cycle. For rigidities around 4-13 GV, we can see a very clear match, letting us estimate daily count rates for different energy bins with a few per cent accuracy. For higher energies, the noise background of the measurements masks the underlying variation.

The result is very interesting and promising for the feasibility of using the modulation potential estimates for shorter time scales. This will lead to a better understanding of the variability of the overall modulation and the possibility of utilizing and combining NM and spacecraft measurements. The results will be useful in space climate (e.g. long-term solar variation induced from cosmogenic isotopes) and space weather (e.g. CME's/Forbush decreases, CIR's, Flares/GLE's) research. Future work with additional datasets and analysis of the different LIS models is planned.

How to cite: Väisänen, P., Bertucci, B., Tomassetti, N., Orcinha, M., Duranti, M., and Usoskin, I.: Daily heliospheric modulation potential (V23) and modelled GCR dataset compared to space measurements of the GCR energy spectrum., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5753, https://doi.org/10.5194/egusphere-egu24-5753, 2024.

We report on multi-spacecraft measurements of a solar energetic particle (SEP) event that occurred on 13 March 2023. The Parker Solar Probe (PSP) mission was situated on the far side of the Sun as seen from Earth at a radial distance of only 49 solar radii and observed a very strong event including the associated CME and its shock passing over the spacecraft only four hours after the solar eruption. Solar Orbiter, BepiColombo, STEREO A, near-Earth spacecraft, and MAVEN at Mars were all situated within 50 degrees in longitude, and observed the event as well, proving its widespread character. Clear signatures of shock-driven energetic storm particle events were present at Solar Orbiter, STEREO A, and near-Earth spacecraft suggesting that the interplanetary CME-driven shock had a longitudinal extent of about 160 degrees. However, the solar event was accompanied by a series of pre-event CMEs and comparison with ENLIL simulation results suggest that the ESP events were associated with shocks driven by other CMEs. This scenario of particle re-acceleration at different pre-event-associated shocks, provides a new scenario for the generation of widespread SEP events. 

How to cite: Dresing, N., Jebaraj, I., Palmerio, E., Palmroos, C., Cohen, C., Mitchell, G., Lee, C., Wei, W., Asvestari, E., Jarry, M., Muro, G., Rodríguz-García, L., and Wijsen, N.: A new scenario for widespread solar energetic particle events based on multi-spacecraft observations of the 13 March 2023 event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6034, https://doi.org/10.5194/egusphere-egu24-6034, 2024.

We present a new multi-spacecraft SEP event catalog for events observed in solar cycle 25. Observations from five different viewpoints are utilized, which are provided by Solar Orbiter, Parker Solar Probe, STEREO A, BepiColombo, and the near-Earth spacecraft Wind and SOHO. The catalog is an output of the SERPENTINE project, funded through the European Union’s Horizon 2020 framework programme. We provide key SEP parameters for > 25 MeV protons, > 1 MeV electrons, and ∼100 keV electrons. Furthermore, basic parameters of the associated flare and type-II radio burst are listed, as well as the coordinates of the observer and solar source locations.

An event is included in the catalog if at least two spacecraft detect a significant proton event with energies > 25 MeV. SEP onset times are determined using the Poisson-CUSUM method. SEP peak times and intensities refer to the global intensity maximum. If different viewing directions are available, we use the one with the earliest onset for the onset determination and the one with the highest peak intensity for the peak identification. We furthermore aim at using the highest possible time resolution. Therefore, time averaging of the SEP intensity data is only applied if necessary to determine clean event onsets and peaks. 

Associated flares were identified using observations from near Earth and Solar Orbiter. Associated type II bursts were determined from ground-based observations in the metric frequency range and from spacecraft observations in the decametric range.

The current version of the catalog contains 45 multi-spacecraft events observed in the period from Nov 2020 until May 2023, of which 13 were widespread events and four were classified as narrow-spread events. Using X-ray observations by GOES/XRS and Solar Orbiter/STIX we were able to identify the associated flare in all but four events. Using ground-based and spacecraft radio observations we found an associated type-II radio burst for 40 events. In total the catalog contains 141 single event observations out of which 18 (39) have been observed at radial distances below 0.6 AU (0.8 AU). 

We acknowledge funding by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004159 (SERPENTINE).   

How to cite: Dresing, N. and the SERPENTINE SEP Catalog Team: The solar cycle 25 multi-spacecraft solar energetic particle event catalog of the SERPENTINE project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6092, https://doi.org/10.5194/egusphere-egu24-6092, 2024.

On 2022 January 20, the Energetic Particle Detector on board Solar Orbiter detected a solar energetic particle (SEP) event showing unusual sunward-directed fluxes. Near-Earth spacecraft separated by 17° in longitude from Solar Orbiter measured classic antisunward-directed fluxes. Parker Solar Probe and MAVEN, separated by 130° and 216° respectively from Solar Orbiter, observed the particle event as well, suggesting a widespread event of nearly 360° in the heliosphere. The SEP event was associated with an M5-class X-ray flare and a CME with a speed of 1400 km/s. The energetic particles reached 3 MeV and 100 MeV energies for electrons and protons, respectively.

The aim of this study is to disentangle how the particles are able to spread throughout the heliosphere and how the local heliospheric conditions affect the acceleration and transport of the particles at different spacecraft locations. This work presents the observations and analyses that lead to a scenario in which the solar source injected energetic particles into the solar wind and within a preceding interplanetary coronal mass ejection (ICME) that was already present in the heliosphere at the time of the SEP event onset. In particular, Solar Orbiter measured the particles injected along the longest leg of an ICME still connected to the Sun at the time of the particle release.

How to cite: Rodríguez-García, L., Gómez-Herrero, R., Dresing, N., Balmaceda, L. A., Palmerio, E., Espinosa Lara, F., Kouloumvakos, A., Jebarah, I., Palmroos, C., Laitinen, T., Lee, C., Cohen, C., Fedeli, A., Cernuda, I., Roco, M., Malandraki, O., and Rodríguez-Pacheco, J.: The circumsolar solar energetic particle event on 2022 January 2022, particle spread within and outside a magnetic cloud, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6131, https://doi.org/10.5194/egusphere-egu24-6131, 2024.

Predictions of the intensities of solar particle events are often fraught with uncertainties. Insufficient knowledge and understanding of the solar sources of the particles, and the conditions in the corona and in the inner heliosphere, as well as magnetic connectivity, have been limiting factors in making further progress.
This presentation covers a study done by one of the Work Packages of the SERPENTINE project, and is based on the analysis of lists prepared by two other work packages of the same project, and logically consists of two parts.
In the first part we performed a statistical analysis of a list of 45 multi-spacecraft events in solar cycle 25 observed by five spacecraft located in the inner Heliosphere (Solar Orbiter, Parker Solar Probe, Stereo A, Bepi Colombo), and one located at 1 AU close to the Earth (SOHO or Wind). The list, while prepared with a focus on the detection of protons above 25 MeV by two or more spacecraft, contains also information about electron observations around 100 keV and 1 MeV, respectively.  Aiming to investigate the processes which are responsible for spreading energetic particles in longitude and latitude, and to estimate the importance of perpendicular diffusion in the latitudinal direction, we considered, together with other parameters, not only the longitudinal distances to the source, but also the differences in the total angle. In this part of our study we used methods such as correlation analysis and principal component analysis, and applied them to the list as a whole, as well as to different types of events. For example, we found that in the case of narrow-spread events perpendicular diffusion is sufficient to explain the spreading of particles from the solar source into the heliosphere, while in the case of wide-spread events an additional acceleration source is needed. We also evaluated the role of the speeds and sizes of the associated coronal mass ejections, as well as features of EUV waves appearing in the events, and relate different types of microwave (radio) emission to different groups of events.
In the second part of this work we performed a statistical analysis of a list of 61 interplanetary shocks, observed by Solar Orbiter.  By using a superposed epoch analysis, we built a statistical picture of ion time profiles around the shock front in several energy ranges. We also investigated which shock parameters are more important for particle energization by propagating interplanetary shocks, particularly in the case of an overlap in these lists.

This study has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004159 (SERPENTINE).

How to cite: Kartavykh, Y., Heber, B., Wimmer-Schweingruber, R. F., Dresing, N., Trotta, D., Kollhoff, A., Droege, H., Klassen, A., Kilpua, E., Gieseler, J., Droege, W., Gomez-Herrero, R., Espinosa Lara, F., Rodriguez-Garcia, L., Rodríguez-Pacheco, J., and Vainio, R.: Statistical study of multi-spacecraft events and shocks observed in solar cycle 25, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6233, https://doi.org/10.5194/egusphere-egu24-6233, 2024.

Solar Energetic Particle Analysis Platform for the Inner Heliosphere (SERPENTINE) is a 42-months-long EU/H2020 project that started in January 2021 and focuses on the physics of Solar Energetic Particle (SEP) acceleration and transport. The project (see https://serpentine-h2020.eu) provides answers for three science questions:

(Q1) what are the primary reasons for widespread SEP events;

(Q2) what are the mechanisms responsible for acceleration ions from suprathermal to near-relativistic energies in coronal and interplanetary shocks; and

(Q3) what is the role of shocks in the acceleration of electrons in SEP events.

SERPENTINE makes use of the present capabilities provided by inner heliospheric missions such as Solar Orbiter, Parker Solar Probe and BepiColombo. In addition to the scientific objectives, the project develops and releases to the community a large number of analysis tools to facilitate the interpretation of observations. Also event catalogs and high-level datasets are produced and distributed.

We will give a summary of the results of the project. Some of the science highlights include the several identified causes of widespread events related to both sources and transport (Q1), the role of local and averaged properties of shocks in ion acceleration (Q2), and the observational evidence of shocks as the primary accelerators of MeV electrons in gradual SEP events (Q3).

How to cite: Vainio, R., Dresing, N., Gieseler, J., Palmroos, C., Kilpua, E., Price, D., Trotta, D., Horbury, T., Kartavykh, Y., Heber, B., Wimmer-Schweingruber, R., Plotnikov, I., Gómez-Herrero, R., and Rodriguez-Pacheco, J.: Solar Energetic Particle Analysis Platform for the Inner Heliosphere (SERPENTINE): Summary of Project Results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6382, https://doi.org/10.5194/egusphere-egu24-6382, 2024.

Numerical tools for realistic modelling of energetic processes in the heliosphere, with the prospect of forecasting space weather, are in high demand. Of particular interest are solar energetic particles (SEPs), comprising high-energy charged particles linked to solar eruptive phenomena. During large SEP events, protons can be accelerated to energies ranging from tens of MeV up to a few GeV per nucleon, posing a dangerous threat to astronauts and spacecraft. While the precise acceleration mechanism behind SEP events is still an open challenge, observations indicate that the intensities of SEPs are highly influenced by the large-scale solar wind configuration. Transient structures such as coronal mass ejections (CMEs) or stream interaction regions (SIRs) perturb the interplanetary (IP) magnetic field, ultimately altering the transport of SEPs. In this context, we share recent results obtained with the energetic particle transport code PARADISE. By utilising realistic and complex solar wind configurations derived from magnetohydrodynamic (MHD) models such as EUHFORIA and the MPI-AMRVAC-based model Icarus, the code solves the focused transport equation in a stochastic manner to obtain spatio-temporal intensity distributions of SEPs in the inner heliosphere. Our studies focus on particle acceleration at IP shocks related to CMEs and SIRs.

How to cite: Husidic, E., Wijsen, N., Poedts, S., and Vainio, R.: Modelling energetic particle transport with the PARADISE code, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6854, https://doi.org/10.5194/egusphere-egu24-6854, 2024.

    The exploration of the inner heliosphere has been limited by large gravitational potential differences. Consequently, the propagation processes of solar ejecta such as Interplanetary Coronal Mass Ejections (ICMEs) and Solar Energetic Particles (SEPs) are somewhat problematic. Recent orbital engineering developments and other advancements have enabled the deployment of multiple probes, such as BepiColombo and Solar Orbiter. This has provided a unique opportunity for multi-point observations of solar eruptions, allowing for the tracking of their radial and longitudinal evolution. 

    This study focuses on radiation data acquired by “Solar Particle Monitor (SPM)” onboard BepiColombo for solar physics. SPM is the housekeeping instrument, particularly more suited for highly energetic particles such as Solar Energetic Particles (SEP) and Galactic Cosmic Ray (GCR) than other instruments. However, it provides only time-series data of count rates and deposited energies. To extract valuable information about the incident charged particles, including their type, number, energy, and direction, a radiation simulation toolkit Geant4 (Allison et al., 2016) is employed.

    The mass SPM model was defined in the model space, incorporating an aluminum shield to estimate radiation shielding effects from surrounding equipment and walls of spacecraft. The thickness of the shield in each direction is determined by comparing SPM measurements with simulation results, identifying the combination of thicknesses that aligns most closely with observed trends. The study also reproduces the electron flux during BepiColombo's Earth swing-by in 2020 using the AE9 radiation model (Ginet et al., 2013), comparing the simulated results with actual measurements to determine effective shield thicknesses. Additionally, the method proposed by Park et al. (2021), utilizing transformation matrices to derive incident particle energy spectra from observed spectra, is applied.

    Our research extends the analysis to the recovery time constants of Forbush Decreases, resulting from ICME shielding GCR which the spacecraft encountered in 2022. The study aims to analyze the structural changes induced by the interaction between ICMEs and solar wind during their propagation. Future applications of the analysis are planned for Solar Energetic Particle (SEP) studies, contributing to the understanding of SEP propagation processes through multi-point observations.

    The implications of the results are significant, especially considering the predicted peak of the 11-year solar activity cycle in 2025. BepiColombo, having already captured numerous phenomena, necessitates further analysis using the established calibration method. The study underscores the potential applicability of housekeeping devices commonly equipped on spacecraft for scientific observations. If applied to other probes, similar methods not only expand the scope of scientific observations but also contribute to the growth of the solar observation network within the heliosphere.

How to cite: Kinoshita, G., Ueno, H., Murakami, G., and Yoshioka, K.: Simulation for the calibration of radiation data acquired by Solar Particle Monitor/MMO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7297, https://doi.org/10.5194/egusphere-egu24-7297, 2024.

   Solar energetic particle (SEP) events are major outbursts of energetic charged particle radiation from the Sun. These events are related to solar flares and fast coronal mass ejections (CMEs). Flares are presumed to accelerate particles in magnetic reconnection processes, whereas fast (speeds > 1000 km s^–1) CMEs drive shock waves through the corona that are known to be able to accelerate particles. Electron acceleration has traditionally been ascribed to reconnection in flares whereas proton acceleration is believed to be efficient in CME-driven shocks. Recent observational evidence [1], however, suggests that shocks may be important in electron acceleration as well. Almost all major eruptions are related to both flares and CMEs so the association of the accelerated particles to these eruptive phenomena is often subject to debate. Using novel spacecraft observations of strong SEP events detected in solar cycle 25, we aim at identifying the parent acceleration region of the observed electron and proton events.

We have analyzed a set of 45 SEP events between Nov 2020 and May 2023 using data from multiple spacecraft including Solar Orbiter, near-Earth spacecraft (SOHO and Wind), STEREO-A and BepiColombo. We make use of peak intensities of >25-MeV protons and ~100 keV and ~1 MeV electrons and perform correlation studies of these peak intensities with each other as well as with the associated flare intensity. We separate the events into those that are well-connected (angular separation ≤ 35°) or poorly-connected (angular separation > 35°) to the flare by the interplanetary magnetic field.

We find significant correlations between electron and proton peak intensities. While events detected by poorly-connected observers show a single population of events, consistent with the idea that these particles are all accelerated by the spatially-extended CME-driven shock, events observed in well-connected regions show two populations: One population has higher proton peak intensities that correlate with electron peak intensities similarly to the poorly-connected events. These are most likely shock associated.  The other population has low proton intensities that are less well correlated with electron peak intensities. This population is suggested to show a dominant contribution of the flare.

References:
[1] Dresing, N. Kouloumvakos, A., Vainio, R., Rouillard, A., Astrophys. J. Lett., 925, L2

How to cite: Farwa, G., Dresing, N., Gieseler, J., Palmroos, C., Vuorinen, L., Jensen, S., Heber, B., Kühl, P., Richardson, I., Valkila, S., and Vainio, R.: Electron and proton peak intensities in solar energetic particle events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7917, https://doi.org/10.5194/egusphere-egu24-7917, 2024.

Solar energetic particle (SEP) events are increases of ions and electrons caused
by solar activity namely flares and coronal mass ejections. While the most
energetic ion population is well studied, SEP events accelerating electrons above
20 MeV have only been reported from measurements by ISEE III in the 1980’s
and the Kiel Electron Telescope (KET).
The KET aboard Ulysses launched in 1990 and measured the electron flux in
the energy range from 4 MeV to above 6 GeV. Here we report on observations
of ultra-relativistic electrons and show spectra of electron events during solar
cycle 22 and 23 until the end of 2008. The maximum electron energy exceeded
100 MeV during the August 16, 2001 SEP event.
This study has received funding from the European Union’s Horizon 2020
research and innovation programme under grant agreement No. 101004159
(SPEARHEAD).

How to cite: Köberle, M., Heber, B., and Jöhnk, C.: Measurements of ultra-relativistic electrons during solar energetic particle events - Results from the Ulysses Kiel Electron Telescope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8445, https://doi.org/10.5194/egusphere-egu24-8445, 2024.

Solar energetic particles (SEPs) are high-energy charged particles associated with solar eruptions. They constitute a major component of the heliospheric radiation environment, presenting a key space weather hazard. SEPs are accelerated at solar flares and at shock waves driven by coronal mass ejections, but the relative importance of these sources is not fully understood — particularly in the case of electrons. In addition to the underlying acceleration mechanisms, the evolution of a SEP event is highly influenced by transport in the interplanetary space. Anisotropy of the intensity-pitch-angle distribution is an important quantity that can be used to infer information about these effects, especially when multi-spacecraft observations are available. We investigate the first-order anisotropy of electrons and protons in SEP events of the solar cycle 25 using observations from multiple spacecraft of the inner-heliospheric fleet. We pay special attention to the methodology of determining anisotropy and its uncertainty from four-sector telescope (SOLO EPD/EPT and STEREO SEPT) measurements, in which pitch-angle coverage of the telescopes significantly influences the observed anisotropy. We present our methodology and the preliminary results of our statistical analysis, where we study the peaks and durations of anisotropic periods in high-energy electron and proton events as a function of particle energy and longitudinal separation.

How to cite: Vuorinen, L., Dresing, N., Brüdern, M., Gieseler, J., and Palmroos, C.: Statistical analysis of first-order anisotropy in multi-spacecraft solar energetic particle events of the solar cycle 25, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8560, https://doi.org/10.5194/egusphere-egu24-8560, 2024.

The origins of energetic electrons with energies ranging from a few tens of keV to tens of MeV in the inner heliosphere are manifold. They include Galactic Cosmic Rays, Jovian electrons as well as sporadic Solar Energetic Electron (SEE) events. Their energy spectra provide insights into the acceleration at the source and transport processes in the heliosphere.

The SOlar and Heliospheric Observatory (SOHO) was launched in December 1995 with the Electron Proton Helium INstrument (EPHIN) measuring electrons from 150 keV to several MeV. However, its measuring capability was reduced due to the loss of two detectors in 1997 and 2017, respectively. Thus from 2017 onwards only two electron channels, one in the range from 300 keV to one MeV and one “integral channel” that measures between 300 keV and 10 MeV.

In this contribution we present a new data product for electron spectra based on the onboard histograms. This data product has the advantage of providing the total energy loss in the first two detectors with good statistics compromising energy loss determination via PHA data and counting statistics of the single channel. Using the so-called bow-tie method we were able to derive several energy channels between 300 keV and about 1 MeV. We present first results and compare them with instruments from other missions.

The SOHO/EPHIN project is supported under Grant 50 OC 2102 by the German Bundesministerium für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR). This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE).

How to cite: Jensen, S., Heber, B., Hörlöck, M., Kollhoff, A., Kühl, P., and Sierks, H.: Energy spectra of 300 keV to 1 MeV electrons from the SOHO Electron Proton Helium INstrument (EPHIN), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8772, https://doi.org/10.5194/egusphere-egu24-8772, 2024.

How to cite: Kilpua, E., Good, S., Vainio, R., Ala-Lahti, M., Dresing, N., Gieseler, J., Koikkalainen, V., Osmane, A., Ruohotie, J., Soljento, J., Trotta, D., Cohen, C., Horbury, T., and Bale, S.: Turbulent structure of CME-driven sheath regions and their role as energizing charged particles in interplanetary space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8897, https://doi.org/10.5194/egusphere-egu24-8897, 2024.

Solar Energetic Particle (SEP) events can pose a significant radiation hazard for human and robotic space exploration activities. Therefore SEP forecasting systems are needed to support operations. The REleASE system (A. Posner, 2007) utilizes the fact that near relativistic electrons (1 MeV electrons have 94% of the speed of light) travel faster than ions (30 MeV protons have 25% of the speed of light) and are always present in hazardous SEP events. Their early arrival can be used to forecast the expected proton flux. Originally REleASE uses real time data from SOHO/EPHIN near Earth. Since the instrument is aging we recently adapted the method to STEREO-A/HET and used the period from June to November 2023 when STEREO-A passed the Earth to compare the REleASE forecasts from the different instruments.

This study has received funding from the National Aeronautics and Space Administration under grant agreement No. TXS0150642 (HESPERIA RELEASE).

How to cite: Dröge, H., Heber, B., Kollhoff, A., Kühl, P., Malandraki, O., and Posner, A.: Solar Energetic Proton forecasting with REleASE during STEREO-A’s flyby of Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9560, https://doi.org/10.5194/egusphere-egu24-9560, 2024.

Measurement of space weather is key to understanding, preventing, and mitigating the adverse effects of space weather events. Ground-based detectors and satellite sensors provide coverage of energetic particles in their respective domains, however, there remains scope for intermediary devices and instrumentation.

We present a novel energetic particle detector which has undergone development and deployment on radiosonde systems. The small form-factor and light weight instrument is composed of a CsI(Tl) scintillator coupled to a PiN photodiode and is capable of count rate and energy discrimination. Recent energy calibrations suggest the instrument is sensitive to a range of energies from 30 keV to 9.4 MeV. The microscintillator detector is therefore an ideal instrument for space weather investigations.

During previous flights, the microscintillator detector responded to low energy particles in the stratosphere, particularly observing energetic electron precipitation events. Recent research however has focussed on understanding and improving the detector performance at temperatures comparable to the atmospheric environment, and modifying the internal microcontroller system for interfacing with the new industry standard Vaisala RS41 radiosonde system.

How to cite: Tabbett, J. and Aplin, K.: Development of a balloon-borne radioactivity detector for space weather measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9954, https://doi.org/10.5194/egusphere-egu24-9954, 2024.

The recently expanded fleet of heliospheric spacecraft presents unique opportunities for exploring solar eruptive phenomena such as coronal mass ejections (CMEs) and solar energetic particles (SEPs) from multiple vantage points. However, the task of integrating diverse observations collected by different instruments across various spacecraft poses a notable challenge. To maximize the utilization of this data within the broader scientific community, the EU Horizon 2020 project SERPENTINE aims to offer a versatile array of tools. These tools, provided as open-source Python Jupyter Notebooks, cater to scientists with limited programming expertise. Alongside comprehensive examples illustrating the utilization of the multi-spacecraft spatial setup and solar magnetic connection plotter Solar-MACH, an analysis platform for studying the energetic particle component of the in-situ observations of SEP events has been developed. This analysis platform comprises visualization tools (e.g., energetic particle time series or dynamic spectra) and analytical software capable of automatically determining SEP onsets or estimating particle path length and injection time via a time-shift analysis approach. Our poster will provide an overview of the available toolkit and instructions on its utilization, which can be seamlessly accessed on SERPENTINE’s dedicated JupyterHub server in the cloud.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004159 (SERPENTINE).

How to cite: Gieseler, J., Palmroos, C., Dresing, N., Kouloumvakos, A., Morosan, D. E., Price, D. J., Trotta, D., Vuorinen, L., Yli-Laurila, A., Asvestari, E., Valkila, S., and Vainio, R.: Open-Source Analysis Platform for Solar Energetic Particles provided by SERPENTINE, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10356, https://doi.org/10.5194/egusphere-egu24-10356, 2024.

Solar energetic particles (SEPs) are highly energetic charged particles that have their origin of acceleration in strong space-weather driving phenomena that the Sun produces, e.g., solar flares and coronal mass ejections. These particles pose a radiation hazard to both technological equipment and living organisms in space, which is why the nature of these events is an important subject of study in the modern age where space technology is being applied more and more every day.

An SEP event is the result of a burst of SEPs arriving at an observer. Especially the onset time of an SEP event at varying energies is a key piece of information in relating the in-situ particle measurements to the remote-sensing observations of solar eruptions. Accurate knowledge of the onset time is an indispensable requirement for identifying the acceleration mechanisms and the source of the energetic particles. What traditional methods lack, however, is the assessment of the uncertainty related to the onset time.

Our method employs a unique combination of a statistical quality control scheme, Poisson-CUSUM, coupled with statistical bootstrapping. By choosing random samples from the background intensity preceding an SEP event and varying the integration time of the data, the method is able to produce a set of distributions of possible onset times. From this set of distributions we extract the most probable onset time and uncertainty intervals relating to this set of distributions. 

The uncertainty of onset times in a range of different energies is also in a direct connection to the uncertainty of a derived path length and inferred solar injection time of the particles, two extremely important pieces of information that velocity dispersion analysis yields, which is yet another motivator behind developing the method presented here

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004159 (SERPENTINE).

How to cite: Palmroos, C., Dresing, N., and Gieseler, J.: A New Method for Finding SEP Event Onset Times and Evaluating Their Uncertainty: Poisson-CUSUM-bootstrap Hybrid Method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10365, https://doi.org/10.5194/egusphere-egu24-10365, 2024.

The fleet of present and future space missions aimed at studying the Sun and the solar-terrestrial relationships carry
particle detectors, among other instruments. The monitoring of intense solar activity and solar energetic particle (SEP)
events provide fundamental contributions to Space Weather and Space Weather science. Unfortunately, very few of these instruments are optimized
for the  measurement of the proton differential flux above 200 MeV/n. We show that by increasing this minimum energy to 400-600 MeV/n it is possible to infer the trend of the differential flux with small uncertainties up to GeV energies, while this is not the case if the measurements are limited  to 200 MeV/n. To this purpose, we report on the characteristics of a single instrument meant for the detection of  solar flares and high-energy particles, galactic magnetar activity and gamma-ray burst observations. The instrument is based on hydrogenated amorphous silicon as a sensitive material that presents an excellent radiation hardness and finds application for particle beam characterization and medical purposes.

How to cite: Grimani, C. and Sabbatini, F. and the HASPIDE Collaboration: A Hydrogenated amorphous silicon detector for Space Weather Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10520, https://doi.org/10.5194/egusphere-egu24-10520, 2024.

Solar energetic particles (SEPs) pose a significant radiation hazard to both technologies and human beings in space. SEPs undergo acceleration to higher energy levels through various eruptive phenomena, specifically, solar flares and coronal mass ejections (CMEs). Based on these sources, SEP events can be classified as impulsive and gradual events, respectively, although more recent findings showed that large SEP events contain both sources (solar flare reconnection and CME shock waves). Greater risk is attributed to CME shock-driven events due to their larger quantity of accelerated particles and longer duration. In such SEP events, solar particles are considered to be accelerated by the diffusive shock acceleration process in CME-driven coronal shocks. The role of inhomogeneous magnetic field-induced adiabatic focusing in the one dimensional diffusive shock acceleration (DSA) process is not effectively studied. Hence, in our numerical study, we aim to understand the effects of adiabatic focusing on coronal shock acceleration and to investigate whether a free escape boundary could yield similar results in the absence of focusing. This involves employing two models: one featuring a finite and homogeneous upstream region, eliminating focusing, and another one incorporating a weakening magnetic field, facilitating particle escape through the focusing effect. We present the results from a one-dimensional oblique shock model with a mean free path similar to  Bell’s theory (Bell, 1978) using Monte Carlo simulations. This research is funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 955620.

References 

Bell, A. R. 1978, MNRAS, 182, 147

How to cite: Annie John, L., Nyberg, S., Vuorinen, L., Vainio, R., Afanasiev, A., Poedts, S., and Wijsen, N.: Effects of adiabatic focusing in 1D coronal shock acceleration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11246, https://doi.org/10.5194/egusphere-egu24-11246, 2024.

Since its start in 2021, the Solar EneRgetic ParticlE aNalysis plaTform for the INner hEliosphere (SERPENTINE) Project funded by EU H2020 program is using multi-spacecraft observations to investigate the origin of Solar Energetic Particles (SEPs) and providing new tools and datasets for the heliophysics community. SERPENTINE distributes new catalogues covering past and recent multipoint observations of SEP events, as well as their associated coronal mass ejections and interplanetary shocks. New SEP-related high-level data products from BepiColombo and Solar Orbiter missions, with added scientific value will be also provided in the near future. In this work, we summarize the structure, contents, and functionalities of the SERPENTINE Project Data Center (https://data.serpentine-h2020.eu/), a web-based interface providing open access to the various catalogues and high-level data products resulting from the project.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004159 (SERPENTINE).

How to cite: Gómez-Herrero, R., Espinosa Lara, F., Rodríguez-Pacheco, J., Rodríguez-García, L., Cernuda, I., Roco, M., Vainio, R., Dresing, N., Kartavykh, Y., Kilpua, E. K. J., Trotta, D., Plotnikov, I., Price, D., Heber, B., Horbury, T. S., and Wimmer-Schweingruber, R. F. and the The SERPENTINE Team: The SERPENTINE Project Data Center, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12767, https://doi.org/10.5194/egusphere-egu24-12767, 2024.

The Canadian SWeeping Energetic Particle Telescope (SWEPT) targets an assessment of the pitch angle dependence of particular space radiation, and will address and characterize the energy and directional dependence of this space radiation in the lunar environment. The project focuses on an assessment of the fundamental plasma processes which accelerate the particles to create this severe radiation hazard for astronauts in deep space, and assess radiation risk mitigation. By using an innovative sweeping look direction to determine the angular and energy dependence of the radiation on the Lunar Gateway, the SWEPT can assess the temporally evolving solar energetic particle (SEP) radiation in the heliosphere, emitted in solar eruptions and accelerated at interplanetary shocks, as well as address the impacts of primary and secondary radiation hazards on the Lunar Gateway. The SWEPT will also contribute to the development of effective deep space radiation mitigation strategies, such as those based on the early arrival of solar energetic electrons in advanceof SEP protons for humans on the lunar surface or in the lunar vicinity.

How to cite: Fedosejevs, R., Mann, I., Tiedje, H., Ozeke, L., Gan, K., Yu, B., Barona, D., Rowlands, N., Caldwell, D., Smith, K., and Amjad, M.: The Canadian SWeeping Energetic Particle Telescope (SWEPT): Steerable Energy and Pitch Angle Resolved Energetic Particle Measurements on the Lunar Gateway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13125, https://doi.org/10.5194/egusphere-egu24-13125, 2024.

The main driver of the acceleration of solar energetic particles (SEPs) is believed to be shocks driven by coronal mass ejections (CMEs). Extreme ultraviolet (EUV) waves are coronal disturbances that have been interpreted as the propagating footpoint of CME-driven shocks on the solar surface. One of the key questions in SEP research is the timing of the SEP release with respect to the time when the EUV wave magnetically connects with an observer. Taking advantage of the measurements by Parker Solar Probe (PSP) and Solar Orbiter (SolO) close to the Sun, we investigate a SEP event that occurred on 2021 September 28 and was observed at four different locations by SolO, PSP, STEREO-A, and the near-Earth spacecraft. During this time, SolO, PSP, and STEREO-A shared similar nominal magnetic footpoints but were at different heliocentric distances. We find that the SEP release times estimated at these four locations were delayed compared to the times when the EUV wave intercepted the footpoints of the nominal magnetic fields connecting to each spacecraft by around 30 to 60 minutes. Combining observations in multiple wavelengths from radio to EUV wavelengths passing by white light, with a geometrical shock model based on multi-viewpoint observations, we analyze the associated shock properties, and discuss the acceleration and delayed release processes of SEPs in this event as well as the accuracy and limitations of using EUV waves to determine the SEP acceleration and release times.

How to cite: Zhuang, B., Lugaz, N., Lario, D., Kwon, R. Y., Chrysaphi, N., Niehof, J., Gou, T., and Zhao, L.: Acceleration and Release of Solar Energetic Particles Associated with a Coronal Shock on 2021 September 28 Observed by Four Spacecraft, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13567, https://doi.org/10.5194/egusphere-egu24-13567, 2024.

Interplanetary shocks are efficient sources of accelerated particles and are often associated with high-energy proton/ion flux enhancements known as energetic storm particle (ESP) events. In situ spacecraft observations of particle fluxes near the shocks can be used to obtain energy spectra, providing very useful information for the investigation of the acceleration mechanisms. In this work we analysed the kinetic energy spectra of proton flux enhancements associated with ESP events observed by various spacecraft. ESP events associated with diverse shock conditions and geometries (e.g. quasi-perpendicular and quasi-parallel) were investigated. In addition, some of the events occurred during intervals in which Solar Energetic Particle (SEP) events were also ongoing, providing a background of pre-accelerated particles. The analysis of the shape of the observed spectra was used to identify which are the most plausible acceleration mechanisms at work. The turbulent magnetic field fluctuations upstream and downstream of the shocks were also studied to the aim of obtaining information about their possible role in particle acceleration.

This research has been carried out in the framework of the CAESAR (Comprehensive spAce wEather Studies for the ASPIS prototype Realization) project, supported by the Italian Space Agency and the National Institute of Astrophysics through the ASI-INAF n. 2020-35-HH.0 agreement for the development of the ASPIS (ASI Space weather InfraStructure) prototype of scientific data centre for Space Weather.

How to cite: Lepreti, F., Chiappetta, F., Laurenza, M., Benella, S., and Consolini, G.: Proton energy spectra of energetic storm particle events and magnetic field turbulent fluctuations nearby the associated interplanetary shocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14142, https://doi.org/10.5194/egusphere-egu24-14142, 2024.

Interplanetary (IP) shocks are important sites of particle acceleration in the Heliosphere and can be observed in-situ utilizing spacecraft measurements. Such observations, crucial to address important aspects of energy conversion for a variety of astrophysical systems.

From this point of view, 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. The general trends observed by Solar Orbiter and other spacecraft in the near-Earth environment for such shocks, highlighting their typical parameters, will be presented first. Then, the presence shock-induced wave activity in association with such shocks and their association with the presence of energetic particles will be discussed, summarizing some of the work performed in the framework of the the Solar EneRgetic ParticlE aNalysis plaTform for the INner hEliosphere (SERPENTINE) Project funded by EU H2020. Finally, particular emphasis will be devoted on the role of space/time irregularities at IP shocks and their effect on suprathermal particle production, focusing on some of the most interesting shocks observed by Solar Orbiter. 

How to cite: Trotta, D., Hietala, H., Horbury, T. S., Vainio, R., Dresing, N., Dimmock, A., Blanco-Cano, X., Kartavykh, Y., Wimmer-Schweingruber, R., Kilpua, E., Jebaraj, I., Gieseler, J., Espinosa Lara, F., and Gomez Herrero, R.: Interplanetary shocks and particle energisation in the inner heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15030, https://doi.org/10.5194/egusphere-egu24-15030, 2024.

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 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 SSDA model is able 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.

Figure: The one-dimensional stochastic shock drift acceleration Monte Carlo model geometry used to investigate electron acceleration and transport at heliospheric shock waves. 

How to cite: Nyberg, S., Vainio, R., Vuorinen, L., and Afanasiev, A.: Stochastic shock drift acceleration of electrons: Monte Carlo simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15162, https://doi.org/10.5194/egusphere-egu24-15162, 2024.

RADEM (Radiation Hard Electron Monitor) is a versatile detector of energetic particles designed for measurements of Jupiter's harsh radiation environment. It is one of the instruments on the ESA JUICE (Jupiter Icy Moons Explorer) mission launched on April 14^th, 2023. RADEM was switched on for a short commissioning phase shortly after the spacecraft launch and since August 2023 has been carrying on observations of the interplanetary radiation environment. The instrument will be operational throughout the JUICE mission from its cruise phase to the nominal scientific segment around the giant planet and its moons. RADEM was designed to detect electrons up to 40 MeV and protons up to 250 MeV enabling for covering of the most intense and hazardous regimes of the Jupiter radiation belts. Energy distributions of both protons and electrons are unfolded using eight semi-logarithmic energy bins. It allows for measurements of the spectral shapes and dynamic changes in the radiation intensity. RADEM also contains a detector sensitive to the direction of the incoming radiation with an angular coverage of 35% of the sky. Combined spectroscopic and angular measurements will allow for more accurate studies and mapping of the radiation around Jupiter and its moons. The instrument also has a dedicated heavy-ion detector designed to measure heavy-ion linear energy transfer between 0.1 and 10 MeV/cm/mg^-1. RADEM's primary purpose as a radiation monitor is to observe mission dose levels for safety concerns of the spacecraft and its scientific payload. In addition, its spectroscopic measurements in the higher energy range provide valuable extensions to other instruments from the JUICE payload. In particular, the Particle Environmental Package suite of instruments optimized for particle and ion energies up to about 1 MeV will obtain data prolongation up to about 100 MeV. RADEM operation during the cruise phase opens up a unique opportunity for conducting real-time, continuous observations of the Solar System radiation environment. It covers the current, twenty-fifth solar cycle including the solar maximum expected in 2025. With the JUICE-RADEM monitoring the radiation in the space between Venus and Mars orbits one obtains a data set useful for our future manned and unmanned explorations of these two neighboring planets. In this contribution, we will present the first RADEM observations of the interplanetary radiation environment including initial reports of detected SEPs (Solar Energetic Particles). The presented data set will cover the period since September 2023. The data will be correlated with observations from other instruments flying onboard spacecraft around the Earth or in interplanetary space such as e.g. BeppiColombo and Solar Orbiter.

How to cite: Hajdas, W. and Galli, A. and the RADEM collaboration: RADEM on JUICE's first observations of the interplanetary radiation environment , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15788, https://doi.org/10.5194/egusphere-egu24-15788, 2024.

High energy protons and Helium in the heliosphere originate from multiple sources. Solar Energetic Particle events (SEPs), Anomalous Cosmic Rays (ACRs) and Galactic Cosmic Rays (GCRs) are prominent examples. Their energy spectra provide insights into acceleration and transportation processes.

The SOlar and Heliospheric Observatory (SOHO) was launched December 1995 with the Electron Proton Helium INstrument (EPHIN) measuring protons and Helium from 4 MeV/nuc to 52 MeV/nuc with an additional open ended integral channel. However, its measuring capability was reduced due to the loss of two detectors in 1997 and 2017, respectively.

Using Pulse Height Analysis (PHA) data in the integral channel, we present methods to derive energy spectra for protons up to more than 100 MeV and Helium spectra up to some 250 MeV/nuc. First results and comparisons to other instruments will be presented.

The SOHO/EPHIN project is supported under Grant 50 OC 2102 by the German Bundesministerium für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR). This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE).

How to cite: Hörlöck, M., Jensen, S., Heber, B., Kühl, P., and Sierks, H.: High energy proton and Helium spectra from SOHOs Electron Proton Helium Instrument, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16054, https://doi.org/10.5194/egusphere-egu24-16054, 2024.

Collisionless shock waves (CSWs) in plasma, prevalent in diverse astrophysical contexts, are key to understanding cosmic particle acceleration. These shock waves, observable in environments from heliospheric planetary bow shocks to supernova remnants (SNRs), efficiently convert kinetic energy to thermal energy and accelerate particles to sub-relativistic and relativistic energies. A particular focus is on electrons accelerated by these shocks, as they generate electromagnetic radiation, making astrophysical shocks like SNRs observable. Despite their significance, gaps remain in our understanding of the dynamic mechanisms behind these universal accelerators, underscoring the necessity for in-depth, direct in situ measurements. Heliospheric shocks offer a unique opportunity for such in situ studies, particularly those that are strong and fast, potentially mirroring SNR shocks. This study highlights the groundbreaking in situ observations of the fastest heliospheric shock wave yet, traveling at nearly 1% the speed of light, captured by the pioneering Parker Solar Probe. Positioned just 0.23 astronomical units from the Sun, the probe directly measured the acceleration of electrons and ions to high energies amidst intense electromagnetic activity. A landmark discovery was the acceleration of electrons to ultra-relativistic speeds, with energies reaching up to 6 Million electron volts (MeV). This observation not only provides unprecedented insights into the mechanisms of particle acceleration in CSWs but also bridges the gap in our understanding of similar processes in more distant astrophysical phenomena like SNRs. The findings from the Parker Solar Probe open new avenues for exploring and comprehending the intricate processes of cosmic particle acceleration.

How to cite: Krasnoselskikh, V., Jebaraj, I. C., Agapitov, O., Vuorinen, L., Choi, K.-E., Gedalin, M., Wijsen, N., Afanasiev, A., Kouloumvakos, A., Mitchell, J. G., Vainio, R., Hill, M., and Raouafi, N.:  In situ Observations of Ultra-Relativistic ElectronAcceleration in the Fastest Heliospheric Shock Wave by Parker Solar Probe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16660, https://doi.org/10.5194/egusphere-egu24-16660, 2024.

The identification of the phenomena responsible for the acceleration of solar energetic particles (SEP) still challenges current research and limits our forecasting abilities of SEP events. Even the most recent space missions, such as Solar Orbiter and Parker Solar Probe, are still not reaching close enough distances to the Sun to be able to make direct measurements of the acceleration processes without the effects of transport mechanisms.

The analysis of SEP spectra is crucial to infer the underlying acceleration mechanisms of SEPs as different mechanisms are characterised by different spectral shapes and features. Making this connection can, however, be challenging as transport effects are also known for altering spectral shapes, and these processes are not fully understood either.

Our analysis focuses on solar energetic electrons (SEEs). The acceleration of SEEs, especially by shocks, still raises multiple questions in our field. In our analysis we use the novel measurements of the Energetic Particle Detector (EPD) on board
the Solar Orbiter spacecraft. EPD detects energetic particles with unprecedented time and energy-resolution (1-second resolution covering energies from the suprathermal to relativistic range). This data product, together with Solar Orbiter’s varying distances to the Sun, allows us to characterise features of the energy spectra of SEEs better than ever before and to pin down transport effects.

We determine the peak intensity spectra of more than 200 SEE events using newly developed techniques, taking into account velocity dispersion as well as the pitch angle coverage of the instruments. We determine and characterise the spectral features of each event by fitting the spectra with multiple mathematical models.

We will present the results of our statistical analysis and discuss which spectral features can be associated with acceleration or transport effects.

How to cite: Fedeli, A., Dresing, N., Gieseler, J., Vainio, R., Gómez-Herrero, R., Espinosa, F., Warmuth, A., and Schuller, F.: Energy spectra of Solar Energetic Electron Events Observed with Solar Orbiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16787, https://doi.org/10.5194/egusphere-egu24-16787, 2024.

Investigating the connection between solar variability and energetic radiation in the heliosphere is of fundamental importance for assessing radiation exposure and associated risks in space missions.

Our research focuses on the solar modulation phenomenon of cosmic rays, that is, on the long-term variation of the cosmic-ray flux and its association with the solar activity cycle.

Here we present our endeavors to establish an effective and predictive model of solar modulation. 
Our model incorporates fundamental physics processes of particle transport such as diffusion, drift, convection and adiabatic cooling, to compute the energy spectrum and temporal evolution of the cosmic radiation in the inner heliosphere.

Calibration and validation of our model are performed using the most recent cosmic-ray data from space-based detectors, such as AMS-02 on the International Space Station, along with multichannel observations of solar activity and interplanetary parameters.

This comprehensive model not only demonstrates good results in reproducing observations but also showcases its potential in space radiation monitoring and forecasting, offering valuable insights for evaluating exposure in future space missions.

How to cite: Pelosi, D., Bertucci, B., Tomassetti, N., Reis Orcinha, M., Fiandrini, E., and Barao, F.: An effective and predictive model for the long-term variations of Cosmic Rays in the Heliosphere", EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16994, https://doi.org/10.5194/egusphere-egu24-16994, 2024.

The Relativistic Electron Alert System for Exploration (REleASE) forecasting metric, developed by Posner (2007), utilizes electron data collected by the Electron Proton Helium Instrument (EPHIN) aboard the SOHO spacecraft. Our project aims to enhance the probability of detection, decrease the false alarm rate and extend the warning time by implementing various remote sensing techniques. These include automatic flare detection and localization, as well as automatic radio burst detection using the ROBUST algorithm developed at the University of Graz.
Historically, a range of diagnostics for Solar Energetic Particle (SEP) events based on radio observations from Earth has been developed since the 1960s, which are to some extent utilized in contemporary prediction models. These diagnostics span from the occurrence of long-lasting broadband radio emissions (cm-m waves) to the spectra of microwave bursts (mm-cm waves). The presence of radio emission at meter wavelengths (e.g., type III bursts) is crucial, since it indicates particle injection into the high corona, but is absent in confined flares, where no particles escape from the active region and no CME is available to accelerate particles higher up.
Moreover, our project explores the extent to which diagnostics across diverse frequency ranges can enhance the REleASE system. Initial results of this integration and its impact on the accuracy of SEP event forecasting will be presented.

How to cite: Martens, J., Dröge, H., Heber, B., Klein, K.-L., Berdermann, J., Banys, D., Wissing, J. M., Wilken, V., and Höfig, L.: Advancing Solar Energetic Particle Event Forecasting: Integrating Remote Sensing Techniques into the Relativistic Electron Alert System for Exploration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17271, https://doi.org/10.5194/egusphere-egu24-17271, 2024.

A Ground Level Enhancement (GLE) event can be observed as an increase in the background of ground-based neutron monitor observations and is often associated with an increase of >500 MeV space-based proton flux measurements. GLE events begin as very high-energy SEP events associated with GeV protons. For such events to be detected at sea level, proton energies must exceed about 433 MeV. To mitigate for potential impacts on space systems, avionics and human health, space-based and ground-based monitoring of these particles is essential, and so is having reliable real-time warning systems. Here we present two products, respectively, “GLE alert++” and “HESPERIA UMASEP-500”, that have been fully integrated as federated products on the ESA SWE Portal for this purpose. GLE alert++, built by the Athens Cosmic Ray Group of the National and Kapodistrian University of Athens, issues alerts when a GLE event has been registered and is based on ground-based neutron monitor observations. From the space-based approach, the EU HORIZON2020 HESPERIA UMASEP-500 product provides forecasts of GLE events and >500 MeV protons relying on GOES satellite soft X-ray and high-energy proton observations. Examples of how these two products complement each other will be given, as well as how using them together can in some instances provide more information for users of these services. (Work performed in the frame of ESA Space Safety Programme’s network of space weather service development and pre-operational activities, and supported under ESA Contract 4000134036/21/D/MRP.)

How to cite: Crosby, N., Mavromichalaki, H., Malandraki, O., Gerontidou, M., Karavolos, M., Lingri, D., Makrantoni, P., Papailiou, M., Paschalis, P., and Tezari, A.: Very High Energy Solar Energetic Particle Events and Ground Level Enhancement Events: Forecasting and Alerts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17642, https://doi.org/10.5194/egusphere-egu24-17642, 2024.

How to cite: Romaneehsen, L., Marquardt, J., and Heber, B.: Charge sign dependence of recurrent Forbush Decreases in 2016, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18790, https://doi.org/10.5194/egusphere-egu24-18790, 2024.

On March 28, 2022, a particle flux increase was recorded at very different energies by the several particle instruments on board the BepiColombo (BC) spacecraft. Specifically, an increase in the low-energy ion flux was measured by the SERENA/PICAM instrument and one in both the proton (1.5 – 20.7 MeV) and electron (>0.5 MeV) flux was detected by the BERM radiation monitor. These observations are consistent with the occurrence of a Solar Energetic Particle (SEP) event. This study presents a comprehensive analysis of the observed SEP event, exploiting BC's unique vantage point to explore temporal, spatial, and energetic characteristics, as well as observations from other spacecraft in the inner heliosphere. In conjunction with BC's observations, we used data from the STEREO-A, which is very well magnetically connected with BC along the spiral magnetic field, and data provided by spacecraft positioned at the Lagrangian point L1, such as ACE and WIND, which are radially connected with BC. The findings provide insights into the physical mechanisms governing SEP events, offering a perspective on their solar origin, propagation, and evolution within the heliosphere.

How to cite: Stumpo, M., Laurenza, M., Benella, S., Milillo, A., Plainaki, C., Orsini, S., Varsani, A., Laky, G., Barabash, S., Williamson, H., Nillson, H., Sanchez-Cano, B., Murakami, G., Saito, Y., Hadid, L., Hayner, D., Aronica, A., Di Bartolomeo, P. P., Kazakov, A., and Moroni, M. and the other authors: Observations of a Solar Energetic Particle Eventon March 28th 2022 by the BepiColombo Satellite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20152, https://doi.org/10.5194/egusphere-egu24-20152, 2024.

The Heavy Ion Instrument (HIS) onboard Solar Orbiter measures mass, charge, and full 3-D velocities of ions in the energy/charge range 0.5-75keV/charge. Using the data from HIS we study how interplanetary events like shocks or CME fronts create suprathermal tails in the velocity distribution and how those tails change with time. HIS observed the passage of three interplanetary shocks during the period October 2021 - May 2022. The three events were characterized by the acceleration of plasma from the solar wind energy regime (~1keV per amu/charge) to higher energies (5-75 keV), commonly referred to as suprathermal ions; later during the events, energetic particles (100keV and above) were measured by the EPD instrument. This energization process was characterized by a clear dependence upon mass/charge, and found consistent with preferential acceleration of ions present in the high energy tails of solar wind distributions, the seed population. Details of the distribution functions during the three events are presented and contrasted to each other.

How to cite: Livi, S., Owen, C., Louarn, P., Bruno, R., Fedorov, A., D'Amicis, R., Ho, G., Alterman, B., Lepri, S., Raines, J., Dewey, R., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., and Wurz, P.: Observations of Suprathermal Ions(5-75 keV) in Association with Shocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20809, https://doi.org/10.5194/egusphere-egu24-20809, 2024.

NASA's Artemis missions are taking astronauts back to the Moon with a view towards Mars. The dynamic space climate and space weather environment is a concern for space radiation operations and the protection of astronauts. The NASA Space Radiation Analysis Group (SRAG) at Johnson Space Center is developing the requirements and tools needed for quick operational response to space weather events during mission operations. To estimate long-timescale changes in the galactic cosmic ray (GCR) background due to solar modulation, SRAG maintains and develops NASA's Badhwar-O'Neill galactic cosmic ray (GCR) model. On short timescales, SRAG provides measurements, tools, expertise, and console support to keep crew safe during explosive solar energetic particle (SEP) events. In the past few years, SRAG, in collaboration with NASA Community Coordinated Modeling Center (CCMC) and the Moon to Mars Space Weather Analysis Office (M2M), has been working directly with the research community to onboard SEP models into real time operations. Real time forecasts are visualized in the SEP Scoreboards developed by CCMC and currently under evaluation by SRAG for radiation operations. An intensive validation effort has been ongoing to develop the infrastructure and standards for the validation of SEP model performance. This effort has broadly engaged the US, European, and worldwide scientific community through community challenges as well as focused on the evaluation of model performance in a real time operational environment. These efforts and preliminary outcomes will be described.

How to cite: Whitman, K.: Addressing the Dynamic Energetic Particle Environment for Space Radiation Operations at NASA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21303, https://doi.org/10.5194/egusphere-egu24-21303, 2024.

Acceleration of charged particles in solar flares, during reconnection of magnetic field lines in coronal loops, and by shock waves in the solar corona and interplanetary space are some of the substantial physical processes being studied by the Solar Orbiter mission. Cross-analysis of the light curves of the non-thermal parts of X-ray flares energy spectra registered by the Spectrometer Telescope for Imaging X-rays (STIX), and high-energy charged particle spectrograms recorded by the Energetic Particle Detector (EPD) suite assist us in furthering our understanding of these events.

The anomalies and events in interplanetary space such as shocks, CIRs, ICMEs, solar and interplanetary radio bursts, SEPs being investigated in situ regime are typically associated with solar X-ray flares and/or SDO/AIA measurements of the solar atmosphere in multiple wavelengths when sources are on the visible side of the solar disk. In cases where the powerful flare occurs on the Sun's backside, the massive CME can reach the volumes in the interplanetary space right at the opposite side of the CME’s seed and manifests in different forms of irregularities in the solar wind parameters and magnetic field components as well in enhanced energetic particle fluxes. Such types of occasions are of particular interest due to their near-global impact on the inner heliosphere.

In this study, we conduct a cross-analysis of the data derived from the Solar Wind Analyzer Proton-Alpha Sensor (SWA-PAS), Magnetometer (MAG), and EPD suite onboard the Solar Orbiter for the period of 13-14 March 2023, when a high-speed CME launched from near 180° from Earth accelerated an enormous quantity of high energy charged particles, from electrons to iron ions. At the time SolO was located 26°East of the Earth-Sun line at a distance of about 0.6 au. Even so, the CME quickly reached the spacecraft and manifested as a very sharp and strong shock at the front of which particles were accelerated additionally. In the analysis, we involve the data from the Suprathermal Ion Spectrograph (SIS), the SupraThermal Electrons and Protons (STEP), and the Electron Proton Telescope (EPT) of the EPD suite.

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: Dudnik, O., Yakovlev, O., Mason, G., Ho, G., Kouloumvakos, A., Wimmer-Schweingruber, R., Rodriguez-Pacheco, J., Espinosa Lara, F., Gómez Herrero, R., Dudnik, B., and Képa, A.: Energetic particles observed by Solar Orbiter associated with a sharp shock wave passage from the solar backside event of March 13-14, 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21919, https://doi.org/10.5194/egusphere-egu24-21919, 2024.

Astrophysical simulations require trade-offs between compute time and physical accuracy. This frequently includes targeting certain physical scales at the expense of others. Simulations investigating solar coronal heating and solar wind acceleration usually select either high resolution for a small domain or low resolution for a global domain. Bridging this gap requires linking structures present on the solar surface to both the middle corona (approximately 1.5 - 6 solar radii) and the solar wind. In this work we analyze three simulations of the global solar corona that vary the resolution of the surface boundary condition while keeping the same parameterization of a thermodynamic, wave-turbulence-driven magnetohydrodynamic model. We quantify structural differences endemic to each simulation using spherical harmonic decomposition and associated statistics. We use this information to examine how surface resolution influences heating and magnetic complexity in the corona and solar wind and the subsequent impacts on density, temperature, and flow structure. In principle, this can enable more efficient subgrid modeling in future low resolution simulations.

How to cite: Evans, C., Downs, C., Schmit, D., and Crowley, J.: Quantifying how surface complexity influences properties of the solar corona and solar wind, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1196, https://doi.org/10.5194/egusphere-egu24-1196, 2024.

Radio bursts from nearby active M-dwarfs have been frequently reported and extensively studied in solar or planetary paradigms. Whereas, their substructures or fine structures remain rarely explored despite their potential significance in diagnosing the plasma and magnetic field properties of the star. Such studies in the past have been limited by the sensitivity of radio telescopes. Here we report the inspiring results from the high time-resolution observations of a known flare star AD Leo with the Five-hundred-meter Aperture Spherical radio Telescope. We detected many radio bursts in the 2 days of observations with fine structures in the form of numerous millisecondscale sub-bursts. Sub-bursts on the first day display stripe-like shapes with nearly uniform frequency drift rates, which are possibly stellar analogs to Jovian S-bursts. Sub-bursts on the second day, however, reveal a different blob-like shape with random occurrence patterns and are akin to solar radio spikes. The new observational results suggest that the intense emission from AD Leo is driven by electron cyclotron maser instability, which may be related to stellar flares or interactions with a planetary companion.

How to cite: Zhang, J. and Tian, H.: Fine Structures of Radio Bursts from Flare Star AD Leo with FAST Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1947, https://doi.org/10.5194/egusphere-egu24-1947, 2024.

The nonlinear evolution of Alfvén waves in the solar corona leads to the generation of Alfvénic turbulence. This description of the Alfvén waves involves parametric instabilities where the parent wave decays into slow mode waves giving rise to density fluctuations. These density fluctuations, in turn, play a crucial role in the modulation of the dynamic spectrum of type III radio bursts, which are observed at the fundamental of local plasma frequency and are sensitive to the local density. During observations of such radio bursts, fine structures are detected across different temporal ranges. In this study, we examine density fluctuations generated through the parametric decay instability (PDI) of Alfvén waves as a mechanism to generate striations in the dynamic spectrum of type III radio bursts using magnetohydrodynamic simulations of the solar corona. An Alfvén wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, which subsequently undergo the PDI instability. The type III burst is modeled as a fast-moving radiation source that samples the background solar wind as it propagates to emit radio waves. We find the simulated dynamic spectrum to contain striations directly affected by the multiscale density fluctuations in the wind.

How to cite: Sishtla, C., Jebaraj, I., Pomoell, J., Magyar, N., Pulupa, M., Kilpua, E., and Bale, S.: The Effect of the Parametric Decay Instability on the Morphology of Coronal Type III Radio Bursts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3450, https://doi.org/10.5194/egusphere-egu24-3450, 2024.

The study of characteristics, size, and shape variations of corotating interaction region (CIR) with changes in heliocentric distance is of scientific interest. The unique orbit parameters of the Solar Orbiter spacecraft (SOLO) and its set of equipment provide an opportunity to address the posed question. In our study, an attempt has been made to identify CIR regions using only data from the SOLO instruments.

The methodology for identifying CIR is well-developed. It involves in-situ observations of solar wind parameters, such as those proposed in the works of Hajra and Sunny, and verifies the potential presence of high-speed streams (HSS) from coronal holes. Such verification can be performed using SDO/AIA extreme ultraviolet observation data. This methodology can be easily implemented considering the near-Earth satellite constellation. Often, the trajectory of the SOLO passes out of the visibility range of near-Earth solar observation facilities, and there is no opportunity to verify the presence of coronal holes on the solar disk, which could be sources of HSS. In such cases, it is necessary to rely solely on the data from the SOLO instruments.

During the analysis of RPW instrument data, it was observed that sometimes the instrument registers shock events not confirmed by SWA instrument data. However, these events demonstrate an intense increase in solar wind speed and other parameters. The hypothesis has been put forward that multiple activations of the RPW instrument's SBM1 algorithm within a day can be used as a marker for the spacecraft's presence in the CIR zone. To validate this hypothesis, a comparative analysis of RPW data at the time of SBM1 events is conducted, comparing it with data from the SWA-PAS instrument. Based on the examples considered, a conclusion is drawn regarding the ability to track the spacecraft's entry and exit moments from the CIR region and assess the changes in CIR parameters when the spacecraft is within it.

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: Chechotkin, D., Yakovlev, O., and Bilokon, O.: Detection of a corotating interaction region in solar wind using RPW and SWA instruments of the Solar Orbiter mission., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3926, https://doi.org/10.5194/egusphere-egu24-3926, 2024.

To forecast the solar wind arriving at Earth in advance, and hence its impacts on technology, it is important to have a good understanding of how the solar wind is generated by the solar corona. Helium is a major constituent of the corona/solar wind that plays an important role in the energy budget of the corona and the acceleration of the solar wind. Helium abundance varies significantly with the solar cycle and in the different types of fast and slow solar winds. We present the newly-developed multi-species IRAP Solar Atmospheric Model (ISAM) which solves for the coupled transport of both neutral and charged particles between the chromosphere and the corona, including a self-consistent treatment of collisional and ionisation processes. We exploit ISAM to study the mechanisms that regulate Helium abundance in the source region of the fast and slow solar winds and contrast numerical results with and without Helium included in the model. We compare our model outputs with as many observations as possible, including Helios, Parker Solar Probe and Solar Orbiter data, in particular from the Proton and Alpha particle Sensor, SWA-PAS. We show that our simulations are in good agreement with previous studies, in particular that the solar cycle variation in Helium abundance can be explained by differences in abundance found for each solar wind type by ISAM, when just using diffusion in the model and not (yet) including the ponderomotive force. 

How to cite: Thomas, S., Rouillard, A., Lomazzi, P., Poirier, N., and Blelly, P.-L.: Simulating Differences in Helium Abundances between Fast and Slow Solar Winds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3962, https://doi.org/10.5194/egusphere-egu24-3962, 2024.

We present our findings on long-lasting radio emissions above a sunspot, analogous to planetary auroral radio emissions. These emissions are typically characterized by highly polarized, intense radio bursts, generally attributed to electron cyclotron maser (ECM) emission from energetic electrons in regions with converging magnetic fields, such as planetary polar areas. Similar bursts have been observed in magnetically active low-mass stars and brown dwarfs, often prompting analogous interpretations. Here we report observations of long-lasting solar radio bursts with high brightness temperature, wide bandwidth, and high circular polarization fraction akin to these auroral and exo-auroral radio emissions, albeit two to three orders of magnitude weaker than those on certain low-mass stars. Our spatial, spectral, and temporal analysis indicate that the source is situated above a sunspot where a strong, converging magnetic field is present. The morphology and frequency dispersion of the source align with ECM emissions, likely driven by energetic electrons from recurring nearby solar flares. These observations provide new insights into the nature of intense solar radio bursts and suggest a potential model for understanding aurora-like radio emissions in other flare stars with significant starspots.

How to cite: Yu, S., Chen, B., Sharma, R., Bastian, T., Mondal, S., Gary, D., Luo, Y., and Battaglia, M.: Detection of long-lasting aurora-like radio emission above a sunspot, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4218, https://doi.org/10.5194/egusphere-egu24-4218, 2024.

As the solar wind streams propagate with different speeds through the interplanetary space, they meet and interact. This leads to the formation of large interaction regions, one of which is the rarefaction regions (RRs). RRs develop at the trailing edge of the fast solar wind stream and come from an area of small longitudinal extent on the Sun. They exhibit a fine and complex structure, and the stream interface position is usually unclear. Superposed epoch analysis of the proton and alpha parameters for different regions within RRs reveals gradual transitions in many of them. Moreover, majority of our observations show that most of the RR plasma parameters correspond to the fast solar wind characteristics, only the alpha-proton drift velocity decreases from the beginning of RR. We investigate different ways of its reduction in the interplanetary space and show that this feature is likely associated with the mirroring of the multi-component solar wind. We identify the composition boundary where the alpha relative abundance and alpha-proton temperature ratio change abruptly from the values typical for the fast wind toward slow wind values. We suggest that this boundary is the most probable candidate for the stream interface. Based on these findings, we speculate that the RR formation occurs near the Sun and formulate two possible scenarios.

How to cite: Ďurovcová, T., Šafránková, J., and Němeček, Z.: How the structure of rarefaction regions develops?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4309, https://doi.org/10.5194/egusphere-egu24-4309, 2024.

Coronal mass ejections (CMEs) are the strongest drivers of space weather. Measurements of the plasma parameters of CMEs, particularly magnetic fields entrained in the CME plasma, are crucial to understand their propagation, evolution, and geo-effectiveness. Spectral modeling of gyrosynchrotron (GS) emission from CME plasma has long been regarded as one of the most promising remote observation techniques for estimating spatially resolved CME plasma parameters. However, imaging the very low flux density CME GS emission in close proximity to the Sun with orders of magnitude higher flux density, has proven to be rather challenging. This challenge has only recently been met using the combination of data from the Murchison Widefield Array (MWA) and the recently developed spectropolarimetric snapshot imaging pipeline optimized for this data (P-AIRCARS). This has now brought routine detection of GS within reach, and the next challenge to be overcome is that of constraining the large number of free parameters in GS models. A few of these parameters are degenerate, and need to be constrained using the limited number of spectral measurements typically available. We present studies of spectropolarimetric modeling GS emissions from two different CMEs, which establish that these degeneracies can be broken using polarimetric imaging. 

However, this methodology is only useful to measure CME magnetic fields up to ~10 R๏. At  higher coronal heights and inner heliosphere CME magnetic fields can be estimated by measuring Faraday rotation of linearly polarized galactic/extragalactic radio sources. This method has been used using small field of view (FoV) instruments at high frequency (e.g., VLA) to measure magnetic fields along a single line of sight (LoS). We have recently started exploring the FR measurements due to CME using the MWA. The  advantage of using the MWA is its wide FoV and lower observing frequency. Lower observing frequency provides sensitivity to smaller magnetic fields. At the same time, wide FoV will provide simultaneous measurements along multiple LoSs and enable estimation of vector magnetic fields by constraining empirical flux-rope models of CMEs.  We present the challenges which need to be overcome to achieve these goals and some initial results.  

How to cite: Kansabanik, D., Oberoi, D., Vourlidas, A., and Mondal, S.: Measuring Magnetic Fields of Coronal Mass Ejection in Corona and Inner Heliosphere using Wide Field of View Spectro-polarimetric Radio Imaging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4450, https://doi.org/10.5194/egusphere-egu24-4450, 2024.

The goal of this study is to narrow down the uncertainties global modeling and PFSS back-tracing introduces when source regions are identified for in-situ data collections. We use the Space Weather Modeling Framework's Multi-Ion Alfven Wave Solar atmosphere Model with non-equilibrium ionization of heavy ions (NEI) to connect the remote sensing and in-situ signatures of solar wind properties from formation into the heliosphere. We use the NEI resulting charge state distributions and in-situ plasma properties to identify and connect source regions and their relating spectral emission signatures. The advantage of 3D modeling is that it enables data decomposition along the line-of-sight and study the effect of individual processes that result in the synthetic and actual observables. 

How to cite: Szente, J., Landi, E., and van der Holst, B.: Global Modeling of Heavy Ions in the Solar Corona and Inner Heliosphere with Multi-Ion-AWSoM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6603, https://doi.org/10.5194/egusphere-egu24-6603, 2024.

The solar wind variations during a solar cycle are critical in understanding the solar wind acceleration mechanism in different phases of the solar cycle. It is also important in predicting the solar wind distribution in the heliosphere. This problem has been investigated from different aspects, from data analysis to numerical modeling. Previous observations have shown that the distribution of fast and slow wind are different between solar minimum and maximum. In this study, we study the solar wind variations based on a first-principles model, the Alfven Wave Solar atmosphere Model (AWSoM) developed at the University of Michigan. Huang et al. (2023) have used the ADAPT-GONG magnetograms in the last solar cycle to drive the solar wind model and shown that one of the input parameters of the model, the Poynting flux parameter, can be empirically predicted with the open field area. Moreover, they suggested that the average energy deposition rate in the open field regions is approximately constant during a solar cycle. In this study, we use the GONG synoptic magnetograms, and determine if similar conclusions are also valid. We also systematically compare the model performance between the two different input magnetograms.

How to cite: Huang, Z., Toth, G., Sachdeva, N., and van der Holst, B.: The solar wind in the last solar cycle driven by ADAPT-GONG and GONG magnetograms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6743, https://doi.org/10.5194/egusphere-egu24-6743, 2024.

The SunDish and Solaris projects are devoted to solar radio imaging and monitoring up to 100 GHz using existing INAF large radio telescopes in Italy, and smaller and flexible radio telescopes in development for polar regions. This powerful network can complement other existing ground-based and space-based facilities aimed at the direct monitoring of the solar atmosphere both for Heliophysics science and Space Weather awareness.

The SunDish Project aims to map the brightness temperature of the solar atmosphere in the radio band to reveals plasma processes mostly originating from free-free emission in the local thermodynamic equilibrium, providing a probe of physical conditions in a wide range of atmospheric layers. In particular, long-term diachronic observations of the solar disk at high radio frequencies represents an effective tool to characterise the vertical structure and physical conditions of the solar chromosphere both for quiet and active regions during their evolution at different phases of the solar cycle. Within this context, the Medicina 32-m and SRT 64-m radiotescopes could have an important role in the international solar radio science panorama.
After a first test campaign aimed at defining and optimising solar imaging requirements for the radio telescopes, the system is ready for systematic monitoring of the Sun to provide: (1) accurate measurement of the brightness temperature of the radio quiet Sun component, that has been poorly explored in the 20-26 GHz range to date, and representing a significant constraint for atmospheric models; (2) characterisation of the flux density, spectral properties and long-term evolution of dynamical features (active regions, coronal holes, loop systems, streamers and the coronal plateau). One of our future scientific goals is the comparison of our results with recently updated flare catalogs, based on GOES and AGILE data, in order to correlate our active regions data with the flares detections. The prediction of powerful flares through the detection of peculiar spectral variations in the active regions is a valuable forecasting probe for the Space Weather hazard network. For more information and early science results see: https://sites.google.com/inaf.it/sundish

The Solaris Project is a scientific and technological project aimed at the development of a smart Solar monitoring system at high radio frequencies based on innovative single-dish imaging techniques, recently approved as a permanent observatory in Antarctica. It combines the implementation of dedicated and interchangeable high-frequency receivers on existing small single-dish radio telescope systems (1.5/2.6-m class) available in our laboratories and in Antarctica, to be adapted for Solar observations. Operations in Antarctica will offer unique observing conditions (very low sky opacity and long Solar exposures) and unprecedented Solar monitoring in radio W-band (70-120 GHz). This opens for the identification and spectral analysis of active regions before, after and during the occurrence of Solar flares. For more information see: https://sites.google.com/inaf.it/solaris

How to cite: Mulas, S. and the SunDish and Solaris: Single-dish solar imaging at high radio frequencies: SunDish & Solaris Projects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8939, https://doi.org/10.5194/egusphere-egu24-8939, 2024.

Stream interaction regions (SIRs) are formed when the fast solar wind streams with their origin in coronal holes (CHs) interact with the surrounding slow solar wind in the Heliosphere. Previous studies have analyzed different types of CHs and the resulting characteristics of SIRs at 1 AU (e.g., Heinemann et al., 2018, Samara et al., 2022). For the inner heliosphere, however, research on the relation between CH morphology and HSS/SIR characteristics is scarce. We extract CH morphologies from SDO/AIA and use solar wind parameters from multiple spaceraft, including Parker Solar Probe, Solar Orbiter, STEREO-A, ACE and WIND. Combining in-situ measurements and remote sensing image data, we show the evolution and statistics of solar wind profiles in HSSs/SIRs in the inner Heliosphere for multiple cases from Solar Cycle 24 and 25. 

How to cite: Milošić, D., Temmer, M., Heinemann, S., and Hofmeister, S.: Evolutions of Stream Interaction Region in the Inner Heliosphere and Coronal Hole Morphologies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9337, https://doi.org/10.5194/egusphere-egu24-9337, 2024.

Solar radio emissions provide several unique diagnostics tools of the solar corona, which are otherwise inaccessible. However, imaging the very dynamic coronal emissions spanning a large range of angular scales at radio wavelengths is extremely challenging. Due to large numbers of antennas, at GHz frequencies, MeerKAT radio telescope is possibly globally the best-suited instrument at present for providing high-fidelity spectroscopic snapshot solar images. At GHz frequencies the Sun has much higher flux density than any other astronomical sources in the sky. Hence, observing the Sun with sensitive radio telescopes like MeerKAT requires one to attenuate the solar signal suitably for optimum operation of the instrument. We embarked on our voyage of  MeerKAT solar observation using the sidelobes of the primary beam. The images show extremely good morphological similarities with the EUV images as well as the simulated radio images at MeerKAT frequencies demonstrating the high-fidelity of these images. Although this approach was successful, it is naturally better to observe the Sun in the main lobe of the primary beam using suitable attenuation in the signal chain to keep the system in the linear regime. We have been working towards this and will present the current status of our efforts toward commissionsing solar observations with the MeerKAT. Once commissioned, this will enable a host of novel studies, open the door to a large unexplored phase space with significant discovery potential, and also pave the way for solar science with the upcoming Square Kilometre Array-Mid telescope, for which MeerKAT is a precursor.

How to cite: Oberoi, D., Kansabanik, D., Gouws, M., Buchner, S., and Mondal, S.: Toward Commissioning Solar Observations with MeerKAT: Opening a New Frontier in Solar Radio Physics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9971, https://doi.org/10.5194/egusphere-egu24-9971, 2024.

It is now known that the fast solar wind streams originating from coronal holes can have a significant contribution to geomagnetic activity, particularly during periods of low solar activity. Moreover, coronal holes, many of which are long lived and overall time steady structures, have proven to be ideal hunting grounds for understanding the fast solar wind. In this regard, automated detection schemes are nowadays a standard approach for locating coronal holes in EUV images from the Solar Dynamics Observatory (SDO). However, several inevitable factors make this automatic identification challenging. While discrepancies between detection schemes have been noted in the literature, a comprehensive assessment of these discrepancies, which is still lacking, is of equal importance. Here we present the first community dataset for comparing automated coronal hole detection schemes. This dataset consists of 29 SDO images, all of which were selected by experienced observers to challenge automated schemes. We then use this dataset as input to 14 widely-applied automated schemes to study coronal holes and collect their detection results. From this, we select and study three SDO images that exemplify the most important lessons learned from this effort. We find that different detection schemes highlight significantly different physical properties of coronal holes. Motivated by these outcomes, we look into the effect of these results on the inferred magnetic connectivity in the corona by comparing the detected coronal hole boundaries to magnetic model solutions. These results, along with the database, will provide rich inputs to our understanding of coronal holes and their connection to the solar wind.

How to cite: Majumdar, S., Reiss, M., Muglach, K., Mason, E., Davies, E., and Chakraborty, S. and the S2-01 ISWAT Team: A Community Dataset for Comparing Automated Coronal Hole Detection Schemes and its Imprint on Magnetic Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10009, https://doi.org/10.5194/egusphere-egu24-10009, 2024.

With the growing number of solar probes across the inner heliosphere, our community, now more than ever, is well placed to continuously track the formation and supersonic expansion of the solar wind from the Sun. To capture the conditions of solar wind release connected to heliospheric structures, it is fundamental to link near-synchronous measurements of its state in the corona to the associated stream’s interplanetary propagation. This goal can be achieved through well-aligned spacecraft conjunctions, measuring local plasma conditions, with integrated remote sensing observations of the stream’s coronal birthplace. As such, this work traces a solar wind stream from its source to interplanetary space through combined remote (Solar Orbiter/FSI and SPICE, SDO/AIA, Hinode/EIS) and in situ (Parker Solar Probe, Solar Orbiter) observations of the same solar wind stream at two heliospheric distances. Using remote coverage of the source region’s thermal and elemental composition properties, the solar wind is connected throughout the heliosphere by its heavy ion composition to relate energetics of the wind at different stages of its heliospheric evolution to its source region conditions. 

How to cite: Rivera, Y., Badman, S., Ervin, T., Landi, E., Raymond, J., Reeves, K., Roy, S., Stevens, M., and Varesano, T.: Examining the Coronal Source and Inner Heliospheric Evolution of a Stream Sampled by Parker Solar Probe and Solar Orbiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11649, https://doi.org/10.5194/egusphere-egu24-11649, 2024.

The Sun is a subject to vivid research due to its significant impact on our daily existence. We know about the periodic behaviour in the structure of the Sun, the 11-year solar cycle, but we have yet to fully understand what it means for the inner heliosphere and how it affects the solar wind. Accurately modelling these structural changes in the solar Corona on large time scales is important to understand and even predict solar weather patterns that could potentially influence Earth's magnetic field, telecommunications, and even space missions. Fully comprehending these changes is crucial for enhancing our ability to forecast and prepare for potential solar events that might affect various aspects of our technological infrastructure and space exploration endeavours. 

To this end, we have prepared a database of solar corona and inner heliosphere simulations with the Space Weather Modeling Framework’s Alfvén Wave Solar atmosphere Model (SWMF/AWSoM) during Solar Cycles 24 and 25. Using SolarSoft’s FORWARD we study the distribution and emission of solar wind origins, such as coronal holes and active regions, throughout the solar cycles and analyse how well AWSoM is reproducing them at different phases of the solar cycle. We also compare how 1AU in-situ plasma measurements are predicted and how it relates to the reproduction of the origin of the solar wind in the corona.  

Studying the reproducibility of the coronal and heliospheric plasma throughout decades of time can prove invaluable in understanding changes in the solar structure during a solar cycle and benchmark the accuracy of the models’ predictive power in the future. 

How to cite: Koban, G., Szente, J., and van der Holst, B.: Studying the Long-Term Variability of the Solar Corona Using Modeling and Remote-Sensing Observations , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12058, https://doi.org/10.5194/egusphere-egu24-12058, 2024.

When solar wind plasma propagates outward, the electron density decreases rapidly with solar distance, and charge states of heavy ions freeze in at 1 to 5 solar radii. Thus, charge states of heavy ions carry important information about the temperature profile in the lower corona. Oxygen and Iron ions are the most abundant heavy ions in the solar wind, and their data quality is relatively higher than that of other heavy ion species.Statistically, the averaged charge states of O and Fe in the solar wind usually maintain a weak positive correlation, sometimes exhibiting a strong positive correlation in solar wind associated with Coronal Mass Ejections (CMEs). The averaged charge states of O and Fe also correlate with solar wind speed and the solar cycle.

In this study, we use ten years of in-situ solar wind Oxygen and Iron ion data obtained from the Solar Wind Ion Composition Spectrometer (SWICS) aboard the Advanced Composition Explorer (ACE). The data set is derived from Pulse Height Analysis (PHA) data, ensuring high time resolution (12 minutes).

We identify around one hundred structures (time periods) where the averaged charge states of Fe and O exhibit significant anti-correlations (Spearman rank correlation coefficient lower than -0.5). These structures have distinct signatures. We analyze the time scales of these structures, the magnitudes of the averaged charge state variations for O and Fe, the temporal lags between the onset and end of those variations , the distribution of structures in the solar wind (e.g., whether they are associated with Interplanetary Coronal Mass Ejections (ICMEs) and their relative position within ICMEs), and their distribution in the solar cycle.

Compared to more widely occurring positive correlation structures, anti-correlation structures are rarer and more interesting, reflecting the complex variations in the radial temperature profile and electron density profile of the lower corona. Large-scale anti-correlation structures suggest the presence of a relatively stable radial energy transfer process within 1 to 5 solar radii.

How to cite: Gu, C., Heidrich-Meisner, V., and Wimmer-Schweingruber, R. F.: Report on In Situ Observations of the Anti-Correlated Variations in Freeze-in Temperatures of Heavy Ions in the Solar Wind, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12235, https://doi.org/10.5194/egusphere-egu24-12235, 2024.

Radio emissions have a wide exploitation potential both in the remote diagnosis of their plasma sources, often impossible to explore in-situ, but also in the context of space weather for developing realistic forecasting models for the effects of energetic solar events, such as coronal plasma ejections (CMEs) on modern technologies on ground and in space. Here we discuss the importance of first-principle radiative models, not only for these applications but especially for developing realistic models for type-II and type-III radio emissions whose plasma sources are likely to be explored in situ by different satellites and spacecraft. At this early stage, first-principle radiative models combine a fundamental kinetic theory for describing wave instabilities in plasma sources, with numerical simulations of their saturation by nonlinear processes that generate free-propagating radio waves. We also discuss a series of further additions, in particular with nonlinear theories of the various wave-wave couplings responsible for the generation of radio emissions.

How to cite: Lazar, M., Lopez, R. A., Shaaban, S. M., and Poedts, S.: A plea for first-principles radiative models in solar energetic events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12703, https://doi.org/10.5194/egusphere-egu24-12703, 2024.

We investigate the evolution of  spatial distribution of solar wind sources by means of an extended time series of data-driven 3D simulations that cover solar 2 activity cycles. We examine the corresponding solar wind acceleration profiles as a function of source latitude and time, and highlight consequences for the interpretation of Parker Solar Probe (PSP) and Solar Orbiter (SolO) in-situ measurements. We relate magnetic connectivity jumps with solar wind plasma signatures, and discuss their occurrence frequency and amplitudes at different epochs of the solar cycle, on and off the ecliptic plane.
We also indicate impacts on the rotation profile of the solar corona and on the occurrence of regions of enhanced poloidal and toroidal flow shear that can drive plasma instabilities.  Finally, we search for and test geometrical parameters alternative to the standard ones currently used in semi-empirical solar wind forecasting methods.

How to cite: Pinto, R., Rouillard, A., and Indurain, M.: Solar wind flows across the solar activity cycle, connectivity and plasma signatures on and off the ecliptic plane, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13385, https://doi.org/10.5194/egusphere-egu24-13385, 2024.

Solar flares are often accompanied by intense radio emissions, particularly notable in the form of fast-drifting type III bursts. These bursts are generated by suprathermal electron beams that are accelerated at solar flare reconnection sites. These electron beams travel outward along open magnetic field lines, passing through the corona and interplanetary medium. Type III Radio Storms, characterized by nearly continuous type III radio burst activity, can persist for hours or days. This study reports on a significant type III storm observed between 2023-09-20 and 2023-09-27, observed simultaneously by STEREO-A and Parker Solar Probe. During this interval, the spacecraft were longitudinally separated by 5 to 45 degrees, providing a unique opportunity to examine both radial and longitudinal variations in type III storms. Additionally, the Solar Orbiter's position on the opposite side of the Sun, complemented by SDO data, enabled nearly 360-degree solar coverage in EUV during this event. This extensive coverage allowed for the correlation of individual radio bursts with EUV images, offering a comprehensive view of the full Sun. Our findings contribute to the understanding of solar flare dynamics and electron beam propagation in solar eruptions.

How to cite: Krupar, V., Kruparova, O., Szabo, A., and Lario Loyo, D.: Comprehensive Analysis of a Type III Radio Storm Using Multi-Spacecraft Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13818, https://doi.org/10.5194/egusphere-egu24-13818, 2024.

It is well known that flare-accelerated electrons can produce hard X-ray (HXR) emission and Type-III radio bursts. The HXR emission is produced by the accelerated electrons propagating towards the chromosphere where they deposit their energy. In contrast, Type-III radio bursts are produced by the accelerated electron beams traveling toward the outer solar atmosphere. Hence a temporal correlation between these two kinds of emission may imply a common origin of the accelerated electrons providing insight into the acceleration process, and allowing us to connect electrons at the Sun to those in the heliosphere On 2022-Nov-11 11:30 - 12:00 UT, the Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter observed a highly energetic flare event with an excellent time resolution of 0.5 s. Simultaneously there were observations of multiple coronal and interplanetary Type-III radio bursts from several instruments such as WIND/WAVES, I-LOFAR, and ORFEES spanning the frequency range from 1 - 1000 MHz.We find an excellent temporal correlation between the X-ray and radio time series. We do multiwavelength imaging analysis using AIA, STIX, and NRH to locate the acceleration origin and track the electron beams during the eruption.

How to cite: Bhunia, S., Hayes, L., Klein, K. L., Gallgaher, P. T., Maloney, S., and Vilmer, N.: Localising Signatures of Particle Acceleration During Solar Flare in Low Solar Atmosphere Using Combined EUV, X-ray and Radio Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14105, https://doi.org/10.5194/egusphere-egu24-14105, 2024.

For decades, the focus of polarimetric solar radio studies has been solely on circular polarization. This stemmed from the fact that the strong differential Faraday rotation in coronal plasma should completely obliterate any linear polarization component even if it were to be present (e.g., Grognard & McLean, 1973). Consequently, after a few reports in the late 50s and early 60s of successful detection of linearly polarized radio emissions from the Sun, the  consensus has essentially been to dismiss any detected linear polarization in the observed dynamic spectra as instrumental artifacts (e.g., Grognard & McLean, 1972; Boischot & Lecacheux, 1975). This assumption has been routinely used in calibrating solar polarimetric observations, even for recent studies (Morosan et al. 2022). The state-of-the-art polarimetric calibration algorithm, P-AIRCARS (Kansabanik et al., 2022a, 2022b, 2023) does not rely on any such assumptions. It provides high-fidelity and high-dynamic-range spectropolarimetric snapshot solar radio images using a new-generation instrument, the Murchison Widefield Array (MWA). This enables us to explore a part of phase space which was hitherto unexplored.

Using P-AIRCARS and the MWA, we present the first robust imaging-based evidence for linearly polarized emission in metre-wavelength solar radio bursts. This finding is corroborated by simultaneous observations with the upgraded Giant Metrewave Radio Telescope at the same spectral band. Moreover, our estimated upper limit on the Rotation Measure (RM) of ~50 rad m-2 are orders of magnitude lower than the previous estimates based on coronal models (e.g., ~103 rad m-2 by Bhonsle & McNarry, 1964). This low RM implies that the linear polarized emission has traversed much lower electron column densities, suggesting that it originates at much higher coronal heights. Interestingly, detections of linear polarization in stellar radio bursts have also been reported recently (Callingham et al., 2021; Bastian et al., 2022). We conclude by exploring some physical scenarios which can potentially give rise to such linearly polarized emissions in the solar corona.

How to cite: Dey, S., Kansabanik, D., Mondal, S., and Oberoi, D.: First robust detection of linear polarization from solar radio bursts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14421, https://doi.org/10.5194/egusphere-egu24-14421, 2024.

Type-II solar radio bursts are plasma emissions generated by magnetohydrodynamic shocks that are predominantly driven by coronal mass ejections (CMEs), the most potent drivers of space weather. These narrow-bandwidth (~few MHz) emissions show slow drift towards lower frequencies in the dynamic spectrum and appear at the fundamental and harmonic of the local plasma frequency. The evolution and geo-effectiveness of CMEs are governed by their magnetic fields and interaction with the coronal magnetized plasma. Therefore, understanding the CME-entrained magnetic fields and the ambient medium is important. Polarimetric properties of type-II bursts provide promising diagnostics for measuring and understanding the magnetic field strength, and topology at the CME-shocks. In the literature, their polarization properties have been reported to vary from being unpolarized to very strongly circularly polarized, and no linear polarization has ever been reported. The vast majority of these studies rely on dynamic spectra which can only provide spatially integrated information. Instruments like Murchison Widefield Array (MWA) and robust spectropolarimetric snapshot solar imaging pipeline, P-AIRCARS, (Kansabanik et al., 2022, 2023) have enabled high-fidelity and high-dynamic range solar radio imaging with good temporal, spectral and reasonable angular resolution. Benefiting from these, we have used the MWA to carry out detailed imaging polarimetric characterization of a type-II solar radio burst. We detect a weak circular polarization of ~ 4% during the type II. We also report the first imaging detection of low levels of linearly polarized type-II emission. This robust but surprising detection goes against the conventional wisdom that differential coronal Faraday rotation should wipe out any linear polarization signatures in coronal emissions. We characterize the polarimetric structures in both circular and linear polarizations, meticulously investigating their temporal and spectral evolutions. Our study marks the start of the use of polarimetric imaging observations to further the understanding of type-II radio bursts and coronal propagation.  

How to cite: Majee, P., Kansabanik, D., and Oberoi, D.: First detailed polarimetric study of a type-II solar radio burst with the Murchison Widefield Array, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15960, https://doi.org/10.5194/egusphere-egu24-15960, 2024.

Magnetic reconnection is a fundamental process in astrophysical plasma, as it enables the dissipation of energy at kinetic scales as well as large-scale reconfiguration of the magnetic topology. In the solar wind, its quantitative role in plasma dynamics and particle energization remains an open question that is starting to come into focus as more missions now probe the inner heliosphere. To more efficiently detect magnetic reconnection in-situ using automated and modern methods is one of the challenges that can bring us closer to understanding the impact of magnetic reconnection on its surrounding magnetized environment.

In this presentation, we make use of existing databases to focus on the evolution of magnetic reconnection properties through the heliosphere, using several space missions such as Parker Solar Probe (PSP), Solar Orbiter and Wind. We investigate the properties of small-scale reconnecting current sheets found in the turbulent solar wind as a function of radial distance and plasma source. In parallel, we also make use of PSP-Solar Orbiter alignments to study how the large-scale and high-shear reconnection occurring at the heliospheric current sheet evolves as it propagates in the solar wind. Finally, we emphasize how reconnection has a high impact on coherent structure evolution such as coronal mass ejection erosion or merging.

Collectively, these results show that magnetic reconnection is ubiquitous in the solar wind and occurs in a wide variety of settings, with a high impact on its surrounding environment. We discuss how the recent growth of available in-situ spacecraft mission data inside the Earth orbit promises further substantial progress in our understanding of magnetic reconnection occurrence, properties and impact in the solar wind. 

How to cite: Fargette, N., Eastwood, J., Waters, C., Lavraud, B., Eriksson, S., Phan, T., Oieroset, M., Stawarz, J., and Franci, L.: On the evolution of magnetic reconnection in the solar wind, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16041, https://doi.org/10.5194/egusphere-egu24-16041, 2024.

Coronal holes (CHs) have long been known as one of the main sources of high-speed solar wind streams, but recent evidence suggests that active regions (ARs) also play a significant role as solar wind sources. In this study, we aim to investigate the impact of both CHs and ARs as source regions of the solar wind. Both structures can be identified in extreme ultra-violet (EUV) solar images several days before they become geoeffective. We exploit this relation to construct a model that forecasts the solar wind speed at L1. First, we accurately detect and track the evolution of CHs and ARs over time by employing a segmentation algorithm on solar images. Next, we extract features from the indicated regions in EUV images and magnetograms, such as area and location of the source regions and the corresponding magnetic field configurations. These features, along with solar wind data from previous solar rotations and the current state of the solar cycle, are assimilated over time in a data-driven model that predicts the hourly solar wind speed at L1 four days in advance. During model training, we particularly focus on preserving the distribution of observed solar wind speeds to overcome a common drawback of data-driven solar wind speed prediction models, namely the underprediction of the peak values of solar storms. By adding a suitable regularization to the loss function, we force our model to follow the physical behavior more closely, which results in a significantly improved accuracy for predicting solar storms. Finally, we use our model to draw conclusions about the physical relevance of CHs and ARs for solar wind speed models. The model's performance is evaluated through cross-validation on 14 years of data and compared to other state-of-the-art models.

How to cite: Collin, D., Shprits, Y., Bianco, S., Inceoglu, F., Hofmeister, S., and Gallego, G.: Forecasting solar wind speed from coronal holes and active regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18676, https://doi.org/10.5194/egusphere-egu24-18676, 2024.

Detailed interferometric radio observations of solar activity allow us to constrain the dynamics of high-energy electron beams accelerated in flares and coronal mass ejections (CME). We have studied in detail the small-scale solar radio bursts, which accompanied one of the three homologous solar eruptions that originated from the western solar limb on November 04, 2015. We have used interferometric observations from the Murchison Widefield Array to image the multi-frequency emission in several radio channels between 80 and 300 MHz with 1-second resolution and 20 arcsec-pixels. The event began with a strong type II radio burst, and was followed by a separation of the emission into stationary and moving sources, the latter clearly related to the propagating CME structure. The observations show simultaneous multi-frequency flickering of intensity along a persistent off-limb structure related to the CME-driven shock wave, connecting the stationary and moving sources. This flickering emission persisted for more than 30 minutes. We present an analysis of its dynamics, its relation to the CME flux rope, the expected magnetic configurations, and electron beam properties. These observations provide valuable information about the evolution and kinematics of the CME in its early stages. 

How to cite: Kozarev, K.: Dynamics of Persistent Low-Frequency Radio Pulsations During the November 04, 2015 CME, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18797, https://doi.org/10.5194/egusphere-egu24-18797, 2024.

Coronal Mass Ejections (CMEs), and ever-changing solar wind conditions, drive processes in the Earth’s space-environment (the magnetosphere and ionosphere) which can strongly affect satellite communications, navigation systems, and power grids upon which society relies. Mitigation strategies are heavily dependent on accurate forecasting of the likely impact of space-weather conditions on operations. The tracking of plasma structures, and turbulence within, in the inner-heliosphere is now made possible by the LOw Frequency ARray (LOFAR, the world’s largest low-frequency radio-telescope) through observations of the scintillation of radio waves from astronomical sources propagating through these plasma structures. Information obtained through LOFAR can be augmented with in situ measurements from existing missions and the planned ESA Vigil mission to be stationed at L5, as well as other remote-sensing techniques, to provide an unprecedented advance warning of space weather detrimental to society. The Radio Investigations for Space Environment Research (RISER) project will provide a comprehensive understanding of the Earth’s space-environment through the use of novel radio observations and modelling techniques to investigate coupling between solar-driven inner-heliospheric structures and the Earth.

RISER will address the following key questions in the space-weather domain:

• How can we better attribute magnetospheric-ionospheric response to inner-heliospheric variability?

• How well can we establish a direct connection between parameters that characterise structures in the inner-heliosphere with the geo-effectiveness of geomagnetic disturbances?

• How can we identify and track plasma structures in the inner-heliosphere using scintillation data from low-frequency radio telescopes in a systematic way before they reach Earth?

• What is the value of improved forecasts of adverse space weather conditions when using radio-telescope observations and enhanced science of the inner heliosphere- magnetosphere-ionosphere system?

   

  Here, we give an overview of RISER, its high-level objectives, the importance and relevance to advancing our understanding of space-weather science and impacts, as well as a brief overview of the LOFAR-UK upgrades.

How to cite: Barnes, D., Bisi, M., Fallows, R., Forte, B., Milan, S., Jackson, D., Jackson, B., Odstrcil, D., and Chang, O.: Radio Investigations for Space Environment Research (RISER): An Overview, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19133, https://doi.org/10.5194/egusphere-egu24-19133, 2024.

How to cite: Di Bartolomeo, P. P., Alberti, T., Milillo, A., Giovannelli, L., Varsani, A., Laky, G., Aronica, A., Benella, S., D'Amicis, R., Heyner, D., Kazakov, A., Mangano, V., Massetti, S., Moroni, M., Noschese, R., Orsini, S., Plainaki, C., Sordini, R., and Stumpo, M.: Study of Dynamics and Evolution of Solar Wind during BepiColombo and Solar Orbiter Radial Alignment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20004, https://doi.org/10.5194/egusphere-egu24-20004, 2024.

Turbulent magnetic dynamo models were created about fifty years ago to describe the growth of the average magnetic energy in random convective plasma flows. A typical feature of such models is the generation threshold, when the exponential growth of magnetic energy begins only at sufficiently large magnetic Reynolds numbers Rm. In particular, one of the first models, proposed in the 70th by Kazantsev and Kraichnan, predicts a generation threshold in the region of Reynolds numbers of the order of 100. This threshold is difficult to achieve even for modern laboratory experiments, and therefore many studies in recent years have been devoted to clarifying this critical value. However, there is a sufficient disadvantage of usually used turbulent dynamo model – the assumption about delta-correlated in time random velocity field. This nonphysical assumption makes one unconfident in the correctness of the estimate of the dynamo threshold. In this work, using shell MHD models, we are trying to find out how accurate Kazantsev’s estimate of the generation threshold is, and how this threshold depends on the flow velocity, diffusion coefficients, and hydrodynamic helicity. This work was supported by the BASIS Foundation grant no. 21-1-3-63-1.

How to cite: Abushzada, I. and Yushkov, E.: A turbulent dynamo threshold in the shell-model approximation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-260, https://doi.org/10.5194/egusphere-egu24-260, 2024.

The Solar Orbiter (SO) mission provides a unique opportunity to study the evolution of turbulence in the solar wind across different distances from the sun and different plasma conditions. We use SO observations of extended intervals of homogeneous solar wind turbulence to investigate under what conditions the turbulent cascade in the solar wind is supported by either, or both of two distinct phenomenologies, (i) wave- wave interactions and (ii) coherent structure formation and interaction.

We identify nine Solar Orbiter observations of extended intervals of homogeneous solar wind turbulence where each interval is over 10 hours long without current-sheet crossings and other large events. We perform a systematic scale-by-scale decomposition of the observed magnetic field using two wavelets that are known to discriminate between wave-packets and discontinuities, the Daubechies 10 (Db10) and Haar respectively.

A characteristic of turbulence is that the probability distributions (pdfs) of fluctuations obtained on small scales exhibit extended supra-Gaussian tails, and as the scale is increased, the moments decrease and there is ultimately a cross-over to Gaussian pdfs at the outer scale of the turbulence. Using quantile quantile plots, we directly compare the fluctuations pdfs obtained from Haar and Db10 decompositions. This reveals three distinct regimes of behaviour. On larger scales, deep within the inertial range (IR), both the Haar and Db10 decompositions give essentially the same fluctuation pdfs. On the smallest scales, deep within the kinetic range (KR), the pdfs are distinct in that the Haar wavelet fluctuations have a much broader distribution, and the largest fluctuations are associated with coherent structures. On intermediate scales, that span the IR-KR scale break identified from the power spectra, the pdf is composed of two populations, a core with a common pdf functional form for the Haar and Db10 fluctuations, and extended tails where the Haar fluctuations dominate. This establishes a cross-over between wave-packet dominated phenomenology in the IR, to coherent structure dominated phenomenology in the KR. We find that the intermediate range of scales is quite narrow around 0.9 au so that the crossover from wave-packet to coherent structure dominated phenomenology is quite abrupt. At around 0.3au, the crossover occurs over a broader range of scales extending down to the 0.25s scale and up to 4s.

As coherent structures and wave-wave interactions have been proposed as candidates to mediate the turbulent cascade, these results offer new insights into the evolution of the turbulent cascade with distance from the sun.

How to cite: Bendt, A., Chapman, S., and Dudok de Wit, T.: The relative prevalence of wave-packets and coherent structures in the inertial and kinetic ranges of turbulence as seen by Solar Orbiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1136, https://doi.org/10.5194/egusphere-egu24-1136, 2024.

The paper analyzes the power spectra of solar wind velocity and magnetic field fluctuations that are computed in the frequency range around the break between inertial and kinetic scales. The study uses measurements of the Bright Monitor of the Solar Wind (BMSW) on board Spektr-R with a time resolution of 32 ms complemented with 10 Hz magnetic field observations from Wind propagated to the Spektr-R location and compare them with observations of Solar Orbiter and Parker Solar Probe closer to the Sun. We concentrate on the ion kinetic scale and investigate statistically the role of parameters like the fluctuation amplitudes of parallel and perpendicular magnetic field components, collisional age, temperature anisotropy or ion and electron beta. Our discussion encompasses the interplay of magnetic field and plasma fluctuations that characterize this dynamic environment and reveals that although the ion beta controls a position of the spectral break between the inertial and kinetic ranges, other mentioned parameters determine the steepness of the kinetic range spectrum of both quantities. We are showing that these statistical results are in line with theoretical considerations.

How to cite: Safrankova, J., Nemecek, Z., Pitna, A., Nemec, F., and Franci, L.: Magnetic field and ion velocity spectra in the solar wind from inertial to kinetic scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4307, https://doi.org/10.5194/egusphere-egu24-4307, 2024.

The solar wind flowing from the solar corona at supersonic and super-Alfvénic speeds is the subject of intense research at present. Numerous studies focused on temporal variability of plasma parameters, crucial to define solar wind plasma, showed that spectral distributions exhibit Power-law dependence. Additionally, examinations of its fluctuations revealed a distinctive evolution in shape of PDF’s shifting from Gaussian (Maxwellian) to peaked and heavy-tailed distributions, towards smaller scales. 

Turbulence stands as a complex, nonlinear, and multiscale phenomenon, based on a sophisticated cascade theory. While its complete description remains an unsolved challenge, various statistical methods such as structural functions or power spectra offer partial insights. Although the well-established Kolmogorov theory (K41) holds in the inertial region of magnetized plasma [10.1103/PhysRevE.78.026414], its applicability at smaller scales or higher frequencies is known to be an exception. Thus, alternative methods, such as a kinetic treatment, should be considered. 

Common approaches rely on various plasma parameters and processes, limiting their applicability in highly dynamic turbulence like the solar wind. Consequently, an alternative approach based on the framework of stochastic processes theory, particularly Markov processes, has been introduced to characterize energy transfer across the turbulent cascade. Statistical evidence suggests that turbulence has Markov properties. Furthermore, the differential equation of the Markov process can be extracted directly from data. Estimation of the Kramers-Moyal coefficients plays a pivotal role in discerning the form of the Fokker-Planck (or equivalently Langevin) equation that governs the evolution of the PDF with scale for the increments. Models based on a drift force and diffusion strength depending on scale have been emerging as a viable approach for elucidating the dynamics of solar wind turbulence, hence this method can be considered as a junction between the statistical and dynamical analysis.

Based on the data collected by the Magnetospheric Multiscale (MMS) mission’s satellites, we delve into the subject of turbulence on inertial, sub-ion, and kinetic scales. Building upon prior Markovian analysis of turbulence of the transfer of magnetic-to-magnetic field fluctuations in the near-Earth space environment [10.1093/mnras/stad2584, 10.3847/1538-4357/aca0a0], we also extend our investigation to ion velocity-to-velocity and magnetic-to-velocity cases. However, we direct our focus towards the purer statistical facet of the analysis, joint with the elements of dynamical approach. We analyze whether the transfer of increments exhibits `local` or `non-local` character, which in this context, they describe the scales involved in interactions that lead to the turbulent cascade. Additionally, we observe a global scale-invariance in relation to the Fokker-Planck equation, for a magnetic field case. 

Finally, we briefly discuss a potential non-parametric approach, namely a stochastic dynamical jump-diffusion model, or alternatively a multi-fractal approach, which can be useful to describe the underlying process accurately. We believe that such a comparative approach spanning diverse conditions is meaningful, as it aims to unveil any underlying universality within the statistical properties of the near-Earth solar wind space plasma at the intricate kinetic and sub-ion scales.

Acknowledgments: This work has been supported by the National Science Centre, Poland (NCN), through grant No. 2021/41/B/ST10/00823.

How to cite: Wójcik, D. and Macek, W. M.: Probing Small Scale Solar Wind Turbulence: Markovian Analysis and Scale Interactions from Inertial to Kinetic Regimes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6582, https://doi.org/10.5194/egusphere-egu24-6582, 2024.

Compressible plasma turbulence is prevalent in planetary plasma environments. However, our current understanding of turbulence injection and dissipation in the highly-compressible magnetosheath is still quite limited. Previous studies have suggested that pickup ion instabilities originating from the far-extended neutral exospheres of Mars may contribute to energy injection, leading to the frequent observation of plateau-like spectral characteristics in the Martian magnetosheath. Nonetheless, it remains unclear how the turbulence cascade rates vary with local parameters related to the bow shock geometry and pickup ions. In this investigation, we conduct a joint analysis of Tianwen-1 and MAVEN data to unveil spectral characteristics and the varying turbulence cascade rates under different bow shock geometries. By employing the exact laws of compressible magnetohydrodynamics turbulence, we observe a systematic increase in cascade rates with the shock normal angle. As the geometry transitions from quasi-parallel to quasi-perpendicular, the ratio between the turbulence cascade rates of the upstream solar wind and the downstream magnetosheath increases by 20-30 times. Furthermore, we find that the turbulence cascade rate of cases exhibiting plateau-like spectral shapes increases more significantly with the shock normal angle compared to those without plateau-like features. Our findings offer new insights into understanding turbulence injection and dissipation downstream of collisionless super-critical bow shocks in space and astrophysical plasmas.

How to cite: Jiang, W., Li, H., Hadid, L., Andrés, N., Daniel, V., and Wang, C.: Significant Enhancement of Turbulence Cascade Rates Downstream of Quasi–perpendicular Bow Shock at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7031, https://doi.org/10.5194/egusphere-egu24-7031, 2024.

In the solar wind turbulence, proton temperature fluctuations are highly intermittent, especially at small scales in the inertial range. This phenomenon may contain information about solar wind intermittent heating. However, the physical nature of the temperature intermittency is not yet clear. Based on the measurements from Solar Orbiter between 2020 and 2023, we identify temperature intermittent structures in the fast and slow solar wind, respectively. We compare the nature and kinetic effects of them. According to the variations of proton temperature and magnetic field when the temperature intermittency occurs, we classify the temperature intermittency in the fast wind into the following five categories: (1) 20% of the cases are identified as linear magnetic holes with local temperature enhancement, and a majority of them are unstable to mirror-mode (MM) instability. (2) 18% are related to tangential current sheets also with local temperature enhancement. (3) 9% are tangential discontinuities with a temperature interface, which could separate two different parcels of plasma. (4) 15% of the cases are accompanies by local temperature decrease that may be also due to MM instability. (5) 25% of the cases show a chain of magnetic field variations probably related to Alfven vortices. In the slow wind, the situation is different. The temperature intermittent structures are mainly associated with firehose instability. These results will help to further understand the intermittent dissipation process in the solar wind turbulence.

How to cite: Wang, X., Wang, Y., and Yuan, H.: Nature of temperature intermittency in the solar wind turbulence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7045, https://doi.org/10.5194/egusphere-egu24-7045, 2024.

We present wave and turbulence observations by the DSCOVR spacecraft during solar flare and CME events. Over 9-day period, the spectral indices within the magnetic field power spectral density (PSD) in the RTN and mean-field-aligned (MFA) coordinates do not agree. In the inertial range the transverse PSD follows a Kraichnan–Iroshinikov -3/2 index when in MFA coordinates, while in the RTN frame the same PSD is more complex showing Kolmogorov -5/3 index at lower frequencies followed by a shallow index close to -1 at the inertial subrange before steepening to -2 close to the He+ cyclotron frequency. We show that the differences are due to the changing interplanetary magnetic field (IMF) direction relative to the solar wind velocity within the CME periods. We present evidence of wave-wave modulation and suggest that lower frequency waves in the solar wind can modulate the growth rates/propagation of ion cyclotron waves providing a method to transfer energy in the solar wind to smaller scales. Furthermore, we suggest that the Kraichnan–Iroshinikov -3/2 index in the inertial range can be explained by combining containment due to wave generation/propagation and stochastic Brownian motion in the solar wind. When these two phenomena are equal, they combine to create a -3/2 index.

How to cite: Loto'aniu, P. and Krista, L.: Spectral Indices and Evidence of Wave-Wave Modulation in Observations of the Interplanetary Magnetic Field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7101, https://doi.org/10.5194/egusphere-egu24-7101, 2024.

The HelioSwarm mission was selected as a MIDEX mission by NASA in February 2022 for launch in 2029 with a nominal duration of 15 months. Its main objectives are to reveal the 3D spatial structure and dynamics of turbulence in a weakly collisional plasma and to investigate the mutual impact of turbulence near boundaries (e. g., Earth’s bow shock and magnetopause) and large-scale structures evolving in the solar wind (e. g., coronal mass ejection, corotating interaction region). The HelioSwarm mission will also contribute to the space weather science and to a better understanding of the Sun-Earth relationship. It consists of a platform (Hub) and eight smaller satellites (nodes) evolving along an elliptical orbit with an apogee ~ 60 and a perigee ~15 Earth radii. These 9 satellites, three-axis stabilised, will provide 36 pair combinations and 126 tetrahedral configurations covering the scales from 50~km (subion scale) to 3000 km (MHD scale). It will be the first mission able to investigate the physical processes related to cross-scale couplings between ion and MHD scales by measuring, simultaneously at these two scales, the magnetic field, ion density and velocity variations. Thus each satellite is equipped with the same instrument suite. A fluxgate magnetometer (MAG from Imperial College, UK) and a search-coil magnetometer (SCM) provide the 3D measurements of the magnetic field fluctuations whereas a Faraday cup (FC, SAO, USA) performs the ion density and velocity measurements. In addition, the ion distribution function is measured at a single point onboard the Hub by the iESA instrument, allowing to investigate the ion heating in particular. The SCM for HelioSwarm provided by LPP and LPC2E is strongly inherited of the SCM designed for the ESA JUICE mission. It will be mounted at the tip of a 3m boom and will cover the frequency range associated with the ion and subion scales in the near-Earth environment [0.1-16Hz] with the following sensitivities [15pT/√Hz at 1 Hz and 1.5 pT/√Hz at 10 Hz]. The iESA, developped by IRAP and LAB, is inherited from the PAS instrument operating on the ESA Solar Orbiter mission. It will provide the ion distribution function at high time and angular resolutions, respectively 0.150 s and 3°. Furthermore the energy range will be ~200 eV to 20 keV with 8% energy resolution. Status of the development of SCM and iESA prototypes will be presented.

How to cite: Le Contel, O., Lavraud, B., Retino, A., Kretzschmar, M., Génot, V., Alexandrova, O., Mansour, M., Amoros, C., Jannet, G., Baruah, R., Mehrez, F., Camus, T., Alison, D., Grigoriev, A., Revillet, C., Studniarek, M., Mirioni, L., Agrapart, C., Sou, G., and Geyskens, N. and the HelioSwarm team: The French contribution for the NASA HelioSwarm mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9272, https://doi.org/10.5194/egusphere-egu24-9272, 2024.

Turbulence is three-dimensional, multiscale disorder. Characterizing turbulence requires determining how energy is injected into, transported through, and removed from these systems. One can study the three-dimensional structure by using measurements from at least four spatial points combined with appropriate analysis approaches to estimate spatial gradients and distributions of power at a given scale. Such techniques have been applied to data from spacecraft missions such as MMS and Cluster, but are limited to a single scale associated with the average inter-spacecraft distance. Given that future selected and proposed spacecraft missions, including HelioSwarm and Plasma Observatory, will have many more than four measurement points, with separations between the spacecraft spanning different characteristic spatial scale lengths, we consider the extension of previously implemented analysis techniques to these multipoint, multiscale configurations. In particular, we consider the propagation of measurement error through the wave telescope technique as a function of the number of measurements points and configuration to demonstrate the impact on accurate resolution of the underlying wavevectors. We also explore the optimal selection of subsets of measurement points to more accurately measure the properties of plane waves and wave packets with wavevectors spanning the spatial scales encompassed by a representative multispacecraft observatory.

How to cite: Klein, K. and Broeren, T.: Analysis Techniques for Future Multipoint, Multiscale Observatories, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10703, https://doi.org/10.5194/egusphere-egu24-10703, 2024.

Alfvén wave turbulence models are the foundation of many investigations into the winds and EUV/X-ray emission from cool, solar-like stars. The models are used to estimate mass loss rates, magnetic spin down and exoplanet habitability. However, the models currently rely on ad-hoc estimates of critical parameters. One such parameter is the perpendicular correlation length, L_⊥ (the energy injection length scale), whose value has significant influence over the turbulent heating and mass loss rates. Using the Coronal Multi-channel Polarimeter, a ground based corona-graph, we provide the first measurements of the correlation length of Alfvénic waves at the base of the corona. Our analysis shows the values are broadly homogeneous through the corona and have a distribution sharply peaked around 7.6 - 9.3 Mm. The measured correlation length is comparable to the expected scales associated with supergranulation. The results also suggest a discrepancy between the coronal values of L_⊥, theoretical transport models for the evolution of L_⊥ with distance from the Sun, and previous estimates of L_⊥ beyond the Alfvén critical zone. We suggest a thesis as to the missing physics.

How to cite: Morton, R. and Sharma, R.: Transverse energy injection scales at the base of the solar corona, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11006, https://doi.org/10.5194/egusphere-egu24-11006, 2024.

The origin and evolution of non-equilibrium characteristics of electron velocity distribution functions (eVDFs) in the solar wind are still not well understood. They are key in understanding heat conduction and energy transport in weakly collisional plasma, as well as in the scenario at the origin of the solar wind. Due to low collision rates in the solar wind, the electron populations develop temperature anisotropies and velocity drifts in the proton frame, as well as suprathermal tails and heat fluxes along the local magnetic field direction. These non-thermal characteristics are highly variable, and the processes that control them remain an open question.  

We present here a recent work on enhanced measurements of solar wind eVDFs from Wind at 1AU. This work is based on a sophisticated algorithm that calibrates eVDFs with plasma Quasi Thermal Noise data in order to accurately and systematically characterize the non-thermal properties of the eVDFs, as well as those of their Core, Halo and Strahl components.  Indeed, the core, halo and strahl populations are fitted to determine their densities, temperatures and temperature anisotropies as well as their respective drift velocities with respect of the ion velocity (or solar wind speed).  The density, temperature and temperature anisotropy, as well as the parallel heat flux of the total eVDFs are also computed. 

We use a 4-year-long dataset composed of all these parameters at solar minimum to enable statistically significant analyses of solar wind electron properties. We estimate collisional proxies such as collisional age and Knudsen number, and discuss usually neglected effects. In addition to the total electron heat flux, we also compute the heat flux contributions from the core, halo and strahl and discuss the interplay between these three components.  We finally show estimates of the so-called Thermal Force, a drag or Coulomb friction between ions and the electron components that arises naturally from the non-thermal character of the eVDFs, even in the absence of current. This TF enhances the parallel electric field and plays an important, but usually neglected, role in two fluid energy transfers between electrons and ions. It is parallel to the heat flux that causes it, however its role in understanding the observed heat flux remains to be explored.  This statistically-significant work allows a local, quantitative measure of Coulomb coupling that maybe important with possibly other microphysical processes to locally control non-thermal properties.

How to cite: Salem, C., Pulupa, M., Verscharen, D., and Yoon, P.: New Insights on Solar Wind Electrons at 1 AU: Collisionality, Heat Flux, and Thermal Force, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13061, https://doi.org/10.5194/egusphere-egu24-13061, 2024.

Precisely how and where energy transfer between scales in the Solar Wind takes place remains an open question. We use the occurrence of conditions predicted by linear theory to promote the growth of kinetic instabilities, to infer how turbulence drives temperature anisotropies. We analyse Solar Orbiter data by applying the measure of local energy transfer (LET) derived from the Politano and Pouquet exact law to identify the relative distributions of energy transfer processes in the solar wind. We quantify these processes with the application of a radial rate of strain computed from single spacecraft data, a measure that we define as an approximation of the strain rate in fully three-dimensional turbulence. We find good agreement with the theoretical prediction that velocity shear is responsible for driving temperature anisotropies. We conclude that the turbulent velocity field plays a key role in the creation of unstable conditions in the Solar Wind.

How to cite: Opie, S., Verscharen, D., Chen, C., Owen, C., Isenberg, P., Sorriso-Valvo, L., Franci, L., and Matteini, L.: Energy transfer in the Solar Wind: The interplay between turbulence and kinetic instabilities., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13402, https://doi.org/10.5194/egusphere-egu24-13402, 2024.

The differential heating of electrons and ions by turbulence in weakly collisional magnetized plasmas and the scales at which such energy dissipation is most effective are still debated. Using a large data sample measured in the Earth’s magnetosheath by the Magnetospheric Multiscale mission
and the coarse-grained energy equations derived from the Vlasov-Maxwell system we find evidence of a balance over two decades in scales between the energy cascade and dissipation rates. The decline of cascade rate at kinetic scales (in contrast with a constant one in the inertial range), is balanced by increasing ion and electron heating rates, estimated via the pressure-strain. Ion scales are found to contribute most effectively to ion heating, while electron heating originates equally from ion and electron scales. These results can potentially impact the current understanding of particle heating in turbulent magnetized plasmas as well as their theoretical and numerical modeling.

How to cite: Manzini, D., Sahraoui, F., and Califano, F.: On the Cascade-Dissipation Balance in Astrophysical Plasmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15798, https://doi.org/10.5194/egusphere-egu24-15798, 2024.

We study intermittent coherent structures in solar wind magnetic turbulence from MHD to kinetic plasma scales using  Parker Solar Probe data during its first perihelion (at 0.17 au). These structures are energetic events localized in time and covering wide range of scales. We detect them using Morlet wavelets. For the first time, we apply a multi-scale analyses in physical space to study these structures. At large MHD scales, we find (i) current sheets including switchback boundaries and (ii) Alfvén vortices. Within these large scale events, there are  embedded structures at smaller scales: typically  Alfvén vortices at ion scales and a compressible vortices at sub-ion scales. To quantify the relative importance of different type of structures, we do a statistical comparison of the observed structures with the expectations of models of the current sheets and vortices. This comparison is based on amplitude anisotropy of magnetic fluctuations within the structures. The results show the dominance of Alfvén vortices at all scales in contrast to the widespread view of dominance of current sheets. The number of coherent structures grows from the MHD to the sub-ion scales. For one MHD scale structure there are ∼10 ion scale structures and ∼50  sub-ion scale structures. In general, there are multiple structures of ion and sub-ion scales embedded within one MHD structure. There are also examples of non-embedded structures at ion and sub-ion scales.

How to cite: Alexandrova, O., Vinogradov, A., Demoulin, P., Artemyev, A., Maksimovic, M., Mangeney, A., and Bale, S.: Embedded coherent structures from MHD to sub-ion scales in turbulent solar wind: PSP observations at 0.17 au, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17557, https://doi.org/10.5194/egusphere-egu24-17557, 2024.

The Voyager 1 and 2 are only the two spacecraft that have arrived and passed through the heliospheric boundaries. Based on the plasma data from Voyager 2 spacecraft, the electron quasi-thermal noise (QTN) is investigated by using of the electron population model consisting of a core with Maxwellian distribution and a halo with kappa distribution. The power spectra of the electron QTN is calculated at different heliocentric distances from 1 AU to 110 AU. The parametric dependence of the QTN power spectra and the effective Debye length on the model parameters, such as the density ratio and temperature ratio of the halo to the core, kappa index and the antenna length, are discussed further. The results show that the electron QTN spectrum consists of a plateau in the low frequency band f < fpt, a prominent peak at the plasma frequency fpt, and a rapid decreasing part in the high frequency band f > fpt. The QTN plateau level basically falls down outwards until the termination shock crossing at about 84 AU, after which the plateau rebounds a little near the heliopause. Although the model parameters can be very variable, the QTN plateau level does not present more than the double change in a fairly wide range of the model parameters. The presented results can be useful for future deep-space explorations in the heliosphere and can provide valuable references for the design of onboard detectors.

How to cite: Li, Y.-L., Chen, L., and Wu, D.-J.: Radial Distribution of Electron Quasi-thermal Noise in the Outer Heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17726, https://doi.org/10.5194/egusphere-egu24-17726, 2024.

Earth's magnetosheath is a medium where plasma parameters can take a wide range of values and where plasma fluid properties can vary greatly, depending on the distance to the bow shock and the upstream solar wind conditions. Plasma turbulence that develops in the magnetosheath is also affected by these changes, thus giving rise to a similar variety of turbulence regimes.

With the data collected during the MMS unbiased magnetosheath campaign, it is now possible to explore the plasma parameter space of the magnetosheath and study turbulence properties with a set of high-cadence in-situ measurements. This dataset was gathered from February 1st 2023 to April 1st 2023 and consists of 15 inbound magnetosheath crossings from which 300 burst-data intervals were collected. During each crossing, the burst-mode measurements were taken for 3 minutes every 6 minutes, without imposing any selection criteria to collect the data. The length of the time intervals and their time resolution make them suitable to study the turbulent dynamics around the ion spectral break.

In this work we will study the different contributions to the energy cascade rate (measured by means of scaling laws derived from the Hall-MHD equations) and their dependence on plasma conditions, like the plasma beta, and turbulence properties, such as the spectral index and turbulence anisotropy.

How to cite: Montagud-Camps, V., Toledo-Redondo, S., Hellinger, P., Verdini, A., Papini, E., Stawarz, J., Sorriso-Valvo, L., F. Albert, I., and Castilla, A.: An unbiased view of the contributions to turbulence cascade in Earth's magnetosheath., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17757, https://doi.org/10.5194/egusphere-egu24-17757, 2024.

Magnetospheric coherent structures related to the dynamics of the dayside magnetopause frontier for a northward IMF configuration, are analyzed using global 3D MHD simulations. The main goal is to reach a synthetic scenario on the formation of 3D unstable/stable structures developed in different steps from the dayside to the night side. They are: (i) the Kelvin-Helmholtz (K-H) vortexes are generated along and outside the magnetopause near the dayside region, while other K-H vortexes are generated along and inside the magnetopause;  (ii) Those vortexes frozen to the magnetic field  at the inner sides of the magnetopause at both dusk/dawn sides extend towards the north and south.  They face each other near the north and south ionosphere with counter inverse rotation to form the so-called “inverse” Karman vortexes; (iii) both rows of vortexes are shed off soon from the magnetopause; (iii) these vortexes are unstable in one each row, adjust, and evolve into a marginal stable Kármán vortex street; (iv) these Kármán vortexes soon are reformed into stable longitudinal (stream-wise) coherent vortexes and survive for long time over large distances x~-130 to -140Re in the magnetotail. All these processes lead to the formation of magnetospheric coherent turbulent structures. 

How to cite: Cai, D., Fujita, S., and Lembege, B.: Inverse and Forward Alfvenic Kármán Vortex and Magnetospheric Coherent Turbulent Structures in 3D Global MHD Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20199, https://doi.org/10.5194/egusphere-egu24-20199, 2024.

The existing Alfven Wave Turbulence Based Solar Atmosphere Model (AWSoM) as used in the SWMF framework of the University of Michigan to simulate the Solar Corona and Inner Heliosphere (i.e. to 1 AU heliocentric distance) meets an ideological problem while compared with the equations for turbulence usually employed in modeling the outer heliosphere (i.e. beyond 1 AU). While for the turbulence in the outer heliosphere the energy difference (the difference between the averaged kinetic and magnetic energy densities) is used as one of the Reynolds-averaged quantity describing the local state of turbulence, the present AWSoM model lacks the energy difference at all. 

Besides an evident inconsistency between the models of turbulence, employing the different sets of variables below and beyond 1 AU, to have a full description of turbulence is important by two reasons, both relating to the charged particle transport producing the radiation hazards in space. First, for simulation both solar energetic particle and galactic cosmic rays at 1 AU a computational domain should extend at least to 2-3 AU. Second, even if below 1 AU the energy difference effect on turbulence might be negligible and not necessary to be included into the turbulence model, it is still needed to calculate transport coefficients for the high energy charged particles in the turbulent magnetic field. To evaluate it from the averaged quantities characterizing the turbulence, both the total energy density and the said energy difference are needed. 

In the presented research, an extra equation for the energy difference in introduced and solved in such way that at small heliocentric distances the turbulence model reduces to that used in the AWSoM with no loss in generality. On the other hand at larger heliocentric distances it becomes very close (if not identical) to the typical outer heliosphere model. In addition to averaged energetic characteristics of turbulence we evaluate the correlation spatial scales for directions parallel and perpendicular to the averaged interplanetary magnetic field was well as the transport coefficients for high-energy charged particles

How to cite: Sokolov, I., Usmanov, A., van der Holst, B., and Gombosi, T.: Unified Alfven Wave Turbulence Based Model for Energy and Particle Transport in Solar Corona and Heliosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20578, https://doi.org/10.5194/egusphere-egu24-20578, 2024.

With the help of a two-dimensional (2-D) particle-in-cell (PIC) simulation model, we investigate the long-time evolution of a quasi-parallel shock. Part of upstream ions are reflected by the shock front, and their interactions with the incident ions excite low-frequency magnetosonic waves in the upstream. Detailed analyses have shown that the dominant wave mode is caused by the resonant ion-ion beam instability, and the wavelength can reach tens of the ion inertial lengths. Although these plasma waves are directed toward the upstream in the upstream plasma frame, they are brought by the incident plasma flow toward the shock front, and their amplitude is enhanced during the approaching. The interaction of the upstream plasma waves with the shock leads to the cyclic reformation of the shock front. When crossing the shock front, these large-amplitude plasma waves are compressed and evolve into current sheets in the transition region of the shock. At last, magnetic reconnection occurs in these current sheets, accompanying with the generation of magnetic islands. Simultaneously, there still exist another kind of plasma waves with the wavelength of several ion inertial lengths in the ramp of the shock. The current sheets in the transition region are distorted and broken into several segments when this kind of plasma waves are transmitted into the downstream, where magnetic reconnection and the generated islands have a much smaller size.

How to cite: Lu, Q., Guo, A., Yang, Z., Lu, S., and Wang, R.: Upstream plasma waves and downstream magnetic reconnection at a reforming quasi-parallel shock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-85, https://doi.org/10.5194/egusphere-egu24-85, 2024.

We use the Magnetospheric Multiscale mission to study electron kinetic entropy across Earth's quasi-perpendicular bow shock. We perform a statistical study of how the change in electron entropy depends on the different plasma parameters associated with a collisionless shock crossing. We find that the change in electron entropy exhibits strong correlations with upstream electron plasma beta, Alfvén Mach number, and electron thermal Mach number. The source of entropy generation is investigated by correlating the change in electron entropy across the shock to the measured electric and magnetic field wave power strengths for different frequency intervals within different regions in the shock transition layer. The electron entropy change is observed to be greater for higher electric field wave power within the shock ramp and shock foot for frequencies between the lower hybrid frequency and electron cyclotron frequency. This implies electrostatic waves are important for electron kinetic entropy generation at Earth's quasi-perpendicular bow shock but also for the non-adiabatic electron heating at quasi-perpendicular shocks.

How to cite: Lindberg, M., Wallner, A., Berglund, S., and Vaivads, A.: Statistical Study of Electron Kinetic Entropy Generation at Earth's Quasi-perpendicular Bow Shock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1836, https://doi.org/10.5194/egusphere-egu24-1836, 2024.

When plasma and magnetic field discontinuities in the solar wind interact with Earth’s magnetic field, they can significantly alter the properties and dynamics of Earth’s bow shock, magnetosheath, and magnetopause. In this study, we investigate magnetosheath dynamic pressure enhancements generated by the interaction between a solar wind rotational discontinuity with Earth’s bow shock in a 2D simulation run of the global magnetospheric hybrid-Vlasov model Vlasiator. We find that as the discontinuity is advected into the bow shock, several fast-mode pulses associated with enhanced dynamic pressure are launched toward the Earth. In addition, the interaction between discontinuity and shock generates transient enhancements of dynamic pressure at the bow shock that move Earthward together with the discontinuity. We find that the fast-mode pulses are able to traverse the magnetosheath and disturb the magnetopause. This finding differs from the results of previous studies using 2D and 3D MHD simulations as well as spacecraft measurements, which concluded that magnetopause disturbances should be caused by the rotational discontinuity itself and the dynamic pressure enhancement associated with it.

How to cite: Suni, J., Palmroth, M., Turc, L., Battarbee, M., Pfau-Kempf, Y., Dubart, M., Ganse, U., Kotipalo, L., Tarvus, V., and Workayehu, A.: Magnetosheath dynamic pressure enhancements associated with a solar wind rotational discontinuity: Results from a hybrid-Vlasov simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2111, https://doi.org/10.5194/egusphere-egu24-2111, 2024.

3D velocity distribution functions (VDFs) of He⁺ pickup ions (PUIs) were used to trace local physical processes around interplanetary shocks. He⁺ PUIs are measured by PLasma And SupraThermal Ion Compostion (PLASTIC) instrument onboard the Solar Terrestrial Relations Observatory (STEREO) in an unprecedented cadence and angular/velocity resolutions with mass and charge state unambiguously determined. We focused on the VDFs in terms of the interplanetary magnetic field orientation in the solar wind frame and indipendently evaluated the acceleration, heating, and pitch-angle scattering for both perpendicular and parallel shocks with notable differences. For the perpendicular shock: (a) Reflected and energized particles were found in the upstream, and the PUI properties were isolated between upstream and downstream, (b) Strong heating is observed in the sheath region, (c) Suprathermal particles are found in the sheath region and attributed to the compression within the solar wind, and (d) Universal pitch-angle scattering were found through out the ICME. For the parallel shock: (a) Locaized heating and acceleration were found around the shock location, (b) Harder suprathermal particle distributions were found near the shock, suggesting diffusive shock processes, (c) Weak or no sheath heating was observed, and (d) Pitch angle scattering were correlated with magnetic field power spectral density at the Helium cyclotron.

How to cite: Ogasawara, K., Kucharek, H., Klecker, B., Dayeh, M., and Ebert, R.: Helium pickup ion 3D velocity distributions at interplanetary shocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2220, https://doi.org/10.5194/egusphere-egu24-2220, 2024.

Properties of the region upstream of planetary bow shocks depend strongly on the direction of the interplanetary magnetic field. For quasi-parallel bow shocks, 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 shocks. Yet many properties of SLAMS are not well known at Earth and even less so at other planets.

Here we present results on the occurrence and other properties of SLAMS at the Martian foreshock with the help of magnetic field and ion data from NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN). SLAMS are identified by three criteria. First, a magnetic field three times stronger than the background magnetic field is required. Second, SLAMS should have an elliptic polarization so that it can be differentiated from a shock oscillation. Last, it takes place upstream of the bow shock. The results presented here can offer comparative insights with SLAMS at Earth for exploring potential dependencies on system size and other magnetospheric parameters.

How to cite: Wong Chan, T. K., Karlsson, T., and Bergman, S.: Statistical study of SLAMS at the Martian foreshock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3121, https://doi.org/10.5194/egusphere-egu24-3121, 2024.

Short Large-Amplitude Magnetic Structures (SLAMS) are common magnetic field signatures observed in the foreshock region of collisionless quasi-parallel shocks. SLAMS are non-linear isolated structures, defined to have an amplitude of more than 2 times the background magnetic field. They have been suggested to grow from ultra-low frequency (ULF) waves that are common in the foreshock region, and are believed to play important roles in the formation of quasi-parallel shocks, influencing the properties and dynamics of the shock and also associated particle energization.   

In this work, we use data from the Cluster and Magnetospheric Multiscale (MMS) missions to statistically study the properties of SLAMS in the foreshock region of Earth. We use an automated method to detect SLAMS in the data, producing a comprehensive database of SLAMS detections. The size, morphology and propagation velocity of SLAMS are then studied using statistical approaches, investigating the dependence on several parameters, such as amplitude, upstream conditions and distance from the bow shock. 

How to cite: Bergman, S., Karlsson, T., and Wong Chan, T. K.: Statistical properties of Short Large-Amplitude Magnetic Structures (SLAMS) in the foreshock region of Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3125, https://doi.org/10.5194/egusphere-egu24-3125, 2024.

The study of jets downstream of Earth's bow shock has been a subject of extensive investigation for over a decade due to their close connection with shock dynamics and their profound impact on the geomagnetic environment. While the variability of the solar wind and its interaction with Earth's magnetosphere provide valuable insights into jets across a range of parameters, a broader parameter space can be explored by examining the downstream of other planetary bow shocks. Here we report the existence of anti-sunward and sunward jets downstream of Jovian bow shock and show their close association to magnetic discontinuities. The anti-sunward jets are possibly generated by a shock--discontinuity interaction. Finally, through a comparative analysis of jets observed at Earth, Mars, and Jupiter, we show that the size of jets scales with the size of bow shock.

How to cite: Zhou, Y., Raptis, S., Wang, S., Shen, C., Ren, N., and Ma, L.: Magnetosheath jets at jupiter and across the solar system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3342, https://doi.org/10.5194/egusphere-egu24-3342, 2024.

Ion reflection is known to be a key component of particle energisation and heating in super-critical collisionless shockwaves. As a source of free energy, reflected ions drive stream instabilities in the shock foot, create magnetic perturbations, and contribute to magnetic field amplification in the upstream and downstream regions of quasi-perpendicular shocks. Where ions reflect from the shock ramp multiple times, a longer dwell time in the shock foot allows for more opportunities for interaction with non-stationary and turbulent shock processes, which can result in injection into processes such as diffusive shock acceleration and shock drift acceleration. To characterise the pathway to multiple ion reflection, we perform a series of 2D and 3D hybrid particle-in-cell simulations (fluid electron, particle ions) over a parameter range typical of Earth’s bow shock, varying Mach number, plasmas betas, and the angle between the shock normal and upstream magnetic field (θ_Bn). This enables a parametric investigation of the density fraction of multiply reflected ions both upstream and downstream of the shock, for protons and for heavier ion components of the solar wind such as He²⁺. We discuss methods for identification of multiply-reflected ions in kinetic plasma simulations, corresponding analogues for observations (where available), and investigate their impact on shock energetics. By examining the partial moments of reflected ions in two- and three-dimensional simulations, we also explore which shock processes drive multiple reflection.

How to cite: Gingell, I. and Madanian, H.: Hybrid simulations of multiple reflection of protons and heavy ions at Earth’s bow shock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3966, https://doi.org/10.5194/egusphere-egu24-3966, 2024.

Transient upstream mesoscale structures (TUMS) are an important topic in the field of research of the near-Earth environment. These events form upstream of the Earth's bow shock and can perturb regions downstream it, i.e. magnetosheath and magnetopause. They can even affect the magnetosphere and ionosphere causing a range of space weather phenomena during periods without noticeable solar activity. There is still much to learn about the TUMS and the way they interact with the near-Earth environment. We are only beginning to understand how the different types of the TUMS relate to each other. In the past it has been shown that traveling foreshocks may contain foreshock cavitons, spontaneous hot flow anomalies and foreshock compressional boundaries (FCB). Here we present the first evidence, that traveling foreshocks may be bounded on at least one of their edges by hot flow anomalies (HFA) and by events that look like hybrids between HFAs and FCBs. We show two case studies observed by the Cluster and MMS constellations. Such studies enable us to better understand all the ways in which the solar-terrestrial interactions occur.

How to cite: Kajdic, P., Blanco-Cano, X., Rojas Castillo, D., Archer, M., Turc, L., Pfaum-Kempf, Y., LaMoury, A., Liu, T., Raptis, S., Vinicius, M., Lee, S., Shutao, Y., Hao, Y., Sibeck, D., Zhang, H., Omidi, N., Wang, B., Lin, Y., and Escoubet, P.: Hot Flow Anomalies Delimiting Traveling Foreshocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4145, https://doi.org/10.5194/egusphere-egu24-4145, 2024.

Dynamic pressure variations that are upstream from the magnetopause can interact with the coupled magnetospheric and ionospheric system, causing significant auroral responses, which indicates magnetospheric compressions, wave propagations and disturbances of current system. Recent studies have shown that not only large-scale solar wind structures but also locally-generated foreshock transients can be associated with strong dynamic pressure variations and further induce such auroral responses. However, how these auroral responses evolve in 2D perspective and how the corresponding current system and electron precipitation evolve in 2D perspective are still unclear. Thus, in our study, we used the coordinated observations between THEMIS probes and the ground-based all-sky images at South Pole to statistically investigate the 2D evolution of discrete and diffuse auroral responses to both solar wind structures and foreshock activities. The discrete auroral evolution shows that the dynamic pressure variations upstream from the magnetopause can induce upward field-aligned currents near the magnetopause in the magnetosphere. These currents can extend earthward and most of them extend duskward, causing the bifurcation of auroral oval. The diffuse auroral patterns reveal that in the ionosphere, the area with compression-related electron precipitations propagates poleward. The azimuthal motion of compression-related electron precipitations can be either dawnward or duskward, depending on the azimuthal propagation of the magnetospheric compressions. We further found that the location, size and associated dynamic pressure change of the upstream solar-wind or foreshock transients can modify the shape and 2D evolution of the corresponding auroral patterns.

How to cite: Wang, B. and Xu, X.: The 2D evolution of the M-I responses to solar wind/foreshock transients based on the coordinated observation between THEMIS and ground-based ASI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5084, https://doi.org/10.5194/egusphere-egu24-5084, 2024.

Transient enhancements in the dynamic pressure, so-called magnetosheath jets or simply jets, are abundant in the magnetosheath.
They propagate from the bow shock towards the magnetopause. On their way through the magnetosheath, jets interact with the
ambient plasma. The scale size of jets is determined almost exclusively with statistical studies, but not for individual jet events.
We use multipoint measurements from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission
to study the passage of a single jet and obtain its size. We observe an evasive motion of the plasma on the jet path. Using this
flow pattern we can reconstruct the position of the central axis of this jet along its propagation direction. This allows us to
estimate the spatial distribution of the dynamic pressure within the jet. Furthermore, the size perpendicular to the
propagation direction can be estimated for different cross sections. Using this method, the scale size of individual jet events
can be determined with multiple spacecraft. In principle, only two spacecraft are needed if we assume a simplified geometry.
In the case we investigated, both the dynamic pressure and the perpendicular size increase along the propagation axis from
the front part towards the center of the jet and decrease again towards the rear part.

How to cite: Pöppelwerth, A., Glebe, G., Mieth, J. Z. D., Koller, F., Karlsson, T., Vörös, Z., and Plaschke, F.: Scale Size Estimation of Magnetosheath Jets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5564, https://doi.org/10.5194/egusphere-egu24-5564, 2024.