Particle acceleration and radiation are fundamental cosmic processes that significantly contribute to the universe’s energy density, driven by phenomena ranging from solar flares to supernova explosions. Shock waves, prevalent across various spatial scales, play a key role in converting kinetic energy into plasma heating and particle acceleration. Recent advancements from missions such as the Parker Solar Probe (PSP) have provided unprecedented insights into the dynamics of shock waves within the heliosphere, thereby enhancing our understanding of these critical energy conversion mechanisms.
In this talk, I will present findings from two recent studies that leverage the PSP’s unique proximity to the Sun and its advanced, high-fidelity instrumentation. First, we analyzed one of the fastest shocks ever observed on March 13, 2023, revealing the efficient acceleration of electrons up to and exceeding 6 MeV and the collective acceleration of ions from the thermal solar wind. Second, we made the surprising discovery of synchrotron radiation emanating from ultra-relativistic electrons in both a quasi-parallel and a quasi-perpendicular shock, with the quasi-parallel shock exhibiting significantly higher radiation intensities due to more effective electron acceleration. These results are consistent not just with theoretical models of strong cosmic shocks, but also observations. This offers an unprecedented opportunity to bridge in situ heliospheric observations with remote observations of phenomena such as supernova remnants.
How to cite: Jebaraj, I. C., Agapitov, O., Gedalin, M., Krasnoselskikh, V., Vuorinen, L., Miceli, M., Dresing, N., Cohen, C., Balikhin, M., Kouloumvakos, A., Palmerio, E., Wijsen, N., Mitchell, J. G., McComas, D., Rawafi, N., Kilpua, E., Vainio, R., and Bale, S.: Scale-Invariant Particle Energization and Radiation – Foundations for Building a Cosmic Bridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10616, https://doi.org/10.5194/egusphere-egu25-10616, 2025.
In this paper, we discuss the changes to the magnetosheath plasma due to interaction with a density structure within the magnetic cloud an interplanetary coronal mass ejection that impacted Earth and caused significant perturbations in plasma boundaries. The bow shock breathing motion is evident due to the changes in the upstream dynamic pressure. A solitary magnetic enhancement forms in the inner magnetosheath with characteristics of a fast magnetosonic shock wave, propagating earthward and perpendicular to the background magnetic field. We show that the magnetosheath plasma is heated twice, during the bow shock crossing and during the interaction with the fast magnetosonic shock inside the magnetosheath. Following these events, a sunward motion of the magnetosheath plasma is evident. Analysis of ion distributions indicates that the sunward flows are caused by the reflection of flux tubes within the fast magnetosonic shock near the magnetopause boundary.
How to cite: Madanian, H.: Solitary magnetic structure and sunward flows in the dayside magnetosheath, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20631, https://doi.org/10.5194/egusphere-egu25-20631, 2025.
The redistribution of the directed flow energy in a collisionless shock is the central problem of shock physics. The incident ion energy is transferred to ion and electron heating, acceleration of a small fraction of particles, and enhance- ment of the magnetic field. The mean magnetic field enhancement is determined by the standard boundary conditions. Recently, shocks were observed in which the amplitude of the persisting downstream magnetic fluctuations exceeded the mean downstream field. The question of the ubiquity of the phenomenon is of utmost importance since it would require re-consideration of the boundary conditions. It may also mean that the effective magnetic field in supernova remnant shocks may be currently grossly underestimated. The proposed research will exploit the data accumulated by the Magnetospheric Multiscale (MMS) mission to determine the de- pendence of the relative amplitude of the downstream magnetic fluctuations on the main shock parameters: shock angle, Mach number, and upstream temperature.
How to cite: golan, M., gedalin, M., and Golan, M.: Observations of persistent downstream magnetic oscillations at the Earth bow shock , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16, https://doi.org/10.5194/egusphere-egu25-16, 2025.
In this study we investigate the formation of magnetosheath jets before, during, and after the interaction between Earth's bow shock and a solar wind rotational discontinuity in a 2D ecliptic simulation run of the global magnetospheric hybrid-Vlasov model Vlasiator. Magnetosheath jets are transient enhancements of dynamic pressure downstream of collisionless shocks, and they have been observed in Earth's magnetosheath, the magnetosheaths of other planets, as well as the sheaths of interplanetary shocks. Rotational discontinuities (RD) are boundaries where the components of the magnetic field and velocity tangential to the boundary change abruptly, and they have been observed by spacecraft in the solar wind and in Earth's magnetosheath. Both spacecraft observations and previous simulation studies have shown that RDs interacting with the bow shock can generate dynamic pressure pulses in the magnetosheath.
Studying magnetosheath jets is important because they have been shown to potentially have magnetospheric effects if impacting the magnetopause, and while travelling through the magnetosheath they can modify its properties. Statistical studies of simulations and spacecraft observations have shown that jets tend to form mainly at Earth's quasi-parallel bow shock, that is where the interplanetary magnetic field (IMF) direction is nearly parallel to the shock normal, but they have also been observed downstream of the quasi-perpendicular shock. By studying the formation and properties of jets at the quasi-parallel and quasi-perpendicular shock at different times in the simulation, we aim to shed light on the differences between jets forming at different parts of the shock, and during different stages of interaction between an RD and the bow shock.
How to cite: Suni, J., Palmroth, M., Turc, L., Battarbee, M., Pfau-Kempf, Y., and Ganse, U.: Rotational discontinuity-generated magnetosheath jets at Earth's quasi-perpendicular bow shock: Results from a hybrid-Vlasov simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1683, https://doi.org/10.5194/egusphere-egu25-1683, 2025.
Recent studies suggest that magnetosheath jets can form at the boundaries of a hot flow anomaly (HFA) during shock-discontinuity interaction by solar wind's compression and less efficient deceleration from a curved bow shock. Here, based on Magnetospheric Multiscale (MMS) data and an 3D global hybrid simulation, we report two large-scale jets at the boundaries of an HFA that together with the HFA reached more than 20 Earth radii in width, thus representing a large-scale restructuring of the dayside magnetosheath. Since shock-discontinuity interaction is a universal process that can occur at all planets, we expect that magnetosheath restructuring under such mechanisms is also universal across the solar system.
How to cite: Zhou, Y., Guo, J., Raptis, S., Wang, S., Shue, J.-H., Wang, B., Lu, Q., Zhang, J., Shen, C., and Shao, P.: Magnetosheath Restructuring by Shock-Discontinuity Interaction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4963, https://doi.org/10.5194/egusphere-egu25-4963, 2025.
The bow shock at Earth is created when the super-Alfvénic solar wind interacts with Earth’s magnetosphere and is slowed to sub-Alfvénic velocities. Depending on the angle θBn between the interplanetary magnetic field and the bow shock normal, the shock is defined to be either quasi-perpendicular (θBn > 45°) or quasi-parallel (θBn < 45°). In the quasi-parallel regime, the upstream region magnetically connected to the shock, called the foreshock, is highly dynamic and characterized by various plasma instabilities and wave activity. Short Large-Amplitude Magnetic Structures (SLAMS) are non-linear isolated magnetic field signatures commonly observed in this region. They are believed to grow from ultra-low frequency (ULF) waves which are common in the foreshock.
SLAMS are suggested to be important for the formation of the quasi-parallel shock. They are propagating upstream towards the sun, but generally with a propagation velocity smaller than the solar wind velocity. Consequently, they are convected downstream towards the shock. If they obtain high propagation velocities they should, however, be able to become stationary in the bow shock frame of reference and studies have suggested that the shock itself is composed of a patchwork of SLAMS.
In this work, we use multipoint measurements made by the Cluster mission to make a statistical analysis of the propagation velocity of SLAMS in the foreshock of Earth. We study the dependence on other properties of the SLAMS, such as their amplitude, and parameters related to the upstream environment.
How to cite: Bergman, S., Karlsson, T., Wong Chan, T. K., and Trollvik, H.: Statistical Study of the Propagation Velocity of Short Large-Amplitude Magnetic Structures (SLAMS) in the Foreshock of Earth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5884, https://doi.org/10.5194/egusphere-egu25-5884, 2025.
Properties of the region upstream of planetary bow shock depend strongly on the direction of the interplanetary magnetic field. For quasi-parallel bow shock, part of the solar wind ions are reflected back upstream from the shock and this reflected ion population triggers instabilities resulting in a turbulent region. In the quasi-parallel case, reflected particles travel far upstream, creating an extended turbulent foreshock region. Within this region, Short Large-Amplitude Magnetic Structures (SLAMS) can frequently be found, which are suggested to play a pivotal role in the formation of planetary bow shock. Yet many properties of SLAMS are not well known at Earth and even less so at other planets.
SLAMS are identified by three criteria. First, a magnetic field amplitude twice the background magnetic field is required. Second, SLAMS should exhibit an elliptic polarization so that it can be differentiated from a shock oscillation. Last, it takes place upstream of the bow shock.
Here we present results on the occurrence and other properties of SLAMS at different planetary foreshock including Mars, Mercury and Saturn using the respective space missions. The results presented here can also offer comparative insights with SLAMS found at Earth for exploring potential dependencies on system size, and other magnetospheric and solar wind parameters.
How to cite: Wong Chan, T. K., Karlsson, T., Bergman, S., and Trollvik, H.: Statistical study of SLAMS at different planetary foreshock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6562, https://doi.org/10.5194/egusphere-egu25-6562, 2025.
Short large-amplitude magnetic structures (SLAMS) are seen as critical elements in collisionless shocks with quasi-parallel geometries. They can pre-accelerate solar wind ions into suprathermal energy as an injection mechanism for Diffusive Shock Acceleration. To understand the details of the injection problem, we present direct observations of nonstationarity of a SLAMS, using Magnetosperic Multiscale (MMS) measurement in a sting-of-pearls configuration separated by several hundreds of kilometers. We find that the upstream edge of the SLAMS serves as a local quasi-perpendicular shock front to reflect and accelerate solar wind ions. Accumulation of reflected ions results in upstream expansion of the SLAMS ramp and the reflecting point may change their location. Whistlers grow quickly as the SLAMS ramp propagates towards upstream and distort the SLAMS in return.
How to cite: Wang, M., Khotyaintsev, Y., and Graham, D.: Multipoint Observations of Nonstationarity of a Short Large-Amplitude Magnetic Structure (SLAMS), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11679, https://doi.org/10.5194/egusphere-egu25-11679, 2025.
We examine the possibility of remotely sensing Earth’s bow shock location, orientation, and velocity, via gyrosensing the plasma ions reflected from the shock. In this work, we present a remote gyrosensing approach to quantifying the bow shock properties for various interplanetary magnetic field orientations by analyzing reflected particles with different gyrophases and pitch angles. Then we suggest an analytical formalism for predicting the bow shock characteristics based on the azimuthal and zenith look angles of the reflected ions as observed by ElectroStatic Analyzers (ESA) on a single probe near the bow shock. The proposed method will be tested and verified with FPI ion instrument measurements onboard Magnetospheric MultiScale (MMS) spacecraft.
How to cite: Barani, M., Sibeck, D., McFadden, J., Bonnell, J., Wilson, L., and Koval, A.: Remote Gyrosensing of the Earth's Bow Shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14505, https://doi.org/10.5194/egusphere-egu25-14505, 2025.
It is common wisdom that collisionless shocks become nonplanar and nonstationary at sufficiently high Mach numbers. Whatever the shock structure, the upstream and downstream fluxes of the mass, momentum, and energy should be equal. These conservation laws are satisfied at low Mach numbers when the shock front is planar and stationary. When this becomes impossible, inhomogeneity and time dependence, presumably as rippling, develop. Using test particle analysis in a model shock profile, this study shows that the shock structure changes as a kind of "phase transition" when the Mach number is increased while the shock angle, the upstream beta, and the magnetic compression are kept constant.
How to cite: Gedalin, M.: A "phase transition" from a planar stationary profile to a rippled structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2077, https://doi.org/10.5194/egusphere-egu25-2077, 2025.
The size of collisionless shock waves is believed to play an important role in determining the maximum energy gain of particles accelerated at heliospheric and astrophysical shocks.
In this study, we use the Parker Solar Probe and Solar Orbiter gravity assists at Venus to investigate electron acceleration at the Venusian bow shock.
The identified Venusian shock crossings are compared to terrestrial bow shock crossings with similar shock parameters using the Magnetospheric Multiscale (MMS) mission. The aim of the comparison is to uncover potential differences between the two different types of bow shocks and how the size of collisionless bow shocks affects electron acceleration.
Preliminary results indicate a harder average spectral index (p ~ 3.5±0.6) for suprathermal electrons observed at Venus's bow shock than those found at Earth's bow shock (p ~ 4.9±0.8) for similar Mach number and shock angle.
How to cite: Lindberg, M. and Hietala, H.: Electron Acceleration Comparison of the Venusian and Terrestrial Bow Shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2626, https://doi.org/10.5194/egusphere-egu25-2626, 2025.
Collisionless shock waves are ubiquitous in astrophysical plasmas, from supernova remnants and planetary atmospheres to coronal mass ejections and laboratory experiments. These shocks are known to be efficient particle accelerators, crucial for understanding the origin of cosmic rays, including ultra-relativistic particles. This study presents a novel model of reinforced shock acceleration for electrons, integrating in-situ data from NASA's Magnetospheric Multiscale (MMS) and Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction (ARTEMIS) missions. Focusing on Earth's planetary environment, our analysis reveals a suprathermal electron injection threshold, demonstrating how a multiscale framework involving foreshock transient phenomena, a suprathermal seed population, and wave-particle interactions can systematically accelerate suprathermal electrons to relativistic energies. By merging theoretical advancements in astrophysical plasmas and shock physics with these multi-spacecraft observations, we address the persistent electron injection problem and explore the broader applicability of our model to other planetary environments within our solar system and beyond, including stellar and interstellar contexts.
How to cite: Raptis, S., Lalti, A., Lindberg, M., Turner, D., Caprioli, D., and Burch, J.: Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4552, https://doi.org/10.5194/egusphere-egu25-4552, 2025.
The solar wind and interplanetary magnetic field parameters observed in situ by the SWA and MAG instruments onboard the Solar Orbiter mission provide a unique opportunity to identify interplanetary (IP) shock waves at various distances from the Sun on the rising phase of the 25th solar activity cycle.
In the frame of this work, to recognize IP shocks, we applied a semi-automated method on the base of quality factors comprising the solar wind velocity, density characteristics, and total interplanetary magnetic field parameters. As an example, we identified a few tens of various IP shocks that occurred in the inner heliosphere, at radial distances of 0.29–0.95 AU from the Sun. Most of them were classified as FF-type shock waves, with only a few events identified as FR-, SF- and SR-type shock waves. The semi-automatic algorithm mentioned was used to determine the time of passage of the shock wave front through the spacecraft’s location.
Moreover, we calculated the typical kinetic and magnetohydrodynamic characteristics of each identified shock wave. In particular, the radial dependences of parameters such as the density ratio (rN), magnetic field (rB) ratio, plasma beta (βus), Alfvén velocity (VA), the angle between the shock normal and the interplanetary magnetic field (QBn), shock wave front velocity (Vsh), sound speed (Vs) and magnetosonic speed (Vfms) were analyzed. Additionally Alfvén (MA) and magnetosonic (Mfms) Mach numbers were studied. Finally, the dependence of the number of identified shock waves on radial distance was also examined and compared with solar flares activity.
This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.
How to cite: Yakovlev, O., Dudnik, O., and Wawrzaszek, A.: Interplanetary shock waves semi-automated identified as seen by Solar Orbiter., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6223, https://doi.org/10.5194/egusphere-egu25-6223, 2025.
Shocklets are compressive, linearly polarized magnetosonic structures that have been widely observed in the Earth's foreshock. They form due to wave steepening and dispersive effects, often accompanied by whistler wave precursors. At Earth these structures are characterized by steepened upstream edges, magnetic compression below 2, and associations with hot diffuse ion distributions. Shocklets play a crucial role in energy transfer and wave-particle interactions in collisionless shocks. While most studies have focused on Earth's foreshock, some evidence suggests their presence at Venus, raising questions about their existence in other planetary foreshocks.
In this study, we investigate the presence of shocklets in Mercury's foreshock using data from the MESSENGER mission. The timescales of Hermean shocklet candidates range from 3 to 30 seconds. Our preliminary analysis reveals that shocklets at Mercury exhibit greater diversity compared to those observed at Earth. While some structures resemble typical Earth-like shocklets, characterized by a sharp leading edge with whistler wave precursors followed by a slower relaxation, we also identify ULF magnetosonic waves accompanied by high-frequency fluctuations that display initial signs of wave steepening which could correspond to an early stage of the Earth-like shocklet. Our findings highlight the complex and dynamic wave activity in Mercury's unique solar wind environment.
How to cite: Rojas-Castillo, D., Vaquero Bautista, C. A., Blanco-Cano, X., Plaschke, F., Kajdic, P., Pump, K., and Heyner, D.: Shocklets in the vicinity of Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7432, https://doi.org/10.5194/egusphere-egu25-7432, 2025.
Earth’s magnetosheath, the region between Earth’ magnetic field and the bow shock, gives rise to a plethora of transients, waves, and instabilities. Each effect changes the plasma parameter distribution, impacting the behaviour of the plasma that finally hits our magnetic field. Turbulence plays a crucial role in how energy injected into the system by transients or instabilities is transported and dissipated from large to small scales. We are investigating the role magnetosheath pressure enhancements (or so-called jets) play in adding to the turbulence in the system. These jets often plough through the system with high velocity, interacting with the surrounding environment, and slow down the further they travel. The propagation of jets is still largely unexplored, in particular when considering plasma turbulence. We aim to quantify whether jets drive turbulence in the magnetosheath plasma, and whether turbulent plasma fluctuations impact the propagation of jets. Magnetic orientation and distance to the shock are considered in the analysis in order to disentangle their impact on the effects. We are using MMS spacecraft measurements for the analysis of individual jet cases, and THEMIS spacecraft for a statistical analysis at event times when several spacecraft were close to the flow of jet events.
How to cite: Koller, F., Chen, C., and Hietala, H.: Turbulence Surrounding Magnetosheath Jets: Are Pressure Enhancement Stirring the Magnetosheath?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14042, https://doi.org/10.5194/egusphere-egu25-14042, 2025.
Localised dynamic pressure enhancements – jets – have been observed downstream of both planetary and more recently interplanetary shocks. At planetary environments, jets are known to drive enhanced particle acceleration, large-amplitude magnetic field variations and reconnecting current sheets.
The analysis of interplanetary jets observed by Wind spacecraft near the Earth showed that their properties are similar to those of magnetosheath jets. Furthermore, we found jets also at low beta, low Mach number interplanetary shocks, i.e., conditions that are rare for the Earth’s bow shock.
Following the jet identification approach we introduced for Wind data, here we now apply it to Solar Orbiter measurements made at various heliocentric distances.
How to cite: Hietala, H., Shirazul, K., Trotta, D., Webb, P., Vuorinen, L., and Koller, F.: Investigating jets downstream of interplanetary shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17988, https://doi.org/10.5194/egusphere-egu25-17988, 2025.
Solar wind directional discontinuities can generate transient mesoscale structures such as foreshock bubbles and hot flow anomalies (HFAs) upstream of Earth's bow shock. These structures can have a global impact on the near-Earth environment, and understanding their formation conditions is crucial to evaluate their contribution to solar wind-magnetosphere coupling. Here we present the results of a global 2D hybrid-Vlasov simulation (with 3D electromagnetic fields) of the interaction of a rotational discontinuity with near-Earth space, performed with the Vlasiator model. The magnetic field rotates by 90 degrees from ortho-Parker spiral to Parker spiral orientation across the discontinuity. As the discontinuity enters the simulation domain, a foreshock bubble forms duskward of the Sun-Earth line, where the foreshock is initially located. Shortly after the discontinuity makes first contact with the bow shock at the subsolar point, we find that a structure with enhanced temperature and strongly deflected flows develops at the intersection of the discontinuity with the bow shock. This structure displays typical features of an HFA. However, HFA formation requires electric fields pointing towards the discontinuity on at least one side, a condition which is not initially met in our simulation. We demonstrate that the prior generation of the foreshock bubble provides the necessary conditions for HFA formation. We then investigate the evolution of both structures as the discontinuity travels antisunward, showing that the foreshock bubble signatures tend to weaken while the HFA grows. We also report a large-scale bow shock deformation, with the bow shock expanding several Earth radii outward of its initial position within the compressed edge of the foreshock bubble. Our results provide new clues regarding the formation and evolution of large-scale foreshock transients and their impact on the shock.
How to cite: Turc, L., Archer, M. O., Zhou, H., Pfau-Kempf, Y., Suni, J., Kajdic, P., Blanco-Cano, X., Dahani, S., Lipsanen, V., Tao, S., Battarbee, M., and Palmroth, M. and the ISSI team 555: Foreshock bubbles can modify their solar wind discontinuities enabling secondary transients to form, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10989, https://doi.org/10.5194/egusphere-egu25-10989, 2025.
Low Mach number, fast magnetosonic, dispersive shocks are formed if the characteristic scale of the shock front exceeds the characteristic the spatial scale associated with resistive processes. In these cases, dispersion arrests the nonlinear steepening of the shock front. According to the established view, a whistler wave precursor, whose wave vector is parallel to the shock normal, is formed in oblique dispersive shocks provided that the Mach number does not exceed the Whistler Critical Mach number Mw. Numerical simulations and data obtained by the MMS satellites are used to investigate the evolution of the properties of the upstream whistler precursor as the Mach number increases above Mw.
How to cite: Balikhin, M., Agapitov, O., Krasnoselskikh, V., Roytershteyn, V., Walker, S., Gedalin, M., Jebaraj, I. C., and Colomban, L.: Whistler Critical Mach Number Concept Revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12010, https://doi.org/10.5194/egusphere-egu25-12010, 2025.
The bow shock of Mars provides a compelling example of a mass-loaded, supercritical shock. A key challenge in space plasma physics is understanding the mechanisms of particle acceleration that occur at collisionless shocks. Due to extensive studies, the terrestrial foreshock is often considered a benchmark for interactions between planetary magnetospheres and the solar wind. The MAVEN mission at Mars is offering a wealth of data, simultaneously opening a window to study the Martian foreshock in detail.
In this context, we present new measurements of velocity distribution functions of suprathermal protons upstream of Mars' bow shock. We identify backstreaming beams aligned (FAB) and misaligned with the interplanetary magnetic field (IMF) direction for various shock geometries. FAB bulk velocities are found to be well-distributed in relation to the shock speed. Our analysis reveals that, compared to their terrestrial counterparts, Martian FABs exhibit slower sunward motion. Additionally, it appears that these FABs originate from a shock region where the IMF lines form an angle of 20-50 degrees with the shock normal— a smaller source region than that of Earth's bow shock.
These findings rule out specular reflection as the mechanism behind beam production. Typically, terrestrial FABs are produced through a quasi-adiabatic process that preserves the first invariant to some extent. In contrast, the new Martian observations provide a valuable comparison between the foreshocks of Earth and Mars, shedding light on key differences and enhancing our understanding of these planetary phenomena.
How to cite: Meziane, K., Mazelle, C., Simon-Wedlund, C., Halekas, J., Hamza, A., Bertucci, C., Mitchell, D., and Espley, J.: Ion acceleration at Mars Bow Shock - Results from MAVEN, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12526, https://doi.org/10.5194/egusphere-egu25-12526, 2025.
Using Magnetospheric Multiscale (MMS) data from Earth orbit, an automated clustering algorithm has been employed to classify dayside MMS data into four distinct regions: magnetosphere, magnetosheath, solar wind, and ion foreshock, as detailed in Toy-Edens et al. [JGR 2024]. Applied to eight years of MMS data, over 25,000 bow shock crossings were identified from all four MMS spacecraft. Using that event database, we highlight a series of results including: new, 3-dimensional, parameterized boundary model fits for the bow shock; statistical characteristics of the quasi-parallel and quasi-perpendicular bow shock; and a new 4-point timing algorithm to systematically determine bow shock normal directions. We detail new results concerning the accuracy and performance of the shock normal results, showing that this new approach works remarkably well. We also highlight some new results of kinetic shock behavior and compare those directly to results from state-of-the-art simulations of and corresponding predictions for collisionless shocks. We end with a discussion of future work, in which we hope to train a parameterized generative model for collisionless shock crossing data as a function of upstream plasma characteristics. Our hope is to be able to apply that model to collisionless shocks beyond 1 au, validating its performance with shock observations from other systems (including Venus, Mars, Jupiter, etc.), and ultimately apply it to solar and other astrophysical shocks that are beyond our reach for in situ observations.
How to cite: Turner, D., Toy-Edens, V., Mo, W., and Young, S.: Employing machine learning techniques for systematic and statistical studies of collisionless shocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13753, https://doi.org/10.5194/egusphere-egu25-13753, 2025.
Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections, and by the interaction of fast solar wind with slow streams of plasma. These shocks can be preceded by extended wave and suprathermal ion foreshocks perturbing large extensions of the heliosphere. In a recent study (Trotta et al., 2024 it was shown that the interaction between two interplanetary coronal mass ejections (ICMEs) can drive a forward and a reverse shock with similarities to those bounding stream interaction regions (SIRs). In this work we analyse the microstructure of this event observed by Solar Orbiter on March 8th, 2022 at 0.5 AU. We find that wave characteristics change from one ICME to the other. Inside the first ICME waves have a broad band sprectrum. In contrast, there are regions in the second ICME with very monochromatic waves. In both cases, waves are associated with proton and alpha particle distributions that show a super-Alfvenic drift, suggesting local wave generation. Larger amplitude waves due to ion reflection are found upstream of the forward shock forming an extended foreshock. Although the shock was weak, reflected populations include alpha particles, and O6+ ions. Of particular interest is the fact that monochromatic ion cyclotron waves associated with anisotropic (Tperp >Tpar) ion distributions are found in the region between the two ICMEs. Our results show how ICME-ICME interaction can result in regions with a variety of microstructure phenomena in the inner heliosphere.
How to cite: Blanco-Cano, X., Trotta, D., Kieokaew, R., Livi, S., Hietala, H., Kajdic, P., Rojas-Castillo, D., Dimmock, A., Larosa, A., Hornury, T., Vainio, R., and Jian, L.: Microstructure at a fully formed Forward-Reverse Shock pair due to the interaction between two Coronal Mass Ejections observed at 0.5 AU., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14236, https://doi.org/10.5194/egusphere-egu25-14236, 2025.
Collisionless diffusive shock waves are the primary mechanism for the production of high energy particles in the Sun, with the solar flare terminal shock waves located in the lower solar atmosphere providing the seed particles for the generation of high energy particles. Whether flare terminal shocks can trigger ground-level enhancement events with energies reaching GeV remains a mystery. Solar cosmic ray particle streams play a crucial role in the space weather environment, and in the heliospheric plasma bubble, solar high energy particle events at lower energy ranges typically exhibit single power law spectra, while at higher energy ranges, solar high energy particle events often have multi-power-law spectral features with "knee" and "ankle" breaks. The intrinsic mechanism behind these significant spectral changes is not yet clear. Through simulation comparisons, it was found that the particle spectra produced by the termination shocks of double solar flares in the low-energy range are double power-law spectra that soften to harden, whereas the spectra produced by single flare shock are single power-law spectra. We believe this is due to the stronger acceleration capability caused by the superposition of double shocks. Thus, it reveals that multi-shock interactions can lead to changes in the particle spectra.
How to cite: Wang, X.: Compare the differences in the high-energy particle spectra accelerated by single and double flare shocks., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20995, https://doi.org/10.5194/egusphere-egu25-20995, 2025.
