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In fusion plasma physics, the large-scale trajectories of energetic particles in magnetic confinement devices are known as orbits. To effectively and efficiently be able to work with orbits, the Orbit Weight Computational Framework (OWCF) was developed. The OWCF constitutes a set of scripts, functions and applications capable of computing, visualizing and working with quantities related to fast-ion (FI) orbits in toroidally symmetric fusion devices. The current version is highly integrated with the DRESS code, which enables the OWCF to compute and analyze the orbit sensitivity for arbitrary neutron- and gammadiagnostics. However, the framework is modular in the sense that any future codes (e.g. FIDASIM) can be easily integrated. The OWCF can also compute projected velocity spectra for FI orbits, which play a key role in many FI diagnostics. Via interactive applications, the OWCF can function both as a tool for investigative research but also for teaching. The OWCF will be used to analyze and simulate the diagnostic results of current and future fusion experiments such as ITER. The orbit weight functions computed with the OWCF can be used to reconstruct the FI distribution in terms of FI orbits from experimental measurements using tomographic inversion.

The Joint European Torus (JET) has recently conducted its second deuterium-tritium (DT) experimental campaign DTE2, providing unique opportunity for studying both physics and engineering aspects of nuclear fusion plasmas. This also allowed the exploitation of new diagnostics and technologies that were not available during the first JET DT campaign held in 1997. Among these new instruments, the enhancement projects of the JET nuclear diagnostics lead to the development and installation of synthetic single crystal diamond detectors along different collimated line of sights. This paper describes the single crystal diamond-based diagnostic suite of the JET tokamak and the enhanced 14 MeV neutron diagnostic capabilities in terms of neutron yield and high resolution neutron spectroscopy. The diamond characterization measurements and the calibration procedure at JET are shown, together with performance of the diamond based neutron spectrometer as 14 MeV neutron yield monitor which allows the separation of 2.5 MeV and 14 MeV neutrons in trace tritium plasmas. The first high-resolution 14 MeV neutron spectroscopy measurements in neutral beam injection-heated DT plasmas are presented, allowing thermal and non-thermal neutron component separation. Prospects for the diagnose of DT burning plasmas such as ITER and SPARC will be presented.

Divertor tiles after Joint European Torus-ITER like wall (JET-ILW) campaigns and dust collected after JET-C and JET-ILW operation were examined by a set of complementary techniques (full combustion and radiography) to determine the total, specific and areal tritium activities, poloidal tritium distribution in the divertor and the presence of that isotope in individual dust particles. In the divertor tiles, the majority of tritium is detected in the surface region and, the areal activities in the ILW divertor are in the 0.5-12 kBq cm-2 range. The activity in the ILW dust is associated mainly with the presence of carbon particles being a legacy from the JET-C operation. The total tritium activities show significant differences between the JET operation with ILW and the earlier phase with the carbon wall (JET-C) indicating that tritium retention has been significantly decreased in the operation with ILW.

Mars, lacking an intrinsic dynamo, is an ideal laboratory to comparatively study induced magnetospheres, which can be found in other terrestrial bodies as well as comets. Additionally, Mars is of particular interest to further exploration due to its loss of habitability by atmospheric escape and possible future human exploration. In this context, we propose the Mars Magnetospheric Multipoint Measurement Mission (M5), a multi-spacecraft mission to study the dynamics and energy transport of the Martian induced magnetosphere comprehensively. Particular focus is dedicated to the largely unexplored magnetotail region, where signatures of magnetic reconnection have been found. Furthermore, a reliable knowledge of the upstream solar wind conditions is needed to study the dynamics of the Martian magnetosphere, especially the different dayside boundary regions but also for energy transport phenomena like the current system and plasma waves. This will aid the study of atmospheric escape processes of planets with induced magnetospheres. In order to resolve the three-dimensional structures varying both in time and space, multi-point measurements are required. Thus, M5 is a five spacecraft mission, with one solar wind monitor orbiting Mars in a circular orbit at 5 Martian radii, and four smaller spacecraft in a tetrahedral configuration orbiting Mars in an elliptical orbit, spanning the far magnetotail up to 6 Mars radii with a periapsis just outside the Martian magnetosphere of 1.8 Mars radii. We not only present a detailed assessment of the scientific need for such a mission but also show the resulting mission and spacecraft design taking into account all aspects of the mission requirements and constraints such as mass, power, and link budgets. Additionally, different aspects of the mission programmatics like a possible mission timeline, cost estimates, or public outreach are shown. The common requirements for acceptance for an ESA mission are considered. The mission outlined

Context. In past decades, several spacecraft have visited comets to investigate their plasma environments. In the coming years, Comet Interceptor will make yet another attempt. This time, the target comet and its outgassing activity are unknown and may not be known before the spacecraft has been launched into its parking orbit, where it will await a possible interception. If the approximate outgassing rate can be estimated remotely when a target has been identified, it is desirable to also be able to estimate the scale size of the plasma environment, defined here as the region bound by the bow shock. Aims. This study aims to combine previous measurements and simulations of cometary bow shock locations to gain a better understanding of how the scale size of cometary plasma environments varies. We compare these data with models of the bow shock size, and we furthermore provide an outgassing rate-dependent shape model of the bow shock. We then use this to predict a range of times and cometocentric distances for the crossing of the bow shock by Comet Interceptor, together with expected plasma density measurements along the spacecraft track. Methods. We used data of the location of cometary bow shocks from previous spacecraft missions, together with simulation results from previously published studies. We compared these results with an existing model of the bow shock stand-off distance and expand on this to provide a shape model of cometary bow shocks. The model in particular includes the cometary outgassing rate, but also upstream solar wind conditions, ionisation rates, and the neutral flow velocity. Results. The agreement between the gas-dynamic model and the data and simulation results is good in terms of the stand-off distance of the bow shock as a function of the outgassing rate. For outgassing rates in the range of 1027-1031-s-1, the scale size of cometary bow shocks can vary by four orders of magnitude, from about 102 km to 106 km, for an ionisation rate, flow ve

Context. The direction of the interplanetary magnetic field determines the nature of the interaction between a Solar System object and the solar wind. For comets, it affects the formation of both a bow shock and other plasma boundaries, as well as mass-loading. Around the nucleus of a comet, there is a diamagnetic cavity, where the magnetic field is negligible. Observations by the Rosetta spacecraft have shown that, most of the time, the diamagnetic cavity is located within a solar-wind ion cavity, which is devoid of solar wind ions. However, solar wind ions have been observed inside the diamagnetic cavity on several occasions. Understanding what determines whether or not the solar wind can reach the diamagnetic cavity also advances our understanding of cometsolar wind interaction in general. Aims. We aim to determine the influence of an interplanetary magnetic field directed radially out from the Sun that is, parallel to the solar wind velocity on the cometsolar wind interaction. In particular, we explore the possibility of solar wind protons entering the diamagnetic cavity under radial field conditions. Methods. We performed global hybrid simulations of comet 67P/Churyumov-Gerasimenko using the simulation code Amitis for two different interplanetary magnetic field configurations and compared the results to observations made by the Rosetta spacecraft. Results. We find that, when the magnetic field is parallel to the solar wind velocity, no bow shock forms and the solar wind ions are able to enter the diamagnetic cavity. A solar wind ion wake still forms further downstream in this case. Conclusions. The solar wind can enter the diamagnetic cavity if the interplanetary magnetic field is directed radially from the Sun, and this is in agreement with observations made by instruments on board the Rosetta spacecraft.

The magnetized solar wind drives a current system around Mars that maintains its induced magnetosphere. The solar wind also transfers its energy to the atmospheric ions, causing continuous atmospheric erosion, which has a profound impact on the planet’s evolution history. Here, we use Amitis, a Graphics Processing Unit (GPU)-based hybrid plasma model to first reproduce the global pattern of the net electric current and ion currents under an interplanetary magnetic field perpendicular to the solar wind flow direction. The resultant current distribution matches the observations and reveals more details. Using the electric field distribution characterized earlier with the same model, we calculate for the first time the spatial distribution of energy transfer rate to the plasmas in general and to different ion species at Mars. We find out that (1) the solar wind kinetic energy is the dominant energy source that drives Martian induced magnetosphere, (2) the energy flux of the shocked solar wind flows from the magnetic equatorial plane towards the plasma sheet in the induced magnetotail, (3) both the bow shock and the induced magnetospheric boundary are dynamos where plasma energy is transferred to the electromagnetic field, and (4) the planetary ions act as loads and gain energy from the electromagnetic field. The most intense load region is the planetary ion plume. The general pattern of the energy transfer rate revealed in this study is common for induced magnetospheres. Its variabilities with the upstream conditions can provide physical insight into the observed ion escape variabilities.

We calculate the momentum spectrum of electron-positron pairs created via the Schwinger mechanism by a class of four-dimensional electromagnetic fields called e-dipole fields. To the best of our knowledge, this is the first time the momentum spectrum has been calculated for 4D, exact solutions to Maxwell's equations. Moreover, these solutions give fields that are optimally focused, and are hence particularly relevant for future experiments. To achieve this we have developed a worldline instanton formalism where we separate the process into a formation and an acceleration region.

Earth-space traversing electromagnetic waves become attenuated as they propagate through the atmosphere. The sources of attenuation are weather phenomena in the Troposphere, and scintillation and absorption in the Ionosphere. On behalf of Arctic Space Technologies AB, an empirical model based on data from the last decade was built in Python, in order to estimate the level of attenuation and provide a better picture of the frequency environment at the site in Piteå. By utilizing recommendations from the International Telecommunication Union Radiocommunication Sector, and constraining the project to only consider the case where the satellite is at an 5° apparent elevation in Piteå, and a range of weather phenomena a nuanced picture can be obtained. It was found that the attenuation from the Ionosphere in typical satellite frequency bands is not of significance, and therefore only the Tropospheric sources were considered. The results showed that the S-band is the most reliable band to utilize, since little to no changes were observed for a range of weather scenarios. For the X-band, larger changes in the level of attenuation were observed for higher levels of precipitation, yet not as severe as for the Ku- and Ka- bands. However, for the Ku- and Ka-bands, large fluctuations in the attenuation were observed for different cases. In conclusion, the attenuation at Arctic space's site in Piteå for the S- and X-bands are the lowest and least effected by changes in weather. On the other hand, the Ku- and Ka-bands should be used predominantly under good weather circumstances.

In July 2031, a new chapter in the exploration of the Jovian system will begin with the arrival of the Jupiter Icy Moons Explorer (Juice) at Jupiter. Launched on April 14 2024 as part of ESA’s Cosmic Vision programme, the mission aims to study Jupiter and its icy Galilean moons Callisto, Europa, and Ganymede. Juice carries a whole suite of instruments for in-situ and remote ground observations, one of which is the Jovian plasma Dynamics and Composition analyser (JDC). As a part of the Particle Environment Package (PEP), the particle detector will measure the energy, mass, charge and arrival direction of ions and electrons in the Jovian magnetosphere. Spacecraft charging caused by interactions between the spacecraft and its surrounding plasma environment poses a significant problem for JDC because the electrostatic potential of the spacecraft accelerates/decelerates charged particles, resulting in distorted measurements, particularly for the lowest energy particles. In this report, we show the results of spacecraft charging and instrument simulations performed in the Spacecraft Plasma Interaction System (SPIS) for the solar wind and Earth’s magnetosheath—two environments that Juice will encounter at the start of the cruise phase. We found that the conductive surfaces that cover the majority of the spacecraft become positively charged as a result of a large photoelectron current in both the solar wind and magnetosheath environments. We show that these surfaces are expected to reach potentials of 9 V in the solar wind and 4 V in the magnetosheath. The four radiators on Juice that are covered with dielectric paint and shaded by the sun shield become negatively charged in both simulated environments. The radiator potentials can be as low as -40 V in the solar wind and -100 V in the magnetosheath. We also conclude that due to blocking by the spacecraft main body, the ion population cannot be sampled in the solar wind unless a spacecraft roll is performed. Furthermore, d

Cosmic rays are ultra-relativistic particles traveling near the speed of light permeating the galaxy. Collisionless shock waves with their ubiquity throughout the universe and excellent capability of accelerating charged particles offer an explanation to the origin of cosmic rays. It is well established that the particles are predominately accelerated at young supernova remnant shocks through a mechanism called Diffusive Shock Acceleration (DSA). However, this theory only applies if the particles already have a relativistic starting energy. Therefore, the charged particles must be pre-accelerated up to relativistic energies by some unknown mechanism(s) before being injected into the cosmic ray acceleration process. This is known as the injection problem and a lot of effort has been put into resolving it over the past decades. This thesis will use spacecraft data from NASA's Magnetospheric Multiscale (MMS) mission to study electron acceleration at Earth's collisionless bow shock. In particular, we will study what mechanisms are able to accelerate electrons from solar wind thermal energies (~20 eV) up to mildly relativistic energies 10-100 keV. Paper III and Paper IV set out to study energetic electron events observed at Earth's bow shock by MMS. In Paper III, we investigate the most promising candidate for a solution to the long-standing electron injection problem, the Stochastic Shock Drift Acceleration (SSDA) mechanism. SSDA successfully describes a mechanism for electrons to be accelerated up to mildly relativistic energies. However, only one previous observation of the theory exists. Building on that study, we provide further evidence in favor of the theory by showing good agreement between predictions and observations. Observational evidence of an alternative electron acceleration mechanism is presented in Paper IV. The observation displays an increase in electron flux up to ~60 keV, and inconsistent features with the SSDA mechanism. The event exhibits bi-direct, QC 20231222

The fast-ion phase-space distribution function in axisymmetric tokamak plasmas is completely described by the three constants of motion: energy, magnetic moment and toroidal canonical angular momentum. In this work, the observable regions of constants-of-motion phase-space, given a diagnostic setup, are identified and explained using projected velocities of the fast ions along the diagnostic lines-of-sight as a proxy for several fast-ion diagnostics, such as fast-ion D alpha spectroscopy, collective Thomson scattering, neutron emission spectroscopy and gamma-ray spectroscopy. The observable region in constants-of-motion space is given by a position condition and a velocity condition, and the diagnostic sensitivity is given by a gyro-orbit and a drift-orbit weighting. As a practical example, 3D orbit weight functions quantifying the diagnostic sensitivity to each point in phase-space are computed and investigated for the future COMPASS-Upgrade and MAST-Upgrade tokamaks.

In the JET DTE2 deuterium-tritium campaign, neutron diagnostics were employed to measure 14 MeV neutrons originating from D(T,n)4He reactions. In discharge 99965, a diamond matrix detector (KM14) and a magnetic proton recoil (MPRu) detector with a vertical and an oblique line-of-sight were used, respectively. At the timepoints of interest, a significant decrease in the expected diagnostic signals can be observed as electromagnetic wave heating in the ion cyclotron range of frequencies (ICRF) is switched off. Utilizing only TRANSP simulation data, the fast-ion distribution is found to have been likely composed mostly of trapped orbits. In contrast, analysis performed using orbit weight functions revealed that the majority of neutrons in the KM14 MeV and MPRu

We present new model results for H2O, O2, H2, O, and H in the atmosphere of Ganymede. The results are obtained from a collision-less 3D Monte-Carlo model that includes sublimation, ion and electron sputtering, and ion and electron radiolysis. Because Ganymede has its own magnetic field, its immediate plasma environment is particularly complex. The interaction between Ganymede's and Jupiter's magnetospheres makes it highly variable in both space and time. The recent Juno Ganymede flyby provided us with new data on the electron local environment. Based on the electron measurements recorded by the Jovian Auroral Distributions Experiment (JADE), we implement two electron populations, one for the moon's polar regions and one for the moon's auroral regions. Comparing the atmospheric contribution of these newly defined electron populations to the overall source and loss processes is one of the main goals of this work. Our analysis shows that for H2O, sublimation remains the most important source process even after accounting for the new electron populations, delivering more than three orders of magnitude more H2O molecules to the atmosphere than all other source processes combined. The source fluxes for O2 and H2, on the other hand, are dominated by radiolysis induced by the auroral electrons, assuming that the electron fluxes JADE measured during Juno's transit of Ganymede's magnetopause current layer are representative of auroral electrons. Atomic O and H are mainly added to the atmosphere through the dissociation of O2 and H2, which is primarily induced by auroral electrons. Our understanding of Ganymede's atmosphere today is mainly based on spectroscopic observations. The interpretation of spectroscopic data strongly depends on assumptions taken, though. Our analysis shows that for a holistic understanding of Ganymede's atmosphere, simultaneous observations of the moon's surface, atmosphere, and full plasma environment (thermal and energetic ions and electrons) at diff

The role of thermal fluctuations on the stimulated Raman backscattering instability is investigated by means of Vlasov and particle-in-cell (PIC) simulations in a regime of strong linear Landau damping of the Langmuir wave. The instability is initially convective and amplifies thermal noise, leading to a low-amplitude back-scattered laser sideband. Linear Landau damping of the Langmuir sideband modifies and flattens the electron velocity distribution function at the resonant velocity, leading to a gradual decrease in the Landau damping rate and an increase in the convective amplification. The Langmuir wave traps electrons resulting in a rapid nonlinear absolute instability and large amplitude flashes of backscattered light off large amplitude Langmuir waves with trapped electrons, leading to the production of hot electrons. Conditions for simulating realistic thermal noise with Vlasov and PIC simulations are discussed and defined., Funding Agencies|Strategic Research Program of Chinese Academy of Sciences [2022-06725]; Swedish Research Council [EP/R004773/1, EP/M009386/1]; EPSRC (UK) [XDA25050100]; Strategic Priority Research Program of Chinese Academy of Sciences [11991074, 12135009]; National Natural Science Foundation of China [101052200-EUROfusion]; European Union via the Euratom Research and Training Programme

Ablating a target with an ultraintense laser pulse can create a cloud of collisionless plasma. A density ramp forms, in which the plasma density decreases and the ion's mean speed increases with distance from the plasma source. Its width increases with time. Electrons lose energy in the ion's expansion direction, which gives them a temperature anisotropy. We study with one-dimensional particle-in-cell simulations the expansion of a dense plasma into a dilute one, yielding a density ramp similar to that in laser-plasma experiments and a thermal-anisotropy-driven instability. Non-propagating Weibel-type wave modes grow in the simulation with no initial magnetic field. Their magnetic field diffuses across the shock and expands upstream. Circularly polarized propagating Whistler waves grow in a second simulation, in which a magnetic field is aligned with the ion expansion direction. Both wave modes are driven by non-resonant instabilities, they have similar exponential growth rates, and they can leave the density ramp and expand into the dilute plasma. Their large magnetic amplitude should make them detectable in experimental settings., Funding: Swedish Research Council; [2022-06725]

We study plasma density variations within the ionosphere and their effects on trans-ionospheric signals, with a geodetic focus on Sweden from 2014 to 2023. We look for temporal, spatial, seasonal, and solar cycle patterns. We also discuss the percentage of occurrence of ionospheric irregularities and GNSS signal disturbances within the data at hand. We use in situ data collected by ESA-Swarm satellites and ground data provided by the Lantmäteriet-Swepos network ionosphere monitor. We find that high-latitude regions are susceptible to displaying more irregular electron density fluctuations (i.g., polar cap patches) than mid-latitudes. We also find that GNSS signal interference resulting in increased receivers’ positioning uncertainty is predominant at high latitudes. On the other hand, increased positioning uncertainty may be detected at noon in mid-latitude regions, mainly due to solar radiation exposure. Furthermore, hourly geomagnetic effects at high latitudes induce enhanced electron density fluctuations and positioning uncertainty at night. Findings also show more electron density fluctuations around winter and less in summer. Moreover, we find that the solar cycle influences the intensity of electron density fluctuations and positioning uncertainty, with the seasonal effects being more pronounced during periods of increased solar activity. Finally, results show that when ionospheric irregularities are observed, disturbances in GNSS signals may be detected, leading to imprecision in positioning services. Furthermore, we see that the absence of ionospheric irregularities results in a generally safe path for GNSS signals, which is beneficial for positioning accuracy. This comprehensive research enhances our understanding of ionospheric behavior in higher latitude environments and its impact on GNSS signals. Future research in this field could go deeper into the specific mechanisms driving electron density fluctuations and scintillation effects, explore additional

The current response of a hot magnetized plasma to a radio-frequency wave is non-local, turning the electromagnetic wave equation into an integro-differential equation. Non-local physics gives rise to wave physics and absorption processes not observed in local media. Furthermore, non-local physics alters wave propagation and absorption properties of the plasma. In this work, an iterative method that accounts for parallel non-local effects in 2D axisymmetric tokamak plasmas is developed, implemented, and verified. The iterative method is based on the finite element method and Fourier decomposition, with the advantage that this numerical scheme can describe non-local effects while using a high-fidelity antenna and wall representation, as well as limiting memory usage. The proposed method is implemented in the existing full wave solver FEMIC and applied to a minority heating scenario in ITER to quantify how parallel non-local physics affect wave propagation and dissipation in the ion cyclotron range of frequencies (ICRF). The effects are then compared to a reduced local plane wave model, both verifying the physics implemented in the model, as well as estimating how well a local plane wave approximation performs in scenarios with high single pass damping. Finally, the new version of FEMIC is benchmarked against the ICRF code TORIC., QC 20240502

The solar wind and its embedded magnetic field, the interplanetary magnetic field (IMF) together with magnetic reconnection power the large-scale plasma and magnetic flux circulation in the Earth's magnetosphere-ionosphere system. This circulation is termed as convection and its strength is controlled by the north-south IMF component (IMF Bz). In recent years, an interest has arisen to investigate the lesser-known role of the dusk-dawn component (IMF By) in convection. It has been previously known though that prevailing nonzero IMF By can cause plasma flow asymmetries in the high-latitude ionosphere, but how the magnetospheric flows, for instance, in the magnetotail plasma sheet are affected, remains to be investigated. In this article, we introduce the recent progress and the latest achievements in the research of the influence of IMF By on tail plasma sheet convection. The research progress has been rapid and it has revealed that both fast and slow convection are affected in a manner that is in accordance with the asymmetries observed in the ionospheric convection. The results indicate the significance of the IMF By component on magnetospheric convection and they represent a major advance in the field of solar wind-magnetosphere coupling.

The solar wind interacts with all solar system bodies, inducing different types of dynamics depending on their atmospheric and magnetic environments. We here outline some key open scientific questions related to this interaction, with a focus on the Moon and Mars, that may be addressed by future Mars and Moon missions by the European Space Agency's Human and Robotic Exploration programme. We describe possible studies of plasma interactions with bodies with and without an atmosphere, using multi-point and remote measurements, and energetic particle observations, as well as recommend some actions to take.

NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Ex- plorer (OSIRIS-REx) spacecraft arrived at the near-Earth rubble pile asteroid (101955) Bennu in December 2018, where it took high resolution images of the surface. The im- ages revealed that the surface is covered with boulders of various sizes. The morphology of these boulders can provide valuable information about the body’s history and the mechanical properties of the regolith. In this work, I use OSIRIS-REx images to map the outline of boul- ders on Bennu in two different geologic units: a Rugged Unit and a Smooth Unit. The two units are differentiated by surface texture, shape features and geologic features. This work was implemented using the open-source software QGIS. I compare the two units’ boulder morphology firstly in terms of boulder roughness by looking at the shape factors solidity (to what extent a boulder’s area equals that of its convex hull area) and circularity (to what extent a boulder’s perimeter is similar to the circumference of a circle with the same area). Then I study boulder compactness, by looking at the shape factors elongation (the ratio between its minor and major axis) and roundness (to what extent a boulder’s area resembles that of a circle enclosing the boulder). Despite the geologic differences, I find that there is no significant difference in the boulder roughness and compactness between the two units. Both regions’ boulders possess a large variation of values that overlap significantly. My results match well with laboratory impact experiments, implying that the regolith was created by a catastrophic impact, which is in agreement with Bennu’s status as a rubble-pile asteroid. I also find that the Smooth Unit tends to have smaller boulders (0.579 ± 0.35 m) with more boulders mapped (total 2426) than the Rugged Unit (0.711 ± 0.48 m, total 1774 boulders mapped). Finally, I show that smaller boulders tend to be rounder and less rough than larg

This study presents evidence of stably trapped electrons at Jupiter's moon Ganymede. We model energetic electron pitch angle distributions and compare them to observations from the Galileo Energetic Particle Detector to identify signatures of trapped particles during the G28 encounter. We trace electron trajectories to show that they enter Ganymede's mini-magnetospheric environment, become trapped, and drift around the moon for up to 30 min, in some cases stably orbiting the moon multiple times. Conservation of the first adiabatic invariant partially contributes to energy changes throughout the electrons' orbits, with additional acceleration driven by local electric fields, before they return to Jupiter's magnetosphere or impact the surface. These trapped particles manifest as an electron population with an enhanced flux compared to elsewhere within the mini-magnetosphere that are detectable by future spacecraft.

Induced magnetospheres form around planetary bodies with atmospheres through the interaction of the solar wind with their ionosphere. Induced magnetospheres are highly dependent on the solar wind conditions and have only been studied with single spacecraft missions in the past. Without simultaneous measurements of solar wind variations and phenomena in the magnetosphere, establishing a link between both can only be done indirectly, using statistics over a large set of measurements. This gap in knowledge could be addressed by a multi-spacecraft plasma mission, optimized for studying global spatial and temporal variations in the magnetospheric system around Venus, which hosts the most prominent example of an induced magnetosphere in our solar system. The MVSE mission comprises four satellites, of which three are identical scientific spacecraft, carrying the same suite of instruments probing different regions of the induced magnetosphere and the solar wind simultaneously. The fourth spacecraft is the transfer vehicle which acts as a relay satellite for communications at Venus. In this way, changes in the solar wind conditions and extreme solar events can be observed, and their effects can be quantified as they propagate through the Venusian induced magnetosphere. Additionally, energy transfer in the Venusian induced magnetosphere can be investigated. The scientific payload includes instrumentation to measure the magnetic field, electric field, and ion–electron velocity distributions. This study presents the scientific motivation for the mission as well as requirements and the resulting mission design. Concretely, a mission timeline along with a complete spacecraft design, including mass, power, communication, propulsion and thermal budgets are given. This mission was initially conceived at the Alpbach Summer School 2022 and refined during a week-long study at ESA's Concurrent Design Facility in Redu, Belgium.

Using the high-time-resolution data from the Magnetospheric Multiscale mission, precursor waves upstream of foreshock transient (FT) shocks are statistically investigated using the four-spacecraft timing method. The wave frequencies and wave vectors determined in the plasma rest frame (PRF) are shown to follow the cold plasma dispersion relation for whistler waves. Combining with the feature of the right-hand polarization in the PRF, the precursors are identified as whistler-mode waves around the lower hybrid frequency. The occurrence of whistler precursors is independent of the Alfvén Mach number and the FT shock normal angle. More importantly, all the whistler precursors have group velocities pointing upstream in the shock frame, suggesting the dispersive radiation to be a possible generation mechanism. The study improves the understanding of not only the whistler precursors but also the overall FT shock dynamics.

Context. Solar wind ions backscattering is a fundamental plasma-surface interaction process that may occur on all celestial bodies exposed to the solar wind and lacking a significant atmosphere or magnetosphere. Yet, observations have been limited to the regolith-covered Moon and Phobos, one of the Martian moons. Aims. We aim to expand our knowledge of the process to include comets by investigating the backscattering of solar wind protons from the surface of comet 67P/Churyumov-Gerasimenko. Methods. We used one of the ion spectrometers on board ESA s Rosetta spacecraft to search for evidence of backscattered solar wind protons from the cometary surface. The signal of interest was expected to be very weak and several statistical treatments of the data were essential to eliminate any influence from background noise and instrumental effects. Due to limited knowledge of the signal location within the observed parameter space, we conducted a statistical analysis to identify the most probable conditions for detecting the signal. Results. No significant solar wind backscattered protons were ever observed by the instrument. The statement applies to the large spectrum of observation conditions. An upper limit of the backscattered proton flux is given, as well as an upper limit of the backscattering efficiency of 9 A 104. Conclusions. The surface of comet 67P/Churyumov-Gerasimenko distinguishes itself as a notably weak reflector of solar wind protons, with its backscattering efficiency, at most, as large as the lowest observed backscattering efficiency from the lunar regolith.

In this study, we investigate statistical features of polar cap north (PCN) and south (PCS) indices in response to various interplanetary conditions (interplanetary magnetic field [IMF] orientation in three-dimensions) and terrestrial conditions (seasonal and magnetic local time [MLT] locations of the index stations). The concurrent PCN-PCS pairs for 1998–2002 and 2004–2018 are divided based on their sign type (positive-positive, negative-negative, negative-positive, and positive-negative PCN-PCS pairs) and time coverage (the times when both index stations are in the dawn/dusk MLT sector during northern summer/winter). Analyzing the IMF orientation dependence on the occurrence probabilities of concurrent indices and on the differences between the indices in various sign types for each time coverage reveals that the statistical features in PCN-PCS pairs obtained in the dawn MLT sector can be largely explained by the effects of the three-component IMF (related to the polar cap convection patterns) combined with season (related to the hemispheric asymmetry in solar illumination-induced ionospheric conductance). However, those obtained in the dusk MLT sector are controlled dominantly by seasonal effects rather than IMF orientation effects. Our findings indicate that PCN-PCS pair data provide local views about the solar wind-magnetosphere-ionosphere (SW-M-I) coupling system with different control efficiencies of IMF orientation and season depending on the MLT location of the stations. Therefore, introducing polar cap indices recorded simultaneously at various locations in both hemispheres and analyzing them are strongly required to infer global views of the coupled SW-M-I system in the open field regions with higher confidence.

Recent advancements in plasma physics are intensifying the demand for advanced diagnostic techniques in fusion research, particularly for the upcoming ITER fusion reactor. The ITER fusion reactor is projected to be ten times more powerful than its predecessors, imposing higher constraints on operational parameters. To meet ITER's requirements, such as the fuel ion ratio nt/nd and fuel ion temperature Ti, a High Resolution Neutron Spectrometer System (HRNS) has been proposed. This thesis focuses on the Thin-foil proton recoil (TPR) spectrometer, an integral part of the HRNS, with an emphasis on its application and validation within the ITER context. The research encompasses two main areas: spectrometer simulations and experimental validation. Through a combination of custom transport code and Geant4 simulations, the study investigates the optimization of the TPR spectrometer's design in terms of efficiency and energy resolution. Additionally, selected design performance under ITER-like conditions has been investigated. These simulations are critical in assessing the spectrometer's capabilities and limitations during operation at ITER. Subsequent experimental validation, conducted using a DT neutron generator and a TPR spectrometer prototype, verified the existing simulation framework in terms of energy resolution and background discrimination methods. We examined a Tandem neutron spectrometer, used in fusion plasma diagnostics at JET to further investigate TPR spectrometer diagnostic possibilities. Tandem spectrometer was operational during JET's first DT campaign, the spectrometer shares the neutron detection principles of the TPR. The fuel ion ratio nt/ntot was determined using the Tandem data together with inputs from PENCIL or TRANSP, for previously not analysed JET discharges. Our findings indicate that estimation of nt/ntot is feasible using either PENCIL or TRANSP. Furthermore, the research demonstrates that TPR based neutron spectrometers can be effec

When the supersonic solar wind interacts with Earth’s magnetosphere it forms a shock wave. However, due to the low densities in space, inter-particle collisions play an insignificant role in its dynamics. Earth's bow shock is an example of a collisionless shock, ubiquitous throughout the universe. Their dynamics are complex and their physics remains an active field of research. In this thesis, we use high-resolution measurements from NASA's Magnetospheric Multiscale (MMS) spacecraft to study the plasma wave activity across Earth’s bow shock and its effects on electron heating. In Paper I we train a convolutional neural network (CNN) to identify the different plasma regions that MMS crosses. In Paper II we use the results of this CNN to compile a database of time intervals in which MMS crosses Earth’s bow shock, which we use to find suitable events to tackle the science questions of interest. In Paper III we use multispacecraft methods to properly characterize obliquely propagating whistler waves running upstream of the shock. By analyzing the ion and electron distribution functions we find that their likely source is the instability between the incoming electrons and reflected ions. Shifting our focus to Debye scale electrostatic waves, in Paper IV we develop a method to measure their 3D wave vector based on single-spacecraft interferometry. We are in the process of using this method to study the evolution of Debye scale electrostatic waves across quasi-perpendicular shocks (see Chapter 7). Finally, in Paper V we investigate the electron heating mechanism across quasi-perpendicular shocks. We find the heating mechanism to depend on the Alfvénic Mach number in the deHoffman-Teller frame . We also find that at high the heating

Dark bubble cosmology is an alternative paradigm to compactification, which can circumvent issues of moduli stabilization and scale separation. In this paper we investigate how electromagnetic fields can be incorporated in this framework. Worldvolume fields backreact on the ambient universe in which the bubble expands, which in turn affects the energy-momentum distribution and the effective gravity induced on the brane. We compute these effects, showing that the resulting four-dimensional cosmology consistently includes electromagnetic waves.

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, selfmodulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma -based accelerators and represent the first characterization of hosing.

The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions, and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere. Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission. Here, we describe current community efforts to prepare for SMILE, and the benefits and context various experiments that have explicitly expressed support for SMILE can offer. A dedicated group of international scientists representing many different experiment types and geographical locations, the Ground-based and Additional Science Working Group, is facilitating these efforts. Preparations include constructing an online SMILE Data Fusion Facility, the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar, and the consideration of particular observing strategies and spacecraft conjunctions. We anticipate growing interest and community engagement with the SMILE mission, and we welcome novel ideas and insights from the solar-terrestrial community.

Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we explore the plasma properties of Martian magnetotail current sheets (CS), to further understand the solar wind interaction with Mars and ion escape. There are some CS exhibit energetic oxygen ions that show narrow beam structures in the energy spectrum, which primarily occurs in the hemisphere where the solar wind electric field (Esw) is directed away from the planet. On average, these CS have a higher escaping flux than that of the CS without energetic oxygen ion beams, suggesting different roles in ion escape. The CS with energetic oxygen ion beams exhibits different proton and electron properties to the CS without energetic oxygen ion beams, indicating their different origins. Our analysis suggests that the CS with energetic oxygen ion beams may result from the interaction between the penetrated solar wind and localized oxygen ion plumes.

We investigate turbulence in magnetic reconnection jets in the Earth’s magnetotail using data from the Magnetospheric Multiscale spacecraft. We show that signatures of a limited inertial range are observed in many reconnection jets. The observed turbulence develops on the timescale of a few ion gyroperiods, resulting in intermittent multifractal energy cascade from the characteristic scale of the jet down to the ion scales. We show that at sub-ion scales, the fluctuations are close to monofractal and predominantly kinetic Alfvén waves. The observed energy transfer rate across the inertial range is ∼108 J kg−1 s−1, which is the largest reported for space plasmas so far.

The Kelvin-Helmholtz (KH) instability can transport mass, momentum, magnetic flux, and energy between the magnetosheath and magnetosphere, which plays an important role in the solar-wind-magnetosphere coupling process for different planets. Meanwhile, strong density and magnetic field asymmetry are often present between the magnetosheath (MSH) and magnetosphere (MSP), which could affect the transport processes driven by the KH instability. Our magnetohydrodynamics simulation shows that the KH growth rate is insensitive to the density ratio between the MSP and the MSH in the compressible regime, which is different than the prediction from linear incompressible theory. When the interplanetary magnetic field (IMF) is parallel to the planet's magnetic field, the nonlinear KH instability can drive a double mid-latitude reconnection (DMLR) process. The total double reconnected flux depends on the KH wavelength and the strength of the lower magnetic field. When the IMF is anti-parallel to the planet's magnetic field, the nonlinear interaction between magnetic reconnection and the KH instability leads to fast reconnection (i.e., close to Petschek reconnection even without including kinetic physics). However, the peak value of the reconnection rate still follows the asymmetric reconnection scaling laws. We also demonstrate that the DMLR process driven by the KH instability mixes the plasma from different regions and consequently generates different types of velocity distribution functions. We show that the counter-streaming beams can be simply generated via the change of the flux tube connection and do not require parallel electric fields. The growth of Kelvin-Helmholtz (KH) instability is not sensitive to the density asymmetry Magnetic field asymmetry affects KH instability differently during northward and southward interplanetary magnetic field (IMF) conditions Different ion velocity distributions can be generated during northward IMF conditions

Polyimide foils were irradiated with MeV ions below charge state equilibrium and etched in sodium hypochlorite solution to measure the material depth below which ion tracks occurred. It was observed that no etchable ion tracks were formed in the first few nanometres of the foil as the electronic stopping power was below the damage threshold. The damage threshold was crossed at a certain depth in the foil and intermittent tracks began to form. The measurement of depth for crossing the damage threshold in polyimide enabled verification of the previously theoretical models for the evolution of nonequilibrium charge variation of electronic stopping power during charge state equilibration of energetic ions and explicitly demonstrated that the equilibration process plays a role in ion-induced nanostructure formation.

The experiments on medium-size stellarator Uragan-2M (U-2M) in Kharkiv, Ukraine, are carried on in support of the Wendelstein 7-X (W7-X) experimental program. The scenario ion cyclotron frequency range (ICRF) plasma production at the hydrogen minority regime had been experimentally tested on U-2M and was qualified at the Large Helical Device (LHD). The paper presents the results of further research on the ICRF plasma production. The ICRF discharge studies were carried out in a H2 + He mixture with a controlled hydrogen concentration ranging from few percents to 75%. The two-strap like antenna mimicks the W7-X antenna operated in monopole phasing. The applied RF power was in the range of ∼100 kW. Relatively dense plasma of up to Ne ∼ 1019 m−3 was produced near the first harmonic of the hydrogen cyclotron frequency. The maximum temperature of the electrons and ions was not more than a few tens of electron volt. The characteristic features of RF plasma production and the propagation of electromagnetic waves in the experimental conditions are discussed. The experiments on U-2M and LHD indicate that the minority scenario of ICRF plasma production appears to be scalable and could be used in large stellarator machines. This is, in particular, important for the future experiments ICRF production of target plasma in W-7X in conditions where electron cyclotron resonance heating start-up is not possible.

A comet flyby, like the one planned for ESA's Comet Interceptor mission, places stringent requirements on spacecraft resources. To plan the time line of in situ plasma and neutral gas observations during the flyby, the size of the comet magnetosphere and neutral coma must be estimated well. For given solar irradiance and solar wind conditions, comet composition, and neutral gas expansion speed, the size of gas coma and magnetosphere during the flyby can be estimated from the gas production rate and the flyby geometry. Combined with flyby velocity, the time spent in these regions can be inferred and a data acquisition plan can be elaborated for each instrument, compatible with the limited data storage capacity. The sizes of magnetosphere and gas coma are found from a statistical analysis based on the probability distributions of gas production rate, flyby velocity, and solar wind conditions. The size of the magnetosphere as measured by bow shock standoff distance is 105-106 km near 1 au in the unlikely case of a Halley-type target comet, down to a nonexistent bow shock for targets with low activity. This translates into durations up to 103-104 seconds. These estimates can be narrowed down when a target is identified far from the Sun, and even more so as its activity can be predicted more reliably closer to the Sun. Plasma and neutral gas instruments on the Comet Interceptor main spacecraft can monitor the entire flyby by using an adaptive data acquisition strategy in the context of a record-and-playback scenario. For probes released from the main spacecraft, the inter-satellite communication link limits the data return. For a slow flyby of an active comet, the probes may not yet be released during the inbound bow shock crossing.

Strong field physics close to or above the Schwinger limit are typically studied with vacuum as initial condition or by considering test particle dynamics. However, with a plasma present initially, quantum relativistic mechanisms such as Schwinger pair creation are complemented by classical plasma nonlinearities. In this work we use the Dirac-Heisenberg-Wigner formalism to study the interplay between classical and quantum mechanical mechanisms in the regime of ultrastrong electric fields. In particular, the effects of initial density and temperature on the plasma oscillation dynamics are determined. Finally, comparisons with competing mechanisms such as radiation reaction and Breit-Wheeler pair production are made.

We study the evolution of electrostatic plasma waves, using the relativistic Vlasov equation extended by the Landau-Lifshitz radiation reaction, accounting for the back-reaction due to the emission of single particle Larmor radiation. In particular, the Langmuir wave damping is calculated as a function of wave number, initial temperature, and initial electric field amplitude. Moreover, the background distribution function loses energy in the process, and we calculate the cooling rate as a function of initial temperature and initial wave amplitude. Finally, we investigate how the relative magnitude of wave damping and background cooling varies with the initial parameters. In particular, it is found that the relative contribution to the energy loss associated with background cooling decreases slowly with the initial wave amplitude.

TOFOR is a time-of-flight (TOF) neutron spectrometer located at the Joint European Torus (JET) with a vertical sightline of the JET plasma. It consists of 5 start (denoted S1) and 32 stop (denoted S2) plastic scintillation detectors which can be used in coincidence to generate a TOF spectrum. Spectroscopic analysis of the neutron TOF spectra produced by the JET plasma is regularly performed to determine, e.g., the fuel ion ratio and the presence of fast ion species in the fusion plasma. TOFOR has been upgraded with a new digital data acquisition (DAQ) system, denoted TOFu, which consists of 10 waveform digitizers with a total of 40 channels, 37 of which are connected to the photomultiplier output of the different S1 and S2 detectors. This paper presents a technical overview of the TOFu system and describes the offline analysis capabilities of TOFu which were not available with the previous DAQ system. Two experimental JET discharges are studied and used to show that the signal-to-background ratio is improved by almost 200% for the 2.5 MeV neutron signal and almost 400% for the 14 MeV neutron signal using the new offline analysis capabilities.

Electron temperature anisotropy-driven instabilities such as the electron firehose instability (EFI) are especially significant in space collisionless plasmas, where collisions are so scarce that wave-particle interactions are the leading mechanisms in the isotropization of the distribution function and energy transfer. Observational statistical studies provided convincing evidence in favor of the EFI constraining the electron distribution function and limiting the electron temperature anisotropy. Magnetic reconnection is characterized by regions of enhanced temperature anisotropy that could drive instabilities-including the electron firehose instability-affecting the particle dynamics and the energy conversion. However, in situ observations of the fluctuations generated by the EFI are still lacking and the interplay between magnetic reconnection and EFI is still largely unknown. In this study, we use high-resolution in situ measurements by the Magnetospheric Multiscale spacecraft to identify and investigate EFI fluctuations in the magnetic reconnection exhaust in the Earth's magnetotail. We find that the wave properties of the observed fluctuations largely agree with theoretical predictions of the non-propagating EF mode. These findings are further supported by comparison with the linear kinetic dispersion relation. Our results demonstrate that the magnetic reconnection outflow can be the seedbed of EFI and provide the first direct in situ observations of EFI-generated fluctuations.

The Earth's magnetosphere and its bow shock, which is formed by the interaction of the supersonic solar wind with the terrestrial magnetic field, constitute a rich natural laboratory enabling in situ investigations of universal plasma processes. Under suitable interplanetary magnetic field conditions, a foreshock with intense wave activity forms upstream of the bow shock. So-called 30 s waves, named after their typical period at Earth, are the dominant wave mode in the foreshock and play an important role in modulating the shape of the shock front and affect particle reflection at the shock. These waves are also observed inside the magnetosphere and down to the Earth's surface, but how they are transmitted through the bow shock remains unknown. By combining state-of-the-art global numerical simulations and spacecraft observations, we demonstrate that the interaction of foreshock waves with the shock generates earthward-propagating, fast-mode waves, which reach the magnetosphere. These findings give crucial insight into the interaction of waves with collisionless shocks in general and their impact on the downstream medium.

The plasma environment at a comet can be divided into different regions with distinct plasma characteristics. Two such regions are the solar wind ion cavity, which refers to the part of the outer coma that does not contain any solar wind ions anymore; and the diamagnetic cavity, which is the region of unmagnetized plasma in the innermost coma. From theory and previous observations, it was thought that under usual circumstances no solar wind ion should be observable near or inside of the diamagnetic cavity. For the first time, we report on five observations that show that protons near solar wind energies can also be found inside the diamagnetic cavity. We characterize these proton signatures, where and when they occur, and discuss possible mechanisms that could lead to protons penetrating the inner coma and traversing the diamagnetic cavity boundary. By understanding these observations, we hope to better understand the interaction region of the comet with the solar wind under nonstandard conditions. The protons detected inside the diamagnetic cavity have directions and energies consistent with protons of solar wind origin. The five events occur only at intermediate gas production rates and low cometocentric distances. Charge transfer reactions, high solar wind dynamic pressure and a neutral gas outburst can be ruled out as causes. We suggest that the anomalous appearance of protons in the diamagnetic cavity is due to a specific solar wind configuration where the solar wind velocity is parallel to the interplanetary magnetic field, thus inhibiting mass-loading and deflection.

Solar wind measurements carried out by NASA's Wind spacecraft before, during, and after the passing of an interplanetary coronal mass ejection (ICME), detected on 12 - 14 September 2014, have been used in order to examine several properties of magnetohydrodynamic (MHD) turbulence. Spectral indices and flatness scaling exponents of magnetic field, velocity, and proton density measurements were obtained, and provided a standard description of the characteristics of turbulence within different sub-regions of the ICME and its surroundings. This analysis was followed by the validation of the third-order moment scaling law for isotropic, incompressible MHD turbulence in the same sub-regions, which confirmed the fully developed nature of turbulence in the ICME plasma. The energy transfer rate was also estimated in each ICME sub-region and in the surrounding solar wind. An exceptionally high value was found within the ICME sheath, accompanied by enhanced intermittency, possibly related to the powerful energy injection associated with the arrival of the ICME.

Determination of the wave mode of short-wavelength electrostatic waves along with their generation mechanism requires reliable measurement of the wave electric field. We show that for such waves the electric field measured by Magnetospheric MultiScale becomes unreliable when the wavelength is close to the probe-to-probe separation. We develop a method, based on spin-plane interferometry, to reliably determine the full three-dimensional wave vector of the observed waves. We test the method on synthetic data and then apply it to ion acoustic wave bursts measured in the solar wind. By studying the statistical properties of ion acoustic waves in the solar wind, we retrieve the known results that the wave propagation is predominantly field aligned. We also determine the wavelength of the waves. We find that the nominal value is around 100 m, which when normalized to the Debye length corresponds to scales between 10 and 20 Debye lengths.

The Cassini spacecraft made in-situ measurements of Titan's plasma environment during 126 close encounters between 2004 and 2017. Here we report on observations from the Radio and Plasma Waves System/Langmuir probe instrument (RPWS/LP) from which we have observed, primarily on the outbound leg, a localized increase of the electron density by up to 150 cm−3 with respect to the background. This feature, appearing as an electron density spike in the data, is found during 28 of the 126 flybys. The data from RPWS/LP, the electron spectrometer from the Cassini Plasma Spectrometer package , and the magnetometer is used to calculate electron densities and magnetic field characteristics. The location of these structures around Titan with respect to the nominal corotation direction and the sun direction is investigated. We find that the electron density spikes are primarily observed on the dayside and ramside of Titan. We also observe magnetic field signatures that could suggest the presence of current sheets in most cases. The density spikes are extended along the trajectory of the spacecraft with the horizontal scale of ∼537 ± 160 km and vertical scale ∼399 ± 163 km. We suggest that the density spikes are formed as a result of the current sheet formation.

Electron heating at collisionless shocks in space is a combination of adiabatic heating due to large-scale electric and magnetic fields and non-adiabatic scattering by high-frequency fluctuations. The scales at which heating happens hints to what physical processes are taking place. In this letter, we study electron heating scales with data from the Magnetospheric Multiscale (MMS) spacecraft at Earth's quasi-perpendicular bow shock. We utilize the tight tetrahedron formation and high-resolution plasma measurements of MMS to directly measure the electron temperature gradient. From this, we reconstruct the electron temperature profile inside the shock ramp and find that the electron temperature increase takes place on ion or sub-ion scales. Further, we use Liouville mapping to investigate the electron distributions through the ramp to estimate the deHoffmann-Teller potential and electric field. We find that electron heating is highly non-adiabatic at the high-Mach number shocks studied here. Plain Language Summary Shock waves appear whenever a supersonic medium, such as a plasma, encounters an obstacle. The plasma, which consists of charged ions and free electrons, is heated by the shock wave through interactions with the electromagnetic fields. In this work, we investigate how electrons are heated at plasma shocks. A key parameter to electron heating is the thickness of the layer where the heating takes place. Here, we use observations from the four Magnetospheric Multiscale spacecraft that regularly cross the standing bow shock that forms when the supersonic plasma, known as the solar wind, encounters Earth's magnetic field. We find that the thickness of the shock is larger than previously reported and is on the scales where ion physics dominate. We also find that the electron heating deviates significantly from simple adiabatic heating.

A collisionless shock is a self-organized structure where fields and particle distributions are mutually adjusted to ensure a stable mass, momentum and energy transfer from the upstream to the downstream region. This adjustment may involve rippling, reformation or whatever else is needed to maintain the shock. The fields inside the shock front are produced due to the motion of charged particles, which is in turn governed by the fields. The overshoot arises due to the deceleration of the ion flow by the increasing magnetic field, so that the drop of the dynamic pressure should be compensated by the increase of the magnetic pressure. The role of the overshoot is to regulate ion reflection, thus properly adjusting the downstream ion temperature and kinetic pressure and also speeding up the collisionless relaxation and reducing the anisotropy of the eventually gyrotropized distributions.