In theory the width of the quasi-perpendicular bow shock ramp is on the scale of a few electron inertial lengths, but as this work will show the quasi-perpendicular bow shock at Mars is often wider. This is important because it implies that the conditions at Mars create a behaviour at the shock which cannot be described by current theory. Furthermore, the width could affect processes at the shock such as energy transfer of the ions and their subsequent thermalization. To investigate the cause of the width, two sets of quasi-perpendicular bow shock crossings measured by MAVEN are compared, one of unusual width (average 370 km or 5r$_{gi}$), and one of typical width (average 30 km or 0.7r$_{gi}$). These sets are labeled wide and thin shocks respectively. It is seen that the wide shocks have no distinct overshoot and have a higher level of magnetic field fluctuations than the thin shocks. Factors that are known to affect the standoff distance, such as the magnetosonic Mach number and mass loading of the solar wind by planetary species, were found not to affect the width of the bow shock. It is found that the temperature of the solar wind plasma increases more as it passes through a wide than a thin shock, indicating that ions are thermalized to a larger extent than at thin shocks. The larger-than-predicted by theory width of the Martian quasi-perpendicular bow shock indicate that there are conditions at Mars which we do not yet understand.

Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from 0.1RE to 5.0RE (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on Graphics Processing Units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.

Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from 0.1 RE to 5.0 RE (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on Graphics Processing Units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.

The present atmosphere of Venus contains almost no water, but recent measurements indicate that in its early history Venus had an Earth-like ocean. Understanding how the Venusian atmosphere evolved is important not only for Venus itself, but also for understanding the evolution of other planetary atmospheres. In this study, we quantify the escape rates of oxygen ions from the present Venus to infer the past of the Venusian atmosphere. We show that an extrapolation of the current escape rates back in time leads to the total escape of 0.02-0.6 m of a global equivalent layer of water. This implies that the loss of ions to space, inferred from the present state, cannot account for the loss of an historical Earth-like ocean. We find that the O+ escape rate increases with solar wind energy flux, where more energy available leads to a higher escape rate. Oppositely, the escape rate decrease slightly with increased EUV flux, though the small variation of EUV flux over the measured solar cycle may explain the weak dependency. These results indicate that there isn’t enough energy transferred from the solar wind to Venus’ upper atmosphere that can lead to the escape of the atmosphere over the past 3.9 billion years. This means that the Venusian atmosphere didn’t have as much water in its atmosphere as previously assumed or the present-day escape rates don’t represent the historical escape rates at Venus. Otherwise, some other mechanisms have acted to more effectively remove the water from the Venusian atmosphere.

On the bow shock in front of Earth flows current due to the curl of interplanetary magnetic field across the shock. It is uncertain whether the bow shock current closes on the magnetopause, into the ionosphere along magnetic field lines, or both. We present simultaneous observations from MMS, AMPERE, and DMSP during a period of strong $B_y$, weakly negative $B_z$, and small $B_x$. This IMF orientation should lead to current flowing mostly south-north on the shock. AMPERE shows current poleward of the Region 1 currents flowing into the northern polar cap and out of the south, consistent with bow shock current closing along open field lines; a DMSP flyover confirms that this current is poleward of the convection reversal boundary. Additionally, we investigate bow shock current closure for these conditions using an MHD simulation. We conclude that the evidence points to partial closure of bow shock current through the ionosphere.

Geomagnetically induced currents or GICs are signatures of a rapidly time-varying magnetic field (dB/dt) and occur mainly during substorms and storms. When, where and why exactly GICs may occur, is still vague. Thus, we investigated storms for the last 40 years (from 1980 with a storm-list created by W.T. Walach) and analyzed the negative and positive dB/dt spikes (threshold of 500 nT/min) in the north and east component using a worldwide coverage (SuperMAG). Our analysis confirmed the existence of two dB/dt spikes “hotspots” located in the pre-midnight and in the morning MLT sector, independently of the geographic location of the stations. The associated physical ionospheric phenomena are most probably substorm current wedge (SCW) onsets and westward travelling surges (WTS) in the evening sector, and wave- or vortex-like current flows in Omega bands in the morning sector. Additionally, we observed a spatio-temporal evolution of the negative northern dB/dt spikes. The spikes initially occur in the pre-midnight sector, and then develop in time towards the morning sector. This spatio-temporal sequence is correlated with bursts in the AE index, and can be repeated several times throughout a storm. Finally, we investigated the intensity (Dst and AE) of the storms compared to the number of dB/dt spikes, but we did not find any correlation. This result implies that moderate storm with many spikes can be as (or more) dangerous for ground-based infrastructures than a major storm with fewer dB/dt spikes. Our findings may help to improve the GICs forecast to accurately predict dB/dt spikes.

Plasma structures with enhanced dynamic pressure, density or speed are often observed in Earth’s magnetosheath. We present a statistical study of these structures, known as jets and fast plasmoids, in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks. Using measurements from the four Magnetospheric Multiscale (MMS) spacecraft and OMNI solar wind data from 2015–2017, we present observations of jets during different upstream conditions and in the wide range distances from the bow shock. Jets observed downstream of the quasi-parallel bow shock are seen to propagate deeper and faster into the magnetosheath and on towards the magnetopause. We estimate the shape of the structures by treating the leading edge as a shock surface, and the result is that the jets are elongated in the direction of propagation but also that they expand more quickly in the perpendicular direction as they propagate through the magnetosheath.