Plasma entities, known as magnetosheath jets, with higher dynamic pressure than the surrounding plasma, are often seen at Earth. They generate waves and contribute to energy transfer in the magnetosheath. Affecting the magnetopause, they cause surface waves and transfer energy into the magnetosphere, causing throat auroras and magnetic signatures detectable on the ground. We show that jets exist also beyond Earth’s environment in the magnetosheath of Mars, using data obtained by the MAVEN spacecraft. Thus, jets can be created also at Mars, which differs from Earth by its smaller bow shock, and they are associated with an increased level of magnetic field fluctuations. Jets couple large and small scales in magnetosheaths in the solar system and can play a similar part in astrophysical plasmas.

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.

<p>In this study we have identified wide quasi-perpendicular bow shock events at Mars. We have compared these to thin quasi perpendicular bow shock events in an effort to identify a cause. To ensure they are quasi-perpendicular we have used two methods to determine the normal of the shock, the local mixed-mode coplanarity method, and a global normal from a bow shock model. We found that the wide bow shocks were on average 370 km (5 r<sub>gi</sub>), and the thin ones on average 30 km (0.7 r<sub>gi</sub>). Both the wide and thin events were found at the nose and at the flank, with no difference in location. We looked into whether factors that affect standoff distance also affect width. Magnetosonic Mach number proved not to affect the width. At comets it is known that standoff distance of the shock is affected by mass loading, and we investigated whether that could be the cause also at Mars. We found however that the wide shocks on average have lower upstream ion density of H<sup>+</sup>, H<sub>2</sub><sup>+</sup>, O<sup>+</sup> and O<sub>2</sub><sup>+</sup>, leading to the conclusion that mass loading is unlikely to be the cause. We investigated the difference in downstream and upstream temperature for all events and found that the wide events had a higher difference in the flow direction, which could mean that more energy is transferred at the wider bow shock. </p> <p>Furthermore we have looked into bow shock asymmetry with respect to the electric convective field. The asymmetry has been observed at the infant bow shock at comets, and due to the similarity of Mars and comets, such as the lack of a dipole field and scale of system relative to ion gyroradius, there is grounds to believe it can affect also the Martian bow shock. </p>