The fine structure of the subsolar MPB current layer from MAVEN observations: Implications for the Lorentz force

Abstract

<p>We report on the local structure of the Martian subsolar Magnetic Pileup Boundary (MPB) from minimum variance analysis of the magnetic field measured by the MAVEN spacecraft for six orbits. In particular, we detect a well defined current layer within the MPB’s fine structure and<br>provide a local estimate of its current density and compare these results with the current density obtained by multi-fluid simulations.<br>This current is of the order of hundreds of nAm<sup>-2</sup> which results in a sunward Lorentz force of the order of 10<sup>-14</sup> Nm<sup>-3</sup>. We compare these results with multifluid numerical simulations.<br>This force is associated with the gradient of the magnetic pressure, it accounts for the deflection of the solar wind ions near the MPB and for the acceleration of solar wind electrons which carry the interplanetary magnetic field through the MPB into the MPR. We also find that the<br>thickness of the MPB current layer is of the order of both the upstream (magnetosheath) solar wind proton inertial length and convective gyroradius. The former is consistent with the demagnetization of the ions due to the Hall electric field, an effect observed recently at the Earth magnetopause, while the latter would imply kinetic processes are important at the MPB.<br>This study supports recent results that report the presence of a steady current system around Mars in a similar way to the Earth.</p>