The Structure of the Martian Quasi-perpendicular Supercritical Shock as
seen by MAVEN
Abstract
The Martian bow shock is a rich example of a supercritical, mass-loaded
collisionless shock that coexists with ultra-low frequency upstream
waves that are generated by the pick-up of exospheric ions. Its small
size (comparable with the solar wind ion gyroradius) raises questions
related to which particle acceleration and energy dissipation mechanism
can take place. The study of the Martian shock structure is crucial to
comprehend its microphysics and is of special interest to understand the
solar wind - planet interaction with a virtually unmagnetized body. We
report on a complete identification and first characterization of the
supercritical substructures of the Martian quasi-perpendicular shock,
under the assumption of a moving shock layer, using MAVEN magnetic field
and solar wind plasma observations for two examples of shock crossings.
We obtained substructures length-scales comparable from those of the
Terrestrial shock, with a narrow shock ramp of the order of a few
electron inertial lengths. We also observed a well defined foot (smaller
than the proton convected gyroradius) and overshoot that confirm the
importance of ion dynamics for dissipative effects.