Thin current sheets downstream of the Earth’s bow shock

Abstract:

The Earth’s bow shock has been the primary laboratory for collisionless shock research for decades. In the absence of particle collisions, such shocks are rich in particle and field phenomena, including non-thermal particle energization/heating, particle acceleration, waves and turbulence. The primary shock transition is readily identified in spacecraft data and is believed to be the prime location for the initiation of the processes responsible for the partition of incident energy flux amongst the various particle populations and electromagnetic fields. However, the disparate signatures of those processes persist well into the downstream region. Recent reports show that magnetic phenomena, including the generation of thin current sheets and magnetic reconnection are present both in the main shock transition and in the downstream magnetosheath. We have studied a traversal of the subsolar magnetosheath by the MMS spacecraft, characterizing and quantifying the occurrence and consequences of thin current sheets in terms of plasma heating and structure. The observations suggest that such sheets play a role in the overall relaxation of the magnetosheath plasma as it progresses toward the magnetopause.