Reconnection and Turbulence in the Bow Shock Transition

Exploration of Earth’s bow shock has revealed that the disordered or turbulent shock transition region can generate thin current sheets at ion and electron kinetic scales. These structures can undergo magnetic reconnection, which can contribute significantly to particle heating and dissipation, and hence to the energetics of the shock. I will first discuss the observational evidence for magnetic reconnection at the bow shock, with principal focus on NASA’s Magnetospheric Multiscale mission (MMS). Using MMS, we have performed broad surveys of current structures within both the shock transition region itself and the magnetosheath further downstream. These surveys demonstrate that this phenomenon is common across a broad range of shock parameters, and that the prevalence of current sheets reduces with distance from the shock. Second, I will explore the mechanisms for generating reconnecting current sheets in the shock layer using a series of hybrid and fully-kinetic particle-in-cell simulations. These simulations show that instabilities of whistler waves in the shock foot can generate reconnecting current sheets and magnetic islands, which can survive through the shock layer and propagate far downstream into the magnetosheath.