Role of electron physics in slow mode shocks

Much of the theoretical understanding concerning the structure and essential properties of the slow mode shock has been obtained from hybrid calculations in which a full kinetic description is used for the ions while the electrons are approximated as a massless adiabatic fluid. Owing to the relatively broad spatial and relatively slow temporal scales of the slow shock, one would expect this approximation to be well justified. In this work we reexamine the importance of electron dynamics using one-dimensional fully kinetic simulations which fully resolve all relevant spatial and temporal electron scales. The resulting shock structure and ion heating are in excellent agreement with hybrid simulations, indicating that the dissipation arising from kinetic electrons is relatively minor. However, electron heating is somewhat larger, and clear non-Maxwellian features are observed. In the upstream region, back-streaming electrons give rise to double-peaked distributions, while in the downstream region, bi-Maxwellian distributions are observed with Tell > T e ⊥. Although the acceleration mechanism for the back-streaming electrons is not fully understood, we present evidence that resonant wave-particle interactions may play an important role.

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