Collisionless Shock as a Self-Regulatory System

This is the authors' abstract. We don't add key points for this paper.

A magnetohydrodynamical (MHD) shock is a discontinuity with a plasma flow across it. Conservation of mass, momentum, and energy requires the corresponding fluxes to be equal on both sides of the discontinuity. The tangential components of the electric field do not change either. A collisionless shock is not a discontinuity. Collisionless shocks have nontrivial transition regions, determined by the nonlinear interaction of charged particles with the electromagnetic fields. Whatever the interaction and structure may be, the conservation laws and the electrodynamic constraints must be maintained throughout. Depending on the incident plasma parameters, the shock structure evolves to adjust itself to the conservation laws. Self-regulation means that the required structure develops even if we do not understand the specific microscopic mechanisms of the structure development. We review here the basic field profiles and ion behavior of self-regulating shocks.