The evolution of the electric field at a nonstationary perpendicular shock

Abstract

Particle-in-cell simulations evidenced that supercritical, quasiperpendicular shocks are nonstationary and may suffer a self-reformation on the ion gyroscale. In this brief communication, we investigate the evolution of the electric field at a nonstationary, supercritial perpendicular shock. The contributions of the ion Lorentz, Hall, and electron pressure terms to the electric field are analyzed. During the evolution of the perpendicular shock, a new ramp may be formed in front of the old ramp, and its amplitude becomes larger and larger. At last, the new ramp exceeds the old one, and such a nonstationary process can be formed periodically. When the new ramp begins to be formed in front of the old ramp, the Hall term becomes more and more important. The electric field Ex is dominated by the Hall term when the new ramp exceeds the old one. The significance of the evolution of the electric field on shock acceleration is also discussed.