Emission of nonlinear whistler waves at the front of perpendicular supercritical shocks: Hybrid versus full particle simulations

Abstract

New behavior of strictly perpendicular shocks in supercritical regime is analyzed with the help of both two‐dimensional (2‐D) hybrid and full particle electromagnetic simulations. Surprisingly, in both simulation cases, the shock front region appears to be dominated by emission of coherent large amplitude whistler waves for some plasma conditions and shock regimes. These whistler waves are oblique with respect to the shock normal as well as to the upstream magnetic field and are phase‐standing in the shock rest frame. A parametric study shows that these whistler waves are emitted in 2‐D perpendicular shocks and, simultaneously, the self‐reformation of the shock front associated with reflected ions disappears; the 2‐D shock front is almost quasi‐stationary. In contrast, both corresponding one‐dimensional (1‐D) hybrid and full particle simulations performed in similar plasma and Mach regime conditions show that the self‐reformation takes place for 1‐D perpendicular shock. These results indicate that the emission of these 2‐D whistler waves can inhibit the self‐reformation in 2‐D shocks. Possible generating mechanisms of these waves emissions and comparison with previous works are discussed.