Effects of electron pressure in quasi‐parallel collisionless shocks

Abstract

The effects of a finite electron pressure on quasi‐parallel collisionless shocks are examined by means of numerical simulations. The simulation is performed using a nonperiodic hybrid code in which the ion dynamics are followed exactly and the electrons are treated as a massless fluid of finite pressure. The results of the simulations show that the electron pressure significantly improves the stationarity of the shock structure. The finite electron pressure also leads to an electrostatic potential across the shock as expected. The potential structure is localized and stable at a low‐Alfvén Mach number (MA = 2), but for a higher Mach number (MA = 4) it is nonlocal and unstable. In either case the change in potential energy is on the order of the downstream electron parallel thermal energy. Power spectral analysis of the upstream waves shows that they are right‐hand polarized whistlers phase standing in the shock frame.