Cross-Shock Potential Electron Heating in 2D PIC Simulations of Quasi-Perpendicular Low-Beta Shocks

We study thermal electron heating in 1D and 2D PIC simulations of collisionless quasi-perpendicular shocks. We employ ion/electron mass ratio 200, fast Mach number 1--4, total plasma beta 0.25, and pre-shock magnetic field 55--85$^\circ$ from shock normal. We first focus on one subcritical shock with a phase-standing whistler wave precursor along the shock normal and little to no ion reflection. The heating is well described by a cross-shock parallel potential comprising both narrow peaks and a secular rise spanning the length of the shock's whistler precursor. The potential peaks coincide with magnetic troughs and host a broad spectrum of field-aligned electron acoustic waves. The electron temperature and potential jumps are lower in 2D than in 1D, which we attribute to enhanced phase-space mixing in 2D. In the parameter sweep of Mach number and pre-shock magnetic field angle, we find that the cross-shock potential is more sensitive to field angle in 1D than in 2D.