Anomalous electron heating in laboratory magnetized quasi-perpendicular collisionless shocks

We present laboratory results from supercritical, magnetized collisionless shock experiments (MA 10, β~ 1). We report the first observation of fully-developed shocks ($R=4$ compression ratio and a downstream region decoupled from the piston) after seven upstream ion gyration periods. A foot ahead of the shock exhibits super-adiabatic electron and ion heating. We measure the electron temperature Tₑ = 115 eV and ion temperature Tᵢ = 15 eV upstream of the shock; whereas, downstream, we measure Tₑ=390 eV and infer Tᵢ=340 eV, consistent with both Thomson scattering ion-acoustic wave spectral broadening and Rankine-Hugoniot conditions. The downstream electron temperature has a $30$-percent excess from adiabatic and collisional electron-ion heating, implying significant collisionless anomalous electron heating. Furthermore, downstream electrons and ions are in equipartition, with a unity electron-ion temperature ratio Tₑ/Tᵢ = 1.2.