Microinstabilities in the Transition Region of Weak Quasi-perpendicular Intracluster Shocks

Microinstabilities play important roles in both entropy generation and particle acceleration collisionless shocks. Recent studies have suggested that the transition zone of quasi-perpendicular ($Q_{\perp}$) shocks high-beta ($\beta=P_{\rm gas}/P_{\rm B}$) intracluster medium (ICM), ion temperature anisotropy due to reflected-gyrating ions could trigger Alfv\'en cyclotron (AIC) instability ion-mirror instability, while electron induced by magnetic field compression excite whistler electron-mirror instability. Adopting numerical estimates for anisotropies found particle-in-cell (PIC) simulations $Q_{\perp}$-shocks with sonic Mach numbers, $M_{\rm s}=2-3$, we carry out a linear stability analysis these microinstabilities. The kinetic properties microinstabilities ensuing plasma waves on scales are described wide ranges parameters, including dependence $\beta$ ion-to-electron mass ratio. In addition, nonlinear evolution examined performing 2D PIC periodic boundary conditions. We find $\beta\approx 20-100$, AIC induce ion-scale generate shock surface ripples supercritical above critical number, AIC}^{*} \approx 2.3$. Also electron-scale generated primarily high-$\beta$ resulting multi-scale from thought be essential injection diffusive mechanism ICM.