On magnetic field amplification and particle acceleration near non-relativistic collisionless shocks: Particles in MHD Cells simulations

We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and supra-thermal particles. Such interaction is depicted by combining a grid-based magneto-hydrodynamics description of the thermal fluid with particle-in-cell techniques devoted to the dynamics of supra-thermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider non-relativistic super-Alfénic shocks with various magnetic field obliquity. We recover all the features from previous studies when the magnetic field is parallel to the normal to the shock. In contrast with previous particle-in-cell and hybrid simulations, we find that particle acceleration and magnetic field amplification also occur when the magnetic field is oblique to the normal to the shock but on larger timescales than in the parallel case. We show that in our oblique shock simulations the streaming of supra-thermal particles induces a corrugation of the shock front. Such oscillations of both the shock front and the magnetic field then locally helps the particles to enter the upstream region and to initiate a non-resonant streaming instability and finally to induce diffuse particle acceleration.