Institute for Advanced Study Astrophysics Seminar

Nonlinear magnetic structures can be generated in the vicinity of collisionless shocks by streaming of accelerated particles and as part of the shock structure evolution. I will discuss the effects of these nonlinearities on particle pre-heating and injection into the shock acceleration process. Such fluctuations provide a way for the shock to continuously adjust the level of injection that leads to a nonlinear steady state. I will present the results of test particle, paritlce-in-cell, and MHD-PIC simulations that allow probing these effects on different spatial and temporal scales. In nonrelativistic to mildly relativistic shocks, applicable to supernova remnants, radio supernovae, or internal shocks in GRBs, the nonlinear structures can lead to steeper spectra of accelerated electrons. In relativistic shocks, they are responsible for the vigorous shock reformation, generation of vorticity at the shock, and the survival of downstream amplified magnetic field.