Role of Nonlinear Landau Damping for Cosmic-Ray Transport

We present the first assessment, using hybrid PIC simulations, of the role of nonlinear Landau damping in the process of self-generated scattering in a high β plasma, conditions appropriate for CR scattering in the halo of the Galaxy. The drift speed of CRs reduces due to scattering, but remains super-Alfvénic due to damping. Furthermore, this damping process manifests itself in the form of heating of the background plasma. We also show that the damping leads to an inverse cascade process, consisting of producing nonresonant large scale modes, a novel result with many potential phenomenological implications.