Speaker
Description
Over the past decades, there has been growing observational and theoretical evidence that cosmic-ray-induced instabilities play an important role in both acceleration and transport of cosmic rays (CRs). For instance, the efficient acceleration of charged particles in supernova remnant shocks requires rapidly growing instabilities, so much so that none of the proposed processes seem sufficient to warrant acceleration to PeV energies. At the same time, there has been growing evidence of suppressed diffusivity around pulsar wind nebulae, in the form of the so-called TeV halos, which also seems to suggest that something peculiar is being caused by the particles escaping these sources.
In this work, we investigate whether an acoustic instability triggered by the presence of a CR pressure gradient can lead to significant self-confinement of charged particles in the vicinity of shocks, as well as of CRs escaping pulsar wind nebulae surrounded by a bow shock. We validate the expected growth rate and diffusion coefficient suppression induced by such instability using magnetohydrodynamic (MHD) and MHD + particle-in-cell simulations.
