The Issue with Diffusive Shock Acceleration
arXiv:1909.06288
Abstract
We discuss the recent developments in the theory of diffusive shock acceleration (DSA) by using both first-principle kinetic plasma simulations and analytical theory based on the solution of the convection/diffusion equation. In particular, we show how simulations reveal that the spectra of accelerated particles are significantly steeper than the predicted by the standard theory of DSA for strong shocks, in agreement with several observational pieces of evidence. We single out which standard assumptions of test-particle and non-linear DSA are violated in the presence of strong (self-generated) magnetic turbulence and put forward a novel theory in better agreement with the particle spectra inferred with multi-wavelength observations of young SN remnants, radio-supernovae, and Galactic cosmic rays.
8 pages, 2 figures, 36th International Cosmic Ray Conference (ICRC2019), held July 24th-August 1st, 2019 in Madison, WI, U.S.A