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EP: Fachverband Extraterrestrische Physik

EP 1: Astrophysics I

EP 1.3: Vortrag

Montag, 16. März 2026, 15:30–15:45, KH 01.019

On the cosmic-ray diffusion tensor in dynamical galactic halos — Jens Kleimann¹, •Horst Fichtner¹, Michael Stein², Ralf-Juergen Dettmar², Dominik Bomans², and Sean Oughton³ — ¹Theoretische Physik IV, Ruhr-Universität Bochum, Germany — ²Astronomisches Institut, Ruhr-Universität Bochum, Germany — ³Department of Mathematics, University of Waikato, New Zealand

Galactic halos separate the interstellar from the intergalactic medium. One question related to their physics is: How are cosmic rays transported within these dynamic regions of low density plasma permeated by a turbulent magnetic field? An understanding of cosmic-ray transport in galactic halos is of significance for explaining, e.g., the radio continuum measurements of synchrotron radiation from energetic electrons. Of central importance for the transport is the spatial diffusion tensor of cosmic rays, which can be computed in an ab-initio manner if the turbulence in the background medium is known. After a ’hydrodynamic validation’, which revealed a persistent instability of the near-axis flow and could be traced to the galaxy mass, we present numerical solutions of the Reynolds-averaged single-fluid MHD equations. This way we obtained the physical properties of both large-scale MHD and small-scale turbulent quantities and, by employing a state-of-the-art nonlinear theory, the coefficients of parallel and perpendicular diffusion. The simulation results reveal variations in turbulence quantities in a dynamical halo that translate in a significant variation of the corresponding diffusion tensor of cosmic rays.

Keywords: cosmic rays; diffusive transport; galactic halos; turbulence; MHD