Michał Hanasz

Institute of Astronomy, Nicolaus Copernicus University

Session X: Poster session

Thursday 14th September 2023 12:00 – 13:00

abstract:
Recent theoretical and numerical studies incorporating cosmic rays (CRs) into the global modelling of magnetized interstellar medium demonstrate that CRs can play an essential role in generating large-scale galactic magnetic fields while driving galactic winds.

We construct a global model of NGC891 based on the observational characteristics of this galaxy. We assume that on large scales, the dynamics of the magnetized ISM is driven by Cosmic Rays. We apply the algorithm of energy-dependent propagation of CR electrons in the ”Cosmic Ray Energy SPectrum” (CRESP) module of PIERNIK MHD code to model CR propagation in this galaxy. The overall propagation of cosmic rays is described by an energy-dependent diffusion-advection equation. We assume a piece-wise power-law, isotropic CR distribution function and apply a conservative, finite volume-type propagation of CR gas in momentum space.

The numerical models exhibit CR-driven galactic and magnetic field amplification by CR-driven dynamo. We perform a parameter study of the system by varying the efficiency of conversion of supernova energy to CRs, the magnitude and momentum dependence of the CR electron diffusion coefficients. We consider the advection, diffusion, adiabatic changes, synchrotron, and inverse-Compton losses.
We use the dynamical models of spectral evolution of synchrotron emitting electrons to generate synchrotron emission maps at different radio frequencies together with maps of spectral index and Faraday rotation. We demonstrate that including the spectral evolution of CR electron population, combined with MHD modelling of galaxies, opens new opportunities for observational diagnostics of ISM dynamics and CR propagation parameters and for verification of galactic magnetic field structures and amplification models.