Synchrotronsignatures fromthecosmic-raydrivendynamo Dominik Wólta´nski, Mateusz Ogrodnik & Michał Hanasz Centre for Astronomy, Nicolaus Copernicus University, Toru´n, Poland Abstract We investigate synchrotron emission of galactic interstellar medium with the aid of a new Cosmic Ray Energy Spectrum Module (CRESP) for modeling energy-dependent transport of CR electrons. The module solves the Focker-Planck equation for a piece-wise power-law distribution function, with synchrotron and adiabatic cooling effects taken into account together with diffusive and advective propagation of CR electrons on an Eulerian grid. To demonstrate capabilities of the new module we perform numerical simulations of the CR electron spectrum in a galaxy similar to the Milky Way. The simulation results allow us to construct synthetic radio-maps of synchrotron radio-emission. Motivation Numerical studies of dynamical effects of cosmic rays in galaxies, including magnetic ﬁeld ampli- ﬁcation and galactic winds relying on a single- component propagation of CRs (Schlickeiser & Lerche, 1985), demonstrated formation of X-shaped magnetic ﬁelds in galactic halos (Hanasz, Wólta´nski & Kowalik, 2009) as well as magnetic arms (Beck, 2016) (Kulpa-Dybeł et al., 2011). This simpliﬁed treatment of CRs does not enable, however, to model galactic synchrotron emission with precision sufﬁ- cient to confront CR propagation models with the wealth of data coming from radio observations. In this contribution we demonstrate that coupling the MHD system of equations with the CRESP solver of Focker-Planck equation, within PIERNIK code (see poster by Mateusz Ogrodnik et al), makes it pos- sible to model evolution of the CR electron spectrum, and thereby to construct synthetic radio-maps of po- larized synchrotron emission from disk galaxies. ISM model with CR protons and electrons We assume that magnetized galactic interstellar medium (ISM) is stratiﬁed by vertical gravity of the stellar and dark matter components. The initial dis- tribution of interstellar gas and galactic gravity fol- low the model of the Milky Way by Ferriere (1998), while regular initial magnetic ﬁeld is assumed to be purely toroidal and its strength corresponds to pressure equilibrium with thermal gas. The basic characteristics of the model are similar to the global model of CR-driven dynamo by Hanasz, Wólta´nski & Kowalik (2009), except that initial magnetic ﬁeld is currently set near energy equipartition with thermal gas. The thermal gas component is described by the stan- dard set of MHD equations. We assume that super- novae (SNe) explode randomly in the disk and that 10% of SN explosion energy is converted to energy of CRs consisting of CR protons and electrons, while the thermal energy output from SNe is neglected. We assume that CR protons diffuse anizotropically along magnetic ﬁeld lines and are dynamically cou- pled to the thermal gas. We assume an Eulerian grid of 384x384x192 cells spanning Lx × Ly × Lz = 76 kpc×76 kpc×38 kpc in x, y, z directions, extended with the CR electron spectrum distributed over 16 bins spanning the energy range of 10 −105mec2. Acknowledgements This work has been supported by the (Polish) National Science Centre through the grant No. 2015/19/ST9/02959. Calculations were carried out at the Academic Computer Centre in Gda´nsk. CR electron spectrum and synchrotron emission We assume also that CR electrons are represented by a piece-wise power-law distribution function and are described by the Focker-Planck equation (Miniati, 2001, see poster by Mateusz Ogrodnik et al.). We take into account advection, energy-dependent (D ∝p0.5), magnetic ﬁeld-aligned diffusion as well as adiabatic and synchrotron cooling effects in dynamical evolution of CR electrons in the wind driven by CR protons. We construct synthetic radio-maps of polarized synchrotron emission of CR electrons by integration of Stokes parameters I, U and Q along the line of sight, with Faraday rotation taken into accoun