tokens: Weisz et al. 2011 ). According to numerical simulations, the tidal-driven changes in star formation are rather short-lived, with a typical duration of the activity of about 10 8 yr ( Di Matteo et al. 2008 ). Strong starbursts during which the star formation rate is increased by a factor larger than 5 are rare. IC 1613 is a good example of a dwarf that calmly produces stars over its entire lifetime, while showing also some fluctuations ( Skillman et al. 2014 ). The galaxy has a small H i mass of 8 × 10 7 and a stellar mass of 1.1 × 10 8 ( Woo et al. 2008 ). The current SFR is 0.003 M ⊙ yr −1 ( Mateo 1998 ), but the SFH reveals some episodes in the galaxy life with theSFR enhancement of about threefold ( Skillman et al. 2014 ). Another aspect of evolution of low-mass galaxies not addressed in numerical experiments to date is the often observed irregular distribution of star-forming regions in galactic disks. Such an asymmetric distribution is evident in for example IC 10, dominated by a giant H ii region in its southern part. The observed morphology and the strength of magnetic field are strongly related to the distribution of H ii regions within the galactic disk ( Chyży et al. 2016 ). So as to address the above issues, in this paper a series of 3D simulations of the CR-driven dynamo for low-mass galaxies are performed. In the first place, we simulate a calm evolution of galaxies at different speeds of rotation and different (but constant in time) levels of star formation activity. Below, we introduce a starburst (a rapid enhancement of star formation) and study its impact on magnetic field, while finally investigating how a localised starburst, restricted to just part of the galactic disk, changes the magnetic field topology, and how this is related to the topology for the global starburst. 2 Numerical model and setup 2.1 Cosmic-ray-driven dynamo The CR-driven dynamo model in dwarf/irregular galaxies has been implemented into a numerical code called godunov-mhd ( Kowal et al. 2009 ). The code solves the system of resistive magnetohydrodynamic (MHD) equations in a conservative form in 3D space (e.g. Goedbloed Poedts 2004 ): where ρ , p , and v are the gas density, pressure, and velocity, respectively, p cr is the cosmic-ray pressure, A is the vector potential, B ≡∇× A is the magnetic field, φ is the gravitational potential, η is the magnetic turbulent diffusivity and I is the identity matrix. To close the system an isothermal equation of state is assumed: where c s is the isothermal speed of sound and γ is the adiabatic index of the gas. Cosmic rays form a key component of the model. In our case they are approximated as a fluid, whose evolution is described by the diffusion-advection transport equation following ( Schlickeiser Lerche 1985 ): where e cr is the CR energy density, K̂ is the diffusion tensor, v is the plasma velocity, p cr is the CR pressure, and Q is the source term of e cr . CR pressure is related to the e cr via the adiabatic CR
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