Magnetic Field Amplification and Saturation by Turbulence in A Relativistic Shock Propagating through An Inhomogeneous Medium

¹ Institute of Astronomy, National Tsing-Hua University, Hsinchu, Taiwan R.O.C.
² Institute of Physics and Astronomy, Universitat Potsdam, Potsdam-Golm, Germany
³ Institute of Nuclear Physics PAN, Kraków, Poland
⁴ Department of Physics and Astronomy, University of Nevada, Las Vegas, NV, USA
⁵ CSPAR, University of Alabama in Huntsville, Huntsville, AL, USA
⁶ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, USA

Abstract

We perform two-dimensional relativistic magnetohydrodynamic simulations of a mildly relativistic shock propagating through an inhomogeneous medium. Simulation results show that the postshock region becomes turbulent owing to preshock density inhomogeneity, and the magnetic field is strongly amplified due to the stretching and folding of field lines in the turbulent velocity field. The amplified magnetic field evolves into a filamentary structure in two-dimensional simulations. The magnetic energy spectrum is flatter than the Kolmogorov spectrum and indicates that the so-called small-scale dynamo is occurring in the postshock region.