TURBULENCE AND MAGNETIC FIELD AMPLIFICATION IN SUPERNOVA REMNANTS: INTERACTIONS BETWEEN A STRONG SHOCK WAVE AND MULTIPHASE INTERSTELLAR MEDIUM

We examine magnetohydrodynamic simulations of the propagation of a strong shock wave through the interstellar two-phase medium composed of small-scale cloudlets and diffuse warm neutral medium in two-dimensional geometry. The preshock two-phase medium is provided as a natural consequence of the thermal instability that is expected to be ubiquitous in the interstellar medium. We show that the shock-compressed shell becomes turbulent owing to the preshock density inhomogeneity, and magnetic field amplification takes place in the shell. The maximum field strength is determined by the condition that plasma beta similar to 1, which gives the field strength on the order of 1 mG in the case of shock velocity similar to 10(3) km s(-1). The strongly magnetized region shows filamentary and knotlike structures in two-dimensional simulations. The spatial scale of the regions with a magnetic field of similar to 1 mG in our simulation is roughly 0.05 pc, which is comparable to the spatial scale of the X-ray hot spots recently discovered in supernova remnants where the magnetic field strength is indicated to be amplified up to the order of 1 mG. This result may also suggest that the turbulent region with a locally strong magnetic field is expected to be spread out in the region with frequent supernova explosions, such as in the Galactic center and starburst galaxies.