Formation of anomalous slow shocks in anisotropic plasmas

Pressure anisotropy is a characteristic of space plasmas. Linear magnetohydrodynamic (MHD) theories have shown that the properties of hydromagnetic waves may greatly be modified by the pressure anisotropy. In particular, slow waves may exhibit the anomalous behaviors of positive density-magnetic field correlation, faster propagation speed relative to the intermediate wave and right-handed polarization. This paper examines the formation of anomalous slow shocks by solving the gyrotropic MHD and Hall-MHD equations numerically for the evolution of an initial current sheet that separates two regions of plasma and magnetic field. It is shown that it is possible to have slow shock move ahead the intermediate shock with upstream flow being super-Alfvénic and the downstream being firehose unstable as well as anomalous slow shocks with δΒδρ > 0 and right-handed polarization.