Gamma-ray burst internal shocks with magnetization

Abstract

(Please note that the abstract has been significantly shorted) We investigate Gamma-ray Burst (GRB) internal shocks with moderate magnetization, with the magnetization parameter $σ$ ranging from 0.001 to 10. Possible magnetic dissipation in the stripped magnetized shells is also taken into account through introducing a parameter $k$ ($0<k\leq 1$), which is the ratio of the electric field strength of the downstream and the upstream. By solving the general MHD jump conditions, we show that the dynamic evolution of the shock with magnetic dissipation is different from the familiar one obtained in the ideal MHD limit. In view of the possible high degree of linear polarization of GRB 021206 and the identification of a possible highly magnetized flow in GRB 990123 and GRB 021211, we suggest that a mildly magnetized internal shock model ($0.01<σ<1$) with moderate magnetic dissipation is a good candidate to explain the GRB prompt emission data.