Amir Levinson. Interaction of a magnetized shell with an ambient medium: limits on impulsive magnetic acceleration
Natural Sciences / Physics / Astrophysics
Submitted on: Jun 08, 2012, 05:00:35
Description: The interaction of relativistic magnetized ejecta with an ambient medium is studied for a range of structures and magnetization of the unshocked ejecta. We particularly focus on the effect of the ambient medium on the dynamics of an impulsive, high-sigma shell. It is found that for sufficiently high values of the initial magnetization $sigma_0$ the evolution of the system is significantly altered by the ambient medium well before the shell reaches its coasting phase. The maximum Lorentz factor of the shell is limited to values well below $sigma_0$; for a shell of initial energy $E=10^{52}E_{52}$ ergs and size $r_0=10^{12}T_{30}$ cm expelled into a medium having a uniform density $n_i$ we obtain $Gamma_{rm max}simeq180(E_{52}/T_{30}^3 n_i)^{1/8}$ in the high sigma limit. The reverse shock and any internal shocks that might form if the source is fluctuating are shown to be very weak.