MAGNETICALLY LIMITED X-RAY FILAMENTS IN YOUNG SUPERNOVA REMNANTS

摘要

We discuss the damping of strong magnetic turbulence downstream of the forward shock of young supernova remnants (SNRs). We find that strong magnetic fields that have been produced by the streaming instability in the upstream region of the shock or by other kinetic instabilities at the shock may be efficiently damped, so the region of enhanced magnetic field strength would typically have a thickness of the order l_d = 10~(16)-10~(17) cm. The nonthermal X-ray filaments observed in young SNRs are thus possibly limited by the magnetic field and not by the energy losses of the radiating electrons. Therefore, the thickness of the filaments would not be a measure of the magnetic field strength, and claims of efficient cosmic-ray acceleration on account of a runaway streaming instability would appear premature.