Relativistic magnetic reconnection at X-type neutral points
Department of PhysicsHiroshima University, Higashi-Hiroshima 739-8526, Japan
Received: 24 January 2011
Accepted: 1 April 2011
Context. The relativistic effects in the oscillatory damping of magnetic disturbances near two-dimensional X-points are investigated.
Aims. By taking displacement current into account, we study new features of extremely magnetized systems, in which the Alfvén velocity is almost the speed of light.
Methods. The frequencies of the least-damped mode are calculated using linearized relativistic MHD equations for wide ranges of the Lundquist number S and the magnetization parameter σ.
Results. The oscillation and decay times depend logarithmically on S in the low resistive limit. This logarithmic scaling is the same as for nonrelativistic dynamics, but the coefficient becomes small as ~σ − 1/2 with increasing σ. These timescales approach constant values in the high resistive limit: the oscillation time becomes a few times the light crossing time, irrespective of σ, and the decay time is proportional to σ so is longer for a highly magnetized system.
Key words: magnetohydrodynamics (MHD) / magnetic reconnection / relativistic processes
© ESO, 2011