The tearing instability in relativistic magnetohydrodynamics

Magnetic energy dissipation in relativistic plasmas is a crucial process operating in many environments typical of high-energy astrophysics, such as pulsar winds and nebulae, magnetars, and magnetized disks around black holes. In many cases such dissipation is required to be of explosive type, given that flaring activity is often observed in such objects in the form of sudden releases of gamma rays. Here we discuss the role of the aspect ratio of the reconnecting current sheet, which, as for classic and Hall magnetohydrodynamics (MHD), when sufficiently small it is known to lead to a very rapid evolution of the spontaneous tearing instability and to explosive secondary reconnection events (super-tearing or plasmoid instability). Multi-dimensional simulations of resistive, relativistic MHD are presented for various magnetizations and plasma betas, and 2D results show a quasi-universal evolution, occurring on the ideal (relativistic) Alfv n time.