Magnetic Reconnection Instabilities in Soft-Gamma Repeaters

Abstract

We examine an external trigger mechanism that gives rise to the intense soft gamma-ray repeater (SGR) giant flares. Out of the three giant flares, two showcased the existence of a precursor, which we show to have had initiated the main flare. We develop a reconnection model based on the hypothesis that shearing motion of the footpoints causes the materialization of a Sweet-Parker current layer in the magnetosphere. The thinning of this macroscopic layer due to the development of an embedded super-hot turbulent current layer switches on the impulsive Hall reconnection, which powers the giant flare. We show that the thinning time is on the order of the pre-flare quiescent time.

4 pages, 2 figures, submission for the Proceedings of the Thirteenth Marcel Grossman Meeting on General Relativity edited by Kjell Rosquist, Robert T Jantzen, Remo Ruffini World Scientific, Singapore, 2013