engleski

Instability of the Sweet-Parker-like current layer

A two−dimensional reconnecting current sheet is studied numerically in magnetohydrodynamics approach with the aim of getting more insight on the nature of the instability taking place. At studied value of Lundquist number S=10^4 and Reynolds number R=10^4 a Sweet–Parker–like current sheet is observed to form, followed by the fragmentation, which leads to the fast reconnection. The Sweet–Parker–like current sheet does not reach the stationary state characteristic of the Sweet–Parker reconnection. Rather, it evolves very slowly and is therefore identified as a quasiequilibrium current sheet. It has increasing ratio of the length and width (aspect ratio) whose maximum is found to correspond with the detected fragmentation. This qualitative scenario is confirmed for the simulations with the initial Harris and force–free equilibria applied, for the periodic and open–boundary conditions with uniform and non–uniform grid prescribed, respectively, and for varying sizes of the numerical system.

quasiequilibrium current sheet, impulsive bursty reconnection, tearing-mode instability, aspect ratio

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