On the onset of the plasmoid instability
- Observatoire Astronomique, 11 rue de l'Observatoire, 67100 Strasbourg (France)
A numerical study of magnetic reconnection in two-dimensional resistive magnetohydrodynamics for marginally unstable Sweet-Parker current sheets that are subject to plasmoid formation is carried out. Despite the procedure used to form the primary Sweet-Parker-like current layer, that is different with respect to previous studies, the reconnection layer is unstable to the plasmoid instability for a Lundquist number greater than the expected critical value S{sub c} Almost-Equal-To 10{sup 4}. For Lundquist numbers S Greater-Than-Or-Equivalent-To S{sub c}, the instability exhibits a quasi-periodic behaviour consisting of formation, rapid growth, and evacuation of a moving magnetic island. The so called 'plasmoid' breaks up the primary current layer and significantly enhances the maximum current density over the value expected from Sweet-Parker theory. This local enhancement spatially coincides with the downstream X-point of the magnetic island and is associated with the formation of a pair of slow-mode Petschek-like shocks bounding the outflowing plasma. These results suggest that the inter-plasmoid current layers forming in high-Lundquist-number plasmas (S Much-Greater-Than S{sub c}) could not be simply described as marginally stable Sweet-Parker current sheets.
- OSTI ID:
- 22086115
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 19; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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