X-point collapse and saturation in the nonlinear tearing mode reconnection

N. F. Loureiro, S. C. Cowley, W. D. Dorland, M. G. Haines, A. A. Schekochihin

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Abstract

We study the nonlinear evolution of the resistive tearing mode in slab geometry in two dimensions. We show that, in the strongly driven regime (large Δ′), a collapse of the X point occurs once the island width exceeds a certain critical value ∼1/Δ′. A current sheet is formed and the reconnection is exponential in time with a growth rate ∞η1/2, where η is the resistivity. If the aspect ratio of the current sheet is sufficiently large, the sheet can itself become tearing-mode unstable, giving rise to secondary islands, which then coalesce with the original island. The saturated state depends on the value of Δ′. For small Δ′, the saturation amplitude is ∞Δ′ and quantitatively agrees with the theoretical prediction. If Δ′ is large enough for the X-point collapse to have occurred, the saturation amplitude increases noticeably and becomes independent of Δ′.

Original languageEnglish (US)
Article number235003
JournalPhysical review letters
Volume95
Issue number23
DOIs
StatePublished - Dec 2 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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