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′.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)