Scaling of magnetic reconnection in low and high-β regimes

Abstract:

Low-β reconnection, where the magnetic field is dominated by a strong out-of-plane component, is pertinent to laboratory magnetic confinement devices, the solar corona, and other magnetically dominated astrophysical environments. The high-β regime, where this out-of-plane component is weak, has application in the magnetosphere. It has been suggested that fast dispersive waves are responsible for the fast timescales of reconnection in both the high-β and low-β regimes. Here we show from two-fluid simulations that low-β reconnection is fast in cases with and without such waves. To understand this, we construct a quantitative model of the dissipation region (DR) and benchmark it against the fluid simulations. We find that the DR self-adjusts to give a rate that is independent of DR physics in both cases, and in good agreement with kinetic results. We also compare two-fluid simulations of high-β reconnection with the recent kinetic results of Karimabadi et al. PRL 107, 025002 (2011), for flux-rope interactions in large systems in which flux pile-up and bouncing become important.