SH43A-2429
Resistive Magnetohydrodynamic Simulations of Fast Reconnection in Thin Current Sheets: Analysis of the Linear and Nonlinear Stages of the "Ideal" Tearing Mode
Thursday, 17 December 2015
Poster Hall (Moscone South)
Simone Landi1, Luca Del Zanna1, Emanuele Papini2, Fulvia Pucci3 and Marco Velli4, (1)University of Florence, Florence, Italy, (2)Max-Planck-Insitut, Solar System Research, Göttingen, Germany, (3)University of Rome Tor Vergata, Rome, Italy, (4)University of California Los Angeles, Los Angeles, CA, United States
Abstract:
Thin current sheets are known to be unstable to tearing and even super-tearing modes, leading to explosive reconnection events as required to explain the rapid release of magnetic energy in astrophysical plasmas (solar flares, magnetar bursts, dissipation in pulsar winds). Here we study by means of resistive, compressible MHD simulations the behavior of current sheets whose inverse aspect ratio scales with the Lundquist number S as S-1/3, known to give rise to fast, ideal reconnection, with an evolution and growth that are independent of S. In the linear phase we retrieve the expected eigenmodes and the growth rate, which can be as high as γ ≈ 0.6 τA-1, where τA is the ideal Alfvénic time set by the macroscopic scales. The nonlinear stages are characterized by the coalescence of magnetic islands and by secondary reconnection events, obeying the same critical scaling with the local S, leading to the production and ejection of plasmoids on increasingly shorter timescales. Preliminary simulations of the ideal tearing mode are presented also for magnetically dominated plasmas, in the relativistic MHD regime.
