2014/12/31 by Anna Tenerani, Antonio Franco Rappazzo, Marco Velli +1 · 1 citation
Physics and Astronomy · #physics.plasm-ph
paper · pdf · doi:10.1088/0004-637x/801/2/145
Accepted for publication in The Astrophysical Journal on January 16, 2015
arxiv created 2015/02/11 · arxiv updated 2015/06/23
This paper studies the growth rate of reconnection instabilities in thin current sheets in the presence of both resistivity and viscosity. In a previous paper, Pucci and Velli (2014), it was argued that at sufficiently high Lundquist number S it is impossible to form current sheets with aspect ratios L/a which scale as L/a∼ Sα with α> 1/3 because the growth rate of the tearing mode would then diverge in the ideal limit S→∞. Here we extend their analysis to include the effects of viscosity, (always present in numerical simulations along with resistivity) and which may play a role in the solar corona and other astrophysical environments. A finite Prandtl number allows current sheets to reach larger aspect ratios before becoming rapidly unstable in pile-up type regimes. Scalings with Lundquist and Prandtl numbers are discussed as well as the transition to kinetic reconnection