Fast Tearing Mode Instability in Thin Current Sheets Embedded in a Jet
Abstract
A longstanding problem has been to understand why at relatively low Lundquist number current sheets are observed to be stable with respect to the tearing mode. In particular, simulations suggest that instability sets-in above a minimum aspect ratio A which is around A 100. Assuming a scaling with the Lundquist number S as A S1/2 (as in Sweet Parker sheets), this implies the existence of a critical Lundquist number of around Sc 104 as has been numerically seen.While it is known that flows along current sheets have a stabilizing effects, the existence of a threshold for instability in terms of Lundquist number and aspect ratio of the current sheet has not yet been theoretically satisfactorily shown. Here we approach this problem starting with a simple one dimensional equilibrium current sheet embedded in a sheared flow (Bickley jet) to locally mimic the dynamics of current sheets. It is known that the growth rate of the tearing mode increases with the aspect ratio, while the latter should have little effects on flows. Here we therefore extend and generalize previous linear studies to a wider range of Lundquist and Alfvén Mach numbers, by varying the current sheet aspect ratio, assuming a generic scaling A Sα. This study is complementary to the stability of two-dimensional current sheet configurations with flows.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH51B2594T
- Keywords:
-
- 2164 Solar wind plasma;
- INTERPLANETARY PHYSICSDE: 2169 Solar wind sources;
- INTERPLANETARY PHYSICSDE: 7509 Corona;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY