Processes of fragmentation cascade in large-scale magnetic reconnection
Abstract
Magnetic field reconnection is now generally accepted as the key mechanism for energy release in solar flares and other eruptive events in astrophysical and space plasmas. However, direct application of magnetic-reconnection theory to the physics of solar flares (and other large-scale events) faces a crucial issue for a long time: All known micro-physical processes leading to the change of magnetic field topology (i.e. the reconnection) require very thin current sheets (~1 m in the solar corona). On the other hand, the typical flare current-layer width, estimated either from observations or from the dimensional considerations, is about six orders of magnitude larger. It is thus clear that some mechanisms of consecutive fragmentation of the current density (and corresponding magnetic field) structure have to play a role. In this contribution we aim at identifying all such possible processes and studying some of them in more detail. In order to cover a large range of scales we use high-resolution MHD simulations combined with larger-scale kinetic (PIC) modelling. Our recent research has shown that the cascade towards small scales is the result of mutual positive feedback between the Lorentz-force driven instabilities (such as tearing and the fragmenting coalescence), and their flow- and pressure-field driven counterparts (typically Kelvin-Helmholtz and ballooning instabilities).
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39..101B