Spontaneous current sheet fragmentation and particle acceleration in cascading magnetic reconnection in solar flares
Abstract
The question how is the magnetic energy -accumulated in solar eruptive flares on relatively large scales (the thickness of the current layer behind ejected CME is supposed to be approx. 1000 km) -transported towards the dissipative scales (approx. 10 m in the solar corona) re-mains as one of the main open issues in the solar flare theory. To resolve this problem, Shibata and Tanuma (Earth, Planet Space 53, 2001) have suggested a concept of cascading (or 'fractal') reconnection. We studied this concept using numerical MHD simulations involving AMR tech-nique in order to gain broader range of resolved scales. The results of our simulations confirmed relevance of the mechanism of tearing cascade suggested by Shibata and Tanuma. In addition to that, we found further fragmentation of the current layer in the perpendicular direction: secondary current sheets are formed between interacting magnetic islands (plasmoids). These current layers are possibly subjected to the same kind of processes (tearing cascade + forced coalescence of tearing-formed plasmoids) as the original (global) current layer formed as conse-quence of CME ejection. Thus, we suggest to supplement the original cascading-reconnection scenario by the possibility of spontaneous current sheet fragmentation in the second dimen-sion. This finding is in agreement with general expectations of spontaneous isotropisation of the turbulent cascade. Propagation of the cascading process to he second dimension increases the efficiency of the reconnection process and has also clear consequences for theory of particle acceleration in the solar flares as such a fragmented current sheet can host many non-ideal regions capable to accelerate particles.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1955B