EDP Sciences
Free access
Volume 425, Number 1, October I 2004
Page(s) 333 - 343
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20040458

A&A 425, 333-343 (2004)
DOI: 10.1051/0004-6361:20040458

Proton acceleration in a single-loop disrupted during collision of two moving solitary magnetic kinks

J. I. Sakai and A. Kakimoto

Laboratory for Plasma Astrophysics, Faculty of Engineering, Toyama University, 3190, Gofuku, Toyama, 930-8555, Japan
    e-mail: sakaijun@eng.toyama-u.ac.jp

(Received 17 March 2004 / Accepted 9 June 2004)

We investigate a new model of single-loop flare based on the fact that a magnetic flux tube with axial current can be explosively disrupted during collision of two moving solitary magnetic kinks (MoSMaK), particularly paying attention to an acceleration mechanism of high energy protons. By using three-dimensional electromagnetic fields obtained from a resistive three-dimensional MHD equations during the single-loop flare, we investigate the orbit of many protons to obtain their energy spectra. We found that the protons can be accelerated to $\gamma$-ray-emitting energies ( >1 MeV) with double power-law spectra up to about 25 MeV. There appears a breaking point of the index of the power-law spectra from 1.8 to 2.1 near 10 MeV. The protons are accelerated mainly in one direction along the loop by the electric field produced near the three-dimensional localized current associated with the magnetic reconnection process in the disrupted loop. We study the loop disruption for two different plasma beta in the center of the loop; $\beta=0.5$ and $\beta=0.05$. In a high beta case ( $\beta=0.5$), the disruption of the loop is more violent than that of $\beta=0.05$. We found that the proton acceleration for the case of $\beta=0.5$ occurs mainly at two different regions; one is inside the loop and the other is in the upper part of the disrupting loop. However, the energy spectra of protons are very similar for both cases.

Key words: acceleration of particles -- magnetohydrodynamics (MHD) -- plasmas -- Sun: flares

© ESO 2004