Internal Shocks in the Magnetic Reconnection Jet in Solar Flares: Dependence on Resistivity Model

S.Tanuma & K.Shibata

Space solar missions such as Yohkoh and RHESSI observe the hard X- and gamma-ray emission from energetic electrons in impulsive solar flares. Their energization mechanism, however, is unknown. In this paper, we suggest that the internal shocks are created in the reconnection jet and that they are possible sites of particle acceleration. We examine how magnetic reconnection creates the multiple shocks by performing two-dimensional resistive magnetohydrodynamic simulations. In this paper, we use a very small grid to resolve the diffusion region. As a result, we find that the current sheet becomes thin due to the tearing instability, and it collapses to a Sweet-Parker sheet. The thin sheet becomes unstable to the secondary tearing instability. Fast reconnection starts by the onset of anomalous resistivity immediately after the secondary tearing instability. During the bursty, time-dependent magnetic reconnection, the secondary tearing instability continues in the diffusion region where the anomalous resistivity is enhanced. As a result, many weak shocks are created in the reconnection jet. Furthermore, we also find that the many strong oblique shocks are created because the reconnection jet starts to oscillate by Kelvin-Helmholtz-like instability with some parameters (for example, resistivity model). This situation produces turbulent reconnection. We suggest that multiple fast shocks are created in the jet and that the energetic electrons can be accelerated by these shocks.

Correspondence

Shuniti Tanuma (tanuma@kwasan.kyoto-u.ac.jp), Kwasan Observatory, Kyoto University

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