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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