Annihilation of Magnetic Islands at the Top of Solar Flare Loops. (arXiv:2110.08526v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Y/0/1/0/all/0/1">Yulei Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cheng_X/0/1/0/all/0/1">Xin Cheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ding_M/0/1/0/all/0/1">Mingde Ding</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_Q/0/1/0/all/0/1">Quanming Lu</a>
The dynamics of magnetic reconnection in the solar current sheet (CS) is
studied by high-resolution 2.5-dimensional MHD simulation. With the commence of
magnetic reconnection, a number of magnetic islands are formed intermittently
and move quickly upward and downward along the CS. When colliding with the
semi-closed flux of flare loops, the downflow islands cause a second
reconnection with a rate even comparable with that in the main CS. Though the
time-integrated magnetic energy release is still dominated by the reconnection
in main CS, the second reconnection can release substantial magnetic energy,
annihilating the main islands and generating secondary islands with various
scales at the flare loop top. The distribution function of the flux of the
second islands is found to follow a power-law varying from
$fleft(psiright)simpsi^{-1}$ (small scale) to $psi^{-2}$ (large scale),
which seems to be independent with background plasma $beta$ and if including
thermal conduction. However, the spatial scale and the strength of the
termination shocks driven by main reconnection outflows or islands decrease if
$beta$ increases or thermal conduction is included. We suggest that the
annihilation of magnetic islands at the flare loop top, which is not included
in the standard flare model, plays a non-negligible role in releasing magnetic
energy to heat flare plasma and accelerate particles.
The dynamics of magnetic reconnection in the solar current sheet (CS) is
studied by high-resolution 2.5-dimensional MHD simulation. With the commence of
magnetic reconnection, a number of magnetic islands are formed intermittently
and move quickly upward and downward along the CS. When colliding with the
semi-closed flux of flare loops, the downflow islands cause a second
reconnection with a rate even comparable with that in the main CS. Though the
time-integrated magnetic energy release is still dominated by the reconnection
in main CS, the second reconnection can release substantial magnetic energy,
annihilating the main islands and generating secondary islands with various
scales at the flare loop top. The distribution function of the flux of the
second islands is found to follow a power-law varying from
$fleft(psiright)simpsi^{-1}$ (small scale) to $psi^{-2}$ (large scale),
which seems to be independent with background plasma $beta$ and if including
thermal conduction. However, the spatial scale and the strength of the
termination shocks driven by main reconnection outflows or islands decrease if
$beta$ increases or thermal conduction is included. We suggest that the
annihilation of magnetic islands at the flare loop top, which is not included
in the standard flare model, plays a non-negligible role in releasing magnetic
energy to heat flare plasma and accelerate particles.
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