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A magnetic reconnection scenario of the Bastille-Day 2000 flare
Boris V. Somov Submitted: 2002-06-26 19:31
On the basis of Yohkoh Hard X-ray Telescope
data and the magnetograms taken by the SOHO MDI and the
Solar Magnetic Field Telescope at Huairou Solar
Observing Station, we suggest an interpretation of
the well-observed `Bastille-Day 2000' flare.
The large-scale structure and dynamics
of the flare, as seen in hard X-rays, can be
explained in terms of the three-dimensional
reconnection at a separator in the corona.
More specifically, we suggest that before
two-ribbon flares with significant decrease of a distance
between the HXR footpoints, like the Bastille-Day flare,
the bases of magnetic field separatrices are moved by the
large-scale photospheric flows of two types. First,
the shear flows, which are parallel to the photospheric
neutral line, increase the length of field lines
in the corona and produce an excess of
magnetic energy. Second, the converging flows, i.e. the
flows directed to the neutral line, create the pre-flare
current layers in the corona and provide an excess of
energy sufficient to produce a large flare.
During the flare, both excesses of magnetic energy are
released completely or partially. In the Bastille-Day flare,
the model describes two kinds of apparent
motions of the HXR kernels. One is an increase of a
distance between the flare ribbons in which the HXR
kernels appear. The effect results from fast
reconnection in a coronal current layer. The second
effect is a decrease of the distance between the kernels
moving to each other as a result of relaxation of
magnetic tensions generated by the photospheric shear flows.
Authors: Boris V. Somov, Takeo Kosugi, Hugh S. Hudson, Taro Sakao, and Satoshi Masuda
Publication Status: ApJ (submitted)
Last Modified: 2002-06-26 19:31
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