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Wei Liu Submitted: 2007-09-12 15:56
We present data analysis and interpretation of an M1.4-class flare observed with
the Reuven Ramaty High Energy Solar Spectroscopic Imager ({it RHESSI}) on April 30, 2002.
This event, with its footpoints occulted by the solar limb, exhibits a rarely observed,
but theoretically expected, double-source structure in the corona.
The two coronal sources, observed over the 6-30 keV range, appear at different altitudes and
show energy-dependent structures with the higher-energy emission being closer together.
Spectral analysis implies that the emission at higher energies in the inner region between the two sources
is mainly {it nonthermal}, while the emission at lower energies in the outer region is primarily {it thermal}.
The two sources are both visible for about 12 minutes and have similar light curves and power-law
spectra above about 20 keV. These observations suggest that the magnetic reconnection site lies
between the two sources. Bi-directional outflows of the released energy in the form of
turbulence and/or particles from the reconnection site can be the source of the observed radiation.
The spatially resolved thermal emission below about 15 keV, on the other hand,
indicates that the lower source has a larger emission measure but a lower temperature than the upper source.
This is likely the result of the differences in the magnetic field and plasma density of the two sources.
Authors: Wei Liu, Vahé Petrosian, Brian R. Dennis, and Yan Wei Jiang
Projects: RHESSI
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Publication Status: Revised version submitted to ApJ, available at ADS or astro-ph/arXiv:0709.1963
Last Modified: 2007-10-31 20:52
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