Episodic X-ray Emission Accompanying the Activation of an Eruptive Prominence: Evidence of Episodic Magnetic Reconnection |
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Wei Liu Submitted: 2009-02-10 22:52
We present an X-ray imaging and spectroscopic study of a partially occulted (N16W93) C7.7 flare on 2003 April 24 observed by RHESSI that accompanied a prominence eruption observed by TRACE. (1) The activation and rise of the prominence occurs during the preheating phase of the flare. The initial X-ray emission appears as a single coronal source at one leg of the prominence and it then splits into a double source. Such a source splitting happens three times, each coinciding with an increased X-ray flux and plasma temperature, suggestive of fast reconnection in a localized current sheet and an enhanced energy release rate. In the late stage of this phase, the prominence displays a helical structure. These observations are consistent with the tether-cutting and/or kink instability model for triggering solar eruptions. (2) The eruption of the prominence takes place during the flare impulsive phase. Since then, there appear signatures predicted by the classical CSHKP model of two-ribbon flares occurring in a vertical current sheet trailing an eruption. These signatures include an EUV cusp and current-sheet-like feature (or ridge) above it. There is also X-ray emission along the EUV ridge both below and above the cusp, which in both regions appears closer to the cusp at higher energies in the thermal regime (lesssim20 keV). This trend is reversed in the nonthermal regime. (3) Spectral analysis indicates thermal X-rays from all sources throughout the flare, while during the impulsive phase there is additional nonthermal emission which primarily comes from the coronal source below the cusp. This source also has a lower temperature (T=20 pm 1 vs.~25 pm 1 MK), a higher emission measure (EM=[3.3 pm 0.4] vs.~[1.2 pm 0.4] imes 1047 cm-3), and a much harder nonthermal spectrum (electron power-law index delta=5.4 pm 0.4 vs.~8 pm 1) than the upper sources.
Authors: Wei Liu, Tong-Jiang Wang, Brian R. Dennis, Gordon D. Holman
Projects: RHESSI,TRACE
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Publication Status: ApJ (2009 June 10, Vol 698, p. 632-?640), also astro-ph/arXiv:0902.1805
Last Modified: 2009-08-24 10:59
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