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Motion of 3-6 keV Nonthermal Sources Along the Legs of a Flare Loop View all abstracts by submitter

Linhui Sui   Submitted: 2006-05-31 13:03

Observations of nonthermal X-ray sources are critical to studying electron acceleration and transport in solar flares. Strong thermal emission radiated from the pre-heated plasma before the flare impulsive phase often makes it difficult to detect low-energy X-ray sources that are produced by relatively low-energy nonthermal electrons. Knowledge of the distribution of these low-energy nonthermal electrons is particularly important in determining the total nonthermal electron energy in solar flares. We report on an 'early impulsive flare' in which impulsive hard X-ray emission was seen early in the flare before the soft X-ray emission had risen significantly, indicating limited plasma pre-heating. Early in the flare, RHESSI < 25 keV images show coronal sources that moved first downward and then upwards along the legs of a flare loop. In particular, the 3-6 keV source appeared as a single coronal source at the start of the flare, and then it envolved into two coronal sources moving down along the two legs of the loop. After nearly reaching the two footpoints at the hard X-ray peak, the two sources moved back up to the looptop again. RHESSI images and light curves all indicate that nonthermal emission dominated at energies as low as 3-6 keV. We suggest that the evolution of both the spectral index and the low-energy cutoff of the injected electron distribution could result in the accelerated electrons reaching a lower altitude along the legs of the dense flare loop and hence result in the observed downward and upward motions of the nonthermal sources.

Authors: Sui, L., Holman, G. D., and Dennis, B. R.
Projects: RHESSI

Publication Status: ApJ, Letter (in press)
Last Modified: 2006-05-31 16:14
Go to main E-Print page  Solar prominence merging  Fe XIX observations of active region brightenings in the corona  Edit Entry  Download Preprint  Delete Entry 

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