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Properties of the Acceleration Regions in Several Loop-structured Solar Flares View all abstracts by submitter

Jingnan Guo   Submitted: 2012-06-18 06:40

Using {em RHESSI} hard X-ray imaging spectroscopy observations, we analyze electron flux maps for a number of extended coronal loop flares. For each event, we fit a collisional model with an extended acceleration region to the observed variation of loop length with electron energy E, resulting in estimates of the plasma density in, and longitudinal extent of, the acceleration region. These quantities in turn allow inference of the number of particles within the acceleration region and hence the filling factor f -- the ratio of the emitting volume to the volume that encompasses the emitting region(s). We obtain values of f that lie mostly between 0.1 and 1.0; the (geometric) mean value is f = 0.20 x div 3.9, somewhat less than, but nevertheless consistent with, unity. Further, coupling information on the number of particles in the acceleration region with information on the total rate of acceleration of particles above a certain reference energy (obtained from spatially-integrated hard X-ray data) also allows inference of the specific acceleration rate (electron s-1 per ambient electron above the chosen reference energy). We obtain a (geometric) mean value of the specific acceleration rate eta(20 keV) = (6.0 x / div 3.4) x 10-3 electrons s-1 per ambient electron; this value has implications both for the global electrodynamics associated with replenishment of the acceleration region and for the nature of the particle acceleration process.

Authors: Guo, Jingnan; Emslie, A. Gordon; Massone, Anna Maria; Piana, Michele
Projects: None

Publication Status: ApJ, in press
Last Modified: 2012-06-18 12:25
Go to main E-Print page  Study of flare energy release using events with numerous type III-like bursts in microwaves  Observations of Plasma Upflow in a Warm Loop with Hinode/EIS  Edit Entry  Download Preprint  Delete Entry 

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