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The Specific Acceleration Rate in Loop-structured Solar Flares - Implications for Electron Acceleration Models View all abstracts by submitter

Jingnan Guo   Submitted: 2013-03-06 01:42

We analyze electron flux maps based on RHESSI hard X-ray imaging spectroscopy data for a number of extended coronal loop flare events. For each event, we determine the variation of the characteristic loop length L with electron energy E, and we fit this observed behavior with models that incorporate an extended acceleration region and an exterior ''propagation'' region, and which may include collisional modification of the accelerated electron spectrum inside the acceleration region. The models are characterized by two parameters: the plasma density n in, and the longitudinal extent L0 of, the acceleration region. Determination of the best-fit values of these parameters permits inference of the volume that encompasses the acceleration region and of the total number of particles within it. It is then straightforward to compute values for the emission filling factor and for the specific acceleration rate (electrons per second per ambient electron above a chosen reference energy). For the 24 events studied, the range of inferred filling factors is consistent with a value of unity. The inferred mean value of the specific acceleration rate above E_0=20 keV is sim10-2 s-1, with a 1-sigma spread of about a half-order-of-magnitude above and below this value. We compare these values with the predictions of several models, including acceleration by large-scale, weak (sub-Dreicer) fields, by strong (super-Dreicer) electric fields in a reconnecting current sheet, and by stochastic acceleration processes.

Authors: Jingnan Guo, A. Gordon Emslie, Michele Piana
Projects: RHESSI

Publication Status: ApJ, 2013, 766, 28
Last Modified: 2013-03-08 08:49
Go to main E-Print page  Phase relations for seismology of photospheric flux tubes  Plasmoid Ejections and Loop Contractions in an Eruptive M7.7 Solar Flare: Evidence of Particle Acceleration and Heating in Magnetic Reconnection Outflows  Edit Entry  Download Preprint  Delete Entry 

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