http://www.cnr.it/ontology/cnr/individuo/prodotto/ID207623

PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES (Articolo in rivista)

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PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES (Articolo in rivista) (literal)

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Jingnan Guo1, A. Gordon Emslie2, Anna Maria Massone3, and Michele Piana1,3 (2012)
PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES
in The Astrophysical journal
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Jingnan Guo1, A. Gordon Emslie2, Anna Maria Massone3, and Michele Piana1,3 (literal)

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1 Dipartimento di Matematica, Università di Genova, Via Dodecaneso 35, 16146 Genova, Italy 2 Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101, USA 3 CNR-SPIN, Via Dodecaneso 33, I-16146 Genova, Italy (literal)

Titolo

PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES (literal)

Abstract

Using 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 ×/÷ 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 ?(20 keV) =(6.0 ×/÷ 3.4) × 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. (literal)

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