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Turbulent pitch-angle scattering and diffusive transport of hard-X-ray producing electrons in flaring coronal loops View all abstracts by submitter

Eduard Kontar   Submitted: 2013-12-11 23:26

Recent observations from {em RHESSI} have revealed that the number of non-thermal electrons in the coronal part of a flaring loop can exceed the number of electrons required to explain the hard X-ray-emitting footpoints of the same flaring loop. Such sources cannot, therefore, be interpreted on the basis of the standard collisional transport model, in which electrons stream along the loop while losing their energy through collisions with the ambient plasma; additional physical processes, to either trap or scatter the energetic electrons, are required. Motivated by this and other observations that suggest that high energy electrons are confined to the coronal region of the source, we consider turbulent pitch angle scattering of fast electrons off low frequency magnetic fluctuations as a confinement mechanism, modeled as a spatial diffusion parallel to the mean magnetic field. In general, turbulent scattering leads to a reduction of the collisional stopping distance of non-thermal electrons along the loop and hence to an enhancement of the coronal HXR source relative to the footpoints. The variation of source size L with electron energy E becomes weaker than the quadratic behavior pertinent to collisional transport, with the slope of L(E) depending directly on the mean free path lambda again pitch angle scattering. Comparing the predictions of the model with observations, we find that lambda sim(108-109) cm for sim30 keV, less than the length of a typical flaring loop and smaller than, or comparable to, the size of the electron acceleration region.

Authors: Kontar, E. P.; Bian, N. H.; Emslie, A. G.; Vilmer, N.
Projects: RHESSI

Publication Status: accepted in ApJ
Last Modified: 2013-12-12 11:38
Go to main E-Print page  Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112,  Observation of Heating by Flare-accelerated Electrons in a Solar Coronal Mass Ejection  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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