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Title: On the variation of solar flare coronal X-ray source sizes with energy

Observations with RHESSI have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold target model and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here, we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch angle distribution of the accelerated electrons, and the effects of collisional pitch angle scattering. The finite temperature results in the thermal diffusion of electrons, which leads to the observationally inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch angle and scattering within the target, cause the projected propagation distance parallel to the guiding magnetic field to be reduced, so that a one-dimensional interpretation can overestimate the actual density by a factor of up to ∼6. The implications of these results for the determination of acceleration region properties (specific accelerationmore » rate, filling factor, etc.) are discussed.« less
Authors:
; ;  [1] ;  [2]
  1. School of Physics and Astronomy, University of Glasgow, G12 8QQ Glasgow (United Kingdom)
  2. Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)
Publication Date:
OSTI Identifier:
22356817
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; DENSITY; DISTANCE; DISTRIBUTION; GAMMA RADIATION; HARD X RADIATION; INCLINATION; INJECTION; MAGNETIC FIELDS; ONE-DIMENSIONAL CALCULATIONS; PLASMA; SCATTERING; SOLAR FLARES; SUN; THERMAL DIFFUSION; TRAJECTORIES; X-RAY SOURCES