2014/04/07 by Natasha L. S. Jeffrey, Eduard P. Kontar, Nicolas H. Bian +1
Physics and Astronomy · #Acceleration #Astrophysics and Cosmic Phenomena #Context (archaeology) #Diffusion #Electron #Electron density #Ionosphere and magnetosphere dynamics #Particle acceleration #Scattering #Solar and Space Plasma Dynamics #Solar flare #Solar physics #Solar wind #astro-ph.HE #astro-ph.SR #physics.plasm-ph
paper · pdf · doi:10.1088/0004-637x/787/1/86
45 pages, 9 figures, accepted for publication in ApJ
arxiv created 2014/04/07 · openalex publication_date 2014/05/06 · arxiv updated 2015/06/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 acceleration rate, filling factor, etc.) are discussed.