The variation of solar flare coronal X-ray source lengths with energy
Abstract
Observations with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of coronal source extent with electron energy has been discussed in the context of streaming 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. I will discuss how this investigation was extended 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 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 give an overestimate of the actual density by a factor of 3-6. The implications of these results for the determination of acceleration region properties such as specific acceleration rate and filling factor will also be discussed.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E1328J