Physics – Plasma Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsh21c..04p&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SH21C-04
Physics
Plasma Physics
[7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7554] Solar Physics, Astrophysics, And Astronomy / X-Rays, Gamma Rays, And Neutrinos, [7807] Space Plasma Physics / Charged Particle Motion And Acceleration, [7833] Space Plasma Physics / Mathematical And Numerical Techniques
Scientific paper
Acceleration and transport of high-energy particles and fluid dynamics of atmospheric plasma are interrelated aspects of solar flares, but for simplicity they were artificially separated in the past. We present here self-consistently combined Fokker-Planck modeling of particles and hydrodynamic simulation of flare plasma. Energetic electrons are modeled with the Stanford unified code of acceleration, transport, and radiation, while plasma is modeled with the NRL flux tube code (Mariska et al. 1989). We calculated the collisional heating rate directly from the particle transport code, which is more accurate than those in previous studies based on approximate analytical solutions. We used a more realistic spectrum of injected electrons provided by the stochastic acceleration model of Petrosian & Liu (2004), which has a smooth transition from a quasi-thermal background at low energies to a nonthermal tail at high energies. The inclusion of low-energy electrons results in relatively more heating in the corona (vs. chromosphere) and thus a larger downward heat conduction flux. The interplay of electron heating, conduction, and radiative loss leads to stronger chromospheric evaporation than obtained in previous studies, which had a deficit in low-energy electrons due to an arbitrarily assumed low-energy cutoff. The energy and spatial distributions of energetic electrons and bremsstrahlung photons bear signatures of the changing density distribution caused by chromospheric evaporation. In particular, the density jump at the evaporation front gives rise to enhanced X-ray emission, which could be responsible for the X-ray sources moving along flare loops observed by RHESSI (Sui et al. 2006, ApJL 645; Liu et al. 2006, ApJ 649). Various energy contents from the simulations can be used to test the empirical Neupert effect. This technique can also be applied to investigate a variety of high-energy processes in solar, space, and astrophysical plasmas, such as planetary auroras. Geometry of the model flare loop assumed in this study.
Liu Wende
Mariska John T.
Petrosian Vahe
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