Polarization diagnostics of proton beams in solar flares
Abstract
Description
We review the problem of proton beam bombardment of solar chromosphere considering the self-consistent NLTE polarized radiation transfer in hydrogen lines. Several observations indicate a linear polarization of the H-alpha line of the order of 5% or higher and preferentially in radial direction. This polarization is often explained as anisotropic collisional excitation of the n=3 level by vertical proton beams. Our calculations indicate that deceleration of the proton beam with initial power-law energy distribution together with increased electron and proton densities in the H-alpha forming layers lead to a negligible line polarization. Thus the proton beams seem not to be a good candidate for explanation of the observed polarization degree. On the other hand, the effect of electric return currents could perhaps provide a better explanation of the observed linear polarization. We report the new calculations of this effect.
6 pages, 6 figures; will appear in the proceedings of the "Solar Magnetism and Dynamics & THEMIS Users meeting", 2006 November 15-17, Meudon, France
6 pages, 6 figures; will appear in the proceedings of the "Solar Magnetism and Dynamics & THEMIS Users meeting", 2006 November 15-17, Meudon, France