Letter to the Editor
Influence of non-thermal processes on line asymmetries in solar flares
Received 3 September 1996 / Accepted 28 November 1996
We make line profile calculations for a flare atmosphere considering simultaneously the effect of non-thermal excitation and ionization of the hydrogen atoms caused by precipitating high-energy electrons, and the effect of possible chromospheric downflows. The results confirm the earlier finding that a downflow, if confined to the upper chromosphere, can sometimes produce a blue asymmetry of the H line. In addition, we find that the existence of such non-thermal effects tends to enhance the blue-asymmetry magnitude. In particular, the larger the energy flux, or the harder the energy spectrum for the beam electrons, the easier it will be to produce a blue-asymmetric H profile, which is simultaneously intensified and broadened. Possible reasons which make the blue asymmetry less popular than the red asymmetry in observations are discussed.
Key words: Line: profiles Sun: flares
Send offprint requests to: M.D. Ding (Nanjing University)
© European Southern Observatory (ESO) 1997
Online publication: July 8, 1998