Hα spectral signatures of solar flare nonthermal electrons, conductive flux, and coronal pressure

We have calculated Hα line profiles based primarily on the static moddel flare chromospheres of Ricchizzi and Canfield, which show the effects of enhanced fluxes of nonthermal electrons and heat, as well as enhanced pressure, on the temperature, density, and ionization structure of the chromosphere. Both hydrostatic and impulsive phase models are examined. Hydrostatic model atmospheres with substantial electron heating characteristically produce wide and bright Hα profiles with a central reversal (measured by the ratio of central to peak intensity) that is insensitive to the electron heating rate. In the impulsive atmospheres, however, the central reversal does depend, to some degree, on the nonthermal electron heating rate. Enhabced thermal conduction reduces the width and total intensity of the profiles. High thermal conduction alone cannot account for flare Hα enhancements. High coronal pressure dramatically increases the width and total intensity of the Hα profiles, while reducing the central reversal