THE INFLUENCE OF CHROMOSPHERIC CONDENSATION ON H-ALPHA LINE-PROFILES

The influence of the chromospheric condensation on Halpha line profiles for the thermal model of a solar flare has been empirically studied in this paper. The so-called thermal model here means that there is no temperature increase relative to the quiet-Sun chromosphere but with a chromospheric condensation in the lower part of its transition region, which case is assumed to represent the early stage of the impulsive phase. The main results include: when the temperature within the condensation region is assumed to be equal to that in front of it, the influence is to create an additional absorption profile overlapping on the original one; by increasing the condensation strength, the Halpha line profile changes from a little line-center increase to broadened red asymmetry, then to the reversed red asymmetry, and finally to two independent absorption profiles; the thickness of the condensation determines the absorption of the additional profile; descending the transition region has no obvious effect on the basic characteristic of the Halpha line profile except a little increase in the line center. Assuming that the temperature within the condensation is higher than that ahead of the condensation, the calculated Halpha line profiles may be strong enough to be comparable with the observations., This means that if the condensation in the purely thermal model can reach a higher temperature, we may also use only thermal origin to explain a chromospheric flare.