Diagnostics of the Heating Processes in Solar Flares Using Chromospheric Spectral Lines

We have calculated the H$\alpha$ and Ca {\sc ii} 8542 {\AA} line profilesbased on four different atmospheric models, including the effects of nonthermalelectron beams with various energy fluxes. These two lines have differentresponses to thermal and nonthermal effects, and can be used to diagnose thethermal and nonthermal heating processes. We apply our method to an X-classflare that occurred on 2001 October 19. We are able to identify quantitativelythe heating effects during the flare eruption. We find that the nonthermaleffects at the outer edge of the flare ribbon are more notable than that at theinner edge, while the temperature at the inner edge seems higher. On the otherhand, the results show that nonthermal effects increase rapidly in the risephase and decrease quickly in the decay phase, but the atmospheric temperaturecan still keep relatively high for some time after getting to its maximum. Forthe two kernels that we analyze, the maximum energy fluxes of the electronbeams are $\sim$ 10$^{10}$ and 10$^{11}$ ergs cm$^{-2}$ s$^{-1}$, respectively.However, the atmospheric temperatures are not so high, i.e., lower than orslightly higher than that of the weak flare model F1 at the two kernels. Wediscuss the implications of the results for two-ribbon flare models.Comment: 6 pages, 9 figures, accepted for publication in Ap