Excitation of Helium Resonance Lines in Solar Flares

摘要

The authors have calculated helium resonance line intensities for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft x-rays. This reprint examines the differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining (1) which of these models most nearly represents the density vs. temperature structure and soft x-ray flux in the flaring solar transition regions, and (2) the temperature and dominant mechanism of formation of the helium line spectrum during a flare.