Physical conditions in the chromosphere of a two-strand solar flare with ejection

Abstract

Chromosphere layers of solar flares were investigated according to the observed profiles of the H_α line. A two-strand flare was observed on September 4, 1990. Spectra were obtained with the ATsU-26 solar horizontal telescope at Terskol Peak Observatory (3100 m). Spectra photometry is performed for two bright nodes of one strand of the flare. Some profiles are superposed to the ejection. The observed profiles are characterized by high emissions in the wings of the H_α line (up to 10–12 Å) under relatively low intensity in the center of H_α (r = 0.35–0.6). To explain such profile behavior we calculated flare models with two or three components. Separate components of the model correspond to unresolved details in the flare area and therefore the averaged profile is calculated. Emission in the far wings is explained by model components with deep heating of chromosphere layers. These occupy 5–12% of the total area. Noticeable emission asymmetry is explained by ray velocities of up to 70 km/s and more. The models are determined by agreement of the observed and calculated profiles. We processed several photometric profiles for seven observations. The temperature in the models with deep heating in the lower cromosphere is increased by 1000–2500 K with respect to the model with an undisturbed chromosphere VAL-C. The second feature of the observed profiles is their high asymmetry and shift with respect to the undisturbed profiles. This can be explained by the opposite motion of the material. We revealed that for the most of the profiles the line-of-sight velocities were directed to the observer in the upper chromosphere (10–100 km/s) and from the observer in the lower chromosphere (5–20 km/s).