SPECTRAL STUDY LOWER SOLAR ATMOSPHERE OF THE ACTIVE REGION SITE WITH THE ELLERMAN BOMB AND ACCOMPANYING Hα-EJECTIONS

Abstract

The results of studying in details the features formation and development of the Ellerman bomb (EB) and accompanying Hα-ejections arose on the NOAA 11024 active region site, are presented. This site was in the region of emerging new magnetic flux. Spectral data with high spatial and temporal resolution were obtained with the French–Italian solar telescope THEMIS on July 4, 2009. Spectra with the Hα line and with the spectral region λλ ≈ 630 nm were used. Stokes I profiles were obtained with an interval corresponding to 160 km on the Sun surface. The Hα line profiles obtained for different periods of EB development were asymmetric with an excess of emission in the short-wavelength wing. The temporal variations of intensity in the Hα line wings at distances ±0.1 and ±0.16 nm from its center indicated that two periods can be distinguished in EB evolution: the preheating phase and the flaring phase, during which the gradual and pulse energy release occurred. Hα-ejections (surges) are small-scale eruptions of cold matter in the solar atmosphere. In all spectra they were visible in the absorption. The surge profiles were projected onto the blue or red Hα line wing. Its Doppler shifts were used to calculate the line-of-sight velocities (Vlos) of chromospheric matter in surges. The velocity distribution in the surges indicated their multi-flow structure. One of the surges showed signs of plasma vortex motions. Most surges occurred with a high velocity – Vlos up reached -110 km/s, and down to 90 km/s. We obtained temporal Vlos variations in a wide interval (140 ─ 490 km) of photospheric heights for the area of EB development and its immediate surroundings. At all photospheric levels predominantly upward motions were found. In the central part of the EB in the upper layer of the photosphere the Vlos varied between -0.5 ÷ 0.2 km/s, in the lower layer – -1.1 ÷ -0.1 km/s. An increase the core intensity of all photospheric lines was correlated in time with an increase of the emission intensity in the Hα line wings. The new observational data for the Ellerman bomb and accompanying Hα-ejections, which have been obtained and analyzed, can be used to verify existing and create new theoretical models.