Flare on 2011 September 22 and coronal mass ejection from observations in the He i 10830-Å line

Abstract

In this paper, we present the results from a study of the X1.4/2N flare and the accompanying coronal mass ejection (CME) on 2011 September 22 from observations of the spectral region around the He i 10830-Å line. In the study, 20 He i 10830-Å line images of the full disc of the Sun and 20 dopplerograms were obtained. Parts of the active region (AR) 11302 with steady blueshift were detected on the dopplerograms. The velocities of the flows were 10–40 km s⁻¹. Expansion was a characteristic feature of this event; it was observed for more than 2 h and was associated with the development of the CME. A transient coronal hole (TCH) was found in the unipolar magnetic field near the AR from the images in the He i 10830-Å line and from the dopplerograms. The profiles of the He i 10830-Å line in the flare loops were obtained for different moments of the process. The half-width of the helium line at the limb was ≈4.2 Å at the beginning of the observations, and remained ≈3.5 Å until 11:45 ut. On subsequent scans, the half-width slowly decreased to ≈2 Å. The time dependence of the power of energy release in the He i 10830-Å line for the process at the limb was found to have several peaks associated with the development of the CME. We conclude that in the period 11:15–11:50 ut, the non-thermal impact ionization of helium accompanied by recombination was the prevailing mechanism by which the triplet levels were filled corresponding to the He i 10830-Å line. The total energy released in the active process of 2011 September 22 at the limb in the He i 10830-Å line is estimated to be ≈10³⁰ erg.