The solar plasma conditions in the source regions
of two explosive events

¹ Instituto Nacional de Astrofísica, Optica y Electrónica, Apartado Postal 51 y 216, Puebla, Pue., Z.P. 72000, México e-mail: mend@inaoep.mx
² Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
³ Instituto de Geofísica, UNAM, México

Received: 11 October 2006
Accepted: 7 November 2008

Abstract

We analyze the ultraviolet emission during two explosive events (EEI and EEII) recorded by SUMER aboard SOHO in the wavelength range from 749 Å to 789 Å. The events occurred near the centre of the solar disk on 17 November 1996. An attempt is made to separate the emission of the primary energy release from that of the accelerated plasma. We want to establish the characteristics of the sources, in particular, how large they are and how they are spatially distributed with respect to each other. Gaussian fits were calculated to estimate the radiances of the brightest emissions in our wavelength range for the core of the lines and their blue and red wings. The maximum of each Gaussian approximation was used to define the spatial distributions of the components. The electron densities were obtained with the help of the O v line ratio. The relationship between the densities and the spatial distribution of the radiances is then analyzed. The distributions of EEI are more extended than those of EEII, probably due to the different geometries of the observations. In both events, there is an offset in the locations of red and blue components but the offset is greater at EEI than at EEII. The Doppler velocities of the components of EEI were smaller than those of EEII. Also, in both events the density of the red component attained the highest values ( cm^-3). In EEI the electron density distributions of the three components were considerably narrower than the radiance distributions. The peak densities were observed centred with respect to the radiance distributions, suggesting that the sources of the first energy release of this event were near these locations. Both the electron density and the radiance distributions of EEI suggest a jet direction close to the line of sight.