ar094.sterling05 Posted: 07-Jul-96 Updated: Events specified: N/A
A. C. Sterling
Images from the Yohkoh soft X-ray telescope (SXT) indicate that there was virtually no time during the period since launch (August 1991) and 1994 where a single (isolated) active region alone dominated the X-ray emission from the Sun. This means that it was impossible to perform spectral studies of individual active regions using the Yohkoh Bragg crystal spectrometer (BCS) instrument, since BCS lacks spatial resolution. With the decline in solar activity over the past year, however, it has occasionally been possible to find active regions which appear to be isolated on the Sun in X-rays. We propose to carry out studies using BCS for one such active region which appeared on the Sun in March 1996. Our studies will primarily utilize the S XV channel of the BCS, since that channel is sensitive to emissions from plasmas at active region temperatures. We will study the behavior of the spectral lines observed from this region to determine spectral properties such as electron temperatures and non-thermal velocities, etc., in the active region. We will also investigate the time variation of these quantities over an extended period (several days) to determine their variation with time and with morphology of the active region as seen by SXT.