Spectroscopic Diagnostics of the UV Emitting Plasmas in Solar Flares Observed from SMM

Abstract

The transition region exhibits dynamic changes during solar flares. To understand the energy release and transport processes in solar flares, it is important to determine observationally the physical conditions in the flare transition region plasmas, which emit in the UV wavelength ranges. During the Solar Maximum Mission (SMM) we observed many flares in the UV emission lines of Si IV (1402 Å) and 0 IV (1401 Å) using the Ultraviolet Spectrometer and Polarimeter (Woodgate et al. 1983). In this paper we present the Si IV/O IV flare observations, in particular the dynamic evolution of the transition zone plasmas (~ 105 K). We also studied the temporal and spatial correlations between the impulsive UV and hard X-ray bursts.