UV observations of transition-region plasmas in solar flares - Plasma diagnostics and relationships between UV and hard X-ray bursts

The impulsive and gradual phases of solar flares are investigated, comparing simultaneous SMM UVSP and HXRBS observations. Data for several 1980 flares are presented graphically and characterized in detail, with reference to the results of numerical simulations based on theoretical models. Consideration is given to the density and mass velocity in the transition region, the temporal and spatial relationships between the impulsive UV and X-ray bursts, and the relationships between the impulsive and gradual phases.