The energetics of chromospheric evaporation in solar flares

The typical impulsive-phase development of a soft X-ray solar flare is derived from observations of a large set of flares with the Bent Crystal Spectrometer and the Hard X-Ray Burst Spectrometere on the Solar Maximum Mission spacecraft. An indicator of the impulsive phase in soft X-rays in the presence of high-speed plasma upflows with velocities up to 400 km s/sup -1/, temperatures of approx.10/sup 7/ K, and turbulent mass motions of approx.100 km s/sup -1/. This is also a period of increase in the mass and energy of the coronal thermal plasma during a flare.