High-velocity evaporation during the impulsive phase of the 1984 April 24 flare

An analysis is given of the soft X-ray emission, detected with the bent crystal spectrometer of the SMM, during the initial part of the impulsive phase of the April 24, 1984 flare. In this period, soft X-rays are emitted uniquely by a moving source, which can be identified with plasma evaporating from the chromosphere with velocities between 100 and 800 km/s, and they can be characterized by temperatures between 1.5 x 10 to the 7th and 4 x 10 to the 7th K. Three successive injections of evaporating plasma can be clearly distinguished. A mass and energy balance analysis ensures that plasma is almost continuously injected in the flaring loops during the period of observation of upflows. 12 refs.