Continuous energy injection at numerous bright points during soft X-ray flare enhancement

The common assumption that a single volume of plasma produces X-ray emission during solar flares is difficult to reconcile with the very complex structure observed in H spectroheliograms. Nevertheless such a model has been considered reasonably adequate because the rapid rise and slow decay of emission has approximately the form expected when a plasma volume, isolated thermally from its surroundings, is heated quickly in the early stages of the event.Data presented in this paper show that a number of secondary peaks in intensity are usually observed throughout the soft X-ray emission. These can be explained by a model in which the X-ray emission comes from many relatively short-lived volumes of hot plasma. It appears that the lifetime of each such region is about five minutes, while the H spectroheliograms suggest that they are spaced throughout the extended region of activity. The relatively long period of flare activity arises because new volumes of plasma appear as others decay. Since each of these regions has to be energized during its development it is concluded that energy is released throughout the period of the X-ray flare.On leave of absence from the Mullard Space Science Laboratory, University College London WC1E-6BT.