Soft X-ray emission and chromospheric flares

A study is made of several ATM flares, to investigate the effect of soft X-ray heating at chromospheric levels. It is shown that the amount of energy released in Ly and Lyman continuum emissions, and their spatial and temporal behavior, in compact flares correspond to what is expected from model calculations. An additional source of heating, which could be heat conduction, has to be postulated to explain ribbons of enhanced L and C ii 1336 Å emission in large flares. As expected, the effect of X-ray heating is more important in small compact flares than in large ones.