A model for the formation of solar prominences

A model for the formation of prominence condensations in hot coronal loops is proposed. Previous studies have concentrated on cooling the hot plasma by decreasing the coronal heating rate. The difficulty with such models is that when the heating decreases, most of the loop mass is lost by draining onto the chromosphere. It is argued that a prominence condensation is likely to be due to an increase in the heating. The key idea of the model is that the heating increase is spatially dependent so that it is localized nearer to the chromospheric footpoints than to the loop midpoint. Results are presented of numerical simulations of hot loops that are initially heated uniformly, and then undergo heating increases that are concentreated away from the loop midpoint. The temperature at the midpoint first increases, but eventually it collapses to chromospheric values as a result of chromospheric evaporation. Hence, a curious result is obtained, that increasing the heating causes cooling. The resulting densities and time scales agree well with observations. The implications of this model for coronal heating and prominence structure are discussed.