Numerical simulation of the cooling of a solar flare

A one-dimensional hydrodynamics code is used to study the cooling of solar flares. The cooling of the flux tube is calculated for the case in which the atmosphere is initially in thermal equilibrium with a maximum temperature of about 107 K. As the system cools, the evolution of the temperature, density, and velocity is calculated as a function of height for different lengths of the loop. We use the cooling function proposed by Hildner (1974), extended to include temperatures lower than 104 K and the Bremsstrahlung effect for values higher than 106 K. It is found that the cooling time increases as the length of the loop is increased. Furthermore, if a spatially-varying energy source is allowed along the loop length, the cooling time differs from the case with no external heating. In particular, it is seen to decrease as the input heating concentrates at the base of the loop.