## 7. Cooling of the PFL systemIt is generally believed that the post-flare loop plasma cools mainly due to thermal conduction and radiation. To get a simple estimate of the time scale which a hot PFL with temperature of the order K needs to reach temperature of the order K, we used a simple formula of vestka (1987) and we applied a correction to the temperature gradient introduced by Varady & Heinzel (1997). The formula was derived from the energy equation under the assumption of static (), fully ionized plasma. The first and the second term on the right hand side of the equation are approximations of conductive and radiative losses: In this equation is the
correction applied to the temperature gradient,
is the Boltzmann constant, Using the formula above and quantities obtained in previous
sections we calculated the theoretical time dependence of plasma
temperature in the PFL. The model was calculated for the initial
temperature 2.8 MK, which was obtained from the SXT temperature
analysis and a constant electron density
cm
© European Southern Observatory (ESO) 2000 Online publication: March 9, 2000 |