Radiative and conductive cooling in a solar flare

We investigate the radiative and conductive cooling in the solar flare observed by RHESSI on 2005 September 13. The radiative and conductive loss energies are estimated from the observations after the flare onset. Consistent with previous findings, the cooling is increased with time, especially the radiation becomes remarkable on the later phase of flare. According our method, about half of thermal energy is traced by RHESSI soft X-rays, while the other half is lost by the radiative (∼38%) and conductive (∼9%) cooling at end of the hard X-rays in this event. The nonthermal energy input of P _nth (inferred from RHESSI hard X-ray spectrum) is not well correlated with the derivative of thermal energy of \fracdE_thdt\frac{\mathrm{d}E_{\mathrm{th}}}{\mathrm{d}t} (required to radiate the RHESSI soft X-ray flux and spectrum) alone. However, after consideration the radiation and conduction, a high correlation is obtained between the derivative of total thermal energy ( \fracdE_th+E_rad+E_conddt\frac{\mathrm{d}E_{\mathrm{th}}+E_{\mathrm{rad}}+E_{\mathrm{cond}}}{\mathrm{d}t}) and nonthermal energy input (P _nth) from the flare start to end, indicating the relative importance of conductive and direct radiative losses during the solar flare development. Ignoring the uncertainties to estimate the energy from the observations, we find that about ∼12% fraction of the known energy is transferred into the thermal energy for the 2005 September 13 flare.