The Neupert effect suggests a flare model in which the nonthermal emissions are produced by energetic electrons which heat lower corona and chromosphere to produce the thermal emissions. Based on this concept, we investigate the Neupert effect to test the correlation between the hard X-ray spectral index and the time rate of the UV flare area at 1600 or 171 . Using the T RACE and RHESSI observations, we explore these quantities for two solar flares, one on March 14, 2002 and the other on November 1, 2003. The negative dependence between the spectral index and the time rate of the UV flare area is found, especially during the hard X-ray sub-peaks. This finding indicates that the electron-beam-driven heating plays a prominent role in the UV emission of these two flares.
NING ZongJun Purple Mountain Observatory, Nanjing 210008, China
