DIFFERENT BEHAVIORS BETWEEN MICROWAVE AND HARD X-RAY SPECTRAL HARDNESS IN TWO SOLAR FLARES

摘要

We explore the spectral behaviors of microwave and hard X-ray emissions in two solar flares observed by the Nobeyama Radio Polarimeters (NoRP) and the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) on 2003 May 29 and 2004 January 6. The microwave spectral index γ_(MW) is derived from the emissions at two frequency channels of 17 and 35 GHz, and the standard RHESSI data analysis is used to derive the hard X-ray spectral index γ_(HXR). The 2003 May 29 flare displays a soft-hard-soft spectral behavior in the hard X-ray rise-peak-decay phases, but a soft-hard-harder pattern in the microwave emission. The 2004 January 6 flare shows several soft-hard-soft spectral behaviors in its hard X-ray subpeaks, but only one soft-hard-soft pattern in the microwave emission from start to end. The imaging observations show that the thermal emission could be an important contribution to microwave spectral hardening with the time.