The spectral observation of decimetric spikes with very high spectral resolution

Thousands of decimetric spikes were observed with a new spectrometer of Yunnan Observatory on June 24, 2001. The statistical analyses of the bandwidth, polarization degree, and half power duration of these spikes were made. We found that the absolute bandwidth of the spikes is down to the low limit of the instrument's spectral resolution (about 1.4 MHz). 76% of the total spikes have the polarization degree greater than 70%. The distribution of the half power durations concentrates on less than 16 milliseconds. These results support the interpretation of the electron cyclotron maser (ECM) mechanism for the decimetric spikes.     

A solar radio moving type Ⅳ burst of expanding arches type involving multi-sources

A complex solar radio moving type IV burst was observed on 23 September 1998 with the broadband (1.0-2.0 GHz and 2.6-3.8 GHz) spectrometers with high temporal and spectral resolutions at National Astronomical Observatories of China (NAOC). Comparing to the high spatial resolution data of Siberian Solar Radio Telescope (SSRT), we find that this burst is a rare type of moving type IV burst which is caused by the expanding arches, and the spatial structure oscillations of the radio sources are related with the time structure pulsations of the radio emission. Furthermore, the burst is associated with the multiple quasi-periodic long-term pulsations, and this suggests the existence of multi-scale magnetic structures in a large expanding coronal arch. We think the moving type IV burst is due to the synchrotron emission of the energetic electrons trapped in the expanding arch, and the multiple quasi-periodic pulsations are due to the second harmonic plasma emission.