Study on the Radiation Mechanism of Plasmas Near L1 Point Affected by CMEs and the Associated Microwave Bursts

Coronal mass ejections are large-scale magnetic structures expelled from the sun due to MHD processes involving interaction between plasmas and magnetic field in closed field regions. Radiation with different wavelength is emitted because of reciprocity of coronal mass ejections with corona and interplanetary medium. A comprehensive survey is made on coronal mass ejections occurred from February 1999 to August 1999 which were observed by LASCO and the ground radio spectrometer in Purple Mountain Observatory and Yunnan Observatory. Special attentions are focused on the emission mechanisms of space plasmas near L1(the first Lagrange point of solarearth system) which are affected by very large coronal mass ejections. Statistical analysis is also made based on the study of the radiation mechanisms of space plasmas during quiet sun period. The results show that the dominating radiation mechanisms are bremsstrahlung, a small quantity of cyclotron radiation and a less quantity of recombination radiation. Moreover, solar radio microwave bursts which accompany with coronal mass ejections during February 1999 to August 1999 are analyzed. The findings indicate that they are gradual bursts and spike bursts. The dominating radiation mechanisms of the solar radio microwave bursts are bremsstrahlung, cyclotron resonant radiation, plasmas radiation and electronic cyclotron maser radiation.