The Observed Characteristics of a Radio Outburst on the Solar Limb

The observed characteristics of a radio outburst which occurred on the solar limb at 0808UT on April 27, 1981 have been given in details. The morphology of the radio burst, the spectra of microwave bursts and the energy spectra of non-thermal electrons have been analysed preliminarily.The characteristics of the radio outburst areas follows: (a) It is the most intense one which has been observed in our country in the solar maximum years of Cycle 21. The peak flux densities were 3770, 13412, 15318 (sfu) at 3000MHz, 9375MHz and 35GHz respectively. It is also an intense limb outburst, (b) The four major peaks and the many minor peaks were superimposed on the time profile and two peak flux density spectra were formed at 0808UT and 0813.5 UT respectively. The peak frequencies were located at 35GHz and 9375MHz. By means of these results, we may calculate the magnetic field intensity of the microwave region. It was found to be very strong (957 gauss) during the explosive phase, (c) The time profiles of the outburst have been analysed. The result shows that the moment of the occurrence was 0.2-1 minutes earlier at shorter wavelengths than longer wavelenths for one and the same peak or valley. This is of importance to the study of the flare-burst source model, (d) The spectral index and the non-thermal electron energy spectra have been calculated, and it is found that the observed spectral rigidity increased when the energy spectrum of non-thermal electrons was getting harder, so that the radiation flux density was also increased, (e) Such an intense radio outburst was not associated with a large proton event.