Effects of RFI on Solar Microwave Bursts Observed with Hightime Resolution

ABSTRACTSolar microwave burst observations with high time resolution (~ 1 ms) are important but difficult to make. It is shown by the experiments of radiometer at wavelength 21 cm on 1 ms time scale that some ultrafast time structures in microwaves, which includes spike impulses, switch-on and switch-off structures, etc., may not be from solar emission but from RFI (radio-frequency interference) or from radiometer itself. Because of the uncertainty at 21 cm and other several wavelengths, we suggest that joint observations of the solar microwave bursts on 1 ms time scale should be carried out on the peak years of the 22nd solar activity cycle.

Computer Simulation of a Solar Microwave Burst

A simple impulsive event observed at microwave frequencies between 3.2 and 50 GHz is simulated with a homogeneous source model. Intensity and polarization of the 1984 April 26 event are shown in fig. 1a and 1b, respectively. The spectral maximum is close to the observing frequency of 11.8 GHz.The time profiles of the intensity I and the circular polarization ρc at this frequency as well as the spectrum at different characteristic phases (rise, maximum and decay) are calculated and compared with the observation in order to deduce parameters of the microwave source.