Possible link between solar decimeter-wave microbursts and noise storms

Abstract

A statistical study of long-lived solar microbursts (MB) at decimeter-wave frequencies has been performed for the first time. The data are obtained with the radio telescope RATAN-600 and have the form of one-dimensional scans of intensity and circular polarization with a sensitivity of about 5–10 Jy. MB fluxes and polarization degrees lie in the 0.001–0.1 s.f.u. and 10% to 100% intervals, respectively, and individual pulses have durations of one to two seconds. Microbursts can be observed in the same active region over several days. MB are compared to noise storms (NS) at meter-wave frequencies. The analysis indicates that MB are NS manifestations at decimeter-wave frequencies. The possible cause of the significant difference between the radio fluxes of MB and NS is analyzed. It is shown within the framework of a unified model of the generation of MB and NS radio waves that unlike type I bursts MB are associated with the incoherent mechanism of the generation of Langmuir waves. MB emission is, by its nature, closer to the continuous emission of noise storms, but it is pulse-like because of the high rate of pitch-angular diffusion.