Microwave bursts with fine structures in the decay phase of a solar flare

Abstract

This paper presents the microwave bursts with fine structures (FSs) at 1.10-1.34GHz in the decay phase of a solar flare observed by the Chinese Solar Broadband Radio Spectrometer in Huairou, which show a peak-to-peak correlation with 25-50 keV hard X-ray (HXR) bursts observed by RHESSI. In the microwave spectra, we have identified stripe-like bursts such as lace bursts, fiber structures, zebra patterns (ZPs), and quasi-periodic pulsations. We also have detected short narrowband bursts such as dots, type III, and spikes. The lace bursts had rarely been reported, but in this event they are observed to occur frequently in the decay phase of the flare. The similarity between 25 and 50 keV HXR light curve and microwave time profiles at 1.10-1.34GHzsuggests that these microwave FSs are related to the properties of electron acceleration. The electron velocity inferred from the frequency drift rates in short narrowband bursts is in the range of 0.13c-0.53c and the corresponding energy is about 10-85 keV, which is close to the energy of HXR-emitting electrons. From the Alfvén soliton model of fiber structures, the double plasma resonance model of ZPs, and the Bernstein model of the lace bursts, we derived a similar magnetic field strength in the range of 60-70G. Additionally, the physical conditions of the source regions such as height, width, and velocity are estimated. © 2012. The American Astronomical Society. All rights reserved.