High-resolution Observational Features of Type I Solar Radio Bursts

Abstract In this paper, we statistically studied the characteristic features of solar radio Type I bursts observed by Chashan broadband solar radio spectrometer at meter wavelengths from 00:06 to 07:28 UT on 2023 December 13. Based on the image morphology, we develop a method to identify individual Type I bursts on the dynamic spectra from a connected region with a ratio of the duration to bandwidth less than or equal to 3.8 and the area sum (total pixels) greater than 4. In total, 102,073 and 78,773 bursts are detected on right-hand circular polarization and left-hand circular polarization components, respectively. We find Type I bursts with a mean lifetime of 0.7 s, a mean bandwidth of 5.6 MHz, and a relative bandwidth Δ f / f 0 of about 2%–3%. Consistent with the previous findings of hard X-ray pulses, microwave pulses, Type III bursts, and decimetric spikes, Type I bursts exhibit their duration, bandwidth, peak intensity, and area sum with a power-law distribution. From the linear fitting in log–log space, we obtain the slope index between 1 and 3.5 for various parameters. Meanwhile, Type I bursts display the mean polarization degree in the range from −22% to 33%, and different bursts have various degrees. We find that Type I bursts tend to appear as a chain, and the short periods of 0.92 and 1.22 s are detected in two burst chains. Our finding would be an observational constraint for the emission mechanism and physical model of solar Type I radio bursts.