Investigation of Frequency Drift in a Solar Radio Type I Burst Chain

In this paper, we study a type I burst chain exhibiting a negative frequency drift. This event was observed simultaneously on 6 August 2023 by the Daocheng Radio Telescope (DART) and Chashan broad‐band solar radio spectrometer at meter wavelengths (CBSm). It lasted for 174 s, with an average drift rate of −0.48 MHz from 241 to 157 MHz. Based on the fundamental and harmonic emissions of plasma mechanism, this type I burst chain displays its source motion upward with a velocity from 120 km to 540 km after fitting its dynamic spectra with both Newkirk and Aschwanden electron density models. During its lifetime, the source's total displacement of 21–94 Mm is below the DART spatial resolution, resulting into no motion seen on DART images. It is interesting that a mini‐jet is observed simultaneously by SDO/AIA in the radio emission region with a speed of 296 km , which is consistent with the radio source upward motion velocities detected here, indicating that the type I burst chain could possibly originate from the nonthermal electrons accelerated by a moving magnetic reconnection following this mini‐jet. These findings would help us to improve the understanding of the characteristics and origin of type I bursts.