A&A 425, 281-285 (2004)
The jump of reverse drift rate of V-shaped structure and the large-scale inhomogeneity of plasma density in the solar atmosphereF. Y. Xu1, 2 and H. A. Wu1, 2
1 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
2 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
(Received 16 October 2002 / Accepted 31 March 2004 )
A rare solar radio V-shaped structure was observed on August 25, 1999 by the 4.5-7.5 GHz spectrograph of the Purple Mountain Observatory, China. It consists of a reverse drift component followed by a normal drift one, which seems to be an unusual frequency drift event because of the jump of reverse drift rate from 3.22 to 1.53 GHz/s and the fastest drift rate of -3.53 GHz/s. According to their different drift rates, the V-shaped structure can be divided into three parts. By the consideration of plasma emission of an electron beam, a three-component solar atmospheric model with large and small scale lengths , and to describe the equilibrium solar atmosphere and local inhomogeneity as well as the energy loss of the electron beam due to electron-electron collision is proposed. The local scale lengths , cm and c, c at Parts 1 and 2 of the reverse drift component are obtained. The variations of scale length of and , especially , could be responsible for the jump of drift rate. The normal drift rate would be interpreted as the increase of average energy of the electron beam at the mirror due to the decrease in electrons of lower energy via energy loss of collision. The three-component solar atmospheric model and the energy loss of the electron beam are discussed.
Key words: sun: flares -- Sun: radio radiation
© ESO 2004