A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism
Koval, Artem; Chen, Yao; Feng, Shiwei; Liu, Hongyu; Cho, Kyungsuk; Vasanth, Veluchamy; Du, Guohui; Wu, Zhao; Li, Chuanyang
Republic of Korea, China
Abstract
A stationary Type IV (IVs) radio burst was observed on September 24, 2011. Observations from the Nançay RadioHeliograph (NRH) show that the brightness temperature (TB) of this burst is extremely high, over 1011 K at 150 MHz and over 108 K in general. The degree of circular polarization (q ) is between −60 % ∼−100 % , which means that it is highly left-handed circularly polarized. The flux-frequency spectrum follows a power-law distribution, and the spectral index is considered to be roughly −3 ∼−4 throughout the IVs. Radio sources of this event are located in the wake of the coronal mass ejection and are spatially dispersed. They line up to present a formation in which lower-frequency sources are higher. Based on these observations, it is suggested that the IVs was generated through electron cyclotron maser emission.