Microwave fine structure events during solar Minimum

Chengming Tan, CAS Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences

The solar minimum is a period with relatively less of sunspots and solar eruptions, and has been studied less previously. Because the radio signal is agilely respond to the change of solar plasma and magnetic field, we made a comprehensive analysis of the high resolution spectrum data of Chinese spectrometer and spectral radioheliograph: 1) Search different kinds of solar radio bursts around recent solar minima (2007-2009 and 2016-2018); 2) Analyze several typical radio burst events, the negative and positive drifting burst, for example the event of 2015-11-22 and 2016-08-29; super fine spectral structure events with mini-flare and even without sunspot, for example the event of 2008-03-28 and 2017-07-04. These results showed that there were many radio bursts presenting fine structure during solar minima. These events occurred not only in main flares, but also in mini-flares or even without flares, but in regions related with H-alpha filament or magnetic network. We proposed that the weak solar radio bursts observed by telescopes with high sensibility and low interference will help us to understand the basic physical characteristics of small scale solar eruptions.