Chengming T., Baolin T., Yihua Ya., Wei W., Linjie Ch., Fei L., Yujiang D. «Fine structure events in microwave emission during solar minimum» Солнечно-земная физика, 5, № 2, с. 4-10 (2019)

The solar minimum is a period with a relatively smaller number of sunspots and solar eruptions, and has been less studied before. Since the radio signal rapidly responds to the change of solar plasma and magnetic field, we perform a comprehensive analysis of high resolution spectrum data from SBRS and MUSER: 1) a search for solar radio bursts of different kinds in recent solar minima (2007–2009 and 2016–2018); 2) an analysis of several typical radio burst events, negative and positive drifting bursts, for example the November 22, 2015 and August 29, 2016 events; superfine spectral structure events with mini-flares and even without sunspots, for example the March 28, 2008 and July 04, 2017 events. These results show that there were many radio bursts with a fine structure during solar minima. These events occurred not only in powerful flares, but also in faint flares (class C and B by GOES) or even without flares, but in regions related to weak brightenings or ejecta. We assume that the weak solar radio bursts observed by telescopes with high sensitivity and low interference will help us to understand the basic physical characteristics of small-scale solar eruptions.

Sha Li., Yihua Ya., Zhijun Ch., Wei W. «Comparing simulated results of folded and unfolded log-periodic antenna used for observing the Sun» Солнечно-земная физика, 5, № 2, с. 49-54 (2019)

There are two antenna arrays located in Mingantu Spectral Radio Heliograph (MUSER). MUSER-I and MUSER-II cover the frequency band ranging from 0.4 to 2 GHz and from 2 to 15 GHz respectively. A third antenna array covering 30–240 MHz will be established in the coming years. A log-periodic antenna is one of the choices for MUSER low frequency band; it radiates structures capable of maintaining consistent impedance characteristics over a wide bandwidth. Due to the ability of achieving high gain, it is widely used in many broadband applications. In this program, folded and unfolded log-periodic antennas are simulated for the Meridian project. In order to improve its return loss, this antenna is optimized with the width of each pole and the height of the substrate. This optimized process has been implemented in the simulated software HFSS.