Interferometric Observations of the Quiet Sun at 20 and 25 MHz in May 2014

TL;DR

This study presents interferometric observations of the quiet Sun at 20 and 25 MHz, measuring fluxes, sizes, and brightness temperatures, and reports sporadic solar radio bursts observed on one day.

Contribution

First interferometric measurements of the quiet Sun at decameter frequencies using UTR-2, providing flux, size, and temperature data at 20 and 25 MHz.

Findings

Average fluxes of 1050-1100 Jy at 20 MHz and 1480-1570 Jy at 25 MHz.

Angular sizes of 55' and 49' at 20 MHz; 50' and 42' at 25 MHz.

Brightness temperatures around 5.1-5.7 x 10^5 K.

Abstract

Results of solar observations at 20 and 25 MHz by the UTR-2 (\textit{Ukrainian T-shaped Radio telescope of the second modification}) radio telescope in the interferometric session from 27 May to 2 June 2014 are presented. In such a case the different baselines 225, 450, and 675 m between sections of East--West and North--South arms of the radio telescope UTR-2 were used. On 29 May 2014, strong sporadic radio emission consisting of Type III, a Type II and a Type IV bursts was observed. On other days there was no solar radio activity in the decameter range. We discuss the results of observations of such the quiet Sun. Fluxes and sizes of the Sun in East--West and North--South directions were measured. The average fluxes were 1050--1100 Jy and 1480--1570 Jy at 20 and 25 MHz, respectively. Angular sizes of the quiet Sun in equatorial and polar directions were 55' and 49' at 20 MHz and 50' and 42' at 25 MHz. Brightness temperatures of radio emission were Tb = 5.1 10^5 K and Tb = 5.7 10^5 K at 20 and 25 MHz, respectively.