Circular polarization observations of Sun's magnetic field using commercial dish TV antennas

Abstract

The radio astronomy group in the Indian Institute of Astrophysics (IIA) has been carrying out routine observations of radio emission from the solar corona at low frequencies (≈40 - 440 MHz) at the Gauribidanur observatory, about 100 km north of Bangalore. Since IIA has been performing regular observations of the solar photosphere and chromosphere using different optical telescopes in its Kodaikanal Solar Observatory (KSO) also <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sup> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sup> https://www.iiap.res.in/kodai.htm, the possibilities of carrying out Stokes-I and Stokes-V observations of the solar chromosphere using low-cost radio instrumentation to supplement the optical observations are being explored. Note that measurements of Stokes-V help to infer the magnetic field strength of the sunspots. As a part of the exercise, recently the group has developed prototype instrumentation for interferometric observations of radio emission from the solar chromosphere at high frequencies (≈ 11.2 GHz) using three commercial dish TV antennas. The hardware set-up and initial observations are presented.