Circular Polarization Observations of Type II Solar Radio Bursts and the Coronal Magnetic Field

Abstract

It is well known that magnetic field strength (B) in the solar corona can be calculated using the Alfvén Mach number (MA) and Alfvén speed (vA) of the magnetohydrodynamic shock waves associated with coronal type II radio bursts. We show that observations of weak circularly polarized emission associated with the harmonic component of the type II bursts provide independent and consistent estimates of B. For the coronal type II burst observed on 2021 October 9, we obtained B ≈1.5 G and ≈1.9 G at a heliocentric distance (r) of ≈1.8 Re, using the above two techniques, respectively.