Preparing for Heliopolarimetry using New-generation Ground-based Radio Telescopes

Abstract

Coronal mass ejections (CMEs) are large-scale ejections of magnetized plasma from the Sun and are associated with the most extreme space weather events. The geoeffectiveness of a CME is primarily determined by the southward component of its magnetic fields (CME-$B_z$). Recent studies have shown that CMEs evolve significantly in the inner heliosphere ($\sim20-90\ R_\odot$), and relying on extrapolations from low coronal heights can lead to wrong predictions of CME-$B_z$ in the vicinity of Earth. Hence, it is important to measure CME magnetic fields at these heights to improve CME-$B_z$ prediction. A promising method to measure the CME-entrained magnetic field in the inner heliosphere is by measuring the changes in Faraday rotation (FR) of linearly polarized emission from background radio sources as their line-of-sight crosses the CME plasma. Here, we present the current preparation of new-generation ground-based radio telescopes for this purpose.