ASKAP Data Products for Project AS316 (Measurement of Magnetic Fields of Solar Coronal Mass Ejections using Wide Field of View Faraday Rotation Observations): images and visibilities

Full description

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from the Sun, responsible for extreme space weather events. Observations of CMEs by coronagraphs and heliospheric imagers at visible wavelengths provide crucial geometrical and dynamical properties. However, their impact on Earth depends largely on the southward magnetic field component (CME-Bz). Recent studies highlight significant CME evolution in the inner heliosphere (5-15 degree solar elongation), making extrapolations from low coronal heights unreliable for predicting CME-Bz near Earth. Measuring CME magnetic fields at these heights is critical to improving predictions. A promising approach involves observing changes in Faraday rotation (FR) of linearly polarized radio emission from background sources as their line-of-sight crosses CME plasma. While this method has been applied at low coronal heights (< 4-degree solar elongation) using narrow-field JVLA observations, its extension to the inner heliosphere requires an instrument with wide field-of-view (FoV) and robust polarization capabilities -- requirements ideally met by ASKAP. This project proposes observing ~10 large CMEs with a total of 20 hours of ASKAP time in cycle 2025APRS, leveraging an automated triggering system. The unique capabilities of ASKAP will enable simultaneous measurements of CME-entrained magnetic fields across multiple lines of sight in the inner heliosphere, significantly advancing space weather research.