Observing the evolution of the Sun's global coronal magnetic field over eight months

TL;DR

This study presents eight months of continuous observations of the Sun's global coronal magnetic field, revealing its evolution, distribution, and active longitudes, and compares these findings with coronal models.

Contribution

It provides the first extensive time series of global coronal magnetic field measurements, enhancing understanding of solar magnetic dynamics over multiple rotations.

Findings

Magnetic field strengths vary from <1 to 20 Gauss within 1.05-1.6 solar radii.

Active longitude signatures are observed in the coronal magnetic field.

Coronal models generally agree with observations, with some discrepancies at high latitudes.

Abstract

The magnetic field in the Sun's corona stores energy that can be released to heat the coronal plasma and drive solar eruptions. Measurements of the global coronal magnetic field have been limited to a few snapshots. We present observations using the Upgraded Coronal Multi-channel Polarimeter, which provided 114 magnetograms of the global corona above the solar limb spanning approximately eight months. We determined the magnetic field distributions at different solar radii in the corona, and monitored the evolution at different latitudes over multiple solar rotations. We found varying field strengths from <1 to 20 Gauss within 1.05-1.6 solar radii and a signature of active longitude in the coronal magnetic field. Coronal models are generally consistent with the observational data, with larger discrepancies in high-latitude regions.