Estimating Electron Densities in the Middle Solar Corona using White-light and Radio Observations

TL;DR

This paper combines white-light and low-frequency radio observations from OVRO-LWA to estimate electron densities in the middle solar corona, providing a more reliable and complementary measurement method.

Contribution

It introduces a new approach using radio data to estimate coronal electron densities, validated against white-light data and theoretical models.

Findings

Radio-based density estimates agree with white-light measurements.

Derived a new density model valid between 1.7 and 3.5 solar radii.

Demonstrated OVRO-LWA's effectiveness for regular coronal density monitoring.

Abstract

The electron density of the solar corona is a fundamental parameter in many areas of solar physics. Traditionally, routine estimates of coronal density have relied exclusively on white-light observations. However, these density estimates, obtained by inverting the white-light data, require simplifying assumptions, which may affect the robustness of the measurements. Hence, to improve the reliability of coronal density measurements, it is highly desirable to explore other complementary methods. In this study, we estimate the coronal electron densities in the middle corona, between approximately $1.7-3.5R_\odot$, using low-frequency radio observations from the recently commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). The results demonstrate consistency with those derived from white-light coronagraph data and predictions from theoretical models. We also derive a density model valid between 1.7--3.5 $r_\odot$ and is given by $\rho (r')=1.27r'^{-2}+29.02r'^{-4}+71.18r'^{-6}$, where $r'=r/R_\odot$, and $r$ is the heliocentric distance. OVRO-LWA is a solar-dedicated radio interferometer that provides science-ready images with low latency, making it well-suited for generating regular and independent estimates of coronal densities to complement existing white-light techniques.