Coronal Magnetography of a Simulated Solar Active Region from Microwave Imaging Spectropolarimetry

TL;DR

This study simulates microwave imaging spectropolarimetry of a solar active region to evaluate the potential for coronal magnetography, comparing different spectral analysis schemes and their accuracy in retrieving magnetic field parameters.

Contribution

It models the gyroresonance and free-free emission from a realistic solar active region and assesses the effectiveness of automated image-based analysis for coronal magnetic field estimation.

Findings

Image-based analysis yields reasonable magnetic field estimates.

Finite uv sampling introduces systematic errors.

Spectrally-based analysis can improve accuracy with better data.

Abstract

We have simulated the Expanded Owens Valley Solar Array (EOVSA) radio images generated at multiple frequencies from a model solar active region, embedded in a realistic solar disk model, and explored the resulting datacube for different spectral analysis schemes to evaluate the potential for realizing one of EOVSA's most important scientific goals--coronal magnetography. In this paper, we focus on modeling the gyroresonance and free-free emission from an on-disk solar active region model with realistic complexities in electron density, temperature and magnetic field distribution. We compare the magnetic field parameters extrapolated from the image datacube along each line of sight after folding through the EOVSA instrumental profile with the original (unfolded) parameters used in the model. We find that even the most easily automated, image-based analysis approach (Level 0) provides reasonable quantitative results, although they are affected by systematic effects due to finite sampling in the Fourier (uv) plane. Finally, we note the potential for errors due to misidentified harmonics of the gyrofrequency, and discuss the prospects for applying a more sophisticated spectrally-based analysis scheme (Level 1) to resolve the issue in cases where improved uv coverage and spatial resolution are available.