Measurements of Coronal Magnetic Field Strengths in Solar Active Region Loops

TL;DR

This study measures coronal magnetic field strengths in solar active region loops using a novel spectroscopic diagnostic technique, revealing values between 60 and 150 Gauss, which impact understanding of loop dynamics and plasma conditions.

Contribution

The paper introduces a new atomic radiation modeling method to determine coronal magnetic fields from EUV spectral lines, providing direct measurements in active region loops.

Findings

Magnetic field strengths range from 60 to 150 G.

Results influence estimates of Alfvén speeds and plasma beta.

Comparison with previous spectropolarimetric measurements discussed.

Abstract

The characteristic electron densities, temperatures, and thermal distributions of 1MK active region loops are now fairly well established, but their coronal magnetic field strengths remain undetermined. Here we present measurements from a sample of coronal loops observed by the Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode. We use a recently developed diagnostic technique that involves atomic radiation modeling of the contribution of a magnetically induced transition (MIT) to the Fe X 257.262A spectral line intensity. We find coronal magnetic field strengths in the range of 60--150G. We discuss some aspects of these new results in the context of previous measurements using different spectropolarimetric techniques, and their influence on the derived Alfv\'{e}n speeds and plasma $\beta$ in coronal loops.