Measurements of Coronal Magnetic Field Strengths in Solar Active Region Loops

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.