He i Spectropolarimetry of a Supersonic Coronal Downflow Within a Sunspot Umbra

We report spectropolarimetric observations of a supersonic downflow impacting the lower atmosphere within large sunspot umbra. This work is an extension Schad et al. using acquired in He i 10830 Å triplet by Facility Infrared Spectropolarimeter. Downflowing material accelerating along cooled coronal loop reaches peak speeds near 200 km s−1 and exhibits both high speed emission absorption umbra, which we determine to be consequence strong height dependence radiatively controlled source function above Strong profiles close rest wavelengths but with long redshifted tails are also observed at terminus. From polarized spectra, infer longitudinal magnetic field strengths ∼2.4 kG core portion emission, believe strongest ever reported this line. Photospheric same line sight ∼2.8 as inferred Ca 10839 spectral The temperatures highest near-rest similar (∼10 kK), while differential measure analysis Solar Dynamics Observatory/Atmospheric Imaging Assembly data indicates significant increases radiative cooling for between ∼0.5 1 MK plasma associated Combined interpret these context shock induced low atmosphere.