Fast dual-beam spectropolarimetry - first results on scattering polarization measurements with FSP II at the DST

F. ZEUNER; FELLER, A.; IGLESIAS, F. A; K. REARDON

Göttingen

Conferencia; The many Scales of the Universe: Galaxies, their Suns, and their Planets; 2018

German Astronomical Society

Calculations, based on 3D MHD solar atmosphere simulations, of the photo-spheric Sr I 4607 A spectral line, known for its strong scattering polarizationsignals of up to 1%, predict a unique spatial distribution of linear polarization,induced by scattering of the locally fluctuating radiation field, even when observed at disc center. Thus far, however, insuffcient polarimetric sensitivity, spatial resolution and/or low cadence have prevented this pattern in the linear polarization from being detected in observations. We present preliminary results of observations with the Fast Solar Polarimeter (FSP) in the Sr I 4607 A line at disc center, carried out with the Dunn Solar Telescope (DST) at Sacramento Peak, New Mexico. With a high-cadence, dual-beam spectropo-larimeter (FSP II) attached to a modified commercial CMOS camera, noiselevels as low as 5 x 10e-4 per pixel are achieved after 2 minutes of temporalbinning.