Contributed Talk - Splinter HiRes

Wednesday, 20 September 2017, 18:00   (Auditorium MPS)

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

F. Zeuner1 , A. Feller1 , M. van Noort1 , F. A. Iglesias1 and K. Reardon2
1Max Planck Institute for Solar System Research, Göttingen, Germany
2NSO, Sacramento Peak Observatory, Sunspot, New Mexico

Calculations, based on 3D MHD solar atmosphere simulations, of the photospheric Sr I 4607 \AA \ spectral line, known for its strong scattering polarization signals 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, insufficient 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 \AA \ line at disc center, carried out with the Dunn Solar Telescope (DST) at Sacramento Peak, New Mexico. With a high-cadence, dual-beam spectropolarimeter (FSP II) attached to a modified commercial CMOS camera, noise levels as low as 5 \cdot 10^-4 per pixel are achieved after 2 minutes of temporal binning.