Abstract

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. Reardon^2
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.