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Description
We report high-spatial-resolution spectropolarimetric observations of a solar filament and its surrounding region, obtained with the Sunrise Chromospheric Infrared spectro-Polarimeter (SCIP) onboard the SUNRISE III balloon-borne observatory on 15 July 2024.
The target, a filament located near the disk center adjacent to an active region, was monitored for over two hours.
SCIP recorded full Stokes profiles in the Ca II 8542 \AA line, providing, to our knowledge, the first unambiguous detection of linear polarization in a solar filament within this wavelength.
The detected linear polarization signals exceeded the 2$\sigma$ noise level and exhibited characteristic Zeeman double-lobe profiles, distinguishing them from scattering-induced polarization.
Using the weak field approximation, we derived a magnetic field strength of approximately $-80$ G along the line of sight and 300–500 G in the transverse direction.
The magnetic field vector appears nearly parallel to the filament axis in the northeastern portion, while the southeastern part extends beyond the field of view.
Furthermore, we present preliminary analysis of the magnetic structure in the neighboring plage region.
We find intriguing Stokes $V$ sign reversals that appear to be intrinsically linked to the spatial coexistence of emission and absorption components in the Ca II line core, probably reflecting complex chromospheric heating.
These results demonstrate that SCIP opens a new diagnostic window on the vector magnetic structure of the lower chromosphere, complementing existing He I-based observations of the upper chromosphere and providing new insights into the coupling between thermal and magnetic properties in both filaments and active regions.