2026/08/04 by Ryan J. Campbell, Carlos Quintero Noda, Mihalis Mathioudakis +35
Physics and Astronomy · #astro-ph.SR
Accepted for publication in ApJL
arxiv created 2026/08/04 · arxiv updated 2026/08/05
We present high-resolution multi-line spectropolarimetric observations of a quiet-Sun network element obtained with the \sc Sunrise~iii Chromospheric Infrared SpectroPolarimeter. The observations combine photospheric, upper-photospheric, and chromospheric diagnostics at a spatial resolution and polarimetric sensitivity that allow the transverse magnetic structure of the network boundary to be examined directly. We find that the strongest linear polarisation is concentrated in a narrow ridge around the edge of the magnetic element, co-spatial with enhanced transverse magnetic field inferred from multiline inversions. The magnetic azimuth exhibits a coherent, predominantly radial organisation around a more vertical core, consistent with an expanding magnetic canopy. An azimuth proxy derived directly from the observed Fe~i and K~i linear polarisation reproduces the same large-scale organisation, showing that this structure is encoded in the Stokes profiles rather than imposed by the inversion. Response functions and a MURaM-based forward-synthesis test indicate that the Fe~i~8468~Å linear polarisation is sensitive to magnetic azimuth in the upper photosphere, with the closest proxy agreement occurring near logτ≈-3. We find no evidence for strong azimuthal shear between the Fe- and K-sensitive diagnostics. At the network boundary, we also identify localised parasitic-polarity patches associated with complex, multi-lobed Stokes V profiles, and one case in which the Stokes V polarity reverses between photospheric Fe~i and chromospheric Ca~ii lines. These results demonstrate that quiet-Sun network boundaries contain organised upper-photospheric canopy fields together with small-scale mixed-polarity structure, providing new constraints on the three-dimensional magnetic structure of network elements.