Multilobed Stokes V Profiles of the Fe i 407.17 nm Line Observed by Sunrise iii

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Abstract
The near-ultraviolet part of the solar spectrum is densely crowded with spectral lines. Scattered among them are neutral iron lines with bell-shaped intensity profiles forming as high as the mid-chromosphere. Based on 1D model atmospheres, we predicted in our previous paper that these lines have unique multilobed Stokes V profiles even in the absence of gradients in magnetic field inclination or in line-of-sight velocity. The Sunrise Ultraviolet Spectropolarimeter and Imager (SUSI) instrument on board the Sunrise iii flight captured high spectral and spatial resolution observations in one such strong chromospheric Fe i line at 407.17 nm, in and around a sunspot. In these observations, these multilobed V profiles are best seen in the inner parts of the penumbra, where the Stokes V signal is strong and the Stokes I line shape displays the characteristic flattening of the inner wing along with a steep line core. By applying the weak field approximation (WFA) separately to the line core and wings, we infer line-of-sight magnetic field strengths ( B LOS ) at different heights in the atmosphere. We find differences between the inferred B LOS obtained from the line core and wing of up to 700 G. Despite the blend line in the blue wing and the relatively weak Stokes V signals, we show that it is still possible to qualitatively infer B LOS simultaneously at different heights in the atmosphere using the WFA on the Fe i 407.17 nm line.
Funding Information
  • National Aeronautics and Space Administration (#80NSSC18K0934)
  • National Aeronautics and Space Administration (#80NSSC24M0024)
  • EC ∣ Horizon 2020 Framework Programme (824135)
  • EC ∣ Horizon 2020 Framework Programme (101097844)
  • Deutsches Zentrum für Luft- und Raumfahrt (50 OO 1608)
  • Ministerio de Ciencia e Innovación (RTI2018-096886-B-C5)
  • Ministerio de Ciencia e Innovación (PID2021-125325OB-C5)
  • Ministerio de Ciencia e Innovación (PID2024-156066OB-C5)

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