Magnetic Field Stratification in Active-Region Plage from Ca II K and Ca II 8542 Å Spectropolarimetry

@misc{berasategi2026magnetic,
  title = {{Magnetic Field Stratification in Active-Region Plage from Ca II K and Ca II 8542 Å Spectropolarimetry}},
  author = {Iñigo Juanikorena Berasategi and Ernest Alsina Ballester and Javier Trujillo Bueno and Francisco A. Iglesias and Yusuke Kawabata and Juan Sebastián Castellanos Durán and Masahito Kubo and Alex Feller and Yukio Katsukawa and Sami K. Solanki and Jose Carlos del Toro Iniesta and Andreas Lagg and Achim Gandorfer and Pietro Bernasconni and Thomas Kerkefeld and Tino L. Riethmüller and Yoshihiro Naito and Alberto Álvarez-Herrero and H. N. Smitha and David Orozco Suárez and Bianca Grauf and Michael Carpenter and Alexander Bell and Valentín Martínez Pillet and Francisco Javier Bailén and Julian Blanco Rodríguez and Edvarda Harnes and Johannes Hölken and Ryohtaroh T. Ishikawa and Takuma Matsumoto and Takayoshi Oba and Azaymi L. Siu-Tapia and Hanna Strecker and Dušan Vukadinović},
  howpublished = {arXiv},
  year = {2026},
  month = jul,
  doi = {10.48550/arxiv.2607.28102},
  eprint = {2607.28102},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.28102},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Magnetic Field Stratification in Active-Region Plage from Ca II K and Ca II 8542 Å Spectropolarimetry
AU  - Iñigo Juanikorena Berasategi
AU  - Ernest Alsina Ballester
AU  - Javier Trujillo Bueno
AU  - Francisco A. Iglesias
AU  - Yusuke Kawabata
AU  - Juan Sebastián Castellanos Durán
AU  - Masahito Kubo
AU  - Alex Feller
AU  - Yukio Katsukawa
AU  - Sami K. Solanki
AU  - Jose Carlos del Toro Iniesta
AU  - Andreas Lagg
AU  - Achim Gandorfer
AU  - Pietro Bernasconni
AU  - Thomas Kerkefeld
AU  - Tino L. Riethmüller
AU  - Yoshihiro Naito
AU  - Alberto Álvarez-Herrero
AU  - H. N. Smitha
AU  - David Orozco Suárez
AU  - Bianca Grauf
AU  - Michael Carpenter
AU  - Alexander Bell
AU  - Valentín Martínez Pillet
AU  - Francisco Javier Bailén
AU  - Julian Blanco Rodríguez
AU  - Edvarda Harnes
AU  - Johannes Hölken
AU  - Ryohtaroh T. Ishikawa
AU  - Takuma Matsumoto
AU  - Takayoshi Oba
AU  - Azaymi L. Siu-Tapia
AU  - Hanna Strecker
AU  - Dušan Vukadinović
PY  - 2026
DA  - 2026/07/30
PB  - arXiv
DO  - 10.48550/arxiv.2607.28102
UR  - https://arxiv.org/abs/2607.28102
AB  - We investigate the height variation of the line-of-sight (LOS) magnetic field in solar active-region (AR) plage from the upper photosphere to the upper chromosphere using co-spatial ultraviolet (UV) and infrared (IR) spectropolarimetric observations from the Sunrise III stratospheric balloon flight. The Ca II K and Ca II 8542 Å lines provide complementary chromospheric diagnostics, while nearby Fe I lines sample photospheric layers. The LOS magnetic field is inferred from the intensity and circular polarization profiles, applying the weak field approximation for the Ca II lines and the center-of-gravity method for the Fe I lines. The photospheric Fe I lines reveal strong, finely structured magnetic fields of the order of a kG. In contrast, the chromospheric Ca II diagnostics yield systematically weaker fields, typically in the ∼ 100-400 G range, with a more diffuse spatial distribution. Magnetic field maps inferred from the Ca II K line, formed higher in the chromosphere, are smoother and more extended than those derived from the Ca II 8542 Å line, which samples lower heights. We find that the magnetized area increases by a factor of ∼ 2 from the photosphere to the chromosphere. These results provide direct quantitative evidence that magnetic fields in AR plage weaken and expand with height, evolving from compact kG photospheric concentrations into weaker and more spatially extended structures in the upper chromosphere.
ER  -