Sunrise III/SUSI reveals extended and spectrally structured Ca II K emission above the solar limb

Ivan Milić; Christopher M. J. Osborne; Francisco A. Iglesias; Juan Sebastián Castellanos Durán; Damien F. Przybylski; Lakshmi Pradeep Chitta; Sanghita Chandra; Andreas Lagg; Sami K. Solanki; Tino L. Riethmüller; Achim Gandorfer; Alex Feller; Johannes Hoelken; H. N. Smitha; Jose Carlos del Toro Iniesta; Yukio Katsukawa; Pietro Bernasconi; Thomas Berkefeld; Alberto Álvarez-Herrero; Masahito Kubo; Valentín Martínez Pillet; David Orozco Suárez; Bianca Grauf; Michael Carpenter; Alexander Bell; Hanna Strecker; Azaymi L. Siu-Tapia; Pablo Santamarina Guerrero; Julian Blanco Rodríguez; Yusuke Kawabata; Takuma Matsumoto; Ryohtaroh T. Ishikawa; Edvarda Harnes; Takayoshi Oba; Dušan Vukadinović

arXiv · 2609.38575

Sunrise III/SUSI reveals extended and spectrally structured Ca II K emission above the solar limb

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Abstract

The Sunrise III/SUSI instrument performed a sit-and-stare observation of the off-limb emission in the Ca II K line core, with a combination of excellent temporal and spectral resolution. The emission reaches up to 6 Mm above the solar limb, indicating the existence of off-limb structures akin to spicules. In this letter, we describe the spatio-spectral properties of the observed emission, focusing on the spectral line shape resolved in detail by Sunrise III/SUSI, and compare the observation with simple modeling that relies on a numerical simulation of the solar chromosphere. We find that the simulation contains enough cool and dense material at Mm heights to produce off-limb emission, but that the spectral width of these features is slightly lower than observed, necessitating more detailed modeling.

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Ivan Milić, Christopher M. J. Osborne, Francisco A. Iglesias, Juan Sebastián Castellanos Durán, Damien F. Przybylski, Lakshmi Pradeep Chitta, Sanghita Chandra, Andreas Lagg, Sami K. Solanki, Tino L. Riethmüller, Achim Gandorfer, Alex Feller, Johannes Hoelken, H. N. Smitha, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alberto Álvarez-Herrero, Masahito Kubo, Valentín Martínez Pillet, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Hanna Strecker, Azaymi L. Siu-Tapia, Pablo Santamarina Guerrero, Julian Blanco Rodríguez, Yusuke Kawabata, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Edvarda Harnes, Takayoshi Oba, Dušan Vukadinović. 2026-09-29. Sunrise III/SUSI reveals extended and spectrally structured Ca II K emission above the solar limb. https://arxiv.org/abs/2609.38575

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