Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP

Takayoshi Oba; Yukio Katsukawa; Masahito Kubo; Yusuke Kawabata; Takuma Matsumoto; Ryohtaroh T. Ishikawa; Yoshihiro Naito; Toshifumi Shimizu; Hirohisa Hara; Fumihiro Uraguchi; Toshihiro Tsuzuki; Kazuya Shinoda; Tomonori Tamura; Yoshinori Suematsu; Jose Carlos del Toro Iniesta; David Orozco Suárez; Maria Balaguer Jiménez; Azaymi L. Siu-Tapia; Carlos Quintero Noda; Sami K. Solanki; Andreas Lagg; Achim Gandorfer; Pietro Bernasconi; Thomas Berkefeld; Tino L. Riethmüller; Alberto Álvarez-Herrero; H. N. Smitha; Bianca Grauf; Michael Carpenter; Alexander Bell; Valentín Martínez Pillet; Francisco Javier Bailén; Julian Blanco Rodríguez; Juan Sebastián Castellanos Durán; Edvarda Harnes; Johannes Hölken; Francisco A. Iglesias; Hanna Strecker; Dušan Vukadinović

arXiv · 2608.14192

Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP

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Abstract

Acoustic waves propagate into the chromosphere, contributing to energy transport and their dynamics. Their upward propagation is restricted to frequencies above the acoustic cutoff frequency. The magnetic field configuration plays a key role in determining whether acoustic waves can propagate upward because the cutoff frequency is reduced in regions where the field is inclined with respect to gravity, forming so-called magnetoacoustic portals. Previous studies linked magnetic fields and oscillations in quiet regions, but these analyses were based on photospheric magnetic field information, leaving chromospheric structure unconstrained. This study investigates the coupling between acoustic waves and magnetic topology using photospheric and, for the first time, chromospheric spectropolarimetry in a quiet region, obtained with the Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) aboard the Sunrise iii balloon-borne solar observatory launched in 2024. The SCIP sit-and-stare observations sampled magnetic features in which the line-of-sight field strength exhibits multiple sharp spatial peaks in the photosphere while becoming broader and weaker at two heights in the chromosphere, indicating expanding fluxtubes. The chromospheric velocity field in these fluxtubes exhibits strong 5-minute oscillations, while the surrounding regions show weak 3-minute oscillations. In these fluxtubes, sawtooth temporal velocity variations are associated with intensity enhancements, suggesting steepened shocks. Fluxtubes with low-frequency oscillations are identified not only in network regions but also in weak internetwork regions. These results provide observational evidence that fluxtubes expanding into the chromosphere act as magnetoacoustic portals, in both network and internetwork regions, allowing low-frequency waves to propagate upward and driving chromospheric dynamics via shocks.

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Takayoshi Oba, Yukio Katsukawa, Masahito Kubo, Yusuke Kawabata, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Yoshihiro Naito, Toshifumi Shimizu, Hirohisa Hara, Fumihiro Uraguchi, Toshihiro Tsuzuki, Kazuya Shinoda, Tomonori Tamura, Yoshinori Suematsu, Jose Carlos del Toro Iniesta, David Orozco Suárez, Maria Balaguer Jiménez, Azaymi L. Siu-Tapia, Carlos Quintero Noda, Sami K. Solanki, Andreas Lagg, Achim Gandorfer, Pietro Bernasconi, Thomas Berkefeld, Tino L. Riethmüller, Alberto Álvarez-Herrero, H. N. Smitha, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Hanna Strecker, Dušan Vukadinović. 2026-08-14. Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP. https://arxiv.org/abs/2608.14192

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