The umbrella effect: Magnetic canopy topology modulates spatially averaged chromospheric three-minute power
Abstract
Three-minute (∼5 mHz) oscillations are a prominent signature of wave propagation in the solar chromosphere, but their measured power can vary substantially between full-disc observations and small, high-resolution fields of view. We investigate whether chromospheric magnetic canopy topology, particularly its lateral continuity and areal filling, modulates field-of-view-averaged three-minute power. We analyse Hα and Ca II 8542 Å spectral imaging from the Swedish 1-m Solar Telescope, comparing canopy-poor quiet-Sun scenes with canopy-dominated active-region environments, complemented by radiative-MHD Bifrost simulations of canopy-poor and canopy-rich atmospheres. We compute field-of-view-averaged power spectra from fixed-wavelength intensities and bisector-derived velocities in the observations, and from synthetic intensities, velocities, and temperature proxies in the simulations. We also quantify the relation between integrated 3-5 mHz excess power and canopy filling factor, using HMI-based magnetic-field extrapolations for the observations. In both observations and simulations, canopy-poor scenes show clear 3-5 mHz power enhancements, whereas canopy-dominated scenes show strongly reduced measured power. The trend is present in Hα and Ca II 8542 Å intensities and is supported by complementary velocity and temperature proxies. Integrated 3-5 mHz excess power decreases with increasing canopy filling factor. We conclude that chromospheric field-of-view-averaged three-minute power is a topology-weighted observable: dense, laterally continuous magnetic canopies can strongly reduce the measured large-scale three-minute signature without requiring the absence of local wave activity. This provides a practical criterion for interpreting chromospheric oscillation power as a proxy for atmospheric wave energy in the Sun and in magnetised cool-star atmospheres.
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BibTeX
@misc{jafarzadeh2026umbrella,
title = {{The umbrella effect: Magnetic canopy topology modulates spatially averaged chromospheric three-minute power}},
author = {Shahin Jafarzadeh and David B. Jess and Marco Stangalini and Bernhard Fleck and Richard J. Morton and Samuel D. T. Grant and Peter H. Keys and Luc Rouppe van der Voort and Sven Wedemeyer and Tiago M. D. Pereira and Mikołaj Szydlarski and Elias R. Udnæs and Thomas Wiegelmann and Markus Roth},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.30707},
eprint = {2608.30707},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.30707},
}
RIS
TY - UNPB
TI - The umbrella effect: Magnetic canopy topology modulates spatially averaged chromospheric three-minute power
AU - Shahin Jafarzadeh
AU - David B. Jess
AU - Marco Stangalini
AU - Bernhard Fleck
AU - Richard J. Morton
AU - Samuel D. T. Grant
AU - Peter H. Keys
AU - Luc Rouppe van der Voort
AU - Sven Wedemeyer
AU - Tiago M. D. Pereira
AU - Mikołaj Szydlarski
AU - Elias R. Udnæs
AU - Thomas Wiegelmann
AU - Markus Roth
PY - 2026
DA - 2026/08/31
PB - arXiv
DO - 10.48550/arxiv.2608.30707
UR - https://arxiv.org/abs/2608.30707
AB - Three-minute (∼5 mHz) oscillations are a prominent signature of wave propagation in the solar chromosphere, but their measured power can vary substantially between full-disc observations and small, high-resolution fields of view. We investigate whether chromospheric magnetic canopy topology, particularly its lateral continuity and areal filling, modulates field-of-view-averaged three-minute power. We analyse Hα and Ca II 8542 Å spectral imaging from the Swedish 1-m Solar Telescope, comparing canopy-poor quiet-Sun scenes with canopy-dominated active-region environments, complemented by radiative-MHD Bifrost simulations of canopy-poor and canopy-rich atmospheres. We compute field-of-view-averaged power spectra from fixed-wavelength intensities and bisector-derived velocities in the observations, and from synthetic intensities, velocities, and temperature proxies in the simulations. We also quantify the relation between integrated 3-5 mHz excess power and canopy filling factor, using HMI-based magnetic-field extrapolations for the observations. In both observations and simulations, canopy-poor scenes show clear 3-5 mHz power enhancements, whereas canopy-dominated scenes show strongly reduced measured power. The trend is present in Hα and Ca II 8542 Å intensities and is supported by complementary velocity and temperature proxies. Integrated 3-5 mHz excess power decreases with increasing canopy filling factor. We conclude that chromospheric field-of-view-averaged three-minute power is a topology-weighted observable: dense, laterally continuous magnetic canopies can strongly reduce the measured large-scale three-minute signature without requiring the absence of local wave activity. This provides a practical criterion for interpreting chromospheric oscillation power as a proxy for atmospheric wave energy in the Sun and in magnetised cool-star atmospheres.
ER -