Inference of the physical parameters of Hα-absorbing plasma structures in the quiet Sun

¹ Astronomy Program, Department of Physics and Astronomy, Seoul National University Gwanak-gu Seoul 08826, Republic of Korea
² Astronomy Research Center, Seoul National University Gwanak-gu Seoul 08826, Republic of Korea
³ Korea Astronomy and Space Science Institute, Daedeokdae-ro Yuseong-gu Daejeon 34055, Republic of Korea
⁴ Max-Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 37077 Göttingen, Germany
⁵ Space Research and Technology Institute, Bulgarian Academy of Sciences, Acad. Georgy Bonchev Str. Bl. 1 1113 Sofia, Bulgaria
⁶ Research Institute of Natural Sciences, Chungnam National University, 99 Daehak-ro Yuseong-gu Daejeon 34134, Republic of Korea
⁷ Astronomy and Space Science, University of Science and Technology, 217 Gajeong-ro Yuseong-gu Daejeon 34113, Republic of Korea

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Received: 5 August 2025
Accepted: 27 November 2025

Abstract

On-disk Hα light-absorbing plasma structures such as mottles, fibrils, filaments, and Hα jets are observable magnetohydrodynamic features in the upper solar chromosphere. We attempt to determine their physical parameters by regarding them as optical clouds scattering the Hα-line light incident from below. For this purpose, we developed a new inversion, which we call the three-layer background plus three-component cloud model inversion. This new spectral inversion was found to be applicable to every Hα line profile taken from a quiet-Sun region. We used the model parameters inferred from the fitting to determine the temperature and to construct the velocity distribution function at every point in the observed region. This function was used in turn to calculate the column mass, mass flux, kinetic energy, and kinetic energy flux. Our approach yielded three types of Doppler velocities: the mass flux-associated velocity, the kinetic energy-associated velocity, and the kinetic energy flux-associated velocity. We found that the physical parameters of Hα-absorbing structures in a quiet-Sun region resolve the long-standing discrepancy between the Doppler velocities of mottles observed on the disk and the rising speeds of spicules observed off the limb. We also found that the kinetic energy budget of the upper chromosphere is large enough for the radiative loss in the upper chromosphere and corona. These results support the hypothesis that magnetohydrodynamic waves heat the upper atmosphere of the quiet Sun.