Propagating Oscillations in the Lower Atmosphere Under Coronal Holes

• Published in: Solar physics Vol. 296; no. 12
• Main Authors: Chelpanov, Andrei, Kobanov, Nikolai, Chelpanov, Maksim, Kiselev, Aleksandr
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.12.2021; Springer Nature B.V
• Subjects: Alfven waves; Algorithms; Astrophysics and Astroparticles; Atmosphere; Atmospheric Sciences; Chromosphere; Corona; Coronal holes; Fluid flow; Lower atmosphere; Magnetohydrodynamic (MHD) Waves and Oscillations in the Sun’s Corona and MHD Coronal Seismology; Magnetohydrodynamics; Oscillations; Photosphere; Physics; Physics and Astronomy; Propagation; Solar atmosphere; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Spectroscopic observation; Standing waves; Wave propagation; Propagation; Coronal holes–oscillations; Solar–waves
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-021-01909-y

The subject of this study is oscillations in the lower atmosphere in coronal-hole regions, where the conditions are favorable for propagation between the atmospheric layers. Based on spectroscopic observations in photospheric and chromospheric lines, we analyzed the features of the oscillations that show signs of propagation between the layers of the solar atmosphere. Using the cross-spectrum wavelet algorithm, we found that both chromospheric and photospheric signals under coronal holes share a range of significant oscillations with periods around five minutes, while the signals outside coronal holes show no mutual oscillations in the photosphere and chromosphere. The phase shift between the layers indicates a predominantly upward propagation with partial presence of standing waves. We have also tested the assumption that the torsional Alfvén waves propagating in the corona originate in the lower atmosphere. However, the observed line-width oscillations, although similar in period to the Alfvén waves observed earlier in the corona of open-field regions, seem to be associated with other magnetohydrodynamic (MHD) modes. If we assume that the oscillations that we observed are related to Alfvén waves, then perhaps this is only through the mechanisms of the slow-MHD-wave transformation.