Issue |
A&A
Volume 682, February 2024
|
|
---|---|---|
Article Number | A39 | |
Number of page(s) | 11 | |
Section | The Sun and the Heliosphere | |
DOI | https://doi.org/10.1051/0004-6361/202348380 | |
Published online | 31 January 2024 |
Numerical study of non-toroidal inertial modes with l = m + 1 radial vorticity in the Sun’s convection zone
Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: bekki@mps.mpg.de
Received:
25
October
2023
Accepted:
16
November
2023
Various types of inertial modes have been observed and identified on the Sun, including the equatorial Rossby modes, critical-latitude modes, and high-latitude modes. Recent observations have further reported the detection of equatorially antisymmetric radial vorticity modes that propagate in a retrograde direction about three times faster than those of the equatorial Rossby modes, when seen in the corotating frame with the Sun. Here, we study the properties of these equatorially antisymmetric vorticity modes using a realistic linear model of the Sun’s convection zone. We find that they are essentially non-toroidal, involving a substantial radial flow at the equator. Thus, the background density stratification plays a critical role in determining their dispersion relation. The solar differential rotation is also found to have a significant impact by introducing the viscous critical layers and confining the modes near the base of the convection zone. Furthermore, we find that their propagation frequencies are strikingly sensitive to the background superadiabaticity, δ, because the buoyancy force acts as an additional restoring force for these non-toroidal modes. The observed frequencies are compatible with the linear model only when the bulk of the convection zone is weakly subadiabatic (−5 × 10−7 ≲ δ ≲ −2.5 × 10−7). Our result is consistent with but tighter than the constraint independently derived in a previous study (δ < 2 × 10−7), employing the high-latitude inertial mode. It is implied that, below the strongly superadiabatic near-surface layer, the bulk of the Sun’s convection zone might be much closer to adiabatic than typically assumed or it may even be weakly subadiabatic.
Key words: convection / Sun: helioseismology / Sun: interior / Sun: rotation
Publisher note: The inappropriate sentence, introduced by mistake at the end of the 1st paragraph of the Introduction, was deleted on 25 June 2024.
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model.
Open access funding provided by Max Planck Society.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.