Volume 640, August 2020
|Number of page(s)||8|
|Section||Letters to the Editor|
|Published online||04 August 2020|
Letter to the Editor
Predicting frequency changes of global-scale solar Rossby modes due to solar cycle changes in internal rotation
Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: email@example.com, firstname.lastname@example.org
2 Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
3 Center for Space Science, NYUAD Institute, New York University Abu Dhabi, Abu Dhabi, UAE
Accepted: 13 July 2020
Context. Large-scale equatorial Rossby modes have been observed on the Sun over the last two solar cycles.
Aims. We investigate the impact of the time-varying zonal flows on the frequencies of Rossby modes.
Methods. A first-order perturbation theory approach is used to obtain an expression for the expected shift in the mode frequencies due to perturbations in the internal rotation rate.
Results. Using the time-varying rotation from helioseismic inversions we predict the changes in Rossby mode frequencies with azimuthal orders from m = 1 to m = 15 over the last two solar cycles. The peak-to-peak frequency change is less than 1 nHz for the m = 1 mode, grows with m, and reaches 25 nHz for m = 15.
Conclusions. Given the observational uncertainties on mode frequencies due to the finite mode lifetimes, we find that the predicted frequency shifts are near the limit of detectability.
Key words: Sun: rotation / waves / Sun: oscillations / Sun: interior / Sun: activity / hydrodynamics
© C. R. Goddard et al. 2020
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.
Open Access funding provided by Max Planck Society.
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