## Abstract

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 mâ 1 to mâ =â 15 over the last two solar cycles. The peak-To-peak frequency change is less than 1 nHz for the mâ =â 1 mode, grows with m, and reaches 25 nHz for mâ =â 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.

Original language | English (US) |
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Article number | 202038539 |

Journal | Astronomy and Astrophysics |

Volume | 640 |

DOIs | |

State | Published - Aug 1 2020 |

## Keywords

- Hydrodynamics
- Sun: Activity
- Sun: interior
- Sun: oscillations
- Sun: rotation
- Waves

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science