Predicting frequency changes of global-scale solar Rossby modes due to solar cycle changes in internal rotation

C. R. Goddard, A. C. Birch, D. Fournier, L. Gizon

Research output: Contribution to journalArticlepeer-review

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 languageEnglish (US)
Article number202038539
JournalAstronomy and Astrophysics
Volume640
DOIs
StatePublished - 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

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