Helioseismic detection of deep meridional flow

Abstract

Steady meridional flow makes no first-order perturbation to the frequencies of helioseismic normal modes. It does, however, Doppler shift the local wavenumber, thereby distorting the eigenfunctions. For high-degree modes, whose peaks in a power spectrum are blended into continuous ridges, the effect of the distortion is to shift the locations of those ridges. From this blended superposition of modes, one can isolate oppositely directed wave components with the same local horizontal wavenumber and measure a frequency difference which can be safely used to infer the subsurface background flow. But such a procedure fails for the components of the more-deeply-penetrating low-degree modes that are not blended into ridges. Instead, one must analyze the spatial distortions explicitly. With a simple toy model, we illustrate one method by which that might be accomplished by measuring the spatial variation of the oscillation phase. We estimate that by this procedure it might be possible to infer meridional flow deep in the solar convection zone.

23 pages, 9 color figures, submitted to the Astrophysical Journal

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Cited by in corpus (12)

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• Global helioseismic evidence for a deeply penetrating Solar meridional flow consisting of multiple flow cells
• Effects of Asymmetric Flows in Solar Convection on Oscillation Modes
• Supergranules as Probes of the Sun's Meridional Circulation
• Magnetic field topology of the RS CVn star II Pegasi
• Studies of grand minima in sunspot cycles from a flux transport solar dynamo model
• What have we learned from helioseismology, what have we really learned, and what do we aspire to learn?
• A Critical Evaluation of Recent Claims Concerning Solar Rotation
• Verification of the helioseismic Fourier-Legendre analysis for meridional flow measurements
• Inferring solar differential rotation through normal-mode coupling using Bayesian statistics
• Recent Developments in Helioseismic Analysis Methods and Solar Data Assimilation
• Probing the Solar Meridional Circulation using Fourier Legendre Decomposition