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| Paper: |
Helioseismic Measurement of Large-Scale Solar Flows |
| Volume: |
416, Solar-Stellar Dynamos as Revealed by Helio- and Asteroseismology: GONG 2008/SOHO 21 |
| Page: |
15 |
| Authors: |
Woodard, M. F. |
| Abstract: |
Large-scale flows in the deep convection zone, differential
rotation and meridional circulation in particular, are
relatively accessible to seismic probing and provide
observational constraints on convection-zone dynamics and
structure. Flows and other aspherical perturbations
dynamically couple the Sun’s normal oscillation modes.
Mode coupling produces signatures in power spectra of time
series of coefficients in the spherical harmonic decomposition
of the photospheric velocity field, the outstanding signature
being the consequence of azimuthal-order (m)
dependence of the mode frequencies due to differential
rotation. Mode coupling also produces a signature in cross
spectra of distinct spherical-harmonic time series. In this
paper I discuss the problem of using helioseismic cross-spectra
to map large-scale flow in the Sun and prospects for measuring
deep meridional flow. Some preliminary estimates of meridional
and zonal flow from MDI and GONG spherical-harmonic time series
are presented.
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