Time-dependent theory of solar meridional flows

Abstract

We explore consequences for the solar dynamo of a newly-developed physical hypothesis describing a weak coupling of the orbital and rotational motions of extended bodies. The coupling is given by - c ((dL/dt) x omega sub alpha) x r, where dL/dt represents the rate of change of barycentric orbital angular momentum, omega sub alpha is the angular velocity of rotation, r is a position vector identifying a particular location in a coordinate system rotating with the Sun, and c is a coupling efficiency coefficient. This form of coupling has no dependence on tides. The coupling expression defines a non-axisymmetric global-scale acceleration field that varies both in space and with time. Meridional components of acceleration typically dominate in equatorial and middle latitudes, while zonal accelerations become increasingly significant at higher latitudes. A comparison of the waveform of the putative dynamical forcing function with the time series for measured solar meridional flow speeds from Sunspot Cycle 23 yields correlations significant at the 99.9% level. We introduce the possibility of a destructive interaction between the predicted large-scale flows (due to orbit-spin coupling) and the dynamo mechanism(s) of the 22-year magnetic activity cycle; observations in recent cycles of higher meridional flow speeds during episodes of reduced solar sunspot activity may be explained as a consequence of differences between the phasing of the magnetic cycle and the phase of the forcing function. Algorithms are provided for calculating meridional and zonal orbit-spin coupling accelerations within the Sun as a function of latitude, longitude, depth, and time.

70 pages, 5 figures

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