Evolution of Solar Subsurface Meridional Flows in the Declining Phase of Cycle 23

We study the evolution of meridional flows in the solar convection zone extending to a depth of 0.793 R☉ in the period 2000-2003 with helioseismic data taken with the Taiwan Oscillation Network (TON) using the technique of time-distance helioseismology. The meridional flows of each hemisphere formed a single-cell pattern in the convection zone at the solar minimum. An additional divergent flow was created at active latitudes in both hemispheres as the activity developed. The amplitude of this divergent flow correlates with the sunspot number: it increased from solar minimum to maximum (from 1996 to 2000), and then decreased from 2000 to 2003 with the sunspot number. The amplitude of the divergent flow increases with depth from 0.987 R☉ to a depth of about 0.9 R☉, and then decreases with depth at least down to 0.793 R☉.

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