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After removal of the temporal mean at each location, the rotation rate just above and below the base of the convection zone shows marked variations. At least during 1995-2000, the rotation rate at 0.72RSun near the equator appears to vary on a 1.3 y period, with anticorrelated variations at 0.63RSun. These variations are seen in GONG (black) and MDI (red), for two different inversion techniques denoted by filled and open symbols. The signature is not as clear in the more recent (high activity) data. After a recent re-analysis of the GONG data, resulting in 15% more coefficients, preliminary indications are that the signal is still seen. |