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Precise photometry from the Kepler space telescope allows not only themeasurement of rotation in solar-type field stars, but also the determinationof reliable masses and ages from asteroseismology. These critical data haverecently provided the first opportunity to calibrate rotation-age relations forstars older than the Sun. The evolutionary picture that emerges is surprising:beyond middle-age the efficiency of magnetic braking is dramatically reduced,implying a fundamental change in angular momentum loss beyond a critical Rossbynumber (Ro~2). We compile published chromospheric activity measurements for thesample of Kepler asteroseismic targets that were used to establish the newrotation-age relations. We use these data along with a sample of wellcharacterized solar analogs from the Mount Wilson HK survey to develop aqualitative scenario connecting the evolution of chromospheric activity to afundamental shift in the character of differential rotation. We conclude thatthe Sun may be in a transitional evolutionary phase, and that its magneticcycle might represent a special case of stellar dynamo theory.

Stellar Evidence that the Solar Dynamo may be in Transition