STELLAR EVIDENCE THAT THE SOLAR DYNAMO MAY BE IN TRANSITION
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder CO 80301 (United States)
- High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307 (United States)
- Carnegie Observatories, 813 Santa Barbara Street, Pasadena CA 91101 (United States)
Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation–age relations for stars 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 Rossby number (Ro ∼ 2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation–age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.
- OSTI ID:
- 22654274
- Journal Information:
- Astrophysical Journal Letters, Vol. 826, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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