Events

Nearly half a century has passed since the initial indications that stellar rotation slows while chromospheric activity weakens with a power-law dependence on age, the so-called Skumanich relations. This coupled evolution is ultimately driven by angular momentum loss from a stellar wind entrained in the large-scale magnetic field produced by global dynamo action. Recent observational evidence suggests that the global dynamo begins to shut down near the middle of a star’s main-sequence lifetime, leading to a disruption in the production of large-scale magnetic field, a dramatic reduction in angular momentum loss, and a decoupling of further evolution in rotation and activity. For solar-type stars this transition appears to occur near the age of the Sun, when rotation becomes too slow to imprint Coriolis forces on the global convective patterns, reducing the shear induced by differential rotation, and disrupting the large-scale dynamo. I will review the latest evidence for this new understanding of magnetic stellar evolution, including recent constraints on the rate of solar angular momentum loss and measurements of sun-like stars that place solar variability in context.

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