New ideas in stellar magnetism, and the magnetorotational instability

Geoffrey Vasil

February 14, 2013

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Abstract: Understanding the mechanisms behind solar magnetism remains one of the longest-standing unsolved problems in physics. Despite an impressive history of observations, from Galileo’s early drawings of sunspots to the trove of recent data coming from the Solar Dynamics Observatory, no one understands how the sun’s global magnetic dynamo machine operates. Over the last few decades theories have risen and fallen and creative new ideas are needed to make progress. In this talk, I will present a new model for dynamics within the sun’s outer layers. It is based on the magneto-rotational instability (MRI) and, surprisingly, corresponds to the dynamics of a buckling elastic beam under an applied load. This very simple reduced model can possibly help us understand two phenomena that strongly resist explanation to date: (i) the saturation of the MRI via flux and momentum conservation principles, and (ii) the migration of the equator branch of the solar torsional oscillation pattern, which correlates highly with sunspot migration.