(Un)stable stellar magnetic fields and a model of stellar dynamo (Contributed speaker)

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• Fabio Del sordo (Institute of Space Sciences (CSIC))
• Friday 16 September 2022, 09:30-10:15
• Seminar Room 1, Newton Institute.

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DY2W01 - Dynamos in planets and stars - similarities and differences

The present understanding of stellar dynamos still lacks a clear mechanism linking it to magnetic interaction between planets on close-in orbits and their host stars. I here present an analytical model based on the solution for a stellar α-squared dynamo surrounded by a force-free corona and an outer layer consistent with the presence of a Parker stellar wind. This analytical model allows for making predictions on different scenarios. For example, I will show how magnetized close-in exoplanets, such as hot Jupiters, have either no effect or can suppress the stellar dynamo. The first case is related to non-evaporating exoplanets, whilst the second emerges when planetary evaporation is present and implies the presence of currents in the stellar corona. This model may explain the low activity observed for some exoplanet host stars such as HD 209458b, 51 Pegasi, Wasp 18, and GJ1151 . I will also present some global numerical MHD simulations of stellar dynamos to show the central role played by boundary conditions. Magnetic star-planet interaction can therefore quench stellar dynamo,  significantly lowering the level of magnetic activity of stars hosting hot Jupiters.

This talk is part of the Isaac Newton Institute Seminar Series series.

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