Tuesday 15 Aug 2017Dynamo waves in global simulations

Lucia Duarte - University of Exeter

4th Floor Interaction Area 11:15-11:45

Dynamo simulations give us insight about the large scale magnetic fields

observed at the surface of several astrophysical objects like planets and

stars. They also reveal the hidden small scale magnetism out of reach for

observations. These simulations solve the dynamics of the electrically

conducting fluid or gas in the interiors of these objects, where

convection is typically driven by the cooling and shaped by the rotation.

The topology of the resulting large scale fields varies considerably. Here

we will focus on time dependent magnetic field which consist of large

scale features that change periodically in space and time. This

oscillatory behaviour may persist over most of the object's lifetime.

These are dynamo waves and require strong shear flows to generate strong

toroidal fields bands in the interior. The turbulent flows in turn produce

magnetic field as well by twisting, turning and folding field lines. An

offset between this and the toroidal field generation by shear typically

causes the wave-like motion of the field lines. These may be identifiable

at the surface and the best known example is the Sun's butterfly diagram.

We will show some examples of dynamo models with waves and the mechanisms

behind them, that take place in the deep interiors.

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