Tuesday 15 Aug 2017: Dynamo 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.