precdyn_po03all.pdf (26.96 kB)
Dynamo driven by precession in a spherical shell
We use the exact same parameters as Tilgner (2005) in his figure 4, namely a Poincaré number Po=0.3 and a precession angle alpha=120°.
With today's computing resources, we are able to explore the low viscosity regime by reducing the Ekman number E (ratio of kinematic viscosity to spin rate).
The area of the dots is proportional to the magnetic energy.
We find that the minimum magnetic Prandtl number Pm, after decreasing with E, start to increase at low viscosisies.
This means that for geophysical parameters (E<1e-10, Pm<1e-5) dynamo action in a spherical shell is very unlikely.
Note that the sphere is peculiar as the driving is by viscous forces at the boundaries, unlike in a spheroid or ellipsoid.
The runs were performed using the XSHELLS code on the Occigen super-computer.
With today's computing resources, we are able to explore the low viscosity regime by reducing the Ekman number E (ratio of kinematic viscosity to spin rate).
The area of the dots is proportional to the magnetic energy.
We find that the minimum magnetic Prandtl number Pm, after decreasing with E, start to increase at low viscosisies.
This means that for geophysical parameters (E<1e-10, Pm<1e-5) dynamo action in a spherical shell is very unlikely.
Note that the sphere is peculiar as the driving is by viscous forces at the boundaries, unlike in a spheroid or ellipsoid.
The runs were performed using the XSHELLS code on the Occigen super-computer.
