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Direct simulation of planetary and stellar dynamos I: methods and results

Glatzmaier, GA (Santa Cruz)
Thursday 16 September 2004, 15:30-16:40

Seminar Room 1, Newton Institute


The first computer simulations of convection and magnetic field generation in a 3D spherical fluid shell were made two decades ago in an attempt to understand the solar dynamo. Early on the Boussinesq equations were replaced with the anelastic equations to more realistically represent the density-stratified solar interior. Many more global models were developed during the past decade to simulate the geodynamo; however, most have employed the Boussinesq equations because of the relatively small density stratification of the Earth's fluid core. These simulations have demonstrated that thermal convection in a rotating electrically-conducting fluid shell can maintain a global magnetic field. Geodynamo simulations have produced fields that have intensity, structure and time dependence at the surface that are surprisingly similar to those of the geomagnetic field. However, one must question how realistic the dynamo mechanism is well below the surface in these simulations. The early solar convection simulations produced a surface equatorial acceleration similar to the sun's; but the internal differential rotation in those simulations was later shown not to agree with that inferred from helioseismology.

In this first talk I will briefly review some of the numerical models that have been employed in these 3D global simulations. Some example dynamo simulations for the sun, Jupiter and the Earth will be presented. However, because of insufficient computing resources, none of these simulations are strongly turbulent. The challenges for future generation models to overcome this limitation and others will be discussed in the second talk.

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