Dynamo processes in a thin shell geometry
Abstract
Presently active dynamos and signatures of past dynamo action have been detected in bodies throughout the solar system. To better understand dynamo processes in bodies with a thin shell outer core geometry, we are carrying out numerical simulations of magnetic field generation driven by thermal convection in a rotating spherical shell of electrically-conducting fluid. The spherical shell aspect ratio is defined as χ = ri / ro, where ri and ro are the radii of the solid inner core and fluid outer core, respectively. As the aspect ratio increases, the volume of convecting fluid in the outer core spherical shell decreases. In the simulations, the thin fluid shell surrounds a large electrically-conducting solid inner core that has the same conductivity as that of the surrounding fluid. We fix the aspect ratio to be χ = 0.75. This fluid shell is far thinner than that of the Earth's outer core where χ=0.35. The planet Mercury is a possible example of a body with a large aspect ratio core geometry. In addition, Mariner 10 fly-bys of Mercury detected a weak global-scale magnetic field. Thus, Mercury may represent a planet in which magnetic field generation processes are presently occurring within a thin shell outer core geometry. Our present results, at modest parameter values, seem to indicate that it is far more difficult to acheive self-sustaining dynamo action in a thin shell geometry.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMGP31A0176A
- Keywords:
-
- 1507 Core processes (8115);
- 3210 Modeling;
- 5430 Interiors (8147);
- 6207 Comparative planetology;
- 6235 Mercury