HR: 15:25h
AN: GP23A-07    [Abstracts]
TI: Variation of the Dynamo region and sudden termination of Mars Dynamo
AU: * Kuang, W
EM: Weijia.Kuang-1@nasa.gov
AF: NASA Goddard Space Flight Center, Planetary Geodynamics Laboratory, Code 698, NASA GSFC, Greenbelt, MD 20771, United States
AU: Jiang, W
EM: jiangw@umbc.edu
AF: University of Maryland, Baltimore County, Joint Center for Earth systems Technology, UMBC, Baltimore, MD 21250,
AB: Numerical simulation showed that the Mars dynamo could be subcritical towards the end of it history: as the Rayleigh number (measuring the driving force of the dynamo) decreases from the strong-field dynamo domain, the numerical Mars magnetic field remains comparable in magnitude. It vanishes suddenly when the Rayleigh number is lower than a critical value. However, the Mars dynamo will not be reactivated until the Rayleigh number increases to a value much higher than the critical point for the termination of the dynamo. To better understand the termination of the Mars dynamo, it is important to understand first the variation of the dynamo region in which the emf offsets the Joule dissipation. Our initial analysis shows that the dynamo region is often around the tangent cylinder (a co-axial cylindrical surface across the outer core tangent to the inner core boundary at the equator) and extended outward significantly. As the Rayleigh number decreases, the dimension of the region is reduced, and tends to fluctuate stronger in time. These two combined may suggest that there is probably a critical dimension, below which the dynamo region can no longer be sustained by core convection.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1510 Dynamo: theories and simulations
DE: 4255 Numerical modeling (0545, 0560)
DE: 5430 Interiors (8147)
DE: 5440 Magnetic fields and magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting