HR: 17:45h
AN: NG34A-08    [Abstracts]
TI: An Ising Model for the Earth´s Dipole
AU: Dias, V H
EM: vitor@on.br
AF: Observatorio Nacional, Rua General Jose Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil
AU: Dias, V H
EM: vitor@on.br
AF: State University of Rio de Janeiro, Physics Institute, Rua Sao Francisco Xavier 524, Maracana, Rio de Janeiro, RJ 20550-900, Brazil
AU: Franco, J O
EM: jodir@on.br
AF: Observatorio Nacional, Rua General Jose Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil
AU: Franco, J O
EM: jodir@on.br
AF: State University of Rio de Janeiro, Physics Institute, Rua Sao Francisco Xavier 524, Maracana, Rio de Janeiro, RJ 20550-900, Brazil
AU: Fontes, S L
EM: sergio@on.br
AF: Observatorio Nacional, Rua General Jose Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil
AU: * Papa, A R
EM: papa@on.br
AF: Observatorio Nacional, Rua General Jose Cristino 77, Rio de Janeiro, RJ 20921-400, Brazil
AU: * Papa, A R
EM: papa@on.br
AF: State University of Rio de Janeiro, Physics Institute, Rua Sao Francisco Xavier 524, Maracana, Rio de Janeiro, RJ 20550-900, Brazil
AB: Models for the Earth´s liquid core, and in particular, for reversals it produces, are interesting not only from the fundamental point of view but also in order to generate synthetic data (given that the set of known reversals is unique and small). We simulated the complex behavior of the Earth´s liquid core by the relatively simple Ising model (ferromagnetic). We have focused our attention on reversals and their distribution functions. Each ring current was supposed to behave as a magnetic spin while the magnetization of the model was supposed to be proportional to the Earth´s dipole. We compare our results to those by Ito and Seki, the first who used this type of simulation. With that purpose they used the Q2R updating scheme. We have reproduced those simulations and obtained similar results. We have also simulated the 2D Ising system using Metropolis algorithms. Our results seem to better reproduce actual properties of reversals (in particular, the small frequency of near zero magnetization periods). A more realistic approach to simulate eddies is an antiferromagnetic model (neighbor ring currents interact in this way both mechanically and magnetically). Unfortunately the magnetization is not a good order parameter for Ising antiferromagnetic systems and the results are meaningless. A step forward was to simulate the 2D Ising antiferrimagnetic model. Results for this case are also satisfactory when compared to actual reversal distributions. The lack of dynamical ingredients (apparent in actual reversals) is, however, a drawback for these types of models. Some possible trends for future works are advanced.
DE: 0545 Modeling (4255)
DE: 1507 Core processes (1213, 8115)
DE: 1510 Dynamo: theories and simulations
DE: 1535 Reversals: process, timescale, magnetostratigraphy
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting