HR: 0800h
AN: GP21A-0011    [Abstracts]
TI: Possible Expression of the Obliquity Signal in Geomagnetic Field Behavior.
AU: * Fuller, M
EM: mfuller@soest.hawaii.edu
AF: HIGP-SOEST, U. Hawaii, 1680, East-West Rd., Honolulu, HI 96822 United States
AB: If precession plays an important role in powering the geodynamo, there should be some manifestation of precession in geomagnetic field behavior. The work reported here focuses upon the tendency of (1) minima in geomagnetic intensity to correlate with low precession angle in the obliquity signal for the past 800,000 years and (2) reversals to occur during times of low mean amplitude in the obliquity signal for the last 20 myrs. As the geomagnetic intensity records are generated for longer periods, we can test the relation between intensity and obliquity over the extended intervals and preliminary indications are that the same relationship is seen back to 1.2 Ma. Another observation of interest is the stage, or phase, in the obliquity signal at which reversals and excursions began. It appears that for the last reversal and for the Laschamps excursion the onset was during the decrease from the maximum obliquity close to the point of inflection. To test this relationship requires very accurate dating of the excursions and reversals and is probably only available at present for the last reversal and some of the most recent excursions. However, attempts to extend these investigations back in geological time show some promise. It appears that precession may play some role in powering the geodynamo and that realistic tests of the idea should be possible.
DE: 1510 Dynamo: theories and simulations
DE: 1513 Geomagnetic excursions
DE: 1535 Reversals: process, timescale, magnetostratigraphy
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005