HR: 0830h
AN: GP11C-0282 [PDF]
TI: Confirming an Imminent Reversal From Information Content Analysis of a Simulated Geodynamo Compared
With Present Global Field Models
AU: De Santis, A
EM: desantis@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - INGV, Via di Vigna Murata 605, Rome, 00143
Italy
AU: * Tozzi, R
EM: tozzir@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - INGV, Via di Vigna Murata 605, Rome, 00143
Italy
AU: Wicht, J
EM: wicht@linmpi.mpg.de
AF: Max Planck Institut fr Aeronomie, Max-Planck-Str. 2, Katlenburg-Lindau, 37191
Germany
AB:
Concepts of information theory are applied to both global models (IGRF) of the geomagnetic field B of the last century and a
dynamo simulation including a reversal. Temporal behavior of information content of the present observed field suggests that
B is in a chaotic state characterized by timescales close to those of its westward drift and of the convective overturn in
the outer core. The main implication of these results is the possibility that a geomagnetic reversal is currently in
progress. Results from a selfconsistent 3d dynamo simulation have also been examined. This numerical model undergoes nearly
periodic reversals with one reversal period covering roughly one dipole decay time, i.e. 20,000 years. The temporal behavior
of the information content shows the expected linear decrease due to chaotic dissipation on two distinct time scales. A slow
decrease with a memory time of 12,000 years reflects the slow internal reversal process. This is followed by a fast process
with a memory time of 2,000 years, representing the field reversal at the core-mantle-boundary. The latter is ruled by the
advective overturn time. After the reversal, the system increases its information content as if energized until it again
reaches the level it had before the start of the process. Similarities to the behavior of information content in the observed
global field models during the last century suggest that the geomagnetic field might be in the state of fast information
decrease. This implies that the next polarity change might happen within the next 1,000 years.
DE: 1507 Core processes (8115)
DE: 1535 Reversals (process, timescale, magnetostratigraphy)
DE: 1560 Time variations--secular and long term
DE: 3220 Nonlinear dynamics
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting