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Changes in earth's dipole Peter Olson & Hagay Amit

Summary: REVIEW
Changes in earth's dipole
Peter Olson & Hagay Amit
Received: 14 July 2005 /Revised: 11 May 2006 /Accepted: 18 May 2006 / Published online: 17 August 2006
# Springer-Verlag 2006
Abstract The dipole moment of Earth's magnetic field has
decreased by nearly 9% over the past 150 years and by
about 30% over the past 2,000 years according to
archeomagnetic measurements. Here, we explore the causes
and the implications of this rapid change. Maps of the
geomagnetic field on the core­mantle boundary derived
from ground-based and satellite measurements reveal that
most of the present episode of dipole moment decrease
originates in the southern hemisphere. Weakening and
equatorward advection of normal polarity magnetic field
by the core flow, combined with proliferation and growth of
regions where the magnetic polarity is reversed, are
reducing the dipole moment on the core­mantle boundary.
Growth of these reversed flux regions has occurred over the
past century or longer and is associated with the expansion


Source: Amit, Hagay - Institut de Physique du Globe de Paris
Olson, Peter L. - Department of Earth and Planetary Sciences, Johns Hopkins University


Collections: Geosciences