7 November 2002
Geomagnetic jerks: a new twist
Earth's geomagnetic field varies gradually over the years, but four times
in past 50 years there have been sudden changes in the rate of variation,
each lasting a couple of years. These 'geomagnetic jerks' occurred in
1969, 1978, 1991 and 1999. Their short timescale suggests they are the
result of changes in the flow of liquid iron at the surface of the Earth's
core, but the cause of this change has been unknown. A new model explains
geomagnetic jerks in terms of torsional oscillations in the core, a phenomenon
predicted in core flow and numerical dynamo simulations.
The origin of geomagnetic jerks
JEREMY BLOXHAM, STEPHEN ZATMAN & MATHIEU DUMBERRY
Nature 420, 65–68 (2002); doi:10.1038/nature01134
| First
Paragraph | Full
Text (HTML / PDF) |
