Frequently flipping fields (29/3/2006) In the past news story,
Core business, we reported on research that the Earth's magnetic
field may be in the early stages of a polarity reversal. These
geomagnetic flips have occurred hundreds of times in the last
160 million years, and as the last one was 780,000 years ago
many researchers think we are overdue for the next reversal.
Until recently it was thought that the frequency of these
polarity reversals was random, following a Poisson distribution.
However Italian physicists have found that the process is better
described by a Levy distribution — a distribution used for
processes that exhibit "memory" of past events. So the pole
reversals are not independent events, and this information
should inform models of the magnetic dynamo process believed
responsible. But as for when the next flip is due, that still
remains a mystery. You can read about the strange magnetic
fields of Uranus and Neptune in Untangling a magnetic mystery,
and about the important role of the ma