A SWIRLING vortex of molten rock has been found 3000 kilometres beneath the
North Pole.
The Earth鈥檚 magnetic field is thought to be generated by circulation in its
molten outer core. By looking at historical measurements of the magnetic field,
geophysicists Peter Olson and Jonathan Aurnou of Johns Hopkins University in
Baltimore, Maryland, traced a flow of around a quarter of a degree a year in a
region 2400 kilometres across (Nature, vol 402, p 170). 鈥淚t has the
structure of a giant hurricane,鈥� says Olson.