EARTH鈥橲 magnetic field isn鈥檛 doing well. It is fading and breaking out in spots, and nobody knows if it will recover. What鈥檚 worse, it could even vanish altogether for several thousand years. Without this magnetic shield, we would have no protection against the harsh radiation of the solar wind.
Roughly every 200,000 years, the Earth鈥檚 north-south field disappears and then returns with the north and south poles reversed. That hasn鈥檛 happened for nearly 800,000 years, says geophysicist Mike Fuller at the University of Hawaii. 鈥淲e鈥檙e certainly overdue for a reversal.鈥� So researchers at the conference pooled their latest results to assess whether the worst is about to happen.
By studying magnetic particles in lava and clay, Robert Coe at the University of California, Santa Cruz, has seen a steady weakening of the field over the past 2000 years. And ground and satellite measurements suggest the decline is accelerating. Coe clocks it at 5.5 per cent per century 100 years ago, and at 8 per cent per century now.
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Meanwhile Gauthier Hulot at NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, has been tracking a growing region under the southern tip of Africa where the field has already reversed. This phenomenon is familiar to researchers using computers to simulate processes within Earth鈥檚 core: magnetic field models run by geophysicist Paul Olson of Johns Hopkins University develop similar patches of reversed polarity before each field flip.
But despite these warning signs, few scientists seem willing to predict a reversal any time soon. They point out that the field has sunk to even lower levels many times, only to revive again. Asked for his prognosis, Coe concludes, 鈥淲e just don鈥檛 know.鈥�
