Storming research

December 14, 2001

In March 1989, a magnetic storm brought down the electricity grid in Quebec, plunging the province into darkness for nine hours.

Such storms interfere with the electronics on spacecraft and have been linked to the loss of telecommunications spacecraft. But research from the British Antarctic Survey (Bas), published in the American Geophysical Union Journal of Geophysical Research , has settled a 20-year-old controversy that is a crucial to understanding and predicting space weather.

Principal investigator Richard Horne and lead scientists Iain Coleman and Gareth Chisham have been investigating the process that causes magnetic storms in the earth's magnetosphere, a region of the earth's magnetic field extending about 60,000km into space.

This field is known to intermittently connect with the interplanetary magnetic field originating from the sun. This process - known as magnetic reconnection - can transmit huge amounts of energy into the earth's magnetic field. The energy is stored and later released explosively, causing geomagnetic storms that can interfere with satellites, power cables, pipelines and communications.

For 20 years, researchers have debated two hypotheses as to where reconnection occurs, signalling how energy will flow into the magnetosphere.

One school of thought believed it would be at the point on the nose of the magnetosphere closest to the sun. The other argued that it occurred where the interplanetary magnetic field was in the opposite direction to the earth's field.

So far, spacecraft have been used to study reconnection, but they provide only point measurements. However, the signatures of reconnection are transmitted along the earth's magnetic field to the polar regions. The Bas team developed a test that predicts a very distinct signature in ground-based radars that should emerge if the anti-parallel theory is correct.

When they looked through past years' data from radars in the Arctic and Ant-arctic, they found four events with the signature they predicted, giving support for the anti-parallel hypothesis.

"The research highlights the importance of using ground-based radars to complement satellite observations," Dr Horne said.

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