Geomagnetic scientists on extra-terrestrial alert
12 January 2007
Scientists from Geoscience Australia will have more reason to keep an eye on changes to Earth's magnetic field over the coming few years as the sun begins its next 11 year cycle of sunspot activity.
The last "sunspot maximum" occurred in 2000 and was followed by a period of decreasing sunspot numbers, but scientists are now seeing evidence suggesting the number may be starting to rise again. If the normal pattern continues they should peak around 2011.
Geoscience Australia will record any increased activity in the Earth's magnetic field at its geomagnetic monitoring stations at Kakadu and Alice Springs in the Northern Territory, Learmonth and Gnangara in WA, Charters Towers in Queensland, in the ACT near Canberra and in Antarctica at Casey, Mawson and Macquarie Island.
One of the significant effects of sunspots and associated solar flares is the impact on the Earth's magnetic field. The rapid field changes caused by sunspots affect satellite communications such as GPS and telephones as well as powerlines and long pipelines. Geophysicists who monitor the magnetic field liaise closely with Geoscience Australia geodesists who manage GPS base stations so advice can be provided on whether the accuracy of GPS positioning has been affected by any activity.
Another consequence of increased solar activity is auroras. These colourful displays are caused by charged particles from the sun entering the Earth's magnetic field and colliding with gas particles in the atmosphere. Auroras occur more commonly in polar regions. However, the phenomenon may be seen nearer the equator during periods of intense magnetic activity.
An example of what can be expected in the next few years, as solar activity approaches its peak, occurred on 13 December 2006 when a massive solar flare ejected huge amounts of energy and matter from the sun's surface into space.
On Earth, high-frequency radio communications fadeouts and reductions in the precision of GPS services occurred within minutes of the flare and increased magnetic-field activity was observed by ground-based equipment, including Geoscience Australia's geomagnetic sites, and space-based monitoring sites.
The effect of the solar flare was detected in magnetic-field recordings a few minutes after the flare occurred on the sun's surface and was followed around 36 hours later by the arrival at Earth of the ejected particles. The resulting high levels of magnetic-field activity (a magnetic storm) on 14 December 2006 degraded the accuracy of some GPS positions, caused disruptions to magnetic surveying operations and induced anomalous electrical currents in satellite circuits, power lines and pipelines.
Fortunately, because the Earth's position in space was out of the direct path of the ejected energy and matter, the effects were not as significant as would normally accompany solar flares of this size.
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