Ghostly skies on the horizon
31 October 2003
Intense solar activity this week has sent the gaze of southern Australians to the skies, in the hope of catching a glimpse of an auroral show. These ghostly lights produce some of the most spectacular displays of nature. Real-time measurements of the geomagnetic field available on the Geoscience Australia web site can indicate the best times for aurora spotting.
In the past, auroras have been seen in southern areas of Australia, and as far north as southern Queensland, but the conditions need to be right. Rapid changes in the Earth's magnetic field indicate the onset of a magnetic storm and that within hours there may be an aurora.
"In Canberra, people need to look to the south, you need cloud free skies and a dark horizon as the aurora will appear quite low in the sky as a diffuse red glow", says Geoscience Australia geophysicist, Andrew Lewis.
"The aurora may build up gradually, and may only last for 10 to 15 minutes, and perhaps only occur once during the night.
During periods of intense solar activity, charged particles can interfere with the earth's magnetic field, causing damage and disturbance to radio and satellite communications, radar, global positioning system (GPS), spacecraft, powerlines and pipelines.
To monitor and help reduce the potential hazardous effects of magnetic storms, Geoscience Australia maintains a national network of geomagnetic observatories, which are part of a global network that records variations in the earth's magnetic field. These are located within Australia at Alice Springs, Canberra, Charters Towers, Gnangara, Kakadu and Learmonth. There are also three Geoscience Australia observatories in the Antarctic region at Mawson, Casey and Macquarie Island.
During the recent magnetic activity over the last few days the most rapid magnetic variations recorded by the GA observatory network have been at Macquarie Island, where during a half hour period the compass swung through 13 degrees.
The data collected from these observatories is critical to monitor geomagnetic storms. The information is also used for a number of other applications.
"The public can access real-time information on the Earth's magnetic field on the Geoscience Australia web site. The magnetic field is constantly changing, but during a magnetic storm, it is highly erratic and there will be a good chance of seeing an aurora in clear night skies at that time."
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