Ghostly glows and magnetic storms
30 January 2003
For thousands of years, people living near the Earth's poles have witnessed arcs of red, green, yellow and purple light ebb across the clear night sky.
These ghostly lights, known as auroras, produce some of the most spectacular displays of nature - but the geomagnetic storms that cause the aurora can often disturb radio communication and electrical systems.
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 magnetic field indicate the onset of a magnetic storm and that within hours there may be an aurora.
"If conditions are good, with clear skies and you are near polar areas, there is a very good chance that you will see an aurora during a magnetic storm", says Liejun Wang, a geophysicist at Geoscience Australia.
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 Mawon, Casey and Macquarie Island.
The data collected from these observatories is critical to monitor geomagnetic storms. The information is also used for a number of other applications.
Andrew Lewis, a geophysicist at Geoscience Australia says, "the network of observatories addresses national needs for information about the geomagnetic field in the Australian Region." He continues, "the data has applications in magnetic navigation, in mineral exploration, in researching the structure of the Earth's crust and the nature of geomagnetic phenomena, as well as Solar-Terrestrial physics."
Auroras are the only visible sign we have that a magnetic storm is happening. Meanwhile, Geoscience Australia through its network of geomagnetic observatories is monitoring every twitch that solar activities cause in the geomagnetic field.
Further Information About Auroras
Auroras are caused by collisions of charged particles with molecules and atoms in the Earth's thin upper atmosphere, causing them to glow as they release energy. The source of these charged particles is the Sun: events such as solar flares and coronal mass ejections blast one million tonnes of charged particles outwards from the Sun every second.
As this stream of magnetic material approaches the earth, the particles are directed towards the poles by the Earth's magnetic field where they collide with atoms of oxygen and nitrogen producing dazzling auroral displays.
Small-scale magnetic storm activity is occurring nearly all the time. Auroras will only be visible however, during periods of intense magnetic storm activity. The most recent principal magnetic storm occurred on 21 November 2002.
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