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Old 24-01-2009, 11:56 PM
Enchilada
Enhanced Astronomer

Enchilada is offline
 
Join Date: Nov 2008
Location: Sydney, Australia
Posts: 753
FREQUENCY of SOUTHERN AURORAE

In the southern hemisphere, the magnetic pole is placed just off the coast of Antarctica facing towards Australia. From latitudes south of about -45o- being from Tasmania to southern New Zealand will usually see aurorae more frequent than any other populated areas in the south. As the South Island is closer to the magnetic pole, therefore places like Queenstown and Invercargill will see many more aurorae. From Australia, the aurorae is see mainly in its southern parts - namely Tasmania, Southern Victoria and sometime of the South Australia. Aurorae, though less frequently, it has been viewed from latitudes like Sydney, much of New South Wales, and even Brisbane in Queensland. Far more aurorae, however, are visible from the Antarctic continent.

For southern places, from New Zealand’s Invercargill, the number averages five to ten ech month. The probability of aurorae in eastern Australia is smaller roughly being;

- Hobart was twice per month
- Melbourne once per month
- Sydney once every five years
- Brisbane once every ten to fifteen years
- Cairns once or twice per century

Generally the stronger the outburst of geomagnetic activity, the further from the geomagnetic poles an aurorae can be seen. These powerful events are far rarer, so the frequency of the aurora will decrease rapidly. Overall this frequency does changes significantly. It depends mainly on the proximity we are to solar maximum and when the sunspots are near maximum numbers - and this occurs near the earth’s magnetic poles around latitudes of about 60o; namely, Canada and Greenland in the north, Tasmania and New Zealand in the South. The actual magnetic poles show fewer aurorae than occurs about 1 500 kilometres away within the auroral ovals.

In theory, an aurora could be seen anywhere on Earth. It is possible to see aurorae nearer the equator - perhaps possibly as frequently as once or twice each century! Of course, much of this activity is also closely locked-in with the 11.3 year solar sunspot cycle. This explains why more aurorae and more probable nearer, or just after, solar maximum that at minimum. Furthermore, that most aurorae in high geomagnetic latitude will only be seen during solar maximum.
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