When the sun is active, it often produces mass ejections that interact with Earth's magnetic field. Electric currents begin to flow in the upper atmosphere, and these currents produce the aurora borealis, which occurs almost simultaneously around both the north and south poles.
Although infrequent, it is possible to witness an Aurora from Perth. Locations further south than Perth get a better chance.
A good website for Aurora Predictions is www.spaceweather.com , with more detailed information at the Space Environment Center (SEC) of NOAA.
In particular, to see an Aurora from Perth the levels must be around 8 on the KP 3-day index, and 10 + on the NOAA polar maps. Good luck!