Aurora Australis

By Dr Julia Petzl-Berney, UNE Discovery

Everybody has been talking about the aurora lately – and in May it was seen and photographed as far north as Mackay in north Queensland, a rare event in Australia. The reason for this is that the aurora australis (southern lights), and its northern cousin the aurora borealis (northern lights), have been more active than usual, due to an intense geo-magnetic storm which impacted the earth on a weekend in early May. Aurora watchers were rewarded with spectacular displays of colour in the sky, most vivid on Saturday the eleventh of May, but also on following nights in southern latitudes.

Credit: Luke Rasmussen, Powlett River at Dalyston, Southern Victoria

According to UNSW Professor of Chemistry, Timothy Schmidt, in an article in The Conversation, the sun undergoes an 11-year sunspot cycle, and it is approaching its peak. The good news is that we can expect more opportunities to marvel at the aurora over the coming year, before things go quiet again. Professor Schmidt explains that the aurora is caused by high-speed electrons impacting oxygen molecules in the upper atmosphere, where they split them into individual atoms. These atoms emit light until they bump into other oxygen atoms. Because air pressure is lower in the upper atmosphere, there are fewer oxygen atoms, so they have the chance of emitting light before bumping into another atom. This is the reason why the aurora does not occur at ground level, Professor Schmidt explains. The green and red colours, most commonly seen in the aurora, are caused by oxygen atoms, but other elements, such as nitrogen, can emit blue, red or magenta light.

To see the aurora, you need a clear few to the south, preferably away from city lights – the darker the sky, the better. The Australian Space Weather Forecasting Centre (ASWFC) publishes aurora alerts on its website, so you can assess when conditions are right. In addition to the ASWFC, there are numerous social media groups, which help beginners know when and where to look. And then there is the element of luck – being in the right place, at the right time, with a dark sky, and no cloud. It is also good to take a camera or your phone, as long-exposure shots will help capture more light and colour than you may be able to see with your naked eye.

For the aurora to reach as far north as northern NSW and right into Queensland is rare, but next time you are holidaying in Tasmania or on the southern coastline of Australia, it will be worth checking the aurora alert, just in case you have the opportunity for the experience of a lifetime.

To learn more about the aurora, see:

https://theconversation.com/what-causes-the-different-colours-of-the-aurora-an-expert-explains-the-electric-rainbow-229899

https://www.abc.net.au/news/2024-05-13/aurora-australis-displays-still-possible-but-less-likely/103839790