University of Otago physics professor Craig Rodger said the colourful phenomenon was caused by coronal mass ejections (CMEs) — explosions of plasma from the sun that are shot into space.
The material crosses space and can interact with Earth’s magnetic field, causing geomagnetic storms.
The latest CME was expected to arrive tonight, so there was a good chance of seeing aurora if the sky was clear, he said.
"The forecast is for a smallish geomagnetic storm. It’s not going to be a biggie.
"Assuming the forecast is right, and they’re not always right, it will be fine to see aurora from Stewart Island and Dunedin, low-ish on the horizon."
He believed this aurora event might be visible for up to two weeks and more might be visible in the coming months.
"We’re coming up towards solar maximum — a time over a year, to a year and a-half — when there will be much more regular aurora activity."
