Aurora australis in New Zealand: the basics

This page has been on the site since 2003. It has been rewritten from scratch to cover the aurora australis as we understand and watch it today.

What the aurora is

The aurora australis, the southern lights, is light given off high in the atmosphere when charged particles from the Sun's solar wind are steered by Earth's magnetic field into a ring around each magnetic pole. Those particles collide with oxygen and nitrogen between roughly 100 and 400 km up, and the atoms and molecules release that energy as light.

Most of the time the southern auroral oval sits over the Southern Ocean and Antarctica. When a fast stream of solar wind or a coronal mass ejection hits Earth, the oval brightens and expands towards the equator, and that is when New Zealand gets a look.

Why the south sees more

Aurora follows magnetic latitude, not geographic latitude. The south magnetic pole lies off the Antarctic coast, on our side of the continent, so New Zealand sits at a higher magnetic latitude than its map position suggests. Southland, Otago and Rakiura Stewart Island are the best-placed parts of the country, and modest displays are seen from there several times a year. Canterbury and the West Coast need a stronger storm. The North Island usually needs a big one, although May 2024 showed that even Northland can get a clear view when the conditions line up.

The colours

Green is the most common colour, from atomic oxygen emitting at 557.7 nm, typically 100 to 250 km up.
Red also comes from atomic oxygen, at 630.0 nm, but higher up where the air is very thin. Because the red layer is so high, it is often the part seen from further north, sitting as a low red glow on the southern horizon.
Purple, pink and blue come mainly from nitrogen, usually along the lower edges of active rays and curtains.

How often

Aurora activity follows the Sun's roughly 11-year cycle, with the most frequent strong storms around and just after solar maximum. Even in quiet years, a coronal hole stream can produce a good night in the deep south. Displays are hard to predict more than a day or two ahead, which is why most watchers rely on short-range alerts. Our guide to reading an aurora forecast and the NOAA Space Weather Prediction Center's aurora page are good places to start.

What it looks like to the eye

This surprises many first-timers. Unless a display is strong, the aurora often looks like a grey-white or faintly greenish glow low over the southern horizon, sometimes with pale vertical pillars that slowly come and go. Our night vision is poor at seeing colour in faint light, so the vivid greens and reds in photos are mostly what the camera picks up during a long exposure. A phone on night mode will often show colour before your eyes do. During a strong storm, colour and movement become obvious without any help.

Aurora or skyglow?

Plenty of "aurora" reports turn out to be something closer to home. The common mix-ups:

Town light domes. A city or large town beyond the horizon throws up a dome of orange-white light. It stays in the same place all night and is centred on the town's direction, whether that is south or not.
Cloud-lit glow. Low cloud reflects street lighting and can look like a pale band. Check whether stars are visible through it; aurora is transparent, cloud is not.
Greenhouses, stadiums and industrial sites. Large horticultural glasshouses and floodlit grounds can light the sky in odd colours, including pink and purple, and can even produce beams on hazy nights.

How to tell the difference:

Direction. Aurora sits towards the south or south-east to south-west. Note where the nearest towns are.
Change. Aurora shifts over minutes: pillars brighten and fade, arcs drift. A light dome stays the same.
Structure. Rays that line up with each other, like a fence of light, are a strong sign of aurora.
Stars. Stars visible through the glow point to aurora rather than lit cloud.
Data. If space weather readings are quiet, a glow in the north is almost certainly not aurora.

For a practical walk-through of getting out to see it, see how to see and photograph the aurora australis.