Aurora Australis Forecast Guide

A forecast for the southern hemisphere uses the same data as one for the north. The difference is where you point your eyes. Run through these checks before you leave home:

• Kp: the planetary activity index. A higher value pushes the auroral oval toward the equator, in the south as well as the north. See the Kp index page for how it works.
• Bz: the north-south component of the solar wind magnetic field. When Bz turns southward and stays there, energy gets into the magnetosphere and aurora brightens.
• The oval: NOAA's OVATION model shows the southern auroral oval and where the glow is likely to reach. Compare its edge with your latitude.
• Darkness and moon: you need astronomical darkness and, ideally, a moon below the horizon.
• Cloud: a clear southern horizon matters more than anything else in the list.

The live map shows the current oval in both hemispheres, so you can check how close it comes to Australia and southern New Zealand.

Kp is a three-hour index. It tells you how disturbed the field has been, not what is happening in the next ten minutes. A storm with a high Kp can pass through before you are outside, and a modest Kp can produce a surprise display if Bz flips south.

Treat Kp as the headline and Bz as the trigger. Watch both, and expect activity to come in bursts of ten to thirty minutes with quieter stretches between them. Stay out long enough to catch one.

At Australian latitudes you also need to be realistic. Kp has to be high for a display to show over the southern horizon, and strong storms are not common. When the forecast is quiet, there is nothing to see, and no amount of dark sky will change that.

Tasmania is the best-placed state. It is the closest part of Australia to the southern auroral zone, and the south and east coasts have open views over the sea. Check the live status for Hobart and Launceston, and head out of town to a dark coast or hilltop.

The Victorian coast comes next. Melbourne is bright, so use the Mornington Peninsula, the Bellarine, Phillip Island or the Surf Coast, which all look south over water. In South Australia, Adelaide has dark south-facing beaches on the Fleurieu Peninsula, and the south coast of Western Australia has a similar advantage.

Every place in this list needs a strong storm, and the display will usually sit low on the horizon. Open ocean to the south is the ideal foreground, and a hill or tall building blocking the south is the common reason people miss it. The Australia page lists all the cities the site covers.

New Zealand's South Island lies further south than any Australian state and often has better odds. The site does not cover New Zealand, but the same method applies there.

In the southern hemisphere the aurora appears toward the south pole, so face south. At Australian latitudes the display is usually a red or pink glow low on the horizon, with green visible only in a strong storm. A camera will show it earlier than your eyes will.

Take a photo toward the south with a few seconds of exposure and check the result. A pale pink or green band on the screen that you cannot see by eye is a good sign, and you can compare the next shot with how it changes. See aurora colors for what each color means.

The southern winter gives the longest nights, so the practical season runs from about March to September. Around the March and September equinoxes the solar wind couples to Earth's field more efficiently, so there tends to be more activity than at the solstices. Summer evenings are short, and in Tasmania it is hardly dark before 10 pm in December.

The Sun runs in an eleven-year cycle, and the years around its maximum produce more big storms. That helps, but any season can surprise you with a short, strong event. Treat the forecast as the real guide and the calendar as a rough filter.

A full moon floods the sky and hides all but the strongest display. Plan for the days around the new moon if you can. When the moon is up, put it behind you and look at the dark side of the sky.

Cloud is the other. Southern Australia has frequent fronts from the Southern Ocean, and a cloud bank over the southern horizon will block the lights even if the rest of the sky is clear. Check a satellite loop and cloud forecast before you drive, and have a backup spot. Leave your car lights off at the viewpoint, give your eyes time to adapt, and stay out for at least an hour before giving up on the night.