Northern Lights put on a show

THE NORTHERN LIGHTS have been in the news lately, with some impressive displays reported this week. Here’s a plain-language Q&A on the Lights and when and where they can be seen.

Also called the “aurora borealis”, the Northern Lights are big patches of glowing air molecules high up in our atmosphere. The Southern Hemisphere equivalent is the “aurora australis” or Southern Lights.

To see the Northern Lights you have to be located in far northern latitudes, eg. UK, Scandinavia, northern Europe. Likewise, to see the Southern Lights you have to be located in far southern latitudes, eg. Tasmania, New Zealand and the tip of South America. The best view of the Southern Lights is to be had in Antarctica.

The Northern Lights get their name from the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas.

The video above shows what the aurora looks like from space.

What causes them?

They’re caused by an interaction between particles from the Sun, Earth’s magnetic field and Earth’s atmosphere.

The Sun sends out waves of electrically charged particles, sometimes in big clumps. Those particles get caught in Earth’s magnetic field and are funnelled downward from space and toward our north and south poles.

When they hit the molecules in our upper atmosphere, those molecules give off light—a bit like a giant fluorescent tube in the sky.

They occur very high up, in the upper layer of Earth’s atmosphere called the “thermosphere”—essentially, right on the edge of space

The different colours are caused by the different molecules in the air: oxygen produces a green or brownish glow, nitrogen produces a red or blue glow. The glows from oxygen and nitrogen can combine to produce a pink glow.

Here’s a very good video that explains how the aurora is produced:

Can we see them from Australia?

Yes, but you have be far south and away from city lights. During the time of solar maximum (see below), they’re often seen from Tasmania, southern Victoria and southern Western Australia. In the past, I’ve even heard reports of sightings from the Blue Mountains west of Sydney.

Because the Southern Lights occur down near Antarctica, from Australian latitudes they will be seen way down toward our southern horizon (if at all).

I understand that the next 12 months should be good to see them?

Yes. The Sun has an 11-year cycle of activity, and we’re coming up to “solar maximum” sometime in the next 12-18 months. So we can expect many more auroral reports.

Apart from a pretty light show, do they have any other effects on us?

The aurorae themselves don’t have any other effect, but the space weather that causes them can.

Those charged particles from the Sun, and the effect the solar wind can have on Earth’s magnetic field, can cause:

  • Damage or disruption to satellites, eg. GPS, communications, weather, military
  • Disruption to radio communications networks
  • Damage or disruption to electricity grids (due to currents induced into the grid by the changing magnetic field)
  • Damage or disruption to long pipeline systems (ditto)
  • Disruption to mineral exploration (which often relies on magnetic field information)

More information:

Space Weather.com

Aurora Watch

Aurora Alert

Aurora Forecast

Space Weather Prediction Centre

Ionospheric Prediction Service (Australian Government)

Story by Jonathan Nally.

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