Stargazing: Understanding the Northern Lights

Ken Tapping, astronomer with the National Research Council’s Dominion Radio Astrophysical Observatory

My very first encounter with an aurora was in England, before I came to Canada, at the house of a radio amateur.

He was communicating by sending shortwave signals northward, where they reflected off an aurora to radio amateurs all over northern half of our planet. The Morse Code bouncing back from the aurora was really strange. The whistle notes making up the dots and dashes had a strange “warbling” tone and sounded as though they were echoing in some vast, celestial cathedral. It was much more fascinating than the only sighting I had of an aurora from southern England, an elusive green glow in the northern sky that went away after a couple of hours. Then I saw the Canadian version.

In Canada, particularly in the North, the aurora can be truly spectacular: flickering curtains, blobs and rays of green and red, and sometimes bright enough to read by. It’s not surprising that most northern communities around the world have incorporated the northern lights into their mythology and folk lore. There is far too much to summarize here, but two contrasting myths are: don’t look at the aurora while giving birth or your child will be cross-eyed, alternately, children conceived under the aurora will be exceptional.

Scientists have been trying to work out what an aurora is and how it works for well over a hundred years. We now know roughly what is going on, but there are still lots of fundamental things we do not understand. We know for sure that auroras are caused by interactions between the sun, the Earth’s magnetic field and the atmosphere.

The story starts with the solar wind, a blast of atomic particles and magnetic fields flowing out from the sun. It is always there, but varies in speed and density, becoming a solar gale on occasion. Most of the time it is flowing at a few hundred kilometres a second, but sometimes comes at us at thousands of kilometres a second.

The Earth is surrounded by a magnetic field. In the absence of the solar wind it would appear like a huge doughnut, with the holes centred over the north and south magnetic poles. However, the solar wind blows it out into a long, teardrop shape.

Particles from the solar wind are constantly penetrating the Earth’s magnetic field and getting trapped there. The rubbing of the solar wind over the surface of the Earth’s magnetic field makes waves. These run along the magnetic field, down to the ground at northern latitudes. These can be picked up and converted to sound. They sound like “feeding time at a cosmic zoo.”

When the solar wind blows extra hard, more of the Earth’s magnetic field is pushed back into the tail of the teardrop. This drives the stresses higher in in a place that is already highly unstable. The magnetic fields snap, releasing their stored energy. The energy pulses propagate back towards the Earth, where they accelerate particles down into the atmosphere around the magnetic poles, where they collide with atoms of nitrogen and oxygen in the air, making them glow green and red. The sheer variety in auroral displays is due to the range of processes involved, because each may manifest itself in different ways. Space missions have shown that other planets with magnetic fields have auroral displays too.

The beautiful light show is only a tiny part of what is going in the upper reaches of our atmosphere. Huge electric currents are flowing, a menagerie of plasma waves are growing and spreading out, and magnetic fields are doing amazing things. It is intriguing to think that some of the most challenging physics in the universe is going on a few hundred kilometres above our heads.

Venus shines brightly in the west after sunset. After dark, Jupiter dominates the southern sky and Saturn is rising in the southwest. Mars rises about 1 a.m. The moon will be new on June 13.

Ken Tapping is an astronomer with the National Research Council’s Dominion Radio Astrophysical Observatory, Penticton.


Steve Kidd
Senior reporter, Penticton Western News
Email me or message me on Facebook
Follow us on Facebook | Twitter | Instagram

Just Posted

LETTER: Thanks to all who ran in election

To those that were elected, I look forward to your collective stewardship

Kettle Valley Steam Railway holds train ride of terror

Summerland tourist train will have Halloween-themed events

Ballet Kelowna to kick off 16th season with pair of premiers

Fresh off performances in Beijing and Toronto, company will perform at KCT Nov. 16 and 17

LETTER: Support candidates who will assist cannabis industry

Cannabis has often provided extra income for fruit growers or paid the bills for students

COLUMN: Life is So Good: A biography to remember

George Dawson was African American at a time of great racial discrimination

B.C. sailor surprised by humpback whale playing under her boat

Jodi Klahm-Kozicki said the experience was ‘magical’ near Denman Island

VOTE: Nature in Focus reader’s choice photo contest

The Penticton Western News Reader’s Choice photo contest

Who is running in Summerland’s election?

Introducing you to the candidates asking for your vote on Oct. 20

Ovechkin has 4 points as Caps rough up Canucks 5-2

WATCH: Defending champs pick up impressive win in Vancouver

World Junior Hockey fever hits Vernon

Vipers spice up floor ball demonstration at OK Landing School

Shuswap refugee family settles into new, more hopeful life

Father of 10th Syrian family to come to Salmon Arm says learning English, work, top priorities

RCMP seek missing Vernon man

Michael Ramsey, 49, was last seen Oct. 21

B.C. government moves to tighten resource industry regulations

New superintendent will oversee engineers, biologists, foresters

Most Read