aurora colors – The Amazing Sky

All-Sky Aurora #1 (Feb 17, 2015)

The Northern Lights have performed beautifully the last few nights, presenting curtains of light dancing across the sky.

Two nights ago in Churchill, Manitoba we were treated to a “storm level” show of aurora, with the Lights all across the sky in green curtains waving and curling before our eyes.

The curtains tower several hundred kilometres up into the atmosphere, from the lower edge at about 80 km up (still high above the stratosphere) to the curtain tops at about 400 km altitude at the edge of space.

The camera picks up the colours far better than the eye can, recording not only the predominant green hues but also shades of pink, magenta and red.

The magentas and reds come from the sections of the curtains at the highest altitudes, from the top of the auroral curtains. Here, where the atmosphere is a near vacuum, sparse oxygen atoms can glow with a red emission line.

However, there must be a blue component as well, leading to the magenta or pink tones, as in my photos here. Nitrogen can glow in blues and purples and might be contributing to the colours.

The top two photos are from Tuesday night, Feb 17, when storm levels of 5 were in effect worldwide.

All-Sky Auroral Curtains #2 (Feb 18, 2015)

Lower down, at about 100 km altitude, the air is denser and oxygen glows with a brighter green hue, which the eye can detect more easily.

The photo above from last night, with an activity level of just 2, also shows most of the sky covered with a faint emission, with a patchy appearance, with dark “holes” also moving and flowing in the time-lapse movies I shot.

Closer to the horizon, and far to the north, the aurora brightens into the more characteristic green snaking curtains.

This image from three nights ago shows an usually coloured aurora at the start of the night, glowing mostly a deeper red and orange.

The green was still off in the distance far to the east. It arrived a few minutes later as green curtains swept in over us.

But the initial red was from low-energy electrons lighting up just high-altitude oxygen. Only when the higher energy particles arrived did the sky light up green.

I shot all these images with an 8mm fish-eye lens as frames in time-lapse sequences intended for use projected in digital planetarium domes, where the 360° “all-sky” scene would be recreated on the dome as it was in real life.

If you are with a planetarium, contact me if you’d like to get aurora clips.

Our second group of aurora tourists has arrived today at the Churchill Northern Studies Centre, and the weather is warming to a high of -20° C. Balmy!

We’re hoping for more fine displays, though the space weather forecast calls for a quiet magnetic field in the next few days.

Beautiful curtains of light draped across the sky despite the blizzard blowing below.

Last night, February 16, was the last night for aurora viewing for the first aurora tour group hosted by the Churchill Northern Studies Centre.

Despite predictions calling for an active display, we had given up hope of seeing anything, as a blizzard had been raging all day and into the evening. But about 10 pm I knocked on doors down the hall — get up! The Lights are out!

Against all odds, skies cleared enough to reveal a wonderful all-sky display of Northern Lights, with multiple curtains of light snaking over the sky.

The view above overlooks the now derelict launch buildings of the abandoned Churchill Rocket Range, in use from the late 1950s until the 1980s. Some 3500 rockets were fired from here in its heyday, shot into the active auroras that occur here almost nightly under the auroral oval.

This view overlooks the boreal forest on the frozen shore of Hudson Bay, and shows the multiple curtains that twisted and turned across the sky.

Tonight’s display was marked by fringes of magenta, rather than the deeper reds we observed 2 nights ago.

Winds were howling and snow was blowing, but from the shelter of the Centre’s second floor observing deck we could view the display in windless comfort, despite the -30° C temperatures.

The group was delighted at having this bonus viewing night. Now the concern is whether the blizzard will abate enough to allow flights in and out of Churchill Airport. The group might get another night under the Lights!