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.
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.
– Alan, February 19, 2015 / © 2015 Alan Dyer / www.amazingsky.com