7 Secrets of the Aurora in the Northwest Territories
A version of this post originally appeared on the Spectacular Northwest Territories website.
Lean in close. We have a secret to share. It’s about Canada's wildest lightshow.
Late at night. Far from town. Up at the top of the world. Up in the canvas of the sky. When the heavens burst into colour with the most spectacular Auroras on Earth, and do a glorious dance. All for you.
So, if you promise not to tell, we'll let you in on our secret. Here are 7 little-known reasons why the Aurora of the Northwest Territories is a wonder to behold.
In the central Northwest Territories, the Aurora is visible for an average of 200 nights per year. That's nearly every single night of the late summer, autumn, winter, and early spring.
Why is it so frequent here? Because we enjoy crystal-clear skies, ultra-low humidity, and a perfect location beneath the band of maximal Auroral activity – the so-called "Auroral oval."
The Aurora flares up when charged particles from the the sun interact with the Earth's outer atmosphere. The colours of the Aurora vary based on what layer of the atmosphere is being "excited." The most common colour is an eerie green glow. Those Aurora are caused by the excitement of oxygen atoms about 120 kilometres above the Earth's surface.
Sometimes, the Aurora blazes bright violet or crimson. This occurs during Auroral "storms," when charged solar particles penetrate closer to Earth, exciting molecular nitrogen at altitudes as low as 80 kilometers up.
These Auroral storms are intense. During especially vivid lightshows, scientists have measured the energy in the Aurora to be as much as 20 million amperes at 50,000 volts. By comparison, home circuit breakers are typically tripped by currents over 15-30 amperes at 120 volts.
Auroral storms happen when the sun ejects charged particles in a blast of "solar wind." These winds hurtle toward Earth at up to 3 million kilometres per hour, bombarding our magnetosphere and sending the Northern Lights into a frenzied dance.
These blasts of solar wind hit the Earth about 1,500 times per year – several times per day, on average. The bigger the blast, the more vivid the Aurora.
For as long as humans have craned their necks to watch the Aurora, they’ve also bent their ears to hear them. Lots of people swear the lights hiss and crackle. But for a long time, researchers said they were hearing things. Scientifically speaking, the “noisy Aurora” theory seems mad. After all, the lightshow happens in the soundless void of space. But a few years ago, a scientist placed low-frequency microphones beneath a magnetic storm and captured a “weird surging hiss.”