7 Secrets of the Aurora in the Northwest Territories
This article originally appeared on the Spectacular Northwest Territories website.
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 colors of the Aurora vary based on what layer of the atmosphere is being "excited." The most common color is an eerie green glow. Those Aurora are caused by the excitement of oxygen atoms about 75 miles 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 50 miles 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 almost 2 million miles 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.”