Today is the last day of summer. If that makes you feel sad because days will be getting shorter, or mad because you didn’t have as many adventures as you wanted, this should cheer you up: Tomorrow’s arrival of the autumnal equinox makes it even more likely that you can steal a glimpse of the aurora borealis, or Northern Lights.
Believe it or not, these ethereal sky lights actually originate with the sun. Occasionally, solar activity triggers a release of gas, something scientists call a coronal mass ejection (CME). It takes two or three days for these emissions to reach the Earth’s magnetic field, where it generates currents of charged particles upon impact. According to Sten Odenwald, author of The 23rd Cycle: Learning to Live with a Stormy Star, these particles are boosted in energy in Earth’s upper atmosphere, and when they collide with oxygen and nitrogen atoms, they produce dazzling auroral light.
Normally, the Northern Lights are a special treat reserved only for those in higher altitudes, like Canada, Alaska and the Arctic. During a couple of very specific times of year, however, they become easier to see from lower elevations. One peak season for spotting the aurora borealis is in the weeks before and after the vernal equinox, which marks the beginning of spring in the Northern Hemisphere, and the other starts right around the autumnal equinox (now!) and lasts through the end of October.
According to Janet Green, a physicist at the National Oceanic and Atmospheric Administration (NOAA), the times around the equinoxes are when geomagnetic storms — disturbances in the Earth’s magnetic field — are strongest.
Unfortunately, spotting the Northern Lights isn’t like an eclipse or shooting star. There’s no precise way to predict when or where the auroral light will be visible. The best advice we found comes from Joe Rao at Space.com:
“If your newspaper, radio or TV reports that shortwave radio communications have been disturbed or interrupted, and especially if they say this had to do with something happening on the sun, or if you’re a trucker and notice unusual skip conditions on your CB radio, then, that night, the next night and even the next, get out away from city lights and look up toward the north.”
Good luck and happy autumn!
Main photo credit: Magdanatka/Shutterstock