RARE BLUE AURORAS OVER CANADA:
Posted: Thu Jul 29, 2021 3:38 am
I checked the aurora cam in Canada this evening, but they're socked in with clouds so there's nothing right now. 
RARE BLUE AURORAS OVER CANADA: "A solar wind stream hit Earth during the early hours of July 28th. First contact rattled Earth's magnetic field and sparked rare blue auroras over Canada. Joel Weatherly sends this picture of the colorful spray just outside Edmonton:
"Despite light pollution, clouds, and bright moonlight, the auroras put on a spectacular show," says Weatherly. "Note the blue on top!"
Auroras are almost always green, and sometimes red or purple. Blue, however, is rare. Weatherly can thank the Moon for its appearance.
Blue is a sign of bright moonlight hitting the top of the auroras. The process is called "resonant scattering." High up in the aurora zone, ionized nitrogen molecules (N2+) naturally produce blue light, just a little; the geomagnetic glow is usually too faint to see. But when these ions get hit by moonlight, they capture and re-emit blue photons from the Moon. Voilà!--extra blue.
Take some nitrogen, add solar wind, mix with moonlight. That's the recipe for aurora blues. Aurora alerts: SMS Text. "
https://spaceweather.com/
RARE BLUE AURORAS OVER CANADA: "A solar wind stream hit Earth during the early hours of July 28th. First contact rattled Earth's magnetic field and sparked rare blue auroras over Canada. Joel Weatherly sends this picture of the colorful spray just outside Edmonton:
"Despite light pollution, clouds, and bright moonlight, the auroras put on a spectacular show," says Weatherly. "Note the blue on top!"
Auroras are almost always green, and sometimes red or purple. Blue, however, is rare. Weatherly can thank the Moon for its appearance.
Blue is a sign of bright moonlight hitting the top of the auroras. The process is called "resonant scattering." High up in the aurora zone, ionized nitrogen molecules (N2+) naturally produce blue light, just a little; the geomagnetic glow is usually too faint to see. But when these ions get hit by moonlight, they capture and re-emit blue photons from the Moon. Voilà!--extra blue.
Take some nitrogen, add solar wind, mix with moonlight. That's the recipe for aurora blues. Aurora alerts: SMS Text. "
https://spaceweather.com/