A double-burst of solar particles sparked auroral lights over the weekend, as expected — but at least in some parts of the world, the colors were not what you'd expect. Instead of the typical greenish glow, observers reported seeing reds, pinks, violets and even blues.
"It's been many years since I saw the blue in our auroras, but Saturday night they came back," John Welling reported in a note accompanying the photo he posted to SpaceWeather.com.
Pinks, reds and blues also dominated the scene captured on camera early Sunday by Brad Goldpaint, from a vantage point above Oregon's Crater Lake. Goldpaint says the opportunity came about "by pure coincidence."
"Capturing this famous light show had been a dream of mine for several years, but I could not have imagined the lights showing up in my own backyard!" Goldpaint wrote in an email.
The colors of the aurora depend on the wavelength of the light emitted when fast-moving, electrically charged particles from the sun interact with different types of atoms and ions in Earth's upper atmosphere. If the particles hit mostly oxygen atoms, the light will be in the greenish-yellowish-reddish range. Collisions with nitrogen atoms produce the blue, purple and deep red hues.
The altitude of the auroral glow also affects the color: At altitudes between 60 and 120 miles, the oxygen emissions tend toward the green side of the spectrum. At higher altitudes, you'll see more red. Blend all those colors, and you get a beautiful, wide-ranging palette.
Here's a 13-minute recap of three winters' worth of auroral imagery from Sweden. It's all part of "Light Over Lapland: The Aurora Borealis Experience" from Chad Blakley of LightsOverLapland.com on Vimeo. For best results, go full screen and HD. "The movie is a compilation of many thousands of still images captured in Abisko National Park," Blakley writes. "By my calculation I have spent no less than 2,000 hours pointing my camera at the sky recording the northern lights to create this film. ... I am enjoying the midnight sun and all of its warmth, but I am ready for the darkness and the auroras to return."
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