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Spooky auroras light up autumn nights
By Richard Stenger
(CNN) -- Green ghosts, wispy witches and other glowing phantoms are dancing and darting around in the night skies of October, which has proved a particularly productive month for aurora hunters the world over. Sky watchers photographed everything from a floating fairy ring in Norway, multicolor spires in Arizona and pulsating swirls in Australia. In Finland, Juha Kinnunen captured a glowering witch face with a considerable schnozzle and two greenish ghosts looming over the Lapland. "Of those three images, only one looked like a ghost with my own eyes as well, for a brief moment. The other two turned up that 'spooky' during the exposure, which was 4 to 6 seconds," Kinnunen said Wednesday. "This shows you how an active aurora changes shape continuously. The ghost I photographed appeared for one horrifying moment only." Auroras, also known as the northern and southern lights, emit light as highly charged particles from the sun excite atoms and molecules high in Earth's atmosphere, which creates a glow in the same manner as neon lights. While concentrated in the most northerly and southerly regions, particularly strong aurora displays can extend down into the mid-latitudes. Northern lights, for instance, occasionally creep down to Mexico. The seasonal lights tend to perk up in the autumn and spring for reasons that are not entirely clear. What scientists do know is that the strength and scope of the sky shows are directly tied to solar activity.
From time to time the sun unleashes powerful salvos of ionized gas that, if they collide with Earth's magnetic field, can spark nocturnal aurora displays as well as disrupt satellites and power grids. Moreover, coronal holes in the solar disk can leak out strong gusts of solar wind, which can produce the same striking results if headed in our direction. Earth is now exiting a solar wind stream that sparked numerous auroras since October 23, according to NASA's Spaceweather.com, which regularly posts aurora images. "There is a slim chance that trick-or-treaters in the northern United States and Canada might see some ghostly auroras of their own on October 31st," the Web site said. There could be more eye candy in the works in November too. "Currently there's a medium-sized coronal hole on the Sun's visible disk," Kinnunen said. "It probably will create auroras within less than a week."
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