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SOLAR FLARES: After weeks of quiet, solar activity is picking up. New sunspot AR1817 is crackling with C- and M-class solar flares. An M1.5-class eruption on August 12th (1041 UT) created a wave of ionization in the upper atmosphere above Europe and might have hurled a coronal mass ejection toward Earth. Stay tuned for updates. Solar flare alerts: text, voice.
PERSEID METEOR SHOWER UPDATE: The Perseid meteor shower is peaking. Last night, international observers counted as many as 75 Perseids per hour from dark sky sites, a rate that could be surpassed tonight as Earth passes through the densest part of the comet debris stream. The best time to look is during the dark hours between midnight and dawn. [photo gallery] [meteor radar]
NASA's All-Sky Fireball Network has recorded dozens of Perseid fireballs over the southern USA. Astronomer Bill Cooke, who manages the network, plotted their orbits in this diagram of the inner solar system:
The purple orbit traces the path of the parent comet, 109P/Swift-Tuttle. It nicely matches the orbits of the Perseids, color-coded green. Earth is marked by a blue dot where all the curves intersect.
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SPRITES AND JETS OVER OKLAHOMA CITY: High above Earth in the realm of meteors and noctilucent clouds, a strange form of lightning dances at the edge of space. Researchers call the bolts "sprites," and they are as beautiful as they are mysterious. Jason Ahrns, a graduate student from the University of Alaska Fairbanks, photographed a cluster of bright red sprites over Oklahoma City on August 6th. Click on the arrow to view a rare high-speed movie of the phenomenon:
"I normally study auroras," says Ahrns, "but I've become involved in sprites as a side interest." At the time of the photo, Ahrns was flying onboard a Gulfstream V operated by the National Center for Atmospheric Research (NCAR). "We try to get off to the side of sprite-producing storms, ideally about 200 km away, and film them with a couple of Phantom cameras running at 10,000 frames per second. One of the Phantoms has a diffraction grating in front of it to capture high speed spectra, which I don't think has ever been done before."
"We've also managed to record a few sprites over a lightning mapping array so we can identify the exact lightning strike that caused the sprite," he continues. "This has also never done before, and should provide insight into what type of lightning causes sprites."
"Lately," says Ahrns, "I've begun slipping my personal camera into a spare window of the airplane, and the results have been so impressive that we're planning to make a dSLR (digital camera) a regular part of future campaigns. On August 3rd I recorded some blue jets over Oklahoma city; I believe these are the first blue jets recorded by an ordinary dSLR." More tales of sprite-chasing may be found on Ahrns' personal blog.
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