THE NEXT GEOMAGNETIC STORM: A hole in the sun's atmosphere is turning to face Earth. Estimated time of arrival: Aug. 27th. High latitude sky watchers, including those in northern-tier US states, should be alert for auroras on that date. Aurora alerts: SMS Text.
WHAT DOES IT MEAN WHEN THE SUNSET TURNS PURPLE? Yesterday, Tony Phillips of Spaceweather.com was hiking through the Sierra Nevada mountains of central California where an Earth to Sky cosmic ray balloon had landed earlier in the day. (Payload recovered!) As the sun set behind the Sierra crest, the western sky filled with a soft purple glow. "To the naked eye, the violet hue was deep and vivid," says Phillips. "This hasty cell phone picture does not do it justice."
What turned the twilight purple? Volcanoes. This summer, two volcanoes have spewed sulfurous gases into the stratosphere: The Raikoke volcano in the Kirul Islands on June 22nd, and the the Ulawun volcano in New Guinea on August 3rd. Fine volcanic aerosols in the stratosphere scatter blue light which, when mixed with ordinary sunset red, produces a violet hue.
A few hundred miles to the south, Don Davis of Joshua Tree, CA, saw the same purple sunset. With a better camera he snapped this picture:
"Here's the latest of this summer's volcanic twilights," says Davis. "This one was especially bright." The fine, nearly horizontal striations in Davis's picture are telltale signs of material floating through the stratosphere.
The emissions from these volcanoes have spread tens of thousands of miles from the volcanoes themselves, forming a widespread network of filamentary material in the stratosphere. When a filament passes over any given location, sunset sky watchers see purple.
Purple isn't the only thing to look for, says atmospheric optics expert Les Cowley. In addition, he advises, sky watchers should "be alert for a very bright yellow twilight arch, fine cloud structure in the arch seen through binoculars, and long diffuse rays and shadows."
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APOLLO 11 PROOF SILVER DOLLARS: The students of Earth to Sky Calculus weren't even born when Neil Armstrong and Buzz Aldrin landed on the Moon in 1969 years ago. Nevertheless, they "get it." On July 20th, the students launched 50 Apollo 11 silver dollars to the stratosphere onboard a cosmic ray balloon. The coins touched the edge of space 50 years to the day after Neil and Buzz made footprints in the Sea of Tranquillity:
You can have one for $197.95. The students are selling these coins to support their cosmic ray ballooning program. Quantities are limited and more than half have already been sold. Each one comes with a greeting card showing the item in flight and telling the story of its journey to the edge of space.
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