THE NEXT SOLAR WIND STREAM: A hole in the sun's atmosphere is turning toward Earth and spewing a stream a solar wind in our direction. Estimated time of arrival: Jul. 31st or Aug. 1st. High-latitude sky watchers should be alert for auroras on those dates. Aurora alerts: SMS Text.
A BLUE-GREEN FLASH: We've all heard of the green flash, the fleeting pulse of emerald light that sometimes appears just above the setting sun. But have you ever heard of the blue-green flash? Thom Peck photographed one from Poway, California, on July 25th:
Atmospheric optics expert Les Cowley analyzed this flash and found elements of blue mixed with the usual green--"in about equal measure," he says. "This is a rare cloud-top flash."
It turns out, blue flashes are a thing. They're formed in the same way as green flashes: a mirage magnifies tiny differences in the atmospheric refraction of red, green and blue light. Blue flashes are generally harder to see than green flashes, because blue is strongly scattered by intervening air and small dust particles.
When Peck was watching the sun set on July 25th, however, conditions favored both colors. The clouds in Peck's photo were trapped in a marine temperature inversion layer. "Strong temperature gradients produced a strong mirage with well separated colors," explains Cowley. "And a very clean atmosphere allowed the blue to pass unscattered."
OPOD NEWS: If you love atmospheric optics, add Les Cowley's Optics Picture of the Day (OPOD) web site to your bookmarks. After a recent intermission of a few months, OPOD is being updated daily again.
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ALBERT EINSTEIN AT THE EDGE OF SPACE: What would Einstein think!? On June 8, 2019, the students of Earth to Sky Calculus launched a cosmic ray balloon to the stratosphere. This Albert Einstein bobblehead went along for the ride:
Albert contemplated the curve of the Earth for almost 3 hours as the balloon ascended 111,222 feet above the Sierra Nevada Mountains of central California.
You can have him for $99.95. The students are selling these bobbleheads to support their cosmic ray ballooning program. 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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