GEOMAGNETIC STORM FORECAST: Two solar wind streams are approaching Earth. The first will arrive on Aug. 27-28 followed by the second on Sept. 1-2. G1-class geomagnetic storms are possible on both dates, especially Sept. 1-2 when the second "blow" completes the double-whammy of solar wind. High-latitude sky watchers should be alert for auroras. Aurora alerts: SMS Text.
WHY ARE SUNSETS TURNING PURPLE? Every year, on average, about 60 volcanoes erupt somewhere on Earth, shooting ashy plumes of sulfurous gas thousands of feet into the air. Rarely do those plumes make it all the way up to the stratosphere. This summer, however, two volcanoes have done it. The Raikoke volcano in the Kirul Islands (June 22nd) and the Ulawun volcano in New Guinea (Aug. 3rd) both punched through to the stratosphere, sending material as high as 60,000 ft.
The action of these two volcanoes may explain why many sky watchers are starting to notice purple sunsets. Gabriel Cyr of Saint-Elzéar, Quebec, photographed this example on Aug. 25th:
"This has got to be one of those sunsets caused by volcanic [gas] that has accumulated in the stratosphere throughout the year," says Cyr. "The skies were perfectly clear with no tropospheric clouds visible to the naked eye, making the phenomenon easier to distinguish from a 'regular' sunset."
Why purple? Fine volcanic aerosols in the stratosphere scatter blue light which, when mixed with ordinary sunset red, produces a violet hue. The purple color is often preceded by a yellow arch hugging the horizon. As the sun sets, violet beams emerge from the yellow, overlapping to fill the western sky with a soft purple glow. High-quality pictures of the phenomenon often show horizontal bands cross-crossing the yellow arch. These bands are the volcanic gas.
Last night, Greg Ainsworth captured many of these elements in a photo he took from Bozeman, Montana:
"On Aug. 26th, I captured the purplish sunset colors, as well as horizontal banding in the yellow/orange area associated with the volcanic aerosols in the stratosphere," says Ainsworth.
Sky watchers shouldn't expect to see purple every night. The volcanic gas appears to be patchily distributed, bringing strange sunsets on some nights, not all. Clear air, lack of clouds, and country settings improves their visibility. If you photograph one, send us your pictures!
A sharable version of this story may be found here.
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YES, THAT'S A REAL PEARL: It's the first pearl in the stratosphere. On Aug. 19, 2019, the students of Earth to Sky Calculus launched a cosmic ray balloon to the edge of space, 104,002 ft high. This sterling silver pearl necklace went along for the ride:
You can have it for $169.95. The students are selling these pearls to support their cosmic ray ballooning program. Each cultured "space pearl" comes with greeting card showing the necklace in flight and telling the story of its journey to the edge of space and back again. These make great birthday and Christmas gifts.
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