WEEKEND AURORA WATCH: A high-speed stream of solar wind is expected to hit Earth's magnetic field sometime this weekend. Its impact could spark a G1 (minor) to G2-class (moderate) geomagnetic storm with auroras at high latitudes. Aurora alerts: SMS Text
SOLAR FLARE AND RADIO BLACKOUT: Earth-facing sunspot AR3110 erupted on Oct. 1st (2010 UT), producing an impulsive M5.9-class solar flare. NASA's Solar Dynamics Observatory recorded the extreme ultraviolet flash:
Radiation from the flare ionized the top of Earth's atmosphere and caused a shortwave radio blackout over the Pacific side of North America. Ham radio operators, aviators and mariners may have noticed fadeouts and other unusual propagation effects at frequencies below 20 MHz. Solar flare alerts: SMS Text
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THE AURORA THAT'S NOT AN AURORA: On Sept. 26th, a CME struck Earth's magnetic field. During the resulting geomagnetic storm (G2), auroras spread as far south as Missouri. Upon closer inspection, some of the auroras were not auroras. Here is an example from Glidden, Wisconsin:
"I knew the storm was happening, so I headed out to capture the Milky Way with some aurora thrown in," says photographer Michele Sadauskas. "With my first click, I knew something was up. Everything was RED! I happily captured this gigantic SAR arc that went from east to west in the sky."
SARs are red arcs of light that ripple across the sky during some geomagnetic storms. They were discovered in 1956 at the beginning of the Space Age. Researchers didn’t know what they were and unwittingly gave them a misleading name: "Stable Auroral Red arcs" or SARs.
In fact, SARs are neither stable nor auroras. Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow like the picture tube of an old color TV. SARs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth’s ring current system--a donut-shaped circuit of plasma carrying millions of amps around our planet.
Above: SARs photographed by the Dynamics Explorer-1 satellite in 1982. More
SARs are among the reddest things in the sky, with a monochromatic glow at 6300 Å that comes from atomic oxygen in the upper atmosphere. The human eye is relatively insensitive to light at this wavelength, but cameras catch them easily. Pro tip for photographers: Use a 6300 Å filter.
If a geomagnetic storm occurs this weekend (NOAA says "yes"), be alert not only for auroras, but also for auroras not.
more images: from Jeff Berkes of Bayfield, Wisconsin; from Bill Kocken of McGregor, Minnesota
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STERLING SILVER HUMMINGBIRD PENDANT: This hummingbird has touched space. On Sept. 22, 2022, the students of Earth to Sky Calculus launched the sterling silver pendant to the stratosphere onboard a cosmic ray research balloon, more than 117,710 feet high:
You can have it for $149.95. The students are selling hummingbird pendants to pay the helium bill for their cosmic ray ballooning program. Each one comes with a greeting card showing the bird and red lily in flight, and telling the story of their trip to the stratosphere and back again.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
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