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JUNO SPACECRAFT TO FLY BY EARTH: Here's some news you might not hear from NASA because, like much of the US government, the space agency is closed. NASA's Juno spacecraft will slingshot past Earth on October 9th for a velocity boost en route to Jupiter. At closest approach the spacecraft will be only 347 miles from Earth as it gains an extra 16,000 mph for the long journey ahead. Update: During the flyby, Juno's science instruments will sample the Earth environment--a practice run for data-taking at Jupiter years from now. Fortunately, commands to activate Juno's sensors were uploaded before the shutdown. The science experiment can proceed. Radio amateurs are encouraged to beam a message to Juno during the flyby. Juno will be listening.
FARSIDE CORONAL MASS EJECTION: The Earthside of the sun is quiet, but the farside of the sun is not. During the early hours of Oct. 5th, NASA's STEREO-A probe, stationed over the farside, recorded the eruption of a southern hemisphere sunspot. Shortly after 07:30 UT, a coronal mass ejection (CME) flew over the sun's southeastern limb (credit: SOHO):
Radio emissions from shock waves in the CME suggest an expansion velocity of about 700 km/s (1.6 million mph), which is fairly typical of CME speeds. If Earth were in the line of fire, we would probably observe bright polar auroras in a few days. However, this CME is heading away from, not toward our planet.
The active region that produced the blast will rotate onto the Earthside of the sun in about 7 days. If it remains potent, geoeffective solar activity could increase late next week. Solar flare alerts: text, voice.
RED AURORAS: On October 2nd, a CME hit Earth's magnetic field, sparking a G2-class geomagnetic storm. Sky watchers on both ends of the Earth saw auroras; many of the lights were rare shades of red. Minoru Yoneto photographed this example from Queenstown, New Zealand:
"This is how the sky looked 11 hours after the CME impact," says Yoneto, who used a Canon EOS 6D digital camera to record the reds.
Auroras are usually green, and sometimes purple, but seldom do sky watchers see this much red. Red auroras occur some 300 to 500 km above Earth's surface and are not yet fully understood. Some researchers believe the red lights are linked to a large influx of electrons. When low-energy electrons recombine with oxygen ions in the upper atmosphere, red photons are emitted. At present, space weather forecasters cannot predict when this will occur.
During the storm, even more red auroras were observed over the United States in places like Kansas, Ohio, and Oklahoma. Browse the gallery for examples. Aurora alerts: text, voice.
Realtime Aurora Photo Gallery
THE INSTIGATING CME: The CME that hit Earth's magnetic field today left the sun on Sept. 30th, propelled by an erupting magnetic filament. SOHO photographed the CME at the start of its journey, racing away from the sun at 2 million mph (900 km/s):
The CME was impressive, but the underlying explosion was even more so. One movie from NASA's Solar Dynamics Observatory shows the self-destructing filament in the context of the whole sun. Another movie zooms in for a closeup. It catches the filament ripping through the sun's atmosphere and leaving behind a beautiful "canyon of fire."
NOAA forecasters working through the government shutdown estimated an almost-even 45% chance of polar geomagnetic storms when the CME arrived. The CME justified those relatively high odds, sparking a G2-class geomagnetic storm around the poles. Geomagnetic storm alerts: text, voice.
Realtime Space Weather Photo Gallery
Realtime Comet ISON Photo Gallery
Realtime Noctilucent Cloud Photo Gallery
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