Spaceweather: Sun, Moon, Eclipses, Auroras and an East Coast Green Flash

Spaceweather: Sun, Moon, Eclipses, Auroras and an East Coast Green Flash What's up in space:

THE SUN IS STUBBORNLY QUIET: Despite the emergence of a new and unstable sunspot (AR2414), the sun remains stubbornly quiet. There hasn't been a strong flare in weeks, and the sun's X-ray output is very low. NOAA forecasters estimate a scant 10% chance of M-class solar flares on Sept. 13th. Solar flare alerts: text or voice DOUBLE ECLIPSE OF THE SUN: On Sept. 13th, the sun was eclipsed--twice! No one on Earth has ever seen anything like it. Indeed, it was only visible from Earth orbit. NASA's Solar Dynamics Observatory (SDO) recorded the event: The double eclipse began around 06:30 UT when Earth passed directly between the sun and SDO. The observatory watched as the body of our planet moved slowly across the face of the sun, producing a near black-out. When the Earth finally moved aside about an hour later, another eclipse was in progress. This time, the Moon was in the way. A movie from the SDO science team explains the crazy-perfect alignment required for such a view. (In the snaphots above, note how the edge of the Earth looks so much fuzzier than the edge of the Moon. That's because our planet has an atmosphere and the Moon does not.) Meanwhile on Earth, an ordinary partial eclipse was visible. People in South Africa and parts of Antarctica saw the Moon pass in front of the sun, off-center, producing crescent-shaped shadows and strange sunrises. Check the realtime photo gallery for their images. Realtime Space Weather Photo Gallery MORE AURORAS IN THE OFFING: So far, September has been a great month for auroras. A series of solar wind streams, mixed with one or two minor CMEs, has buffeted Earth's magnetic field almost non-stop for the past two weeks. The resulting G1- to G3-class geomagnetic storms have caused displays like this: Minoru Yoneto took the picture on September 11th from Queenstown, New Zealand. "A big stream of solar wind gave us four lovely colors of Southern Lights," he says. One reason for the recent spate of auroras is the coming change of seasons. For reasons that are not fully understood, auroras love equinoxes. At this time of year even gentle gusts of solar wind can spark a nice display of Northern or Southern Lights Two gusts are on the way. NOAA forecasters expect streams of solar wind to reach Earth on Sept. 13th and Sept. 15th, sparking renewed displays of high-latitude auroras. Monitor the realtime photo gallery for updates. Aurora alerts: text or voice Realtime Aurora Photo Gallery EAST COAST GREEN FLASH: Last Monday, Sept. 7th, Spaceweather.com reader Don Koenigsberg woke up early to watch the sun rise from Atlantic City, NJ. He was vacationing on Labor Day. The holiday began with a flash of green: "It was a great way to begin the day," says Koenigsberg. "I thought the video was interesting because green flashes can be difficult to see on the East Coast due to less than ideal atmospheric conditions." Indeed, says atmospheric optics expert Les Cowley, "flashes from the west coast are MUCH more common. Mock-mirage green flashes - the type most frequently photographed - need temperature inversions.  These inversions are readily generated along the west coast by the combination of cold offshore ocean current and warm air from inland. Almost daily green flashes have sometimes been seen from San Francisco!" Green flashes on the east coast tend to be of a different type: "the classical Omega flash," says Cowley. "This occurs when there is warm air immediately over the ocean and the air temperature gradient changes rapidly with height. For the flash to be visible the warm air layers must be below you. An 'Omega flash' is what Koenigsberg witnessed." Mock-mirage flashes, Omega flashes, east coast flashes, west coast flashes: they are all beauties. As Jules Verne wrote in his 1882 novel "Le Rayon Vert" (The Green Ray), they display "a green which no artist could ever obtain on his palette, a green of which neither the varied tints of vegetation nor the shades of the most limpid sea could ever produce the like!" More of this special green may be found in the realtime photo gallery.