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LIMB FLARES: The northwestern limb of the sun is crackling with M-class solar flares. The source appears to be departing sunspot complex 1280-1286. Coronal mass ejections (CMEs) emerging from the blast site are not Earth-directed. Nevertheless, these flares are having a minor effect on Earth as their radiation ionizes our planet's upper atmosphere. For an example, see "Radio-Altering Flare" below the auroras.
AURORA SEASON: September is only 5 days old and it has already been a good month for auroras. With the midnight sun doing a late-summer fade, many Arctic sky watchers are seeing Northern Lights for the first time in months. Sylvain Serre of Ivujivik, Canada, photographed this happy observer on Sept. 3rd:
"For the first time this season, we had clear dark skies in the village of Ivujivik in northern Quebec," says Serre. "The Northern Lights were very bright, dense and colorful."
As shown in the gallery, similar displays have been observed every night this month. More auroras are possible on September 6th - 7th in response to the expected arrival of a minor solar wind stream. In September, it seems, a minor gust of solar wind is all it takes to produce a great show. Stay tuned. Aurora alerts: text, voice.
NEW: September 2011 Aurora Gallery
[previous Septembers: 2010, 2009, 2008, 2007, 2006, 2005, 2004]
RADIO-ALTERING FLARE: On Sunday morning at 1145 UT, an active region on the sun's western limb unleashed a strong M3-class solar flare. NASA's Solar Dynamics Observatory recorded the flash of extreme ultraviolet radiation:
Although the blast site was not directly facing Earth, radiation from the explosion nevertheless ionized Earth's upper atmosphere. This altered the propagation of radio signals around Europe, where it was high-noon at the time of the flare. "I detected a sharp change in signal levels from two radio stations on the VLF band," reports Rob Stammes of Lofoten, Norway. More radio anmolaies were detected by Dave Gradwell in Ireland (data) and a team led by Valter Giuliani in Italy (data). This shows that flares can affect our planet even when the underlying explosions are not "Earth-directed."
Potentially Hazardous Asteroids (
PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding
new ones all the time.
On September 5, 2011 there were 1244 potentially hazardous asteroids.
Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach. | The official U.S. government space weather bureau |
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