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GEOMAGNETIC STORM SPARKS AURORAS: Unsetted solar wind conditions + the possible arrival of a weak CME ignited a G2-class geomagnetic storm during the early hours of April 10th. Northern Lights spilled over the Canadian border into the USA as far south as Idaho, Montana and Colorado. The storm is subsiding now, but NOAA forecasters estimate a 50% chance that it could flare up again before the end of the day. [photo gallery] Aurora alerts: text, voice
A MIXTURE OF DISSIMILAR THINGS: Venus and the Pleiades are converging for a close encounter in the sunset sky. This weekend, the planet and the star cluster will cross paths only 2o apart. Yuri Beletsky photographed the Seven Sisters +1 on April 9th, just one day before closest approach, over the Las Campanas observatory in Chile:
Consider it a mixture of dissimilar things. The Pleiades are elusive. They're best seen out of the corner of your eye, a pretty little surprise that pops out of the night sky when you're staring elsewhere. Venus is just the opposite. Dazzling, bright enough to cast faint shadows on a moonless night, it beams down from the heavens and grabs you when you're not even looking.
In the nights ahead, look west after sunset. Venus pops out of the twilight long before nightfall. As the sky fades to black, you can see the Pleiades, too. The nights of closest approach are Friday, April 10th, and Saturday, April 11th. Bright Venus makes for a stunning contrast against the pinpoint beauty of the star cluster. Observing tip: For maximum contrast, use binoculars.
Realtime Space Weather Photo Gallery
UPSIDE DOWN FORBUSH DECREASE: Last month, on March 17th, a CME hit Earth's magnetic field, sparking the strongest geomagnetic storm of the current solar cycle. Spaceweather.com and the students of Earth to Sky Calculus launched a series of weather balloons--before, during and after the storm--to measure the storm's effect on Earth's upper atmosphere. Here are the results:
During the storm, which lasted for more than two days, cosmic radiation levels in the stratosphere jumped by more than 6%. Radiation levels did not return to normal until a week after the CME strike.
Six percent might not sound like a big increase, but consider the following: Atmospheric radiation levels usually decrease when CMEs sweep past Earth. The effect is called a "Forbush Decrease," named after American physicist Scott Forbush who studied cosmic rays in the early 20th century. Essentially, CMEs sweep aside some of the cosmic rays that surround our planet, causing radiation levels to drop. In Sept. 2014, for instance, our space weather ballooning program detected a sharp Forbush Decrease. A 6% increase--simply because it is an increase--therefore comes as a surprise.
The reason for the jump may lie in the intensity of the St. Patrick's Day geomagnetic storm. While Earth's magnetic field was reverberating on March 17th, high-energy particles normally trapped around Earth's poles spilled down to mid-latitudes where the space weather balloons were launched (from the Sierra Nevada mountains of California). These extra particles could have filled in the deficit and overflowed it, producing an "upside down Forbush Decrease."
These results show that we still have a lot to learn about the response of Earth's atmosphere to solar storms. Stay tuned for more results from the ballooning program.
For specialists: Radiation levels plotted above represent the peak of the Pfotzer maximum, located approximately 65,000 feet above Earth's surface. Each space weather balloon carried four independent radiation detectors sensitive to gamma-rays and ionizing particles in the energy range 10 keV to 20 MeV.
Realtime Eclipse Photo Gallery
Realtime Aurora Photo Gallery
Realtime Comet Photo Gallery
Every night, a network of NASA all-sky cameras scans the skies above the United States for meteoritic fireballs. Automated software maintained by NASA's Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth's atmosphere and many other characteristics. Daily results are presented here on Spaceweather.com.
On Apr. 10, 2015, the network reported 34 fireballs.
In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). [Larger image] [movies]
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 April 10, 2015 there were 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 |
| ||The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| ||Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| ||3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| ||Realtime and archival images of the Sun from SOHO. |
| ||from the NOAA Space Environment Center |
| ||the underlying science of space weather |