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BIG SUNSPOT ERUPTS: After several days of pent-up quiet, big sunspot AR2473 erupted on Dec. 28th (12:49 UT), producing a slow but powerful M1.9-class solar flare. NASA's Solar Dynamics Observatory recorded the blast's extreme ultraviolet glow:
For more than an hour, UV radiation from the flare bathed the top of Earth's atmosphere, ionizing atoms and molecules. This, in turn, disrupted the normal propagation of shortwave radio signals on the dayside of our planet. A NOAA blackout map shows the affected area. Ham radio operators, mariners and aviators in South America, Africa and the south Atlantic Ocean may have noticed fades and blackouts of transmissions below 20 MHz.
The slow explosion also produced a coronal mass ejection (CME). Images from the Solar and Heliospheric Obseratory (SOHO) show a ragged, full-halo CME heading almost directly toward Earth:
The storm cloud will likely reach our planet on Dec. 31st, possibly triggering the first geomagnetic storm of the New Year. NOAA analysts are modeling this CME now; stay tuned for refined forecasts later today when they release their storm track.
Sunspot AR2374 has an unstable 'beta-gamma' magnetic field that could explode again in the hours ahead. NOAA forecasters estimate a 55% chance of additional M-class flares and a 10% chance of X-flares on Dec. 28th. Solar flare alerts: text or voice
Realtime Spaceweather Photo Gallery
THEY'RE BACK! POLAR STRATOSPHERIC CLOUDS: For the second time this month, sky watchers around the Arctic Circle are reporting an outbreak of colorful polar stratospheric clouds (PSCs). Nenne Åman photographed them floating over Arjeplog, Sweden, on Dec. 26th:
"As the sun set, the sky turned into all colours possible," says Åman. "It was like a huge display of northern lights--but no geomagnetic storm. Magic!"
Also known as "nacreous" or "mother of pearl" clouds, icy PSCs form in the lower stratosphere when temperatures drop to around minus 85ºC. That's how cold it has to be for ice crystals to form in the very dry stratosphere. High-altitude sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors by diffraction and interference. Once thought to be mere curiosities, some PSCs are now known to be associated with the destruction of ozone.
"Polar stratospheric clouds far outshine and have much more vivid colours than ordinary iridescent clouds, which are very much poor relations and seen frequently all over the world," writes atmospheric optics expert Les Cowley. "Once seen they are never forgotten."
The best time to look for PSCs is just before sunrise or right after sunset, when the ground is dark but the upper atmosphere is still illuminated by sunlight. Or, you can see them any time in the realtime photo gallery:
Realtime PSC Photo Gallery
ELECTRIC-BLUE CLOUDS SPREADING OVER ANTARCTICA: Noctilucent clouds (NLCs) around the south pole are spreading and brightening. The latest preliminary image from NASA's AIM spacecraft shows more than 10 times the coverage of just one week ago:
The season for southern hemisphere noctilucent clouds (NLCs) began on Dec. 13th with just a few puffy clouds over the frozen continent. Once NLCs first appear, AIM has shown that they rapidly multiply. Indeed, this is happening now, and most of Antarctica will soon be blanketed in electric blue.
Realtime Noctilucent Cloud Photo Gallery
ARMY OF GREEN MEN -- IN SPACE: On Dec. 20th, Spaceweather.com and the students of Earth to Sky Calculus launched their weekly helium balloon to measure cosmic radiation in Earth's atmosphere. This time, there were 56 hitchikers--a platoon of green army men:
Their mission: to raise awareness of spinal cord injuries. #QuaidsArmy sponsored the flight. On September 20th, 2013, twenty-four year old Quaid Mobus of Warren NJ was in a near fatal ATV accident the night before his sister's wedding. Quaid was left paralyzed, requiring extensive lifelong medical attention. Since then, the Army of Green Men have been traveling far and wide to support Quaid and others like him. Dec. 20th marked their first trip to the stratosphere. Learn more at http://www.armyofgreenmen.com/
Realtime Aurora Photo Gallery
Realtime Meteor 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 Dec. 28, 2015, the network reported 6 fireballs.
(5 sporadics, 1 December Leonis Minorid)
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 December 28, 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.
| ||Cosmic Rays in the Atmosphere |
These measurements are based on regular space weather balloon flights: learn more.
|Situation Report -- Oct. 30, 2015 ||Stratospheric Radiation (+37o N) |
|Cosmic ray levels are elevated (+6.1% above the Space Age median). The trend is flat. Cosmic ray levels have increased +0% in the past month. |
|Sept. 06: 4.14 uSv/hr (414 uRad/hr) |
|Sept. 12: 4.09 uSv/hr (409 uRad/hr) |
|Sept. 23: 4.12 uSv/hr (412 uRad/hr) |
|Sept. 25: 4.16 uSv/hr (416 uRad/hr) |
|Sept. 27: 4.13 uSv/hr (413 uRad/hr) |
|Oct. 11: 4.02 uSv/hr (402 uRad/hr) |
|Oct. 22: 4.11 uSv/hr (411 uRad/hr) |
Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly "space weather balloons" to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. Here is the data from our latest flight, Oct. 22nd:
Radiation levels peak at the entrance to the stratosphere in a broad region called the "Pfotzer Maximum." This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are more than 80x sea level.
Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Oct 22th measurements, a plane flying at 45,000 feet is exposed to 2.79 uSv/hr. At that rate, a passenger would absorb about one dental X-ray's worth of radiation in about 5 hours.
The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
| ||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 |
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| ||Web-based high school science course with free enrollment |
| ||the underlying science of space weather |