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M-CLASS SOLAR FLARE: Big sunspot AR2241 erupted on Dec. 18th (21:58 UT), producing a strong M6-class solar flare. Extreme UV radiation from the blast ionized the top of Earth's atmosphere and briefly blacked out HF radio communications over the Pacific Ocean. Stay tuned for updates about a possible Earth-directed coronal mass ejection (CME). Solar flare alerts: text, voice
CHANCE OF MAGNETIC STORMS TODAY: A CME is heading in the general direction of Earth, and it could deliver a glancing blow to our planet's magnetic field later today. Scroll past this SOHO coronagraph movie for storm probabilities:
NOAA forecasters estimate a 50% chance of polar geomagnetic storms. The cloud was hurled into space two days ago by an M9-class explosion in the magnetic canopy of sunspot AR2242. Although the bulk of the CME flew south of the sun-Earth line, a collision is still possible. Computer models suggest a glancing impact on Dec. 19th with magnetic reverberations lasting until the 20th. High-latitude sky watchers should be alert for auroras. Aurora alerts: text, voice
Realtime Space Weather Photo Gallery
RADS ON A PLANE, CONTINUED: Regular readers may remember last month's reports by Dr. Tony Phillips of radiation measurements inside commercial airplanes. During a round-trip between Reno, Nevada, and Washington, DC, he absorbed a dose of ionizing radiation equal to approximately 3 dental x-rays.
Not every trip, however, is so "radioactive." Yesterday, he flew from Reno to San Francisco--a short hop over the Sierras to attend the American Geophysical Union meeting--and the dose was much less. Here is the radiation profile during the flight:
Compared to last month's travel, there was relatively little radiation on this flight. From take-off to landing, the total dose was only about 3% of a dental X-ray -- a hundred times less than before.
Why so little? For one thing, the flight was brief, less than an hour long. Moreover, it was low. The cruising altitude of the small commuter jet was only 26,000 feet compared to as much as 39,000 feet for last month's cross-country flights. When it comes to "rads on a plane," altitude matters a lot. The source of the radiation is cosmic rays from space; the closer you are to space, the more radiation you are going to absorb. Short, low flights are best for avoiding exposure.
The data come from a pair of radiation detectors routinely flown to the stratosphere onboard Earth to Sky Calculus Space Weather Buoys. The pager-sized devices are sensitive to ionizing radiation such as X-rays and gamma-rays in the energy range 10 keV to 20 MeV. Ideally, the two detectors should register the same dose rates throughout the flight. Slight differences between the two curves are an indication of the uncertainty in the measurements.
It is important to note that the sensors Phillips carried onboard the plane do not detect one of the most important forms of radiation: neutrons. Neutrons provide much of the biologically effective radiation dose at altitudes of interest to aviation and space tourism. To account for these uncharged particles, the doses discussed above should be doubled or tripled. To improve our estimates of the total dose rate, the students of Earth to Sky Calculus are evaluating neutron detectors for future balloon missions and plane flights. Stay tuned!
Realtime Space Weather Photo Gallery
EDGE OF SPACE CHRISTMAS CARDS: What do you give to the sky watcher who has everything? How about a Christmas card from the Edge of Space? For only $49.95, the students of Earth to Sky Calculus will fly your holiday greeting or favorite picture to the top of Earth's atmosphere, photograph it, and return the snapshot in time for Christmas. This holiday magic is performed using suborbital helium balloons. The group has previously flown cupcakes, shoes, US presidents, ad banners and telescopes. Contact Dr. Tony Phillips for more information.
Realtime Aurora Photo Gallery
Realtime Meteor 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. 19, 2014, the network reported 16 fireballs.
(12 sporadics, 3 December Leonis Minorids, 1 December Hydrid)
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 19, 2014 there were potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters: 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.
|Asteroid || |
|2014 XB6 || |
|2007 EJ || |
|1991 VE || |
|2004 BL86 || |
|2008 CQ || |
|2000 EE14 || |
| ||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 |