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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, inside planes that flew as high as 39,000 feet, 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:
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.
Compared to last month's travel, there was relatively little radiation detected during this flight. From take-off to landing, the total dose was only about 3% of a dental X-ray -- about 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. 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.
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
LARGE SUNSPOTS: A pair of large sunspots has emerged in the sun's southern hemisphere, and they are almost directly facing Earth. This 48-hour movie from NASA's Solar Dynamics Observatory shows the rapid development of AR2241 and AR2242:
Both of these active regions have unstable 'beta-gamma-delta' magnetic fields that harbor energy for strong explosions. NOAA forecasters estimate a 65% chance of M-flares and a 15% chance of X-flares on Dec. 18th. Because these spots are centrally located on the solar disk, any flares today will likely be Earth-directed. Solar flare alerts: text, voice
Realtime Space Weather Photo Gallery
CHANCE OF STORMS: A coronal mass ejection (CME) is heading in the general direction of Earth, and it could deliver a glancing blow to our planet's magnetic field on Dec. 19th. Scroll past this SOHO coronagraph movie for storm probabilities:
The cloud was hurled into space on Dec. 17th by an M9-class explosion in the magnetic canopy of sunspot AR2242. Although the bulk of the cloud is traveling south of the sun-Earth line, there will be a grazing impact. NOAA forecasters estimate a 50% chance of polar geomagnetic storms when the outskirts of the CME arrive. High-latitude sky watchers should be alert for auroras on Dec. 19th. Solar flare alerts: text, voice
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. 18, 2014, the network reported 13 fireballs.
(9 sporadics, 3 December Leonis Minorids, 1 sigma 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 18, 2014 there were potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Size |
2014 XB6 | Dec 14 | 7.6 LD | 22 m |
2007 EJ | Jan 12 | 68.9 LD | 1.1 km |
1991 VE | Jan 17 | 40.6 LD | 1.0 km |
2004 BL86 | Jan 26 | 3.1 LD | 650 m |
2008 CQ | Jan 31 | 4.8 LD | 36 m |
2000 EE14 | Feb 27 | 72.5 LD | 1.6 km |
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 |