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LEONID METEOR SHOWER: Today, Earth is passing through a stream of debris from Comet 55P/Tempel-Tuttle, source of the annual Leonid meteor shower. People who remember the Leonid meteor storms of the late 90s/early 2000s should know that this is not a storm year. Forecasters expect no more than 15 Leonids per hour during the dark hours before local sunrise. [Live meteor radar]
RADS ON A PLANE--THE RETURN FLIGHT: Regular readers of Spaceweather.com have been following the travels of Tony Phillips, who spent the past week flying commercial jets back and forth across the USA for meetings in Washington DC. In addition to his usual baggage, he carried a pair of radiation sensors onboard. Sitting in the economy section of a US Airways flight from Reno to Phoenix on Nov. 11th, Phillips recorded dose rates which were almost 30 times higher than background dose rates at ground level. On Nov. 15th, he gathered data from a return leg, American Airlines flight 2407 from Washington DC to Chicago. It was only half as bad:
The radiation inside these planes comes from space--that is, cosmic rays that penetrate Earth's atmosphere and reach down to aviation altitudes. In the plot we can see what a difference altitude makes: Cruising at 39,000 feet, the Reno to Phoenix flight was closer to space and thus experienced double the radiation of the DC to Chicago flight cruising at 28,000 feet.
The radiation sensor Phillips used to make these measurements is the same one that Earth to Sky Calculus routinely flies onboard helium balloons to measure cosmic rays in the stratosphere. It detects X-rays and gamma-rays in the energy range 10 keV to 20 MeV, similar to energies used by medical X-ray machines and airport security scanners.
We can put these doses into context by comparing them to medical X-rays. In a single hour flying between Reno and Phoenix on Nov. 11th, the passengers were exposed to about the same amount of radiation as an X-ray at the dentist's office. Such a dose is not a big deal for an occasional flier, but as NASA points out, frequent fliers of 100,000 miles or more can accumulate doses equal to 20 chest X-rays or about 100 dental X-rays. Lead aprons, anyone?
Some experts reading these reports on Spaceweather.com have pointed out that X-rays and gamma-rays represent only a fraction of the radiation present at aviation altitudes. The true dose could be doubled or tripled by neutrons, a component of cosmic rays known to be especially good at delivering energy to human tissue.
Realtime Space Weather Photo Gallery
OLD SUNSPOT CRACKLES WITH FLARES: Apparently, you can't keep a good sunspot down. AR2192, the aging sunspot famous for producing six X-flares in late October, is growing again and poses a renewed threat for strong eruptions. In the past 24 hours, the active region has produced a series of increasingly intense M-class flares, culminating in this M5-flare recorded by NASA's Solar Dynamics Observatory:
The impulsive blast, which peaked on Nov. 16th at 1748 UT, caused an HF radio blackout on the daylit side of Earth that lasted some 10s of minutes. Such blackouts are typically noticed by ham radio operators, mariners at sea, and aviators flying polar routes.
More potent flares could be in the offing. AR2192 has a 'beta-gamma-delta' magnetic field that harbors energy for X-class explosions 10 times stronger than the M-flares we are seeing now. NOAA forecasters estimate a 30% chance that the sunspot will unleash an X-flare in the next 24 hours. Solar flare alerts: text, voice
Sunspot names: AR2192 is making its second trip around the sun. According to tradition, it has been renumbered for its second appparition: AR2209. Renumbering sunspots is a holdover from previous centuries when only one side of the sun was visible. Astronomers watching a sunspot rotate over the sun's eastern limb couldn't be sure if it was a totally new sunspot, or an old sunspot returning from a farside transit; so they numbered every sunspot as if it were new. Fast-forward to 2014: NASA's heliophysics fleet can track sunspots around the entire circumference of the sun. We know this sunspot is old AR2192, but it gets a new number anyway.
Realtime Aurora Photo Gallery
Realtime Comet Photo Gallery
Realtime Eclipse 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 Nov. 17, 2014, the network reported 43 fireballs.
(35 sporadics, 4 Leonids, 2 Northern Taurids, 1 alpha Monocerotid, 1 November theta Aurigid)
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 November 17, 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 WA || |
|2004 JN13 || |
|1998 SS49 || |
|2005 UH3 || |
|2007 EJ || |
|1991 VE || |
|2004 BL86 || |
|2008 CQ || |
| ||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 |