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HERE COMES THE SOLAR WIND: A solar wind stream is approaching Earth with wind speeds as high as 700 km/s. First contact with the fast-moving gas on Dec. 7-8 could produce G1-class geomagnetic storms and auroras at high latitudes. Observers around the Arctic Circle could be in for a fine light show.
The source of this solar wind stream is a hole in the sun's atmosphere, shown here in a Dec. 5th image from NASA's Solar Dynamics Observatory:
This is a "coronal hole"--a region where the sun's magnetic field has opened up, allowing solar wind to escape. Because this hole is broad, the emerging stream of solar wind is broad as well. It should influence Earth for several days after it arrives. Free: Aurora Alerts.
Realtime Aurora Photo Gallery
RED AIRGLOW OVER EUROPE: After nightfall on Dec. 2nd, the sky above Hungary suddenly became impressed by luminous ripples. "It was a once in a lifetime display of airglow in the middle of the light-polluted Europe," reports eye-witness Monika Landy-Gyebnar. Andras Pinter photographed the red corrugations outside the city of Mihályi:
"It was a very-very strong airglow above Hungary," says Pinter, who put together this animation to show the dynamics of the display.
Airglow is aurora-like phenomenon caused by chemical reactions in the upper atmosphere. Human eyes seldom notice the faint glow, but "on Dec. 2nd it was easily visible to the naked eye," adds Landy-Gyebnar. "To the layman, the bands might have looked like a layer of pale thin clouds, but my camera revealed their telltale red color."
The red color of the display was remarkable. Airglow is usually green, the color of light from oxygen atoms some 90 km to 100 km above Earth's surface. Where does the red come from? Instead of oxygen, OH can produce the required color. These neutral molecules (not to be confused with the OH- ion found in aqueous solutions) exist in a thin layer 85 km high where gravity waves impress the red glow with a dramatic rippling structure.
Meanwhile in Slovakia, the usual green color was visible through gaps in clouds. Roman Vanur photographed it from the city of Počúvadlo. "A great display!" he says.
Airglow is more common than you think. Browse the airglow gallery for more apparitions.
Realtime Airglow Photo Gallery
FAR-OUT STOCKING STUFFER: In space, not everything that twinkles is a star. For example, we present the Silver Stars & Moon Space Pendant:
On Dec. 3rd, using a helium balloon the students of Earth to Sky Calculus launched a payload full of these pendants alongside an array of cosmic ray sensors. Together they ascended to an altitude of 117,000 ft. The purpose of the sensors was to measure increasing levels of radiation in the stratosphere. The purpose of the pendants: to pay for the sensors. Our radiation monitoring program is completely crowdfunded, and the pendants are for sale.
You can have one for $69.95. Each pendant comes with a Christmas card showing the pendant at the edge of space and telling the story of its flight. More far out Christmas gifts may be found in the Earth to Sky Store. All proceeds support space weather research.
Realtime Space Weather Photo Gallery
Realtime Sprite 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. 6, 2016, the network reported 27 fireballs.
(19 sporadics, 7 sigma Hydrids, 1 November omega Orionid)
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 6, 2016 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 |
Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:
This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.
What is this all about? 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. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 12% since 2015:
Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.
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 data points in the graph above correspond to the peak of the Reneger-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Reneger and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.
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