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HERE COMES THE SOLAR WIND (AGAIN): 2016 might get one more blast of auroras before the year is over. Another stream of solar wind is heading for Earth, and it should arrive before New Year's Eve. The wind is flowing from a coronal hole (CH) in the sun's atmosphere, shown here in a Dec. 29th image from NASA's Solar Dynamics Observatory:
The action begins during the late hours of Dec. 30th when a co-rotating interaction region (CIR) is expected to hit Earth's magnetic field. CIRs are transition zones between slow- and fast-moving solar wind streams. Solar wind plasma piles up in these regions, producing density gradients and shock waves that do a good job of sparking auroras.
After the CIR arrives, a stream of fast-moving (600 km/s) solar wind will follow. The combined effect could produce G1-class geomagnetic storms and bright Arctic auroras on Dec. 30-31. Happy New Year! Free: Aurora Alerts.
Realtime Aurora Photo Gallery
RUSSIAN SUN PILLAR: On Dec. 27th, Ras Sim of the Russian Urals spotted a beam of light shooting upward from the setting sun. "It was a fantastic sun pillar," says Sim.
Sun pillars are caused by ice in the air. Plate-shaped crystals ice fluttering down from cirrus clouds catch the rays of the setting sun and spread it into a vertical column.
"Watch a leaf or piece of paper flutter and wobble as it falls," says atmospheric optics expert Les Cowley. "Ice crystals in the air wobble, too, and this smears the sun's reflection into a vertical line."
All around the world, the atmosphere is cold enough 5 to 10 km high to produce these ice crystals. That means sun pillars can be seen anywhere. However, the odds of sighting one improve in cold wintry places like northern Russia. Residents of the north should be alert for these beautiful pillars as winter unfolds.
Realtime Space Weather Photo Gallery
EVOLUTION OF A CORONAL HOLE: Christmas 2016 was special for sky watchers around the Arctic Circle. The skies filled with some of the best Northern Lights of the year, including rare outbursts of white and pink. The source of the display: A giant "coronal hole" in the sun's atmosphere sprayed our planet with solar wind. The hole opened up in July 2016 and it has been strobing Earth with solar wind every ~28 days ever since as the hole pirouettes with the slowly rotating sun.
Spaceweather.com reader Stuart Green has prepared a plot showing the evolution of the coronal hole and the effect it has had on the magnetic field at his private observatory in Preston, England. Click on the image to inspect the full 6 months:
Inset images come from NASA's Solar Dynamics Observatory. The coronal hole is the giant dark region, starting small in July, then growing and shape-shifting as the year unfolds.
The background strip chart recording shows the instability of the magnetic field around Green's private observatory. When the coronal hole is facing Earth, big changes are measured.
"I've been recording geomagnetic activity over the past three years using a home built/ home designed magnetometer," says Green. "The sensor is buried in my garden about 0.5m below the surface in an East/West orientation to allow very sensitive (sub nanotesla) measurements of magnetic declination during geomagnetic storms. The plots show the change in magnetic flux density in nanotesla occurring between readings every 2.5 minutes."
Green's presentation suggests that this yawning hole is a long-lived feature on the sun, and it will probably be back as potent as ever 28 days from now. Stay tuned for magnetic unrest--and more Arctic auroras
Realtime Airglow 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. 29, 2016, the network reported 6 fireballs.
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 29, 2016 there were 1754 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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