Marianne's Arctic Xpress wishes you a Happy New Year. Learn to photograph auroras with the experts. Full photography tuition, all clothing, and semi-pro camera equipment included. Groups of 2 to 8 welcome. Book Now
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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 could arrive before New Year's Eve. The wind is flowing from a coronal hole (CH) in the sun's atmosphere, shown here in an image from NASA's Solar Dynamics Observatory:
NOAA forecasters estimate a 40% chance of polar geomagnetic storms on 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 (55% chance, says NOAA) and bright Arctic auroras on Dec. 31st. Happy New Year! Free: Aurora Alerts.
Realtime Aurora Photo Gallery
AURORA 'BLASTER FIRE' RECORDED IN SWEDEN: For centuries, Arctic sky watchers have occasionally reported strange sounds filling the air as Northern Lights danced overhead. Hisses, crackles, and even loud "claps" have been heard and recorded. It may be time to add a new sound to the menagerie: blaster fire.
Photographer Oliver Wright sends this report from inside the Arctic Circle: "On Christmas Night 2016, I was standing beneath an intense display of auroras in Abisko, Sweden, when I heard something that sounded like Star Wars blasters." As the lights danced overhead, a series of rat-a-tat 'swooshes' emanated from a nearby set of power lines. "Other bystanders heard it, too," he says. "I rushed closer to the power lines and was able to record a sample using my iPhone."
To listen, click on the photo–and don't forget to turn up the volume:
Wright says that the sounds waxed and waned in sync with the auroras overhead; the brighter the lights, the louder the sounds. Distance mattered, too: "The sounds grew louder as I approached the power lines, and fainter as I moved away."
Wright is a veteran tour guide working for Lights over Lapland, and he has heard these sounds before–"three times in total. Each time I was standing near power lines." He recalls a particularly intense outburst of "blaster fire" during the powerful St. Patrick's Day Storm of March 2015. In each case, guests and/or friends heard the sounds as well.
What's going on?
"Aurora sounds" have long been a controversial topic. Some researchers insist that they exist only in the imagination of the listener, but there is growing evidence that they are real.
Twas the night before Christmas. Read Oliver Wright's aurora blog.
Perhaps the most commonly reported aurora sounds are "hissing" and "crackling," a bit like static on a radio. These are thought to come from electric fields causing spark discharges at the pointy ends of objects like pine needles or even strands of dry hair. Aurora "claps" have been recorded as well. A researcher in Finland spent 15 years studying this phenomenon and published his results in 2012. He found that a temperature inversion layer in the atmosphere about 70 meters above the ground could cause a separation of + and – charges in the air. During strong geomagnetic storms, the charge separation breaks down, causing air to move and a "clap" to be heard.
The sounds Wright recorded may be a result of "electrophonic transduction"–that is, the conversion of electromagnetic energy into mechanical motion. At the time of the Christmas aurora outburst, magnetic fields around Abisko were seething with activity. Physics 101: Unsettled magnetic fields can cause currents to flow in power lines. Strong low-frequency currents can literally shake objects, launching acoustic vibrations into the air. Wright may have recorded the unique sound of those power lines swaying in response to the magnetic storm.
"This discussion feels poignant with the passing of Carrie Fisher as she was my childhood love and the sound is very reminiscent of Star Wars," notes Wright.
Indeed, "Carrie's Crackles" might be a good name for these heavenly sounds. Around Abisko, people will be listening for more as the next magnetic storm approaches. Stay tuned!
Realtime Space Weather Photo Gallery
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. 30, 2016, the network reported 7 fireballs.
(6 sporadics, 1 December Leonis Minorid)
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 30, 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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