Space Weather Update: 12/18/2016
By Spaceweather.com, 12/18/2016
AURORAS FOR CHRISTMAS? Earth is about to enter a solar wind stream that could spark polar auroras from Dec. 20th through 25th. Geomagnetic storming is most likely on Dec. 21st and 22nd with peak storm levels near G2. Sky watchers around the Arctic Circle should be alert for Northern Lights.
The source of the solar wind is a gigantic hole in the sun’s atmosphere, now directly facing Earth. Earlier today NASA’s Solar Dynamics Observatory photographed the structure, which covers nearly 1/3rd of the solar disk:
This is a “coronal hole”–a region in the sun’s atmosphere where the magnetic field opens up and allows solar wind to escape. We’ve actually seen this coronal hole before–at least twice. It is rotating around with the sun, strobing Earth like a lighthouse every ~27 days. The last two times we experienced its solar wind (Oct. 25-28 and Nov. 23-26), G1– and G2-class magnetic storms sparked bright polar auroras. A repeat performance is likely in the week ahead.
AURORAS, NO SUNSPOTS REQUIRED: For the second day in a row, the sun is blank–no sunspots. Fortunately, sunspots are not required for the aurora borealis. Last night the sunspot number was zero when Sarah Skinner of Abisko, Sweden, witnessed a spray of green lights “bursting out from the top of Mount Nuolja and spreading across the sky with bursts of speeds and energy.” She took this picture from the shore of Lake Torneträsk:
“I was with a group of guests from Lights over Lapland when the clouds started to clear revealing the powerful aurora,” she adds. “We all cheered with excitement!”
This display, and others like it happening nightly around the Arctic Circle, defy a popular misconception about the solar cycle. Many people believe that auroras vanish during periods of low sunspot number. In fact, polar auroras may be seen throughout the 11-year sunspot cycle. Last night, for example, it was not a flaring sunspot that sparked green lights over Abisko; instead, the job was done by a stream of solar wind gently buffeting Earth’s magnetic field. Such streams occur throughout the solar cycle.
The sunspot number will likely hover near zero for the rest of the week. Nevertheless, the forecast calls for bright Arctic auroras as another significant stream of solar wind approaches Earth. Stay tuned for sightings.
A GREEN FLASH OVER DRY LAND: Seaside photographers have a special fondness for the sunset. It’s the time of day for the green flash–a split-second pulse of verdant light that signals the disappearance of the sun beneath the ocean waves. But the sea is not always required. Yesterday in Treviso, Italy, Enrico Finotto was looking across dry land when he witnessed this magnificent green flash:
“It was a complete surprise,” says Finotto.
Atmospheric optics expert Les Cowley explains what happened: “This is a mock-mirage green flash produced by light rays bending as they cross a temperature inversion layer. Such flashes can happen over land as well as the sea. We see more flashes over the sea because the sea horizon is not obscured by hills or buildings. But land flashes can be just as spectacular.”
Moreover, dry land offers an advantage that the sea does not. “Over land you might also see a flash twice!” continues Cowley. “I saw once one from our garden, ran indoors and upstairs to see a repeat performance a few seconds later. Try this on a hill slope but be careful, it can be the stuff of heart attacks!”
ORDER NOW FOR CHRISTMAS DELIVERY: It’s out of this world: the Sirius Space Pendant. To raise money for their space weather ballooning program, the students of Earth to Sky Calculus have flown 3 dozen pendants to the edge of space–and you can have one for $79.95. The pendant comes with a greeting card showing the jewelry in flight and certifying that it has been to the stratosphere and back again.
The pendants flew to the edge of space on Nov. 20, 2016, alongside an array of cosmic radiation sensors. During the flight, the sensors measured the highest radiation levels in the history of our monitoring program. After the balloon exploded, the payload parachuted back to Earth, landing in the snowy San Antonio mountains north of Tonopah, Nevada, where a student team recovered it on Nov. 22nd.
The research of Earth to Sky Calculus is not supported by government grants or corporate donations. Instead, we are entirely crowd-funded. Proceeds from the sale of items like the Sirius Pendant go right back into cutting-edge student research. More edge of space Christmas gifts may be found in the Earth to Sky Store.
All Sky Fireball Network
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, 2016, the network reported 13 fireballs.
(12 sporadics, 1 Comae Berenicid)
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]
Near Earth Asteroids
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, 2016 there were potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:Asteroid
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.
speed: 372.1 km/sec
density: 6.8 protons/cm3
more data: ACE, DSCOVR
Updated: Today at 1849 UTX-ray Solar Flares
6-hr max: A6 1758 UT Dec18
24-hr: A6 1758 UT Dec18
explanation | more data
Updated: Today at: 1800 UTDaily Sun: 18 Dec 16The sun is blank–no sunspots. Credit: SDO/HMI
Sunspot number: 0
What is the sunspot number?
Updated 18 Dec 2016
Current Stretch: 2 days
2016 total: 28 days (8%)
2015 total: 0 days (0%)
2014 total: 1 day (<1%)
2013 total: 0 days (0%)
2012 total: 0 days (0%)
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
Updated 18 Dec 2016
Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Credit: NOAA/OvationPlanetary K-index
Now: Kp= 2 quiet
24-hr max: Kp= 3 quiet
explanation | more data
Interplanetary Mag. Field
Btotal: 5.9 nT
Bz: -0.6 nT south
more data: ACE, DSCOVR
Updated: Today at 1849 UTCoronal Holes: 18 Dec 16
Solar wind flowing from this large coronal hole should reach Earth on Dec. 20-22. Credit: NASA/SDO.Noctilucent Clouds The southern season for noctilucent clouds began on Nov. 17th. Come back to this spot every day to see the “daily daisy” from NASA’s AIM spacecraft, which is monitoring the dance of electric-blue around the Antarctic Circle.
Switch view: Ross Ice Shelf, Antarctic Peninsula, East Antarctica, PolarUpdated at: 12-18-2016 16:55:02
Updated at: 2016 Dec 17 2200 UTC
Probabilities for significant disturbances in Earth’s magnetic field are given for three activity levels: active, minor storm, severe stormUpdated at: 2016 Dec 17 2200 UTCMid-latitudes