By Spaceweather.com, 02/18/2017
WEEKEND AURORAS: Earth’s magnetic field is on the verge of minor storming as our planet moves deeper into a stream of solar wind that arrived on Feb. 16th. A sign of the unrest: Green skies over Alaska. Ronn and Marketa Murray send this picture from just outside Fairbanks:
“Meet Madison, a smart, sweet, beautiful Wish Kid,” say the Murrays. “It was her wish to enjoy these magic lights, and our honor to help her do so. Big thanks to Maddy, her amazing family, andMake-A-Wish Alaska/Washington for giving us an opportunity to to get to know her. She was a bright shining star as auroras filled the sky.”
More lights are possible this weekend as the solar wind continues to buffet Earth’s magnetic field. So far, wind speeds are only moderately high (~500 km/s), but that is enough to spark intermittent auroras of exquisite beauty around the Arctic Circle. Free: Aurora alerts.
A GASH IN THE SUN’S ATMOSPHERE: An unusually wide and sinuous hole has opened in the sun’s atmosphere, and it is stretching like a gash across the sun’s entire southern hemisphere. NASA’s Solar Dynamics Observatoryphotographed the structure using false-color ultraviolet telescopes on Feb. 17th:
This is a “coronal hole” (CH)–a region where magnetic fields open up and allow solar wind to escape. Solar wind flowing from this coronal hole could buffet Earth’s magnetic field, off and on, for the next two weeks. Much of the material will pass to the south of Earth, mitigating its impact. However, even the glancing effects of a two-week solar wind event could support a sustained display of polar auroras. Arctic sky watchers, February could end well for you.
NEUTRONS IN THE STRATOSPHERE: In a joint operation on Feb.12th, the students of Earth to Sky Calculus and their sister club Earth to Sky Maritime launched a neutron counter to the stratosphere onboard a high altitude balloon. Neutrons are an important form of cosmic radiation because they provide much of the biologically effective radiation dose at altitudes of interest to aviation and space tourism. How are these particles distributed through our atmosphere? This is what we wanted to find out.
We’ve just finished reducing the data and can report that the experiment was a success. Neutrons were detected throughout the 2 hour flight covering altitudes from ground level to 113,200 ft:
This first data set shows that neutrons, like gamma rays, peak at the entrance to the stratosphere in a layer known as the Regener-Pfotzer Maximum. Moreover, neutron counts are significantly elevated not only in the stratosphere, but also at lower altitudes where planes fly (20,000 ft to 45,000 ft)–something to think about the next time you buy an airline ticket.
We’ve been monitoring cosmic rays in the atmosphere for more than two years, and find that deep space radiation has been intensifying. Previous payloads measured only X-rays and gamma-rays, however. The addition of a neutron counter to the payload is a major upgrade, providing a more complete picture of the radiation environment. Stay tuned for updates as we improve our technique and gather more data in future flights.
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 Feb. 18, 2017, 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]
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 February 18, 2017 there were 1774 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.
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.
Daily Sun: 18 Feb 17
Sunspot AR2636 poses no threat for strong solar flares. Credit: SDO/HMI
Sunspot number: 14
What is the sunspot number?
Updated 18 Feb 2017
Current Stretch: 0 days
2017 total: 11 days (22%)
2016 total: 32 days (9%)
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 Feb 2017
Current Auroral Oval:
Coronal Holes: 18 Feb 17
An unusually broad coronal hole is cutting across the southern hemisphere of the sun. Credit: NASA/SDO.
Noctilucent Clouds The southern season for noctilucent clouds began on Nov. 17, 2016. 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.
Updated at: 02-17-2017 17:55:02
Updated at: 2017 Feb 17 2200 UTC
Updated at: 2017 Feb 17 2200 UTC