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WEEKEND AURORA WATCH: Earth is moving through a stream of solar wind flowing from a hole in the sun's atmosphere. First contact with the gaseous material on May 20th sparked a G1-class geomagnetic storm and auroras across northern-tier US states from Maine to Washington. More storms are possible on May 21st as solar wind speeds remain elevated above 600 km/s. Free: Aurora Alerts
SOLAR WIND SUMMONS "STEVE": During this Saturday morning's solar wind storm, photographer Harlan Thomas stationed himself among the Hoodoos in the badlands of Alberta, Canada. He hoped to catch a display of auroras. This is what he saw:
"Steve appeared!" says Thomas. "I photographed him behind the silhouettes of the Hoodoos alongside Jupiter and a green picket fence aurora."
"Steve" is the purple arc bisecting the sky. For many years, northern sky watchers have reported this luminous form occasionally dancing among regular auroras. It was widely called a "proton arc" until researchers pointed out that protons probably had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: "Steve."
No one fully understands the underlying physics of the purple ribbon. However, one of the European Space Agency's Swarm satellites recently flew overhead while Steve was active, providing some clues.
This ESA video shows Swarm satellites orbiting above ground-based aurora imagers: more
"As the satellite flew straight though 'Steve,' data from the electric field instrument showed very clear changes," reports Eric Donovan from the University of Calgary. "The temperature 300 km above Earth's surface jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon."
Steve's visit to Alberta on May 20, 2017, coincided with another exotic auroral form: the green "picket fence." These vertical rays are thought to trace lines of magnetic force connecting Earth to space. Luminous green columns show where beams of energetic particles are being guided toward Earth's upper atmosphere by magnetic fields.
Both Steve and the picket fence are filamentary structures associated with beams or ribbons of gas. Coincidence? Hardly. Pictures of the two phenomena show that they often appear together. Consider it another clue.
This is the 2nd time in three nights Thomas has seen Steve. "He also spent 15 minutes with me on May 17th," Thomas says. More visitations could be in the offing this weekend as the solar wind continues to blow. Stay tuned.
Realtime "Steve" Photo Gallery
QUADRUPLE GREEN FLASH: Imagine watching the sun set from a Pacific beach. The fiery disk sinks below the waves, and just before it disappears, a fragment of sun appears to flutter into the air--announced by a flash of green light. Now imagine this happening four times in a row. It happened in San Francisco yesterday when photographer Mila Zinkova witnessed a quadruple green flash:
"Last night's sunset produced some unusual green flashes," says Zinkova. "They were unusual because they lasted a second or two longer than they usually do and because at one point there were four green flashes at once."
Ordinary green flashes rely on a mirage to magnify tiny differences in the atmospheric refraction of red and green light. In this case, temperature gradients above the water produced a complex mirage and, not one, but four flashes. Zinkova's complete video of the event is a must-see.
Realtime Space Weather Photo Gallery
THIS PENDANT HAS TOUCHED SPACE: The radiation monitoring program of Earth to Sky Calculus receives no support from corporate sponsors or government grants. Instead, we are crowd-funded. Or, to be more precise, bling-funded:
To raise money for more cosmic ray balloon flights, on May 6th the students launched a payload of these Northern Lights pendants to the top of Earth's atmosphere. You can have one for $79.95. Each piece of space jewelry comes with a greeting card showing the item in flight and telling the story of its journey to the stratosphere and back. They make great birthday and belated Mother's Day gifts.
More far-out gifts may be found in the Earth to Sky Store. All proceeds support atmospheric radiation monitoring and hands-on STEM education.
Realtime Comet Photo Gallery
Realtime Aurora 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 May. 21, 2017, the network reported 16 fireballs.
(16 sporadics)
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 May 21, 2017 there were 1801 potentially hazardous asteroids.
|
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
2012 EC | 2017-May-16 | 19.5 LD | 4.5 | 74 |
2017 KH3 | 2017-May-24 | 18.7 LD | 20 | 62 |
2017 CS | 2017-May-29 | 8 LD | 9.1 | 468 |
418094 | 2017-Jun-01 | 8 LD | 23.2 | 490 |
2017 KJ3 | 2017-Jun-03 | 11.1 LD | 11.3 | 48 |
2017 HV4 | 2017-Jun-10 | 19.5 LD | 3.9 | 52 |
2017 KF3 | 2017-Jun-12 | 12.9 LD | 11.1 | 39 |
2010 VB1 | 2017-Jun-16 | 10.3 LD | 8.3 | 81 |
471984 | 2017-Jun-18 | 19.1 LD | 7.7 | 102 |
441987 | 2017-Jun-24 | 7.9 LD | 12.7 | 178 |
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 13% 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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