Space Weather Update: 03/17/2017
By Spaceweather.com, 03/17/2017
GREEN SKIES ON ST. PATRICK’S DAY? Today is St. Patrick’s Day. Arctic sky watchers may be able to celebrate with a splash of green in the sky. A weak CIR is expected to hit Earth’s magnetic field on March 17th. CIRs (co-rotating interaction regions) are transition zones between slow- and fast-moving streams of solar wind. Compressed magnetic fields in CIRs often do a good job of sparking auroras. Free: Aurora Alerts
BIG CORONAL HOLE TURNS TOWARD EARTH: A hole has opened in the sun’s atmosphere, and it is turning toward Earth. NASA’s Solar Dynamics Observatory is tracking the opening, which researchers call a “coronal hole” (CH):
Coronal holes are places–big places–where the sun’s magnetic field opens up and allows solar wind to escape. A wide stream of solar wind flowing from this coronal hole is expected to reach our planet on March 23rd. The impact of the solar wind should produce magnetic activity around Earth’s poles and could spark the first auroras of northern spring. Stay tuned. Free: Aurora Alerts
VENUS IS A SKINNY CRESCENT: On March 25th, Venus will pass almost directly between Earth and the sun–an event astronomers call “inferior solar conjunction.” As Venus approaches the sun, the planet is turning its night side toward us, reducing its luminous glow to a thin sliver. Shahrin Ahmad of Kuala Lumpur, Malaysia, photographed the crescent on March 15th:
“Venus is about 17º from sun, and shining at only 4.7% illumination,” says Ahmad. “This is my clearest view so far. “
In the nights ahead, the crescent of Venus will become increasingly thin and circular. The horns of the crescent might actually touch when the Venus-sun angle is least on March 25th. This is the most beautiful time to observe Venus–but also the most perilous. The glare of the nearby sun magnified by a telescope can damage the eyes of anyone looking through the eyepiece.
Anthony J. Cook of the Griffith Observatory has some advice for observers: “I have observed Venus at conjunction, but only from within the shadow of a building, or by adding a mask to the front end of the telescope to fully shadow the optics from direct sunlight. This is tricky with a refractor or a catadioptric, because the optics start at the front end of the tube. Here at Griffith Observatory, I rotate the telescope dome to make sure the lens of the telescope is shaded from direct sunlight, even through it means that the lens will be partially blocked when aimed at Venus. With our Newtonian telescope, I add a curved cardboard mask at the front end of the tube to shadow the primary mirror.”
For the rest of this week Venus can still be observed without elaborate precautions. Point your optics at the Evening Star in the western sky after sunset. Even ordinary binoculars will show the planet’s lovely curve.
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 Mar. 17, 2017, the network reported 18 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 March 17, 2017 there were 1780 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: 17 Mar 17
The sun is blank–no sunspots. Credit: SDO/HMI
Sunspot number: 0
What is the sunspot number?
Updated 17 Mar 2017
Current Stretch: 11 days
2017 total: 23 days (30%)
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 17 Mar 2017
Current Auroral Oval:
Coronal Holes: 17 Mar 17
Solar wind flowing from the indicated coronal hole should reach Earth as early as March 23rd. 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: 02-24-2017 17:55:02
Updated at: 2017 Mar 16 2200 UTC
Updated at: 2017 Mar 16 2200 UTC