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CORONAL HOLE TURNS TOWARD EARTH: A large coronal hole is turning toward Earth, and it is spewing a stream of high-speed solar wind. NOAA forecasters expect the stream to reach our planet on Sept. 28-29 with a 50% chance of G1-class geomagnetic storms when it arrives. At this time of year, even a gentle gust of solar wind can spark bright polar auroras. The incoming stream is almost sure to provoke a nice display. Free: Aurora Alerts
Today's coronal hole. Arrows indicate the flow of solar wind from the yawning magnetic chasm.
Realtime Aurora Photo Gallery
BRIGHT AURORAS: Yesterday, Sept. 25th, Earth passed through a fold in the heliospheric current sheet. The crossing sparked a G1-class geomagnetic storm and bright auroras around the Arctic Circle. Christian Schartner was on an airplane flying from Munich to Iceland when the window filled with an explosion of color:
"What a fantastic start to our Iceland trip!" says Schartner.
Many people have never heard of the heliospheric current sheet. It is one of the biggest things in the solar system--a vast undulating system of electrical currents shaped like the skirt of a ballerina. Earth dips in and out of it all the time. On Sept. 25th, Earth found itself on the side of the current sheet containing negative-polarity magnetic fields. Such fields can open a crack in our planet's magnetosphere, allowing solar wind to pour in and fuel colorful displays like Schartner witnessed.
"Shooting the aurora from inside an airplane was not easy--especially without a tripod," says Schartner. "Thanks to modern technology, I was able to capture it with a fast lens and very high ISO setting." More pictures of the display, inside of airplanes and out, may be found in the photo gallery:
Realtime Aurora Photo Gallery
THE STRANGE THING ABOUT THIS SUNSET.... Yesterday at sunset, Mila Zinkova was looking west from Pacifica CA when "something strange happened," she reports. The sun split into multiple layers and a green flash appeared. But, that wasn't the strange thing. Temperature inversions above the ocean surface frequently distort the setting sun off the Califonia coast. "Take a closer look at the picture," urges Zinkova. "Where did that vertical pillar of light at the bottom come from?" Scroll down for the answer:
"It's the spout of a whale," she explains.
In the complete video she recorded, multiple spouts can be seen grazing the bottom of the miraged sun. "Of course the sunset was unusual not because of whales, but because of some very complex temperature inversions in the atmosphere. While the lowest sun was setting, producing green flashes, the upper suns were not in a hurry to leave. They kept disappearing and reappearing."
Just another evening on the California coast.... Turn up the volume and watch it again.
Realtime Space Weather Photo Gallery
Realtime Sprite Photo Gallery
| ||Cosmic Rays in the Atmosphere |
Updated: Sept. 26, 2016 // Next Flight: Oct. 1, 2016
Sept. 20, 2016: 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.
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 Sep. 26, 2016, the network reported 17 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]
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 September 26, 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.
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