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SOLAR SECTOR BOUNDARY CROSSING: Later today, Nov. 20th, Earth is expected to cross through a fold in the heliospheric current sheet. This "solar sector boundary crossing" could cause geomagnetic unrest around the poles. Arctic sky watchers should be alert for Northern Lights. Realtime: photo gallery
RETURN OF THE BIG CORONAL HOLE: At the end of October, a hole in the sun's atmosphere lashed Earth's magnetic field with solar wind, sparking moderately-strong geomagnetic storms and almost a full week of Arctic auroras. News flash: It's back. The same "coronal hole" is turning toward Earth again. NASA's Solar Dynamics Observatory photographed the structure on Nov. 20th:
Coronal holes are regions in the sun's atmosphere where the magnetic field peels back and allows solar wind to escape. Since our last encounter with this hole in late October it has been transiting the farside of the sun, carried around by the sun's 27-day rotation. Now that it is back we can see that the hole is not quite as large as it was a month ago--but it is still impressive, covering almost 1/3rd of the visible solar disk.
NOAA forecasters expect the leading edge of the emerging solar wind stream to reach Earth on Nov. 22nd, bringing with it a chance of G1-class geomagnetic storms. Stay tuned! Free: Aurora Alerts.
Realtime Aurora Photo Gallery
THANKSGIVING SKIES: Thanksgiving is the biggest travel holiday of the year in the United States. Millions of people board airplanes and fly long hours to visit friends and family. Dreading the trip? Think of it as a sky watching opportunity. There are some things you can see only through the window of an airplane, like this:
Chris Dalla Piazza took the picture on Nov. 9th while flying over Utah. "At first I thought the bright white spot was some kind of internal reflection in the window," says Piazza. "But then I saw that it was flanked by rainbow-colored splashes of light. It was not a reflection."
It was a subsun. Atmospheric optics expert Les Cowley explains : "Look down from the sunny side of an aircraft and you will often see a dazzling reflection of the sun in the clouds. This is a subsun, formed by millions of plate shaped ice crystals acting as mirrors."
"We were indeed flying above a thin layer of icy cirrus clouds," says Piazza.
Ice crystals in those clouds created not only a subsun, but also a pair of sub-sundogs. Many readers have seen regular sundogs flanking the actual sun. Those are formed by an even number of reflections inside ice crystals. An odd number of reflections makes the sub-sundog."
In this article, Cowley describes even more things you can see through the airplane window. Happy Thanksgiving!
Realtime Space Weather Photo Gallery
FLIGHT OF THE SPACE PICKLE: The ballooning program of Earth to Sky Calculus is funded not by government grants or corporate donations. Instead, we rely on crowdfunding. Hence, the flight of the space pickle:
To raise funds for their ongoing research, Spaceweather.com and the students of Earth to Sky Calculus flew two dozen Christmas pickles to the stratosphere. On Nov. 5th, the glass gherkins ascended to an altitude of 111,900 feet, experiencing temperatures as low as -55 C and cosmic ray dose rates more than 100x Earth normal.
You can have one for your own tree. Price: $49.95. All proceeds are used to support cutting-edge student research. The space pickle and other edge of space gifts may be found in the Earth to Sky Store.
Realtime Sprite Photo Gallery
Realtime Airglow 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 Nov. 20, 2016, the network reported 25 fireballs.
(16 sporadics, 4 Northern Taurids, 4 Leonids, 1 Quadrantid)
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 November 20, 2016 there were 1742 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.
| ||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.
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