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EXITING THE SOLAR WIND STREAM: After almost a week inside, Earth is exiting a stream of solar wind that has sparked bright auroras around the Arctic Circle. Another stream is coming. NOAA forecasters estimate a 40% chance of G1-class geomagnetic storms on Jan. 12th when the solar wind arrives. Free: Aurora Alerts
PILEUS CLOUDS: On Jan. 6th, Peter Lowenstein observed a rainbow-colored saucer over Mutare, Zimbabwe--but it wasn't a UFO. "This is a classic example of a pileus cloud," he says.
Pileus clouds form on sunny afternoons when the heat of the summer sun causes cumulus clouds to boil upwards. Roiling toward the sky, cumulus clouds push layers of moist air above them where they cool and condense to form droplet-rich cloud caps or 'pileus' (Latin for cap).
Sometimes, as in Mutare on Jan. 6th, pileus clouds form very quickly. In such cases their water droplets tend to be all the same size--the perfect condition for iridescent colors.
Lowenstein took four pictures over a period of just three minutes. "They show the cloud appearing, then changing shape and color," he says. "One minute later it had disappeared behind the summit of the growing cumulonimbus cloud."
Realtime Space Weather Photo Gallery
CORONAL HOLE: A relatively small hole has opened in the sun's atmosphere. On the sun, "small" means 25 times wider than Earth. NASA's Solar Dynamics Observatory took this picture of the coronal hole (CH) on Jan. 10th:
Coronal holes are places in the sun's atmosphere where the magnetic field opens up and allows solar wind to escape. A stream of solar wind flowing from this hole should reach Earth on Jan. 12th. Because the hole is small, the emerging solar wind stream is narrow. Earth will be inside it for only a day or so.
Coincidentally, Earth is expected to cross a fold in the heliospheric current sheet at about the same time. This will boost the chances of a polar geomagnetic storm to 40%, according to NOAA forecasters. Arctic sky watchers should be alert for auroras on Thursday and Friday nights. Free: Aurora Alerts
Realtime Aurora Photo Gallery
Realtime Airglow Photo Gallery
Realtime Sprite 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 Jan. 10, 2017, the network reported 22 fireballs.
(19 sporadics, 2 Quadrantids, 1 lambda Bootid)
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 January 10, 2017 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.
| ||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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