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ENTERING THE SOLAR WIND STREAM: As predicted, today Earth is feeling the first brush of a solar wind stream that could envelop our planet for the rest of the week. Last night, the stream's leading edge sparked a bright display of auroras over Scandinavia, shown here in a photo from Ole Salomonsen of Tromsø, Norway:
"I drove about an hour from Tromsø and stopped by a river--a great place for reflections," says Salomonsen. "Strong auroras were dancing overhead. It was a fantastic display."
The solar wind is flowing from a large hole in the sun's atmosphere. NASA's Solar Dynamics Observatory photographed the yawning structure directly facing Earth on Jan. 3rd:
Coronal holes are regions where the sun's magnetic field peels back and allows solar wind to escape. The stream of wind emerging from this coronal hole recently blew past NASA's STEREO-A spacecraft with peak speeds near 700 km/s. Now it's our turn as the stream reaches Earth.
NOAA forecasters say there is a 60% to 65% chance of polar geomagnetic storms on Jan. 4th-5th as the fast-moving stream buffets our planet's magnetic field. Residents of the Arctic should expect G1-class geomagnetic storms and bright auroras in the nights ahead. Free: Aurora Alerts.
Realtime Aurora Photo Gallery
ANALEMMA TIMES 9: If you took a picture of the sun at the same time each day, would it remain in the same position? The answer is no, and the figure-8 shape traced out by the sun over the course of a year is called an "analemma." Over the years, many photographers have created analemmas. In 2016, however, Steven Riegel of Colorado Springs CO took it up a notch. He photographed the sun 9 times a day, creating the rare nonalemma:
"I opened up a year-long (1 Jan - 31 Dec 2016) analemma exposure on New Year's Day," explains Riegel. " The result is a record of the position of the sun on the hour between 7:00 am and 3:00 pm every day for a full year."
"The camera is just a light-tight box with a pinhole in the side. I put an 8x10 piece of B/W photo paper inside. The pinhole was uncovered for two minutes each hour by a rotating paper mask attached to a cheap electric clock. The image is burned into the photo paper by the bright sunlight."
" I can't claim originality for the technique, but I've only seen a couple of other similar examples done previously," says Riegel. "It's a nerve-wracking time waiting for the year to see if you set things up correctly!"
Realtime Space Weather 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. 4, 2017, the network reported 25 fireballs.
(19 sporadics, 5 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 4, 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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