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SOLAR WIND SPARKS ARCTIC AURORAS: This weekend, Earth is inside a stream of solar wind flowing from a large hole in the sun's atmosphere. This is causing bright auroras to dance around the Arctic Circle. Last night in Rovaniemi, Finland, photographer M-P Markkanen witnessed this astounding display:
"I was driving home after midnight when, all of a sudden, I noticed in my rear mirror that the sky had just exploded into incredibly fast moving curtains of green, pink and white," says Markkanen. "I had to stop the car on the side of the road, and soon I got to witness the most incredible aurora show I've ever seen! It evolved into fast pulsing and flashing coronas that lasted for an hour or so. It looked like the whole sky was a big ember on a camp fire! Warmed me up a bit although I felt quite cold by then. It was just mind blowing."
Arctic sky watchers should remain alert for auroras on Saturday night as the solar wind continues to blow. Free: Aurora Alerts
Realtime Aurora Photo Gallery
LIGHT PILLARS OVER LATVIA: This morning in Riga, Latvia, photographer Ivo Dinsbergs stepped outside for a wakening breath of brisk winter air. The predawn sky was not peppered with stars, but instead subdivided by vertical columns of light:
These are light pillars, caused by ice crystals in the air which intercept urban lights and spread them into colorful columns. The key ingredients of this phenomenon are ice and light pollution.
"Each pillar was rising directly above an unshielded street light," says Dinsbergs. Intrigued, he decided to collect some crystals from the air and photograph them:
"Most of them were hexagonal plates," he notes.
That's to be expected. Flat six-sided ice crystals are perfectly shaped for making light pillars. The crystals flutter down from low-hanging clouds with their wide flat faces nearly parallel to the ground, much like a leaf falling from a tree. In this way they form an array of mirrors, reflecting street lights up and down, pillar-style.
Light pillars are a common sight in northern towns during winter. Look for more in the realtime photo gallery:
Realtime Space Weather Photo Gallery
SUNSPOTS VANISH, SPACE WEATHER CONTINUES: As 2017 begins, one thing is clear. Sunspots are vanishing. So far, the sunspot number has been zero almost every day: Jan. 1st, 2nd, 4th, 5th, 6th and 7th. A close look at today's sun reveals no dark cores at all:
The increasingly-blank face of the sun is a herald of Solar Minimum. Sunspot numbers rise and fall with an ~11-year period, slowly oscillating between Solar Max and Solar Min. In 2017, the pendulum is swinging toward minimum.
Contrary to popular belief, space weather does not stop when sunspots vanish. The last few nights are proof: Auroras have been raging around the Arctic Circle. The cause of the display is a solar wind stream flowing from a large hole in the sun's atmosphere. Such "coronal holes" are common during solar minimum. No sunspots? No problem.
In fact, a lot of interesting things happen during solar minimum. For instance, as sunspots vanish, the extreme ultraviolet output of the sun decreases. This causes the upper atmosphere of Earth to cool and collapse. With less air "up there" to cause orbital decay, space junk accumulates around our planet.
Also during solar minimum, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. Goodbye sunspots, hello deep-space radiation.
See? That blank sun is more interesting than it looks. Stay tuned for updates as the solar cycle changes.
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. 7, 2017, the network reported 9 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 January 7, 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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