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QUIET WITH AN INCREASING CHANCE OF FLARES: Solar activity is low, but new sunspot AR2353 could break the quiet. The growing active region has a 'beta-gamma' magnetic field that harbors energy for M-class solar flares. Because of this development, the odds of an eruption this weekend are increasing. Solar flare alerts: text, voice
VOLCANIC GAS CIRCUMNAVIGATES THE GLOBE: Last month, on April 22nd, Chile's Calbuco volcano erupted, blowing plumes of ash and sulfurous gas more than 50,000 feet high. Since then, the swirling plumes have spread around the southern hemisphere--traveling eastward from South America to southern Africa to Australia/New Zealand. Just a few days ago, the plumes completed the circle.
"We are seeing volcanic sunsets again in Rio," reports Brazilian photographer Helio de Carvalho Vital, who took this picture on May 17th:
Back in April, Vital was among the first to notice colorful sunsets in the immediate aftermath of Calbuco. "I spotted the first effects of the volcano on April 24 and monitored the bulk of the plume on April 26, 27 and 28 as it was heading east. Colorful sunsets were visible from Rio for a week after that."
A primary color of volcanic sunsets is purple: Fine volcanic aerosols in the stratosphere scatter blue light which, when mixed with ordinary sunset red, produces a violet hue. Purple isn't the only color, though. Volcanic sunsets can also include a bright yellow twilight arch and long diffuse rays and shadows.
After a 3 week intermission, purple has returned to Brazil. "It is subtle," notes Vital. "A camera is required to fully capture the effect. This suggests that the plumes are now much more tenuous than three weeks ago."
A purple sighting last night in New Zealand further suggests that Calbuco's exhaust is thinly spread around the southern hemisphere. Photographers in southern Africa, Argentina, Chile, southern parts of Brazil, and Australia should remain alert for similar displays.
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NOCTILUCENT CLOUD SEASON BEGINS: NASA's AIM spacecraft has spotted a luminous patch of electric-blue drifting across the Arctic Circle. The sighting marks the beginning of the 2015 season for noctilucent clouds (NLCs). "The first clouds appeared on May 19th--a bit earlier than usual," reports Cora Randall, AIM science team member at the University of Colorado. They are located at longitude +90o in this polar image recorded by AIM's CIPS instrument:
The first northern-hemisphere NLCs of 2015, recorded by AIM/CIPS on May 19th
"It is always good to see the beginning of another season," says James Russell of Hampton University, principal investigator for the AIM mission. "What surprises will it bring? We will see. The clouds have never disappointed us."
NLCs are Earth's highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet's surface. The clouds are very cold and filled with tiny ice crystals. When sunbeams hit those crystals, they glow electric-blue.
Noctilucent clouds first appeared in the 19th century after the eruption of super-volcano Krakatoa. At the time, people thought the clouds were caused by the eruption, but long after Krakatoa's ash settled, the clouds remained. In those days, NLCs were a polar phenomenon confined mainly to the Arctic. In recent years they have intensified and spread with sightings as far south as Utah and Colorado. This could be a sign of increasing greenhouse gases in Earth's atmosphere.
Data from AIM have shown that NLCs are like a great "geophysical light bulb." They turn on every year in late spring, reaching almost full intensity over a period of 5 to 10 days. News flash: The bulb is glowing. Stay tuned for sightings.
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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 May. 23, 2015, the network reported 16 fireballs.
(16 sporadics)
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 May 23, 2015 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. | | The official U.S. government space weather bureau |
| | The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| | Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| | 3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| | Realtime and archival images of the Sun from SOHO. |
| | from the NOAA Space Environment Center |
| | the underlying science of space weather |
