Spotless Days Current Stretch: 0 days 2016 total: 16 days (8%) 2015 total: 0 days (0%) 2014 total: 1 day (<1%) 2013 total: 0 days (0%) 2012 total: 0 days (0%) 2011 total: 2 days (<1%) 2010 total: 51 days (14%) 2009 total: 260 days (71%) Updated 15 Jul 2016
Geomagnetic Storms: Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2016 Jul 15 2200 UTC
Friday, Jul. 15, 2016
What's up in space
It's waiting for you: The most successful Aurora Photo Tour on Earth! 100% success rate 4 years in a row and winner of the TripAdvisor Certificate of Excellence Award. Join LapplandMedia's aurora tours in Abisko, Swedish Lapland!
BIG SUNSPOT, LITTLE SOLAR ACTIVITY: After weeks of spotlessness in June, there is now a significant active region on the sun. Except big sunspot AR2565 is, actually, not active. It has a stable magnetic field that poses almost no threat for significant explosions. NOAA forecasters say there is no more than a 1% chance of strong flares on July 15th.
NOCTILUCENT CLOUDS INVADE THE USA: Summer is the season for noctilucent clouds. For sky watchers in the United States, "noctilucent summer" has just begun. On July 14th, a bright bank of electric-blue clouds rippled over the Canadian border into the USA. Greg Johnson of Seattle, Washington, photographed the display over the Puget Sound:
Dustin Guy of Seattle saw them too. "I witnessed the most vibrant NLC display that I've seen in a number of years," he says. "They lit up the water of Lake Washington at 330 AM local time."
NLCs are Earth's highest clouds. They form at the edge of space more than 80 km above Earth's surface, when wisps of summertime water vapor wrap themselves around meteor smoke. The resulting ice crystals glow electric blue in the night sky.
In the 19th century, you had to travel near Arctic latitudes to see these clouds. In recent years, however, they have been sighted as far south as Colorado and Kansas. The spread could be a result of climate change. July is usually the best month for NLCs. Sky watchers in the northern half of the USA should be alert for them for the next two weeks.
Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped ~10 degrees below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.
IRISH DOUBLE SUN HALOES: Noel Keating is an experienced photographer of the sky. He has seen plenty of auroras, noctilucent clouds, and even sun halos. "But I've never seen a double sun halo like the one that appeared over Co. Donegal in the republic of Ireland on July 14th," he says. "It was amazing!"
Sun halos are caused by ice crystals floating in cirrus clouds 5 to 10 km above the ground. Illuminated by sunlight, various crystal shapes give rise to luminous rings and arcs in the daytime sky. The most common halo is a 22 degree circle around the sun. Keating's picture captured that and more.
"There are actually three halos in this picture," says atmospheric optics expert Les Cowley. "The familiar 22 degree halo is the inner circle around the sun. Touching it at top and bottom is an outer oval, a circumscribed halo."
"The large circle crossing the sun, and hanging below it, is an unusual appearance of the parhelic circle. We normally see only fragments of the parhelic circle closer to the horizon. Here the sun is high and it has shrunk to a small circle around the zenith."
The clouds over the British isles must have been filled with such crystals yesterday because, says Cowley, "there were many halos over Ireland and Uk yesterday - a fine day for them." Look for more in the photo gallery:
RAINBOW BREATHING WHALES: "Rainbow breathing whale" sounds like a mythical creature. On July 12th, Mila Zinkova of San Francisco saw one ... for real. She took this picture looking over the edge of the Golden Gate Bridge:
"A few humpback whales crossed under Golden Gate Bridge and entered the Bay," says Zinkova. "Just then I saw their rainbow-colored sprays. It was beautiful!"
This is not mythology. It's physics. When Zinkova took the picture, the sun was behind her back shining down into the droplet-filled exhaust of the whale's spout. Sunbeams reflecting from the water droplets produced a prismatic spray of color just like an ordinary rainbow.
Of course it didn't look ordinary. "The full video," says Zinkova, "may be found here."
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 Jul. 15, 2016, the network reported 29 fireballs. (26 sporadics, 1 psi Cassiopeid, 1 Microscorpiid, 1 July Pegasid)
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]
Near Earth Asteroids
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 July 15, 2016 there were 1713 potentially hazardous asteroids.
These measurements are based on regular space weather balloon flights: learn more.
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. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. For example, here is the data from a flight on Oct. 22, 2015:
Radiation levels peak at the entrance to the stratosphere in a broad region called the "Pfotzer Maximum." This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are more than 80x sea level.
Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Oct 22th measurements, a plane flying at 45,000 feet is exposed to 2.79 uSv/hr. At that rate, a passenger would absorb about one dental X-ray's worth of radiation in about 5 hours.
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.