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 17 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 17 2200 UTC
Sunday, Jul. 17, 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!
AURORA WATCH: A solar wind stream is expected to hit Earth on July 19th, and this could spark G1-class geomagnetic storms around the poles. High-latitude sky watchers should be alert for auroras, especially in the southern hemisphere where dark winter skies favor visibility of faint lights. [aurora gallery]
BIG SUNSPOTS: Solar activity has been low for months. This could soon change. Two big sunspot groups are directly facing Earth, and one of them has an unstable magnetic field that poses a threat for M-class solar flares. Bill Hrudey photographed the active regions on July 16th from Cayman islands:
"Sunspots AR2567 & AR2565 are great imaging targets surrounded by many granules," says Hrudey.
What are granules? The sun is so hot, it literally boils. Granules are bumps on the boiling surface, much like the bumpy surface of water boiling on a hot stove. One difference: While the granules on your stove are only a few centimeters across, granules on the sun are as wide as Texas.
As if granules weren't big enough, the primary dark cores of these sunspots are twice as wide as the entire Earth. Great targets indeed. If you have a solar telescope, take a look.
SOFIA'S SOUTHERN LIGHTS: The Stratospheric Observatory for Infrared Astronomy--a.k.a. "SOFIA"--is currently flying over New Zealand to study stars and galaxies in the Southern Hemisphere. On July 17th, astronomers inside the aircraft made an observation they didn't expect. Ian Griffin sends this report from an altitude of 41,000 feet: "I was lucky enough to have an observers seat aboard tonight's SOFIA flight out of Christchurch," he says. "As we approached 60 degrees south latitude, the sky lit up in a beautiful display of aurora australis."
"Its now 5am and I haven't slept for a day, but I have the biggest smile ever!" says Griffin. "SOFIA is an incredible machine, and to be aboard watching cutting edge science being done as an aurora blazed outside was a truly inspirational experience."
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.
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. 16, 2016, the network reported 34 fireballs. (33 sporadics, 1 alpha Capricornid)
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 17, 2016 there were 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.