NO FIREWORKS FOR THE 4TH OF JULY? An emerging sunspot that unleashed a surprising M1.3-class flare on July 3rd has already vanished. Now the sun is completely blank--no sunspots. The chance of a significant solar flare on the 4th of July is no more than 1%, according to NOAA forecasters. Free: Solar Flare Alerts
INTENSIFYING NOCTILUCENT CLOUD ACTIVITY: Nightfall is supposed to bring darkness. Recent nightfalls in Europe, however, have brought glowing ripples of electric-blue. "Last night, there were the most beautiful noctilucent clouds I have ever seen," says Tamás Csabala, who sends this picture from Debrad, Slovakia:
Marek Nikodem witnessed a similar display over Lake Żnin, near Szubin, Poland. "After a poor start to the season, now is the time of noctilucent clouds. Last night they filled the sky, 140 degrees wide and 110 degrees high, much higher than the zenith. It was unbelievable!"
These and other outbreaks like them are telling us something about the weather in Earth's mesosphere: It's very cold up there. Noctilucent clouds form when summertime wisps of water vapor rise to the top of the atmosphere, coating specks of meteor smoke with fragile crystals of ice. This process requires temperatures as low as 145 K (-128 C). In early June, an unexpected heat wave in the mesosphere temporarily wiped out noctilucent clouds. Their return proves that the heat wave is over.
Noctilucent clouds are usually confined to near-Arctic latitudes. In recent years, however, they have been sighted as far south as Utah and Kansas in the United States. The ongoing apparition in Europe could herald such a widespread display in the nights ahead. Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped ~10 degrees below the horizon. If you see blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud: diagram.
Realtime Noctilucent Cloud Photo Gallery
NOCTILUCENT RADIO ECHOES: Around the Arctic Circle, you can't see noctilucent clouds. Glare from the midnight sun overwhelms their blue glow. Even though Rob Stammes can't see the clouds from Lofoton, Norway, he knows they are there. They show themselves as squiggles on a chart recorder, the signature of polar summertime mesospheric echoes (PSMEs):
"I detected strong PMSEs on 02-03 July 2017," reports Stammes. "This is related to widespread noctilucent clouds visible south of us in Europe."
PMSEs are terrestrial radio stations reflected from an altitude of 80 km to 90 km. That part of Earth's upper atmosphere is called the "mesosphere." It is, coincidentally, the same place noctilucent clouds are found. The exact cause of PMSEs is not yet known; theorists have proposed explanations ranging from steep electron density gradients and "dressed aerosols" to gravity waves and turbulence. The echoes are often accompanied by visible NLCs.
Stammes operates a VHF radio observatory in northern Norway. "I use my VHF receiving system generally for signals from auroras and meteors," says Stammes, "but occasionally I pick up PSMEs, which sound quite different from aurora echoes and other reflection mechanisms."
Realtime Space Weather Photo Gallery
THESE PENDANTS HAVE TOUCHED SPACE: Looking for a far-out gift? On April 15, 2017, the students of Earth to Sky Calculus flew a payload-full of heart-shaped Venus pendants to the stratosphere onboard a high-altitude helium balloon. Here's one floating 111,550 feet above the Sierras of central California:
You can have one for $129.95. Each glittering pendant comes with a greeting card showing the jewelry in flight and telling the story of its journey to the stratosphere and back again.
More items from the edge of space may be found in the Earth to Sky Store. All proceeds support atmospheric radiation monitoring and hands-on STEM education.
Far Out Gifts: Earth to Sky Store
All proceeds support hands-on STEM education