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SOLAR STORM TARGETS EARTH: A pair of CMEs billowed away from the sun on Dec. 16th, and at least one of them appears to be heading for Earth. Propelled in our direction by an erupting filament of magnetism (movie), the storm cloud could produce G1-class geomagnetic storms when it arrives on Dec. 19th. Stay tuned for refinements to the forecast when NOAA storm tracks become available later today. Aurora alerts: text or voice
POLAR STRATOSPHERIC CLOUDS: This week, sky watchers are reporting an outbreak of polar stratospheric clouds (PSCs) around the Arctic Circle. Unlike normal grey-white clouds, which hug Earth's surface at altitudes of only 5 to 10 km, PSCs float through the stratosphere (25 km) and they are fantastically colorful. Truls Tiller photographed these over Tromsø, Norway, on Dec. 16th:
"Here the sun is gone for now," says Tiller, "but this beautiful view makes the winter darkness nice to be in as well. The picture was taken at 10.30 am, in the middle of the 'day.'"
Also known as "nacreous" or "mother of pearl" clouds, the icy structures form in the lower stratosphere when temperatures drop to around minus 85ºC. High-altitude sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors by diffraction and interference. Once thought to be mere curiosities, some PSCs are now known to be associated with the destruction of ozone.
"Nacreous clouds far outshine and have much more vivid colours than ordinary iridescent clouds, which are very much poor relations and seen frequently all over the world," writes atmospheric optics expert Les Cowley. "Once seen they are never forgotten."
Realtime Nacreous Clouds Photo Gallery
ELECTRIC-BLUE CLOUDS APPEAR OVER ANTARCTICA: NASA's AIM spacecraft has detected electric-blue clouds forming over Antarctica. These are noctilucent clouds (NLCs), and their apparition marks the beginning of the 2015-2016 season for NLCs in the southern hemisphere. According to Cora Randall, a member of the AIM science team at the University of Colorado, the first wisps of electric-blue appeared on Dec. 14th:
NLCs are Earth's highest clouds. Seeded by meteor smoke, they form at the edge of space 83 km above Earth's surface. When sunlight hits the tiny ice crystals that make up these clouds, they glow electric blue. NLCs appear during late spring and summer because, ironically, that is when the upper atmosphere is coldest, allowing the ice crystals of NLCs to form. (Northerners reading this story should remember that it is late spring in Antarctica.)
Previous results 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 about 10 days. At the moment, only a few puffs and wisps of NLCs are visible over Antarctica. By Christmas, the whole continent could be blanketed in electric blue as the bulb begins to glow in earnest.
It is interesting that noctilucent clouds over the Antarctic have appeared at about the same time as nacreous clouds (PSCs) over the Arctic. Pure coincidence? Maybe not. Although they are poles apart, the two types of clouds may be linked.
"We do know that the meteorology of the northern winter stratosphere can impact the southern NLC region. A widely-cited mechanism for this teleconnection predicts that a cooling in the Arctic stratosphere – which is consistent with the appearance of PSCs – would lead to a cooling in the Antarctic NLC region, and thus a higher probability of NLC formation."
In other words, nacreous clouds and NLCs should appear at the same time. Just one problem: "The literature to date suggests that the teleconnection is active only in January and February," says Randall. "This year, we could be seeing something new."
Realtime Spaceweather Photo Gallery
METEOR BALLOON IN THE STRATOSPHERE: When the Geminid meteor shower peaked on Dec. 14th, a snowstorm was in progress over the mountains of central California. No stars? No problem. Using a helium balloon, the students of Earth to Sky Calculus launched a low-light camera to photograph the shower high above the obscuring clouds. Their experimental payload ascended to 91,000 feet where the night sky looked like this:
The big white object at the top of the frame is the balloon, surrounded by some of the bright stars and planets of the pre-dawn sky. From the lower stratosphere, the freezing camera was able to see stars as dim as 2nd magnitude. This wasn't as sensitive as the students had hoped, but it was good enough to record several Geminid fireballs. Here are a couple of movies showing Geminids emerging from behind the balloon: fireball #1, fireball #2. In the movies, stars and planets move in a lazy circle around the balloon--a result of the payload's gentle spin--while Geminids streak in straight lines. The camera also recorded the balloon exploding at the apex of the flight, and the payload parachuting back to Earth.
The students plan to observe more meteor showers in the future with even better results. They believe they can boost the sensitivity of the camera by, e.g., warming the payload bay during the flight and improving the camera's focus, pre-launch. If their improvements succeed, they could establish ballooning as a practical and fun way to monitor meteor showers in all kinds of weather.
HEY THANKS! Earth to Sky Calculus wishes to thank KOMO, an ABC News channel in Seattle, for sponsoring this flight. Their generous donation of $500 allowed the students to take the first-ever picture of Geminids from the stratosphere. Readers, if you would like to sponsor a balloon flight, click here.
Realtime Meteor Photo Gallery
Realtime Aurora Photo Gallery
Realtime Comet 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 Dec. 17, 2015, the network reported 31 fireballs.
(24 sporadics, 2 December Monocerotids, 2 Geminids, 2 December Leonis Minorids, 1 sigma Hydrid)
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 December 17, 2015 there were 1646 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 |
These measurements are based on regular space weather balloon flights: learn more.
|Situation Report -- Oct. 30, 2015 ||Stratospheric Radiation (+37o N) |
|Cosmic ray levels are elevated (+6.1% above the Space Age median). The trend is flat. Cosmic ray levels have increased +0% in the past month. |
|Sept. 06: 4.14 uSv/hr (414 uRad/hr) |
|Sept. 12: 4.09 uSv/hr (409 uRad/hr) |
|Sept. 23: 4.12 uSv/hr (412 uRad/hr) |
|Sept. 25: 4.16 uSv/hr (416 uRad/hr) |
|Sept. 27: 4.13 uSv/hr (413 uRad/hr) |
|Oct. 11: 4.02 uSv/hr (402 uRad/hr) |
|Oct. 22: 4.11 uSv/hr (411 uRad/hr) |
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. Here is the data from our latest flight, Oct. 22nd:
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.
| ||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 |
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| ||the underlying science of space weather |