When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.
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QUIET WEEKEND: Solar activitty is low. Not one of the sunspots on the solar disk has the kind of complex magnetic field that poses a threat for strong flares. This should be a quiet weekend on the sun. Aurora alerts: text, voice
RED SPRITES AND GREEN GRAVITY WAVES: As northern summer comes to a close, electrical storms are rumbling across the USA. After nightfall, red sprites can be seen dancing across the cloudtops. On Aug. 20th, Tom A. Warner photographed these speciments above New Underwood, South Dakota:
"On the night of Aug 20th, intense storms developed in north central South Dakota," says Warner. "Skies cleared out to the west and offered a chance to capture some sprites from the northern activity."
He saw not only sprites, but also green-glowing gravity waves. The waves are, literally, the ripple effect of a powerful thunderstorm on the mesosphere some 80 km above Earth's surface. From space, these waves look like a giant atmospheric bull's eye. From the ground, they appear to be green ripples in the sky, as shown in Warner's images.
Left to themselves, gravity waves would be invisible to the human eye. We see them, however, because they are colored green by an aurora-like phenomenon called "airglow." Airglow is caused by an assortment of chemical reactions in the upper atmosphere driven mainly by solar ultraviolet radiation. Gravity waves rippling away from the central axis of a thunderstorm cause temperature and density perturbations in the upper atmosphere. Speaking simplistically, those perturbations alter the chemical reaction rates of airglow, leading to more-bright or less-bright bands depending on whether the rates are boosted or diminished, respectively.
Inhabiting the upper reaches of Earth's atmosphere alongside meteors, noctilucent clouds and some auroras, sprites and mesospheric gravity waves are true space weather phenomena. Now is a good time to see them.
Realtime Sprite Photo Gallery
MARS COMET PASSES STAR CLUSTER: Comet Siding Spring (C/2013 A1) is hurtling toward Mars for a near miss on Oct. 19, 2014. En route, a different near miss occured. On Aug. 28, the "Mars Comet" pass almost directly in front of globular star cluster NGC 362:
"I took the picture shortly after minimum separation between the two," says astrophotographer Damian Peach of Selsey, UK.
Less than two months from now the comet will reach Mars. Although the comet's nucleus will not strike the planet, gas and dust spewing out of the comet's core will likely interact with the Martian atmosphere. There could be a meteor shower, auroras, and other effects that no one can predict. NASA's fleet of Mars spacecraft and rovers will record whatever happens.
Amateur astronomers can monitor the comet's approach to Mars in the months ahead. Right now, Siding Spring is gliding through the southern constellation Tucana glowing about as brightly as a 11th magntitude star. Mid-sized telescopes such as the Comet Hunter equipped with CCD cameras should have no trouble picking it up. [light curve] [ephemeris] [3D orbit]
Realtime Comet Photo Gallery
"LADY AURORA" RETURNS: After a long, long summer day, Arctic skies are darkening again, and in the sunset observers are seeing a dash of green in the twilight blue.
"Lady Aurora is back in town," says Alex Conu, who took this picture last night on Uttakleiv Beach in the Lofoten Islands of Norway.
NOAA forecasters estimate a 15% to 20% of polar geomagnetic storms during the next 24 hours. The odds of Arctic auroras are probably much higher, however, because it doesn't take a full-fledged storm to turn the twilight green at polar latitudes. Aurora alerts: text, voice
Realtime Aurora Photo Gallery
Realtime Space Weather Photo Gallery
Realtime NLC 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 Aug. 30, 2014, the network reported 26 fireballs.
(25 sporadics, 1 alpha Aurigid)
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 August 30, 2014 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 |