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Solar wind
speed: 386.7 km/sec
density: 13.0 protons/cm3
explanation | more data
Updated: Today at 2347 UT
X-ray Solar Flares
6-hr max: B9
2048 UT Aug20
24-hr: C1
0129 UT Aug20
explanation | more data
Updated: Today at: 2300 UT
Daily Sun: 20 Aug 13
Sunspot AR1825 has a 'beta-gamma' magnetic field that poses a threat for M-class solar flares. Credit: SDO/HMI
Sunspot number: 161
What is the sunspot number?
Updated 20 Aug 2013

Spotless Days
Current Stretch: 0 days
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%)
Since 2004: 821 days
Typical Solar Min: 486 days

20 Aug 2013

The Radio Sun
10.7 cm flux: 128 sfu
explanation | more data
Updated 20 Aug 2013

Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Planetary K-index
Now: Kp= 1 quiet
24-hr max: Kp= 1
explanation | more data
Interplanetary Mag. Field
Btotal: 9.0 nT
Bz: 5.6 nT north
explanation | more data
Updated: Today at 2347 UT
Coronal Holes: 20 Aug 13
Solar wind flowing from the indicated coronal hole should reach Earth on Aug. 23-24. Credit: SDO/AIA. is now posting daily satellite images of noctilucent clouds (NLCs), which hover over Earth's poles at the edge of space. The data come from NASA's AIM spacecraft. The north polar "daisy" pictured below is a composite of near-realtime images from AIM assembled by researchers at the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP).
Noctilucent Clouds
Switch view: Europe, USA, Asia, Polar
Updated at: 08-20-2013 12:55:02
NOAA Forecasts
Updated at: 2013 Aug 20 2200 UTC
0-24 hr
24-48 hr
10 %
10 %
01 %
01 %
Geomagnetic Storms:
Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2013 Aug 20 2200 UTC
0-24 hr
24-48 hr
35 %
30 %
10 %
05 %
01 %
01 %
High latitudes
0-24 hr
24-48 hr
10 %
15 %
30 %
30 %
45 %
35 %
Tuesday, Aug. 20, 2013
What's up in space

Listen to radar echoes from satellites and meteors, live on listener-supported Space Weather Radio.

Spaceweather Radio is on the air

OFF-TARGET CME COULD SPARK STORMS: According to NOAA analysts, a CME hurled into space by an M3-class solar flare on August 17th will probably miss Earth. However, Earth will likely pass through the wake of the CME after the cloud itself passes by. This could trigger polar geomagnetic storms despite the CME being off-target. High-latitude sky watchers should be alert for auroras on August 20-21. Aurora alerts: text, voice.

SUNDIVING COMET AND FULL-HALO CME: A small comet plunged into the sun this morning, and just before it arrived, the sun expelled a magnificent full-halo CME. Click to view a movie from the Solar and Heliospheric Observatory (SOHO):

In the final frames of the movie, the comet can be seen furiously vaporizing. Indeed, those were the comet's final frames. It did not emerge again from its flyby of the hot sun. "With a diameter of perhaps a few tens of meters, this comet was clearly far too small to survive the intense bombardment of solar radiation," comments Karl Battams of the Naval Research Lab, who studies sungrazing comets.

The CME (coronal mass ejection) came from an explosion on the farside of the sun. Although the CME and the comet appear to intersect, there was probably no interaction between the two. The comet is in the foreground and the farside CME is behind it.

Occasionally, readers ask if sundiving comets can trigger solar explosions. There's no known mechanism for comets to spark solar flares. Comets are thought to be too small and fragile to destabilize the sun's magnetic field. Plus, this comet was still millions of kilometers from the sun when the explosion unfolded.

The comet, R.I.P., was a member of the Kreutz family. Kreutz sungrazers are fragments from the breakup of a single giant comet many centuries ago. They get their name from 19th century German astronomer Heinrich Kreutz, who studied them in detail. Several Kreutz fragments pass by the sun and disintegrate every day. Most, measuring less than a few meters across, are too small to see, but occasionally a bigger fragment like this one attracts attention.

Realtime Space Weather Photo Gallery

COLORFUL SPRITES OVER NEBRASKA: "August 12th was another successful night in our sprites campaign," reports Jason Ahrns of the University of Alaska Fairbanks. With a team of researchers from NCAR, he has been flying over the midwestern USA onboard a Gulfstream V in search of exotic forms of lightning. As they were photographing a thunderstorm over Nebraska, these six sprites appeared:

These remarkably beautiful discharges were red on top and purple on the bottom. "I really can't explain the color change," says Ahrns. "That's one of the things we hope to investigate with this campaign by capturing high speed spectra."

First documented in 1989 by scientists from the University of Minnesota who photographed strange flashes coming out of the tops of thunderstorms, sprites remain a mystery today. Neither their basic physics nor their effect on the surrounding atmosphere is well understood. "Do sprites have a large scale impact on the middle atmosphere?" asks Ahrns. "Sprites clearly represent some kind of transfer of energy, but is it on a scale that has a significant effect on the weather and climate? We can't answer that without studying them."

The ephemeral nature of sprites (they typically last no more than a few milliseconds) makes them tricky to study. Researchers on the NCAR Gulfstream capture sprites using Phantom cameras running at 10,000 frames per second. "One of the Phantoms has a diffraction grating in front of it to capture high speed spectra, which I don't think has ever been done before," notes Ahrns.

The prettiest pictures, though, come from Arhns' own camera, a dSLR that he mounts in the window of the airplane to capture "beauty shots." The image above is an example. More may be found in Ahrns' personal blog.

Realtime Sprite Photo Gallery

Realtime Meteor Photo Gallery

Realtime Aurora Photo Gallery

Realtime Noctilucent Cloud Photo Gallery
[previous years: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2011]

Realtime Comet Photo Gallery

  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 August 20, 2013 there were 1397 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Miss Distance
1999 CF9
Aug 23
24.7 LD
1.1 km
2013 QR1
Aug 25
8.3 LD
230 m
2002 JR9
Aug 31
63.5 LD
1.4 km
2013 PX6
Sep 21
68.7 LD
1.0 km
1992 SL
Sep 23
70 LD
1.0 km
2000 DK79
Nov 10
49.1 LD
3.2 km
2011 JY1
Nov 13
8.2 LD
57 m
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.
  Essential web links
NOAA Space Weather Prediction Center
  The official U.S. government space weather bureau
Atmospheric Optics
  The first place to look for information about sundogs, pillars, rainbows and related phenomena.
Solar Dynamics Observatory
  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
Solar and Heliospheric Observatory
  Realtime and archival images of the Sun from SOHO.
Daily Sunspot Summaries
  from the NOAA Space Environment Center
  the underlying science of space weather
Space Weather Alerts
  more links...
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