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SpaceWeather.com -- News and information about meteor showers, solar flares, auroras, and near-Earth asteroids
 
Solar wind
speed: 361.0 km/sec
density: 23.2 protons/cm3
explanation | more data
Updated: Today at 2346 UT
X-ray Solar Flares
6-hr max: B3
1906 UT Feb18
24-hr: B4
0512 UT Feb18
explanation | more data
Updated: Today at: 2300 UT
Daily Sun: 18 Feb 12
A sunspot is emerging at the circled location. Credit: SDO/HMI
Sunspot number: 53
What is the sunspot number?
Updated 17 Feb 2012

Spotless Days
Current Stretch: 0 days
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

Updated 17 Feb 2012


The Radio Sun
10.7 cm flux: 104 sfu
explanation | more data
Updated 17 Feb 2012

Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Credit: NOAA/POES
Planetary K-index
Now: Kp= 1 quiet
24-hr max: Kp= 1
quiet
explanation | more data
Interplanetary Mag. Field
Btotal: 9.7 nT
Bz: 5.8 nT south
explanation | more data
Updated: Today at 2347 UT
Coronal Holes: 18 Feb 12
Solar wind flowing from this coronal hole could reach Earth on Feb. 18-19. Because of the coronal hole's far-southern latitude, however, the corresponding solar wind stream could sail south of our planet, making little impact. Credit: SDO/AIA.
SPACE WEATHER
NOAA Forecasts
Updated at: 2012 Feb 18 2200 UTC
FLARE
0-24 hr
24-48 hr
CLASS M
01 %
01 %
CLASS X
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: 2012 Feb 18 2200 UTC
Mid-latitudes
0-24 hr
24-48 hr
ACTIVE
30 %
10 %
MINOR
10 %
01 %
SEVERE
01 %
01 %
High latitudes
0-24 hr
24-48 hr
ACTIVE
40 %
20 %
MINOR
20 %
05 %
SEVERE
05 %
01 %
 
Saturday, Feb. 18, 2012
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

SUNSET PLANETS: The brightest planets in the night sky are aligning for a must-see show in late February and March 2012. You can start looking tonight. [video] [full story].

QUIET SUN: Considering the fact that Solar Maximum is only about one year away, the sun is experiencing some remarkable spells of quiet. One of them is underway right now. There have been no significant flares for more than five days, and the sun's X-ray output has flatlined:

What's going on? In fact, solar activity is on the rise. For instance, an X-class solar flare on Jan. 27th triggered the strongest solar radiation storm since 2005. Also, auroras have been sighted recently as far south as Virginia and Oklahoma. The quiet interregnums are a sign that the current solar cycle, while active, is not quite as strong as other solar cycles that preceded it--like a mild hurricane season in the Gulf of Mexico. According to this point of view, temporary spells of low activity are to be expected. On the other hand, some researchers believe the quiet holds greater significance; it could foreshadow a major drop in solar activity. This is controversial, however, because forecasting the 11-year solar cycle is still an infant science. Indeed, surprises may be in the offing. Stay tuned for updates.

SPY-SAT DISAPPEARING TRICK: US spy satellite Lacrosse 5 occasionally confounds observers by disapppearing: In a matter of seconds, it can fade more than three astronomical magnitudes. Is this a deliberate form of stealth? Most experts think not, but no one outside of classified circles knows for sure what is going on.

To investigate, French astrophotographer Thierry Legault used his satellite-tracking telescope to photograph Lacrosse 5 as it sailed 490 miles above Paris on Jan. 15, 2012, and he caught the spysat in the act of disappearing:

"During the passage, the brightness of the satellite decreased by 10 times in only 4 seconds (a loss of 2.5 magnitudes)," describes Legault. "After 33 seconds of [dark flight] it regained its original brightness. Lacrosse 5 often shows this very singular behaviour, which is called by other observers (especially Marco Langbroek) the 'disappearing trick.'"

Other Lacrosse satellites do not perform the same trick, at least not to this extent, suggesting that the design of Lacrosse 5 differs from its predecessors. The fade is likely caused by some sort of self-shadowing--e.g., maybe some part of the spacecraft such as its solar panels casts a shadow over the main body when the spysat changes attitude.

Even Legault's fine images do not reveal the answer. "The cause of the disappearing trick, as well as the precise shape of the satellite, remain unknown."

Readers, would you like to try catching the tricks of Lacrosse 5? Check SpaceWeather's Simple Satellite Tracker and Flybys App for local flyby times.


January 2012 Aurora Gallery
[previous Januaries: 2010, 2009, 2008, 2007, 2005, 2004]


Comet Lovejoy Gallery
[previous comets: McNaught, Holmes, Lulin, Tuttle, Ikeya-Zhang]

  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 February 18, 2012 there were 1287 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Asteroid
Date(UT)
Miss Distance
Mag.
Size
2009 AV
Feb 16
44.9 LD
--
1.2 km
2000 ET70
Feb 19
17.7 LD
--
1.0 km
2011 CP4
Feb 23
9.1 LD
--
255 m
2008 EJ85
Mar 6
9.1 LD
--
44 m
1999 RD32
Mar 14
57.9 LD
--
2.4 km
2011 YU62
Mar 16
73.4 LD
--
1.3 km
1996 SK
Apr 18
67.2 LD
--
1.6 km
2007 HV4
Apr 19
4.8 LD
--
8 m
2011 WV134
Apr 28
38.6 LD
--
1.8 km
1992 JD
May 2
9.5 LD
--
43 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.
STEREO
  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
Heliophysics
  the underlying science of space weather
Trade Show Displays
   
  more links...
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