Space Weather Warning – Update

Yesterday, I wrote a quick post about what to watch for when expecting a space weather storm to start.  Let’s have another look now that the storm has started:

SWPC summary plot of solar wind and space weather activity over the past day.

The verdict?

  1. The solar wind velocity (yellow line above) jumps somewhat, getting up to 500km/s.  This is a moderate but not impressive jump.
  2. The solar wind density (orange line above) jumps quite significantly, reaching 50 to 60 protons per cubic centimeter.  That’s a very healthy jump compared to yesterday’s measurement of 10ccm, and will definitely drive strong activity at the start of the storm.
  3. The Z-component of the Interplanetary Magnetic Field (IMF BZ, red line at top of plot) is strongly negative.  For a small storm to become a big storm, this is the most important factor (but also the hardest for scientists and forecasters to predict).  Yesterday, I said that we should look out for extended periods of -5 to -10nT; we are now in a two hour (and counting!) period of -20nT!  
  4. But how is the Earth responding?  The bottom two plots show our geomagnetic indices, KP and DST (2nd to bottom and bottom plot, respectively.)  KP reaches 5 and is expected to climb to 7 soon.  DST has dropped to about -100nT, indicating a moderate storm that’s turning into a strong storm.

So far, this is one of the more interesting storms we’ve seen recently, but it has a way to go before becoming a real strong event.  Keep watching IMF BZ to see how this one will play out.