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:
- The solar wind velocity (yellow line above) jumps somewhat, getting up to 500km/s. This is a moderate but not impressive jump.
- 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.
- 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!
- 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.