March 17th, 2015 is turning out to be a very lucky day for sky watchers. A Severe G4 Level (KP=8) Geomagnetic Storm was observed following the passage of a coronal mass ejection (CME). Solar wind speeds increased to near 700 km/s and the Bz component of the interplanetary magnetic field (IMF) pointed sharply south (-20 to -25nT) for long durations, thus helping to intensify storm conditions. Sky watchers at middle to high latitudes should be alert for additional aurora displays during the next 24 hours once it is dark outside. Additional sub-storming will be possible should solar wind conditions cooperate.
The aurora photos making the Internet rounds are unbelievable. The full structure of the aurora is revealed, with the different colors from different spectral lines all visible at once.