SWPC has issued a Warning for a G3 (Strong) geomagnetic storm as a result of the CME that arrived earlier today. Right now, viewers in Asia and Europe are favorably located to see aurora from this storm. The bulk of the CME missed the Earth, which means we expect a shorter than average storm duration, so it may not persist long enough for viewers in North America. Let’s call this a ‘near miss’ for Earth, because if this CME had hit Earth head on, we’d be seeing severe to extreme activity. We’ve thrown lots of different plots at you recently and here’s another one. We know what’s about to hit Earth thanks to the NASA/ACE satellite. The red line near the top of the chart below shows us the strength of the CME magnetic field in the north-south direction. When it’s south (negative) for a long time with big numbers (like now at -30), then we know we’re in for a ride.