EARTH-DIRECTED CME: A dead sunspot exploded today. The corpse of AR2987, which decayed days ago, erupted, and the debris is heading straight for Earth. A CME expected to arrive on April 14th could spark moderately-strong G2-class geomagnetic storms.
Full story @ Spaceweather.com.
The S-shaped magnetic filament at the base of the explosion is a classic "sigmoid structure." Solar magnetic fields often assume this shape just before they explode. One study shows that sigmoid precursors are present in over 50% of CMEs. Indeed, shortly after the explosion, a full-halo CME emerged from the blast site. Here it is. The CME is expected to reach Earth on April 14th; a new NOAA model pinpoints its arrival time at 1100 UTC. The impact could spark a G2-class geomagnetic storm.