The corpse of old sunspot AR2987 exploded yesterday, April 11th, hurling debris directly toward Earth. NASA’s Solar Dynamics Observatory recorded the eruption.
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.
GEOMAGNETIC STORM WATCH (G2-CLASS): A CME is heading for Earth (see below). NOAA forecasters say that G2-class geomagnetic storms are possible when it arrives on April 14th. During such storms, auroras can seen as far south as, e.g., New York and Idaho (geomagnetic latitude 55 degrees).