Sunspot group AR11429 has been busy on its ~2 week journey across the Sun. It has produced many solar flares (including 1 of the biggest of the current solar cycle), coronal mass ejections (CMEs) and solar energetic particles (SEPs). As of March 14, 2012, it has almost rotated out of the view of Earth but on March 13, 2012 the region erupted producing a flare, CME and SEP. The flare, an M7.9 X-ray event, peaked at 17:41 UT.
The resulting CME was first observed in the SOHO/LASCO C2 coronagraph at 17:36 UT, the STEREO Behind Cor2 coronagraph at 17:55 UT and the SOHO/LASCO C3 coronagraph at 17:56 UT.
An increase in energetic protons, indicating the start of a SEP event, was recorded by the GOES particle monitors at 18:10 UT.
The CME had an initial estimated speed of 2250 km/s. Forecasters at the NASA Space Weather Center ran computer a computer model indicating that the flank of the CME will reach Earth at about 6:20 UT (2:20 AM EDT), March 15, 2012 (plus minus 7 hours).
This might result in a minor/moderate geomagnetic storm. The estimated maximum Kp index is 4-6. High latitude aurora watchers should keep a look out for a light show.
The eruption also produced solar radio bursts caused by the flare and the CME.