The Earth has been hit by another CME (I know, we seem to have a target painted on us at the moment) potentially sparking off more auroral activity (as with the last one, it hit when Australia was in darkness, so New Zealand got the southern lights on full beam) according to spaceweather.com. It seems to have died down a lot, and I’ve seen nothing from here, but for the next few nights, keep watching the north for those lights.
But what are the Coronal Mass Ejections and what powers them? One theory involves flux ropes, tight groups of magnetic pathways holding in plasma. The flux ropes form when individual flux tubes (field lines of the magnetic field on which plasma is trapped) get wound together into one structure. One very energetic structure that is held in place as long as the magnetic field outside of it can. Then it bursts into life, shoveling out vast amounts of high density, hot, fast plasma into space. The Hinode satellite has been observing this phenomenon and found flux ropes wound in 30% of the local magnetic field, rather than the 10% previously assumed.
At the other end of the scale, the Cluster satellite has been observing auroral events. The four spacecraft were positioned in such a way as to measure particle energies at different points on a single field line. By looking at how the energies changed with position, the acceleration of the electrons could be directly observed.