A rare phenomenon known as a co-rotating interaction region (CIR) is thought to have been the cause of a large geomagnetic storm that hit Earth over the weekend. Scientists were caught off-guard by the origin of the event, with the impact causing a "crack in the magnetosphere."
Usually, these storms occur when explosions take place on the surface of the Sun – referred to as solar flares. These flares are caused by the intense magnetic fields on the Sun become too tangled.
CIR is caused when two streams of solar wind meet at different speeds, generating huge shock and a build-up of plasma at high speeds – 700km per second in this case – and without the tell-tale sign of a sunspot. This CIR caught astronomers off-guard because it came about without the usual signs of a geomagnetic, which tend to be heralded by a coronal mass ejection (CME).
