What is a geomagnetic storm?

A geomagnetic storm is a significant disturbance of Earth’s magnetic field, caused by elevated solar wind conditions. This can happen when Earth is impacted by a coronal hole high speed stream or a coronal mass ejection (CME), a cloud of particles hurled out from an eruption on the sun. CMEs can give rise to extreme conditions and are responsible for the most intense geomagnetic storms during which aurora may be observed much farther south than usual. Geomagnetic storms can last anywhere from a few hours to several days, depending on the severity of the event and how long elevated solar wind conditions prevail.