Geomagnetic storms

temporary disturbance of the Earth's magnetosphere caused by a disturbance in the interplanetary medium

geomagnetic solar storm

G5 geomagnetic storm

powerful burst of cosmic rays

observed increase of 1.2% in the concentration of carbon-14 isotope in tree rings dated to 774 or 775

unusually large and strong coronal mass ejection

extreme space-weather event

series of solar flares and coronal mass ejections

The '''K-index''' quantifies disturbances in the horizontal component of Earth's magnetic field with an integer in the range 0–9 with 1 being calm and 5 or more indicating a geomagnetic storm. It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval. The label K comes from the German word meaning characteristic digit. The K-index was introduced by Julius Bartels in 1939.

solar storm

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1938 solar storm

exceptionally powerful geomagnetic storm

powerful series of solar storms