A geomagnetic storm is a temporary disturbance of the Earth’s magnetosphere caused by large-scale plasma and magnetic field structures that originate on or near the Sun and interact with our planet’s magnetic environment.
These storms are driven primarily by interplanetary coronal mass ejections and corotating interaction regions at the boundary between high- and low-speed solar wind streams. When these structures reach Earth, the increased solar wind pressure compresses the magnetosphere, and the Sun’s magnetic field transfers energy into Earth’s magnetic system, intensifying plasma movement and electric currents in the magnetosphere and ionosphere. Geomagnetic storms follow the sunspot cycle, occurring most frequently during solar maxima. Effects include auroral displays at unusually low latitudes, disruption of magnetic compasses, radio interference and geomagnetically induced currents that can damage power grids. The Carrington Event of September 1859 remains the largest recorded storm, which destroyed parts of the US telegraph network and shocked operators. In 1989 a geomagnetic storm knocked out power distribution across most of Quebec and produced aurorae as far south as Texas.
