Linked from
The 20 pages that link to Geomagnetic storm, each with the reason it gives.
Solar windBroader topic: Fast streams and interplanetary disturbances can trigger these storms.
AuroraRelated: Strong storms can expand auroras toward lower latitudes and intensify their displays.
Space weatherBroader topic: It is the principal magnetic response to sustained solar forcing.
Solar coronaBroader topic: A geoeffective coronal mass ejection can trigger a geomagnetic storm.
Solar physicsRelated: It is a major terrestrial consequence of intense solar activity.
Van Allen radiation beltRelated: Storms can rapidly alter belt particle populations and intensities.
Space physicsBroader topic: It is a prominent near-Earth outcome of solar–magnetosphere coupling.
HeliophysicsBroader topic: Storms can disrupt power grids, navigation, and satellite operations.
Solar phenomenaRelated: Earth-directed coronal mass ejections can trigger severe storms.