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geomagnetic storm

A Dictionary of Weather

Storm Dunlop

geomagnetic storm 

A violent disturbance of the Earth's geomagnetic field following a solar flare or coronal mass ejection (see corona (3)), and generally ensuing about 24–36 hours after the event. Abrupt variations in the strength and direction of the interplanetary magnetic field, together with associated shockwaves, strongly perturb the magnetosphere and may induce massive currents both in the ionosphere (where satellites may be damaged) and on the surface, leading to disruption or breakdown of power distribution grids. Major storms are usually accompanied by aurorae, often visible at much lower geomagnetic latitudes than normal, with corresponding interference with short-wave radio communications. Conditions usually return to normal after a period of 2–3 days.

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