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The infrastructure and activities of our modern technologically-based society can be adversely affected by rapid magnetic-field variations generated by electric currents in the near-Earth space environment, particularly in the ionosphere and magnetosphere. This is especially true during so-called ‘magnetic storms’. Because the ionosphere is heated and distorted during storms, long-range radio communication, which relies on sub-ionospheric reflection, can be difficult or impossible and global-positioning systems (GPS), which relies on radio transmission through the ionosphere, can be degraded. Ionospheric expansion can enhance satellite drag and thereby make their orbits difficult to control. During magnetic storms, satellite electronics can be damaged through the build up and subsequent discharge of static-electric charges, and astronaut and high-altitude pilots can be subjected to increased levels of radiation. There can even be deleterious effects on the ground: pipe-line corrosion can be enhanced, and electric-power grids can experience voltage surges that cause blackouts. The reason why space-based effects can have consequences down here on the Earth’s surface is related, at least in part, to our answer to another frequently asked question, ‘What is a magnetic field?’. Electric currents in one place can induce electric currents in another place, this action at a distance is accomplished via a magnetic field. So, even though rapid magnetic-field variations are generated by currents in space, very real effects, such as unwanted electric currents induced in electric-power grids, can result down here on the Earth’s surface. More generally, the hazardous effects associated with geomagnetic activity, which are discussed more fully in the Further Reading page of the Geomagnetism website, are one reason why the USGS Geomagnetism Program is part of the Central Region Geohazards Team.

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