During space weather events, fluctuating electrical currents flowing through the upper atmosphere produce changes to the magnetic field at ground level.

This rapidly changing magnetic field induces a geoelectric field that drives currents through the Earth’s surface, known as geomagnetically induced currents (GICs). Because these GICs can flow into and out of grounded equipment, such as transformers in the electricity transmission and distribution networks, space weather can impact the electricity networks on which our modern society and economy depend.

There have been several incidents in recent decades directly linked to large space weather events, such as the Hydro Québec incident in March 1989 and damage to grid transformers in several countries in October/November 2003.