Currents as large as a million-amperes flow through the ionosphere at high latitudes producing the aurora and atmospheric heating effects. These currents are not steady but are fluctuating constantly in space and time. Fluctuating currents produce unsteady magnetic fields that are felt at the Earth's surface. Some rocks carry current better than others. Regions of North America have significant amounts of igneous rock and thus are particularly susceptible to the effects of GICs on man-made systems.
Currents flowing in the ocean contribute to GICs by entering along coastlines.
GICs can enter the complex grid of transmission lines that deliver power throughout the U.S. and other parts of the world through their grounding points. Under extreme space weather conditions, these GICs can cause serious problems for the operation of the power distribution networks by disrupting the operation of transformers that step voltages up and down throughout the network. All Rights Reserved.