Is this what happened to 30 million people today? The Mayor of New York hints of this possibility. Mayor Michael Bloomberg of New York City made the following statement: Today's events where "Probably a natural occurrence which disrupted the power system up there," referring to a power grid based in the Niagara Falls area.

Disturbances caused by solar activity can disrupt these complex power grids. When the Earth's magnetic field captures ionized particles carried by the solar wind, geomagnetically induced currents (GIC) can flow through the power system, entering and exiting the many grounding points on a transmission network. GICs are produced when shocks resulting from sudden and severe magnetic storms subject portions of the Earth's surface to fluctuations in the planet's normally stable magnetic field.

These fluctuations induce electric fields in the Earth that create potential differences in voltage between grounding points which causes GICs to flow through transformers, power system lines, and grounding points. Only a few amps are needed to disrupt transformer operation, but over 100 amps have been measured in the grounding connections of transformers in affected areas.

Anatomy of a Blackout

Previous storms associated with Solar Cycle 22 (the 11-year sunspot cycle that began in 1986) have had an unprecedented impact on electric power systems. The great geomagnetic storm of March 13, 1989, plunged the entire Hydro Quebec system, which serves more than 6 million customers, into a GIC-triggered blackout. Most of Hydro Quebec's neighboring systems in the United States came close to experiencing the same sort of outage.

Less severe geomagnetic storm events in September 1989, March 1991, and October 1991 also hampered utility operations. GIC interactions with new technological devices such as large electric power controllers affected voltage regulation and caused undesired relay operations in the system equipment.

In contrast to today's more severe solar storm cycle, the preceding, relatively quiet 30-year period led designers of electrical systems to overlook the possible influences of GICs. Conventional threats—such as high winds, ice loading, or lightning—did not cause the Hydro Quebec collapse. Rather, it was the consequence of a threat that had never been considered on a system-wide scale across the continental network.

Many portions of the North American power grid are vulnerable to geomagnetic storms. Much of the grid is located in northern latitudes, near the north magnetic pole and the auroral electrojet current and in regions of igneous rock, a geological formation with high electrical resistivity (see figure.) Systems in the upper latitudes of North America are at increased risk because auroral activity and its effects center on the magnetic poles, and the Earth's magnetic north pole is tilted toward North America

The network depends on remote generation sources linked by long transmission lines to delivery points. The effects of GICs build cumulatively over a large geographic scale, overwhelming the capability of the system to regulate voltage and the protection margins of equipment. The Hydro Quebec outage resulted from the linked malfunction of more than 15 discrete protective-system operations. From the initial event to complete blackout, only one-and-a-half minutes elapsed—hardly enough time to assess what was occurring, let alone intervene.