Geomagnetically induced current

The longer-term variations, typically occurring over decades to millennia, are predominantly the result of dynamo action in the Earth's core.

Geomagnetic variations on timescales of seconds to years also occur, due to dynamic processes in the ionosphere, magnetosphere and heliosphere.

The fact that the geomagnetic field does respond to solar conditions can be useful, for example, in investigating Earth structure using magnetotellurics, but it also creates a hazard.

For GIC to be a hazard to technology, the current has to be of a magnitude and occurrence frequency that makes the equipment susceptible to either immediate or cumulative damage.

Significant variation periods are typically from seconds to about an hour, so the induction process involves the upper mantle and lithosphere.

There may even be a risk to low latitude areas, especially during a storm commencing suddenly because of the high, short-period rate of change of the field that occurs on the day side of the Earth.

On 13 March 1989, a severe geomagnetic storm caused the collapse of the Hydro-Québec power grid in a matter of seconds as equipment protective relays tripped in a cascading sequence of events.

Since 1989, power companies in North America, the United Kingdom, Northern Europe, and elsewhere have invested in evaluating the GIC risk and in developing mitigation strategies.

GIC risk can, to some extent, be reduced by capacitor blocking systems, maintenance schedule changes, additional on-demand generating capacity, and ultimately, load shedding.

The complexity of power grids, the source ionospheric current systems and the 3D ground conductivity make an accurate analysis difficult.

[7] By being able to analyze major storms and their consequences we can build a picture of the weak spots in a transmission system and run hypothetical event scenarios.

Damage to the pipeline coating can result in the steel being exposed to the soil or water possibly causing localised corrosion.

If the pipeline is buried, cathodic protection is used to minimise corrosion by maintaining the steel at a negative potential with respect to the ground.