Auroral Electrojets

During a major auroral display, intense electrical currents exist in the ionosphere over Western Canada and Alaska. Flowing mostly eastwest at altitudes near 100 km (60 miles), the currents can be as large as a half million amperes.

Called the auroral electrojets, because the currents flow in relatively confined regions in and near the aurora, the currents nevertheless are diffuse, compared to currents in wires. At times, the electrojets spread over a zone several hundred miles wide.

So far, no one has any concept of how the auroral currents could be harnessed for useful purpose. In fact, as far as the works of man are concerned, the intense currents are more harmful than helpful.

Though the auroral electrojets are high above our heads, they do induce similar currents in the conducting earth beneath our feet, and in other conductors such as electrical transmission lines and metal pipelines. Like the aurora, the auroral eletrojets change rapidly with time. The strongest currents may last only a few minutes, and much of the time they are quite weak.

Currents induced in the Trans-Alaska Pipeline and other pipelines can promote corrosion which limits the lifetime of the pipe. Also, the auroral electrojet currents induce so much current in long electrical transmission lines that power outages can result when protective breakers are tripped. This is a consideration to be taken into account in the design of transmission lines, such as the intertie between Anchorage and Fairbanks, now being contemplated.