Solar storms pose unique risk to northern power grids
DULUTH, Minn. — Many a Minnesotan has been entranced by the sight of northern lights dancing across the evening sky. But the same forces responsible for these celestial displays could pose a danger to power systems, particularly here in the northern part of the state.
The U.S. Geological Survey recently released a study indicating that the frequency of significant solar storms — such as those that produce the aurora borealis — combined with the conductive nature of the region’s crust and geomagnetic forces, make northern Minnesota perhaps the most likely place in the nation to experience potentially powerful geoelectric currents that could disrupt or damage electrical systems in the event of a major solar event, of the sort we would expect to see on a once-per-century basis.
“There are two factors at play here. One is the magnetic field of the earth. … The magnetic field is generated inside the earth. It extends up to the surface and then up into space, where it interacts with the solar wind,” said Jeffrey Love, a research geophysicist for the USGS.
When charged particles from solar flares approach earth, they can produce a geomagnetic storm typically lasting one to three days and giving rise to the aurora borealis.
During an intense geomagnetic storm, Love said, “there can be the generation of geoelectric fields in the solid earth. So it’s a magnetic field and its activity generating an electric field, and it turns out this electric field is in the solid earth because the solid earth is electrically conducting.”
That, in turn, can wreak havoc on the power grid — and local utility officials say they’ve been working for years to prepare for such an event.
Ground and sky
Recent field surveys by the National Science Foundation have started to paint a picture of how geoelectric fields may emanate from the earth’s crust, and they identify the Northland as one of the most conductive spots in the nation.
“In Minnesota it seems — and to some extent in Wisconsin and Iowa — the (geological) structure is such that during a magnetic storm there can be large geoelectric fields generated,” Love said.
He explained the structure is a result of events that occurred about 1.1 billion years ago, when the North American continent nearly split apart.
“When it was doing that, the magma from the Earth’s deep interior flowed up and filled this chasm that was forming. That solidified, and it then changed the mineralogy of the rock that was there to begin with,” Love said.
“That has essentially left a deep scar underneath the surface of North America, and Minnesota in particular. That scar and the resulting effects … left Minnesota with a complicated deep tectonic and geological structure,” he said.
“It’s interesting that this issue of old geology is related to space science, and it’s all conspiring to give us this hazard which seems to be especially acute in Minnesota,” Love said.
A large geomagnetic storm can induce a current that when transferred to the electrical power grid causes the voltage to surge. What’s more, because this is basically a direct current, it can cause additional problems in systems designed to handle alternating current and can burn out transformers.
In 1989, a geomagnetic storm knocked out power to about 6 million people in Quebec and caused millions of dollars of damage.
In 1859, our nation’s telegraph system crackled and fried, sparking fires, when a powerful geomagnetic storm produced what’s now referred to as the Carrington Event. A repeat incident of similar magnitude would likely cause about $2 trillion in damage today, according to recent estimates.
Love said such events might be expected to occur about once per century, based on ongoing monitoring results.
“These magnetic storms we’re talking about are really rare events, but the consequences could be widespread. So even though they don’t happen very often, it would be a bad day if and when one does happen. That’s why we need to make some assessments and understand what that would be like, and these maps are one step in that direction,” he said of the report recently issued by the USGS.
The USGS and the National Science Foundation have not yet completed their map assessing the level of hazard posed by geomagnetic storms, and more funding will be needed to fill in remaining gaps in the Northeast and a swath of the Great Plains. But so far, northern Minnesota has emerged as the area of greatest national concern.
A major geomagnetic storm could potentially result in a prolonged power outage that would take months to resolve. That’s why Love is pleased people are taking the threat seriously.
“Electric power is terribly important for modern society, and preparing for worst-case scenarios is something that’s a legitimate government project,” he said.
Kyle Rogers, a systems performance engineer at Minnesota Power, based in Duluth, said the recent USGS report confirmed what the utility already knew: Its system could be vulnerable to geomagnetic disturbances.