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.
"We've been doing industry-leading research since back in the 1990s on this subject, and one of our former engineers basically wrote the book on geomagnetic disturbances," he said.
Rogers was referring John Kappenman, who started his career at Minnesota Power, then went on to become an expert working with utilities near and far desiring to protect their systems from geomagnetic disruptions. His firm, Storm Analysis Consultants, remains based in Duluth.
"We have legitimate reasons to be very concerned about these problems," Kappenman said. "This could be one of the largest natural disasters that the country could face."
But Rogers said Minnesota Power has taken more precautions than most of its industry peers and claimed: "We've been ahead of the game for 25 to 30 years already."
To the best of his knowledge, Rogers said Minnesota Power has never had an outage due to a geomagnetic disturbance.
"I think that's a testament to our operators for keeping a close eye on our systems infrastructure," he said.
But that doesn't mean the utility assumes its good fortune will continue, said Amy Rutledge, communications director for the company.
"Our operators actually go through training on how to respond when you get a notification. What are the steps that our company needs to take to mitigate this potential event," she said.
Minnesota Power receives advance warnings when solar storms threaten, and Rogers said it prepares and then closely monitors its systems, especially those containing longer stretches of line.
"If part of your system starts to really resonate with a geomagnetic event, your equipment could be at risk of damage. So we monitor that and would remove things from the system if they start to overheat," he said.
While noting that it's better to temporarily cease certain operations than to risk significant damage and the possibility of a prolonged outage, Rogers said he can't remember Minnesota Power ever having to take that step.
"We do have a pretty hardened system already," he said.
Nevertheless, Rogers welcomes the recent data from the USGS report and said it could help shape new industry standards now being developed by the North American Electric Reliability Corp.
"It's extremely useful research for our field, especially as we start to put together a planning model for the rest of the region," he said.
Setting the bar
Kappenman said he believes the power industry could and should do more.
Rogers said Kappenman has a point, noting that many companies have not taken the kinds of precautions Minnesota Power has. He predicted the USGS report and new standards could improve that picture, however.
"The industry as a whole has been dragging their feet on this matter. But they're going to have to address it now. There are going to be regulatory standards that will require them to look at this stuff and train on it and mitigate against geomagnetic disturbances," he said.
Kappenman praised the USGS for its efforts to heighten awareness of the hazard geomagnetic storms can pose but said the power industry could do much more to augment the scientific body of knowledge.
"While I certainly encourage more data gathering by the scientific community in this way, the reality is that we've already gathered a lot of data by electric utility companies measuring for geomagnetic-induced current across the U.S. That coverage far exceeds the coverage that's provided by this scientific effort that the USGS is now involved in," he said.
However, Kappenman said he believes many power producers have not been eager to share their data out of concern that it could result in stricter oversight.
"I recommended to FERC (the Federal Energy Regulatory Commission) that they obtain from electric utilities their data, as well, in order to fill out the rest of the country," he said.
Kappenman said he hopes any new standards will be based on sound science and a true assessment of the hazards posed by geomagnetic storms.
"There's such a big difference between what the electric power industry is proposing and what scientists like myself think are the more appropriate standards that FERC has not yet approved any standards and is continuing deliberations on this topic," he said.