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Lights Out

The power goes out. The aurorae stretch to the tropics. Could a major solar storm mean a year without electricity? | Long Read

Many people the world over have read some kind of portent or omen into the aurorae, particularly in lower latitudes where the light show is rarely seen. We educated folk in our developed countries may be tempted to dismiss them as an interplay of charged particles from the sun, magnetic fields and molecules high in the atmosphere. But perhaps we, too, should look on them as a warning.

The particles from the sun, also known as the solar wind, are always coming at Earth as surely as the sunlight. Luckily for us, Earth’s molten iron core has set up a defense – the electrical currents inside it produce a magnetic field that deflects most of the particle onslaught.

But once or twice per century, the sun whips a few billion tons of plasma from its surface toward the Earth, at speeds of 7 million miles per hour or more. Your garden-variety solar wind takes a few days to reach Earth, but a major storm can move much faster, arriving in 18 hours or less.

Even then, the magnetic field protects Earth’s surface. For a long time, there was nothing to fear but the lights in the sky. However, now that we rely on high-voltage power lines crisscrossing the nation – and all that they enable – space storms are no longer so benign.

If a storm like that takes out important parts of the electrical grid, the outage won’t just last a few hours or a few days. It won’t just be a few cities or counties. The storm could cut the electricity to large swathes of the most populated areas of the U.S., and it could be a year or longer before power is restored.

Until recently, few people appreciated this threat from the sun. Among those few are researchers at U-M who develop software for forecasting space weather. Now, power companies and even the White House are paying attention to space weather’s potential to switch off our modern existence. But are we ready enough to avert disaster?

Transformer trauma

In the interest of competition among electrical utilities, the grid is designed to transmit power over long distances. This is fine while Earth’s magnetic field is stable, but if a huge cloud of plasma connects its magnetic field with Earth’s, Earth’s magnetic field goes haywire. It’s called a geomagnetic storm.

A moving magnetic field induces currents in wires. Because the Earth’s magnetic field isn’t very powerful, you wouldn’t notice extra current in your electronics or your household wiring even in a large geomagnetic storm. The effect would be similar to waving a fridge magnet near the circuitry.

But in very long wires, spanning hundreds of miles, the current can build up, perhaps to hundreds of amperes, explained Ian Hiskens, the Vennema Professor of Engineering and a professor of electrical engineering and computer science. These currents alone would be enough to fry your household wiring. Combined with energy coursing through the grid already, it’s enough to push some of the biggest and most expensive power equipment past its limits.

Large transformers enable utilities to send electricity across the U.S. without wasting a lot of energy due to resistance in the wires. At one end of a long power line, a transformer steps the electricity up to a high voltage, which minimizes the energy loss from resistance. At the other end, a transformer steps the energy down to a safer level for distribution through cities and towns.

The biggest transformers, those typically placed at power stations and at the receiving ends of the long-haul transmission lines, cost tens of millions of dollars to make and take more than six months to build. They are custom pieces of equipment, designed for the particular requirements of the utility and location. Hiskens estimates that there are a few hundred of these very large transformers in the U.S.

“At the moment, there are no spares for them anywhere in the world,” he added.

So if a freak geomagnetic storm were to damage a bunch of them at once, it’s not hard to imagine that recovery would be long and difficult. But what is the risk, really? How bad could it be? And how can we prevent it? These are questions that the White House is asking with its new Space Weather Action Plan, announced in October 2015. For insight into what the answers might be, The Michigan Engineer sought out researchers and professionals who have been thinking about the problem for years.

Solar smackdown

No one really knows the odds that the sun will send us a grid-crippling cloud of plasma in the near future. Pete Riley, senior research scientist and vice president of the San Diego-based Predictive Science Inc., forecast a 12 percent chance of such a storm hitting Earth in the next decade.

Dave Szulczewski, an engineer at the Michigan-based power company DTE, follows industry research on how geomagnetic storms may affect electric utilities. He cited a likelihood of less than 0.02 percent for every two solar cycles, or 22 years.

“Authors who give different risk factors and probabilities caution that there hasn’t been a lot of historical data to draw from,” said Szulczewski.

The existing data comes mainly from two extreme solar storms that occurred before the grid went national. The first was in 1859, when only telegraph wires were around to tell the tale of electrical chaos.

Known as the Carrington Event, the plasma that connected with Earth’s magnetic field sent aurorae into the tropics and turned skies over the U.S. blood red. Operators received shocks, put out fires and found that the lines worked better if they disconnected the batteries. Using information about the lengths of the wires and their operating voltages, researchers have estimated that this represented a rate of change in Earth’s magnetic field of about 5,000 nanotesla per minute (nT/min).

A 1921 event had similar effects, disrupting telephone service and railroad signaling as well. Again, researchers put its strength in the ballpark of 5,000 nT/min.

For a more recent warning shot, a Carrington-scale mass of plasma flew through Earth’s orbit in 2012 – and it would have hit Earth if the eruptions had occurred just a week later.

For some, it's just a bad couple days. Others think it could it be catastrophic. Thomas Overbye

The worst case

Exactly how bad a major solar storm would be is a matter of debate in the power industry, said Thomas Overbye, a professor of electrical and computer engineering at the University of Illinois Urbana-Champaign.

“Some people say the transformers will not be permanently damaged, others think they will,” he said. “For some, it’s just a bad day or bad couple days. Others think it could be catastrophic.”

Overbye added that some groups, concerned that power could go out for months across large regions of the U.S., project that it could lead to a breakdown in social order and deaths due to the scarcity of food, water and medicine. No refrigeration. No running water. No pumps for the gasoline that could get you to civilization, and no financial system to help you buy it. Dark days indeed.

It wouldn’t be such a big deal if the transformers could be replaced in a few weeks, but they take between six and 12 months to build, transport and install. It’s hard to make that time any shorter because the high-grade insulation around the massive coils has to be thoroughly dried out. This prevents electricity from jumping between the loops of wire, explained Hiskens. Even with unlimited money, it can’t be rushed.

We would hope that the Federal Emergency Management Agency (FEMA) has been thinking about what to do in the event of a geomagnetic disaster – and there is evidence that the agency has been looking into it since at least 2008 – but it neglected requests for information. warns that space weather could result in power outages, even rolling blackouts, but it doesn’t mention how long or extensive they might be.

For now, it advises keeping 72 hours’ worth of food and water on hand in the event of a space weather emergency. That won’t get you very far if much of our power infrastructure is out for weeks or months.

The White House plan calls for an evaluation of the resources that will be available in the event of a major outage. It’s hard to send aid when most communications are down and gas stations can’t pump fuel.

One bright spot is that land telephones could be repaired more quickly than the grid, so areas with blackouts – meaning no cell service or Internet – may not be completely cut off. That would make a big difference in assessing the extent of the blackouts, deploying emergency aid and coordinating repairs. Likewise, many radio stations already have backup generators, so we would also have a system for mass communication once access to fuel was established.

The darkened areas of the map show potential outages if a strong geomagnetic storm hit the U.S., based on a computer simulation by Metatech Corporation. The outages could last months or years.

IMAGE:  The darkened areas of the map show potential outages if a strong geomagnetic storm hit the U.S., based on a computer simulation by Metatech Corporation. The outages could last months or years.

Optimism of a sort

But it might not be that bad. Neither Overbye nor Hiskens subscribes to the doomsday prognosis. Hiskens thinks that the grid will have enough life left in it to provide power to a lot of the U.S. some of the time. Communications and at least some of the financial system would be up for part of the day. Refrigerators and freezers may work often enough to allow some food storage. Gasoline could be pumped so that transportation wouldn’t grind to a halt.

“You can think of the extra-high-voltage network as being like superfreeways, and the very-high-voltage network being the interstate system. So if you lose the superfreeways, you can always fall back on the normal freeway system, but there may be congestion and you might need to regulate the traffic,” said Hiskens. But if we lost the very-high-voltage network as well, the beginning of the recovery would be hard going.

Overbye cautions that some of the most at-risk, high-voltage transformers are located at power plants. If these go out, the power plants are disconnected from the grid. But how likely are transformers to sustain damage in a geomagnetic storm? That’s the question Overbye is trying to answer.

He works with utilities, receiving detailed information about their networks. Then his group runs simulations to assess the potential consequences. They identify which transformers are in danger and calculate how much the electrical load on them must be reduced to keep them safe.

If operators reduce the current on a transformer during a storm, then the transformer can tolerate the additional current from the moving magnetic field without overheating.

Overbye’s team considers different storm severities. The worst to hit North America in modern times blacked out Quebec for nine hours in March 1989. The magnetic field changed at about 500 nT/min. Some argue that the 1989 storm damaged an extra-high-voltage transformer at the Salem Nuclear Plant in southern New Jersey. And it was 10 times weaker than the 1859 and 1921 storms.

The best forecasting doesn't do any good if utilities aren't paying attention and ready to take action.

Protecting the grid

One day, transformers may have built-in defenses. The current generated by a geomagnetic storm runs in a loop through the wires between two transformers, down in the ground, back to the first transformer, and up onto the wires again. Disconnecting the ground wire would prevent this current from running, but it would leave the power network vulnerable to more common problems such as lightning strikes and downed wires.

It may be possible to install components on the ground wires that would block or reduce the current induced by a geomagnetic storm, Hiskens explained. But it’s an expensive solution, so utilities won’t be adding this protection until both the technology and the risk of disaster are proven.

For now, the best option is to predict geomagnetic storms and protect transformers on the fly. And for that, we need to have a good handle on exactly what the sun is throwing at us.

U-M is already a leader in space weather preparedness. The National Oceanic and Atmospheric Administration (NOAA) is adopting a simulation developed by U-M’s Center for Space Environment Modeling. NOAA’s Space Weather Prediction Center uses a combination of satellite data, observations of the sun and physics simulations to forecast solar storms that could affect our satellites, air travel, GPS and grid (see “Space Sensitive”). NASA, which needs to warn astronauts of intense radiation within an hour of a flare, runs the U-M space weather modeling software 24/7.

The U-M program takes observations of solar activity and charts the course of any plasma coming toward Earth. Then, it simulates the way that the plasma would interact with the Earth’s magnetic field, predicting the likely geomagnetic disturbance down to the region.

“We can say the largest space weather event will be over Canada. Or Michigan,” said Tamas Gombosi, the Konstantin I. Gringauz Distinguished University Professor of Space Science, Rollin M. Gerstacker Professor of Engineering and director of the Center for Space Environment Modeling. “So then they basically decrease the load on the transformer system in the most affected areas. But this is just becoming operational.”

These simulations are twice as fast as real time, so by the time they are complete, the plasma is halfway here. For an extreme event like the 1859 geomagnetic superstorm, that would leave about eight hours to prepare.

"There are no spares for these transformers anywhere in the world."

Better forecasts

That’s not a lot of time for an event so rare and potentially catastrophic, and some industries are affected within an hour of a flare. So researchers are trying to forecast the eruptions themselves.

For this, they need to understand the details of magnetic activity on the sun. Eruptions occur when the sun’s magnetic field twists and stretches until it snaps. A useful prediction must say when the flare or flares will happen, how big the flares will be and the paths of any plasma clouds thrown from the sun. Gombosi’s team is trying to develop these capabilities.

Space weather forecasters also need to know the direction of the disembodied piece of the sun’s magnetic field. If it has the same alignment as Earth’s field when it arrives, the fields will repel one another, and the plasma will pass around the Earth without harming the grid. But if the fields join up, the wild fluctuations in Earth’s magnetic field could damage transformers. Right now, this crucial detail wouldn’t be known until about 20 minutes before the storm hits, when the cloud passes by the ACE satellite. This satellite monitors particles coming from the sun, and it’s thought to have enough fuel to continue its watch until 2024.

To improve space weather prediction, researchers need more observatories in orbit around the sun, says Gombosi, especially with the 2014 demise of a satellite that helped produce a 360-degree view of our local star. These new weather stations would observe parts of the sun’s surface we can’t see from Earth but that will be spinning to face us within hours.

“It’s like when you have a weather forecast, and you have a weather station just here outside the window,” said Gombosi. “It will tell you what is going on right now. But if you want to know what will happen tomorrow, you need something in Chicago.”

A new vigil

Of course, the best forecasting doesn’t do any good if utilities aren’t paying attention and ready to take action. Fortunately, they’re getting there.

In June 2014, the Federal Energy Regulatory Commission adopted a rule requiring utilities to prepare for geomagnetic disturbances. Companies responsible for the transmission network – or the high-voltage, long-distance portion of the grid – have paid close attention to these nascent regulations, and many have already published procedures for space weather events.

PJM, which operates a transmission network in the eastern and Midwestern U.S., requires that transmission operators monitor individual transformers to look for currents caused by geomagnetic disturbances. These would be direct currents in addition to the alternating currents that utilities send through the network.

Some transformers are fitted with a device that directly measures geomagnetic currents on the grounded line, where the currents come in. A transformer can also be monitored through its temperature and how much power it consumes, measures that can signify whether it is operating outside its preferred range.

PJM’s threshold for concern is a direct current of 10 amperes or more – an equivalent alternating current would be small enough to run on your household circuits. If such a current persists for at least 10 minutes, the operator is required to move to conservative operations. This includes running a lower current through the transformer, which helps keep it from overheating even if a geomagnetic disturbance adds additional current. It could mean temporary power cuts to customers during a severe storm, but most would likely prefer that to the alternative.

Space weather drill

While the transmission network moves energy from power plants to cities and towns, the distribution network takes that power from the major substations to homes and businesses. The lower voltage at the distribution level means less risk, but they, too, are beginning to pay attention to threats from the sun. DTE Energy, which serves southeast Michigan,

handles distribution as well as power generation.

Vinay Bhakkad (MBA ’01), director of emergency and response at DTE, told The Michigan Engineer about actions DTE is taking to prepare for extreme geomagnetic storms. “We subscribe to NOAA’s space weather service, so whenever there is risk of space weather or a solar flare, we get notification,” he said.

The warning initiates a sequence of actions needed to monitor the severity of the geomagnetic storm and mitigate its effects on the network. While we have yet to experience an extreme storm, DTE ran its first space weather drill in the summer of 2015, said Bhakkad. As they would be in a real event, the DTE team was on the phone with colleagues who manage the transmission network during the tabletop exercise.

“The transmission companies are a step ahead of us in terms of preparing for and reacting to the geomagnetic disturbances, and they should be a step ahead of us. They are at a greater risk because of their bigger equipment and higher voltage levels,” said Heather Rivard (BSE Aero ’92, MBA ’04), the vice president of distribution operations for DTE.

Still, DTE is in charge of the transformers at their power plants that connect to the transmission system, so their preparation is necessary to protect access to power in southeast Michigan.

The outlook

Because concern over the potential for a geomagnetic disaster is relatively new, and the events very rare, much is still uncertain. Utilities are teaming up with researchers like Overbye to get a better handle on the real risk to transformers on their networks, and they are developing procedures to follow if a major geomagnetic storm occurs.

Most U.S. electric companies assume that their vulnerability is limited because the most extreme geomagnetic disturbances are thought to occur in the upper latitudes, where the aurora makes a more regular appearance. But Hiskens recently reviewed a study that suggested a space-induced storm could peak at a latitude of about 40 degrees – running right through the northern United States.

The new awareness of space weather is also timely as engineers design grid improvements to make better use of renewable energy generation. Proposals include expanding the extra-high-voltage network to enhance electricity transmission across the country.

If extreme events could be forecast with days to spare rather than hours, power companies would have the opportunity to run through their procedures and notify their customers that temporary outages may occur as they protect the network. After all, no grid operator has experience protecting transformers from Carrington-scale geomagnetic disturbances.

While we’re in better shape than we were 10 years ago, Gombosi warns against complacency. “We don’t know how prepared we are. Just because we talk about it doesn’t mean we are prepared for it,” said Gombosi. And the test is coming. We just don’t know how soon. 

Want to know more? Discover what else is affected by solar activity:



During each 11-year solar cycle, about 10 space storms cause airlines to reroute their polar flights farther south. The protection of the magnetic field is weakest at the poles, and the extra charged particles coming through would expose the passengers and crew to unusually high radiation. It wouldn’t be enough for immediate health effects, but enough that it could violate the stringent regulations against civilian radiation exposure. What’s a few hours of delay compared to cancer risk?


The satellites would take a beating – first from the X-rays and particles travelling near the speed of light, ahead of the main cloud, and then from the plasma itself. But satellites are made to withstand radiation. Put into safe mode, it’s likely that many would survive, albeit with a few years shaved off their lifespans. While the trend on the ground is toward smaller and more integrated circuits, satellites are headed in the other direction. Larger circuits fare better in a particle storm. Space-age retro.


All that electromagnetic activity in the atmosphere creates noise in GPS signals. This is of particular concern to the military, which depends heavily on GPS for the navigation of soldiers as well as drones. Smaller storms can throw off GPS signals as well.


Radio communications are also disrupted by the electromagnetic activity in the atmosphere. Radio transmissions can shift to other frequencies, with one station being replaced by another. They can disappear entirely or even have their ranges extended – previous storms have sent radio broadcasts across the ocean. Cell phones would likely experience similar problems.

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Kate McAlpine
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