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What’s The Real Danger From Solar Flares?

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Over the past week, our sun has been spewing out some pretty powerful solar flares as it lingers in the peak of its 11-year solar cycle. But just how worried should you be about the sun’s radioactive burps?

First, let’s distinguish between several different kinds of solar activity:

Sunspots are huge dark areas on the surface of the sun, formed when fluctuations in the sun’s magnetic field bubble up to the surface. The spots are dark because they are cooler than the other parts of the solar surface around them. Coolness here is pretty relative—a sunspot is still a piping hot 8,000 degrees Fahrenheit (4,500 Celsius), but it is surrounded by material that reaches temperatures of 11,000 degrees F (6,000 C).

Solar flares are gigantic explosions associated with sunspots, caused by the sudden release of energy from “twists” in the sun’s magnetic field. They are intense bursts of radiation that can last for anywhere from minutes to hours.

Coronal mass ejections (CMEs) sometimes coincide with solar flares. They’re huge explosions of matter—gas and magnetized plasma—that rocket away from the sun at millions of miles per hour.

What’s the problem?

Solar flares and CMEs pose no direct threat to humans—Earth’s atmosphere protects us from the radiation of space weather. (If an astronaut out in space is bombarded with the high-energy particles from a CME, he or she could be seriously injured or killed. But most of us won’t have to worry about that situation.) We could, however, feel the effects of CMEs indirectly, through the disruptions to our technology—some of which could have devastating and lingering effects on civilization.

When a CME hits Earth’s magnetosphere—the volume of space around our planet influenced by our magnetic field—if it is directed southward, it will strongly interact with Earth’s northward-oriented magnetic field. When this happens, Earth’s magnetic field is “peeled open like an onion allowing energetic solar wind particles to stream down the field lines to hit the atmosphere over the poles,” NASA explains. “At the Earth’s surface a magnetic storm is seen as a rapid drop in the Earth’s magnetic field strength. This decrease lasts about 6 to 12 hours, after which the magnetic field gradually recovers over a period of several days.”

The geomagnetic storm that results from CME-magnetosphere interactions can muck up all kinds of technology that we rely upon in modern life. Satellites that orbit high up in geosynchronous orbits—many of them communications satellites—are vulnerable to geomagnetic storms, either because they could be penetrated by high-energy particles or because the satellite could become highly charged, causing key components to be damaged by discharging currents.

Even more serious is the potential for CMEs to damage electrical grids. A geomagnetic storm produces electrical currents in conductive material on the ground, including through pipelines, communication cables, and power lines. These large, geomagnetically induced currents can overload transformers and lead to widespread blackouts.

“Imagine large cities without power for a week, a month, or a year,” University of Colorado physicist Daniel Baker said at a 2011 geophysics meeting, according to National Geographic. “The losses could be $1 [trillion] to $2 trillion, and the effects could be felt for years.”

None of this is purely hypothetical. The 1859 solar storm dubbed the Carrington Event, the strongest on record, set auroras flaring as far south as Cuba—and rendered telegraph lines across North America inoperable. A 2003 CME disrupted satellites, high-frequency radio communications, and blacked out the Swedish city of Malmo.

As part of a NASA-funded workshop on space weather impacts, engineer and geomagnetic storm expert John Kappenmann analyzed how a geomagnetic storm on par with a particularly strong one seen in May 1921 would damage the grid. Kappenmann calculated that if the 1921 solar event happened today, more than 130 million people would be likely to lose power and 350 transformers would be at risk for permanent damage. Replacing or repairing those transformers could anywhere from weeks to months; in the interim, everything from clean water to gas stations to cellphone service to transportation would suffer in blacked-out areas.

“The physics of the Sun and of Earth’s magnetic field have not fundamentally changed, but we have,” Kappenman told Popular Science. “We decided to build the power grids, and we’ve progressively made them more vulnerable as we’ve connected them to every aspect of our lives. Another Carrington Event is going to occur someday.”

What can we do?

Ironically, part of the reason high-voltage transformers are vulnerable to geomagnetic storms is due to the measures we’ve taken to protect them from lightning strikes. The ground connections between the transformers that dissipate those power surges also serve as an avenue for geomagnetically-induced currents. Utility companies can guard against severe space weather by fitting key critical transformers with electrical resistors or capacitors—but with a price tag of hundreds of thousands of dollars per transformer, they aren’t jumping to voluntarily install these protections.

More advance warning of potentially damaging CMEs headed for Earth would give utility companies some time to scale back power generation to try and mitigate the effects of geomagnetic currents. Currently, the National Weather Service’s Space Weather Prediction Center can really only give between 10 and 60 minutes’ warning of strong geomagnetic storms. Better space weather forecasting could give us even more time to make preparations to weather the solar storm. Unfortunately, our alarm system is already starting to need upgrades. Many of the satellites we rely upon to monitor the sun’s activity are nearing the end of their operating lifespans, and plans for replacements are scarce.

Overall, “we’re starting to see more awareness” among policymakers about the risks posed by solar storms, Chris Beck of the Electric Infrastructure Security Council told the Washington Post. “Although we’re not quite to the point where we’re actually putting solutions in place.”

Image: NASA/SDO

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