When a faint aurora borealis appeared in the night sky over Colorado last week, scientists in Boulder were well aware that a geomagnetic storm that had emanated from the sun two days earlier was due to arrive.
Forecasting geomagnetic events is the mission of NOAA’s Space Weather Prediction Center, but its interest wasn’t primarily in alerting skygazers to celestial events like the pink and purple aura some Coloradans saw on March 30. A much higher priority in that office, a division of the National Weather Service, involves warning industries that can be damaged by solar eruptions called coronal mass ejections.
CMEs can damage power grids, disrupt communication and navigation systems, interfere with radio transmissions and disturb GPS systems, among other things. The SWPC alerts those industries so they can take precautions.
“We’re not that interested in the aurora,” said Bill Murtagh, a scientist who works in the Boulder office. “We’re interested in the effects on technology.”
There are two Space Weather Prediction Center offices. The Boulder office serves the needs of civilian entities, while the other serves the Department of Defense. That one is located at Offutt Air Force Base near Omaha, Neb.
In the case of last week’s event, scientists detected an active sunspot group two weeks ago that became especially active on March 28, producing two solar flares and CMEs. En route to Earth, they merged into one. When that happens, it’s called a cannibal CME.
“We’ve got to figure out, are these coronal mass ejections Earth-bound?” Murtagh explained. “They can be shooting off to the left or the right or the other side of the sun. Or, when the eruption is just at the right location, they’re heading toward Earth. In this situation, we were quick to realize that they were heading toward Earth. We plug the measurements we make of the eruption into our model and it gives us a sense of if, and when, that thing is going to hit Earth. It was clear that it was going to impact the Earth late on the 30th and into the 31st.”
After a CME is detected, the Boulder scientists turn to a satellite a million miles from Earth, which they use to measure the CME’s brightness, size and speed.
“We’ll take that information, stick it in a model, and the models say, ‘Based on that, this CME is going to get here in 48 hours.’ When the CME hits our spacecraft, now we know it’s about to hit Earth, it’s about 30 minutes away,” Murtagh said. “We can dissect the CME to see what the magnetic structure is, and the temperature. Then we have a good solid understanding of how the Earth’s magnetic field is going to respond to that thing we predicted two days out.”
CME’s can travel at speeds from 1 million to 6 million miles per hour, Murtagh said, adding that the recent one traveled at about 2 million mph. The SWPC alerted power grid operators and managers of other vulnerable systems so they could prepare for a surge of electricity.
“With the power grid, there are two (concerns),” Murtagh said. “One is the vulnerability of our extra high (voltage) transformers. The power grid is an AC (alternating current) network. We induce a DC (direct) current into that system and those transformers do not like that. That can cause heating and damage to the windings of the transformers. It’s one of our big fears. If we get an extreme event, it can damage dozens or even hundreds of those transformers. The consequences to the nation could be significant.”
Another concern is the voltage irregularity resulting from the geomagnetic impulse that could trip up electrical systems.
“That’s a very significant threat, too, that could result in a widespread blackout, but the recovery would be much quicker,” Murtagh said. “It would be like tripping a fuse. That recovery would be measured in hours or a couple of days, still at a cost potentially of billions of dollars to the economy.”
Murtagh said the storm that hit Earth last week was “quite weak,” relatively speaking, so much so that he was surprised it produced an aurora borealis.
A severe CME on the opposite side of the sun in July 2012 caused no damage on Earth, but if it had struck, it could have had catastrophic effects on vulnerable electrical systems. In February this year, Elon Musk’s SpaceX lost three dozen satellites when they were launched during a solar storm that disabled them.
“So many of the technologies we rely on for everything we do today can be affected in one of these storms,” Murtagh said. “We’re doing a lot of work to protect these critical assets from a big event.”
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