Dr. Janet Luhmann sort of wishes Earth had been hit by a giant gust of solar wind in the summer of 2012. Sure, the cloud of magnetically charged protons and electrons would’ve gotten tangled up in our planet’s own magnetic field, probably disabling global positioning and other communications satellites and overloading many of our electrical transformers—potentially knocking us back to the Candle Age. But, she says, “It would have been an interesting experiment.”
The last time a solar gust that fast and powerful struck Earth was in 1859. Known as the Carrington Event, the impact lit up skies with the aurora borealis as far south as Hawaii and Jamaica, and the electrical surge zapped telegraph operators. In 1989, a smaller storm knocked out power across part of Canada. The July 23, 2012, storm hurtled through Earth’s orbit, but missed us by about nine days.
Solar storms are caused by violent eruptions on the sun, events known as coronal-mass ejections. Luhmann, a senior research fellow at the Space Sciences Laboratory, recently co-authored a paper examining what made the 2012 coronal-mass ejection travel so fast, so far, and with such a powerful magnetic field.
The sun, made mostly of hydrogen and helium in an ionized or plasma state, is surrounded by a halo of superheated hydrogen plasma called the corona. The corona constantly releases a solar wind of protons and electrons out into space. Rapid movements in the coronal magnetic field can cause eruptions of plasma that are far larger, and sometimes faster, than the normal solar wind. These coronal-mass ejections, which are often associated with solar flares, may happen just a few times a week during the solar minimum, when the sun is less active. During the solar maximum, which passed in 2013, the mass ejections may happen many times a day. If the resulting solar storm is powerful enough, especially if the ejection’s magnetic field is oriented opposite to Earth’s, the clouds of protons and electrons can compress and interact with Earth’s magnetic field, causing currents on the ground to build in long conductors, like electrical wires. If the currents are strong enough, this blows out transformers.
On July 23, 2012, a NASA spacecraft monitoring the sun observed two enormous eruptions, just minutes apart, burst from the corona at more than 1,800 miles per second. The cloud of plasma actually reached the craft—nearly 90 million miles away—less than 19 hours later, and still traveling at roughly 750 miles per second. Eruptions that strong occur every five or ten years, but most are slowed down when they collide with the slower solar wind, which typically blows at about 250 miles per second. Why, scientists wondered, hadn’t the ambient wind slowed the cloud more?
Most of the time, coronal mass ejections don’t move much faster than the solar wind. A fast-moving eruption, though, can plow through the ambient wind, pushing plasma ahead of it and clearing a path behind itself. Looking back through their data, Luhmann and her co-authors realized that this is what happened on July 19, 2012, when the corona cast out a cloud of plasma at about 1,000 miles per second. When a faster and larger cloud of plasma erupted from this same spot on July 23, it found the solar wind cleared out of its way.
Thankfully, Earth was elsewhere in its orbit during the July 23 eruption. Luhmann says that many power lines are better insulated than those in the time of the Carrington Event, but such a storm would still likely cause widespread damage and the aurora could again be visible as far south as Hawaii and Jamaica.
And that, Luhmann says, would’ve been pretty exciting. “You don’t wish for a huge earthquake or tsunami, because you know bad things happen,” she says. “But by the same token, those things are a wake-up call.” Most people, Luhmann says, don’t have any idea of the danger, and governments and utility companies aren’t well prepared. Similar to a major tsunami, earthquake, or even a meteor impact, it’s unlikely that the Earth will be hit by a huge solar storm in any given year.
But eventually it’ll happen, and we will likely only have a few hours’ warning. A 2012 report by the National Academy of Sciences said that such a storm could cause trillions of dollars in damages, and repairing the damage to the electrical grid could take as long as a decade.
No, Luhmann says, she doesn’t really want that to happen. But just in case, she always keeps a stash of batteries.
Zach St. George’s writing has appeared in the theatlantic.com, usatoday.com, and elsewhere. He plans to survive the Candle Age; just don’t ask him where he’ll get the tallow.