Just shy of 162 years ago—on the morning of September 1st, 1859—a hobbyist astronomer named Richard Carrington peered through his telescope and noted, in the sky, “two patches of intensely bright and white light.” Beyond Carrington’s country estate, telegraphs were failing all over the world. In American cities that night, people strolled gazing at the sky in wonder: “the northern heavens were perfectly illuminated,” a New York Times reporter noted.
This was what would later be dubbed the Carrington Event: a powerful geomagnetic storm which, in NASA’s words, is “arguably, the greatest and most famous space weather event of the last two hundred years.” Occurring as it did in the rapidly modernizing 19th century, as opposed to the hyper-modernized 21st, its effects were mercifully limited. These days, we’ve got a whole lot more electricity flowing: Another Carrington Event could be disastrous.
So, are we at risk for another one? When will the next Carrington Event occur? For this week’s Giz Asks, we reached out to a number of experts to find out.
Deputy Director of the National Center for Atmospheric Research
Tough question and, you guessed it, one without a definitive answer… We could be due one, but it’s always a matter of hot debate in the research world.
The correct answer is that they can come almost any time that the sun is making sunspots. I’m saying that, because even within the sunspot cycle there are specific windows when big storms occur and it’s not always when the sun is making big spots—size doesn’t always matter. However, complexity of those spots does. The vast bulk of major storms originate from what we call ‘delta’ regions—ones that are hideously tangled as they emerge and in short order release that pent-up energy into space in spectacular fashion!
So, if cycle 25 ends up being large, then we might be in for some fireworks at any time, but the last few cycles have seen their biggest storms at the tail end—near the sun’s equator. That’s part of the delta region story!
Then there’s the other factor—when they occur, if they are going to severely impact us. The sun has a “strike zone” where the eruption can be what we call “geo-effective,” and that’s on the eastern side of the sun’s disk, because the events take a certain amount of time to spiral out from the sun to hit us. So there’s the caveat, and likely we’ve dodged a bullet many times in the past—the event of 2012 may be an example of that!
Really, the whole field of space weather—things like solar wind, solar flares, coronal mass ejections, etc.—is in some ways in its infancy. We still have a long way to go when it comes to predicting these things. As things stand, we’re really just getting a kind of snapshot of what’s happening in the solar system.
Associate Director for Science, Heliophysics Science Division, NASA
Several scientists have done statistical studies on the likelihood of a Carrington-like event. In 2012, Peter Riley estimated that within the next decade the chances of a Carrington-like event were somewhere between 10% and 12%. However, more recent studies, using slightly more sophisticated statistics, have come up with somewhat smaller numbers—closer to 2%. The 2012 study modeled the hypothetical superstorm as an independent event, but the thing about events like solar flares and earthquakes is that they’re actually deeply connected to events that precede and follow them. We may in the future be able to do a better job of predicting these things, but it’s going to be a while.
Having said that, we’ve come a long way. We have very sophisticated, physics-based computer models that can give us some understanding of space weather events that might impact Earth or somewhere else in the solar system we care about. These would be events like coronal mass ejections, which is when an eruption on the sun spits out billions of tons of plasma into space.
Most of this activity comes from magnetic areas on the sun, primarily sunspots. If you want to predict what’s happening, you first want to go back and look at the sunspots. To predict whether or not a sunspot is actually going to produce a solar flare, we look at its size and shape, and then we examine past data on similar kinds of sunspots and say: Well, in the past we saw that 9 out of 10 times that kind of sunspot would produce a solar flare of a certain size. We then use that as a probability.
Granted, that’s just counting—it’s not really based on the science, because the physics of what’s happening is really complicated, but we are starting to combine newer and better understandings of the physics with computer models, and there may be a day when we have a more sophisticated computer model that can tell us when a solar flare will occur. And since, in general, the bigger a solar flare is, the more likely it is to lead to one of these solar eruptions, you might then have a better sense of when a solar superstorm will occur.
This would be important information, as these kinds of superstorms can interfere with our ability to communicate with satellites or with each other here on Earth. In some extreme cases, they can actually impact our power grid. Given the tech infrastructure we have now, something like the 1859 Carrington Event would have a much greater impact.
The good news is, we’d have some time—the big blob of stuff released by a solar superstorm takes 1-3 days to get to Earth, so once it’s identified you’d have time to prepare. NOAA would send out an alert to relevant industries, like the airlines and power companies, and let them know that something was coming our way, and then they’d change their flight plans and power down or disconnect certain circuits of the power grid.
Senior Lecturer of Applied Mathematics at the University of Sydney, who studies computational mathematics, fluid mechanics, and solar physics
The short answer is “nobody knows for sure.” To elaborate a little more, solar storms are very much like any other extreme event. It’s almost exactly like asking, “When will the next earthquake hit?” “When will the next big hurricane hit a city with more than 5 million people?” or “When will the next pandemic happen?” In some cases, with extreme events you can have a better idea when they might happen as you get closer to the event. For example, hurricanes move slow enough to track them.
Solar storms are a bit like all of these. We already know they take a few days to get to Earth. But we don’t know about their advanced signatures, if any.
The last time a truly massive event hit Earth was 1859. We don’t know if this was a 1-in-1,000 year event or a 1-in-100 year event, and we are overdue for another. The other thing about solar activity is that, like hurricanes, it goes through “seasons,” although the full cycle is 11 years long. If the you think of the stormy season as summer, then we are in spring right now. The sun should be much more active in about 5 years. That’s the next time a big solar storm is likely to happen. But, of course, we could escape unscathed, and then the next stormy time would be in about 15 years from now, and so on.
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