The Sun and Superflares
Just how big a flare is the Sun capable of producing?
It all began at the end of April, when a large, cool area of the Sun rotated into view. On May 1 observers saw a cluster of sunspots appear there, blemishing the face of our star and then rapidly growing in size. Over the span of a week astronomers tracked the cluster drifting across the disk of the Sun, until, on May 8th, it was pointing almost directly at Earth.
Then, as the Sun shone over Europe, the cluster erupted in a violent flash of light. Solar monitoring satellites picked up a burst of X-rays, a signal that they instantly beamed back to Earth. The eruption also threw out a cloud of solar plasma, thus sending a swarm of energetic particles rushing towards our planet.
Over the following hours and days the cluster erupted again and again, producing a surge of energy and radiation unlike any we had seen in decades. NOAA, the organisation that watches the Sun, issued warnings of an intense geomagnetic storm. Aurora, they knew, would certainly light up the planet’s skies. Radio networks would be disrupted, as would the constellations of satellites flying far overhead.
You might have seen some of the impact. The aurora of early May were spectacular, visible in brilliant colours across much of the world. Even in Hawaii, where the northern lights had not been seen in a century, they made an appearance.
Yet flares, even ones as big as this, are short-lived events: a sudden surge of energy washing over the planet, a wave that recedes almost as soon as it comes. Most - those NOAA classes with the letters M or C - are little more than ripples, inconsequential events that endanger no one.
More powerful flares, however, receive an X designation. And the further up the X class you go, the worse the impact can be. An X2 flare has twice the power of an X1; an X3 has three times the power. The scale is open-ended, so there is, in principle, no limit on how high the number can get. The worst we’ve ever seen - in a few decades of watching - came in at X28, almost three times stronger than the biggest of early May.
So bright was that 2003 flare, however, that the satellite watching - GOES - was left temporarily blind. Its true power may, therefore, have been far higher, perhaps hitting as high as X40 or X50. On the day it erupted, bursting out from the Sun at thousands of miles per hour, the Earth was fortunately placed far from its path. The flare, the most powerful we’ve ever seen, never even came close to hitting us.
If things had been different, as they almost were in 2012, when a massive cloud of solar plasma came within days of hitting us, the consequences on Earth could have been catastrophic. A powerful pulse of magnetic energy would have swept across the planet, sending wild currents surging in power grids and communications networks.
Transformers, the key components of the electrical system, would have overheated and fused, knocking the power grid off-line across an entire continent. In a worst case scenario the Internet itself might have collapsed, creating a global blackout lasting months. The implications that would have had for our globalised planet are almost too awful to ponder.
In 2010, a few years after GOES saw the Sun erupt in a powerful flare, another telescope was carefully watching a faraway star. In many ways that star resembled our own. It burned yellow, just as the Sun does, spun at roughly the same rate, and seemed, more or less, to be made of the same kind of stuff. In other words, the star – KIC9944137 – was, like the Sun, astronomically boring.
That, astronomers were hoping, meant that the star might have planets in orbit around it; planets, indeed, that might look something like Earth. The Kepler telescope was directed to check it out, as part of a regular monitoring of thousands of stars which might host planets. If it did, Kepler would see a repeated pattern of dimming, a sign of a planet moving across the disk of the star.
On March 1, however, KIC9944137 did something unexpected. Instead of dimming, it suddenly brightened. A massive burst of energy a dozen times more powerful than anything ever emitted by our Sun erupted from its surface and raced outwards. We have no idea if any planets stood in the path of that energy; but if they did, they were surely battered by a magnetic and radioactive storm unlike any we could have imagined.
Had such a storm hit Earth, the consequences would have been horrific. Swept by intense magnetic energy, the power systems of entire continents would fall silent; their vital and expensive equipment devastated by surging electrical power. Satellites covering everything from GPS to Starlink would be destroyed, their circuits fried by an overwhelming burst of radiation.
KIC9944137 is not the only sun-like star we’ve seen erupt in violent flares. Time and time again astronomers have spotted them bursting out in rage; pouring scorn and fury on their solar systems. That such events are possible is not in doubt. The only question is whether our own star is capable of doing the same.
This, however, is not an easy question to answer. Unlike many other natural disasters, solar flares leave little trace of their passing. There is no impact crater, no swathe of devastated land. Their occurrence, at least in the technologically innocent past, would have been marked only by strange lights shimmering in the night sky.
And though astronomical records stretch back millennia – ancient civilizations watched the night carefully – they rarely mention auroras. Even when they do, the records are unclear. Ancient Babylonian texts speak, for example, of a night two and a half millennia ago when the sky glowed red and priests foretold omens of the future. Was that really an aurora? Or did it glow red because of fire, or ice crystals glittering high in the atmosphere?
It turns out, however, that an accurate and detailed record of the Sun’s activity has been kept, just not by humans. Instead the record lies buried in the hearts of trees and trapped deep in the polar ice. There, thanks to the interaction between the Sun and the atmosphere, traces of ancient oxygen and carbon can reveal the Sun’s distant past.
That story begins high above the Earth. When a stream of charged solar particles flows towards our planet, as happens almost every day, as part of the solar wind, they first encounter the magnetosphere. This, a vast magnetic shield extending far out into space, traps the particles, directing them towards the polar regions.
The result is the aurora: colourful displays of light dancing far above the ground. A second consequence, however, is a slight rise in levels of carbon-14, a radioactive form of the carbon atom. This, in the form of carbon dioxide gas, tends to make its way into plants and trees, or ends up trapped in bubbles frozen into the polar ice sheets.
Over the centuries, then, trees build up a record of how much carbon-14 is present in the atmosphere. Rises and falls in that record follow the steady cycle of activity the Sun traces – a peak every eleven years, a trough five years later. Every now and then, however, that steady cycle is punctured by a sudden spike, the mark of a big solar flare.
In 2012 Fusa Miyake, a researcher at the University of Nagoya, took delivery of two Japanese cedar trees, each of which lived and died during the eighth century. In most of the tree rings the carbon-14 levels were steady, a sign of normal solar activity. In one of the rings, however, she saw an abrupt spike, a spike larger than any other seen.
Something enormous, it was obvious, must have happened in the year 774 or 775. Two possibilities stood out. Either a massive solar storm had taken pace, one far bigger than anything we’ve seen before, or a supernova had erupted startlingly close to Earth. Since nobody noticed a supernova erupting in the sky – and one like that would have been bright, bright enough to outshine the Moon – the solar storm seems a likelier story.
Later studies, based on trees collected from around the planet, confirmed the event. Something big really did hit the Earth in 774, something that appears to have been unmatched in the last few thousand years. Something, indeed, that was fifty times stronger than any solar flare we have ever seen in modern times. Could it, perhaps, have been a superflare, erupting violently from the Sun?
Even if it was, however, the event appeared to be an odd outlier in recent history. Studies of tree rings stretching back two thousand years showed only one other event in the tenth century that even came close. And nobody alive at the time seems to have noticed the flare, or if they did, they certainly didn’t realise what was happening.
In 2022, however, researchers pushed the solar record back by almost ten thousand years to the end of the last ice age. Two more events, both enormous and ancient, turned up: one in 7176 BC and the other in 5259 BC. More, the researchers think, are probably buried in the data, or lost in fallen trees sunk deep into ancient swamps.
In all, astronomers now reckon such big flares could happen as much as once every four hundred years. That, while not common, is frequent enough that we should worry. After all, our industrialised and wired-up world has already been around for two centuries. Our time might soon be up.
It would start with a warning flashed far from Earth. A handful of satellites maintain a watchful vigil on our Sun, monitoring its every twist and turn. When the flare erupts those satellites will see it, catalogue it and send a message back home. A superflare would be unmissable, a flare so enormous it would blind our satellites. We would thus get, at least, a brief warning that something unprecedented was on the way.
Within minutes a surge of X-ray radiation would smash into the planet, disrupting and heating the upper atmosphere. Hours later, a tsunami of high energy particles would reach the magnetosphere. That would offer some protection: the particles would dance in its field lines, creating brilliant displays of the aurora across the planet.
The beauty of that moment, however, will come with a terrible price. A magnetic storm of unmatched intensity would rip across the planet, sending electrical grids into chaos. Wild currents would overwhelm transformers, knocking them and the rest of the grid offline. The electrical systems that power the Internet, and especially the amplifiers that boost signals making long ocean crossings, would fry, and with them the Internet itself would be in jeopardy.
Riding in the storm’s wake would be a cloud of radioactive particles, each of which the Earth’s magnetic field would send hurtling towards the poles. Astronauts would be forced to run for shelter, desperately praying their radiation shields are able to block the storm. Satellites would fail, or go mad as their computer chips are garbled by the intense radiation. Carbon-14 levels would spike, a signature that would, before long, leave a permanent mark in trees across the world.
The longer-term consequences would be even worse. A superflare of this kind could cause permanent damage to the electrical grids of an entire continent. That would not be easy to fix - not least because the necessary components are not kept in sufficient supply to restore power across such a large area. The disruption would, a paper in 2014 warned, make a superflare the worst natural disaster to hit in centuries.
To restore normalcy, the world would surely need to organise a massive relief effort. But would it be capable of such an effort, in the aftermath of such a disaster, while lacking the communication and power systems needed to function smoothly? And even if we have the capability, would we have the resolve to pull together?
Recent years have sadly shown we are not always capable of acting in our own best interests during a catastrophe. But even when we have, the disasters we have faced have been either small scale or slow moving, giving nations time to respond. A superflare, by contrast, could erupt with just a few hours warning, and create havoc on a massive scale. A successful response is far from guaranteed.
And all that of course, is only if the flare is not too bad. The superflares seen around other stars can be utterly devastating events, powerful enough to destroy the ozone layer and cause a mass extinction of life. Nothing like that has ever been seen in the historical record – but neither does anything yet rule out the possibility.
Yikes! Now I have another thing to worry about that I can't do anything abooot
Both USCG and USN require their Navigators and inspected licenses (I am one 1600 ton master) to be able to navigate celestially ie: not electronics. This requirement was dropped at some point and reinstated in the last 10 years something like that. They are expecting a failure of some sort and want to be prepared. I’d suggest you own paper maps of your area.