How space weather impacts us: A look at some of the worst solar storms in history

Last week, the sun spat out the strongest solar flare of the year so far, a burst of radiation and light that caused brief radio blackouts on the sunlit side of the Earth.

Despite its impressive magnitude — the flare was an X-class, the most severe type of solar flare — it went largely unnoticed to those on the ground not dialled in to space news.

But geomagnetic storms and more serious types of space weather, which can follow solar flares, have the ability to shut down power grids, disrupt aircraft routes, global communications and GPS, and damage satellites and spacecraft.

It has not only happened to us before, but it could happen again.

On Sept. 1, 1859, amateur astronomers Richard Carrington and Richard Hodgson both witnessed a massive flare of light from the sun's surface while observing a cluster of sunspots.

Within a day, a geomagnetic storm had struck the Earth, sparking dazzling arrays of aurora borealis and knocking out telegraph systems across Europe and North America.

Telegraph operators across Europe and North America found their systems overwhelmed and signals down, with some wires overheating so much they triggered fires. Other workers unplugged batteries only to find that the telegraph systems kept humming away, supercharged by the sun.

One superintendent from Boston, Mass., whose observations were recorded in an 1860 article in the American Journal of Science, reported that a telegraph wire between Boston and Fall River "had no battery connected with it on Saturday, and yet there was a current upon it during the entire day."

So what happened?

Today, experts believe that the 1859 geomagnetic storm, now known as the Carrington Event, was caused by at least one, or possibly two, coronal mass ejections (CME).

These are immense eruptions of solar material that often follow a solar flare.

Because the sun's equator rotates faster than its poles, its magnetic fields can get tangled up. When the strain gets too severe, these magnetic fields can snap, releasing a burst of energy or solar material out into space. A solar flare emits radiation that interacts with our upper atmosphere, impacting radio signals, without really affecting us on the ground.

But a CME is a massive eruption of charged particles and plasma, sometimes millions of miles wide, which can travel up to thousands of kilometres per second on solar winds. When its magnetic field slams into the Earth's, it can spark geomagnetic storms that disrupt critical infrastructure. In 1859, that was telegraph operations, but today, it's power grids, satellites and global navigation systems.

Because the northern lights are caused by charged particles interacting with our magnetic field at the poles, a CME can also cause dramatic displays of aurora borealis, like the ones seen during geomagnetic storms in October and May 2024.

Although they can occur independently of each other, stronger solar flares are often accompanied by CMEs, according to Robyn Fiori, a research scientist in the space weather group of the Canadian Hazards Information Service with Natural Resources Canada.

"There's lots of different critical systems that can be impacted by space weather. So it's a good idea to keep track of what's going on," she said.

The last big solar event to have a notable impact on a power grid was in 2003, Fiori said, when a number of geomagnetic storms known as "the Halloween storms" rerouted aircraft, affected GPS systems used for deep-sea drilling, prompted astronauts in the International Space Station to take shelter from radiation in a specific part of the station, damaged a Japanese satellite beyond repair and triggered a power outage in Malmö, Sweden.

This event included a flare so large it overwhelmed the X-ray detectors on a number of satellites. It was later estimated to be an X28 flare, according to the European Space Agency, making it the most powerful in recorded observational history.

The biggest solar storm in Canada's history came in March 1989, when a CME struck Earth's magnetic field, sending electric currents flowing through the rock of the Canadian Shield to the transmission lines of Hydro-Quebec. The resulting province-wide blackout left millions of residents in the darkness and cold for nine hours.

"That's the strongest event that we've had in this technological age," Fiori said, "and it's really what we've used as a benchmark to make sure that systems are safe."

Other notable solar storms include one in 1909 that disrupted telegraph lines across the U.S., and one in 1967 that jammed radar systems operating in Alaska, Greenland and the U.K. amid mounting tensions between NATO and the Soviet Union, briefly sparking concerns of a Soviet attack.

It's been more than two decades since a solar storm caused significant power fluctuations and communications disruptions, but in an increasingly technological world, it's something space forecasters are keeping an eye on to stay a step ahead of the next solar storm.

For the next year or so, solar flares and solar activity will be higher than usual, as we're within the period of solar maximum, the peak of the sun's 11-year cycle.

"We do have a lot of different technologies that are sensitive to space weather. Since 1989, for example, we've become much more dependent on GNSS or GPS for navigation. And that can be impacted by space weather," Fiori said.

She added that Canada, due to its proximity to the northern magnetic pole, is more vulnerable to space weather.

"But it also means that we're in the very best place to observe it so that we can build accurate forecasts."