If those bursts happen to be aimed toward Earth, several related things happen. For one, Earth’s own magnetic field will channel any incoming particles toward the poles. Upon reaching the poles, the particles zip down toward Earth’s surface, where they collide with nitrogen and oxygen molecules to produce the psychedelic greens, blues, purples, and reds of auroras. That’s why auroras usually appear only at high latitudes, because our planet’s magnetic field concentrates incoming particles there. However, massive solar storms release so many particles that the auroras extend much farther toward the equator.

The second major effect involves a distortion of Earth’s magnetic field. You can picture our planet’s magnetic field as a series of curved lines that loop around Earth from pole to pole. (Think back on that grade-school experiment where you placed a bar magnet beneath a sheet of cardboard and sprinkled iron filings on top. The filings arranged themselves into similar lines.) After a solar storm, the incoming blizzard of particles produces a shockwave that effectively “squashes” those magnetic lines together. This disturbance of Earth’s magnetic field is called a geomagnetic storm.

Geomagnetic storms can bamboozle pigeons and other creatures that use Earth’s magnetic field to navigate. The storms can also set off magnetically triggered mines, as happened during the Vietnam War.

On a global scale, geomagnetic storms generate electricity. Just like charged particles in motion create magnetic fields, magnetic fields that are put into motion create electric currents in matter that’s nearby. During geomagnetic storms, the squashing of the magnetic field will induce electric currents within Earth, causing electricity to build up in the ground.

That buildup explains why telegraph systems went haywire in 1859. Electricity from the ground rushed up through poorly grounded equipment and began shocking operators and powering their devices. Earth itself was charging their equipment.

In modern times, geomagnetic storms have wreaked even worse havoc. One storm in 1989 knocked out Québec’s entire power grid; other grids across the United States and Canada experienced severe disturbances as well. And things could have been much worse. The 1989 solar storm was relatively modest. A storm as massive as the 1859 one could have taken down the entire North American power grid.

Satellites are even more vulnerable to solar storms. They’re floating in space, completely exposed; the influx of radiation and particles can scramble their memories and fry their circuits.

All of which leaves space scientists terrified. If a giant solar storm knocked out our satellite and power systems today, the chaos would be unprecedented. Most phones and communications equipment would no longer work, leaving people floundering without information. The loss of power would be especially harrowing, disrupting our ability to distribute food, cool and heat our homes, and provide medical care. Society wouldn’t recover for weeks, if not months, and many people could die.

And the really scary thing is that the 1859 Carrington Event, as it’s now known, was itself only a modest solar storm compared to the truly epic ones that have struck the planet in the past, as a Japanese scientist discovered in 2012.

That year, physics graduate student Fusa Miyake traveled to a lush island off southern Japan to study some ancient cedar trees. She found a stump from one that had reached 1,900 years of age before being chopped down. Miyake extracted a slice of the stump and returned to her lab.

Her research involved measuring carbon-14 levels in individual tree rings. Carbon-14 forms in Earth’s upper atmosphere when particles from space collide with nitrogen atoms. Carbon-14 in turn joins with oxygen molecules to form carbon dioxide, which trickles down and gets incorporated into plants and then the animals that eat them.

Carbon-14 is mildly radioactive, and scientists have been using it to date organic material (such as wood, seeds, and bones) since the 1950s. Miyake, however, did something novel. Most plants take in carbon-14 and distribute it all over their bodies. Trees do something a bit different. In their trunks, trees add a growth ring every year, a shell roughly a millimeter wide. Because the rings are permanent and discrete, any carbon-14 in a given ring must have formed in the atmosphere that same year.

Prior to Miyake, no one had examined carbon-14 levels in individual rings before, because the amount of wood in each ring was so tiny. But by using a highly sensitive technique known as accelerator mass spectrometry, Miyake succeeded in getting solid readings. And when she started going through her 1,900-year-old cedar, millimeter by millimeter, she noticed something strange—a spike of carbon-14 in certain years. One occurred in 774 CE, another in 993 CE. These spikes are now called Miyake events. They also show up in ancient ice sheets as spikes of beryllium-10 and chlorine-36. Scientists don’t know exactly what caused these events, but solar storms are a leading candidate.

Although Miyake is a physicist, her work immediately caused a buzz of excitement in another field—archaeology. It’s not widely known outside the field, but archaeologists often cannot narrow down the dates for important historical events; even carbon-14 dating leaves windows of uncertainty several decades wide. As archaeologist Michael Dee commented, “If the First World War and the Second World War had been in 1914 B.C. and 1939 B.C., we wouldn’t be able to tell those two things apart.”

Miyake events offered a way around that problem. As an example, archaeologists knew from excavations that the Vikings landed in Newfoundland around 1000 CE. They couldn’t narrow the date beyond that, but after hearing about Miyake’s work, a team led by Dee located some timber that the Vikings had used to make longhouses in Newfoundland, then mimicked her work in measuring the carbon-14 levels in each ring.

As expected, most rings showed low, baseline carbon-14 activity. But one ring proved special, with a significant jump in radioactivity. This represented the Miyake event of 993. Once Dee’s team had pinpointed that ring, they simply counted outward toward the edge, since the last ring must correspond to the date the tree was felled. They found 28 rings beyond the Miyake one, meaning the Vikings landed in North America in 993 + 28 = 1021 CE. Mystery solved.

Dee’s group is now eager to shore up fuzzy details about when the first pyramids in Egypt were built and how the Mayan and Aztec calendars align with our modern Gregorian one. And other archaeologists recently used the method to date a Neolithic settlement in northern Greece.

Still, outside of archaeology, the discovery of Miyake events caused more alarm than anything, due to their enormous size. For perspective, the atomic bomb that leveled Hiroshima in 1945 released the energetic equivalent of 15,000 tons of TNT. The Carrington Event far outdid that, releasing the equivalent of 660 billion Hiroshima bombs. But the Miyake events of 774 and 993 were five times bigger than even that. Scientists also now know of one Miyake event from 14,300 years ago that was twice as big as those—the equivalent of 6.6 trillion Hiroshima bombs. It doesn’t take much imagination to grasp the damage that would do to our power grid and satellites.

Space scientists are currently scrambling to understand what causes solar storms and especially how to predict them. Some call themselves “space-weather forecasters.” We know that the presence of sunspots raises the odds of a solar storm, but the correlation isn’t perfect. Other clues or insights are necessary. As for the most worrisome danger, the Miyake events, scientists have not yet systematically surveyed tree rings or ice cores to determine how often they occur. The best guess right now is once every 400 to 2,400 years. So perhaps we’re overdue for one, perhaps not.

Down here on Earth, the appearance of sunshine often marks the end of a stormy period, both meteorologically and metaphorically. “Here comes the sun,” and all that. But that sense of peace and tranquility is an illusion. Our solar system is a volatile place, and when the sun gets ornery, it can unleash vicious storms of its own—the likes of which we should pray we never see again.