Last week, a small viral story appeared in corners of the Internet, warning of a disaster originating from beyond Earth. On Instagram, the now-viral warning was that “a massive solar storm heading toward Earth could affect GPS, Internet and satellites.” From the Times of India, the headline read “powerful solar storm likely to lash Earth on Tuesday.”

While alarming, the story was false. NASA reported a large solar flare July 3, which did cause radio blackouts, but that has long since passed the planet. This Tuesday probably will come and go with radios, satellites and the Internet intact.

Solar weather, however, remains a constant. The phenomenon includes solar flares and coronal mass ejections, which can affect Earth at any time. Scientists monitor the sun, like they do terrestrial weather, and study these events to try to predict when and where they will occur.

So what actually happens when one of those solar storms heads our way?

Frequently Asked Questions

Solar flares and coronal mass ejections

The surface of our sun is an incredibly hot and chaotic place, roiling with immense amounts of energy that create magnetic fields. The interplay between those fields is where solar weather begins.

“There is a solar cycle that waxes and wanes over a period of about 11 years,” said Howard Singer, chief scientist with the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center, which monitors space weather phenomena and provides information for government agencies. “At the start is the solar minimum, and then activity increases and you reach solar maximum before things settle down again.”

Because the sun isn’t a solid body, it rotates faster around its equator than at its poles. Over time, a NASA scientist says, the complex magnetic fields bend, building energy.

“Think of it like a rubber band that keeps getting twisted, and eventually it has to snap,” said C. Alex Young, associate director for science in the heliophysics division at NASA’s Goddard Flight Center in Greenbelt, Md.

This sudden snap is a solar flare, which releases a tremendous amount of energy across the electromagnetic spectrum: radio waves and microwave rays, visible light, ultraviolet light, gamma rays and X-rays, all traveling at the speed of light, fast enough to reach Earth in eight minutes.

“This is probably the largest explosive phenomenon that occurs in the solar system,” Singer said.

As more energy is released by a solar flare, it can create shock waves that accelerate particles away from the sun, causing what is known as a particle storm. These particles can reach Earth almost as fast as solar flares, in less than an hour. With enough energy, a solar flare can project material away from the sun — a coronal mass ejection. Billions of tons of particles spray out from the sun at high speed, potentially reaching Earth in a day or two.

How do scientists measure them?

Monitoring solar weather starts with sunspots, those dark blobs that sometimes appear on the sun’s surface. These are the indicators of fluctuating magnetic fields.

“We’re just toward the beginning of the next solar cycle, so we are starting to see more spots and more magnetic fields twisting up to the surface,” said Phil Scherrer, a professor and senior fellow at the Hansen Experimental Physics Laboratory at Stanford University.

In an 11-year solar cycle, there can be as many as 2,000 solar flares of varying strength. Not all will produce coronal mass ejections, and in the vast expanse of space, fewer of those will hit Earth. By studying sunspots, and continuously monitoring solar activity, scientists can build better predictive models.

“You tend to get more of these events during a large solar cycle, but also during the peak of a solar cycle,” Singer said. “But the important thing to remember is that even the most extreme storms have the potential to happen at any time during the solar cycle.”

What happens when they do reach Earth?

“The energy from a solar flare will interact with the ionosphere — the outermost layer of the atmosphere that’s critical for radio signals,” NASA’s Young said. “When those layers change because they’re heated up, that can cause a degradation in high-frequency radio.”

This could mean, for instance, that a plane traveling in the far northern hemisphere, where the charged particles released by solar weather are drawn by Earth’s magnetic poles, could lose radio contact. Solar flares can also disrupt radio signals used for navigation or disrupt GPS signals. The more energy emitted from the flare, the longer these disruptions can last. For the weakest, it could be a few minutes; for the strongest, it could be hours.

Smaller coronal mass ejections create the kinds of vibrant auroras that awe people in the far Northern and Southern hemispheres as the mass of particles ejected from the sun trigger reactions in Earth’s upper atmosphere.

For stronger events, there could be hazards.

“When this big cloud of solar material gets to Earth, it slams into the Earth’s magnetic field and creates what is called a geomagnetic storm,” Young said. “That can actually change the shape of the Earth’s magnetic field, which can impact spacecraft. One of the things we’re most worried about is that these electrical currents created in the upper atmosphere can be picked up by the large conductors of our power grids.”

Such an event could cause large-scale power outages, disrupting vast swaths of communications and infrastructure. These occurrences are rare, but as the planet becomes increasingly reliant on digital and electronic technology, the potential for a catastrophic event increases.

“Think about how much we depend on technology now,” said Michael Batu, an assistant economics professor at the University of Windsor in Ontario, who has studied the effects of solar weather on economies. “We depend on satellites for our GPS, the Internet, banking transactions, all these systems, and all of these are exposed to this type of risk.”

Such large-scale disruptions have happened before. During a period of intense solar activity in October and November 2003, one solar flare was large enough to exceed the charts used by NOAA. In 1989, the entire province of Quebec in Canada suffered power outages for nine hours. In 1859, in what is known as the Carrington Event, geomagnetic storms reportedly shocked telegraph operators and set some telegraph lines on fire.

“We want to be able to predict and know how to respond to these events,” Singer said, “and to be resilient to their impact.”

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