What Are Solar Flares, and Can They Hurt You?

Whether these large eruptions of radiation from the sun can cause possible health effects is a subject of debate.

The sun is a massive magnetic star with twisting million-degree cyclones that shoot into its upper atmosphere. It gives us light and warmth, helps us grow crops, and gives us a chance to catch some much-needed rays in the summer.

When the energy that's stored in the sun's magnetic fields is suddenly released, huge explosions can happen. These explosions, called solar flares, produce sudden and intense flashes of light and send high-energy particles and a burst of ultraviolet rays into space. Particles can reach the Earth in a few hours or in a few days' time, creating a magnetic storm in the Earth's atmosphere that can last for days, according to NASA.

The flares are classified by severity: some cause radio blackouts around the world and radiation storms in the upper atmosphere. Others have been known to cause problems like transformer explosions and widespread mobile-phone outages, according to Time. They can also cause fluctuations in magnetic fields, which can reach the Earth's surface.

"These take a couple of days to get here, but when they arrive they can interact with our magnetosphere," said Dale Gary, PhD, distinguished professor of physics at the New Jersey Institute of Technology's Center for Solar-Terrestrial Research (NJIT). "That can induce currents in our power lines, and when that happens, transformers can blow or power outages can occur."

If solar flares can do damage like this to machinery and technology, we wondered about what, if any, effects solar flares can have on our health.

Some Say Solar Flares Will Not Affect Your Health

These powerful bursts of radiation are nothing to worry about from a health perspective, according to NASA. "Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground," the space agency said in a September 2017 statement. "However—when intense enough—they can disturb the atmosphere in the layer where GPS and communications signals travel."

Dr. Gary agreed with NASA's statement: "There are potential health effects for anyone exposed to that high-energy radiation, but actually we are protected because those rays and particles get absorbed into our atmosphere."

People on airplanes flying at high altitudes over the poles might be at increased risk for some of this radiation, said Dr. Gary, and occasionally, flight routes are changed during periods of unusual solar activity. But for anyone on the ground, he said, there's not much to worry about, except for potential safety issues that could occur if the power goes out. GPS and traffic-light outages could make for risky driving, for example, or hospitals could theoretically lose access to health data.

Others Say They May Impact Your Health

According to a 2020 Open Access Journal of Biomedical Science report, not everyone has been convinced that solar flares are completely harmless. The area of science dedicated to investigating the connections between human health and solar activity is called "heliobiology," and some researchers contend that the link can be negative.

A variety of health issues may be caused by changes in the solar and geomagnetic environment, according to a 2018 study in Scientific Reports. "Disturbed geomagnetic activity can also exacerbate existing diseases and is correlated with significant increases in cardiac arrhythmia, cardiovascular disease, the incidence of myocardial infarction-related death, alterations in blood flow, increased blood pressure, and epileptic seizures."

Additionally, an April 2014 study published in the journal Stroke found a link between geothermal storms and stroke risk among people in New Zealand, Australia, the United Kingdom, France, and Sweden. The study compared 11,453 hospital reports with daily geomagnetic activity over a 23-year period and found that geomagnetic storms were associated with a 19% increased risk of stroke overall and a 27% increased risk among adults under 65.

The study could not show a cause-and-effect relationship, and the researchers did not have detailed information for all participants about their traditional cardiovascular risk factors. But they speculated that magnetic fluctuations could have an effect on blood pressure, heart rate, blood clotting ability, or circadian rhythms, any of which could have an effect on stroke risk.

Even if the study's assumptions were correct, geomagnetic storms accounted for less than 3% of all strokes during the study's time frame. Considering nearly 17 million strokes occur around the world every year, however, that's almost half a million people. "Although the effect of geomagnetic activity alone is modest," the authors wrote in their paper, "in combination with other risk factors, it could be extremely important."

But Dr. Gary had his doubts: "The change in the magnetic field we're talking about is really small. If you think of the magnetic field that causes your compass needle to point north, we're talking about a 10th of a percent of that fluctuation." Those tiny changes are amplified by our giant power grid, he said, but they're unlikely to have an effect on an individual human body.

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