The solar wind is a flow of particles that comes off the sun at about one million miles per hour and travels throughout the entire solar system. First proposed in the 1950s by University of Chicago physicist Eugene Parker, the solar wind is visible in the halo around the sun during an eclipse and sometimes when the particles hit the Earth’s atmosphere—as the aurora borealis, or northern lights.
While the solar wind protects Earth from other harmful particles coming from space, storms can also threaten our satellite and communications networks.
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What is the solar wind?
The surface of the sun is blisteringly hot at 6,000 degrees Fahrenheit—but its atmosphere, called the corona, is more than a thousand times hotter. It is also incredibly active; those flares and loops are the halo you see around the sun when there’s an eclipse.
Animation courtesy of NASA
The corona is so hot that the sun’s gravity can’t hold it, so particles are flung off into space and travel throughout the solar system in every direction. As the sun spins, burns and burps, it creates complex swirls and eddies of particles. These particles, mostly protons and electrons, are traveling about a million miles per hour as they pass Earth.
This flow of particles, called the “solar wind,” has an enormous impact on our lives. It protects us from stray cosmic rays coming from elsewhere in the galaxy—but the effects of storms on the sun’s surface can also affect our telecommunications networks. The wind would also pose a threat to astronauts traveling through space, so NASA wants to get a better understanding of its properties.
Animation courtesy of NASA
The science behind what is happening on the sun’s surface is enormously complex; read more about it at NASA.
How was the solar wind discovered?
In 1957, Eugene Parker was an assistant professor at the University of Chicago when he began looking into an open question in astrophysics: Are particles coming off of the sun? Such a phenomenon seemed unlikely; Earth’s atmosphere doesn’t flow out into space, and many experts presumed the same would be true for the sun. But scientists had noticed an odd phenomenon: The tails of comets, no matter which direction they traveled, always pointed away from the sun—almost as though something was blowing them away.
Parker began to do the math. He calculated that if the sun’s corona was a million degrees, there had to be a flow of particles expanding away from its surface, eventually becoming extremely fast—faster than the speed of sound. He would later name the phenomenon the “solar wind.”
“And that’s the end of the story, except it isn’t, because people immediately said, ‘I don’t believe it,’” Parker said.