These particles, mostly protons and electrons, are traveling about a million miles per hour as they pass Earth. The wind would also pose a threat to astronauts traveling through space, so NASA wants to get a better understanding of its properties. In , 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?
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 wrote a paper and submitted it to the Astrophysical Journal ; the response from scientific reviewers was swift and scathing. It is extraordinarily difficult to accelerate anything to supersonic speeds in the laboratory, and there is no means of propulsion.
The breakthrough discovery reshaped our picture of space and the solar system. Scientists came to understand that the solar wind not only flows past Earth, but throughout the solar system and beyond.
It also both protects and threatens us. So understanding the precise structure and dynamics and evolution of the solar wind is crucial for civilization as a whole. These are called coronal mass ejections—and if a big one happened to hit Earth, the shockwave could cause chaos and damage to our communication systems. Such a scenario would generate all kinds of disturbances: Aircraft would lose radio communication, GPS would be thrown off by up to miles, and banking, communications and electronic systems could be knocked out.
This has actually happened before: In , a giant solar eruption known as the Carrington Event shut down telegraph and electrical systems for days. There are some precautions we could take if we had advance notice, which is why engineers want to know when a solar storm is incoming. What causes this stream, and how does it affect the Earth? The corona , the sun's outer layer, reaches temperatures of up to 2 million degrees Fahrenheit 1. At this level, the sun's gravity can't hold on to the rapidly moving particles, and they stream away from the star.
The sun's activity shifts over the course of its year cycle, with sun spot numbers, radiation levels, and ejected material changing over time. These alterations affect the properties of the solar wind, including its magnetic field, velocity, temperature and density. The wind also differs based on where on the sun it comes from and how quickly that portion is rotating. The velocity of the solar wind is higher over coronal holes, reaching speeds of up to miles kilometers per second.
The temperature and density over coronal holes are low, and the magnetic field is weak, so the field lines are open to space. These holes occur at the poles and low latitudes, reaching their largest when activity on the sun is at its minimum. Temperatures in the fast wind can reach up to 1 million F , C.
At the coronal streamer belt around the equator, the solar wind travels more slowly, at around miles km per second. Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Astronomy Terms. What Is Solar Wind? What is solar wind caused by? A faint layer of the sun's atmosphere, the corona starts roughly 1, miles above the solar surface and protrudes far into space. About 20 million miles away from that surface, portions of the corona transition into solar wind.
What is the solar wind mostly made of? Do solar flares affect humans? GPS signals we now depend on can get disrupted by solar wind. What happens when Earth's magnetic field interacts with the solar wind?
When solar wind contacts this field, its charged particles get pushed toward Earth's magnetic North and South poles.
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