Astrophysicist Recognized for Discovery of Solar Wind

John Roach
for National Geographic News
August 27, 2003

In 1958 Eugene Parker discovered that a stiff wind blows incessantly from the sun, filling local interstellar space with ionized gas. The discovery forever changed how scientists perceive space and helped explain many phenomena, from geomagnetic storms that knock out power grids on Earth to the formation of distant stars.

Now, for his groundbreaking discovery more than four decades ago, Parker, a professor emeritus of physics, astronomy, and astrophysics at the University of Chicago, will receive the 2003 Kyoto Prize for Lifetime Achievement for Basic Science on November 10 in Japan. The award, which comes with a gold medallion and a check for about U.S. $400,000, is one of three annual Kyoto Prizes that recognize significant contributions to the scientific, cultural, and spiritual development of humankind.

"It is very nice coming late in retirement to know that my work is recognized," said Parker during a break from tending his summer garden to speak with National Geographic News.

Scientists who study the sun and its interactions with interstellar space, the planets, and distant stars say that Parker's discovery of the solar wind opened the door to a new field of astrophysics.

"The existence of the solar wind is a fundamental physical fact, like the atomic nature of matter, and it eluded science until the 1950s and Gene Parker," said Paal Brekke, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, on behalf of the scientists working on the Solar and Heliospheric Observatory (SOHO) project.

The SOHO spacecraft and mission is a joint venture between the European Space Agency and NASA to study the internal structure of the sun, its outer atmosphere, and the origin of the solar wind. The project carries forward the field of research elucidated by Parker.

In addition to the solar wind, Parker's achievements include many contributions to the study of the large-scale dynamics of gas and magnetic fields in space.

He explained the process that creates the solar magnetic field—dynamo theory—and many terms in the area of research known as "cosmical magnetohydrodynamics" bear his name: the Sweet-Parker model of magnetic reconnection, the Parker instability in the interstellar medium, the Parker limit on magnetic monopoles, and the Parker equation describing the propagation and acceleration of energetic particles in space.

Solar Wind

But Parker's most well-known discovery was the solar wind: a flow of ionized gas—plasma—expanding away from the sun's surface into space, ultimately reaching speeds of 200 to 600 miles per second (300 to 1,000 kilometers per second) at large distance, which is 1,000 to 3,000 times the speed of sound in the air on Earth. Before the discovery scientists regarded interstellar space as a vacuum.

The beginning of the wind is best "seen," said Parker, in pictures of a total solar eclipse. During a total solar eclipse the moon passes between the Earth and sun, blocking sunlight from reaching Earth. In pictures of the events, bits of the sun's corona—the outer edge of the sun—can be seen extending out into space.

"Around the 1930s scientists determined the temperature [of the corona] must be a million degrees [Celsius] because of the way it stood out into space," said Parker. "If it weren't so hot, it wouldn't be puffed out so much. Then some very clever spectroscopic detective work confirmed this extraordinary temperature."

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