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International Team Discovers Solar Jet Stream

FRIDAY, AUG. 29, 1997

In the roiling 10,000-degree sun, currents move like the jet streams of Earth, perhaps helping to trigger spectacular solar eruptions, researchers report.

U.S. and European scientists reported Thursday that they have discovered electrically charged plasma gas currents deep under the surface of the sun and moving in patterns near the equator and around both poles.

The solar structures were detected by instruments aboard the Solar and Heliospheric Observatory, a spacecraft jointly operated by the European Space Agency and NASA. The craft is the first to orbit in such a way that it keeps the sun under almost constant observation.

Jesper Schou of Stanford University compared the currents circling the solar poles to the jet stream winds that rip through the Earth’s upper atmosphere and dramatically affect the weather of the planet.

The solar finding, he said, “is completed unexpected” and not thoroughly understood.

The jet streams form rings about the solar sphere at about 75 degrees north and south latitude. The rings are about 17,000 miles across and are moving about 80 mph faster than the surrounding solar material, said Philip Scherrer of Stanford.

Douglas Gough of Cambridge University said the shear forces created between the fast-moving currents and the adjacent plasma may strengthen the magnetic fields of the sun and contribute to solar eruptions. These eruptions, sometimes called sunspots, occur most frequently in latitudes near the polar currents, he said, and then move toward the equator.

Large solar eruptions can have a dramatic effect on the Earth by setting off electromagnetic storms that disrupt radio communication and even cause blackouts.

The SOHO instruments also found six other sun currents, moving rather like rivers, that glide slightly faster than the surrounding plasma near the solar equator. These bands are up to 40,000 miles across and move about 10 miles faster than the gases.

Other currents, running as much as 15,000 miles below the surface, move from the equator toward the solar poles at about 50 miles an hour. At this speed, it takes about a year for material to move from near the equator to the poles, the researchers said.

The currents were detected by a radar imager, called the Michelson Doppler, that measures vertical motion of plasma on the solar surface at 1 million different points each minute. These measurements are then converted by a computer program to data that resemble the seismic readings that are used to study the interior of the Earth.

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