News- 1996

The phenomenon had been a key, missing piece in the explanation of the auroras borealis and australis, or northern and southern lights. Scientists studying the complex interaction between the Earth and the powerful "solar wind" of rarefied, electrically charged particles that flows in turbulent waves outward from the sun have speculated about such polar fountains for many years.

While the northern and southern lights are caused by particles pouring down on the atmosphere from space, researchers were certain that some of the matter turns around and shoots back up along pulsating lines of magnetic force. They also were convinced that a portion of the Earth's own outer atmosphere, or ionosphere, gets caught in the fountain and expelled into space, too.

A satellite orbiting the poles, specially modified to detect low energy hydrogen and oxygen ions rising from the Earth below, has confirmed that the plasma fountains not only exist, but spray about 50 tons of matter daily into space in a narrow column moving about 100,000 mph

The report came yesterday in San Francisco at the annual meeting of the American Geophysical Year, where a team of scientists celebrated a torrent of new data from a set of satellites orbiting the Earth, including one at about a tenth of the way from the Earth to the sun. These satellites measure in unprecendented detail the invisible but powerful forces from the sun that buffet Earth's magnetic field and outer atmosphere.

The fountain of plasma had escaped detection previously because most satellites build up a slight static electric charge due to sunlight. Therefore, previous satellites' electric fields repelled the passing particles, blinding their instruments to them. The satellite in orbit around the Earth's poles, called POLAR, had a special device that shot just enough electric current into space from the satellite to keep it electrically neutral.

Understanding the flows of charged particles from the sun to Earth could pay practical dividends, said Thomas Moore of the NASA Marshall Space Flight Center. He is prinicpal investigator on an experiment called TIDE, for Thermal Ion Dynamics Experiment, aboard the POLAR satellite.

The surging plasmas and magnetic fields that flutter around Earth can cause magnetic storms that damage and sometimes knock out power lines in the northern hemisphere, especially in Canada where lines thousands of miles long can build up huge, unexpected electric currents in response to the surging magnetic fields near the Earth. The fields can also accelerate particles in radiation belts around the Earth to such high energies that they damage the electronic components of communications and other satellites.

"These fountains could contribute to magnetic storms," Moore said.

His report was one of several about the recent results from POLAR and four other satellites - called Geotail, Wind, FAST and SOHO - that are tracing complex orbits covering millions of miles near and around Earth to measure exactly how the planet's magnetic field reacts to the surging solar wind and solar magnetic field.

"The sun is like a jet engine, shooting particles and energy at the Earth," said Mario Acuna of the NASA Goddard Space Flight Center in Maryland. "This year we reached a critical mass in the configuration of satellites that for the first time lets us study the interaction of the Earth and the sun's magnetic fields in detail."

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