May 3, 1996


          Even 'Quiet,' Sun Is Found Very
          Turbulent

          By MALCOLM W. BROWNE

            A   new European-American spacecraft has revealed
               that even when the Sun is relatively quiet, like at
               the present, it is more violently turbulent than
          astronomers had realized.

          At a news conference in Washington on Thursday, solar
          astronomers predicted a rich harvest of new knowledge
          about the complex dynamics of the Sun as data and images
          pour in from the Solar and Heliospheric Observatory ,
          which was launched Dec. 2 from Cape Canaveral, Fla.

          The spacecraft, built by the European Space Agency in
          cooperation with NASA, is the first solar observatory
          capable of round-the-clock observations. Other spacecraft
          observing the Sun have been in orbit around the Earth,
          where the view of the Sun is obstructed with each
          revolution.

          But SOHO, orbiting between the Sun and Earth one
          million miles from the Earth, is at a point where the
          gravitational fields of the Earth and Sun cancel each other
          and has the Sun in continuous view.

          To the surprise of astronomers, some of the first images
          gathered by ultraviolet-sensitive instruments show long,
          feathery plumes spurting millions of miles into space from
          regions near the Sun's poles. Solar experts had not
          expected to see such features in such places at a time when
          the Sun is relatively quiet, that is, free of sunspots, flares
          and giant magnetic storms.

          The intensity of solar storms and magnetic turbulence
          reaches a maximum once every 11 years or so, and at
          present, the Sun is probably near its least active phase. By
          starting its planned 30-month observing schedule during a
          quiet period, SOHO is expected to measure a baseline of
          solar activity, against which the violent phases can be
          compared.

          The spacecraft has three main missions: to investigate the
          outer layer of the Sun, to determine how it expels material
          into space and the effect of this material on the Earth's
          environment, and to probe the Sun's interior structure.
          The spacecraft is also performing some incidental tasks,
          including observations of Comet Hyakutake, which at
          present is hidden from the Earth behind the Sun, but is
          visible to SOHO.

          SOHO's initial results received high praise from
          astronomers not associated with the project.

          Dr. John Leibacher of the National Solar Observatory in
          Tucson, Ariz., said, "SOHO's mission has barely begun,
          but it looks as if its complex suite of instruments will reveal
          many things."

          One of the central challenges, said Dr. Andrea K. Dupree
          of the Harvard-Smithsonian Center for Astrophysics in
          Cambridge, Mass., will be "to see how material gets out
          through the solar surface into the solar wind, when the
          bottom of the sun shakes and quivers."

          The solar wind, a blast of electrically charged particles,
          atoms and molecules streaming from the Sun, interacts with
          the Earth's magnetic field and atmosphere. At times when
          the Sun is most active, the solar wind is intense enough to
          cause surges of electric current that disrupt radio and
          telephone communications.