Gas Currents Hint at Sun’s Inner Workings

Stanford University researchers have identified and measured giant currents of gas moving across the sun’s surface, bringing them a step closer to understanding the interior dynamics of the sun and other stars.

“Although such convection-oriented currents have been looked for before, they had not been detected,” said Philip Scherrer, senior research associate at the Center for Space Science and Astrophysics.

The convection currents work on the solar surface in nearly identical fashion to the way plate tectonics work on the surface of the Earth.

Scientists theorize the convection--or hot materials rising over cooler materials--works similarly to the process within the Earth. The Earth’s interior consists of molten materials, which push huge continental plates around on the surface.

In the Earth, this activity is responsible for such phenomena as the magnetic field, Scherrer said.

“The newly measured giant convection,” he said, “apparently moves huge masses of gas around on the solar surface, mostly laterally across the face of the sun.

Better Understanding

“These observations are the first to clearly demonstrate the plate tectonics of the sun and will lead to a better understanding of the interior dynamics of the sun and stars.”

The observations were made over an eight-year period at Stanford University’s Wilcox Solar Observatory in the foothills near the campus. The observatory is a pyramid-like structure built over a 75-foot pit containing a sensitive spectrograph.

“The main problem was separating data about the relatively slow currents from other solar motions and random fluctuations,” said Richard Bogart, research associate at the space sciences center.

“Fortunately, 1984 was a relatively quiet year on the sun, so the data from that year could be compared to the period of 1979-1982, when the sun was active, to see that the observations were measuring the convective currents and not side effects of sunspots.”

The currents were measured moving in opposite directions, east and west, at 66 feet per second.

“These currents are seen on Earth as superimposed on solar rotation, which is westward” at 6,600 feet per second, Scherrer said.

The observatory was able to produce maps showing the motion of the currents, Scherrer said, which astronomers believe play an important role in solar dynamics--sunspots and other solar activities.

Details Still Unclear

“The detailed mechanism is not known,” he said, “but these observations bring us significantly closer to a better understanding of this mechanism.”

Scherrer, Bogart, research associate J. Todd Hoeksema and Hirokazu Yoshimura of the University of Tokyo reported the observations recently at a Tucson meeting of the solar physics division of the American Astronomical Society.