Sun Rotates At Various Speeds

WASHINGTON (AP) MARCH 30, 2000 — Parallel layers of gas deep within the sun rotate at different speeds, an action that may explain the formation of sunspots and solar flares, new research shows. Using data collected from a sun-watching satellite and from six solar observatories on Earth, Stanford University scientists spotted two layers of gas deep within the sun that slow or speed up in an opposite, but synchronized pattern. "It's not what we expected at all,'' Stanford research physicist Jesper Schou said in a statement. "It comes totally out of the blue.'' The researchers said that the difference in rotation rate occurs above and below at a subsurface layer known as the tachocline which separates two major gas areas of the sun, the convection zone near the surface and the radiative zone, which includes the core. Based on four years of data, the scientists found that the convection zone, just above the tachocline, increased its rotation speed by about 60 feet a second from July 1996 to February 1997. It then slowed and returned to its original speed over the following eight months. At the same time, the radiative zone showed exactly the opposite behavior, slowing down, and then speeding up. The cycle repeated itself every 16 months, or 1.3 years, at the solar equator, but it recurred only every 12 months in the midlatitudes of the sun. Unlike the Earth, the sun is made of gas. This allows parts of the solar sphere to spin at different rates. The puzzling cycle may be related to the forces that create the sun's massive magnetic field and the 11-year cycle of sunspots, but researchers aren't sure. Sunspots are solar storms that shoot out magnetic pulses and ionized particles that, if aimed at Earth, can interrupt communications and power systems. Finding that the rotation cycle matched the 11-year solar cycle "would make sense,'' said Schou. "But a 1.3-year period was unexpected,'' he said. "We don't know what it means.''