SPACE.com -- A Memory the Size of the Sun

Can a Supermodel Forecast Solar Weather?

What is a Solar Maximum and What Happens?

Scientists Study Our Hot Star from Coldest Clime

Predicting the Sun's Weather


	A Memory the Size of the Sun posted: 11:53 am ET 02 February 2000

solar_magnetic_000202

When the solar wind blows, things change. Earth's magnetic field, for one thing, is bombarded with charged particles, forcing the dazzling aurora in the polar skies. Satellites and power grids are put at risk.

On the sun, however, the more things change, the more well, you know. But the adage, according to a new study, is apt when discussing the sun's constantly morphing magnetic field, which researchers say "remembers" a previous shape and reverts to it as the sun goes through various short- and long-term cycles of activity.

The newly discovered feature, involving subtle magnetic structures, appears in the same location every 27 days -- the time it takes the sun to make a full revolution, as viewed from Earth. This occurs regardless of short-term bouts of violent spewing and long-term cycles of changing solar activity, according to Marcia Neugebauer, a visiting scientist at NASA's Jet Propulsion Laboratory (JPL).

Turbulent and messy

Researchers have long known that the sun's energy is created by thermonuclear reactions in the core, but how that energy gets to the surface is not as well understood, and current theories hold that random churning motions are at work. If the process is random, a long-term memory should not be possible.

But while the field varies in strength and direction, Neugebauer said it remains fixed at the same solar longitude.

The new information pinpoints the repetition interval at 27 days and 43 minutes and shows that the sun has kept this steady rhythm for 38 years. Neugebauer said the "turbulence and messiness" of the process has, until now, masked the subtle, recurring magnetic structures.

"Why the sun's magnetic field behaves in this way is a puzzle, but the answer must lie deep within the sun," said Edward Smith, senior research scientist at JPL.

Fluids conducting electricity under the sun's surface generate the magnetic field, Neugebauer explained, and the field's apparent memory is most likely caused by a structure and process occurring deeper inside the sun than previously believed.

"There may be something asymmetric about the sun's interior, perhaps a deep-seated lump of old magnetic field," she said.

Neugebauer said that a better understanding of how the sun generates its magnetic field would help researchers better understand the solar wind and space weather.

The findings are published in the February 1 issue of the Journal of Geophysical Research.