New theory straightens out sun's curved magnetic fields

Contact: Kevin Roark, knroark@lanl.gov, (505) 665-0582 (02-054)

Recent News Los Alamos scientist named Asian American Engineer of the Year Los Alamos scientist featured in NASA science update Los Alamos muon detector could thwart nuclear smugglers Wojciech H. Zurek named Phi Beta Kappa visiting scholar Four Los Alamos physicists honored by American Physical Society Los Alamos National Laboratory organizations earn seven out of 13 NNSA Pollution Prevention awards Carter Hydrick returns to the Bradbury Science Museum Feb. 15 Laboratory supports summer science program New NASA IBEX mission to carry Los Alamos instrument Beason takes top threat reduction post at Los Alamos

WASHINGTON, D.C., May 28, 2002 -- A long-accepted model of the sun’s magnetic fields holds that the fields radiate outwards from the sun into space in great curving arcs in the sun’s equatorial regions and growing ever more radial at higher solar latitudes. That model has been proven only partly right by direct measurements of magnetic fields by the Ulysses solar orbiter and other spacecraft.

Data from Ulysses and other observations have yielded an interesting phenomenon. While the sun’s magnetic fields are usually curved, as expected, sometimes they’re not, actually changing from long arcs to straight radial lines once or twice a month, on average, and at intervals lasting two or three days. One possible explanation for this puzzle was presented by Los Alamos National Laboratory researcher Jack Gosling to the annual meeting of the American Geophysical Union meeting in Washington, D.C., today.

About five years ago Ulysses data confirmed the existence of straight radially-oriented fields and their association with Coronal Mass Ejections about 50 percent of the time. “These observations depart dramatically from the standard model,” said Gosling, of Los Alamos’ Non-Proliferation and International Security Division. “The fields are nearly radial, or straight, for extended periods of time, almost always when the speed of solar wind plasma observed in space is in decline, and about half the time this occurs during a CME. There still is no definitive explanation for why this is happening.”

Gosling’s theory is that dramatic variations in the speed of the solar wind directly associated with the speed at which plasma is ejected from the sun -- specifically a sudden drop in that speed -- along a single magnetic field line produces a straight-line interval along the normally curved field line. “Our suggestion is that open and closed field lines get pinched together causing a ‘charge reconnection’ that opens a closed field line and results in a drop in speed,” said Gosling

Once generally confused with solar flares, images of CMEs are now commonplace. Most of these images are supplied by the Solar and Heliospheric Observatory, a project of NASA and the European Space Agency. Giant closed arcs of ejecta reaching out into space are observed in these events. These arcs illuminate the sun’s magnetic field lines that are carried into space by the CME material, but remain rooted in the sun. Gosling and his colleague Ruth Skoug suggest it is when the footpoints of field lines threading the CMEs reconnect with closed field lines in the surrounding corona that the sudden drops in outflow speed occur and are responsible for intervals of radial magnetic field far out in space.

All of this is important to the understanding of the solar wind, and space weather in general. The solar wind contains huge quantities of charged particles, or ions, that travel at millions of miles per hour and are responsible for geomagnetic events like the aurora phenomena of Earth’s higher latitudes. These geomagnetic events have also caused major communications outages and energetic charged particles found in the deep space solar wind can pose a real threat to astronauts who wish to venture to other planets.

Gosling and Skoug are working on computer simulations of these events with colleagues in San Diego, Calif., to confirm the theory, but are confident that their idea is consistent with data from basic observations. They have also submitted a paper on this theory to the Journal of Geophysical Research.

Gosling is a fellow of the AGU and is currently president of its Space Physics and Astronomy Section. He will also be giving an invited talk at the AGU meeting on what is now known about CME properties and behaviors.

Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy and works in partnership with NNSA's Sandia and Lawrence Livermore national laboratories to support NNSA in its mission.

Los Alamos enhances global security by ensuring safety and confidence in the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction and improving the environmental and nuclear materials legacy of the cold war. Los Alamos' capabilities assist the nation in addressing energy, environment, infrastructure and biological security problems.

The images used in this news release are available from the Los Alamos National Laboratory Public Affairs Office.

Additional news releases related to Space Sciences
Additional news releases from the Nonproliferation and International Security (NIS)