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affecting science, medicine and the environment | MIND

The Unavoidable Attraction of Magnetic Fields

April 12, 2001|K.C. COLE

The sun has a flair for putting on spectacular shows, and last month's was a doozy. Images taken at various National Science Foundation-funded observatories caught our local star in the act of spitting out glowing filaments 22 times the diameter of the Earth--dragon's breath streaming into space for 86,000 miles.

Such flares create the beauteous aurora borealis, or northern lights, which in this case reached as far south as Palm Springs. They can also scramble ground communications, and drag satellites to early deaths by puffing up the atmosphere.

Oddly, these seemingly special effects are created by one of the most familiar (if least understood) forces in the universe, the same invisible influence that keeps a refrigerator magnet stuck to the door. And increasingly, good old magnetic fields are emerging as major players in the universe at large--sculpting everything from the last gasps of dying stars to the dynamic centers of galaxies.

Astrophysicists shudder at this turn of events, because magnetic fields are among the most complicated phenomena they have to deal with. "They're what every astrophysicist loves to ignore because they complicate things enormously," says UCLA's Mark Morris.

No one understands completely how the sun slings out the streams of electrically charged particles produced in the flares--although it has something to do with how the tangled magnetic fields inside the star get twisted as it spins, then snake to the surface and snap.

Still, the sun's act is but a sideshow to what magnetic fields are up to in the rest of the universe.

Last year, for example, astronomers announced that they had discovered surprisingly strong magnetic fields hanging out in the seemingly empty spaces between galaxies--a real puzzle. A magnetic field is produced by moving electric charges, so how do you create strong fields where you don't have many particles?

Other astronomers recently figured out that magnetic fields are responsible for molding multicolored clouds of glowing gas blown off like smoke rings from dying stars.

And last December, astronomers reported that the strange asymmetrical jets blown out of Supernova 1987A were probably caused by--you guessed it--magnetic fields, produced inside the collapsing star.

Magnetic fields in space are a mess to understand because they combine some of the most complicated phenomena in physics: magnetism and fluid flow. The fields are created by flows of electrically charged particles that can swirl around unpredictably like eddies in a stream.

In turn, the magnetic fields can steer the flow of particles, directing them this way or that. This creates more fields, and so on and so forth, the fields and flowing particles pulling each other up by their sometimes beautiful bootstraps.

It's not surprising that astrophysicists would just as soon not get pulled into this vortex. "I deal with magnetic fields all the time, but there's a lot of things I don't understand about them," said the University of Rochester's Adam Frank, whose work helped solve the mystery of the multicolored clouds.

Yet the phenomenon seems unavoidable.

For example, some years ago Morris and colleagues found strange magnetic filaments running hundreds of light-years right through the center of our galaxy, in uncannily straight and narrow rows. Dozens of these tightly bunched parallel fibers have been found, all running perpendicular to the galaxy's nearly flat disk.

The only reasonable explanation seems to be very strong magnetic fields. But if so, where did they come from? Probably they are primordial magnetic fields that became concentrated in the center of our galaxy when it formed, Morris said. But that only pushes the question back in time. "Nobody has figured out how magnetic fields first came into being in our universe," he said. "That's the Holy Grail."

In fact, all the magnetic fields writhing inside stars and interstellar clouds can probably be traced back to the early universe, Morris said.

Even on small scales, of course, magnetism seems magical. A refrigerator magnet sticks to the door because countless unseen atoms inside line up in artfully arranged rows; each atom spins up its own magnetic field with the help of its orbiting electrons.

Magnets manage to speak to each other across the chasm of empty space. Opposites pull each other in as if by invisible hands. Likes shove each other away with a palpable push.

"It's freaky," said Frank, "because you can feel the force, but you can't see it."

And it's not just mystical; it's useful.

Doctors read the magnetic fields of atoms spinning inside our bodies to create images of what ails us. The spinning iron core of the Earth creates a magnetic field strong enough to shield us from those streams of particles the sun spits out in our direction--a global magnetic umbrella. Flipping magnetic fields even store the information kept in computers.

Undeniably attractive, magnetism steers the compass of the universe. Wherever you go, it seems, this force is with you.


Cole can be reached at

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