Space weather secrets unlocked by physicists


Scientists say they've been unraveling some of the mysteries of space weather, the "solar wind" of millions of tons of charged plasma gas the sun spews into space that can batter Earth's magnetic field.

Understanding the phenomenon is important because that battering can result in geomagnetic storms that can cause damage to satellites, knock out terrestrial power grids or interfere with cell phone service, they say.

Predicting such outbursts of solar winds could give sufficient warning for steps to be taking to deal with them, and those predictions may depend on a better understanding of the physics behind space weather, says a number of research teams preparing to present their results at the 56th annual meeting of the American Physical Society's Division of Plasma Physics, taking place in New Orleans.

Among the work to be described are experiments undertaken at Princeton University's Plasma Physics laboratory showing how magnetic reconnection, a volatile process that occurs within solar flares above the surface of the sun, can accelerate solar wind particles to high energies, and how the resulting solar wind "space weather" affects the magnetic field shielding the earth.

In magnetic reconnection, field lines of magnetic energy in the plasma break apart and then violently reconnect, driving huge eruptions of plasma out of the sun.

Just how that reconnection converts magnetic energy into explosive particle energy has been a significant mystery of space weather physics.

Now scientists with the U.S. Department of Energy's Plasma Physics Laboratory have not only confirmed exactly how that transformation occurs but have managed to make experimental measurements of just how much of the magnetic energy is transformed into particle energy.

In a typical reconnection around half of the magnetic energy is converted, with around a third of such conversion heating electrons and two-thirds accelerating the atomic nuclei in the plasma, the researchers are reporting.

"This is a major milestone for our research," says Masaaki Yamada, the principal investigator for the DOE's Magnetic Reconnection Experiment. "We can now see the entire picture of how much of the energy goes to the electrons and how much to the ions in a prototypical reconnection layer."

It is the high energy levels that magnetic reconnection pumps into the electrons and ions that allows them to escape the immense gravity of the sun to become the solar wind that flows outward, becoming the space weather that can have such significant effects on the Earth.

An example of what solar wind and a resulting geomagnetic storm can do is March 1989, when one such storm caused the power grid of Hydro-Quebec to collapse as protection relays were tripped, leaving some 6 million Canadians without power for as long as 9 hours.

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