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The Sciences

37. How Killer Electrons Form in Space

By Stephen OrnesDecember 28, 2007 6:00 AM


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Superstrong pulses in Earth’s magnetic field can drive electrons to near light speed, physicists reported in June. These “killer” electrons can cripple satellites and they present a radiation threat to astronauts. Scientists have long wondered how they accumulate enough energy to zip around in space.

Qiugang Zong, of the University of Massachusetts Lowell, led a team of physicists who analyzed data from the European Space Agency and NASA’s Cluster spacecraft, four satellites situated at the edge of Earth’s magnetic field. The satellites observed the pulses in the wake of an October 2003 magnetic storm triggered by a coronal mass ejection—a plasma spitball shot out by the sun—that slammed into Earth’s magnetosphere. The influx of energetic particles created waves in our planet’s magnetic field, Zong’s team discovered. As the pulses approached Earth, the ultralow frequency waves made the planet’s magnetic field lines oscillate and accelerated electrons traveling along the field lines to extraordinarily high speeds.

“ULF waves are standing waves that stay in their location and vibrate like a string,” Zong says. “It’s amazing that the wave power transfers to the killer electrons.” Zong’s study represents the first time this process has been observed directly.

The storm that the Cluster spacecraft witnessed damaged several satellites and caused power outages in Sweden. Astronauts in the International Space Station were ordered into a heavily shielded module during the storm. Fortunately for surface-­dwelling ­humans, Earth’s magnetic field and atmosphere do a good job protecting us from such killer electrons.

Go to the next story: 38. Math Advance Threatens Computer Security

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