The magnetic field of Earth can “sing” musical notes

By Dr. Tony Philips

This week in Norway, a space weather observatory detected sine waves of exceptional purity rippling through Earth’s polar magnetic field. The waves, which persisted for hours with nearly perfect pitch, have been linked to “tearing instabilities” and explosions in Earth’s magnetic tail–not to mention bright auroras in Arctic skies.

When a stream of solar wind hits Earth, magnetometers around the Arctic Circle normally go haywire, their needles swinging chaotically as local magnetic fields react to the buffeting of the solar wind. On Nov. 18th, however, something quite different happened. Solar wind hit Earth and produced … a pure, almost-musical sine wave:

Rob Stammes recorded the event from the Polarlightcenter, a magnetic observatory in the Lofoten Islands of Norway. “A very stable ~15 second magnetic oscillation commenced and persisted for several hours,” he says. “The magnetic field was swinging back and forth by 0.06 degrees, peak to peak, with the regularity of a metronome.”

Imagine blowing across a piece of paper, making it flutter with your breath. The solar wind can have a similar effect on magnetic fields. The waves Stammes recorded are essentially flutters propagating down the flanks of Earth’s magnetosphere excited by the breath of the sun. Researchers call them “pulsations continuous” — or “Pc” for short.

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