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miércoles, 27 de mayo de 2009

Giant Atmospheric Crashes Detected via Auroras

Using auroras like flashlights, scientists have exposed giant atmospheric waves crashing just above Earth that can endanger satellites (aurora pictures).

When strong winds crash into mountains or large atmospheric disturbances such as thunderstorms and hurricanes, the "explosion" sends invisible "shock waves" of air rippling outward in all directions at hundreds of miles an hour.

Aurora and radar pictures

The atmospheric waves can travel hundreds of miles upward into the highest reaches of the atmosphere. There, they crash against the ionosphere like surf breaking on a beach.

But instead of stopping at the "beach," the atmospheric waves spur smaller, weaker waves inside the ionosphere that generate heat. This heat in turn creates electrical disturbances that can affect the motions and functions of satellites.

Aurora Illumination

The giant air ripples have been detected before, but never so precisely or so far into the atmosphere.

The breakthrough comes courtesy of a new radar system called the Advanced Modular Incoherent Scatter Radar, recently installed near the North Pole in Alaska and Canada. There the system has a front-row seat for the aurora borealis, or northern lights.

Auroras flicker into being when charged particles from the sun strike Earth's magnetic field and are funneled to the Poles, where the particles interact with the atmosphere to colorful effect.

(Related: "Giant 'Space Tornadoes' Spark Auroras on Earth.")

By tracing an aurora's charged particles, the new radar system can paint a better picture of the invisible atmospheric waves—much the way you can "see" a breeze by watching floating, illuminated specks of dust.

"The radar has the ability to take a three-dimensional snapshot of the waves," said study author Michael Nicolls, an atmospheric scientist at SRI International, an independent, nonprofit research institute in California.

"From that, we can figure out which direction the waves are propagating and we can gain knowledge of where and how they are depositing their energies."

Those insights, he said, could lead to better understanding of space weather and its effects on Earth systems such as power grids as well as GPS and other forms of satellite communications.

Findings presented May 25 at an American Geophysical Union meeting in Toronto, Canada.

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