In The Field

AGU: The earth breathing

It may be a bit of poetic fancy, but aeronomers (those who study the upper atmosphere) are talking these days about watching the earth breath. More specifically, a few researchers think they have discovered a “breathing mode” of the upper atmosphere—during which the planet’s gaseous blanket expands and contracts regularly about once every 9 days in a previously unrecognized cycle.

The evidence comes from satellite observations of the thermosphere, the region of sky extending from 85 kilometers to roughly 1,000 km above the surface. Data obtained from Germany’s CHAMP satellite indicate that the density of the thermosphere doubles about every nine days, according to Jeffrey P. Thayer of the University of Colorado at Boulder, one of the researchers who presented data on this newly observed pattern. Geoff Crowley, president of Atmospheric and Space Technology Research Associates in San Antonio, Texas, found a similar 9-day cycle in chemical data taken by the Global Ultraviolet Imager on NASA’s TIMED satellite. Measurements made by the SABER instrument on the same satellite also revealed the 9-day cycle, reported Martin G. Mlynczak of NASA’s Langley Research Center.

Aeronomy researchers were well aware of longer cycles, such as the 27-day pattern that corresponds to the rotational period of the sun, but nobody had looked for shorter patterns, said Thayer. He and his colleagues hypothesize that the sun is also driving the 9 day cycle, as well as some weaker, even shorter period, ones that have emerged from the data.

And who says there’s nothing new under the sun?

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