'Breathing' Earth: Our planet's atmosphere expands and contracts on a regular basis in response to warm 'wind' blasted from the Sun.
Credit: Wikimedia
SAN FRANCISCO: New satellite measurements have revealed that the Earth's upper atmosphere 'breathes' every five, seven or nine days.
Each 'breath' represents a response to changes in the solar wind, which is produced by particles escaping the Sun's upper atmosphere.
The wind fluctuates as the Sun rotates, alternatively heating the upper air of Earth's atmosphere and allowing it to cool. When the atmosphere is hot, it expands; when it is cool, it contracts.
An unexpected change
Scientists have long known that the Earth's atmosphere changes in response to solar fluctuations - but previously it was thought that these fluctuations occurred in cycles of 11 years, 27 days and 24 hours, corresponding to the sunspot cycle and the rotation of the Sun and Earth.
Nobody expected to find variations occurring at other intervals, however.
The cycles were discovered by three different types of satellite observations, reported by scientists on Monday at the American Geophysical Union meeting in San Francisco, California.
One team of researchers looked at minute fluctuations in atmospheric drag, another looked directly at changes in the upper atmosphere's temperature, while a third team examined fluctuations in upper atmospheric gases.
All three groups observed changes in their data occurring in the same cyclical patterns - about three to five times per solar revolution.
Blasting wind
The changes are the result of holes in the Sun's corona (or atmosphere), through which the solar wind blasts at higher speeds than normal. With each revolution of the Sun, the wind jetting from these holes washes across the Earth.
"Think about a searchlight [beam] rotating in 27 days," said Jeffrey Thayer, an aerospace engineer at the University of Colorado in Boulder. "If you have one [beam] you'd see it every 27 days. If you had three, equally distributed, you would see a bright light every nine days. That's essentially what we're seeing here."
