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AGU Meeting: Taking the atmosphere’s pulse
The upper atmosphere is expanding and
contracting in cycles with periods of 5, 7 and 9 days, according to Jeff Thayer
of the University of Colorado, Geoff Crowley of ASTRA, and Marty Mlynczak of
NASA, who spoke about their work at a press briefing at the AGU Fall Meeting.
The researchers believe the density changes are caused by the rotation of solar
coronal holes - dark fixed features on the solar surface that project strong
solar winds - as the sun goes round. The resulting changes in solar wind stream
speed reaching Earth lead to geomagnetic storms and auroras, which act as a
heat source.
This newly discovered “breathing
mode” could affect satellite movements, the avoidance of collisions with
space debris, the electron density in the ionosphere, radio communications, GPS
systems, atmospheric composition, vertical wind circulation, and even weather
at the Earth’s surface. According to Crowley, there are
two potential connections to weather - changes in the ionosphere could cause
thunderstorms, and auroral particles could create nitric oxide that’s then
transported to the lower atmosphere where it could affect ozone distribution at
high latitudes. “We wouldn’t expect a 9 day cycle of weather,” he
said, “but somebody should look at that”.
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