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NEW DETAILS ON ATMOSPHERIC AIR POCKETS THAT SLOW SATELLITES.

Scientists have long known that at times when the sun is highly active, a drag can impede satellites orbiting Earth. The results of this can be serious, as the slowing satellites are forced closer to Earth and can eventually fall all the way back if they do not have sufficient fuel to return to their prior orbits and full speed. Scientists have attributed the drag to air from lower in the atmosphere rising upward, and past research has identified spiky pockets of air rising into the upper atmosphere, but the cause of these pockets has been elusive. A new study published in Geophysical Research Letters has found that a certain type of high-altitude aurora is at least partly responsible for these atmospheric "speed bumps" that threaten satellites.

Scientists studied data collected by the Rocket Experiment for Neutral Upwelling 2 (RENU2) mission, which was launched from Norway in 2015. The data showed that in what are called "neutral upwelling events," multiple passes of auroral arcs moving poleward introduced energy that created the upwelling air that interferes with satellites. These aren't the well-known aurora that can light up the sky at high latitudes, but rather weaker and more distant aurora known as Poleward Moving Auroral Forms (PMAF) that can only be seen from very dark locations on Earth. The PMAF are present at high altitudes and send much of their energy to the upper atmosphere, 150-250 miles above Earth's surface (compared to about 60 miles up for the typical aurora), where low Earth-orbiting satellites reside.

According to lead author Marc Lessard of the University of New Hampshire, the study revealed that the speed bumps "are much more complicated and structured" than they anticipated. The study showed that the upwelling air forms a series of narrow wisps that collectively can span more than 10 miles across, and which can also change their structure slowly as they transfer their energy.

"You can think of the satellites traveling through air pockets or bubbles similar to those in a lava lamp as opposed to a smooth wave," Lessard says. [Source: University of New Hampshire]

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Title Annotation:NOWCAST: NEWS AND NOTES
Publication:Bulletin of the American Meteorological Society
Geographic Code:1USA
Date:Jul 1, 2019
Words:348
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