Scientists figure out how auroras create 'speed bumps' for satellites

April 24, 2019

Scientists have discovered how the aurora creates "speed bumps" which can slow down satellites orbiting the Earth.

Researchers at the University of New Hampshire in the US found that a special type of high-altitude aurora could be pushing pockets of air deep into the outer atmosphere.

"We knew these satellites were hitting 'speed bumps', or 'upswellings', which cause them to slow down and drop in altitude," said Dr Marc Lessard.

"But on this mission we were able to unlock some of the mystery around why this happens by discovering that the bumps are much more complicated and structured."

Dr Lessard, an associate professor of physics at UNH, published the study in the Geophysical Research Letters journal.

Researchers found that lower energy auroras - different from the bright ribbons of light normally seen near the poles - had been prompting strange atmospheric behaviours.

Because these lower-energy auroras known as Poleward Moving Auroral Forms (PMAF) occur at such high altitudes, they transfer more of their energy to the atmosphere.

Instead of sparkling at just 60 miles (100km) above ground, PMAFs are fainter and occur up to 250 miles (400km) above the ground.

They are also responsible for pushing hot air out towards space, although it ultimately will fall back to the Earth - creating a gloopy environment for satellites to travel through.

"You can think of the satellites travelling through air pockets or bubbles similar to those in a lava lamp as opposed to a smooth wave," said Dr Lessard.

Early space exploration missions found that satellites had difficulties in orbit when the sun was active - they began to drag in their orbit, slowing down and potentially falling back to Earth.

For low-Earth orbit satellites, continued orbit is crucial - they perform lots of functions for society from weather pictures through to communications.

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