A new study into the impact of auroras on satellites has confirmed a dark side to their dazzling beauty. The research, published in the journal Geophysical Research Letters, has uncovered a direct link between the appearance of the northern or southern lights and the phenomenon of satellites experiencing a drop in orbital speed. Over time, this correlation can cause satellites with little to no fuel reserves to experience a de-orbit and burn up in Earth's atmosphere.
"We knew these satellites were hitting 'speed bumps,' or 'upswellings', which cause them to slow down and drop in altitude," Marc Lessard, a physicist at UNH, said in a statement. "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."
To pinpoint the cause behind the phantom speed bumps, the researchers in 2015 sent an instrument-laden rocket into a kind of aurora known as Poleward Moving Auroral Forms (PMAF). Unlike their more luminescent counterparts, PMAF's reside at high altitudes and are dimmer and less energetic. You can see a time-lapse of the PMAFs captured during the sounding rocket campaign in the video below.
Based on the data captured by the rocket, the researchers discovered that these high-altitude auroras were transferring more of their energy into the thin atmosphere and heating pockets of air. As these rise and interact with satellites, they create drag and erode orbital velocity.
"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," said Lessard.
The research will likely benefit the design of future satellites destined for low-Earth orbit, with added fuel reserves to account for interactions with high-altitude auroras.