Clemson physicists are part of mission to learn more about the aurora’s atmospheric impact

With dancing reds and greens coloring the sky, the northern lights can put on quite a stunning show.

But in the skies above central and northern Alaska in late March, the northern lights were particularly AWESOME thanks to a research project to study how the aurora affects the upper atmosphere.

As a part of the AWESOME (Auroral Waves Excited by Substorm Onset Magnetic Events) project, researchers, including two Clemson University physicists, fired three sounding rockets into the sky during an auroral substorm. 

The first two rocket payloads released tracers that were widely visible and added blue and white to the green and red auroral display. Vapor tracers from the third rocket, launched four nights later, looked like a bright white ring due to a faulty payload valve.

The goal of the project, led by the University of Alaska Fairbanks, is to learn more about how energy from an auroral substorm affects the usually stable upper atmosphere. The project also includes NASA, Clemson, the University of Michigan, Cornell University, Penn State University, and two nonprofit science organizations, SRI International and The Aerospace Corp.

Knowing how energy from auroral substorms affect the upper atmosphere could improve space weather forecasting, which has implications for radio and satellite communications and spacecraft in low Earth orbit.

All the thermosphere, which reaches from about 60 to 350 miles above the Earth’s surface is what scientists call “convectively or buoyantly stable.” No convection occurs because the warmer air is already at the top, due to absorption of solar extreme ultraviolet radiation.

Upset stability

Energy and momentum injected into the middle and lower thermosphere by auroral substorms, at roughly 60 to 125 miles altitude, may upset that stability.

The long-term theory is that the auroral electrical currents heat the middle and lower thermosphere and that the resulting vertical upwelling is the principal driver of the thermospheric churn. But some believe acoustic-buoyancy waves are also important and may at times be the dominant mixing force.

Emeritus professor Gerald Lehmacher said there’s evidence from ground-based observations that auroras can generate buoyancy waves in the thermosphere.

“Gravity waves transport and distribute energy in the atmosphere, which can change the circulation and composition at larger scales,” he said. 

Because acoustic-buoyancy waves travel vertically and horizontally from where the aurora hits, the aurora-caused atmospheric changes could be initiated over a much broader area than would be expected.

“The waves are driven by buoyancy in the atmosphere in much the same way that waves on the ocean surface are,” said Miguel Larsen, a professor emeritus in the Clemson Department of Physics and Astronomy. 

Now researchers must gather data from the launched ion gauges and magnetometers and images taken at ground stations during the experiments and triangulate them into measurements of winds, a process that will take months.

Adapted from a media release by the University of Alaska Fairbanks.