Katrina Bossert/ASU.

Auroral signatures observed from the CO2 4.3 micrometer emission from space during the October 13–14, 2016, geomagnetic storm.

Auroras appear to human eyes as ethereal curtains of visible light.

But, as a new paper in the journal Geophysical Research Letters explains, there are also scores of auroras visible only to electronic eyes.

“They all have different reasons for occurring,” said lead author Katrina Bossert of ASU. “A lot of them are associated with different excited atoms and molecules in Earth's atmosphere.”

The realm of auroras, like that of the electromagnetic spectrum itself, stretches far beyond the thin sliver of wavelengths visible to humans.

At the edge of space, carbon dioxide makes infrared auroras — counterparts to the visible greens and reds that oxygen makes as it releases energy delivered by solar wind.

“The common aurora that we're familiar with are the emissions in the red line, but there are actually hundreds of different emissions associated with the aurora,” said Bossert, who studies dynamics in the near-space environment.

She says such auroras have many causes and research applications.

“They can tell us about both chemistry that's occurring in Earth's near-space environment, and they can also be associated with higher energy particles or lower energy particles precipitating into Earth's atmosphere,” she said.

Bossert stumbled upon the CO2 aurora in data from NASA's Aqua satellite, which equips an Atmospheric Infrared Sounder that records infrared energy as part of the craft’s observations of Earth’s water cycle.

“I saw this this bizarre signal in the data, and it seemed to be correlated with higher geomagnetic activity,” she said. “And — after digging into it and doing some comparison with other instruments — we found that this was actually associated with carbon dioxide.”

Bossert and colleagues plan to look for long-term auroral patterns in the 20-year data set.

“Are there are seasonal effects to this aurora based on carbon dioxide? Do we see any trends over time in the intensity of these auroras?” she said. “It's going to be very interesting to pull apart what the data are going to tell us in that timespan.”