The ionosphere and aurora wrap around Earth, as seen from the International Space Station.
Most electrons that create the aurora have a moderate amount of energy, but scientists want to know more about how electrons on either side on that scale — more and less energy — affect the electrical properties of the ionosphere, the part of Earth’s upper atmosphere that is ionized by the sun.
These properties define how well the ionosphere conducts electricity. That’s critical in understanding how energy from Earth’s magnetosphere, the protective shield that deflects much of the solar wind, dissipates into the lower atmosphere from the ionosphere and affects space weather.
Higher energy electrons deposit energy in the lower atmosphere, at about 40 miles altitude. Lower-energy electrons transfer, or precipitate, energy at high altitudes, about 90 to 370 miles above Earth.
“What low-energy precipitation does in this high-altitude region is one of the questions we want to answer,” said Doğacan Ozturk, assistant professor at the UAF Geophysical Institute. “Is it creating localized heating? Is it creating gravity waves, atmospheric waves?”
“When all these electrons start moving there, they drive electric currents,” Ozturk said. “This is important for satellites like Starlink.”
Ozturk is collaborating with assistant professor Katrina Bossert of Arizona State University and professor Aaron Ridley from the University of Michigan on a four-year, $945,000 NASA-funded research project awarded this summer to find out more about those low- and high-energy electrons.
Ozturk is the project’s lead investigator. Bossert previously was an assistant professor at UAF. Ridley is the creator of the numerical model the team will use to investigate these particles.
As for high-energy auroral electrons, studies have demonstrated the importance of their precipitation for understanding lower thermosphere activity such as nitrogen oxide production and movement and carbon dioxide emission.
For example, high-energy auroral electrons precipitating at low altitude interact with atmospheric nitrogen and trigger chemical interactions and collisions that produce excited nitrogen dioxide. The excited nitrogen dioxide molecules then return to their normal state by exchanging energy with carbon dioxide molecules in the thin upper atmosphere, exciting them.
The excited CO2 molecules, seeking to return to their normal state, each release an infrared photon.
Sunlight breaks atmospheric molecules apart, knocking off electrons and leaving behind a sea of charged electrons and ions. This population of electrically charged particles is the ionosphere.
Research by Bossert published in 2023 found that NASA’s Aqua Earth observation satellite can detect these CO2 infrared emissions and that they are associated with the aurora. That research shows a ring of carbon dioxide infrared emissions at about 60 kilometers (37 miles) altitude, coinciding with a ring of auroral activity.
“This is very exciting because it shows a new pathway of how auroral energy goes through our atmosphere,” Ozturk said. “Normally, when we talk about auroral altitudes, our definition starts from 90 kilometers above Earth.”
“This carbon dioxide ring shows us that there is more impact from geomagnetic activity than we thought there might be,” she said.
Ozturk and colleagues will use numerical experiments to identify the mechanisms behind lower thermospheric processes such as the carbon dioxide emissions reported by Bossert.
Knowing more about energy transfer of high-energy electrons is also important for understanding large-scale traveling atmospheric and ionospheric disturbances.
These are waves that travel through the neutral atmosphere and ionosphere, respectively, and which affect atmospheric density and electron density. They are often triggered by geomagnetic storms, atmospheric events and other natural phenomena.
The project will add to scientists’ understanding about space weather — events generated by the interaction of solar activity and Earth’s weather — and how it can interfere with satellites, navigation systems and other technology.
The project begins with compiling a list of events during which several satellites and ground-based radar systems are focused on the same area of space. Ground systems include the Geophysical Institute’s incoherent scatter radar at Poker Flat Research Range north of Fairbanks.
From there it will consist of working with a variety of computer models and datasets, including from Poker Flat, to determine the atmospheric impact from the raining down of low- and high-energy electrons from the sun.
Previous studies and models have proved inadequate, Ozturk and colleagues wrote in their proposal to NASA.
Results will benefit upcoming NASA missions such as the Electrojet Zeeman Imaging Explorer and the Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites. Both seek answers to questions about what drives space weather. They are scheduled for launch in 2025.
ADDITIONAL CONTACT: Doğacan Ozturk, dsozturk@alaska.edu
