Newly published results from a 2021 experiment led by a University of Alaska Fairbanks scientist have begun to reveal the particle-level processes that create the type of auroras that dance rapidly across the sky.
The Kinetic-scale Energy and momentum Transport experiment — KiNET-X — lifted off from NASA’s Wallops Flight Facility in Virginia on May 16, 2021, in the final minutes of the final night of the nine-day launch window.
UAF professor Peter Delamere’s analysis of the experiment’s results was published Nov. 19 in Physics of Plasmas.
“The dazzling lights are extremely complicated,” Delamere said. “There’s a lot happening in there, and there’s a lot happening in the Earth’s space environment that gives rise to what we observe.
“Understanding causality in the system is extremely difficult, because we don’t know exactly what’s happening in space that’s giving rise to the light that we observe in the aurora,” he said. “KiNET-X was a highly successful experiment that will reveal more of the aurora’s secrets.”
One of NASA’s largest sounding rockets soared over the Atlantic Ocean into the ionosphere and released two canisters of barium thermite. The canisters were then detonated, one at about 249 miles high and one 90 seconds later on the downward trajectory at about 186 miles, near Bermuda. The resulting clouds were monitored on the ground at Bermuda and by a NASA research aircraft.
The experiment aimed to replicate, on a minute scale, an environment in which the low energy of the solar wind becomes the high energy that creates the rapidly moving and shimmering curtains known as the discrete aurora. Through KiNET-X, Delamere and colleagues on the experiment are closer to understanding how electrons are accelerated.
“We generated energized electrons,” Delamere said. “We just didn’t generate enough of them to make an aurora, but the fundamental physics associated with electron energization was present in the experiment.”
The experiment aimed to create an Alfvén wave, a type of wave that exists in magnetized plasmas such as those found in the sun’s outer atmosphere, Earth’s magnetosphere and elsewhere in the solar system. Plasmas — a form of matter composed largely of charged particles — also can be created in laboratories and experiments such as KiNET-X.
Alfvén waves originate when disturbances in plasma affect the magnetic field. Plasma disturbances can be caused in a variety of ways, such as through the sudden injection of particles from solar flares or the interaction of two plasmas with different densities.
KiNET-X created an Alfvén wave by disturbing the ambient plasma with the injection of barium into the far upper atmosphere.
Sunlight converted the barium into an ionized plasma. The two plasma clouds interacted, creating the Alfvén wave.
That Alfvén wave instantly created electric field lines parallel to the planet’s magnetic field lines. And, as theorized, that electric field significantly accelerated the electrons on the magnetic field lines.
“It showed that the barium plasma cloud coupled with, and transferred energy and momentum to, the ambient plasma for a brief moment,” Delamere said.
The transfer manifested as a small beam of accelerated barium electrons heading toward Earth along the magnetic field line. The beam is visible only in the experiment’s magnetic field line data.
“That’s analogous to an auroral beam of electrons,” Delamere said.
He calls it the experiment’s “golden data point.”
Analysis of the beam, visible only as a varying shades of green, blue and yellow pixels in Delamere’s data imagery, can help scientists learn what is happening to the particles to create the dancing northern lights.
The results so far show a successful project, one that can even allow more information to be gleaned from its predecessor experiments.
“It’s a question of trying to piece together the whole picture using all of the data products and numerical simulations,” Delamere said.
Three UAF students doing their doctoral research at the UAF Geophysical Institute also participated. Matthew Blandin supported optical operations at Wallops Flight Facility, Kylee Branning operated cameras on a NASA Gulfstream III aircraft out of Langley Research Center, also in Virginia, and Nathan Barnes assisted with computer modeling in Fairbanks..
The experiment also included researchers and equipment from Dartmouth College, the University of New Hampshire and Clemson University.
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