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Three NASA-funded rockets are set to launch from Poker Flat Research Range in Fairbanks, Alaska, in an experiment that seeks to reveal how auroral substorms affect the behavior and composition of Earth's far upper atmosphere.
The experiment's outcome could upend a long-held theory about the aurora's interaction with the thermosphere. It may also improve space weather forecasting, critical as the world becomes increasingly reliant on satellite-based devices such as GPS units in everyday life.
The University of Alaska Fairbanks (UAF) Geophysical Institute owns Poker Flat, located 20 miles north of Fairbanks, and operates it under a contract with NASA's Wallops Flight Facility in Virginia, which is part of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The experiment, titled Auroral Waves Excited by Substorm Onset Magnetic Events, or AWESOME, features one four-stage rocket and two two-stage rockets all launching in an approximately three-hour period.
Colorful vapor tracers from the largest of the three rockets should be visible across much of northern Alaska. The launch window is March 24 through April 6.
The mission, led by Mark Conde, a space physics professor at UAF, involves about a dozen UAF graduate student researchers at several ground monitoring sites in Alaska at Utqiagvik, Kaktovik, Toolik Lake, Eagle, and Venetie, as well as Poker Flat. NASA delivers, assembles, tests, and launches the rockets.
"Our experiment asks the question, when the aurora goes berserk and dumps a bunch of heat in the atmosphere, how much of that heat is spent transporting the air upward in a continuous convective plume and how much of that heat results in not only vertical but also horizontal oscillations in the atmosphere?" Conde said.
Confirming which process is dominant will reveal the breadth of the mixing and the related changes in the thin air's characteristics.
"Change in composition of the atmosphere has consequences," Conde said. "And we need to know the extent of those consequences."
Most of the thermosphere, which reaches from about 50 to 350 miles above the surface, is what scientists call "convectively stable." That means minimal vertical motion of air, because the warmer air is already at the top, due to absorption of solar radiation.
When auroral substorms inject energy and momentum into the middle and lower thermosphere (roughly 60 to 125 miles up), it upsets that stability. That leads to one prevailing theory - that the substorms' heat is what causes the vertical-motion churn of the thermosphere.
Conde believes instead that acoustic-buoyancy waves are the dominant mixing force and that vertical convection has a much lesser role. Because acoustic-buoyancy waves travel vertically and horizontally from where the aurora hits, the aurora-caused atmospheric changes could be occurring over a much broader area than currently believed.
Better prediction of impacts from those changes is the AWESOME mission's practical goal.
"I believe our experiment will lead to a simpler and more accurate method of space weather prediction," Conde said.
Two two-stage, 42-foot Terrier-Improved Malemute rockets are planned to respectively launch about 15 minutes and an hour after an auroral substorm begins. A four-stage, 70-foot Black Brant XII rocket is planned to launch about five minutes after the second rocket.
The first two rockets will release tracers at altitudes of 50 and 110 miles to detect wind movement and wave oscillations. The third rocket will release tracers at five altitudes from 68 to 155 miles.
Pink, blue, and white vapor traces should be visible from the third rocket for 10 to 20 minutes. Launches must occur in the dawn hours, with sunlight hitting the upper altitudes to activate the vapor tracers from the first rocket but darkness at the surface so ground cameras can photograph the tracers' response to air movement.
By Rod Boyce
University of Alaska Fairbanks Geophysical Institute
