It's an AWESOME mission

Change in composition of the atmosphere has consequences for communication, navigation and spacecraft operations. And we need to know the extent of those consequences.

THREE NASA ROCKETS are set to launch from Poker Flat Research Range 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 Geophysical Institute owns Poker Flat, located 20 miles north of Fairbanks, and operates it under a contract with NASA’s Wallops Flight Facility, which is part of the Goddard Space Flight Center.

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 all three rockets should be visible across much of northern Alaska. The launch window is March 24 through April 6.

The mission is led by UAF space physics professor Mark Conde of the Geophysical Institute and UAF College of Natural Science and Mathematics and involves several UAF graduate student researchers at several ground monitoring sites. NASA and some of the nation’s top universities are also participating. 

“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 oscillatory waves that involve both vertical and horizontal motion in the atmosphere?’” Conde said.

Conde simplifies it to an aquarium holding freshwater and saltwater. The saltwater sits on the bottom because it is denser.

“There are two ways to get that salty water to come up. You could have a pump pushing it up,” he said, comparing that to the decades-old theory that the aurora’s heating of the cooler lower thermosphere creates convection.

“Or you could have a little agitator stirring it near the top of the tank, which would be like the higher altitude of the thermosphere.”

He believes that little agitator — a wave that creates atmospheric oscillations where the aurora strikes — has some role and could be the main mechanism driving atmospheric movement.

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 for communication, navigation and spacecraft operations,” Conde said. “And we need to know the extent of those consequences.”

All of the thermosphere, which reaches from about 60 to 350 miles, is what scientists call “convectively stable.” No convection occurs because the warmer air is already at the top, due to absorption of solar radiation.

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

Entrenched theory states that the aurora heats the middle and lower thermosphere and that the resulting vertical convection is the principal driver of thermospheric churn.

Conde believes that acoustic-buoyancy waves are also important and may at times be the dominant mixing force. 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 from simple upward convection alone. 

An acoustic-buoyancy wave is a type of atmospheric wave that combines properties of sound waves and buoyancy-driven gravity waves. Together, they can transport energy and momentum vertically and horizontally through the atmosphere.

The acoustic component is the pressure wave created by the rapid expansion of the aurora-heated localized air mass. The buoyancy component comes from gravity, which tries to restore overall atmospheric stability. This creates outward buoyancy-driven oscillations.

Better prediction of impacts from those changes is the AWESOME mission’s practical goal.

“If you’re in the business of trying to predict what would happen over California, for example, I believe our experiment will allow forecasters to use simpler and potentially more accurate methods of space weather prediction,” Conde said.

What actually is happening when atmospheric mixing occurs?

Most sources of energy enter the atmosphere slowly. However, at high latitudes, the aurora can cause rapid energy deposition and correspondingly rapid atmospheric changes.

An auroral substorm is an intense brightening caused by the sudden release of energy stored in the elongated tail of Earth’s magnetosphere on the planet’s night side.

An auroral substorm can increase the temperature of the neutral atmosphere – called the thermosphere above about 60 miles –  to as high as 1,000 degrees. This creates localized expansion and density increases that create drag on satellites, causing orbital decay and requiring adjustment by satellite operators.

Aurora also increases the density of the ionosphere, which consists of charged particles within the thermosphere. These disturbances in the ionosphere disrupt a variety of communications systems, including GPS units, which are subject to signal delays and producing position errors.

Electric fields can drive high-speed motion of these ions and electrons, accelerating them to up to 2,000 mph. This plasma motion can alter the speed and direction of the neutral thermosphere, changing its local composition and temperature. 

This rapid heating is somewhat like throwing a stone in a lake: It creates ripples, or waves. In the atmosphere, these waves propagate energy in the form of temperature and density variations that can affect satellite operations.

The AWESOME mission is designed to measure timing and strength of waves caused by strong localized aurora.

Two two-stage, 42-foot Terrier-Improved Malemute rockets will respectively launch from Poker Flat about 15 minutes and an hour after an auroral substorm begins. A four-stage, 70-foot four-stage Black Brant XII rocket will launch about 45 minutes after the second rocket. 

NASA has several  sounding rocket configurations , from the diminutive Improved Orion at just under 20 feet to the 70-foot, four-stage Black Brant XII in Conde's experiment. The Black Brant XII can produce about 70,000 pounds of thrust, 2½ times that of an Air Force F-16 fighter jet.

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 third rocket but darkness at the surface so ground cameras can photograph the tracers’ response to air movement.

A dozen UAF student and staff researchers, including Poker Flat Chief Scientist Don Hampton, will operate ground observation stations at Utqiagvik, Kaktovik, Toolik Lake, Eagle, Venetie, and Poker Flat.

The experiment involves several partner institutions: University of Michigan, Cornell University, Clemson University, Penn State, NASA’s Goddard Space Flight Center, NASA’s Wallops Flight Facility, and two nonprofit science organizations — SRI International and The Aerospace Corp.

NASA will have approximately 50 NASA Wallops Flight Facility personnel, including civil servants and contractors, at Poker Flat during peak launch operations. NASA will also have about six people on site from its science team.

Rod Boyce is a science writer at the University of Alaska Fairbanks Geophysical Institute. Email: rcboyce@alaska.edu Phone: 907-474-7185