The interaction of the solar wind—variable streams of charged plasma from the Sun—and Earth’s atmosphere produces auroras. These northern and southern lights dance across the night sky and have mesmerized and inspired observers for centuries. For scientists, this dance of light also leads to many questions about how space weather affects Earth’s atmosphere.
In late January 2015, NASA-funded scientists launched a rocket-borne experiment into the northern lights in order to learn more about how they heat the planet’s atmosphere. The Auroral Spatial Structures Probe (ASSP) was launched at 5:41 a.m. on January 28 from the Poker Flat Research Range about 50 kilometers (30 miles) north of Fairbanks, Alaska. The research team captured time-lapse photos of the Oriole IV sounding rocket and payload amidst the aurora borealis (above) and at the moment of liftoff (below).
“This is likely the most complicated mission the sounding rocket program has ever undertaken and it was not easy by any stretch,” said John Hickman, operations manager of the NASA sounding rocket program office at Wallops Flight Facility. “It was technically challenging every step of the way.” All of the rocket-borne experiments were launched from Poker Flats, a site often used by NASA for suborbital sounding rocket launches.
The ASSP carried seven instruments to study the electromagnetic energy that can heat the thermosphere—the second highest layer of the atmosphere—during auroral events. The interaction of waves and particles from the solar wind, Earth’s magnetosphere, and the upper atmosphere can cause “Joule heating.” Essentially, the electrical currents on the edge of space run into a resistant media (the air in the atmosphere) and generate heat in a process similar to that of a toaster coil or electric stove. This heating can expand the atmosphere upward and increase the friction, or drag, on spacecraft and satellites.
The AASP launch occurred just two days after the successful launches of the Mesosphere-Lower Thermosphere Turbulence Experiment (M-TeX) and the Mesospheric Inversion-layer Stratified Turbulence (MIST) experiment. Two pairs of instrumented rockets
were launched about 30 minutes apart to study how turbulence is formed in the presence of inversion layers in the upper atmosphere. This turbulence causes particles to diffuse between atmospheric layers. The MIST launches included the release of harmless trimethyl aluminum vapor to help researchers trace diffusion at high altitude
“Recent solar storms have resulted in major changes to the composition of the upper atmosphere above 80 kilometers (50 miles), where enhancements in nitrogen compounds have been found,” said Richard Collins, upper atmospheric researcher from the University of Alaska. “These compounds can be transported into the middle atmosphere where they can contribute to ozone destruction. However, the meteorological conditions do not always allow such transport to occur. Thus, the impact of solar activity on the Earth is not just about how the Sun is a source of energetic particles, but also how the Earth’s meteorological conditions determine the fate of these particles in the atmosphere.”
Top photographs by Jamie Adkins, NASA. Second photo by Lee Wingfield, NASA. Video copyright Ronn Murray. Caption by Mike Carlowicz, adapted from NASA press releases.