Shooting the (Atmospheric) Breeze with Dr. David J. Knudsen

Dr. David J. Knudsen is Associate Professor of Physics and Astronomy at the University of Calgary. Since coming to Canada in 1992, he has taken part in five Canadian space missions. He has been responsible for developing instruments and for analyzing data collected during missions. His work centres on the causes and consequences of the aurora.

“An encyclopedia article on the aurora gives the impression that this phenomenon is well understood. However, some basic questions remain unanswered despite decades of research. Such articles usually state that the charged particles causing aurora come from the solar wind, but auroral electrons have thousands of times more energy than those of the solar wind.

“It's also possible that auroral electrons don't originate from the solar wind at all, but are drawn from the cool, dense ionosphere into the magnetosphere, where they are energized through mechanisms that are not yet entirely known. “Using detectors as well as rocket and satellite measurements, my work is to measure ionospheric temperatures and winds-winds act as tracers of electric fields that power the aurora. We must fully understand the massive electrical circuit that the auroras are part of before we can accurately explain them.”

Auroras take on spectacular and dynamic forms-curtains, folds, vortices, pulsating patches, flickering rays-whose variable structure is poorly understood. (Photo: © Jouni Joussila)

Dr. Knudsen is involved in the captivating Swarm mission of the European Space Agency's (ESA) Earth Explorer program.

Swarm is an Earth Explorer Opportunity Mission candidate. The Swarm constellation will study the dynamics of the Earth's magnetic field and its interactions with the Earth system. (Image: ESA)

“The Earth's geomagnetic field is changing rapidly, to the degree that the magnetic north pole may leave Canadian territory within the next few decades. There is even speculation that the Earth's magnetic dipole is in the process of flipping, north to south, as geological records show it has done every few hundred thousand years. The Swarm mission will study the geomagnetic field evolution with precision, using a fleet of three satellites orbiting in the ionosphere. ESA has invited Canada to provide all three Swarm satellites with a Canadian electric field instrument (CEFI) based on the suprathermal ion imager (SII)-a Canadian particle detector design that has already proven its capability-in order to gather precise measurements of ion winds.”

GEODESIC, a successful Canadian mission launched in Alaska in 2000, had an SII aboard. Dr. Knudsen led that mission, and he and his team made some interesting findings when they analyzed the data of the 15-minute rocket flight. Missions such as GEODESIC require custom instrumentation. “The SII and similar instruments are so highly specialized that it's impossible to acquire them commercially. In building a device, you become familiar with its capabilities and performance, and this familiarity helps when analyzing the scientific data it collects."

Aurora borealis over Finland. (Photo: © Jouni Joussila)

Space launches are incredibly violent, where instruments get a real shake-up, so glitches can be expected. "During SII's first flight, a malfunction caused the booms holding it and its twin to deploy prematurely. Despite the violent deployment, the SII hung on and was able to complete its mission. One of my students trying to make sense of the data realized that everything came into focus if he considered the resulting position of the boom's early deployment."

The boom deployment is being tested. (Photo: Bristol Aerospace, from the archives of the Institute for Space Research, University of Calgary)

Dr. Knudsen reflects, "The auroras, at the very threshold of space, are just far enough away to make it a serious challenge to get an instrument there in one piece, yet so tantalizingly close as to make the idea of going back irresistible."