Wednesday, 30 November 2005

Refreshments: 1:15 - 1:30 P.M., Talk 1:30 - 2:30PM

Hanscom AFB Conference Center, Bldg 1106 (formerly AFRL Science Center)

Summary: The earth's atmosphere is a source for a host of optical emissions including the airglow, primarily resulting from chemical reactions, and the aurora, generally caused by impact of energetic particles. Similar emissions can also be stimulated by artificial means, in particular, high-power radio waves interacting with the ionospheric plasma. Weak artificial optical emissions have been produced for decades in ionospheric "heating" experiments, where they serve as indicators of particle energy and the spatial distribution of the interactions. Recent optical observations from high-latitude heating facilities in Alaska and Norway have revealed a large number of unexpected effects. These include a strong affinity for the magnetic field direction, ring-like structures well away from the beam center, spatial self-reconfiguration of the interaction region with time, and apparent modification of the natural aurora by structures bright enough to be seen with the naked eye. Although ionospheric skywriting or street-lighting most likely remain decades away, nearer-term potential uses of such technologies include ionospheric irregularity and aeronomy studies and exploration of magnetosphere-ionosphere coupling.

Biography: Todd Pedersen received a bachelor's degree in Japanese from Brigham Young University in 1988. After spending several years working as a translator for firms including Seiko Instruments Inc., he began a graduate program in space physics at Utah State University in 1992 and received his doctorate in 1998, producing a dissertation on incoherent scatter radar observations of polar cap ionospheric patches in Greenland. He was hired directly out of school by the Air Force Research Laboratory at Hanscom Air Force Base, Massachusetts, where he has since become actively involved in optical observations of the ionosphere and ionospheric heating, and has carried out numerous field experiments around the world to image natural airglow and aurora as well as artificial optical emissions. His recent auroral heating work was featured in Nature and has attracted international media attention.