UNCLASSIFIED/UNLIMITED UNCLASSIFIED/UNLIMITED Studies of Ionospheric Processes in the Atmosphere and the Laboratory

The ionosphere can be studied in a variety of ways – observation, modeling, and the simulation of ionospheric processes in the laboratory. Over the last several years we have carried out such studies in two ways, from ground-based observations using astronomical sky spectra, and from laboratory investigations. At altitudes above 200 km, the dominant atmospheric particles are oxygen atoms, and for any collisional studies it is always necessary to inquire as to the role of these atoms. One example is given by the oxygen red line, a ubiquitous emission in dayglow, nightglow, and aurorae, both artificial and induced. In order to understand both the intensity and the decay of this long-lived emission, one must establish the effect of collisions of the red line emitter – O ( 1D) – with ground-state O-atoms. The conclusion reached from application of the laboratory results to atmospheric observations is that the dominant loss process at altitudes relevant to ionospheric modification experiments is in fact collisions with O ( 3P). It follows that measuring the O ( 1D) decay rate provides a measure of the local O-atom density. Another example comes from observation of the O2 Atmospheric bands, which normally emit in the mesosphere, but can also be seen from the lower thermosphere. Again, it is essential to find out how the excited O2 molecules interact with O-atoms. In this paper we demonstrate how laboratory studies are used to address these questions, how the results are applie