Composition and Structure Measurements in an Ionospheric Barium Cloud

R. Narcisi

Jan 1981 · Air Force Geophysics Laboratory, Air Force Systems Command, United States Air Force

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A 48 kg barium payload was launched from Eglin Air Force Base, Florida on 12 December 1980 at 2311 GMT and detonated at 183.7 km. At 2342:50.25 GMT, a second rocket, instrumented with an ion mass spectrometer and pulsed plasma probes, was fired to traverse the barium cloud. Composition, ion density, and structure measurements were acquired up to 241.2 km in both the natural and disturbed ionosphere. The rocket penetrated the barium cloud between 147 and 184 km. In addition to the Ba+, Ba++ produced by H Lyman alpha ionization, and Ca+, an impurity in the barium were detected in the cloud. A peak barium ion concentration of about 6,000,000 ions cu cm was measured at 161 km where the ionospheric NO+ and O2+ ions were essentially eliminated by large recombination loss. The bottom side of the barium cloud had a relatively smooth structure while the top side showed significant density fluctuations. The first experimental evidence of a theoretically predicted E region 'image cloud' was found in the form of an enhanced NO+ layer just below the barium cloud. Unexplained wave-like density variations in O+, NO+, and O2(+) also were seen above the barium cloud to 195 km. A quantitative estimate of the outgassing water vapor concentrations near the payload's surface was made using the fast change transfer rate coefficient for O+ + H2O yields H2O+ + O that created the observed water vapor ions.