Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Paul J. Wolf, PhD


Barium and strontium release experiments were conducted throughout 1991 from the Combined Release and Radiation Effects Satellite (CRRES) to study both natural and man-made disturbances in the earth's ionosphere. A mass spectrometer on the spacecraft counted the Ba and Sr ions as the cloud expanded. In this study, data from the G-1 (in sunlight) and G-11b (in darkness) releases were modeled to understand the source of the ion signals. The model reproduced the Ba+ sun data well assuming photoionization (τ = 28 s) was the primary ionization mechanism. However, it was not able to account for the remaining ion data: (a) Sr has a very long photoionization time constant (τ = 1920 s) and model/data comparisons showed that the Sr ionization rate must be about 60 times greater than the photoionization rate to account for the observed signals. (b) The charge transfer ionization process between Sr/Ba and ambient O+ was not sufficient to reproduce the ionization rates for Sr sun data and Sr/Ba dark data. Processes potentially responsible for the CRRES data include charge stripping and critical velocity ionization (CW). Split peaks in the ion data were also investigated and found to be due to either an instrument sensitivity feature or a two process mechanism.

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