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The interpretation of space shuttle measurements of ionic species

1987; American Geophysical Union; Volume: 92; Issue: A1 Linguagem: Inglês

10.1029/ja092ia01p00273

2156-2202

G. E. Caledonia, James C. Person, Daniel E. Hastings,

Solar and Space Plasma Dynamics

Measurements of ionic species made in the space shuttle bay area during low‐earth orbit are interpreted within the framework of a kinetic analysis that incorporates shuttle cloud/ambient interactions, flow, and electromagnetic phenomena. This analysis indicates that a pressure of water vapor near the shuttle surface of 10 −6 torr is consistent with [H 2 O + ]/[O + ] and [H 3 O + ]/[H 2 O + ] ratios of 0.1 and 0.2, respectively, and the latter ratio is within the range of measurements. For CO 2 the analysis shows that a [CO 2 + ]/[O + ] ratio of 0.01 is consistent with a CO 2 pressure near the shuttle of 8 × 10 −8 . For these conditions the dominant formation of ions is by charge exchange from ambient O + ions, and the dominant loss of ions is by parallel flow along the magnetic field lines. In addition, Monte Carlo calculations of the slowing of the incident O + ions indicate that charge exchange with H 2 molecules occurs before the ions have lost a significant amount of energy when the H 2 O pressure near the shuttle surface is less than 10 −6 to 10 −5 torr.