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Strategic Characteristics of Dynamics Explorer. 1. Retarding Ion Mass Spectrometer and the Consequences for Core Plasma Measurements

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Technical rept. for Sep 1989

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The Retarding Ion Mass Spectrometer RIMS on the Dynamics Explorer I DE I satellite has provided a new range of data, and challenges for studies of the core plasma of the magnetosphere. Analysis of the RIMS data provides a measure of the satellite potential in the inner magnetosphere. As the satellite leaves the inner plasmasphere, it begins to charge positively, crossing the 0 V mark at about 1000cc. The potential rises slowly initially, reaching about 1 V near the plasmapause, at the 100cc point. At lower densities, the potential rises relatively rapidly, reaching 5 V or greater at the 10cc point. For satellite potentials of 1 to 5 V, portions of the ion distribution function are lost to measurement because the ions are repelled by the satellite. In particular, in a multi-temperature plasma, the cold component is easily lost in this potential density regime. It is in this regime where aperture bias techniques have been successfully used, particularly in measurements of field- aligned ion flows such as the polar wind, which have sufficient kinetic energy to overcome electrostatic barriers in front of the aperture plane. At lower densities 10cc, the satellite potential can exceed 5 V. At such potentials the core plasma is lost to the RIMS, and even the aperture bias techniques are no lower successful. Keywords Spacecraft charging Thermal plasmas Mass spectrometry.

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  • Atmospheric Physics
  • Electric and Ion Propulsion
  • Astronautics

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