TABLE 1 PLASMA PARAMETERS/OTV (ORBITAL TRANSFER VEHICLE) is limited to —50 days and thus a high launch frequency of the heavy launch vehicles is required. The total number of SPSs envisioned to supply a substantial amount of the U.S. electrical power requirements will require construction and transport over a period of decades (6). The transfer orbit from low earth orbit to geosynchronous earth orbit will be a spiral that is most tightly wound at lower altitudes. Hence the orbital transfer vehicles will be spending most of their time near the earth where most of the deposition of the 5 keV Ar+ will occur, tending to maximize environmental effects there. The ion beam emitted by the orbital transfer vehicle will have a transverse velocity spread of -0.4 Vb where Vb = 150 km sec 1 is the beam velocity (2). The beam will therefore spread rapidly during its transit time through the plasmasphere (100-200 sec). Typical plasma parameters for an orbital transfer vehicle are shown in Table 1 (2). 3. ION BEAM DYNAMICS AND ION LIFETIMES IN THE PLASMASPHERE In this section we outline the physics of ion beam dynamics and mass loss in processes controlling the magnetosphere. In addition, the lifetimes of the ions constituting the mass loss are discussed. For more detail with a discussion of the underlying physics we refer the reader to our companion paper (3). The ion beam formed by the exhaust of the cargo orbital transfer vehicle possesses a sheath on its outer surface with a thickness of about a Debye length. Within this sheath the polarization electric field responsible for the cross field transport decreases and hence the sheath ions are slowed and inhibited from traversing the local magnetic field with the bulk of the beam. As a consequence of this sheath effect the ion beam constantly loses beam ions leaving them behind during the beam’s motion through the near earth space environment. Curtis and Grebowsky (3) showed that plasma instabilities are ineffective in stopping the beam in the plasmasphere due to the constraints on plasma wave amplification imposed by the rapid change in the diverging beam density. Further, mass loading of the beam by the ambient plasma as studied by Scholer (7) does not appear capable of slowing the bulk of the beam due to its transalfvenic velocity in some regions of space and due to its supersonic motion everywhere. The total mass loss of the ion beam in the magnetosphere is approximately \%-10%
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