Ar+ beam at LEO primarily in the azimuthal direction (perpendicular to the magnetic field) as in Figure 1 until the COTV is more than ~ 200 km from LEO. This thrusting schedule would require orbit plane-change operations to be performed in the magnetosphere rather than at LEO. This is an interesting case in which environmental effects may feed back upon the system design concept. Any form of airglow intensification in the optical range will affect the signal background intensity for optical astronomy based on the ground. However, to put the impact of the COTV argon beam into perspective, it must be pointed out that the airglow modification discussed above is limited to the region at the foot of the field line traversed by the argon beam at LEO. An interference source of such limited spatial and temporal scale must be considered in the context of general optical pollution of the night sky by global industrialization. Thus, for reasons not related to SPS effects, optical astronomy in the next decades will likely be possible only in space. The effects discussed here will not affect optical astronomy in space since astronomical observations in space are likely to be made above the argon airglow layer (~ 250 km). These considerations obviously depend on the signal frequency, for there are other processes which may affect the optical background intensity, e.g., Section V. B. B. Artificial Ionospheric Current Here we move away from LEO and attempt to assess the prompt effects of the interaction between the Ar+ beam and the magnetosphere as described in Section III. B and Figure 8. We recall that the Ar+ beam exchanges energy with the entire ambient magnetosphere (in the flux tubes traversed by the beam) by the propagation of Alfven shock waves, probably before the majority 39
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