Beyond the plasmapause, the dominant loss mechanism is charge exchange with pitch angle scattering by plasma turbulence again playing a significant role. Convective fields which will drive the drift motion of the Ar1 ions in the outer magnetosphere may also contribute significantly to the loss rates (8). 4. POSSIBLE ENVIRONMENTAL IMPACT: COMMUNICATIONS A. Communications Effects Due to Plasmasphere Perturbations From our discussion of beam propagation through the plasmaspnere and the resulting deposition of energetic ArT in substantial quantities over distances of several earth radii and with lifetimes of up to a year, we see that substantial changes may be expected in the near earth plasma environment. In this section we deal specifically with possible effects on terrestrial communications of the enhanced precipitation of energetic ions induced by the 5 keV Ar' beam. It is well known that enhanced precipitation of energetic particles occurring during solar Hares can seriously disrupt communications links (9, 10, 11). Fortunately, these naturally occurring disruptions are of relatively short duration (~ days). However, in the scenario which we present here, there is the potential for communications disruptions over periods of decades as a consequence of the continuous construction of an SPS fleet. Due to their initial injection almost perpendicular to the local ambient magnetic field the deposited energetic Ar+ possess a high level of pitch angle anisotropy. This pitch angle anisotropy provides free energy which drives plasma instabilities and hence plasma turbulence. In addition to the plasma turbulence driven by the energetic Ar4 deposited by the beam, short duration turbuience is also generated by the beam itself as it propagates outward through the plasmasphere. Instabilities expected in this case include the beam-plasma instability driven by the beam’s high velocity, drift wave instabilities driven by the density gradient of Ar’ at the beam’s surface, and the Kelvin-Helmholtz instability driven by the velocity gradient near the beam’s surface resulting from the nonuniformity of the polarization electric field. Due to the beam’s short residence time (100-200 sec) in the plasmasphere the effects of these plasma instabilities on the beam’s attenuation will most likely be minor (3). The plasma turbulence will tend to both isotropize Ar as well as the various naturally occurring components of the plasmasphere population. In particular the radiation belt ions will be affected. These ions, mostly protons, are characterized by high energies and fluxes. For energies E ~ 50 MeV, fluxes greater than IO4 cm 2sec 1 are encountered between/. = 1.2 andL = 1.8 and forE> 0.4 MeV, fluxes above 105 cm2sec 1 exist beyond L = 2.0 (12). The high fluxes of high energy protons exist precisely in the region off s 2.0 where most of the Ar4 deposition occurs as shown in Figure 2. Since the turbulence level will be proportional to the number density of Ar+, precipitation effects may be substantial in the inner radiation belt. A specific instability which could give rise to turbulence that could scatter the radiation belt protons into their loss cones is the electromagnetic ion cyclotron instability. This instability would be driven by Arf anisotropy. The electromagnetic ion cyclotron mode as discussed in the literature (13,14) characteristically displays a multiple harmonic spectrum. The fundamental harmonic is the gyrofrequency of the energetic ions which drive the instability. Such spectra have been observed in the earth’s plasmasphere (15) with many harmonic lines extending up to the vicinity of
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