signal scintillation effects at carrier frequencies of ~ 1 GHz. Currently, most civilian and military communication and navigation systems operate in this frequency region. Drift instabilities draw their energies from the free energy available in plasma density gradients and are instrumental in the diffusion of plasma density concentrations. Observational evidences of drift-induced density striations are available from numerous plasma injections in the magnetosphere ranging from barium releases to nuclear detonations at high altitude. Since these instabilities are not directly related to the beam-exhaust, but are related to the plasma cloud after the streaming plasma beam motion has been randomized, we would expect that rather large areas will be striated. This has recently been confirmed by the CAMEO barium release experiment (Smith et al., 1979). Further, since there is a virtual zoo of drift related instabilities, the scale sizes of the density irregularities will probably be broadband; although, if natural equatorial spread-F condition is any guide, drift- induced density irregularities will probably affect VHF and UHF more severely than frequencies in the gigahertz range. In summary, our assessment effort has identified that plasma instabilities will likely occur and play a significant role in the energy evolution of SPS plasma injections by the COTV. The electrostatic modes of these plasma instabilities generate density irregularities in the form of plasma striations aligned with the geomagnetic field. These irregularities are of the proper size to be potential scattering centers for satellite communication signals, causing signal scintillation effects. The strength of communication interference effects cannot be determined in the present assessment effort because this will require more complete research work. In the natural case, signal scintillation effects are primarily caused by plasma irregularities below 1000 61
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