of plasma and electromagnetic waves. The effects on a particular important mode, the electromagnetic ion cyclotron wave, have been dealt with in detail in the foregoing Subsections. Thus, even the beam-magnetosphere interaction process, is not expected to be entirely a smooth deceleration by action of the Alfven shocks alone, plasma turbulence stimulated by the plasma beam will undoubtedly play a contributory role. From a quasi-thermodynamic point of view, the beam-plasma system is highly unstable because the uniform streaming energy of the beam and the gradients of density and temperature set up between beam plasma and ambient magnetospheric plasma contain free energy. The evolution of this free energy into bound thermal energy is likely to take place by action of plasma instabilities which generate various wave modes in the plasma. Here, we shall first attempt to sort out the zoo of plasma instabilities which would be expected from SPS plasma injections. Some of these, such as the electromagnetic ion cyclotron instability, have been discussed previously; however, we have not yet discussed the effects of instabilities which generate plasma density irregularities which scatter communication signals. The second part of this Subsection shall be devoted to effects upon space communications. The specific causes of plasma instabilities associated with argon plasma injection are a) relative streaming of one plasma (Ar) into another (ambient), b) velocity shear in the argon beam, c) spatial gradients of plasma parameters and d) residual temperature anisotropies left over after beam thermalization. A more comprehensive discussion of plasma instabilities in the magnetosphere can be found in Hasegawa (1975), although this reference does not specifically address SPS effects. The early consequence of such instability effects is the rapid amplification of thermal noise to appreciable amplitudes, such that the beam itself becomes diffused. Thus, plasma instabilities contribute to beam stopping; however, the question of how important these are in 57
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