comparison to the action of Alfven shocks is not yet known, since beam-plasma instabilities have not yet been investigated thoroughly in this context. A list of the major plasma instability species which are relevant to SPS plasma injection is given in Table III. This table is constructed in the hope of classifying and summarizing the characteristics and effects of the zoo of plasma instabilities which may be involved in the evolution of the argon beam free energy. The entries in the "Instability" column, running from top to bottom is meant to roughly parallel the sequence of this evolution. These involve not only the dense (1-100 cm-3 ), relatively cold (~ 1 eV) thermal plasma, but also ring-current and radiation-belt particles whose energies range from keV’s to MeV’s. Another way of classifying the plasma instabilities may be by means of the time and spatial scales involved. This is especially relevant to the electrostatic modes which generate plasma density irregularities interferring with space communications. A partial list of processes in order of increasing time scale: cross-field current-driven instabilities (time scale Re/V ~ milliseconds, where Re is the electron Larmor radius); ion electrostatic modes (time scale = [[spi:math]] is the Ar+ plasma frequency [[spi:math]] 10-2 sec-1); proton electromagnetic cyclotron (EMC) modes (time scale [[spi:math]] 0.1 sec). These are important because they can cause local transfer of energy from the beam to the plasmasphere (first two modes), or because they affect natural magnetospheric processes. There are also magnetohydrodynamic instabilities of considerably larger time scale (e.g., Perkins et al., 1973), which cause deformations of the beam (striations, etc.), but which probably do not transfer much energy from beam to plasmasphere. Kelvin-Helmholtz and drift wave instabilities in Table III are some examples. The spatial scales (perpendicular to B) are, as noted above, the electron and ion Larmor radius, probably with the argon ion 58
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