On the other hand the injected 3.5-keV Ar+ ions might be scattered out of the beam by some mechanism and come to constitute a plasma having a 3.5-keV temperature. In this latter case the injected argon plasma would contribute directly to the ring-current population, and the O+ drawn up from the F-region would constitute the cold-plasma additive. The cold O+ would tend to suppress the electromagnetic proton-cyclotron and helium-cyclotron instabilities of the natural ring current of frequencies below the oxygen gyrofrequency (e.g., Cornwall and Schulz, 1971). However, the hot argon plasma would become anisotropic with time because of charge exchange, and would thus constitute an additional source of free energy for instability (cf. Cornwall, 1977). The argon-cyclotron instability would occur at frequencies somewhat below the argon gyrofrequency. Its growth rate would be enhanced by the presence of cold O+ in the plasmashere (cf. Cornwall and Schulz, 1971). The argon- cyclotron waves would tend to resonate with relativistic electrons (cf. Thorne and Kennel, 1971) and thus to facilitate the loss of such trapped electrons into the atmosphere. These energetic Ar+ begin to act like a man-made ring current of [[spi:math]] 1 keV ions, with a residual pitch-angle anisotropy left over from the initial injection nearly perpendicular to [[spi:math]]. Just what energy and anisotropy are left after the beam-plasma interactions is not know at present; they need to be evaluated in order to make a more complete assessment. This ring current acts much like a natural one, subject to charge exchange, Coulomb scattering, and wave-particle interactions. If charge exchange is the dominant loss process (Coulomb scattering and other forms of energy loss do not effectively remove argon), this ring current may have ~ 1030 ions in it, comparable to the natural ring current. A major difference is that the argon ring current is mostly inside the plasmasphere, while the natural ring current penetrates 51
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