Plasma instability in the electric field of an ion-cyclotron wave

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Abstract
The authors investigate the stability of a collisionless plasma in which the ions are moving relative to the electrons at right angles to the applied magnetic field, under the influence of the electric field of an ion-cyclotron wave, with a velocity u⃗⊥ that is less than or commensurate with the thermal velocity of the ions vi. They study the excitation of longitudinal electrostatic oscillations with frequency and growth rate significantly greater than the gyrofrequency of the ions, but significantly less than that of the electrons, and with a wavelength significantly less than that of the ion-cyclotron wave. It is shown that, when the ion temperature Ti is significantly higher than the electron temperature Te. electron-acousticoscillations are excited in the plasma. The excitation of these oscillations by resonance ions is possible even when u⊥ ≪ vi. When Te ≫ Ti ion-acoustic oscillations are excited in the plasma, the build-up of these oscillations by the ions being the result of absorption by resonance electrons. When Te ⪆ Ti oscillations are excited if the velocity of the ion beam u⊥ is somewhat greater than the thermal velocity of the ions. When Ti ≫ Te. the reactive effect of the oscillations causes the function representing resonance ion distribution in the beam direction to level off and form a plateau. When Te ≫ Ti the unstable ion-acoustic oscillations spread the resonance electron distribution function, which is equivalent to electron heating, and slow down the ion beam.

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