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

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.

Nonlinear structures and anomalous transport in partially magnetized E×B plasmas

“…In the dissipative regime, the negative energy wave is excited due to resonance absorption of wave energy by electron and ions. 8 The reactive instability may occur due to coupling of waves with positive and negative energy. 17,28 For propagation strictly perpendicular to the magnetic field and electrons subject to E × B drift, the resonant condition is ω − k · v E − mΩ ce = 0.…”

“…The electron cyclotron drift instability is of particular interest because it does not require any gradients and may be active in a homogeneous collisionless plasma with electric field perpendicular to the magnetic field. 3,4,8 Largeamplitude waves present in satellite observations of bow shock crossings have been associated with current driven electron-cyclotron instabilities. [9][10][11][12] Presence of the electron cyclotron instabilities has been confirmed by numerical simulations of bow shocks.…”

“…17,28 For propagation strictly perpendicular to the magnetic field and electrons subject to E × B drift, the resonant condition is ω − k • v E − mΩ ce = 0. It has been noted that electron cyclotron drift instability (ECDI) due to linear and/or nonlinear effects 5,8,20,29,30 may in some regimes become similar to the ion-sound instability in unmagnetized plasmas. The transition of the ECDI instability, which in essential way depends on the presence of the magnetic field, into the regime which resembles the ion sound instability in absence of the magnetic field has become a common theme of many earlier works in the literature 30,31 .…”

High-frequency heating in Tokamaks

“…If the ion and electron temperatures are comparable, the energies of the high-frequency motion of particles are at least by the same orders of magnitude less than their mean thermal energies. Thus, the instabilities of the types considered in Refs [9,10] cannot appear in the considered region. It is well known [11] that a decay instability can occur in a sufficiently strong magnetosonic wave, the growth rate being 7% (M -1) w, where M is the Mach number.…”

Exact electron-acoustic solitary waves

“…Such plasmas are common to ring current systems in the earth's magnetosphere, magnetospheric tail, magnetotron devices, and plasma accelerators. Linear properties of electron-acoustic waves have been extensively studied by Sizonenko & Stepanov (1967), Arefev (1970), Lashmore-Davis & Martin (1973), and Goedbloed, Pyatak & Sizonenko (1973). According to the linear theory, these waves propagate almost across the magnetic field with frequency co ce > w > o) ci , and wavelength p t -> A > p e .…”