Ion-acoustic surface waves in a semi-bounded Lorentzian plasma

Abstract

The dispersion properties of the ion-acoustic surface waves propagating on a boundary of semi-bounded Lorentzian (kappa) plasma is kinetically investigated. The real and the imaginary parts of the wave frequency are obtained as functions of the normalized wave number k(x)lambda(e) where k(x) is the x-component of the wave number and lambda(e) is the electron Debye length. The phase speed of the wave is found be decreased as the spectral index kappa of the Lorentzian distribution function is decreased. In the long wavelength limit, it becomes a constant which depends on the value of kappa. The wave displays the resonance at omega(r) = omega(pi)/root 2 as expected in the case of a Maxwellian plasma. The imaginary part of the wave frequency appears to be negative which exhibits the linear wave dissipation in a collisionless plasma called Landau damping. The maximum damping rate is obtained as gamma(max) = 0.14M(kappa)root m/M, where M-kappa is kappa-dependent factor and m/M is the electron-ion mass ratio. Landau damping disappears as k(x)lambda(e) -> infinity.