Nonresonant excitation of surface waves by a normal electric field
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LINEAR PHENOMENA
Nonresonant Excitation of Surface Waves by a Normal Electric Field1 Yu. A. Akimov Karazin Kharkov National University, Institute of High Technologies, pr. Kurchatova 31, Kharkov, 61108 Ukraine Received August 03, 2005; in final form, February 08, 2006
Abstract—A study is made of nonresonant parametric excitation of surface waves by a spatially uniform, timedependent electric pump field directed perpendicular to a plane plasma–dielectric interface. A set of equations is derived that describes the dynamics of surface wave excitation. Expression for the growth rate in the linear stage of instability is obtained, and the threshold amplitude of the external electric field above which the parametric instability can occur is found. The spectrum of the excited waves is analyzed. PACS numbers: 52.35.Mw, 52.40.Hf DOI: 10.1134/S1063780X06110055 1
1. INTRODUCTION Intensive research on surface wave (SW) parametric instability in bounded plasmalike media dates from the 1970–1980s. This research was mainly motivated by the necessity of solving the problem of energy input into the working volume of plasma installations, including controlled fusion devices. Therefore, the main attention in these studies was focused on the parametric excitation of SWs due to the induced scattering of electromagnetic waves incident from a vacuum or dielectric on a semibounded plasma [1–7]. In recent years, this research has received further development in studies of SWs excited during the irradiation of solid targets with ultrashort intense laser pulses [8–15]. Another line of research on SW parametric instability is related to the excitation of SWs by an external homogeneous electric pump field. The effect of a pump field parallel to the medium interface was thoroughly investigated in [16–19], while SW excitation in an unmagnetized plasma by a high-frequency electric field perpendicular to the interface has been studied much more poorly; see, e.g., [20], where the resonant interaction between an ion-acoustic surface wave and an improper electromagnetic wave in a semibounded nonisothermal plasma was considered. In contrast to that paper, our research is aimed at studying a nonresonant parametric instability of two SWs propagating in opposite directions in a cold isotropic plasma that is in a high-frequency electric field normal to the plasma boundary. 2. DISPERSION RELATION AND FIELD DISTRIBUTION OF LINEAR SWs Let us consider a semibounded homogeneous dissipative isotropic plasma that is in contact with a dielec1 The
tric. Let the z axis is directed along the wave propagation direction, while the x axis is perpendicular to the plasma–dielectric interface. The plasma and the dielectric occupy the half-spaces x > 0 and x < 0, respectively. In this case, SWs propagating along the plasma–dielectric interface are E waves and possess two electric field components, E = (Ex, 0, Ez), and one magnetic field component, H = (0, Hy, 0) [21]. The wavenumber kz and frequency ω of these waves satisfy the following relationship: 2 2 ε p εd -, k z =
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