Convective excitation of quasistatic waves in an inhomogeneous anisothermic plasma II. Nonlinear estimates

Nonlinear effects stabilizing the convective instabilities excited in an anisothermic plasma (T_etT_i) at the plasma boundaryaV_s/_Bi) are discussed. Waves having in the linear theory (Part I) the highest growth rates (_Bi) saturate at first. Being excited by a small part of slow plasma electrons (_zTe) only, they saturate at a relatively low level. Further, surface waves with lower frequencies and higher phase velocities (_ph/k_z) become dominant and a broadening of the plasma boundary occurs. For their saturation nonlinear interaction is more important than the quasilinear effects. During the time interval of several_Bi^–1 the longest surface waves withk_yBi/V_s, _Bik_yV_s and_phTe saturate at the absolutely highest level. The plasma boundary broadens in the meanwhile up toaV_s/_Bi. The wave energy is comparable to the whole energy connected with the longitudinal motion of the initially thermal electrons inside this boundary layer. The wave amplitude is large enough to trap the initially cold ions belonging to this layer and heat them up to energies comparable to those of the electron component. The heating process occurs again within several_Bi^–1 and the Larmor radius of the ions is then comparable toV_s/_Bi. Further evolution of the system is governed by the unstable local perturbations.He leaves of absence from thePhysical and Technical Institute, Kharkov, USSR.