Parametric instability of plasma in a weak alternating electric field under lower hybrid resonance conditions

Parametric excitation of longitudinal oscillations of plasma is studied, in a weak alternating electric field with frequency omega 0 close to that of electron-ion hydrodynamic longitudinal oscillations of 'cold' plasma, omega 1 = omega LH (1+(m i /m e )cos 2 theta ) 1 2/, where omega LH is the lower hybrid resonance frequency. The angle theta between the direction of propagation of the oscillations and the magnetic field is close to pi /2. It is shown that oscillations are excited in the plasma with frequencies omega << omega 0 if the drift velocity of the particles in the steady external magnetic field and the alternating electric field is less than the thermal velocity of the ions. Excitation of electron-acoustic, ion-cyclotron and ion-acoustic waves are considered. Conditions are defined for which the oscillations become unstable, and estimates are given for the maximum growth rates of the oscillations.