ON THE THEORY OF CURRENT INSTABILITIES IN PLASMA

Abstract

The main work in this thesis is to study and investigate the excitation of current Buneman's instability (electron-ion two stream instability) which takes place in plasma due to the relative motion of electrons and ions. We consider a different plasma temperature regimes, i.e., isothermal (Te "' T;) and nonisothermal (Te »I; or Te «I;) plasmas. Also, we consider different plasma states, i.e., and unmagnetized and magnetized; collisionless and collisional; homogeneous and inhomogeneous plasmas; without and with applied external electric field.

A linear, quasilinear and nonlinear dispersion relations are derived and solved in 1-D to obtain the frequencies and growth rate of instability under the conditions when the current velocity is slightly exceeds the instability threshold velocity( u=u-ucr <<uc,). Conditions of excitation of current Buneman's instability are also obtained. The possibility of instability depression is discussed for different plasma temperature regimes. External magnetic or electric fields, plasma inhomogeneity, ratio of electron to ion temperature (Te IT;) are found to play a crucial roll via the saturation of such instability.