Linear and nonlinear characteristics of high frequency electrostatic drift waves in absence of collisions

Abstract

High frequency electrostatic drift waves are shown as hybrid modes generated by mixing with cyclotron dynamics and grow at the expense of cyclotron modes due to mode coupling effects. The role of density gradient is to break the symmetry between the two cyclotron branches with strong values of the gradient causing the branch modified by drift to overlap with the cyclotron branch leading to a mode coupling instability. The analysis is carried out in the framework oof a fluid model without invoking collisional or finite Larmor radius effects. A second order nonlinear equation with variable coefficients has been derived to govern the dynamics of high frequency electrostatic drift waves in a moving frame of (2+1) spatio-temporal dimensions to show the wave characteristics in various parameter ranges. The possibilities of excitation of the high frequency electrostatic drift waves have been explored in the context of certain laboratory and astrophysical plasma systems including tokamaks and solar corona where the existence of steeper density gradients is more probable.