NONLINEAR-ANALYSIS OF THE GRADIENT DRIFT INSTABILITY

An analytical study of the gradient drift instability in the equatoria l electrojet of wavelengths in the order of one kilometer is presented . Different mechanisms, linear, non-local and turbulent, are found in the literature to explain the predominance of the 1 km wavelength in t he electrojet. In the present work a simplified model is proposed in w hich the nonlinear evolution of three coupled modes is followed. By co nsidering that one of the modes attains the stationary state, the evol ution of the other two is obtained, and it is found that they follow e quations of the Lotka-Volterra type. A stable stationary nonlinear sol ution for these equations is also found, and the conditions under whic h periodic solutions are possible are analyzed. (C) 1998 Elsevier Scie nce B.V. All rights reserved. PACS: 52.35.Kt; 52.35.Mw; 94.20.Gg; 94.2 0.Vv.