Formation of weak large-scale inhomogeneities in the auroral ionosphere

Interaction of the auroral ionosphere with infrasonic waves propagating at small angles to the horizontal is considered. It is shown that in the case of external electric fields E> or approximately 40 mVxm-1 the infrasonic waves may effectively interact with the F region of the ionosphere by means of conductivity modulation of the ionospheric plasma and the subsequent redistribution of charges at the expense of periodic polarization fields. If angle V between the external electric field E and the horizontal component of the wave vector k satisfies the condition of the spatial resonance V=arc sin (vsub(ph)/usub(d)) (vsub(ph) being the phase velocity of the wave and usub(d) - the velocity of plasma drift), then the amplitude of the travelling perturbation of electron concentration is superior to that of the infrasonic wave