DENSITY IRREGULARITIES IN THE WEAKLY IONIZED NONUNIFORM PLASMA

A rigorous theory of small disturbances in a weakly ionized nonuniform plasma in crossed electric and magnetic fields is developed. Regular inhomogeneities both of plasma density and collision frequency are tak en into account. The analysis of eigenvalues and eigenmodes is perform ed in the electrostatic approximation. It is shown that the inhomogene ity of collision frequency is of fundamental significance, is responsi ble for the creation of boundary conditions, and determines the range of existence and spatial structure of eigenmodes. It is also shown tha t there is no localized mode associated with steep plasma density grad ients. The dispersion relation and altitude behavior of eigenmodes are investigated in the WKB approximation in the case of the exponential profile of collision frequencies, which is natural for the ionospheric E-region. (C) 1997 American Institute of Physics. [S1070-664X(97)0411 1-6].