Nonlocal description of plasma instability in the ionospheric F-region

Abstract

Despite intensive research into the processes of formation of inhomogeneous structure, no standard concepts of the major mechanisms of generation of inhomogeneities have been developed at present. This is primarily true of inhomogeneities in the mid-latitude Fregion, where in contrast to the equatorial and high latitude ionosphere, there are no such strong destabilizing factors as intense electric currents and clusters of charged particles. Theoretical study of the mechanism of gradient-drift instability, which has a leading role in the formation of mid-latitude irregularities, is very difficult in such an interpretation of the processes of irregularity disturbances due to the following reasons. The gradient mechanism, generally speaking, might provide an instability sufficiently effective in its development growth rate, but under the condition of large extension of the initial density disturbances, when the damping rate due to disturbances of electric potential aligned relative to the magnetic field is decreased [I]. However, on one hand, the condition of requiring extremely large extension of irregularities is not experimentally confirmed [2]; and on the other h~nd, large extensions in a 15cal approach to analysis of instability based on a dispersion equation becomes invalid due to the fact that in this case the linear dimensions of inhomogeneities become comparable and even exceed the scales of inhomogeneity of the background ionospheric plasma parameters. Thus the problem of developing the description of instability in the ionospheric plasma in a nonlocal approach becomes real when an assumption of the wave character of disturbances in the direction aligned with the magnetic field is not used. One of the first papers on this problem is [3]. In [4, 5] the hydrodynamic and kinetic theory of plasma instability in crossed fields in the framework of a nonlocal approach is developed. However, in these papers the nonlocality is accounted for in the perpendicular direction relative to the outer magnetic field. A diagram of the analysis of the linear stage of plasma instability of the F-region mid-latitude ionosphere in a nonlocal approach is presented belo~including results of numerical estimates of the effectiveness of the instability.