The existence and structure of large amplitude, stationary, longitudinal plasma oscillations are studied for the case of a simple waterbag distribution of electrons and an immovable background of ions. The analysis employs the one-dimensional Vlasov equation for a plasma of infinite spatial extent. An expression for the maximum amplitude of the oscillations is derived. This maximum amplitude decreases monotonically as the ratio of the electron thermal velocity to the wave phase velocity increases. The structure of the oscillations is expressed analytically in terms of hyperelliptic integrals.

Auroral electron scattering and energy loss are calculated by using for the first time a multiangle equation of transfer at all energies. The results are compared with those obtained by using a Fokker‐Planck equation. Both equations have been solved in terms of their eigensolutions. The equation of transfer has also been solved by numerical integration. Fokker‐Planck solutions agree well with equation of transfer solutions above 3 keV but deviate increasingly at lower energies. A comparison is made between the present Fokker‐Planck results and those of M. Walt at 10 keV, giving good agreement. Energy deposition rates are also found to agree satisfactorily with those obtained previously. The accuracy of integration of the transfer equation is tested by comparing results obtained by the eigenvalue method and the direct integration method. Differences of less than 5% were found at all altitudes, energies, and pitch angles. The predicted backscatter near the upper energy boundary is sensitive to the boundary condition there. Backscatter results for various boundary conditions in energy show both this and the effects of the propagation of the boundary condition toward lower energies. Solutions to the equation of transfer are given between 10 eV and 20 keV, based on a measured auroral electron spectrum. These solutions are compared with similar results by Banks et al. (1974). The results agree above 3 keV but differ below that energy, a finding which is consistent with our comparisons of solutions of the equation of transfer and the Fokker‐Planck equation.

Detailed numerical calculations for the nighttime ionosphere are performed to evaluate the quantitative importance of nighttime radiation fields. Models for the intensities of night sky H I 1216, H I 1026, He I 584, and He II 304‐Å radiation are presented, and the production rates of ion species are calculated. The intensity of the Lyman α and Lyman β radiation fields from terrestrial and extraterrestrial sources is sufficient to maintain the nighttime lower ionosphere at observed electron density levels. Analysis of ion composition data indicates that on winter anomalous days of D region ionospheric absorption the E region is substantially depleted of NO molecules.

The Farley-Buneman instability has been extended to consider higher-frequency shorter-wavelength modes (thus including finite Debye length effects), and these modes are allowed to propagate with a component parallel to the magnetic field (k• • 0). When the current is driven sufficiently hard (drift speeds in the range 2-3 times the ion thermal velocity o•), the growth rates of these modes maximize slightly away from the perpendicular to the magnetic field, and thus the importance of k• • 0 is shown. Although the wavelengths of these maximum growing modes are in the regime of tens of centimeters, the phase velocities are closer to the ion thermal ¾elocity than those modes propagating at 90 ø (k• = 0). Maximum growth rates of off-angle p{opagation for different densities and collision frequencies are sh6wn. Also, growth rates o'f unstable waves in the radar regime (1-10 m) are shown for drift velocities 1.5v, and 3v•. In the present note we consider the linear theory of the electrojet instability with finite Debye length effects for modes having a small component parallel to the magnetic field (k• • 0). We focus our attention especially in the parameter regions where the nature of the instability changes from resistive to reactive (for a large range of parameters applicable to the electrojet the instability is probably resistive-inductive rather than purely resistive or purely reactive). We present numerical results relevant to the equatorial and the auroral electrojet and discuss their effect on the radar backscattered spectra. For the convenience of the reader we give a simple physical description of the nature of the electrojet type instability (resistive or reactive) in the appendix.

We have performed a model calculation of the ion heating rate due to electrostatic ion cyclotron turbulence in the topside ionosphere, with the assumption that the formation of a plateau on the electron velocity distribution is inhibited. Ion temperature profiles are obtained and the implications of the heating effect on anomalous resistivity calculations are discussed.