B. Krane

Spectral properties of low‐frequency electrostatic waves in the ionospheric E region

The spectral properties of low frequency electrostatic waves in the polar cap E region over northern Scandinavia were studied experimentally by instruments on the Rocket and Scatter Experiment (ROSE) rockets. Fluctuations in plasma density were detected as well as potential differences between boom-mounted probes. By comparison of the spectral index for fluctuations in the potential signal and plasma density, evidence is obtained for deviations from Boltzmann distributions in the electron dynamics, which would predict fluctuations in density and potential to be proportional, with the same constant of proportionality at all frequencies. Investigations of the cross correlation between density and potential signals demonstrate that the phase between the two increases approximately linearly with frequency. Empirical relations are obtained for the frequency dependence of the amplitude and phase relations between fluctuations in density and potential.

Low-frequency electrostatic waves in the ionospheric E region

Low-frequency electrostatic waves in the ionospheric E region are studied by analyzing data obtained by instrumented rockets. We identify the origin of the enhanced fluctuation level to be the Farley–Buneman instability. The basic information on instability, such as altitude varying spectra and speed of propagation are obtained. Comparison of power spectra for the fluctuations in plasma density and electrostatic potential, respectively, provides information on the electron dynamics. A bispectral analysis gives indications of phase-coherent couplings within the wave spectrum, while higher order structure functions indicate some intermittent features of the turbulence.

Nonlinear wave interactions in two-electron-temperature plasmas

The evolution of nonlinear electron plasma waves is considered for cases where the electron distributions are characterized by more than one temperature component. The standard models for the decay spectrum of electron plasma waves are significantly modified in such cases, since the presence of electron acoustic modes in multi-temperature plasmas opens a new decay channel for the high frequency plasma waves. In particular, long wavelength Langmuir waves can decay to shorter wavelengths. A set of equations are derived for describing weakly nonlinear waves in two-electron temperature plasmas. The results are illustrated by numerical solutions of the basic equations in two spatial dimensions. The analysis is extended to cases characterized by many temperatures, and a possibility of including Landaudamping in a simple time-reversible form is discussed.