A theory that accounts for the generation of short-wavelength irregularities in the equatorial electrojet for an electron drift velocity below the ion-acoustic speed is presented. Long-wavelength (tens of meters) horizontally propagating waves driven unstable by the ambient ionization density gradient are found not to steepen very much, even though they are nondispersive. However, the local vertical velocity and horizontal density gradient associated with these waves are capable of generating the meter-wavelength obliquely propagating irregularities detected in radar observations.

Generation of small-scale irregularities in the equatorial electrojet.

A nonlinear unified theory of type I and II irregularities is presented that explains their principal observed characteristics. The power spectrum is predicted by using Kolmogoroff-type conservation law for the power flow in cascading eddies.

Unified theory of Type I and Type II irregularities in the equatorial electrojet

An attempt is made to explain the type II irregularities observed by Balsley in the equatorial E region. Vertical gradients in the plasma density appear to be essential for the excitation of the instability responsible for the irregularities. An interesting by-product of the calculations is that the Farley instability is recovered by making use of a fluid picture for both ion and electron components.

Type II irregularities in the equatorial electrojet

We present a theory of rising bubbles (or sharp density depletions) in the equatorial ionosphere. Both ion inertia and ion-neutral collisions are included. In the collision-dominated case the bubble velocity is independent of its size, while in the collisionless case it is proportional to the square root of the bubble size.

Theory of Rayleigh-Taylor bubbles in the equatorial ionosphere

Barium ion clouds striation formation above E layer ascribed to LF gradient drift instability

Formation of striations in ionospheric plasma clouds

It is shown that a weakly ionized plasma column in an axial magnetic field and an inward‐directed radial electric field—a Penning discharge at higher pressures—is unstable against a macroscopic m = 1 perturbation. The instability is analyzed by dimensional analysis. The applicability of this method is discussed. A steady‐state model of some experimental Penning discharges is developed. On the basis of this model, the critical magnetic field for the onset of instability as predicted by the theory agrees well with the values observed. The instability discussed here is caused by the presence of a third fluid, the neutrals, in an electron‐ion plasma. The same mechanism is also applicable to the initial phase of some rotating plasmas of the homopolar type.

F. C. Hoh

Papers

Instability of Penning‐Type Discharges