A plasma instability resulting in field-aligned irregularities in the ionosphere

TLDR

The study develops a theory of the two‑stream ion wave instability in a plasma, aiming to explain field‑aligned irregularities in the ionosphere. The theory incorporates ion and electron collisions with neutrals and a uniform magnetic field to model the instability. Applying the theory to the ionosphere predicts spontaneous ionization density irregularities aligned with magnetic field lines, matching observed equatorial and polar field‑aligned irregularities associated with electrojets.

Abstract

A theory of the two-stream ion wave instability in a plasma is developed that takes into account both the effect of collisions of the ions and electrons with neutral particles and the presence of a uniform magnetic field. Applying the results to the ionosphere, we find that irregularities of ionization density should arise spontaneously in regions in which a sufficiently strong current is flowing normal to the magnetic field lines. These irregularities will be strongly aligned with the magnetic field and may have a wide range of wavelengths. The various predictions of the theory are in agreement with the observed characteristics of certain field-aligned irregularities found in the equatorial ionosphere that are associated with the equatorial electrojet. Similar irregularities often appear in the polar ionosphere during auroral displays; it seems very likely that these are caused by the auroral electrojet.