Excitation of Field Aligned Sound Waves by Electron Streams

Abstract

Irregularities moving across the magnetic field in aurorae and electrojets are explained as sound waves excited by streaming electrons. A three-component gas dynamical analysis (neutrals, ions, electrons) predicts growth of waves propagating across the field with velocity (8 KT/3m)/2 provided the streaming velocity reaches a certain threshold which is somewhat higher than this value, and the waves will travel more slowly than (8 KT/3m)/2 when the electrons are a good deal faster than the threshold, which would account for an observed velocity spread. (Author)