Models for quasi-periodic electric fields and associated electron precipitation in the auroral zone

On four rocket flights, quasi-periodic electric fields were observed in the nighttime auroral oval and in the polar cleft. These fields had periods of between 0.5 and 3 s and amplitudes from 2 to 30 mV/m and exhibited left-hand and right-hand elliptical polarization. Electric field intensifications often coincided wih bursts of energetic electron precipitation, on occasion modulated wih nearly the same period as the fields. The events in the auroral oval were associated with substorms and visual auroral activity. The spectral and polarization properties of the observed fields suggest that they represented the electric components of Pc 1 or Pi 1 micropulsations. To model these waves and the concurrent electron flux variations, different mechanisms for wave excitation, electron acceleration, and wave-particle interaction are considered. One likely interpretation attributes the micropulsations to Birkeland current chopping by an unstable double layer located at approx. =1-R/sub E/ altitude. The double layer is also assumed to accelerate the observed electrons, the electron flux variations being due either to the inherent variations of the double layer or to its interaction with the micropulsations. Because of the sparcity of parameters measured so far the models are provisional. Follow-up experiments are proposed to investigate the poblem further