The inverted V natuxe of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, leads to the conclusion that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

It has been found that the perturbation in the geomagnetic field produced by the auroral electrojet also perturbs the pitch‐angle distribution of the precipitated electrons that are the dominant contributors to the auroral ionization within which it is assumed the auroral electrojet flows. To study this interaction in detail, a computer program has been developed for model calculations. This program computes: (1) the electron concentration profile in the ionosphere from a given pitch‐angle and energy distribution of the ionizing electrons, and (2) the changes in the pitch‐angle distribution created by the geomagnetic field deformations caused by the auroral electrojet current system itself. Results from preliminary computations are discussed. It is shown that the interaction can cause significant time variations in an initially time‐stationary electron precipitation event. Thus, for the first time it is seen that naturally occurring atmospheric ‘feed‐back’ effects can account for some of the dynamic auroral variations without requiring the auroral source itself to vary in time. The variations are governed by the pitch‐angle distribution and the total flux of precipitated electrons, as well as by the normal loss parameters in the upper atmosphere. For medium‐to‐strong electron precipitation events, the calculated periodicity of the variations lies in the range 50–200 seconds, which is in agreement with some of the direct observations of auroral electron periodicities.

Particle observations by the Rice University/ONR satellite Aurora 1 have revealed a large universal‐time variation in the low‐energy electron fluxes in the northern polar region during summertime. The electron fluxes are highest near 1800–2000 UT, both on the night‐ and the day‐side of the earth above ∼75° invariant latitudes, whereas a minimum in the fluxes is reached between 0600 and 1200 UT. It is suggested that these variations are associated with the diurnal changes in the tilt of the geomagnetic axis relative to the solar wind direction.

The effects of electron beam emissions from Spacelab were recorded with onboard diagnostic instruments. The variation of the Spacelab-shuttle potential with respect to the ambient plasma near the scientific air lock was investigated. Data on the waves and instabilities triggered by the electron beams are discussed. Within the electron gyrofrequency and electron plasma frequency range, strong signals were detected by both electric and magnetic antennas during the beam emissions. The frequencies of the emitted waves were compared to the characteristic plasma frequencies to enable mode identification.

The high-latitude boundary (LN) of energetic electrons (E • 40 key) quasi-trapped at an altitude of 1000 km was studied with the satellite Injun I over North America during periods of magnetic quiet and magnetic storms in 1961. The boundary was very sharp during disturbed periods, and it moved farther from the pole during larger disturbances. The electron intensity south of LN increased during magnetic disturbances, and the electron spectrum was much softer than normal just at the boundary. Throughout two magnetic storms in October and December 1961, the boundary (L•) of the energetic electron flux coincided with the boundary of the auroral absorption of radio waves. Quantitative correlation of the intensities of the two phenomena is discussed. 997