Measurements of highly collimated short-duration bursts of auroral electrons and comparison with existing auroral models

The pitch-angle distributions, energy spectra, and temporal and spatial variations of auroral electrons with energies from 40 ev to 100 kev were measured with the Twins 2 rocket payloads to an altitude of 800 km. Enhancements of electrons with energies of ∼5 kev, pitch angle α≤10°, and intensities of up to 5×10s particles cm−2 sec−1 ster−1 were observed occasionally. The enhancements were sometimes by a factor of 10, even while electrons with energies of ∼12 kev at these pitch angles showed no changes (nor did those with energies between ∼40 ev and 100 kev at 30°≤α≤60°). The bursts were thought to be temporal in origin, and they lasted for the minimum resolvable time of ∼0.1 sec up to times of several seconds. The altitude of the source of the bursts of field-aligned electrons is believed to be less than 1 RE, and their occurrence is not clearly related either to the ever-present auroral continuum nor to the electrons with a few kiloelectron volts that cause auroral luminosity. We examine several existing theories of auroral particle acceleration and/or precipitation and show them each to be inadequate (as presently formulated) to individually explain all the observations. A potpourri model of adaptations of all these theories is shown to be adequate, but its reality is not otherwise established. Field-line merging and diffusion by wave-particle interactions are considered to be commonly occurring phenomena.