Counterstreaming electon beams at altitudes of approx.1 R/sub E/ over the auroral zone

Intense beams of electrons with energies in the keV range have been streaming simultaneously both parallel and antiparallel to the magnetic field direction at altitudes between 4000 and 8000 km at auroral latitudes. The peak flux observed was 3 x 1011 (cm2 s sr keV)-1 at an energy of 160 eV. The beams are often tightly collimated with widths in pitch angle as narrow as approx.1 0. Analysis of the energy spectrums of the beams and the simultaneously observed loss cones in the trapped electron population shows that the energization of the beams cannot be understood as acceleration by a simple quasi-static parallel electric field. Alternative models include acceleration by wave-particle interactions or by fluctuating electric fields. One candidate model consistent with the observations is outlined in which the energetic electrons in the counterstreaming electron beams are accelerated from the ambient cold plasma by multiple flickering double layers located in the 1-R/sub E/ altitude range