Generation models of electron conics

Electron distribution functions (EDFs) with a peak oblique to the magnetic field, adjacent to but distinct from loss-cone features, have been observed by the DE 1, Viking, and S3-3 spacecraft in passes through the nightside auroral zone, polar cap, dayside cusp, and extended dayside auroral oval. Using particle simulations, two types of wave excitation and particle acceleration mechanisms which may contribute to producing these electron conic distributions are investigated. The first involves excitation of upper-hybrid waves by the electron loss cone, and the subsequent perpendicular heating of the background and thermal electrons. The second involves excitation of downward propagating parallel modes by an auroral electron beam which frequently accompanies the upflowing electron conics. These modes provide parallel acceleration, which modifies the GDF. Those electrons which are not lost to the atmosphere and mirror back up the magnetic field line give rise to enhancements in the GDF at the edge of the loss cone.