To explain the presence of the so-called ''bounce-phase-bunched'' ion distributions (eV range to ~20 keV) observed in the earth's geosynchronous magnetosphere, Quinn and Southwood (1982) examined the general properties of what they called the ''convection'' mechanism. This mechanism is associated with a sudden earthward displacement of curved field lines resulting from the short-lived application of an intense, east-west electric field. To explore its properties a quantitative computer model of the mechanism has been constructed that incorporates the dipolarization of the field line shapes, and recent transient electric field measurements. It is confirmed that the mechanism easily generates the bounce-phase-bunched ion distributions in question and that for some particles it can give rise to dramatic ion energization in the field parallel direction associated with the violation of the second adiabatic invariant.

It is shown additionally that depending on initial conditions the mechanism can generate dramatically field aligned distributions. It is hypothesized that the convection surge mechanism is fundamentally associated with the processes responsible for transporting tail populations to the middle (geosynchronous) regions of the earth's magnetosphere, and it is proposed that a key general characteristic of geosynchronous ion pitch angle distributions, field-aligned low energies and field-perpendicular high energies, is a signature of this energization mechanism. The presence of field aligned ions cannot be presumed to be a signature of recent ionospheric extraction.