Energy sources of field-aligned currents: Auroral electron energization

[1] The electron acceleration region in field-aligned currents is considered not as an isolated system but as being embedded in a global circuit. Such a view permits clear identification of the "generator region'' and the energy source driving the currents. The global perspective permits a critical appraisal of the appropriateness of using an electric potential to describe the electron acceleration and of criticisms of steady potential acceleration models. We find that ion energy is the source of electron acceleration and that in practice, an electric potential can be useful and appropriate for some circuits.