Fig. 4: Illustration of the coupling between magnetospheric processes and the auroral acceleration region.
From: Evidence for Alfvén waves powering auroral arc via a static electric potential drop
a Details of the auroral acceleration region (AAR) inferred from observations with the well-known behavior of the associated upward parallel electrical current (\({J}_{\parallel }\)) and charged particles. Electrons are accelerated toward the ionosphere, producing discrete arcs. O+ ions are accelerated away from the Earth. Our electron and ion observations suggest that the parallel potential drop \({\Phi }_{\parallel }\) of the AAR was 1–10 kV and around 1.5 RE above the ionosphere (Figs. 6 and 7). b Summarization of the energy fluxes along the magnetic field lines of the AAR, the nominal values of these energy fluxes, and other relevant processes. The detailed analysis of the energy budget is shown in Fig. 6 (for the discrete arc \({F}_{{arc}}\) and inverted-V electrons \({F}_{e}\)), Fig. 7 (for the O+ outflows \({F}_{O}\)), and Fig. 3 (for the Poynting flux \(S\)). The energy fluxes obtained from our observations suggest that the Alfvén waves, presumably generated by dynamical processes in the magnetotail, power the discrete arc via the electron and ion acceleration within the AAR.
