Precipitation of suprathermal ionospheric ions accelerated in the conjugate hemisphere

Low‐energy particle data from the AUREOL 3 satellite were examined in order to characterize latitude‐energy precipitation bands of low‐energy ions (<3 keV) sometimes detected embedded in the discrete auroral regions. A clear energy dispersion is observed, the less energetic ions being observed equatorward of higher‐energy precipitation. Generally the latitudinal extent of this structure is about ΔΛ ≃ 0.5°. Detailed ion energy spectra were used to infer that ionospheric ions are energized in the conjugate ionosphere, presumably in inverted‐V structures, and undergo velocity‐dependent electric drift effects during a single bounce. Model calculations and direct ion composition measurements clearly demonstrate that the H+ ions are predominant in these structures. Furthermore in several cases a double energy band is observed associated with each side of the conjugate V‐shaped electrostatic potential structure.