Observations concerning the relationship between the quiet-time ring current and electron temperatures at trough latitudes

The relationship between the simultaneously observed positions of the maximum omnidirectional flux of the quiet-time ring current positive ions (Λ φ) and the maximum electron temperature Λ T in the trough is studied in the midnight sector of the topside ionosphere. Λ φ maps to the inner edge of the plasma sheet where ring current fluxes change from nearly isotropic to trapped. At altitudes near 2500 km, the electron temperature at trough latitudes were always sharply peaked. Although Λ φ varied with the level of geomagnetic activity, ( Λ φ − Λ T ) did not. These observations support the hypothesis that the quiet-time ring current is the source of elevated electron temperatures found near the plasmapause. Below 1300 km, peaked electron temperature distributions in the trough were not consistent features of the data. It is shown that ( Λ φ − Λ T ) increased with decreasing altitude. The possible influences of a westward component to the convective electric field and ionospheric refraction of ion cyclotron waves are discussed.