Energetic particle measurements from within ionospheric structures responsible for auroral acceleration processes

Measurements of energetic electrons (0.07 ≤ E ≤ 24 keV) and ions (0.5 ≤ E ≤16 keV) on the S3‐3 satellite show features which are interpreted in terms of parallel potential drops of up to several‐kilovolt magnitude existing simultaneously both above and below the satellite. This leads to the inference that the satellite is within an auroral acceleration region. Two events of this type are examined in which the satellite is in the 7000‐ to 8000‐km altitude range and at auroral latitudes. Both events are interpreted as traversals of an ‘inverted V’ acceleration region of broad latitudinal width (2°–4°). In both cases, one can infer a vertical extent to the acceleration region of ≳10³ km.