The characteristics of magnetic-field-aligned electrostatic-potential differences in the structure of an inverted V event were examined by using data on the pitch angle and energy distributions of electrons and ions obtained with the polar-orbiting S3-3 satellite. Potential differences were found to occur simultaneously above and below the altitude of the satellite (?7260 km). Both of these potential differences were determined from an analysis of the electron distributions. The analysis also yielded the magnetic field intensity B1 above the satellite a distance of ?1200 km, implying an apparent electric field of <?1 mV/m. The total potential difference was found to have an inverted V distribution in latitude with a peak value of ?4.3 kV and a latitudinal width of ~1≡. Upward-flowing H+ and O+ ions, with pitch angles <?10¿ were observed in the structure. Their energy spectra were peaked at energies near the potential differences below the satellite but were very broad indicating perpendicular heating and an ion source within the potential region. Implications to theory are discussed.