Two sounding rockets were launched near simultaneously into the late evening auroral zone from Poker Flat and Fort Yukon, Alaska, on February 7, 1984, placing two payloads on nearly the same magnetic field lines simultaneously. The Black Brant X payload, with an apogee of 1040 km, measured dc electric fields of ~300 mV/m, while the lower altitude Terrier-Malemute payload (apogee 640 km) measured only typical ionospheric electric fields under ~100 mV/m. These measurements imply a parallel potential of several kV below the higher payload, most probably occurring between the two payloads. The exact value of the parallel potential is dependent on the motion of the potential structure with respect to the payload. There is some evidence of an ~2-kV potential drop between the payloads in the electron data. Nonadiabatic electron trajectories are also implied. No possible resistive mechanism to support the parallel field is observed in the 100-Hz to 10-kHz frequency band. The existence of resistance-producing turbulence at other frequencies or of a type not measured by the probes, or localized parallel potentials not coincident with the payload trajectories, are thus implied.

The observation of apparent ''secondaries'' at all altitudes implies either a potential barrier of hundreds of electron volts that trapped these electrons above the region of upward electric field or that the secondaries were actually locally accelerated electrons originating out of the cold background. The plasma conditions encountered at 1000 km are unusual for sounding rockets. During the highest electric fields and lowest densities, a 5.8-m antenna measured significantly larger dc electric fields than a 3-m antenna. Internal consistency checks, the near-sinusoidal nature of the spin-dependent waveform, and the >10 &lgr;Debye separation of the booms from the payload lead to the conclusion that the longer boom measurements were correct, the payload wake having interfered with the shorter antennas. ¿ American Geophysical Union 1990