Low frequency electrostatic turbulence in the polar cap E-region

Electrostatic turbulent fluctuations in a broad frequency band are detected in the polar cap E-region over Greenland by an instrumented rocket payload. The fluctuations were detected by potential-difference measurements on two sets of boom-mounted spherical probes. The direction and magnitude of the phase velocity of the fluctuations was determined by standard correlation techniques. The driving mechanism for the turbulence is identified as the Farley-Buneman instability. Deviations from the predictions of a linear stability analysis indicate the effect of nonlinear saturation mechanisms. A correlation time 20 to 150 ms along the rocket trajectory is determined, indicating that the fluctuations are essentially statistically independent for altitude separations greater than 50 m. A conditional analysis of the signals indicate that a good approximation can be described by Gaussian statistics. The data exclude the possibility of wave steepening as a saturation mechanism for the linear instability.