Low-frequency electrostatic fluctuations detectedby the instruments on the Rocket and Scatter Experiment (ROSE) rockets inthe E region over northern Scandinavia are analyzed.It is demonstrated that the time-resolved statistical properties of the fluctuationsdeviate significantly from those associated with a Gaussian process. The characteristicsof the fluctuations are analyzed with particular attention to non-Gaussianeffects and phase-coherent mode couplings of electrostatic fluctuations. Non-Gaussianeffects are analyzed by means of the kernel estimator for probability densityfor short data segments. Short-time phase-coherent effects are analyzed andquantified by means of the squared wavelet bicoherence, which has desirablestatistical properties in the frequency regions of interest. The results arecompared with similar results from rocket data obtained over S¿ndreStr¿mfjord in Greenland. The results show a remarkable similarity,indicating that the observed phase coherence is a robust feature of the saturatedstage of the E region instabilities.