Low frequency electrostatic waves being spontaneously excited in the ionospheric electrojet are studied by instrumented rockets. The data are obtained by four spherical probes placed at two booms in such a way that the probes on the deployed booms form the corners of a tetrahedron. By this construction, the probes can give information of all three vector components of electric fields in the ionosphere. Signals from probe-potential differences are available on ground for further processing. We report results from detailed statistical studies of low frequency long wavelength electric field fluctuations, with particular attention to intermittent features in the data. We find that the largest amplitudes of the fluctuating fields are confined to...