On the turbulent spectrum of equatorial spread F: A comparison between laboratory and space results

We compare space and laboratory instabilities of the flute mode type. In space the classic gravitationally driven Rayleigh‐Taylor mode is studied. In the laboratory, centrifugal force provides an effective gravity. In both cases we find that classical diffusion is adequate to explain the spectrum but for different reasons. In particular, no drift wave modes need be involved to provide anomalous diffusion in the space case. Owing to the large physical space available in space, the spectrum covers a huge range of k values and drift waves are not generated. In the laboratory case the large fluctuation level is compressed into a small portion of k space. This greatly increases the drift wave growth rate. The space case is typically studied using radar Bragg scales deep in the diffusive subrange, scales which we think are populated by a three‐wave coupling process. In the laboratory, drift waves are generated but are probably part of the overall linkage of large to small scales. Curiously, even though the spectra are quite similar, the evolution of the two systems seems to be quite different.