Turbulence and Intermittency in the Winter Cusp Ionosphere Studied With the ICI Sounding Rockets

The characteristics of turbulent plasma in the winter cusp ionosphere is studied based on in‐situ data from the Investigation of Cusp Irregularities (ICI) sounding rockets. The electron density fluctuations from ICI‐2 and ICI‐3 missions have been analyzed for the whole flight, using advanced time‐series analysis techniques. The analysis of the autocorrelation scale is indicative of the turbulence integral scale and marks the onset of the turbulent cascade from large to small scales in the power spectrum density of the rocket data. The power spectrum is typical for a turbulent field. The turbulent structures are persistent in the data, which are quantified by analyzing the Probability Distribution Functions (PDFs) and their deviations from the Gaussian distribution. The kurtosis analysis indicates the presence of intermittency. These results are compared with the Local Intermittence Measure ‐ LIM, which confirms the presence of small scale intermittent structures. The turbulence measured by rockets appears well developed and covers frequencies between 1 Hz and several hundred Hz. There is a good agreement with the previous results, suggesting that density fluctuations in the ionospheric cusp agree with the turbulence framework in which intermittent processes transfer energy across different scales. Key Points Sounding rocket in situ observations show a complex behavior similar to a turbulent field in the ionospheric cusp The integral scale of the turbulence exhibits large‐scale structures of the order of tens of kilometers Density fluctuations agree with the turbulence framework in which intermittent processes transfer energy across different scales