Turbulence and Intermittency in the Winter Cusp Ionosphere studied with the ICI Sounding Rockets

Space plasmas display fluctuations and nonlinear behavior at a broad range of scales, being in most cases in a turbulent state. The majority of these plasmas are also considered to be heated, with dissipation of turbulence as a possible explanation. Despite of many studies and advances in research, many aspects of the turbulence, heating and their interaction with several space plasma phenomena (e.g., shocks, reconnection, instabilities, waves), remain to be fully understood and many questions are still open. Plasma irregularities and turbulence are believed common in the F-region ionosphere and because of their impact on the GNSS and the human activity in the polar regions, a detailed understanding is required. This study provides a characterization of the turbulence developed inside the polar-cusp ionosphere, including features as intermittency, not extensively addressed so far. The electron density of ICI-2 and ICI-3 missions have been analyzed using advanced time-series analysis techniques and a standard diagnostics for intermittent turbulence. The following parameters have been obtained: the autocorrelation function, that gives useful information about the correlation scale of the field; the energy power spectra, which show the average spectral indexes 1.7, not far from the Kolmogorov value observed at MHD scales, while a steeper power law is suggested below kinetic scales. In addition, the Probability Distribution Functions of the scale-dependent increments display a typical deviation from Gaussian that increase towards small scales due to intense field fluctuations, indication of the presence of intermittency and coherent structures. Finally, the high kurtosis and his scaling exponent reveals an efficient intermittency, usually related to the occurrence of structures. This study strengthens the idea that that density fluctuations in the ionospheric cusp seem to agree with the turbulence framework in which intermittent processes transfer energy across different scales.