Structure functions and intermittency in ionospheric plasma turbulence

Abstract

Abstract. Low frequency electrostatic turbulence in the ionospheric E-region is studied by means of numerical and experimental methods. We use the structure functions of the electrostatic potential as a diagnostics of the fluctuations. We demonstrate the inherently intermittent nature of the low level turbulence in the collisional ionospheric plasma by using results for the space-time varying electrostatic potential from two dimensional numerical simulations. An instrumented rocket can not directly detect the one-point potential variation, and most measurements rely on records of potential differences between two probes. With reference to the space observations we demonstrate that the results obtained by potential difference measurements can differ significantly from the one-point results. It was found, in particular, that the intermittency signatures become much weaker, when the proper rocket-probe configuration is implemented. We analyze also signals from an actual ionospheric rocket experiment, and find a reasonably good agreement with the appropriate simulation results, demonstrating again that rocket data, obtained as those analyzed here, are unlikely to give an adequate representation of intermittent features of the low frequency ionospheric plasma turbulence for the given conditions.

Fluctuations in the direction of propagation of intermittent low‐frequency ionospheric waves

“…Our results indicate a significant intermittency of the long‐wavelength part of the FB instability, where previous studies [ Dyrud et al , 2008] referred to small wavelengths (i.e., small spatial separations in the structure functions). For the present case, the gradient instability may contribute to the growth rate .…”

“…The DC electric field strength was changing during the flight (typically E 0 ≈ 40 mV m −1 upleg and E 0 ≈ 60 mV m −1 downleg), so in reality we have data from two independent experiments. (Related numerical studies of Dyrud et al [2008] use the maximum peak value of E 0 ≈ 70 mV m −1 to emphasize the nonlinear features.) The changes in are mostly in magnitude: the direction is almost constant.…”

“…Intermittency effects are often found to be an important characteristic of turbulent fluctuations in plasmas as well as in fluids. For short‐wavelength E region irregularities we have investigated such phenomena using standard structure function analysis [ Dyrud et al , 2008]. Our present study contains a study of intermittency for the long‐wavelength part of the spectrum.…”

Plasma turbulence and coherent structures in the polar cap observed by the ICI‐2 sounding rocket

“…Here we first presented the results from the Fourier bicoherence and extended the analysis to wavelet‐based bicoherence, which is more robust and less biased when studying short data segments [ van Milligen et al , ; Dudok de Wit and Krasnosel'skikh , ]. Higher‐order statistics have also been extensively used in the analysis of turbulence for satellite data [e.g., Horbury and Balogh , ; Sahraoui , ; Salem et al , ; Chian and Miranda , ] and for rocket experiments [e.g., Krane et al , ; Dyrud et al , , ]. Here we presented a study related to plasma irregularities in the high‐latitude F region comprising both higher‐order spectra and higher‐order statistics, and we have chosen two representative cases for detailed analysis: a trailing edge of the cold polar cap patch that was characterized by sawtooth structures (Case A) and a density enhancement subject to cusp auroral particle precipitation (Case B).…”

“…The bispectrum has been used for studying the mode coupling in various experiments such as laboratory [Kim and Powers, 1979], rocket [LaBelle and Lund, 1992;Larsen et al, 2002;Dyrud et al, 2006], or satellite experiments [e.g., Lagoutte et al, 1989;Masson et al, 1999]. Higher-order statistics have also been extensively used in the analysis of turbulence for satellite data [e.g., Horbury and Balogh, 1997;Sahraoui, 2008;Salem et al, 2009;Chian and Miranda, 2009] and for rocket experiments [e.g., Krane et al, 2010;Dyrud et al, 2008].…”