Structure functions and intermittency in ionospheric plasma turbulence

Low frequency electrostatic turbulence in the io- nospheric E-region is studied by means of numerical and ex- perimental 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 us- ing results for the space-time varying electrostatic potential from two dimensional numerical simulations. An instrumen- ted rocket can not directly detect the one-point potential va- riation, 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 po- tential difference measurements can differ significantly from the one-point results. It was found, in particular, that the in- termittency signatures become much weaker, when the pro- per 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, ob- tained as those analyzed here, are unlikely to give an ade- quate representation of intermittent features of the low fre- quency ionospheric plasma turbulence for the given condi- tions. (Chandrasekhar, 1957) that the second order structure func- tion, as a function of spatial separations, can be obtained by simple dimensional arguments, apart from a numeri- cal constant. For the longitudinal second order velocity structure function in the universal Kolmogorov-Oubokhov range of homogeneous isotropic turbulence we thus find 92(r)