Abstract
Ground-based amplitude measurements of GNSS signal during ionospheric
scintillation are analyzed using prevalent data analysis tools developed
in the fields of fluid and plasma turbulence. One such tool is the
structure function of order $q$, with $q = 1$ to $q = 6$, which
reduces to the computation of the second order difference in the GPS
signal amplitude at various time lags, and allows for the exploration of
dominant length scales in the propagation medium. We report the
existence of a range where the structure function is linear with respect
to time lag. This linear time-segment could be considered as an analog
to the inertial range in the context of neutral and plasma turbulence
theory. Below the linear range, the structure function increases
nonlinearly with time lag, again in good concordance with the
intermittent character of the signal, given that a parallel is drawn
with turbulence theory. Quantitatively, the slope of the structure
function in the linear range is in good agreement with the scaling
exponent determined from in-situ measurements of the electrostatic
potential at low altitude (E-region) and the electron density at the
topside ionosphere (F-Region). This in turn suggests the conjecture that
scintillation could be considered a proxy for ionospheric turbulence.
Furthermore, we have found that the probability distribution function of
the second order difference in the signal amplitude has non-Gaussian
features at large time-lags; a result that seems inconsistent with
equilibrium statistical physics which suggests a Gaussian distribution
for the conventional random walk processes.