Wave-induced fluctuations in ionospheric electron content: A model indicating some observational biases

Abstract

By assuming that a plane atmospheric wave acts on a plane‐stratified F layer in the presence of a constant geomagnetic field, we derive an expression for the resulting perturbations in total columnar electron content as a function of wave and ionospheric‐layer parameters and of the orientation of the column through the ionosphere. Although idealized, the model not only correctly predicts the order of magnitude of the observed perturbations but also makes visible much of the physics that determines the magnitude of wave‐induced total‐content fluctuations observed by using satellite transmissions through the ionosphere. Geomagnetic constraints on ion motion and a tendency for total‐content fluctuation to be greatest when the ground‐satellite path lies in a surface of constant atmospheric wave phase combine to introduce strong experimental biases that favor the observation of some waves and prevent the observation of others. The effects of these biases must be fully removed before total‐content measurements can yield the statistical properties of atmospheric waves at ionospheric heights that may be useful in locating wave sources or in characterizing the dynamic state of the ionosphere.

Total electron content variations due to nonclassical traveling ionospheric disturbances: Theory and Global Positioning System observations

“…Clearly, then, measurements of TEC are biased against certain viewing directions to the satellite. Evans [1977] states that the best viewing direction lies parallel to the phase fronts of the disturbance (that is, perpendicular to kr); Georges and Hooke [1970] provide the analysis necessary to back up this assertion. The bias introduced by the orientation of the ray path between the satellite and the observer relative to the phase fronts of the TID will be termed "viewing bias" throughout this paper.…”

“…As such, variations in TEC are ambiguous indicators of changes in electron density along that path (e.g., due to plasma motion). For example, a 2 percent decrease in TEC may be caused by an overall TIDs [Hooke, 1968;Georges and Hooke, 1970;Davis, 1973] is based on the daytime ionospheric response to internal gravity waves (or acoustic waves) in the lower atmosphere with upwardly propagating energy flux. Gravity waves exhibit neutral wind perturbations that grow in amplitude with increasing height.…”

Characterizing Coseismic Ionospheric Disturbance for Surface-Rupturing Earthquakes

“…Then I integrate over the LOS to obtain TEC. In the following section I describe the analytical model developed by Georges & Hooke (1970), which replaces the time and LOS integration with a 1D analytical approximation. I go through the same 3 steps as in the current section, beginning with the acoustic wave.…”

“…The velocity of the charged ions, v i , is equal to the component of the neutral wave parallel with the geomagnetic field (Georges & Hooke, 1970):…”

“…To invert for the acoustic wave, they divide the observed TEC by the transfer function. To obtain the transfer function, they rely on an analytical model developed by Georges & Hooke (1970) (hereafter G&H analytical method). This method relies on two key assumptions: 1) a plane wave approximation of the propagating wave and 2) a 1D electron density divergence in the vertical direc- …”