Empirical Parameterization of Broadband VLF Attenuation in the Earth-Ionosphere Waveguide

It has long been known that the ionospheric absorption of HF radio waves is dependent on the electron density in the ionosphere. This paper examines two aspects of the absorption calculation that have not been as thoroughly investigated. First, the correct method to calculate ionospheric absorption is explored; while the Sen Wyller ray trace formulation is generally cited as the best approximation in the D and E regions of the ionosphere, the Appleton-Hartree formulation is more consistent with the theory in the F region of the ionosphere. It is shown that either ray trace formulation can be used to calculate ionospheric absorption if the correct collision frequencies are utilized. Another frequently overlooked aspect of the attenuation calculation are the variations in the electron-neutral and electron-ion collision frequencies as a function of local time, season, latitude, and solar cycle. These variations result in differences on the order of 30% in the total ionospheric attenuation and should be included in absorption calculations.

Collision frequency

Ionospheric reflection

High frequency

10.1002/2017rs006256

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Citations (39)

Ray trace calculation of ionospheric propagation at lower frequencies

Radio Science (2006)

Michael H. Reilly

The Raytrace/Ionospheric Conductivity and Electron Density–Bent‐Gallagher model has been revised to make it applicable to ionospheric propagation at low radio frequencies (0.5–5.0 MHz), where the ionosphere and magnetic anisotropy drastically alter propagation paths and provide a severe test of propagation model algorithms. The necessary revisions are discussed, and the model is applied to the problem of ionospheric penetration from a source below the ionosphere to a receiver above the ionosphere. It is necessary to include the electron collision frequency in the Appleton‐Hartree index of refraction in order to permit ionospheric penetration for radio frequencies below the maximum plasma frequency (e.g., whistler modes). The associated reformulation of the ray trace equations for a complex index of refraction is straightforward. Difficulties with numerical methods are cited for the lowest frequencies, and future improvements are indicated.

Whistler

Ionospheric reflection

Earth–ionosphere waveguide

High frequency

10.1029/2005rs003338

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Citations (3)

Statistical characteristics of anomalous radio wave absorption in the ionosphere during sudden ionospheric disturbances

Geomagnetism and Aeronomy (1979)

E. A. Benediktov

Ionospheric propagation

High frequency