Theory and Calculation for the Effect of a Homogeneous, Cylindrically Symmetric Disturbance on ELF (Extremely Low Frequency) Propagation.
Research rept. Dec 84-Jul 85,
NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
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A simple surface propagation model is commonly used to estimate the effects of ionospheric disturbances on extremely low frequency ELF propagation, Though often adequate, one shortcoming of the model is its failure to allow for excitation by the broad-side component of a horizontal dipole. That excitation can be quite significant in a sporadic-E environment, when the modal polarization can contain a substantial mixture of TE component. In this study a beginning is made on ELF propagation model development which allows for broadside excitation as well as a systematic allowance for height gain effects. The development is for a flat earth with a laterally homogeneous, cylindrically symmetric disturbance centered over the transmitter. The method utilizes normal-mode decomposition. Matching equations at the boundary of the disturbance are developed by evaluating height gain integrals, and it is shown that this method is tantamount to simply matching the ground vertical electric and azimuthal magnetic fields at the boundary. Results for a sporadic-E type environment indicate substantial departures from the surface propagation model and WKB predictions.
- Radiofrequency Wave Propagation