Theory and calculation for the effect of a homogeneous, cylindrically symmetric disturbance on ELF (Extremely Low Frequency) propagation
Abstract
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 broadside component of a horizontal dipole. That excitation can be quite significant in a sporadicE 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 normalmode 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 sporadicE type environment indicate substantial departures from the surface propagation model and WKB predictions.
 Publication:

Research Report
 Pub Date:
 July 1985
 Bibcode:
 1985nosc.reptR....P
 Keywords:

 Extremely Low Frequencies;
 Ionospheric Disturbances;
 Signal Transmission;
 Amplification;
 Computation;
 Decomposition;
 Electric Fields;
 Height;
 Homogeneity;
 Integrals;
 Magnetic Fields;
 Matching;
 Models;
 Normality;
 Predictions;
 Symmetry;
 Transmitters;
 Communications and Radar