Theory of the electromagnetic transient response of the ionosphere for plane wave excitation

Summary The reflection and transmission of a transient plane wave by an ionosphere with a linear electron density profile and constant collision frequency are calculated. The exact frequency domain solution is inverted numerically, and the resultant reflected and transmitted waveforms are found to satisfy causality. A linearly varying, nondispersive dielectric half-space is also considered, but the nonphysical nature of the model causes the reflected waveform to be noncausal. Using convolution the waveforms for a step modulated sinusoid excitation are also obtained from the impulse response of the ionosphere. The results provide insight into the physical mechanism involved in the ionospheric propagation of HF electromagnetic pulsed signals.