Energy flow in terrestrial controlled-source electromagnetic geophysics

Visualisations of the flow of electromagnetic energy based on the time-averaged Poynting vector have yielded important and sometimes counter-intuitive physical insights in the case of electric circuits containing resistors and inductors. Less well-understood is the flow of electromagnetic energy in spatially contiguous media excited by grounded sources. In geophysics, for example, it is important for readers to recognise how geological structures help shape controlled-source electromagnetic responses. It is demonstrated herein using energy flow visualisations how a resistive layer impeding vertical electric current flow will produce a larger anomalous response to grounded-source excitation at the Earth's surface than an equivalent conductive layer.