1. Wave attenuation in absorbing media

This section begins with a reminder of the main properties of plane radio waves propagated in a vacuum (or in air). The wave equation and Maxwell's equations are examined together, and two closely related concepts emerge: the propagation constant, and the displacement and conduction currents. The propagation analysis thus developed enables us to dissociate two families of media identified by their electrical conductivity properties σ. According to the data in table 1 , we agree to call a moderately conductive medium, a substance whose electrical conductivity falls below 100S.m ^-1 .

This boundary is obviously arbitrary, as the dynamics of σ variation are considerable, going from 10 ⁷ S.m ^-1...