Source dependent transmission line parameters - plane wave vs TEM excitation

Maxwell's equations for a thin, infinite and lossless wire above perfectly conducting ground are transformed into the form of the telegrapher equations. The occurring line parameters are complex-valued functions and gauge- and source-dependent. Choosing plane wave excitation and grazing incidence, it is shown that the corresponding electromagnetic fields, Poynting vectors, currents and potentials assume TEM structure. This result is confirmed by a direct TEM solution of the telegrapher equations.