Talk:Zenneck wave

The illustration looks like a transverse wave. That is to say, the direction of wave propagation is at right angles to the vector field. This needs explanation. Jim Bowery (talk) 19:24, 21 July 2021 (UTC)

Zenneck Wave vs. Surface Plasmon Polariton (SPP)

What is said in this article is not correct. The surface wave that propagates at the boundary between a half space with a positive real part of the permittivity and a half space with a negative real part of the permittivity is called a surface plasmon polariton (SPP). The most common example is air over a metal such as gold or silver, which is plasmonic at optical frequencies (the real part of the permittivity is negative). A Zenneck wave is a surface wave that exists at the boundary of two materials, both of which have a positive real part of the permittivity (an example is air over a lossy earth). The physics of the two waves are different, even though they both correspond to the same type of pole in the complex plane.

The Zenneck wave for air over the earth is basically a slightly inhomogeneous plane wave that is incident from the air region at the (complex) Brewster angle on the surface of the earth. This wave can legitimately be called a surface wave as it is a valid solution of the boundary value problem and the fields decay exponentially in both vertical directions, away from the interface. However, this wave will never get excited by a simple source such as a dipole. This is because the Zenneck-wave pole is not captured when deforming the original path of integration to the steepest-descent path for the spectral-domain integral that represents the field. This explains why, far away from a vertical electric dipole over the earth, the field will never resemble that of the Zenneck wave. (The original famous Lake Seneca experiment confirmed this.)

The SPP is a surface wave that also decays exponentially in both directions away from the interface. However, the SPP mode will be physically excited by a dipole source near the interface. This is because the SPP pole is located in a region of the complex plane where the pole is captured during the deformation of the original path to the steepest-descent path. Far away from a dipole source, the field of the SPP will dominate the total field, as long as the loss is low enough. This is because the field of the SPP decays radially as one over the square root of the radial distance, until the exponential decay damps it out.

Elee1l5 (talk) 18:16, 24 February 2022 (UTC)

Propagation in vacuum?

Can Zenneck waves propagate in a vacuum? 130.76.25.63 (talk) 22:16, 15 March 2023 (UTC)

If you mean vacuum over a lossy half space of material, then yes. Elee1l5 (talk) 22:16, 16 March 2023 (UTC)