On the existence conditions for a fast surface wave
K.Z. Rukhadzec aAlexeev Nizhnii Novgorod State Technical University, Minina str. 24, Nizhnii Novgorod, 603600, Russian Federation bLomonosov Moscow State University, Department of Physics, Leninskie Gory 1 build. 2, Moscow, 119991, Russian Federation cProkhorov General Physics Institute of the Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119942, Russian Federation
Conditions are obtained for the existence of a fast-moving surface electromagnetic wave (with a speed close to the speed of light in the vacuum) on a flat interface between the vacuum and an isotropic dissipative medium with a permittivity ε = ε′ + iε". The interfaces considered include vacuum—seawater, vacuum—metal, vacuum—plasma, and vacuum—dielectric. Conditions for the existence of negligibly damped surface waves are considered for extremely high (vacuum—seawater, vacuum—metal) and very low (vacuum—plasma, vacuum—dielectric) ε" values. It is shown that at least in these two limit cases, the phase wave velocity Vp and the group wave velocity Vg pass synchronously through the speed of light c in the vacuum, which can be considered the reason why surface waves exist at the interface between the vacuum and a collisionless plasma (with ε′ < −1 and Vp, g < c) and do not exist at the interface between the vacuum and a weakly absorbing dielectric (with ε′ > 1 and Vp, g > c). In the first limit case, it is shown that both the phase and group velocities pass c at ε′ = −3/4, implying that a surface wave exists at the vacuum—metal interface (with ε′ < −3/4), but that a surface wave (Zenneck’s wave) cannot exist at the vacuum—seawater interface (with ε′ > −3/4).