The preventive role of Snell's law in mode conversion from Z- to whistler-mode waves in an inhomogeneous magnetoplasma with a low density

Electromagnetic waves with different modes, such as Z-, whistler-, LO- and RX- modes are found in different regions of the Earth magnetosphere and in the magnetosphere of other planets. Since whistler-mode waves influence the behavior of the magnetosphere, and they are used as experimental tools to investigate the upper atmosphere, they are important. On the other hand, the mode conversion process can be considered as one of the processes of generating electromagnetic waves that can occur under certain conditions. Usually, propagation waves in an inhomogeneous plasma are a necessary, but not a sufficient condition for a mode conversion process. Snell’s law has an important role in the mode conversion process. Although, this law lets a mode conversion occur from Z- to LO-mode waves, in a case from Z- mode to whistler mode waves, it plays a preventive role. The aim of this paper is to demonstrate the preventive role of Snell’s law in a mode conversion from Z- to Whistler-mode waves in an inhomogeneous magnetoplasma with a low density. We used the dispersion relation in the magnetoplasma with a low density and for an oblique wave normal angle. By applying the Snell’s law, we showed that with the propagation of the Z-mode waves in an inhomogeneous plasma, there is not any matching point between Z- and Whistler mode waves, and for any wave normal angle always an evanescent layer exists between the two modes. In this case, Snell’s law prevents the mode conversion from occurring. It also prevents the transfer of energy from one to another mode waves.