Isotropic approximation errors in geometrical-optical description of ionospheric propagation of radio waves

Isotropic approximation, i.e. neglect of magnetic field effects, is widely used to simplify the geometrical optics description of ionospheric propagation of radio waves. However, this description under certain conditions may produce a significant error. In this study, ray traycing is performed to examine an isotropic approximation error in relation to operating frequency and radiation angles.