Abstract
The propagation mechanism of very low latitude (geomagnetic latitudes of less than 20°) whistlers is poorly understood. This paper examines the propagation characteristics of non-ducted propagation, but we use three-dimensional ray tracing for realistic ionosphere/magnetosphere models, the electron density profile with latitudinal and longitudinal gradients and the International Geomagnetic Reference Field (IGRF) magnetic field model instead of the conventional dipole model. By assuming small possible tilts (in the latitudinal and longitudinal direction) of the initial wave normal angle in the input southern hemisphere, we have found that it is possible for us to detect, at a very low latitude position in the northern ionosphere, some whistler rays penetrate through the ionosphere, but some others can not. On the basis of systematic analysis of important parameters, we come to the general conclusion that the occurrence local times of whistlers are depend on the ionospheric model, especially latitudinal and longitudinal gradients of the electron density.
