Ray tracing study of whistlers guided by a field-aligned depression of electron density in the magnetosphere

摘要: Abstract The properties of VLF waves guided by a field-aligned depression electron density in different models the magnetosphere are studied. Ray tracing calculations show that guidance from one hemisphere to other is made possible existence Gaussian cross-section trough. occurs only at inner side trough, when it located L ⩽ 2.2 and ⩾ 4.0 for winter night model 1.5 summer day magnetosphere. All analyzed troughs modelled with same 15% effective width 215 km equatorial plane. Initial latitude ranges various wave normal directions, which rays successfully guided, moved equatorward trough centre. For initial defined so corresponding reach 300 altitude conjugate final angle inside ionospheric transmission cone. para-longitudinal mode or gradient trapping mode, depending on positions. Changing these positions, there continuous transition ray path other. main difference characteristics behaviour geomagnetic field. A has lower value this parameter than mode. deeply enters slight latitudinal gradients field responsible determining type guiding whistlers These characterized an upper cut-off frequency almost 0.5 ƒ Bmin .