On the similarity features of normalized frequency spectrograms of magnetospherically reflected whistlers

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Abstract
A modified electron whistler dispersion law is derived to be used for analytical and numerical investigation of magnetospherically reflected (MR) whistlers' propagation for finite ratio ωc/ωp of electron gyrofrequencies to plasma frequencies if the wave frequency is much less than ωp. The contribution of ions is included in the value of the lower hybrid resonance frequency only. Ray‐tracing simulations are carried out in order to reproduce MR whistler spectrograms typical of those observed on high‐altitude equatorial and low‐altitude satellites. It is found that spectrograms of MR whistlers with frequencies normalized to the equatorial electron gyrofrequency at the L shell of wave observation are close to each other when satellites are located on the equator at different altitudes (or at low altitude and different latitudes). Moreover, normalized frequencies corresponding to flattening of traces on spectrograms at large group delay times can be obtained by following me path of a single extreme quasi‐resonant whistler ray starting downward at the equator with a group velocity direction corresponding to the resonance cone. On the basis of obtained results, a possible interpretation of the origin and spectral characteristics of discrete plasmaspheric emissions is discussed.