Ion cyclotron whistlers related to heavy minor ions observed by the akebono satellite and their distribution in the inner magnetosphere

It is well known that lightning whistler waves are caused by lightning discharge; these waves propagate along geomagnetic field lines as R-mode plasma waves of less than several tens kHz. Ion cyclotron whistler waves, which are electromagnetic ion cyclotron (EMIC) mode waves, have a close relation to lightning whistlers. Propagation characteristics of ion cyclotron whistler strongly depend on ion concentrations in plasma as well as nature of general EMIC waves. Gurnett et al.(1965) proposed a generation mechanism for ion cyclotron whistlers along their propagation characteristics. One of the most important features is the lowest frequency of an ion cyclotron whistler that denotes the local crossover frequency (ω_cr) of the EMIC mode wave. The asymptotic frequency of a typical ion cyclotron whistler is close to each local ion cyclotron frequency (Ω_i). These facts suggest that we can estimate the ion species and concentrations at a local point or in the propagation path of the waves by analyzing these characteristics of ion cyclotron whistlers.