Characteristics of Dispersion and Occurrence Rate of Whistlers at Low Latitudes during One Solar Cycle

Electron-density variations inthe magnetosphere at a geocentric distance of~1.50 earth radii are deduced from whistler dispersion data during one solar cycle from the year 1958 to 1968. The less sensitivity to the long-term variation of solar activity of the magnetosphere than the ionosphere was found. Also the variation of whistler dispersion at low latitude shows a semi-annual change, which will be discussed in comparison with the ionospheric f0F2 variation. Moreover, the characteristics of occurrence rate of low latitude whistlers are investigated with special reference to the solar-cycle and annual variations. These features on occurrence rate are explained in terms of ionospheric absorption, and duct formation.

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