Comparison of certain VLF noise phenomena with the lower hybrid resonance frequency calculated from simultaneous ion composition measurements

Abstract

Certain VLF noise phenomena commonly observed with electric dipole antennas on the Alouette, OGO, and Injun 5 spacecraft have been associated with the lower hybrid resonance frequency of the ionospheric medium in the vicinity of the spacecraft. By using simultaneous VLF and ion mass spectrometer data from OGO 4, it has now become possible to compare the characteristic frequencies of these noise bands with the lower hybrid resonance frequency fLH calculated directly from ion composition measurements. The results of the study show a clear correspondence between the independent observations over a wide range of variation of fLH. Some differences between the VLF and the spectrometer results are also evident and suggest that the characteristic frequencies of lower hybrid resonance noise phenomena observed by satellite-borne VLF receivers may not always be determined in the immediate vicinity of the spacecraft.