A semi-automated whistler analyser

A system to facilitate the analysis of wide-band VLF data from goniometer receivers has been designed and built and is now in use. Whistlers and other types of VLF phenomena are selected from a background of noise and from these signals are obtained their frequency-time dependence and direction of arrival, which can then be used to study magnetospheric morphology and dynamics. The system, which uses a spectrum analyser and programmable tracking filter, combines the human skill in pattern recognition, discrimination and selection with the speed, efficiency and accuracy of modern electronic digital techniques.