Color spectrograms of very-low-frequency Poynting flux data

This paper discusses a new method of processing the VLF electric and magnetic field data from the Injun 5 satellite to produce color frequency-time spectrograms with the color indicating the Poynting flux direction, up or down the geomagnetic field. The Poynting flux sensing technique used on Injun 5 employs one electric and one magnetic antenna, both oriented perpendicular to the geomagnetic field and to each other. With this antenna geometry the Poynting flux direction, up or down the geomagnetic field, can be determined from the cross-correlation between the electric and magnetic field signals. The technique used to process these signals employs a new type of spectrum analyzer/cross-correlator to determine the cross-correlation between the electric and magnetic field signals as a function of frequency and time. These data can be displayed as a two-color frequency-time spectrogram by using appropriate display techniques. A survey of complex VLF radio noise phenomena analyzed by using this technique is presented.