Fine structure of whistlers recorded digitally at Halley, Antarctica

Abstract

Two whistlers recorded digitally at Halley, Antarctica ( L = 4.3) were analyzed by matched filtering with 10 Hz frequency resolution. For the construction of the matched filter, a more realistic description of the whistler waveform than has been used for lower latitude whistlers was applied. The ( ƒ, t) pairs obtained, together with the corresponding magnitudes, gave a high resolution dynamic spectrum which revealed the fine structure of the whistlers. Whistlers which appeared as well defined, discrete, single traces on a conventional spectrogram, turned out to be composed of several components covering various parts of the spectrum. Further analysis of the strongest and longest component of a whistler resulted in high resolution travel time residual curves similar to those obtained by the ray tracing method or by averaging of numerous occurrences of whistlers in the same duct. The matched filter method of analysis can provide new insights into the details of ducted whistler propagation. It also yields the amplitude variation vs time (or vs frequency) along the whistler trace, thus potentially giving information about the spectrum of the source spheric, and/or the frequency dependence of magnetospheric amplification due to wave-particle interactions.