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H.O. Rucker, M. Leitner (Space Research Institute, Graz, Austria)
The non-thermal radio emission of Jupiter is since decades a well-known phenomenon exhibiting features on times scales varying from hours to milliseconds. Jovian millisecond (or S-)bursts are closely connected to Io-triggered emissions and provide a variety of features in the frequency versus time diagram, the so-called dynamic spectrum. Generally speaking, the averaged properties of these emission structures could be explained by the adiabatic motion (eventually under the influence of local or global parallel-electric fields) of electrons along field lines connecting Io with Jupiter, producing radio emission close to the gyrofrequency by means of the cyclotron maser instability (CMI theory). However, the explanation of detailed S-burst features by physical models is still regarded as an open problem.
Spectral analysis is the dominant process in the investigation of dynamic spectra obtained by radio telescopes. Spectral averaging is necessary in order to get a convergent estimation of the Fourier spectrum. Even highly developed digital receiving systems are limited with regard to frequency and time resolution, leaving the analysis of S-bursts at a level which is unable to explore the eventual substructures of these features. The high variability in time suggests an application of the Wavelet transform. As can be shown by simulations as well by real data analysis, specific parts of information - yet hidden in a dynamic spectrum - may provide an important key in the understanding of the corresponding physical process.