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Time‐frequency decomposition of signals in a current disruption event
Author(s) -
Lui A. T. Y.,
Najmi A.H.
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl03229
Subject(s) - amplitude , signal (programming language) , frequency domain , wavelet , time–frequency analysis , low frequency , acoustics , wavelet transform , physics , current (fluid) , signal processing , cascade , noise (video) , computer science , telecommunications , optics , artificial intelligence , radar , image (mathematics) , computer vision , thermodynamics , programming language , chemistry , chromatography
Wavelet transform has recently been developed to the level of sophistication suitable for application to signal processing in magnetospheric research. We explore this new technique in decomposing signals in the time‐frequency domain by first conducting continuous wavelet transform on a test signal to show its ability to resolve multiple‐frequency components embedded within white noise of half the amplitude as the signal. We then use this tool to examine the large‐amplitude magnetic fluctuations observed during a current disruption event. The results show the current disruption to be a multiscale phenomenon, encompassing low‐ as well as high‐frequency components. The lowest‐frequency component appears to behave quite independently from the higher‐frequency components. The analysis shows for the first time that in current disruption the high‐frequency components constitute a broadband excitation with a nonstationary nature, i.e., some oscillations appear to cascade from high to low frequency as time progresses.