Open AccessShock profile analysis using wavelet transform
Author(s) -
Gedalin M.,
Newbury J. A.,
Russell C. T.
Publication year - 1998
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/97ja03593
Subject(s) - quasiperiodic function , morlet wavelet , shock (circulatory) , wavelet , amplitude , shock wave , physics , wavelet transform , geology , mechanics , optics , computer science , discrete wavelet transform , medicine , artificial intelligence , condensed matter physics
We study the fine structure of the collisionless shock front, paying particular attention to the large gradients and internal structure within the ramp and to quasiperiodic structures in the ramp vicinity. In order to separate random steep gradients with low amplitudes from steep large‐amplitude formations, we apply Gaussian wavelet transforms suitable for this task. We analyze several high Mach number shocks and show that ramp substructure is not uncommon and that the typical scales of the steepest gradient features are significantly smaller than the shock transition width (provided they are stationary in the shock frame). We apply the Morlet wavelet transform to the magnetic field data in order to identify quasiperiodic patterns which may last only several periods. It is likely that short quasiperiodic wave trains dominate in the wave activity. Such wave trains are not always associated with the ramp itself.