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Investigation of the chevron structure of some Pcl pulsations
Author(s) -
Gendrin Roger,
Laurent Georges
Publication year - 1979
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/gl006i003p00197
Subject(s) - chevron (anatomy) , ion , helium , plasma , physics , computational physics , geophysics , atomic physics , geology , astrophysics , nuclear physics , paleontology , quantum mechanics
A new variety of fine frequency structure of some Pcl geomagnetic pulsations has been recently reported. For these pulsations, each periodic element consists of a chevron‐shaped combination of rising and falling tones. A careful spectral analysis of one of these events, based upon a new numerical technique known as the Modified Moving Window Method (MMWM) allows us to establish the reality of this structure. This is tentatively interpreted in terms of propagation in a magnetospheric plasma containing a non negligible fraction of helium ions, the presence of helium ions resulting in a minimum in the ULF group velocity between the ion hybrid and ion crossover frequencies.