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Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves
Author(s) -
Takahashi Kazue,
Waters Colin,
Glassmeier KarlHeinz,
Kletzing Craig A.,
Kurth William S.,
Smith Charles W.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021780
Subject(s) - physics , amplitude , longitudinal wave , plasmasphere , magnetic field , computational physics , field line , harmonics , toroid , equator , standing wave , field (mathematics) , magnetosphere , acoustics , wave propagation , optics , plasma , astronomy , mathematics , quantum mechanics , voltage , pure mathematics , latitude
The power spectrum of the compressional component of magnetic fields observed by the Van Allen Probes spacecraft near the magnetospheric equator in the dayside plasmasphere sometimes exhibits regularly spaced multiple peaks at frequencies below 50 mHz. We show by detailed analysis of events observed on two separate days in early 2014 that the frequencies change smoothly with the radial distance of the spacecraft and appear at or very near the frequencies of the odd harmonics of mutiharmonic toroidal mode standing Alfvén waves seen in the azimuthal component of the magnetic field. Even though the compressional component had a low amplitude on one of the selected days, its spectral properties are highlighted by computing the ratio of the spectral powers of time series data obtained from two spatially separated Van Allen Probes spacecraft. The spectral similarity of the compressional and azimuthal components suggests that the compressional component contains field line resonance characteristics.