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Ionospheric Alfvén resonator as seen by Freja satellite
Author(s) -
Grzesiak Marcin
Publication year - 2000
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 - 10.1029/1999gl010747
Subject(s) - ionosphere , resonator , earth's magnetic field , physics , satellite , field line , computational physics , geophysics , phase (matter) , spectral line , electric field , fourier transform , alfvén wave , magnetic field , optics , astronomy , quantum mechanics , magnetohydrodynamics
Sharp increase of the Alfvén speed above the ionosphere is expected to create a resonant cavity for the Alfvén waves traveling along the geomagnetic field lines (so‐called Ionospheric Alfvén Resonator). The wavelet transform has been used to analyze magnetic and electric fields recorded on Freja satellite. Cross‐phase spectra between field components in the frequency range 0.5–10 Hz reveal a pattern similar to that predicted theoretically for the resonator. The Fourier cross‐phase spectra fail to show any characteristic features. We conclude that this is due to the spatial structure of the resonator which can be examined only with local analysis techniques.