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Fine structure in the spectra of low latitude field line resonances
Author(s) -
Samson J. C.,
Waters C. L.,
Menk F. W.,
Fraser B. J.
Publication year - 1995
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 - 10.1029/95gl01770
Subject(s) - field line , physics , plasmasphere , spectral line , earth's magnetic field , waveguide , wkb approximation , computational physics , field (mathematics) , harmonics , line (geometry) , magnetic field , reflection (computer programming) , magnetopause , magnetosphere , geophysics , optics , astronomy , geometry , mathematics , quantum mechanics , voltage , computer science , pure mathematics , programming language
The power spectra of low latitude (L<3), ground‐based recordings of dayside geomagnetic pulsations in the 10‐100 mHz band indicate that these pulsations come from discrete, driven field line resonances which are coupled to compressional, magnetohydrodynamic, cavity or waveguide modes. The spectral bands of individual harmonics of the field line resonances seen by the magnetometers have envelopes which are typically 10's of mHz wide but also show a fine scale structure of almost equispaced peaks with separations of about 3 to 5 mHz. A WKB analysis of a cavity or waveguide model shows that the fine structure is likely due to field line resonances driven by waveguide modes with turning points within the plasmasphere and reflection at the dayside magnetopause.