Open AccessMultipoint observation of fast mode waves trapped in the dayside plasmasphere
Author(s) -
Takahashi Kazue,
Bonnell John,
Glassmeier KarlHeinz,
Angelopoulos Vassilis,
Singer Howard J.,
Chi Peter J.,
Denton Richard E.,
Nishimura Yukitoshi,
Lee DongHun,
Nosé Masahito,
Liu Wenlong
Publication year - 2010
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 - 10.1029/2010ja015956
Subject(s) - plasmasphere , physics , amplitude , standing wave , phase velocity , phase (matter) , noon , toroidal and poloidal , geophysics , computational physics , magnetic field , magnetosphere , astrophysics , toroid , plasma , optics , atmospheric sciences , quantum mechanics
Multipoint observations of a dayside Pc4 pulsation event provide evidence of fast mode waves trapped in the plasmasphere (plasmaspheric cavity mode or virtual resonance). Time History of Events and Macroscale Interactions during Substorms (THEMIS)‐A, the primary source of data for the present study, was moving outward near noon and detected poloidal oscillations, characterized by the azimuthal electric field component E y and the radial and compressional magnetic field components B x and B z . The structure of the plasmasphere was constructed from the mass density radial profile estimated from the frequency of toroidal standing Alfvén waves observed at this spacecraft. The outer edge of the plasmapause (the maximum of the equatorial Alfvén velocity V Aeq ) was located at L ∼ 7, and the minimum of V Aeq was located at L ∼ 4, forming a potential well structure required for mode trapping. Relative to the ground magnetic pulsations observed in the H component at a low‐latitude station ( L = 1.5), the E y component exhibited a broad amplitude maximum around L ∼ 3.5 and maintained a nearly constant phase from L = 2 to L = 5. In contrast, the B z component exhibited an amplitude minimum and switched its phase by 180° at L = 3.8. This radial mode structure is consistent with theoretical models of mode trapping. Also, the E y and B z components oscillated ±90° out of phase, as is expected for radially standing waves.