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Nonlinear acceleration of dispersive effects in field line resonances
Author(s) -
Lu J. Y.,
Rankin R.,
Marchand R.,
Tikhonchuk V. T.
Publication year - 2003
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 - 10.1029/2003gl016929
Subject(s) - nonlinear system , physics , computational physics , acceleration , dispersion (optics) , alfvén wave , dipole , perpendicular , field line , magnetic field , field (mathematics) , geophysics , mechanics , classical mechanics , optics , geometry , magnetohydrodynamics , mathematics , quantum mechanics , pure mathematics
Nonlinear dynamics of a dispersive field line resonance (FLR) is investigated in a dipolar magnetic geometry using a new finite element code TOPO. Time dependent dispersion and steepening of the perpendicular Alfvén velocity profile lead to the acceleration of dispersive effects and to localization of the FLR within an ionospheric density cavity. Consequently, shear Alfvén waves are trapped between turning points inside nonlinear density perturbations. This results in a complicated nonlinear FLR structure and an associated overlap of timescales for dispersion and nonlinearity. We show that nonlinear effects lead to fine scale structuring produced by the interplay of nonlinear and dispersive effects. We discuss the relevance of our results to observations of FLR's in the auroral zone.