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On Arnol'd diffusion in a perturbed magnetic dipole field
Author(s) -
Warren Harry P.,
Bhattacharjee A.,
Mauel Michael E.
Publication year - 1992
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 - 10.1029/92gl00776
Subject(s) - dipole , physics , adiabatic invariant , magnetic field , magnetic dipole , magnetosphere particle motion , diffusion , amplitude , classical mechanics , adiabatic process , field (mathematics) , quantum electrodynamics , condensed matter physics , quantum mechanics , mathematics , pure mathematics
For certain initial conditions, the motion of charged particles in a magnetic dipole field is well described by the hierarchy of adiabatic invariants: the magnetic moment μ , the longitudinal invariant J , and the magnetic flux ψ . Electrostatic waves that break the axisymmetry of the dipole field and resonate with the drift motion can generate large‐scale or so‐called thick‐layer chaos in ψ . This chaos will drive Arnol'd diffusion in μ and J , making the motion asymptotically unstable. Previous studies involving mappings [ Tennyson et al ., 1980; Kook and Meiss , 1989] have found the thick‐layer Arnol'd diffusion rate to be proportional to the square of the perturbtion amplitude, consistent with quasilinear theory. Here we present numerical evidence that for many cases of physical interest, such as particle motion in a perturbed dipole field, the thick‐layer diffusion rate is greatly attenuated from the quasilinear result.