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Nonlinear interaction of energetic ring current protons with magnetospheric hydromagnetic waves
Author(s) -
Chan Anthony A.,
Chen Liu,
White Roscoe B.
Publication year - 1989
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/gl016i010p01133
Subject(s) - physics , magnetosphere , adiabatic invariant , gyroradius , ring current , proton , dipole , earth's magnetic field , quantum electrodynamics , nonlinear system , charged particle , magnetic dipole , guiding center , computational physics , classical mechanics , magnetic field , atomic physics , ion , quantum mechanics
In order to study nonlinear wave‐particle interactions in the Earth‧s magnetosphere we have derived Hamiltonian equations for the gyrophase‐averaged nonrelativistic motion of charged particles in a perturbed dipole magnetic field. We assume low frequency (less than the proton gyrofrequency) fully electromagnetic perturbations, and we retain finite Larmor radius effects. Analytic and numerical results for the stochastic threshold of energetic protons (≳ 100 keV) in compressional geomagnetic pulsations in the Pc 5 range of frequencies (150‐600 seconds) are presented. These protons undergo a drift‐bounce resonance with the Pc 5 waves which breaks the second (longitudinal) and third (flux) adiabatic invariants, while the first invariant (the magnetic moment) and the proton energy are approximately conserved. The proton motion in the observed spectrum of waves is found to be strongly diffusive, due to the overlap of neighboring primary resonances.