Nonadiabatic behavior of the magnetic moment of a charged particle in a dipole magnetic field

Non-adiabatic behavior of the magnetic moment of a charged particle in a dipole magnetic field is studied both numerically and analytically in the presence of a low frequency electrostatic wave with azimuthal component. We obtained numerically two characteristic conditions for the breakdown of μ; one is independent of the wave frequency, and the other forms a spike-like structure in the wave frequency-particle energy space. We showed analytically that the former is caused by the direct interaction between the particle and the electrostatic wave during the gyromotion and that the latter is caused by two kinds of resonances, i.e., the bounce-E x B drift resonance and the wave-drift resonance. The unstable conditions obtained by theoretical consideration showed good agreements with those of numerical results. (author)