Orbits of Charged Particles in a Dipole Magnetic Field

Abstract:

Via numerical calculation of the Lyapunov exponent of orbits of charged particles trapped by a dipole magnetic field, we report the discovery of a set of quasi-periodic orbits. Compared with orbits studied with the guiding center approximation, particles at these orbits have much higher energies and magnetic moments. They therefore move around the equatorial plane and have access to a large radial range so that the guiding center approximation is not applicable. These orbits may have significant implications on study of magnetospheric physics. There are also unstable quasi-periodic orbits whose measure in the phase space is negligible and are not expected to have any observational effects.