Physics of Plasma Confined by a Dipole Magnetic Field

The proposed work is to conduct and analyze two specific experiments using the newly assembled Collisionless Terrella Experiment (CTX). The results from these experiments will significantly expand our understanding of collisionless particle transport in planetary magnetospheres. They will be used to test basic theories of chaos and transport induced by dynamic and static non-axisymmetric perturbations to a dipole magnetic field. For the first experiment, energetic electrons trapped within the dipole magnetic field will be generated by operating our microwave plasma source so as to directly heat the high-field regions of the dipole. As seen elsewhere, these electrons will become unstable to a spectrum of low-frequency interchange instabilities and induce collisionless radial transport. We will measure the amplitude, frequency, and wavelength of the fluctuations, the condition for the onset of chaos, and the magnitude of the resulting transport. We will also be able to observe marginally-stable pressure profiles and test theories of adiabatic transport. For the second experiment, we will impose a multipolar static perturbation to the energetic electron plasma breaking azimuthal symmetry and destroying conservation of angular momentum. By measuring the decrease in the confinement of the trapped electrons as the magnitude of the perturbation is increased, we will be able to document the conditions leading to three-dimensional chaos. These experiments will be guided and interpreted by numerical and theoretical analysis. By making correlations between laboratory and numerical simulations, we will demonstrate how magnetic fluctuations can induce transport and heating of energetic particles in dipole fields and establish models for similar processes occurring in planetary magnetospheres.