Magnetospheric Hydromagnetic Waves: Internal and External Coupling

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The objective of this project is to obtain a quantitative understanding of magnetospheric hudromagnetic modes and their coupling to external and internal sources of free energy, such as the ring current. Three interrelated areas of study will be followed: (1) inner magnetospheric cavity modes, (2) general properties of field line resonance modes, and (3) excitation of internally-driven field line resonance modes by energetic ring current particles. Key questions to be examined are: (1) what is the cavity mode structure in the inner magnetosphere and the frequencies one should expect to see in ground and satellite magnetic data and what is the efficiency of transport from the outer magnetosphere, (2) what controls the field line resonant mode radial structure, and (3) what causes the nonlinear saturation of the drift-bounce resonant mode, and what is the self-consistent effect of the mode on ion motion. The methods to be employed are: (1) for the cavity mode study, eigenmode analysis in dipole and general geometry and MHD simulations, (2) for the field line resonance mode study, MHD simulations in box and dipole geometry including finite Larmor radius effects as well as ionospheric damping, and (3) for the study of internally-driven field line resonance modes, hybrid MHD/gyrokinetic simulations in box and dipole geometry. The goal is to incorporate the key physics which has not yet been included in studies of these modes. Comparisons with spacecraft data will be made to test the theoretical predictions and yield new insights into observed wave properties and associated particle measurements.