Studies of Wave-Particle Interactions for Interstellar Pickup Ions in the Solar Wind

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The proposer has recently modeled the scattering of interstellar pickup protons, including wave dispersion and multiple resonances, under conditions appropriate to the distant equatorial heliosphere. The wave power generated by this scattering was used to drive a turbulent cascade which heated solar wind protons through its dissipation. Although the model reproduced much of the particle temperature behavior observed by Voyager 2, the results at the greatest radial distances showed too much heating, indicating that model improvements were needed. The PI now plans several new studies of these wave-particle interactions (which influence the evolution of turbulence, dominate energy fluctuations in the outer heliosphere, and determine the effect of interstellar pickup ions on the solar wind environment), while improving the model's treatment of turbulence. The PI will incorporate thermal effects into the dispersion of resonant waves in his equatorial model. He will then extend the model's treatment of dispersive resonant scattering to include the unequal intensities of inward and outward propagating waves produced by pickup in a non-azimuthal magnetic field. This more general analysis will allow the modeling of turbulent evolution at all heliolatitudes. The PI will also apply this new dispersive analysis to the behavior of pickup ions in a quasi-radial magnetic field, in order to address questions concerning sporadic wave generation and incomplete pitch-angle scattering associated with in situ pickup ion observations.