Global Solar Wind Structure: Effects of Pickup Protons

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This award is made in response to a proposal submitted to and reviewed under the NSF/DOE Partnership in Basic Plasma Science and Engineering, joint solicitation NSF 09-596.This project will study the effects of interstellar pickup protons on the structure and dynamics of the outer heliosphere. This requires creating a three-dimensional magneto-hydrodynamic (MHD) solar wind model, by integrating a model that accounts for the pickup protons as a separate fluid, together with a one-dimensional turbulence transport model. The approach being adopted treats the solar wind plasma as a mixture of three comoving species - solar wind protons, electrons, and pickup protons - and includes separate mass and energy equations for the solar wind protons and electrons, and for the pickup protons. The final model will therefore account for the energy transfer from pickup protons to solar wind protons and for the plasma heating due to turbulent dissipation.Using the tilted-dipole approximation or representative solar magnetograms to prescribe boundary conditions at the coronal base will enable calculation of the global structure of the solar wind out to 100 astronomical units for all phases of solar activity, which can then be compared with observations from the Voyager spacecraft. The study will examine the heating and deceleration of the solar wind in the outer heliosphere, the role of pickup ions in the physical processes of the outer heliosphere, interactions between large and small scales, and the interplay between turbulence and the solar wind.The results of this research will be useful in studies of other astrophysical plasmas, in particular that of the interstellar medium, where thermal plasma and energetic particles are coupled via waves, as well as coronal mass ejections and cosmic ray propagation, and the solar wind interaction with the local interstellar medium. This work will use and further develop methods employed in industrial and engineering applications, establishing a strong cross-disciplinary interest.