Studies of Magnetohydrodynamic Turbulence and Turbulence in the Interplanetary Medium

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This grant focuses on plasma turbulence in the magnetohydrodynamic (MHD) model, with an emphasis on implications for space plasmas and S/T research. A major continuing goal is the identification and characterization of basic dynamical processes in MHD turbulence. Prior results on incompressible turbulent relaxation processes such as selective decay and dynamic alignment will be extended to three dimensions and generalized to moderately compressible magnetofluids. Further study and application of turbulent reconnection and turbulence driven by large scale velocity shear will be pursued. These turbulence theory studies involve both analytical studies and extensive direct numerical simulations. Study and development of numerical algorithms for compressible turbulence simulations is also undertaken. A second major area of emphasis is the study of turbulence in the interplanetary medium at MHD scales, involving a high degree of interplay with the basic theory and extensive comparisons with observational data. Major undertakings in interplanetary studies include further development of the consequences of nearly incompressible MHD theory, completion and numerical implementation of an analytical model for theory, completion and numerical implementation of an analytical model for the evolution of interplanetary turbulence, including couplings of the local turbulence to large scale gradients, and the further study of dissipation mechanisms acting near ion gyroscales in the solar wind plasma. A third and closely related area of study involves the effects of MHD turbulence on charged particle acceleration and scattering, especially due to induced electric fields. The overall aim is to understand MHD processes and hence interplanetary 'weather'. //