UNIVERSITY OF ALABAMA IN HUNTSVILLE
Grant: $438,228 - National Science Foundation - Aug. 16, 2009
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Award Description: The Principal Investigator (PI) will investigate the anomalous diffusion of energetic charged particles in fusion, space, and astrophysical plasmas using a combination of theory, simulations, and observations. He intends to focus on the role of non-classical (non-Gaussian) phenomena in anomalous diffusion in the collisionless solar wind, specifically the magnetic field-line random walk of energetic charged particles in the solar wind. In this investigation, the PI will develop and test theories for the non-classical magnetic field-line random walk and energetic charged particle diffusive transport, including a numerical kinetic transport model to solve the standard cosmic ray equation (modified to include fractional derivative terms for non-classical anomalous diffusion). The PI will recruit and supervise a graduate student to work on a Ph.D. thesis as part of this project, and he will encourage minority graduate students to apply. The PI plans to include this graduate student as an integral participant in the analysis of non-Gaussian anomalous transport of energetic charged particles at collisionless shocks. In this way, the project will link research and education and contribute to the training of the next generation of space plasma physicists.
Project Description: We took the first step in developing an improved theory for how magnetic field lines random walk in the magnetic field turbulence in the low density plasma environment of interplanetary space. Previous linear and nonlinear theories of magnetic-field-line random walk are really only applicable in weak turbulence situations and thus do not apply to the strong turbulence situations that occur near shock waves in interplanetary space, for example. In the new theory random fluctuations in the magnetic field directed along the mean magnetic field were included, while in the past this component was assumed to be negligibly small. The results show that previous weak turbulence theories for magnetic field-line random walk agree with the results from our new more general theory as long as the variations in the turbulent magnetic field is of the same magnitude or less than the magnitude of the average magnetic field. However, compared to our new theory, previous theories strongly overestimate the amount of field-line random walk when the variation in the magnetic field is larger than the magnitude of the mean magnetic field. This work is an essential step forward in our goal to develop a more general theory for energetic charged particle anomalous diffusion across the large-scale interplanetary magnetic field that also holds for strong turbulence situations. The development of the theory benefitted enormously from a recent visit from Dr. Andreas Shalchi from Germany at CSPAR, one of the leading experts on this topic in the world today. The new theory has been written up and was recently submitted to the Astrophysical Journal for publication.
Jobs Summary: No jobs created/retained (Total jobs reported: 0)
Project Status: Less Than 50% Completed
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