Brent Foy (Committee Member), Ivan Medvedev (Committee Member), Amit Sharma (Advisor)
Master of Science (MS)
The study of solar-terrestrial plasma is concerned with processes in magnetospheric, ionospheric, and cosmic-ray physics involving different particle species and even particles of different energy within a single species. Instabilities in space plasmas and the earth's atmosphere are driven by a multitude of free energy sources such as velocity shear, gravity, temperature anisotropy, electron, and, ion beams and currents. Microinstabilities such as Rayleigh-Taylor and Kelvin-Helmholtz instabilities are important for the understanding of plasma dynamics in presence of magnetic field and velocity shear. Modeling these turbulences is a computationally demanding processes; requiring large memory and suffer from excessively long runtimes. Previous works have successfully modeled the linear and nonlinear growth phases of Rayleigh-Taylor and Kelvin-Helmholtz type instabilities in ionospheric plasmas using finite difference methods. The approach here uses a two-fluid theoretical ion-electron model by solving two-fluid equations using iterative procedure keeping only second order terms. It includes the equation of motion for ions and electrons, the continuity equations for both species, and the assumption that the electric drift and gravitational drift are of the same order. The effort of this work is to focus on developing a new pseudo-spectral, highly-parallelizable numerical approach to achieve maximal computational speedup and efficiency. Domain decomposition along with Message Passing Interface (MPI) functionality was implemented for use of multiple processor distributed memory computing. The global perspective of using Fourier Transforms not only adds to the accuracy of the differentiation process but also limits memory calling when performing calculations. An original method for calculating the Laplacian for a periodic function was developed that obtained a maximum speedup of 2.98 when run on 16 processors, with a theoretical max of 3.63. Using this method as a backbone for parallelizing the RT-KH solution, the final program achieved a speedup of 1.70 when calculating only first order terms, and 1.43 when calculating up to second order.
Department or Program
Department of Physics
Year Degree Awarded
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