Advanced Space Plasma Simulations Using a High-Order Accurate Method and the Magnetohydrodynamics with Embedded Particle-in-Cell Model

[摘要] Global magnetohydrodynamics (MHD) models have been important tools for space physics research in recent decades. In order to improve the numerical accuracy and the physics capability of an MHD mode, a fifth-order accurate finite difference scheme for hyperbolic equations on block-adaptive curvilinear grids is developed to improve the accuracy of the Michigan MHD model BATS-R-US. To model kinetic phenomena, like magnetic reconnection, BATS-R-US is two-way coupled with a particle-in-cell (PIC) code iPIC3D to incorporate kinetic physics into a global model. The two-way coupled model is called magnetohydrodynamics with embedded particle-in-cell (MHD-EPIC) model. This dissertation research focuses on the development of the fifth-order scheme and the applications of the MHD-EPIC model. The fifth-order finite-difference scheme constructs the face fluxes with a monotonicity preserving limiter MP5, and achieves high-order spatial derivatives by a flux correction step. This scheme is generalized to curvilinear grids with a free-streaming discretization. For the locally refined mesh, high-order accuracy is also achieved by careful interpolation of ghost cells near the grid resolution changes. Numerical tests are presented to demonstrate the accuracy and robustness of the algorithm.The MHD-EPIC model is applied to study Earth;;s dayside magnetopause reconnection and Mercury;;s magnetotail reconnection. From the Earth simulation, the generation and evolution of flux transfer events (FTEs) are studied. It is found the magnetic field signature of FTEs at their early formation stage is similar to a `crater FTE;;. After the FTE core field grows to a significant value, it becomes an FTE with typical flux rope structure. Kinetic phenomena, such as the crescent electron phase space distribution, the Larmor electric field, and the lower hybrid drift instability are identified from the global simulation. The Mercury simulations apply MHD-EPIC to study the magnetotail reconnection. The properties of the magnetotail flux ropes agree well with the MESSENGER observations. The reconnection dawn-dusk asymmetry also arises from the simulations; the reconnection jets are stronger on the dawn side, which agrees with the MESSENGER observations.

[发布机构] University of Michigan

[效力级别] Magnetohydrodynamics with embedded particle-in-cell model

[关键词] Fifth-order accurate scheme for hyperbolic equation;Magnetohydrodynamics with embedded particle-in-cell model;Atmospheric;Oceanic and Space Sciences;Science;Atmospheric, Oceanic & Space Science