| Description |
The primary objective of this dissertation is to investigate the behavior of ground-level electric fields along coastlines during geomagnetic storms. Robust, three-dimensional (3-D) Maxwell's equations finite-difference time-domain (FDTD) models of the near-Earth environment (< 110 kilometers in altitude) are used to predict ground-level electric fields in greater detail than previously possible. The motivation behind this work is to protect electric power grids. During geomagnetic storms, geomagnetically induced currents (GICs) may be generated along grounded conductors, which may then couple to electric power grids and cause blackouts. Ocean-continent boundary regions are of particular concern because of the sharp contrast in electrical conductivity between the ocean and continent. This contrast may generate high amplitude geoelectric fields and thus cause power grids in coastal regions to be more vulnerable to space weather hazards. Using FDTD, the complete physics of the disturbed ionosphere may be accommodated as well as realistic coastal geometries. This research is a component of the NSF PREEVENTS Track 2 project: Comprehensive Hazard Analysis for Resilience to Geomagnetic Extreme Disturbances (CHARGED). A second objective of this dissertation is to propose a new and efficient algorithm for electromagnetic wave propagation in magnetized plasma. When modeling electromagnetic wave propagation particularly above ~1 kHz in the ionosphere, the ionosphere should be treated as an anisotropic medium. The significant benefit provided by the new proposed algorithm is that it requires only a single update to the ionospheric iv current density update equation even when the time step increment for the current density update equation is smaller than the Courant limit for Maxwell's equations. A stability criterion based on Eigenvalue analysis is provided. The last objective of this dissertation is to introduce Hierarchical Data Format 5 (HDF5) as an efficient parallel input-output (I/O) scheme, particularly for global FDTD models involving a complex arrangement of trapezoidal cells, merging of cells, and triangular cells, but which also can be used for any other FDTD models. |
