GEM: Numerical Modeling of Ultra-Low-Frequency (ULF) Waves and the Production of Geomagntically Induced Currents

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

The magnetic field of the Earth is not static and is constantly fluctuating. Magnetic field lines can, in some sense, be thought of like strings on a musical instrument, like a guitar or harp. Just like the strings of a harp, these field lines are of different lengths and have different densities, so each field line fluctuates at its own frequency. In addition, the region around the Earth can also act as one of a set of kettle drums that also have their own frequency. These fluctuations give rise to electrical currents that flow through space and can often flow on and beneath the surface of the Earth. These currents can have important effects, such as disruptions in the power grid and corrosion of oil and gas pipelines. A computer model was developed to describe the currents flowing in space and their effect on ground currents. The proposed work will further improve this model by including more realistic conditions based on statistical models and satellite measurements of the density of particles in space. This work will also support a graduate student who will learn more about computer simulation as well as the issues. Ultra-low-frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. The primary goal of the proposed research is to extend our models of these waves and to apply these models to better understand the structure of ULF waves in a more realistic magnetosphere and to relate observations in space and on the ground, particularly regarding the excitation of geomagnetically induced currents (GICs). In previous work, the proposers have developed a three-dimensional numerical model in dipole geometry to describe the propagation of ULF waves in the inner magnetosphere. They have also developed a similar code in spherical geometry that covers all latitudes. A major task will be to integrate the dipole code and the spherical code. The proposers will base the underlying density structure in the inner magnetosphere on empirical models of the ionosphere and plasmasphere. The model results will be compared with data from the Van Allen Probes and other platforms in space, as well as with observations from ground magnetometers. This project will investigate the response of the magnetosphere-ionosphere coupling system to external perturbations, such as the interaction of the magnetosphere with interplanetary shocks with the perturbations induced during substorms. The proposers will also investigate the excitation of geomagnetically induced currents (GICs) on the ground by extending the model from the ionosphere through to the ground. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.