Gary develops global three-dimensional time-dependent computer models to study the structure and dynamics of the interiors of planets and stars. The first in this series of models was written in the 1980s to study the solar dynamo. A modified version of this model was used for pre-flight studies and post-flight analyses of a rotating fluid dynamics experiment flown aboard NASA Space Shuttles in 1985 and 1995. In his studies of geodynamics he has simulated global circulation and convection in the Earth's atmosphere, mantle and core. He has also simulated convection and magnetic field generation in the deep interiors of giant gas planets like Jupiter and Saturn.

Gary and colleagues, Paul Roberts (UCLA) and Rob Coe (UCSC), study the internal magnetohydrodynamics of the Earth's core, i.e., the geodynamo. This is the mechanism in the Earth's fluid outer core that maintains the geomagnetic field. Their computer simulations span millions of years, using an average numerical time step of 15 days. At the surface of the model Earth, the simulated magnetic field has an intensity, an axial dipole dominated structure, and a westward drift of the non-dipolar structure that are all similar to the Earth's. The model's solid inner core rotates slightly faster than the surface of the model Earth; this computer modeling result in 1995 served as a prediction for the Earth that several seismic analyses now support. Several spontaneous reversals of the magnetic dipole polarity also occur in the simulations, similar to those seen in the Earth's paleomagnetic record.

Gary and his former graduate student Tami Rogers (now an assistant professor at the University of Arizona) study the internal magnetohydrodynamics of the sun using his computer codes and hers. Their simulations illustrate how gravity waves in the sun's deep radiative interior may be excited by turbulence in the outer convection zone.

Gary and his former graduate student Martha Evonuk (now at the Universität Bayreuth) study the internal magnetohydrodynamics of giant planets using his spectral dynamo code and her finite volume code. A recent dynamo simulation of a giant planet maintains a banded zonal wind profile on the surface and a dipole dominated magnetic field, similar to that measured on Saturn.

Gary and his former graduate student Darcy Ogden (now an assistant professor at the University of California San Diego) study the supersonic multiphase dynamics of explosive volcanic eruptions using a library of computer codes, CFDLib, from the Los Alamos National Laboratory. When a standing shock wave (Mach disk) forms above the vent their simulations predict a flow profile within the erupting column that is very different than that which has been assumed in simple parameterized models.

Gary, Francis Nimmo and their graduate student Erinna Chen study circulations and induced magnetic fields in the subsurface oceans of Europa and Titan driven by tidal potentials using 3D MHD simulations.

Gary, Nic Brummell and their graduate student Katelyn White study magnetic field generation in laboratory dynamo experiments using 3D dynamo simulations.

Publications