STUDIES OF LARGE-SCALE EARTH POTENTIALS ACROSS OCEANIC DISTANCES

This paper describes some ongoing research to characterize and underst and the large-scale (on the order of several thousand kilometers) geoe lectric potentials that can be induced within the Earth by fluctuation s of the geomagnetic field. An understanding of these induced potentia ls can be important for carrying out some geophysical investigations, as well as for solving numerous engineering problems related to the de sign and deployment of long, conducting installations on the Earth's s urface. Such installations include the systems used to power long-dist ance cables, electrical power distribution networks, and pipeline corr osion-control systems. The magnitude of the induced potentials fluctua tes significantly in time and in spatial extent. It reflects both the highly variable nature of the Earth's space plasma environment that pr oduces the geomagnetic fluctuations and the heterogeneous nature of th e geological structure of the Earth's surface and upper mantle. Presen t-day models of Earth's magnetic fluctuations are insufficient to pred ict the geopotentials reliably, particularly the extreme geopotentials that might be experienced on a specific long route. Thus, such geopot ential measurements as those described in this paper on AT&T cables in the Atlantic and Pacific Oceans can contribute important knowledge of the Earth's geophysical environment, as well as new geopotential info rmation for engineering design.