Ceddes, noticed in the case of a number of aurorae that the earth currents
which accompanied the displays and seriously interfered with telephonic and telegraphic communication frequently began on the afternoon preceding the auroral display.
Faults are electromagnetic hot zones where electrical currents from the atmosphere are interacting with the subsurface currents called telluric or Earth currents.
The strike locations appear to be controlled more by geologically driven Earth currents than by topography, or by vegetation, or by infrastructure," he said.
Earth currents also occur in shallower stratigraphic layers from 5,000-30,000-foot depths.
Lightning forms when "dart leaders" descend below a thunderstorm, which typically are between 10,000-25,000-foot elevations, seeking a connection to Earth currents.
Earth currents appear to be the strongest determinant as to the physical location of c2g strikes.
The researchers at DML propose it's because the Earth currents are eating away at pipelines and speeding up corrosion.
These changes complement previous additions of materials on the Bergeron graphical analysis of reflection behavior, the ABCD matrix, and earth currents and formulas for the impedance of ground return circuits, as well as a descriptive treatment of the elliptical cylindrical waveguide and the expansion of Chapter 1 to emphasize the dependence of the line parameters on frequency and temperature.
Also included are several appendices on: vector analysis-definitions and formulas, Bessel functions, parallel-slab equivalent of a slotted coaxial line, earth currents and distributed impedances, low temperature impedance effects, and a table of physical constants.