Comment on “Hy‐wire measurements of atmospheric potential” by R. H. Holzworth

Abstract

Measurement of the temporal variation of the global electrical circuit is becoming of increasing interest to the scientific community. Holzworth (1983) suggests that a tethered balloon at about 500 m over Wallops Island may have recorded variations of the global electrical circuit. This note discussed the general problem of how meteorological processes in the lower atmosphere control the variation of atmospheric potential and thus mask the global signal. It is shown that the reported tethered balloon potential measurements occurred (1) when changes in aerosol number density spectrum would have been expected and (2) when changes in convection may have occurred. These meteorological processes modulate the atmospheric electric field intensity locally. There is no correlation when the curve determined by the UT hourly average of the tethered balloon potentials is correlated with the hourly UT variation of the global circuit as represented by the Carnegie curve. For the abrupt drops in potential that occurred coincident with the breakup of fog or discontinuation of the morning rise in temperature to be due to changes in the global circuit would require more than 50% of the several thousand global thunderstorms to stop abruptly; this is unlikely. Because of the occurrence of fog and convection of hazy air rich in space charge, a coastal region is particularly inappropriate for attempts to measure the global circuit variation. Aside from problems related to location, the excessive voltages reported in the tethered balloon data suggest some problem with the measuring technique itself. These data give potentials at 530 m which are 48% higher than comparable aircraft measurements. Extrapolated to the ionosphere, the tethered balloon potential profiles would generally give ionospheric potentials on the order of 500 kV, which is well beyond the values measured in any other program.