New Evidence for a Global Atmospheric Electric Circuit on Venus

The electrical environment of Venus has been investigated through extensive considerations of whether lightning has been detected in the atmosphere [1]. Although an important process, the presence or absence of lightning does not completely describe Venus’ electrical environment. Little consideration has been made of other related aspects, such as the possible presence of a global atmospheric electric circuit, as is present on Earth. In this context, lightning would be regarded as the source in a possible global circuit, which distributes charge across a planet. New arguments for and against a global electric circuit in Venus’ atmosphere are presented here which arise from re-analysis of data from the Venera 13 & 14 landers.

On Earth, the global atmospheric electric circuit connects regions of disturbed weather to distant regions of fair weather, by current flow between the conducting ionosphere and surface. Disturbed weather regions produce the potential difference between these conducting layers, which drives the current flow. The presence of a similar global circuit on other planets has been proposed, but their existence remains an open question, which motivates further work [2].

The Venera 13 & 14 landers descended through Venus’ atmosphere carrying a wealth of instrumentation. Each lander carried a point discharge sensor, which recorded electrical discharges between the spacecraft and the atmosphere [3]. The discharges recorded were difficult to explain using existing models of Venus’ environment, so it was previously proposed that low atmosphere haze layers could have caused them [4]. Further evidence for these haze layers has been provided by spectroscopic data from the Venera landers, which showed significant atmospheric extinction in the same region [5]. We have attempted to investigate whether it would be plausible for haze layers to cause both the electrical and extinction effects, and whether this favours a global electric circuit in Venus’ atmosphere.

To investigate this, a model describing electrical interactions in Venus’ atmosphere has been produced. The effects of different haze layers on Venus’ electrical environment were able to be studied, via different inputs to the model. The haze layer properties have been constrained by the spectroscopic observations. Results from the electrical modeling were compared with the electrical discharges recorded by the landers, allowing us to determine the conditions which best recreate these observations. Our investigations show that similar results to the observed Venera data can be produced by the electrical model when the effects of a global atmospheric electric circuit are included, but not when they are neglected. These findings are not definitive, but they do provide supporting evidence for the presence of a global electric circuit in Venus’ atmosphere.

References:
[1] R.D. Lorenz (2018). Progress in Earth and Planetary Science, 5. [2] K.L. Aplin (2006). Surveys in Geophysics 27. 63-108. [3] L. Ksanfomality et al. (1982). Soviet Astronomy Letters, 8. 230–232. [4] R.D. Lorenz (2018). Icarus, 307. 146-149. [5] B. Grieger (2003). Proceedings of the International Workshop Planetary Probe Atmospheric Entry and Descent Trajectory Analysis and Science. 63–70.