Electric fields, dynamics of SO2 concentration, possible vulcanism on Venus

This is an overview of the continuing debate regarding electromagnetic pulses detected by Pioneer Venus and Venera 11 to 14. The Venera pulses were presumed to be similar to terrestrial lightning. Pioneer Venus, on the night side of the planet, detected no light flashes. Vertical profiles revealed the source of the pulses to be well below the cloud layer. Furthermore, both the Venera craft and the Pioneer Venus probes encountered dense plasma at about 12 km, yet the probes were thousands of km apart, indicating a global, electrically active zone. It was presumed that the source of the discharges is volcanic activity. A description is offered of the OEFD experiment, which detected the pulses on the Pioneer Venus, and the nature of whistlers and their propagation is explained. Its findings are interpreted to support the existence of volcanic activity. The arguments for and against vulcanism on Venus are weighted, including changes in the SO2 content of the atmosphere, which the author believes is connected with volcanic eruption. Arguments are presented in favor of tectonic activity on Venus, e.g., the need to release heat from the decay of uranium, thorium, and potassium within the planet.