Plasma instabilities in the Venus nightside ionosphere

Lightning on Venus has been suggested by many researchers. The evidence for this lightning has been claimed to be impulsive electric field signals which have been detected by a number of spacecraft. However, others have proposed that the observed signals are a result of local ionospheric plasma instabilities and do not originate in the lower atmosphere. An investigation of 100 Hz electric field signals detected within the ionosphere of Venus has been conducted. The study encompassed both previously published 100 Hz signals which have been identified as being a result of lightning in the lower atmosphere and data which was newly selected for this research. It is shown that the 100 Hz signals result most often from the lower hybrid plasma wave mode. The remaining signals are from other plasma instabilities due to magnetic field and/or ion density gradients.