Lightning on Venus - Orbiter detection of whistler signals

Taylor et al. (1979) presented preliminary evidence for lightning on Venus, based on Pioneer Venus orbiter detection of whistler mode signals as the spacecraft first traversed the nightside ionosphere near periapsis. The initial periapsis eclipse season for the orbiter has been completed, and the plasma wave instrument obtained low-altitude nightside data for about 100 orbits. An analysis is presented of the impulsive whistler mode signals measured during these orbits, and the connection with atmospheric lightning is discussed. It is shown that the signals are detected in the 100-Hz channel when the local magnetic field is sufficiently strong and steady and when the field is oriented to point down below the ionosphere.