Lightning in the Jovian water cloud

The vertical location of the lightning superbolts seen on the Voyager images of Jupiter has been determined using a comparison between the measured spot sizes for single flashes with the intensity distributions calculated from various assumptions about the altitude of the flash. A Monte Carlo model was used to describe the light scattering in the clouds, aerosols, and gases of the Jupiter atmosphere. Best agreement between the measurements and the model predictions was obtained when the lightning activity was assumed to occur in a lower cloud centered at the 5-bar pressure level, whereas the width predicted for lightning in the ammonia cloud was much smaller than the measured widths. The results imply that the lightning observed by the Voyager must be in a cloud much deeper than the ammonia cloud. The lower cloud is expected to be composed of water or a mixture of water and ammonium hydrosulfide.