Time Variability of the Radio Brightness Distribution of Saturn
F. van der Tak, I. de Pater, A. Silva, R. Millan (UC Berkeley)
We present radio images of Saturn, taken in 1990-1995 with the VLA and BIMA telescopes. The data from 1990 confirm the existence of the bright band at Northern mid-latitudes. It is seen at 6 cm, but not at 3.6 cm wavelength, which sets strong limits on the pressure level at which the condensation of ammonia occurs.
The images from 1995, the first to display the Southern hemisphere, show that this hemisphere is brighter than the Northern by about 5 %.
In 1994, bands were visible at 2 cm wavelength at latitudes +10 and +40 degrees, unlike the flat brightness distribution seen in previous years. In 1995, the 6 cm band had disappeared, although it had been visible throughout the 1980's. A band at latitude -40 degrees was visible for the first time. We discuss possible causes for the variability of these bands.