A NEW DETERMINATION OF JUPITER RADIO ROTATION PERIOD

The result of a measurement of the period of rotation of Jupiter's inn er magnetosphere with unprecendented precision is presented. The measu rement was made from the University of Florida database of 35 appariti ons of Jovian decametric observations at frequencies of 18, 20, and 22 MHz between 1957 and 1994. The mean of our 24 independent measurement s was 9(h)55(m)29(s).685, and the standard deviation of the mean was 0 (s).0034. The System III (1965) Jovian rotation period value that is c urrently accepted by the International Astronomical Union is greater t han our value by 7.4 times our standard deviation; it appears to be in need of revision. We set an upper limit of 27 milliseconds per year o n a possible drift of the rotation period as measured by our method.