Control of Jovian Radio Emission by Callisto

Abstract

Galileo has been in orbit around Jupiter since December 1995 and a large database has been collected. We present the results of a survey of the plasma wave data for the frequency range 2.0 MHz to 5.6 MHz, the low frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon Io is well known, and Ganymede control has been more recently indicated, we report that a small but significant portion of DAM emission is seen to be correlated with the orbital phase of Callisto. While the occurrence rate of emission controlled by Ganymede and Callisto is considerably less than for Io, the power levels can be nearly the same. We estimate the power of the Callisto-dependent emission to be Ο70% of the Io-dependent radio emission and about the same as the Ganymede-dependent radio emission. This result indicates an Alfvén current system associated with Callisto, and thus a significant interaction of the magnetosphere of Callisto with that of Jupiter as is believed to exist for both Io and Ganymede.