Detection of Jupiter decametric emissions controlled by Europa and Ganymede with Voyager/PRA and Cassini/RPWS

摘要

The Jovian high-latitude radio emissions produced by Jupiter's magnetosphere extend from a few kilohertz to 40 MHz. Part of the decametric (DAM) emissions are driven by the Galilean moon Io (Io-DAM). As UV aurorae have been detected at the footprint of Europa and Ganymede, we expect that these moons drive Jovian radio emissions as well. To check this assumption, we used the ExPRES simulation code (Exoplanetary and Planetary Radio Emissions Simulator) to predict dynamic spectrum (time-frequency spectograms) of the radio emissions controlled by the four Galilean moons. Then we compared the simulations to the Voyager/PRA and Cassini/RPWS radio observations of Jupiter (1979, and between 2000 and 2003, respectively). We present the first clear evidence for the existence of decametric emissions controlled by Europa and Ganymede. Their statistical analysis allows us to describe the average properties of the Europa-DAM and Ganymede-DAM emissions such as their spectrum, temporal variability, and occurrence as a function of moon phase and subobserver's longitude.