The effect of Io on Jupiter's decametrìc emissions

The innermost Galilean satellite of Jupiter, Io, has been observed to strongly modulate the probability and intensity of Jupiter’s decametric emissions. The effect is most pronounced at frequencies greater than 30 MHz. Radiation occurs from two configurations of Jupiter and Io, the first when Io is 90° from superior geocentric conjunction (s.g.c.) and Jupiter’s longitude is near 120°, and the second when Io is 240° from s.g.c. and Jupiter’s longitude is near 230°.