The Io-controlled decametric radiation

The (magnetic) amplitude of the Alfvén waves emitted by Io is related to the growth rate of coherent cyclotron radiation. The growth rate is large only in the dense parts of the Jovian ionosphere. The amplitude varies as a function of sub-Io longitude. This together with the beaming of the cyclotron radiation is used to explain the observed emission pattern of Io-controlled decametric radiation from Jupiter.