Polarization of Jovian hectometric emission

Abstract

We have studied the polarization properties of the Jovian hectometric (HOM) emission observed in the low‐frequency band 1.2–1326 kHz by the planetary radio astronomy (PRA) experiment aboard the Voyager spacecraft. We have shown that the complex morphology of HOM can be explained by simultaneous radiations from two independent 100% oppositely polarized sources. Analysis of data recorded under different antenna‐source configurations indicates that the existence of a linear component in HOM is very unlikely. We show that the apparent degree of circular polarization measured by the PRA instrument, which practically ranges from −1 to +1, is the result of fluctuations in the relative intensities of the two HOM circular components. The observed distribution of the degree of circular polarization is accurately reproduced by assuming that the intensity distribution of each individual HOM circular component follows an exponentially decreasing probability law. The emission mode, source location, and beaming of the HOM components are inferred from the polarization properties of the emission. A global model for the hectometric and decametric (DAM) Jovian emissions in which the left and right HOM components are identified with the left and right non‐Io DAM components, respectively, is outlined.