Extended Survey of Saturn Z‐Mode Wave Intensity Through Cassini's Final Orbits

Abstract

AbstractSimilar to whistler mode chorus, Z‐mode emission is an efficient diffusive scatterer of electrons possibly resulting in resonant acceleration. We present results of a survey of both the low‐band (5 kHz) and for the first time the high‐band (20 kHz) intensity of these emissions, based on over 11 years of Cassini Radio and Plasma Wave Science instrument data including nine ring‐grazing orbits and two proximal orbits, which occurred at the end of the mission. We distinguish these emissions using density and polarization measurements and calculate the mean intensity as a function of frequency and spatial coordinates. We find that the average low‐band Z‐mode intensity peak is P0 ~7 × 10−8 nT2, while the high‐band peak is much lower at P0 ~10−9 nT2. The spatial distribution of intensity differs for each emission band implying different source regions and perhaps different source mechanisms.