ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-28-1013-2010 Source mechanism of Saturn narrowband emission Menietti J. D. 1 Yoon P. H. 2 3 Sheng-Yi Ye 1 Cecconi B. 4 Rymer A. M. 5 Dept. of Physics and Astronomy, University of Iowa, Iowa City, IA, USA Institute for Physical Science and Technology, University of Maryland, College Park, MD, USA School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701, Korea LESIA-CNRS, Observatoire de Paris, Meudon, France Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA 27 04 2010 28 4 1013 1021 Copyright: © 2010 J. D. Menietti et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/28/1013/2010/angeo-28-1013-2010.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/28/1013/2010/angeo-28-1013-2010.pdf

Narrowband emission (NB) is observed at Saturn centered near 5 kHz and 20 kHz and harmonics. This emission appears similar in many ways to Jovian kilometric narrowband emission observed at higher frequencies, and therefore may have a similar source mechanism. Source regions of NB near 20 kHz are believed to be located near density gradients in the inner magnetosphere and the emission appears to be correlated with the occurrence of large neutral plasma clouds observed in the Saturn magnetotail. In this work we present the results of a growth rate analysis of NB emission (~20 kHz) near or within a probable source region. This is made possible by the sampling of in-situ wave and particle data. The results indicate waves are likely to be generated by the mode-conversion of directly generated Z-mode emission to O-mode near a density gradient. When the local hybrid frequency is close <I>n</I> <I>f</I><sub>ce</sub> (<I>n</I> is an integer and <I>f</I><sub>ce</sub> is the electron cyclotron frequency) with <I>n</I>=4, 5 or 6 in our case, electromagnetic Z-mode and weak ordinary (O-mode) emission can be directly generated by the cyclotron maser instability.

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