Source mechanism of Saturn narrowband emission

J. Menietti (1) , P. H. Yoon (2, 3) , Sheng-Yi Ye (1) , Baptiste Cecconi (4, 5) , Abigail M. Rymer (6)

1 Department of Physics and Astronomy, Iowa State University
2 Institute for Physical Science and Technology, University of Maryland
3 School of Space Research, Kyung Hee University
4 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
5 Physique des plasmas
6 APL - Johns Hopkins University Applied Physics Laboratory [Laurel, MD]

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 n f_ce (n is an integer and f_ce is the electron cyclotron frequency) with n=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.

Domaines: Astrophysique [astro-ph]

J. Menietti, P. H. Yoon, Sheng-Yi Ye, Baptiste Cecconi, Abigail M. Rymer. Source mechanism of Saturn narrowband emission. Annales Geophysicae, 2010, 28, pp.1013-1021. ⟨10.5194/angeo-28-1013-2010⟩. ⟨hal-03691960⟩