The Role of Intense Upper Hybrid Resonance Emissions in the Generation of Saturn Narrowband Emission. Issue 7 (30th July 2019)

• Record Type: Journal Article
• Authors: Menietti, J. D.; Yoon, P. H.; Pisa, D.; Averkamp, T. F.; Sulaiman, A. H.; Kurth, W. S.; Santolík, O.; Arridge, C. S.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 7(2019)
• Page Start: 5709
• Page End: 5718
• Publication Date: 2019-07-30
• Subjects: Saturn upper hybrid resonances -- Saturn Z‐mode emission -- Saturn narrowband emission; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2019JA026855
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Twenty high‐inclination ring‐grazing orbits occurred in the final period of the Cassini mission. These orbits intercepted a region of intense Z ‐mode and narrowband (NB) emission (Ye et al., 2010, https://doi.org/10.1029/2009JA015167 ) along with isolated, intense upper hybrid resonance (UHR) emissions that are often associated with NB source regions. We have singled out such UHR emission seen on earlier Cassini orbits that also lie near the region crossed by the ring‐grazing orbits. These previous orbits are important because Cassini electron phase‐space distributions are available and dispersion analysis can be performed to better understand the free energy source and instability of the UHR emission. We present an example of UHR emission on a previous orbit that is similar to that observed during the ring‐grazing orbits. Analysis of the observed plasma distribution of the previous orbit leads us to conclude that episodes of UHR emission and NB radiation observed during the ring‐grazing orbits are likely due to plasma distributions containing loss cones, temperature anisotropies, and strong density gradients near the ring plane. Z ‐mode emissions associated with UHR and NB emission can be in Landau resonance with electrons to produce scattering or acceleration (Woodfield et al., 2018, https://doi.org/10.1038/s41467‐018‐07549‐4 ). Key Points: Upper hybrid resonances (UHR) occur at Saturn near the magnetic equator on high‐inclination inner magnetospheric orbits These regions can be sources of Z ‐mode and narrowband (NB) emission Observed electron plasma distribution contains a weak loss cone unstable to Z ‐ and O ‐mode wave growth.