The Role of Intense Upper Hybrid Resonance Emissions in the Generation of Saturn Narrowband Emission

Menietti, J. D.; Yoon, Peter H.; Píša, D.; Averkamp, T. F.; Sulaiman, A. H.; Kurth, W. S.; Santolı́k, O.; Arridge, C. S.

doi:10.1029/2019ja026855

Cited by 8 publications

(15 citation statements)

References 29 publications

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“…Source regions for narrowband Z‐mode at Saturn are not well understood, but may be near density gradients along the inner edge of the Enceladus torus and near the ring plane in the inner magnetosphere, as well as near Saturn kilometric radiation source regions (cf. Menietti Yoon et al., 2016, Menietti et al., 2019). Subsequent to the survey of low‐latitude whistler mode we present a preliminary analysis of possible Z‐mode based on Juno orbits to date.…”

Section: Introductionmentioning

confidence: 98%

Low‐Latitude Whistler‐Mode and Higher‐Latitude Z‐Mode Emission at Jupiter Observed by Juno

et al. 2021

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Whistler‐mode chorus emission is important in the scattering and acceleration of electrons and filling of the radiation belts at Jupiter. In this work whistler mode magnetic intensity levels at Jupiter are comprehensively binned and parameterized. The frequency range of whistler mode under study extends from the proton cyclotron frequency, fcH, to fceq/2, where fceq is the cyclotron frequency mapped to the magnetic equator. Parametric dependence of magnetic plasma wave intensity is obtained versus frequency, latitude, and M‐shell, as determined using a current magnetic field model based on Juno data. The results extend similar analyses of Jupiter whistler‐mode emission obtained by the Galileo spacecraft, particularly on the nightside, and provide better coverage in latitude. Peaks in whistler‐mode emission occur near M ∼ 8–9, similar to previous studies, with average peak intensities approaching 10−2 nT2, as also found by Galileo on the dayside. Auroral hiss and probably Z‐mode are observed at higher latitudes. Jovian chorus emissions near an equatorial source region are more broad‐banded than terrestrial chorus, and are coincident with a broad‐banded electron distribution of free energy and strong electron scattering to large pitch angles. Intense whistler mode within a young plasma injection region is also observed, similar to injections in Saturn's magnetosphere. Future study of wave particle interactions within the chorus source region will be important. Possible Z‐mode emission at significant intensity levels is observed in Jupiter's inner magnetosphere, more intense, but not unlike Z‐mode observed at Saturn.

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Section: Introductionmentioning

confidence: 98%

Low‐Latitude Whistler‐Mode and Higher‐Latitude Z‐Mode Emission at Jupiter Observed by Juno

et al. 2021

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“…Figure 1(a) gives an example of RPWS measurements with the detected 5 and 20 kHz NB emissions from 2009 May 1−3. NB emissions are also referred to as "n-SMR" emissions (narrowband Saturn myriametric radiation) for signals in the 3-10 kHz frequency range (Louarn et al 2007), and "n-SKR" in the 10-40 kHz range (Lamy et al 2008) and more recently 5 and 20 kHz NB emissions (Ye et al 2009;Wang et al 2010;Menietti et al 2019;Wing et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Menietti et al (2016Menietti et al ( , 2019 studied the generation mechanism of Z mode emissions for both 5 and 20 kHz and the relation of upper hybrid resonance with NB emissions by analyzing the growth rates of the waves based on the electron phase space distribution measured by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS; Young et al 2004). Case studies show the wave normal angel of the Z mode to be usually smaller than 30° (Menietti et al 2018a(Menietti et al , 2018b, and DF results show two possible source regions: one at high latitude on the same magnetic field lines as SKR and another one at the equatorial region interior to the plasma torus (Menietti et al 2018b).…”

Section: Introductionmentioning

confidence: 99%

“…NB emissions have been extensively studied by using earlier Cassini RPWS data, including their spatial distribution (Ye et al 2009), intensity (Wang et al 2010), polarization (Ye et al 2010b), source location (Ye et al 2009), and excitation mechanism (Menietti et al 2009(Menietti et al , 2019Ye et al 2009). However, earlier studies were based on data obtained from a limited orbit coverage and many studies used only cases to study other characteristics such as the generation mechanism (Menietti et al 2016), source location (Ye et al 2009), and wave particle interaction (Gu et al 2013;Woodfield et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…However, these results have not been published formally. Some researchers use the goniopolarimetric (DF) data to identify the wave mode case by case since NB emissions are believed to be the L-O mode and Z mode, which would have a circular polarization with different senses (Ye et al 2010b;Woodfield et al 2018;Menietti et al 2019). No full analysis of the 5 and 20 kHz NB emissions' polarization has been published.…”

Section: Introductionmentioning

confidence: 99%

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Statistical Study on Spatial Distribution and Polarization of Saturn Narrowband Emissions

Fischer

et al. 2021

ApJ

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The spatial distribution and polarization of Saturn narrowband (NB) emissions have been studied by using Cassini Radio and Plasma Wave Sciences data and goniopolarimetric data obtained through an inversion algorithm with a preset source located at the center of Saturn. From 2004 January 1 to 2017 September 12, NB emissions were selected automatically by a computer program and rechecked manually. The spatial distribution shows a preference for high latitude and intensity peaks in the region within 6 Saturn radii (R s ) for both 5 and 20 kHz NB emissions. 5 kHz NB emissions also show a local time preference roughly in the 18:00−22:00 sector. The Enceladus plasma torus makes it difficult for NB emissions to propagate to the low latitude regions outside the plasma torus. The extent of the low latitude regions where 5 and 20 kHz NB emissions were never observed is consistent with the corresponding plasma torus density contour in the meridional plane. 20 kHz NB emissions show a high circular polarization while 5 kHz NB emissions are less circularly polarized with | | < V 0.6 for majority of the cases. And cases of 5 kHz NB emissions with high circular polarization are more frequently observed at high latitude especially at the northern and southern edges of the Enceladus plasma torus.

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Reflection and Refraction of the L‐O Mode 5 kHz Saturn Narrowband Emission by the Magnetosheath

Fischer

et al. 2022

Geophysical Research Letters

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Emissions near 10 kHz are also reported (Menietti et al., 2009), but this needs further study. Case studies have shown that the Z-mode NB (at both 5 and 20 kHz) can be generated by temperature anisotropy and loss cone distributions in the low latitude region interior to the plasma torus, whereas the modulation analysis and direction finding results indicate a possible auroral source (Menietti et al., 2011(Menietti et al., , 2016(Menietti et al., , 2018. More events to check the plasma distribution near the source region will help to further explore the generation of the Z mode NB. According to the Z-mode dispersion relation, the initially generated Z-mode NB would be trapped in a "Channel" formed by the iso-surfaces of the f uh and f L = 0 (f uh upper hybrid frequency, f L = 0 Z-mode cut-off frequency; Sonwalkar et al., 2004). These "trapped" Z-mode NB can mode convert to the "free space" L-O mode NB at density gradients (Menietti et al., 2019;Ye, Menietti, et al., 2010). Due to the blockage of the high density plasma torus (centered at the equatorial plane) generated by the cryovolcanic activity of the moon Enceladus, the L-O mode NB originally generated interior to the plasma torus would propagate to high latitudes unhindered, creating a low latitude shadow zone outside the plasma torus (S. Ye, Menietti, et al., 2010). However, 5 kHz NB is still observed at low latitudes outside the plasma torus. How did these NB bypass the plasma torus?

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The Role of Intense Upper Hybrid Resonance Emissions in the Generation of Saturn Narrowband Emission

Cited by 8 publications

References 29 publications

Low‐Latitude Whistler‐Mode and Higher‐Latitude Z‐Mode Emission at Jupiter Observed by Juno

Low‐Latitude Whistler‐Mode and Higher‐Latitude Z‐Mode Emission at Jupiter Observed by Juno

Statistical Study on Spatial Distribution and Polarization of Saturn Narrowband Emissions

Reflection and Refraction of the L‐O Mode 5 kHz Saturn Narrowband Emission by the Magnetosheath

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