The Statistical Morphology of Saturn’s Equatorial Energetic Neutral Atom Emission

Kinrade, Joe; Bader, Alexander; Paranicas, C.; Mitchell, D. G.; Constable, D. A.; Arridge, C. S.; Cowley, S. W. H.; Provan, G.

doi:10.1029/2020gl091595

Cited by 5 publications

(11 citation statements)

References 74 publications

(132 reference statements)

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“…We observed that this creates an exponential tail toward low fluxes in the histograms, visible as a straight line in the log‐log scaled histograms in Figures 5c–5f and in good agreement with the real data shown in Kinrade, Bader, et al. (2020).…”

Section: Instrument Response and Effects Of The Projection On The Flu...supporting

confidence: 90%

“…These may be caused by the periodic thinning and thickening of Saturn's equatorial plasma sheet by planetary period oscillation systems, two rotating systems for field‐aligned currents which originate near Saturn's poles and span its entire magnetosphere (e.g., Cowley & Provan, 2017; Jackman et al., 2016; Provan et al., 2018). This thickness modulation is also observed in the statistical ENA intensity (Kinrade, Bader, et al., 2020) and may trigger periodic reconnection in the magnetotail (e.g., Bader et al., 2019; Bradley et al., 2018, 2020).…”

Section: Introductionmentioning

confidence: 76%

“…A first use case of this set is presented in Kinrade, Bader, et al. (2020), where we investigate the statistical distribution of ENAs in Saturn's equatorial plane. We hope that this processed data set will improve the accessibility of Cassini‐INCA ENA observations and stimulate further important research on the dynamics of Saturn's magnetosphere.…”

Section: Discussionmentioning

confidence: 99%

“…The real data histograms, however, show observations of much lower fluxes, many orders of magnitude below the lowest fluxes observable by the detector (see also Kinrade, Bader, et al. [2020]). This is an effect of the projection procedure—one pixel in the projection grid may be intersected by more than one INCA pixel.…”

Section: Instrument Response and Effects Of The Projection On The Flu...mentioning

confidence: 99%

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A Complete Data Set of Equatorial Projections of Saturn's Energetic Neutral Atom Emissions Observed by Cassini‐INCA

et al. 2021

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Energetic neutral atom (ENA) imaging is a useful technique for analyzing the interaction between hot space plasmas and neutral gas in planetary magnetospheres. Energetic ions can undergo charge exchange with a neutral population -the planetary exosphere, for example -to create an ENA particle that carries information on the original ion's energy and direction of motion. This ENA continues on its trajectory, unaffected by electromagnetic fields, and can be observed by a remote detector. Remote sensing of an ENA population hence provides spectral, compositional, and pitch angle information of the source plasma. As the observed

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Section: Instrument Response and Effects Of The Projection On The Flu...supporting

confidence: 90%

Section: Introductionmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Instrument Response and Effects Of The Projection On The Flu...mentioning

confidence: 99%

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A Complete Data Set of Equatorial Projections of Saturn's Energetic Neutral Atom Emissions Observed by Cassini‐INCA

et al. 2021

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“…Instead, they offer an independent validation of earlier findings, which indicated that the pointing of Saturn's inner convective electric field can be highly variable with L‐shell and time (Andriopoulou et al., 2013; Roussos et al., 2019). Recently, the mission‐averaged ENA image shows a similar radial offset toward the postnoon sector (Kinrade et al., 2021), validating the long‐term direction using an independent data set and measurement approach.…”

Section: Discussionmentioning

confidence: 63%

Saturn's Inner Magnetospheric Convection in the View of Zebra Stripe Patterns in Energetic Electron Spectra

et al. 2021

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In the terrestrial inner radiation belt, the energy spectrogram of energetic electrons (10-100s keV) sometimes contains one or multiple peaks (Datlowe et al., 1985;Imhof & Smith, 1966;Imhof et al., 1981aImhof et al., , 1981b. These peaks form regular patterns that map on constant bounce-averaged drift frequencies across the entire inner radiation belt (Sauvaud et al., 2013). These features were named "zebra stripes" by Ukhorskiy et al. (2014). Ukhorskiy et al. (2014) first suggested that the stripes are produced by a global process modulating particles' drift motion. Later in Van Allen Probes era, the patterns are observed to be tightening and narrowing during consecutive inner belt crossings (Lejosne & Roederer, 2016;Liu et al., 2016). Liu et al. ( 2016) have shown that a single monochromatic uniform electric field is sufficient for reproducing the key characteristics of the stripes. The authors pointed out that the electric field distorts the electrons' drift shell, so that the electrons detected by the spacecraft at different times are actually originating from different L-shells with different Phase Space Density (PSD). Lejosne and Mozer (2020) further studied the relation of zebra stripes and geomagnetic activity and revealed that zebra stripes are usually triggered during substorm onsets when the penetration electric field is enhanced in the plasmasphere. Similar zebra stripe patterns have been distinguished in Saturn's electron radiation belt (Müller et al., 2010;Paranicas et al., 2007), but only recently it became apparent that their occurrence in the  E 100 keV to few MeV range can be explained by global-scale electric fields as at Earth (Hao et al., 2020). Similarly, Hao et al. (2020 attributed this pattern to a convective electric field with an approximate noon-to-midnight orientation and reproduced the stripe patterns seen by Cassini. Indirect evidence in Juno and Galileo data hinted that zebra stripes may also exist at Jupiter but at much higher energies (  E 1 MeV) due to the stronger magnetic field and faster rotation of the planet compared to Saturn and Earth. Noncorotational convection flows at Saturn have long been a candidate among the key sources of the Saturnian electron radiation belt. There are a variety of loss mechanisms in the radiation belt, such as wave-particle scattering into the atmospheric loss cone and electron absorption or energy loss at the Saturnian massive ring system, moons, neutral gas cloud, and dusty rings (

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A Possible Unified Picture for the Connected Recurrent Magnetic Dipolarization, Quasi‐Periodic ENA Enhancement, SKR Low‐Frequency Extension and Narrowband Emission at Saturn

Xu,

Yao,

et al. 2023

JGR Space Physics

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Magnetic Dipolarization, a hallmark indicator of the formation of field‐aligned currents, plays a crucial role in the energy dissipative processes that occur within planetary magnetospheres. Saturn’s magnetic dipolarization was found to recur after one planetary rotation, suggesting a potential correlation with the corotating current systems. The observation of enhanced Energetic Neutral Atoms (ENA) within Saturn's inner magnetosphere serves as a diagnostic tool, revealing the existence of a rotating, dynamic partial ring current system. By utilizing multiple datasets from Cassini, this study advances the understanding of the interrelationship between ENA emission and magnetic dipolarization. Our results suggest the possibility of a coupling between the Partial Ring Current system revealed by the ENA emission and magnetic dipolarization. Furthermore, a temporal correlation was found between the ENA emissions and two distinct radio emissions. This study discusses potential causal relationships among these phenomena and first time proposes a global unified physical picture.

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The Statistical Morphology of Saturn’s Equatorial Energetic Neutral Atom Emission

Cited by 5 publications

References 74 publications

A Complete Data Set of Equatorial Projections of Saturn's Energetic Neutral Atom Emissions Observed by Cassini‐INCA

A Complete Data Set of Equatorial Projections of Saturn's Energetic Neutral Atom Emissions Observed by Cassini‐INCA

Saturn's Inner Magnetospheric Convection in the View of Zebra Stripe Patterns in Energetic Electron Spectra

A Possible Unified Picture for the Connected Recurrent Magnetic Dipolarization, Quasi‐Periodic ENA Enhancement, SKR Low‐Frequency Extension and Narrowband Emission at Saturn

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