Local time dependences of oxygen ENA periodicities at Saturn

Carbary, J. F.; Mitchell, D. G.; Brandt, P. C.

doi:10.1002/2014ja020214

Cited by 6 publications

(3 citation statements)

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“…Copious fluxes of these neutral atoms originate from Saturn as well as its magnetosphere. The processing of these data is the same as used in previous analyses [ Carbary et al , , , , ; Carbary and Mitchell , ]. Pixels from each INCA frame were projected onto the equatorial plane and geometrically corrected using the cosine of the pixel zenith angle (angle between pixel look direction and planetary spin axis).…”

Section: Data Set and Processingmentioning

confidence: 99%

“…This report will first consider the data set and processing, which is the same as that of the previous Cassini ENA investigations [ Carbary et al , , ; Carbary and Mitchell , ]. One keogram from one F ring orbit is selected for analysis.…”

Section: Introductionmentioning

confidence: 99%

“…ENA periodicities are similar to those of the radio emissions, magnetic fields, and charged particles [ Carbary et al , , ]. Some ENA periodicities exhibit dual periodicities whose observation and amplitude depends on local time, in much the same way as SKR observations depend on local time [ Carbary et al , ]. Simulations of periodic injections of energetic particles, which drift around Saturn in its magnetic field and collide with neutrals, are one way of interpreting these ENA periodicities [ Brandt et al , ].…”

Section: Introductionmentioning

confidence: 99%

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Midnight flash model of energetic neutral atom periodicities at Saturn

Carbary

Mitchell

2017

JGR Space Physics

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The Ion Neutral Camera on the Cassini spacecraft made images of energetic H atoms (25–55 keV) over a 3 day span in 2017. The images were projected onto the equatorial plane of Saturn, and a keogram was made by interpolating the projections in local time at 9 RS (1 RS = 60268 km). The keogram intensities show strong periodicities near the 10.79 h period of Saturn's energetic particles and exhibit a slope commensurate with corotation at that period. These periodic fluxes intensify near midnight but are weaker near noon. A “midnight flash” model can explain this behavior in terms of a searchlight rotating at 10.79 h that intensifies in the midnight sector. The model can also describe similar activity in Saturn's kilometric radiation and magnetic fields, although the “flash” must be shifted to the dawn‐to‐noon sector.

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Section: Data Set and Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Midnight flash model of energetic neutral atom periodicities at Saturn

Carbary

Mitchell

2017

JGR Space Physics

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A new approach to Saturn's periodicities

Carbary

2015

JGR Space Physics

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Saturn's magnetospheric periodicities are commonly thought to have a dual nature, one period originating from the southern hemisphere and a slightly different period from the northern. Both periods vary a few percent over time intervals of years and apparently merged a few months after Saturn equinox. These periodicities have not been explained. The dual‐period waveform is generally represented as the superposition of two sinusoids with nearly equal periods. However, dual‐period waves can also result from an amplitude modulation of a carrier periodicity, from frequency modulation of the carrier, from random phase jumps in the carrier, and from small, random changes in the period itself. While such simple phenomena are well known in the radio community, they can serve as possible explanations for how a single planetary period can appear as the dual (or multiple) periods observed in Saturn's magnetosphere. Candidates for modulation and randomization include the solar wind pressure and speed, the orbital periods of moons of Saturn, or even the trajectory of the Cassini orbiter itself.

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