Theory of ring sweeping of energetic particles

Paranicas, C.; Cheng, Andrew

doi:10.1029/91ja01136

Cited by 14 publications

(5 citation statements)

References 14 publications

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“…Other loss mechanisms resulting in a depletion of 90° particles are for example wave‐particle interactions, magnetic drift shell splitting, shadowing effects or satellite sweeping effects caused by Europa. The latter can be excluded because the satellite sweeping loss rate is an order of magnitude too low to explain the observed signature [ Paranicas and Cheng , 1991]. Drift shell splitting is able to explain butterfly/bidirectional distributions only on the dayside or the nightside of the magnetosphere, but not at all local times simultaneously.…”

Section: Discussionmentioning

confidence: 99%

In‐situ observations of a neutral gas torus at Europa

Lagg

Krupp

Woch

et al. 2003

Geophysical Research Letters

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[1] A persistent pattern in the pitch angle distributions of energetic protons near the orbit of Europa has been observed with the Energetic Particles Detector (EPD) on board the Galileo spacecraft during each of the Europa orbit crossings in the last 7 years. The proton fluxes at energies larger than 220 keV peak at equatorial pitch angles of 90°whereas fluxes of lower energy protons (80 -220 keV) at this pitch angle are depleted. We propose that a Jupiter-surrounding neutral gas torus in the vicinity of the orbit of Europa is responsible for the depletion of energetic particle fluxes by charge exchange collisions. In order to reproduce the observed depletion signature an average neutral number density of 20 to 50 cm À3 is required.

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Section: Discussionmentioning

confidence: 99%

In‐situ observations of a neutral gas torus at Europa

Lagg

Krupp

Woch

et al. 2003

Geophysical Research Letters

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“…Data are fur- Figure 2b because the E ring nominally extends from about L = 3 to L = 8 [Showalter et al, 1991]. Modeling the tings as in the work of Paranicas and Cheng [1991] shows that at constant K, absorption rates also increase with increasing /x. This is because bounce times decrease with increasing /x and for Saturn's tings, which are in the magnetic equatorial plane, higher/x ions interact with the tings more frequently.…”

Section: Converting Data To Phase Space Densitiesmentioning

confidence: 95%

“…Figure 6 shows that away from satellite locations, ring absorption is also higher for the nearequatorial protons. The dependence of ring absorption rates on K is related to the path length of the particle through the ting, the bounce time and the drift rate [Paranicas and Cheng, 1991]. Figure 6 also shows the absorption rate at Mimas is about 2 orders of magnitude higher than the absorption rate in the nearby rings.…”

Section: Energetic Protonsmentioning

confidence: 97%

Evidence of a source of energetic ions at Saturn

Paranicas¹,

Cheng²,

Mauk³

et al. 1997

J. Geophys. Res.

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Abstract. We calculate phase space densities, in terms of adiabatic invariants of charged particle motion, using the low-energy charged particle (LECP) data from the Voyager 2 encounter with Saturn. Ion data are corrected for electron contamination. For all energies considered here, phase space density at fixed first and second adiabatic invariant, f(L), increases with increasing equatorial pitch angle. Evidence exists for a source of low-energy ions ( In this study we present data from the low-energy charged particle (LECP) experiment on Voyager 2 in the inner magnetosphere of Saturn (L < 7). We consider ions with energies 0.066 < E < 4.2 MeV and protons with energies 54 < E < 152 MeV. The low-energy ions have previously been analyzed as phase space densities (see below) by Armstrong et al. [1983], but the high-energy protons have not. These energy ranges are chosen because corresponding detector count rates are high in Saturn's inner magnetosphere and the sector fields of view are narrow enough to give reasonable pitch angle information.Armstrong et al. [1983] have previously determined low-energy ion phase space densities for Saturn's magnetosphere using some of the LECP data that we present here. That study considered data generally at larger L values, and only below a few megaelectronvolts. Armstrong's method used data 0nly when the instrument was in a "stepping mode" and for which a full angular sweep was obtained. Here we do not make this restriction, allowing all data available in particular energy channels to be considered. We have also included an important cor-

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“…The electron loss due to the sweeping effect by the main and gossamer rings was evaluated in accordance with a method described by Paranicas and Cheng [1991]. We again assumed the simple absorption of electrons when they collided with the ring particles.…”

Section: Physical Model For Jupiter's Radiation Beltmentioning

confidence: 99%

Short-term changes in Jupiter's synchrotron radiation at 325 MHz: Enhanced radial diffusion in Jupiter's radiation belt driven by solar UV/EUV heating

et al. 2011

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[1] The total flux density of Jupiter's synchrotron radiation (JSR) at 325 MHz was observed in 2007 with the Iitate Planetary Radio Telescope to investigate short-term variations in Jupiter's radiation belt with a time scale of a few days to a month. The total flux density showed a series of short-term increases and subsequent decreases. The variations in JSR and the Mg II solar UV/EUV index showed positive correlations, but the variations in JSR were preceded by those of the Mg II index by 3-5 days. The positive correlation supports a theoretical prediction that an enhancement in the radial diffusion driven by thermospheric winds in the upper atmosphere causes changes in relativistic electron distributions in both the radiation belt and the total flux density of JSR. The radial diffusion model was used to examine the hypothesis that temporal changes in the radial diffusion rate could be an origin of the short-term variation. The model includes physical processes such as radial diffusion, energy degradation by the synchrotron radiation, and several loss processes. We applied a radial diffusion coefficient of 3 × 10 −8 L 3 /s and found a suitable solution that accounted for both the time scale of the short-term variations and the 4 day time lag. The model also showed that strong electron loss processes other than the synchrotron radiation are needed to explain the electron distribution in low L regions. An empirical electron distribution model showed that the synchrotron radiation does not act as a loss of electrons in such areas.Citation: Tsuchiya, F., H. Misawa, K. Imai, and A. Morioka (2011), Short-term changes in Jupiter's synchrotron radiation at 325 MHz: Enhanced radial diffusion in Jupiter's radiation belt driven by solar UV/EUV heating,

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Theory of ring sweeping of energetic particles

Cited by 14 publications

References 14 publications

In‐situ observations of a neutral gas torus at Europa

In‐situ observations of a neutral gas torus at Europa

Evidence of a source of energetic ions at Saturn

Short-term changes in Jupiter's synchrotron radiation at 325 MHz: Enhanced radial diffusion in Jupiter's radiation belt driven by solar UV/EUV heating

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