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1

Remote sounding of Io plasma torus using Jovian DAM/HOM radio emission  

NASA Astrophysics Data System (ADS)

We study the frequency and time variations of Jovian decametric (DAM) and hectometric (HOM) emissions recorded by RPWS experiment onboard Cassini spacecraft during its Jupiter flyby. It is shown that HOM radiations are highly affected by refraction effects caused by the Io plasma torus. This effect has been reported for the first time by Lecacheux et al. (JGR, 85, 1980) using Voyager/PRA data. The capabilities of the RPWS experiment leads us to re-investigate such type of phenomena, so-called "attenuation band" in literature (Gurnett et al., GRL, 25, 1998), with the aim to derive electron density distribution in the Io plasma torus, and Jovian source locations in the auroral regions. A statistical analysis covering a period of four months permits the variation of the Io plasma torus to be studied, taking into consideration the spacecraft magnetic latitude, and also the central meridian longitude (i.e. CML). First results show that attenuation bands can occur at frequency up to 6 MHz, overlapping HOM but also DAM non-Io-controlled emissions. There are two distinct attenuation bands, related each to one sense of DAM circular polarization, therefore to the corresponding Jovian auroral zone. In addition, they suggest repetitive and steady features in the plasma torus, and also irregular variation, exhibited by propagation effects of radio wave through the Io torus. These results are compared to previous (Voyager and Ulysses) and more recent (Galileo and Cassini) investigations.

Boudjada, M. Y.; Galopeau, P. H. M.; Lecacheux, A.; Rucker, H. O.

2009-04-01

2

Evidence for an Io plasma torus influence on high-latitude Jovian radio emission  

NASA Astrophysics Data System (ADS)

We report the discovery with the Ulysses unified radio and plasma wave (URAP) instrument of features in the Jovian hectometer (HOM) wavelength radio emission spectrum which recur with a period about 2-4% longer than the Jovian System III rotation period. We conclude that the auroral HOM emissions are periodically blocked from ``view'' by regions in the torus of higher than average density and that these regions rotate more slowly than System III and persist for considerable intervals of time. We have reexamined the Voyager planetary radio astronomy (PRA) data taken during the flybys in 1979 and have found similar features in the HOM spectrum. Contemporaneous observations by Brown (1994) show an [SII] emission line enhancement in the Io plasma torus that rotates more slowly than System III by the same amount as the HOM feature.

Kaiser, M. L.; Desch, M. D.; Brown, M. E.

1996-01-01

3

The Jovian SII torus - Its longitudinal asymmetry  

NASA Astrophysics Data System (ADS)

The variations with Jovian magnetic longitude observed in the intensity of the S II emission from the plasma torus surrounding Jupiter near the orbit of Io are investigated. Spectrographic observations of S II emission from 2.1 to 8.3 Jupiter radii from the planet obtained from 1976 to 1979 were examined to determine emission intensities in relation to position. The detected emission is found to be sharply confined to a magnetic latitude within 12 deg of the equator and a region inside 6.7 Jupiter radii, just outside of Io's orbit, with maximum emission at a magnetic longitude of 260 deg. The region of maximum brightness is observed to include the active centers for the currents expected in the flux tubes connected with Io, support of the magnetic anomaly models of Dressler and Hill (1979). Electron temperatures between 10 to the 3.92 and 10 to the 4.80, and densities of 10 to the 4.2/cu cm and a S II column abundance of 1.5 x 10 to the 13th/sq cm are estimated for the brightness region near the ansa of the emission torus. An order of magnitude difference between S II column abundances obtained in the present investigation and found by Brown (1978) is attributed to a change in sulfur content, possibly related to Ionian volcanic activity, while electron temperatures and densities are found to remain fairly constant.

Trafton, L.

1980-04-01

4

Jovian plasma torus interaction with Europa. Plasma wake structure and effect of inductive magnetic field: 3D hybrid kinetic simulation  

NASA Astrophysics Data System (ADS)

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with O++ and S++ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive magnetic dipole and low oceanic shell conductivity).

Lipatov, A. S.; Cooper, J. F.; Paterson, W. R.; Sittler, E. C., Jr.; Hartle, R. E.; Simpson, D. G.

2013-03-01

5

Jovian Lightning-generated Whistlers: A Diagnostic for Plasma Properties in the Io Torus  

Microsoft Academic Search

It is known that lightning-generated VLF waves, called whistlers, propagate into the Earth's magnetosphere along paths dictated by the local magnetic field strength and plasma density. Their sensitivity to plasma density has made them a valuable tool for remotely estimating the density in the magnetosphere. Optical measurement of lightning on Jupiter suggest that whistler should also be present in the

K. Wang; R. M. Thorne; R. B. Horne

1996-01-01

6

Jovian plasma torus interaction with Europa: 3D hybrid kinetic simulation. First results  

Microsoft Academic Search

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo orbiter

A. S. Lipatov; J. F. Cooper; W. R. Paterson; E. C. Sittler; R. E. Hartle; D. G. Simpson

2010-01-01

7

Jovian's plasma torus interaction with Europa: 3D hybrid kinetic simulation  

Microsoft Academic Search

The hybrid kinetic model approach supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of the existing measurements for surface and atmospheric composition from

A. S. Lipatov; J. F. Cooper; W. R. Paterson

2009-01-01

8

Convective transport of plasma in the inner Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

The transport of plasma in the inner Jovian magnetosphere is investigated according to the corotating convection model of Hill et al. (1981), emphasizing mathematical aspects of the theory. A simplified but physically plausible boundary condition at the inner Io torus, representing a 5 percent density enhancement of S(+) ions in an 'active sector' that is fixed in Jovian (system III) longitude is employed. The convection electric field pattern resulting from this longitudinal mass anomaly alone is investigated, and then the theory to include the effects of Coriolis force and plasma acceleration is generalized. It is found that even a small (about 5 percent) longitudinal asymmetry of the inner torus produces a convection system capable of removing torus plasma from the magnetosphere on a time scale of order one month.

Liu, W. W.; Hill, T. W.

1990-04-01

9

Local time dependence of Io plasma torus  

NASA Astrophysics Data System (ADS)

We study the frequency and time variations of the Jovian decametric (DAM) and hectometric (HOM) emissions recorded by the RPWS experiment onboard Cassini spacecraft during its Jupiter flyby. It is shown that the HOM radiations are principally subject to refraction effects caused by the Io plasma torus. We analyze the Jovian radio dynamic spectra recorded from the end of November 2000 to the second week of January 2001. During this period, the spacecraft approached Jupiter from a distance of more than 500 RJ to 137 RJ (closest approach on December 30, 2010) and back to about 250 RJ. We attempt in this study to investigate the local time (LT) dependence of the attenuation band due to refraction effects caused by the presence of the Io plasma torus. We analyze the spectral features of the attenuation band taking into consideration three local time intervals [10.0 LT, 13.2 LT], [13.6 LT, 16.5 LT], and [16.7 LT, 20 LT]. A statistical study leads us to characterize the spectral features of the attenuation band principally on the dayside and the late afternoon sector of the planet. This will allow us to discuss the LT variation of the electronic density of the Io plasma torus versus the central meridian longitude (CML) and the Jovian magnetic latitude.

Boudjada, M. Y.; Galopeau, P. H. M.

2012-04-01

10

Mass-injection rate from Io into the Io plasma torus  

Microsoft Academic Search

Theoretical arguments to the effect that both plasma and energy are supplied to the Jovian magnetosphere from primarily internal sources are presented. Two major assumptions are made: (1) that Io is the source of plasma for the Jovian magnetosphere, and that the outward flow of plasma from the torus is the means of drawing from the kinetic energy of rotation

A Dessler

1980-01-01

11

Studies of Io's atmosphere and plasma torus  

SciTech Connect

Jupiter's hot and cold plasma tori and the atmosphere of Io, a jovian moon located in a nearly circular orbit at a distance of 5.9 jovian radii from the center of Jupiter are examined. For the hot torus the ion partitioning and energy balance are modeled by assuming that there are independent sources of neutral sulfur and oxygen atoms, that the thermal electrons have a density of 2000/cu cm and a temperature of 5 eV. In the model of energy and mass balance of the cold torus its primary source of plasma is considered a radial diffusion inward from the hot torus. The time scale for this process is assumed to be identical to that required for energetic electrons to supply the energy necessary to power the synchrotron radiation. Charge exchange between thermal ions and an extended neutral cloud of sulfur and oxygen produces fresh ions which are accelerated to corotation by the magnetic field of Jupiter. These fresh accelerated ions are the source of energy which powers the cold torus emissions. The main ion loss mechanism is a two-step process whereby charge exchange between ions and neutral molecules transforms ions into fast neutrals. Since it is generally agreed that the source of neutrals to the hot and cold tori is the atmosphere of Io, then in order to better understand torus processes the behavior of Io's atmosphere needs to be understood. Numerical gasdynamic SO2 models of sublimation and volcanic atmospheres of Io are developed by means of computer simulations. Using a fine computational grid and the computational capabilities of the Cray supercomputers, the relevant atmospheric properties such as pressure, density, temperature, and velocity are found. Day side and night side atmospheres were investigated. It was found that volcanoes form an extended atmosphere on Io. A sublimation H2S atmosphere was also investigated.

Moreno, M.A.

1989-01-01

12

Detection of Jovian whistler mode chorus; implications for the Io torus aurora  

SciTech Connect

Near the Io torus outer boundary (Lapprox. =8), the Voyager 1 plasma wave instrument detected high frequency (f) waves near one-half the electron cyclotron frequency f/sub c/. High resolution waveform measurements demonstrate that these fapprox. =F/sub c//2 signals are banded whistler mode chrous at f< or approx. =f/sub c//2 and half-cyclotron frequency emissions with f slightly above f/sub c//2. The high resolution spectral information, and the theory of whistler mode waves, permit us to estimate the density (approx.2.5 cm/sup -3/), energy (few keV), and omnidirectional energy flux (10/sup 2/ ergs/cm/sup 2/-sec) of the electrons resonant with the chorus. Chorus precipitates about 6 ergs/cm/sup 2/-sec of few keV electron energy to the Jovian ionosphere at L=8. Electrostatic emission, probably electron cyclotron half-harmonic modes, have also been detected near the magnetic equator in the Io torus region. At L=8, the multimode pitch-angle diffusion associated with the detected waves should produce a precipitation flux about a factor two below the 50 ergs/cm/sup 2/-sec required to generate the observed auroral emission; however, the flux could well be larger deeper within the torus.

Coroniti, F.V.; Scarf, F.L.; Kennel, C.F.; Kurth, W.S.; Gurnett, D.A.

1980-01-01

13

Jovian's plasma torus interaction with Europa. Plasma wake structure: 3D hybrid kinetic simulation and comparison with E4 flyby Galileo's observations  

Microsoft Academic Search

Abstract The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from Galileo orbital

A. S. Lipatov; J. F. Cooper; W. R. Paterson; E. C. Sittler; R. E. Hartle

2010-01-01

14

Departure from corotation of the IO plasma torus: local plasma production  

Microsoft Academic Search

The departure of the Jovian magnetosphere from rigid corotation is adequately explained by outward plasma transport at distances L> or approx. =10. The departure of 5% observed in the Io plamsa torus, however, is too large to be accounted for simply by plasma transport. We propose local plasma production to be the main factor determining the corotation lag in the

D. H. Jr. Pontius; T. W. Hill

1982-01-01

15

Physics of Spherical Torus Plasmas  

SciTech Connect

Broad and important progress in plasma tests, theory, new experiments, and future visions of the spherical torus (ST, or very low aspect ratio tokamaks) have recently emerged. These have substantially improved our understanding of the potential properties of the ST plasmas, since the preliminary calculation of the ST magnetohydrodynamic equilibria more than a decade ago. Exciting data have been obtained from concept exploration level ST experiments of modest capabilities (with major radii up to 35 cm), making important scientific contributions to toroidal confinement in general. The results have helped approval and construction of new and/or more powerful ST experiments, and stimulated an increasing number of theoretical calculations of interest to magnetic fusion energy. Utilizing the broad knowledge base from the successful tokamak and advanced tokamak research, a wide range of new ST physics features has been suggested. These properties of the ST plasma will be tested at the 1 MA level with major radius up to similar to 80 cm in the new proof of principle devices National Spherical Torus Experiment (NSTX, U.S.) [M. Peng , European Conf. Abst. 22C, 451 (1998); S. M. Kaye , Fusion Technol. 36, 16 (1999); M. Ono , "Exploration of Spherical Torus Physics in the NSTX Device," 17th IAEA Fusion Energy Conf., paper IAEA-CN-69/ICP/01 (R), Yokohama, Japan (1998)], Mega Ampere Spherical Tokamak (MAST, U.K.) [A. C. Darke , Fusion Technol. 1, 799 (1995); Q. W. Morris , Proc. Int. Workshop on ST (Ioffe Inst., St. Petersburg, 1997), Vol. 1, p. 290], and Globus-M (R.F.) [V. K. Gusev , European Conf. Abst. 22C, 576 (1998)], which have just started full experimental operation. New concept exploration experiments, such as Pegasus (University of Wisconsin) [R. Fonck and the PEGASUS Team, Bull. Am. Phys. Soc. 44, 267 (1999)], Helicity Injected Tokamak-II (HIT-II, University of Washington) [T. R. Jarboe , Phys. Plasmas 5, 1807 (1998)], and Current Drive Experiment-Upgrade (CDX-U, Princeton Plasma Physics Laboratory) [M. Ono , Proceedings of the 16th International Conference on Fusion Energy (IAEA, Vienna, 1997), Vol. 2, p. 71] and other experiments in Japan and Brazil, etc., present additional opportunities for important progress. This tutorial paper summarizes our understanding and projections of the physics of the ST plasmas, the investigation of which will hopefully bring new enthusiasm and advancements for fusion energy science research in the U.S. and the world. (C) 2000 American Institute of Physics. [S1070-664X(00)97905-9].

Peng, Yueng Kay Martin [ORNL

2000-01-01

16

Ray tracing of Jovian kilometric radiation  

SciTech Connect

Results of computer ray tracing of Jovian kilometric from 56.2 kHz to 1 MHz in a model Jovian magnetosphere with an Io torus are presented. Ray tracing calculations indicate that the Io torus presents a propagation barrier to the radiation and that the Jovian kilometric radiation must be generated in the L-O mode from a source near Jupiter on field lines passing through the Io torus. One effect of the Io torus is to refract the rays away from the magnetic equator forming a shadow zone at radial distances beyond the torus. In general, at radial distances greater than 10 Jovian radii, as the wave frequency increases (>200 kHz) so does the magnetic latitude of the shadow zone. These and other features of the ray tracing calculations are in good qualitative agreement with the observations from the plasma wave receiver and planetary radio astronomy experiment on board both Voyager 1 and 2.

Green, J.L.; Gurnett, D.A.

1980-01-01

17

Detection of Jovian whistler mode chorus; implications for the Io torus aurora  

Microsoft Academic Search

Near the Io torus outer boundary (Lapprox. =8), the Voyager 1 plasma wave instrument detected high frequency (f) waves near one-half the electron cyclotron frequency f\\/sub c\\/. High resolution waveform measurements demonstrate that these fapprox. =F\\/sub c\\/\\/2 signals are banded whistler mode chrous at f< or approx. =f\\/sub c\\/\\/2 and half-cyclotron frequency emissions with f slightly above f\\/sub c\\/\\/2. The

F. V. Coroniti; F.L. Scarf; C. F. Kennel; W. S. Kurth; D. A. Gurnett

1980-01-01

18

Jovian magnetospheric plasma effects at Europa and Ganymede (Invited)  

Microsoft Academic Search

Europa and Ganymede are imbedded in the Jovian magnetospheric plasma. This plasma alters their surfaces producing tenuous surface boundary-layer atmospheres (Johnson, 2002). That is, the interactions of the desorbed neutrals with the surface determine the composition and morphology of their atmospheres (Cassidy et al. 2009; Cipriani et al. 2009). Those neutrals that escape the satellite remain gravitationally bound to Jupiter

R. E. Johnson; T. A. Cassidy; A. R. Hendrix; C. Paranicas; F. Cipriani; F. Leblanc; J. F. Cooper

2009-01-01

19

Io's interaction with the plasma torus  

Microsoft Academic Search

A new model for the interaction of Io with the dense corotating plasma of the Io torus is described which involves pickup and Alfven waves carrying a field-aligned current. Pickup refers to the process whereby ions freshly created near Io are accelerated by the corotational electric field. It is shown that the pickup current is connected to a field-aligned current

C. K. Goertz

1980-01-01

20

Alfven wave propagation in the Io plasma torus  

SciTech Connect

Gurnett and Goertz (1981) proposed that the large number of discrete arcs observed in the Jovian decametric radio emission is caused by multiple reflections of Alfven waves excited by Io. In this paper the plasma measurements that were made by the Voyager I plasma science experiment have been combined with a model of Jupiter's magnetic field to calculate the time an Alfven wave takes to travel between Io and Jupiter's ionosphere and the period of subsequent bounces between the northern and southern hemispheres. The result is a wave pattern extending around Jupiter as the multiply reflected Alfven waves are carried away from Io by the corotating magnetospheric plasma. Although the whole pattern continually changes over the 13 hours Io takes to move through 360/sup 0/ of Jovigraphic longitude, a general longitudinal structure is exhibited independent of the position of Io, due to the geometry of the magnetic field and the distribution of plasma in the Io torus. If the Alfven waves stimulate the decametric radio emission, then the wave pattern predicts specific properties of the decametric emission which can be compared with radio observations.

Bagenal, F.

1983-04-01

21

Remote sensing of possible plasma density bubbles in the inner Jovian dayside magnetosphere  

NASA Astrophysics Data System (ADS)

During the 2001 Cassini encounter with Jupiter, the Radio and Plasma Wave Science (RPWS) instrument detected fine spectral and temporal structure with broadband kilometric radiation. Applying known electron cyclotron harmonic radiation models, this microstructure is interpreted as originating from a plasma density depletion or bubble at the edge of the Io torus. The microstructure became very complicated at the event beginning and end (formation of broadband bursty structures), and this is interpreted as originating from high-frequency (3-4 s period) density waves or fingers found at the edge of the larger density bubble. Such high-frequency structure at the edges of plasma bubbles is reminiscent of small-scale structure associated with terrestrial spread-F density irregularities. We suggest that the narrow extended fingers, observed on a convex portion of the Io torus surface, result from the interchange instability that is shredding the outer edges of the plasma bubble. A similar set of circumstances occurring on a larger scale may explain the emission of Jovian radio bull's-eye emission observed previously by Ulysses.

Farrell, W. M.; Kaiser, M. L.; Kurth, W. S.; Desch, M. D.; Gurnett, D. A.; Hospodarsky, G. B.; MacDowall, R. J.

2004-09-01

22

Interaction of Io with the plasma torus  

SciTech Connect

The author develops models and numerical simulations of the neutral and plasma environment near Io. He first examines the basic picture of the formation of the torus. He finds that this picture can be used to infer properties of Io and of the torus as a whole. He also presents models of the neutral density in Io's exosphere. Flow of the torus plasma past Io is examined by developing time-dependent global MHD simulations of the interaction. The simulations solve the nonlinear, compressible MHD equations self-consistently. The initial and boundary conditions are the only assumptions imposed. 2D and 3D simulations are developed that include the effect of mass loading by ionization of neutrals in Io's exosphere. The 3D simulations confirm the presence of the expected Alfven wings and field-aligned currents, and also show that important slow and fast mode perturbations are generated in the plasma by Io. All three MHD modes interact near Io. Mass loading by ionization increases the plasma density and decreases the plasma velocity near Io, particularly in Io's wake.

Linker, J.A.

1987-01-01

23

Io plasma torus electrons - Voyager 1  

NASA Astrophysics Data System (ADS)

A thermal Maxwellian component of the electron distribution function, together with a suprathermal, non-Maxwellian one, are featured in the present analysis of in situ plasma electron observations made by the Voyager 1 plasma science experiment in the Io plasma torus. A large difference in the hot electron pressure P(H) is noted between the inbound and the outbound data; this is interpreted as a latitudinal gradient, with P(H) being maximum at the magnetic equator. The presence of a neutral corona around Io is inferred from the observed decrease and symmetry with respect to Io of the cold electron temperature.

Sittler, E. C.; Strobel, D. F.

1987-06-01

24

Observations of Plasmas in the Jovian Magnetosphere.  

National Technical Information Service (NTIS)

The interplanetary probe Pioneer 10 has opened a new frontier for studies of planetary magnetospheres with its exciting flyby of the planet Jupiter. The plasma instrumentation aboard Pioneer 10 was designed for detailed measurements of the solar wind and ...

L. A. Frank K. L. Ackerson J. H. Wolfe J. D. Mihalov

1975-01-01

25

The dynamic expansion and contraction of the Jovian plasma sheet  

NASA Astrophysics Data System (ADS)

Observations suggesting the sequential expansion and compression of the Jovian plasma sheet are reported. Plasma flow in the vicinity of Jupiter was monitored by the four modulated-grid Faraday cups on board each of the Voyager spacecraft at times of closest Jupiter approach. Sensor measurements reveal the flow of magnetospheric plasma to be directed away from the equatorial current sheet near local noon and to be directed towards the sheet in the dusk to midnight sector. The observed flow patterns are interpreted in terms of short-time-scale perturbations of magnetic flux tubes due to the compression of the dayside magnetosphere by the solar wind. It is noted that such a dynamic motion is quite different from what would be expected of slower, quasi-static equilibrium plasma sheet expansion and contraction.

Belcher, J. W.; McNutt, R. L.

1980-10-01

26

Empirical model of the Io plasma torus: Voyager measurements  

Microsoft Academic Search

We present a description of plasma conditions in the Io plasma torus, between 5 and 10 RJ, based on Voyager 1 observations obtained in March 1979. The model includes updated analyses of Plasma Science (PLS) data obtained along the spacecraft trajectory as well as Ultraviolet Spectrometer (UVS) observations of composition made remotely from Jupiter. The plasma characteristics observed along the

Fran Bagenal

1994-01-01

27

Steady-State Plasmas in KT5D Magnetized Torus  

Microsoft Academic Search

Steady-state plasma generated by electron cyclotron resonance (ECR) wave in the KT5D magnetized torus was studied using a fast high-resolution camera and Langmuir probes. It was found that both the discharge patterns taken by the camera and the plasma parameters measured by the probes were very sensitive to the working gas pressure and the magnetic configuration of the torus both

Zhenhua Zhu; Min Xu; Yi Yu; Zhijiang Wang; Ronghua Lu; Yizhi Wen; Changxuan Yu; Jinxiu Ma; Shude Wan; Wandong Liu; Baonian Wan; Yanping Zhao; Jiangang Li; Longwen Yan; Qingwei Yang; Xuantong Ding

2007-01-01

28

On the energy crisis in the Io plasma torus  

NASA Astrophysics Data System (ADS)

Recent calculations of the energy balance of the Io plasma torus show that the observed UV and EUV radiation cannot be maintained solely via energy input by the ion pickup mechanism. Current theoretical models of the torus must be modified to include non-local energy input. It is argued that the required energy may be supplied by inward diffusion of energetic heavy ions with energies less than about 20 keV.

Smith, R. A.; Bagenal, F.; Cheng, A. F.; Strobel, D. F.

1988-06-01

29

Jovian magnetosphere: a post-Voyager view  

SciTech Connect

Results of observational and theoretical work presented at the Rice University Conference on the Physics of the Jovian Magnetosphere (February 27-29, 1980) are summarized and used to elucidate the post-Voyager status of the understanding of Jovian magnetosphere dynamics. Works considered treat earth-based and Voyager observations of the Io torus, decametric and kilometric radio emissions, corotation of magnetospheric plasma with the magnetic field, and theoretical studies of mechanisms of particle acceleration, diffusion and loss in the magnetosphere and interplanetary space. Issues remaining to be resolved by future research are also indicated, particularly questions of the discrepancy between plasma flow measurements obtained on the two plasma experiments on each Voyager spacecraft, and the localization of the source of torus plasma.

Hill, T.W.

1981-01-20

30

Jovian plasma sheet morphology: particle and field observations by the Galileo spacecraft  

Microsoft Academic Search

We present results from an investigation of the plasma sheet encounter signatures observed in the Jovian magnetosphere by the Energetic Particles Detector (EPD) and Magnetometer (MAG) onboard the Galileo spacecraft. Maxima in ion flux were used to identify over 500 spacecraft encounters with the plasma sheet between radial distances from Jupiter from 20 to 140RJ during the first 25 orbits

L. S. Waldrop; T. A. Fritz; M. G. Kivelson; K. Khurana; N. Krupp; A. Lagg

2005-01-01

31

Jovian plasma sheet density profile from low-frequency radio waves  

NASA Astrophysics Data System (ADS)

By using planetary radio astronomy (PRA), plasma wave system (PWS), and magnetometer (MAG) data from Voyager 1 and 2 (V1 and V2), essential features of the nightside Jovian plasma sheet are derived, and the density gradient of the corotating plasma structure in the middle Jovian magnetosphere is calculated. The PRA experiment gives information about the plasma wave polarization. The density profile of the plasma sheet is determined using the hinge point position of the plasma disk derived from MAG data, and the low-frequency cutoffs observed at three frequencies (562 Hz, 1 kHz, and 1.78 kHz) from the PWS experiment. It is shown that the hinge point position varies with the solar wind ram pressure.

Rucker, H. O.; Ladreiter, H. P.; Leblanc, Y.; Jones, D.; Kurth, W. S.

1989-04-01

32

Global ENA Imaging of the Jovian Magnetosphere: A Tool for Global Exploration of the Giant Accelerator of Energetic Particles and Their Interaction with the Torus Region and Moons (Invited)  

NASA Astrophysics Data System (ADS)

The Europa-Jupiter System Mision (EJSM) has required a synergistic approach within the JGO-JEO constellation to unravel fundamental and universal magnetospheric processes, by using powerful combinations of in-situ and global imaging measurement. The Japanese Space Agency is also considering a possible Jupiter Magnetospheric Orbiter (JMO), enabling triple point measurements and multi-point imaging to ensure simultaneous and continuous observations - a key requirement for revealing how the magnetosphere couples to the ionosphere as well as to the plasma sources. Energetic Neutral Atom (ENA) imaging is so far the only technique capable of obtaining global images of the magnetospheric energetic ion population in the ~3-300 keV range, which otherwise would have remained invisible. ENA cameras on Cassini and the terrestrial IMAGE mission have revealed global, explosive acceleration processes and their connection to the ionosphere, aurorae and radio emissions. Therefore, the technique is considered to be game-changing and one of the required measurement techniques in the payload definition for both JGO and JMO. In this presentation we discuss how ENA imaging can make use of the synergistic approach of EJSM to explore global acceleration, MI-coupling, relation to aurorae and radio emissions, transport, solar wind control, constrain torus neutral gas evolution and provide global context for moon-magnetosphere interactions in the Jovian magnetosphere. We use past measurements and a data-derived model to simulate ENA images through a realistic camera response function along the JGO orbit and explore the scientific value added by in-situ and imaging measurements from JMO. The presentation is concluded by summarizing the critical technical requirements of ENA cameras, such as energy and mass range, geometrical factor and background/foreground rejection that must be met in order to operate in the harsh Jovian environment while achieving the highest priority science objectives.

Brandt, P. C.; Mitchell, D. G.; Mauk, B. H.; Paranicas, C.; Krupp, N.

2010-12-01

33

Alfven wave propagation in the Io plasma torus  

NASA Astrophysics Data System (ADS)

Voyager 1 plasma measurements are combined with a model of Jupiter's magnetic field to calculate the time required for an Alfven wave to travel between Io and Jupiter's ionosphere, and the period of subsequent bounces between the northern and southern hemispheres of Io. The result is a wave pattern which extends around Jupiter as the multiply reflected Alfven waves are carried away from Io by the corotating magnetospheric plasma, exhibiting a general longitudinal structure which is independent of Io's position due to magnetic field geometry and Io torus plasma distribution. If the Alfven waves simulate decametric radio emission, the wave pattern predicts specific decametric emission properties for comparison with radio observation.

Bagenal, F.

1983-04-01

34

Charge exchange cross sections for the Io plasma torus  

SciTech Connect

An impact parameter method for calculating cross sections as a function of incident ion energy is used in conjunction with an improved exchange energy formulation to update several of the charge exchange cross sections currently used in Io plasma torus modeling. New cross sections for S{sup +} + S{sup 2+} {yields} S{sup 2} + S{sup +} and Na{sup +} on neutral targets, useful in analyzing the fast Na jets observed at Io, are also calculated.

McGrath, M.A.; Johnson, R.E. (Univ. of Virginia, Charlottesville (USA))

1989-03-01

35

Source characteristics and locations of hectometric radio emissions from the northern Jovian hemisphere  

NASA Astrophysics Data System (ADS)

Northern Jovian hectometric (HOM) radio emissions, detected from high Jovian latitudes by the Unified Radio and Plasma Wave experiment on the Ulysses spacecraft, were observed at all Jovian longitudes. This emission was observed to be predominantly right-hand circularly polarized, but some left-hand circular polarization was observed implying the presence of O mode emissions from the northern Jovian hemisphere. Intense HOM emissions, with well-defined directions and polarizations, were often confined to similar longitudinal regions where intense HOM emissions were previously observed at low latitudes. The present analysis confirms that these northern HOM sources lie in the Jovian polar regions on magnetic field lines that pass through the Io plasma torus. The observations may be consistent with emission from either a filled cone beam or a longitudinal distribution of thin hollow cones.

Reiner, M. J.; Fainberg, J.; Stone, R. G.

1993-02-01

36

The Io Plasma Torus During the Cassini Flyby of Jupiter  

NASA Astrophysics Data System (ADS)

Much of our current understanding of the Io plasma torus comes from the analysis and modeling of observations made by the Ultraviolet Imaging Spectrograph (UVIS) during the Cassini spacecraft's flyby of Jupiter (October 2000 through March 2001). The sensitivity, resolution, and imaging capabilities of UVIS coupled with the temporal coverage of the observations make this a particularly rich dataset. However, previous work has focused almost exclusively on a 45-day period during approach from 2000 October 1 to 2000 November 14. Here, we present results from the Cassini UVIS observations of the Io plasma torus made from 2000 November 15 to 2001 March 17. In particular, we focus on how these new results fit into the picture emerging from the analysis of observations from the initial flyby period: namely, that longitudinal variations in electron temperature, electron density, and ionization state are an omnipresent feature in the Io torus and are caused by a sub-corotating source of hot electrons that is, in turn, modulated by its position in System III longitude.

Steffl, A. J.; Shinn, A. B.

2011-12-01

37

Turbulent Parameter Evolution in Madison Symmetric Torus RFP Plasmas  

NASA Astrophysics Data System (ADS)

Using Fourier analysis and chaos theory, the turbulent parameters have been used to characterize turbulence in many different plasma systems. The Fourier components measure the characteristic frequency that is associated with instabilities that drive turbulence, the amount of energy associated with turbulence and the rate at which that energy moves between scales. The chaos components measure the complexity and volatility of the fluctuations. The Madison Symmetric Torus provides a plethora of plasma regimes to study turbulence and its associated transitions. Magnetic field fluctuations measurements have been made during the ramp-up, sawtooth crash, and equilibrium phases of a standard discharge, along with the increased confinement period during poloidal pulse current drive (PPCD). While the Fourier components of the turbulent parameters are independent of plasma current, the chaotic components show that the complexity and volatility are dependent on both plasma current and density.

Titus, J. B.; Mezonlin, E. D.; Alexander, A. B.; Johnson, J. A., III

2012-10-01

38

Scale Invariance in Madison Symmetric Torus RFP Turbulent Plasmas  

NASA Astrophysics Data System (ADS)

Recent studies have shown that turbulence may be a second-order phase transition. Lambda-like profiles of the turbulent parameters have been seen in various types of plasmas, including reversed-field pinch, glow discharge, and laser-induced plasmas. Another signature characteristic of any second-order phase transition is scale invariance. The Hurst exponent characterizes scale invariance by finding negative or positive autocorrelations in a long time series. The Hurst exponent, already found in previous RFP plasmas at RFX, has been found and studied on Madison Symmetric Torus (MST) RFP plasmas. Given the right Hurst exponent, this may show that turbulence is scale invariant, giving more evidence towards turbulence being a second-order phase transition.

Titus, James B.; Mezonlin, Ephrem; Johnson, Joseph A.; Chernyshev, Fedor

2011-11-01

39

Linear Stability Analysis of a Hot Plasma in a Solid Torus  

NASA Astrophysics Data System (ADS)

This paper is a first step toward understanding the effect of toroidal geometry on the rigorous stability theory of plasmas. We consider a collisionless plasma inside a torus, modeled by the relativistic Vlasov-Maxwell system. The surface of the torus is perfectly conducting and it reflects the particles specularly. We provide sharp criteria for the stability of equilibria under the assumption that the particle distributions and the electromagnetic fields depend only on the cross-sectional variables of the torus.

Nguyen, Toan T.; Strauss, Walter A.

2013-10-01

40

Numerical Simulation of Rotation-Driven Plasma Transport In the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

A Jupiter version of the Rice Convection Model (RCM-J) was developed with support of an earlier NASA SR&T grant. The conversion from Earth to Jupiter included adding currents driven by centrifugal force, reversing the planetary magnetic field, and rescaling various parameters. A series of informative runs was carried out, all of them solving initial value problems. The simulations followed an initial plasma torus configuration as it fell apart by interchange instability. Some conclusions from the simulations were the following: 1. We confirmed that, for conventional values of the torus density and ionospheric conductance, the torus disintegrates by interchange instability on a time scale of approx. one day, which is 1-2 orders of magnitude shorter than the best estimates of the average residence time of plasma in the torus. 2. In the model, the instability could be slowed to an arbitrary degree by the addition of sufficient impounding energetic particles, as suggested earlier by Siscoe et al (1981). However, the observed energetic particles do not seem sufficient to guarantee impoundment (e.g., Mauk et al., 1996). 3. Whether inhibited by impoundment or not, the interchange was found to proceed by the formation of long fingers, which get thinner as they get longer. This picture differed dramatically from the conventional radial-diffusion picture (e.g., Siscoe and Summers (1981)), more superficially with the outward-moving-blob picture (Pontius and Hill, 1989). The obvious limitation of the original RCM-J was that it could not represent a plasma source. We could represent the decay of a pre-existing torus, but we could not represent the way ionization of material from Io continually replenishes the plasma. We consequently were precluded from studying a whole set of fundamental issues of torus theory, including whether the system can come to a steady state.

Wolf, Richard A.

1997-01-01

41

Characteristics of hot plasma in the Jovian magnetosphere - Results from the Voyager spacecraft  

NASA Astrophysics Data System (ADS)

Measurements of the intensities, energy spectra, angular variations, and composition characteristics of the low-energy ion populations (approximately 30 keV to 4 MeV) obtained by both Voyager spacecraft in the outer (more than about 10 Jupiter radii) Jovian magnetosphere are reported and interpreted. Also shown are some of the energetic electron measurements. Using the spectral and angular ion measurements, density and pressure profiles in the magnetosphere are constructed and then compared with results reported by the plasma wave and plasma science investigations (density) and the magnetic field investigation (pressure).

Krimigis, S. M.; Carbary, J. F.; Keath, E. P.; Bostrom, C. O.; Axford, W. I.; Gloeckler, G.; Lanzerotti, L. J.; Armstrong, T. P.

1981-09-01

42

Observation of ion temperature anisotropy on the Io plasma torus using a high-dispersion spectrograph with an integral field unit  

NASA Astrophysics Data System (ADS)

Atoms and molecules originated from volcanic eruption on Jovian satellite Io are ionized and form a donut-shaped region along Io's orbit which is called Io plasma torus. Although ion pickup in the plasma torus is expected to maintain high temperature anisotropy, the value of anisotropy, its longitudinal distribution and variability have not been clear yet. A new high-dispersion spectrograph with an integral field unit (IFU) enables to measure line width of ion emission and its latitudinal scale height distribution simultaneously which derive ion temperatures parallel and perpendicular to the magnetic field. The observation of sulfur ion emission, [SII] 671.6nm and 673.1nm, was made at Haleakala Observatory in Hawaii from March 1st through 20th, 2013 using the high-dispersion spectrograph (R = 67,000) with the IFU coupled to a 40-cm telescope. The IFU consist of 96 optical fibers. The fibers are arranged in 12 by 8 array at a telescope focus corresponding to 41'' by 61'' with a spatial resolution of 5.1'' on the sky. Based on a preliminary result from the observation that produced 40 spectral datasets, there is a System III variation on the parallel ion temperature which is derived from north-south distribution of torus emission. There is also a System III variation on the torus brightness at the equator showing an anti-correlation with the parallel ion temperature. System III variation of total flux-tube contents (FTCs) was relatively small compared to the variation of ion parallel temperature and torus brightness at the equator. As for an ion thermal anisotropy, it varied from 1 through 5 at a radial distance of 5.9 Jovian radii depending on System III longitude. Average values of anisotropy were 2.4 on dusk ansa and 2.0 on dawn ansa. However, as for the absolute value of parallel ion temperature and thermal anisotropy, we need to consider about line-of-sight (LOS) integration effect at the torus edge which causes an overestimate of ion parallel temperature. More accurate analysis including correction of LOS effect using a torus emission model will be presented at the meeting.

Kagitani, Masato

2013-10-01

43

High Performance Plasmas on the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) has produced toroidal plasmas at low aspect ratio (A = R/a = 0.86 m/0.68 m approximately equal to 1.3, where R is the major radius and a is the minor radius of the torus) with plasma currents of 1.4 MA. The rapid development of the machine has led to very exciting physics results during the first full year of physics operation. Pulse lengths in excess of 0.5 sec have been obtained with inductive current drive. Up to 4 MW of High Harmonic Fast Wave (HHFW) heating power has been applied with 6 MW planned. Using only 2 MW of HHFW heating power clear evidence of electron heating is seen with HHFW, as observed by the multi-point Thomson scattering diagnostic. A noninductive current drive concept known as Coaxial Helicity Injection (CHI) has driven 260 kA of toroidal current. Neutral-beam heating power of 5 MW has been injected. Plasmas with beta toroidal (= 2 mu(subscript ''0'')

/B(superscript ''2'') = a measure of magnetic confinement efficiency ) of 22% have been achieved, as calculated using the EFIT equilibrium reconstruction code. Beta-limiting phenomena have been observed, and the maximum beta toroidal scales with I(subscript ''p'')/aB(subscript ''t''). High frequency (>MHz) magnetic fluctuations have been observed. High-confinement mode plasmas are observed with confinement times of >100 msec. Beam-heated plasmas show energy confinement times in excess of those predicted by empirical scaling expressions. Ion temperatures in excess of 2.0 keV have been measured, and power balance suggests that the power loss from the ions to the electrons may exceed the calculated classical input power to the ions.

D.A. Gates; M.G. Bell; R.E. Bell; J. Bialek; T. Bigelow; M. Bitter; P. Bonoli; D. Darrow; P. Efthimion; J. Ferron; E. Fredrickson; L. Grisham; J. Hosea; D. Johnson; R. Kaita; S. Kaye; S. Kubota; H. Kugel; B. LeBlanc; R. Maingi; J. Manickam; T.K. Mau; R.J. Maqueda; E. Mazzucato; J. Menard; D. Mueller; B. Nelson; N. Nishino; M. Ono; F. Paoletti; S. Paul; Y-K.M. Peng; C.K. Phillips; R. Raman; P. Ryan; S.A. Sabbagh; M. Schaffer; C.H. Skinner; D. Stutman; D. Swain; E. Synakowski; Y. Takase; J. Wilgen; J.R. Wilson; W. Zhu; S. Zweben; A. Bers; M. Carter; B. Deng; C. Domier; E. Doyle; M. Finkenthal; K. Hill; T. Jarboe; S. Jardin; H. Ji; L. Lao; K.C. Lee; N. Luhmann; R. Majeski; H. Park; T. Peebles; R.I. Pinsker; G. Porter; A. Ram; M. Rensink; T. Rognlien; D. Stotler; B. Stratton; G. Taylor; W. Wampler; G.A. Wurden; X.Q. Xu; L. Zeng; and the NSTX Team

2001-07-10

44

Mode conversion at the Jovian plasma sheet boundary  

NASA Astrophysics Data System (ADS)

The plasma wave data obtained by Galileo in Jupiter's magnetosphere often exhibit three distinct frequency bands in the frequency range between a few hertz and a few kilohertz. It is shown that these emissions are generally electromagnetic. They are identified by relating their characteristic frequencies to the solutions of the cold plasma dispersion relation. Four modes are possible: X, Z, O, and whistler. Knowing the electron gyrofrequency fee measured by the fluxgate magnetometer, we have considered two different hypotheses for the observed lower-frequency cutoff of the intermediate frequency emissions which occur below fee. Under these assumptions, characteristic frequencies have been computed from the cold plasma theory and compared with the set of cutoff frequencies derived from the observations. Consistency checks lead to the identification of the intermediate frequency band as being on O mode with a low-frequency cutoff at the electron plasma frequency fp. Below the O mode, Galileo detects whistler mode emissions (below fp). Above fee the observed emission is consistent with being X mode. An attempt is made to identify the source of the O mode radiation. Quasi-electrostatic waves are sometimes identified below the upper hybrid frequency when the plasma sheet boundary is crossed. We suggest that these electrostatic waves, which are presumably generated by field-aligned electron beams flowing along plasma sheet boundary, are successively mode converted into Z and later O mode. Thus the O mode observed mostly outside the plasma sheet is generated by mode conversion of primary electrostatic waves.

Perraut, Sylvaine; Roux, Alain; Louarn, Philippe; Gurnett, Donald A.; Kurth, Willaim S.; Khurana, K. K.

1998-07-01

45

Ratio of oxygen to sulfur in the Io plasma torus  

NASA Astrophysics Data System (ADS)

The relative concentrations of O and S ions in the hot dense region of the Io plasma torus (IPT) are investigated by means of model calculations based on collisional diffusive equilibrium. The spectroscopic constraints and uncertainties encountered in calculating the ion partitioning and the modeling procedures employed are discussed, and the results are presented in tables and graphs and compared with Voyager EUV data and the rocket observations of Skinner and Durrance (1986). It is found that the observed O and S emission from the IPT can be reproduced by models with approximately equal partitioning between O and S species. The assumptions and analyses leading to the conclusion (Moreno et al., 1985) that the IPT is S-dominated (by 3 to 1 or more) are analyzed in detail and rejected.

Shemansky, D. E.

1987-06-01

46

Particle transport in pellet fueled JET (Jet European Torus) plasmas  

SciTech Connect

Pellet fueling experiments have been carried out on the Joint European Torus (JET) tokamak with a multi-pellet injector. The pellets are injected at speeds approaching 1400 m/s and penetrate deep into the JET plasma. Highly peaked electron density profiles are achieved when penetration of the pellets approaches or goes beyond the magnetic axis, and these peaked profiles persist for more than two seconds in ohmic discharges and over one second in ICRF heated discharges. In this dissertation, analysis of electron particle transport in multi-pellet fueled JET limiter plasmas under a variety of heating conditions is described. The analysis is carried out with a one and one-half dimensional radial particle transport code to model the experimental density evolution with various particle transport coefficients. These analyses are carried out in plasmas with ohmic heating, ICRF heating, and neural beam heating, in limiter configurations. Peaked density profile cases are generally characterized by diffusion coefficients with a central (r/a < 0.5) diffusivity {approximately}0.1 m{sup 2}/s that increases rapidly to {approximately}0.3 m{sup 2}/s at r/a = 0.6 and then increases out to the plasma edge as (r/a){sup 2}. These discharges can be satisfactorily modeled without any anomalous convective (pinch) flux. 79 refs., 60 figs.

Baylor, L.R.

1990-01-01

47

Role of the plasma acceleration time in the dynamics of the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

The time needed to accelerate plasma in the Jovian magnetosphere to the self-consistent flow imposed by coupling to the ionosphere is proportional to the Pedersen conductivity times the magnetic field divided by the flux tube content. Where this acceleration time becomes longer than the plasma outflow time, it is not possible to maintain magnetospheric plasma in corotation with the planet; comparison of the two time scales gives a general estimate of the limiting distance for corotation, identical to that previously derived by Hill from a specific flow model. At distances well beyond this limit, the magnetosphere becomes effectively decoupled from the ionosphere. In describing rotationally driven radial diffusion, inertial effects must be included whenever the acceleration time is not short compared to the eddy circulation time; they impose an upper bound on the circulation time proportional to the corotational period.

Vasyliunas, V. M.

1994-03-01

48

Magnetic reconnection in the Jovian tail: X-line evolution and consequent plasma sheet structures  

NASA Astrophysics Data System (ADS)

Magnetic reconnection in planetary magnetospheres plays important roles in energy and mass transfer in the steady state, and also possibly in transient large-scale disturbances. In this paper we report observations of a reconnection event in the Jovian magnetotail by the Galileo spacecraft on 17 June 1997. In addition to the tailward retreat of a main X-line, signatures of recurrent X-line formations are found by close examination of energetic particle anisotropies. Furthermore, detailed analyses of multi-instrumental data for this period provide various spatiotemporal features in the plasma sheet. A significant density decrease was detected in the central plasma sheet, indicative of the transition to lobe (open field line) reconnection from plasma sheet (closed field line) reconnection. When Galileo vertically swept through the plasma sheet, a velocity layer structure was observed. We also analyze a strong southward magnetic field which is similar to dipolarization fronts observed in the terrestrial magnetotail: the ion flow (˜450 km s-1) was observed behind the magnetic front, whose thickness of 10000-20000 km was of the order of ion inertial length. The electron anisotropy in this period suggests an anomalously high-speed electron jet, implying ion-electron decoupling behind the magnetic front. Particle energization was also seen associated with these structures. These observations suggest that X-line evolution and consequent plasma sheet structures are similar to those in the terrestrial magnetosphere, whereas their generality in the Jovian magnetosphere and influence on the magnetospheric/ionospheric dynamics including transient auroral events need to be further investigated with more events.

Kasahara, S.; Kronberg, E. A.; Krupp, N.; Kimura, T.; Tao, C.; Badman, S. V.; Retinň, A.; Fujimoto, M.

2011-11-01

49

Jovian Magnetospheric Plasma and Energetic Particle Interaction with Ganymede's Magnetic Field and Surface  

NASA Astrophysics Data System (ADS)

The Galileo Orbiter flybys of Ganymede revealed a rich variety of features associated with the newly discovered intrinsic dipolar magnetic field of Ganymede. Dropouts in plasma flows clearly indicated transitions from Jovian to Ganymedian magnetospheric domains. Transitions from open polar to closed field lines were probed by directional distributions of energetic particles. Numerical modeling predicted strong magnetic shielding of the equatorial region against penetration by energetic electrons and protons below 10 MeV. We review comparisons of time histories, moments, and directional distributions for data from the Galileo Plasma Spectrometer (PLS) and Energetic Particle Detector (EPD) instruments to survey these magnetic and surface interaction features. The earlier numerical models for particle penetration to the surface in the open and closed field regions are updated from parameters provided by the combined analysis. Orbit phase variations and time-averages of penetrating particle energy fluxes are modeled for orbiting spacecraft such as the planned Juice Icy Moons Explorer (JUICE).

Cooper, J. F.; Paterson, W. R.; Sittler, E. C., Jr.; Stone, S. M.

2012-09-01

50

Developments in Jovian Radio Emissions Tomography and Observations Techniques  

NASA Astrophysics Data System (ADS)

Jupiter radio emission is known to be the most powerful nonthermal planetary radiation. In recent years specifically space-based observations allow us to permanently cover a large frequency band(from 100 kHz up to 40 MHz combined with ground-based telescopes)of the Jovian spectrum. The Plasma and Wave Science experiment onboard Galileo enables the observation of Jovian kilometric and hectometric emissions; Wind/WAVES and ground-based telescopes (mainly Decametric Array in Nancay, France, and UTR-2 in Kharkov, Ukraine) cover also hectometric and mainly decametric emissions. Specific geometrical configurations between Cassini approaching Jupiter and Wind spacecraft orbiting Earth, with Galileo orbiting Jupiter and Wind, in combination with ground-based observations provide a new approach to perform Jovian radio tomography. The tomography technique is used to analyze ray paths of Jovian radio emission observed in different directions (e.g. solar and anti-solar direction) and for different declination of Earth. The developments of Jovian radio emission tomography in recent years treated refraction effects and its connection to the local magnetic field in the radio source as well as the radio wave propagation through the Io torus and the terrestrial ionosphere. Most recently ground-based multi-site and simultaneous Jupiter decametric radio observations by means of digital spectropolarimeter and waveform receiver provide the basis of a new data analysis treatment. The above addressed topics are without exemption deeply connected to the plasma structures the radio waves are generated in and propagating through.

Rucker, H. O.; Boudjada, M. Y.; Leitner, M.; Lecacheux, A.; Aubier, M.; Konovalenko, A.; Galopeau, P. H. M.; Shaposhnikov, V.

2001-06-01

51

Ion cyclotron waves in the Io torus during the Galileo encounter: Warm plasma dispersion analysis  

Microsoft Academic Search

During the Galileo-Io flyby, nearly field-aligned, left-hand circularly polarized ion cyclotron waves were observed in a band near the sulfur-dioxide ion gyrofrequency. We have performed a warm plasma dispersion analysis using nominal Io torus composition ratios, pickup ion “ring”-type velocity-space distributions, and a thermal background plasma of typical torus temperature. Analysis shows that the SO2+ wave is dominant, particularly as

D. E. Huddleston; R. J. Strangeway; J. Warnecke; C. T. Russell; M. G. Kivelson; F. Bagenal

1997-01-01

52

Plasma interaction of Io with its plasma torus  

NASA Astrophysics Data System (ADS)

Theoretical concepts of the Io-plasma interaction: approaches to modeling - dimensionless parameters, fluid equations, the local interaction, the far-field interaction; Observations of local interactions and their interpretation: Galileo - in situ measurements, small-scale magnetic field perturbations, Io's aurora; Far-field effects and their implications: footprint emissions at IR and UV wavelengths, radio emission.

Saur, Joachim; Neubauer, Fritz M.; Connerney, J. E. P.; Zarka, Philippe; Kivelson, Margaret G.

53

Two-Dimensional Transport Studies for the Composition and Structure of the Io Plasma Torus.  

National Technical Information Service (NTIS)

The overall objective of this project is to investigate the roles of local and spatially extended plasma sources created by Io, plasma torus chemistry, and plasma convective and diffusive transport in producing the long-lived S(+), S(++) and O(+) radial r...

W. H. Smyth

2003-01-01

54

Pitch-angle diffusion by whistler mode waves near the Io plasma torus  

Microsoft Academic Search

As Voyager 1 traversed the inner radiation belt of Jupiter, wave-particle interactions involving energetic electrons and whistler mode turbulence were strongly affected by the presence of the Io plasma torus. Within the high density torus the resonant electron energy was low and the associated high index of refraction yielded high B-to-E ratios for the wave fields, leading to very strong

F.L. Scarf; F. V. Coroniti; D. A. Gurnett; W. S. Kurth

1979-01-01

55

Moderate-Resolution EUV Spectra of the Io Plasma Torus During the Galileo I24 Visit  

NASA Astrophysics Data System (ADS)

Spectral images of the Io plasma torus from about 165 hours of observation by the Extreme Ultraviolet Explorer (EUVE) spacecraft were analyzed by a spectral-resolution-enhancing deconvolution algorithm in order to estimate averaged torus properties during Galileo's I24 torus encounter and also in June, 1996. Because of our analysis' improved spectral resolution (? ? ?1 to 2 Ĺ), we are able to separate lines arising from different ion species better than in earlier studies. Here we estimate emission-weighted whole-torus averages of electron temperature and ion fraction. Comparing the 1996 and I24 observations, the torus electrons were hotter (5.5+/-0.5 vs 4.6+/-0.3 eV), the torus was brighter (2.9 vs 1.9*E11 W over 350<=? <=735 Ĺ), and the sulfur/oxygen ratio was higher (0.8 vs 0.55) in the earlier epoch. When separately analyzing the dawn and dusk halves of the torus during I24, we estimate that the dusk half is a few tenths of an eV hotter than at dawn. In our presentation, we will discuss analysis of the data by System III longitude and orbital phase relative to Io. We have also put new constraints on the values of electron impact collision line strengths for many EUV lines in the range 350<=? <=735 Ĺ that are of interest for understanding the torus and other sulfur and oxygen plasmas. These numbers are useful for modeling EUV torus spectra at both moderate and low spectral resolution. This work was supported by the NASA Planetary Atmospheres, Planetary Magnetospheres, and JSDAP programs.

Herbert, F.; Gladstone, G. R.

2000-10-01

56

Two-Dimensional Transport Studies of Radial and Longitudinal Structure in the Io Plasma Torus  

NASA Astrophysics Data System (ADS)

A two-dimensional transport model is being developed for studying the radial and System III longitudinal density structures in the Io plasma torus. The structure of the Io plasma torus is highlighted by the so-called S+ ribbon, which is the most-observed (6716Ĺ, 6731Ĺ) ground-based radial feature in the torus. The observed asymmetric radial positions at east (dawn) and west (dusk) elongations of the S+ emission peak and their System III longitudinal dependences were successfully modeled by Smyth and Marconi (JGR, 103, 9091, 1998) using a two-dimensional transport model with a highly localized plasma source at Io's position, no plasma sinks, and an east-west electric field. The location of the ribbon was determined by the interplay of the Iogenic plasma point source, the east-west electric field, and an outward increasing transport rate. This transport model has recently been improved to include, in addition, spatially-extended plasma sources and also plasma loss processes to understand the more detailed radial and longitudinal structure of S+ and S++ in the plasma torus. Ion production rates for the spatially-extended plasma source are determined from the AER Neutral Cloud Model with an exobase neutral source based on a modified-sputtering flux distribution. Significant progress toward understanding the formation of peaks in S+ with western elongation L-shell values of LW = 5.3 and 5.6, and the peak in S++ at LW = 5.7 will be presented.

Delamere, P. A.; Smyth, W. H.; Marconi, M. L.

2001-11-01

57

Source characteristics of Jovian narrow-band kilometric radio emissions  

NASA Astrophysics Data System (ADS)

New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.

Reiner, M. J.; Fainberg, J.; Stone, R. G.; Kaiser, M. L.; Desch, M. D.; Manning, R.; Zarka, P.; Pedersen, B.-M.

1993-07-01

58

Periodic bursts of Jovian non-Io decametric radio emission  

NASA Astrophysics Data System (ADS)

During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ?1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ˜25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

Panchenko, M.; Rucker, H. O.; Farrell, W. M.

2013-03-01

59

Periodic bursts of Jovian non-Io decametric radio emission.  

PubMed

During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period [Formula: see text] longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every [Formula: see text] days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

Panchenko, M; Rucker, H O; Farrell, W M

2013-03-01

60

NET (Next European Torus) Plasma Facing Materials Behaviour under Erosion and Redeposition Regimes in PISCES.  

National Technical Information Service (NTIS)

First wall and divertor target plate materials envisaged for the Next European Torus (NET) were investigated in the PISCES-A plasma facility. Since chemical erosion could be quite critical in a machine like NET, SiC-impregnated carbon, 2-D carbon weave, w...

E. Franconi Y. Hirooka R. W. Conn K. W. Leung B. LaBombard

1989-01-01

61

Effect of plasma shaping on performance in the National Spherical Torus Experiment  

Microsoft Academic Search

The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving betat~40%. Precise

D. A. Gates; R. Maingi; J. Menard; S. Kaye; S. A. Sabbagh; G. Taylor; J. R. Wilson; M. G. Bell; R. E. Bell; S. Bernabei; J. Bialek; T. Biewer; W. Blanchard; J. Boedo; C. Bush; M. D. Carter; W. Choe; N. Crocker; D. S. Darrow; W. Davis; L. Delgado-Aparicio; S. Diem; J. Ferron; A. Field; J. Foley; E. D. Fredrickson; R. E. Hatcher; W. Heidbrink; K. Hill; J. C. Hosea; T. R. Jarboe; D. W. Johnson; R. Kaita; C. Kessel; S. Kubota; H. W. Kugel; J. Lawson; B. P. Leblanc; K. C. Lee; F. Levinton; J. Manickam; R. Maqueda; R. Marsala; D. Mastrovito; T. K. Mau; S. S. Medley; H. Meyer; D. R. Mikkelsen; D. Mueller; T. Munsat; B. A. Nelson; C. Neumeyer; N. Nishino; M. Ono; S. Paul; W. Peebles; M. Peng; C. Phillips; A. Pigarov; R. Pinsker; A. Ram; S. Ramakrishnan; R. Raman; D. Rasmussen; M. Rensink; G. Rewoldt; J. Robinson; P. Roney; L. Roquemore; E. Ruskov; P. Ryan; H. Schneider; C. H. Skinner; D. R. Smith; A. Sontag; V. Soukhanovskii; T. Stevenson; D. Stotler; B. Stratton; D. Stutman; D. Swain; E. Synakowski; Y. Takase; K. Tritz; A. Von Halle; M. Wade; R. White; J. Wilgen; M. Williams; W. Zhu; S. J. Zweben; R. Akers; P. Beiersdorfer; R. Betti; T. Bigelow

2006-01-01

62

Effects of Io's volcanos on the plasma torus and Jupiter's magnetosphere  

Microsoft Academic Search

Io's volcanism can have dominant effects on Jupiter's magnetosphere. A model is developed in which a neutral gas torus is formed at Io's orbit by volcanic SOâ escaping from Io. Ionization and dissociation of volcanic SOâ is shown to be the dominant source of plasma in Jupiter's magnetosphere. The failure of Voyager observations to confirm predictions of the magnetic anomaly

A. F. Cheng

1980-01-01

63

Ion cyclotron waves in the Io torus during the Galileo encounter: Warm plasma dispersion analysis  

Microsoft Academic Search

During the Galileo-Io flyby, nearly field-aligned, left-hand circularly polarized ion cyclotron waves were observed in a band near the sulfur-dioxide ion gyrofrequency. We have performed a warm plasma dispersion analysis using nominal Io torus composition ratios, pickup ion 'ring'-type velocity-space distributions, and a thermal background plasma of typical toms temperature. Analysis shows that the SO2(+) wave is dominant, particularly as

D. E. Huddleston; R. J. Strangeway; J. Warnecke; C. T. Russell; M. G. Kivelson; F. Bagenal

1997-01-01

64

Effects of Io's volcanos on the plasma torus and Jupiter's magnetosphere  

Microsoft Academic Search

A model is presented of a neutral gas torus produced in Io's orbit by volcanic SO2 escaping from Io whose ionization and dissociation is the main source of plasma in Jupiter's magnetosphere. A 30-50 keV S and O ion plasma results from ionization of S and O atoms in highly eccentric elliptical orbits around Jupiter; these atoms are created by

A. F. Cheng

1980-01-01

65

Decametric modulation lanes as a probe for inner jovian magnetosphere  

NASA Astrophysics Data System (ADS)

We use the specific scintillations of jovian decametric radio sources (modulation lanes), which are produced by plasma inhomogeneities in the vicinity of that planet, to probe the inner magnetosphere of Jupiter. The positions and frequency drift of 1762 lanes have been measured on the DAM spectra from archives. A special 3D algorithm is used for space localization of field-aligned magnetospheric inhomogeneities by the frequency drift of modulation lanes. As a result, the main regions of the lane formation are found: the Io plasma torus; the magnetic shell of the Gossamer Ring at Thebe and Amalthea orbits; and the region above the magnetic anomaly in the northern magnetosphere. It is shown that modulation lanes reveal the depleted magnetic tubes in practically unvisited, innermost regions of the jovian magnetosphere. The local and probably temporal plasma enhancement is found at the magnetic shell of Thebe satellite. Hence, the modulation lanes are a valuable instrument for remote sensing of those parts of jovian magnetosphere, which are not studied yet in situ.

Arkhypov, Oleksiy V.; Rucker, Helmut O.

2013-11-01

66

Ring Current Impoundment of the Io Plasma Torus  

Microsoft Academic Search

A newly discovered feature in the Io plasma formation that may be described as a ramp separating a high-density plasma ledge on its Jupiterward side from the lower-density radially distended Io plasma disc on its anti-Jupiterward side is observed to coincide with a marked inward decrease in the ring current population. The spatial congruency of the counter-directed maximal gradients in

G. L. Siscoe; A. Eviatar; R. M. Thorne; J. D. Richardson; F. Bagenal; J. D. Sullivan

1981-01-01

67

Formation of zebra pattern in low-frequency Jovian radio emission  

NASA Astrophysics Data System (ADS)

We investigate the formation of zebra-like fine spectral structures (consisting of several parallel bands in the dynamic spectrum) in the Jovian broadband kilometric radiation; such radio bursts were observed by Cassini in 2000/2001. We assume that the emission is generated due to a plasma mechanism in the Io plasma torus. We have shown that the double plasma resonance effect (that was proposed earlier as a formation mechanism of the solar zebra patterns) is able to produce the observed spectral structures. The observed frequency drifts are caused, most likely, by the dynamics of the electron acceleration site. The required conditions in the emission source are discussed.

Kuznetsov, A. A.; Vlasov, V. G.

2013-01-01

68

Jovian Magnetospheric Interactions with Io, Amalthea, and the Planetary Rings: Current and Expected Results from the Galileo Orbiter Heavy Ion Counter  

Microsoft Academic Search

The energetic (keV to MeV) heavy ion population in the inner jovian magnetosphere, out to Io's orbit, originates mostly from acceleration of Io plasma torus ions and contributes to erosion of satellite surfaces and ring particles by sputtering. Photo- and plasma-ionization of iogenic neutrals, magnetospheric pickup of the resultant ions, and magnetospheric acceleration processes produce high fluxes of oxygen and

J. F. Cooper

2002-01-01

69

Periodic bursts observed in Jovian decametric radio emission  

NASA Astrophysics Data System (ADS)

Dynamic radio spectra of Jovian decametric radio emission (DAM) acquired by STEREO/ WAVES, Wind/WAVES and Cassini/RPWS instruments have been analyzed in a frequency range from few MHz up to ˜16 MHz during the time interval between the years 2002-2008. The non-Io component of the DAM, which is the subject of our study, appears mainly in a form of arcs in time-frequency coordinates and is generally modulated by the Jovian ˜9.925 - hour rotation period (System III). Nevertheless, we have found several unusual episodes when non-Io related bursts recurred with a period of ˜10.07 hour which is ˜1.5% longer than the System III and shorter than the period of System IV (System III + 3%). The bursts were observed in a frequency range from ˜4-5 MHz to ˜12-16 MHz. Typically, the bursts recurred very periodically during several Jovian days with decreasing intensity and displayed negative drift in time-frequency domain. All bursts were detected within the same sector of Jovian Central Meridian Longitude (III), between 300° and 60° (via 360°) of CML (III), close to the region of non-Io-C source. The absence of any correlation with the position of Io has been found. Since the bursts were observed sequentially by STEREO-A and STEREO-B, as well as by Wind and Cassini during several Jovian rotations with proper time delay we can conclude that the source of the periodic bursts sub-corotates with Jupiter and it may be active during longer periods of time. The possible relation between the Io plasma torus and ˜10.07-hour periodic bursts of the DAM is discussed.

Panchenko, M.; Rucker, H. O.; Kaiser, M. L.; Bougeret, J. L.; Gurnett, D. A.

2009-12-01

70

Discovery of Soft X-Ray Emission from Io, Europa, and the Io Plasma Torus  

Microsoft Academic Search

We report the discovery of soft (0.25-2 keV) X-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (greater than 10 keV) H, O, and S ions from the region of the IPT seems to be the likely source of the X-ray emission from the Galilean satellites. According to

Ronald F. Elsner; G. Randall Gladstone; J. Hunter Waite; Frank J. Crary; Robert R. Howell; Robert E. Johnson; Peter G. Ford; Albert E. Metzger; Kevin C. Hurley; Eric D. Feigelson; Gordon P. Garmire; Anil Bhardwaj; Denis C. Grodent; Tariq Majeed; Allyn F. Tennant; Martin C. Weisskopf

2002-01-01

71

Dawn-dusk electric field asymmetry of the Io plasma torus  

Microsoft Academic Search

The effects of a combined convection and corotation electric field across the Io plasma torus are considered. A dawn-to-dusk electric field EC will modify the orbits of charged particles shifting them toward dawn. The radial drift imposed by the perturbed orbits implies a local time-dependent modulation of low-energy ion and electron temperatures with particles hotter at dusk than at dawn.

D. D. Barbosa; M. G. Kivelson

1983-01-01

72

Plasma response to lithium-coated plasma-facing components in the National Spherical Torus Experiment  

SciTech Connect

Experiments in the National Spherical Torus Experiment ( NSTX) have shown beneficial effects on the performance of divertor plasmas as a result of applying lithium coatings on the graphite and carbon-fiber-composite plasma-facing components. These coatings have mostly been applied by a pair of lithium evaporators mounted at the top of the vacuum vessel which inject collimated streams of lithium vapor toward the lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode plasmas run immediately after the application of lithium, performance modifications included decreases in the plasma density, particularly in the edge, and inductive flux consumption, and increases in the electron and ion temperatures and the energy confinement time. Reductions in the number and amplitude of edge-localized modes (ELMs) were observed, including complete ELM suppression for periods of up to 1.2 s, apparently as a result of altering the stability of the edge. However, in the plasmas where ELMs were suppressed, there was a significant secular increase in the effective ion charge Z(eff) and the radiated power as a result of increases in the carbon and medium-Z metallic impurities, although not of lithium itself which remained at a very low level in the plasma core, <0.1%. The impurity buildup could be inhibited by repetitively triggering ELMs with the application of brief pulses of an n = 3 radial field perturbation. The reduction in the edge density by lithium also inhibited parasitic losses through the scrape-off-layer of ICRF power coupled to the plasma, enabling the waves to heat electrons in the core of H-mode plasmas produced by NBI. Lithium has also been introduced by injecting a stream of chemically stabilized, fine lithium powder directly into the scrape-off-layer of NBI-heated plasmas. The lithium was ionized in the SOL and appeared to flow along the magnetic field to the divertor plates. This method of coating produced similar effects to the evaporated lithium but at lower amounts.

Bell, M. G. [Princeton Plasma Physics Laboratory (PPPL); Kugel, H. [Princeton Plasma Physics Laboratory (PPPL); Kaita, R. [Princeton Plasma Physics Laboratory (PPPL); Zakharov, L. E. [Princeton Plasma Physics Laboratory (PPPL); Schneider, H [Princeton Plasma Physics Laboratory (PPPL); LaBlanc, B. P. [Princeton Plasma Physics Laboratory (PPPL); Mansfield, D.K. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Maingi, R. [Oak Ridge National Laboratory (ORNL); Ding, S. [Academia Sinica, Institute of Plasma Physics, Hefei, China; Kaye, S. [Princeton Plasma Physics Laboratory (PPPL); Paul, S.F. [Princeton Plasma Physics Laboratory (PPPL); Gerhardt, S.P. [Princeton Plasma Physics Laboratory (PPPL); Canik, John [ORNL; Hosea, J. [Princeton Plasma Physics Laboratory (PPPL); Taylor, G. [Princeton Plasma Physics Laboratory (PPPL)

2009-01-01

73

Plasma response to lithium-coated plasma-facing components in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on the performance of divertor plasmas as a result of applying lithium coatings on the graphite and carbon-fiber-composite plasma-facing components. These coatings have mostly been applied by a pair of lithium evaporators mounted at the top of the vacuum vessel which inject collimated streams of lithium vapor toward the lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode plasmas run immediately after the application of lithium, performance modifications included decreases in the plasma density, particularly in the edge, and inductive flux consumption, and increases in the electron and ion temperatures and the energy confinement time. Reductions in the number and amplitude of edge-localized modes (ELMs) were observed, including complete ELM suppression for periods of up to 1.2 s, apparently as a result of altering the stability of the edge. However, in the plasmas where ELMs were suppressed, there was a significant secular increase in the effective ion charge Zeff and the radiated power as a result of increases in the carbon and medium-Z metallic impurities, although not of lithium itself which remained at a very low level in the plasma core, <0.1%. The impurity buildup could be inhibited by repetitively triggering ELMs with the application of brief pulses of an n = 3 radial field perturbation. The reduction in the edge density by lithium also inhibited parasitic losses through the scrape-off-layer of ICRF power coupled to the plasma, enabling the waves to heat electrons in the core of H-mode plasmas produced by NBI. Lithium has also been introduced by injecting a stream of chemically stabilized, fine lithium powder directly into the scrape-off-layer of NBI-heated plasmas. The lithium was ionized in the SOL and appeared to flow along the magnetic field to the divertor plates. This method of coating produced similar effects to the evaporated lithium but at lower amounts.

Bell, M. G.; Kugel, H. W.; Kaita, R.; Zakharov, L. E.; Schneider, H.; Le Blanc, B. P.; Mansfield, D.; Bell, R. E.; Maingi, R.; Ding, S.; Kaye, S. M.; Paul, S. F.; Gerhardt, S. P.; Canik, J. M.; Hosea, J. C.; Taylor, G.; NSTX Research Team

2009-12-01

74

Characteristic of hot plasma in the Jovian magnetosphere: Results from the Voyager spacecraft  

Microsoft Academic Search

The low-energy charged particle (LECP) experiment on the Voyager 1 and 2 spacecraft made measurements of the intensity, energy spectra, angular distributions and composition of ions (30 keV< or approx. =E< or approx. = 150 MeV) and the electrons (14 keV< or approx. =E< or approx. =10 MeV) during encounters with the Jovian magnetosphere in 1979. Detailed analysis of the

S. M. Krimigis; J. F. Carbary; E. P. Keath; C. O. Bostrom; W. I. Axford; G. Gloeckler; L.J. Lanzerotti; T. P. Armstrong

1981-01-01

75

Ion densities and velocities in the inner plasma torus of Saturn  

NASA Astrophysics Data System (ADS)

We present plasma data from the Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP), mapping the ion density and velocity of Saturn's inner plasma torus. Data from 129 orbits, recorded during the period from the 1st of February 2005 to the 27th of June 2010, are used to map the extension of the inner plasma torus. The dominant part of the plasma torus is shown to be located in between 2.5 and 8 Saturn radii (1 RS=60,268 km) from the planet, with a north-southward extension of ą2RS. The plasma disk ion density shows a broad maximum in between the orbits of Enceladus and Tethys. Ion density values vary between 20 and 125 cm-3 at the location of the density maximum, indicating considerable dynamics of the plasma disk. The equatorial density structure, |z|<0.5RS, shows a slower decrease away from the planet than towards. The outward decrease, from 5 RS, is well described by the relation neq=2.2×104(1/R)3.63. The plume of the moon Enceladus is clearly visible as an ion density maximum of 105 cm-3, only present at the south side of the ring plane. A less prominent density peak, of 115 cm-3, is also detected at the orbit of Tethys, at ˜4.9RS. No density peaks are recorded at the orbits of the moons Mimas, Dione, and Rhea. The presented ion velocity v shows a clear general trend in the region between 3 and 7 RS, described by v=1.5R2-8.7R+39. The average v starts to deviate from corotation at around 3 RS, reaching ˜68% of corotation close to 5 RS.

Holmberg, M. K. G.; Wahlund, J.-E.; Morooka, M. W.; Persoon, A. M.

2012-12-01

76

Io and Its Plasma Environment  

Microsoft Academic Search

We describe and examine the interaction of Io with its plasma torus and the Jovian magnetic field in the context of several currently popular models. We address three specific matters. First, we discuss fea- tures implied by sub-Alfvenic flow which must be common to all models. Next, we examine the magnetic signature observed near Io by the Goddard Space Flight

David J. Southwood; Margaret G. Kivelson; Raymond J. Walker; James A. Slavin

1980-01-01

77

Unified Ideal Stability Limits for Advanced Tokamak and Spherical Torus Plasmas  

SciTech Connect

Ideal magnetohydrodynamic stability limits of shaped tokamak plasmas with high bootstrap fraction are systematically determined as a function of plasma aspect ratio. For plasmas with and without wall stabilization of external kink modes, the computed limits are well described by distinct and nearly invariant values of a normalized beta parameter utilizing the total magnetic field energy density inside the plasma. Stability limit data from the low aspect ratio National Spherical Torus Experiment is compared to these theoretical limits and indicates that ideal nonrotating plasma no-wall beta limits have been exceeded in regimes with sufficiently high cylindrical safety factor. These results could impact the choice of aspect ratio in future fusion power plants.

J.E. Menard; M.G. Bell; R.E. Bell; D.A. Gates; S.M. Kaye; B.P. LeBlanc; S.A. Sabbagh; E.D. Fredrickson; S.C. Jardin; R. Maingi; J. Manickam; D. Mueller; M. Ono; F. Paoletti; Y.-K.M. Peng; V. Soukhanovskii; D. Stutman; E.J. Synakowski; the NSTX research team

2003-02-06

78

Spatial distribution of plasma in the Io Torus  

Microsoft Academic Search

In situ measurements of ion densities and temperatures have been analyzed to produce profiles of these plasma parameters along the Voyager 1 inbound trajectory between 7 and 5 R\\/sub J\\/. The temperature profile shows a sharp decrease by a factor of approx.50 between 5.8 and 5.2R\\/sub J\\/ corresponding to a temperature gradient of approx.7 x 10⁾ per R\\/sub J\\/. The

Fran Bagenal; James D. Sullivan; George L. Siscoe

1980-01-01

79

Study of local time dependence of the attenuation band associated to the Jovian hectometric emission  

NASA Astrophysics Data System (ADS)

We study the phenomenological spectral features of the Jovian hectometric (HOM) emission recorded during the Jupiter flyby by the RPWS experiment onboard the Cassini spacecraft. The capability of this experiment allowed a frequency coverage from a few hertz to 16 MHz with a large dynamic range of about 80 dB. HOM emission was regularly observed several weeks before and after the closest approach of the planet. We analyze the Jovian radio dynamic spectra recorded from the end of November 2000 to the second week of January 2001. During this period, the spacecraft approached Jupiter from a distance of more than 500 RJ to 137 RJ (closest approach on December 30, 2010) and back to about 250 RJ. We attempt in this study to investigate the local time (LT) dependence of the attenuation band due to refraction effects caused by the presence of the Io plasma torus. We analyze the spectral features of the attenuation band taking into consideration three local time intervals [10.0 LT, 13.2 LT], [13.6 LT, 16.5 LT], and [16.7 LT, 20 LT]. A statistical study leads us to characterize the spectral features of the attenuation band principally on the day-side and the late afternoon sector of the planet. This will allow us to discuss the LT variation of the electronic density of the Io plasma torus versus the central meridian longitude (CML) and the Jovian magnetic latitude.

Boudjada, M. Y.; Galopeau, P. H. M.

2011-10-01

80

The emission of narrow-band Jovian kilometric radiation  

NASA Astrophysics Data System (ADS)

A model based on the nonlinear coupling of electrostatic plasma waves is proposed to explain the emission of the narrow-band Jovian kilometric radiation (nKOM) observed by the Voyager spacecraft. It is shown that upper-hybrid branch electrostatic waves propagating through the inhomogeneities in the outer periphery of the Io plasma torus can attain the proper geometry for localized upconversion interactions leading to pump depletion. Plasma waves propagating into a weak density gradient and reflected at the critical layer interact with the incident waves leading to the electromagnetic emission, which is beamed at large angles with respect to the background magnetic field. In general, both L-O and R-X mode waves can be generated. The observed power and net polarization (L-O) are consistent with pump depletion of electrostatic waves at a level of about 10 mV/m. A possible excitation mechanism for the electrostatic waves is also discussed.

Fung, S. F.; Papadopoulos, K.

1987-08-01

81

The effect of lithium surface coatings on plasma performance in the National Spherical Torus Experiment  

SciTech Connect

National Spherical Torus Experiment [which M. Ono et al., Nucl. Fusion 40, 557 (2000)] high-power divertor plasma experiments have shown, for the first time, that benefits from lithium coatings applied to plasma facing components found previously in limited plasmas can occur also in high-power diverted configurations. Lithium coatings were applied with pellets injected into helium discharges, and also with an oven that directed a collimated stream of lithium vapor toward the graphite tiles of the lower center stack and divertor. Lithium oven depositions from a few milligrams to 1 g have been applied between discharges. Benefits from the lithium coatings were sometimes, but not always, seen. These benefits sometimes included decreases in plasma density, inductive flux consumption, and edge-localized mode occurrence, and increases in electron temperature, ion temperature, energy confinement, and periods of edge and magnetohydrodynamic quiescence. In addition, reductions in lower divertor D, C, and O luminosity were measured.

Kugel, H. W.; Bell, M. G.; Bell, R.; Gates, D.; Gray, T.; Kaye, S.; Kaita, R.; LeBlanc, B.; Majeski, R.; Mansfield, D.; Menard, J.; Mueller, D.; Ono, M.; Paul, S.; Roquemore, A. L.; Ross, P. W.; Schneider, H.; Skinner, C. H.; Stevenson, T.; Timberlake, J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] (and others)

2008-05-15

82

Resistive magnetohydrodynamic simulations of helicity-injected startup plasmas in National Spherical Torus eXperiment  

NASA Astrophysics Data System (ADS)

The generation of helicity-injected startup plasmas in National Spherical Torus eXperiment (NSTX), including flux surface closure, is studied using resistive-magnetohydrodynamic simulations with plasma flows, currents, ohmic heating and anisotropic thermal conduction. An injection-voltage pulse shape is used that separates the injection and closure phases allowing elucidation of the physics. The formation of an X-point near the helicity-injection gap is triggered as the injector voltage drops to zero. Near the forming X-point, magnetic pressure due to toroidal field entrained in the E × B plasma flow from the helicity-injection gap drops, allowing resistive magnetic reconnection even though the total injected current is almost constant. Where appropriate, the simulations are compared with Transient Coaxial Helicity Injection experiments in the NSTX spherical tokamak, which have demonstrated the formation of a promising candidate for non-inductive startup plasmas [Raman et al., Phys. Rev. Lett. 90, 075005 (2003)].

Hooper, E. B.; Sovinec, C. R.; Raman, R.; Ebrahimi, F.; Menard, J. E.

2013-09-01

83

Volcanically emitted sodium chloride as a source for Io's neutral clouds and plasma torus.  

PubMed

The atmosphere of Jupiter's satellite Io is extremely tenuous, time variable and spatially heterogeneous. Only a few molecules--SO2, SO and S2--have previously been identified as constituents of this atmosphere, and possible sources include frost sublimation, surface sputtering and active volcanism. Io has been known for almost 30 years to be surrounded by a cloud of Na, which requires an as yet unidentified atmospheric source of sodium. Sodium chloride has been recently proposed as an important atmospheric constituent, based on the detection of chlorine in Io's plasma torus and models of Io's volcanic gases. Here we report the detection of NaCl in Io's atmosphere; it constitutes only approximately 0.3% when averaged over the entire disk, but is probably restricted to smaller regions than SO2 because of its rapid photolysis and surface condensation. Although the inferred abundance of NaCl in volcanic gases is lower than predicted, those volcanic emissions provide an important source of Na and Cl in Io's neutral clouds and plasma torus. PMID:12511948

Lellouch, E; Paubert, G; Moses, J I; Schneider, N M; Strobel, D F

2003-01-01

84

Modeling of the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

A paraboloid model of the Jovian magnetosphere is presented. The magnetopause is approximated by a paraboloid of revolution. Magnetospheric magnetic field consists of a planet dipole field, a magnetodisc field, a magnetotail current sheet field and a partially penetrating interplanetary magnetic field. All magnetospheric magnetic fields are screened by the magnetopause currents. The purpose of this paper is to discuss a possibility to compare the Jovian magnetospheric electric fields and plasma motions caused by the unipolar inductor and the solar wind MHD generator. this is one of the approaches to the fundumental question regarding the nature of the global plasma convection and corotation in the Jupiter's magnetosphere.

Belenkaya, E. S.

2001-09-01

85

Retarding field energy analyzer for the Saskatchewan Torus-Modified plasma boundary.  

PubMed

The retarding field energy analyzer (RFA) is a simple and reliable diagnostic technique to measure the ion temperature in the scrape-off layer and edge of magnetic fusion devices. Design and operation features of a single-sided (facing the ion flow) RFA for ion temperature measurements in the Saskatchewan Torus-Modified (STOR-M) tokamak are described. Its compact size (21 x 15 x 20 mm3) allows RFA measurements without perturbing plasma significantly. Both ion and electron temperature have been measured by RFA in the STOR-M tokamak. A method is proposed to correct the effects of ion flow on the ion temperature using the simultaneously measured Mach number. The measured electron temperature is consistent with the previously reported Langmuir probe data. Abnormal behavior of the RFA has been observed in both ion and electron modes when RFA is inserted deep into the plasma. PMID:19895062

Dreval, M; Rohraff, D; Xiao, C; Hirose, A

2009-10-01

86

Retarding field energy analyzer for the Saskatchewan Torus-Modified plasma boundary  

SciTech Connect

The retarding field energy analyzer (RFA) is a simple and reliable diagnostic technique to measure the ion temperature in the scrape-off layer and edge of magnetic fusion devices. Design and operation features of a single-sided (facing the ion flow) RFA for ion temperature measurements in the Saskatchewan Torus-Modified (STOR-M) tokamak are described. Its compact size (21x15x20 mm{sup 3}) allows RFA measurements without perturbing plasma significantly. Both ion and electron temperature have been measured by RFA in the STOR-M tokamak. A method is proposed to correct the effects of ion flow on the ion temperature using the simultaneously measured Mach number. The measured electron temperature is consistent with the previously reported Langmuir probe data. Abnormal behavior of the RFA has been observed in both ion and electron modes when RFA is inserted deep into the plasma.

Dreval, M.; Rohraff, D.; Xiao, C.; Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

2009-10-15

87

Plasma Shape Control on the National Spherical Torus Experiment (NSTX) using Real-time Equilibrium Reconstruction  

SciTech Connect

Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which is used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared to a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal-field coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.

D.A. Gates; J.R. Ferron; M. Bell; T. Gibney; R. Johnson; R.J. Marsala; D. Mastrovito; J.E. Menard; D. Mueller; B. Penaflor; S.A. Sabbagh; T. Stevenson

2005-04-15

88

Acceleration of compact torus plasma rings in a coaxial rail-gun  

SciTech Connect

We discuss here theoretical studies of magnetic acceleration of Compact Torus plasma rings in a coaxial, rail-gun accelerator. The rings are formed using a magnetized coaxial plasma gun and are accelerated by injection of B/sub theta/ flux from an accelerator bank. After acceleration, the rings enter a focusing cone where the ring is decelerated and reduced in radius. As the ring radius decreases, the ring magnetic energy increases until it equals the entering kinetic energy and the ring stagnates. Scaling laws and numerical calculations of acceleration using a O-D numerical code are presented. 2-D, MHD simulations are shown which demonstrate ring formation, acceleration, and focusing. Finally, 3-D calculations are discussed which determine the ideal MHD stability of the accelerated ring.

Hartman, C.W.; Hammer, J.H.; Eddleman, J.

1985-05-16

89

Spherical Torus Plasma Interactions with Large-area Liquid Lithium Surfaces in CDX-U  

SciTech Connect

The Current Drive Experiment-Upgrade (CDX-U) device at the Princeton Plasma Physics Laboratory (PPPL) is a spherical torus (ST) dedicated to the exploration of liquid lithium as a potential solution to reactor first-wall problems such as heat load and erosion, neutron damage and activation, and tritium inventory and breeding. Initial lithium limiter experiments were conducted with a toroidally-local liquid lithium rail limiter (L3) from the University of California at San Diego. Spectroscopic measurements showed a clear reduction of impurities in plasmas with the L3, compared to discharges with a boron carbide limiter. The evidence for a reduction in recycling was less apparent, however. This may be attributable to the relatively small area in contact with the plasma, and the presence of high-recycling surfaces elsewhere in the vacuum chamber. This conclusion was tested in subsequent experiments with a fully toroidal lithium limiter that was installed above the floor of the vacuum vessel. The new limiter covered over ten times the area of the L3 facing the plasma. Experiments with the toroidal lithium limiter have recently begun. This paper describes the conditioning required to prepare the lithium surface for plasma operations, and effect of the toroidal liquid lithium limiter on discharge performance.

R. Kaita; R. Majeski; M. Boaz; P. Efthimion; B. Jones; D. Hoffman; H. Kugel; J. Menard; T. Munsat; A. Post-Zwicker; V. Soukhanovskii; J. Spaleta; G. Taylor; J. Timberlake; R. Woolley; L. Zakharov; M. Finkenthal; D. Stutman; G. Antar; R. Doerner; S. Luckhardt; R. Maingi; M. Maiorano; S. Smith

2002-01-18

90

Final Technical Report on DOE Grant for Modeling of Plasma Rotation in the National Spherical Torus Experiment  

SciTech Connect

This is the final technical report on the Modeling of Plasma Rotation in National Spherical Torus Experiment (NSTX) DOE Grant No. DE-FG02-02ER54679. The research subjects, technical abstracts, and publications where details of the research results can be found are reported here.

Shaing, K. C.

2009-07-09

91

Effect of plasma shaping on performance in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving ?t~40%. Precise plasma shape control has been achieved on NSTX using real-time equilibrium reconstruction. NSTX has simultaneously achieved elongation ?~2.8 and triangularity ?~0.8. Ideal MHD theory predicts increased stability at high values of shaping factor S?q95Ip/(aBt), which has been observed at large values of the S~37[MA/(m.T)] on NSTX. The behavior of ELMs is observed to depend on plasma shape. A description of the ELM regimes attained as shape is varied will be presented. Increased shaping is predicted to increase the bootstrap fraction at fixed Ip. The achievement of strong shaping has enabled operation with 1 s pulses with Ip=1 MA, and for 1.6 s for Ip=700 kA. Analysis of the noninductive current fraction as well as empirical analysis of the achievable plasma pulse length as elongation is varied will be presented. Data are presented showing a reduction in peak divertor heat load due to increasing in flux expansion.

Gates, D. A.; Maingi, R.; Menard, J.; Kaye, S.; Sabbagh, S. A.; Taylor, G.; Wilson, J. R.; Bell, M. G.; Bell, R. E.; Bernabei, S.; Bialek, J.; Biewer, T.; Blanchard, W.; Boedo, J.; Bush, C.; Carter, M. D.; Choe, W.; Crocker, N.; Darrow, D. S.; Davis, W.; Delgado-Aparicio, L.; Diem, S.; Ferron, J.; Field, A.; Foley, J.; Fredrickson, E. D.; Harvey, R.; Hatcher, R. E.; Heidbrink, W.; Hill, K.; Hosea, J. C.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kessel, C.; Kubota, S.; Kugel, H. W.; Lawson, J.; Leblanc, B. P.; Lee, K. C.; Levinton, F.; Manickam, J.; Maqueda, R.; Marsala, R.; Mastrovito, D.; Mau, T. K.; Medley, S. S.; Meyer, H.; Mikkelsen, D. R.; Mueller, D.; Munsat, T.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ono, M.; Park, H.; Park, W.; Paul, S.; Peebles, W.; Peng, M.; Phillips, C.; Pigarov, A.; Pinsker, R.; Ram, A.; Ramakrishnan, S.; Raman, R.; Rasmussen, D.; Redi, M.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Roquemore, L.; Ruskov, E.; Ryan, P.; Schneider, H.; Skinner, C. H.; Smith, D. R.; Sontag, A.; Soukhanovskii, V.; Stevenson, T.; Stotler, D.; Stratton, B.; Stutman, D.; Swain, D.; Synakowski, E.; Takase, Y.; Tritz, K.; Halle, A. Von; Wade, M.; White, R.; Wilgen, J.; Williams, M.; Zhu, W.; Zweben, S. J.; Akers, R.; Beiersdorfer, P.; Betti, R.; Bigelow, T.

2006-05-01

92

Surface Treatment of a Lithium Limiter for Spherical Torus Plasma Experiments  

SciTech Connect

The concept of a flowing lithium first wall for a fusion reactor may lead to a significant advance in reactor design, since it could virtually eliminate the concerns with power density and erosion, tritium retention, and cooling associated with solid walls. As part of investigations to determine the feasibility of this approach, plasma interaction questions in a toroidal plasma geometry are being addressed in the Current Drive eXperiment-Upgrade (CDX-U) spherical torus (ST). The first experiments involved a toroidally local lithium limiter (L3). Measurements of pumpout rates indicated that deuterium pumping was greater for the L3 compared to conventional boron carbide limiters. The difference in the pumpout rates between the two limiter types decreased with plasma exposure, but argon glow discharge cleaning was able to restore the pumping effectiveness of the L3. At no point, however, was the extremely low recycling regime reported in previous lithium experiments achieved. This may be due to the much larger lithium surfaces that were exposed to the plasma in the earlier work. The possibility will be studied in the next set of CDX-U experiments, which are to be conducted with a large area, fully toroidal lithium limiter.

Kaita, R.; Majeski, R.; Doerner, R.; Antar, G.; Timberlake, J.; Spaleta, J.; Hoffman, D.; Jones, B.; Munsat, T.; Kugel, H.; Taylor, G.; Stutman, D.; Soukhanovskii, V.; Maingi, R.; Molesa, S.; Efthimion, P.; Menard, J.; Finkenthal, M.; Luckhardt, S.

2001-03-20

93

Comparative Study of Low-aspect Torus Plasmas and Extension to the New Device TS-4  

NASA Astrophysics Data System (ADS)

Comparative study of low-aspect ratio (? 1.5) torus plasmas (CT) has been made experimentally using the TS-3 (Tokyo university Spherical torus) device. It enables us to produce all of low-aspect ratio tokamaks (STs), spheromaks and reversed-field pinches (RFPs) using combination of Z-discharge and poloidal field coil induction. It was found that decay time ?_Psi of single CT increased with increasing its q-value. The ?_Psi value of high-q ST (q? 3) is about 2 times longer than that of RFP, because of higher electron temperature T_e, small magnetic fluctuation ? B and low anomalous resistivity. We also studied the high-beta properties of those CTs by use of high-power heating effect of their merging. When two CTs with equal flux are merged together, magnetic reconnection heats mainly the plasma ion up to 100eV within 10? sec. Maximum heating power of the merging and attained beta value of CT were as large as 10MW and 40%, respectively. Decay time of each heated CT was generally longer than that of the same single CT. Even in the case of heated CTs, the flux decay rate (1/?_Psi) and ? B decrease generally with increasing q-value. An interesting finding is that ?_Psi fell abruptly and ? B increased significantly when q value exceeds a critical value (? 3). Causes and mechanisms for life-time limiting factor will be made clear by measuring mode number of the magnetic fluctuation. High-n ballooning instability is the most probable cause for this large magnetic fluctuation in this high-beta and high-q regime.

Ohshima, Yoichi; Toyota, Hiroyuki; Ono, Yasushi; Katsurai, Makoto

1999-11-01

94

Compact torus  

SciTech Connect

The objective of the compact torus approach is to provide toroidal magnetic-field configurations that are based primarily on plasma currents and can be freed from closely surrounding mechanical structures. Some familiar examples are the current-carrying plasma rings of reversed-field theta pinches and relativistic-electron smoke ring experiments. The spheromak concept adds an internal toroidal magnetic field component, in order to enhance MHD stability. In recent experiments, three different approaches have been used to generate spheromak plasmas: (1) the reversed-field theta pinch; (2) the coaxial plasma gun; (3) a new quasi-static method, based on the initial formation of a toroidal plasma sleeve around a mechanical ring that generates poloidal and toroidal fluxes, followed by field-line reconnection to form a detached spheromak plasma. The theoretical and experimental MHD stability results for the spheromak configuration are found to have common features.

Furth, H.P.

1980-10-01

95

Density dependence of trace tritium transport in H-mode Joint European Torus plasma  

NASA Astrophysics Data System (ADS)

Tritium transport in edge localized mode (ELM) high confinement (H-mode) plasmas is analyzed here as a function of density for discharges from the recent trace tritium experimental campaign performed on Joint European Torus. In this campaign small amounts of tritium have been puffed or injected (with neutral beam injectors) into deuterium plasmas [K.-D. Zastrow, J. M. Adams, Yu. Baranov et al., Plasma Phys. Controlled Fusion 46, B255 (2004)]. Information about the tritium has been obtained from the evolution of the profiles of neutron emission simulated via the TRANSP [R. J. Goldston, D. C. McCune, H. H. Towner, S. L. Davis, R. J. Hawryluk, and G. L. Schmidt, J. Comput. Phys. 43, 61 (1981)] and SANCO (L. Lauro-Taroni, B. Alper, R. Giannella, K. Lawson, F. Marcus, M. Mattioli, P. Smeulders, and M. Von Hellermann, Proceedings of the 21st European Conference on Controlled Fusion and Plasma Physics, Montpelier, France, 1994) codes. A strong inverse correlation of tritium transport with plasma density is found in this analysis. The low tritium transport at high density is close to neoclassical values while the transport becomes strongly anomalous in low density plasmas. The thermal transport does not exhibit such a strong density dependence, leading to a varying ratio of thermal to tritium transport in these discharges. An interpretation of the density effects on the trace tritium transport, partially based on the test particle simulations in plasmas with stochastic magnetic field, is proposed. A simple model for the tritium diffusion coefficient and convective velocity, which includes the modification of the neoclassical particle diffusion in presence of electromagnetic turbulence [A. I. Smolyakov and P. N. Yushmanov, Nucl. Fusion 35, 383 (1993)] completed with an empirical density dependence, is developed. This model has positive ? dependence in agreement with the results of the similarity experiments performed for trace tritium transport.

Voitsekhovitch, I.; Garbet, X.; McDonald, D. C.; Zastrow, K.-D.; Adams, M.; Baranov, Yu.; Belo, P.; Bertalot, L.; Budny, R.; Conroy, S.; Cordey, J. G.; Garzotti, L.; Mantica, P.; McCune, D.; Ongena, J.; Parail, V.; Popovichev, S.; Stork, D.; Whiteford, A. D.

2005-05-01

96

Long Pulse High Performance Plasma Scenario Development for the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment [Ono et al., Nucl. Fusion, 44, 452 (2004)] is targeting long pulse high performance, noninductive sustained operations at low aspect ratio, and the demonstration of nonsolenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulations based on neutral beam injection (NBI)-heated plasmas are made to understand the impact of various modifications and identify the requirements for (1) high elongation and triangularity, (2) density control to optimize the current drive, (3) plasma rotation and/or feedback stabilization to operate above the no-wall limit, and (4) electron Bernstein waves (EBW) for off-axis heating/current drive (H/CD). Integrated scenarios are constructed to provide the transport evolution and H/CD source modeling, supported by rf and stability analyses. Important factors include the energy confinement, Zeff, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and qmin>1.0. Simulations show that noninductive sustained plasmas can be reached at IP=800 kA, BT=0.5 T, 2.5, N5, 15%, fNI=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high plasmas can be reached at IP=1.0 MA, BT=0.35 T, 2.5, N9, 43%, fNI=100%, and q(0)>1.5 with NBI H/CD and 3.0 MW of EBW H/CD, density control, and 25% higher global energy confinement than experiments. A scenario for nonsolenoidal plasma current rampup is developed using high harmonic fast wave H/CD in the early low IP and low Te phase, followed by NBI H/CD to continue the current ramp, reaching a maximum of 480 kA after 3.4 s.

Kessel, C.E.; Bell, R.E.; Bell, M.G.; Gates, D.A.; Harvey, R.W.

2006-01-01

97

Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)  

NASA Astrophysics Data System (ADS)

The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high ?T in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it operates with plasma currents up to 1.5 MA and elongations of up to 2.6 at a toroidal field up to 0.45 T. New facility, and diagnostic and modelling capabilities developed over the past two years have enabled the NSTX research team to make significant progress towards establishing this physics basis for future ST devices. Improvements in plasma control have led to more routine operation at high elongation and high ?T (up to ~40%) lasting for many energy confinement times. ?T can be limited by either internal or external modes. The installation of an active error field (EF) correction coil pair has expanded the operating regime at low density and has allowed for initial resonant EF amplification experiments. The determination of the confinement and transport properties of NSTX plasmas has benefitted greatly from the implementation of higher spatial resolution kinetic diagnostics. The parametric variation of confinement is similar to that at conventional aspect ratio but with values enhanced relative to those determined from conventional aspect ratio scalings and with a BT dependence. The transport is highly dependent on details of both the flow and magnetic shear. Core turbulence was measured for the first time in an ST through correlation reflectometry. Non-inductive start-up has been explored using PF-only and transient co-axial helicity injection techniques, resulting in up to 140 kA of toroidal current generated by the latter technique. Calculated bootstrap and beam-driven currents have sustained up to 60% of the flat-top plasma current in NBI discharges. Studies of HHFW absorption have indicated parametric decay of the wave and associated edge thermal ion heating. Energetic particle modes, most notably toroidal Alfvén eigenmodes and fishbone-like modes result in fast particle losses, and these instabilities may affect fast ion confinement on devices such as ITER. Finally, a variety of techniques has been developed for fuelling and power and particle control.

Kaye, S. M.; Bell, M. G.; Bell, R. E.; Bernabei, S.; Bialek, J.; Biewer, T.; Blanchard, W.; Boedo, J.; Bush, C.; Carter, M. D.; Choe, W.; Crocker, N.; Darrow, D. S.; Davis, W.; Delgado-Aparicio, L.; Diem, S.; Ferron, J.; Field, A.; Foley, J.; Fredrickson, E. D.; Gates, D. A.; Gibney, T.; Harvey, R.; Hatcher, R. E.; Heidbrink, W.; Hill, K.; Hosea, J. C.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kessel, C.; Kubota, S.; Kugel, H. W.; Lawson, J.; LeBlanc, B. P.; Lee, K. C.; Levinton, F.; Maingi, R.; Manickam, J.; Maqueda, R.; Marsala, R.; Mastrovito, D.; Mau, T. K.; Medley, S. S.; Menard, J.; Meyer, H.; Mikkelsen, D. R.; Mueller, D.; Munsat, T.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ono, M.; Park, H.; Park, W.; Paul, S.; Peebles, T.; Peng, M.; Phillips, C.; Pigarov, A.; Pinsker, R.; Ram, A.; Ramakrishnan, S.; Raman, R.; Rasmussen, D.; Redi, M.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Roquemore, A. L.; Ruskov, E.; Ryan, P.; Sabbagh, S. A.; Schneider, H.; Skinner, C. H.; Smith, D. R.; Sontag, A.; Soukhanovskii, V.; Stevenson, T.; Stotler, D.; Stratton, B.; Stutman, D.; Swain, D.; Synakowski, E.; Takase, Y.; Taylor, G.; Tritz, K.; von Halle, A.; Wade, M.; White, R.; Wilgen, J.; Williams, M.; Wilson, J. R.; Zhu, W.; Zweben, S. J.; Akers, R.; Beiersdorfer, P.; Betti, R.; Bigelow, T.; Bitter, M.; Bonoli, P.; Bourdelle, C.; Chang, C. S.; Chrzanowski, J.; Domier, C.; Dudek, L.; Efthimion, P. C.; Finkenthal, M.; Fredd, E.; Fu, G. Y.; Glasser, A.; Goldston, R. J.; Greenough, N. L.; Grisham, L. R.; Gorelenkov, N.; Guazzotto, L.; Hawryluk, R. J.; Hogan, J.; Houlberg, W.; Humphreys, D.; Jaeger, F.; Kalish, M.; Krasheninnikov, S.; Lao, L. L.; Lawrence, J.; Leuer, J.; Liu, D.; Luhmann, N. C.; Mazzucato, E.; Oliaro, G.; Pacella, D.; Parsells, R.; Schaffer, M.; Semenov, I.; Shaing, K. C.; Shapiro, M. A.; Shinohara, K.; Sichta, P.; Tang, X.; Vero, R.; Walker, D.; Wampler, W.

2005-10-01

98

Sub-hour modulation of non-Io Jovian decametric emission  

NASA Astrophysics Data System (ADS)

The variability of Jovian decametric emission (DAM), which is not controlled by the Io satellite (non-Io), is studied at time scales from 1 minute to 1 hour with DAM records of 1991-2007 from the archive of Nancay Radio Observatory. We found that the internal structure of the non-Io radio storms has the dominating periodicity of 21 ą 2 min on average. This estimate practically coincides with the periodicity of Io-related emission and with fundamental eigenoscillations of transversal magnetic pulsations in the Io's plasma torus. Moreover, the average duration of an arc in non-Io DAM dynamic spectra is estimated to be 7.0 ą 0.3 min, although the most probable value is 5.3 ą0.7 min, which corresponds to Io-related arcs and the 3rd & 4th harmonics of torus proper oscillations. Our results could be interpreted in terms of electron acceleration in field-aligned electric fields of standing Alfven waves generated by Io and trapped in the Io torus. This interpretation agrees with the previous arguments for the location of some sources of Non-Io emission on the magnetic shell of the Io plasma torus. However, the aurora component of non-Io DAM is not excluded, as the suggested DAM modulation by the fundamental mode of genoscillations inherent in aurora magnetic lines is undetectable in our analysis because of the short duration of non-Io radio storms.

Arkhypov, O. V.; Rucker, H. O.

2009-04-01

99

Io's nonlinear MHD-wave field in the heterogeneous Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Io's relative motion in the plasma torus strongly perturbs the incident magnetoplasma. The waves generated by Io then propagate through the dense plasma torus, the low-density magnetospheric plasma and finally reach the Jovian ionosphere producing the well-known Io footprint. Direct spacecraft observations by the Voyager and Galileo spacecraft demonstrated that Io's interaction is nearly fully saturated, i.e. the plasma flow close to Io is nearly brought to a halt in conjunction with a strong magnetic field perturbation. Here we use a nonlinear, three-dimensional, time-dependent MHD model to examine how the Io-generated waves propagate, are partly reflected at plasma density gradients, and nonlinearly interact. In this work, we concentrate on the basic properties of the wave propagation based on a simplified magnetic field geometry. Despite the idealization, structural features such as the shape and morphology of the Io footprint and its wake can be qualitatively compared to measured data. We show that a strong and saturated interaction fundamentally modifies Io's wave field from the linear wave morphology picture traditionally studied. In particular, we find that due to the strong and thus nonlinear interaction the standard law of reflection completely breaks down. Io's Alfvén waves are reflected in Jupiter's ionosphere nearly anti-parallel to the incident wave. We also notice overlapping and blending together of the multiply reflected Alfvén wings with increasing strength of Io's interaction. This could be a possible explanation for the disappearance of multiple footprints when Io moves to the torus center.

Jacobsen, S.; Neubauer, F. M.; Saur, J.; Schilling, N.

2007-05-01

100

Ultraviolet observations of the atmosphere of Io and the plasma torus  

SciTech Connect

Observations of Jupiter's satellite Io and the plasma torus encompassing its orbit have been made with the International Ultraviolet Explorer (IUE) satellite. The near-ultraviolet sunlight reflected by Io has been observed for the first time in high-resolution, in an effort to determine the atmospheric abundance of sulfur dioxide, thought to be the main component near the surface. An upper limit of 2 {times} 10{sup 17} cm{sup {minus}2} been placed on the average column density, implying that a collisionally-thick SO{sub 2} atmosphere of intermediate density may be present on Io with sufficiently large densities near the terminator to reproduce the evening ionospheric profile measured by Pioneer 10. Neutral oxygen and sulfur emissions have been detected for the first time in the atmosphere of Io. The O I emissions are consistent with torus electrons of temperature (T{sub e}) {approximately} 5 eV interacting with the exosphere. Based on the upper limit of 5 Io-radii placed on the radius of the source region, minimum oxygen column densities in the range 4-7 {times} 10{sup 13} cm{sup {minus}2} are required to produce the observed emissions by 5 eV electrons with a density (n{sub e}) of 2000 cm{sup {minus}3}. Larger densities are required for lower T{sub e}, n{sub e}, and/or spatial extent. Lower and upper limits to the sulfur column density are 2.2 {times} 10{sup 12} and 7 {times} 10{sup 15}cm{sup {minus}2}. With estimated excitation rates for the S I multiplets, sulfur column densities in the range 1-3 {times} 10{sup 13} cm{sup {minus}2} have been obtained for T{sub e} = 5 eV and n{sub e} = 2000 cm{sup {minus}3}.

Ballester, G.E.

1989-01-01

101

Low-frequency waves and instabilities in stratified, gyrotropic, multicomponent plasmas: Theory and application to plasma transport in the Io torus  

Microsoft Academic Search

We extend our previous study of low-frequency waves and instabilities in stratified, gyrotropic (with a thermal pressure characterized by P$\\\\perp$ ? P$\\\\parallel$), two-component plasmas to multicomponent plasmas. We then apply our theoretical findings to the plasma transport driven by the interchange instability in the Io torus. Our derivation starts with the correct calculation, from the Vlasov equation, of the contributions

N. André; K. M. Ferričre

2004-01-01

102

Confinement of pure electron plasmas in the Columbia Non-neutral Torus  

SciTech Connect

The Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is a stellarator used to study non-neutral plasmas confined on magnetic surfaces. A detailed experimental study of confinement of pure electron plasmas in CNT is described here. Electrons are introduced into the magnetic surfaces by placing a biased thermionic emitter on the magnetic axis. As reported previously, the insulated rods holding this and other emitter filaments contribute to the radial transport by charging up negatively and creating ExB convective transport cells. A model for the rod-driven transport is presented and compared to the measured transport rates under a number of different conditions, finding good agreement. Neutrals also drive transport, and by varying the neutral pressure in the experiment, the effects of rod-driven and neutral-driven transport are separated. The neutral-driven electron loss rate scales linearly with neutral pressure. The neutral driven transport, presumably caused by electron-neutral collisions, is much greater than theoretical estimates for neoclassical diffusion in a classical stellarator with strong radial electric fields. In fact the confinement time is on the order of the electron-neutral collision time. Ion accumulation, electron attachment, and other effects are considered, but do not explain the observed transport rates.

Berkery, John W.; Pedersen, Thomas Sunn; Kremer, Jason P.; Marksteiner, Quinn R.; Lefrancois, Remi G.; Hahn, Michael S.; Brenner, Paul W. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2007-06-15

103

Progress towards high performance plasmas in the National Spherical Torus Experiment (NSTX)  

Microsoft Academic Search

The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high betaT in order to advance the spherical torus (ST) concept. In order to do this, NSTX utilizes up to 7.5 MW of neutral beam injection, up to 6 MW of high harmonic fast waves (HHFWs), and it

S. M. Kaye; M. G. Bell; R. E. Bell; S. Bernabei; J. Bialek; T. Biewer; W. Blanchard; J. Boedo; C. Bush; M. D. Carter; W. Choe; N. Crocker; D. S. Darrow; W. Davis; L. Delgado-Aparicio; S. Diem; J. Ferron; A. Field; J. Foley; E. D. Fredrickson; D. A. Gates; T. Gibney; R. Harvey; R. E. Hatcher; W. Heidbrink; K. Hill; J. C. Hosea; T. R. Jarboe; D. W. Johnson; R. Kaita; C. Kessel; S. Kubota; H. W. Kugel; J. Lawson; B. P. LeBlanc; K. C. Lee; F. Levinton; R. Maingi; J. Manickam; R. Maqueda; R. Marsala; D. Mastrovito; T. K. Mau; S. S. Medley; J. Menard; H. Meyer; D. R. Mikkelsen; D. Mueller; T. Munsat; B. A. Nelson; C. Neumeyer; N. Nishino; M. Ono; S. Paul; T. Peebles; M. Peng; C. Phillips; A. Pigarov; R. Pinsker; A. Ram; S. Ramakrishnan; R. Raman; D. Rasmussen; M. Redi; M. Rensink; G. Rewoldt; J. Robinson; P. Roney; A. L. Roquemore; E. Ruskov; P. Ryan; S. A. Sabbagh; H. Schneider; C. H. Skinner; D. R. Smith; A. Sontag; V. Soukhanovskii; T. Stevenson; D. Stotler; B. Stratton; D. Stutman; D. Swain; E. Synakowski; Y. Takase; G. Taylor; K. Tritz; A. von Halle; M. Wade; R. White; J. Wilgen; M. Williams; J. R. Wilson; W. Zhu; S. J. Zweben; R. Akers; P. Beiersdorfer; R. Betti; T. Bigelow; M. Bitter; P. Bonoli; C. Bourdelle; C. S. Chang; J. Chrzanowski; C. Domier; L. Dudek; P. C. Efthimion; M. Finkenthal; E. Fredd; G. Y. Fu; A. Glasser; R. J. Goldston; N. L. Greenough; L. R. Grisham; N. Gorelenkov; L. Guazzotto; R. J. Hawryluk; J. Hogan; W. Houlberg; D. Humphreys; F. Jaeger; M. Kalish; S. Krasheninnikov; L. L. Lao; J. Lawrence; J. Leuer; D. Liu; N. C. Luhmann; E. Mazzucato; G. Oliaro; D. Pacella; R. Parsells; M. Schaffer; I. Semenov; K. C. Shaing; M. A. Shapiro; K. Shinohara; P. Sichta; X. Tang; R. Vero; D. Walker; W. Wampler

2005-01-01

104

Measurement of the magnetic field in a spherical torus plasma via electron Bernstein wave emission harmonic overlap  

NASA Astrophysics Data System (ADS)

Measurement of the magnetic field in a spherical torus by observation of harmonic overlap frequencies in the electron Bernstein wave (EBW) spectrum has been previously suggested [V. F. Shevchenko, Plasma Phys. Rep. 26, 1000 (2000)]. EBW mode conversion to X-mode radiation has been studied in the Current Drive Experiment-Upgrade spherical torus (T. Jones, Ph.D. thesis, Princeton University, 1995) with emission measured at blackbody levels [B. Jones et al., Phys. Rev. Lett. 90, 165001 (2003)]. Sharp transitions in the thermally emitted EBW spectrum have been observed for the first two harmonic overlaps. These transition frequencies are determined by the magnetic field and electron density at the mode conversion layer in accordance with hot-plasma wave theory. Prospects of extending this measurement to higher harmonics, necessary in order to determine the magnetic field profile, and high-? equilibria are discussed for this proposed magnetic field diagnostic.

Jones, B.; Taylor, G.; Efthimion, P. C.; Munsat, T.

2004-03-01

105

Edge plasma physics issues for the Fusion Advanced Studies Torus (FAST) in reactor relevant conditions  

NASA Astrophysics Data System (ADS)

To have reliable predictions of the thermal loads on the divertor plates and of the core plasma purity in the proposed Fusion Advanced Studies Torus (FAST) tokamak, numerical self-consistent simulations have been made for the H-mode and steady-state scenario by using the 2D multi-fluid code COREDIV. In the simulations full W plasma facing components, foreseen for basic operation, as well as liquid lithium divertor targets have been considered. Impurity seeding, for reducing divertor heat loads, was allowed. The overall picture shows that, marginally in the intermediate and, necessarily in the high density H-mode scenarios (average density langnerang = 2 × 1020 m-3 and 5 × 1020 m-3, respectively), impurity seeding should be foreseen with W as target material; however, only a small amount of Ar (0.03% atomic concentration), not affecting the core purity, is sufficient to maintain the divertor peak loads below 18 MW m-2, which represents the safety limit for the W monoblock technology, presently accepted for the ITER divertor tiles. Li always needs additional impurities for decreasing divertor heat loads. At low plasma densities (but >=1.3 × 1020 m-3), typical of steady-state regimes, W alone is effective in dissipating the input power by radiative losses, without excessive core contamination. Impurity seeding would lead to excessive W sputtering by Ar and too high Zeff. The impact of unmitigated giant (1.5 MJ) type I edge localized modes on the W divertor targets was also analysed: the resulting maximum energy load of 1 MJ m-2, larger than the tolerable one by a factor of 3, seems not difficult to recover by foreseen mitigation tools.

Maddaluno, G.; Zagórski, R.; Pericoli Ridolfini, V.; Apicella, M. L.; Calabrň, G.; Crisanti, F.; Cucchiaro, A.; Pizzuto, A.; Ramogida, G.

2009-09-01

106

Magnetic Equilibrium and Stability Simulations of the National Spherical Torus Experiment Plasmas  

NASA Astrophysics Data System (ADS)

The numerical code EFIT(L. Lao, et al., Nucl. Fusion 25, 1611 (1985).) has been modified to accommodate the geometry of the National Spherical Torus Experiment (NSTX). Equilibrium solutions are calculated for both fixed and free boundary conditions to determine the operational space of NSTX plasmas. The p(?) and ff'(?) equilibrium profiles are chosen either generically or from time dependent experimentally produced profiles, measured in various operational regimes (L-mode, H-mode, etc.) of the DIII-D tokamak. Results supporting the design of the external magnetic diagnostics are shown. Particular attention is given to assess sufficient coverage of the diagnostic setup, since the main future use of the code will be for equilibrium reconstruction. The stability codes GATO(L. Bernard,Comput. Phys. Commun. 21, 377 (1981).) and PEST(R. Grimm, et al., Comput. Phys. Commun. 16, 253 (1976).) will be used, in conjunction with EFIT, to study the effects of configuration and location of the passive plates on the stability of the various equilibria.

Paoletti, F.; Sabbagh, S.; Garofalo, A.; Kaita, R.; Kaye, S.; Hatcher, R.; Lao, L.; Lazarus, E.; Turnbull, A.

1997-11-01

107

Full Toroidal Imaging of Non-axisymmetric Plasma Material Interaction in the National Spherical Torus eXperiment  

SciTech Connect

A pair of two dimensional fast cameras with a wide angle view (allowing a full radial and toroidal coverage of the lower divertor) was installed in the National Spherical Torus Experiment in order to monitor non-axisymmetric effects. A custom polar remapping procedure and an absolute photometric calibration enabled the easier visualization and quantitative analysis of non-axisymmetric plasma material interaction (e.g., strike point splitting due to application of 3D fields and effects of toroidally asymmetric plasma facing components).

Filippo Scotti, A.L. Roquemore, and V. A. Soukhanovskii

2012-07-11

108

Full toroidal imaging of non-axisymmetric plasma material interaction in the National Spherical Torus Experiment divertor.  

PubMed

A pair of two dimensional fast cameras with a wide angle view (allowing a full radial and toroidal coverage of the lower divertor) was installed in the National Spherical Torus Experiment in order to monitor non-axisymmetric effects. A custom polar remapping procedure and an absolute photometric calibration enabled the easier visualization and quantitative analysis of non-axisymmetric plasma material interaction (e.g., strike point splitting due to application of 3D fields and effects of toroidally asymmetric plasma facing components). PMID:23127038

Scotti, Filippo; Roquemore, A L; Soukhanovskii, V A

2012-10-01

109

Simultaneous observations of Jovian quasi-periodic radio emissions by the Galileo and Cassini spacecraft  

Microsoft Academic Search

The gravity-assist flyby by Cassini of Jupiter on 30 December 2000 and the extended Galileo orbital mission provided a unique opportunity to obtain simultaneous measurements with two spacecraft of many Jovian plasma wave and radio emissions. One of these emissions is Jovian type III radio emissions, also known as Jovian quasi-periodic (QP) emissions. The simultaneous observations of the QP emissions

G. B. Hospodarsky; W. S. Kurth; B. Cecconi; D. A. Gurnett; M. L. Kaiser; M. D. Desch; P. Zarka

2004-01-01

110

A consistent understanding of the ribbon structure for the Io plasma torus at the Voyager 1, 1991 ground-based, and Galileo J0 epochs  

NASA Astrophysics Data System (ADS)

A new four-dimensional (three spatial and local time) empirical model for the Io plasma torus is presented that includes several System III longitude asymmetries and a dawn-dusk electric field with variable direction and magnitude. The model is used to analyze and compare observations for the peak density structure of the plasma torus acquired at the 1979 Voyager 1, the 1991 ground-based, and the 1995 Galileo J0 epochs. The mean magnitude of the dawn-dusk electric field is determined to be much smaller at the 1991 ground-based epoch than at the Voyager 1 and Galileo J0 epochs. A consistent understanding of the radial structure for the density peaks in the plasma torus may then be achieved for these epochs if the dawn-dusk electric field departs by ˜20° from the true dawn-dusk direction and if account is taken of absolute density changes. The ratio of the electron density in the inner and outer plasma torus varies significantly for the three epochs and indicates different temporal evolutions in the balance of the plasma torus production and loss processes. The undisturbed electron density at Io's position in the plasma torus is calculated and has significantly different values at the three epochs; it is shown for each epoch to undergo large variations as Io changes its location in heliocentric phase angle and System III longitude. These large variations provide a wide variety of changing upstream plasma conditions for Io's atmospheric formation, local aurora and distant footprint emissions, and electrodynamic interaction.

Smyth, William H.; Peterson, Charles A.; Marconi, Max L.

2011-07-01

111

Efficient generation of noninductive, off-axis, Ohkawa current, driven by electron Bernstein waves in high ?, spherical torus plasmas  

NASA Astrophysics Data System (ADS)

Off-axis rf-driven current can play a critical role in sustaining high ?, spherical torus (ST) plasmas without a central solenoid. Numerical modeling of electron Bernstein wave current drive (EBWCD) for a ?~40% ST plasma predicts efficient, off-axis, Ohkawa EBWCD. Current can be efficiently driven at r/a>0.5 where the large trapped electron fraction precludes conventional Fisch-Boozer current drive and provides favorable conditions for Ohkawa EBWCD. Calculated normalized current drive efficiency increases with r/a and is a factor of 2 higher at r/a=0.7 than has been obtained with electron cyclotron current drive near the axis of large aspect ratio tokamaks.

Taylor, G.; Efthimion, P. C.; Kessel, C. E.; Harvey, R. W.; Smirnov, A. P.; Ershov, N. M.; Carter, M. D.; Forest, C. B.

2004-10-01

112

Radio-frequency electromagnetic field measurements for direct detection of electron Bernstein waves in a torus plasma  

SciTech Connect

To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.

Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi [Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8568 (Japan)

2009-02-15

113

Divertor Heat Flux Mitigation in High-Performance H-mode Plasmas in the National Spherical Torus Experiment.  

SciTech Connect

Experiments conducted in high-performance 1.0-1.2 MA 6 MW NBI-heated H-mode plasmas with a high flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub p} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the lower single null configuration with higher-end elongation 2.2-2.4 and triangularity 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using high magnetic flux expansion and partial detachment of the outer strike point at several D{sub 2} injection rates, while good core confinement and pedestal characteristics were maintained. The partially detached divertor regime was characterized by a 30-60% increase in divertor plasma radiation, a peak heat flux reduction by up to 70%, measured in a 10 cm radial zone, a five-fold increase in divertor neutral pressure, and a significant volume recombination rate increase.

Soukhanovskii, V A; Maingi, R; Gates, D; Menard, J; Paul, S F; Raman, R; Roquemore, A L; Bell, R E; Bush, C; Kaita, R

2008-09-22

114

Investigation of self-organized criticality behavior of edge plasma transport in Torus experiment of technology oriented research  

SciTech Connect

The self-organized criticality (SOC) behavior of the edge plasma transport has been studied using fluctuation data measured in the plasma edge and the scrape-off layer of Torus experiment of technology oriented research tokamak [H. Soltwisch et al., Plasma Phys. Controlled Fusion 26, 23 (1984)] before and during the edge biasing experiments. In the 'nonshear' discharge phase before biasing, the fluctuation data clearly show some of the characteristics associated with SOC, including similar frequency spectra to those obtained in 'sandpile' transport and other SOC systems, slowly decaying long tails in the autocorrelation function, values of Hurst parameters larger than 0.5 at all the detected radial locations, and a radial propagation of avalanchelike events in the edge plasma area. During the edge biasing phase, with the generation of an edge radial electric field E{sub r} and thus of E{sub r}xB flow shear, contrary to theoretical expectation, the Hurst parameters are substantially enhanced in the negative flow shear region and in the scrape-off layer as well. Concomitantly, it is found that the local turbulence is well decorrelated by the E{sub r}xB velocity shear, consistent with theoretical predictions.

Xu, Y.H.; Jachmich, S.; Weynants, R.R.; Huber, A.; Unterberg, B.; Samm, U. [Laboratory for Plasma Physics, Ecole Royale Militaire/Koninklijke Militaire School, Euratom-Belgian State Association, Avenue de la Renaissance 30, B-1000 Brussels (Belgium); Institute fuer plasmaphysik, Forschungzentrum Juelich GmbH, D-52425 Juelich (Germany)

2004-12-01

115

Large density variation predicted along the magnetic axis for cold electron plasmas in the Columbia Nonneutral Torus (CNT)  

SciTech Connect

Cold pure electron plasmas confined in Penning-Malmberg traps with mirror fields are known to exhibit density variations along field lines, such that the density is roughly proportional to the magnetic field strength, n{approx}B. The Columbia Nonneutral Torus (CNT) is the first stellarator designed to study pure electron plasmas, and exhibits substantial mirroring, with B{sub max}{approx_equal}1.8B{sub min}. However, results of a three-dimensional equilibrium solver, presented in this Letter, predict a factor of 5.3 increase in density from the minimum-field cross section to the maximum-field cross section along the magnetic axis, for a 1.5 cm Debye length plasma (a{approx_equal}15 cm for CNT). In this Letter, it is shown that the density variation of electron plasmas in mirror traps can be significantly enhanced in a device that has a cross section that varies from cylinder-like to slab-like, such as the CNT. A simple analytic expression is derived that describes the axial density variation in such a device, and it is found to agree well with the computational predictions for CNT.

Lefrancois, Remi G.; Pedersen, Thomas Sunn [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2006-12-15

116

Modulation of the jovian ring current due to impulsive volcanism on Io  

NASA Astrophysics Data System (ADS)

Orbit-to-orbit changes in the ring/magnetodisc current system at Jupiter were inferred from Galileo magnetometer data by Russell et al. (2001) and indicated modulations of around 5 nT which lasted for less than one Galileo orbit. These observations showed both positive magnetic field perturbations, associated with compression of the magnetosphere by the solar wind, and negative perturbations associated with an increase in the mechanical stresses involved in force balance with the jxB force (Leisner et al., 2007). In this study we examine the role that impulsive volcanism on Io might play in driving the latter type of ring current modulations. We use recent UV observations of the Io plasma torus (Yoneda et al., 2010) to model diffusion of iogenic material throughout the jovian system. The resulting timedependent profiles of flux tube are used in an Euler potential model of the jovian magnetodisc (Achilleos et al., 2010) to quantitatively investigate changes in the ring current associated with impulsive volcanic eruptions on Io. We also comment on the possibility of impulsive events on Enceladus driving the saturnian ring current perturbations reported by Leisner et al. (2007).

Arridge, C. S.; Achilleos, N.; Guio, P.

2012-09-01

117

Characteristics of Jovian ionospheric Alfvén resonator observed by using wave modulations of L-burst emissions  

NASA Astrophysics Data System (ADS)

On 4 June 2008 UT, the position of the satellite Io with respect to Jupiter was the so-called Io-A, we observed Jovian decametric (DAM) radio emissions using a waveform receiver (WFR) and detected wave modulations (WMs) in the DAM emissions. WMs appeared four times at intervals of approximately 7 min for durations of 3-10 s each. We found that the WMs had fundamental frequencies of 2.5-5 Hz, and the 1st and 2nd harmonics of these frequencies were odd resonances at the fundamental frequencies. Simulations confirmed that strong Alfvén waves arrive at the polar regions of Jupiter at 5-7 min intervals when Io is located at the center of the Io plasma torus, and Io was located at that location when WMs were detected. The 7 min intervals of WMs are consistent with the characteristic periods of Alfvén waves, suggesting the existence of the ionospheric Alfvén resonator (IAR) expected in the system of Jupiter. Thus far, few observations have suggested the existence of IAR in Jupiter. In this research, we suggest the existence of IAR in Jupiter by using a WFR and the millisecond modulations of Jovian L-burst emissions.

Koshida, T.; Shibata, T. F.; Taguchi, S.; Misawa, H.

2010-12-01

118

Jovian dust streams: A monitor of Io's volcanic plume activity  

USGS Publications Warehouse

Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s-1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10-3 and 10 kg s-1, and is typically in the range of 0.1 to 1 kg s-1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes. Copyright 2003 by the American Geophysical Union.

Kruger, H.; Geissler, P.; Horanyi, M.; Graps, A. L.; Kempf, S.; Srama, R.; Moragas-Klostermeyer, G.; Moissl, R.; Johnson, T. V.; Grun, E.

2003-01-01

119

Effect of isotope mass on transport simulations of Joint European Torus high-mode plasmas with Edge Localized Modes  

NASA Astrophysics Data System (ADS)

The effect of isotopic mass on heat and particle transport in Joint European Torus (JET) [P.-H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasma discharges is studied using the Multi-Mode model in the BALDUR predictive transport code [Bateman et al., Phys. Plasmas 5, 1793 (1998)]. Temperature and density profiles from these simulations generally agree with the experimentally measured profiles for high-mode JET discharges with Edge Localized Modes in hydrogen, deuterium, and tritium discharges. It is surprising that a purely gyro-Bohm transport model, used in these simulations, correctly predicts the experimentally observed improvement in confinement as the isotope mass is increased-given the fact that gyro-Bohm diffusion coefficients increase with isotope mass when the shapes of all the plasma profiles are held fixed. However, in the JET experiment, it was found that the electron and ion temperature at the top of the edge pedestal increases systematically as the isotope mass in increased (J. G. Cordey et al., Report No. JET-P (98)53, 1998). The numerical simulations reported here show that this increase in the edge temperatures and subsequent broadening of the temperature profiles account for the improvement in confinement as the isotope mass is increased.

Bateman, Glenn; Kritz, Arnold H.; Parail, Vassili V.; Cordey, J. G.

1999-12-01

120

Observers requested for Jovian Extinction Events (JEE2012)  

NASA Astrophysics Data System (ADS)

Scotty Degenhardt (Santa Fe, NM), a pioneer in the use of video for timing eclipses of solar system and stellar objects and a research member of the International Occultation Timing Association (IOTA), and colleagues are working on modeling the Jovian dust field, moon atmospheres, and Io's Torus through Jovian Extinction Events (JEE). He has invited AAVSO observers to participate by observing these events and reporting their observations. He writes: "The next Jovian Mutual Event season (JME) is still almost two years away. But the interaction of the Jovian moons is upon us. In July and August there are multiple opportunities to record dimmings of Jovian moons via extinction of their light by the atmospheres of other moons and/or by the dust and gas material in the Torus of Io...Europa's atmosphere is documented to extend out to about 25 Europa radii from its surface. There will be numerous conjunctions, or close misses of Europa with Io and Ganymede over the next several months. Our previous study of JMEs and JEEs have shown that the source of dimming in these events is the moon that is behind the moon possessing a known tenuous atmosphere. The upcoming conjunction JEEs provide the best opportunity to document this extinction phenomenon and give rise to the possibility of inverting the light curve to produce a 3D model of the dust and gasses in the Jovian system...JEE2012 is a great opportunity for amateur and professional astronomers to work together to accomplish something no one thought was possible. That is to actually detect and measure the tenuous atmospheres surrounding some of the moons of Jupiter as well as this same material that is captured in a torus ring around Jupiter, called the Torus of Io. A complete current prediction kit through Aug 2102 is available here: http://scottysmightymini.com./JEE/JEE2012_Jun_Aug.zip. A summary table of upcoming events is here: http://scottysmightymini.com/JEE/JEE2012_Jun_Aug_Table.htm. A FAQ ! file describing the JEE2012 Program is here: http://scottysmightymini. com/JEE/JEE2012_FAQ.htm. It is important to note that we have developed a better prediction method which gives one a predicted light curve so one has a basis to know when and how long to observe. BVR observations are preferred, if possible; spectroscopy is also requested. Details of the observation procedure are given in the prediction kit, as are individual ephemerides for each extinction event. Once you have obtained data, please contact Scotty Degenhardt regarding data reduction.

Waagen, Elizabeth O.

2012-07-01

121

Inference of the angular velocity of plasma in the Jovian magnetosphere from the sweepback of magnetic field  

NASA Astrophysics Data System (ADS)

The averaged angular velocity of plasma from magnetic observations is evaluated using plasma outflow rate as a parameter. New techniques are developed to calculate the normal and azimuthal components of the magnetic field in and near to the plasma sheet in a plasma sheet coordinate system. The revised field components differ substantially from the quantities used in previous analyses. With the revised field values, it appears that during the Voyager 2 flyby for an outflow rate of 2.5 x 10 exp 29 amu/s, the observed magnetic torque may be sufficient to keep the plasma in corotation to radial distances of 50 Rj in the postmidnight quadrant.

Khurana, K. K.; Kivelson, M. G.

1993-01-01

122

Stellar and Jovian vortices  

SciTech Connect

The characteristics of 'Jovian' vortices (the large vortices observed in the atmospheres of Jupiter, Saturn, Neptune) are summarized, and the existence of similar structures in the atmospheres of stars is considered theoretically. The problem of vortex maintenance is addressed, including potential vorticity, numerical simulations of Jovian vortices, and cyclones and anticyclones; the Great Red Spot of Jupiter is described on the basis of Voyager data; the evidence for convective generation of vertical vorticity in the sun is examined; the possibly vortical nature of the large spots of RS CVn stars is discussed; and models of spots on rapidly rotating hot stars are surveyed. 62 refs.

Dowling, T.E.; Spiegel, E.A. (Florida Univ., Gainesville (USA))

1990-12-01

123

The JET (Joint European Torus) multipellet launcher and fueling of JET plasmas by multipellet injection  

SciTech Connect

A new multipellet long-pulse plasma fueling system is in operation on JET. In the initial experimental phase, a variety of plasma density profile shapes have been produced with peak to average values ranging up to 2.5 and peak plasma density up to 1.2 )times) 10/sup 20/m/sup )minus/3). 7 refs., 4 figs

Milora, S.L.; Schmidt, G.L.; Jernigan, T.C.; Baylor, L.R.; Combs, S.K.; Houlberg, W.A.; Schissel, D.; Colestock, P.; Hammett, G.; Zarnstorff, M.; Kupschus, P.; Cheetham, A.; Denne, B.; Gadeberg, M.; Gowers, C.; Gondhalekar, A.; Tubbing, B.

1988-01-01

124

The Jovian magnetospheric magnetic and electric fields: Effects of the interplanetary magnetic field  

Microsoft Academic Search

The purpose of this paper is to study using a constructed magnetospheric magnetic field model the electric fields and plasma motions caused by Jupiter's rotation and the solar wind MHD generator. Analysis of observations shows that a complicated differential rotation system is operating in the jovian magnetosphere. Observational data also reveal the presence of solar wind plasma in the jovian

E. S. Belenkaya

2004-01-01

125

High performance Joint European Torus (JET) plasmas for deuterium--tritium operation with the MkII divertor  

SciTech Connect

Planned experiments in the Joint European Torus [{ital Plasma Physics and Controlled Fusion Research}, Proceedings, 13th International Conference, Washington, D.C., 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 27] (JET) with deuterium--tritium (D--T) plasmas require high fusion performance for {alpha}-particle heating studies and for investigation of isotope dependence in conditions relevant to the International Thermonuclear Experimental Reactor [Plasma Phys. Controlled Fusion {bold 37}, A19 (1995)]. In deuterium plasmas, the highest neutron rates have been obtained in the hot-ion high-confinement mode (H mode) which is ultimately limited by magnetohydrodynamic (MHD) phenomena when the pressure gradient approaches ideal ballooning and kink stability limits in the vicinity of the edge transport barrier. Results are reported confirming the MkII divertor`s increased closure and pumping in this regime, progress in understanding the MHD-related termination is discussed, and the use of ion cyclotron resonance heating (ICRH) in combination with high-power neutral beams to increase the neutron yield is described. In separate experiments internal transport barriers have been established through careful programming of the current ramp and heating waveforms, and neutron emission comparable with the best hot-ion H-modes achieved. Steady-state H-mode discharges exhibiting edge localized modes (ELMs) in reactor-like configurations and conditions have been demonstrated, including cases in which relevant dimensionless parameter values are preserved, ready also for testing in D--T. {copyright} {ital 1997 American Institute of Physics.}

Jones, T.T. [JET Joint Undertaking, Abingdon, OX14 3EA (United Kingdom); Jet Team

1997-05-01

126

Beta-limiting MHD Instabilities in Improved-performance NSTX Spherical Torus Plasmas  

SciTech Connect

Global magnetohydrodynamic stability limits in the National Spherical Torus Experiment (NSTX) have increased significantly recently due to a combination of device and operational improvements. First, more routine H-mode operation with broadened pressure profiles allows access to higher normalized beta and lower internal inductance. Second, the correction of a poloidal field coil induced error-field has largely eliminated locked tearing modes during normal operation and increased the maximum achievable beta. As a result of these improvements, peak beta values have reached (not simultaneously) {beta}{sub t} = 35%, {beta}{sub N} = 6.4, <{beta}{sub N}> = 4.5, {beta}{sub N}/l{sub i} = 10, and {beta}{sub P} = 1.4. High {beta}{sub P} operation with reduced tearing activity has allowed a doubling of discharge pulse-length to just over 1 second with sustained periods of {beta}{sub N} {approx} 6 above the ideal no-wall limit and near the with-wall limit. Details of the {beta} limit scalings and {beta}-limiting instabilities in various operating regimes are described.

J.E. Menard; M.G. Bell; R.E. Bell; E.D. Fredrickson D.A. Gates: S.M. Kaye; B.P. LeBlanc; R. Maingi; D. Mueller; S.A. Sabbagh; D. Stutman; C.E. Bush; D.W. Johnson; R. Kaita; H.W. Kugel; R.J. Maqueda; F. Paoletti; S.F Paul; M. Ono; Y.-K.M. Peng; C.H. Skinner; E.J. Synakowski; the NSTX Research Team

2003-05-29

127

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas  

SciTech Connect

Use of a large-area liquid lithium surface as a first wall has significantly improved the plasma performance in the Current Drive Experiment-Upgrade (CDX-U) at the Princeton Plasma Physics Laboratory. Previous CDX-U experiments with a partially-covered toroidal lithium limiter tray have shown a decrease in impurities and the recycling of hydrogenic species. Improvements in loading techniques have permitted nearly full coverage of the tray surface with liquid lithium. Under these conditions, there was a large drop in the loop voltage needed to sustain the plasma current. The data are consistent with simulations that indicate more stable plasmas having broader current profiles, higher temperatures, and lowered impurities with liquid lithium walls. As further evidence for reduced recycling with a liquid lithium limiter, the gas puffing had to be increased by up to a factor of eight for the same plasma density achieved with an empty toroidal tray limiter.

R. Kaita; R. Majeski; M. Boaz; P. Efthimion; G. Gettelfinger; T. Gray; D. Hoffman; S. Jardin; H. Kugel; P. Marfuta; T. Munsat; C. Neumeyer; S. Raftopoulos; V. Soukhanovskii; J. Spaleta; G. Taylor; J. Timberlake; R. Woolley; L. Zakharov; M. Finkenthal; D. Stutman; L. Delgado-Aparicio; R.P. Seraydarian; G. Antar; R. Doerner; S. Luckhardt; M. Baldwin; R.W. Conn; R. Maingi; M. Menon; R. Causey; D. Buchenauer; M. Ulrickson; B. Jones; D. Rodgers

2004-06-07

128

Compact Torus plasma ring accelerator: a new type driver for inertial confinement fusion  

SciTech Connect

We discuss the acceleration of magnetically-confined plasma rings to provide a driver for ICF. The acceleration of plasma rings is predicted to be efficient and following focusing, to generate ion-bombardment power in the range 10/sup 15/ to 10/sup 16/ W/cm/sup 2/ at a total deposition energy of multimegajoules. The simplicity of plasma ring accelerator suggests that a 5 MJ (on target) driver would cost in the range 1 to 5 $/joule. First experimental tests of the accelerator are described.

Hartman, C.W.; Eddleman, J.L.; Hammer, J.H.; Meeker, D.L.

1986-08-22

129

Dual periodicity of the Jovian Magnetosphere  

SciTech Connect

Jupiter's magnetic field, like that of the Sun, and perhaps Saturn, exhibits a clear, persistent dual periodicity, the two Jovian periods differing by almost exactly 3%. The authors offer a provisional definition of a new Jovian longitude system (which is called system 4) to organize magnetospheric data that are not stationary in system 3. They show that available, independent data sets, covering a time interval of 4 years, which either drift in system 3 or show no particular organization in system 3, fit mutually consistent patterns in system 4. All of the data sets covering several rotations of the planet that are presently available to them, including Voyager observations of ultraviolet and narrow-band kilometric emissions and ground-based optical observations, are organized in either system 3, system 4, or both. Using these data, they derive provisional values for a transformation between systems 3 and 4: {lambda} {sub 4} = {lambda} {sub 3} + 338 {minus} 25.486(t {minus} 2443874.5) where t is the Julian day and fractional day of the observation. There are pronounced 14.1-day variations in a number of Jovian Magnetospheric phenomena. One possible interpretation of the system 4 modulation is that it is a sideband resulting from the 14.1-day amplitude modulation of system 3 phenomena. Alternately, the 14.1-day period could be explained if it is assumed that the existence of an active sector that is fixed in system 4 but drifts approximately 25.5/d relative to the active sector in system 3. When the system 3 and system 4 activity maxima are aligned, magnetospheric activity, such as radio emissions and torus asymmetries, is enhanced, and when the activity maxima are anti-aligned, magnetospheric activity is subdued.

Sandel, B.R. (Univ. of Arizona, Tucson (USA)); Dessler, A.J. (Rice Univ., Houston, TX (USA))

1988-06-01

130

High-harmonic Fast Wave Heating and Current Drive Results for Deuterium H-mode Plasmas in the National Spherical Torus Experiment  

SciTech Connect

A critical research goal for the spherical torus (ST) program is to initiate, ramp-up, and sustain a discharge without using the central solenoid. Simulations of non-solenoidal plasma scenarios in the National Spherical Torus Experiment (NSTX) [1] predict that high-harmonic fast wave (HHFW) heating and current drive (CD) [2] can play an important roll in enabling fully non-inductive (fNI {approx} 1) ST operation. The NSTX fNI {approx} 1 strategy requires 5-6 MW of HHFW power (PRF) to be coupled into a non-inductively generated discharge [3] with a plasma current, Ip {approx} 250-350 kA, driving the plasma into an HHFW H-mode with Ip {approx} 500 kA, a level where 90 keV deuterium neutral beam injection (NBI) can heat the plasma and provide additional CD. The initial approach on NSTX has been to heat Ip {approx} 300 kA, inductively heated, deuterium plasmas with CD phased HHFW power [2], in order to drive the plasma into an H-mode with fNI {approx} 1.

G. Taylor, P.T. Bonoli, R.W. Harvey, J.C. hosea, E.F. Jaeger, B.P. LeBlanc, C.K. Phillisp, P.M. Ryan, E.J. Valeo, J.R. Wilson, J.C. Wright, and the NSTX Team

2012-07-25

131

Energetic particles in the jovian magnetotail.  

PubMed

When the solar wind hits Jupiter's magnetic field, it creates a long magnetotail trailing behind the planet that channels material out of the Jupiter system. The New Horizons spacecraft traversed the length of the jovian magnetotail to >2500 jovian radii (RJ; 1 RJ identical with 71,400 kilometers), observing a high-temperature, multispecies population of energetic particles. Velocity dispersions, anisotropies, and compositional variation seen in the deep-tail (greater, similar 500 RJ) with a approximately 3-day periodicity are similar to variations seen closer to Jupiter in Galileo data. The signatures suggest plasma streaming away from the planet and injection sites in the near-tail region (approximately 200 to 400 RJ) that could be related to magnetic reconnection events. The tail structure remains coherent at least until it reaches the magnetosheath at 1655 RJ. PMID:17932283

McNutt, R L; Haggerty, D K; Hill, M E; Krimigis, S M; Livi, S; Ho, G C; Gurnee, R S; Mauk, B H; Mitchell, D G; Roelof, E C; McComas, D J; Bagenal, F; Elliott, H A; Brown, L E; Kusterer, M; Vandegriff, J; Stern, S A; Weaver, H A; Spencer, J R; Moore, J M

2007-10-12

132

Characteristics of Jovian ionospheric Alfvén resonator observed by using wave modulations of L-burst emissions  

NASA Astrophysics Data System (ADS)

On June 4, 2008 UT, we observed Jovian decametric radio emissions at Iitate Observatory, Tohoku University, Japan, by using a waveform receiver developed by us. The observation frequency was between 21 and 23 MHz, and the Io-CML phase was the so-called "Io-A" phase. The waveform receiver used a digital down-converter chip; therefore, it could carry out continuous observations over a 12-h period. We detected negative spectra of quenched background L-burst emissions with a negative drift rate of approximately -5 MHz/s. We called these phenomena slow-drift shadow (SDS) events. Between 1859:18 and 1859:30 UT, sudden drift rate changes occurred in the leading and trailing edges of the SDS events. Such SDS slope changes occurred once or twice at a frequency between 21.4 and 22.1 MHz [Koshida et al., JGR, 2010]. Between 1938 and 2000 UT, the background L-burst emissions exhibited wave modulations (WMs). SDS-like phenomena were intermittently observed in this observation period; however, the WMs were observed four times every 7 min at 1938, 1945, 1952, and 1959 UT. The duration of each WM ranged from 3 to 10 s. We analyzed the modulation frequencies of the WMs by using Fourier transformation and the spectra of the WMs that were partially extracted from their dynamic spectra with a bandwidth of 50 kHz and durations of 3.4 or 6.8 s. The three-dimensional least squares method was used to stabilize the base power of the Fourier transformed spectra, and the applied frequencies ranged from 2 to 40 Hz. We defined the 98% significance level of the stabilized spectra according to the statistical distribution by using a method introduced in Arkhypov and Rucker [A&A, 2006]. We could detect the fundamental frequencies of the WMs, and their 1st harmonics; we could also detect some 2nd harmonics whose frequencies were odd multiples of the fundamental frequencies. The observations of decametric radio emissions have shown that the most frequent modulation period of the emissions is 7 min; in addition, the simulations of the Alfvén waves traveling along the Io flux tube have shown that the modulation period is equivalent to the round-trip period of Alfvén waves between the Jovian north polar region and the boundary of the Io plasma torus. Su et al. [JGR, 2006] estimated the characteristic frequencies of a Jovian ionospheric Alfvén resonator for varied scale heights and plasma densities. If the scale height and plasma density of the Jovian ionosphere are higher than a certain level in our observation period, the calculated characteristic frequencies are similar to our observational results. If the scale height is less than 1000 km, unrealistic dense plasmas are required. Therefore, the cyclotron maser instability must be damped. This gives rise to the question of the generation mechanism of Jovian L-burst radio emissions.

Koshida, Tomonori; Shibata, Takashi F.; Taguchi, Satoshi; Misawa, Hiroaki

2010-05-01

133

Jovian type III radio bursts  

NASA Astrophysics Data System (ADS)

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

1989-06-01

134

The fluctuating magnetic field in the middle jovian magnetosphere: initial Galileo observations  

NASA Astrophysics Data System (ADS)

The region of the jovian magnetosphere from 10-24 planetary radii is a region of strong, nearly dipolar, magnetic field through which the plasma added to the Io torus must pass as it convects and diffuses outward to the magnetodisk region and ultimately to be lost down the tail. Magnetic fluctuations can be used to diagnose the processes present in this plasma. Herein we examine magnetic fluctuations at frequencies below 0.04 Hz observed in the middle magnetosphere on a single pass of the Galileo spacecraft. These frequencies are generally well below the ion gyro-frequencies in this portion of the magnetosphere. Near perijove, about 10.7 RJ on this orbit, the equatorial region is not more disturbed than off the equator, but it is quite disturbed at the outer edge of this dipolar region near 24 RJ where the magnetic field becomes weak. These fluctuations are quasi-periodic, strongly compressional, and incoherent resembling somewhat the mirror mode. Conversely, the region off the equator is quiet in this outer portion of the middle magnetosphere. In the quasi-dipolar region there are irregular transverse fluctuations everywhere Galileo travels. Compressional transient events are also observed that may mark flux tube interchange. An unusual structure that could be due to the outward convection of Europas wake is also seen. In toto, these fluctuations indicate that the middle magnetosphere is a very dynamic region.

Russell, C. T.; Huddleston, D. E.; Khurana, K. K.; Kivelson, M. G.

1998-12-01

135

GEOLogic: Terrestrial and Jovian Planets  

NSDL National Science Digital Library

In this two-part example, students are given clues about properties about the terrestrial and Jovian planets respectively and asked to match up the planet with the correct equatorial radius, mean orbital velocity, and period of rotation.

Guertin, Laura

136

Satellite Atmosphere and Io Torus Observations  

NASA Astrophysics Data System (ADS)

NASA's Planetary Astronomy Program has supported a vigorous three-year program of groundbased observations and detailed analysis of the Jupiter/Io system. Our work focused on Io's escaping atmosphere and the plasma torus that it creates.

Schneider, Nicholas

2004-01-01

137

Generation Of High Non-inductive Plasma Current Fraction H-mode Discharges By High-harmonic Last Wave Heating In The National Spherical Torus Experiment  

SciTech Connect

1.4 MW of 30 MHz high-harmonic fast wave (HHFW) heating, with current drive antenna phasing, has generated a Ip = 300kA, BT (0) = 0.55T deuterium H-mode plasma in the National Spherical Torus Experiment that has a non-inductive plasma current fraction, fNI = 0.7-1. Seventy-five percent of the non-inductive current was generated inside an internal transport barrier that formed at a normalized minor radius, r/a {approx} 0.4 . Three quarters of the non-inductive current was bootstrap current and the remaining non-inductive current was generated directly by HHFW power inside r/a {approx} 0.2.

Taylor, G; Kessel, C E; LeBlanc, B P; Mueller, D; Phillips, D K; Valeo, E J; Wilson, J R; Ryan, P M; Bonoli, P T; Wright, J C

2012-02-13

138

The Jovian Moons  

NSDL National Science Digital Library

This series of webpages is part of a course, called Astronomy 161: The Solar System, offered by the Department of Physics and Astronomy at the University of Tennessee. This section covers the moons of Jupiter and their features, such as: Io and its seething interior, active surfaces, volcanoes, torus and flux tube; Europa and its smoothness, cracked ice plains and history; Ganymede and its tectonic motion, young and old surfaces, history, and structure; Callisto and its geological deadness, maximal cratering density, Valhalla impact center, and history; and others.

2007-07-09

139

Ground-based imaging of the Io plasma torus and sodium neutral cloud during Galileo's I24 and I25 encounters.  

NASA Astrophysics Data System (ADS)

We report ground-based observations of [SII] 6731 /AA/ and NaI 5890,5896 /AA/ made in conjunction with Galileo's Io encounters last fall. Images were taken simultaneous with the I24 encounter in October 1999 and shortly after the I25 encounter in November 1999 using coronagraphic optics at the Catalina Observatory 61'' telescope near Tucson. These observations provide an essential global context for understanding in situ} measurements made by Galileo as it passed through the plasma torus. We find that the ribbon feature generally seen in ground-based observations of the ionized sulfur torus (Schneider and Trauger, ApJ, 450, 450, 1995) is present during both the I24 and I25 encounters. We present variations in the brightness and location of this feature as a function of magnetic longitude during the Galileo encounters as well as a discussion of the persistence of this feature from 1988 to the present. We also discuss the presence or absence of Io's sodium features, including the slowly escaping extended neutral cloud, the fast sodium directional feature, and the molecular ion stream. The implications for Io's atmospheric escape are considered in light of these data. This work is supported by the NASA Planetary Astronomy Program and the Jupiter System Data Analysis Program.

Burger, M. H.; Schneider, N. M.; Hunten, D.; Sprague, A.; Hill, R.

2000-10-01

140

Mechanism of Radial Redistribution of Energetic Trapped Ions Due to m=2/n=1 Internal Reconnection in Joint European Torus Shear Optimized Plasmas  

SciTech Connect

Internal radial redistribution of MeV energy ICRF-driven hydrogen minority ions was inferred from neutral particle analyzer measurements during large amplitude MHD activity leading to internal reconnection in Shear Optimized plasmas in the Joint European Torus (JET). A theory is developed for energetic ion redistribution during a reconnection driven by an m=2/n=1 internal kink mode. Plasma motion during reconnection generates an electric field which can change the energy and radial position of the energetic ions. The magnitude of ion energy change depends on the value of the safety factor at the plasma core from which the energetic ions are redistributed. A relation is found for corresponding change in canonical momentum. P(subscript phi), which leads to radial displacement of the ions. The model yields distinctive new features of energetic ion redistribution under such conditions. Predicted characteristics of ion redistribution are compared with the NPA measurements, and good correlation is found. Sometimes fast ions were transported to the plasma edge due to interaction with a long-lived magnetic island which developed after the reconnection and had chirping frequency in the laboratory frame. Convection of resonant ions trapped in a radially moving phase-space island is modeled to understand the physics of such events.

N.N. Gorelenkov; A. Gondhalekar; A.A. Korotkov; S.E. Sharapov; D. Testa; and Contributors to the EFDA-JET Workprogramme

2002-01-18

141

Torus instability.  

PubMed

The expansion instability of a toroidal current ring in low-beta magnetized plasma is investigated. Qualitative agreement is obtained with experiments on spheromak expansion and with essential properties of solar coronal mass ejections, unifying the two apparently disparate classes of fast and slow coronal mass ejections. PMID:16907312

Kliem, B; Török, T

2006-06-26

142

Torus Instability  

SciTech Connect

The expansion instability of a toroidal current ring in low-beta magnetized plasma is investigated. Qualitative agreement is obtained with experiments on spheromak expansion and with essential properties of solar coronal mass ejections, unifying the two apparently disparate classes of fast and slow coronal mass ejections.

Kliem, B. [Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam (Germany); Toeroek, T. [Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

2006-06-30

143

Exploration of spherical torus physics in the NSTX device  

Microsoft Academic Search

The National Spherical Torus Experiment (NSTX) is being built at Princeton Plasma Physics Laboratory to test the fusion physics principles for the spherical torus concept at the MA level. The NSTX nominal plasma parameters are R0 = 85 cm, a = 67 cm, R\\/a >= 1.26, Bt = 3 kG, Ip = 1 MA, q95 = 14, elongation kappa <=

M. Ono; S. M. Kaye; Yueng Kay Martin Peng; G. Barnes; W. Blanchard; M. D. Carter; J. Chrzanowski; L. Dudek; R. Ewig; D. Gates; R. E. Hatcher; T. Jarboe; S. C. Jardin; D. Johnson; R. Kaita; M. Kalish; C. E. Kessel; H. W. Kugel; R. Maingi; R. Majeski; J. Manickam; B. McCormack; J. Menard; D. Mueller; B. A. Nelson; B. E. Nelson; C. Neumeyer; G. Oliaro; F. Paoletti; R. Parsells; E. Perry; N. Pomphrey; S. Ramakrishnan; R. Raman; G. Rewoldt; J. Robinson; A. L. Roquemore; P. Ryan; S. Sabbagh; D. Swain; E. J. Synakowski; M. Viola; M. Williams; J. R. Wilson

2000-01-01

144

Ion anisotropies in the outer Jovian magnetosphere  

SciTech Connect

We present results from the Voyager 1 and 2 low-energy charged particle measurement of ion anisotropies in the outer Jovian magnetosphere (R> or approx. =20 R/sub J/). Theses anisotropies represent the first observed from an instrument rotating in the spin plane of Jupiter. For the several ion species ivestigated the first-order anisotropies are all strongly in the corotational sense throughout most of the Jovian magnestophere and out to the magnetopause on the dayside. There is some evidence for a small component of outward flow in the corotating region. Beyond approx.130--150 R/sub J/ along the Voyager outbound trajectories the anisotropies indicate a magnetospheric wind flowing outward from Jupiter. The change corotational to tailward flow on the nightside occurs well inside the magnetopause. The anisotropy amplitudes increase linearly with radial distance and, in the disc regions, decrease with distance from the magnetodisc mid-plane. In one case examined in detail using separtely identified H, He, and O/S ions the convection speed at 58 R/sub J/ is found to agree with the corotation speed (..cap omega..R) to within approx.3%. A linear Compton-Getting analysis reveals that the convective speeds in the dayside magnetosphere are in agreement with rigid corotation whenever the plasma flow direction is approximately in the corotation sense, while at other times the convection speeds are substantially less than corotation.

Carbary, J.F.; Krimigis, S.M.; Keath, E.P.; Gloeckler, G.; Axford, W.I.; Armstrong, T.P.

1981-09-30

145

A Simulation Study of the Response of the Jovian Magnetosphere to Changes in the Solar Wind Dynamic Pressure and Interplanetary Magnetic Field  

Microsoft Academic Search

A rapidly rotating equatorial current sheet and plasma sheet dominates the Jovian magnetosphere. We have used a global magnetohydrodynamic (MHD) simulation to investigate the effects of changes in the solar wind dynamic pressure and interplanetary magnetic field (IMF) on the Jovian magnetospheric configuration with emphasis on changes in the equatorial plasma sheet. We have carried out three numerical experiments: 1.

R. J. Walker; T. Ogino; K. Fukazawa

2003-01-01

146

Partial Torus Instability  

NASA Astrophysics Data System (ADS)

Flux ropes are now generally accepted to be the magnetic configuration of Coronal Mass Ejections (CMEs), which may be formed prior or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its instability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, the partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches one, the critical index goes to a maximum value that depends on the distribution of the external magnetic field. We demonstrate that the partial torus instability helps us to understand the confinement, growth, and eventual eruption of a flux rope CME.

Olmedo, Oscar; Zhang, J.

2010-05-01

147

Compact torus studies: Final report  

SciTech Connect

The compact torus (CT) device has been proposed for use in some applications which are of interest in Laboratory programs in the areas of pulsed power and inertial confinement fusion. These applications involve compression and acceleration of CT plasmas. The RACE (Ring Accelerator Experiment) experimental program at Livermore has been initiated to study these applications. The work reported here involves studies of plasma physics and other aspects of these compact torus applications. The studies conducted identify specific problem areas associated with the CT device and examine these areas in some detail. This report contains studies of three particular problem areas of the CT applications. These three areas are: the general nonlinear properties of the CT as a magnetohydrodynamic (MHD) equilibrium, particle simulation of the compression of the CT, with a focus on the non-MHD effects, and nonlinear RF interaction problems in the CT.

Morse, E.C.

1987-06-01

148

PARIS to Hektor, A Mission to the Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

PARIS (Planetary Access with Radioisotope Ion-drive System) spacecraft enable a new class of missions to the outer solar system. The high power-to-mass ratio of new radioisotope power systems enables New-Frontiers class missions that carry a significant a science payload to new destinations. The PARIS spacecraft take advantage of the high-efficiency of Stirling radioisotope generators (SRGs) or new thermoelectric converters to provide the power for an electric propulsion system. These low-thrust missions launched to a high C3 are especially effective for exploring objects in shallow gravity wells. The Jovian Trojan asteroids are very primitive bodies located near the Jovian L4 and L5 Lagrange points and are discussed as targets in the Solar System Decadal Survey. There are estimated to be more than 105 Jovian Trojans greater than 1 km in diameter. We consider a PARIS mission that can reach the asteroids in less than 5 years, orbit 624 Hektor, the largest of the Jovian Trojans, and go on to orbit at least one other nearby object. The candidate payload for this mission includes wide-field and narrow-field cameras, a UV-Vis-IR spectrograph, gamma-ray and neutron spectrometers, and plasma and energetic particle spectrometers. About 900 W of power are required. The launch mass would be slightly less than 1000 kg. The < 5 year trip time is dependent on having the next generation power sources with a specific power of > 8W/kg.

Gold, R. E.; Ensworth, C. B.; McNutt, R. L.; Ostdiek, P. H.; Prockter, L. M.

2005-12-01

149

ALBEDOS OF SMALL JOVIAN TROJANS  

Microsoft Academic Search

We present thermal observations of 44 Jovian Trojan asteroids with diameters D ranging from 5 to 24 km. All objects were observed at a wavelength of 24 m with the Spitzer Space Telescope. Measurements of the thermal emission and of scattered optical light, mostly from the University of Hawaii 2.2 m Telescope, together allow us to constrain the diameter and

Yanga R. Fernandez; David Jewitt; Julie E. Ziffer

2009-01-01

150

Albedos of Small Jovian Trojans  

Microsoft Academic Search

We present thermal observations of 44 Jovian Trojan asteroids with diameters D ranging from 5 to 24 km. All objects were observed at a wavelength of 24 mum with the Spitzer Space Telescope. Measurements of the thermal emission and of scattered optical light, mostly from the University of Hawaii 2.2 m Telescope, together allow us to constrain the diameter and

Yanga R. Fernández; David Jewitt; Julie E. Ziffer

2009-01-01

151

Partial Torus Instability  

NASA Astrophysics Data System (ADS)

Flux ropes are now generally accepted to be the magnetic configuration of coronal mass ejections (CMEs), which may be formed prior to or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its stability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index of the overlying constraining magnetic field. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding as the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, a partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches 1, the critical index goes to a maximum value. We demonstrate that the PTI helps us to understand the confinement, growth, and eventual eruption of a flux-rope CME.

Olmedo, Oscar; Zhang, Jie

2010-07-01

152

PARTIAL TORUS INSTABILITY  

SciTech Connect

Flux ropes are now generally accepted to be the magnetic configuration of coronal mass ejections (CMEs), which may be formed prior to or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its stability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index of the overlying constraining magnetic field. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding as the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, a partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches 1, the critical index goes to a maximum value. We demonstrate that the PTI helps us to understand the confinement, growth, and eventual eruption of a flux-rope CME.

Olmedo, Oscar; Zhang Jie, E-mail: oolmedo@gmu.ed [Department of Computational and Data Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

2010-07-20

153

Joule heating of the Jovian ionosphere by corotation enforcement currents  

NASA Astrophysics Data System (ADS)

A simple magnetodisk model is used to estimate the Joule heating rate, for several causes of departure from the corotation during whose enforcement heat is deposited on the Jovian magnetosphere. Following compression or expansion of the magnetosphere, the magnetospheric plasma sub- or super-rotates due to conservation of angular momentum and thermal energy is deposited in the ionosphere at a rate of 10 to the 12th W for 100,000 sec while rotational speed is adjusted toward the corotation with the planet. Day-night asymmetry in trajectory of rotational motion of plasma, due to magnetospheric configuration asymmetry, may also produce energy dissipation of a similar magnitude as the rotational speed is adjusted. The corotation enforcement current therefore deposits as much heat as the dynamo current from Io, and plays an important role in the energetics and dynamics of the Jovian magnetosphere.

Nishida, A.; Watanabe, Y.

1981-11-01

154

The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment  

SciTech Connect

Lithium wall coatings have been shown to reduce recycling, suppress edge-localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document the effect of gradually increasing lithium wall coatings on the discharge characteristics, with the reference ELMy discharges obtained in boronized, i.e. non-lithiated conditions. We observed a continuous but not quite monotonic reduction in recycling and improvement in energy confinement, a gradual alteration of edge plasma profiles, and slowly increasing periods of ELM quiescence. The measured edge plasma profiles during the lithium-coating scan were simulated with the SOLPS code, which quantified the reduction in divertor recycling coefficient from similar to 98% to similar to 90%. The reduction in recycling and fuelling, coupled with a drop in the edge particle transport rate, reduced the average edge density profile gradient, and shifted it radially inwards from the separatrix location. In contrast, the edge electron temperature (T-e) profile was unaffected in the H-mode pedestal steep gradient region within the last 5% of normalized poloidal flux, psi(N); however, the T-e gradient became steeper at the top of the H-mode pedestal for 0.8 < psi(N) < 0.94 with lithium coatings. The peak pressure gradients were comparable during ELMy and ELM-free phases, but were shifted away from the separatrix in the ELM-free discharges, which is stabilizing to the current-driven instabilities thought to be responsible for ELMs in NSTX.

Maingi, Rajesh [ORNL; Boyle, D. P. [Princeton University; Canik, John [ORNL; Kaye, S. [Princeton Plasma Physics Laboratory (PPPL); Skinner, C. H. [Princeton Plasma Physics Laboratory (PPPL); Allain, J. P. [Purdue University; Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Bell, M. G. [Princeton Plasma Physics Laboratory (PPPL); Gerhardt, S. P. [Princeton Plasma Physics Laboratory (PPPL); Gray, Travis K [ORNL; Jaworski, M. A. [Princeton Plasma Physics Laboratory (PPPL); Kaita, R. [Princeton Plasma Physics Laboratory (PPPL); Kugel, H. W. [Princeton Plasma Physics Laboratory (PPPL); Le Blanc, B. P. [Princeton Plasma Physics Laboratory (PPPL); Manickam, J. [Princeton Plasma Physics Laboratory (PPPL); Mansfield, D.K. [Princeton Plasma Physics Laboratory (PPPL); Menard, J. E. [Princeton Plasma Physics Laboratory (PPPL); Osborne, T. H. [General Atomics; Raman, R. [University of Washington, Seattle; Roquemore, A. L. [Princeton Plasma Physics Laboratory (PPPL); Sabbagh, S. A. [Columbia University; Snyder, P. B. [General Atomics; Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL)

2012-01-01

155

The Effect of Progressively Increasing Lithium Coatings on Plasma Discharge Characteristics, Transport, Edge Profiles, and ELM Stability in the National Spherical Torus Experiment  

SciTech Connect

Lithium wall coatings have been shown to reduce recycling, suppress edge localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document the effect of gradually increasing lithium wall coatings on the discharge characteristics, with the reference ELMy discharges obtained in boronized, i.e. non-lithiated, conditions. We observed a continuous but not quite monotonic reduction in recycling and improvement in energy confinement, a gradual alteration of edge plasma profiles, and slowly increasing periods of ELM quiescence. The measured edge plasma profiles during the lithium coating scan were simulated with the SOLPS code, which quantified the reduction in divertor recycling coefficient from ~98% to ~90%. The reduction in recycling and core fueling, coupled with a drop in the edge particle transport rate, reduced the average edge density profile gradient, and shifted it radially inward from the separatrix location. In contrast, the edge electron temperature (Te) profile was unaffected in the H-mode pedestal steep gradient region within the last 5% of normalized poloidal flux, N; however, the region of steep Te gradients extended radially inward from the top of the H-mode pedestal for 0.8< N <0.94 with lithium coatings. The peak pressure gradients were comparable during ELMy and ELM-free phases, but were shifted away from the separatrix in the ELM-free discharges, which is stabilizing to the current driven instabilities thought to be responsible for ELMs in NSTX.

Maingi, Rajesh [ORNL; Boyle, D. P. [Princeton University; Canik, John [ORNL; Kaye, S. M. [Princeton Plasma Physics Laboratory (PPPL); Skinner, C. H. [Princeton Plasma Physics Laboratory (PPPL); Allain, J. P. [Purdue University; Bell, M. G. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Gray, Travis K [ORNL; Jaworski, M. A. [Princeton Plasma Physics Laboratory (PPPL); Kaita, R. [Princeton Plasma Physics Laboratory (PPPL); Kugel, H. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B. P. [Princeton Plasma Physics Laboratory (PPPL); Mansfield, D.K. [Princeton Plasma Physics Laboratory (PPPL); Osborne, T. H. [General Atomics; Raman, R. [University of Washington, Seattle; Sabbagh, S. A. [Columbia University; Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL)

2012-01-01

156

Studies of Plasma Flow Past Jupiters Satellite Io  

NASA Astrophysics Data System (ADS)

We have investigated the interaction of Io, Jupiter's innermost Galilean satellite, with the Io plasma torus, and the interaction of Ganymede with the corotating Jovian plasma. With the successful insertion of the Galileo spacecraft into orbit around Jupiter, many new observations have been made of the Jovian magnetosphere. Some of the most exciting results thus far have been in regards to Jupiter's satellites, Io and Ganymede. In both cases the large perturbations to the background (Jovian) magnetic field have been consistent with the satellites' possession of an intrinsic magnetic field. The gravity measurements implying a differentiated core at both Io and Ganymede makes internal generation of a magnetic field by dynamo action in these satellites plausible, and, in the case of Ganymede, the identification of an intrinsic field is apparently unambiguous. For Io the situation is less clear, and further analysis is necessary to answer this important question. During the past year, we have used time-dependent three-dimensional magnetohydrodynamic (MHD) simulations to study these plasma-moon interactions. The results from these simulations have been used directly in the analysis of the Galileo magnetometer data. Our primary emphasis has been on the Io interaction, but we recently presented results on the Ganymede interaction as well. In this progress summary we describe our efforts on these problems to date.

Linker, Jon A.

1997-01-01

157

Influence of vacuum toroidal field on two-fluid flowing equilibria of helicity-driven spherical torus plasmas  

SciTech Connect

Two-fluid flowing equilibrium configurations of a helicity-driven spherical torus (HD-ST) in the realistic confinement region, including a flux conserver and a coaxial helicity source, are numerically determined by means of the combination of the finite difference and the boundary element methods. It is found from the numerical results that electron fluid near the central conductor is tied to a vacuum toroidal field and ion fluid is not. The magnetic configurations change from the high-q HD-ST (safety factor, q>1) with a paramagnetic toroidal field and low-{beta} (volume average {beta} value, <{beta}>{approx_equal}2%) through the helicity-driven spheromak and reversed-field pinch to the ultra-low-q HD-ST (0{approx_equal}18%) as the vacuum toroidal field at the inner edge regions decreases and reverses the sign. The two-fluid effects are more significant in this equilibrium transition when the ion diamagnetic drift has the same direction as the ExB one.

Kanki, T.; Nagata, M. [Department of Maritime Science and Technology, Japan Coast Guard Academy, 5-1 Wakaba, Kure, Hiroshima 737-8512 (Japan); Department of Electrical Engineering and Computer Sciences, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2201 (Japan)

2006-07-15

158

New Horizons Exploration of the Jovian Magnetotail  

NASA Astrophysics Data System (ADS)

A key issue of the jovian magnetosphere is how plasma is lost from the system down the magnetotail. Are large plasmoids ejected sporadically via explosive reconnection events (e.g. by analogy with Earth) or is there a steady "drizzle" of plasma from small scale disconnections of highly stretched out magnetic flux tubes? Furthermore, is there a significant solar-wind-driven Dungey cycle with a return, Jupiter-ward flow from a distant X-line? Again, by analogy with Earth, how much solar wind plasma enters the high latitude magnetopause mixes with magnetospheric plasma (from Io)? Voyager observations indicated burst of material flowing away from Jupiter between ~100-200 Rj on the dawn flank and showed that the magnetotail of Jupiter extends past the orbit of Saturn. Galileo measurements indicated periodic bursts of material being ejected tailward on the nightside as well as occasional supercorotational bursts on the in the morning plasma sheet. But very little is known about structure and processes on the dusk flank and at the critical distances of a few hundred Rj. Thus, the fortunate traversal down the magnetotail of the New Horizons spacecraft, on its way to Pluto, has provided a fantastic opportunity to address the above scientific questions.

Bagenal, F.; New Horizons, P.; New Horizons, S.

2007-12-01

159

Polarization of Jovian hectometric emission  

NASA Astrophysics Data System (ADS)

The polarization properties of the Jovian hectometric (HOM) emission observed in the low-frequency band 1.2-1326 kHz by the planetary radio astronomy (PRA) experiment aboard the Voyager spacecraft have been studied. It is shown that the complex morphology of HOM can be explained by simultaneous radiations from two independent 100 percent oppositely polarized sources. Analysis of data recorded under different antenna-source configurations indicates that the existence of a linear component in HOM is very unlikely. It is shown that the apparent degree of circular polarization measured by the PRA instrument, which practically ranges from -1 to +1, is the result of fluctuations in the relative intensities of the two HOM circular components. A global model for the hectometric and decametric (DAM) Jovian emissions in which the left and right HOM components are identified with the left and right non-Io DAM components, respectively, is outlined.

Ortega-Molina, Arturo; Lecacheux, Alain

1991-07-01

160

High confinement and high density with stationary plasma energy and strong edge radiation cooling in the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94)  

SciTech Connect

An overview of the results obtained so far for the radiative I-mode regime on the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94) [{ital Proceedings of the 16th IEEE Symposium on Fusion Engineering} (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1995), Vol. 1, p. 470] is given. This regime is obtained under quasistationary conditions with edge neon seeding in a pumped limiter tokamak with circular cross section. It combines high confinement and high {beta} (up to a normalized beta, {beta}{sub n}=2) with low edge q values (down to q{sub a}=2.8) and high density even above the Greenwald limit together with dominant edge radiative heat exhaust, and therefore shows promise for the future of fusion research. Bulk and edge properties of these discharges are described, and a detailed account is given of the energy and particle confinement and their scaling. Energy confinement scales linearly with density as for the nonsaturated Ohmic Neo-Alcator scaling, but the usual degradation with total power remains. No deleterious effects of the neon seeding on fusion reactivity and plasma stability have been observed. {copyright} {ital 1997 American Institute of Physics.}

Messiaen, A.M.; Ongena, J.; Unterberg, B.; Boedo, J.; Fuchs, G.; Jaspers, R.; Konen, L.; Koslowski, H.R.; Mank, G.; Rapp, J.; Samm, U.; Vandenplas, P.E.; Van Oost, G.; Van Wassenhove, G.; Waidmann, G.; Weynants, R.R.; Wolf, G.H.; Bertschinger, G.; Bonheure, G.; Brix, M.; Dumortier, P.; Durodie, F.; Finken, K.H.; Giesen, B.; Hillis, D.; Hutteman, P.; Koch, R.; Kramer-Flecken, A.; Lyssoivan, A.; Mertens, P.; Pospieszczyk, A.; Post-Zwicker, A.; Sauer, M.; Schweer, B.; Schwelberger, J.; Telesca, G.; Tokar, M.Z.; Uhlemann, R.; Vervier, M.; Winter, J. [Laboratoire de Physique des Plasmas, Laboratorium voor Plasmafysica, Association EURATOM-Belgian State, Ecole Royale Militaire-B-1000 Brussels, Koninklijke Militaire School (Belgium)]|[Institut fuer Plasmaphysik, Forschungszentrum Juelich GmbH Association Euratom-KFA, D-52425 Juelich (Germany)]|[Fusion Energy Research Program, Mechanical Engineering Division, University of California at San Diego, La Jolla, California 92093 (United States)]|[FOM Instituut voor Plasmafysica Rijnhuizen Associatie FOM-EURATOM, Nieuwegein (The Netherlands)]|[Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

1997-05-01

161

Integration of Microsoft Windows Applications with MDSplus Data Acquisition on the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory  

SciTech Connect

Data acquisition on the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory (PPPL) has increasingly involved the use of Personal Computers (PC's) and specially developed ''turn-key'' hardware and software systems to control diagnostics. Interaction with these proprietary software packages is accomplished through use of Visual Basic, or Visual C++ and COM (Component Object Model) technology. COM is a software architecture that allows the components made by different software vendors to be combined into a variety of applications. This technology is particularly well suited to these systems because of its programming language independence, standards for function calling between components, and ability to transparently reference remote processes. COM objects make possible the creation of acquisition software that can control the experimental parameters of both the hardware and software. Synchronization of these applications for diagnostics, such as CCD camer as and residual gas analyzers, with the rest of the experiment event cycle at PPPL has been made possible by utilization of the MDSplus libraries for Windows. Instead of transferring large data files to remote disk space, Windows MDSplus events and I/O functions allow us to put raw data into MDSplus directly from IDL for Windows and Visual Basic. The combination of COM technology and the MDSplus libraries for Windows provide the tools for many new possibilities in versatile acquisition applications and future diagnostics.

Dana M. Mastrovito

2002-03-14

162

Long-term study of longitudinal dependence in primary particle precipitation in the north Jovian aurora  

NASA Astrophysics Data System (ADS)

The wavelength-dependent absorption apparent in IUE spectra of the north Jovian aurora is analyzed to determine the column density of hydrocarbons above the altitude of the FUV auroral emission. Both the magnetotail and torus auroral zone models are considered in estimating zenith angles, with very similar results obtained for both models. It is found that the hydrocarbon column density above the FUV emission displays a consistent dependence on magnetic longitude, with the peak density occurring approximately coincident with the peak in the observed auroral intensity. Two distinct scenarios for the longitude dependence of the column density are discussed. In one, the Jovian upper atmosphere is longitudinally homogeneous, and the variation in optical depth is due to a variation in penetration, and thus energy, of the primary particles. In the other, the energy of the primaries is longitudinally homogeneous, and it is aeronomic properties which change, probably due to auroral heating.

Livengood, T. A.; Strobel, D. F.; Moos, H. W.

1990-07-01

163

Overview of results from the National Spherical Torus Experiment (NSTX)  

Microsoft Academic Search

The mission of the National Spherical Torus Experiment (NSTX) is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high

D. A. Gates; J. Ahn; J. Allain; R. Andre; R. Bastasz; M. Bell; R. Bell; E. Belova; J. Berkery; R. Betti; J. Bialek; T. Biewer; T. Bigelow; M. Bitter; J. Boedo; P. Bonoli; A. Boozer; D. Brennan; J. Breslau; D. Brower; C. Bush; J. Canik; G. Caravelli; M. Carter; J. Caughman; C. Chang; W. Choe; N. Crocker; D. Darrow; L. Delgado-Aparicio; S. Diem; D. D'Ippolito; C. Domier; W. Dorland; P. Efthimion; A. Ejiri; N. Ershov; T. Evans; E. Feibush; M. Fenstermacher; J. Ferron; M. Finkenthal; J. Foley; R. Frazin; E. Fredrickson; G. Fu; H. Funaba; S. Gerhardt; A. Glasser; N. Gorelenkov; L. Grisham; T. Hahm; R. Harvey; A. Hassanein; W. Heidbrink; K. Hill; J. Hillesheim; D. Hillis; Y. Hirooka; J. Hosea; B. Hu; D. Humphreys; T. Idehara; K. Indireshkumar; A. Ishida; F. Jaeger; T. Jarboe; S. Jardin; M. Jaworski; H. Ji; H. Jung; R. Kaita; J. Kallman; O. Katsuro-Hopkins; K. Kawahata; E. Kawamori; S. Kaye; C. Kessel; J. Kim; H. Kimura; E. Kolemen; S. Krasheninnikov; P. Krstic; S. Ku; S. Kubota; H. Kugel; R. La Haye; L. Lao; B. LeBlanc; W. Lee; K. Lee; J. Leuer; F. Levinton; Y. Liang; D. Liu; N. Luhmann Jr.; R. Maingi; R. Majeski; J. Manickam; D. Mansfield; R. Maqueda; E. Mazzucato; D. McCune; B. McGeehan; G. McKee; S. Medley; J. Menard; M. Menon; H. Meyer; D. Mikkelsen; G. Miloshevsky; O. Mitarai; D. Mueller; S. Mueller; T. Munsat; J. Myra; Y. Nagayama; B. Nelson; X. Nguyen; N. Nishino; M. Nishiura; R. Nygren; M. Ono; T. Osborne; D. Pacella; S. Paul; W. Peebles; B. Penaflor; M. Peng; C. Phillips; A. Pigarov; M. Podesta; J. Preinhaelter; A. Ram; R. Raman; D. Rasmussen; A. Redd; H. Reimerdes; G. Rewoldt; P. Ross; C. Rowley; E. Ruskov; D. Russell; D. Russell; P. Ryan; S. Sabbagh; M. Schaffer; E. Schuster; S. Scott; K. Shaing; P. Sharpe; V. Shevchenko; K. Shinohara; V. Sizyuk; C. Skinner; A. Smirnov; D. Smith; S. Smith; P. Snyder; W. Solomon; A. Sontag; V. Soukhanovskii; T. Stoltzfus-Dueck; D. Stotler; T. Strait; B. Stratton; D. Stutman; R. Takahashi; Y. Takase; N. Tamura; X. Tang; G. Taylor; C. Taylor; K. Tritz; D. Tsarouhas; A. Turrnbull; G. Tynan; M. Ulrickson; J. Urban; E. Utergberg; M. Walker; W. Wampler; J. Whaley; W. Wang; A. Welander; R. White; J. Wilgen; R. Wilson; K. Wong; J. Wright; Z. Xia; X. Xu; D. Youchison; G. Yu; H. Yuh; L. Zakharov; D. Zemlyanov; S. Zweben

2009-01-01

164

Modeling and investigative studies of Jovian low frequency emissions  

NASA Astrophysics Data System (ADS)

Jovian decametric (DAM) and hectometric (HOM) emissions were first observed over the entire spectrum by the Voyager 1 and 2 flybys of the planet. They display unusual arc-like structures on frequency-versus-time spectrograms. Software for the modeling of the Jovian plasma and magnetic field environment was performed. In addition, an extensive library of programs was developed for the retrieval of Voyager Planetary Radio Astronomy (PRA) data in both the high and low frequency bands from new noise-free, recalibrated data tapes. This software allows the option of retrieving data sorted with respect to particular sub-Io longitudes. This has proven to be invaluable in the analyses of the data. Graphics routines were also developed to display the data on color spectrograms.

Menietti, J. D.; Green, James L.; Six, N. Frank; Gulkis, S.

1986-08-01

165

The Jovian magnetospheric magnetic and electric fields: Effects of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to study using a constructed magnetospheric magnetic field model the electric fields and plasma motions caused by Jupiter's rotation and the solar wind MHD generator. Analysis of observations shows that a complicated differential rotation system is operating in the jovian magnetosphere. Observational data also reveal the presence of solar wind plasma in the jovian magnetosphere. However, the processes by which it crosses the magnetopause are left unexplained. Here we present an approach to the fundamental problem of the nature of the global plasma convection and corotation in the jovian magnetosphere. The constructed model allows us to map the various parts of the magnetosphere into the ionosphere and vice versa in order to correlate them with the different regions and processes.

Belenkaya, E. S.

2004-04-01

166

Observations of the Jovian UV aurora by Voyager  

NASA Astrophysics Data System (ADS)

The observations of the Jovian aurora made by the Voyager UV spectrometer (UVS) during 1979 are analyzed, with special consideration given to the model fitting process. Several different estimates of the function specifying auroral arc geometry were tried, with the Broadfoot et al. (1981) estimate, found by probing with the tip of the UVS slit, giving the best agreement; this agreement is slightly better than the agreement with the Io torus footprint computed by Roederer et al. (1977). The results suggest that the UVS observations are more sensitive to the surface field geometry than are the Voyager flyby in situ observations. The results of a study of intensity maximum positions indicate that the particles exciting the spatially variable portion of the aurora are drifting west, implying either that these particles are electrons or that they are positive ions drifting east more slowly than the corotation lag of the Io torus region carries them to the west. The latter case is most consistent with the high-energy charged particle measurements.

Herbert, F.; Sandel, B. R.; Broadfoot, A. L.

1987-04-01

167

Joint Observations of Low-Frequency Jovian Radio Emissions with the Cassini and Galileo Spacecraft  

Microsoft Academic Search

The Cassini gravity-assisted flyby of Jupiter has provided nearly continuous Radio and Plasma Wave System (RPWS) data from the early part of 2000 to the present (the distance between the Cassini spacecraft and Jupiter has ranged from 137 to over 5000 Jovian radii). During this period, the Galileo Plasma Wave System (PWS) in orbit around Jupiter has also obtained many

G. B. Hospodarsky; W. S. Kurth; D. A. Gurnett; M. L. Kaiser; P. Zarka; B. Cecconi

2002-01-01

168

Flow and shear behavior in the edge and scrape-off layer of L-mode plasmas in National Spherical Torus Experiment  

SciTech Connect

Fluctuations in the edge and scrape-off layer (SOL) of L-mode plasmas in the National Spherical Torus Experiment [Kaye et al., Phys. Plasmas 8, 1977 (2001)] as observed by the gas puff imaging (GPI) diagnostic are studied. Calculation of local, time resolved velocity maps using the hybrid optical flow and pattern matching velocimetry code enables analysis of turbulent flow and shear behavior. Periodic reversals in the direction of the poloidal flow near the separatrix are observed. Also, poloidal velocities and their radial shearing rate are found to be well correlated with the fraction of D{sub {alpha}} light contained in the SOL, which acts as a measure of turbulent bursts. The spectra of GPI intensity and poloidal velocity both have a strong feature near 3 kHz, which appears to correspond with turbulent bursts. This mode exhibits a poloidal structure with poloidal wavenumber of 7.7 m{sup -1} for GPI intensity and 3.4 m{sup -1} for poloidal velocity, and the poloidal velocity fluctuations near 3 kHz remain coherent over length scales in excess of the turbulent scales. Furthermore, recent SOL turbulence simulations find a parameter regime that exhibits periodic bursty transport and shares many qualitative similarities with the experimental data. Strong correlations between the shearing rate and the turbulent bursts are observed for time periods of {approx}2 ms, but the relationship is complicated by several factors. Finally, measurements of the radial profiles of the Reynolds shear stresses are reported. These radial profiles exhibit many similarities for several shots, and a region with positive radial gradient is seen to be coincident with local flow shear.

Sechrest, Y.; Munsat, T. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); D'Ippolito, D. A.; Myra, J. R.; Russell, D. [Lodestar Research Corporation, Boulder, Colorado 80301 (United States); Maqueda, R. J.; Zweben, S. J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)

2011-01-15

169

Stratification-driven instabilities in the Jovian, Kronian and Terrestrial magnetospheres  

NASA Astrophysics Data System (ADS)

The outward radial plasma transport is one of the dominant processes of plasma loss in the Jovian and Kronian magnetospheres. This outward plasma transport is believed to be triggered by the centrifugal interchange instability (a Rayleigh-Taylor type instability with the centrifugal force playing the role of the gravity) and to proceed through the interchange of magnetic flux tubes. The existence of a slow and permanent outward plasma transport via curvature-driven translational motions from the inner to the outer regions of the Terrestrial plasmasphere has also been postulated, even during prolonged periods of quiet geomagnetic conditions when substorms disturbances are absent. Evidence for these processes operating in the Jovian, Kronian and Terrestrial magnetospheres have recently been reported using data from the Galileo, Cassini, and Cluster spacecraft. Motivated by these observations, we will first revisit theoretically the stability criteria of low-frequency waves in plasmas representative of the Jovian, Kronian, and Terrestrial magnetospheres. We will then apply our theoretical results to realistic equatorial distributions of plasma and magnetic field in the inner regions of the Jovian, Kronian and Terrestrial magnetospheres, in order to gain new insights on plasma transport in these environments.

Andre, Nicolas; Ferriere, Katia; Lemaire, Joseph

170

Real-time Equilibrium Reconstruction and Isoflux Control of Plasma Shape and Position in the National Spherical Torus Experiment (NSTX)  

SciTech Connect

The implementation of the rtEFIT-isoflux algorithm in the digital control system for NSTX has led to improved ability to control the plasma shape. In particular, it has been essential for good gap control for radio-frequency experiments, for control of drsep in H-mode studies, and for X-point height control and {kappa} control in a variety of experiments.

D. Mueller; D.A. Gates; J.E. Menard; J.R. Ferron; S.A. Sabbagh

2004-08-11

171

Spherical Torus Pathway to Fusion Power  

Microsoft Academic Search

Spherical Torus (ST) as an example of confinement concept innovation to enable a potentially attractive pathway to fusion power is discussed. Given the anticipated high performance in small size, the ST plasma could be used to stimulate innovation also in engineering, technology, and material combinations to provide a smarter, cheaper, faster pathway. This pathway could complement the mainline program based

Martin Peng

1998-01-01

172

Resistive Drift Waves in a Bumpy Torus  

SciTech Connect

A computational study of resistive drift waves in the edge plasma of a bumpy torus is presented. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally efficient systematic study of the impact of the magnetic field structure on drift wave stability.

J.L.V. Lewandowski

2004-01-12

173

Design of the ITER torus prototype cryopump  

Microsoft Academic Search

Forschungszentrum Karlsruhe (FZK) is developing the ITER prototype torus exhaust pumping system, comprising eight identical cryosorption pumps to provide a high pumping speed and capacity, and fast regeneration. The prototype pump features an integral inlet valve with a nominal diameter of 800mm which can be closed during the plasma pulse operation for on-line regeneration. The pump design is incorporating the

V. Hauer; J.-C. Boissin; Chr. Day; H. Haas; A. Mack; D. Murdoch; R. Lässer; M. Wykes

2007-01-01

174

Jovian slow-drift shadow events  

NASA Astrophysics Data System (ADS)

We observed negative spectra of quenched background L burst emissions with a negative drift rate of -5 MHz s-1 by using a waveform receiver developed by Koshida [2009]. We named this phenomenon a slow-drift shadow event (SDS event). The leading and trailing edges of these SDS events showed a sudden change in their drift rates at similar frequencies. Wavy SDS-like phenomena were also observed with a frequency of 15 Hz. Both S bursts and the ionospheric Alfvén resonator have similar characteristic frequencies. The local potential jumps were discovered near the Jovian decametric (DAM) source regions by Hess et al. (2007b, 2009). SDS slope changes may be related to similar features. We have attempted to quantitatively estimate the background plasma densities by assuming that the background L burst emissions were generated by cyclotron maser instability (CMI) and that the SDS events were related to the Alfvén wave. The estimated background plasma densities were in the range of 5 × 106-2 × 107 cm-3. Since fp/fc ? 0.87-1.7, the CMI must be quenched. This give rises to the question of what induced the SDS events.

Koshida, Tomonori; Ono, Takayuki; Iizima, Masahide; Kumamoto, Atsushi

2010-01-01

175

Slow-mode shock candidate in the Jovian magnetosheath  

NASA Astrophysics Data System (ADS)

We discuss some interesting plasma observations in the Jovian magnetosheath by the onboard plasma instruments of the Cassini spacecraft during the 2000-2001 Jupiter flyby. We propose that the observations are consistent with a slow-mode shock transition. In the terrestrial magnetosheath, a number of observations have been made that are consistent with slow-mode waves or shocks. In addition, a number of observations have established that, at least occasionally, slow-mode structures form at the plasma sheet-lobe boundary in the terrestrial magnetotail, related to X lines associated with reconnection. There has been only one previously reported observation of a slow-mode shock-like transition in the Jovian plasma environment. This observation was made in the dayside magnetosheath. The observation we report here was made well downstream of the magnetosphere in Jupiter's magnetosheath, at local time ˜19:10. For our analysis we have used the data from the Cassini Plasma Spectrometer (CAPS) the Magnetospheric Imaging Instrument (MIMI) and the Magnetometer (MAG). The bow shock crossings observed by Cassini ranged downstream to -600 RJ from the planet

Bebesi, Z.; Szego, K.; Balogh, A.; Krupp, N.; Erdos, G.; Rymer, A. M.; Lewis, G. R.; Kurth, W. S.; Young, D. T.; Dougherty, M. K.

2010-04-01

176

Research support for plasma diagnostics on Elmo Bumpy Torus: investigation of diamagnetic diagnostics for the electron rings  

SciTech Connect

Diamagnetic diagnostics for the EBT electron rings are fundamental to the experiment. The diamagnetic flux pickup loops on each cavity output signals proportional to ring perpendicular energy. A data analysis technique is described, which in its simplest form is subtracting 1/4 the signal from each neighboring cavity pickup loop from the central one's, which provides a signal proportional to the energy in a single ring. The calibration factor relating absolute perpendicular energy to diamagnetic signal depends weakly on the geometrical model for the ring. Calculations with a bumpy cylinder MHD equilibrium code give calibration factors in reasonable agreement (20%) to the values obtained using a simple, concentric cylindrical current sheet model. The cylindrical current sheet model is used to show that diamagnetic field components measured external to the plasma require high precision or correlation with other diagnostics in order to fix model parameters. A computer simulation shows an assumption of constant ring thickness and energy density with increasing length (and energy) is compatible to diamagnetic field observations on NBT.

Carpenter, K.H.

1981-02-01

177

Momentum transfer between the Io plasma wake and Jupiter's ionosphere  

NASA Astrophysics Data System (ADS)

The interaction between Io and Jupiter is dramatically illustrated by recent ultraviolet and infrared imaging of Jupiter's ionosphere. Bright auroral emissions are observed at the base of Io's flux tube with emissions at the footprint of Io's wake extending large distances downstream (roughly 100° around Jupiter). We propose as a possible explanation for the persisting wake emissions a subcorotating torus flux tube downstream from Io that results in high-latitude parallel electric fields. The transfer of momentum to the subcorotating Iogenic plasma from first the corotating torus and eventually the Jovian ionosphere via the Alfvénic interaction result in intense field-aligned currents which can lead to the formation of parallel electric fields. By comparing the field-aligned current density of the initial Alfvénic disturbance generated by the stagnated flow in Io's wake to the required current density for steady state acceleration of the flux tube we infer a current limitation, or momentum decoupling, caused by a high-latitude field-aligned potential drop. As a result, the subcorotating flux tube is partially decoupled from the Jovian ionosphere and auroral emissions persist for large distances downstream of the initial Io-disturbed flux tube. Model results suggest that the extended wake emissions are initially driven by a ˜70 kV cross-wake potential, which is consistent with observed auroral emissions caused by electron precipitation with energy on the order of tens of keV.

Delamere, P. A.; Bagenal, F.; Ergun, R.; Su, Y.-J.

2003-06-01

178

ConcepTest: Jovian Planet Characteristics  

NSDL National Science Digital Library

The characteristics of four planets are listed below. Which planet is most likely to be classified as Jovian? a. Mainly rocky, volcanism, low gravity. b. Mainly rocky, no volcanism, high gravity. c. Mainly gaseous, ...

179

Jovian Chromophore Characteristics from Multispectral HST Images.  

National Technical Information Service (NTIS)

The chromophores responsible for coloring the jovian atmosphere are embedded within Jupiter's vertical aerosol structure. Sunlight propagates through this vertical distribution of aerosol particles, whose colors are defined by omega-bar (sub 0)(lambda), a...

A. A. Simon-Miller D. Banfield N. J. Chanover P. D. Strycker P. J. Gierasch

2011-01-01

180

Source location of the Jovian hectometric radiation via ray-tracing technique  

NASA Astrophysics Data System (ADS)

The source location of the Jovian hectometric radiation (HOM) was investigated by ray tracing using realistic magnetic field and plasma models. The results strongly indicate that the HOM sources lie within the tail-field aurora, whose field lines connect the polar regions to the Jovian magnetic tail, at distances from 2 to 7 Jupiter radii from Jupiter's center. Although the exact source location in magnetic latitude is related to the assumed cone half-angle theta, an HOM source at the tail-field auroral region accounts for a large variety of the phenomena observed so far.

Ladreiter, H. P.; Leblanc, Y.

1990-05-01

181

ALBEDOS OF SMALL JOVIAN TROJANS  

SciTech Connect

We present thermal observations of 44 Jovian Trojan asteroids with diameters D ranging from 5 to 24 km. All objects were observed at a wavelength of 24 {mu}m with the Spitzer Space Telescope. Measurements of the thermal emission and of scattered optical light, mostly from the University of Hawaii 2.2 m Telescope, together allow us to constrain the diameter and geometric albedo of each body. We find that the median R-band albedo of these small Jovian Trojans is about 0.12, much higher than that of 'large' Trojans with D>57 km (0.04). Also the range of albedos among the small Trojans is wider. The small Trojans' higher albedos are also glaringly different from those of cometary nuclei, which match our sample Trojans in diameter, however, they roughly match the spread of albedos among (much larger) Centaurs and trans-Neptunian objects. We attribute the Trojan albedos to an evolutionary effect: the small Trojans are more likely to be collisional fragments and so their surfaces would be younger. A younger surface means less cumulative exposure to the space environment, which suggests that their surfaces would not be as dark as those of the large, primordial Trojans. In support of this hypothesis is a statistically significant correlation of higher albedo with smaller diameter in our sample alone and in a sample that includes the larger Trojans. This correlation of albedo and radius implies that the true size distribution of small Trojans is shallower than the visible magnitude distribution alone would suggest, and that there are approximately half the Trojans with D>1 km than previously estimated.

Fernandez, Yanga R. [Department of Physics, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816-2385 (United States); Jewitt, David [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Ziffer, Julie E. [Department of Physics, University of Southern Maine, 96 Falmouth Street, Portland, ME 04104-9300 (United States)

2009-07-15

182

Albedos of Small Jovian Trojans  

NASA Astrophysics Data System (ADS)

We present thermal observations of 44 Jovian Trojan asteroids with diameters D ranging from 5 to 24 km. All objects were observed at a wavelength of 24 ?m with the Spitzer Space Telescope. Measurements of the thermal emission and of scattered optical light, mostly from the University of Hawaii 2.2 m Telescope, together allow us to constrain the diameter and geometric albedo of each body. We find that the median R-band albedo of these small Jovian Trojans is about 0.12, much higher than that of "large" Trojans with D>57 km (0.04). Also the range of albedos among the small Trojans is wider. The small Trojans' higher albedos are also glaringly different from those of cometary nuclei, which match our sample Trojans in diameter, however, they roughly match the spread of albedos among (much larger) Centaurs and trans-Neptunian objects. We attribute the Trojan albedos to an evolutionary effect: the small Trojans are more likely to be collisional fragments and so their surfaces would be younger. A younger surface means less cumulative exposure to the space environment, which suggests that their surfaces would not be as dark as those of the large, primordial Trojans. In support of this hypothesis is a statistically significant correlation of higher albedo with smaller diameter in our sample alone and in a sample that includes the larger Trojans. This correlation of albedo and radius implies that the true size distribution of small Trojans is shallower than the visible magnitude distribution alone would suggest, and that there are approximately half the Trojans with D>1 km than previously estimated.

Fernández, Yanga R.; Jewitt, David; Ziffer, Julie E.

2009-07-01

183

Structure within Jovian hectometric radiation  

NASA Astrophysics Data System (ADS)

Observations of Jovian hectometric radio emission (HOM) by the Voyager planetary radio astronomy (PRA) experiment at frequencies from 300 kHz to 1.3 MHz indicate persistent dynamic spectral features that had not been previously studied. The features of interest appear as ``lanes'' of decreased emission intensity within the otherwise persistent HOM. The lanes are apparent in intensity and occurrence probability spectrograms of frequency versus Jovian System III (1965) longitude. In the investigation of the morphology of these features, we use inbound and outbound Voyager 2 data at Jupiter to show that the lane occurrence and characteristics do not depend on local time over the range sampled. Occurrence probability spectrograms of frequency versus magnetic latitude are created from the portion of the data when the spacecraft was between 0° and +10° magnetic latitude. These spectrograms represent both the inbound and outbound passes and are quite similar despite the different longitude ranges. A simple extension of decametric (DAM) arc features into the HOM wavelength does not account for all the lane features, giving further evidence that HOM is an independent emission component. Polarization signatures for the data show that the polarization is predominantly right-hand circular and that it does not reverse across the lanes, suggesting the emission is from the same hemisphere. In addition, we investigate possible effects due to solar wind variations and find that the occurrence of the lanes appears to be independent of times of low and high solar wind densities. The intensity of the HOM emission on either side of the lanes is comparable, implying that the lane is probably not a result of a gap between fundamental and second harmonic emission regions. We present these data and analyses as a morphological study to establish that the lane features are an important part of the HOM emission and should be considered in HOM emission models. At this time, no theory of the source of the lanes explains all the observed features. .

Higgins, Charles A.; Green, James L.; Thieman, James R.; Fung, Shing F.; Candey, Robert M.

1995-10-01

184

Investigation of Jovian satellites and the origin of Jovian system by LAPLACE  

Microsoft Academic Search

LAPLACE (ESA-JAXA joint mission for the Jovian system) was selected as one of future ESA scientific missions Cosmic Vision in October 2007. LAPLACE is a mission with three spacecrafts aiming at coordinated observations of Jovian satellites and the magnetosphere, atmosphere and interior of Jupiter. An orbiter around Europa or Ganymede is involved. There is a possibility that JAXA (Japan Aerospace

Sho Sasaki; Tatsuaki Okada; Atsushi Yamaji; Masaki Fujimoto; Yasumasa Kasaba; Jun Kimura; Masahiro Ikoma; Hauke Hussmann; Kiyoshi Kuramoto

2008-01-01

185

Computation of Three Dimensional Tokamak and Spherical Torus Equilibria  

SciTech Connect

A nominally axisymmetric plasma con?guration, such as a tokamak or a spherical torus, is highly sensitive to non-axisymmetric magnetic perturbations due to currents outside of the plasma. The high sensitivity means that the primary interest is in the response of the plasma to very small perturbations, | ?(over) ?/?(over)? | ? 10–2 to 10–4, which can be calculated using the theory of perturbed equilibria. The Ideal Perturbed Equilibrium Code (IPEC) is described and applied to the study of the plasma response in a spherical torus to such external perturbations.

Jong-kyu Park, Allen H. Boozer, and Alan H. Glasser

2007-05-07

186

Io Atmosphere and Torus  

Microsoft Academic Search

Three 16 hour periods (a Vilspa shift and a contiguous US1 shift) are requested in order to study the recently discovered emissions of the atmosphere of Io and to compare the ionization balance in the outer part of the Io torus with that near the core (~6 RJ ). These spectra will also be used to study the long-term stability

H. Warren Moos

1988-01-01

187

Jovian Planet Finder optical system  

NASA Astrophysics Data System (ADS)

The Jovian Planet Finder (JPF) is a proposed NASA MIDEX mission to place a highly optimized coronagraphic telescope on the International Space Station (ISS) to image Jupiter-like planets around nearby stars. The optical system is an off-axis, unobscured telescope with a 1.5 m primary mirror. A classical Lyot coronagraph with apodized occulting spots is used to reduce diffracted light from the central star. In order to provide the necessary contrast for detection of a planet, scattered light from mid-spatial-frequency errors is reduced by using super-smooth optics. Recent advances in polishing optics for extreme-ultraviolet lithography have shown that a factor of >30 reduction in midfrequency errors relative to those in the Hubble Space Telescope is possible (corresponding to a reduction in scattered light of nearly 1000x). The low level of scattered and diffracted light, together with a novel utilization of field rotation introduced by the alt-azimuth ISS telescope mounting, will provide a relatively low-cost facility for not only imaging extrasolar planets, but also circumstellar disks, host galaxies of quasars, and low-mass substellar companions such as brown dwarfs.

Krist, John E.; Clampin, Mark; Petro, Larry; Woodruff, Robert A.; Ford, Holland C.; Illingworth, Garth D.; Ftaclas, Christ

2003-02-01

188

Multicolor photometry of outer Jovian satellites  

NASA Astrophysics Data System (ADS)

Multicolor photometry was obtained of satellites J6 Himalia, J7 Elara, and J10 Lysithea in the prograde cloud of outer Jovian satellites, and of J8 Pasiphae, J9 Sinope, and J11 Carme in the retrograde cloud. The data for J9 are fragmentary; otherwise, the satellites all look like C-class asteroids, except J11, which shows a remarkable brightness in the ultraviolet. The absence of D-class spectra among the outer Jovian satellites suggests that they were not derived from the same population as the outer-belt and Trojan asteroid populations.

Tholen, D. J.; Zellner, B.

1984-05-01

189

On the mechanism of particle heating and acceleration in the Jovian ionosphere  

NASA Astrophysics Data System (ADS)

The acceleration mechanism of the charged particles connected with a potential difference along the Jovian magnetic field is proposed. This model is developed on the basis of the known phenomenon of the partially ionized magnetized plasma resistance increase in the presence of a nonstationary current. The region of high resistance is formed above the ionosphere plasma density maximum when the Io current tube is going through this region. For typical Jovian ionosphere conditions the resistance is increased by about seven orders. The potential difference accelerates particles up to several MeV in this region. Here, we also take into account that the efficiency of electron acceleration is limited by the Bunneman turbulence excited due to an electron-ion relative motion. The plasma is heated due to the Joule dissipation and the Bunneman turbulence by several orders of keV.

Shaposhnikov, V. E.; Zaitsev, V. V.

1993-05-01

190

Experimental Results of OH Regime Investigation in Globus-M Spherical Torus  

Microsoft Academic Search

Plasma parameters were measured in novel spherical torus Globus-M in highly shaped plasmas with aspect ratio, A > 1.5, elongation, k < 1.9, triangularity < 0.5. Plasma column was created by direct induction method with the currents up to Ip 0.3 MA in the magnetic field, Bt - 0.08 - 0.5 T. In Globus-M spherical torus plasma column is closely

Victor Golant; Vasily Gusev; Roman Levin; Yuriy Petrov; Nikolay Sakharov

2001-01-01

191

Characteristics of Jovian ionospheric Alfven resonator observed by using wave modulations of L-burst emissions  

NASA Astrophysics Data System (ADS)

On June 4, 2008 UT, the position of the satellite Io with respect to Jupiter was the so-called Io-A, we observed Jovian decametric (DAM) radio emissions using a waveform receiver (WFR). The frequency range was 21-23 MHz and polarization was RH. We detected negative spectra at negative drift rates of approximately 5 MHz/s quenched background DAM emissions. We called this phenomenon as slow-drift shadow (SDS) events. 38 minutes after the detection of the SDS events, the background DAM emissions that exhibited wave modulations (WMs). The SDS events and WMs are considered to be the same phenomenon, because both phenomena quenched the background L-burst emissions at a negative drift rate of approximately 5 MHz/s. Sudden SDS slope changes occurred once or twice in the frequency range of 21.4 to 22.1 MHz. WMs appeared four times at intervals of approximately 7 min for durations of 3-10 s each. Furthermore, we found that the positive drift rates of WMs were several times higher than the negative drift rates. A part of the spectrum of the WMs was extracted from the dynamic spectra whose bandwidth was 50 kHz. The modulation frequency of the WMs was determined by using Fourier transformation of the spectrum. We found that the WMs had fundamental frequencies of 2.5-5 Hz, and the 1st and 2nd harmonics of these frequencies were odd resonances at the fundamental frequencies. We consider that the SDS events may be related to E|| in DAM source region. The 7-min intervals of WMs are consistent with the characteristic period of Alfven waves that are trapped along the magnetic field lines that link the northern and southern polar regions of Jupiter via the Io plasma torus, suggesting the existence of ionospheric Alfven resonator (IAR) expected in the system of Jupiter. It is known that inertial Alfven waves can accelerate electrons up to tens of kiloelectron volts above the polar regions of Jupiter, where the Alfven velocity approaches the light velocity. With the assumption that the SDS events and WMs were induced through the interaction between these accelerated electrons and the mechanism that generated the background DAM emissions, the estimated bulk energies of the electrons accelerated toward Jupiter are several kiloelectron volts and those of the electrons accelerated away from Jupiter are hundreds of electron volts. We suppose that strong Alfven waves arrived at the northern polar region of Jupiter at intervals of approximately 7 min; these resonated in the IAR within a few seconds and gave rise to the WMs in the DAM emissions. In this research, we suggest the existence of IAR in the system of Jupiter by using a WFR and the millisecond modulations of Jovian L-burst emissions.

Koshida, T.; Shibata, T.; Taguchi, S.; Misawa, H.

2010-12-01

192

Radiation characteristics of quasi-periodic radio bursts in the Jovian high-latitude region  

NASA Astrophysics Data System (ADS)

Ulysses had a "distant encounter" with Jupiter in February 2004. The spacecraft passed from north to south, and it observed Jovian radio waves from high to low latitudes (from +80° to +10°) for few months during its encounter. In this study, we present a statistical investigation of the occurrence characteristics of Jovian quasi-periodic bursts, using spectral data from the unified radio and plasma wave experiment (URAP) onboard Ulysses. The latitudinal distribution of quasi-periodic bursts is derived for the first time. The analysis suggested that the bursts can be roughly categorized into two types: one having periods shorter than 30 min and one with periods longer than 30 min, which is consistent with the results of the previous analysis of data from Ulysses' first Jovian flyby [MacDowall, R.J., Kaiser, M.L., Desch, M.D., Farrell, W.M., Hess, R.A., Stone, R.G., 1993. Quasi-periodic Jovian radio bursts: observations from the Ulysses radio and plasma wave. Experiment. Planet. Space Sci. 41, 1059-1072]. It is also suggested that the groups of quasi-periodic bursts showed a dependence on the Jovian longitude of the sub-solar point, which means that these burst groups are triggered during a particular rotational phase of the planet. Maps of the occurrence probability of these quasi-periodic bursts also showed a unique CML/MLAT dependence. We performed a 3D ray tracing analysis of the quasi-periodic burst emission to learn more about the source distribution. The results suggest that the longitudinal distribution of the occurrence probability depends on the rotational phase. The source region of quasi-periodic bursts seems to be located at an altitude between 0.4 and 1.4 Rj above the polar cap region ( L>30).

Kimura, Tomoki; Tsuchiya, Fuminori; Misawa, Hiroaki; Morioka, Akira; Nozawa, Hiromasa

2008-12-01

193

A possible intrinsic mechanism for the quasi-periodic dynamics of the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Most regions of the Jovian magnetosphere covered by the Galileo spacecraft measurements undergo quasi-periodic modulations with a time period of several Earth days. These modulations appear in various field and particle properties. Most prominent are periodically recurring ion flow bursts associated with disturbances in the meridional component of the magnetic field in the Jovian magnetotail or variations of the energy spectral shape of the particle distribution associated with the stretching and dipolarization of the magnetic field. Each individual cycle of these modulations is believed to represent a global reconfiguration of the Jovian magnetosphere. We present a simple conceptual model for these periodic processes assuming (1) ion mass loading from internal plasma sources and (2) fast planetary rotation causing magnetotail field line stretching due to centrifugal forces. This leads to a magnetotail configuration favoring magnetic reconnection. Magnetic reconnection causes plasmoid formation and release as well as dipolarization of field lines connected to the planet. Continued mass loading leads again to a stretching of the tail field lines. Our model shows that the suggested intrinsic mechanism can explain the observed periodicities of several days in Jovian substorm-like processes.

Kronberg, E. A.; Glassmeier, K.-H.; Woch, J.; Krupp, N.; Lagg, A.; Dougherty, M. K.

2007-05-01

194

Studying the Jovian System with small telescopes  

NASA Astrophysics Data System (ADS)

We describe a learning activity performed at the Aula Espazio Gela UPV/EHU in which students of the Master of Space Science and Technology study the Jovian System (Jupiter and satellites) and deduce some of its parameters using their own images obtained with telescopes ranging from 11 to 20 inch in diameter by means of the lucky-imaging technique.

Sanchez-Lavega, Agustin; del Rio Gaztelurrutia, T.; Hueso, R.

2013-10-01

195

A Global Magnetohydrodynamic Model of Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pioneer 10 and 11, Voyager I and 2 and Ulysses, have revealed that the Jovian magnetosphere is a vast, complicated system. The Jovian aurora also has been monitored for several years. Like auroral observations at Earth, these measurements provide us with a global picture of magnetospheric dynamics. Despite this wide range of observations, we have limited quantitative understanding of the Jovian magnetosphere and how it interacts with the solar wind. For the past several years we have been working toward a quantitative understanding of the Jovian magnetosphere and its interaction with the solar wind by employing global magnetohydrodynamic simulations to model the magnetosphere. Our model has been an explicit MHD code (previously used to model the Earth's magnetosphere) to study Jupiter's magnetosphere. We continue to obtain important insights with this code, but it suffers from some severe limitations. In particular with this code we are limited to considering the region outside of 15RJ, with cell sizes of about 1.5RJ. The problem arises because of the presence of widely separated time scales throughout the magnetosphere. The numerical stability criterion for explicit MHD codes is the CFL limit and is given by Cmax)(Delta)t/(Deltax less than 1 where Cmax is the maximum group velocity in a given cell, (Delta)x is the grid spacing and (Delta)t is the time step. If the maximum wave velocity is Cw and the flow speed is Cf, Cmax = Cw + Cf. Near Jupiter the Alfven wave speed becomes very large (it approaches the speed of light at one Jovian radius). Operating with this time step makes the calculation essentially intractable. Therefore under this funding we have been designing a new MHD model that will be able to compute solutions in the wide parameter regime of the Jovian magnetosphere.

Walker, Raymond J.

2001-01-01

196

Jovian electron jets in interplanetary space  

NASA Astrophysics Data System (ADS)

The COSPIN/KET experiment onboard Ulysses has been monitoring the flux of ˜ 3-20 MeV electrons in interplanetary space since the launch of Ulysses in October 1990. The origin of these electrons has been known for a long time to be the Jovian magnetosphere. Propagation models assuming interplanetary diffusion of these electrons in the ideal Parker magnetic field were successfully developed in the past. The average electron flux measured by our experiment agrees with these models for most of the times before and after the Jovian flyby of February 1992, i.e. in and out of the ecliptic down to 28° S of heliographic latitude for the last data presented here (end of March 1993). However, in addition to this average flux level well accounted for by diffusion in an ideal Parker field, we have found very short duration electron events which we call "jets", characterized by: (i) a sharp increase and decrease of flux; (ii) a spectrum identical to the electron spectrum in the Jovian magnetosphere; and (iii) a strong first-order anisotropy. These jets only occur when the magnetic field at Ulysses lies close to the direction of Jupiter, and most of the time (86% of the events) points outwards from Jupiter, i.e. has the same polarity after the flyby as the Jovian dipole (North to South). These events are interpreted as crossings by Ulysses of magnetic flux tubes or sheets directly connected to the location of the Jovian magnetosphere from which electrons escape into interplanetary space. The average thickness of these sheets is ˜ 10 11cm or ˜ 14 Jovian radii. These jets are clearly identified up to 0.4 a.u. before the Jupiter flyby in the ecliptic plane, and up to 0.9 a.u. out of the ecliptic. Moreover, the characteristic rocking of the electron spectrum in the Jovian magnetosphere with a 10 h periodicity is found to be present during the jets, and predominantly during them. In the past, this modulation has been reported to be present in interplanetary space as far as 1 a.u. upwind of Jupiter, a fact which cannot be accounted for by diffusion in the average Parker magnetic field. Our finding gives a simple explanation to this phenomenon, the 10 h modulation being carried by the "jet" electrons which travel with no appreciable diffusion along magnetic field lines with a direction far from the ideal Parker spiral.

Ferrando, P.; Ducros, R.; Rastoin, C.; Raviart, A.

1993-11-01

197

Tether radiation in Juno-type and circular-equatorial Jovian orbits  

NASA Astrophysics Data System (ADS)

Wave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determine the current in the overall tether circuit. In a cold plasma model, radiation occurs mainly in the Alfvén and fast magnetosonic modes, exhibiting a large refraction index. The radiation impedance of insulated tethers is determined for both modes and either mission. Unlike the Earth ionospheric case, the low-density, highly magnetized Jovian plasma makes the electron gyrofrequency much larger than the plasma frequency; this substantially modifies the power spectrum for either mode by increasing the Alfvén velocity. Finally, an estimation of the radiation impedance of bare tethers is considered. In LJO, a spacecraft orbiting in a slow downward spiral under the radiation belts would allow determining magnetic field structure and atmospheric composition for understanding the formation, evolution, and structure of Jupiter. Additionally, if the cathodic contactor is switched off, a tether floats electrically, allowing e-beam emission that generate auroras. On/off switching produces bias/current pulses and signal emission, which might be used for Jovian plasma diagnostics.

Sanchez-Torres, A.; Sanmartin, J. R.

2011-12-01

198

Field-aligned Currents in Io's Plasma Wake  

NASA Astrophysics Data System (ADS)

Since the discovery of Io-controlled decametric radio emissions, the interaction between Io and Jovian magnetosphere has been studied intensively. Two types of interaction have been proposed so far. One is electric circuit model, in which the induced currents flow between Io and the Jovian ionosphere along the magnetic flux tube threading Io. The other is Alfvén wing model. A wing forms in the perturbed magnetic field lines behind Io, the Alfvénic currents develop in the wing rather than along the magnetic flux tubes. More recently, auroral emission associated with Io's footprint and its trailing emission were observed. Such auroral arc may extend longitudinally westward for more than 100 degrees. This trail of aurora is brightest near Io and dims with increasing downstream distance. There is no clear theoretical understanding of the physics that generates this downstream aurora. However it is generally believed that Io's plasma wake is associated with this phenomenon and field-aligned currents lead to downstream emissions. Along with the above two types of the interaction between Io and its surrounding medium, there are also two theoretical frameworks in which these downstream emissions can be interpreted. The first one is corotational lag. When an Io-perturbed (mass loading and/or Io's conductivity) magnetic flux tube moves slowly relative to Jovian magnetosphere, an electric field would be induced at the equatorial plane of the flux tube, which in turn causes a current perpendicular to the field lines that is connected by field-aligned currents. The Lorentz force due to the perpendicular current would play the role of bring the lagged plasma up to corotation. The second is Alfvén wave, in which the Io-perturbed Alfvén wave is reflected between the Jovian ionosphere and the torus edge, driving particles into loss cone. Our present study attempts to use a MHD method to solve the above problem. MHD simulations of Io-Jupiter interaction has been carried out by several groups and yielded some suggestive results, but these studies concentrated primarily on the vicinity of Io and did not treat the Jovian ionospheric effect realistically. To investigate the mechanism for emissions in the trailing tail, a model extending longitudinally more than 100 degrees and latitudinally from the southern Jovian ionosphere to the northern ionosphere is needed. In particular, such a model should reflect both the non-uniform magnetic field and the non-uniform plasma distributions together with realistic boundary conditions. To tackle this problem with available computer resources, we provide instead an equivalent approach "theory of thin filament motion". Our model is indeed a one-dimensional MHD simulation that satisfies all the above requirements and has the advantage of using much less computer resources than the earlier MHD models, which in turn allows us to try various physical conditions within limited computing time. We assume Io's plasma wake can be regarded as a tail of thin magnetic flux tubes perturbed by Io successively. In this assumption, a flux tube is considered as thin if the pressure variations across the flux tube are negligible compared to the total external pressure (gas plus magnetic pressure) representing the effects of the enveloping magnetized plasma (Jovian magnetosphere). Furthermore we assume that in Io's reference frame the variations of the physical quantities along the downstream distance do not change with time. After converting to the corotating frame, the study of Io's plasma wake can be simplified to investigate the evolution of a magnetic flux tube in Io's wake with appropriate initial conditions. Our simulations suggest that the mechanism for producing wake aurora could not be explained by either Alfvén wave or electric circuit alone, rather, the underlying physics possesses the characteristics typical for both Alfvén wave and corotational lag models. An upstream-coming flux tube must be in contact with Io for approximately 500 seconds, until a tilt angle of about 4 degrees has been develo

Chen, Chuxin

2008-09-01

199

Minimisation of the Hydrogenic Inventory of the ITER Neutral Beamline and Torus CryoSorption Pumps  

Microsoft Academic Search

The tritium inventory of all the ITER torus cryopumps open to the vacuum vessel has an administrative limit of 120 g, including tritium bound to hydrocarbon compounds formed by combination of fuel gas with carbon plasma-facing components. The total hydrogenic inventory of each of the torus cryopumps has to be less than that resulting in a deflagration pressure of 0.2

Wykes

2005-01-01

200

Spherical Torus Center Stack Design  

SciTech Connect

The low aspect ratio spherical torus (ST) configuration requires that the center stack design be optimized within a limited available space, using materials within their established allowables. This paper presents center stack design methods developed by the National Spherical Torus Experiment (NSTX) Project Team during the initial design of NSTX, and more recently for studies of a possible next-step ST (NSST) device.

C. Neumeyer; P. Heitzenroeder; C. Kessel; M. Ono; M. Peng; J. Schmidt; R. Woolley; I. Zatz

2002-01-18

201

Spherical torus center stack design  

SciTech Connect

The low aspect ratio spherical torus (ST) configuration requires that the center stack design be optimized within a limited available space, using materials within their established allowables. This paper presents certer stack design methods developed by the National Spherical Torus Experiment (NSTX) Project Team during the initial design of NSTX, and more recently for studies of a possible next step ST (NSST) device.

Neumeyer, C. L. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL

2002-01-01

202

Overview of recent physics results from the National Spherical Torus Experiment (NSTX)  

Microsoft Academic Search

The National Spherical Torus Experiment (NSTX) has made considerable progress in advancing the scientific understanding of high performance long-pulse plasmas needed for future spherical torus (ST) devices and ITER. Plasma durations up to 1.6 s (five current redistribution times) have been achieved at plasma currents of 0.7 MA with non-inductive current fractions above 65% while simultaneously achieving betaT and betaN

J. E. Menard; M. G. Bell; R. E. Bell; S. Bernabei; J. Bialek; T. Biewer; W. Blanchard; J. Boedo; C. E. Bush; M. D. Carter; W. Choe; N. A. Crocker; D. S. Darrow; W. Davis; L. Delgado-Aparicio; S. Diem; C. W. Domier; D. A. D'Ippolito; J. Ferron; A. Field; J. Foley; E. D. Fredrickson; D. A. Gates; T. Gibney; R. E. Hatcher; W. Heidbrink; K. W. Hill; J. C. Hosea; T. R. Jarboe; D. W. Johnson; R. Kaita; S. M. Kaye; C. E. Kessel; S. Kubota; H. W. Kugel; J. Lawson; B. P. LeBlanc; K. C. Lee; F. M. Levinton; N. C. Luhmann Jr.; R. P. Majeski; J. Manickam; D. K. Mansfield; R. Maqueda; R. Marsala; D. Mastrovito; T. K. Mau; E. Mazzucato; S. S. Medley; H. Meyer; D. R. Mikkelsen; D. Mueller; T. Munsat; J. R. Myra; B. A. Nelson; C. Neumeyer; N. Nishino; M. Ono; H. K. Park; S. F. Paul; T. Peebles; M. Peng; C. Phillips; A. Pigarov; R. Pinsker; A. Ram; S. Ramakrishnan; R. Raman; D. Rasmussen; M. Rensink; G. Rewoldt; J. Robinson; P. Roney; A. L. Roquemore; E. Ruskov; P. Ryan; S. A. Sabbagh; H. Schneider; C. H. Skinner; D. R. Smith; A. Sontag; V. Soukhanovskii; T. Stevenson; D. Stotler; B. C. Stratton; D. Stutman; D. Swain; E. Synakowski; Y. Takase; G. Taylor; K. Tritz; A. von Halle; M. Wade; R. White; J. Wilgen; M. Williams; J. R. Wilson; H. Yuh; L. E. Zakharov; W. Zhu; S. J. Zweben; R. Akers; P. Beiersdorfer; R. Betti; T. Bigelow; M. Bitter; P. Bonoli; C. Bourdelle; C. S. Chang; J. Chrzanowski; L. Dudek; P. C. Efthimion; M. Finkenthal; E. Fredd; G. Y. Fu; A. Glasser; R. J. Goldston; N. L. Greenough; L. R. Grisham; N. Gorelenkov; L. Guazzotto; R. J. Hawryluk; J. Hogan; W. Houlberg; D. Humphreys; F. Jaeger; M. Kalish; S. Krasheninnikov; L. L. Lao; J. Lawrence; J. Leuer; D. Liu; G. Oliaro; D. Pacella; R. Parsells; M. Schaffer; I. Semenov; K. C. Shaing; M. A. Shapiro; K. Shinohara; P. Sichta; X. Tang; R. Vero; M. Walker; W. Wampler

2007-01-01

203

Computational compact torus experiment  

SciTech Connect

We describe a typical 2D magnetohydrodynamic (MHD) calculation of rundown of plasma in a coaxial, magnetized gun and injection of the plasma and reconnection of the embedded magnetic fields to form a compact toroidal plasma.

Eddleman, J.L.; McNamara, B.; Nash, J.K.; Shearer, J.W.; Turner, W.C.

1980-12-24

204

Exploration of Jovian Magnetosphere and Trojan Asteroids by a Solar Power Sail Mission  

NASA Astrophysics Data System (ADS)

Europa Jupiter System Mission (EJSM) is a proposed international mission to explore Jupiter, Jovian satellites and environment. EJSM consists of (1) The Jupiter Europa Orbiter (JEO) by NASA, (2) the Jupiter Ganymede Orbiter (JGO) by ESA, (3) the Jupiter Magnetospheric Orbiter (JMO) studied by JAXA. (4) The Europa lander is also studied by Roscosmos. Together with plasma instruments on board JEO and JGO, JMO will investigate the fast and huge rotating magnetosphere to clarify the energy procurement from Jovian rotation to the magnetosphere, to clarify the interaction between the solar wind the magnetosphere. JMO will clarify the characteristics of the strongest accelerator in the solar system. JMO will investigate the role of Io as a source of heavy ions in the magnetosphere. Proposed instruments on board JMO are magnetometers, low-energy plasma spectrometers, medium energy particle detectors, energetic particle detectors, electric field / plasma wave instruments, a dust detector, an ENA imager, and EUV spectrometer. JAXA is studying solar power sail for deep space explorations following the successful ion engine mission Hayabusa. This is not only solar sail (photon propulsion) but also include very efficient ion engines where electric power is produced solar panels within the sail. Currently we are studying a mission to Jupiter and one (or two) of Trojan asteroids, which are primitive bodies with information of the early solar system as well as raw solid materials of Jovian system. As the main spacecraft flies by Jupiter heading for an asteroid, it will deploy JMO spinner around Jupiter.

Sasaki, S.; Fujimoto, M.; Kasaba, Y.; Kawaguchi, J.; Kawakatsu, Y.; Mori, O.; Takashima, T.; Tsuda, Y.; Yano, H.; Jupiter Exploration Working Group

2009-04-01

205

On dust emissions from the jovian system  

NASA Astrophysics Data System (ADS)

As described by Gruen et al., the dust impact detector on the Ulysses spacecraft detected a totally unexpected series of dust streams in the outer solar system near the orbit of Jupiter. Five considerations lead us to believe that the dust streams emanate from the jovian system itself: the dust streams only occur within about 1 AU of the jovian system, with the strongest stream being the one closest to Jupiter (about 550 RJ away); the direction from which they arrive is never far from the line-of-sight direction to Jupiter; the time period between streams is about 28 (+/- 3) days; the impact velocities are very high--mostly around 40 km/s; and we can think of no cometary, asteroidal, or interstellar source that could give rise to the above four phenomena (such streams have never before been detected).

Zook, H. A.; Gruen, E.; Baguhl, M.; Balogh, A.; Bame, S. J.; Fechtig, H.; Forsyth, R.; Hanner, M. S.; Horanyi, M.; Kissel, J.

1993-03-01

206

Electron capture decay in Jovian planets  

NASA Astrophysics Data System (ADS)

Following the commonly acknowledged fact that the decay of K-40 substantially contributes to the heating of planetary interiors, an examination is made of the possibility that interior heat in the Jovian planets and stars, where interior pressures may exceed 45 Mbar, may be generated by the pressure-accelerated electron capture decay of a variety of isotopes. The isotopes considered encompass K-40, V-50, Te-123, La-138, Al-26, and Cl-36.

Zito, R. R.; Schiferl, D.

1987-12-01

207

A new perspective concerning the influence of the solar wind on the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

The solar wind exerts a strong influence on the Jovian magnetosphere in changing its volume, in energizing plasma, and in stimulating the aurora and a host of other associated effects. However, whereas at Earth the dominant solar terrestrial coupling process is magnetic reconnection, the dominant energy reservoir in Jupiter's magnetospheric plasma, continually present, is the kinetic energy of its rotating plasma disk. This ``flywheel'' produces effects with no terrestrial analogy, some of which we describe here. The most surprising prediction from the analysis of this paper is that remotely sensed symptoms of Jovian magnetospheric activity are likely to occur in conjunction with solar wind pressure decreases. Compressions of the magnetosphere produced by forward shocks and other solar wind pressure increases will heat the magnetospheric plasma but substantially reduce the ionosphere-magnetosphere current systems. The intensity of dayside aurora and of radio wave emissions associated with increased ionospheric-magnetospheric current systems will tend to anticorrelate with magnetospheric compressions and correlate with expansions. The link to the aurora is based on an argument that the auroral zone maps to the plasma disk of the middle magnetosphere and is thus linked to plasma sheet dynamics. The effect of expansion on the plasma sheet is to increase the parallel pressure, setting up conditions that can produce detached plasma ``blobs'' and enhance mass loss. The analysis is particularly apposite in light of the opportunities for observing solar wind-Jovian interactions using data from both the Galileo and the Cassini spacecraft during the Cassini flyby of Jupiter in late 2000, ideally supplemented by auroral imaging with ground-based and Hubble telescopes.

Southwood, D. J.; Kivelson, M. G.

2001-04-01

208

Torus Workshop 2012  

NASA Astrophysics Data System (ADS)

The nature and origin of the dusty material at the heart of active galaxies - whether it is inflowing, outflowing, its relation to star formation, etc. - has profound implications for our understanding of the evolution and lifecycle of AGN. A sound understanding of local AGN will also allow us to model them with confidence and apply our models to forthcoming observations of objects in the distant Universe. The last few years have seen numerous developments in the field: exquisitely sensitive Spitzer spectra have revealed the infrared properties of large numbers of AGN; mid-infrared interferometry is an increasingly mature technique; and models of increasing sophistication have been developed to explore the observations, to name just a few examples. The Torus 2012 workshop was held at the University of Texas, San Antonio in December 2012. Specialists in these and related areas gathered to share knowledge, debate ideas, and come to the best possible understanding of the dusty structures in AGN.

Mason, R.; Alonso-Herrero, A.; Packham, C.

2012-12-01

209

New periodicity in Jovian decametric radio emission  

NASA Astrophysics Data System (ADS)

We report on the finding of a new periodicity in the Jovian decametric radio emission (DAM). Periodic bursts of non-Io component of DAM which recur with a period 1.5% longer than the Jupiter rotation (System III) have been found in the dynamic radio spectra acquired by STEREO/WAVES, Wind/WAVES and Cassini/RPWS during the years 2002-2008. Typically, the bursts appear very periodically over several Jovian days with a decreasing intensity and they display a negative frequency drift. All the bursts were detected within the same sector of Jovian Central Meridian Longitude (III), between 300° and 60° (via 360°) of CML (III), close to the region of the non-Io-C source. No correlation has been found with the position of Io. Considering the simultaneous stereoscopic observations onboard STEREO-A and STEREO-B, as well as Wind and Cassini we can conclude that the sources of the periodic bursts most probably sub-corotate with Jupiter.

Panchenko, M.; Rucker, H. O.; Kaiser, M. L.; St. Cyr, O. C.; Bougeret, J.-L.; Goetz, K.; Bale, S. D.

2010-03-01

210

Jovian Radio Burst Remote Sensing of Solar Wind Triggered Jovian Magnetospheric Activity: Ulysses Observations  

NASA Astrophysics Data System (ADS)

In 2003 and early 2004, the Ulysses spacecraft descended from high heliographic latitudes towards perihelion, bringing it relatively close to Jupiter. The geometry of this distant flyby (0.8 AU closest approach) caused Ulysses to spend more than 6 months above a jovicentric latitude of 50 deg at a range of less than 2 AU, while the spacecraft traversed a considerable range of Jovian local time (9 hrs to 17 hrs). During much of this time interval, Jupiter was intercepted each solar rotation by two corotating high density structures and sector boundaries. From the perspective of Ulysses, the radio response of the magnetosphere to a given corotating structure was the intensification of either Jovian broad-band kilometric (bKOM) emission or of a combination of emissions, including bKOM and Jovian narrow-band kilometric (nKOM) emission. Such enhancements have been studied previously with Voyager, Ulysses, Galileo, and Cassini radio data. For Ulysses observations in 1991 and 1992, in particular, the typical scenario was brightening in the Jovian bKOM emission, followed by a sudden cessation of the bKOM emission and an onset of an nKOM "event" that lasted for some 120 hours (Reiner et al., 2000). For the sequences of events in 2003-2004, the two episodes per solar rotation; driven by high speed streams and/or current sheet crossing, clearly have different morphologies. In this presentation, variations in solar wind kinetic pressure and magnetic field direction (measured by Ulysses) are analyzed as triggers of Jovian magnetospheric activity, indicated by the intense radio emissions. Several intervals when magnetic clouds intercept Jupiter and produce Jovian radio events are also examined.

MacDowall, R. J.; Desch, M. D.; Kaiser, M. L.; Reiner, M. J.; Forsyth, R. J.; McComas, D. J.

2004-12-01

211

Overview of the Helicity Injected Torus Program  

NASA Astrophysics Data System (ADS)

The Helicity Injected Torus with Steady Inductive Helicity Injection (SIHI) spheromak experiment (HIT-SI) [Jarboe, Fus. Tech., (36)1, p.85, 1999] addresses critical issues for spheromaks, including current drive, operation at high beta, and confinement. HIT-SI features an optimal high-beta plasma shape and current profile, steady-state operation, minimal plasma-wall interaction, and injected power always flowing into the plasma. HIT-SI has a ``bow-tie'' shaped 1 cm thick Cu flux conserver with major radius R = 0.33 m and axial extent of 0.57 m. A half torus helicity injector at each end of the flux conserver produces conjugate sinusoidal flux (4 MW peak) and loop voltages (20 MW peak) at 5 kHz by IGBT-based switching power amplifiers. Injector flux and loop voltages are phase controlled to maintain power flow always inward. Insulating breaks for the oscillating flux and loop voltage are provided by a novel double viton o-ring system. HIT-SI uses the diagnostic suite previously used by the HIT-II experiment, (presented in an accompanying poster.) Results and 3D MHD simulations will be presented.

Nelson, B. A.; Jarboe, T. R.; Hamp, W. T.; Izzo, V. A.; O'Neill, R. G.; Redd, A. J.; Sieck, P. E.; Smith, R. J.

2004-11-01

212

Design point studies for future spherical torus devices  

SciTech Connect

A Systems Code analysis has been developed which provides a tool for the assessment of design points for future spherical torus (ST) devices. The code includes algorithms for plasma physics as well as engineering aspects, which are necessarily simplified but sufficient to capture the essential design-driving considerations. This paper describes the methodology and presents some example cases from ongoing studies.

Neumeyer, C. L. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL; Rutherford, P. H. [Princeton Plasma Physics Laboratory (PPPL)

2003-01-01

213

Galileo observations of ion cyclotron waves in the Io torus  

Microsoft Academic Search

Ion cyclotron waves generated near Io have been observed on four Galileo passes of the plasma torus, in December 1995, October 1999, November 1999, and February 2000. The waves have frequencies near the gyrofrequencies of SO+2 and SO+ ions, and are propagating at angles up to 40° to the ambient magnetic field. These waves are generated by ring-beam distributions of

X. Blanco-Cano; C.T. Russell; R. J. Strangeway; M. G. Kivelson; K. K. Khurana

2001-01-01

214

Origin of ''modulation lines'' in the dynamic spectrum of Jovian decameter radio emission  

SciTech Connect

The dynamic spectra are calculated for two possible mechanisms of formation of ''modulation lines'' in the dynamic spectrum of Jovian decameter radio emission: 1) the Cotton--Mouton effect in the Jovian ionosphere and magnetosphere and 2) frequency modulation of the intensity in the source; the characteristic signs distinguishing spectra with bands due to the Cotton--Mouton effect from spectra in which the bands appear as a result of the action of the second mechanism are indicated. The conditions for the development of the Cotton--Mouton effect and of modulation of the frequency spectrum in the source on Jupiter are discussed. Electron concentrations of 10/sup 3/--10/sup 4/ el/cm/sup 3/ are sufficient to explain the ''modulation lines'' by the Cotton--Mouton effect in the Jovian ionosphere or lower magnetosphere. The difficulties in explaining (by analogy with the zebra structure in solar radio emission) modulation of the frequency spectrum in the source by the intense excitation of plasma waves in layers where the condition for double plasma resonance at harmonics of the electron or ion gyrofrequency is satisfied are pointed out.

Zheleznyakov, V.V.; Shaposhnikov, V.E.

1979-09-01

215

Monte Carlo simulation of energization of Jovian trapped electrons by recirculation  

NASA Astrophysics Data System (ADS)

The recirculation model for particle acceleration in the Jovian magnetosphere is studied by means of Monte Carlo simulation. The recirculation model combines the conventional radial and pitch angle diffusion processes with the essentially energy-conserving latitudinal diffusion in low altitudes and the pitch angle scattering in the plasma disk. This process has been proposed to explain the pitch angle and spectral characteristics of MeV electrons observed by Pioneer in the Jovian magnetosphere. The simulation confirms that the dumbbell-type anisotropy and the high-energy tail of the energy spectrum can be produced from the recirculation process if the rate of the low-altitude cross-L diffusion is comparable to that of the conventional radial diffusion.

Fujimoto, M.; Nishida, A.

1990-04-01

216

Relativistic wave-particle interaction in magnetospheric plasmas  

NASA Astrophysics Data System (ADS)

The interaction between electromagnetic waves and high energy particles both in the magnetosphere of Earth and Jupiter has been investigated in a great detail. Different models for the electron distribution function has been used to determine the synchrotron radiation in the Jovian inner magnetosphere and the growth rate of R- mode waves in a relativistic plasma. Using a bi-loss-cone distribution function (composed of a high anisotropic component and a quasi-isotropic component), the whistler- mode wave growth has been calculated for the interchange events in the Io torus and for chorus emissions during a terrestrial substorm. We demonstrated that the path integrated gain can be dramatically enhanced over quiescent condition; exceed 20 e-foldings in the interchange event or approach 10 e-foldings during the terrestrial substorm. The wave excitation can cause strong pitch angle scattering leading to quasi-isotropic pitch angle distributions during Jovian interchange event and the terrestrial substorm. The relativistic wave- particle resonant diffusion curves for electron cyclotron resonance with both electromagnetic subluminous waves (electromagnetic R mode and L mode) and superluminous waves (R-X mode, L-O mode and L-X mode) have been constructed and their application are studied to electron acceleration in the Earth magnetosphere at the locations both inside and outside the plasmapause.

Xiao, Fuliang

2001-06-01

217

Next-step spherical torus experiment and spherical torus strategy in the course of development of fusion energy  

Microsoft Academic Search

A spherical torus (ST) fusion energy development path which is complementary to the proposed tokamak burning plasma experiments such as ITER is described. The ST strategy focuses on a compact component test facility (CTF) and high performance advanced regimes leading to more attractive Demo and power plant scale reactors. To provide the physical basis for the CTF an intermediate step

M. Ono; M. Peng; C. Kessel; C. Neumeyer; J. Schmidt; J. Chrzanowski; D. Darrow; L. Grisham; P. Heitzenroeder; T. Jarboe; C. Jun; S. Kaye; J. Menard; R. Raman; T. Stevenson; M. Viola; J. Wilson; R. Woolley; I. Zatz

2004-01-01

218

The Jovian Auroral Distributions Experiment (JADE) on the Juno Mission to Jupiter  

NASA Astrophysics Data System (ADS)

The Jovian Auroral Distributions Experiment (JADE) on Juno provides the critical in situ measurements of electrons and ions needed to understand the plasma energy particles and processes that fill the Jovian magnetosphere and ultimately produce its strong aurora. JADE is an instrument suite that includes three essentially identical electron sensors (JADE-Es), a single ion sensor (JADE-I), and a highly capable Electronics Box (EBox) that resides in the Juno Radiation Vault and provides all necessary control, low and high voltages, and computing support for the four sensors. The three JADE-Es are arrayed 120? apart around the Juno spacecraft to measure complete electron distributions from ˜0.1 to 100 keV and provide detailed electron pitch-angle distributions at a 1 s cadence, independent of spacecraft spin phase. JADE-I measures ions from ˜5 eV to ˜50 keV over an instantaneous field of view of 270?×90? in 4 s and makes observations over all directions in space each 30 s rotation of the Juno spacecraft. JADE-I also provides ion composition measurements from 1 to 50 amu with m/?m˜2.5, which is sufficient to separate the heavy and light ions, as well as O+ vs S+, in the Jovian magnetosphere. All four sensors were extensively tested and calibrated in specialized facilities, ensuring excellent on-orbit observations at Jupiter. This paper documents the JADE design, construction, calibration, and planned science operations, data processing, and data products. Finally, the Appendix describes the Southwest Research Institute [SwRI] electron calibration facility, which was developed and used for all JADE-E calibrations. Collectively, JADE provides remarkably broad and detailed measurements of the Jovian auroral region and magnetospheric plasmas, which will surely revolutionize our understanding of these important and complex regions.

McComas, D. J.; Alexander, N.; Allegrini, F.; Bagenal, F.; Beebe, C.; Clark, G.; Crary, F.; Desai, M. I.; De Los Santos, A.; Demkee, D.; Dickinson, J.; Everett, D.; Finley, T.; Gribanova, A.; Hill, R.; Johnson, J.; Kofoed, C.; Loeffler, C.; Louarn, P.; Maple, M.; Mills, W.; Pollock, C.; Reno, M.; Rodriguez, B.; Rouzaud, J.; Santos-Costa, D.; Valek, P.; Weidner, S.; Wilson, P.; Wilson, R. J.; White, D.

2013-05-01

219

Galileo Measurements of the Jovian Electron Radiation Environment  

NASA Astrophysics Data System (ADS)

The Galileo spacecraft Energetic Particle Detector (EPD) has been used to map Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii (1 jovian radius = 71,400 km). The electron count rates from the instrument were averaged into 10-minute intervals over the energy range 0.2 MeV to 11 MeV to form an extensive database of observations of the jovian radiation belts between Jupiter orbit insertion (JOI) in 1995 and end of mission in 2003. These data were then used to provide differential flux estimates in the jovian equatorial plane as a function of radial distance (organized by magnetic L-shell position). These estimates provide the basis for an omni-directional, equatorial model of the jovian electron radiation environment. The comparison of these results with the original Divine model of jovian electron radiation and their implications for missions to Jupiter will be discussed. In particular, it was found that the electron dose predictions for a representative mission to Europa were about a factor of 2 lower than the Divine model estimates over the range of 100 to 1000 mils (2.54 to 25.4 mm) of aluminum shielding, but exceeded the Divine model by about 50% for thicker shielding for the assumed Europa orbiter trajectories. The findings are a significant step forward in understanding jovian electron radiation and represent a valuable tool for estimating the radiation environment to which jovian science and engineering hardware will be exposed.

Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

2003-12-01

220

Jovian cusp processes: Implications for the polar aurora  

Microsoft Academic Search

Recently, high temporal and spatial resolution Hubble Space Telescope (HST) imaging in the ultraviolet (UV) has revealed a new feature in Jupiter's polar aurora. Of highly variable intensity, while remaining persistently near local noon, a polar “spot” of aurora has been suggested to be associated with the jovian cusp. The main jovian X-ray source also appears to be colocated with

E. J. Bunce; S. W. H. Cowley; T. K. Yeoman

2004-01-01

221

Characteristics of Energy Transport of Li-conditioned and non-Li-conditioned Plasmas in the National Spherical Torus Experiment (NSTX).  

National Technical Information Service (NTIS)

The transport properties of NSTX plasmas obtained during the 2008 experimental campaign have been studied and are reported here. Transport trends and dependences have been isolated, and it is found that both electron and ion energy transport coefficients ...

B. Wan B. P. LeBlanc H. Kugel R. Kaita R. E. Bell S. Ding S. Paul S. M. Kaye

2009-01-01

222

Torus fractalization and intermittency.  

PubMed

The bifurcation transition is studied for the onset of intermittency analogous to the Pomeau-Manneville mechanism of type I, but generalized for the presence of a quasiperiodic external force. The analysis is concentrated on the torus-fractalization (TF) critical point that occurs at some critical amplitude of driving. (At smaller amplitudes the bifurcation corresponds to a collision and subsequent disappearance of two smooth invariant curves, and at larger amplitudes it is a touch of attractor and repeller at some fractal set without coincidence.) For the TF critical point, renormalization group (RG) analysis is developed. For the golden mean rotation number a nontrivial fixed-point solution of the RG equation is found in a class of fractional-linear functions with coefficients depending on the phase variable. Universal constants are computed that are responsible for scaling in phase space (alpha=2.890 053... and beta= -1.618 034...) and in parameter space (delta(1)=3.134 272... and delta(2)=1.618 034...). An analogy with the Harper equation is outlined, which reveals important peculiarities of the transition. For amplitudes of driving less than the critical value the transition leads (in the presence of an appropriate reinjection mechanism) to intermittent chaotic regimes; in the supercritical case it gives rise to a strange nonchaotic attractor. PMID:12188817

Kuznetsov, Sergey P

2002-06-24

223

The Helcity Injected Torus--II Experiment  

NASA Astrophysics Data System (ADS)

The Helicity Injected Torus--II (HIT--II) spherical torus is capable of both Coaxial Helicity Injection (CHI) and transformer action current drive. Using only CHI, the previous experiment HIT drove over 250 kA of toroidal plasma current, using a passive W-sprayed copper shell to provide equilibrium and stability currents. HIT--II has a major radius of R = 0.3, minor radius of a = 0.2, aspect ratio A = R/a = 1.5, with an on axis magnetic field of up to Bo = 0.67 T. HIT--II provides equilibrium control, CHI flux boundary conditions, and transformer action using 28 poloidal field coils (PFCs). The PFCs are energized by insulated gate bipolar transistors (IGBT) power supplies providing active feedback of the poloidal flux boundary conditions using programmed waveforms. Stability to wave phenomena associated with current drive is provided down to approximately 10 kHz by a 6 mm thick stainless steel. Capabilities for wall conditioning include solid target boronization, baking, hydrogen and helium glow discharge cleaning, and titanium gettering. With minimal wall conditioning and only using CHI, HIT--II has driven over 150 kA of plasma current, and has shown the first evidence of n=1 activity without Ti gettering. Results from operations involving more aggressive wall conditioning and transformer action will be presented.

Nelson, B. A.; Jarboe, T. R.; Ewig, R.; Hoffman, C. S.; Holcomb, C. T.; Kahle, W. J.; McCollam, K. J.; Raman, R.; Redd, A. J.; Rogers, J. A.; Shumlak, U.; Smith, R. J.

1998-11-01

224

Radial transport within the Jovian main ring  

NASA Astrophysics Data System (ADS)

Due to their fast transport times through the Jovian system, the dust-sized grains within Jupiter's main ring are thought to be continually replenished. A likely source for these particles is meteoroid bombardment into parent bodies within the main ring as well as the small moons Metis and Adrastea. The main ring appears distinctly different in low phase angle Galileo SSI images than at high phase angles. Low phase angle images reveal two bright bands at the outer egde of the main ring. These bands may represent the locations of macroscopic ring particles. Showalter et al. (1987, Icarus, 69, 458-498) found that the size distribution of micron-sized grains follows a power law distribution with an index of 2.5 + 0.5. Such a distribution is believed to be consistent with a meteoroid bombardment origin for the smaller ring particles. Using Galileo SSI and NIMS data, we have determined that the particles follow a broken power law size distribution between 0.1 and 100 microns: a relatively steep power law distribution above 15 microns and a shallower one at smaller sizes. Size-dependent particle loss and transport processes may explain this deviation from a simple power law distribution. Previous models have invoked such processes to explain other characteristics of the Jovian ring system. We have incorporated these results into a simple model of radial transport for the ring particles to determine which, if any, of the physical processes previously examined can explain our derived size distribution and resolve the differences between the ring's profile as seen at high and low phase angles. We will report on the initial results of our efforts to model radial transport in the Jovian main ring.

Brooks, S. M.; Esposito, L. W.; Showalter, M. R.; Throop, H. B.

2003-04-01

225

Numerical simulation of baroclinic Jovian vortices  

NASA Astrophysics Data System (ADS)

We examine the evolution of baroclinic vortices in a time-dependent, nonlinear numerical model of a Jovian atmosphere. The model uses a normal-mode expansion in the vertical, using the barotropic and first two baroclinic modes. Results for the stability of baroclinic vortices on an f plane in the absence of a mean zonal flow are similar to results of Earth vortex models, although the presence of a fluid interior on the Jovian planets shifts the stability boundaries to smaller length scales. The presence of a barotropic mean zonal flow in the interior stabilizes vortices against instability and significantly modifies the finite amplitude form of baroclinic instabilities. The effect of a zonal flow on a form of barotropic instability produces periodic oscillations in the latitude and longitude of the vortex as observed at the level of the cloud tops. This instability may explain some, but not all, observations of longitudinal oscillations of vortices on the outer planets. Oscillations in aspect ratio and orientation of stable vortices in a zonal shear flow are observed in this baroclinic model, as in simpler two-dimensional models. Such oscillations are also observed in the atmospheres of Jupiter and Neptune. The meridional propagation and decay of vortices on a beta plane is inhibited by the presence of a mean zonal flow. The direction of propagation of a vortex relative to the mean zonal flow depends upon the sign of the meridional potential vorticity gradient; combined with observations of vortex drift rates, this may provide a constraint on model assumption for the flow in the deep interior of the Jovian planets.

Achterberg, R. K.; Ingersoll, A. P.

1994-02-01

226

IUE observations of the Jovian dayglow emission  

NASA Astrophysics Data System (ADS)

IUE spectra of Jupiter are examined in light of recent models put forward to explain the anomalously bright ultraviolet emissions seen from the upper atmospheres of the outer planets. Chi-squared fits of the IUE spectra with model spectra produced by two proposed excitation mechanisms, electron impact and fluorescence of solar radiation, result in consistently higher chi-squared values for the solar fluorescence model. No conclusive evidence is found in the IUE data for the dominance of solar fluorescence over electron excitation in producing the Jovian dayglow emission.

McGrath, M. A.; Feldman, P. D.; Ballester, G. E.; Moos, H. W.

1989-06-01

227

Next-Step Spherical Torus Experiment and Spherical Torus Strategy in the Fusion Energy Development Path  

SciTech Connect

A spherical torus (ST) fusion energy development path which is complementary to proposed tokamak burning plasma experiments such as ITER is described. The ST strategy focuses on a compact Component Test Facility (CTF) and higher performance advanced regimes leading to more attractive DEMO and Power Plant scale reactors. To provide the physics basis for the CTF an intermediate step needs to be taken which we refer to as the ''Next Step Spherical Torus'' (NSST) device and examine in some detail herein. NSST is a ''performance extension'' (PE) stage ST with the plasma current of 5-10 MA, R = 1.5 m, and Beta(sub)T less than or equal to 2.7 T with flexible physics capability. The mission of NSST is to: (1) provide a sufficient physics basis for the design of CTF, (2) explore advanced operating scenarios with high bootstrap current fraction/high performance regimes, which can then be utilized by CTF, DEMO, and Power Plants, and (3) contribute to the general plasma/fusion science of high beta toroidal plasmas. The NSST facility is designed to utilize the Tokamak Fusion Test Reactor (or similar) site to minimize the cost and time required for the design and construction.

M. Ono; M. Peng; C. Kessel; C. Neumeyer; J. Schmidt; J. Chrzanowski; D. Darrow; L. Grisham; P. Heitzenroeder; T. Jarboe; C. Jun; S. Kaye; J. Menard; R. Raman; T. Stevenson; M. Viola; J. Wilson; R. Woolley; I. Zatz

2003-10-27

228

Space Propulsion via Spherical Torus Fusion Reactor  

SciTech Connect

A conceptual vehicle design enabling fast outer solar system travel was produced predicated on a small aspect ratio spherical torus nuclear fusion reactor. Analysis revealed that the vehicle could deliver a 108 mt crew habitat payload to Saturn rendezvous in 204 days, with an initial mass in low Earth orbit of 1630 mt. Engineering conceptual design, analysis, and assessment were performed on all major systems including nuclear fusion reactor, magnetic nozzle, power conversion, fast wave plasma heating, fuel pellet injector, startup/re-start fission reactor and battery, and other systems. Detailed fusion reactor design included analysis of plasma characteristics, power balance and utilization, first wall, toroidal field coils, heat transfer, and neutron/X-ray radiation.

Williams, Craig H.; Juhasz, Albert J.; Borowski, Stanley K.; Dudzinski, Leonard A. [NASA Glenn Research Center (United States)

2003-01-15

229

Paris to Hektor: A Concept for a Mission to the Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

This paper presents an example of a new class of planetary exploration missions that is been enabled by the combination of the three technologies of advanced radioisotope power systems, electric propulsion, and expendable launch vehicles. These PARIS (Planetary Access with Radioisotope Ion-drive System) missions are optimized for rendezvous with outer solar system bodies in shallow gravity wells. They are low-thrust missions that are launched to a high C3 and use their electric propulsion systems to slow them to enable orbit insertion or landing on the target body. The PARIS spacecraft can be powered by traditional Radioisotope Thermoelectric Generators (RTGs), but will benefit greatly from the improved power-to-mass ratio of Stirling radioisotope generators (SRGs) that results from their high conversion efficiency. These New-Frontiers class missions can carry a significant science payload to the Jovian Trojan asteroids. The Trojans are very primitive bodies located near the Jovian L4 and L5 Lagrange points. The PARIS to Hektor mission can reach the asteroids in less than 5 years, orbit 624 Hektor, the largest of the Jovian Trojans, and go on to orbit at least one other nearby object. There are estimated to be more than 105 Jovian Trojans greater than 1 km in diameter. The PARIS to Hektor spacecraft has a candidate payload that includes wide-field and narrow-field cameras, a UV-Vis-IR spectrograph, gamma-ray and neutron spectrometers, and plasma and energetic particle spectrometers. The power system generates about 900 W and the launch mass is slightly less than 1000 kg. The trip time is 5 years if ``classic'' GPHS RTGs are used for power. Next generation Stirling radioisotope generators (SRGs), with a demonstrated thermal conversion efficiency of > 30% and an estimated specific power of > 8W/kg would reduce the travel time to about 4 years.

Gold, Robert E.; McNutt, Ralph L.; Napolillo, David H.; Schaefer, Edward D.; Tanzman, Jennifer R.; Fiehler, Douglas I.; Hartka, Theodore J.; Mehoke, Douglas S.; Ostdiek, Paul H.; Persons, David F.; Prockter, Louise M.; Vernon, Steven R.

2007-01-01

230

Latitudinal structure within Jovian hectometric radiation  

NASA Astrophysics Data System (ADS)

Jovian hectometric radio emission (HOM: 300-3000 kHz) has a number of persistent structural features associated with it as observed by the Voyager 1, Voyager 2, Ulysses, and Galileo spacecraft for specific jovigraphic latitudes (-4° to +7.1°) and local times (0.3 to 10.5 hours). Most notable are the presence of HOM emission between 270° and 120° central meridian longitude (CML) and the region of reduced emission intensity (a ``gap'') between 120° and 270°. We displayed the Ulysses and Galileo data using time-frequency occurrence probability spectrograms and show that the observed HOM emission features are nearly identical to those observed by the Voyager spacecraft. This implies that the HOM structure is long-lived and fixed in its longitudinal position within the Jovian magnetosphere. HOM structure depends on small changes in the observer's jovigraphic latitude, so the different jovigraphic latitudes of the spacecraft were used to probe the HOM beam structure. From this analysis we found that the CML width of the main HOM gap is directly correlated to the latitude of the spacecraft. We conclude that the latitudinal thickness of the HOM beam is about 12°, extending from -5° to +7° magnetic latitude.

Higgins, Charles A.; Thieman, James R.; Fung, Shing F.; Green, James L.; Candey, Robert M.

1998-11-01

231

New Results in Jovian Mode Observations  

NASA Astrophysics Data System (ADS)

Numerous works have been published developing theoretical models for the structure of the Jovian core. The most recent complete model in the literature is that of Gudkova and Zharkov (1999), which detailed several models varying in both their core molecular-metallic phase transition pressure levels and core mass. It was the hope of the authors that the models would be used, ``as soon as relevant observations are performed'' for identifying modes and improving the models. Thus far, this does not seem to have happened, although it is clear that work is ongoing with such instruments as SYMPA and the Juno orbiter. We attacked this problem in the vein of Thomson, Maclennan, and Lanzerotti (1995), analyzing measurements of magnetic field and high-energy particles from the Jovian close-approach time periods of both Voyager II and Ulysses. The comparison between the predicted mode frequencies and the signatures in the spectra of the measurements of the two spacecraft show a number of high-probability matches to model frequencies. Additionally, there are observed frequencies and splittings that are not explained by the model, and it is our hope that these findings will spur further work in the field, improving the model(s) to match the experimental findings.

Burr, W.; Thomson, D. J.

2010-12-01

232

Initial Diagnostics for the National Spherical Torus Experiment  

SciTech Connect

The spherical torus (ST) approach to magnetic confinement has many attractive features as both a fusion reactor concept and a volume neutron source. The National Spherical Torus Experiment (NSTX) is under construction at the Princeton Plasma Physics Laboratory (PPPL), and it is designed to achieve plasma parameters needed for a proof-of-principle test of the ST concept. Discharges with magnetic fields of 2.3 kG on axis and plasma currents of 1 MA will be heated with 6 MW of radio frequency (RF) power and 5 MW of neutral beams, and pulse lengths up to 5 seconds are planned. Central electron temperatures of about 4 keV are expected with RF heating, and theoretical studies show that high values of b and b{sub n} can be achieved.

A.L. Roquemore; B. McCormack; D. Johnson; H. Kugel; R. Kaita; and the NSTX Team

1999-06-01

233

Dust charging in the dense Enceladus torus  

NASA Astrophysics Data System (ADS)

The key parameter of the dust-plasma interactions is the charge carried by a dust particle. The grain electrostatic potential is usually calculated from the so called orbit-motion limited (OML) model [1]. It is valid for a single particle immersed into collisionless plasmas with Maxwellian electron and ion distributions. Apparently, such a parameter regime cannot be directly applied to the conditions relevant for the Enceladus dense neutral torus and plume, where the plasma is multispecies and multistreaming, the dust density is high, sometimes even exceeding the plasma number density. We have examined several new factors which can significantly affect the grain charging in the dust loaded plasma of the Enceladus torus and in the plume region and which, to our knowledge, have not been investigated up to now for such plasma environments. These include: (a) influence of the multispecies plasma composition, namely the presence of two electron populations with electron temperatures ranging from a few eV up to a hundred eV [2], a few ion species (e.g. corotating water group ions, and protons, characterized by different kinetic temperatures), as well as cold nonthermalized new-born water group ions which move with Kepler velocity [3]; (b) effect of the ion-neutral collisions on the dust charging in the dense Enceladus torus and in the plume; (c) effect of high dust density, when a grain cannot be considered as an isolated particle any more (especially relevant for the plume region, where the average negative dust charge density according to Cassini measurements is of the order or even exceeds the plasma number density [4,5]). It turns out that in this case, the electrostatic potential and respective dust charge cannot be deduced from the initial OML formalism and there is a need to incorporate the effect of dust density into plasma fluxes flowing to the grain surface to calculate the grain equilibrium charge; (e) since the dust in the planetary rings comes in a wide spectrum of sizes from macromolecules to the boulders of a few m in sizes, it becomes important to examine the effect of dust size distribution on the equilibrium particle potential. The obtained results might be of importance for understanding the main physical processes occurring in the planetary rings including the problem of dust transport as well as for interpretations of Cassini plasma measurements in Saturn's rings. [1] M. Horányi, Annu. Rev. Astron. Astrophys., 34, 383, (1996). [2] B. L. Fleshman et al. Geophys. Res. Lett., 36, L03202, (2010). [3] R. L. Tokar, et al., Geophys. Res. Lett., 36, L13203, (2009). [4] T. W. Hill, et al., J. Geophys. Res., 117, A05209, (2012). [5] M. Shafiq, et al., Planet. Space Sci., 59, 17, (2010).

Yaroshenko, Victoria; Lühr, Hermann; Morfill, Gregor

2013-04-01

234

Origin of ultraviolet emission source in the Jovian ionosphere at the feet of the Io flux tube  

NASA Astrophysics Data System (ADS)

A model for an explanation of far ultraviolet (FUV) emissions observed from the Io flux tube footprints at the Jovian ionosphere is presented. An acceleration of electrons and ions of the ionospheric plasma up to sufficient energies for an effective excitation of H2 Lyman and Werner bands is proposed. The neutral particles within the Jovian ionosphere are excited due to their collisions with the charged particles relatively moving to the neutrals in the ionospheric plasma. The motion is induced by the Ampčre force which arises due to the interaction between the electric current flowing within the Io magnetic flux tube and its own specific magnetic field. It is established that only a sufficiently strong field-aligned current is capable of providing the required velocity of the relative motion. Our estimates show that in principle the proposed mechanism can provide the level of FUV emissions observed from the Io flux tube footprints.

Shaposhnikov, Vladimir E.; Zaitsev, Valerii V.; Rucker, Helmut O.; Litvinenko, Galina V.

2001-11-01

235

Cassini/mimi Observations of Jovian Particle Emissions After Jupiter Flyby  

NASA Astrophysics Data System (ADS)

The MIMI investigation comprises three sensors, the Ion and Neutral Camera (INCA), Charge-Energy-Mass-Spectrometer (CHEMS), and Low Energy Magneto- spheric Measurement System (LEMMS) covering the energy ranges 7 keV/nuc 3 Mev) and protons (1.6 < E < 160 Mev) from the back end of the dual field-of-view telescope. Following Jupiter closest approach at ~139RJ on December 30, 2000, Cassini moved past the dusk flank of the magnetosphere and en- countered Jovian plasma to distances > 103RJ downstream of the planet. In this work we report results of a search for Jovian particle emissions to distances of ~5x103RJ, or over 2AU away from the planet, as Cassini continues on its trajectory to a Saturn encounter on July 1, 2004. The relative location of Jupiter and Cassini is such that con- nection of the magnetosphere/magnetotail through the Interplanetary Magnetic Field (IMF) is readily achievable. Preliminary data suggest Jovian plasma events to at least ~2AU downstream, manifested by the presence of S+ ions. Some events appear to be associated with solar wind disturbances due to solar particle emissions in mid-to-late 2001, as observed by ACE at 1AU. The results of the search will be reported and their significance in terms of plasma loss through the magnetotail will be compared with expectations from the magnetospheric wind source identified by the Voyager missions.

Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Livi, S.; Krupp, N.

236

Characteristics of Energy Transport of Li-conditioned and non-Li-conditioned Plasmas in the National Spherical Torus Experiment (NSTX)  

SciTech Connect

The transport properties of NSTX plasmas obtained during the 2008 experimental cam- paign have been studied and are reported here. Transport trends and dependences have been isolated, and it is found that both electron and ion energy transport coefficients have strong dependences on local values of n?T, which in turn is strongly dependent on local current density profile. Without identifying this dependence, it is difficult to identify others, such as the dependence of transport coefficients on Bp (or q), Ip and Pheat. In addition, a comparison between discharges with and without Lithium wall conditioning has been made. While the trends in the two sets of data are similar, the thermal transport loss, especially in the electron channel, is found to strongly depend on the amount of Lithium deposited, decreasing by up to 50% of its no-Lithium value.

S. Ding, S.M. Kaye, R.E. Bell, R. Kaita, H. Kugel, B.P. LeBlanc, S. Paul, B. Wan

2009-10-21

237

Temperature Structure and Emergent Flux of the Jovian Planets.  

National Technical Information Service (NTIS)

Long path, low temperature, moderate resolution spectra of methane and ammonia, broadened by hydrogen and helium, are used to calculate non-gray model atmospheres for the four Jovian planets. The fundamental and first overtone of hydrogen contributes enou...

C. Sagan P. Silvaggio

1978-01-01

238

The JIRAM (Jovian InfraRed Auroral Mapper) Experiment  

Microsoft Academic Search

JIRAM is an imager spectrometer proposed for the Juno mission to Jupiter. JIRAM would add the capability of imaging and making spectra of the Jovian aurora, the hot spots and exploring the troposphere between 1 and 10 bars.

A. Coradini; A. Adriani; G. Filacchione; J. I. Lunine; G. Magni; M. Cosi; L. Tommasi

2006-01-01

239

Dust spectrometry in the Jovian System  

NASA Astrophysics Data System (ADS)

The Galileo spacecraft characterised the dust environment in the jovian system. The discoveries included an extended dusty ring system, the nano-metre sized stream particles originating from the moon Io, and the dust exospheres around the Galilean satellites Ganymed, Europa and Callisto [2]. The study of the nanodust-magnetosphere interaction and the compositional analysis of dust particles ejected by the surfaces of Ganymed or Europa offer unique future opportunities. New dust instrumentation is a factor of 10 more sensitive then the former Galileo detector and adds compositional analysis for moon surface studies complementary to neutral gas or ion particle investigations. A dust spectrometer performs complementary measurements with respect to neutral gas or ion investigations and is highly sensitive for organic, salty water ice and mineral particles.

Srama, R.; Kempf, S.; Postberg, F.; Schmidt, J.; Krüger, H.; Thissen, R.; Sternovsky, Z.; Engrand, C.; Fiege, K.; Horanyi, M.; Khalisi, E.; Mocker, A.; Moragas-Klostermeyer, G.; Otto, K.; Spahn, F.; Sterken, V.; Grün, E.; Röser, H. P.

2011-10-01

240

Jovian decametric arcs and Alfven currents  

NASA Astrophysics Data System (ADS)

The Voyager Planetary Radio Astronomy (PRAD) experiment revealed prominent 'arcs' when the radio intensity at 1-40 MHz was displayed in time-frequency coordinates. These data are consistent with multiple currents flowing along longitudinally separated Jovian magnetic flux tubes, each current radiating conically at angles up to about 90 deg. The spacings between adjacent PRA arcs, and also between adjacent S burst arc segments observed at the Nancay Observatory, were analyzed and found to be so brief, less than 1-3 min, that either these currents and any associated Alfven waves survive for at least a few circulations of Jupiter by Io (a hypothesis independently supported by the observations of arcs at all Io phase angles), or each such Alfven current can radiate at several different cone-angles simultaneously (a hypothesis independently supported by the observation of such behavior in the S burst arcs).

Staelin, D. H.; Garnavich, P. M.; Leblanc, Y.

1988-05-01

241

Shapes and Densities of Jovian Trojan Objects  

NASA Astrophysics Data System (ADS)

We will use optical CCD photometric lightcurve observations of Jovian Trojan objects to study their shapes and densities. Although these objects are sometimes called Trojan ``asteroids", recent work suggests that these objects may have formed far beyond Jupiter and then were subsequently captured into their present ``clouds" at the L4 and L5 Lagrange points of the Sun-Jupiter system. Thus, these objects may be closer in physical nature to icy comets than to rocky/ metallic asteroids. The scientific goal of the work proposed here is to derive density estimates for a sample of a dozen or more Trojans to compare with density estimates for comets, asteroids, Centaurs, and KBOs. We trust that a good density estimate for the Trojan class of objects will help elucidate the origin of this group of objects and the ``big picture" of the history of minor bodies in the solar system.

Romanishin, William; Cooper, Erin

2008-08-01

242

Phase Curves of Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

The provenance of the Jovian Trojan asteroids, found at the stable L4 and L5 Lagrange points of Jupiter's orbit, has long been a topic of debate. For decades most researchers believed that they formed in situ, but recent evidence, both theoretical and observational, suggests that the Trojans may have formed at greater heliocentric distances. The observational evidence is based primarily upon the similar spectral properties and albedos of large Trojans to those of cometary nuclei (e.g. Abell et al. 2005). The phase curve--the variation of an asteroid's light with phase angle--carries information about nature and texture of the surface. The two Trojan asteroids whose phase curves have been well studied to data appear to show no strong surge in brightness near zero phase angle, unlike most dark main belt asteroids. We propose to determine phase curves for five additional Trojan asteroids.

French, Linda M.; Lederer, Susan; Stephens, Robert

2010-02-01

243

Recent results in the Los Alamos compact torus program  

SciTech Connect

A Compact Toroid is a toroidal magnetic-plasma-containment geometry in which no conductors or vacuum-chamber walls pass through the hole in the torus. Two types of compact toroids are studied experimentally and theoretically at Los Alamos: spheromaks that are oblate in shape and contain both toroidal and poloidal magnetic fields, and field-reversed configurations (FRC) that are very prolate and contain poloidal field only.

Tuszewski, M.; Armstrong, W.T.; Barnes, C.W.

1983-01-01

244

Exploration of Spherical Torus Physics in the NSTX Device  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is being built at the Princeton Plasma Physics Laboratory to test the fusion physics principles for the Spherical Torus (ST) concept at the MA level. The NSTX nominal plasma parameters are R {sub 0} = 85 cm, a = 67 cm, R/a greater than or equal to 1.26, B {sub T} = 3 kG, I {sub p} = 1 MA, q {sub 95} = 14, elongation {kappa} less than or equal to 2.2, triangularity {delta} less than or equal to 0.5, and plasma pulse length of up to 5 sec. The plasma heating/current drive (CD) tools are High Harmonic Fast Wave (HHFW) (6 MW, 5 sec), Neutral Beam Injection (NBI) (5 MW, 80 keV, 5 sec), and Coaxial Helicity Injection (CHI). Theoretical calculations predict that NSTX should provide exciting possibilities for exploring a number of important new physics regimes including very high plasma beta, naturally high plasma elongation, high bootstrap current fraction, absolute magnetic well, and high pressure driven sheared flow. In addition, the NSTX program plans to explore fully noninductive plasma start-up, as well as a dispersive scrape-off layer for heat and particle flux handling.

Barnes, G.; Blanchard, W.; Kaye, S.; Ono, M.; Peng, M.; et al.

1998-11-01

245

Jovian Cusp Processes: Implications for the Polar Aurora  

NASA Astrophysics Data System (ADS)

Jupiter's polar emissions, which include all auroral emission lying poleward of the main auroral oval, are ordered by magnetic local time, indicating external control by the solar wind interaction with the jovian magnetosphere. The main auroral oval itself appears fixed with respect to the planet, an indication of planetary control, and is understood to be associated with magnetosphere-ionosphere coupling, and the transfer of angular momentum from the ionosphere to the middle magnetosphere plasma. We have recently considered the flows present in Jupiter's ionosphere in terms of three different regimes: the sub-corotational flows associated with the main auroral oval, the Vasyliunas cycle associated with the down-tail loss of plasmoids (predominantly a feature of the dusk-side magnetosphere), and the Dungey-cycle flows which are associated with the interaction of the solar wind and embedded interplanetary magnetic field with the magnetosphere, principally via reconnection. Motivated by this picture, we consider from a theoretical standpoint what the effects of pulsed dayside magnetic reconnection will be at Jupiter. This will generate a twin-vortical flow pattern in the ionosphere across the open-closed field line boundary, associated with a bi-polar (i.e. upward and downward) field-aligned current pair. These currents will be of order ˜1-2 MA, representing <10% of the magnetopause current, flowing in a region ~1000 km across at ionospheric heights, such that the field-aligned current densities peak at ˜1 ? A m-2. Here we investigate the conditions under which such currents may be carried in either magnetospheric or cusp plasmas, and consider the consequences for auroral emissions at UV and X-ray wavelengths.

Bunce, E. J.; Cowley, S. W.; Yeoman, T. K.

2003-12-01

246

Torus generated by Escherichia coli  

NASA Astrophysics Data System (ADS)

The bioluminescence images of unstirred cultures show that lux reporter E. coli (0.10 mg biomass per ml of the broth medium) in 6.4-10 mm diameter circular containers induce center-fluid-rising toroidal convection of ?1 mm/min. The bioconvective torus is stable in a Teflon vessel and is deformed by 3.2-4.4 mm wavelength azimuthal waves in polystyrene or glass vessels.

Šimkus, R.; Kirejev, V.; Meškien?, R.; Meškys, R.

2009-02-01

247

Composition of energetic particles in the Jovian magnetotail  

NASA Astrophysics Data System (ADS)

The New Horizons spacecraft offered a unique opportunity to explore the distant Jovian magnetotail to over 2565 Jovian Radii. Previous observations of ion abundances were available only out to ~150 Jovian Radii. During the 100+-day exploration of the magnetotail, New Horizons observed a number of energetic particle bursts, similar to particle bursts observed by Galileo much closer to Jupiter. We examine the composition of these dynamic structures and compare the ion abundances with those found in more quiescent regions. We show that the composition of these energetic bursts is Iogenic and suggest it is within these bursts that Jupiter releases the bulk of its energetic material. We report on the ion composition ratios as a function distance down the Jovian magnetotail, finding an increasing intrusion of interplanetary He into the tail with distance from the planet. These observations show that the radial gradients in particle flux observed by Galileo in the magnetotail close to Jupiter extend deep into the magnetotail. We observed large electron intensities at the noon magnetopause crossing and continuous strong 10-h modulations in electron intensity to nearly 500 Jovian Radii toward the tail. Our current hypothesis is that Jupiter enforces azimuthal rotation on some fields to distances of over a few hundred Jovian Radii. At distances greater than 500 Jovian Radii we observed long-duration periods of strong electron anisotropy beaming down the magnetotail. Intermittent observations of 10-h electron modulations continue into distant regions of the magnetotail and we suggest these are a signature of occasional field line connection to the magnetosphere.

Haggerty, D. K.; Hill, M. E.; McNutt, R. L.; Paranicas, C.

2009-02-01

248

The radiation impedance of electrodynamic tethers in a polar Jovian orbit  

NASA Astrophysics Data System (ADS)

Juno, the second mission in the NASA New Frontiers Program, will both be a polar Jovian orbiter, and use solar arrays for power, moving away from previous use of radioisotope power systems (RPSs) in spite of the weak solar light reaching Jupiter. The power generation at Jupiter is critical, and a conductive tether could be an alternative source of power. A current-carrying tether orbiting in a magnetized ionosphere/plasmasphere will radiate waves. A magnitude of interest for both power generation and signal emission is the wave impedance. Jupiter has the strongest magnetic field in the Solar Planetary System and its plasma density is low everywhere. This leads to an electron plasma frequency smaller than the electron cyclotron frequency, and a high Alfven velocity. Unlike the low Earth orbit (LEO) case, the electron skin depth and the characteristic size of plasma contactors affect the Alfven impedance.

Sánchez-Torres, A.; Sanmartín, J. R.; Donoso, J. M.; Charro, M.

2010-04-01

249

Correlating east-west asymmetries in the Jovian magnetosphere and the Io sodium cloud  

NASA Astrophysics Data System (ADS)

Three east-west intensity asymmetries in the Jupiter system that would appear to an earth observer in optical S+, extreme ultraviolet S++ and optical Na emissions are reviewed. The three asymmetries imply that some combination of the plasma torus number densities and electron temperature is, on the long-term average, larger west of Jupiter than east of Jupiter. A small east-to-west electric field, previously proposed to explain the ion intensity asymmetries, is also shown to provide a natural explanation for the sodium intensity asymmetry. A long-term average east-to-west electric field of about 3 mV/m and a corresponding west-to-east offset of about 0.16 Jupiter radii for the plasma torus at Io's orbital distance are implied. On a shorter time scale, the east-west electric field appears to be time variable and may be readily monitored from earth by observations of the sodium cloud.

Smyth, W. H.; Combi, M. R.

1987-09-01

250

Jovian Ethane Aurora During the Cassini Flyby  

NASA Astrophysics Data System (ADS)

Auroral emission by ethane was observed from Jupiter with the Heterodyne Instrument for Planetary Wind and Composition, HIPWAC, in December 5-8, 2000 and in February 24-28, 2001, during the Cassini spacecraft flyby of Jupiter. Shapes of individual ethane emission lines near 12 microns from Jupiter's polar regions were measured at spectral resolving power of 1,000,000. These observations were conducted in concert with scheduled observations of the Jovian auroral region by the Cassini Composite Infrared Spectrometer (CIRS) before and after closest approach December 30, 2000, complementing CIRS' broad spectral and spatial coverage, and unique vantage point with groundbased measurements at extremely high spectral resolution and spatial resolution comparable to that at closest approach. Preliminary analysis indicates lower ``hot spot" enhancement than previously observed and a brighter emission on the north relative to that of the south auroral region. The results will be compared with CIRS data and with a long-term database relating to temporal variations in the activity of Jupiter's mid-infrared aurora. Work was supported by the NASA Planetary Astronomy Program.

Kostiuk, T.; Livengood, T. A.; Schmülling, F.; Buhl, D.; Fast, K. E.; Flasar, M.; Rozmarynowski, P.; Hewagama, T.

2001-11-01

251

Io-related Jovian decametric arcs  

NASA Astrophysics Data System (ADS)

In this work an empirical modeling technique is used to analyze certain Io-caused emission (ICE) structures in the Jovian decametric radio spectrographic data. Taking into account that some of these ICE structures have the appearance of great arcs with internal arclike fine structure, a geometrical model is developed in which the observed emission is seen to result from conical emission beams emanating from source regions carried on corotating field lines which are excited only as they cross an excitation zone centered on the Io flux tube. The model is also applied to the analysis of a limited set of spectrograms of the traditional Io-related sources Io A, Io B, and Io D. In some of these spectra it was possible to identify multiple-ICE structures. The model results for these spectra are consistent with a physical model in which emission is occurring from multiple spaced flux tubes positioned ahead of and moving with Io, and lend credence to the multiple Alfven wave reflection hypothesis.

Wilkinson, M. H.

1989-09-01

252

Superfine Structure of Jovian Millisecond Radio Bursts  

NASA Astrophysics Data System (ADS)

Jupiter decameter (DAM) radio emission mainly consists of wide-band radio storms with time scales in seconds (L-bursts) and milliseconds (S-bursts), the latter comprising a series of short pulses with duration of a few to tens of milliseconds, and strongly controlled by the satellite Io. First in-depth analysis of the subpulse structure was made by Carr and Reyes (1999) with the discovery of successive deep envelope modulations, with time resolution better than 30 microseconds, and during these subpulse periods the discovery of phase coherence. Recent observations by means of the newly developed waveform receiver (at present unsurpassed in spectral resolution) and connected to the decameter world-largest radio telescope UTR-2 (Kharkov) yielded waveform measurements of Jovian S-bursts which have been analyzed by the wavelet analysis method. Main outcome of the present investigation is the detection of clear signatures of microsecond modulations, providing evidence of a superfine burst structure with the following parameters: a) instantaneous frequency band of one separated microsecond pulse of 100 to 300 kHz, b) time duration of one separated micropulse of 6 to 15 microseconds, and c) time interval between closest subsequent microsecond pulses of 5 to 25 microseconds. The apparent frequency drift of a millisecond burst evidently results from sequentially decreasing frequencies of subsequent subpulses, each representing an island of phase coherent gyrating electron bunches.

Rucker, H. O.; Litvinenko, G.; Taubenschuss, U.; Leitner, M.; Lecacheux, A.; Konovalenko, A.

2004-05-01

253

Multiple Alfven wave reflections excited by Io: origin of the Jovian decametric arcs  

Microsoft Academic Search

The recent Voyager radio astronomy measurements near Jupiter show that the Jovian decametric radiation consists of numerous discrete features called decametric arcs which are observed at all Jovian longitudes. It is generally believed that these arcs are produced by an interaction of Io with the Jovian magnetosphere. In this paper we propose that the large number of decametric arcs is

D. A. Gurnett; C. K. Goertz

1981-01-01

254

Occurrence and source characteristics of the high-latitude components of Jovian broadband kilometric radiation  

NASA Astrophysics Data System (ADS)

Ulysses had a "distant encounter" with Jupiter when it was within 0.8 AU of the planet during February, 2004. The passage of the spacecraft was from north to south, and observations of the Jovian radio waves were carried out for a few months from high to low latitudes (+80° to +10°) of Jupiter. The statistical study performed during this "distant encounter" event provided the occurrence characteristics of the Jovian broadband kilometric radiation (bKOM), including the high-latitude component as follows: (1) the emission intensity of bKOM was found to have a sinusoidal dependence with respect to the central meridian longitude (CML), showing a broad peak at ˜180°, (2) bKOM was preferably observed in the magnetic latitudinal range from ˜+30° to +90°, and the emission intensities at the high latitudes were found to be two times larger than that at the equatorial region, and (3) the emission intensity was controlled possibly by the sub solar longitude (SSL) of Jupiter. The intensity had a sharp peak around SSL ˜210°. A 3D ray tracing approach was applied to the bKOM in order to examine the source distribution. It was suggested that: (1) the R-X mode waves generated through the Cyclotron Maser Instability process would be unable to reproduce the intense high-latitude component of the bKOM, (2) the L-O mode, which was assumed to be generated at frequencies near the local plasma frequency, was considered to be the dominant mode for past and present observations at mid- and high-latitudinal regions, and (3) the high-latitude component of bKOM was found to have a source altitude of 0.9-1.5 Rj (Rj: Jovian radii), and to be distributed along magnetic field lines having L>10.

Kimura, Tomoki; Tsuchiya, Fuminori; Misawa, Hiroaki; Morioka, Akira; Nozawa, Hiromasa

2008-06-01

255

ELMO Bumpy Torus data base  

SciTech Connect

This document describes a set of computer programs developed to facilitate storage and retrieval of data generated by the ELMO Bumpy Torus (EBT) experiment. The data is stored in a collection of files which contain either raw or analyzed data from diagnostics connected to the experiment. An on-line index of steady-state machine conditions, diagnostic or analysis status information, and raw or analyzed data values unifies the file collection into a data base. The index is implemented under the System 1022 data base management system.

Stanton, J.S.

1981-03-01

256

Analysis of Jovian decametric data: Study of radio emission mechanisms  

NASA Astrophysics Data System (ADS)

The Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) have produced the finest set of Jovian decametric radio emission data ever obtained. Jovian decametric L-burst and S-burst arcs were characterized and the data reconciled with models for the radio emission geometry and mechanisms. The first major results involve comparisons of the distribution of arc separations with longitudes. The identification and analyses of systematic variations in the PRA data have yielded interesting results, but only the most obvious features of the data were examined. Analyses of the PRA data were extended with the use of new 6-Sec formats that are more sensitive to the S-bursts.

Staelin, D. H.; Arias, T. A.; Garnavich, P. M.; Rosenkranz, P. W.

1985-01-01

257

Wavelet Analysis of Jovian Stratospheric Temperatures  

NASA Astrophysics Data System (ADS)

Breaking gravity waves are expected to be important in the energy and momentum budgets of the stratospheres of Titan and the jovian planets (e.g., French and Gierasch 1974, JAS 31, 1701; Roques et al. 1994, A&A 288, 985; Young et al. 2001, Icarus, in press), based on temperature fluctuations seen in profiles derived from stellar occultations or the Galileo ASI. Fourier analyses (Cooray et al. 1998, Icarus 132, 298; Sicardy et al. 1999, Icarus 142, 357, Young et al. 2001, in prep) show that these fluctuations have the same power-law dependence on vertical wavenumber as those observed in the Earth's atmosphere (Allen & Vincent 1995, JGR 100, 1327) or predicted theoretically (Smith et al. 1987, JAS 44, 1404; Hines 1991, JAS 48, 1360), supporting the gravity-wave interpretation. However, Fourier analysis is poor at describing local behavior. For this reason, wavelets (localized in both space and wavenumber) are often used to study turbulence and gravity waves (e.g., Sato and Yamada 1994, JGR 99, 20623; Yamada & Ohkitani 1991, Prog. Theor. Phys. 86, 799; Farge et al. 2001, Phys. Rev. Lett. 87, 054501). Wavelet decomposition of stellar occultation data can be accompished by first describing the refractivity as a product of an exponential and a sum of wavelet purturbations, and then generating model lightcurves. Furthermore, a wavelet decomposition approach to modeling stellar occultations maintains the flexibility of inversion techniques (by not assuming an a priori functional form), and the rigor of forward modeling (by including effects such as finite star size and wave optics). This work was supported in part by grants from NASA's PG&G and Planetary Atmospheres programs.

Young, L. A.

2001-11-01

258

Cassini and Wind stereoscopic observations of Jovian nonthermal radio emissions: Measurement of beam widths  

NASA Astrophysics Data System (ADS)

During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January the Jovian longitude difference between the two spacecraft was about 5°, whereas for the August-September Earth flyby of Cassini, the angle ranged from 0° to about 2.5° (the Jovicentric latitudinal difference was <0.3° during both intervals). With these separations the instantaneous widths of the walls of the hollow conical radiation beams of some of the decametric arcs were measured by cross correlating dynamic spectra. The results suggest that the typical width is approximately 1.5°+/-0.5°. The conical beams seem to move at Io's revolution rate for Io-controlled arcs. Additionally, some of the nonarc hectometric wavelength emissions show some properties of both wide and very narrow beam widths.

Kaiser, M. L.; Zarka, P.; Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.

2000-07-01

259

Minimisation of the Hydrogenic Inventory of the ITER Neutral Beamline and Torus Cryo-Sorption Pumps  

SciTech Connect

The tritium inventory of all the ITER torus cryopumps open to the vacuum vessel has an administrative limit of 120 g, including tritium bound to hydrocarbon compounds formed by combination of fuel gas with carbon plasma-facing components. The total hydrogenic inventory of each of the torus cryopumps has to be less than that resulting in a deflagration pressure of 0.2 MPa (the design pressure of the ITER vacuum vessel of which the torus and neutral beam cryopump pressure boundaries are a part) following a hydrogen-air ignition. Since the neutral beamline fuelling is with protium and deuterium only, these pumps do not significantly contribute to the 120 g tritium limit. The hydrogenic inventories of both the torus and neutral beam cryopumps add to the total for the vacuum vessel following an in-vessel ingress of coolant from a failed water-cooled component, wherein hydrogen is produced from steam reacting with hot metallic dust. There is therefore a large incentive to keep the peak inventories of both the torus and neutral beamline cryopumps as low as practicable. The paper describes the regeneration patterns of the torus and neutral beamline cryopumps that are used to attain this goal while achieving the required vacuum conditions commensurate with the reference ITER pulse scenarios.

Wykes, M

2005-07-15

260

Polarization measurements of Jovian radio emissions at high-magnetic latitudes observed by Ulysses spacecraft  

NASA Astrophysics Data System (ADS)

In early 2004, the Unified Radio And Plasma wave (URAP) experiment onboard Ulysses measured the Stokes parameters of Jovian kilometric radiations at northern high-latitudes during the "distant encounter" flyby. Ulysses observed from more than +80 deg to less than +10 deg of Jovicentric latitude for several months. The observation indicated that quasi-periodic (QP) bursts and narrowband kilometric emissions (nKOM) have LH polarization (V~+1). Therefore, we conclude that these emissions are LO mode waves. This is consistent with several previous observations at low-latitudes (~0 deg) and mid-latitudes (~-40 deg) (e.g., Daigne and Leblanc, 1986; MacDowall et al., 1993). On the other hand, it was shown that broadband kilometric radiations (bKOM) have RH polarization (V~-1) at high-latitudes. This result does not agree with our previous study based on the combination of observed location of bKOM and ray tracing, which showed these emissions as LO mode waves (Kimura et al., 2008). We confirmed by additional ray tracing analyses that a solution can allow LO mode waves to be observed with RH polarization at high-latitudes. This result would constrain generation and propagation processes for Jovian radio components observed at high-latitudes.

Kimura, T.; MacDowall, R. J.; Hess, R. A.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2009-04-01

261

Polarization measurements of Jovian radio emissions at high-magnetic latitudes observed by Ulysses spacecraft  

NASA Astrophysics Data System (ADS)

In early 2004, the Unified Radio And Plasma wave (URAP) experiment onboard Ulysses measured the Stokes parameters of Jovian kilometric radiations at northern high-latitudes during the "gdistant encounter"h flyby. Ulysses observed from more than +80 deg to less than +10 deg of Jovicentric latitude for several months. The observation indicated that quasi-periodic (QP) bursts and narrowband kilometric emissions (nKOM) have LH polarization (V~+1). Therefore, we conclude that these emissions are LO mode waves. This is consistent with several previous observations at low-latitudes (~0 deg) and mid-latitudes (~-40 deg) (e.g., Daigne and Leblanc, 1986; MacDowall et al., 1993). On the other hand, it was shown that broadband kilometric radiations (bKOM) have RH polarization (V~-1) at high-latitudes. This result does not agree with our previous study based on the combination of observed location of bKOM and ray tracing, which showed these emissions as LO mode waves (Kimura et al., 2008). We confirmed by additional ray tracing analyses that a solution can allow LO mode waves to be observed with RH polarization at high-latitudes. This result would constrain generation and propagation processes for Jovian radio components observed at high-latitudes.

Kimura, T.; MacDowall, R. J.; Hess, R. A.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2008-12-01

262

Plasmadynamic hypervelocity dust injector for the National Spherical Torus Experiment  

SciTech Connect

The design and construction of a plasmadynamic device to accelerate dust to hypervelocities is presented. High speed dust will be used to measure magnetic field lines in the National Spherical Torus Experiment. The plasma gun produces a high density (n{sub e}{approx_equal}10{sup 18} cm{sup -3}) and low temperature (a few eV) deuterium plasma, ejected by JxB forces which provide drag on the dust particles in its path. The dust will be entrained by the plasma to velocities of 1-30 km/s, depending on the dust mass. Carbon dust particles will be used, with diameters from 1 to 50 {mu}m. The key components of the plasmadynamic accelerator are a coaxial plasma gun operated at 10 kV (with an estimated discharge current of 200 kA), a dust dispenser activated by a piezoelectric transducer, and power and remote-control systems.

Ticos, Catalin M.; Wang Zhehui; Dorf, Leonid A.; Wurden, Glen A. [Plasma Physics Group P-24, Magnetized Fusion Energy Team, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-10-15

263

Modeling the Interaction of Europa with the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

The interaction of Jupiter's corotating magnetosphere with Europa's subsurface water ocean is responsible for the observed induced dipolar magnetic field. Furthermore the pick-up process of newly ionized particles from Europa's neutral atmosphere alters the magnetic and electric field topology around the moon. We use the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) of the Space Weather Modeling Framework (SWMF) to model the interaction of Europa with the Jovian magnetosphere. The BATS-R-US code solves the governing equations of magnetohydrodynamics (MHD) in a fully 3D adaptive mesh. In our approach we solve the equations for one single ion species, starting from the work by Kabin et al. (J. Geophys. Res., 104, A9, 19983-19992, 1999) accounting for the exospheric mass loading, ion-neutral charge exchange, and ion-electron recombination. We continue by separately solving the electron pressure equation and furthermore extend the magnetic induction equation by the resistive and Hall terms. The resistive term accounts for the finite electron diffusivity and thus allows a more adequate description of the effect of magnetic diffusion due to collisions [Ledvina et al., Sp. Sci. Rev., 139:143-189, 2008]. For this purpose we use ion-electron and electron-neutral collision rates presented by Schunk and Nagy (Ionospheres, Cambridge University Press, 2000). The Hall term allows ions and electrons to move at different velocities while the magnetic field remains frozen to the electrons. The assumed charge neutrality of the ion-electron plasma is maintained everywhere at all times. The model is run at different phases of Jupiter's rotation reflecting the different locations of Europa with respect to the center of the plasma sheet and is compared to measurements obtained by the Galileo magnetometer [Kivelson et al., J. Geophys. Res., 104:4609-4626, 1999]. The resulting influence on the induced magnetic dipolar field is studied and compared to the results from the different Galileo fly-bys. We will show preliminary results of this work with application to future missions to the Jupiter-Europa system.

Rubin, M.; Combi, M. R.; Daldorff, L.; Gombosi, T. I.; Hansen, K. C.; Jia, X.; Kivelson, M. G.; Tenishev, V.

2011-12-01

264

Electron Acceleration by Plasma Waves in the Io Flux Tube  

NASA Astrophysics Data System (ADS)

Io's interaction with the jovian magnetosphere generates auroral and radio emissions. The underlying electron acceleration process is not well understood and only few observations exist to constrain the theoretical models. The Galileo spacecraft made a number of low altitudes passes near Io and the plasma wave/particle instruments have collected new information. The source of energy for the electron acceleration is in all likelihood supplied from the Alfvén wings that stretch out from both poles of Io into the two Jovian hemispheres. Here we will present observations that help understand how the electromagnetic energy in the Alfvén wings is transformed into particle acceleration. In particular, intense electromagnetic waves at frequencies up to several times the local proton gyrofrequency have been observed while Galileo was passing over the south and north poles of Io (flybys I25 and I31, respectively). Hot and warm parallel electron beams have been observed during the I0 and I27 flybys, respectively. For some technical reason no particles instrument was on during I25. At the time that this abstract is written data are not yet available from the I32 south polar pass but observations similar to those obtained during the I25 and I31 flybys are expected. We suggest the following three-steps acceleration process: (1) Due to the strongly inhomogeneous conductivity of Io's ionosphere, the currents flowing along the Alfvén wings are distributed inside the whole Alfvén tube and not only on its surface. (2) As the plasma density of the Io torus decreases with increasing latitude, the currents of the Alfvén wings become strongly unstable for "high-frequency/small scale" electromagnetic waves. (3) The current driven "high-frequency/small-scale" waves generated in the direction of Jupiter which are not reflected at the boundary of the Io torus, are able to accelerate efficiently magnetospheric electrons by Landau resonance, up to the required energies and flux. The observation of electron beams during the flyby I31 (and I32) would provide a critical test for this interpretation.

Chust, T.; Roux, A.; Kurth, W. S.; Gurnett, D. A.

2001-12-01

265

The systematic calculation of adiabatic structure of Jovian planet atmospheres  

Microsoft Academic Search

We investigate vertical profiles of adiabatic lapse rate, amount of condensed species, and static stability of the Jovian planet atmospheres by using a newly developed calculation method. Our method consists of three procedures as follows: (1) equilibrium composition is calculated by minimizing Gibbs free energy for various temperatures and pressures, (2) entropy is calculated for the equilibrium composition, and (3)

K. Sugiyama; M. Odaka; K. Kuramoto; Y.-Y. Hayashi

2002-01-01

266

Infrared Spectroscopic Studies of the Jovian Ionsophere and Aurorae  

NASA Astrophysics Data System (ADS)

We review recent spectroscopic studies of the ionosphere of Jupiter. These demonstrate the importance of the H3+ molecular ion in understanding not only the ion-molecule chemistry of the jovian upper atmosphere, but of its energetics and dynamics as well. Comparisons are made with a new three-dimensional, global circulation model of Jupiter's ionosphere and thermosphere, JIM.

Miller, S.; Rego, D.; Achilleos, N.; Stallard, T. S.; Prangé, R.; Dougherty, M.; Joseph, R. D.; Tennyson, J.; Aylward, A.; Meuller-Wodarg, I.; Rees, D.

267

Surface History and Evolution of Small Jovian Trojans  

Microsoft Academic Search

We propose to measure the albedo distribution of the Jovian Trojan asteroids that populate the small end of the known population (4 to 7 km radius). The overarching goal is to (a) understand the collisional and surficial evolution of these objects, and (b) study the connection between these relatively primitive asteroids and the similarly primitive comets. The proposed observations will

Yanga Fernandez; David Jewitt

2004-01-01

268

Io as a source of the jovian dust streams  

Microsoft Academic Search

Streams of dust emerging from the direction of Jupiter were discovered in 1992 during the flyby of the Ulysses spacecraft, but their precise origin within the jovian system remained unclear. Further data collected by the Galileo spacecraft, which has been orbiting Jupiter since December 1995, identified the possible sources of dust as Jupiter's main ring, its gossamer ring, comet Shoemaker-Levy

A. L. Graps; E. Grün; H. Svedhem; H. Krüger; M. Horányi; A. Heck; S. Lammers

2000-01-01

269

Jovian Dust Streams Revisited - Cassini Dust Detector At Jupiter  

NASA Astrophysics Data System (ADS)

Both, the dust detectors on board the Galileo spacecraft and the Ulysses spacecraft recorded within about 1 AU from Jupiter, periodic bursts of dust impacts, with periods of about 28 days, originating from the Jovian system. Furthermore, time- frequency analysis of impact data recorded by the Galileo instrument inside the Jovian system revealed that the dust streams are also modulated with harmonics of Jupiter's orbital period. This indicates that the stream particles are strongly interacting with the inclined Jovian magnetic field. Current theoretical models of the grain- field interaction lead to grain speeds of about 300 km/s and grain sizes of about 10 nm. Stream particles were also recorded by the dust instrument on board of the Cassini spacecraft when Cassini was approaching Jupiter in 2000. Although the Cassini dust instrument is in many aspects superior to its progenitors the measurements were strongly affected by the fixed instrument mounting. First data analysis indicates that the Cassini instrument observed dust streams moving through the instrument field of view on very short time scales. Furthermore, we will present evidence that the instru- ment recorded 2 streams at the same time having different angles with respect to the Jovian line of sight. Such effects are most likely caused by the interaction of the grains with the interplanetary magnetic field.

Kempf, S.; Srama, R.; Gün, E.; Krüger, H.; Burton, M.; Cda Team

270

Particles, environments and possible ecologies in the Jovian atmosphere  

Microsoft Academic Search

The eddy diffusion coefficient is estimated as a function of altitude, separately for the Jovian troposphere and mesosphere. Complex organic molecules produced by the Ly alpha photolysis of methane may possibly be the absorbers in the lower mesosphere which account for the low reflectivity of Jupiter in the near ultraviolet. The optical frequency chromophores are localized at or just below

C. Sagan; E. E. Salpeter

1976-01-01

271

Probabilistic models of the Jovian magnetopause and bow shock locations  

Microsoft Academic Search

[1] New three-dimensional models of the Jovian magnetopause and bow shock were derived by combining spacecraft observations with boundary characteristics inferred from a magnetohydrodynamic (MHD) simulation. The MHD simulation provides polynomial forms parameterized by solar wind dynamic pressure. Observations from Pioneer 10 and 11, Voyager 1 and 2, Ulysses, and Galileo were used to establish the probability that regions surrounding

S. P. Joy; M. G. Kivelson; R. J. Walker; K. K. Khurana; C. T. Russell

272

Analysis of Jovian decamteric data: Study of radio emission mechanisms  

NASA Astrophysics Data System (ADS)

This research effort involved careful examination of Jovian radio emission data below 40 MHz, with emphasis on the informative observations of the Planetary Radio Astronomy experiment (PRA) on the Voyager 1 and 2 spacecraft. The work is divided into three sections, decametric arcs, decametric V bursts, and hectometric modulated spectral activity (MSA).

Staelin, D. H.; Rosenkranz, P. W.; Arias, T. A.; Garnavich, P. N.; Hammerschlag, R.

1986-08-01

273

Wormholes in chemical space connecting torus knot and torus link pi-electron density topologies.  

PubMed

Möbius aromaticities can be considered as deriving from cyclic delocalized pi-electron densities rho(r)(pi) which have the topological form of either a two-component torus link or a single-component torus knot. These two topological forms are distinguished by their (non-zero) linking number L(k), which describes how many times the two components of a torus link cross each other or the single component of a torus knot crosses with itself. The special case of Hückel or benzenoid aromaticity is associated with a pi-electron density that takes the form of a two-component torus link for which the linking number is zero. A class of molecule has been identified which here is termed a Janus aromatic, and which bears the characteristics of both a two-component torus link and a single-component torus knot in the topology of the pi-electron density. This is achieved by the formation of one (or more) wormholes or throats in the pi-electron density connecting the two torus forms, which can impart a Janus-like dual personality to the aromaticity of the system. The impact of such wormholes on the overall pi-delocalized aromaticity of such molecules is approximately estimated using a NICS(rcp) index, and subdivides into two types; those where the forms of aromaticity associated with a torus link and a torus knot cooperate and those where they oppose. PMID:19224034

Rzepa, Henry S

2009-01-13

274

WISE/NEOWISE OBSERVATIONS OF THE JOVIAN TROJAN POPULATION: TAXONOMY  

SciTech Connect

We present updated/new thermal model fits for 478 Jovian Trojan asteroids observed with the Wide-field Infrared Survey Explorer (WISE). Using the fact that the two shortest bands used by WISE, centered on 3.4 and 4.6 {mu}m, are dominated by reflected light, we derive albedos of a significant fraction of these objects in these bands. While the visible albedos of both the C-, P-, and D-type asteroids are strikingly similar, the WISE data reveal that the albedo at 3.4 {mu}m is different between C-/P- and D-types. The albedo at 3.4 {mu}m can thus be used to classify the objects, with C-/P-types having values less than 10% and D-types have values larger than 10%. Classifying all objects larger than 50 km shows that the D-type objects dominate both the leading cloud (L {sub 4}), with a fraction of 84%, and trailing cloud (L {sub 5}), with a fraction of 71%-80%. The two clouds thus have very similar taxonomic distribution for these large objects, but the leading cloud has a larger number of these large objects, L {sub 4}/L {sub 5} = 1.34. The taxonomic distribution of the Jovian Trojans is found to be different from that of the large Hildas, which is dominated by C- and P-type objects. At smaller sizes, the fraction of D-type Hildas starts increasing, showing more similarities with the Jovian Trojans. If this similarity is confirmed through deeper surveys, it could hold important clues to the formation and evolution of the two populations. The Jovian Trojans does have similar taxonomic distribution to that of the Jovian irregular satellites, but lacks the ultra red surfaces found among the Saturnian irregular satellites and Centaur population.

Grav, T. [Planetary Science Institute, Tucson, AZ 85719 (United States); Mainzer, A. K.; Bauer, J. M.; Masiero, J. R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Nugent, C. R., E-mail: tgrav@psi.edu [Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095 (United States)

2012-11-01

275

Tracking people on a torus.  

PubMed

We present a framework for monocular 3D kinematic pose tracking and viewpoint estimation of periodic and quasi-periodic human motions from an uncalibrated camera. The approach we introduce here is based on learning both the visual observation manifold and the kinematic manifold of the motion using a joint representation. We show that the visual manifold of the observed shape of a human performing a periodic motion, observed from different viewpoints, is topologically equivalent to a torus manifold. The approach we introduce here is based on the supervised learning of both the visual and kinematic manifolds. Instead of learning an embedding of the manifold, we learn the geometric deformation between an ideal manifold (conceptual equivalent topological structure) and a twisted version of the manifold (the data). Experimental results show accurate estimation of the 3D body posture and the viewpoint from a single uncalibrated camera. PMID:19147879

Elgammal, Ahmed; Lee, Chan-Su

2009-03-01

276

Combinatorial quantisation of the Euclidean torus universe  

NASA Astrophysics Data System (ADS)

We quantise the Euclidean torus universe via a combinatorial quantisation formalism based on its formulation as a Chern-Simons gauge theory and on the representation theory of the Drinfel'd double DSU(2). The resulting quantum algebra of observables is given by two commuting copies of the Heisenberg algebra, and the associated Hilbert space can be identified with the space of square integrable functions on the torus. We show that this Hilbert space carries a unitary representation of the modular group and discuss the role of modular invariance in the theory. We derive the classical limit of the theory and relate the quantum observables to the geometry of the torus universe.

Meusburger, C.; Noui, K.

2010-12-01

277

Reactor assessments of advanced bumpy torus configurations  

SciTech Connect

Recently, several configurational approaches and concept improvement schemes were introduced for enhancing the performance of the basic ELMO Bumpy Torus (EBT) concept and for improving its reactor potential. These configurations include planar racetrack and square geometries, Andreoletti coil systems, and bumpy torus-stellarator hybrids (which include twisted racetrack and helical axis stellarator-snakey torus). Preliminary evaluations of reactor implications of each of these configurations have been carried out based on magnetics (vacuum) calculations, transport and scaling relationships, and stability properties. Results indicate favorable reactor projections with a significant reduction in reactor physical size as compared to conventional EBT reactor designs carried out in the past.

Uckan, N.A.; Owen, L.W.; Spong, D.A.; Miller, R.L.; Ard, W.B.; Pipkins, J.F.; Schmitt, R.J.

1983-01-01

278

Random Walks as Motions on the Torus  

NASA Astrophysics Data System (ADS)

Introducing motions with variable inclinations on the torus, we intend to treat random walks as stochastic-type motions on the torus. Compared with the probability density for sojourn time of the classical harmonic oscillator, the limiting density for random walks becomes also uniform on the torus if we define new variables. The famous aresine law can be interpreted in terms of new variables and its paradoxical feature disappears. This fact suggests that we can interprete other seemingly curious phenomena in the probability theory in terms of dynamical system.

Sabata, Hideki

1981-05-01

279

New Capabilities and Results for the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) produces plasmas with toroidal aspect ratio as low as 1.25, which can be heated by up to 6 MW High-Harmonic Fast Waves and up to 7 MW of deuterium Neutral Beam Injection. Using new poloidal fields coils, plasmas with cross-section elongation up to 2.7, triangularity 0.8, plasma currents Ip up to 1.5 MA and normalized currents Ip/a?BT up to 7.5 MA/m?T have been achieved. A significant extension of the plasma pulse length, to 1.5 s at a plasma current of 0.7 MA, has been achieved by exploiting the bootstrap and NBI-driven currents to reduce the dissipation of poloidal flux. Inductive plasma startup has been supplemented by Coaxial Helicity Injection (CHI) and the production of persistent current on closed flux surfaces by CHI has now been demonstrated in NSTX. The plasma response to magnetic field perturbations with toroidal mode numbers n = 1 or 3 and the effects on the plasma rotation have been investigated using three pairs of coils outside the vacuum vessel. Recent studies of both MHD stability and of transport benefitted from improved diagnostics, including measurements of the internal poloidal field using the motional Stark effect (MSE). In plasmas with a region of reversed magnetic shear in the core, now confirmed by the MSE data, improved electron confinement has been observed.

M.G. Bell, R.E. Bell, D.A. Gates, S.M. Kaye, H. Kugel, B.P. LeBlanc, F.M. Levinton, R. Maingi, J.E. Menard, R. Raman, S.A. Sabbagh, D. Stutman and the NSTX Research Team

2008-02-29

280

Fast Acting Ionization Vacuum Gauge for JIPP T-II Torus.  

National Technical Information Service (NTIS)

The torus JIPP T-II in Institute of Plasma Physics is a composite device of stellarator and Tokamak, being operated as Tokamak at present. In present Tokamak type discharge, a technic of pulsed gas injection by puffing during discharge has been developed,...

S. Kato S. Tanahashi K. Azumai T. Ito K. Matsuura

1978-01-01

281

Summary of TFTR (Tokamak Fusion Test Reactor) diagnostics, including JET (Joint European Torus) and JT-60  

Microsoft Academic Search

The diagnostic instrumentation on TFTR (Tokamak Fusion Test Reactor) and the specific properties of each diagnostic, i.e., number of channels, time resolution, wavelength range, etc., are summarized in tables, grouped according to the plasma parameter measured. For comparison, the equivalent diagnostic capabilities of JET (Joint European Torus) and the Japanese large tokamak, JT-60, as of late 1987 are also listed

K. W. Hill; K. M. Young; L. C. Johnson

1990-01-01

282

Maintenance Method for Tokamak Fusion Reactors with Downward Access to Torus Inboard Structures  

Microsoft Academic Search

A concept of tokamak fusion reactor maintenance is presented. Reactor structures and maintenance machines are arranged so that the component inside a shielding structure can be replaced through the hatches located on the upper side of the torus shielding structure. The plasma vacuum boundary is constituted by the inside wall of the shielding structure. The magnet vacuum chamber contains two

Yoshio GOMAY; Takataro HAMAJIMA; Tsutomu HONDA; Kazunori KITAMURA; Tadashi MUNAKATA; Takao UCHIDA; Mitsugi YAMAGUCHI; Harumi YAMATO; Kiyoshi SAKO; Hiromasa IIDA

1981-01-01

283

Plasma conditions and the structure of the Jovian ring  

Microsoft Academic Search

We explore the dynamics of small charged dust particles in Jupiter's innermost magnetosphere and show that the systematic charge variation of the grains results in surprisingly short lifetimes. Assuming a constant production of small dust particles via continual micrometeoroid bombardment of the larger parent bodies of the main ring, this model reproduces remote sensing observations of the ring\\/halo region at

Mihály Horányi; Antal Juhász

2010-01-01

284

Plasma conditions and the structure of the Jovian ring  

NASA Astrophysics Data System (ADS)

We explore the dynamics of small charged dust particles in Jupiter's innermost magnetosphere and show that the systematic charge variation of the grains results in surprisingly short lifetimes. Assuming a constant production of small dust particles via continual micrometeoroid bombardment of the larger parent bodies of the main ring, this model reproduces remote sensing observations of the ring/halo region at Jupiter made by Voyager, Galileo, Cassini, and New Horizons spacecraft and observations from the ground by the Keck telescope during ring plane crossings. We use this model to make predictions for the dust impact rates for the JUNO mission, which is expected to traverse this region multiple times starting in 2016.

Horányi, Mihály; Juhász, Antal

2010-09-01

285

Pitch angle diffusion by whistler mode waves in the jovian magnetosphere and diffuse auroral precipitation  

NASA Astrophysics Data System (ADS)

Bounce-averaged pitch angle diffusion rates of electrons due to whistler mode waves have been calculated in the Jupiter's magnetosphere. Variations of electron density, magnetic field, wave intensity and upper cut-off frequency along the particle bounce trajectory have been taken into account. Field line tracing is performed to obtain the loss-cone size associated with the VIP 4 magnetic field model including the external field due to azimuthal current sheet. Numerical calculations have been carried out at L shells 10, 12, 15, 18, and 20. The longitudinal variations of electron energy precipitation into the atmosphere leading to diffuse aurora have been modelled. It is found that observed wave amplitudes at L ? 15 are insufficient to put electrons on strong pitch angle diffusion whereas at L = 18 and 20 electrons of energies ?30 keV can be put on strong diffusion. At L = 10 electron energy precipitation supports auroral brightness of 25 kR in the northern and 36 kR in the southern hemisphere at west longitude ˜10-60°. At shells L = 12 and 15 auroral brightness less than 10 kR is obtained. This is in accord with Voyager observation of jovian UV aurora just beyond the Io torus (7-12RJ). At L = 18 maximum auroral brightness 73 kR in the northern hemisphere at west longitude of 163° and 30 kR in the southern hemisphere for west longitudes ?50° are obtained. This is in agreement with the diffuse auroral brightness measured by Hubble Space Telescope (HST). Observations of longitudinal variation of diffuse auroral brightness are, however, required to ascertain the present findings.

Tripathi, A. K.; Singhal, R. P.; Singh, K. P.; Singh, O. N.

2013-07-01

286

Ion cyclotron waves in the Io torus: Wave dispersion, free energy analysis, and SO 2 + source rate estimates  

Microsoft Academic Search

As the Galileo spacecraft passed through the I0 torus, ion cyclotron waves were observed near the sulfur dioxide ion gyrofrequency. The toms plasma is continually replenished by the ionization of neutral particles from I0. It is well known that sulfur dioxide dissociates rapidly, so that the corotating toms plasma consists of predominantly sulfur and oxygen ions. However, for the small

D. E. Huddleston; R. J. Strangeway; J. Warnecke; C. T. Russell; M. G. Kivelson

1998-01-01

287

Jovian X-Ray Aurora and Energetic Oxygen Ion Precipitation  

SciTech Connect

The X-ray line spectra of highly charged oxygen ions excited by charge transfer interaction with the molecular hydrogen in the auroral atmosphere of Jupiter are calculated. The calculations utilize our calculated cross sections of state-selective charge transfer and the available cross-section data of ionization and stripping. Comparison of these spectra with high-resolution spectral observations may provide a sensitive probe of the characteristics of the heavy ions precipitating into the Jovian auroral atmosphere. On the basis of the much higher X-ray efficiency of heavy ions than of electrons, it is concluded that the Jovian aurora may be accounted for by a combination of energetic heavy-ion precipitation and energetic electron precipitation, which produces the auroral X-ray and ultraviolet emissions, respectively. (c) (c) 1999. The American Astronomical Society.

Liu, Weihong; Schultz, D. R.

1999-11-20

288

Ultraviolet Emission from Oxygen Precipitating into Jovian Aurora  

SciTech Connect

The ultraviolet emission-line spectra of precipitating oxygen atoms and ions excited by charge transfer interaction with the molecular hydrogen in the auroral atmosphere of Jupiter are calculated using our computed cross sections of state-selective charge transfer. The charge transfer processes preferentially populate the ground states of neutral oxygen and low-charge ions and the highly excited states of high-charge ions, yielding low UV and high X-ray efficiencies, respectively. Much weaker than the underlying emission spectrum of H2 excited by energetic electron precipitation, the UV emission from oxygen is not expected to be discernible in the Jovian auroral spectrum. This reconciles the absence of UV emission with the presence of X-ray emission from the heavy ions precipitating in the Jovian aurora. (c) (c) 2000. The American Astronomical Society.

Liu, Weihong; Schultz, D. R.

2000-02-10

289

Theoretical predictions of deuterium abundances in the Jovian planets  

SciTech Connect

Current concepts for the origin of the Jovian planets and current constraints on their interior structure are used to support the argument that the presence of large amounts of 'ice' (H2O, CH4, and NH3) in Uranus and Neptune indicates temperature low enough to condense these species at the time Uranus and Neptune formed. Such low temperatures, however, imply orders-of-magnitude fractionation effects for deuterium into the 'ice' component if isotopic equilibration can occur. The present models thus imply that Uranus and Neptune should have D/H ratio at least four times primordial, contrary to observation for Uranus. It is found that the Jovian and Saturnian D/H should be close to primordial regardless of formation scenario.

Hubbard, W.B.; MacFarlane, J.J.

1980-01-01

290

Divine-Garrett Model and Jovian synchrotron emission  

NASA Astrophysics Data System (ADS)

Simulations of synchrotron emission from relativistic electrons trapped in Jupiter's magnetic field are used to evaluate the energetic electron distribution of the Divine-Garrett Jupiter radiation belt model at radial distances less than 4 Jovian radii. The fundamental characteristic of synchrotron emission, narrow beaming from gyrating electrons, provides the basis for constraints on both the magnetic field and the distribution of particles in the inner magnetosphere. A comparison between model results and observations is presented. The results suggest the Divine Garrett model significantly underestimates the number of relativistic electrons (>1 MeV) present in Jupiter's inner magnetosphere. The results also indicate that the pitch angle distribution of relativistic electrons in the Jovian radiation belts is different than assumed in the Divine-Garrett model. These results have important implications for the development of self-consistent models of Jupiter's magnetosphere and the planning of future missions requiring close flybys of Jupiter.

Bolton, Scott J.; Levin, Steven M.; Gulkis, Samuel L.; Klein, Michael J.; Sault, Robert J.; Bhattacharya, Bidushi; Thorne, Richard M.; Dulk, George A.; Leblanc, Yolande

291

Jovian H2 dayglow emission (1978-1989)  

NASA Astrophysics Data System (ADS)

The IUE data set accumulated through 10 years of Jovian equatorial observations is used to measure the long-term temporal variation of the H2 dayglow emission. The model that best fits the data indicates a possible correlation between long-term solar activity and the Jovian H2 emission in the region 1500-1700 A between 1978 and 1989, which spans the decline in solar activity for solar cycle 21 and the rise in solar activity accompanying solar cycle 22. The magnitude of the observed variation is closer to that of the solar Ly-alpha flux than the 10.7 cm radio flux. Short-wavelength H2 band emission intensity is inconsistent with the amount of long-wavelength emission but may be reconciled if relatively low-energy excitation or fluorescence of solar radiation is invoked. No persistent longitudinal feature analogous to the H I Ly-alpha can be identified.

McGrath, M. A.; Ballester, G. E.; Moos, H. W.

1990-07-01

292

Initial physics results from the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a~=1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of high harmonic fast wave (HHFW) heating and current drive, 5 MW of neutral beam injection (NBI) and co-axial helicity injection (CHI) for noninductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high ?t and high-bootstrap current fraction, and to develop methods for noninductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA and with a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit, respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 ms was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and ?t=21% were produced.

Kaye, S. M.; Bell, M. G.; Bell, R. E.; Bialek, J.; Bigelow, T.; Bitter, M.; Bonoli, P.; Darrow, D.; Efthimion, P.; Ferron, J.; Fredrickson, E.; Gates, D.; Grisham, L.; Hosea, J.; Johnson, D.; Kaita, R.; Kubota, S.; Kugel, H.; Leblanc, B.; Maingi, R.; Manickam, J.; Mau, T. K.; Maqueda, R. J.; Mazzucato, E.; Menard, J.; Mueller, D.; Nelson, B.; Nishino, N.; Ono, M.; Paoletti, F.; Paul, S.; Peng, Y.-K. M.; Phillips, C. K.; Raman, R.; Ryan, P.; Sabbagh, S. A.; Schaffer, M.; Skinner, C. H.; Stutman, D.; Swain, D.; Synakowski, E.; Takase, Y.; Wilgen, J.; Wilson, J. R.; Zhu, W.; Zweben, S.; Bers, A.; Carter, M.; Deng, B.; Domier, C.; Doyle, E.; Finkenthal, M.; Hill, K.; Jarboe, T.; Jardin, S.; Ji, H.; Lao, L.; Lee, K. C.; Luhmann, N.; Majeski, R.; Medley, S.; Park, H.; Peebles, T.; Pinsker, R. I.; Porter, G.; Ram, A.; Rensink, M.; Rognlien, T.; Stotler, D.; Stratton, B.; Taylor, G.; Wampler, W.; Wurden, G. A.; Xu, X. Q.; Zeng, L.

2001-05-01

293

Physics results from the National Spherical Torus Experiment  

SciTech Connect

The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a {approx} 1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of High Harmonic Fast Wave (HHFW) heating and current drive, 5 MW of Neutral Beam Injection (NBI), and Co-Axial Helicity Injection (CHI) for non-inductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high-{beta}{sub t} and high-bootstrap current fraction, and to develop methods for non-inductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA, stored energies up to 55 kJ, {beta}{sub t} {approx} 10%, and a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 msec was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and {beta}{sub t}=21% were produced.

Kaye, S.; Bell, M. [and others

2000-11-01

294

Initial Physics Results From the National Spherical Torus Experiment  

SciTech Connect

The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a approximately equal to 1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of High Harmonic Fast Wave (HHFW) heating and current drive, 5 MW of Neutral Beam Injection (NBI) and Co-Axial Helicity Injection (CHI) for non-inductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high-bt and high-bootstrap current fraction, and to develop methods for non-inductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA and with a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 msec was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and bt =21% were produced.

Kaye, S.M.; Bell, M.G.; Bell, R.E.; Bialek, J. [and others

2001-01-03

295

JEREMI- Jovian Electron Radiation Environment for Mission Investigation  

NASA Astrophysics Data System (ADS)

In 1983, Divine and Garrett presented a model of charged particle distribution, between 1 eV and several MeV, in Jupiter magnetosphere. This model is based primarily on a few scattered in situ measurements returned by experiments on the Pioneer and Voyager spacecraft. More recently, new in-situ measurements acquire with new experiments like GALILEO EPD, and many other observations like synchrotron emission, for example, are available and are not taken into account in this model. On the other side, there is a physical model of Jovian electron radiation belts: Salammbo-3D (see the other abstract of the same authors in the same session). It is valid in the L range 1-9.5 and for energies included between a few hundreds of keV to several hundreds of MeV. Salammbo-3D is based on the understanding of major physical processes playing an important role in the Jovian trapped electron dynamics (moons, rings, synchrotron, etc.). This model is now mature enough to get very good agreement between simulations and observations (Pioneer, synchrotron observations). All elements are here to propose an updated Jovian electron belt model, JEREMI (Jovian Electron Radiation Environment for Mission Investigation). This is done by combining the two approaches described previously: - When Salammbo-3D is valid (in term of L range and energy range) it is considered in priority. - Otherwise the old Divine and Garrett model will be considered. In order to appreciate the progress with the JEREMI model, comparisons with in-flight measurements (Pioneer, Galileo) and with synchrotron observations (VLA) will be given considering JEREMI or Divine and Garrett models. Finally, flux estimation along a Jupiter Polar orbiter will be given with the two models.

Bourdarie, S.; Sicard, A.

2003-04-01

296

The systematic calculation of adiabatic structure of Jovian planet atmospheres  

NASA Astrophysics Data System (ADS)

We investigate vertical profiles of adiabatic lapse rate, amount of condensed species, and static stability of the Jovian planet atmospheres by using a newly developed calculation method. Our method consists of three procedures as follows: (1) equilibrium composition is calculated by minimizing Gibbs free energy for various temperatures and pressures, (2) entropy is calculated for the equilibrium composition, and (3) adiabatic curve dS = 0 is obtained by seeking the temperature and pressure relationship under which the value of entropy is conserved. The charcteristics of our method is that no information on the details of corresponding chemical reactions is needed. Therefore, one of the advantages of our method is that we do not have to modify the numerical code when we consider an atmosphere with a different set of elemental compositions and potential temperatures. In previous studies, the adiabatic profile of Jovian planet atmospheres has been obtained by direct calculation of entropy conservation for ascending air parcel according to given chemical reactions (Weidenschilling and Lewis, 1973, Icarus, 20 465--476). We estimate dependency of vertical profiles of adiabatic lapse rate, amount of condensed species, and static stability on elemental composition for each Jovian planet atmosphere. In this series of calculations, the initial abundances of condensable species are taken from the solar abundance to several ten times the solar. The results of these calculations systematically reveal the effect of atmospheric composition on structure of atmosphere, which are useful for consideration not only of vertical distribution of cloud layers, but also of dynamics of cloud convection within the Jovian planet atmospheres.

Sugiyama, K.; Odaka, M.; Kuramoto, K.; Hayashi, Y.-Y.

2002-09-01

297

A Nuclear Ramjet Flyer for Exploration of Jovian Atmosphere  

NASA Astrophysics Data System (ADS)

We investigated the design, operation, and data gathering possibilities of a nuclear-powered ramjet flyer in the Jovian atmosphere. The MITEE nuclear rocket engine can be modified to operate as a ramjet in planetary atmospheres. (Note: MITEE is a compact, ultra-light-weight thermal nuclear rocket which uses hydrogen as the propellant.) To operate as a ramjet, MITEE requires a suitable inlet and diffuser to substitute for the propellant that is pumped from the supply tanks in a nuclear rocket engine. Such a ramjet would fly in the upper Jovian atmosphere, mapping in detail temperatures, pressures, compositions, lightning activity, and wind speeds in the highly turbulent equatorial zone and the Great Red Spot. The nuclear ramjet could operate for months because: (1) the Jovian atmosphere has unlimited propellant, (2) the MITEE nuclear reactor is a (nearly) unlimited power source, and (3) with few moving parts, mechanical wear should be minimal. This paper presents a conceptual design of a ramjet flyer and its nuclear engine. The flyer incorporates a swept-wing design with instruments located in the twin wing-tip pods (away from the radiation source and readily shielded, if necessary). The vehicle is 2 m long with a 2 m wingspan. Its mass is 220 kg, and its nominal flight Mach number is 1.5. Based on combined neutronic and thermal/hydraulic analyses, we calculated that the ambient pressure range over which the flyer can operate to be from about 0.04 to 4 (terrestrial) atmospheres. This altitude range encompasses the three uppermost cloud layers in the Jovian atmosphere: (1) the entire uppermost visible NH3 ice cloud layer (where lightning has been observed), (2) the entire NH4HS ice cloud layer, and (3) the upper portion of the H2O ice cloud layer.

Maise, G.; Powell, J.; Paniagua, J.; Lecat, R.

2001-01-01

298

Confinement of Neutral Beam Ions in the National Spherical Torus Experiment  

SciTech Connect

The loss of neutral-beam ions to the wall has been measured in the National Spherical Torus Experiment (NSTX) by means of thermocouples, an infrared (IR) camera, and a Faraday cup probe. The losses tend to exhibit the expected dependences on plasma current, tangency radius of the injector, and plasma outer gap. However, the thermocouples and the Faraday cups indicate substantially different levels of loss and this difference has yet to be understood.

D.S. Darrow; S.S. Medley; A.L. Roquemore; A. Rosenberg

2001-12-18

299

Observational constraint on Jovian active longitude controlling decameter emissions  

NASA Astrophysics Data System (ADS)

The occurrence probability of the Io-controlled Jovian decameter radio emissions depends on both the central meridian longitude (CML) and the phase of the satellite Io. Recent investigations by Galopeau et al. (J. Geophys. Res. 112, 2007) have shown that some specific Jovian 'active' longitudes favour the radiation by considering that the emissions are produced near the local gyrofrequency, along an active magnetic field line carried away by Io along its revolution around Jupiter, within a hollow cone of constant angle. This model involves the cyclotron maser instability as the mechanism at the origin of the radio emission. The observed occurrence probability happens to be larger in some specific regions of the CML-Io phase diagram, the so-called Io-controlled emissions and well-known as Io-A, Io-B, Io-C and Io-D 'sources'. In the present investigation, we model four boxes representing the typical Io-controlled source regions in this diagram. We discuss the consequences and the constraints on the location of the Jovian active longitude at the origin of the Io-controlled radiation simultaneously for both hemispheres. The first results show that the active longitude model can only explain part of the emissions coming from restricted zones of the CML-Io phase diagram. This is particular the case for the emissions of the Io-D source.

Galopeau, P. H. M.; Boudjada, M. Y.

2009-04-01

300

WISE/NEOWISE OBSERVATIONS OF THE JOVIAN TROJANS: PRELIMINARY RESULTS  

SciTech Connect

We present the preliminary analysis of over 1739 known and 349 candidate Jovian Trojans observed by the NEOWISE component of the Wide-field Infrared Survey Explorer (WISE). With this survey the available diameters, albedos, and beaming parameters for the Jovian Trojans have been increased by more than an order of magnitude compared to previous surveys. We find that the Jovian Trojan population is very homogenous for sizes larger than {approx}10 km (close to the detection limit of WISE for these objects). The observed sample consists almost exclusively of low albedo objects, having a mean albedo value of 0.07 {+-} 0.03. The beaming parameter was also derived for a large fraction of the observed sample, and it is also very homogenous with an observed mean value of 0.88 {+-} 0.13. Preliminary debiasing of the survey shows that our observed sample is consistent with the leading cloud containing more objects than the trailing cloud. We estimate the fraction to be N(leading)/N(trailing) {approx} 1.4 {+-} 0.2, lower than the 1.6 {+-} 0.1 value derived by Szabo et al.

Grav, T. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Mainzer, A. K.; Bauer, J.; Masiero, J.; Eisenhardt, P. R. M.; Blauvelt, E.; DeBaun, E.; Elsbury, D.; Gautier, T. IV; Gomillion, S.; Hand, E.; Wilkins, A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Spahr, T. [Minor Planet Center, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); McMillan, R. S. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Walker, R. [Monterey Institute for Research in Astronomy, Marina, CA 93933 (United States); Cutri, R. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Wright, E., E-mail: tgrav@pha.jhu.edu [Division of Astronomy and Astrophysics, UCLA, Los Angles, CA 90095 (United States)

2011-11-20

301

WISE/NEOWISE Observations of the Jovian Trojans: Preliminary Results  

NASA Astrophysics Data System (ADS)

We present the preliminary analysis of over 1739 known and 349 candidate Jovian Trojans observed by the NEOWISE component of the Wide-field Infrared Survey Explorer (WISE). With this survey the available diameters, albedos, and beaming parameters for the Jovian Trojans have been increased by more than an order of magnitude compared to previous surveys. We find that the Jovian Trojan population is very homogenous for sizes larger than ~10 km (close to the detection limit of WISE for these objects). The observed sample consists almost exclusively of low albedo objects, having a mean albedo value of 0.07 ą 0.03. The beaming parameter was also derived for a large fraction of the observed sample, and it is also very homogenous with an observed mean value of 0.88 ą 0.13. Preliminary debiasing of the survey shows that our observed sample is consistent with the leading cloud containing more objects than the trailing cloud. We estimate the fraction to be N(leading)/N(trailing) ~ 1.4 ą 0.2, lower than the 1.6 ą 0.1 value derived by Szabó et al.

Grav, T.; Mainzer, A. K.; Bauer, J.; Masiero, J.; Spahr, T.; McMillan, R. S.; Walker, R.; Cutri, R.; Wright, E.; Eisenhardt, P. R. M.; Blauvelt, E.; DeBaun, E.; Elsbury, D.; Gautier, T., IV; Gomillion, S.; Hand, E.; Wilkins, A.

2011-11-01

302

Partially collisional model of the Titan hydrogen torus  

SciTech Connect

Occasional collision effects are encompassed by the present numerical model of atomic hydrogen densities in Titan's hydrogen torus, which is noted to be azimuthally symmetric; the torus density peaks sharply at Titan's orbit, and rapidly decreases in the both radially outward and perpendicular directions. Collisions of Saturnian atoms with the torus population produce a corona. Without this coronal population, the torus model would not reproduce the Voyager 2 Lyman-alpha intensities. These observations may nevertheless be modelled by a torus-plus-corona model that also reconciles the Pioneer 11 torus observations with those of the two Voyager spacecraft. 33 references.

Hilton, D.A.; Hunten, D.M.

1988-02-01

303

Reconnection and Flows in the Jovian Magnetotail as Inferred From Magnetometer Observations  

NASA Astrophysics Data System (ADS)

Some of the auroral polar bright spots at Jupiter are thought to originate through reconnection in the Jovian magnetotail [Grodent et al., 2004; Radioti et al., 2008]. Understanding the statistics of magnetotail reconnection will, therefore, contribute to interpreting the polar aurora. Dynamics in the Jovian magnetotail have been identified from energetic particle data, but a thorough survey of the magnetic field data is yet to be completed. An initial study [Vogt et al., 2007] identified events whose magnetic signatures suggest that magnetic reconnection is taking place in the Jovian magnetotail at distances from 30 to 150 RJ. In the initial analysis, events were characterized by increases in |B?|, the north-south component of the magnetic field, over background levels, with less restrictive criteria placed on periods of negative B?. We have recently focused on improving our quantitative event selection criteria, with particular emphasis on establishing the required increase in |B?|. This has proved to be a delicate task. Although the number and duration of the events vary with the identification criteria, the strongest events are selected by all those applied. Here we analyze events that satisfy quite stringent identification criteria. We distinguish between locations inside or outside of a neutral line, which we infer through the sign of B?. The background Jovian field points southward (B?> 0) near the equator and we assume that a northward or negative B? occurs when the spacecraft is located tailward of a reconnection x-line. Most events with (B? < 0) are observed in the post-midnight sector and at radial distances larger than ~90 RJ. Using the sign of B? as a proxy for the flow direction, we compare with previous studies that identified intermittent flows from particle anisotropy [Kronberg et al. 2005, 2007]. In the specific cases illustrated there we find that our events occur in conjunction with increases in the particle anisotropies, though our strict selection criteria miss some intervals of increased anisotropy. However, all but one of the disturbed intervals reported by Kronberg et al. [2005, 2007] occur in the post- midnight sector, but we have identified scores of additional events pre-midnight. We have also examined changes to the bendback angle, which represents how swept back the field line is with respect to the radial direction. By assuming that in events lasting less than 5 hours the azimuthal component of the flow changes to conserve angular momentum and that the field is frozen into the flow, we can infer changes of the radial plasma flow from changes of the bendback angle. We find that large, fast changes of the bendback angle occur in the majority of our events. By conservation of angular momentum we expect that the bendback of the field line will increase as plasma flows outward; we also expect negative B? during such times. Therefore we examine the correlation between the sign of B? and the change of the bendback angle in our events. We will discuss the distribution of events and their inferred properties as functions of radial distance and local time.

Vogt, M. F.; Kivelson, M. G.; Khurana, K. K.; Joy, S. P.; Walker, R. J.

2008-12-01

304

Comparative study on dynamics associated with terrestrial and Jovian substorms  

NASA Astrophysics Data System (ADS)

Terrestrial substorms have been studied for over four decades and our understanding about this phenomenon has improved through those studies. However, many issues regarding substorms are still controversial, especially the initiation mechanism of substorm onset. To understand the initiation mechanism, we have to first answer some important questions. What is the substorm expansion onset? What is the physics behind its phenomenological definition? Where does the initiation start? What is the relation of tail reconnection with near-Earth onsets? Where does tail reconnection occur? While one way to understand better the physics of substorms is to increase the number of spacecraft and the resolution of ground observations, another way is to compare substorm phenomena between different planets. In this study, we investigate the different phases of substorms both on the Earth and Jupiter. For Jovian dynamic event, we need to know if they are substorms? How are they driven? How can we better understand terrestrial substorms through studying Jovian substorms? We used Polar, GOES, Cluster and ground-station observations to study terrestrial substorms and used the Galileo observations to study Jovian dynamic events. A 3-day growth phase of Jovian substorm is discovered, which is also found driven by the internal processes including mass-loading at Io instead of the solar wind. This discovery establishes the substorm nature of those dynamics events which have counterparts of key elements of terrestrial substorms, including the connection of those events with the Jupiter's polar auroral activity. Near-planet dipolarization caused by the mid-tail reconnection is also investigated. In the near-Earth tail region, dipolarizations appear to be associated with mid-tail reconnections, near-tail flow braking and formation of substorm current wedge. In both magnetospheres, major onsets of substorms are found to be due to the major tail reconnection which can globally release the loaded energy and return the accumulated magnetic flux in magnetotails. This major change of magnetotail energy and flux status should be used to define the expansion onset of terrestrial substorms. Through comparison of dipolarizations on the geosynchronous orbit (GOES) and 9 R E near-tail region (Polar), it is found that dipolarization region starts within a narrow region and then expands both in the radial and azimuthal directions. The near-Jupiter dipolarizations and plasmoids are used to infer the Jovian tail reconnection site and the most possible location of Jovian tail neutral point is found at the post-midnight sector and 80 RJ from the planet. It is also very found that the Jovian tail reconnection starts within a confined region and expands afterwards, which is consistent with the narrow width of initial near-Earth dipolarization region and suggests tail reconnection associated with substorms mostly starts from a neutral point instead of a neutral line.

Ge, Yasong

305

Phenomenology of internal reconnections in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The behavior of large scale magnetohydrodynamic modes was investigated in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] during reconnection events using combined analysis of magnetic probe signals, and soft x-ray data. The comparison of mode dynamics during precursor and disruption stages in T-11M (V. S. Vlasenkov et al., in Proceedings of the 6th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Berchtesgaden, 6-13 October 1976, p. 95) (small circular plasma), Tokamak Fusion Test Reactor [R. J. Hawryluk et al., Plasma Phys. Controlled Fusion 33, 1509 (1991)] (large circular plasma), and NSTX (large spherical plasma) was done. The analysis shows that the sequence of events of minor and major internal reconnection events (IRE) in NSTX is essentially similar to that for disruptions in moderate aspect ratio tokamaks. The main feature of disruption dynamics apparently affected by the small aspect ratio in NSTX appears in the relatively slow thermal quench event (5-10 times longer compared to ordinary tokamaks), which precedes the major IRE. The coincidence of the electron and neutron quench times during the major IRE leads us to the conclusion that the fast ions and hot electrons leave the center of a plasma column simultaneously, i.e., convectively.

Semenov, I.; Mirnov, S.; Darrow, D.; Roquemore, L.; Fredrickson, E. D.; Menard, J.; Stutman, D.; Belov, A.

2003-03-01

306

Theory and observations of electrostatic ion waves in the cold Io torus  

NASA Astrophysics Data System (ADS)

A study of the ELF plasma wave environment of the cold Io torus in Jupiter's magnetosphere is made. Voyager 1 data are presented which show three distinct types of electrostatic ion waves occurring there: the Buchsbaum ion-ion mode just below the proton cyclotron frequency f(cp), hydrogen Bernstein modes at (n + 1/2) f(cp), and lower hybrid waves near f(LHR). The presence of these waves at their characteristic frequencies is consistent with a predominantly heavy ion plasma composed of singly ionized sulfur and oxygen ions along with a small admixture of protons. The hydrogen Bernstein modes are tightly confined to the magnetic equator, occurring within + or - 4 deg of it, while the Buchsbaum mode is localized to the dense heavy ion plasma of the cold torus near the centrifugal equator. A general theory for excitation of the waves based on the ion pickup process is developed.

Barbosa, D. D.; Kurth, W. S.

1990-05-01

307

A Collective Scattering System for Measuring Electron Gyroscale Fluctuations on the National Spherical Torus Experiment  

SciTech Connect

A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.

D.R. Smith, E. Mazzucato, W. Lee, H.K. Park, C.W. Domier, and N.C. Luhmann, Jr.

2009-02-13

308

Slicing the Torus: Obscuring Structures in Quasars  

NASA Astrophysics Data System (ADS)

Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas. It is normally assumed that the obscuration occurs in an oblate "obscuring torus", that begins at the radius at which the most refractive dust can remain solid. The most famous form of this torus is a donut-shaped region of molecular gas with a large scale-height. While this model is elegant and accounts for many phenomena at once, it does not hold up to detailed tests. Instead the obscuration in AGNs must occur on a wide range of scales and be due to a minimum of three physically distinct absorbers. Slicing the "torus" into these three regions will allow interesting physics of the AGN to be extracted.

Elvis, Martin

2012-07-01

309

The radiation impedance of a current-carrying conductor in a JUNO-like Jovian orbit  

NASA Astrophysics Data System (ADS)

The so-called electrical power generation problem for exploration of the outer planets could be solved deploying an electrodynamic tether. Wave radiation by a conductor carrying a steady current in a polar, highly eccentric, low perijove orbit, as in the planned NASA Juno mission, is considered. The high Jupiter's oblateness produces fast apsidal precession over the meridional plane. In a cold plasma model, radiation occurs in the Alfven and Fast Magnetosonic modes, exhibiting large refraction index. The radiation impedance in both modes is determined for a representative arc in the orbits. Unlike the Earth ionospheric case, the low-dense and highly-magnetized Jovian plasma makes the electron-gyrofrequency to plasma-frequency ratio large [1]; this substantially modifies the power spectrum in either mode. [1] Sánchez-Torres, A., Sanmarté J.R., Donoso, J.M., Charro, M., J. Adv. Space Res. (2010), a ?n, doi :10.1016/j.asr.2009.12.007; Sanmarté J.R., Martínez-Sánchez, M., J. Geophys. Res. 100, a pp. 1677-1686 (1995).

Sánchez-Torres, Antonio; Sanmartin, Juan R.

310

Conditions at the expanded Jovian magnetopause and implications for the solar wind interaction  

NASA Astrophysics Data System (ADS)

Using idealized models of the magnetosheath and magnetosphere magnetic fields, plasma densities, and plasma flow, we test for the steady state viability of processes mediating the interaction between the solar wind and the Jovian magnetosphere. The magnetopause is modeled as an asymmetric paraboloid with variable asymmetry. The subsolar standoff of the magnetopause has been shown to exhibit a bimodal probability distribution (Joy et al., 2002). Only the expanded magnetopause is considered, with a standoff of ˜90 RJ. We test where on the magnetopause surface large-scale reconnection may be affected by either a shear flow or diamagnetic drift due to a pressure gradient across the magnetopause boundary. We also test for the onset of the Kelvin-Helmholtz instability. We find that reconnection is inhibited on the dawn flank due to the large shear flows in this region, regardless of magnetopause shape or interplanetary magnetic field orientation. The presence of a high energy plasma population in the magnetosphere may inhibit reconnection over much of the magnetopause area, except when the fields are antiparallel. Additionally, most of the dawn flank of the magnetopause is Kelvin-Helmholtz unstable, regardless of magnetopause asymmetry; and the dusk flank tailward of the planet is Kelvin-Helmholtz unstable when the magnetopause is highly oblate.

Desroche, M.; Bagenal, F.; Delamere, P. A.; Erkaev, N.

2012-07-01

311

On modulation lanes in spectra of Jovian decametric radio emission: low magnetosphere  

NASA Astrophysics Data System (ADS)

Modulation lanes in spectra of Jovian decametric radio emission are formed by radiation scattering on field-aligned inhomogeneities in the magnetosphere of the planet. Numeral algorithm for localization of magnetospheric inhomogeneities by the frequency drift of modulation lanes is used for the study of Jovian inner magnetosphere.

Arkhipov, A. V.

2004-09-01

312

Transport of a few-MEV jovian and galactic electrons at solar maximum  

NASA Astrophysics Data System (ADS)

The heliospheric modulation of galactic and jovian electrons is studied using a three-dimensional, steady-state model based on Parker's transport equation including the jovian source. The model is developed to study both jovian and galactic electrons. It is illustrated how the electron intensity-time profile along the Ulysses trajectory is effected as compared to the 3-10 MeV electron flux observed from its launch until the recent solar maximum conditions by varying. The relative contributions of the jovian and galactic electrons to the total electron intensity is also shown along the Ulysses trajectory. For this changes in the solar wind speed, the jovian source strenght and the diffusion tensor are made. To explain these observations we find that the enhancement of the perpendicular diffusion coefficient toward the heliospheric poles must be reduced with increasing solar activity.

Ferreira, S. E. S.; Potgieter, M. S.; Heber, B.; Fichtner, R.; Kissmann, R.

2003-08-01

313

Long-term changes in Jovian synchrotron radio emission - Intrinsic variations or effects of viewing geometry?  

NASA Astrophysics Data System (ADS)

Possible causes of the observed long-term variation of Jovian synchrotron radio emission, including both intrinsic changes in the Jovian radiation belts and apparent changes due to variations in the Jovigraphic declination of the earth, DE, are investigated. An increase in diffusion rate with other parameters held constant results in an inward displacement of the peak emission radial distance that is not observed. Effects of viewing geometry changes are examined. The possible importance of such effects is suggested by a correlation between the total decimetric radio flux and DE, which varies between -3.3 and +3.3 deg during one Jovian orbital period. Because the Jovian central meridian longitudes where the magnetic latitude passes through zero during a given Jovian rotation change substantially with DE and since significant longitudinal asymmetries exist in both the volume emissivity and the latitudinal profile of the beam, the total intensity should be at least a partial function of D sub E.

Hood, L. L.

1993-04-01

314

Unfolding the torus: Oscillator geometry from time delays  

NASA Astrophysics Data System (ADS)

We present a simple method of plotting the trajectories of systems of weakly coupled oscillators. Our algorithm uses the time delays between the “firings” of the oscillators. For any system of n weakly coupled oscillators there is an attracting invariant n-dimensional torus, and the attractor is a subset of this invariant torus. The invariant torus intersects a suitable codimension-1 surface of section at an ( n-1)-dimensional torus. The dynamics of n coupled oscillators can thus be reduced, in principle, to the study of Poincaré maps of the ( n-1)-dimensional torus. This paper gives a practical algorithm for measuring the n-1 angles on the torus. Since visualization of 3 (or higher) dimensional data is difficult we concentrate on n=3 oscillators. For three oscillators, a standard projection of the Poincaré map onto the plane yields a projection of the 2-torus which is 4-to-1 over most of the torus, making it difficult to observe the structure of the attractor. Our algorithm allows a direct measurement of the 2 angles on the torus, so we can plot a 1-to-1 map from the invariant torus to the “unfolded torus” where opposite edges of a square are identified. In the cases where the attractor is a torus knot, the knot type of the attractor is obvious in our projection.

Ashwin, P.; Swift, J. W.

1993-12-01

315

Jovian S emission: Model of radiation source  

NASA Astrophysics Data System (ADS)

A physical model of the radiation source and an excitation mechanism have been suggested for the S component in Jupiter's sporadic radio emission. The model provides a unique explanation for most of the interrelated phenomena observed, allowing a consistent interpretation of the emission cone structure, behavior of the integrated radio spectrum, occurrence probability of S bursts, location and size of the radiation source, and fine structure of the dynamic spectra. The mechanism responsible for the S bursts is also discussed in connection with the L type emission. Relations are traced between parameters of the radio emission and geometry of the Io flux tube. Fluctuations in the current amplitude through the tube are estimated, along with the refractive index value and mass density of the plasma near the radiation source.

Ryabov, B. P.

1994-04-01

316

Millimeter/submillimeter Fourier Transform Spectroscopy of Jovian Planet Atmospheres  

NASA Astrophysics Data System (ADS)

A new Fourier transform spectrometer, built for use at the Caltech Submillimeter Observatory, has been used to observe all four of the jovian planets (Jupiter, Saturn, Uranus, and Neptune) in the millimeter-submillimeter wavelength range (0.3-3.0 mm). These observations have resulted in the detection of the PH_3 1-0 rotational line (266.9 GHz) in Saturn, and the PH _3 3-2 (800.5 GHz) line in both Jupiter and Saturn. Because PH_3 is a disequilibrium species, it is an important tracer of vertical mixing and upper atmospheric photochemistry, and can therefore be used to derive dynamical and chemical properties of the jovian atmospheres. A jovian planet radiative transfer code has been used to model the observed PH_3 lineshapes. Using the FTS, a spectral line survey covering the entire range of submillimeter frequencies observable from the ground has also been performed on Jupiter at Saturn at a resolution of 200 MHz. This survey has yielded the tentative detection of HCl (and possibly HCN) in Saturn and, again with the aid of radiative transfer modeling, provided a great number of improved upper limits on the concentrations of many other species. Finally, Uranus and Neptune have been observed in the 1300 ?m atmospheric window which contains the CO 2-1 transition. This line was not detected in either planet, placing upper limits on the tropospheric CO mole fraction of 0.5 ppm in Uranus and 1.4 ppm in Neptune. A new Fourier transform spectrometer, built for use at the Caltech Submillimeter Observatory, has been used to observe all four of the jovian planets (Jupiter, Saturn, Uranus, and Neptune) in the millimeter-submillimeter wavelength range (0.3-3.0 mm). These observations have resulted in the detection of the PH_3 1-0 rotational line (266.9 GHz) in Saturn, and the PH _3 3-2 (800.5 GHz) line in both Jupiter and Saturn. Because PH_3 is a disequilibrium species, it is an important tracer of vertical mixing and upper atmospheric photochemistry, and can therefore be used to derive dynamical and chemical properties of the jovian atmospheres. A jovian planet radiative transfer code has been used to model the observed PH_3 lineshapes. Using the FTS, a spectral line survey covering the entire range of submillimeter frequencies observable from the ground has also been performed on Jupiter at Saturn at a resolution of 200 MHz. This survey has yielded the tentative detection of HCl (and possibly HCN) in Saturn and, again with the aid of radiative transfer modeling, provided a great number of improved upper limits on the concentrations of many other species. Finally, Uranus and Neptune have been observed in the 1300 ?m atmospheric window which contains the CO 2-1 transition. This line was not detected in either planet, placing upper limits on the tropospheric CO mole fraction of 0.5 ppm in Uranus and 1.4 ppm in Neptune.

Weisstein, Eric Wolfgang

1996-01-01

317

National Spherical Torus Experiment (NSTX) and Planned Research  

SciTech Connect

The U.S. fusion energy sciences program began in 1996 to increase emphasis on confinement concept innovation. The NSTX [1,2] is being built at PPPL as a national fusion science research facility in response to this emphasis. NSTX is to test fusion science principles of the Spherical Torus (ST) plasmas, which include: (1) High plasma pressure in low magnetic field for high fusion power density, (2) Good energy confinement is a small-size plasma, (3) Nearly fully self-driven (bootstrap) plasma current, (4) Dispersed heat and particle fluxes, and (5) Plasma startup without complicated inboard solenoid magnet. These properties of the ST plasma, if verified, would lead to possible future fusion devices of high fusion performance, small size, feasible power handling, and improved economy. The design of NSTX is depicted in Fig.1. The device is designed to study plasmas with major radius up to 85 cm, minor radius up to 68 cm, elongation up to 2, with flexibility in forming double-null, single-null, and inboard limited plasmas. The nominal operation calls for a toroidal field of 0.3 T for 5 s at the major radius, and a plasma current at 1 MA with q {approximately} 10 at edge. It features a compact center stack containing the inner legs of the toroidal field coils, a full size solenoid capable of delivering 0.6 Wb induction, inboard vacuum vessel, and composite carbon tiles. The center stack can be replaced without disturbing the main device, diagnostics, and auxiliary systems. The vessel will be covered fully with graphite tiles and can be baked to 350 C. Other wall conditioning techniques are also planned.

Kaye, S.; Neumeyer, C.; Ono, M.; Peng, M.

1999-11-13

318

Methane Absorption Coefficients for the Jovian Planets and Titan  

NASA Astrophysics Data System (ADS)

We combined 11 data sets of methane transmission measurements within 0.4-5.5 micrometer wavelength in order to better understand the variation of methane absorption with temperature and pressure for conditions in the atmospheres of the Jovian planets and Titan. Eight data sets are based on published laboratory measurements. Another two data sets come from two spectrometers onboard the Huygens probe that measured methane absorption inside Titan's atmosphere (Tomasko et al. 2008, PSS 56, 624). We present the data with a refined analysis. The last data set consists of Hubble Space Telescope images of Jupiter taken in 2005 and 2007 as Ganymede started to be occulted by Jupiter. Using Ganymede as a light source, we probed Jupiter's stratosphere with large methane pathlengths. Below 1000 nm wavelength, we find methane absorption coefficients generally similar to those by Karkoschka (1998, Icarus 133, 134). We added descriptions of temperature and pressure dependence, which are typically small in this wavelength range. Data in this wavelength range are consistent with each other, except between 882 and 902 nm wavelength where laboratory data predict larger absorptions in the Jovian atmospheres than observed. We present possible explanations. Above 1000 nm, our analysis of the Huygens data confirms methane absorption coefficients by Irwin et al. (2006, Icarus 181, 309) at their laboratory temperatures. Huygens data are consistent with Irwin's model of the pressure dependence of methane absorption. However, when large extrapolations were needed, such as from laboratory data above 200 K to Titan's temperatures near 80 K, Irwin's model of temperature dependence predicts absorption coefficients up to 100 times lower than measured by Huygens. We combined Irwin's and Huygens' data to obtain more reliable methane absorption coefficients for the temperatures in the atmospheres of the Jovian planets and Titan. This research was supported by NASA grants NAG5-12014 and NNX08AE74G.

Karkoschka, Erich; Tomasko, M. G.

2009-09-01

319

Coupling of pressure waves to clouds in the Jovian troposphere  

NASA Astrophysics Data System (ADS)

The receipt for a successful study of the Jovian interior structure is given by the association of seismology and precise visible photometry. In this framework, the micro-satellite project Jovis, presented to the French space agency (Mosser et al. 2004), is for Jupiter a copy of what the Europen space mission COROT is for the stars (Baglin et al. 1998). The Jovian visible flux being dominated by the albedo map, an accurate analysis of the cloud response to a seismic wave is needed. Therefore, we have revisited the propagation of sound waves in the Jovian troposphere, in order to estimate how they affect the uppest clouds layer, composed of ammonia ice. First, considering Jupiter as a mirror, the expected variations of the reflected solar flux due to the smooth distorsions are about the ppm level for a 50 cm s-1 amplitude wave. Second, introducing thermodynamics, we determine the phase transitions induced by the waves in the clouds. These phase changes are linked to the ice particles growth, and limited by kinetics. A Mie model (Mishchenko et al 2002) associated to a simple radiation transfer model allows us to estimate that the final albedo fluctuations of the cloud perturbed by a seismic wave can reach the 70-ppm level. This gain of a factor 70 makes the phenomenon easier to observe and opens new prospectives for the seismic study of Jupiter : low amplitude modes, high degrees modes. špace{1cm} Baglin et al. 1998. 185 IAU. Symp. pp. 301. Kyoto. Mosser et al. 2004. SF2A-2004 pp. 257. EdP-Sciences, Les Ulis. Mishchenko et al. 2002. Scatt. Abs. Em. Light Small Particles pp. 158-190. Cambridge University Press.

Gaulme, P.; Mosser, B.

2004-11-01

320

Jovian periodicities (˜10 h, ˜40 min) on Ulysses’ Distant Jupiter Encounter observations around the Halloween CIR events  

NASA Astrophysics Data System (ADS)

We analyzed data from four different instruments (HI-SCALE, URAP, SWOOPS, VHM/FGM) onboard Ulysses spacecraft (s/c) and we searched for possible evidence of Jovian emissions when the s/c approached Jupiter during the times of Halloween events (closest time approach/position to Jupiter: February 5, 2004/ R = 1683 R J, ? = ˜49°). In particular, we analyzed extensively the low energy ion measurements obtained by the HI-SCALE experiment in order to examine whether low energy ion/electron emissions show a symmetry, and whether they are observed at north high latitudes upstream from the jovian bow shock, as is known to occur in the region upstream from the south bow shock as well ( Marhavilas et al., 2001). We studied the period from October 2003 to March 2004, as Ulysses moved at distances 0.8-1.2 AU from the planet at north Jovicentric latitudes <75°, and we present here an example of characteristic Jovian periodicities in the measurements around a CIR observed by Ulysses on days ˜348-349/2003 ( R = 1894 R J, ? = 72°). We show that Ulysses observed low energy ion (˜0.055-4.7 MeV) and electron (>˜40 keV) flux and/or spectral modulation with the Jupiter rotation period (˜10 h) as well as variations with the same period in solar wind parameters, radio and magnetic field directional data. In addition, characteristic strong ˜40 min periodic variations were found superimposed on the ˜10 h ion spectral modulation. Both the ˜10 h and ˜40 min ion periodicities in HI-SCALE measurements were present in several cases during the whole period examined (October 2003 to March 2004) and were found to be more evident during some special conditions, for instance during enhanced fluxes around the start (forward shock) and the end (reverse shock) of CIRs. We infer that the Jovian magnetosphere was triggered by the impact of the CIRs, after the Halloween events, and it was (a) a principal source of forward and reverse shock-associated ion flux structures and (b) the cause of generation of ˜10 h quasi-periodic magnetic field and plasma modulation observed by Ulysses at those times.

Anagnostopoulos, G. C.; Louri, I.; Marhavilas, P.; Sarris, E. T.

2009-02-01

321

Some spectral characteristics of the hectometric Jovian emission  

SciTech Connect

The study of the dynamic spectra of hectometric Jovian emission (f<1.3 MHz) for the period January to June 1978 from the planetary radio astronomy (PRA) experiment on the Voyager 1 and 2 spacecraft shows that its shape is stable with the rotation of the planet. However, there are noticeable differences between the spectra observed at one-month intervals by one spacecraft, or simultaneously by the two spacecraft, which can be clearly related neither to an effect of Io nor the the Jovicentric decination of the observer.

Lecacheux, A.; Moller-Pedersen, B.; Riddle, A.C.; Pearce, J.B.; Boischot, A.; Warwick, J.W.

1980-12-01

322

Coupling of acoustic waves to clouds in the jovian troposphere  

NASA Astrophysics Data System (ADS)

Seismology is the best tool for investigating the interior structure of stars and giant planets. This paper deals with a photometric study of jovian global oscillations. The propagation of acoustic waves in the jovian troposphere is revisited in order to estimate their effects on the planetary albedo. According to the standard model of the jovian cloud structure there are three major ice cloud layers (e.g., [Atreya et al., 1999. A comparison of the atmospheres of Jupiter and Saturn: Deep atmospheric composition, cloud structure, vertical mixing, and origin. Planet Space Sci. 47, 1243-1262]). We consider only the highest layers, composed of ammonia ice, in the region where acoustic waves are trapped in Jupiter's atmosphere. For a vertical wave propagating in a plane parallel atmosphere with an ammonia ice cloud layer, we calculate first the relative variations of the reflected solar flux due to the smooth oscillations at about the ppm level. We then determine the phase transitions induced by the seismic waves in the clouds. These phase changes, linked to ice particle growth, are limited by kinetics. A Mie model [Mishchenko et al., 2002. Scattering, Absorption, and Emission of Light by Small Particles. Cambridge Univ. Press, Cambridge, pp. 158-190] coupled with a simple radiation transfer model allows us to estimate that the albedo fluctuations of the cloud perturbed by a seismic wave reach relative variations of 70 ppm for a 3-mHz wave. This albedo fluctuation is amplified by a factor of ˜70 relative to the previously published estimates that exclude the effect of the wave on cloud properties. Our computed amplifications imply that jovian oscillations can be detected with very precise photometry, as proposed by the microsatellite JOVIS project, which is dedicated to photometric seismology [Mosser et al., 2004. JOVIS: A microsatellite dedicated to the seismic analysis of Jupiter. In: Combes, F., Barret, D., Contini, T., Meynadier, F., Pagani, L. (Eds.), SF2A-2004, Semaine de l'Astrophysique Francaise, Les Ulis. In: EdP-Sciences Conference Series, pp. 257-258].

Gaulme, Patrick; Mosser, Benoît

2005-11-01

323

Overview of results from the National Spherical Torus Experiment (NSTX)  

NASA Astrophysics Data System (ADS)

The mission of the National Spherical Torus Experiment (NSTX) is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high ? operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale length. Results from n = 3 braking studies are consistent with the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of high harmonic fast-waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap current fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance li ~ 0.4 with strong shaping (? ~ 2.7, ? ~ 0.8) with ?N approaching the with-wall ?-limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction fNI ~ 71%. Instabilities driven by super-Alfvénic ions will be an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvénic. Linear toroidal Alfvén eigenmode thresholds and appreciable fast ion loss during multi-mode bursts are measured and these results are compared with theory. The impact of n > 1 error fields on stability is an important result for ITER. Resistive wall mode/resonant field amplification feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with ? above the no-wall limit. Other highlights are results of lithium coating experiments, momentum confinement studies, scrape-off layer width scaling, demonstration of divertor heat load mitigation in strongly shaped plasmas and coupling of coaxial helicity injection plasmas to ohmic heating ramp-up. These results advance the ST towards next step fusion energy devices such as NHTX and ST-CTF.

Gates, D. A.; Ahn, J.; Allain, J.; Andre, R.; Bastasz, R.; Bell, M.; Bell, R.; Belova, E.; Berkery, J.; Betti, R.; Bialek, J.; Biewer, T.; Bigelow, T.; Bitter, M.; Boedo, J.; Bonoli, P.; Boozer, A.; Brennan, D.; Breslau, J.; Brower, D.; Bush, C.; Canik, J.; Caravelli, G.; Carter, M.; Caughman, J.; Chang, C.; Choe, W.; Crocker, N.; Darrow, D.; Delgado-Aparicio, L.; Diem, S.; D'Ippolito, D.; Domier, C.; Dorland, W.; Efthimion, P.; Ejiri, A.; Ershov, N.; Evans, T.; Feibush, E.; Fenstermacher, M.; Ferron, J.; Finkenthal, M.; Foley, J.; Frazin, R.; Fredrickson, E.; Fu, G.; Funaba, H.; Gerhardt, S.; Glasser, A.; Gorelenkov, N.; Grisham, L.; Hahm, T.; Harvey, R.; Hassanein, A.; Heidbrink, W.; Hill, K.; Hillesheim, J.; Hillis, D.; Hirooka, Y.; Hosea, J.; Hu, B.; Humphreys, D.; Idehara, T.; Indireshkumar, K.; Ishida, A.; Jaeger, F.; Jarboe, T.; Jardin, S.; Jaworski, M.; Ji, H.; Jung, H.; Kaita, R.; Kallman, J.; Katsuro-Hopkins, O.; Kawahata, K.; Kawamori, E.; Kaye, S.; Kessel, C.; Kim, J.; Kimura, H.; Kolemen, E.; Krasheninnikov, S.; Krstic, P.; Ku, S.; Kubota, S.; Kugel, H.; La Haye, R.; Lao, L.; LeBlanc, B.; Lee, W.; Lee, K.; Leuer, J.; Levinton, F.; Liang, Y.; Liu, D.; Luhmann, N., Jr.; Maingi, R.; Majeski, R.; Manickam, J.; Mansfield, D.; Maqueda, R.; Mazzucato, E.; McCune, D.; McGeehan, B.; McKee, G.; Medley, S.; Menard, J.; Menon, M.; Meyer, H.; Mikkelsen, D.; Miloshevsky, G.; Mitarai, O.; Mueller, D.; Mueller, S.; Munsat, T.; Myra, J.; Nagayama, Y.; Nelson, B.; Nguyen, X.; Nishino, N.; Nishiura, M.; Nygren, R.; Ono, M.; Osborne, T.; Pacella, D.; Park, H.; Park, J.; Paul, S.; Peebles, W.; Penaflor, B.; Peng, M.; Phillips, C.; Pigarov, A.; Podesta, M.; Preinhaelter, J.; Ram, A.; Raman, R.; Rasmussen, D.; Redd, A.; Reimerdes, H.; Rewoldt, G.; Ross, P.; Rowley, C.; Ruskov, E.; Russell, D.; Ruzic, D.; Ryan, P.; Sabbagh, S.; Schaffer, M.; Schuster, E.; Scott, S.; Shaing, K.; Sharpe, P.; Shevchenko, V.; Shinohara, K.; Sizyuk, V.; Skinner, C.; Smirnov, A.; Smith, D.; Smith, S.; Snyder, P.; Solomon, W.; Sontag, A.; Soukhanovskii, V.; Stoltzfus-Dueck, T.; Stotler, D.; Strait, T.; Stratton, B.; Stutman, D.; Takahashi, R.; Takase, Y.; Tamura, N.; Tang, X.; Taylor, G.; Taylor, C.; Ticos, C.; Tritz, K.; Tsarouhas, D.; Turrnbull, A.; Tynan, G.; Ulrickson, M.; Umansky, M.; Urban, J.; Utergberg, E.; Walker, M.; Wampler, W.; Wang, J.; Wang, W.; Welander, A.; Whaley, J.; White, R.; Wilgen, J.; Wilson, R.; Wong, K.; Wright, J.; Xia, Z.; Xu, X.; Youchison, D.; Yu, G.; Yuh, H.; Zakharov, L.; Zemlyanov, D.; Zweben, S.

2009-10-01

324

Spherical torus approach to magnetic fusion development  

Microsoft Academic Search

The low aspect ratio tokamak or spherical torus (ST) approach offers the two key elements needed to enable magnetic confinement fusion to make the transition from a government-funded research program to the commercial marketplace: a low cost, low power, small size market entry vehicle and a strong economy of scale in larger devices. Within the ST concept, a very small

R. D. Stambaugh; V. S. Chan; P. A. Anderson

1996-01-01

325

Large N reduction on a twisted torus  

SciTech Connect

We consider SU(N) lattice gauge theory at infinite N defined on a torus with a CP invariant twist. Massless fermions are incorporated in an elegant way, while keeping them quenched. We present some numerical results which suggest that twisting can make numerical simulations of planar QCD more efficient.

A. Gonzalez-Arroyo; Rajamani Narayanan; H. Neuberger

2005-10-01

326

Space Propulsion via Spherical Torus Fusion Reactor  

Microsoft Academic Search

A conceptual vehicle design enabling fast outer solar system travel was produced predicated on a small aspect ratio spherical torus nuclear fusion reactor. Analysis revealed that the vehicle could deliver a 108 mt crew habitat payload to Saturn rendezvous in 204 days, with an initial mass in low Earth orbit of 1630 mt. Engineering conceptual design, analysis, and assessment were

Craig H. Williams; Albert J. Juhasz; Stanley K. Borowski; Leonard A. Dudzinski

2003-01-01

327

Jovian-like aurorae on Saturn.  

PubMed

Planetary aurorae are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. Earth's main auroral oval is formed through interactions with the solar wind, whereas that at Jupiter is formed through interactions with plasma from the moon Io inside its magnetic field (although other processes form aurorae at both planets). At Saturn, only the main auroral oval has previously been observed and there remains much debate over its origin. Here we report the discovery of a secondary oval at Saturn that is approximately 25 per cent as bright as the main oval, and we show this to be caused by interaction with the middle magnetosphere around the planet. This is a weak equivalent of Jupiter's main oval, its relative dimness being due to the lack of as large a source of ions as Jupiter's volcanic moon Io. This result suggests that differences seen in the auroral emissions from Saturn and Jupiter are due to scaling differences in the conditions at each of these two planets, whereas the underlying formation processes are the same. PMID:18563160

Stallard, Tom; Miller, Steve; Melin, Henrik; Lystrup, Makenzie; Cowley, Stan W H; Bunce, Emma J; Achilleos, Nicholas; Dougherty, Michele

2008-06-19

328

Comparison of Plasma Results in EBT-1 and NBT-1M.  

National Technical Information Service (NTIS)

Plasma results from the ELMO Bumpy Torus (EBT-1) and Nagoya Bumpy Torus (NBT-1M) experiments are compared. Both devices have 24 mirror field coils arranged to form a torus, and both use 18-GHz electron cyclotron resonance heating power. The main differenc...

R. J. Colchin J. C. Glowienka

1984-01-01

329

Energetic Ion Behavior in the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is a low aspect ratio (R/a approximately equal to 1.3) device with auxiliary heating from neutral beam injection (NBI) and high harmonic fast wave (HHFW) heating. Typical NSTX parameters are R(sub)0 = 85 cm, a = 67 cm, I(sub)p less than or equal to 1.5 MA, B(sub)T = 0.3-0.6 T. Three co-directed deuterium neutral beam sources have injected P(sub)NB less than or equal to 6.2 MW at energies E(sub)b less than or equal to 100 keV. HHFW heating has delivered up to P(sub)RF approximately equal to 6 MW to deuterium and helium plasmas.

S.S. Medley; R.E. Bell; E.D. Fredrickson; A.L. Roquemore

2003-06-26

330

Characterization and parametric dependencies of low wavenumber pedestal turbulence in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The spherical torus edge region is among the most challenging regimes for plasma turbulence simulations. Here, we measure the spatial and temporal properties of ion-scale turbulence in the steep gradient region of H-mode pedestals during edge localized mode-free, MHD quiescent periods in the National Spherical Torus Experiment. Poloidal correlation lengths are about 10 ?i, and decorrelation times are about 5 a/cs. Next, we introduce a model aggregation technique to identify parametric dependencies among turbulence quantities and transport-relevant plasma parameters. The parametric dependencies show the most agreement with transport driven by trapped-electron mode, kinetic ballooning mode, and microtearing mode turbulence, and the least agreement with ion temperature gradient turbulence. In addition, the parametric dependencies are consistent with turbulence regulation by flow shear and the empirical relationship between wider pedestals and larger turbulent structures.

Smith, D. R.; Fonck, R. J.; McKee, G. R.; Thompson, D. S.; Bell, R. E.; Diallo, A.; Guttenfelder, W.; Kaye, S. M.; LeBlanc, B. P.; Podesta, M.

2013-05-01

331

Infrared observations of the jovian system from voyager 2.  

PubMed

Infrared spectra obtainedfrom Voyager 2 have provided additional data on the Jovian system, complementing those obtained from Voyager 1. The abundance ratio of ethane to acetylene in Jupiter's atmosphere appears to be about three times larger in the polar regions than at lower latitudes. A decidedly hemispherical asymmetry exists, with somewhat higher ratios prevailing in northern latitudes. An overall increase in the abundance ratio by a factor of about 1.7 appears to have occurred between the Voyager 1 and 2 encounters. Global brightness temperature maps of Jupiter at 226 and 602 cm(-1) exhibit a large amount of local- and planetary-scale structure, as well as temporal variability. Although heterogeneous cloud structure and ammonia concentration in the lower troposphere may contribute to the appearance of the 226-cm(-1) map, the detail in the 602-cm(-1) maps probably represents the actual horizontal thermal structure near the tropopause and suggests that dynamical heating and cooling processes are important. Low-latitude surface temperatures on the Galilean satellites rangefrom approximately 80 K on the dark sides to 155 K at the subsolar point on Callisto. Below a thin insulating layer, the thermal inertia of Callisto is somewhat greater than that of Earth's moon. Upper limits on the infrared optical depth of the Jovian ring rangingfrom approximately 3 x 10(-4) at 250 cm(-1) to 3 x 10(-3) at 600 cm(-1) have been found. PMID:17733912

Hanel, R; Conrath, B; Flasar, M; Herath, L; Kunde, V; Lowman, P; Maguire, W; Pearl, J; Pirraglia, J; Samuelson, R; Gautier, D; Gierasch, P; Horn, L; Kumar, S; Ponnamperuma, C

1979-11-23

332

Scientific Mission for National Spherical Torus Experiment (NSTX)  

NASA Astrophysics Data System (ADS)

The NSTX will be designed and built to test innovative scientific principles of high-temperature collisionless spherical torus (ST) plasmas. The ST plasmas promise, for example, stability with high average beta ( ~ 45 %) and pressure-driven current fraction ( ~ 90 %); confinement associated with strong magnetic well and shear; current startup and sustainment for minimized magnetic flux and helicity per plasma current; and power and particle handling in thick SOL plasmas dominated by MHD instabilities. Successful outcome from NSTX and complementary experiments (e.g., MAST in U.K. and GLOBUS-M in R.F.) would establish for the first time the physics basis for small, efficient and economical D-T fusion cores. The ST fusion cores could permit in a decade several exciting applications, such as testing D-T fusion burn; developing neutron science; developing fusion materials, engineering, and technology; eliminating difficult fission wastes; and producing tritium. These applications would in turn establish the scientific and technical basis for proceeding with the Pilot, Demonstration, and eventually Power Plants to produce relatively clean and economic energy.

Peng, M.; Ono, M.; Kaye, S.; Goldston, R.

1996-11-01

333

The plasma wave environment of Europa  

Microsoft Academic Search

The Galileo spacecraft has executed nine close flybys of Jupiter's moon Europa for which plasma wave observations were obtained. This paper presents an analysis of the observations from these flybys taking into consideration the variable geometry of the trajectories in an attempt to characterize the general plasma-wave environment associated with the interaction of the Jovian magnetosphere with the moon. A

W. S. Kurth; D. A. Gurnett; A. M. Persoon; A. Roux; S. J. Bolton; C. J. Alexander

2001-01-01

334

Performance of a pneumatic hydrogen-pellet injection system on the Joint European Torus  

Microsoft Academic Search

A pneumatic-based, hydrogen isotope pellet injector that was developed at the Oak Ridge National Laboratory (ORNL) has been used in recent plasma fueling experiments on the Joint European Torus (JET). The injector consists of three independent machine-gun-like mechanisms (nominal pellet sizes of 2.7, 4.0, and 6.0 mm in diameter) and features repetitive operation (1–5 Hz) for quasi-steady-state conditions (>10 s).

S. K. Combs; T. C. Jernigan; L. R. Baylor; S. L. Milora; C. R. Foust; P. Kupschus; M. Gadeberg; W. Bailey

1989-01-01

335

Operation and reliability of a pneumatic hydrogen pellet injection system on the Joint European Torus  

Microsoft Academic Search

Developed at the Oak Ridge National Laboratory, the pneumatic-based, hydrogen-isotope, pellet injector was installed on the Joint European Torus (JET) during 1987 and has since been used in plasma fueling experiments. The injector consists of three independent machine-gun-like mechanisms (nominal pellet sizes of 2.7, 4.0, and 6.0 mm in diameter), and it features repetitive operation (1-5 Hz) for quasi-steady-state conditions

S. K. Combs; T. C. Jernigan; L. R. Baylor; S. L. Milora; C. R. Foust; P. Kupschus; M. Gadeberg; W. Bailey

1989-01-01

336

Summary of TFTR (Tokamak Fusion Test Reactor) diagnostics, including JET (Joint European Torus) and JT-60  

SciTech Connect

The diagnostic instrumentation on TFTR (Tokamak Fusion Test Reactor) and the specific properties of each diagnostic, i.e., number of channels, time resolution, wavelength range, etc., are summarized in tables, grouped according to the plasma parameter measured. For comparison, the equivalent diagnostic capabilities of JET (Joint European Torus) and the Japanese large tokamak, JT-60, as of late 1987 are also listed in the tables. Extensive references are given to publications on each instrument.

Hill, K.W.; Young, K.M.; Johnson, L.C.

1990-05-01

337

The national spherical torus experiment (NSTX) research programme and progress towards high beta, long pulse operating scenarios  

Microsoft Academic Search

A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, high confinement operation and its physics basis. This research has been enabled by facility capabilities developed during 2001 and 2002, including neutral beam (up to 7 MW) and high harmonic fast wave (HHFW) heating (up to 6 MW), toroidal fields up to 6 kG, plasma

E. J. Synakowski; M. G. Bell; R. E. Bell; T. Bigelow; M. Bitter; W. Blanchard; J. Boedo; C. Bourdelle; C. Bush; D. S. Darrow; E. D. Fredrickson; D. A. Gates; M. Gilmore; L. R. Grisham; J. C. Hosea; D. W. Johnson; R. Kaita; S. M. Kaye; S. Kubota; H. W. Kugel; B. P. LeBlanc; K. Lee; R. Maingi; J. Manickam; R. Maqueda; E. Mazzucato; S. S. Medley; J. Menard; D. Mueller; B. A. Nelson; C. Neumeyer; M. Ono; F. Paoletti; H. K. Park; S. F. Paul; Y.-K. M. Peng; C. K. Phillips; S. Ramakrishnan; R. Raman; A. L. Roquemore; A. Rosenberg; P. M. Ryan; S. A. Sabbagh; C. H. Skinner; V. Soukhanovskii; T. Stevenson; D. Stutman; D. W. Swain; G. Taylor; A. Von Halle; J. Wilgen; M. Williams; J. R. Wilson; S. J. Zweben; R. Akers; R. E. Barry; P. Beiersdorfer; J. M. Bialek; B. Blagojevic; P. T. Bonoli; R. Budny; M. D. Carter; C. S. Chang; J. Chrzanowski; W. Davis; B. Deng; E. J. Doyle; L. Dudek; J. Egedal; R. Ellis; J. R. Ferron; M. Finkenthal; J. Foley; E. Fredd; A. Glasser; T. Gibney; R. J. Goldston; R. Harvey; R. E. Hatcher; R. J. Hawryluk; W. Heidbrink; K. W. Hill; W. Houlberg; T. R. Jarboe; S. C. Jardin; H. Ji; M. Kalish; J. Lawrance; L. L. Lao; K. C. Lee; F. M. Levinton; N. C. Luhmann; R. Majeski; R. Marsala; D. Mastravito; T. K. Mau; B. McCormack; M. M. Menon; O. Mitarai; M. Nagata; N. Nishino; M. Okabayashi; G. Oliaro; D. Pacella; R. Parsells; T. Peebles; B. Peneflor; D. Piglowski; R. Pinsker; G. D. Porter; A. K. Ram; M. Redi; M. Rensink; G. Rewoldt; J. Robinson; P. Roney; M. Schaffer; K. Shaing; S. Shiraiwa; P. Sichta; D. Stotler; B. C. Stratton; Y. Takase; X. Tang; R. Vero; W. R. Wampler; G. A. Wurden; X. Q. Xu; J. G. Yang; L. Zeng; W. Zhu

2003-01-01

338

The National Spherical Torus Experiment (NSTX) research programme and progress towards high beta, long pulse operating scenarios  

Microsoft Academic Search

A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, high confinement operation and its physics basis. This research has been enabled by facility capabilities developed during 2001 and 2002, including neutral beam (up to 7 MW) and high harmonic fast wave (HHFW) heating (up to 6 MW), toroidal fields up to 6 kG, plasma

D. W. Johnson; L. R. Grisham; S. J. Zweben; D. A. Gates; C. Bush; E. J. Synakowski; J. C. Hosea; W. Blanchard; Michael G. Bell; S. Sabbagh; V. Soukhanovskii; R. Raman; Y. K. M. Peng; M. Ono; T. Stevenson; E. D. Fredrickson; Shigeru Kubota; P. C. Efthimion; C. Bourdelle; J. R. Wilson; R. Maqueda; S. M. Kaye; R. Kaita; R. Maingi; D. S. Darrow; M. Bitter; Henry W. Kugel; C. H. Skinner; J. Wilgen; A. Von Halle; G. Taylor; D. Mueller; D. W. Swain; P. M. Ryan; A. Rosenberg; S. Ramakrishnan; C. K. Phillips; S. Paul; H. K. Park; F. Paoletti; J. Boedo; M. Williams; Mark A. Gilmore; B. LeBlanc; T. Bigelow; R. E. Bell; A. L. Roquemore; William R. Wampler; S. S. Medley; D. Stutman; J. Menard; E. Mazzucato; C. Neumeyer; B. A. Nelson; K. Lee; J. Manickam

2004-01-01

339

Spherical torus: an approach to compact fusion at low field. Initial ignition assessments  

SciTech Connect

Initial assessments of ignition devices based on the spherical torus concept suggest that an ignition spherical torus (IST) can be highly cost-effective and exceptionally small in unit size. Assuming advanced methods of current drive and confinement and beta scalings with plasma current, a D-T IST with a toroidal field of 2 to 3 T is estimated to have a major radius ranging from 1 m to 1.6 m, and a fusion power less than 60 MW. For the nominal IST (at 2 T and 1.6 m), the direct cost of the nuclear island is estimated to be about $120 M with a total direct cost about $340 M in mid-1984 dollars based on the Fusion Engineering Design Center (FEDC) cost algorithm. For ISTs with higher field and smaller size (e.g., at 3 T and 1 m), further reductions of the cost of the nuclear island are estimated. In case of confinement scaling with the plasma size only, strong plasma paramagnetism (self-generated magnetic field) in the spherical torus may still serve to compensate for the projected confinement shortfall.

Peng, Y.K.M.; Strickler, D.J.; Borowski, S.K.; Hamilton, W.R.; Reid, R.L.; Haines, J.R.; Lee, V.D.; Gorker, G.E.; Kalsi, S.S.; Riemer, B.W.

1985-01-01

340

Spherical torus: An approach to compact fusion at low field. Initial ignition assessments  

NASA Astrophysics Data System (ADS)

Initial assessments of ignition devices based on the spherical torus concept suggest that an ignition spherical torus (IST) can be highly cost-effective and exceptionally small in unit size. Assuming advanced methods of current drive and confinement and beta scalings with plasma current, a D-T IST with a toroidal field of 2 to 3 T is estimated to have a major radius ranging from 1 m to 1.6 m, and a fusion power less than 60 MW. For the nominal IST (at 2 T and 1.6 m), the direst cost of the nuclear island is estimated to be about $120 M with a total direct cost about $340 M in mid-1984 dollars based on the Fusion Engineering Design Center (FEDC) cost algorithm. For ISTs with higher field and smaller size (e.g., at 3 T and 1 m), further reductions of the cost of the nuclear island are estimated. In case of confinement scaling with the plasma size only, strong plasma paramagnetism (self-generated magnetic field) in the spherical torus may still serve to compensate for the projected confinement shortfall.

Peng, Y. K. M.; Strickler, D. J.; Borowski, S. K.; Hamilton, W. R.; Reid, R. L.; Haines, J. R.; Lee, V. D.; Gorker, G. E.; Kalsi, S. S.; Riemer, B. W.

341

Non-inductive Start-up and Formation of Spherical Torus by Using Electron Cyclotron Range of Frequency on LATE  

SciTech Connect

Non-inductive start-up and formation of spherical torus by using electron cyclotron range of frequency have been studied in the LATE device with microwaves at 2.45 GHz and 5 GHz. A plasma current is initiated and ramped up to I{sub p}{approx_equal}8.1 kA with a 2.45 GHz microwave power of 35 kW, and I{sub p}{approx_equal}20 kA with a 5 GHz power of 190 kW, resulting in the formation of a spherical torus.

Uchida, M.; Tanaka, H.; Maekawa, T. [Graduate School of Energy Science, Kyoto University, Kyoto 606-8502 (Japan)

2009-11-26

342

Q torus in N=2 supersymmetric QED  

SciTech Connect

We construct 'flying saucer' solitons in supersymmetric N=2 gauge theory, which is known to support Bogomol'nyi-Prasad-Sommerfield domain walls with a U(1) gauge field localized on its worldvolume. We demonstrate that this model supports exotic particlelike solitons with the shape of a torus. Q tori, and also similar solitons of higher genera, are obtained by folding the domain wall into an appropriate surface. Nontrivial cycles on the domain wall worldvolume (handles) are stabilized by crossed electric and magnetic fields inside the folded domain wall. Three distinct frameworks are used to prove the existence of these flying saucer solitons and study their properties: the worldvolume description (including the Dirac-Born-Infeld action), the bulk-theory description in the sigma-model limit, and the bulk-theory description in the thin-edge approximation. In the sigma-model framework the Q torus is shown to be related to the Hopf Skyrmion studied previously.

Bolognesi, S. [Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen O (Denmark) and University of Southern Denmark, DK-5230 Odense (Denmark); William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Shifman, M. [William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2007-12-15

343

The Torus as a Disk Outflow  

NASA Astrophysics Data System (ADS)

Instead of a toroidal hydrostatic structure, disk outflow too can explain AGN obscuration: the torus is the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. A central component of star formation, such outflows unify naturally many AGN observations, including broad line emission. Disk winds predict that both the torus and BLR disappear at low mass accretion rates because the accretion onto the central black hole can no longer sustain the required cloud outflow rate. This disappearance has been observed in low-luminosity AGN. Recent COSMOS observations reveal two stages in the broad line disappearance. In this talk I offer an explanation that incorporates as a byproduct the "intermediate" Seyfert galaxies (type 1.x) into the unification scheme.

Elitzur, Moshe

2012-12-01

344

Operational Regimes of the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is a proof-of-principle experiment designed to study the physics of Spherical Tori (ST), i.e., low-aspect-ratio toroidal plasmas. Important issues for ST research are whether the high-eta stability and reduced transport theoretically predicted for this configuration can be realized experimentally. In NSTX, the commissioning of a digital real-time plasma control system, the provision of flexible heating systems, and the application of wall conditioning techniques were instrumental in achieving routine operation with good confinement. NSTX has produced plasmas with R/a {approx} 0.85 m/0.68 m, A {approx} 1.25, Ip * 1.1 MA, BT = 0.3-0.45 T, k * 2.2, d * 0.5, with auxiliary heating by up to 4 MW of High Harmonic Fast Waves, and 5 MW of 80 keV D0 Neutral Beam Injection (NBI). The energy confinement time in plasmas heated by NBI has exceeded 100 ms and a toroidal beta (bT = 2m0

/BT02, where BT0 is the central vacuum toroidal magnetic field) up to 22% has be en achieved. HHFW power of 2.3 MW has increased the electron temperature from an initial 0.4 keV to 0.9 keV both with and without producing a significant density rise in the plasma. The early application of both NBI and HHFW heating has slowed the penetration of the inductively produced plasma current, modifying the current profile and, thereby, the observed MHD stability.

D. Mueller; M.G. Bell; R.E. Bell; M. Bitter; T. Bigelow; P. Bonoli; M. Carter; J. Ferron; E. Fredrickson; D. Gates; L. Grisham; J.C. Hosea; D. Johnson; R. Kaita; S.M. Kaye; H. Kugel; B.P. LeBlanc; R. Maingi; R. Majeski; R. Maqueda; J. Menard; M. Ono; F. Paoletti; S. Paul; C.K. Phillips; R. Pinsker; R. Raman; S.A. Sabbagh; C.H. Skinner; V.A. Soukhanovskii; D. Stutman; D. Swain; Y. Takase; J. Wilgen; J.R. Wilson; G.A. Wurden; S. Zweben

2002-06-03

345

Reversed-field pinch studies in the Madison Symmetric Torus  

SciTech Connect

Studies of large-size (R = 1.5 m, a = 0.5 m), moderate current (I < 750 kA) reversed-field pinch (RFP) plasmas are carried out in the Madison Symmetric Torus in order to evaluate and improve RFP confinement, study general toroidal plasma MHD issues, determine the mechanism of the RFP dynamo, and measure fluctuation-induced transport and anomalous ion heating. MST confinement has been improved by reduction of magnetic field errors with correction coils in the primary circuit and reduction of impurities using boronization; high densities have been achieved with hydrogen pellet injection. MHD tearing modes with poloidal mode number m = 1 and toroidal mode numbers n = 5--7 are prevalent and nonlinearly couple to produce sudden relaxations akin to tokamak sawteeth. Edge fluctuation-induced transport has been measured with a variety of insertable probes. Ions exhibit anomalous heating, with increases of ion temperature occuring during strong MHD relaxation. The RFP dynamo has been studied with attention to various possible mechanisms, including motion-EMF drive, the Hall effect, and superthermal electrons. Initial profile control experiments have begun using insertable biased probes and plasma guns. The toroidal field capacity of MST will be upgraded during Summer, 1993 to allow low-current tokamak operation as well as improved RFP operation.

Hokin, S.; Almagri, A.; Cekic, M.; Chapman, B.; Crocker, N.; Den Hartog, D.J.; Fiksel, G.; Henry, J.; Ji, H.; Prager, S.; Sarff, J.; Scime, E.; Shen, W.; Stoneking, M.; Watts, C.

1993-04-03

346

Electron Bernstein Wave Experiment on the Madison Symmetric Torus  

SciTech Connect

A system to heat electrons and possibly drive off-axis field-aligned current is under development on the Madison Symmetric Torus RFP. Staged experiments have reached an input power of 150 kW at 3.6G Hz and have produced a localized increase in SXR emission during rf injection. This measured emission is consistent with modeling in its location, energy spectrum and dependence on radial diffusion within the plasma. The emission is strongest in the region where ray tracing predicts deposition of the injected power. The multi-chord SXR camera used is sensitive to 4-7 keV photons. Enhanced emission in this energy range is consistent with Fokker-Plank modeling of EBW injection. The enhanced SXR emission vanishes quickly when radial diffusion in the plasma is high (as indicated by m = 0 magnetic activity); this is also consistent with Fokker-Plank modeling. An increase of boron emission (and presumably boron within the plasma) is also observed during EBW injection. This presents an alternative explanation to the enhanced SXR emission. Subsequent experiments with a different antenna at 100 kW input showed a small increase in SXR emission near 3 keV. A higher frequency experiment (5.5 GHz) with more input power available is currently under construction. Initial tests are centered on a circular waveguide launcher which requires only a 5 cm circular port in the vacuum vessel and has a target launch power of 400 kW.

Anderson, J. K.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; Seltzman, A. H. [Department of Physics, University of Wisconsin, Madison WI 53706 (United States)

2009-11-26

347

Progress towards high performance, steady-state Spherical Torus  

NASA Astrophysics Data System (ADS)

The Spherical Torus is exploring the benefits of modifying the field line structure from that in more moderate aspect ratio devices. For an ST-based Component Test Facility and, ultimately a Demo device, it is essential to develop high performance, steady-state operational scenarios. The scientific issues are energy confinement, MHD stability at high beta, non-inductive sustainment, power and particle handling and solenoid-free start-up. NSTX has demonstrated CTF-relevant discharges with 60% non-inductively driven current sustained over a resistive skin-time, and a product ?_NH_89P approaching 15 at 0.8 MA plasma current. At 1.2 MA, the plasma ?T has reached 35%. In future, NSTX will be exploring advanced regimes with 100% non-inductively driven current, ?T up to 40% and ?N up to 8 which are sustained much longer than the skin-time. Modeling shows that this can be facilitated by some device improvements, including increasing the plasma elongation at high triangularity, active stabilization of resistive wall modes power and particle control using advanced walls and off-axis current drive using EBW. In addition to coaxial helicity injection, solenoid-free start-up concepts utilizing external poloidal field coils are being pursued on NSTX.

Ono, Masayuki

2003-10-01

348

Generation of parallel electric fields in the Jupiter-Io torus wake region  

NASA Astrophysics Data System (ADS)

Infrared and ultraviolet images have established that auroral emissions at Jupiter caused by the electromagnetic interaction with Io not only produce a bright spot, but an emission trail that extends in longitude from Io's magnetic footprint. Electron acceleration that produces the bright spot is believed to be dominated by Alfvén waves whereas we argue that the trail or wake aurora results from quasi-static parallel electric fields associated with large-scale, field-aligned currents between the Io torus and Jupiter's ionosphere. These currents ultimately transfer angular momentum from Jupiter to the Io torus. We examine the generation and the impact of the quasi-static parallel electric fields in the Io trail aurora. A critical component to our analysis is a current-voltage relation that accounts for the low-density plasma along the magnetic flux tubes that connect the Io torus and Jupiter. This low-density region, ˜ 2 R J from Jupiter's center, can significantly limit the field-aligned current, essentially acting as a “high-latitude current choke.” Once parallel electric fields are introduced, the governing equations that couple Jupiter's ionosphere to the Io torus become nonlinear and, while the large-scale behavior is similar to that expected with no parallel electric field, there are substantial deviations on smaller scales. The solutions, bound by properties of the Io torus and Jupiter's ionosphere, indicate that the parallel potentials are on the order of 1 kV when constrained by peak energy fluxes of a few milliwatts per square meter. The parallel potentials that we predict are significantly lower than earlier reports.

Ergun, R. E.; Ray, L.; Delamere, P. A.; Bagenal, F.; Dols, V.; Su, Y.-J.

2009-05-01

349

Ulysses COSPIN/KET observations of Jovian electron jets during the distant Jupiter encounter  

NASA Astrophysics Data System (ADS)

The COSPIN/KET experiment on-board Ulysses has been monitoring the flux of 3-20 MeV electrons in interplanetary space since the launch in October 1990. Between 1 and 10 AU Jovian, and galactic particles contribute continously to the few-MeV electron intensities. During it's recent descend to low latitudes the Ulysses spacecraft approached the planet Jupiter within 1 AU. However, in addition to the average intensity level well accounted for by diffusion, we report in this contribution very short duration electron events, which are called Jovian electron jets, characterized by: (i) a sharp increase and decrease of flux: (ii) a spectrum identical to the electron spectrum in the Jovian magnetosphere; and iii) a strong anisotropy. We compare our results with similar events, observed during the Jovian flyby in 1992.

Heber, B.; Kunow, H.; Raviart, A.; Forsyth, R.

350

Ulysses COSPIN/KET Observations of Jovian Electron Bursts During the Distant Jupiter Encounter  

NASA Astrophysics Data System (ADS)

The COSPIN/KET experiment on-board Ulysses has been monitoring the flux of 3-20 MeV electrons in interplanetary space since launch in October 1990. Between 1 and 10 AU Jovian and galactic particles contribute continously to the few-MeV electron intensities. During it's recent descend to low latitudes the Ulysses spacecraft approached Jupiter to less than 1~AU. However, in addition to the average intensity level well accounted for by diffusion, we report in this contribution very short duration electron events, which are called Jovian electron jets, characterized by: (i) a sharp increase and decrease of flux: (ii) a spectrum identical to the electron spectrum in the Jovian magnetosphere; and iii) a strong anisotropy. The results are compared with similar events observed during the Jovian close flyby in 1992.

Heber, B.; Forsyth, R.; Kunow, H.; Raviart, A.

2004-05-01

351

Investigating the origins of the Jovian decimetric emission's variability  

NASA Astrophysics Data System (ADS)

The long-term variability of the Jovian radiation observed at 13-cm wavelength over 30 years is investigated using a physical model of the radiation belts. The model enables us to quantify the effect of the geometric parameter DE on the synchrotron emission. When a full Jupiter rotation is taken into account in the computations, the variability of the total radio flux with DE is only ?1% of that measured. Such a dependence is not detectable. In contrast, radio fluctuations observed at a central meridian longitude (CML) and caused by DE changes can be very important, up to 10% of that measured. This strong dependence of the total radio flux on the geometric factor can result in difficulties for examining the origins of the Jovian synchrotron emission's fluctuations during periods where times of observation are not covering large CML range values. The numerical computations reveal that the variability either of the populations injected near the outer boundary of our simulations (Io's orbit) or the inward radial transport can, independently or in combined action, conduct variability in the decimetric emission. The theoretical fluctuations required in our computations for reproducing the radio measurements do not confirm any direct correlation between the long-term changes in the radio data and the radial transport driven by solar wind conditions or solar radio fluxes. Nevertheless, a linear relationship between the total radio flux and solar wind ram pressure for the period of 1970 to 2002 is established. The maximum correlation is reached when the Psw data are shifted by ?2.7 years prior to the radio observations. Using this time-lag in the computations, the simulation results show that (Psw)? can be associated with the variations of the particle injections and the radial transport. The correlation coefficient, associated with the fit between radio data and simulated radio flux densities, is 0.59 for the period of 1971-2002, 0.93 for the period of 1971-1972, and 0.83 for the periods of 1975-1989 and 1992-1995. The index ? is set to 0.35 when only particle injections are fluctuating with time, to 0.50 when temporal variations are driving the radial transport, and to 0.15-0.20 when the particles injected in the inner magnetosphere and their transport are simultaneously following the variations of the solar wind ram pressure. The model suggests that the solar wind ram pressure fluctuations can be related to variations of the Jovian decimetric emission on timescales of months, particularly to the enhancements in total radio flux observed in 1987, 1988, 1990 and 1994. Our results thus support the idea that the increase in radio emission in July 1994 was due to the impact of Comet Shoemaker-Levy 9 into Jupiter, in addition to the response of the Jovian magnetosphere to steep changes in solar wind conditions. The divergence between observations and simulations indicates that mechanisms other than those discussed in the modeling must govern the radiation belts dynamics for the periods of 1972-1975 and 1996-2002.

Santos-Costa, D.; Bolton, S. J.; Thorne, R. M.; Miyoshi, Y.; Levin, S. M.

2008-01-01

352

The Secular Variation of The Jovian Intrinsic Magnetic Field  

NASA Astrophysics Data System (ADS)

The Galileo orbiter measurements of Jupiter's magnetic field when combined with the Pioneer 11 magnetic measurements are sufficiently accurate to resolve the secular change in the internal magnetic field in the dipole and quadrupole magnetic field. We find first that the longitude of the dipole moment has drifted eastward by 2 deg. indicating that the system III period based on the rotation of the magnetic field is 9 ms shorter than previously believed. The tilt angle of the dipole has apparently increased by 0.3 deg. of the five quadrupole terms go2 has apparently changed at a rate of 1.6% per year relative to the root mean sum of field strength at second order. The other four terms change at a rate closer to 0.2% per year. Overall the secular change of the jovian field seems very Earth-like.

Russell, C. T.; Yu, Z. J.; Khurana, K. K.; Joy, S. P.; Kivelson, M. G.

353

Dynamo region and the equatorial electrojet in the Jovian atmosphere  

NASA Astrophysics Data System (ADS)

The existence of the dynamo region is identified in the atmosphere of Jupiter. It is found that the dynamo region extends from an altitude of 130 km (0.153 mbar) to 330 km (0.027 microbar) reckoned from zero altitude corresponding to 43.8 mbar pressure level. Physical features of the equatorial electrojet in the ionosphere of Jupiter are modelled in detail. The Jovian equatorial electrojet has a maximum eastward current density of about 1.5 A/sq km at an altitude of 270 km (0.33 microbar) with a latitudinal half width of about + or - 11 degrees. The thickness of the equatorial half width is 100 km in altitude range. The type I instability in the electrojet can exist only if the electron streaming velocity exceeds the value of about 250 m/s.

Raghavarao, R.; Dagar, R.

1983-06-01

354

Is the Jovian auroral H3+ emission polarised?  

NASA Astrophysics Data System (ADS)

Context. Measurement of linear polarisation in Earth's thermospheric oxygen red line can be a useful observable quantity for characterising conditions in the upper atmosphere; therefore, polarimetry measurements are extended to other planets. Since FUV emissions are not observable from the ground, the best candidates for Jupiter auroral emissions are H3+ infrared lines near 4 ?m. This ion is created after a chemical process in the Jovian upper atmosphere. Thus the anisotropy responsible of the polarisation cannot be the particle impact as in the Earth case. Aims: The goal of this study is to detect polarisation of H3+ emissions from Jupiter's aurora. Methods: Measurements of the H3+ emissions from Jupiter's southern auroral oval were performed at the UK Infrared Telescope using the UIST-IRPOL spectro-polarimeter, with the instrument slit positioned perpendicular to Jupiter's rotation axis. Data were processed by dividing the slit into 24 bins. Stokes parameters (u, q and v), polarisation degree and direction were extracted for each bin and debiased. Results: More than 5 bins show polarisation with a confidence level above 3?. Polarisation degrees up to 7% are detected. Assuming the auroral intensity is constant during the 8 waveplate positions exposure time, i.e. around 10 min, strong circular polarisation is present, with an absolute value of the Stokes v parameter up to 0.35. Conclusions: This study shows that polarisation is detectable in the Jovian infrared auroras, but new measurements are needed to be able to use it to characterise the ionospheric environment. At present, it is not possible to propose a mechanism to explain this polarisation owing to the lack of theoretical work and laboratory experiments concerning the polarisation of H3+ .

Barthelemy, M.; Lystrup, M. B.; Menager, H.; Miller, S.; Lilensten, J.

2011-06-01

355

Why Is a Titan-generated Nitrogen Torus Not Observed In Saturn's Magnetosphere?  

NASA Astrophysics Data System (ADS)

Prior to Cassini's arrival at Saturn, Titan-generated nitrogen ions were thought to dominate heavy plasma in Saturn's magnetosphere. Therefore, the presence of a Titan nitrogen torus was anticipated. However, it is now known water-group ions dominate Saturn's heavy ion magnetospheric plasma. While nitrogen ions have been detected beyond the orbit of Rhea, these ions appear to be primarily originating from the Enceladus plumes with little nitrogen plasma detected in the magnetosphere near Titan's orbit. In fact, pick-up oxygen ions from Enceladus are much more abundant than nitrogen in Titan’s orbit. These results appear inconsistent with the expectation that Titan's dense relatively unprotected atmosphere should provide a significant source of heavy particles to Saturn's magnetosphere. This inconsistency suggests that the plasma environment at Titan's orbit is much more complex than originally anticipated. In this talk, we expand on our previous research that categorizes the plasma environments near Titan to include all locations along Titan's orbit. Using these categories, we develop characteristic plasma spectra of each type of environment, update ionization lifetimes for each region and apply these results in a 3D Monte Carlo model to more accurately examine the fate of nitrogen and methane escaping Titan's atmosphere to support the possible presence of a Titan torus despite the lack of observations. We also present preliminary Cassini data analysis that is focused on regions where such a torus could be detected. This work is supported by the NASA Cassini Data Analysis Program and NASA JPL contract 1243218 for Cassini MIMI and CAPS investigation.

Smith, Howard T.; Johnson, R. E.; Rymer, A. M.; Mitchell, D. G.; Coates, A.; Lewis, G.; Young, D. T.

2012-10-01

356

PROBING THE LARGE-SCALE TOPOLOGY OF THE HELIOSPHERIC MAGNETIC FIELD USING JOVIAN ELECTRONS  

SciTech Connect

Jupiter's magnetosphere acts as a point source of near-relativistic electrons within the heliosphere. In this study, three solar cycles of Jovian electron data in near-Earth space are examined. Jovian electron intensity is found to peak for an ideal Parker spiral connection, but with considerable spread about this point. Assuming the peak in Jovian electron counts indicates the best magnetic connection to Jupiter, we find a clear trend for fast and slow solar wind to be over- and under-wound with respect to the ideal Parker spiral, respectively. This is shown to be well explained in terms of solar wind stream interactions. Thus, modulation of Jovian electrons by corotating interaction regions (CIRs) may primarily be the result of changing magnetic connection, rather than CIRs acting as barriers to cross-field diffusion. By using Jovian electrons to remote sensing magnetic connectivity with Jupiter's magnetosphere, we suggest that they provide a means to validate solar wind models between 1 and 5 AU, even when suitable in situ solar wind observations are not available. Furthermore, using Jovian electron observations as probes of heliospheric magnetic topology could provide insight into heliospheric magnetic field braiding and turbulence, as well as any systematic under-winding of the heliospheric magnetic field relative to the Parker spiral from footpoint motion of the magnetic field.

Owens, M. J.; Horbury, T. S. [Space and Atmospheric Physics, Imperial College, London SW7 2AZ (United Kingdom); Arge, C. N. [Air Force Research Laboratory/Space Vehicles Directorate, Kirtland Air Force Base, NM 87117 (United States)

2010-05-10

357

Initial Results from the Lost Alpha Diagnostics on Joint European Torus  

SciTech Connect

Two devices have been installed in the Joint European Torus (JET) vacuum vessel near the plasma boundary to investigate the loss of energetic ions and fusion products in general and alpha particles in particular during the upcoming JET experiments. These devices are (i) a set of multichannel thin foil Faraday collectors, and (ii) a well collimated scintillator which is optically connected to a charge-coupled device. Initial results, including the radial energy and poloidal dependence of lost ions from hydrogen and deuterium plasmas during the 2005–06 JET restart campaign, will be presented.

Darrow, Doug; Cecil, Ed; Ellis, Bob; Fullard, Keith; Hill, Ken; Horton, Alan; Kiptily, Vasily; Pedrick, Les; Reich, Matthias

2007-07-25

358

Transport theory for potato orbits in an axisymmetric torus with finite toroidal flow speed  

SciTech Connect

Transport theory for potato orbits in the region near the magnetic axis in an axisymmetric torus such as tokamaks and spherical tori is extended to the situation where the toroidal flow speed is of the order of the sonic speed as observed in National Spherical Torus Experiment [E. J. Synakowski, M. G. Bell, R. E. Bell et al., Nucl. Fusion 43, 1653 (2003)]. It is found that transport fluxes such as ion radial heat flux, and bootstrap current density are modified by a factor of the order of the square of the toroidal Mach number. The consequences of the orbit squeezing are also presented. The theory is developed for parabolic (in radius r) plasma profiles. A method to apply the results of the theory for the transport modeling is discussed.

Shaing, K. C. [University of Wisconsin; Peng, Yueng Kay Martin [ORNL

2004-01-01

359

Numerical study of the Columbia high-beta device: Torus-II  

SciTech Connect

The ionization, heating and subsequent long-time-scale behavior of the helium plasma in the Columbia fusion device, Torus-II, is studied. The purpose of this work is to perform numerical simulations while maintaining a high level of interaction with experimentalists. The device is operated as a toroidal z-pinch to prepare the gas for heating. This ionization of helium is studied using a zero-dimensional, two-fluid code. It is essentially an energy balance calculation that follows the development of the various charge states of the helium and any impurities (primarily silicon and oxygen) that are present. The code is an atomic physics model of Torus-II. In addition to ionization, we include three-body and radiative recombination processes.

Izzo, R.

1981-01-01

360

Mechanical design considerations of a spherical torus volumetric neutron source  

SciTech Connect

The mechanical design of a spherical torus based volumetric neutron source (ST VNS) is being studied under the support of a DOE-SBIR funding. A device capable of staged operation from a neutron wall loading of 0.5-5.0 MW/m(2) has been scoped out, as the physics and engineering design assumptions are raised from modest to aggressive levels. Margins in the design are ensured since operation of the VNS will be adequate st a wall loading of 2 MW/m(2). The device has a naturally diverted plasma with major radius of 1.07 m, a minor radius of 0.77 m for an aspect ratio of 1.4, an elongation of 3 and triangularity of 0,6. In the neutral beam driven version, the plasma current is 11.1 MA and the toroidal field at the plasma major radius is 2.13 T, The baseline fusion power is 151 MW giving an average neutron wall loading of 2 MV/m(2) on the outboard side over an accessible area of over 15 m(2) for blanket testing. The device utilizes a normal Cu conducting bell jar as the return leg of the toroidal field current, a concept developed at the Oak Ridge National Laboratory. The current is carried by an unshielded single-turn center post (CP) made of dispersion strengthened Cu which is cooled by water in a single pass from top to bottom. A special sliding electrical interface between the CP and the bell jar is provided on the upper end to allow for differential expansion and to isolate the CP from tensile and torsional forces from the bell jar. The ohmic heating in the CP is 153 MW at the start of operation and increases to 178 MW after 3 full power years of operation. Over this period the maximum Cu temperature does not exceed 160 C. This report primarily deals with the design of the CP, one of the most challenging Issues of a low aspect ratio spherical torus. Maintenance approaches for the Or and the divertor assemblies have been determined and are addressed in the paper.

Sviatoslavky, I. N. [University of Wisconsin, Madison; Peng, Yueng Kay Martin [ORNL

1998-01-01

361

D-He-3 spherical torus fusion reactor system study  

NASA Astrophysics Data System (ADS)

This system study extrapolates present physics knowledge and technology to predict the anticipated characteristics of D-He3 spherical torus fusion reactors and their sensitivity to uncertainties in important parameters. Reference cases for steady-state 1000 MWe reactors operating in H-mode in both the 1st stability regime and the 2nd stability regime were developed and assessed quantitatively. These devices would a very small aspect ratio (A=1,2), a major radius of about 2.0 m, an on-axis magnetic field less than 2 T, a large plasma current (80-120 MA) dominated by the bootstrap effect, and high plasma beta (greater than O.6). The estimated cost of electricity is in the range of 60-90 mills/kW-hr, assuming the use of a direct energy conversion system. The inherent safety and environmental advantages of D-He3 fusion indicate that this reactor concept could be competitive with advanced fission breeder reactors and large-scale solar electric plants by the end of the 21st century if research and development can produce the anticipated physics and technology advances.

Macon, William A., Jr.

1992-04-01

362

Electron Bernstein Wave Experiment on the Madison Symmetric Torus  

SciTech Connect

A 0.25 MW system designed to heat electrons and drive current via the electron Bernstein wave is in its early stages of operation on the Madison Symmetric Torus reversed field pinch. The antenna is a grill of four half-height S-band waveguides with each arm powered by a separate, phase controlled traveling wave tube amplifier. Coupling to the plasma (as measured by ratio of reflected power) is very dependent on the relative phasing. The total reflected power can be maintained at or below 25%, similar to that measured for a two-waveguide full height grill[1]. The antenna face is outfitted with a pair of triple Langmuir probes to measure local electron density; the density gradient at the upper hybrid resonance (typically within 1-2 cm of the antenna) is expected to strongly influence coupling efficiency. Conditioning of the antenna is currently underway and total system power is expected to reach 0.25 MW, or roughly a fourth of the Ohmic input power in target plasmas. The x-ray spectrum (5-200 keV) is monitored as a way to detect modification to the electron distribution as full transmitter power is approached.

Anderson, J. K.; Cox, W. A.; Forest, C. B.; McMahon, S. M. [Department of Physics, University of Wisconsin, Madison WI 53706 (United States)

2007-09-28

363

Electron Bernstein Wave Research on the National Spherical Torus Experiment  

SciTech Connect

Off-axis electron Bernstein wave current drive (EBWCD) may be critical for sustaining noninductive high-beta National Spherical Torus Experiment (NSTX) plasmas. Numerical modeling results predict that the {approx}100 kA of off-axis current needed to stabilize a solenoid-free high-beta NSTX plasma could be generated via Ohkawa current drive with 3 MW of 28 GHz EBW power. In addition, synergy between EBWCD and bootstrap current may result in a 10% enhancement in current-drive efficiency with 4 MW of EBW power. Recent dual-polarization EBW radiometry measurements on NSTX confirm that efficient coupling to EBWs can be readily accomplished by launching elliptically polarized electromagnetic waves oblique to the confining magnetic field, in agreement with numerical modeling. Plans are being developed for implementing a 1 MW, 28 GHz proof-of-principle EBWCD system on NSTX to test the EBW coupling, heating and current-drive physics at high radio-frequency power densities.

G. Taylor; A. Bers; T.S. Bigelow; M.D. Carter; J.B. Caughman; J. Decker; S. Diem; P.C. Efthimion; N.M. Ershov; E. Fredd; R.W. Harvey; J. Hosea; F. Jaeger; J. Preinhaelter; A.K. Ram; D.A. Rasmussen; A.P. Smirnov; J.B. Wilgen; J.R. Wilson

2005-04-21

364

Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment  

SciTech Connect

High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.

J.R. Wilson; R.E. Bell; S. Bernabei; M. Bitter; P. Bonoli; D. Gates; J. Hosea; B. LeBlanc; T.K. Mau; S. Medley; J. Menard; D. Mueller; M. Ono; C.K. Phillips; R.I. Pinsker; R. Raman; A. Rosenberg; P. Ryan; S. Sabbagh; D. Stutman; D. Swain; Y. Takase; J. Wilgen; the NSTX Team

2003-02-11

365

On the Bimodal Distribution of the Jovian and Kronian Magnetopause and Bow Shock Locations  

NASA Astrophysics Data System (ADS)

A comprehensive statistical analysis of observed Jovian magnetopause and bow shock crossings revealed a bimodal distribution in the standoff distances of these boundaries [Joy et al., JGR, 2002], which was attributed to bimodality in the solar wind dynamic pressure. Recently a similar bimodality was identified also in the location of the Kronian magnetopause based on Cassini observations [Achilleos et al., Saturn Book Symposium, 2008]. It is still controversial whether this bimodality at Saturn is a result of a corresponding bimodal distribution in the solar wind or comes from internal magnetospheric processes characteristic to rotationally driven magnetospheres with significant internal mass loading rates. We investigate this question in two different ways. First, we analyze propagated upstream solar wind data at Jupiter and Saturn to test the presence of bimodality in the solar wind driving. For this purpose we use 13 years of upstream data obtained by the Michigan Solar Wind Model (MSWiM) that is a 1.5-D MHD model to propagate solar wind conditions from 1 AU to the outer planets. Second, we use our 3-D global MHD model of Saturn's magnetosphere to test whether the model can produce a bimodal distribution of standoff distances under conditions of low solar wind dynamic pressure and relatively high mass loading rate. Our model includes two magnetospheric plasma sources, a major disk-like source from Enceladus and the rings and a secondary toroidal plasma source from Titan. We fit a 9-parameter analytical magnetopause model and a 4-parameter bow shock model for Saturn to the simulated MHD boundaries at different times of the simulation to obtain a simulated distribution of the standoff distances. We expect that the internal magnetospheric dynamics is more likely to cause the observed bimodal distribution in the Kronian magnetopause locations rather than a bimodal distribution in the upstream solar wind.

Gombosi, T. I.; Zieger, B.; Hansen, K. C.

2008-12-01

366

Curved noncommutative torus and Gauss-Bonnet  

NASA Astrophysics Data System (ADS)

We study perturbations of the flat geometry of the noncommutative two-dimensional torus T?2 (with irrational ?). They are described by spectral triples (A?,,D), with the Dirac operator D, which is a differential operator with coefficients in the commutant of the (smooth) algebra A? of T?. We show, up to the second order in perturbation, that the ?-function at 0 vanishes and so the Gauss-Bonnet theorem holds. We also calculate first two terms of the perturbative expansion of the corresponding local scalar curvature.

Dabrowski, Ludwik; Sitarz, Andrzej

2013-01-01

367

Imaging the Jovian Magnetosphere in Energetic Neutral Atoms with the Cassini/Huygens Magnetospheric Imaging Instrument Ion and Neutral Camera  

NASA Astrophysics Data System (ADS)

During the flyby of Jupiter on its cruise to Saturn, the Cassini/Huygens spacecraft collected unique data with a broad assortment of instruments. The Magnetospheric Imaging Instrument (MIMI) measured in-situ energetic ions and electrons, performed charge and mass analysis of both interstellar pickup ions and Jovian source ions, and remotely imaged the Jovian magnetosphere in energetic neutral atom (ENA) emissions. The ENA images were measured with the Ion and Neutral Camera (INCA) [Mitchell et al., 1998]. INCA images ENA in the velocity range from about 1200 km/s to 8000 km/s, which for hydrogen corresponds to about 8 keV to about 350 keV. Jupiter, as expected based on Voyager measurements [Kirsch et al., 1981; Cheng 1986], is a weak ENA source. The expected INCA response was modeled by Mauk et al., 1998. The INCA sensor was run in a mode for which images were obtained only below about 80 keV/nucleon. The images obtained are quite close to the predictions of Mauk et al., both in conformation and in intensity. They are consistent with the source strength of the Jovian magnetosphere remaining essentially constant between 1979 and 2001. Rough inferences as to the composition of the ENA show that there is a mix of hydrogen as well as heavier atoms, most probably oxygen and sulfur. These first-ever images of Jupiter's magnetosphere provide a taste of what we can look forward to at Saturn, although the distance of this flyby (140 Rj) allows only hints of the magnetospheric structure to be resolved with this instrument, which is designed for a closer vantage point. Mitchell, D. G., A. F. Cheng, K. C. Hsieh, S. M. Krimigis, E. P. Keath, S. E. Jaskulek, B. H. Mauk, R. W. McEntire, E. C. Roelof, C. E. Schlemm, B. E. Tossman, and D. J. Williams, The ion neutral camera for the Cassini Mission to Saturn and Titan, Measurement Techniques in Space Plasmas, Fields, R. F. Pfaff, J. E. Borovsky, and D. T. Young, ed., Geophysical Monograph 103, p281, AGU, 1998. Kirsch, E., S. M. Krimigis, J. Johl, and E. Keath, Upper limits for X-ray and energetic neutral particle emission from Jupiter: Voyager 1 results, Geophys. Res. Lett., 8, 169, 1981. Mauk, B.H., S.M. Krimigis, D.G. Mitchell, and E.C. Roelof, Energetic neutral atom imaging of Jupiter's magnetosphere using the Cassini MIMI instrument, Adv. Space Res., 21, 1483, 1998.

Mitchell, D. G.; Krimigis, S. M.; Mauk, B. H.

2001-05-01

368

Mixed Branes and M(atrix) Theory on Noncommutative Torus  

Microsoft Academic Search

We derive the noncommutative torus compactification of M(atrix) theory\\u000adirectly from the string theory by imposing mixed boundary conditions on the\\u000amembranes. The relation of various dualities in string theory and M(atrix)\\u000atheory compactification on the noncommutative torus are studied.

F. Ardalan; H. Arfaei; M. M. Sheikh-Jabbari

1998-01-01

369

Laboratory Studies of Ammonia Ices Relevant to the Jovian Atmosphere  

NASA Astrophysics Data System (ADS)

Ammonia ice condensation and cloud formation microphysics are topics of relevance for understanding the atmospheres of the giant planets. Ammonia ices are also considered important components of the icy satellites found in the outer solar system, and are thought to play an important role in their geological activity. Although observational evidence and thermochemical models suggest ammonia clouds in the Jovian atmosphere should be ubiquitous, less than only 1% of Jupiter's atmosphere appears covered by spectrally identifiable ammonia clouds, with a clear preference in turbulent regions.1,2 The paradox of the rather scarce spectroscopic signatures of ammonia clouds and their appearance in turbulent regions suggests that the nascent ammonia clouds may undergo processing that modifies their spectroscopic properties. No relevant laboratory experimental results are available to resolve this problem. Two possible sources of processing that have been suggested in the literature include photochemical solid-state modification (''tanning'') and coating of ammonia particles by other substances present in the stratospheric haze.2,3 We are performing laboratory investigations with the objective to provide information on the photophysical and chemical processes that control the optical properties of the Jovian ammonia clouds. In the experiments, thin ice films of ammonia are coated with organic molecules, such as saturated and aromatic hydrocarbons, and characterized by infrared spectroscopy. Preliminary results indicate suppression of the ammonia absorption feature at 2.7 ? m by a thin layer of hydrocarbons. The implications for the spectral signatures of ammonia clouds in the atmospheres of Jupiter and Saturn will be discussed. Funding from the NSF Planetary Astronomy Program under grant AST-0206270 is gratefully acknowledged. The participation of Rhiannon Meharchand and Christina Baer was made possible by the NSF Research Experiences for Undergraduates Program under grant PHY-0353745. 1. S. K. Atreya and A.-S. Wong, Eos. Trans. 84(46), Fall. Meet. Suppl., Abstract A12A-0072 (2003), and references therein. 2. K. H. Baines, R. W. Carlson, and L. W. Kamp, Icarus 159, 74 (2002). 3. A.-S. Wong, Y. L. Yung, and A. J. Friedson, Geophys. Res. Lett. 30, 1447 (2003).

Meharchand, R. T.; Boulter, J. E.; Baer, C. E.; Kalogerakis, K. S.

2004-12-01

370

The dynamics of jovian white ovals from formation to merger  

NASA Astrophysics Data System (ADS)

In early 1998 two of the three, long-lived anticyclonic, jovian white ovals merged. In 2000 the two remaining white ovals merged into one. Here we examine that behavior, as well as the dynamics of three earlier epochs: the Formation Epoch (1939-1941), during which a nearly axisymmetric band broke apart to form the vortices; the Kármán Vortex Street Epoch (1941-1994), during which the white ovals made up the southern half of two rows of vortices, and their locations oscillated in longitude such that the white ovals often closely approached each other but did not merge; and the Pre-merger Epoch (1994-1997), during which the three white ovals traveled together with intervening cyclones from the northern row of the Kármán vortex street in a closely spaced group with little longitudinal oscillation. We use a quasi-geostrophic model and large-scale numerical simulation to explain the dynamics. Our models and simulations are consistent with the observations, but none of the observed behavior is even qualitatively possible without assuming that there are long-lived, coherent cyclones longitudinally interspersed with the white ovals. Without them, the white ovals approach each other and merge on a fast, advective timescale (4 months). A necessary ingredient that allows the vortices to travel together in a small packet without spreading apart is that the strong, eastward-flowing jetstream south of the white ovals is coincident with a sharp gradient in background potential vorticity. The jet forms a Rossby wave and a trough of the wave traps the white ovals. In our simulations, the three white ovals were trapped before they merged. Without being trapped, the amount of energy needed to perturb two white ovals so that they merge exceeds the atmosphere's turbulent energy (which corresponds to velocities of ˜1 m s -1) by a factor of ˜100. The mergers of the white ovals BC and DE were not observed directly, so there is ambiguity in labeling the surviving vortices and identifying which vortices might have exchanged locations. The simulation and modeling make the identifications clear. They also predict the fate of the surviving white oval and of the other prominent jovian vortex chains.

Youssef, Ashraf; Marcus, Philip S.

2003-03-01

371

Plasmonics properties of nano-torus: An FEM method  

NASA Astrophysics Data System (ADS)

Nano-torus particles are promising in nano-photonics applications. In this paper, we investigate the plasmonics resonant spectrum of torus and the corresponding horizontal and vertical dimers with the finite element method (FEM) based on strict electromagnetic theory. Compared with sphere, single torus and horizontal dimer under perpendicular polarization are characterized with narrower line width and wider tunability throughout visible and infrared frequencies. These properties make single torus and horizontal dimer suitable for high sensitivity sensing. Furthermore, Purcell factor and local field enhancement of horizontal dimer which are important to high efficient single photon devices are one order of magnitude higher than those of single torus respectively. However, vertical dimer under perpendicular polarization has no above advanced characteristics.

Shi, Qiang; Yu, Zhongyuan; Liu, Yumin; Gong, Hui; Yin, Haozhi; Zhang, Wen; Liu, Jiantao; Peng, Yiwei

2012-10-01

372

ULYSSES radio and plasma wave observations in the Jupiter environment  

Microsoft Academic Search

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded

R. G. Stone; B. M. Pedersen; C. C. Harvey; P. Canu; N. Cornilleau-Wehrlin; M. D. Desch; C. de Villedary; J. Fainberg; W. M. Farrell; K. Goetz; R. A. Hess; S. Hoang; M. L. Kaiser; P. J. Kellogg; A. Lecacheux; N. Lin; R. J. MacDowall; R. Manning; C. A. Meetre; N. Meyer-Vernet; M. Moncuquet; V. Osherovich; M. J. Reiner; A. Tekle; J. Thiessen; P. Zarka

1992-01-01

373

Calculations of Neutral Beam Ion Confinement for the National Spherical Torus Experiment  

SciTech Connect

The spherical torus (ST) concept underlies several contemporary plasma physics experiments, in which relatively low magnetic fields, high plasma edge q, and low aspect ratio combine for potentially compact, high beta and high performance fusion reactors. An important issue for the ST is the calculation of energetic ion confinement, as large Larmor radius makes conventional guiding center codes of limited usefulness and efficient plasma heating by RF and neutral beam ion technology requires minimal fast ion losses. The National Spherical Torus Experiment (NSTX) is a medium-sized, low aspect ratio ST, with R=0.85 m, a=0.67 m, R/a=1.26, Ip*1.4 MA, Bt*0.6 T, 5 MW of neutral beam heating and 6 MW of RF heating. 80 keV neutral beam ions at tangency radii of 0.5, 0.6 and 0.7 m are routinely used to achieve plasma betas above 30%. Transport analyses for experiments on NSTX often exhibit a puzzling ion power balance. It will be necessary to have reliable beam ion calculations to distinguish among the source and loss channels, and to explore the possibilities for new physics phenomena, such as the recently proposed compressional Alfven eigenmode ion heating.

M.H. Redi; D.S. Darrow; J. Egedal; S.M. Kaye; R.B. White

2002-06-27

374

2D divertor design calculations for the Nataional High-power Advanced Torus Experiment  

SciTech Connect

The National High Power Advanced Torus Experiment is a concept for a new facility to address the FESAC Theme of "Taming the Plasma-Material Interface." This concept exploits the compactness and excellent access provided by low aspect ratio to achieve a high ratio of exhaust power to major radius in order to study the integration of high-performance, long-pulse plasmas with a reactor-relevant high heat flux plasma boundary. Predictions of the scrape-off-layer plasma characteristics are presented, as calculated with the 2D edge modeling code SOLPS. Calculations in a variety of magnetic geometries indicate that very high levels of divertor heat flux can be expected, with peak values far in excess of the power handling capabilities of presently-used materials. Possible methods to reduce the heat flux to acceptable levels are discussed.

Canik, John [ORNL; Maingi, R. [Oak Ridge National Laboratory (ORNL); Owen, Larry W [ORNL; Menard, J. [Princeton Plasma Physics Laboratory (PPPL); Goldston, R. [Princeton Plasma Physics Laboratory (PPPL); Kotschenreuther, M. [University of Texas, Austin; Valanju, P. [University of Texas, Austin; Mahajan, S. [University of Texas, Austin

2009-01-01

375

JOVIAN EARLY BOMBARDMENT: PLANETESIMAL EROSION IN THE INNER ASTEROID BELT  

SciTech Connect

The asteroid belt is an open window on the history of the solar system, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions (SFDs). In this work, we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depends on the SFD of the primordial planetesimals. If the asteroid belt was dominated by planetesimals less than 100 km in diameter, the primordial bombardment would have caused the erosion of bodies smaller than 200 km in diameter. If the asteroid belt was instead dominated by larger planetesimals, the bombardment would have resulted in the destruction of bodies as big as 500 km.

Turrini, D.; Coradini, A.; Magni, G., E-mail: diego.turrini@ifsi-roma.inaf.it [Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, 00133, Rome (Italy)

2012-05-01

376

Characterization of Jovian Planets in Solar-like Planetary Systems  

NASA Astrophysics Data System (ADS)

FAME and SIM will push the limitations of the search for planetary systems to sensitivities approaching the detection of earth-like planets. To better understand the origins of such planets we will want to model the planetary systems in which they are found. Unfortunately, the data provided for the outer planets in such systems is limited by the proposed 5 year missions of these spacecraft. Thus in most cases, a detailed study of the orbital parameters of outer planets in these systems will have to await later missions. Fortunately, for 21 nearby stars studied with the University of Pittsburgh's Multichannel Astrometric Photometer (MAP), milliarc second (mas) data spanning 25 years will be available. Simulations indicate that the orbital parameters (all nonlinear) of the jovian planets of any of these systems can be modeled at significantly higher precision than possible with the spacecraft data alone. For any solar like planetary system found in this sample, the resulting parameters will allow the study of orbital spacing and stability, co-plainer motion, and planetary masses at a significantly higher precision than would have otherwise been available for another decade. Simulation results and the target list are presented.

Gatewood, G.; Coban, L.; Persinger, T.; Reiland, T.

2000-05-01

377

Probabilistic models of the Jovian magnetopause and bow shock locations  

NASA Astrophysics Data System (ADS)

New three-dimensional models of the Jovian magnetopause and bow shock were derived by combining spacecraft observations with boundary characteristics inferred from a magnetohydrodynamic (MHD) simulation. The MHD simulation provides polynomial forms parameterized by solar wind dynamic pressure. Observations from Pioneer 10 and 11, Voyager 1 and 2, Ulysses, and Galileo were used to establish the probability that regions surrounding Jupiter fall inside or outside these boundary surfaces. The magnetopause location was found to have a bimodal probability distribution with the two most probable standoff distances at 63 RJ (? = 4 RJ) and 92 RJ (? = 6 RJ). The bow shock location distribution appears bimodal, but a single distribution function description cannot be ruled out at the 95% confidence level. The mean bow shock standoff distance is 84 RJ (? = 16 RJ). Analysis of solar wind measurements near 5.2 AU (interplanetary magnetic field, dynamic pressure, and Alfvén Mach number) suggests that the bimodal distribution of boundary positions results at least in part from the bimodal distribution of solar wind parameters in the vicinity of Jupiter. The probability density distributions of these parameters within and between regions of disturbed solar wind, caused by corotating interaction regions and coronal mass ejections, are statistically distinct. Smaller variations were also observed in these parameters over the solar cycle.

Joy, S. P.; Kivelson, M. G.; Walker, R. J.; Khurana, K. K.; Russell, C. T.; Ogino, T.

2002-10-01

378

A Troop of Trojans: Photometry of 24 Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

Because of their greater distance from the Sun, the Jovian Trojans have been less studied than main belt asteroids. Although they are numerous (nearly 6000 have well determined orbits as of July 2013), the Trojans remain mysterious in many ways. Their spectra are unlike those of any meteorites in terrestrial collections. The spectra and the low albedos of Trojans, however, bear a strong resemblance to those of cometary nuclei (Abell et al. 2005; Fornasier et al. 2007; Emery et al. 2011). The Nice Model (Morbidelli et al. 2005; 2009) predicts that the Trojans may well be objects that originated with today's Kuiper Belt Objects. The rotation of asteroids larger than ~50 km in diameter seems to be determined largely by collisions, while that of smaller bodies is shaped primarily by YORP forces and torques (Pravec et al. 2008). We are surveying the rotation properties of Trojans to see whether similar trends are present. We find an abundance of slow rotators, including the first documented tumbler among the Trojans. We present 24 new Trojan lightcurves, mostly from objects ranging from 30-50 km in diameter. We also discuss observations of five sub-20 km Trojans, whose rotation properties are consistent with cometary densities. This research was supported by National Science Foundation Grant AST-1212115, by NASA Grant NNX-08AO29G, and by an American Astronomical Society Small Research Grant.

French, Linda M.; Stephens, R. D.; Coley, D. R.; Wasserman, L. H.; La Rocca, D.; Vilas, F.

2013-10-01

379

Spectral and Waveform Observations of Jovian Decametric Radio Emission  

NASA Astrophysics Data System (ADS)

Within the frame of the EU-INTAS project "New Frontiers in Decametre Radio Astronomy" research groups of France (Observatoire de Paris-Meudon), Austria (Space Research Institute Graz) and Ukraine (Radioastronomy Institute Kharkov) cooperate in the investigation of Jovian decametric radio observation and analysis of data obtained by simultaneous measurement campaigns using digital spectropolarimeters (DSP) at the radio telescopes Nancay (France) and Kharkov (Ukraine) in combination with a newly developed waveform receiver (WFR) additionally installed at Kharkov. Both devices (DSP and WFR) are fully digital receiving systems with high sensitivity and high spectral resolution. Especially the waveform receiver is capable of retaining the real received waveform of the emission for a time period of up to five seconds. A general spectral overview will be given on different Io-related radio storms explaining the capabilities of simultaneos high frequency and time resolution observations by almost identical DSPs separated East-West by about 3500 km. At selected periods of time especially for high millisecond burst activity the WFR was put into operation. These data provide the key for further detailed studies on internal structures and phase changes within single millisecond radio bursts.

Rucker, H. O.; Leitner, M. L.; Lecacheux, A.; Konovalenko, A.

2000-10-01

380

Dusty plasmas in the solar system  

Microsoft Academic Search

The processes that lead to charging of dust grains in a plasma are briefly reviewed. Whereas for single grains the results have been long known, the reduction of the average charge on a grain by 'Debye screening' has only recently been discovered. This reduction can be important in the Jovian ring and in the rings of Uranus. The emerging field

C. K. Goertz

1989-01-01

381

Imaging the Jovian Magnetosphere in Energetic Neutral Atoms with the Cassini\\/Huygens Magnetospheric Imaging Instrument Ion and Neutral Camera  

Microsoft Academic Search

During the flyby of Jupiter on its cruise to Saturn, the Cassini\\/Huygens spacecraft collected unique data with a broad assortment of instruments. The Magnetospheric Imaging Instrument (MIMI) measured in-situ energetic ions and electrons, performed charge and mass analysis of both interstellar pickup ions and Jovian source ions, and remotely imaged the Jovian magnetosphere in energetic neutral atom (ENA) emissions. The

D. G. Mitchell; S. M. Krimigis; B. H. Mauk

2001-01-01

382

Real Time Control System for the National Spherical Torus Experiment (NSTX)  

SciTech Connect

The NSTX is a national facility for the study of plasma confinement, heating, and current drive in a low aspect ratio, spherical torus (ST) configuration. The ST configuration is an alternate magnetic confinement concept which is characterized by high {beta} (ratio plasma pressure to magnetic field pressure) and low toroidal field compared to conventional tokamaks, and could provide a pathway to the realization of a practical fusion power source. The NSTX depends on a real time, high speed, synchronous, and deterministic control system acting on a system of thyristor rectifier power supplies to (1) establish the initial magnetic field configuration; (2) initiate plasma within the vacuum vessel; (3) inductively drive plasma current; and (4) control plasma position and shape. For the initial ''day 0'' 1st plasma operations (Feb. 1999), the system was limited to closed loop proportional-integral current control of the power supplies based on preprogrammed reference waveforms. For the next ''day 1'' phase of operations beginning mid-summer 1999 the loop will be closed on plasma current and position. The ultimate ''day 2'' system is envisioned to include real time reconstruction of the plasma internal current distribution so that control can be exercised over internal plasma parameters such as current and pressure profile. This paper addresses the day 1 system, with emphasis on the magnet power supply control. Companion papers address plasma control.

C. Neumeyer; D. Gates; R. Hatcher; S. Kaye; T. Gibney [and others

1999-06-01

383

Polarization and direction of arrival of Jovian quasiperiodic bursts observed by Cassini  

NASA Astrophysics Data System (ADS)

Jovian quasiperiodic (QP) radio bursts are suspected to be associated with relativistic particle accelerations occurring with a quasiperiodicity between a few minutes and a few tens of minutes in Jupiter's polar magnetosphere. Understanding the excitation and propagation of QP bursts could help us to better understand this periodic energization process. A first necessary step is to measure the wave mode, source location, and directivity of QP bursts. For that purpose, we performed a statistical analysis of goniopolarimetric measurements of QP bursts made with the Radio and Plasma Wave Science investigation (RPWS) onboard Cassini spacecraft during the Jupiter flyby of 2000-2001. We studied two groups of QP bursts on 22 and 23 December 2000, and we found consistent source directions about 50 RJ north of Jupiter with an error bar ?20 RJ. Statistics of the Stokes parameters indicate that QP bursts are partially left-handed polarized (V > 0, Q, U < 0). Together with the direction finding results, these polarization statistics imply that QP bursts observed from low latitudes are L-O mode waves which have been excited in the northern polar source, have propagated toward high latitudes, and then got refracted equatorward in the magnetosheath. Dependence of the Stokes parameters on the longitude indicates that QP bursts are excited within a particular phase range of the planetary rotation, when the system III longitude of the sub-solar point is between 260° and 480°. This implies that QP radio bursts and associated particle accelerations always occur within the same rotational sector, suggesting the existence of a recurrent magnetospheric disturbance at the planetary rotation period. Finally, we propose a possible scenario for the generation and propagation of QP bursts by combining the results of the present study with those of other recent observational and theoretical studies.

Kimura, T.; Cecconi, B.; Zarka, P.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2012-11-01

384

High resolution Thomson scattering for Joint European Torus (JET)  

SciTech Connect

A Thomson scattering system is being developed for Joint European Torus with 15 mm spatial resolution and a foreseen accuracy for temperature better than 15% at a density of 10{sup 19} m{sup -3}. This resolution is required at the internal transport barrier and edge pedestal and it can not be fully achieved with the present light detection and ranging systems. The laser for this system is Nd:YAG, 5 Joule, 20 Hz. Scattering volumes from R=2.9 m to R=3.9 m are imaged onto 1 mm diameter fibers, with F/25 collection aperture. Two fibers are used per scattering volume. Using optical delay lines, three scattering volumes are combined in each of the 21 filter polychromators. The signals are recorded with transient digitizers, which allow the combined time delayed signals to be resolved. Knowledge of the time delay between signals allows the use of correlation techniques in determining signal levels. The ac output of the amplifier is used, which tolerates a higher level of background signal without affecting dynamic range. The noise resulting from plasma light is determined directly.

Pasqualotto, R.; Nielsen, P.; Gowers, C.; Beurskens, M.; Kempenaars, M.; Carlstrom, T.; Johnson, D. [EFDA-CSU Culham, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein (Netherlands); General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2004-10-01

385

Temporal variation of the Jovian H I Lyman alpha emission (1979-1986)  

NASA Astrophysics Data System (ADS)

The results of long-term monitoring of the Jovian Lyman-alpha brightness with the IUE are presented. The measurements span the current solar cycle from maximum in late 1979 to the present period of minimum solar activity. The long-term variation seen in the brightness during the declining phase of the cycle matches the decrease in the solar Lyman-alpha flux during this period and is significantly smaller than the variability implied by Pioneer 10 for the first half of the cycle. The hydrogen bulge, a region of enhanced and variable Lyman-alpha emission located near magnetic longitude 100 deg, has been a persistent feature of the Jovian upper atmosphere throughout the eight-year period of the observations, and the average bulge intensity has also followed the solar cycle decrease in Lyman-alpha. Implications for the Jovian upper atmosphere and the electroglow phenomenon on Jupiter during the observational period are discussed.

Skinner, T. E.; Deland, M. T.; Ballester, G. E.; Coplin, K. A.; Feldman, P. D.; Moos, H. W.

1988-01-01

386

Low-frequency Jovian emission and solar wind magnetic sector structure  

NASA Astrophysics Data System (ADS)

The Earth, Jupiter and Saturn emit non-thermal low-frequency radiations with similar characteristics. For the Earth and Saturn, the radio emissions are known to fluctuate with a time scale of several days, correlated with variations of the solar wind or related phenomena at the planet1-4. Several studies of the jovian radiation at decametre wavelengths, from ground-based observations, suggest that the non-Io-controlled emission fluctuates in response to the sector structure of the interplanetary magnetic field5-9. We study here the long-term fluctuations of the jovian emission at hectometre and kilometre wavelengths. We use observations from the Planetary Radio Astronomy (PRA) experiment aboard the two Voyager spacecraft. We show that these emissions are strongly affected by the magnetic sector structure at Jupiter. This leads us to discuss the position of the sources of emission in the jovian magneto-sphere.

Zarka, P.; Genova, F.

1983-12-01

387

Quantum-Mechanical Dualities on the Torus  

NASA Astrophysics Data System (ADS)

On classical phase spaces admitting just one complex-differentiable structure, there is no indeterminacy in the choice of the creation operators that create quanta out of a given vacuum. In these cases the notion of a quantum is universal, i.e. independent of the observer on classical phase space. Such is the case in all standard applications of quantum mechanics. However, recent developments suggest that the notion of a quantum may not be universal. Transformations between observers that do not agree on the notion of an elementary quantum are called dualities. Classical phase spaces admitting more than one complex-differentiable structure thus provide a natural framework to study dualities in quantum mechanics. As an example we quantise a classical mechanics whose phase space is a torus and prove explicitly that it exhibits dualities.

Isidro, José M.

388

ORIGIN OF THE DIFFERENT ARCHITECTURES OF THE JOVIAN AND SATURNIAN SATELLITE SYSTEMS  

SciTech Connect

The Jovian regular satellite system mainly consists of four Galilean satellites that have similar masses and are trapped in mutual mean-motion resonances except for the outer satellite, Callisto. On the other hand, the Saturnian regular satellite system has only one big icy body, Titan, and a population of much smaller icy moons. We have investigated the origin of these major differences between the Jovian and Saturnian satellite systems by semi-analytically simulating the growth and orbital migration of proto-satellites in an accreting proto-satellite disk. We set up two different disk evolution/structure models that correspond to Jovian and Saturnian systems, by building upon previously developed models of an actively supplied proto-satellite disk, the formation of gas giants, and observations of young stars. Our simulations extend previous models by including the (1) different termination timescales of gas infall onto the proto-satellite disk and (2) different evolution of a cavity in the disk, between the Jovian and Saturnian systems. We have performed Monte Carlo simulations and have shown that in the case of the Jovian systems, four to five similar-mass satellites are likely to remain trapped in mean-motion resonances. This orbital configuration is formed by type I migration, temporal stopping of the migration near the disk inner edge, and quick truncation of gas infall caused by Jupiter opening a gap in the solar nebula. The Saturnian systems tend to end up with one dominant body in the outer regions caused by the slower decay of gas infall associated with global depletion of the solar nebula. The total mass and compositional zoning of the predicted Jovian and Saturnian satellite systems are consistent with the observed satellite systems.

Sasaki, T.; Ida, S. [Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Stewart, G. R., E-mail: takanori@geo.titech.ac.j, E-mail: ida@geo.titech.ac.j, E-mail: gstewart@lasp.colorado.ed [Laboratory for Atmospheric and Space Physics, University of Colorado, Campus Box 392, Boulder, CO 80309-0392 (United States)

2010-05-10

389

Progress Towards High-Performance, Steady-State Spherical Torus  

SciTech Connect

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fastwave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I{sub P} {approx}500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Lawrence Livermore National Laboratory

2004-01-04

390

Progress towards high-performance, steady-state spherical torus.  

SciTech Connect

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I{sub p} {approx} 500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Lee, S.G (Korea Basic Science Institute, Taejon, Republic of Korea); Kugel, W. (Princeton University, NJ); Efthimion, P. C. (Princeton University, NJ); Kissick, M. W. (University of Wisconsin, WI); Bourdelle, C. (CEA Cadarache, France); Kim, J.H (Korea Advanced Institute of Science and Technology, Taejon, Republic of Korea); Gray, T. (Princeton University, NJ); Garstka, G. D. (University of Wisconsin, WI); Fonck, R. J. (University of Wisconsin, WI); Doerner, R. (University of California, San Diego, CA); Diem, S.J. (University of Wisconsin, WI); Pacella, D. (ENEA, Frascati, Italy); Nishino, N. (Hiroshima University, Hiroshima, Japan); Ferron, J. R. (General Atomics, San Diego, CA); Skinner, C. H. (Princeton University, NJ); Stutman, D. (Johns Hopkins University, Baltimore, MD); Soukhanovskii, V. (Princeton University, NJ); Choe, W. (Korea Advanced Institute of Science and Technology, Taejon, Republic of Korea); Chrzanowski, J. (Princeton University, NJ); Mau, T.K. (University of California, San Diego, CA); Bell, Michael G. (Princeton University, NJ); Raman, R. (University of Washington, Seattle, WA); Peng, Y-K. M. (Oak Ridge National Laboratory, Oak Ridge, TN); Ono, M. (Princeton University, NJ); Park, W. (Princeton University, NJ); Hoffman, D. (Princeton University, NJ); Maqueda, R. (Los Alamos National Laboratory, Los Alamos, NM); Kaye, S. M. (Princeton University, NJ); Kaita, R. (Princeton University, NJ); Jarboe, T.R. (University of Washington, Seattle, WA); Hill, K.W. (Princeton University, NJ); Heidbrink, W. (University of California, Irvine, CA); Spaleta, J. (Princeton University, NJ); Sontag, A.C (University of Wisconsin, WI); Seraydarian, R. (University of California, San Diego, CA); Schooff, R.J. (University of Wisconsin, WI); Sabbagh, S.A. (Columbia University, New York, NY); Menard, J. (Princeton University, NJ); Mazzucato, E. (Princeton University, NJ); Lee, K. (University of California, Davis, CA); LeBlanc, B. (Princeton University, NJ); Probert, P. H. (University of Wisconsin, WI); Blanchard, W. (Princeton University, NJ); Wampler, William R.; Swain, D. W. (Oak Ridge National Laboratory, Oak Ridge, TN); Ryan, P.M. (Oak Ridge National Laboratory, Oak Ridge, TN); Rosenberg, A. (Princeton University, NJ); Ramakrishnan, S. (Princeton University, NJ); Phillips, C.K. (Princeton University, NJ); Park, H.K. (Princeton University, NJ); Roquemore, A. L. (Princeton University, NJ); Paoletti, F. (Columbia University, New York, NY); Medley, S. S. (Princeton University, NJ); Fredrickson, E. D. (Princeton University, NJ); Kessel, C. E. (Princeton University, NJ); Stevenson, T. (Princeton University, NJ); Darrow, D. S. (Princeton University, NJ); Majeski, R. (Princeton University, NJ); Bitter, M. (Princeton University, NJ); Neumeyer, C. (Princeton University, NJ); Nelson, B.A. (University of Washington, Seattle, WA); Paul, S. F. (Princeton University, NJ); Manickam, J. (Princeton University, NJ); Ostrander, C. N. (University of Wisconsin, WI); Mueller, D. (Princeton University, NJ); Lewicki, B.T (University of Wisconsin, WI); Luckhardt, S. (University of California, San Diego, CA); Johnson, D.W. (Princeton University, NJ); Grisham, L.R. (Princeton University, NJ); Kubota, Shigeru (University of California, Los Angeles, CA); Gates, D.A. (Princeton University, NJ); Bush, C. (Oak Ridge National Laboratory, Oak Ridge, TN); Synakowski, E.J. (Princeton University, NJ); Schaffer, M. (General Atomics, San Diego, CA); Boedo, J. (University of California, San Diego, CA); Maingi, R. (Oak Ridge National Laboratory, Oak Ridge, TN); Redi, M. (Princeton University, NJ); Pinsker, R. (General Atomics, San Diego, CA); Bigelow, T. (Oak Ridge National Laboratory, Oak Ridge, TN); Bell, R. E. (Princeton University, NJ)

2004-06-01

391

Progress towards high-performance, steady-state spherical torus  

SciTech Connect

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values beta(T) of up to 35% with a near unity central beta(T) have been obtained. NSTX will be exploring advanced regimes where beta(T) up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (similar to60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I-p similar to 500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Ono, M. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL

2003-01-01

392

Progress Towards High Performance, Steady-state Spherical Torus  

SciTech Connect

Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction ({approx}60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip {approx} 500 kA. In parallel, start-up using radio-frequency current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

M. Ono; M.G. Bell; R.E. Bell; T. Bigelow; M. Bitter; W. Blanchard; J. Boedo; C. Bourdelle; C. Bush; W. Choe; J. Chrzanowski; D.S. Darrow; S.J. Diem; R. Doerner; P.C. Efthimion; J.R. Ferron; R.J. Fonck; E.D. Fredrickson; G.D. Garstka; D.A. Gates; T. Gray; L.R. Grisham; W. Heidbrink; K.W. Hill; D. Hoffman; T.R. Jarboe; D.W. Johnson; R. Kaita; S.M. Kaye; C. Kessel; J.H. Kim; M.W. Kissick; S. Kubota; H.W. Kugel; B.P. LeBlanc; K. Lee; S.G. Lee; B.T. Lewicki; S. Luckhardt; R. Maingi; R. Majeski; J. Manickam; R. Maqueda; T.K. Mau; E. Mazzucato; S.S. Medley; J. Menard; D. Mueller; B.A. Nelson; C. Neumeyer; N. Nishino; C.N. Ostrander; D. Pacella; F. Paoletti; H.K. Park; W. Park; S.F. Paul; Y.-K. M. Peng; C.K. Phillips; R. Pinsker; P.H. Probert; S. Ramakrishnan; R. Raman; M. Redi; A.L. Roquemore; A. Rosenberg; P.M. Ryan; S.A. Sabbagh; M. Schaffer; R.J. Schooff; R. Seraydarian; C.H. Skinner; A.C. Sontag; V. Soukhanovskii; J. Spaleta; T. Stevenson; D. Stutman; D.W. Swain; E. Synakowski; Y. Takase; X. Tang; G. Taylor; J. Timberlake; K.L. Tritz; E.A. Unterberg; A. Von Halle; J. Wilgen; M. Williams; J.R. Wilson; X. Xu; S.J. Zweben; R. Akers; R.E. Barry; P. Beiersdorfer; J.M. Bialek; B. Blagojevic; P.T. Bonoli; M.D. Carter; W. Davis; B. Deng; L. Dudek; J. Egedal; R. Ellis; M. Finkenthal; J. Foley; E. Fredd; A. Glasser; T. Gibney; M. Gilmore; R.J. Goldston; R.E. Hatcher; R.J. Hawryluk; W. Houlberg; R. Harvey; S.C. Jardin; J.C. Hosea; H. Ji; M. Kalish; J. Lowrance; L.L. Lao; F.M. Levinton; N.C. Luhmann; R. Marsala; D. Mastravito; M.M. Menon; O. Mitarai; M. Nagata; G. Oliaro; R. Parsells; T. Peebles; B. Peneflor; D. Piglowski; G.D. Porter; A.K. Ram; M. Rensink; G. Rewoldt; P. Roney; K. Shaing; S. Shiraiwa; P. Sichta; D. Stotler; B.C. Stratton; R. Vero; W.R. Wampler; G.A. Wurden

2003-10-02

393

Observation of Compressional Alfven Modes During Neutral-Beam Heating on the National Spherical Torus Experiment  

SciTech Connect

Neutral-beam-driven compressional Alfven eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from {approx}0.2{omega}{sub ci} to {approx}1.2{omega}{sub ci} . The frequency has a scaling with toroidal field and plasma density consistent with Alfven waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer.

Fredrickson, E. D.; Gorelenkov, N.; Cheng, C. Z.; Bell, R.; Darrow, D.; Johnson, D.; Kaye, S.; LeBlanc, B.; Menard, J.; Kubota, S. (and others)

2001-10-01

394

Observation of compressional Alfvén modes during neutral-beam heating on the national spherical torus experiment.  

PubMed

Neutral-beam-driven compressional Alfvén eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2omega(ci) to approximately 1.2omega(ci). The frequency has a scaling with toroidal field and plasma density consistent with Alfvén waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer. PMID:11580654

Fredrickson, E D; Gorelenkov, N; Cheng, C Z; Bell, R; Darrow, D; Johnson, D; Kaye, S; LeBlanc, B; Menard, J; Kubota, S; Peebles, W

2001-09-13

395

Analysis of heavy ion beam probe potential measurement errors in the Madison Symmetric Torus  

SciTech Connect

The heavy ion beam probe on the Madison Symmetric Torus is capable of measuring the plasma potential at radial locations from about {rho}=r/a=0.3 to 0.75. Radial potential scans from two energy analyzer detectors have been used to assess measurement accuracy since they should produce identical profiles. The effects of analyzer characteristics, system alignment, sample volume locations and shapes, probing beam control, the quality of confining magnetic field information available, etc., have been assessed to determine the overall quality of the potential measurements. The accuracy of the measurements is found to be quite good relative to the potentials measured.

Zhang, X.; Lei, J.; Connor, K.A.; Demers, D.R.; Schoch, P.M.; Shah, U. [Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2004-10-01

396

Observation of Compressional Alfven Modes during Neutral Beam Heating on the National Spherical Torus Experiment  

SciTech Connect

Neutral-beam-driven compressional Alfven eigenmodes (CAE) at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment (NSTX). The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2 to approximately 1.2 omega(subscript ''ci''). The frequency has a scaling with toroidal field and plasma density consistent with Alfven waves. The modes have been observed with high bandwidth magnetic pick-up coils and with a reflectometer.

E.D. Fredrickson; N. Gorelenkov; C.Z. Cheng; R. Bell; D. Darrow; D. Johnson; S. Kaye; B. LeBlanc; J. Menard; S. Kubota; W. Peebles

2001-10-03

397

Numerical studies of transport in the Columbia Non-neutral Torus  

SciTech Connect

The confinement of pure electron plasmas in the Columbia Non-neutral Torus (CNT) stellarator is limited by the presence of unconfined orbits. The existence of a very large electric field across magnetic surfaces should preclude such unconfined orbits. However variations in the electric potential on magnetic surfaces, inherent to the CNT equilibrium, add to the complexity of the trajectories and lead to bad orbits. We have written a code using magnetic coordinates to integrate the electron drift trajectories in the electric and magnetic fields expected in CNT equilibria. Results of such calculations are presented showing that there exists unconfined orbits in CNT if the potential is not constant on surfaces.

Durand de Gevigney, B.; Pedersen, T. Sunn; Boozer, A. H. [Columbia University, New York, NY 10027 (United States)

2009-03-30

398

Short-Scale Turbulent Fluctuations Driven by the Electron-Temperature Gradient in the National Spherical Torus Experiment  

SciTech Connect

Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k?e 0:1 0:4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient.

Mazzucato, E. [Princeton Plasma Physics Laboratory (PPPL); Smith, D. R. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Kaye, S. [Princeton Plasma Physics Laboratory (PPPL); Davis, W. [Princeton Plasma Physics Laboratory (PPPL); Hosea, J. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Wilson, J. R. [Princeton Plasma Physics Laboratory (PPPL); Ryan, Philip Michael [ORNL; Domier, C. W. [University of California, Davis; Luhmann, N. C. [University of California, Davis; Yuh, H. [Nova Photonics; Lee, W. [Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea; Park, H. [Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea

2008-01-01

399

A Spherical Torus Nuclear Fusion Reactor Space Propulsion Vehicle Concept for Fast Interplanetary Piloted and Robotic Missions  

Microsoft Academic Search

A conceptual space vehicle concept to support NASA's 21^st century requirements was designed to enable human, multi-month travel throughout the outer solar system. The design was predicated on an ignited, spherical torus fusion reactor (R=2.5 m; a=1.25 m) burning spin polarized D^3He fuel and operating at high beta (30%). Peaked plasma temperature (50 keV) and number density (5×10^20 m-3) profiles

C. H. Williams; S. K. Borowski; L. A. Dudzinski; A. J. Juhasz

1999-01-01

400

Jovian thundercloud research with ground-based telescope and spacecraft  

NASA Astrophysics Data System (ADS)

The latest observational and theoretical studies suggest that thunderstorms, i.e., strong moist convective clouds in Jupiter's atmosphere are very important not only as an essential ingredient of meteorology of Jupiter, which determines the large scale structures such as belt/zone and big ovals, but also as a potentially very useful tool for probing the water abundance of the deep atmosphere, which is crucial to constrain the behavior of volatiles in early solar system. Here we suggest a very simple high-speed imaging unit onboard Jovian orbiter, Optical Lightning Detector, OLD, optimized for detecting optical emissions from lightning discharge in Jupiter. OLD consists of radiation-tolerant CMOS sensors and two H Balmer Alpha line (656.3nm) filters. In normal sampling mode the frame intervals is 29ms with a full frame format of 512x512 pixels and in high-speed sampling mode the interval could be reduced down to 0.1ms by concentrating a limited area of 30x30 pixels. Weight, size and power consumption are about 1kg, 16x7x5.5 cm (sensor) and 16x12x4 cm (circuit), and 4W, respectively, though they can be reduced according to the spacecraft resources. Also we plan to investigate the optical flashes using a ground-based middle-sized telescope, which will be built by Hokkaido University, with narrow-band high speed imaging unit. Observational strategy with such optical lightning detectors and spectral imagers, which enable us to estimate the horizontal motion and altitude of clouds, will be introduced.

Takahashi, Yukihiro; Nakajima, Kensuke; Takeuchi, Satoru; Sugiyama, Ko-Ichiro; Sato, Mitsuteru; Fukuhara, Tetsuya; Sato, Soga; Yair, Yoav; Aplin, Karen; Fischer, Georg

2010-05-01