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1

Preliminary Results from a Coordinated Hisaki/Chandra/XMM-Newton Study of the Jovian Aurora and Io Plasma Torus  

NASA Technical Reports Server (NTRS)

We present preliminary results from a coordinated Hisaki/Chandra/XMM-Newton observational campaign of the Jovian aurora and Io plasma torus. The data were taken over a three week period in April, 2014. Jupiter was observed continuously with Hisaki, six times with the Chandra/HRC instrument for roughly 12 hours per observation, and twice by XMM-Newton. The goal of this observational campaign was to understand how energy and matter are exchanged between the Jovian aurora, the IPT, and the Solar wind. X-ray observations provide key diagnostics on highly stripped ions and keV electrons in the Jovian magnetosphere. We use the temporal, spatial, and spectral capabilities of the three instruments to search for correlated variability between the Solar wind, the EUV-emitting plasma of the IPT and UV aurora, and the ions responsible for the X-ray aurora. Preliminary analysis suggests a strong 45 min periodicity in the EUV emission from the electron aurora. There is some evidence for complex variability of the X-ray auroras on scales of tens of minutes. There is also clear morphological changes in the X-ray aurora that do not appear to be correlated with either variations in the IPT or Solar wind.

Kraft, Ralph; Kimura, Tomoki; Elsner, Ronald; Branduardi-Raymont, Graziella; Gladstone, Randy; Badman, Sarah Victoria; Ezoe, Yuichiro; Murakami, Go; Murray, Stephen S.; Roediger, Elke; Tsuchiya, Fuminori; Yamazaki, Atsushi; Yoshikawa, Ichiro; Yoshioka, Kazuo

2014-01-01

2

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

3

Jovian Plasmas Torus Interaction with Europa. Plasma Wake Structure and Effect of Inductive Magnetic Field: 3D Hybrid Kinetic Simulation  

NASA Technical Reports Server (NTRS)

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 Oþ þ and Sþ þ 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, David G.

2013-01-01

4

Jovian Plasma Torus Interaction with Europa: 3D Hybrid Kinetic Simulation. First results  

NASA Technical Reports Server (NTRS)

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 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 etal.,2007;Shematovichetal.,2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyro radius 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).Non-thermal distributions of upstream plasma will be addressed in future work. Photoionization,electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider two models for background plasma:(a) with O(++) ions; (b) with O(++) and S(++) ions. The majority of O2 atmosphere is thermal with an extended cold population (Cassidyetal.,2007). A few first simulations already include an induced magnetic dipole; however, several important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work.

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

2010-01-01

5

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

6

In situ observations of Io torus plasma  

NASA Technical Reports Server (NTRS)

The physical properties of the Io plasma formation deduced from in situ observations are described. The torus plasma is characterized by spatially distinct regions with steep gradients in plasma parameters between them. The innermost region has a cool plasma which collapses toward the centrifugal equator and gives rise to a distinctive localized concentration of plasma well inside of Io's orbit. The next region has a warm plasma which includes the L-shell of Io and is the presumed injection region of the plasma. Other regions, known as the plasma ledge and ramp, are described. The changes in plasma characteristics are accounted for by centrifugally driven flux tube interchange diffusion to provide radial mass transport. The ramp is shown to result from impoundment of the plasma by the inner edge of the energetic particle population. It is also shown how the power required to excite the ultraviolet emissions of the torus and the Jovian aurora determines the rate at which new plasma is fed into the torus.

Sullivan, J. D.; Siscoe, G. L.

1982-01-01

7

Characterization of jovian plasma embedded dust particles  

E-print Network

As the data from space missions and laboratories improve, a research domain combining plasmas and charged dust is gaining in prominence. Our solar system provides many natural laboratories such as planetary rings, comet comae and tails, ejecta clouds around moons and asteroids, and Earth's noctilucent clouds for which to closely study plasma-embedded cosmic dust. One natural laboratory to study electromagnetically-controlled cosmic dust has been provided by the Jovian dust streams and the data from the instruments which were on board the Galileo spacecraft. Given the prodigious quantity of dust poured into the Jovian magnetosphere by Io and its volcanoes resulting in the dust streams, the possibility of dusty plasma conditions exist. This paper characterizes the main parameters for those interested in studying dust embedded in a plasma with a focus on the Jupiter environment. I show how to distinguish between dust-in-plasma and dusty-plasma and how the Havnes parameter P can be used to support or negate the possibility of collective behavior of the dusty plasma. The result of applying these tools to the Jovian dust streams reveals mostly dust-in-plasma behavior. In the orbits displaying the highest dust stream fluxes, portions of orbits E4, G7, G8, C21 satisfy the minimum requirements for a dusty plasma. However, the P parameter demonstrates that these mild dusty plasma conditions do not lead to collective behavior of the dust stream particles.

Amara L. Graps

2006-09-12

8

Long-term variability of [SII] emissions from the Io plasma torus between 1997 and 2000  

Microsoft Academic Search

Long-term optical observation of the Io plasma torus provides a great deal of information on the plasma environment in the Jovian magnetosphere. We made imaging observations of [SII] emissions (?? 673.1, 671.6 nm) from the Io plasma torus using a transportable telescope system for the period from 1997 to 2000. From the data we obtained intensity variations and average radial

H. Nozawa; H. Misawa; S. Takahashi; A. Morioka; S. Okano; R. Sood

2004-01-01

9

Plasma in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

It is shown that the plasma in Jupiter's ionosphere is collisionless above a certain level. In the outer magnetosphere, where the rotational force dominates the gravitational force, the collisionless plasma has a beam-like distribution and gives rise to a two-stream instability. This leads to trapping of plasma in the centrifugally dominated region of the magnetosphere. Plasma is lost by recombination. Equilibrium-trapped particle densities are calculated by requiring a balance between trapping by wave-particle interaction and loss by recombination. The results are compared with recent observations from Pioneer 10. It is suggested that the observations require an unexplained ion-heating mechanism. Some consequences of the model are discussed.

Goertz, C. K.

1975-01-01

10

Chandra Observations of Io and the Io Plasma Torus  

NASA Technical Reports Server (NTRS)

Chandra observed the Jovian system for approximately 1 day with ACIS-S in Nov, 1999, and approximately 10 hours with HRC-I in Dec, 2000. Among the many results of great interest to planetary scientists are the detection of x-ray emission from the Io Plasma Torus (IPT) and, very faintly, associated with the Jovian moon Io itself. The IPT is an almost self-generating donut of S and O ions in Io's orbit that ultimately derive from volcanoes on the surface. While EUV and visible emissions from the IPT are relatively well understood to result from low charge state transitions of S and O and from electron impact, the x-ray emissions are too energetic to be explained this way and seem to require the presence of higher charge states of S and O. We present current ideas as to origins of these x-ray emissions.

Elsner, Ronald F.; Gladstone, G. R.; Waite, J. H., Jr.; Grodent, D. C.; Crary, F. J.; Metzger, A. E.; Hurley, K. C.; Ford, P.; Feigelson, E.; Garmire, G.; Whitaker, Ann (Technical Monitor)

2001-01-01

11

Standing hydromagnetic waves in the Io plasma torus - Voyager 1 observations  

NASA Technical Reports Server (NTRS)

An attempt to analyze Voyager 1 magnetic field data for the existence of any ultralow-frequency hydromagnetic waves in the Io plasma torus is presented. The coincidence between the increase in wave activity and the entry into the Io plasma torus is in support of treating the torus as a low Alfven velocity region and thus as a hydromagnetic waveguide. A first theoretical treatment of hydromagnetic wave propagation within the torus suggests that decoupling of toroidal and poloidal type oscillations can occur under the condition of axisymmetry of the wave field. Numerical calculations of the fundamental mode toroidal and first harmonic poloidal eigenperiods for a model Jovian magnetosphere give values quite in agreement with the observed periods. Observations of nearly axisymmetric, decoupled toroidal and poloidal mode eigenoscillations of the Io plasma torus suggest a large-scale source mechanism for the detected magnetic field fluctuations.

Glassmeier, K.-H.; Neubauer, F. M.; Ness, N. F.; Acuna, M. H.

1989-01-01

12

The Encounter of P/Shoemaker-Levy 9 with the Jovian Plasma and Extended Sodium Cloud  

NASA Technical Reports Server (NTRS)

The encounter of comet P/Shoemaker-Levy 9 with Jupiter during July, 1994, provided an unprecedented opportunity to observe any potential perturbations in the Jovian plasma torus and extended sodium cloud as the comet entered the planet's atmosphere. Though the most obvious affect of the encounter was the distinctive response of the visible disk to the impact of the cometary fragments, the potential disruptions to the extended Jovian atmosphere and the restoration of the system to equilibrium also provided a test for the current interpretation of the Jovian plasma torus and sodium magneto-nebula. The observations that were performed for this grant were made by a complementary group of researchers and could not have been made if the individuals worked singly. In a sense, the exciting opportunity provided by this astronomical event also provided a mechanism to test the potential of pooling limited resources from several sources to construct a state-of-the-art spectrally resolving instrument, to acquire the necessary time and resources from institutions that maintain world-class optical telescopes, to perform the observations with the assistance of students, and to analyze the data sets.

Niciejewski, R. J.

1997-01-01

13

Drift wave instability in the Io plasma torus  

NASA Technical Reports Server (NTRS)

A linear normal mode analysis of the drift wave instability in the Io plasma torus was carried out on the basis of the Richmond (1973) and Huang et al. (1990) analyses of drift waves in the vicinity of the earth's plasmapause. Results indicate that the outer torus boundary is linearly unstable to the growth of electrostatic drift waves. It is shown that the linear growth rate is proportional to the ion drift frequency and to the ratio of the flux tube charge content to the Jovian ionospheric Pedersen conductance. It is also shown that various theoretical models of global radial transport in Jupiter's atmosphere (including corotating convection, interchange diffusion, and transient flux tube convection) can be understood as plausible nonlinear evolutions of electrostatic drift waves.

Huang, T. S.; Hill, T. W.

1991-01-01

14

Structure of the Jovian magnetotail from plasma wave observations  

Microsoft Academic Search

Plasma wave measurements from the outbound passes of Voyager 1 and 2 are used to study the plasma density and structure of the Jovian magnetotail. Two principal types of plasma waves are observed in the magnetotail, continuum radiation and narrowband emissions near the electron gyrofrequency. The low frequency cutoff of the continuum radiation can be used to determine the local

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

1980-01-01

15

Jovian magnetospheric plasma effects at Europa and Ganymede (Invited)  

NASA Astrophysics Data System (ADS)

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 in a toroidal-shaped cloud until they are ionized and contribute to the ambient plasma. Since gas-phase species are readily identified, the gravitationally bound and toroidal components are of interest as extensions of the satellite’s surface. If these atmospheres were only populated by thermal desorption, they would have a small subsolar water component (Shematovich et al. 2005) and the trace volatiles would be rapidly depleted. However, Europa and Ganymede orbit in a region of the Jovian magnetosphere in which the trapped plasma density and temperature are relatively high. This plasma and the solar EUV flux chemically alter and erode their surfaces, processes often lumped together as sputtering. Early laboratory results were used to predict the principal atmospheric component, O2, and its average column density (Johnson et al. 1982). Since loss of H2 accompanies the formation and ejection of O2 from ice (Johnson and Quickenden 1997), and, since H2 escapes more readily than the heavier species, hydrogen is a principal species in the neutral torus (Smyth and Marconi 2006) and a primary source of protons for the Jovian magnetosphere. Atmospheric simulations using models for the surface composition, data on the radiation flux, and laboratory data have been used in to interpret the available observations and to suggest which trace species might be detectable by an orbiting spacecraft. Models for the atmospheres of Europa and Ganymede and their relation to the plasma-weathered surfaces will be described in which redistribution and loss to the surface compete with loss due to ionization and pick-up, direct escape, and dissociation. Our interest is the relationship of the morphology and composition of the atmosphere and to its surface properties and the possibility of detection of atmospheric species (Johnson et al. 2009). References: Cassidy, T.A., et al, Trace constituents of Europa's atmosphere, Icarus (2009) Cipriani, F., et al, Exospheric signatures of alkali abundances in Europa's regolith, GRL 36, 2009 Johnson, R.E., et al. Planetary applications of ion-induced erosion of condensed-gas-frost.NuclInstrMethods 198, 147-157, 1982. Johnson, R.E., T.I.Quickenden, Photolysis & Radiolysis of Ice on Outer Solar System Bodies, JGR 102, 10985, 1997. Johnson, R.E., Surface Boundary Layer Atmospheres, in Atmospheres in the Solar System: Comparative Aeronomy Geophys.Mono. 130, 203-219 (2002) Johnson, R.E., et al."Composition and Detection of Europa's Sputter-Induced Atmosphere", in Europa, Eds. R. Pappalardo et al. (2009) in press. Shematovich, V.I., et al "Surface-bounded Atmosphere of Europa", Icarus 173, 480-498 (2005). Smyth W.H.,M.L. Marconi, Europa's atmosphere, gas tori, and magnetospheric implications, 181, 2, 510-526, 2006

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

2009-12-01

16

Long Term Monitoring of the Io Plasma Torus During the Galileo Encounter  

NASA Technical Reports Server (NTRS)

In the fall of 1999, the Galileo spacecraft made four passes into the Io plasma torus, obtaining the best in situ measurements ever of the particle and field environment in this densest region of the Jovian magnetosphere. Supporting observations from the ground are vital for understanding the global and temporal context of the in situ observations. We conducted a three-month-long Io plasma torus monitoring campaign centered on the time of the Galileo plasma torus passes to support this aspect of the Galileo mission. The almost-daily plasma density and temperature measurements obtained from our campaign allow the much more sparse but also much more detailed Galileo data to be used to address the issues of the structure of the Io plasma torus, the stability mechanism of the Jovian magnetosphere, the transport of material from the source region near Io, and the nature and source of persistent longitudinal variations. Combining the ground-based monitoring data with the detailed in situ data offers the only possibility for answering some of the most fundamental questions about the nature of the Io plasma torus.

Brown, Michael E.

2002-01-01

17

Ray tracing of Jovian kilometric radiation  

NASA Technical Reports Server (NTRS)

Results of computer ray tracing of Jovian kilometric radiation 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 (greater than 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 Voyagers 1 and 2.

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

1980-01-01

18

Warm flux tubes in the E-ring plasma torus: Initial Cassini magnetometer observations  

NASA Astrophysics Data System (ADS)

Initial Cassini magnetometer observations in the E-ring plasma torus reveal the presence of previously unreported diamagnetic decreases in the magnetic field. The decrease in magnetic pressure on these flux tubes implies the presence of additional plasma energy densities up to 1 keV/cm3. They are less stretched than surrounding flux tubes suggesting the centrifugal force acting on them is less, possibly because they have a lower mass content or lower azimuthal velocity than their neighbors. Outward from these isolated tubes, at about 6 Saturn radii, an irregular transition from predominantly cool to predominantly warm flux tubes is observed. A similar boundary is observed in the jovian magnetosphere at the outer edge of the Io torus. Both the saturnian and jovian boundaries are candidates for the interchange instability but other processes may also be acting. ULF waves are associated with some, but not all, of these flux tubes.

Leisner, J. S.; Russell, C. T.; Khurana, K. K.; Dougherty, M. K.; André, N.

2005-06-01

19

Implication for the solar wind effect on the Io plasma torus  

Microsoft Academic Search

Sporadic enhancements of [SII] 673.1 nm emissions from the Io plasma torus were found in ground-based observations in 1998 and 1999. Just after the onset of the enhancement on September 21, 1999, narrow-band kilometric (nKOM) radiation began to be observed by the Galileo\\/PWS in the Jovian magnetosphere. During this period, quasi-periodic burst groups (Morioka et al., 2006) were also observed

H. Nozawa; H. Misawa; M. Kagitani; F. Tsuchiya; S. Takahashi; A. Morioka; T. Kimura; S. Okano; H. Yamamoto; R. Sood

2006-01-01

20

Implication for the solar wind effect on the Io plasma torus  

NASA Astrophysics Data System (ADS)

Sporadic enhancements of [SII] 673.1 nm emissions from the Io plasma torus were found in ground-based observations in 1998 and 1999. Just after the onset of the enhancement on September 21, 1999, narrow-band kilometric (nKOM) radiation began to be observed by the Galileo/PWS in the Jovian magnetosphere. During this period, quasi-periodic burst groups (Morioka et al., 2006) were also observed by the PWS, and Jovian ``auroral flare'' (Waite et al., 2001) events were found on the same day by the Hubble Space Telescope. The sudden appearances of both nKOM radiation and auroral flare suggest the arrival of a remarkable solar-wind disturbance at the Jovian magnetosphere. In this paper, we present evidence that these enhancements are stochastic, related to solar wind disturbances.

Nozawa, H.; Misawa, H.; Kagitani, M.; Tsuchiya, F.; Takahashi, S.; Morioka, A.; Kimura, T.; Okano, S.; Yamamoto, H.; Sood, R.

2006-08-01

21

The physics of spherical torus plasmas  

Microsoft Academic Search

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

Y.-K. M. Peng; Yueng Kay Martin

2000-01-01

22

Plasma waves in the Jovian magnetosphere  

Microsoft Academic Search

Any waves which are influenced by the presence of a plasma are called plasma waves. In general, plasma waves can be classified as either electromagnetic, which have both electric and magnetic fields, or electrostatic, which have no magnetic field. The recent Voyager encounters provide the basis for the first comprehensive investigation of plasma waves in the magnetosphere of Jupiter. The

D. A. Gurnett; F. L. Scarf

1983-01-01

23

Energy partitioning in the Io plasma torus  

NASA Technical Reports Server (NTRS)

The Io plasma torus, which emits substantial amounts of EUV radiation from multiply ionized oxygen and sulfur, represents one of the significant discoveries of the Voyager 1 mission. The present study is concerned with the effects of various physical processes on the density and energy partitioning of the Io plasma torus. For the ions the dominant effects, which have different relative importance in different parameter regimes, are electron impact ionization, charge exchange, electron-ion collisions, and confinement time loss. Attention is given to a physical model, the solution of the quasi-linear equations, the obtained results, and an interpretation of observations in relation to the model results.

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

1985-01-01

24

Revised ion temperatures for Voyager plasma measurements in the Io plasma torus  

NASA Technical Reports Server (NTRS)

A calculation error in previous computations of ion temperatures in the Io plasma torus of the Jovian magnetosphere from Voyager plasma-science-experiment measurements is reported, and its effects on subsequently published studies are evaluated. It is found that the temperatures reported by Bagenal et al. (1980) and Bagenal and Sullivan (1981) for Jupiter and by Bridge et al. (1981) for Saturn are half the correct values, with major effects on ionic-species scale heights, plasma-density maps, and flux-tube content estimations. The temperatures given by Bridge et al. (1979) and McNutt et al. (1981) are not affected by the error. A corrected isodensity contour map is presented, and uncertainties in the measurement of ion temperatures are discussed.

Bagenal, F.; Mcnutt, R. L., Jr.; Belcher, J. W.; Bridge, H. S.; Sullivan, J. D.

1985-01-01

25

Io plasma torus electrons - Voyager 1  

NASA Technical Reports Server (NTRS)

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., Jr.; Strobel, Darrell F.

1987-01-01

26

Io's interaction with the plasma torus  

NASA Astrophysics Data System (ADS)

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 carried by an Alfven wave. The combination of currents allows for a self-consistent determination of the electric field in Io's vicinity. Using a simplified solution for the electric field, the total pickup rate, field-aligned current, enhancement of plasma density in Io's vicinity, thermal energy injected into the torus, UV radiation power, and inertial drag on the magnetosphere are calculated. All observations made by Voyager are compatible with an electron impact ionization mechanism and a neutral SO2 Io atmosphere with a density of 10 to the 9th/cu cm.

Goertz, C. K.

1980-06-01

27

X-ray probes of magnetospheric interactions with Jupiter's auroral zones, the Galilean satellites, and the Io plasma torus  

Microsoft Academic Search

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the jovian system is a source of X-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are both powerful sources of X-ray emission. Chandra observations revealed X-ray emission from the Io plasma torus and from the Galilean moons Io, Europa,

R. F. Elsner; B. D. Ramseya; J. H. Waite Jr; P. Rehak; R. E. Johnson; J. F. Cooper; D. A. Swartz

2005-01-01

28

Cassini UVIS observations of the Io plasma torus  

Microsoft Academic Search

In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near-sinusoidal variations in ion composition as a function of azimuthal position. The azimuthal variation in composition is such that the mixing

A. J. Steffl; P. A. Delamere; F. Bagenal

2006-01-01

29

Velocity shear impoundment of the Io plasma torus  

Microsoft Academic Search

The Io plasma torus apparently has a much longer lifetime than anticipated on the basis of simple theoretical stability analyses. This quandary is particularly evident at the outer edge of the torus, the plasma ramp, where the steep radial gradient in plasma content indicates the presence of some confining influence. Previous attempts to explain this feature have focused on the

Duane H. Pontius; R. A. Wolf; T. W. Hill; R. W. Spiro; Y. S. Yang; W. H. Smyth

1998-01-01

30

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

SciTech Connect

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 SO/sub 2/ escaping from Io. Ionization and dissociation of volcanic SO/sub 2/ 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 model is naturally explained. A 30--50 KeV sulfur and oxygen ion plasma is formed in the outer magnetosphere, with density roughly equal to the proton density there, by ionization of sulfur and oxygen atoms on highly eccentric elliptical orbits around Jupiter. When these atoms are ionized in the outer magnetosphere, they are swept up by the Jovian magnetic field and achieve 30--50 keV energies. Such atoms are created by dissociative attachment of SO/sub 2/ by < or approx. =10 eV electrons. Substantial losses of radiation-belt charged particles result from passage through the neutral gas torus. Such losses can account for observed anomalies in charged particle depletions near Io; these could not be understood in terms of satellite sweeping alone. Substantial ionization energy loss occurs for < or approx. =1 MeV protons and < or approx. =100 keV electrons; losses of < or approx. =1 MeV protons are much greater than for comparable energy electrons. Losses of < or approx. =1 MeV per nucleon ions are also severe. Other consequences of the model include intrinsic time variability in the Jovian magnetosphere, on times > or approx. =10/sup 6/ s, caused by variations in Io's volcanic activity. Charged particle losses in the neutral gas torus tend to yield dumbbell-shaped pitch-angle distributions. Negative ions are predicted in the Io plasma torus.

Cheng, A.F.

1980-12-01

31

The physics of spherical torus plasmas  

NASA Astrophysics Data System (ADS)

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 ˜80 cm in the new proof of principle devices National Spherical Torus Experiment (NSTX, U.S.) [M. Peng et al., European Conf. Abst. 22C, 451 (1998); S. M. Kaye et al., Fusion Technol. 36, 16 (1999); M. Ono et al., "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 et al., Fusion Technol. 1, 799 (1995); Q. W. Morris et al., Proc. Int. Workshop on ST (Ioffe Inst., St. Petersburg, 1997), Vol. 1, p. 290], and Globus-M (R.F.) [V. K. Gusev et al., 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 et al., Phys. Plasmas 5, 1807 (1998)], and Current Drive Experiment-Upgrade (CDX-U, Princeton Plasma Physics Laboratory) [M. Ono et al., 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.

Peng, Y.-K. M.

2000-05-01

32

The transmission of Alfven waves through the Io plasma torus  

NASA Astrophysics Data System (ADS)

The nature of Alfven wave propagation through the Io plasma torus was investigated using a one-dimensional model with uniform magnetic field and an exponential density decrease to a constant value. The solution was interpreted in terms of a wave that is incident upon the torus, a reflected wave, and a wave that is transmitted through the torus. The results obtained indicate that Io's Alfven waves may not propagate completely through the plasma torus, and, thus, the WKB theory and ray tracing may not provide meaningful estimates of the energy transport.

Wright, A. N.; Schwartz, S. J.

1989-04-01

33

Ion and electron angular distributions in the Io torus region of the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

Angular distributions are presented of ion (about 0.5-2 MeV) and electron (greater than 10 MeV) fluxes measured during the Voyager 1 spacecraft passage through the inner regions of the Jovian magnetosphere. In the regions of peak flux intensities, just outside the orbit of Io, the ion angular distributions are most sharply peaked at 90 deg local pitch angle, a configuration consistent with diffusion of the particles inward from large radial distances. Inside the orbit of Io the lower-energy ions exhibit angular distributions depleted at 90 deg local pitch angles, suggesting the possibility of charge-exchange scattering loss of these particles. In the vicinity of the Io flux tube, no significant effect is observed in the flux or pitch angle distributions of the ions. The relativistic electrons are depleted in the flux tube region and exhibit an asymmetrical pitch angle distribution, with more electrons appearing to arrive from the equatorial region (the direction of Io) than from the low-altitude mirror point.

Lanzerotti, L. J.; Maclennan, C. G.; Armstrong, T. P.; Krimigis, S. M.; Lepping, R. P.; Ness, N. F.

1981-01-01

34

Ganymede's interaction with the jovian plasma from hybrid simulation  

NASA Astrophysics Data System (ADS)

Ganymede is a unique object: it is the biggest moon of our solar system, and the only satellite which has its own intrinsic magnetic field leading to the formation of a small magnetosphere. The magnetosphere of Ganymede being embedded in the Jovian magnetosphere, the environment of the Galilean moon presents the only known case of interaction between two magnetospheres (Kivelson et al. 1996). This peculiar interaction has been investigated by means of a 3D parallel multi-species hybrid model based on a CAM-CL algorithm (Mathews et al. 1994). This generic model has been largely used for other magnetized or unmagnetized bodies such as Mars (Modolo et al. 2005; 2006 and 2012), Titan (Modolo et al. 2007, Modolo and Chauteur 2008) or Mercury (Richer et al. 2012). IIn this formalism, ions have a kinetic description whereas electrons are considered as an inertialess fluid which ensure the neutrality of the plasma and contribute to the total current and electronic pressure. Maxwell's equations are solved to compute the temporal evolution of electromagnetic field. The hybrid simulation describes the dynamics of the magnetospheric plasma, composed of O+ and H+ ions, and Ganymede's ionospheric plasma (W+, H2+, H+). Similarly to Paty and Winglee (2004), a density profile with a scale height of 125km of the ionospheric plasma is loaded and feeded during the simulation. Charge exchange leading to H2+ and H+ are also computed. To represent Ganymede's magnetosphere a magnetic dipole is implemented at initialization with dipolar moments values taken from Kivelson et al, 2002. This dipole is progressively distorted and lead to the formal of the mini-magnetopshere. Simulation results also emphasize the presence of Alfvén wings and are in good agreement with other simulation results (Jia et al, 2008, Paty et al, 2008). Hybrid simulations are performed on a uniform cartesian grid with a spatial resolution of about 200 km. Simulations results are presented and compared to magnetometer and particle observations obtained during G1 and G2 Galileo flybys.

Leclercq, L.; Modolo, R.; Hess, S.; Leblanc, F.

2013-12-01

35

Io: IUE observations of its atmosphere and the plasma torus  

NASA Technical Reports Server (NTRS)

Two of the main components of the atmosphere of Io, neutral oxygen and sulfur, were detected with the IUE. Four observations yield brightnesses that are similar, regardless of whether the upstream or the downstream sides of the torus plasma flow around Io is observed. A simple model requires the emissions to be produced by the interaction of O and S columns in the exospheric range with 2 eV electrons. Cooling of the 5 eV torus electrons is required prior to their interaction with the atmosphere of Io. Inconsistencies in the characteristics of the spectra that cannot be accounted for in this model require further analysis with improved atomic data. The Io plasma torus was monitored with the IUE. The long-term stability of the warm torus is established. The observed brightnesses were analyzed using a model of the torus, and variations of less than 30 percent in the composition are observed, the quantitative results being model dependent.

Ballester, G. E.; Moos, H. W.; Feldman, P. D.; Strobel, D. F.; Skinner, T. E.; Bertaux, J.-L.; Festou, M. C.

1988-01-01

36

Ion Temperature Control of the Io Plasma Torus  

NASA Technical Reports Server (NTRS)

We report on observational and theoretical studies of ion temperature in the Io plasma torus. Ion temperature is a critical factor for two reasons. First, ions are a major supplier of energy to the torus electrons which power the intense EUV emissions. Second, ion temperature determines the vertical extent of plasma along field lines. Higher temperatures spread plasma out, lowers the density and slows reaction rates. The combined effects can play a controlling role in torus energetics and chemistry. An unexpected tool for the study of ion temperature is the longitudinal structure in the plasma torus which often manifests itself as periodic brightness variations. Opposite sides of the torus (especially magnetic longitudes 20 and 200 degrees) have been observed on numerous occasions to have dramatically different brightness, density, composition, ionization state, electron temperature and ion temperature. These asymmetries must ultimately be driven by different energy flows on the opposite sides, presenting an opportunity to observe key torus processes operating under different conditions. The most comprehensive dataset for the study of longitudinal variations was obtained by the Cassini UVIS instrument during its Jupiter flyby. Steffl (Ph.D. thesis, 2005) identified longitudinal variations in all the quantities listed above wit the exception of ion temperature. We extend his work by undertaking the first search for such variation in the UVIS dataset. We also report on a 'square centimeter' model of the torus which extend the traditional 'cubic centimeter' models by including the controlling effects of ion temperature more completely.

Delamere, P. A.; Schneider, N. M.; Steffl, A. J.; Robbins, S. J.

2005-01-01

37

Numerical simulation of plasma transport driven by the Io torus  

NASA Technical Reports Server (NTRS)

The Rice convection model (RCM) has been modified to a form suitable for Jupiter (RCM-J) to study plasma interchange motion in and near the Io plasma torus. The net result of the interchange is that flux tubes, heavily loaded with torus plasma, are transported outward, to be replaced by tubes containing little low-energy (less than 1 keV) plasma. The process is numerically simulated in terms of time evolution from an initial torus that is longitudinally asymmetric and with gradually decreasing density outward from Io's orbit. In the simulations, the nonlinear stage of the instability characteristically exhibits outreaching fingers of heavily-loaded flux tubes that lengthen at an accelerating rate. The principal finding is that the primary geometrical form of outward transport of torus plasma in Jupiter's magnetosphere is through long, outward-moving fingers of plasma. In the simulations, the fingers mainly form in the active sector of the Io torus (the heavier side of the asymmetric torus), and they are spaced longitudinally roughly 20 deg apart.

Yang, Y. S.; Wolf, R. A.; Spiro, R. W.; Dessler, A. J.

1992-01-01

38

Warm flux tubes in Saturn's cool E-ring plasma torus  

NASA Astrophysics Data System (ADS)

As Cassini passed through Saturn's E ring, the magnetometer onboard observed a number of diamagnetic cavities isolated in time from any other disturbance. The decrease in magnetic pressure within these flux tubes implies the presence of an additional plasma energy density of up to 1 keV/cm3. The magnetic fields within these cavities are more dipolar and hence less stressed than their neighbors, suggesting that they may contain less mass or are traveling at a lower azimuthal velocity relative to their surroundings. The magnetometer also observed at about 6 Saturn radii, outward from these tubes, an irregular transition from predominantly cool to predominantly warm flux tubes. In the jovian magnetosphere, at the outer edge of the Io torus, a similar boundary has been found. Well inside the location of the jovian boundary, inward moving flux tubes have been reported in the Galileo magnetometer data. These tubes have enhanced field strength and have been interpreted as depleted flux tubes. The saturnian flux tubes exhibit magnetic strength decreases, but they still may contain less plasma than their surroundings. In short, the two differently appearing phenomena may both be different expressions of the same process.

Leisner, J. S.; Russell, C. T.; Khurana, K. K.; Dougherty, M. K.; Andre, N.

2005-05-01

39

On the energy crisis in the Io plasma torus  

NASA Technical Reports Server (NTRS)

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, Robert A.; Bagenal, Fran; Cheng, Andrew F.; Strobel, Darrell

1988-01-01

40

A study of the large-scale dynamics of the jovian magnetosphere using the Galileo plasma wave experiment  

Microsoft Academic Search

Using observations of the Galileo PWS experiment, we show that energetic phenomena recurrently occur in the jovian magnetosphere. They are characterized by intensifications of the auroral radio emissions and the creation of new sources of radiations in the outer regions of the Io torus. Simultaneously, modifications of the structure of the plasmasheet are observed at large distance (more than 60

Philippe Louarn; A. Roux; S. Perraut; W. Kurth; D. Gurnett

1998-01-01

41

High time resolution plasma wave and magnetic field observations of the Jovian bow shock  

Microsoft Academic Search

High time resolution (60 ms) Voyager magnetometer and plasma wave measurements of a strong (fast Mach number 16), quasi-perpendicular Jovian bow shock reveal an abrupt change in the plasma wave spectrum at the leading edge of the shock foot. Upstream electron plasma waves terminate at the leading edge, and are replaced by a lower-frequency broadband spectrum of ion-acoustic-like waves, which

S. L. Moses; F. V. Coroniti; C. F. Kennel; F. L. Scarf; E. W. Greenstadt; W. S. Kurth; R. P. Lepping

1985-01-01

42

The plasma physics of the Jovian decameter radiation.  

NASA Technical Reports Server (NTRS)

We have assumed that the decameter radiation from Jupiter is produced near the local electron gyrofrequency and is amplified as it propagates out of the Jovian magnetosphere. We have derived the growth rate for radiation that propagates almost perpendicular to the direction of the magnetic field. When the electrons are described by a loss-cone distribution function, the growth rate is large enough to lead to a large amplification factor over a source of 100-4000 km, depending on the choice of parameters. Because we expect low-energy electrons to be trapped in the Jovian dipole field regardless of the position of the satellite Io, we maintain that this model provides a plausible mechanism for the decametric radiation not associated with Io.

Goldstein, M. L.; Eviatar, A.

1972-01-01

43

Lo's Interaction with the Plasma Torus: Galileo Magnetometer Report  

Microsoft Academic Search

Galileo magnetometer data at 0.22-second resolution reveal a complex interaction between Io and the flowing plasma of the Io torus. The highly structured magnetic field depression across the downstream wake, although consistent with a magnetized Io, is modified by sources of currents within the plasma that introduce ambiguity into the interpretation of the signature. Highly monochromatic ion cyclotron waves appear

M. G. Kivelson; K. K. Khurana; R. J. Walker; J. Warnecke; J. A. Linker; D. J. Southwood; C. Polanskey

1996-01-01

44

Modeling the Jovian Current Sheet and Inner Magnetosphere  

Microsoft Academic Search

istence of a dense, heavy-ion plasma torus near Io's orbit, these results provide a natural framework for understanding the origins of the magnetodisc in the Jovian magnetosphere. Goertz [1976] had originally defined the magnetosphere as being structured into three distinct regions, with the inner magnetosphere (R < 10 R j) being described as current free. Estimates of the inner edge

J. E. P. Connerney; M. H. Acuña; N. F. Ness

1981-01-01

45

Physics of the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

List of tables; Foreword James A. Van Allen; Preface; 1. Jupiter's magnetic field and magnetosphere Mario H. Acuña, Kenneth W. Behannon and J. E. P. Connerney; 2. Ionosphere Darrell F. Strobel and Sushil K. Atreya; 3. The low-energy plasma in the Jovian magnetosphere J. W. Belcher; 4. Low-energy particle population S. M. Krimigis and E. C. Roelof; 5. High-energy particles A. W. Schardt and C. K. Goertz; 6. Spectrophotometric studies of the Io torus Robert A. Brown, Carl B. Pilcher and Darrell F. Strobel; 7. Phenomenology of magnetospheric radio emissions T. D. Carr, M. D. Desch and J. K. Alexander; 8. Plasma waves in the Jovian magnetosphere D. A. Gurnett and F. L. Scarf; 9. Theories of radio emissions and plasma waves Melvyn L. Goldstein and C. K. Goertz; 10. Magnetospheric models T. W. Hill, A. J. Dessler and C. K. Goertz; 11. Plasma distribution and flow Vytenis M. Vasyliunas; 12. Microscopic plasma processes in the Jovian magnetosphere Richard Mansergh Thorne; Appendixes; References; Index.

Dessler, A. J.

2002-08-01

46

Simulation of Plasma Interaction with Io's Atmosphere  

Microsoft Academic Search

One dimensional Direct Simulation Monte Carlo (DSMC) simulations are used to examine the interaction of the jovian plasma torus with Io's sublimation atmosphere. The hot plasma sweeps past Io at ~57 km\\/s due to the external Jovian magnetic and corotational electric fields and the resultant energetic collisions both heat and dissociate the neutral gas creating an inflated, mixed atmosphere of

Chris H. Moore; Hao Deng; David B. Goldstein; Deborah Levin; Philip L. Varghese; Laurence M. Trafton; Bénédicte D. Stewart; Andrew C. Walker

2011-01-01

47

Low energy ion distribution measurements in Madison Symmetric Torus plasmas  

SciTech Connect

Charge-exchange neutrals contain information about the contents of a plasma and can be detected as they escape confinement. The Florida A and M University compact neutral particle analyzer (CNPA), used to measure the contents of neutral particle flux, has been reconfigured, calibrated, and installed on the Madison Symmetric Torus (MST) for high temperature deuterium plasmas. The energy range of the CNPA has been extended to cover 0.34–5.2?keV through an upgrade of the 25 detection channels. The CNPA has been used on all types of MST plasmas at a rate of 20?kHz throughout the entire discharge (?70?ms). Plasma parameter scans show that the ion distribution is most dependent on the plasma current. Magnetic reconnection events throughout these scans produce stronger poloidal electric fields, stronger global magnetic modes, and larger changes in magnetic energy all of which heavily influence the non-Maxwellian part of the ion distribution (the fast ion tail)

Titus, J. B., E-mail: jtitus@cepast.famu.edu; Mezonlin, E. D. [Florida A and M University, Tallahassee, Florida 32310 (United States); Johnson, J. A. [Pyramid Plasmas LLC, Lawrenceville, Georgia 30043 (United States)

2014-06-15

48

Cassini-plasma interactions in the Enceladus torus  

NASA Astrophysics Data System (ADS)

This study reports the results of the first simulations of spacecraft-plasma interactions within the proposed Enceladus torus, a radially narrow toroidal region surrounding Saturn that contains a high density of water-group neutrals. Charge exchange collisions scatter these neutrals and replace a fraction of the co-rotating ions with a new and slower-moving ion population. The newly-created ions are moving near the local Keplerian speed, slower than the co-rotation speed, and are ''picked-up'' by Saturn's magnetic field. These water-group ions are detected throughout the Enceladus torus including regions far from Enceladus [1,2]. Three-dimensional particle-in-cell self-consistent code is applied to find the potential and plasma distributions around the spherical model of Cassini in a complicated plasma environment of the Enceladus torus. The modeling includes two types of water group ions (co-rotating, and non-thermalized pick-up ions), plasma flows, photoemission due to solar UV radiation, and flyby geometry. As input data the parameters derived from the Cassini plasma spectrometer measurements obtained in 2005 on Oct. 11, and 29, Nov. 27, and Dec. 24 [1] are employed. The numerical simulations show that the pick-up ions significantly modify the spatial structure of the plasma perturbations, arising in the vicinity of the orbiter in comparison to that obtained for only co-rotating ions [3]. The plasma species produce a specific strongly inhomogeneous configuration with a self-consistent charge separation between the different plasma components in the electric field of the orbiter. The highly energetic co-rotating water group ions are mainly responsible for the configuration of the plasma wake. The region extending up to a few electron Debye lengths downstream of the spacecraft reveals negative potentials that are a significant fraction of the thermal electron energy. Arising wake electric fields capture the cold, pick-up ions and lead to a strong enhancement of their density in the direct vicinity of the orbiter downstream. Here the ratio of the trapped to primary ion density reaches values of 5. Simulations reveal also the existence of an extended region with extremely low density of the pick-up ions upstream of the spacecraft. The obtained results can be of importance for understanding the main physical processes occurring in Saturn's magnetosphere and for reliable interpretations of Cassini electric field and plasma measurements near the icy moon Enceladus. [1] R. L. Tokar et al. Geophys. Res. Lett., 35, L14202 (2008). [2] R. L. Tokar et al. Geophys. Res. Lett., 36, L13203 (2009). [3] V. V. Yaroshenko et al. J. Geophys. Res., 116, A12218 (2011)

Yaroshenko, V. V.; Miloch, W. J.; Morfill, G. E.

2012-04-01

49

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

50

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

51

Longitudinal modulation of hot electrons in the Io plasma torus  

NASA Astrophysics Data System (ADS)

The longitudinal modulation in the Io torus has been an open question for decades. A major clue was provided by the discovery of the key modulation of the hot electron population, at both the System III and System IV periods. However, very little progress has been made in explaining the origin of these hot electron modulations. We propose that the hot electrons population is powered by the inward motion of empty flux tubes (i.e. related to the outward transport of the Iogenic plasma), which has been observed in the torus. We propose that the System IV and System III modulation of the hot electron population corresponds to modulation of the intensity of the current system and of the efficiency of the electron acceleration, respectively. We build on the latest models of the Io current system to describe the current system associated with the motion of the empty flux tubes, and the associated electron acceleration. The System III modulation of the hot electron population, due to the modulation of the efficiency of the electron acceleration, can then be related to the topology of the magnetic field. We show through calculation and simulation that the electron acceleration related to the inward motion of the empty flux tube may explain the observations. We discuss the energy budget and show that it is in favor of our hypothesis.

Hess, S. L. G.; Delamere, P. A.; Bagenal, F.; Schneider, N.; Steffl, A. J.

2011-11-01

52

Electromagnetic gyrokinetic simulation of turbulence in torus plasmas  

NASA Astrophysics Data System (ADS)

Gyrokinetic simulations of electromagnetic turbulence in magnetically confined torus plasmas including tokamak and heliotron/stellarator are reviewed. Numerical simulation of turbulence in finite beta plasmas is an important task for predicting the performance of fusion reactors and a great challenge in computational science due to multiple spatio-temporal scales related to electromagnetic ion and electron dynamics. The simulation becomes further challenging in non-axisymmetric plasmas. In finite beta plasmas, magnetic perturbation appears and influences some key mechanisms of turbulent transport, which include linear instability and zonal flow production. Linear analysis shows that the ion-temperature gradient (ITG) instability, which is essentially an electrostatic instability, is unstable at low beta and its growth rate is reduced by magnetic field line bending at finite beta. On the other hand, the kinetic ballooning mode (KBM), which is an electromagnetic instability, is destabilized at high beta. In addition, trapped electron modes (TEMs), electron temperature gradient (ETG) modes, and micro-tearing modes (MTMs) can be destabilized. These instabilities are classified into two categories: ballooning parity and tearing parity modes. These parities are mixed by nonlinear interactions, so that, for instance, the ITG mode excites tearing parity modes. In the nonlinear evolution, the zonal flow shear acts to regulate the ITG driven turbulence at low beta. On the other hand, at finite beta, interplay between the turbulence and zonal flows becomes complicated because the production of zonal flow is influenced by the finite beta effects. When the zonal flows are too weak, turbulence continues to grow beyond a physically relevant level of saturation in finite-beta tokamaks. Nonlinear mode coupling to stable modes can play a role in the saturation of finite beta ITG mode and KBM. Since there is a quadratic conserved quantity, evaluating nonlinear transfer of the conserved quantity from unstable modes to stable modes is useful for understanding the saturation mechanism of turbulence.

Ishizawa, A.; Maeyama, S.; Watanabe, T.-H.; Sugama, H.; Nakajima, N.; Nakajima

2015-04-01

53

Modeling of Spherical Torus Plasmas for Liquid Lithium Wall Experiments  

SciTech Connect

Liquid metal walls have the potential to solve first-wall problems for fusion reactors, such as heat load and erosion of dry walls, neutron damage and activation, and tritium inventory and breeding. In the near term, such walls can serve as the basis for schemes to stabilize magnetohydrodynamic (MHD) modes. Furthermore, the low recycling characteristics of lithium walls can be used for particle control. Liquid lithium experiments have already begun in the Current Drive eXperiment-Upgrade (CDX-U). Plasmas limited with a toroidally localized limiter have been investigated, and experiments with a fully toroidal lithium limiter are in progress. A liquid surface module (LSM) has been proposed for the National Spherical Torus Experiment (NSTX). In this larger ST, plasma currents are in excess of 1 MA and a typical discharge radius is about 68 cm. The primary motivation for the LSM is particle control, and options for mounting it on the horizontal midplane or in the divertor region are under consideration. A key consideration is the magnitude of the eddy currents at the location of a liquid lithium surface. During plasma start up and disruptions, the force due to such currents and the magnetic field can force a conducting liquid off of the surface behind it. The Tokamak Simulation Code (TSC) has been used to estimate the magnitude of this effect. This program is a two dimensional, time dependent, free boundary simulation code that solves the MHD equations for an axisymmetric toroidal plasma. From calculations that match actual ST equilibria, the eddy current densities can be determined at the locations of the liquid lithium. Initial results have shown that the effects could be significant, and ways of explicitly treating toroidally local structures are under investigation.

R. Kaita; S. Jardin; B. Jones; C. Kessel; R. Majeski; J. Spaleta; R. Woolley; L. Zakharo; B. Nelson; M. Ulrickson

2002-01-29

54

Low energy energetic neutral atom imaging in the Jovian system  

NASA Astrophysics Data System (ADS)

We modeled low energy energetic neutral atoms fluxes originating from the interaction of Jovian magnetospheric plasma with the surface of Ganymede and from charge exchange reactions in the Io torus. We then calculated the instrument response of the Jovian Neutrals Analyzer instrument (JNA) to these fluxes. JNA is part of the proposed Particle Environment Package (PEP) for ESA's JUICE mission and is based on the Energetic Neutral Atom instrument (ENA) built for the BepiColombo Magnetospheric Orbiter. JNA is an imaging energetic neutral atom instrument for energies from 10eV to 3.3keV and it provides angular as well as mass resolution for major neutral species. Depending on magnetic field configuration magnetospheric plasma is able to precipitate onto the surface of Ganymede. The plasma surface interaction produces energetic neutral atoms by backscattering and/or sputtering that travel on ballistic trajectories. Imaging of the energetic neutral atoms fluxes allows to remotely study the precipitation pattern onto the surface, its dependence on magnetic field configuration and its evolution over time. Simulated JNA images are shown for typical conditions. Energetic neutral atoms are also generated by charge exchange reactions in the Io torus. Energetic neutral atoms allow us to study torus dynamics remotely. We show expected energetic neutral atoms fluxes and simulated JNA data from imaging the Io torus from a vantage point outside of Europa's orbit well reachable by the JUICE mission.

Futaana, Yoshifumi; Wieser, Martin; Barabash, Stas

2013-04-01

55

Full Wave Modeling of Alfvén Wave Propagation in the Io Plasma Torus  

NASA Astrophysics Data System (ADS)

The description of Alfvén waves propagating in the Io plasma torus has often been considered in the WKB approximation, considering only the Alfvén travel time and possible reflection at the boundaries of the torus. However, for waves that have scale lengths comparable to the scale height of the torus, this procedure will break down and a full wave solution must be considered. Using plasma parameters based on Voyager and Galileo data, we have determined eigenmodes of Alfvén waves propagating in the torus and coupled to Jupiter's ionosphere, and determined the Green's function as a function of frequency for waves excited when Io is at different latitudinal positions within the torus due to the inclination of Io's orbit with respect to the centrifugal equator. This calculation serves as input for a three-dimensional simulation of the propagation of these Alfvén waves. This model may give insight as to the structure of the aurora trailing the footpoint of the Io flux tube.

Lysak, R. L.; Bagenal, F.; Delamere, P.

2006-12-01

56

X-ray probes of magnetospheric interactions with Jupiter's auroral zones, the Galilean satellites, and the Io plasma torus  

NASA Astrophysics Data System (ADS)

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the jovian system is a source of X-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are both powerful sources of X-ray emission. Chandra observations revealed X-ray emission from the Io plasma torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is due to bombardment of their surfaces by highly energetic magnetospheric protons, and oxygen and sulfur ions. These ions excite atoms in their surfaces leading to fluorescent X-ray emission lines. These lines are produced against an intense background continuum, including bremsstrahlung radiation from surface interactions of primary magnetospheric and secondary electrons. Although the X-ray emission from the Galilean moons is faint when observed from Earth orbit, an imaging X-ray spectrometer in orbit around one or more of these moons, operating from 200 eV to 8 keV with 150 eV energy resolution, would provide a detailed mapping of the elemental composition in their surfaces. Surface resolution of 40 m for small features could be achieved in a 100-km orbit around one moon while also remotely imaging surfaces of other moons and Jupiter's upper atmosphere at maximum regional resolutions of hundreds of kilometers. Due to its relatively more benign magnetospheric radiation environment, its intrinsic interest as the largest moon in the Solar System, and its mini-magnetosphere, Ganymede would be the ideal orbital location for long-term observational studies of the jovian system. Here we describe the physical processes leading to X-ray emission from the surfaces of Jupiter's moons and the properties required for the technique of imaging X-ray spectroscopy to map the elemental composition of their surfaces, as well as studies of the X-ray emission from the planet's aurora and disk and from the Io plasma torus.

Elsner, R. F.; Ramsey, B. D.; Waite, J. H.; Rehak, P.; Johnson, R. E.; Cooper, J. F.; Swartz, D. A.

2005-11-01

57

Impact of Plasma Chemistry on Io's Atmosphere  

Microsoft Academic Search

We present results of an investigation of the jovian plasma torus' interaction with Io's sublimation atmosphere using the direct simulation Monte Carlo (DSMC) method which is appropriate for solving rarefied flows such as Io's atmosphere. Accurate simulation of Io's atmosphere is critical for modeling the supply of material to the torus and understanding the morphology and intensity of the electron

Chris H. Moore; H. Deng; D. B. Goldstein; D. Levin; P. L. Varghese; L. M. Trafton; A. C. Walker; B. D. Stewart

2010-01-01

58

Extreme ultraviolet explorer satellite observation of Jupiter's Io plasma torus  

NASA Technical Reports Server (NTRS)

We present the first Extreme Ultraviolet Explorer (EUVE) satellite observation of the Jupiter system, obtained during the 2 day period 1993 March 30 through April 1, which shows a rich emission-line spectrum from the Io plasma torus spanning wavelengths 370 to 735 A. The emission features correspond primarily to known multiplets of oxygen and sulfur ions, but a blended feature near 372 A is a plausible Na II transition. The summed detected energy flux of (7.2 +/- 0.2) x 10(exp -11) ergs/sq cm(s) corresponds to a radiated power of approximately equal to 4 x 10(exp 11) W in this spectral range. All ansa emissions show a distinct dawn-dusk brightness asymmetry and the measured dusk/dawn ratio of the bright S III lambda-680 feature is 2.3 +/- 0.3, significantly larger than the ratio measured by the Voyager spacecraft ultraviolet (UV) instruments. A preliminary estimate of ion partitioning indicates that the oxygen/sulfur ion ratio is approximately equal to 2, compared to the value approximately equal to 1.3 measured by Voyager, and that (Na(+))/(e) greater than 0.01.

Hall, D. T; Gladstone, G. R.; Moos, H. W.; Bagenal, F.; Clarke, J. T.; Feldman, P. D.; Mcgrath, M. A.; Schneider, N. M.; Shemansky, D. E.; Strobel, D. F.

1994-01-01

59

Simulating the Structure of Currents in the Middle Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

We have developed a new global magnetohydrodynamic (MHD) simulation of the interaction between the solar wind and the magnetosphere of a rapidly rotating planet and applied it to Jupiter. The main source of plasma in the Jovian magnetosphere is thought to be the Io plasma torus. At Jupiter the Alfven velocity approaches the speed of light at 1RJ. Since the time step necessary to advance the MHD equations goes as the inverse of the Alfven velocity in explicit simulations, it is impractical to include the Io torus in the simulation domain. Therefore in previous simulations the Io torus source has been modeled by setting the inner boundary condition [c.f. Walker et al., Planet Space Sci., 49, 237, 2001]. In this calculation we have used a semi-implicit approach in which we add inertia to the highest frequency modes. With this approach the time step is proportional to the inverse of the convection velocity. Therefore we can include the torus source self-consistently. We are using the simulation to study the configuration of the middle (r<60RJ) Jovian magnetosphere with emphasis on the field aligned currents that couple the magnetosphere to the ionosphere. We will compare the configuration from the new model with that from the existing code.

Linker, J. A.; Lionello, R.; Ogino, T.

2001-12-01

60

Momentum Transport in Electron-Dominated Spherical Torus Plasmas  

SciTech Connect

The National Spherical Torus Experiment (NSTX) operates between 0.35 and 0.55 T, which, when coupled to up to 7 MW of neutral beam injection, leads to central rotation velocities in excess of 300 km/s and ExB shearing rates up to 1 MHz. This level of ExB shear can be up to a factor of five greater than typical linear growth rates of long-wavelength ion (e.g., ITG) modes, at least partially suppressing these instabilities. Evidence for this turbulence suppression is that the inferred diffusive ion thermal flux in NSTX H-modes is often at the neoclassical level, and thus these plasmas operate in an electron-dominated transport regime. Analysis of experiments using n=3 magnetic fields to change plasma rotation indicate that local rotation shear influences local transport coefficients, most notably the ion thermal diffusivity, in a manner consistent with suppression of the low-k turbulence by this rotation shear. The value of the effective momentum diffusivity, as inferred from steady-state momentum balance, is found to be larger than the neoclassical value. Results of perturbative experiments indicate inward pinch velocities up to 40 m/s and perturbative momentum diffusivities of up to 4 m2/s, which are larger by a factor of several than those values inferred from steady-state analysis. The inferred pinch velocity values are consistent with values based on theories in which low-k turbulence drives the inward momentum pinch. Thus, in Spherical Tori (STs), while the neoclassical ion energy transport effects can be relatively high and dominate the ion energy transport, the neoclassical momentum transport effects are near zero, meaning that transport of momentum is dominated by any low-k turbulence that exists.

Kaye, S. M.; Solomon, W.; Bell, R. E.; LeBlanc, B. P.; Levinton, F.; Menard, J.; Rewoldt, G.; Sabbagh, S.; Wang, W.; Yuh, H.

2009-02-24

61

Energy branching in the Io plasma torus - The failure of neutral cloud theory  

NASA Technical Reports Server (NTRS)

Model calculations are used to explore the energy source characteristics of the energy branching of the hot Io plasma torus. It is assumed that the energy is derived from the kinetic energy acquired by ions created in the rotating planetary magnetic field, and that Coulomb collisions with the electron gas control the flow of energy to the ionizing and radiative processes. The results show that neutral cloud theory is qualitatively inadequate. It is shown that neutral cloud theory can only support a dominantly singly ionized system (at the measured electron densities in the plasma torus) and that it fails to predict observed plasma properties relative to variations in number density.

Shemansky, D. E.

1988-01-01

62

On the structure of the Io Torus  

NASA Technical Reports Server (NTRS)

Since the plasma flow near Io is reduced, neutrals originating in charge exchange are not energetic enough to leave the Jovian system and are therefore distributed over an extensive region, as indicated by the sodium cloud. New ions subsequently created in the distributed neutral atomic cloud as a result of charge exchange or electron impact ionization are picked up by the corotating magnetic field, and the radial current driven by the pickup process cannot close in the Io torus, so that it must instead be connected to the planetary ionosphere by field-aligned currents. These field-aligned currents will flow away from the equator at the outer edge of the neutral cloud, and towards it at the inner edge. It is found that the Jovian ionospheric photoelectrons also cannot supply the current flowing away from the equator, so that torus ions accelerated by a parallel electric field could be involved. The parallel potential drop is large enough to push the torus into the Jovian atmosphere, explaining both the sharp, discontinuous change of flux tube content and ion temperature at L equals 5.6, as well as the generation of Auroral-type hiss at that point.

Goertz, C. K.; Ip, W.-H.

1982-01-01

63

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

64

Cassini UVIS observations of the Io plasma torus. II. Radial variations  

NASA Astrophysics Data System (ADS)

On January 14, 2001, shortly after the Cassini spacecraft's closest approach to Jupiter, the Ultraviolet Imaging Spectrometer (UVIS) made a radial scan through the midnight sector of Io plasma torus. The Io torus has not been previously observed at this local time. The UVIS data consist of 2-D spectrally dispersed images of the Io plasma torus in the wavelength range of 561-1912 Å. We developed a spectral emissions model that incorporates the latest atomic physics data contained in the CHIANTI database in order to derive the composition of the torus plasma as a function of radial distance. Electron temperatures derived from the UVIS torus spectra are generally less than those observed during the Voyager era. We find the torus ion composition derived from the UVIS spectra to be significantly different from the composition during the Voyager era. Notably, the torus contains substantially less oxygen, with a total oxygen-to-sulfur ion ratio of 0.9. The average ion charge state has increased to 1.7. We detect S(V) in the Io torus at the 3 ? level. S(V) has a mixing ratio of 0.5%. The spectral emission model used can approximate the effects of a nonthermal distribution of electrons. The ion composition derived using a kappa distribution of electrons is identical to that derived using a Maxwellian electron distribution; however, the kappa distribution model requires a higher electron column density to match the observed brightness of the spectra. The derived value of the kappa parameter decreases with radial distance and is consistent with the value of ?=2.4 at 8 RJ derived by the Ulysses URAP instrument (Meyer-Vernet et al., 1995). The observed radial profile of electron column density is consistent with a flux tube content, NL2, that is proportional to r-2.

Steffl, Andrew J.; Bagenal, Fran; Stewart, A. Ian F.

2004-11-01

65

Spectrophotometric studies of the Io Torus  

NASA Technical Reports Server (NTRS)

A toroidal volume near Io's orbit is made luminous by multiple optical and ultraviolet line emissions excited by resonant scattering of sunlight and by electron collisions. These emitting atoms and ions have been lost from Io. The spectrophotometric measurements of these emissions and their physical interpretation are considered. It is now known that the flow of material from Io dominates the particle and energy budgets of the Jovian magnetosphere. The observed emitting species in the Io torus are examined, and the atomic clouds are discussed, taking into account morphology and kinematics, atomic cloud supply rates, ion-atom collisions, and charge-exchange collisions. Observations and studies concerning the plasma torus are reported, giving attention to the forbidden lines, the extreme ultraviolet lines, and aspects of ion temperature and spatial distribution. Two types of radial transport in the Io torus include the ballistic motion of neutrals escaping from Io and the cross-L transport of ions.

Brown, R. A.; Pilcher, C. B.; Strobel, D. F.

1983-01-01

66

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Roth, J. R.

1976-01-01

67

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma  

NASA Technical Reports Server (NTRS)

Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Roth, J. R.

1976-01-01

68

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 carbonfiber- 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 towards the lower divertor. In 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 ELMs were observed, including complete ELM suppression for periods 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.

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

2009-08-20

69

Periodic bursts of Jovian non-Io decametric radio emission  

PubMed Central

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. PMID:23585696

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

2013-01-01

70

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

71

Periodic Bursts of Jovian Non-Io Decametric Radio Emission  

NASA Technical Reports Server (NTRS)

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 approx. = 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 deg. and 60 deg. (via 360 deg.). 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 approx. 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.

2013-01-01

72

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

E-print Network

- 1 - Spherical Torus Plasma Interactions with Large-Area Liquid Lithium Surfaces in CDX-U R. KAITA followed by discharges utilizing a large area liquid lithium pool as the target. The benefits of a surface surface contact is primarily with a large-area liquid lithium limiters. Surface conditioning

California at Los Angeles, University of

73

A three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus  

Microsoft Academic Search

A three barrel repeating pneumatic pellet injector was developed for plasma fueling of the Joint European Torus (JET) tokamak. The versatile device consists of three independent machine gun-like mechanisms that operate at cryogenic temperature (10 to 20 K). Individual extruders provide a continuous supply of solid hydrogen isotope to each gun assembly, where a reciprocating breech side cutter forms and

S. K. Combs; S. L. Milora; L. R. Baylor; C. R. Foust; F. E. Gethers; D. O. Sparks

1987-01-01

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

Resonant instability near the two-ion crossover frequency in the Io plasma torus  

NASA Astrophysics Data System (ADS)

Thorne and Scarf (1984) have presented evidence for the existence of intense low-frequency fluctuating electric fields in the Io plasma torus. Two distinct mechanisms have been proposed for this phenomenon, namely, ion cyclotron instability which occurs at intermediate latitude, and whistler instability near the equator. The present investigation is concerned with a quantitative appraisal of each of these mechanisms, taking into account an evaluation of the net convective growth rate of waves along ray paths which traverse the Io torus. Aspects of wave propagation near the crossover frequency are considered along with questions regarding the resonant interaction with energetic particles.

Thorne, R. M.; Moses, J. J.

1985-07-01

76

Numerical simulation of fine structure in the Io plasma torus produced by the centrifugal interchange instability  

NASA Astrophysics Data System (ADS)

The Io plasma torus as a whole has a radial width scale ~1 R J , much larger than the width of the localized Io plasma source (~1 R Io ~ R J /39). One of the most prominent features of the Io torus observed by the Voyager spacecraft and Earth-based instruments is the ``ribbon'' structure near Io's orbit. The stability properties of this narrower ribbon structure embedded within the larger torus have been investigated by the Rice Convection Model for Jupiter. Four initial plasma distributions having different radial widths are each represented by 82 longitudinally symmetric edges establishing 41 levels of the flux tube mass content ? with the peak ? value at Io's orbit. The same initial perturbation is put on each of these edges and is subjected to centrifugal interchange. Our simulations produce regularly spaced long, thin fingers moving outward from the outer edges. It is shown that the azimuthal width of the interchange convection cells (the distance between outflowing fingers in the nonlinear stage of development) is proportional to the radial width scale of the initial distribution that produced them. The constant of proportionality is ~0.5. Since the exponential growth rate is essentially proportional to the azimuthal wave number of the disturbance and hence is inversely proportional to its azimuthal width, the ribbon-scale interchange structures grow faster than torus-scale interchange structures.

Wu, H.; Hill, T. W.; Wolf, R. A.; Spiro, R. W.

2007-02-01

77

Numerical Simulation Of Fine Structure In The Io Plasma Torus Produced By The Centrifugal Interchange Instability  

NASA Astrophysics Data System (ADS)

The Io plasma torus as a whole has a radial width scale ~1R_J, much larger than the width of the localized Io plasma source (~1RIo? R_J/39). One of the most prominent features of the Io torus observed by the Voyager spacecraft and earth-based instruments is the 'ribbon' structure near Io's orbit. The stability properties of this narrower ribbon structure embedded within the larger torus have been investigated by the Rice Convection Model for Jupiter (RCM-J). Four initial plasma distributions having different radial widths are each represented by 82 longitudinally symmetric edges establishing 41 levels of the flux-tube mass content ? with the peak ? value at Io's orbit. The same initial perturbation is put on each of these edges and is subjected to centrifugal interchange. Our simulations produce regularly spaced long thin fingers moving outward from the outer edges. It is shown that the dominant azimuthal width scale of the interchange convection cells (fingers) in their nonlinear stage of development is proportional to the radial width scale of the initial distribution that produced them. The constant of proportionality is ~ 0.5. Since the exponential growth rate is essentially proportional to the azimuthal wave number of the disturbance, and hence inversely proportional to its azimuthal width, the ribbon-scale interchange structures grow faster than torus-scale interchange structures.

Wu, H.; Hill, T. W.; Wolf, R. A.; Spiro, R. W.

2006-12-01

78

Discovery of an Io-correlated energy source for Io's hot plasma torus  

NASA Astrophysics Data System (ADS)

Energy flowing into Io's hot plasma torus from a local-time correlated source and from an Io-related source are discussed, and a correlation of the brightness of the ansae of the torus with the apparent orbital phase of Io is reported. It is shown that the energy flows cause an azimuthal modulation of the brightness of the torus that is correlated with the position of Io, and the plasma downstream from Io is shown to be brighter in S III 685-A emission, which indicates a higher electron temperature. Differences in electron temperature inferred from spectral analyses account for all observed differences in brightness, implying that no change in the composition or density of the hot plasma occurs. The mechanism regulating the Io-related source is clearly distinct from the mechanism driving the local time source, although both draw on the same pool of energy, and the combination of the two sources is easily capable of supplying all the energy radiated by the torus.

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

1982-04-01

79

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

NASA Technical Reports Server (NTRS)

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 ribbon structures of the plasma torus, their System III longitude and local-time asymmetries, their energy sources and their possible time variability. To accomplish this objective, two-dimensional [radial (L) and System III longitude] plasma transport equations for the flux-tube plasma content and energy content will be solved that include the convective motions for both the east-west electric field and co-rotational velocity-lag profile near Io s orbit, radial diffusion, and the spacetime dependent flux-tube production and loss created by both neutral-plasma and plasma-ion reaction chemistry in the plasma torus. For neutral-plasma chemistry, the project will for the first time undertake the calculation of realistic three-dimensional, spatially-extended, and time-varying contributions to the flux-tube ion-production and loss that are produced by Io's corona and extended neutral clouds. The unknown two-dimensional spatial nature of diffusion in the plasma transport will be isolated and better defined in the investigation by the collective consideration of the foregoing different physical processes. For energy transport, the energy flow from hot pickup ions (and a new electron source) to thermal ions and electrons will be included in investigating the System III longitude and local-time temperature asymmetries in the plasma torus. The research is central to the scope of the NASA Sun-Earth Connection Roadmap in Quest II Campaign 4 "Comparative Planetary Space Environments" by addressing key questions for understanding the magnetosphere of planets with high rotation rates and large internal plasma sources and, in addition, is of considerable importance to the NASA Solar System Exploration Science Theme. In this regard, Jupiter is the most extreme example with its rapid rotation and with its inner Galilean satellite Io providing the dominant plasma source for the magnetosphere.

Smyth, William H.

2003-01-01

80

Electron Beams in the Jovian Magnsetosphere  

NASA Astrophysics Data System (ADS)

In this presentation we discuss observations of electron beams in the Jovian magnetosphere, observational constraints for heating or acceleration of electrons to produce the beams, and the significance of the beams in relationship with plasma dynamics, auroral luminosities, and magnetospheric current systems. Beams are observed in three different regions. (1) Jupiter's middle magnetosphere is threaded by beams of electrons with energies 10's of keV and likely greater. The electron distributions are field-aligned and bidirectional. These electrons may be an important seed population for more energetic distributions of electrons in the magnetosphere. They are observed at radial distances from Jupiter about 15 - 30 R_J spanning the region of the magnetosphere that is magnetically conjugate to the main ring of auroral luminosity. This also is the region where plasma motion begins to differ significantly from corotation. At Earth, upward beams of electrons are typically observed in association with regions of downward current. This may also be true at Jupiter, although the Jovian beams are observed in a region that is commonly thought to be part of an upward current system. (2) Beams with similar characteristics also are observed in association with flux-tube interchange events in the Io plasma torus, and (3) in the very near vicinity of Io where extreme mass-loading causes stagnation of plasma in Io's rest frame. Thus, the breakdown of corotation, or difference in motion compared to surrounding plasma, is a feature that may point to a common physical mechanism for the origins of these beams in three otherwise different regions.

Paterson, W. R.; Frank, L. A.; Ackerson, K. L.

2005-12-01

81

Effect of anode ring arrangement on the spectroscopic characteristics of the NASA Lewis bumpy torus plasma  

NASA Technical Reports Server (NTRS)

The modified Penning discharge in the NASA Lewis Bumpy Torus is normally produced by an anode ring at high voltage in each of the 12 magnetic mirror midplanes. For this investigation, the plasma was run with 12, 6, 3, and 1 anode rings. When 3 anode rings were used, the spectroscopically determined relative electron density and mean ion residence time increase by factors of 10 and 5, respectively, in one mode of operation. The discharge is observed to uniformly fill all bumps around the torus regardless of the anode arrangement and number. A plasma density on axis of 10 to the 11th power cm/3 is estimated for the 3 anode case in one mode of operation based on an observed discharge current to ion loss rate correlation and a measured mean ion residence time of .5 msec.

Richardson, R. W.

1974-01-01

82

Effect of anode ring arrangement on the spectroscopic characteristics of the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

The modified Penning discharge in the NASA Lewis Bumpy Torus is normally produced by an anode ring at high voltage in each of the 12 magnetic mirror midplanes. For this investigation, the plasma was run with 12, 6, 3, and 1 anode rings. When 3 anode rings were used, the spectroscopically determined relative electron density and mean ion residence time increased by factors of 10 and 5, respectively, in one mode of operation. The discharge is observed to uniformly fill all bumps around the torus regardless of the anode arrangement and number. A plasma density on axis of 100 billion per cu cm is estimated for the 3-anode case in one mode of operation based on an observed discharge current to ion loss rate correlation and a measured mean ion residence time of .5 msec.

Richardson, R. W.

1974-01-01

83

Study of plasma confinement in ELMO Bumpy Torus with a heavy-ion beam probe  

SciTech Connect

Plasma confinement in ELMO Bumpy Torus (EBT) is generally strongly dependent on an ambipolar electric field. Spatially resolved measurements of the resulting electric space potential phi/sub sp/ have been made in a single plasma cross section by the heavy-ion beam probe. This diagnostic injects a 4-60-keV beam of (usually) Cs/sup +/ ions into the plasma. Measurement of the energy of Cs/sup 2 +/ secondary ions leaving the plasma gives a continuous monitor of the local space potential. In addition, the total detected Cs/sup 2 +/ ion current is proportional to the product of the local electron density and the ionization rate, which, in turn, is a function of the electron temperature. This signal, nf(T/sub e/), is sensitive to all three electron distributions found in EBT - those of the cold surface plasma, the warm core plasma, and the hot electron ring.

Bieniosek, F. M.

1981-01-01

84

Observations of plasmas in the Io torus with the Galileo spacecraft  

Microsoft Academic Search

On December 7, 1995, the Galileo spacecraft passed through the Io torus near the magnetic equatorial plane of Jupiter. High-resolution measurements of positive ions and electrons in the energy\\/charge (E\\/Q) range of 0.9 V to 52 kV were acquired over the jovicentric radial distances of 5.6 to 7.8RJ. At radial distances beyond Io's orbit at 5.9RJ the plasma instrument (PLS)

L. A. Frank; W. R. Paterson

2000-01-01

85

Three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus  

Microsoft Academic Search

A three-barrel repeating pneumatic pellet injector has been developed for plasma fueling of the Joint European Torus (JET) tokamak. The versatile device consists of three independent machine-gun-like mechanisms that operate at cryogenic temperatures (10--20 K). Individual extruders provide a continuous supply of solid hydrogen isotope to each gun assembly, where a reciprocating breech-side cutter forms and chambers cylindrical pellets from

S. K. Combs; S. L. Milora; L. R. Baylor; C. R. Foust; F. E. Gethers; D. O. Sparks

1988-01-01

86

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

Microsoft Academic Search

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

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

2002-01-01

87

Spherical torus plasma interactions with large-area liquid lithium surfaces in CDX-U  

Microsoft Academic Search

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

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

2002-01-01

88

A new electron density profile measurement for comparative study of law-aspect torus plasmas  

NASA Astrophysics Data System (ADS)

A CO2 laser interferometer system with time and spatial resolution has been developed in TS-3 (university of Tokyo, Spherical torus-3) experiment to measure electron density profile of merging CT/STs.\\x81@The new Michelson type interferometer system has the probe composed of a reflection mirror and glass tube which is installed axially inside the cylindrical vacuum vessel. Its spatial scan enables the single channel interferometer to measure 1-D electron density profile in z-direction. A CW CO2 laser is used to measure the time evolution of electron density profile and heterodyne system using infrared acousto-optic modulator is introduced to realize a precise measurement in plasma with high electron density. The TS-3 device can produce various kinds of law-aspect torus plasma such as ST (spherical tokamak) and spheromak, RFP (reversed field pinch) and FRC (field reversed configuration) inside a single vacuum vessel. In this study, comparative study of ST, spheromak and RFP by electron density profile measurement will be reported. It was found that merging RFPs and spheromaks have higher electron density at the mid-plane than the merging tokamaks. The electron density profile is flat and has a gradient near the separatrix in the high q formation such as tokamak, on the contrary. These phenomena will be investigated in details by measuring merging speed, thermal pressure and flux distribution. A particle confinement time of measured law-aspect ratio torus plasma will be discussed based on those data.

Hayashiya, Hitoshi

2000-10-01

89

Implications of Depleted flux Tubes in the Jovian Magnetosphere  

NASA Technical Reports Server (NTRS)

A rare but persistent phenomenon in the jovian magnetosphere is the occurrence of apparently depleted flux tubes, whose magnetic pressures are significantly above ambient levels. These flux tubes occur about 0.25% of the observing time in the region of the Io torus in the Galileo high resolution data. The importance of these tubes is that they can return to the inner magnetosphere the magnetic flux that has been convected radially outward with the iogenic plasma to the tail. The paucity of these tubes is consistent with the expected flux return rates if the tubes are moving inward at an average rate of about 5-10 km/s in the torus. Depleted flux tubes have yet to be observed inside of the lo orbit where the plasma beta is lower than in the hot torus. Estimates of the plasma density outside the tube from plasma wave measurements enable the average perpendicular temperature to be obtained from the magnetic field change. Extrapolating this temperature back to lo, we obtain an average ion temperature of approximately 60 eV. These values are generally consistent with earlier Voyager observations but on the low side of their range of uncertainty, and agree quite well with contemporaneous Galileo measurements where these are available.

Russell, C. T.; Kivelson, M. G.; Kurth, W. S.; Gurnett, D. A.

2000-01-01

90

Fuelling and plasma flow change by compact torus injection into the STOR-M Tokamak  

NASA Astrophysics Data System (ADS)

The Saskatchewan TORus Modified (STOR-M) tokamak is equipped with a Compact Torus (CT) injector for tangential (toroidal) injection of a high density plasmoid at a velocity of 150 km/s. The objectives of CT injection (CTI) are to fuel the core region of tokamak and optimize the bootstrap current in future reactors by control of the plasma pressure gradient. After CTI, the line averaged density along central chord increases from ne˜x 10^12 to 1.5 x 10^13 [cm-3]. Measurement of soft X-ray bremsstrahlung emission profile indicates a steeper density gradient is generated after the asymmetric density profile is formed and the profile become symmetry again in STOR-M. Intrinsic impurity ion flows have been measured with ion Doppler spectroscopy. Significant radial velocity shear from center to edge region is observed even in Ohmic discharges. The toroidal flow direction is found to depend on the plasma current direction. CTI also modifies toroidal plasma flow. The edge plasma flow increases by 5 km/s 1millisecond after CTI. During these milliseconds of time, toroidal flow shear is also increased from 214.3 to 285.7 [10^3 x1/s]. A few milliseconds later than that time, plasma flow slows down, but plasma confinement is improved. H? emission decreases by 50%.

Onchi, Takumi; Liu, Yelu; Dreval, Mykola; McColl, David; Xiao, Chijin; Hirose, Akira; Asai, Tomohiko; Wolfe, Sean

2012-10-01

91

Characteristics of the NASA Lewis bumpy-torus plasma generated with positive applied potentials  

NASA Technical Reports Server (NTRS)

Experimental observations were made during steady-state operation of a bumpy-torus plasma at input powers up to 150 kW in deuterium and helium gas and with positive potentials applied to the midplane electrodes. In this steady-state ion heating method a modified Penning discharge is operated such that the plasma is acted upon by a combination of strong electric and magnetic fields. Experimental investigation of a deuterium plasma revealed electron temperatures from 14 to 140 eV and ion kinetic temperatures from 160 to 1785 eV. At least two distinct modes of operation exist. Experimental data shows that the average ion residence time in the plasma is virtually independent of the magnetic field strength. Data was taken when all 12 anode rings were at high voltage, and in other symmetric configurations in which the toroidal plasma was generated by applying positive potentials to six anode rings, three anode rings, and a single anode ring.

Roth, J. R.; Gerdin, G. A.; Richardson, R. W.

1976-01-01

92

System III variations in apparent distance of Io plasma torus from Jupiter  

NASA Technical Reports Server (NTRS)

System III variations in apparent distance of the Io plasma torus from Jupiter are examined on the basis of data obtained from UVS scans across Jupiter's satellite system. The displacement of the dawn and dusk ansae are found to be unexpectedly complex. The displacements are unequal and both ansae are in motion with the motion of the approaching ansa being the lesser of the two. The radial motions, as measured from either the center of Jupiter or the offset-tilted dipole, are of unequal magnitude and have the System III periodicity. It is concluded that the cross-tail electric field that causes these torus motions is concentrated on the dusk ansa, varied with the System III period, and shows magnetic-anomaly phase control. It is found that the dawn-dust asymmetry in brightness is not explained simply by the cross-tail electric field. It is concluded that there is a heating mechanism that causes the dusk side of the Io plasma torus to be brighter than the dawn side.

Dessler, A. J.; Sandel, B. R.

1992-01-01

93

First observations of partially neutralized and quasineutral plasmas in the Columbia Non-neutral Torus  

NASA Astrophysics Data System (ADS)

The Columbia Non-neutral Torus (CNT) is the first stellarator devoted to the study of pure electron, partially neutralized and positron-electron plasmas. To date, CNT usually operates with electron rich plasmas (with negligible ion density) [1], but a stellarator can also confine plasmas of arbitrary degree of neutralization. In CNT the accumulation of ions alters the equilibrium of electron plasmas and a global instability has been observed when the ion fraction exceeds 10 %. A characterization of this instability is presented in [2], analyzing its parameter dependence and spatial structure (non- resonant with rational surfaces). A new set of experiments is currently underway studying plasmas of arbitrary degree of neutralization, ranging from pure electron to quasineutral plasmas. Basic observations show that the plasma potential decouples from emitter bias when we increase the degree of the neutralization of our plasmas. Partially neutralized plasmas are also characterized by multiple mode behavior with dominant modes between 20 and 200 kHz. When the plasma becomes quasineutral, it reverts to single mode behavior. The first results on partially neutralized plasmas confined on magnetic surfaces will be presented. [1] J. Kremer, PRL 97, (2006) 095003 [2] Q. Marksteiner, PRL 100 (2008) 065002

Sarasola, Xabier; Brenner, Paul; Hahn, Michael; Pedersen, Thomas

2009-11-01

94

Cassini UVIS Observations of the Io Plasma Torus. 3; Observations of Temporal and Azimuthal Variability  

NASA Technical Reports Server (NTRS)

In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near sinusoidal variations in ion composition as a functions of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II us strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 h -- 1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System UV period defined by [Brown, M. E., 1995. J. Geophys. Res. 100, 21683-21696]. Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2-5%, the amplitude of the S II and S IV compositional variation ranged between 5 and 25% during the UVIS observations. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ration (minimum S IV mixing ratio) is aligned with a System III longitude of 200 deg +/-, the amplitude is a factor of 4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

Steffl, A. J.; Delamere, P. A.; Bagenal, F.

2006-01-01

95

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

96

The proton concentration in the vicinity of the Io plasma torus  

NASA Technical Reports Server (NTRS)

Observations of lightning-generated whistlers conducted with the aid of the Voyager 1 plasma wave instrument during the March, 1979 encounter of Jupiter have been employed in numerous studies involving Jupiters's inner magnetosphere. In an investigation carried out by Tokar et al. (1982), the Voyager whistler observations were combined with heavy ion charged particle measurements in the Io torus to determine the light ion charge concentration along the whistler propagation paths. In the investigation, simple models were used for the plasma distribution along the propagation paths. In the present study, an improved model is used for the plasma distribution in the inner magnetosphere. The adopted model treats a plasma in diffusive equilibrium under the action of gravitational, centrifugal, and ambipolar electric field forces.

Tokar, R. L.; Gurnett, D. A.; Bagenal, F.

1982-01-01

97

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

SciTech Connect

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. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Sovinec, C. R. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Raman, R. [Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195 (United States)] [Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195 (United States); Ebrahimi, F. [Department of Astrophysical Sciences, Princeton University, New Jersey 08544 (United States) [Department of Astrophysical Sciences, Princeton University, New Jersey 08544 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Menard, J. E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2013-09-15

98

Electrostatic waves in the Jovian magnetosphere  

Microsoft Academic Search

Observations by the plasma wave receivers on Voyager 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are

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

1980-01-01

99

Mass-loading and diffusion-loss rates of the Io plasma torus  

NASA Technical Reports Server (NTRS)

Limits to the mass-loading and diffusion-loss rates of ions in the Io plasma torus have been calculated on the assumption that observed optical emissions are controlled by electron-ion collisions. Calculations of the yield of emission from the vicinity of Io limit the mass-loading rate to the order of 10 to the 27th per s for S II or O II, on the grounds that electron-excited emissions associated with the location of Io have not been observed in the optical spectrum. This mass-loading limit is dependent on the assumptions that Io is the source of torus particles and that most of the neutral atoms are converted to ions within 1 R(J) of Io. According to the calculations presented below, the observed partitioning of sulfur ion species in the hot torus at the time of Voyager 1 encounter indicates that the diffusion-loss time of the ions is of the order of 1/D = 100 days. The two results limiting the mass-loading and diffusion-loss rates are compatible and suggest that the energy required to maintain the observed radiated power cannot be supplied by acceleration of ions formed at Io in Jupiter's rotating magnetic field.

Shemansky, D. E.

1980-01-01

100

Characteristics of the NASA Lewis bumpy torus plasma generated with high positive or negative applied potentials  

NASA Technical Reports Server (NTRS)

The toroidal ring of plasma contained in the NASA Lewis bumpy-torus superconducting magnet facility may be biased to positive or negative potentials approaching 50 kilovolts by applying direct-current voltages of the respective polarity to 12 or fewer of the midplane electrode rings. The electric fields which are responsible for heating the ions by E/B drift then point radially outward or inward. The low-frequency fluctuations below the ion cyclotron frequency appeared to be dominated by rotating spokes.

Roth, J. R.; Gerdin, G. A.

1976-01-01

101

In situ detection of interplanetary and Jovian nanodust with radio and plasma  

E-print Network

the radio (Warwick et al., 1982) nor the plasma wave (Scarf et al., 1982) instrument was designed to do so on a number of spacecraft in various environments, using instruments that were generally not designed to do so

Demoulin, Pascal

102

Plasma transport in the Io torus - The importance of microscopic diffusion  

NASA Technical Reports Server (NTRS)

This paper considers the question of whether the distribution of mass in the Io plasma torus is consistent with the concept of interchange eddy transport. Specifically, the flux tube content exhibits a gradual decrease with increasing radial distance from the source near Io without any evidence for substantial density irregularity associated with the plasma source or loss. Using a simple one-dimensional numerical model to simulate macroscopic interchange eddy transport, it is demonstrated that this smooth equilibrium distribution of mass can occur but only with the inclusion of a minimal level of small scale microscopic mixing at a rate approaching Bohm diffusion. Otherwise, the system exhibits a chaotic appearance which never approaches an equilibrium distribution. Various physical mechanisms for the microscopic diffusion process which is required to provide a sufficiently rapid mixing of material between the macroscopic eddies are discussed.

Mei, YI; Thorne, Richard M.

1991-01-01

103

Observation of instability-induced current redistribution in a spherical-torus plasma.  

PubMed

A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER. PMID:17026371

Menard, J E; Bell, R E; Gates, D A; Kaye, S M; LeBlanc, B P; Levinton, F M; Medley, S S; Sabbagh, S A; Stutman, D; Tritz, K; Yuh, H

2006-09-01

104

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

105

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

106

Observation of Instability-Induced Current Redistribution in a Spherical-Torus Plasma  

SciTech Connect

A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.

Menard, J. E.; Bell, R. E.; Gates, D. A.; Kaye, S. M.; LeBlanc, B. P.; Medley, S. S. [Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States); Levinton, F. M.; Yuh, H. [Nova Photonics Inc., Princeton, New Jersey (United States); Sabbagh, S. A. [Columbia University, New York, New York (United States); Stutman, D.; Tritz, K. [Johns Hopkins University, Baltimore, Maryland (United States)

2006-09-01

107

In situ detection of interplanetary and Jovian nanodust with radio and plasma  

E-print Network

on a number of spacecraft in various environments, using instruments that were generally not designed to do so Voyager, despite the fact that neither the radio (Warwick et al., 1982) nor the plasma wave (Scarf et al., 1982) instrument was designed to do so. These pionneering re- sults opened the way to micro dust

Demoulin, Pascal

108

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

109

Particle Modeling of the Io Inner Torus Boundary  

NASA Astrophysics Data System (ADS)

The Galileo spacecraft passed through the Io torus and its inner boundary on December 7, 1995 and November 5, 2002, during the J0 and A34 passes. Measured plasma densities on both passes indicated a steep gradient at the Io torus inner boundary located between 4.5 and 5 jovian radii (Io is at 5.9 Rj), as well as a much less steep gradient in the outer torus, with a boundary at distances greater than 8 Rj. A simple particle model for Iogenic ion pickup and torus formation developed by Wang et al. (2001) produced an ion distribution which spans distances as far as ~0.5 Rj (20 Io radii) away from Io, as was observed by Galileo. Unlike observations, however, the modeled torus inner boundary is not steep and is much closer to Jupiter. It is possible that an outward transport of ions in the inner torus via flux tubes or some other mechanism will steepen the inner torus boundary. We alter the pickup conditions of the Wang et al. model and couple it to a simple radial convection model in an attempt to reproduce the observed inner boundary density gradient and location. In the Wang et al. model, which assumed a background plasma flow velocity at Io equal to the corotation velocity (74 km/s), the ion pickup velocity is 57 km/s. Decreasing the speed of the plasma flow, such that the ion pickup velocity is 20 km/s, is sufficient to move the inner boundary from ~3.4 Rj to ~4.7Rj.

Cowee, M. M.; Wang, Y. L.; Russell, C. T.; Gurnett, D. A.

2004-05-01

110

Volcanic control of the Io atmosphere and neutral and plasma torus  

NASA Technical Reports Server (NTRS)

Rate equations for the column density of Io's atmosphere and the number density of neutral atoms and ions in the torus have been formulated in terms of surface sublimation and venting of volcanic gases, sputtering efficiency, thermal escape, and the plasma processes that take place in the torus which included electron impact ionization, charge exchange, and transport. In the limit of low volcanic activity, estimates of the densities can be obtained, and the baseline configuration that would exist in the absence of volcanic activity is found. Solution of the coupled steady state rate equations shows that the densities are sensitive, to a varying degree, to the level of Io volcanism. The steady state densities predicted by the model are consistent with a volcanic flux of no more than 10 to the 12th/sq cm per sec. This is significantly lower than the values obtained on the basis of resurfacing rates and appears to imply that surface lava flows play a major role in the resurfacing process.

Eviatar, Aharon

1987-01-01

111

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

112

Rocket FUV Observations of the Io Plasma Torus During the Shoemaker-Levy/9 Impacts  

NASA Technical Reports Server (NTRS)

We observed the Io torus from 820-1140 A on universal time (UT) 20.25 July 1994 from a sounding rocket telescope/spectrograph. These observations serve as only the fourth published spectrum of the torus in this wavelength range, and the only far ultraviolet (FUV) data documenting the state of the torus during the Shoemaker Levy 9 Impacts.

Stern, S. A.; Slater, D.; Cash, W.; Wilkinson, E.; Green, J.; Gladstone, R.

1995-01-01

113

A three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus  

NASA Astrophysics Data System (ADS)

A three barrel repeating pneumatic pellet injector was developed for plasma fueling of the Joint European Torus (JET) tokamak. The versatile device consists of three independent machine gun-like mechanisms that operate at cryogenic temperature (10 to 20 K). Individual extruders provide a continuous supply of solid hydrogen isotope to each gun assembly, where a reciprocating breech side cutter forms and chambers cylindrical pellets from the extrusion; the deuterium pellets are then accelerated in the gun barrels with compressed hydrogen gas (pressures up to 105 bar) to velocities less than or = to 1.5 km/s. The injector features three nominal pellet sizes and repetitive operation for quasi-steady-state conditions. The design allows the gun barrels to be mechanically aligned for accurate aiming. A remote, stand-alone control and data acquisition system is used for injector operation. The injector system was installed on JET. The design features, operation, and performance characteristics of the injector are described.

Combs, S. K.; Milora, S. L.; Baylor, L. R.; Foust, C. R.; Gethers, F. E.; Sparks, D. O.

114

Properties of the Io plasma torus inferred from Voyager EUV data  

NASA Technical Reports Server (NTRS)

A physical model for the Io plasma torus is constructed to explain the EUV radiative emission observed by the Voyager UV spectrometer. Electron impact excitation rate coefficients for electronic transitions of S III, S IV, O II and O III are calculated by the method of distorted waves (Davis, Kepple, and Blaha, 1976); these coefficients account for the asymmetric shape of the 686 A feature. It is concluded that the electron gas must have a distribution function with a non-Maxwellian tail. An approximate representation of the distribution function as two temperature components requires a cold component of 3.5-4 eV and density of 2000 per cu cm and a hot component of about 100 eV and density of 50-100 per cu cm to satisfy observational constraints.

Strobel, D. F.; Davis, J.

1980-01-01

115

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

116

A three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus  

SciTech Connect

Pellet fueling, the injection of frozen hydrogen isotope pellets at high velocity, has been used to improve plasma performance in various tokamak experiments. In one recent experiment, the repeating pneumatic hydrogen pellet injector was used on the Tokamak Fusion Test Reactor (TFTR). This machine gun-like device, which was developed at the Oak Ridge National Laboratory (ORNL) with an objective of steady-state fueling applications, was characterized by a fixed pellet size and a maximum repetition rate of 4 to 6 Hz for several seconds. It was used to deliver deuterium pellets at speeds ranging from 1.0 to 1.5 km/s into TFTR plasma discharges. In the first experiments, injection of single, large (nominal 4-mm-diam) pellets provided high plasma densities in TFTR (1.8 x 10/sup 14/ cm/sup -3/ on axis). After a conversion to smaller (nominal 2.7-mm-diam) pellets, the pellet injector was operated in the repeating mode to gradually increase the plasma density, injecting up to five pellets on a single machine pulse. This resulted in central plasma densities approaching 4 x 10/sup 14/ cm/sup -3/ and n tau values of 1.4 x 10/sup 14/ cm/sup -3/s. For plasma fueling applications on the Joint European Torus (JET), a pellet injector fashioned after the prototype repeating pneumatic design has been developed. The versatile injector features three repeating guns in a common vacuum enclosure; the guns provide pellets that are 2.7, 4.0, and 6.0 mm in diameter and can operate independently at repetition rates of 5, 2.5, and 1 Hz, respectively. The injector has been installed on JET. A description of the equipment is presented, emphasizing the differences from the original repeating device. Performance characteristics of the three pneumatic guns are also included.

Combs, S.K.; Milora, S.L.; Baylor, L.R.; Foust, C.R.; Gethers, F.E.; Sparks, D.O.

1987-01-01

117

Exploring a small sawtooth regime in Joint European Torus plasmas with counterinjected neutral beams  

SciTech Connect

During a recent reversed toroidal field (B{sub T}) campaign at the Joint European Torus (JET), experiments were performed to investigate the effect on sawteeth of neutral beam injection (NBI)-driven toroidal plasma rotation counter to the direction of the toroidal plasma current and B{sub T}. A power scan at constant density has permitted analytical continuation, into the reversed B{sub T} domain, of previous experiments with forward field and hence corotation. Earlier JET results were confirmed, indicating that counter-NBI results in sawtooth periods shorter than in the Ohmic regime. This study has demonstrated that, whereas with co-NBI the sawtooth period increases with power, with counter-NBI the sawtooth period initially decreases with power passing through a minimum at 4 MW. Clearly this trend also manifests itself in terms of the toroidal plasma rotation, for which a minimum is observed for counter-rotation frequency {approx}3 kHz. Sawteeth smaller than Ohmic sawteeth are found to be easier to obtain with perpendicular counter-NBI, for which heating penetrates deeper into the core. The sign and magnitude of the toroidal rotation, the penetration of heating to the electrons, and the peaking of the fast-ion pressure profile in the core may all play an important role in modifying the sawtooh period.

Nave, M.F.F.; Koslowski, H.R.; Coda, S.; Graves, J.; Brix, M.; Buttery, R.; Challis, C.; Giroud, C.; Stamp, M.; Vries, P. de [Associacao EURATOM/IST, Centro de Fusao Nuclear, 1049-001 Lisbon (Portugal); Association EURATOM-FZ-Juelich, Institut fuer Plasmaphysik, Trilateral Euregio Cluster, D-52425 Juelich (Germany); Association EURATOM-Confederation Suisse, EPFL SB CRPP, Station 13, 1015 Lausanne (Switzerland); Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)

2006-01-15

118

Neutral cloud theory of the Jovian nebula: Anomalous ionization effect of superthermal electrons  

NASA Technical Reports Server (NTRS)

The standard model of the Jovian nebula postulates that its particle source is the extended cloud of neutral sulfur and oxygen atoms that escape from the satellite Io and become ionized through electron impact from the corotating plasma. Its energy source is the gyroenergy acquired by newly formed pickup ions as they are swept up to corotation velocity by the planetary magnetic field. Elastic collisions between plasma ions and electrons cool the ions and heat the electrons, while inelastic collisions cool the electrons and excite the ions to radiate intense line emission, which is the primary energy-loss mechanism for the plasma. This neutral cloud theory of the Io plasma torus, as it has come to be known, has been the subject of recent critcism which asserts that the theory cannot account for the observed charge state of the plasma which features O(+) and S(2+) as the dominant ions. It is shown in this work that the inclusion of a small population of super-thermal electrons is required to achieve the correct ion partitioning among various charge states. It is also argued that the anomalous ionization effect of the superthermal electrons is responsible for the overall spatial bifurcation of the nebula into a hot multiply charged plasma region outside of 5.7 Jovian radii and a cool singly ionized plasma inside this distance.

Barbosa, D. D.

1994-01-01

119

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

120

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

NASA Astrophysics Data System (ADS)

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 E ×B 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.

2007-06-01

121

Measurement of The Magnetic Field in a Spherical Torus Plasma via Electron Bernstein Wave Emission Harmonic Overlap Measurement of The Magnetic Field in a Spherical Torus Plasma via Electron Bernstein Wave Emission Harmonic Overlap  

SciTech Connect

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. Reports 26 (2000) 1000]. 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 (2003) article no. 165001]. 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 beta equilibria are discussed for this proposed magnetic field diagnostic.

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

2004-01-28

122

Factors controlling the occurrence of the Jovian decametric radio emission  

NASA Astrophysics Data System (ADS)

The statistical analysis of occurrence of Io-related Jovian decametric radio (DAM) emission shows that the occurrence of the emission increase when Io is in the longitude range 120° -300° (Io's longitude in the frame III). Another result of the statistical analysis is a predominance of DAM emission sources in the northern hemisphere of Jupiter. We show that these phenomena are the result of the joint effect of two factors - the variation of the efficiency of particle acceleration in the ionosphere of the satellite Io and the variation of the broadening of the angular spectrum of accelerated particles during their pass through Io's plasma torus depending on Io's longitude. The planes of the rotational, magnetic and centrifugal (for Io's torus) equators do not coincide. As a result the magnetic field near the satellite Io, which determines the accelerated particle efficiency [1], changes periodically. The most effective acceleration takes place in the longitude range 120° ? ?Io ? 300° . Just in this longitude range the satellite Io appears to be "screened" by the plasma torus of the southern hemisphere. Making their way to the southern hemisphere, the particles are scattered in the torus plasma 2° , within which they and withdrawn from a narrow range of pitch-angles ??0 can reach the southern hemisphere [2]. Therefore in the mentioned longitude range northern sources of DAM emission should be concentrated. At the same time in the longitude range, where the "screening" effect of the plasma torus in the southern direction is negligible, the efficiency of the accelerated mechanism is essentially smaller due to the decrease of the magnetic field near Io. Therefore the southern sources turn to be weaker and are located mainly outside the longitude range, where the emission from the northern sources predominates. Since the emission from the northern sources predominates, the active longitudes are determined basically by this emission and are in the range 120° ? ?Io ? 300° . The distribution of accelerated electron fluxes near the southern foot of the magnetic tube of Io coincides well with the distribution of the occurrence of the left-hand polarized emission from the source Io-C. References 1. Zaitsev V. V., Shaposhnikov V. E., Rucker H. O. 2003, Astronomy Report, 80, 761. 2. Zaitsev V. V., Shaposhnikov V. E., Rucker H. O. 2006, Astronomy and Astrophysics, in press.

Zaitsev, V. V.; Shaposhnikov, V. E.; Rucker, H. O.

123

The variation of Io's auroral footprint brightness with the location of Io in the plasma torus  

NASA Astrophysics Data System (ADS)

Ultraviolet and near-infrared observations of auroral emissions from the footprint of Io's magnetic Flux Tube (IFT) mapping to Jupiter's ionosphere have been interpreted via a combination of the unipolar inductor model [Goldreich, P., Lynden-Bell, D., 1969. Astrophys. J. 156, 59-78] and the multiply-reflected Alfvén wave model [ Belcher, J.W., 1987. Science 238, 170-176]. While both models successfully explain the general nature of the auroral footprint and corotational wake, and both predict the presence of multiple footprints, the details of the interaction near Io are complicated [ Saur, J., Neubauer, F.M., Connerney, J.E.P., Zarka, P., Kivelson, M.G., 2004. In: Bagenal, F., Dowling, T.E., McKinnon, W.B. (Eds.), Jupiter: The Planet, Satellites and Magnetosphere. Cambridge University Press, Cambridge, UK, pp. 537-560; Kivelson, M.G., Bagenal, F., Kurth, W.S., Neubauer, F.M., Paranicas, C., Saur, J., 2004. In: Bagenal, F., Dowling, T.E., McKinnon, W.B. (Eds.), Jupiter: The Planet, Satellites and Magnetosphere. Cambridge University Press, Cambridge, UK, pp. 513-536]. The auroral footprint brightness is believed to be a good remote indicator of the strength of the interaction near Io, indicating the energy and current strength linking Io with Jupiter's ionosphere. The brightness may also depend in part on local auroral acceleration processes near Jupiter. The relative importance of different physical processes in this interaction can be tested as Jupiter's rotation and Io's orbital motion shift Jupiter's magnetic centrifugal equator past Io, leading to longitudinal variations in the plasma density near Io and functionally different variations in the local field strength near Jupiter where the auroral emissions are produced. Initial HST WFPC2 observations found a high degree of variability in the footprint brightness with time, and some evidence for systematic variations with longitude [Clarke, J.T., Ben Jaffel, L., Gérard, J.-C., 1998. J. Geophys. Res. 103, 20217-20236], however the data were not of sufficient quality to determine functional relationships. In this paper we report the results from a second, more thorough study, using a series of higher resolution and sensitivity HST STIS observations and a model for the center to limb dependence of the optically thin auroral emission brightness based on measurements of the auroral curtain emission distribution with altitude. A search for correlations between numerous parameters has revealed a strong dependence between Io's position in the plasma torus and the resulting footprint brightness that persists over several years of observations. The local magnetic field strength near Jupiter (i.e. the size of the loss cone) and the expected north/south asymmetry in auroral brightness related to the path of currents generated near Io through the plasma torus en route to Jupiter appear to be less important than the total plasma density near Io. This is consistent with the near-Io interaction being dominated by collisions of corotating plasma and mass pickup, a long-standing view which has been subject to considerable debate. The brightness of the auroral footprint emissions, however, does not appear to be proportional to the incident plasma density or energy, and the interpretation of this result will require detailed modeling of the interaction near Io.

Serio, Andrew W.; Clarke, John T.

2008-09-01

124

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 β{sub 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

S M Kaye; e al

2006-01-01

125

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

126

Three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus  

SciTech Connect

A three-barrel repeating pneumatic pellet injector has been developed for plasma fueling of the Joint European Torus (JET) tokamak. The versatile device consists of three independent machine-gun-like mechanisms that operate at cryogenic temperatures (10--20 K). Individual extruders provide a continuous supply of solid hydrogen isotope to each gun assembly, where a reciprocating breech-side cutter forms and chambers cylindrical pellets from the extrusion; the deuterium pellets are then accelerated in the gun barrels with compressed hydrogen gas (pressures up to 105 bar) to velocities less than or equal to1.5 km/s. The injector features three nominal pellet sizes (2.7, 4.0, and 6.0 mm) and repetitive operation (5, 2.5, and 1 Hz, respectively) for quasi-steady-state conditions (>10 s). The design allows the gun barrels to be aligned mechanically for accurate aiming. A remote stand-alone control and data acquisition system is used for injector operation. The injector system has been installed on JET. The design features, operation, and performance characteristics of the injector are described.

Combs, S.K.; Milora, S.L.; Baylor, L.R.; Foust, C.R.; Gethers, F.E.; Sparks, D.O.

1988-05-01

127

Io's interaction with the plasma torus - A self-consistent model  

NASA Astrophysics Data System (ADS)

The interaction between Io and the plasam torus is simulated by a three-dimensional numerical model which allows the calculation of electric fields, current-density distributions, and magnetic fields in Io's vicinity and in the Alfven wings. The model is self-consistent in the sense that the influence of magnetic field disturbances on the electric field is taken into account and vice versa. A two-dimensional elliptic differential equation for the electric potential is derived by using Euler potentials. The current density in Io's vicinity is decomposed into poloidal and toroidal fields. This representation allows an effective integration to get the magnetic-field disturbances. Pedersen, Hall, inertial (or polarization), and field-aligned currents are calculated. Results for different upstream plasma conditions and atmosphere/ionosphere models are presented, and the consequences of variations in neutral density, Alfvenic Mach number, and other parameters are discussed. A series of simple spherically symmetric atmosphere/ionosphere models with neutral gas densities (1-10) x 10 to the 16th/cu m are investigated. Comparison with Voyager magnetic-field measurement gives agreement for a column density of 7.5 x 10 to the 21st/sq m (surface density N0 = 5 x 10 to the 16th/cu m, scale height H = 150 km).

Wolf-Gladrow, D. A.; Neubauer, F. M.; Lussem, M.

1987-09-01

128

Liquid-metal plasma-facing component research on the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

Liquid metal plasma-facing components (PFCs) have been proposed as a means of solving several problems facing the creation of economically viable fusion power reactors. Liquid metals face critical issues in three key areas: free-surface stability, material migration and demonstration of integrated scenarios. To date, few demonstrations exist of this approach in a diverted tokamak and we here provide an overview of such work on the National Spherical Torus Experiment (NSTX). The liquid lithium divertor (LLD) was installed and operated for the 2010 run campaign using evaporated coatings as the filling method. Despite a nominal liquid level exceeding the capillary structure and peak current densities into the PFCs exceeding 100 kA m-2, no macroscopic ejection events were observed. The stability can be understood from a Rayleigh-Taylor instability analysis. Capillary restraint and thermal-hydraulic considerations lead to a proposed liquid-metal PFCs scheme of actively-supplied, capillary-restrained systems. Even with state-of-the-art cooling techniques, design studies indicate that the surface temperature with divertor-relevant heat fluxes will still reach temperatures above 700 °C. At this point, one would expect significant vapor production from a liquid leading to a continuously vapor-shielded regime. Such high-temperature liquid lithium PFCs may be possible on the basis of momentum-balance arguments.

Jaworski, M. A.; Khodak, A.; Kaita, R.

2013-12-01

129

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

130

Spherical torus fusion reactor  

DOEpatents

The object of this invention is to provide a compact torus fusion reactor with dramatic simplification of plasma confinement design. Another object of this invention is to provide a compact torus fusion reactor with low magnetic field and small aspect ratio stable plasma confinement. In accordance with the principles of this invention there is provided a compact toroidal-type plasma confinement fusion reactor in which only the indispensable components inboard of a tokamak type of plasma confinement region, mainly a current conducting medium which carries electrical current for producing a toroidal magnet confinement field about the toroidal plasma region, are retained.

Martin Peng, Y.K.M.

1985-10-03

131

A Consistent Ribbon Structure for the Io Plasma Torus at the Voyager 1 and Galileo J0 Epochs  

NASA Astrophysics Data System (ADS)

The peak density structure for the plasma torus electrons and heavy ions occurs radially near and inside of Io's orbit. This structure has been documented remotely by ground-based observations at the dawn and dusk ansae in S+ (6716 Å, 6731 Å) and S++ (9531 Å) emissions and from Voyager 2 UVS observations at the 35 degree pre-dawn and pre-dusk ansae for S++ (685Å) emission. It has also been documented by in situ observations by the Voyager 1 PLS instrument for the O+, S+, S++ ions and electrons at pre-dusk local-times and by the Galileo PWS and PLS instruments for electrons at noon local-time. The focus of this presentation is to compare the radial location of the peak density structure for the S+ ions (so-called ribbon feature) acquired at different local-times from ground-based (Schneider and Trauger, Ap. J. 450, 450, 1995) and Voyager (Bagenal, JGR 99, 11043, 1994) measurements and inferred from Galileo measurements (Gurnett et al., Science, 274, 391, 1996; Frank and Paterson, JGR 99, 11043, 2000). This is accomplished by the application of a newly developed more accurate, four-dimensional (three spatial dimensions and local-time) empirical model for the plasma torus. This model includes System III longitudinal asymmetries and also local-time asymmetries created by a dawn-dusk electric field that is equipotential along the magnetic field lines and has an adjustable magnitude and direction. It is found that all of the measurements can be fit by a set of different magnitudes and directions for the dawn-dusk electric field and that a limited range of such solutions is possible for the three measurements that allow a consistent radial location for the S+ ribbon feature, resolving a long-standing issue for the plasma torus (Bagenal et al., GRL 24, 2119, 1997). Information will be presented to illustrate the nature of these solutions.

Smyth, William H.; Peterson, C. A.; Marconi, M. L.

2008-09-01

132

A 12-coil superconducting 'bumpy torus' magnet facility for plasma research.  

NASA Technical Reports Server (NTRS)

A retrospective summary is presented of the performance of the two-coil superconducting pilot rig which preceded the NASA Lewis bumpy torus. The NASA Lewis bumpy torus facility consists of 12 superconducting coils, each with a 19 cm i.d. and capable of producing magnetic field strengths of 3.0 teslas on their axes. The magnets are equally spaced around a major circumference 1.52 m in diameter, and are mounted with the major axis of the torus vertical in a single vacuum tank 2.59 m in diameter. The design value of maximum magnetic field on the magnetic axis (3.0 T) has been reached and exceeded.

Roth, J. R.; Holmes, A. D.; Keller, T. A.; Krawczonek, W. M.

1972-01-01

133

Fishbones in Joint European Torus plasmas with high ion-cyclotron-resonance-heated fast ions energy content  

SciTech Connect

In Joint European Torus (JET) [P. J. Lomas, Plasma Phys. Controled Fusion 31, 1481 (1989)], discharges with ion cyclotron resonance heating only, low-density plasmas and high fast ions energy contents provided a scenario where fishbones behavior has been observed to be related with sawtooth activity: Crashes of monster sawteeth abruptly changed the type of observed fishbones from low-frequency fishbones [B. Coppi and F. Porcelli, Phys. Rev. Lett. 57, 2272 (1986)] to high-frequency fishbones [L. Chen, R. White, and M. Rosenbluth, Phys. Rev. Lett. 52, 1122 (1984)]. During periods between crashes, the type of observed fishbones gradually changed in the opposite way. Two new fishbones regimes have been observed in intermediate stages: Fishbones bursts covering both high and low frequencies and low amplitude bursts of both types occurring simultaneously. Both sawtooth and fishbones behavior have been explained using a variational formalism.

Nabais, F.; Borba, D.; Mantsinen, M.; Nave, M.F.F.; Sharapov, S.E.; Joint [Association European Atomic Energy Community/Instituto Superior Tecnico (EURATOM/IST), Centro de Fusyo Nuclear, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); Association European Atomic Energy Community/National Technology Agency (EURATOM/TEKES), Helsinki University of Technology, Espoo (Finland); Association European Atomic Energy Community/Instituto Superior Tecnico (EURATOM/IST), Centro de Fusyo Nuclear, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); Association European Atomic Energy Community/United Kingdom Atomic Energy Authority (EURATOM/UKAEA) Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom)

2005-10-01

134

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

135

Remote sensing of the energy of Jovian auroral electrons with STIS: a clue to unveil plasma acceleration processes  

NASA Astrophysics Data System (ADS)

The polar aurora, an important energy source for the Earth's upper atmosphere, is about two orders of magnitude more intense at Jupiter where it releases approximately 10 GW in Jupiter's thermosphere. So far, HST observations of Jupiter's aurora have concentrated on the morphology and the relationship between the solar wind and the brightness distribution. While STIS-MAMA is still operational, time is now critical to move into a new era where FUV long-slit spectroscopy and the spatial scanning capabilities of HST are combined. We propose to use this powerful tool to remotely sense the characteristics of the precipitated electrons by slewing the spectral slit over the different auroral components. It will then be possible to associate electron energies with spatial auroral components and constrain acceleration mechanisms {field-aligned acceleration, magnetic field reconnection, pitch angle electron scattering} associated with specific emission regions. For this, a combination of FUV imaging with STIS long slit spectroscopy will map the spatial variations of the auroral depth and thus the energy of the precipitated electrons. These results will be compared with current models of the Jovian magnetosphere-ionosphere interactions and will provide key inputs to a 3-D model of the Jupiter's atmosphere global heat budget and dynamics currently under development. This compact timely program is designed to provide a major step forward for a better understanding of the physical interactions taking place in Jupiter's magnetosphere and their effects on giant planets' atmospheres, a likely paradigm for many giant fast spinning planets with massive magnetic field in the universe.

Gerard, Jean-Claude

2013-10-01

136

Characteristics and performance of a superconducting bumpy-torus magnet facility for plasma research  

NASA Technical Reports Server (NTRS)

The NASA Lewis bumpy-torus facility consists of 12 superconducting coils, each 19 cm i.d. and capable of 3.0 T on its axis. The coils are equally spaced around a toroidal array with a major diameter of 1.52 m; they are mounted with the major axis of the torus vertical in a single vacuum tank 2.6 m in diameter. Tests of the facility mapped out its magnetic, cryogenic, vacuum, mechanical, and electrical performance. The design value of the maximum magnetic field on the magnetic axis, 3.0 T, was reached and exceeded. A maximum magnetic field of 3.23 T was held for a period of 60 minutes. When the coils were charged to a maximum magnetic field of 3.35 T, the coil system went normal without apparent damage or degradation of performance.

Roth, J. R.; Holmes, A. D.; Keller, T. A.; Krawczonek, W. M.

1973-01-01

137

Explanation of the inward displacement of Io's hot plasma torus and consequences for sputtering sources  

NASA Technical Reports Server (NTRS)

Radial profiles of the ion density and flux-tube content in the Io torus have peak values inside Io's orbit, even though Io is the effective source of these ions. Formation of an inward peak constrains either the velocity distributions or source regions of sputtered neutrals. A further constraint is that the ionization of neutrals on trapped trajectories that return to Io's surface must be limited. A dominant sulphur source is most easily reconciled with these constraints.

Linker, J. A.; Kivelson, M. G.; Moreno, M. A.; Walker, R. J.

1985-01-01

138

Explanation of the inward displacement of Io's hot plasma torus and consequences for sputtering sources  

NASA Astrophysics Data System (ADS)

Radio profiles of the ion density and flux-tube content in the Io torus have peak values inside Io's orbit, even though Io is the effective source of these ions. Formation of an inward peak constrains either the velocity distributions or source regions of sputtered neutrals. A further constraint is that the ionization of neutrals on trapped trajectories that return to Io's surface must be limited. A dominant sulphur source is most easily reconciled with these constraints.

Linker, J. A.; Kivelson, M. G.; Moreno, M. A.; Walker, R. J.

1985-05-01

139

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

140

Processes and properties of edge-localised instabilities in 2T 2MA plasmas in the Joint European Torus  

NASA Astrophysics Data System (ADS)

During July 2012, 150 almost identical H-mode plasmas were consecutively created in the Joint European Torus, providing a combined total of approximately 8 minutes of steady-state plasma with 15 000 Edge Localised Modes (ELMs). In principle, each of those 15 000 ELMs are statistically equivalent. Here, the changes in edge density and plasma energy associated with those ELMs are explored, using the spikes in Beryllium II (527 nm) radiation as an indicator for the onset of an ELM. Clearly different timescales are observed during the ELM process. Edge temperature falls over a 2 ms timescale, edge density and pressure fall over a 5 ms timescale, and there is an additional 10 ms timescale that is consistent with a resistive relaxation of the plasma's edge. The statistical properties of the energy and density losses due to the ELMs are explored. For these plasmas the ELM energy (?E) is found to be approximately independent of the time between ELMs, despite the average ELM energy ( ) and average ELM frequency (f) being consistent with the scaling of ?1 /f . Instead, beyond the first 0.02 s of waiting time between ELMs, the energy losses due to individual ELMs are found to be statistically the same. Surprisingly no correlation is found between the energies of consecutive ELMs either. A weak link is found between the density drop and the ELM waiting time. Consequences of these results for ELM control and modelling are discussed.

Webster, A. J.; Webster, S. J.

2014-11-01

141

Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus  

SciTech Connect

Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm{sup 3}), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.

Choe, Kyumin; Jung, Bongki [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)] [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Chung, Kyoung-Jae, E-mail: jkjlsh1@snu.ac.kr [Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)] [Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Hwang, Y. S. [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of) [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

2014-02-15

142

Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus.  

PubMed

Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm(3)), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented. PMID:24593595

Choe, Kyumin; Jung, Bongki; Chung, Kyoung-Jae; Hwang, Y S

2014-02-01

143

A 12 coil superconducting bumpy torus magnet facility for plasma research  

NASA Technical Reports Server (NTRS)

A summary is presented of the performance of the two-coil superconducting pilot rig which preceded the NASA Lewis bumpy torus. This pilot rig was operated for 550 experimental runs over a period of 7 years. The NASA Lewis bumpy torus facility consists of 12 superconducting coils, each with a 19 cm in diameter and capable of producing magnetic field strengths of 3.0 teslas on their axes. The magnets are equally spaced around a major circumference 1.52 m in diameter, and are mounted with the major axis of the torus vertical in a single vacuum tank 2.59 m in diameter. The design value of maximum magnetic field on the magnetic axis (3.0 teslas) was reached and exceeded. A maximum magnetic field of 3.23 teslas was held for a period of 60 minutes, and the coils did not go to normal. When the coils were charged to a maximum magnetic field of 3.35 teslas, the coil system was driven normal without damage to the facility.

Roth, J. R.; Holmes, A. D.; Keller, T. A.; Krawczonek, W. M.

1972-01-01

144

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

145

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

Microsoft Academic Search

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

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

2012-01-01

146

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

147

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

148

Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)  

NASA Technical Reports Server (NTRS)

The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.

Tan, A.

1990-01-01

149

The role of the interaction between Jovian plasma and icy surface in the generation of Ganymede's exosphere (invited)  

NASA Astrophysics Data System (ADS)

The interaction of Jupiter's magnetospheric plasma with Ganymede intrinsic magnetic field and with its icy surface is mainly responsible for the generation of a neutral environment around Ganymede. In the current work, we simulate the major exospheric components, water and oxygen, of Jupiter's moon Ganymede applying a 3-D Monte Carlo modeling technique. The model takes into consideration the effect of water sublimation in the warmer regions and the combined effects of the precipitation of Jupiter's magnetospheric ions determined by the moon's intrinsic field, and the surface release processes of sputtering and radiolysis. The intrinsic magnetic field imposes the existence of non-homogeneously distributed ion-precipitation zones on Ganymede's surface implying also a spatially inhomogeneous neutral release. Our results are summarized as follows: a) the maximum contribution to the exosphere comes from sublimated water and is located at small altitudes above the moon's subsolar point; b) there is a close correspondence of the near-surface spatial distribution of the directly sputtered-water molecules with the open-closed magnetic field lines boundary, that also agrees well with the Galileo magnetic field and plasma flow measurements; c) the molecular oxygen exosphere comprises two different regions: the first one is an homogeneous, relatively dense, close to the surface thermal-oxygen region (extending to some 100s of km above the surface) and the second one is a less homogeneous region of more energetic oxygen molecules resulting from direct sputtering to the surface; the later has a spatial distribution that depends both on the plasma surface impact and the moon's surface temperature distribution (that determines the actual efficiency of radiolysis); d) a slight asymmetry in the modelled oxygen exosphere appears between Jupiter and anti-Jupiter direction, that seems to be consistent with the HST observations of Ganymede's auroral emissions.

Plainaki, Christina; Milillo, Anna; Massetti, Stefano; Mura, Alessandro; Jia, Xianzhe; Orsini, Stefano; De Angelis, Elisabetta; Mangano, Valeria; Rispoli, Rosanna

2014-05-01

150

Modelling and observing Jovian electron propagation times  

NASA Astrophysics Data System (ADS)

During the Pioneer 10 Jovian encounter, it was observed that the Jovian magnetosphere is a strong source of low energy electrons. These electrons are accelerated in the Jovian magnetosphere and then propagate through the interplanetary medium to reach Earth, sampling the heliospheric magnetic field (HMF) and its embedded turbulence. With the current constellation of near Earth spacecraft (STEREO, SOHO, ACE, ect.) various aspects of Jovian electron transport at/near Earth can be studied in 3D (spatially). During a CME, the plasma between the Earth and Jupiter becomes more disturbed, inhibiting the transport of these electrons to Earth. With the passage of the CME beyond Jupiter, quite-time transport conditions persist and increases of the electron flux at Earth are observed (so-called quite time increases). Using multi-spacecraft observation during such an event, we are able to infer the propagation time of these electrons from Jupiter to Earth. Using a state-of-the-art electron transport model, we study the transport of these electrons from Jupiter and Earth, focusing on their propagation times. These computed values are also compared with observations. We discuss the implications of these results from a particle transport point-of-view.

Toit Strauss, Du; Potgieter, Marius; Kopp, Andreas; Heber, Bernd

2012-07-01

151

Dynamical and compositional variations of energetic particles in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Io's volcanic activity leads to a large population of neutral gas, ions, and electrons in Jupiter's inner magnetosphere largely in a torus engulfing Io's orbit. Charge exchange frees some ions but roughly a ton/s of the gas and plasma leaves by other means. The massive Jovian magnetotail, stretching at least 4 AU to Saturn's orbit, is the conduit for draining this material away. Owing to the fortuitous trajectory of the New Horizons spacecraft as it flew by Jupiter en route to Pluto, measurements of the charged-particle population were made over 2600 RJ (1 Jovian radius = 71,400 km) almost straight down the giant planet's previously unexplored magnetotail. We now know that the magnetotail is rich with phenomena including 3 day quasi-periodicities in both ion intensity and plasma speed; 10 hour variations related to the planetary rotation rate both near the plasmasheet and as far as 1500 RJ down the tail; bursts of heavy ions originating 400 RJ from the planet (a possible magnetic reconnection site) and streaming down the tail to 2000 RJ; gradual and short-term composition variability; energetic electrons streaming down the tail; both sharp discontinuities and gradual transitions in plasma regimes (seen as the spacecraft passed through numerous distinct spatial structures); giant expanding plasma formations; stringy flux tubes; and, encroaching solar wind material in the center of the tail. Two related phenomena are the bursts of ions exhibiting velocity dispersion and the compositional changes during these events relative to the quiet tail and near-Jupiter composition. Understanding this relationship will help us to understand the origin of the particles, the evolution of the magnetic field structure with distance, and the local spatial structure.

Hill, Matthew; Haggerty, Dennis; McNutt, Ralph

152

Spherical torus fusion reactor  

DOEpatents

A fusion reactor is provided having a near spherical-shaped plasma with a modest central opening through which straight segments of toroidal field coils extend that carry electrical current for generating a toroidal magnet plasma confinement fields. By retaining only the indispensable components inboard of the plasma torus, principally the cooled toroidal field conductors and in some cases a vacuum containment vessel wall, the fusion reactor features an exceptionally small aspect ratio (typically about 1.5), a naturally elongated plasma cross section without extensive field shaping, requires low strength magnetic containment fields, small size and high beta. These features combine to produce a spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost.

Peng, Yueng-Kay M. (Oak Ridge, TN)

1989-01-01

153

Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas  

NASA Astrophysics Data System (ADS)

A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as ? e , ?e ? , the MHD ? parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when ?e and ?e ? were relatively low, ballooning parity modes were dominant. As time progressed and both ?e and ?e ? increased, microtearing became the dominant low-k? mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-k?, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

Kaye, S. M.; Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

2014-08-01

154

A hydrocarbon reaction model for low temperature hydrogen plasmas and an application to the Joint European Torus  

NASA Astrophysics Data System (ADS)

A model of collisional processes of hydrocarbons in hydrogen plasmas has been developed to aid in computer modeling efforts relevant to plasma-surface interactions. It includes 16 molecules (CH up to CH4, C2H to C2H6, and C3H to C3H6) and four reaction types (electron impact ionization/dissociative ionization, electron impact dissociation, proton impact charge exchange, and dissociative recombination). Experimental reaction rates or cross sections have been compiled, and estimates have been made for cases where these are not available. The proton impact charge exchange reaction rates are calculated from a theoretical model using molecular polarizabilities. Dissociative recombination rates are described by the equation A/TB where parameter A is fit using polarizabilities and B is estimated from known reaction rates. The electron impact ionization and dissociation cross sections are fit to known graphs using four parameters: threshold energy, maximum value of the cross section, energy at the maximum, and a constant for the exponential decay as energy increases. The model has recently been used in an analysis of the Joint European Torus [P. H. Rebut, R. J. Bickerton, and B. E. Keen, Nucl. Fusion 25, 1011 (1985)] MARK II carbon inner divertor using the WBC Monte Carlo impurity transport code. The updated version of WBC, which includes the full set of hydrocarbon reactions, helps to explain an observed asymmetry in carbon deposition near the divertor.

Alman, D. A.; Ruzic, D. N.; Brooks, J. N.

2000-05-01

155

Direct plasma measurements in the Io torus and inner magnetosphere of Jupiter  

Microsoft Academic Search

The details of positive ion measurements made in the inner magnetosphere are discussed. Attention is also given to an analysis of these measurements to obtain plasma composition, flow speeds, and temperatures and to the assumptions made in the analysis. These results for the positive ions are then combined with the direct measurements of plasma electrons between 5.7 and 9 Jupiter

Fran Bagenal; J. D. Sullivan

1981-01-01

156

Motion of magnetized vacuum arc plasma beam in a quarter-torus  

Microsoft Academic Search

An analytical solution is obtained that describes the distribution of plasma density, the electron and ion velocities, the electric field and the current in the magnetized plasma beam in a toroidal magnetic filter. Analytical expressions for the filter efficiency as function of the toroidal magnetic field are also derived. The effect of the centrifugal and diamagnetic ion drifts on the

B. Alterkop; E. Gidalevich; S. Goldsmith; R. L. Boxman

1996-01-01

157

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

158

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.

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

2004-06-03

159

Progress in Understanding Error-field Physics in NSTX Spherical Torus Plasmas  

SciTech Connect

The low aspect ratio, low magnetic field, and wide range of plasma beta of NSTX plasmas provide new insight into the origins and effects of magnetic field errors. An extensive array of magnetic sensors has been used to analyze error fields, to measure error field amplification, and to detect resistive wall modes in real time. The measured normalized error-field threshold for the onset of locked modes shows a linear scaling with plasma density, a weak to inverse dependence on toroidal field, and a positive scaling with magnetic shear. These results extrapolate to a favorable error field threshold for ITER. For these low-beta locked-mode plasmas, perturbed equilibrium calculations find that the plasma response must be included to explain the empirically determined optimal correction of NSTX error fields. In high-beta NSTX plasmas exceeding the n=1 no-wall stability limit where the RWM is stabilized by plasma rotation, active suppression of n=1 amplified error fields and the correction of recently discovered intrinsic n=3 error fields have led to sustained high rotation and record durations free of low-frequency core MHD activity. For sustained rotational stabilization of the n=1 RWM, both the rotation threshold and magnitude of the amplification are important. At fixed normalized dissipation, kinetic damping models predict rotation thresholds for RWM stabilization to scale nearly linearly with particle orbit frequency. Studies for NSTX find that orbit frequencies computed in general geometry can deviate significantly from those computed in the high aspect ratio and circular plasma cross-section limit, and these differences can strongly influence the predicted RWM stability. The measured and predicted RWM stability is found to be very sensitive to the E × B rotation profile near the plasma edge, and the measured critical rotation for the RWM is approximately a factor of two higher than predicted by the MARS-F code using the semi-kinetic damping model.

E. Menard, R.E. Bell, D.A. Gates, S.P. Gerhardt, J.-K. Park, S.A. Sabbagh, J.W. Berkery, A. Egan, J. Kallman, S.M. Kaye, B. LeBlanc, Y.Q. Liu, A. Sontag, D. Swanson, H. Yuh, W. Zhu and the NSTX Research Team

2010-05-19

160

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

161

Experimental observations and model calculations of impurity radiation in a plasma gun compact torus experiment  

SciTech Connect

Several types of radiation measurements were performed on the Beta II compact forms experiment. Among these are time integrated spectra ranging in wavelength from the vuv to the uv, time resolved bolometer measurements of radiation from the x-ray to the infrared, and time and wavelength resolved measurements of certain spectral lines. It is difficult to relate any one of these measurements to plasma parameters of interest such as temperature, density, or impurity content. In this report we compare the results of these, and other measurements with two simple models of the power balance in the plasma in order to estimate the effect of carbon and oxygen impurities on plasma lifetime.

Goldenbaum, G.C.; Granneman, E.H.A.; Hartman, C.W.; Prono, D.S.; Taska, J.; Turner, W.C.

1982-08-10

162

Effects of large area liquid lithium limiters on spherical torus plasmas  

Microsoft Academic Search

Use of a large-area liquid lithium surface as a limiter 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

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

2005-01-01

163

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas  

Microsoft Academic Search

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

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

2004-01-01

164

Edge transport and turbulence reduction with lithium coated plasma facing components in the National Spherical Torus Experiment  

SciTech Connect

The coating of plasma facing components (PFCs) with lithium improves energy confinement and eliminates ELMs in the National Spherical Torus Experiment, the latter due to a relaxation of the density and pressure profiles that reduces the drive for peeling-ballooning modes. 2-D interpretive transport modeling of discharges without and with lithium shows that a reduction in the PFC recycling coefficient from R {approx} 0.98 to R {approx} 0.90 is required to match the drop in D{sub {alpha}} emission with lithium coatings. A broadening of the edge barrier region showing reduced transport coefficients is observed, with a {approx}75% drop of the D and {chi}{sub e} from 0.8 < {psi}{sub N} < 0.93 needed to match the profile relaxation with lithium coatings. Turbulence measurements using an edge reflectometry system as well as high-k microwave scattering show a decrease in density fluctuations with lithium coatings. These transport changes allow the realization of very wide pedestals, with a {approx}100% width increase relative to the reference discharges.

Canik, J. M.; Maingi, R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Kubota, S. [University of California-Los Angeles, Los Angeles, California 90095 (United States); Ren, Y.; Bell, R. E.; Guttenfelder, W.; Kugel, H. W.; LeBlanc, B. P. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Callen, J. D. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Osborne, T. H. [General Atomics, San Diego, California 92186 (United States); Soukhanovskii, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2011-05-15

165

Positional Coincidence of H2O Maser and a Plasma Obscuring Torus in Radio Galaxy NGC 1052  

E-print Network

We present multi-frequency simultaneous VLBA observations at 15, 22 and 43 GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three continuum images reveal a double-sided jet structure, whose relative intensity ratios imply that the jet axis is oriented close to the sky plane. The steeply rising spectra at 15-43 GHz at the inner edges of the jets strongly suggest that synchrotron emission is absorbed by foreground thermal plasma. We detected H2O maser emission in the velocity range of 1550-1850 km/s, which is redshifted by 50-350 km/s with respect to the systemic velocity of NGC 1052. The redshifted maser gas appears projected against both sides of the jet, in the same manner as the HI seen in absorption. The H2O maser gas are located where the free-free absorption opacity is large. This probably imply that the masers in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus of NGC 4258. Such circumnuclear structure can be the sence of accreting onto the central engine.

Satoko Sawada-Satoh; Seiji Kameno; Kayoko Nakamura; Daichi Namikawa; Katsunori M. Shibata; Makoto Inoue

2008-02-28

166

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

167

Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas  

SciTech Connect

A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as ?{sub e},??{sub e}{sup ?}, the MHD ? parameter, and the gradient scale lengths of T{sub e}, T{sub i}, and n{sub e} were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when ?{sub e} and ?{sub e}{sup ?} were relatively low, ballooning parity modes were dominant. As time progressed and both ?{sub e} and ?{sub e}{sup ?} increased, microtearing became the dominant low-k{sub ?} mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-k{sub ?}, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting T{sub e} for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

Kaye, S. M., E-mail: skaye@pppl.gov; Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2014-08-15

168

Characterization of the plasma edge in the National Spherical Torus Experiment  

Microsoft Academic Search

Using a set of existing and recently installed edge diagnostics, an examination of the characteristics of the edge plasma in NSTX has begun. The three more recent instruments, a four-channel divertor bolometer, a fast-reciprocating edge Langmuir probe, and a fast 2D camera imaging helium puffed at the edge join an IR divertor camera, fast neutral pressure gauges,a high resolution camera

S. F. Paul; J. Boedo; R. Maingi; V. A. Soukhanovskii; S. Z. Zweben; M. Rensink; M. Fenstermacher

2002-01-01

169

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

170

Observation of dust torus with poloidal rotation in direct current glow discharge plasma  

NASA Astrophysics Data System (ADS)

Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (˜130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

Kaur, Manjit; Bose, Sayak; Chattopadhyay, P. K.; Sharma, Devendra; Ghosh, J.; Saxena, Y. C.

2015-03-01

171

The JOVIAL Project for Jovian Seismology  

NASA Astrophysics Data System (ADS)

Jovian seismology is a unique tool to determine the internal structure of the giant planet. It could uncover the size and mass of the core, if any, the existence of a “plasma phase transition” between the molecular and the metallic hydrogen envelope, reveal the internal dynamic, and more generally address the formation and evolution of giant planets in the solar system giving a point of comparison for extra solar planets. Jovian seismology requires special observing tool. SYMPA (Schmider et al. 2007; Gaulme et al. 2008) was the first project specially designed for those objectives. A new type of instrument, a Doppler Imager, had been developed. The project permitted for the first time the measurement of the fundamental acoustic frequency of Jupiter (Gaulme et al. 2011). It also validated the principle of the instrument. However, several limitations appeared during the observations. The main one was the poor temporal coverage. A new version of the Doppler Spectro Imager (DSI) has been studied extensively in the framework of the development of a space instrument for the JUICE mission. A prototype of this new device is presently developed in the laboratory (Soulat et al. 2011) and shows excellent sensitivity and stability. It will be tested on the sky in January 2014. The JOVIAL project foresees the installation of three similar instruments on three telescopes around the Earth (Japan, France, and USA) that will provide the necessary continuity in the observations. We expect to observe winds in the Jovian atmosphere with a precision better than 2 m/s and to detect modes with amplitude as low as 5 cm/s up to the degree ? = 10 at least. The main objective of the project is the detection of the Jovian core.

Schmider, F. X.; Appourchaux, T.; Gaulme, P.; Guillot, T.; Sato, B.; Murphy, N.; Daban, J. B.; Gay, J.; Soulat, L.; Baudin, F.; Boumier, P.; Ollivier, M.; Bordé. P.; Jackiewicz, J.; Ida, S.; Showman, A. P.

2013-12-01

172

Time-Variable Phenomena in the Jovian System  

NASA Technical Reports Server (NTRS)

The current state of knowledge of dynamic processes in the Jovian system is assessed and summaries are provided of both theoretical and observational foundations upon which future research might be based. There are three sections: satellite phenomena and rings; magnetospheric phenomena, Io's torus, and aurorae; and atmospheric phenomena. Each chapter discusses time dependent theoretical framework for understanding and interpreting what is observed; others describe the evidence and nature of observed changes or their absence. A few chapters provide historical perspective and attempt to present a comprehensive synthesis of the current state of knowledge.

Belton, Michael J. S. (editor); West, Robert A. (editor); Rahe, Jurgen (editor); Pereyda, Margarita

1989-01-01

173

Night Side Jovian Aurora  

NASA Technical Reports Server (NTRS)

Jovian aurora on the night side of the planet. The upper bright arc is auroral emission seen 'edge on' above the planetary limb with the darkness of space as a background. The lower bright arc is seen against the dark clouds of Jupiter. The aurora is easier to see on the night side of Jupiter because it is fainter than the clouds when they are illuminated by sunlight. Jupiter's north pole is out of view to the upper right. The images were taken in the clear filter (visible light) and are displayed in shades of blue.

As on Earth, the auroral emission is caused by electrically charged particles striking the upper atmosphere from above. The particles travel along the magnetic field lines of the planet, but their origin is not fully understood. The field lines where the aurora is most intense cross the Jovian equator at large distances (many Jovian radii) from the planet. The faint background throughout the image is scattered light in the camera. This stray light comes from the sunlit portion of Jupiter, which is out of the image to the right. In multispectral observations the aurora appears red, consistent with glow from atomic hydrogen in Jupiter's atmosphere. Galileo's unique perspective allows it to view the night side of the planet at short range, revealing details that cannot be seen from Earth. These detailed features are time dependent, and can be followed in sequences of Galileo images.

North is at the top of the picture. A grid of planetocentric latitude and west longitude is overlain on the images. The images were taken on November 5, 1997 at a range of 1.3 million kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

1997-01-01

174

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.

Laura Guertin

175

Electrodynamic Tethers for Jovian Exploration  

NASA Technical Reports Server (NTRS)

This is an artist's concept of an orbiting space vehicle in the Jovian system using an electrodynamic tether propellantless propulsion system. Electrodynamic tethers offer the potential to greatly extend and enhance future scientific missions to Jupiter and the Jovian system. Like Earth, Jupiter posses a strong magnetic field and a significant magnetosphere. This may make it feasible to operate electrodynamic tethers for propulsion and power generation.

2004-01-01

176

Spectro Imaging of the Jovian Aurora  

NASA Astrophysics Data System (ADS)

Our primary interest is the diagnostic of the Lyman alpha emission in several particular regions of the Jovian auroral region, together with records of the H2 Lyman and Werner emission which is necessary for its interpretation. High resolution spectra around the Lyman alpha line with STIS and grating E140H will give access to atmospheric parameters at and above the auroral source, along the slit centered on the region of interest {[H] from radiative transfer modeling of the reversed Lyman alpha profile, T from temperature sensitive H2 lines}, and to information concerning the precipitating particles responsible for the excitation {search for an extended red-shifted wing typical of energetic proton precipitation, and for Doppler shifts and line asymmetries indicative of superthermal proton inflows or outflows}. Low resolution spectra taken at the same place with STIS and grating G140L will provide complementary information, in particular on the hydrocarbon column density abov e the source, required to establish the local vertical structure of the auroral atmosphere and fully interpret the spectra in terms of preciptating particle diagnostics. Previous HST observations with GHRS and FOC have shown that a wide variety of auroral processes takes place in a series of localized specific features. Consequently, we will target with particular care a few specific areas: {1, 2} the so-called 'main oval' at the footprint of the magnetic shell 30 RJ both sides of longitude 150 deg. { 120 and 200 deg.}, {3} the polar emission along the meridian 160 deg., {4} the 'low-latitude' spot magnetically conjugate of the outer Io torus at about the same longitude, and {5} the neighborhood of the Io flux tube footprint whenever possible. Since the spectra must not be contaminated by signatures of different processes acting in nearby areas, particular attention will be paid to good pointing of the aperture, which will be checked at high accuracy by taking images of bot h h emispheres in the same visit. In addition, the general auroral morphology at the time of the observations must be recorded during the previous or the next Jovian rotation in the wavelength ranges of major importance for the interpretation of the spectra {especially to estimate the contribution of various orders in the Echelle spectra}. Finally, the experience gained in the last two years has confirmed that the scientific return of the observations will be increase by orders of magnitude if the are taken while Galileo is taking in-situ particle and field measurements in the Jovian magnetosphere.

Prange, Renee

1997-07-01

177

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.

178

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

179

A theory of the Io phase asymmetry of the Jovian decametric radiation  

NASA Technical Reports Server (NTRS)

An explanation of an asymmetry in the occurrence probability of the Io-dependent Jovian decametric radiation is proposed. Io generates stronger Alfven waves toward the south when it is in the northern part of the torus. This wave then generates decametric radiation in the northern ionosphere after it reflects in the southern ionosphere. The asymmetry then results from computing the propagation time of the alfven wave along this trajectory. The ray paths of the decameter radiation are calculated using a three dimensional ray tracing program in the Jovian ionosphere. Variations in the expected probability plots are computer for two models of the Jovian ionosphere and global magnetic field, as well as for several choices of the ratio of the radiated frequency to the X-mode cutoff frequency.

Hashimoto, K.; Goldstein, M. L.

1982-01-01

180

The use of neutral beam heating to produce high performance fusion plasmas, including the injection of tritium beams into the Joint European Torus (JET)  

SciTech Connect

The neutral beam injection (NBI) system of the Joint European Torus (JET) [[ital Plasma] [ital Physics] [ital and] [ital Controlled] [ital Nuclear] [ital Fusion] [ital Research] (International Atomic Energy Agency, Vienna, 1985), Vol. 1, p. 11] has proved to be an extremely effective and flexible heating method capable of producing high performance plasmas and performing a wide range of related physics experiments. High fusion performance deuterium plasmas have been obtained in the hot-ion (HI) H-mode regime, using the central particle fueling and ion heating capabilities of the NBI system in low target density plasmas, and in the pellet enhanced plasma (PEP) H-mode regime, where the good central confinement properties of pellet fueled plasmas are exploited by additional heating and fueling as well as the transition to H mode. The HI H-mode configuration was used for the First Tritium Experiment (FTE) in JET in which NBI was used to heat the plasma using 14 D[sup 0] beams and, for the first time, to inject T[sup 0] using the two remaining beams. These plasmas had a peak fusion power of 1.7 MW from deuterium--tritium (D--T) fusion reactions. The capability for injection of a variety of beam species (H[sup 0], D[sup 0], [sup 3]He[sup 0], and [sup 4]He[sup 0]) has allowed the study of confinement variation with atomic mass and the simulation of [alpha]-particle transport. Additionally, the use of the NBI system has permitted an investigation of the plasma behavior near the toroidal [beta] limit over a wide range of toroidal field strengths.

Thompson, E.; Stork, D.; de Esch, H.P.L. (JET Joint Undertaking, Abingdon, Oxon 0X14 3EA (United Kingdom)); the JET Team

1993-07-01

181

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

NASA Astrophysics Data System (ADS)

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 Exploration Agency) will take a role on the magnetosphere spinner. Japanese scientists working on the origin and evolution of Jupiter, satellite evolution, and astrobiology have been participating in the LAPLACE working group in Japan. Detailed observation of Jovian satellites Europa, Ganymede, Callisto and Io as well as smaller satellites such as Amalthea would be important also for the study of the origin of Jovian system. Resurfacing processes on Europa and Ganymede should be studied to know the properties of the internal oceans. The processes can be investigated by infrared observation for salt minerals and amorphous/crystal ices. Not only the thickness of icy crust of Europa but also thickness of the ocean and its bottom topography should be important targets, which would be investigated by gravity and magnetism measurements. For both Europa and Ganymede, the surface layering and structure of icy crust should be an interesting geological target, which will be clarified by subsurface radar. In Japan, KAGUYA is observing the Moon, and Venus remote sensing mission (PLANET-C) and Mercury mission Bepi Colombo will be launched in 2011 and 2013, respectively. Several instruments such as cameras, spectrometers, a laser altimeter, a radar, a magnetometer, plasma instruments, and a dust detector should come from the heritage of instruments on board KAGUYA, PLANET-C, and BepiColombo.

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

182

The Jovian electron spectrum: 1978-1984  

Microsoft Academic Search

Observations of Jovian electrons through six consecutive 13-month Jovian synodic periods from 1978 to 1984 have been made by the University of Chicago electron spectrometer onboard the ISEE-3 (ICE) spacecraft. The Jovian electron spectrum was determined from 5 to 30 MeV and was found to have a shape which is not a power law in kinetic energy, but cuts off

P. A. Evenson; P. Meyer; D. Moses

1985-01-01

183

Emissions from neutrals and ions in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

Observations of the system of neutrals and plasma surrounding Jupiter and originating at Io and their interpretation are reviewed, and related processes are discussed. The optical emission detected from the neutral cloud around Jupiter is treated, and results of measurements of the thermal electron density, the ion and electron temperatures are presented. The results of studies of the EUV emissions are considered, and the mechanisms and rates of ionization of neutral material to form the plasma torus are discussed along with the radial diffusion processes that transport plasma through and out of the torus. Finally, the competing plasma loss process of dielectronic recombination is addressed.

Pilcher, C. B.; Strobel, D. F.

1982-01-01

184

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

185

Jovian Planet Systems Are jovian planets all alike?  

E-print Network

· Jupiter and Saturn ­ Mostly H and He gas ­ Rocky Core · Uranus and Neptune ­ Mostly hydrogen compounds: water (H2O), methane (CH4), ammonia (NH3) ­ Some H, He ­ Rocky core Density Differences · Uranus · Models suggest cores of jovian planets have similar composition · Lower pressures inside Uranus

Crenshaw, Michael

186

The interplanetary modulation and transport of Jovian electrons  

NASA Technical Reports Server (NTRS)

Based on simultaneous measurements by Pioneer 11 of the 3-6 MeV Jovian electron flux, interplanetary magnetic field magnitude, and solar wind speed, the interplanetary transport of energetic particles is studied. It is found that corotating interaction regions (CIR's) greatly inhibit electron transport across the average field direction. Cross-field transport is also influenced by the degree of compression of the solar wind since CIR's are areas of compressed solar wind plasma. The propagation of Jovian electrons is studied by a model that includes the effects of CIR's. The model tests whether or not the three-dimensional convection-diffusion theory adequately describes the cross-field transport of electrons. The model is also valid for Jovian electron observations from earth-orbiting satellites. The model may be further applied to 1 AU from the sun where it is found that the cross-field diffusion of electrons explains why Jovian electrons are detected at the earth even during periods when the interplanetary magnetic field does not connect the earth directly to Jupiter.

Conlon, T. F.

1978-01-01

187

Galileo dust data from the jovian system: 2000 to 2003  

NASA Astrophysics Data System (ADS)

The Galileo spacecraft was the first man-made satellite of Jupiter, orbiting the planet between December 1995 and September 2003. The spacecraft was equipped with a highly sensitive dust detector that monitored the jovian dust environment between approximately 2 and 370 RJ (jovian radius RJ=71 492 km). The Galileo dust detector was a twin of the one flying on board the Ulysses spacecraft. This is the tenth in a series of papers dedicated to presenting Galileo and Ulysses dust data. Here we present data from the Galileo dust instrument for the period January 2000 to September 2003 until Galileo was destroyed in a planned impact with Jupiter. The previous Galileo dust data set contains data of 2883 particles detected during Galileo's interplanetary cruise and 12 978 particles detected in the jovian system between 1996 and 1999. In this paper we report on the data of additional 5389 particles measured between 2000 and the end of the mission in 2003. The majority of the 21 250 particles for which the full set of measured impact parameters (impact time, impact direction, charge rise times, charge amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the impact rates frequently exceeded 10 min -1. Surprisingly large impact rates up to 100 min -1 occurred in August/September 2000 when Galileo was far away (?280RJ) from Jupiter, implying dust ejection rates in excess of 100 kg s -1. This peak in dust emission appears to coincide with strong changes in the release of neutral gas from the Io torus. Strong variability in the Io dust flux was measured on timescales of days to weeks, indicating large variations in the dust release from Io or the Io torus or both on such short timescales. Galileo has detected a large number of bigger micron-sized particles mostly in the region between the Galilean moons. A surprisingly large number of such bigger grains was measured in March 2003 within a four-day interval when Galileo was outside Jupiter's magnetosphere at approximately 350 RJ jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003 provided the first actual comparison of in-situ dust data from a planetary ring with the results inferred from inverting optical images. Strong electronics degradation of the dust instrument due to the harsh radiation environment of Jupiter led to increased calibration uncertainties of the dust data.

Krüger, H.; Bindschadler, D.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Moissl, R.; Morfill, G. E.; Polanskey, C.; Roy, M.; Schwehm, G.; Srama, R.

2010-06-01

188

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

189

Studies of Plasma Flow Past Jupiters Satellite Io  

NASA Technical Reports Server (NTRS)

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

190

The Madison Symmetric Torus  

SciTech Connect

The Madison Symmetric Torus (MST) is the newest and largest reversed field pinch presently in operation. It incorporates a number of design features that set it apart from other pinches, including the use of the conducting shell as both a vacuum vessel and single-turn toroidal field coil. Specially insulated voltage gaps are exposed to the plasma. Magnetic field errors at these gaps as well as at the various diagnostic and pumping ports are minimized through a variety of techniques. The physics goals of MST include study of the effect of large plasma size on confinement and the investigation, in detail, of RFP turbulence, dynamo and transport. Details of the design and initial operation of the device are presented.

Dexter, R.N.; Kerst, D.W.; Lovell, T.W.; Prager, S.C.; Sprott, J.C.

1990-03-01

191

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

192

Pioneer 10/11 data analysis of the plasma analyzer experiment  

NASA Technical Reports Server (NTRS)

The Pioneer 10 plasma analyzer detected the 10 plasma torus. Evidence was found of corotating ions which appear to be primarily S (++) and O (++) in the Pioneer 10 plasma data as the spacecraft moved inward from 6.9 to 5.4 R sub J. The Pioneer plasma analyzer was effective in obtaining information on the heavy ion populations in the Jovian magnetosphere. Interplanetary solar wind plasma shocks can trap energetic particles (cosmic rays) for weeks and out to distances of 17 AU. Energetic particles (o.5 MeV to 20 MeV) were confined between two plasma shocks from solar flares as the shocks propagated outward in the solar system.

Intriligator, D. S.

1982-01-01

193

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

194

Models of Jovian decametric radiation. [astronomical models of decametric waves  

NASA Technical Reports Server (NTRS)

A critical review is presented of theoretical models of Jovian decametric radiation, with particular emphasis on the Io-modulated emission. The problem is divided into three broad aspects: (1) the mechanism coupling Io's orbital motion to the inner exosphere, (2) the consequent instability mechanism by which electromagnetic waves are amplified, and (3) the subsequent propagation of the waves in the source region and the Jovian plasmasphere. At present there exists no comprehensive theory that treats all of these aspects quantitatively within a single framework. Acceleration of particles by plasma sheaths near Io is proposed as an explanation for the coupling mechanism, while most of the properties of the emission may be explained in the context of cyclotron instability of a highly anisotropic distribution of streaming particles.

Smith, R. A.

1975-01-01

195

National Spherical Torus Experiment (NSTX) Torus Design, Fabrication and Assembly  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is a low aspect ratio spherical torus (ST) located at Princeton Plasma Physics Laboratory (PPPL). Fabrication, assembly, and initial power tests were completed in February of 1999. The majority of the design and construction efforts were constructed on the Torus system components. The Torus system includes the centerstack assembly, external Poloidal and Toroidal coil systems, vacuum vessel, torus support structure and plasma facing components (PFC's). NSTX's low aspect ratio required that the centerstack be made with the smallest radius possible. This, and the need to bake NSTXs carbon-carbon composite plasma facing components at 350 degrees C, was major drivers in the design of NSTX. The Centerstack Assembly consists of the inner legs of the Toroidal Field (TF) windings, the Ohmic Heating (OH) solenoid and its associated tension cylinder, three inner Poloidal Field (PF) coils, thermal insulation, diagnostics and an Inconel casing which forms the inner wall of the vacuum vessel boundary. It took approximately nine months to complete the assembly of the Centerstack. The tight radial clearances and the extreme length of the major components added complexity to the assembly of the Centerstack components. The vacuum vessel was constructed of 304-stainless steel and required approximately seven months to complete and deliver to the Test Cell. Several of the issues associated with the construction of the vacuum vessel were control of dimensional stability following welding and controlling the permeability of the welds. A great deal of time and effort was devoted to defining the correct weld process and material selection to meet our design requirements. The PFCs will be baked out at 350 degrees C while the vessel is maintained at 150 degrees C. This required care in designing the supports so they can accommodate the high electromagnetic loads resulting from plasma disruptions and the resulting relative thermal expansions between the PFC's and the vacuum vessel on which supports are attached. This paper will provide a brief review of the issues associated with the design, fabrication and assembly of the NSTX Torus system including those outlined above.

C. Neumeyer; G. Barnes; J.H. Chrzanowski; P. Heitzenroeder; et al

1999-11-01

196

Factors affecting ion kinetic temperature, number density, and containment time in the NASA Lewis bumpy-torus plasma  

NASA Technical Reports Server (NTRS)

The degree of toroidal symmetry of the plasma, the number of midplane electrode rings, the configuration of electrode rings, and the location of the diagnostic instruments with respect to the electrode rings used to generate the plasma are discussed. Impurities were deliberately introduced into the plasma, and the effects of the impurity fraction on ion kinetic temperature and electron number density were observed. It is concluded that, if necessary precautions are taken, the plasma communicates extremely well along the magnetic field lines and displays a high degree of symmetry from sector to sector for a wide range of electrode ring configurations and operating conditions. Finally, some characteristic data taken under nonoptimized conditions are presented, which include the highest electron number density and the longest particle containment time (1.9 msec) observed. Also, evidence from a paired comparison test is presented which shows that the electric field acting along the minor radius of the toroidal plasma improves the plasma density and the calculated containment time more than an order of magnitude if the electric field points inward, relative to the values observed when it points (and pushes ions) radially outward.

Roth, J. R.

1977-01-01

197

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

198

The Io sulfur torus in 1981  

NASA Technical Reports Server (NTRS)

A Fabry-Perot spectrometer was used to obtain images of the Io torus in emission lines of S II (wavelength 6716 and 6731) and S III (wavelength 9531) in February and March 1981, on the 2.1 meter telescope at KPNO. The S II and S III images showed a large variation in brightness and radial extent. There is an indication the S II and S III emissions in the warm torus are correlated. The S II and S III emissions in the warm torus also have similar scale heights along the magnetic field lines of approximately 0.6 to 0.72 R sub J. The east-west asymmetry in the S II images taken at similar magnetic longitudes, but 2.5 Jovian rotations apart, supports the theory of convective motions suggested by others. In addition to the images, simultaneous measurements of the S II (6731 wavelength) line profile were also made on one night using a Fabry-Perot scanning spectrometer on the 4 meter at KPNO. The S II spectral scans implied ion temperatures of 52 (+ or - 10) x 10 to the 3rd at 5.2 to 5.6 R sub J from Jupiter and a minimum temperature of at least 3 x 10 to the 5th K at 6 R sub J from Jupiter.

Oliversen, Ronald J.; Scherb, Frank; Roesler, Fred L.

1986-01-01

199

Expansion of the main auroral oval at Jupiter : evidence for Io's control over the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

In spring 2007, New Horizons' Jupiter fly-by provided a unique opportunity for the largest observation campaign dedicated to the Jovian aurora ever carried out by the Hubble Space Telescope. UV images of the aurora have been acquired on a quasi-daily basis from mid-February to mid-June 2007. Polar projection of the auroral emissions clearly show a continuous long-term expansion of main oval additionally to day by day variations. The main oval moved so much that the Ganymede footprint, which is usually located equatorward of the main emissions, has even been observed inside of it. Simultaneously, the occurrence rate of large equatorward isolated auroral features increased over the season. These emission patches are generally attributed to injections of depleted flux tubes. On 6th June, one of these features exceptionally moved down to the Io footpath. The Io footprint seemed to disappear while the footprint moved through this patch of emission. This disappearance is a unique case among all the UV images of the aurora acquired during the last 12 years. We suggest that all these changes seen in the Jovian aurora are evidence for a major reconfiguration of the magnetosphere induced by increased volcanic activity on Io. Indeed, New Horizons observed particularly intense activity from the Tvashtar volcano in late February 2007. Moreover, sodium cloud brightening caused by volcanic outbursts have also been seen in late May 2007. According to our interpretation, repeated volcanic outbursts beefed up the plasma torus density and its mass outflow rate. This caused the corotation breakdown boundary to migrate closer to Jupiter. Consequently, the main auroral oval moved equatorward. As heavy flux tubes move outward, sparsely filled ones should be injected into the inner magnetosphere in order to conserve the magnetic flux in this region. This phenomenon could explain the large number of injection signatures observed in May-June 2007. Such a cloud of depleted flux tubes probably disrupted the Io-magnetosphere interaction, leading to an abnormally faint Io footprint.

Bonfond, B.; Grodent, D.; Gérard, J.-C.; Stallard, T.; Clarke, J. T.; Yoneda, M.; Radioti, A.; Gustin, J.

2012-04-01

200

Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas  

SciTech Connect

First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.

Cazzaniga, C., E-mail: carlo.cazzaniga@mib.infn.it; Gorini, G.; Nocente, M. [Department of Physics “G. Occhialini,” University of Milano Bicocca, Piazza della Scienza 3, Milano (Italy) [Department of Physics “G. Occhialini,” University of Milano Bicocca, Piazza della Scienza 3, Milano (Italy); Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, via Roberto Cozzi 53, Milano (Italy); Sundén, E. Andersson; Binda, F.; Ericsson, G. [Department of Physics and Astronomy, EURATOM-VR Association, Uppsala University, Uppsala (Sweden)] [Department of Physics and Astronomy, EURATOM-VR Association, Uppsala University, Uppsala (Sweden); Croci, G.; Grosso, G.; Cippo, E. Perelli; Tardocchi, M. [Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, via Roberto Cozzi 53, Milano (Italy)] [Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, via Roberto Cozzi 53, Milano (Italy); Giacomelli, L.; Rebai, M. [Department of Physics “G. Occhialini,” University of Milano Bicocca, Piazza della Scienza 3, Milano (Italy)] [Department of Physics “G. Occhialini,” University of Milano Bicocca, Piazza della Scienza 3, Milano (Italy); Griesmayer, E. [Atominstitut, Vienna University of Technology (Austria)] [Atominstitut, Vienna University of Technology (Austria); Kaveney, G.; Syme, B. [Culham Centre for Fusion Energy, Culham OX143DB (United Kingdom)] [Culham Centre for Fusion Energy, Culham OX143DB (United Kingdom); Collaboration: JET-EFDA Contributors

2014-04-15

201

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

202

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

203

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

NASA Technical Reports Server (NTRS)

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.

1990-01-01

204

Low-energy energetic neutral atom imaging of Io plasma and neutral tori  

NASA Astrophysics Data System (ADS)

Io's plasma and neutral tori play significant roles in the Jovian magnetosphere. We present feasibility studies of measuring low-energy energetic neutral atoms (LENAs) generated from the Io tori. We calculate the LENA flux between 10 eV and 3 keV. The energy range includes the corotational plasma flow energy. The expected differential flux at Ganymede distance is typically 103-105 cm-2 s-1 sr-1 eV-1 near the energy of the corotation. It is above the detection level of the planned LENA sensor that is to be flown to the Jupiter system with integration times of 0.01-1 s. The flux has strong asymmetry with respective to the Io phase. The observations will exhibit periodicities, which can be attributed to the Jovian magnetosphere rotation and the rotation of Io around Jupiter. The energy spectra will exhibit dispersion signatures, because of the non-negligible flight time of the LENAs from Io to the satellite. In 2030, the Jupiter exploration mission JUICE will conduct a LENA measurement with a LENA instrument, the Jovian Neutrals Analyzer (JNA). From the LENA observations collected by JNA, we will be able to derive characteristic quantities, such as the density, velocity, velocity distribution function, and composition of plasma-torus particles. We also discuss the possible physics to be explored by JNA in addition to the constraints for operating the sensor and analyzing the obtained dataset.

Futaana, Yoshifumi; Barabash, Stas; Wang, Xiao-Dong; Wieser, Martin; Wieser, Gabriella S.; Wurz, Peter; Krupp, Norbert; Brandt, Pontus C.:son

2015-04-01

205

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

DOE PAGESBeta

Fluctuations in the edge and scrape-off layer (SOL) of L-mode plasmas in the National Spherical Torus Experiment (NSTX) [S. M. 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 (HOP-V) 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? 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-1 for GPI intensity and 3.4 m-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 (SOLT) 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 ~ 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. [Univ. of Colorado, Boulder, CO (United States); Munsat, T. [Univ. of Colorado, Boulder, CO (United States); D’Ippolito, D. A. [Lodestar Research Corp., Boulder, CO (United States); Maqueda, R. J. [Princeton Plasma Physics Lab., NJ (United States); Myra, J. R. [Lodestar Research Corp., Boulder, CO (United States); Russell, D. [Lodestar Research Corp., Boulder, CO (United States); Zweben, S. J. [Princeton Plasma Physics Lab., NJ (United States)

2011-01-10

206

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

207

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 (NSTX) [S. M. 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 (HOP-V) 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? 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-1 for GPI intensity and 3.4 m-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 (SOLT) 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 ~ 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. [Univ. of Colorado, Boulder, CO (United States); Munsat, T. [Univ. of Colorado, Boulder, CO (United States); D’Ippolito, D. A. [Lodestar Research Corp., Boulder, CO (United States); Maqueda, R. J. [Princeton Plasma Physics Lab., NJ (United States); Myra, J. R. [Lodestar Research Corp., Boulder, CO (United States); Russell, D. [Lodestar Research Corp., Boulder, CO (United States); Zweben, S. J. [Princeton Plasma Physics Lab., NJ (United States)

2011-01-10

208

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

209

The Interplanetary Medium and the Jovian dust Streams  

NASA Astrophysics Data System (ADS)

Between November 2002 and August 2005 the Ulysses spacecraft approached Jupiter sim 0 8 AU at its closest distance and detected 28 new dust particle streams The tiny positively charged dust grains sim 10 nm in the streams are accelerated away from Jupiter by its co-rotational electric field to very high speeds 200 km s -1 Data indicate that once outside the Jovian magnetosphere the Corotating interaction Regions CIRs --and possibly to a minor extent the Coronal mass ejections CMEs - collimate the Jovian dust grain flux in the well known Jovian dust streams On the whole there seems to be a previous CIR for every set of streams and the duration of the set of steams matches roughly the duration of the CIR indicating a confinement of the dust stream particles in the compressed regions of the interplanetary plasma Besides most dust stream peaks and the precedent CIR peaks seem to be separated by an interval roughly similar to the time needed by a dust particle to travel from the source to the spacecraft s detector

Flandes, A.; Krueger, H.

210

National Spherical Torus Experiment (NSTX) Power Supply Real Time Controller  

E-print Network

for the study of plasma confinement, heating, and current drive in a low aspect ratio, spherical torus (ST plasma within the vacuum vessel; 3) inductively drive plasma current; and 4) control plasma position loop voltage ionizes the fuel gas · Plasma current is driven by induction via OH coil · PF coils (1a, 1

211

Galileo dust data from the jovian system: 2000 to 2003 H. Kruger a,b,, D. Bindschadler c  

E-print Network

Galileo dust data from the jovian system: 2000 to 2003 H. Kr¨uger a,b,�, D. Bindschadler c , S/magnetosphere interaction Interplanetary dust Dusty plasmas a b s t r a c t The Galileo spacecraft was the first man approximately 2 and 370 RJ (jovian radius RJ¼71 492 km). The Galileo dust detector was a twin of the one flying

Hamilton, Douglas P.

212

Torus knots as Hopfions  

NASA Astrophysics Data System (ADS)

We present a direct connection between torus knots and Hopfions by finding stable and static solutions of the extended Faddeev-Skyrme model with a ferromagnetic potential term. (P,Q)-torus knots consisting of |Q| sine-Gordon kink strings twisted P/Q times into the poloidal cycle along the toroidal cycle on a toroidal domain wall carry the Hopf charge PQ, which demonstrates that Hopfions can be further classified according to torus knot type.

Kobayashi, Michikazu; Nitta, Muneto

2014-01-01

213

Jovian Lightning and Moonlit Clouds  

NASA Technical Reports Server (NTRS)

Jovian lightning and moonlit clouds. These two images, taken 75 minutes apart, show lightning storms on the night side of Jupiter along with clouds dimly lit by moonlight from Io, Jupiter's closest moon. The images were taken in visible light and are displayed in shades of red. The images used an exposure time of about one minute, and were taken when the spacecraft was on the opposite side of Jupiter from the Earth and Sun. Bright storms are present at two latitudes in the left image, and at three latitudes in the right image. Each storm was made visible by multiple lightning strikes during the exposure. Other Galileo images were deliberately scanned from east to west in order to separate individual flashes. The images show that Jovian and terrestrial lightning storms have similar flash rates, but that Jovian lightning strikes are a few orders of magnitude brighter in visible light.

The moonlight from Io allows the lightning storms to be correlated with visible cloud features. The latitude bands where the storms are seen seem to coincide with the 'disturbed regions' in daylight images, where short-lived chaotic motions push clouds to high altitudes, much like thunderstorms on Earth. The storms in these images are roughly one to two thousand kilometers across, while individual flashes appear hundreds of kilometer across. The lightning probably originates from the deep water cloud layer and illuminates a large region of the visible ammonia cloud layer from 100 kilometers below it.

There are several small light and dark patches that are artifacts of data compression. North is at the top of the picture. The images span approximately 50 degrees in latitude and longitude. The lower edges of the images are aligned with the equator. The images were taken on October 5th and 6th, 1997 at a range of 6.6 million kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

1997-01-01

214

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

215

Torus knot state asymptotics  

E-print Network

The state of a knot is defined in the realm of Chern-Simons topological quantum field theory as a holomorphic section on the SU(2) character manifold of the peripheral torus. We compute the asymptotics of the torus knot states in terms of the Alexander polynomial, the Reidemeister torsion and the Chern-Simons invariant. We also prove that the microsupport of the torus knot state is included in the character manifold of the knot exterior. As a corollary we deduce the Witten asymptotics conjecture for the Dehn filling of the torus knots and asymptotic expansions for the colored Jones polynomials.

Laurent Charles

2011-07-23

216

GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1029/, Detecting nanoparticles at radio frequencies: Jovian  

E-print Network

] and plasma wave [Scarf et al., 1982] instruments on the Voyager 2 spacecraft, which did not carry FREQUENCIES We analyse wave observations by the Cassini/RPWS instrument performed during the Jovian fly at about the solar wind speed. The observed wave pulses are produced by ionisation of dust grains impact

Demoulin, Pascal

217

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

Microsoft Academic Search

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

S. Sasaki; M. Fujimoto; Y. Kasaba; J. Kawaguchi; Y. Kawakatsu; O. Mori; T. Takashima; Y. Tsuda; H. Yano

2009-01-01

218

Heavy ions from Galilean satellites and the centrifugal distortion of the Jovian magnetosphere  

Microsoft Academic Search

Heavy ions produced in the atmosphere of the Galilean satellites are a potentially significant source of plasma in the Jovian magnetosphere. Such ions will rapidly be accelerated to the corotation velocity, and the associated centrifugal force far exceeds that of gravity. Satellite ions are thus confined near the equator with a centrifugal scale height that depends linearly on their thermal

T. W. Hill; F. C. Michel

1976-01-01

219

Radiation chemistry in the Jovian stratosphere - Laboratory simulations  

NASA Technical Reports Server (NTRS)

The results of the present low-pressure/continuous-flow laboratory simulations of H2/He/CH4/NH3 atmospheres' plasma-induced chemistry indicate radiation yields of both hydrocarbon and N2-containing organic compounds which increase with decreasing pressure. On the basis of these findings, upper limits of 1 million-1 billion molecules/sq cm/sec are established for production rates of major auroral-chemistry species in the Jovian stratosphere. It is noted that auroral processes may account for 10-100 percent of the total abundances of most of the observed polar-region organic species.

Mcdonald, Gene D.; Thompson, W. R.; Sagan, Carl

1992-01-01

220

Wake flowfields for Jovian probe  

NASA Technical Reports Server (NTRS)

The wake flow field developed by the Galileo probe as it enters the Jovian atmosphere was modeled. The wake produced by the probe is highly energetic, yielding both convective and radiative heat inputs to the base of the probe. A component mathematical model for the inviscid near and far wake, the viscous near and far wake, and near wake recirculation zone was developed. Equilibrium thermodynamics were used for both the ablation and atmospheric species. Flow fields for three entry conditions were calculated. The near viscous wave was found to exhibit a variable axial pressure distribution with the neck pressure approximately three times the base pressure. Peak wake flow field temperatures were found to be in proportion to forebody post shock temperatures.

Engel, C. D.; Hair, L. M.

1980-01-01

221

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

222

Spherical torus, compact fusion at low field  

SciTech Connect

A spherical torus is obtained by retaining only the indispensable components on the inboard side of a tokamak plasma, such as a cooled, normal conductor that carries current to produce a toroidal magnetic field. The resulting device features an exceptionally small aspect ratio (ranging from below 2 to about 1.3), a naturally elongated D-shaped plasma cross section, and ramp-up of the plasma current primarily by noninductive means. As a result of the favorable dependence of the tokamak plasma behavior to decreasing aspect ratio, a spherical torus is projected to have small size, high beta, and modest field. Assuming Mirnov confinement scaling, an ignition spherical torus at a field of 2 T features a major radius of 1.5 m, a minor radius of 1.0 m, a plasma current of 14 MA, comparable toroidal and poloidal field coil currents, an average beta of 24%, and a fusion power of 50 MW. At 2 T, a Q = 1 spherical torus will have a major radius of 0.8 m, a minor radius of 0.5 m, and a fusion power of a few megawatts.

Peng, Y.K.M.

1985-02-01

223

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, ...

224

National Spherical Torus Experiment (NSTX) Power Supply Real Time Controller  

E-print Network

for the study of plasma confinement, heating, and current drive in a low aspect ratio, spherical torus (ST field configuration; 2) initiate plasma within the vacuum vessel; 3) inductively drive plasma ionizes the fuel gas . Plasma current is driven by induction via OH coil . PF coils (1a, 1b, 2, 3

225

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

226

Field-aligned currents in Io's plasma wake  

NASA Astrophysics Data System (ADS)

In Io's reference frame, the downstream distribution of various physical quantities in Io's plasma wake can be regarded as unchangeable with respect to time. A magnetic flux tube in a specific position in the wake can be related to a state of its evolution after been perturbed by Io. Thus the investigation of the wake can be transferred to the study of an Io-perturbed flux tube in the Jovian corotational frame. A magnetohydrodynamics approach called "The theory of a thin filament motion" is employed here. Our simulations suggest that 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 developed, before it is released downstream. A perturbed flux tube would undergo a subcorotational motion in Io's plasma wake. This motion is inevitably modulated by Alfvén wave bouncing back and forth inside the Io plasma torus. The scale of the subcorotation region is in the order of one Jovian radius. The distribution of the simulated field-aligned currents downstream is consistent with the observed wake aurora brightness profile; in particular, the periodic structure in the current distribution is in agreement with recent infrared and FUV observations showing the presence of secondary spots in the auroral emissions.

Chen, Chuxin

2008-09-01

227

Jovian electrons at 1 AU - 1978-1984  

Microsoft Academic Search

Observations of 5 - 30 MeV Jovian electrons from 1978 to 1984 have been made at 1 AU by the University of Chicago electron spectrometer onboard the ISEE 3 spacecraft. The six consecutive 13 month Jovian synodic periods covered by these observations span the interval of maximum solar activity. The 13 month variation in the Jovian electron intensity measured by

D. Moses

1987-01-01

228

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

229

The Jovian boundary layer as formed by magnetic-anomaly effects  

NASA Technical Reports Server (NTRS)

A model is presented in which a plasma boundary layer of Jupiter is formed from plasma of internal origin. It is proposed that, unlike the Earth's boundary layer, which is thought to consist principally of solar wind plasma, Jupiter's boundary layer consists principally of sulphur and oxygen from the Io plasma torus, plus a small component of hydrogen from Jupiter's ionosphere. Fresh plasma is supplied to the boundary layer once each planetary rotation period by a convection pattern that rotates with Jupiter.

Dessler, A. J.

1979-01-01

230

Recurrent Modulation of Jovian Electron intensities: Ulysses KET measurements  

NASA Astrophysics Data System (ADS)

Corotating Interaction Regions are regions in the heliosphere that are formed at the leading edges of high-speed solar wind streams originating in coronal holes. Their effects on the propagation of energetic particles are known. Here we concentrate on the modulation of Jovian electrons by CIRs observed with the Kiel Electron Telescope. After its launch on Oct. 6, 1990 Ulysses followed an in-ecliptic path towards Jupiter. The closest approach to the giant planet occurred on Feb. 8, 1992, when Ulysses began its out-ofecliptic dive. During that period the flux of 2-10 MeV electrons, originating from Jupiter, were modulated by Corotating Interaction regions until the spacecraft reached a latitude of about 30 degree. Due to the orbital periods of Jupiter and Ulysses, the spacecraft came again close to the planet in 2004. As in 1992 and 1993 the MeV electron fluxes were modulated by CIRs in 2005. In 2006 this modulation stoped again, when the spacecraft was above 30 degree latitude. In order to understand this decay we present a detailed analysis of a series of recurrent Jovian electron decreases and its relation to the solar wind plasma parameters. It was found that the decreases are correlated with enhanced variation in the Bn component.

Dunzlaff, P.; Heber, B.; Sternal, O.; et al.

231

Saturn in hot water: viscous evolution of the Enceladus torus  

E-print Network

The detection of outgassing water vapor from Enceladus is one of the great breakthroughs of the Cassini mission. The fate of this water once ionized has been widely studied; here we investigate the effects of purely neutral-neutral interactions within the Enceladus torus. We find that, thanks in part to the polar nature of the water molecule, a cold (~180 K) neutral torus would undergo rapid viscous heating and spread to the extent of the observed hydroxyl cloud, before plasma effects become important. We investigate the physics behind the spreading of the torus, paying particular attention to the competition between heating and rotational line cooling. A steady-state torus model is constructed, and it is demonstrated that the torus will be observable in the millimeter band with the upcoming Herschel satellite. The relative strength of rotational lines could be used to distinguish between physical models for the neutral cloud.

Alison J. Farmer

2008-06-09

232

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

233

Simulation of Plasma Interaction with Io's Atmosphere  

NASA Astrophysics Data System (ADS)

One dimensional Direct Simulation Monte Carlo (DSMC) simulations are used to examine the interaction of the jovian plasma torus with Io's sublimation atmosphere. The hot plasma sweeps past Io at ˜57 km/s due to the external Jovian magnetic and corotational electric fields and the resultant energetic collisions both heat and dissociate the neutral gas creating an inflated, mixed atmosphere of SO2 and its daughter products. The vertical structure and composition of the atmosphere is important for understanding Io's mass loading of the plasma torus, electron excited aurora, and Io's global gas dynamics. Our 1D simulations above a fixed location on the surface of Io allows the O+ and S+ ions to drift down into the domain where they then undergo elastic and charge exchange collisions with the neutral gas. Each electron's position is determined by the motion of a corresponding ion; however, the electrons retain their own velocity components which are then used during elastic, ionization, and excitation collisions with the neutral gas. Charge exchange creates fast neutral O and S atoms. Molecular Dynamic/Quasi-Classical Trajectory (MD/QCT) calculations are used to generate total and reaction cross sections for energetic O+SO2 collisions [1] as well as for O+O2 collisions. In addition, the model accounts for photo-dissociation assuming the atmosphere is optically thin. Our previous plasma heating model (without chemistry) agrees well with the vertical structure of the current model at lower altitudes where the gas is collisional; however, at high altitudes (>100 km) significant differences among the models appear. The current model's constant E and B fields results in reacceleration of the ions and electrons to a constant E×B drift velocity towards the surface after collisions with the neutral gas and, while the results are an upper limit on the plasma interaction strength, the results indicate that joule heating is significant, causing large changes in the vertical structure of the atmosphere. Plasma heating of, not momentum transfer to, the atmosphere dominates even for radially inward plasma flows resulting in a hot, inflated atmosphere. The scale heights for the various species were found to be a competition between the hydrodynamic scale height based on the gas constant (for the mixture if collisional) and the production rate from dissociation of SO2 which depends on the local SO2 density and available plasma energy at that altitude.

Moore, Chris H.; Deng, Hao; Goldstein, David B.; Levin, Deborah; Varghese, Philip L.; Trafton, Laurence M.; Stewart, Bénédicte D.; Walker, Andrew C.

2011-05-01

234

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

235

Numerical Simulation of Baroclinic Jovian Vortices  

Microsoft Academic Search

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

Richard K. Achterberg; Andrew P. Ingersoll

1994-01-01

236

Revisiting Jovian-resonance Induced Chondrule Formation  

NASA Astrophysics Data System (ADS)

It is proposed that planetesimals perturbed by Jovian mean-motion resonances are the source of shock waves that form chondrules. It is considered that this shock-induced chondrule formation requires the velocity of the planetesimal relative to the gas disk to be on the order of >~ 7 km s-1 at 1 AU. In previous studies on planetesimal excitation, the effects of Jovian mean-motion resonance together with the gas drag were investigated, but the velocities obtained were at most 8 km s-1 in the asteroid belt, which is insufficient to account for the ubiquitous existence of chondrules. In this paper, we reexamine the effect of Jovian resonances and take into account the secular resonance in the asteroid belt caused by the gravity of the gas disk. We find that the velocities relative to the gas disk of planetesimals a few hundred kilometers in size exceed 12 km s-1, and that this is achieved around the 3:1 mean-motion resonance. The heating region is restricted to a relatively narrowband between 1.5 AU and 3.5 AU. Our results suggest that chondrules were produced effectively in the asteroid region after Jovian formation. We also find that many planetesimals are scattered far beyond Neptune. Our findings can explain the presence of crystalline silicate in comets if the scattered planetesimals include silicate dust processed by shock heating.

Nagasawa, M.; Tanaka, K. K.; Tanaka, H.; Nakamoto, T.; Miura, H.; Yamamoto, T.

2014-10-01

237

Measurements of the Jovian radiation belts  

Microsoft Academic Search

The University of California at San Diego trapped radiation detector measured proton and electron fluxes, angular distributions, and energy spectra throughout the Pioneer 10 flyby of Jupiter last December. Here the instrumentation and calibrations are described, and good values for particle fluxes in the inner and outer regions are presented. The major features of the Jovian radiation belts are described,

R. W. Fillius; C. E. McIlwain

1974-01-01

238

Raman scattering in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

On December 8 and 9, 1976, the 1024 channel Reticon silicon photodiode array detector in the coude spectrograph of a 2.7 m telescope was used to obtain spectra of Jupiter and the moon. Three separate data sets were obtained, including one of the Jovian equatorial region, one of the Jovian north polar cap, and one of Mare Serenetatis on the moon. A correlation analysis was conducted. The autocorrelation function of the Jovian spectrum was calculated and the autocorrelation function of the lunar spectrum was subtracted from it. The analysis made it possible to detect Raman scattering by H2 in the atmosphere of Jupiter. The pure rotational H2 S(0) and S(1) lines were detected. The ratio of the relative number of Raman scattered photons in the S(0) and S(1) features indicate that the H2 in the Jovian atmosphere is in the equilibrium, rather than the normal state. Therefore some sort of nonradiative process is responsible for transitions between the ortho and para states of H2.

Cochran, W. D.; Trafton, L.; Macy, W., Jr.; Woodman, J. H.

1981-01-01

239

Mirror mode structures in the Jovian magnetosheath  

Microsoft Academic Search

Mirror mode waves are commonly observed in planetary magnetosheaths. Their magnetic signatures are often periodic but occasionally appear as intermittent increases of field magnitude (peaks) or as intermittent decreases (dips). We define quantitative mirror structure identification criteria and statistically analyze the distributions of the various forms. A survey of all the relevant magnetometer data in the Jovian magnetosheath reveals that

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

2006-01-01

240

Jupiter Torus Diagram  

NASA Technical Reports Server (NTRS)

A cut-away schematic of Jupiter's space environment shows magnetically trapped radiation ions (in red), the neutral gas torus of the volcanic moon Io (green) and the newly discovered neutral gas torus of the moon Europa (blue). The white lines represent magnetic field lines.

Energetic neutral atoms (ENA) are emitted from the Europa torus regions because of the interaction between the trapped ions and the neutral gases. The Magnetospheric Imaging Instrument on NASA's Cassini spacecraft imaged those energetic neutral atoms in early 2001 during Cassini's flyby of Jupiter. Energetic neutral atoms also come from Jupiter when radiation ions impinge onto Jupiter's upper atmosphere.

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages Cassini for NASA's Office of Space Science, Washington, D.C.

2003-01-01

241

Studies of accelerated compact toruses  

SciTech Connect

In an earlier publication we considered acceleration of plasma rings (Compact Torus). Several possible accelerator configurations were suggested and the possibility of focusing the accelerated rings was discussed. In this paper we consider one scheme, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focusing) during acceleration. Because the allowable acceleration force, F/sub a/ = kappaU/sub m//R where (kappa < 1), increases as R/sup -2/, the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case, however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency.

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

1983-01-04

242

Supply of trans-Europa Neutral Torus by the Surface-bounded Atmosphere of Europa  

NASA Astrophysics Data System (ADS)

Magnetospheric ion sputtering is an important source of neutrals at the icy Galilean satellites [1-3]. The Cassini Magnetosphere Imaging Instrument (MIMI) has detected [4] a neutral cloud located at Europa's orbit and likely consisting of sputtering products. A collisional Monte Carlo model of Europa's surface-bounded atmosphere in which the thermal and sputtering sources of H2O molecules and their molecular fragments are accounted for was developed [5]. Dissociation and ionization of H2O and O2 by magnetospheric electrons, solar UV radiation and photoelectron impact, and collisional ejection from the atmosphere by the low energy plasma are taken into account. The surface-bounded O2 atmosphere of Europa originates from a balance between radiolysis of the satellite icy surface by the solar UV radiation and high-energy magnetospheric plasma and the collisional ejection from the surface-bounded atmosphere by the low-energy plasma. The enhanced oxygen production rate found earlier [6] is used along with comparable H2O ejection rate. Calculations show that the atmospheric chemical composition is determined by both the water and oxygen photochemistry in the near-surface atmospheric region, escape of suprathermal neutrals into the Jovian system, and the adsorption-desorption exchange by radiolytic water products with the satellite surface. It is shown, as was the case for the sodium atmosphere [7], that the oxygen and hydrogen loss from Europa's atmosphere supplies its gas torus [8]. The calculated oxygen supply rates are in the range (6-10)x1027 atoms per second depending on the ratio of thermal (evaporation) and nonthermal (sputtering) source rates. Using an oxygen ionization rate of 2.0x10-6 s-1 the estimate of the total number N of neutrals in the torus is (3.0 - 5.0)x1033 O atoms. This should be doubled to take into account the escape of atomic and molecular hydrogen. This eatimate approaches that inferred from observations [4] (4.5 - 9.0)x1033 atoms. Therefore, the collisional Monte Carlo model of Europa's surface-bounded atmosphere may be able to provide the required supply of neutrals to the trans-Europa gas torus in the inner Jupiter's magnetosphere. [1] Johnson, R.E., et al. 1998. Europa's Surface and Sputter-Produced Ionosphere. GRL 25, 3257-3260. [2] Cooper, J.F.,et al.2001. Energetic Ion and Electron Irradiation of the Icy Galilean Satellites. Icarus 149, 133-159. [3] Johnson, R.E., et al. 2003. Radiation Effects on the Surface of the Galilean Satellites, ed. F. Bagenal, Jupiter: Planet, Satellites & Magnetosphere, Cambridge University Press, Cambridge, in press. [4] Mauk B. H., et al. 2003. Energetic neutral atoms from a trans-Europa gas torus at Jupiter, Nature 421, 920-922. [5] Shematovich, V.I., R.E. Johnson, and J.F. Cooper 2003. Surface-bounded Oxygen Atmosphere of Europa. EGS-AGU-EGU Joint Assembly, abstract 13094, Nice, France. [6] Shematovich, V.I. and R.E. Johnson 2001. Near-Surface Oxygen Atmosphere at Europa. Adv. Space Res. 27, 1881-1888. [7] Leblanc, F., R.E. Johnson and M.E. Brown 2002. Europa's Sodium Atmosphere: an Ocean Source? Icarus 159, 132-144. [8] Eviatar, A., A. Bar-Nun, and M. Podolak 1985. Europan surface phenomena. Icarus 61, 185-191.

Shematovich, V.; Johnson, R. E.; Cooper, J. F.; Wong, M. C.

2003-12-01

243

Statistics of depleted flux tubes in the jovian magnetosphere  

NASA Astrophysics Data System (ADS)

On many of its passes through the Io torus the Galileo spacecraft has detected the presence of what appear to be thin magnetic flux tubes with fields somewhat higher than their surroundings. On these flux tubes the magnetic pressure is sufficiently above the pressure of neighboring tubes that it is possible the plasma contributions to the pressure within these tubes are depleted. Due to their short duration, they are only detectable in high time-resolution magnetometer data. Herein we survey all high time-resolution data that are available over the full Galileo mission and present a final statistical study. These tubes occupy 0.32% of the torus outside the orbit of Io. None are found inside. Their strength indicates that the ratio of the thermal pressure to magnetic pressure in the outer torus is about 2%. Comparison of the observed electron density in the neighborhood of these tubes indicates that the ion temperature is in the range 30-100 eV, consistent with other estimates. The amount of magnetic flux transported by these thin tubes could supply the amount of magnetic flux mass-loaded and transported to the magnetotail if the inward velocity is about 300 times that of the outward transport. Finally, the thin flux tubes are found in clusters, as they would occur if they resulted from the breakup of larger flux tubes.

Russell, C. T.; Kivelson, M. G.; Khurana, K. K.

2005-08-01

244

Jovian S burst generation by Alfvén waves  

NASA Astrophysics Data System (ADS)

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tubes connecting Io or Io's wake to Jupiter. Electrons responsible for the emission are thought to be accelerated from Io to Jupiter. We present simulations of this hot electron population under the assumption of acceleration by Alfvén waves in the Io flux tube. Outside of limited acceleration regions where a parallel electric field associated with Alfvén waves exists, the electrons are supposed to have an adiabatic motion along the magnetic field lines. Near Jupiter a loss cone appears in the magnetically mirrored electron population, which is able to amplify extraordinary (X) mode radio waves. The X-mode growth rate is computed, which allows us to build theoretical dynamic spectra of the resulting Jovian radio emissions, whose characteristics match those observed for Jovian S bursts.

Hess, S.; Mottez, F.; Zarka, P.

2007-11-01

245

Io control of Jovian radio emission  

NASA Technical Reports Server (NTRS)

The possibility of Io controlling Jovian decametric radio emission, particularly in the region below 22 MHz, is discussed. Results of a two-year survey at 26.3 at 26.3 MHz are presented which demonstrate the control of Io over a high-intensity storm component of the radio emission and the independence of a weak radio component from the phase of Io, as was observed at lower frequencies. It is thus hypothesized that Io control is a flux-dependent rather than a frequency-dependent phenomenon, and results of analyses at 18 and 10 MHz which support this hypothesis are presented. The apparent correlation between frequency and Io control is thus shown to result from a selection effect due to the increase of non-Io emission with decreasing frequency and relative antenna detection threshold. This result implies a contiguous Io-controlled source region extending out several Jovian radii along the Io flux tube.

Desch, M. D.

1980-01-01

246

Rotation Properties of Three Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

The spin properties of the Jovian Trojan asteroids have not been extensively studied due to their distance from the Sun and their low albedos. We present a progress report on a program to determine well-sampled light curves for the Jovian Trojans. Rotation data will be presented for 884 Priamus, 4489 88AK, and 4834 Thoas. Data were obtained in October 2009 and July 2010 using the SMARTS 1.0-meter and 0.9-meter telescopes, respectively, at Cerro Tololo Interamerican Observatory near La Serena, Chile. Images were processed and measured with IRAF, and periods determined using the Canopus software package. This research was supported by Cottrell College Science Award grants from the Research Corporation (LMF and DAR; SML) and support from the Lunar and Planetary Institute (SML).

Lederer, Susan M.; French, L. M.; Rohl, D. A.; Friedrich, K.; Hufford, T.; Jasmim, F. Luzia; Khairunnisa, A.; Šilha, J.

2010-10-01

247

Vertical shear in the Jovian equatorial zone.  

NASA Technical Reports Server (NTRS)

Jupiter photographs taken in two different wavelength regions (blue and red) are studied for clues to differing Jovian atmosphere motions. The relative motions of features visible on these photographs may be interpreted as a vertical shear at visible cloud level. The value obtained implies that the north equatorial zone must be about 0.35 deg K warmer than the adjacent equatorial zone. Deeper in the atmosphere the reverse must hold.

Layton, R. G.

1971-01-01

248

Forward and inverse modeling for jovian seismology  

NASA Astrophysics Data System (ADS)

Jupiter is expected to pulsate in a spectrum of acoustic modes and recent re-analysis of a spectroscopic time series has identified a regular pattern in the spacing of the frequencies (Gaulme, P., Schmider, F.-X., Gay, J., Guillot, T., Jacob, C. [2011]. Astron. Astrophys. 531, A104). This exciting result can provide constraints on gross jovian properties and warrants a more in-depth theoretical study of the seismic structure of Jupiter. With current instrumentation, such as the SYMPA instrument (Schmider, F.X. [2007]. Astron. Astrophys. 474, 1073-1080) used for the Gaulme et al. (Gaulme, P., Schmider, F.-X., Gay, J., Guillot, T., Jacob, C. [2011]. Astron. Astrophys. 531, A104) analysis, we assume that, at minimum, a set of global frequencies extending up to angular degree ?=25 could be observed. In order to identify which modes would best constraining models of Jupiter's interior and thus help motivate the next generation of observations, we explore the sensitivity of derived parameters to this mode set. Three different models of the jovian interior are computed and the theoretical pulsation spectrum from these models for ??25 is obtained. We compute sensitivity kernels and perform linear inversions to infer details of the expected discontinuities in the profiles in the jovian interior. We find that the amplitude of the sound-speed jump of a few percent in the inner/outer envelope boundary seen in two of the applied models should be reasonably inferred with these particular modes. Near the core boundary where models predict large density discontinuities, the location of such features can be accurately measured, while their amplitudes have more uncertainty. These results suggest that this mode set would be sufficient to infer the radial location and strength of expected discontinuities in Jupiter's interior, and place strong constraints on the core size and mass. We encourage new observations to detect these jovian oscillations.

Jackiewicz, Jason; Nettelmann, Nadine; Marley, Mark; Fortney, Jonathan

2012-08-01

249

Charge exchange in the Io torus and exosphere  

NASA Technical Reports Server (NTRS)

Charge-exchange cross sections and their velocity dependence have been estimated for the most important reactions in the Io torus and exosphere. The methods used for calculating the cross sections are given and discussed in some detail. For symmetric-resonant single and double charge exchange, the cross sections are slowly varying functions of velocity. For inelastic charge-exchange collisions, the transition probabilities into a given final state can depend critically on velocity. Models are described which can be used to estimate both the most rapid charge-exchange processes and those states which play an important role. Calculated cross sections are used to obtain reaction rates as a function of radial position, demonstrating the importance of charge exchange in the inner torus. Charge-exchange reactions of torus ions with molecular species in Io's exosphere may yield a net supply of neutrals and plasma to the torus.

Johnson, R. E.; Strobel, D. F.

1982-01-01

250

The Torus Routing Chip  

Microsoft Academic Search

The torus routing chip (TRC) is a selftimed chip that performs deadlock-freecut-through routing ink-aryn-cube multiprocessor interconnection networks using a new method of deadlock avoidance calledvirtual channels. A prototype TRC with byte wide self-timed communication channels achieved on first silicon a throughput of 64 Mbits\\/s in each dimension, about an order of magnitude better performance than the communication networks used by

William J. Dally; Charles L. Seitz

1986-01-01

251

Plasma current start-up by the outer ohmic heating coils in the Saskatchewan TORus Modified (STOR-M) iron core tokamak  

NASA Astrophysics Data System (ADS)

A plasma current up to 15 kA has been driven with outer ohmic heating (OH) coils in the STOR-M iron core tokamak. Even when the inner OH coil is disconnected, the outer OH coils alone can induce the plasma current as primary windings and initial breakdown are even easier in this coil layout. This result suggests a possibility to use an iron core in a spherical tokamak to start up the plasma current without a central solenoid. The effect of the iron core saturation on the extension of the discharge pulse length has been estimated for further experiments in the STOR-M tokamak.

Mitarai, O.; Xiao, C.; McColl, D.; Dreval, M.; Hirose, A.; Peng, M.

2015-03-01

252

Plasma current start-up by the outer ohmic heating coils in the Saskatchewan TORus Modified (STOR-M) iron core tokamak.  

PubMed

A plasma current up to 15 kA has been driven with outer ohmic heating (OH) coils in the STOR-M iron core tokamak. Even when the inner OH coil is disconnected, the outer OH coils alone can induce the plasma current as primary windings and initial breakdown are even easier in this coil layout. This result suggests a possibility to use an iron core in a spherical tokamak to start up the plasma current without a central solenoid. The effect of the iron core saturation on the extension of the discharge pulse length has been estimated for further experiments in the STOR-M tokamak. PMID:25832230

Mitarai, O; Xiao, C; McColl, D; Dreval, M; Hirose, A; Peng, M

2015-03-01

253

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

254

Discrimination between Jovian radio emissions and Saturn electrostatic discharges  

E-print Network

Discrimination between Jovian radio emissions and Saturn electrostatic discharges G. Fischer,1 W in the frequency range of a few MHz can be due to Jovian radio emissions or SEDs (Saturn electrostatic discharges caused by lightning in Saturn's atmosphere. We show a method for discriminating between these two

Gurnett, Donald A.

255

JOVIAN RADIO EMISSIONS: AN EARLY OVERVIEW OF GALILEO  

E-print Network

JOVIAN RADIO EMISSIONS: AN EARLY OVERVIEW OF GALILEO OBSERVATIONS W. S. Kurth , D. A. Gurnett , S the Galileo investigation of Jovian radio emissions. While some of the Galileo results are already quite interest- ing and novel, this report serves primarily to introduce the Galileo observations and place them

Gurnett, Donald A.

256

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

257

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

NASA Astrophysics Data System (ADS)

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 sulfur ions at total energies above 40 MeV which are measured by the Heavy Ion Counter (HIC) instrument on the Galileo Orbiter. Directional measurements during the spacecraft's 20-second spin period allow determination of local anisotropy distributions with respect to magnetic pitch angles of magnetospheric ions and to absorption by satellite surfaces approached during close flybys. Numerical modeling of anisotropy data from these flybys allows limits to be set on the ion charge states and on models for the magnetic environments including possible presence of internal field sources. The Io phase of the Galileo satellite tour has concluded with successful HIC and magnetometer data return from five of seven flybys, including two passes (I31 and I32) over Io's poles. The absorption signatures from the polar passes are very different from the more equatorial ones (J0, I24, I27) and modeling is in progress to determine best-fit configurations of Io's global magnetic environment. Due to high electronic thresholds for the heavy ion measurements, HIC has been insensitive to magnetospheric electron and proton backgrounds during these flybys and is expected to return good data for the upcoming Amalthea flyby on Nov. 5, 2002. This assumes that spacecraft systems will survive the return to perijove (2.0 Rj) just outside Jupiter's main ring (1.8 Rj), first traversed by Pioneer 11 in Dec. 1974 and again by the Galileo Probe twenty-one years later. Detectors on both of these latter spacecraft resolved the cutoff of magnetospheric ion flux by interaction with the jovian ring particles and/or the shepard satellites, and part of this interaction region within the gossamer ring zone extending outwards from the main ring will also be accessible to HIC. It would be highly desirable from engineering (e.g., radiation effects on electronics) and magnetospheric science perspectives if real-time telemetry from HIC and other durable systems could be returned as long as possible for the final plunge through the ring system and the innermost ion radiation belt, first discovered by Galileo Probe. One of the first reports on post-launch science data from Galileo Orbiter concerned measurements of solar flare ions by HIC, and it seems appropriate that the final science and engineering data could also returned by that instrument. Particular acknowledgement of encouragement and support is given to the late Dr. Thomas L. Garrard of the HIC group at Caltech. Deep thanks are due to Dr. Edward C. Stone, the HIC Principal Investigator, and to Dr. Christina M. S. Cohen, for continuous support of HIC science data processing at Caltech. The local support at GSFC of Dr. Neil Gehrels, HIC Co-Investigator, has been deeply appreciated. Funding through Raytheon ITSS is gratefully acknowledged for contract NASW-99029 from NASA's Jovian System Data Analysis Program and for NAS5-98156 from the Space Science Data Operations Office at NASA Goddard Space Flight Center.

Cooper, J. F.

2002-05-01

258

Evidence for global electron transportation into the jovian inner magnetosphere  

NASA Astrophysics Data System (ADS)

Jupiter’s magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves.

Yoshioka, K.; Murakami, G.; Yamazaki, A.; Tsuchiya, F.; Kimura, T.; Kagitani, M.; Sakanoi, T.; Uemizu, K.; Kasaba, Y.; Yoshikawa, I.; Fujimoto, M.

2014-09-01

259

Evidence for global electron transportation into the jovian inner magnetosphere.  

PubMed

Jupiter's magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves. PMID:25258073

Yoshioka, K; Murakami, G; Yamazaki, A; Tsuchiya, F; Kimura, T; Kagitani, M; Sakanoi, T; Uemizu, K; Kasaba, Y; Yoshikawa, I; Fujimoto, M

2014-09-26

260

The Jovian surface condition and cooling rate  

NASA Technical Reports Server (NTRS)

A theory which is almost fully analytic is used to investigate Jupiter's cooling rate. A simple model of contraction with adiabatic interior structure gives a total cooling time to the present in good agreement with the age of the solar system. The interplay between the surface condition and the cooling rate is discussed. The current rate of change of the effective temperature is calculated to be -1 K per 0.145 billion yr. Discrepancies with fully numerical investigations of the Jovian age and cooling rate are noted.

Hubbard, W. B.

1977-01-01

261

The origin of chondrules at jovian resonances  

PubMed

Isotopic dating indicates that chondrules were produced a few million years after the solar nebula formed. This timing is incompatible with dynamical lifetimes of small particles in the nebula and short time scales for the formation of planetesimals. Temporal and dynamical constraints can be reconciled if chondrules were produced by heating of debris from disrupted first-generation planetesimals. Jovian resonances can excite planetesimal eccentricities enough to cause collisional disruption and melting of dust by bow shocks in the nebular gas. The ages of chondrules may indicate the times of Jupiter's formation and dissipation of gas from the asteroidal region. PMID:9445468

Weidenschilling; Marzari; Hood

1998-01-30

262

The Influence of The Galilean Satellites on Radio Emissions From The Jovian System  

NASA Technical Reports Server (NTRS)

The Galilean satellites influence radio emissions from the Jovian system in a variety of ways. The best and most familiar example of these is the Io control of decametric radiation discovered in 1964 by Bigg. Voyager observations of broadband kilometric radiation revealed a low-latitude shadow zone cast by the Io torus at frequencies between a few tens of kHz and about 1 MHz. Voyager also discovered narrowband kilometric radio emissions emanating from the outer edge of the torus. In this paper we will discuss expansions in the suite of satellite influences based on new observations by Galileo. These include the discovery of Ganymede's magnetosphere and evidence of radio emissions generated via mode conversion from upper hybrid waves in the frequency range of about 20 - 100 kHz. There is evidence that Ganymede may control some of the hectometric or low-frequency decametric radio emissions based on occultation measurements and statistical studies of radio emission occurrence as a function of Ganymede phase. Direction-finding measurements in the vicinity of Io suggest that a portion of the hectometric emissions may be generated near the lo L-shell. A rotationally modulated attenuation band in the hectometric emission appears to be the result of scattering at or near the Io L-shell where the waves propagate nearly parallel to the magnetic field. There is even a tantalizing hint of a Europa connection to the source of narrowband kilometric radiation.

Kurth, W. S.; Gurnett, D. A.; Menietti, J. D.

2000-01-01

263

Jovian modulation of interplanetary electrons as observed with Voyagers 1 and 2  

NASA Technical Reports Server (NTRS)

The release of magnetospheric electrons from Jupiter into interplanetary space is modulated by the Jovian rotation period. The Voyager 1 and 2 observations showed that the modulation period agrees on the average with the synodic period of Jupiter (9h 55m 33.12s), but over intervals of weeks it can differ from the synodic period by several minutes. The lack of exact synchronization is attributed to changes of the plasma population in the Jovian magnetosphere. The Jovian modulation appears to be a persistent feature of the interaction between the solar wind and the magnetosphere and the disappearance of the modulation away from Jupiter is attributed to interplanetary propagation conditions. This leads to the following limits on the diffuse coefficient for interplanetary electrons: kappa perpendicular is or = 8 x 10 to the 19th power sq cm/s and kappa parallel is or = 10 to the 21st power sq cm/s. Modulation was still detectable at 3.8 A.U. behind Jupiter in the far magnetotail. This requires a mean free path in the tail 0.75 A.U. and good field connection along the tail to Jupiter.

Schardt, A. W.; Mcdonald, F. B.; Trainor, J. H.

1982-01-01

264

Next Step Spherical Torus Design Studies  

SciTech Connect

Studies are underway to identify and characterize a design point for a Next Step Spherical Torus (NSST) experiment. This would be a ''Proof of Performance'' device which would follow and build upon the successes of the National Spherical Torus Experiment (NSTX) a ''Proof of Principle'' device which has operated at PPPL since 1999. With the Decontamination and Decommissioning (D&D) of the Tokamak Fusion Test Reactor (TFTR) nearly completed, the TFTR test cell and facility will soon be available for a device such as NSST. By utilizing the TFTR test cell, NSST can be constructed for a relatively low cost on a short time scale. In addition, while furthering spherical torus (ST) research, this device could achieve modest fusion power gain for short-pulse lengths, a significant step toward future large burning plasma devices now under discussion in the fusion community. The selected design point is Q=2 at HH=1.4, P subscript ''fusion''=60 MW, 5 second pulse, with R subscript ''0''=1.5 m, A=1.6, I subscript ''p''=10vMA, B subscript ''t''=2.6 T, CS flux=16 weber. Most of the research would be conducted in D-D, with a limited D-T campaign during the last years of the program.

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

2002-11-08

265

Spherical Torus Pathway to Fusion Power  

NASA Astrophysics Data System (ADS)

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 on the tokamak in making the desired progress in fusion energy sciences. The ST pathway could include a small VNS (Volume Neutron Source) with low fusion amplification (Q ˜ 1-2) for Fusion Energy Development (energy technology) and a small Pilot Plant with high Q (˜15-30) to practice Fusion Power Demonstration. Success in these steps also enhances the possibility for competitive non-electric applications of interest to society in time scales shorter than electric power generation. The scientific basis for these possibilities will be tested in the U.S. by the Proof of Principle experiment NSTX (National Spherical Torus Experiment) presently being built, and could be completed by a Proof of Performance and Optimization experiment such as a small DTST (Deuterium-Tritium Spherical Torus). Utilization of facilities and equipment already available in the U.S. would minimize the time and cost for these experiments and accelerate the approach to the stage of Fusion Energy Development.

Peng, Martin

1998-03-01

266

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

267

A theory of Jovian decameter radiation  

NASA Astrophysics Data System (ADS)

A theory of the Jovian decameter radiation is presented based on the assumed existence of beams of energetic electrons in the inner Jovian magnetosphere. Beam-like electron distributions are shown to be unstable to the growth of both upper hybrid and lower hybrid electrostatic waves. The upconversion of these waves to fast extraordinary mode electromagnetic radiation is calculated by using a fluid model. Two possibilities are considered. First, a random phase approximation is made which leads to a very conservative estimate of intensity that can be expected in decameter radiation. The alternative possibility is also considered, viz, that the upconversion process is coherent. A comparison of both processes suggests that an incoherent interaction may be adequate to account for the observed intensity of decametric radiation, except perhaps near the peak of the spectrum (8 MHz). The coherent process is intrinsically more efficient and can easily produce the observed intensity near 8 MHz if only 0.01% of the energy in the beam is converted to electrostatic energy.

Goldstein, M. L.; Sharma, R. R.; Ben-Ari, M.; Eviatar, A.; Papadopoulos, K.

1983-02-01

268

Recent Progress on Spherical Torus Research  

SciTech Connect

The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ~ 1.5, well below the normal tokamak operating range of A ? 2.5. As the aspect ratio is reduced, the ideal tokamak beta ? (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as ? ~ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation ?, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of attractive fusion energy power source. Since the start of the two megaampere class ST facilities in 2000, National Spherical Torus Experiment (NSTX) in the US and Mega Ampere Spherical Tokamak (MAST) in UK, active ST research has been conducted worldwide. More than sixteen ST research facilities operating during this period have achieved remarkable advances in all of fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

Ono, Masayuki [PPPL; Kaita, Robert [PPPL

2014-01-01

269

JUICE: a European mission to the Jovian system  

NASA Astrophysics Data System (ADS)

JUpiter ICy moons Explorer (JUICE) will perform detailed investigations of Jupiter and its system with particular emphasis on Ganymede as a planetary body and potential habitat. The overarching theme for JUICE is: The emergence of habitable worlds around gas giants. At Ganymede, the mission will characterize in detail the ocean layers; provide topographical, geological and compositional mapping of the surface; study the physical properties of the icy crusts; characterize the internal mass distribution, investigate the exosphere; study Ganymede’s intrinsic magnetic field and its interactions with the Jovian magnetosphere. For Europa, the focus will be on the non-ice chemistry, understanding the formation of surface features and subsurface sounding of the icy crust over recently active regions. Callisto will be explored as a witness of the early solar system. JUICE will perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants. The circulation, meteorology, chemistry and structure of the Jovian atmosphere will be studied from the cloud tops to the thermosphere. The focus in Jupiter’s magnetosphere will include an investigation of the three dimensional properties of the magnetodisc and in-depth study of the coupling processes within the magnetosphere, ionosphere and thermosphere. Aurora and radio emissions will be elucidated. JUICE will study the moons’ interactions with the magnetosphere, gravitational coupling and long-term tidal evolution of the Galilean satellites. JUICE highly capable scientific payload includes 10 state-of-the-art instruments onboard the spacecraft plus one experiment that uses the spacecraft telecommunication system with ground-based radio telescopes. The remote sensing package includes a high-resolution multi-band visible imager (JANUS) and spectro-imaging capabilities from the ultraviolet to the sub-millimetre wavelengths (MAJIS, UVS, SWI). A geophysical package consists of a laser altimeter (GALA) and a radar sounder (RIME) for exploring the surface and subsurface of the moons, and a radio science experiment (3GM) to probe the atmospheres of Jupiter and its satellites and to perform measurements of the gravity fields. An in situ package comprises a particle package (PEP) including plasma and energetic particle sensors, neutral gas mass spectrometer, and two ENA imagers, a magnetometer (J-MAG) and a radio and plasma wave instrument (RPWI), including electric fields sensors and a Langmuir probe. An experiment (PRIDE) using ground-based Very-Long-Baseline Interferometry (VLBI) will provide precise determination of the moons ephemerides. The launch of the JUICE spacecraft is foreseen in June 2022. After the Jupiter orbit insertion in January 2030, the spacecraft will perform a 2.5 years tour in the Jovian system investigating the atmosphere and magnetosphere of the giant. Gravity assists at Callisto will shape the trajectory to perform two targeted Europa flybys aiming at raising the orbit inclination up to 30 degrees. More than 10 Callisto flybys will enable unique remote observations of the moon and in situ measurements in its vicinity. The mission will culminate in a dedicated 8 months orbital tour around Ganymede. The presentation will give a status of the JUICE mission in the end of the definition phase, its science scenario, observation strategy, and the payload.

Titov, Dmitrij; Dougherty, Michele K.; Wahlund, Jan-Erik; Barabash, Stas; Palumbo, Pasquale; Iess, Luciano; Piccioni, Giuseppe; Hussmann, Hauke; Langevin, Yves; Jaumann, Ralf; Altobelli, Nicolas; Fletcher, Leigh; Gurvits, Leonid; Gladstone, Randy; Erd, Christian; Hartogh, Paul; Bruzz, Lorenzo

270

Summary of US compact torus experiments  

SciTech Connect

During the past several years a rapid increase has occurred in compact torus (CT) research in the United States, reflecting renewed interest in this simplified reactor consequences of this configuration. This paper reviews early approaches to CT formation and results and summarizes present experimental studies. Recent experiments have demonstrated a number of macroscopic aspects of the CT, including the conditions under which a macroscopically stable CT can be formed and maintained. Scaling experiments and more detailed studies of plasma transport in progress are discussed along with experiments under construction.

Hartman, C.W.

1981-03-11

271

High-speed three-wave polarimeter-interferometer diagnostic for Madison symmetric torus  

E-print Network

developed on the Madison symmetric torus reversed field pinch to provide simultaneous measurement infrared FIR laser interferometry and polarimetry have been successfully used to diagnose reversed field, simultaneous interferometer and polar- imeter measurements are necessary to accurately assess plasma

Wisconsin at Madison, University of

272

Jovian electrons at 1 AU - 1978-1984  

NASA Technical Reports Server (NTRS)

Data on Jovian electrons sensed with a spectrometer on board the ISEE spacecraft at 1 AU are studied in terms of intensity variations over time and shape and variations of the electron spectra with time. Design and performance features of the electron spectrometer are described. The analyses cover solar cycle modulation of intensity, the synodic intensity modulation, micromodulation over a period of days, and adiabatic deceleration of electrons propagating in the expanding solar wind. Emphasis is placed on the effects of maximum solar activity on Jovian electron emission and propagation, noting a confirmed 13 mos intensity variation in the Jovian electrons.

Moses, Dan

1987-01-01

273

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

274

Jovian Chromophore Characteristics from Multispectral HST Images  

NASA Technical Reports Server (NTRS)

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), and we remotely observe the culmination of the radiative transfer as I/F(lambda). In this study, we employed a radiative transfer code to retrieve omega-bar (sub 0)(lambda) for particles in Jupiter's tropospheric haze at seven wavelengths in the near-UV and visible regimes. The data consisted of images of the 2008 passage of Oval BA to the south of the Great Red Spot obtained by the Wide Field Planetary Camera 2 on-board the Hubble Space Telescope. We present derived particle colors for locations that were selected from 14 weather regions, which spanned a large range of observed colors. All omega-bar (sub 0)(lambda) curves were absorbing in the blue, and omega-bar (sub 0)(lambda) increased monotonically to approximately unity as wavelength increased. We found accurate fits to all omega-bar (sub 0)(lambda) curves using an empirically derived functional form: omega-bar (sub 0)(lambda) = 1 A exp(-B lambda). The best-fit parameters for the mean omega-bar (sub 0)(lambda) curve were A = 25.4 and B = 0.0149 for lambda in units of nm. We performed a principal component analysis (PCA) on our omega-bar (sub 0)(lambda) results and found that one or two independent chromophores were sufficient to produce the variations in omega-bar (sub 0)(lambda). A PCA of I/F(lambda) for the same jovian locations resulted in principal components (PCs) with roughly the same variances as the omega-bar (sub 0)(lambda) PCA, but they did not result in a one-to-one mapping of PC amplitudes between the omega-bar (sub 0)(lambda) PCA and I/F(lambda) PCA. We suggest that statistical analyses performed on I/ F(lambda) image cubes have limited applicability to the characterization of chromophores in the jovian atmosphere due to the sensitivity of 1/ F(lambda) to horizontal variations in the vertical aerosol distribution.

Strycker, Paul D.; Chanover, Nancy J.; Simon-Miller, Amy A.; Banfield, Don; Gierasch, Peter J.

2011-01-01

275

Large amplitude MHD waves upstream of the Jovian bow shock  

NASA Technical Reports Server (NTRS)

Observations of large amplitude magnetohydrodynamics (MHD) waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 mHz have a direction of minimum variance along the direction of the average magnetic field. The direction of minimum variance of these fluctuations lies at approximately 40 deg. to the magnetic field and is parallel to the radial direction. We argue that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the plasma rest frame. A linear instability analysis is presented which suggests an explanation for many of the observed features of the observations.

Goldstein, M. L.; Smith, C. W.; Matthaeus, W. H.

1983-01-01

276

Neutral cloud and heavy ion inner torus at Saturn  

Microsoft Academic Search

Voyager plasma data are used in conjunction with laboratory data on water molecule sputter-yields and energy distributions to calculate the morphology of the Saturn neutral water molecule and dissociated water molecule-product torus coexisting with the E-ring and icy satellites of this planet. Plasma production rates determined for this cloud exhibit a structure with distance from Saturn as well as from

R. E. Johnson; M. K. Pospieszalska; E. C. Jr. Sittler; A. F. Cheng; L. J. Lanzerotti

1989-01-01

277

Operational Regimes of the National Spherical Torus Experiment  

Microsoft Academic Search

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

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

2002-01-01

278

Vesta, Ceres and the Jovian Early Bombardment  

NASA Astrophysics Data System (ADS)

Vesta and Ceres are among the oldest objects that formed in the Solar System, likely predating the formation of the giant planets. Through their histories, the surfaces of the two targets of the Dawn mission would have suffered several periods of intense bombardment which shaped their present morphologies. Here we report the results of our investigation of the collisional histories of Vesta and Ceres at the time of the formation of Jupiter. The formation of the giant planet caused in fact an intense early bombardment in the asteroid belt. In those scenarios where they survived, both asteroids had their surfaces saturated by craters as big as 150 km and a few as big as 200 - 300 km. In the case of Vesta, such Jovian early bombardment would have significantly eroded the crust, likely exposing the upper mantle or causing effusive phenomena similar to lunar maria.

Turrini, D.; Coradini, A.; Magni, G.

2011-10-01

279

Magnetohydrodynamic Modeling of the Jovian Magnetosphere  

NASA Technical Reports Server (NTRS)

Under this grant we have undertaken a series of magnetohydrodynamic (MHD) simulation and data analysis studies to help better understand the configuration and dynamics of Jupiter's magnetosphere. We approached our studies of Jupiter's magnetosphere in two ways. First we carried out a number of studies using our existing MHD code. We carried out simulation studies of Jupiter s magnetospheric boundaries and their dependence on solar wind parameters, we studied the current systems which give the Jovian magnetosphere its unique configuration and we modeled the dynamics of Jupiter s magnetosphere following a northward turning of the interplanetary magnetic field (IMF). Second we worked to develop a new simulation code for studies of outer planet magnetospheres.

Walker, Raymond

2005-01-01

280

A Dynamical Survey of the Jovian System  

NASA Astrophysics Data System (ADS)

By now many studies have been made of the orbital stability and fate of asteroids, comets, and Kuiper Belt objects, both real and virtual (e.g., Wisdom and Holman, A.J. 102, 1258, 1991). Although simulation of a satellite system presents somewhat different problems from a planetary system, preliminary studies also have been made of hypothetical material orbiting Saturn (Burns and Gladman, Planet. Space Sci. 46, 1401, 1998). However, the dynamical environment of the Jovian system has not been explored until now. Using the SWIFT integrator of Levison and Duncan (Icarus 108, 18, 1994), we have simulated small particles orbiting Jupiter in the presence of the Galilean satellites Io, Europa, Ganymede, and Callisto. Perturbations from Jupiter's oblateness (J2 and J4) and from the Sun were also included. Particles were started at random longitudes in prograde circular orbits in the plane of Jupiter's equator. Of 400 particles spread uniformly in semimajor axis from 3.28 to 32.61 Jupiter radii (from inside Io to outside Callisto), only 259 survived for the 9638-year duration of the simulation. All of the other 141 collided with a Galilean moon; none hit Jupiter itself, or escaped the Jovian system. Most particle removals outside the immediate vicinity of a moon are attributed to low-order mean-motion resonances. In contrast, 1:1 resonances (Trojan, tadpole, and horseshoe-type orbits) proved quite stable on the 10000-year timescale. Except for such co-orbital particles, each satellite rapidly cleared its own ``chaotic zone'' where high-order resonances overlap (Wisdom, A.J. 85, 1122, 1980.) JLA acknowledges the advice of Luke Dones and the support of the San Jose State U. Foundation. ARD thanks Jack Lissauer for advice and support.

Dobrovolskis, A. R.; Alvarellos, J. L.; Zahnle, K.

2000-10-01

281

The global morphology of the Europa neutral torus from Cassini Energetic Neutral Atom (ENA) observations and implications for JUICE  

NASA Astrophysics Data System (ADS)

From about December 2000 to January 2001 the Ion Neutral Camera (INCA) on board the Cassini spacecraft imaged Jupiter in Energetic Neutral Atoms (ENA) that are created when singly charged ions charge exchange with neutral gas atoms or molecules. The INCA observations were obtained from a distance of about 137-250 Jovian planetary radii (RJ) over an energy range from about 10 to 300 keV. We present underlying neutral torus gas morphologies by simulating INCA images using an empirical ion distribution model and a range of theoretical gas model distributions. Just like Mauk et al. (2003), who used a different analysis technique, we find that the INCA images are consistent with a neutral torus at the orbital distance of Europa (9.5 RJ). However, within the limitations of instrument resolution, we present also possible solutions of a longitudinally asymmetric torus distribution and its implication for neutral gas release and loss rates from Europa. The Jovian Energetic Neutral and Ions (JENI) camera is the second generation ENA camera based on INCA and was selected for the science payload of the Jupiter Icy Moon Explorer (JUICE) mission, planned for launch around 2022 and orbit insertion around Jupiter in 2030. Using the same forward simulation technique as above, we use the INCA observations to demonstrate what we expect the JENI camera to observe in orbit around Jupiter and Ganymede.

Brandt, P. C.; Mauk, B.; Mitchell, D. G.; Paranicas, C.; Barabash, S. V.

2013-12-01

282

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

283

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

284

Cassini detection of water-group pick-up ions in the Enceladus torus R. L. Tokar,1  

E-print Network

Cassini detection of water-group pick-up ions in the Enceladus torus R. L. Tokar,1 R. J. Wilson,1 R), Cassini detection of water-group pick-up ions in the Enceladus torus, Geophys. Res. Lett., 35, L14202, doi 2008; published 24 July 2008. [1] This study reports direct detection by the Cassini plasma

Johnson, Robert E.

285

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

286

Cassini First Observations and Inferences about Small-Scale Plasma Transport in Saturn's Inner Magnetosphere  

NASA Astrophysics Data System (ADS)

The first Cassini observations reveal a very dynamic plasmasphere within the inner Saturnian magnetosphere. This corotation-dominated region is known to contain various neutral and plasma populations and Voyager spacecraft observations suggest that important radial processes redistribute the locally created plasma out to the remote magnetospheric regions. There is now considerable evidence with Cassini observations that this outward transport operates at least partly through the development of the centrifugal instability (a Rayleigh-Taylor type instability) and proceed through the interchange of magnetic flux tubes. We present here some of the latest Cassini multi-instrumental observations which are suggestive of the importance of this instability in redistributing the Saturnian magnetospheric plasma. First, we start from the identification of the main regions and plasma sources in Saturn's magnetosphere. Then, we discuss the signatures of plasma transport via interchanging flux tubes inside 10 Saturn radii and replace them in the context of our recent theoretical modelling of the centrifugal instability. Finally, we point out their similarities with previously identified signatures of interchanging flux tubes near the Io torus by the Galileo spacecraft, allowing the interesting possibility of carrying out a comparative study of the Jovian and Saturnian environments.

André, N.; Blanc, M.

2005-12-01

287

DISCOVERY OF TWO ADDITIONAL JOVIAN IRREGULARS  

SciTech Connect

We report on the discovery of two previously undetected irregular satellites of Jupiter (S/2010 J 1 and S/2010 J 2) during recovery observations of other known satellites. S/2010 J 1 was discovered with the Palomar 200 inch Hale telescope on September 7 UT of 2011, while S/2010 J 2 was discovered on September 8 with the 3.5 m Canada-France-Hawaii Telescope. The satellites have r-band magnitudes of 23.2 {+-} 0.3 and 24.0 {+-} 0.3, for S/2010 J 1 and S/2010 J 2, respectively, indicating diameters of {approx}2-3 km. Both S/2010 J 1 and S/2010 J 2 are on bound retrograde orbits. Time-averaged integrated orbits suggest the association to the Carme and Ananke groups, respectively. Given that the satellites were discovered within a small field during the routine observations of the previously known irregulars, their discovery agrees with predictions that other moons of similar sizes remain undetected in the Jovian Hill sphere.

Alexandersen, M.; Gladman, B. [Department of Physics and Astronomy, 6224 Agricultural Road, University of British Columbia, Vancouver BC (Canada); Veillet, C. [Canada-France-Hawaii Telescope Corporation, P.O. Box 1597, Kamuela, HI 96743 (United States); Jacobson, R.; Brozovic, M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States); Rousselot, P., E-mail: mikea@astro.ubc.ca [Institut UTINAM, CNRS-UMR 6213, Observatoire de Besancon, BP 1615, 25010 Besancon Cedex (France)

2012-07-15

288

Chemistry and spectroscopy of the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

A comprehensive review is given of the chemistry and spectroscopic studies of the Jovian atmosphere. Thermochemical equilibrium models for determining atmospheric composition are considered along with possible disequilibrating processes, and studies of the photochemistry of H2, CH4, NH3, H2S, and PH3 using the modeling methods are summarized. It is shown that photodissociation and advection are the major disequilibrating processes in Jupiter's atmosphere, that lightning and charged-particle bombardment are relatively minor factors in the planet's bulk chemistry, and that the existence of living organisms on the planet is highly improbable. Spectroscopic investigations of Jupiter are discussed, emphasizing recent observations of absorption bands due to CH4, NH3, H2, He, and D. Spectroscopic abundance determinations are examined for H2, HD, CH4, CH3D, NH3, C2H6, C2H2, and PH3. Upper limits are given for the abundances of several unobserved gases in the visible atmosphere, including H2S, HCl, SiH4, benzene, purines, pyrimidines, and their derivatives.

Prinn, R. G.; Owen, T.

1976-01-01

289

Energetic protons in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The time histories, angular distributions and energy spectra of energetic protons were measured over an energy range extending from 0.2 - 20 MeV for the four passes of Pioneers 10 and 11 through the Jovian magnetosphere. Azimuthal asymmetries appear to dominate with time variations also contributing to the very complex topology. On the inbound P-10 pass the expected corotation anisotropy was not observed in the outer magnetosphere supporting the probable existence of a planetary wind in this region. Near the dawn meredian particle streaming away from the planet begins at about 15 RJ. On both the P-10 inbound and P-11 outbound passes, there are regions where only partial corotation is achieved. In the mid-magnetosphere, field-aligned streaming away from the near-equatorial current sheet region is the most prominent feature. At mid-latitudes in the subsolar regime, the streaming pattern is more chaotic and its magnitude is smaller. Qualitative discussions are presented for a number of possible mechanisms which could produce this streaming.

Mcdonald, F. B.; Schardt, A. W.; Trainor, J. H.

1979-01-01

290

Ulysses jovian latitude scan of high-velocity dust streams originating from the jovian system  

NASA Astrophysics Data System (ADS)

In February 2004 the Ulysses spacecraft had its second flyby at Jupiter at 0.8 AU distance from the planet. Twenty-eight dust streams emanating from the jovian system were measured between November 2002 and August 2005 while the spacecraft was within 4 AU of the planet, scanning jovigraphic latitudes from +75? to -25?. The highest dust fluxes were measured in mid 2004 at the passage of the equatorial plane of the planet when more than 2000 impacts per day were measured. The grain impact direction is correlated with the polarity and strength of the interplanetary magnetic field. At high jovigraphic latitudes, the impact rates show a periodicity of 26 days, closely matching the solar rotation period, while at the jovian equator the streams fluctuate with twice this period. The 14-day subharmonic streams alternate in arrival direction and are correlated with the pointing of the interplanetary magnetic field. Dust fluxes measured above and below the equatorial plane roughly decrease with the inverse square of the distance from the planet while along the equatorial plane dust fluxes are enhanced by up to 2 orders of magnitude.

Krüger, Harald; Graps, Amara L.; Hamilton, Douglas P.; Flandes, Alberto; Forsyth, Robert J.; Horányi, Mihaly; Grün, Eberhard

2006-08-01

291

Ulysses jovian latitude scan of high-velocity dust streams originating from the jovian system  

NASA Astrophysics Data System (ADS)

In February 2004 the Ulysses spacecraft had its second flyby at Jupiter at 0 8 AU distance from the planet 28 dust streams emanating from the jovian system were measured between November 2002 and August 2005 while the spacecraft was within 4 AU of the planet scanning jovigraphic latitudes from 75° to -25° The highest dust fluxes were measured in mid 2004 at the passage of the equatorial plane of the planet when more than 2000 impacts per day were measured The grain impact direction is correlated with the polarity and strength of the interplanetary magnetic field At high jovigraphic latitudes the impact rates show a periodicity of 26 days closely matching the solar rotation period while at the jovian equator the streams fluctuate with twice this period The 14-day subharmonic streams alternate in arrival direction and are correlated with the pointing of the interplanetary magnetic field Dust fluxes measured above and below the equatorial plane roughly decrease with the inverse square of the distance from the planet while along the equatorial plane dust fluxes are enhanced by up to 2 orders of magnitude

Krueger, H.; Graps, A. L.; Hamilton, D. P.; Flandes, A.; Gruen, E.

292

Analogies between Jovian magnetodisk and heliospheric current sheet  

NASA Astrophysics Data System (ADS)

Recently due to the development of spatial missions the famous model by E. Parker [1] faced with some problems, such as the effect of magnetic flux excess and the existence of latitude component of magnetic field [2]. Thus the incomplete knowledge about large scale current system of heliospheric current sheet (HCS) motivated us to construct and investigate the self-consistent axisymmetric stationary MHD model of HCS and to compare it with earlier presented model of Jupiterian magnetodisk [3]. Both HCS and magnetodisk have inner plasma sources (i.e. the Sun in case of HCS and satellite Io in case of Jupiter); also they depend on the centrifugal force at small distances and on corotation processes. They both have strong radial component of current density, thin elongated structure etc. Thus in the frame of the MHD model we have calculated for HCS the parallel currents (analogous to Jovian Birkeland currents) and we obtained the latitude component of the magnetic field. The results of the model allowed us to explain the magnetic flux excess by the existence of the self-consistent HCS magnetic field. The decrease of radial magnetic field from the distance from the Sun as the power -5/3 obtained by numerical calculations is in good agreement with experimental data. Generally this model can be applied for the quiet period of the low solar activity when the perturbation of HCS structure named “ballerina skirt” does not play any role. References: 1. Parker E. N., Astrophys. J., V. 128, 664, pp. 664-676, 1958. 2. Khabarova O. V., ??????????????? ??????, V. 90, ?11, pp. 919-935, 2013. 3. Kislov R.A. et al., Bull. MSU, Physics and Astron., 2013

Kislov, Roman; Khabarova, Olga; Malova, Helmi

293

Periodicities of Jovian broad-band kilometric radiation observed by Ulysses  

NASA Astrophysics Data System (ADS)

Observations of the Unified Radio and Plasma Wave (URAP) instrument onboard the Ulysses spacecraft have been used to analyze periods inherent in the Jovian broad-banded kilometric radio emission (bKOM) between 29 and 47 kHz. It is demonstrated, by using power spectrum analysis and linear prediction time filtering that the long-term fluctuations of the bKOM signal are triggered by the solar wind, particularly by the solar wind density, while no association was found with the solar wind velocity. In addition, there seem to be some inherent periodicities in the bKOM events which cannot be fully attributed to the influence of solar wind plasma quantities by these techniques.

Rabl, G. K. F.

1993-11-01

294

Initial Results From The Jovian Electrodynamic Tether Systems (JETS) Study  

NASA Technical Reports Server (NTRS)

The Jovian system with its rapid planetary rotation and strong magnetic field presents exciting opportunities for the use of electrodynamic (EM) tethers in system applications on a Jovian spacecraft. Previous analysis for a radial, 10-km length tether demonstrated the possibility of propulsive forces as large as 50 N and power generation levels as high as 10^6 W for low perijov passing trajectories. For orbital positions beyond approximately 15 Jovian radii, JETS can be used simultaneously for power and increases in the orbital altitude. Previous study demonstrated the physical feasibility of EM tether use at Jupiter, but did not address the issues of limited gravity gradient force for tether extension and power regulation needed before JETS can be implemented as a practical spacecraft system. This presentation will discuss these issues and current progress in an ongoing systems feasibility study.

Gallagher, D. L.; Garbe, G. P.; Moore, J.; Talley, C.; Rose, M. Franklin (Technical Monitor)

2001-01-01

295

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

296

A time dependent model of the Jovian current sheet  

NASA Technical Reports Server (NTRS)

Analysis of vector helium magnetometer measurements during the Pioneer 10 outbound pass through the Jovian magnetosphere reveals that the average location of the near-equatorial current sheet is a surface whose shape is determined by the velocity at which the magnetic perturbations produced by a rotating tilted dipole propagate to large radial distances. A model is presented which is a surface encircling the planet and rotating rigidly with it. Based on a linear fit to the times of the current sheet crossings, a formula is derived for the surface representing the average position of the near-equatorial current sheet in the Jovian magnetosphere.

Kivelson, M. G.; Coleman, P. J., Jr.; Froidevaux, L.; Rosenberg, R. L.

1978-01-01

297

Analysis and Modeling of Jovian Radio Emissions Observed by Galileo  

NASA Technical Reports Server (NTRS)

Our studies of Jovian radio emission have resulted in the publication of five papers in refereed journals, with three additional papers in progress. The topics of these papers include the study of narrow-band kilometric radio emission; the apparent control of radio emission by Callisto; quasi-periodic radio emission; hectometric attenuation lanes and their relationship to Io volcanic activity; and modeling of HOM attenuation lanes using ray tracing. A further study of the control of radio emission by Jovian satellites is currently in progress. Abstracts of each of these papers are contained in the Appendix. A list of the publication titles are also included.

Menietti, J. D.

2003-01-01

298

Lorentz resonances and the structure of the Jovian ring  

NASA Technical Reports Server (NTRS)

Charged dust orbiting through spatially periodic planetary magnetic fields will experience time-variable electromagnetic forces. When the forcing frequencies are nearly commensurate with the particle's orbital frequency, the particle undergoes large out-of-plane and radial excursions. Specific 'Lorentz' resonances, corresponding to particular spatial periodicities in the magnetic field, occur on either side of synchronous orbit. Lorentz resonance locations and strengths for the Jovian and Saturnian rings are described. The boundaries of the halo of the Jovian ring, and perhaps other ring structures, are near resonances.

Burns, J. A.; Schaffer, L. E.; Showalter, M. R.; Greenberg, R. J.

1985-01-01

299

On the proposed triggering of Jovian radio emissions  

NASA Technical Reports Server (NTRS)

Calvert (1985) has proposed that a solar type III radio bursts can trigger the onset of certain Jovian hectometer wavelength emissions. It is shown, using the data obtained by the Voyager Planetary Radio Astronomy experiment, that this triggering hypothesis is not supported statistically. Furthermore, the causality of this proposed triggering is questioned because much of the Jovian hectometer emission is due to a quasi-continuous radio source rotating, in lighthouse fashion, with Jupiter. Thus, an observed 'onset' of emission is simply a function of the observer's position in local time around Jupiter.

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

1985-01-01

300

Milne and Torus Universes Meet  

E-print Network

Three dimensional quantum gravity with torus universe, T^2xR topology is reformulated as the motion of a relativistic point particle moving in an Sl(2,Z) orbifold of flat Minkowski spacetime. The latter is precisely the three dimensional Milne Universe studied recently by Russo as a background for Strings. We comment briefly on the dynamics and quantization of the model.

Andrew Waldron

2004-08-11

301

Confinement of Neutral Beam Ions in the National Spherical Torus Experiment  

Microsoft Academic Search

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

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

2001-01-01

302

Edge ion heating by launched high harmonic fast waves in the National Spherical Torus Experiment  

E-print Network

Edge ion heating by launched high harmonic fast waves in the National Spherical Torus Experiment T power High Harmonic Fast Wave (HHFW) rf heating in helium plasmas, with the poloidal ion temperature MHz HHFW launched by the NSTX antenna is expected and observed to heat core electrons, but plasma ions

Biewer, Theodore

303

The Ultraviolet Spectrum of the Jovian Dayglow  

NASA Technical Reports Server (NTRS)

The ultraviolet spectra of molecular hydrogen H2 and HD due to solar fluorescence and photoelectron excitation are calculated and compared with the Jovian equatorial dayglow spectrum measured at 3 A resolution at solar maximum. The dayglow emission is accounted for in both brightness and spectral shape by the solar fluorescence and photoelectron excitation and requires no additional energy source. The emission is characterized by an atmospheric temperature of 530 K and an H2 column density of 10(exp 20) cm(exp -2). The dayglow spectrum contains a cascade contribution to the Lyman band emission from high-lying E and F states. Its relative weakness at short wavelengths is due to both self-absorption by H2 and absorption by CH4. Strong wavelength coincidences of solar emission lines and absorption lines of H2 and HD produce unique line spectra which can be identified in the dayglow spectrum. The strongest fluorescence is due to absorption of the solar Lyman-beta line at 1025.72 A by the P(1) line of the (6, 0) Lyman band of H2 at 1025.93 A. The fluorescence lines due to absorption of the solar O 6 line at 1031.91 A by vibrationally excited H2 via the Q(3) line of the (1, 1) Werner band at 1031.86 A are identified. The fluorescence lines provide a sensitive measure of the atmospheric temperature. There occurs an exact coincidence of the solar O 6 line at 1031.91 A and the R(0) line of the (6, 0) Lyman band of HD at 1031-91 A, but HD on Jupiter is difficult to detect due to the dominance of the H2 emission where the HD emission is particularly strong. Higher spectral resolution and higher sensitivity may make possible such a detection. The high resolution (0.3 A) spectra of H2 and HD are presented to stimulate search for the HD on Jupiter with the Hubble Space Telescope.

Liu, Weihong; Dalgarno, A.

1995-01-01

304

Simulations of accelerating currents in Io's plasma wake  

NASA Astrophysics Data System (ADS)

The evolution of an Io-perturbed flux tube was studied numerically via magnetohydrodynamics MHD approach of a thin filament Our simulations suggest that the mechanism for producing wake aurora could not be explained by either Alfvén wave or electric circuit alone 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 developed before it is released downstream A magnetic field depression forms downstream as a result of the continual departure of the flux tubes from Io which in turn has significant influence on the motion of a flux tube A perturbed flux tube would undergo a subcorotational motion in Io s plasma wake This motion is inevitably modulated by Alfvén wave bouncing back and forth between the equatorial plane and the boundary of Io plasma torus The scale of the subcorotation region is in the order of 1 Jovian radius The distribution of the simulated accelerating currents downstream is consistent with the observed wake aurora brightness profile

Chen, C. X.

305

Near-Infrared Spectroscopy of Himalia An Irregular Jovian Satellite  

NASA Technical Reports Server (NTRS)

Spectra of the irregular Jovian satellite Himalia were obtained with the Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini during the Jupiter Flyby on December 18-19, 2000. These are the first spectral data of an irregular satellite beyond 2.5 microns. Additional information is contained in the original extended abstract.

Brown, R. H.; Baines, K.; Bellucci, G.; Bibring, J.-P.; Buratti, B.; Capaccioni, F.; Cerroni, P.; Clark, R.; Coradini, A.; Cruikshank, D.

2002-01-01

306

Physical Analysis of the Jovian Synchrotron Radio Emission  

Microsoft Academic Search

We present results of our recent investigation of the Jovian synchrotron emission based on a particle transport code. The features of the two-dimensional brightness distributions, radio spectra and beaming curves are correlated to the different phenomena driven the dynamics of the electron radiation belts. The adiabatic invariant theory was used for performing this analysis work. The theoretical approach first enabled

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

2006-01-01

307

Source characteristics and radiation mechanism of Jovian anomalous continuum  

Microsoft Academic Search

We investigate the characteristics of the Jovian anomalous continuum (JAC) in interplanetary space and in the magnetosheath, using Ulysses observations. Some new source characteristics of JAC were obtained in addition to those found by previous authors [e.g., Kaiser, 1998]. JAC tends to occur when the solar wind dynamic pressure decreases after a rapid increase. We confirm and show more concretely

A. Morioka; T. Yuasa; Y. S. Miyoshi; F. Tsuchiya; H. Misawa

2004-01-01

308

Galileo observes electromagnetically coupled dust in the Jovian magnetosphere  

Microsoft Academic Search

Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had flybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable

E. Grün; H. Krüger; A. L. Graps; D. P. Hamilton; A. Heck; G. Linkert; H. A. Zook; S. Dermott; H. Fechtig; B. A. Gustafson; M. S. Hanner; M. Horányi; J. Kissel; B. A. Lindblad; D. Linkert; I. Mann; J. A. M. McDonnell; G. E. Morfill; C. Polanskey; G. Schwehm; R. Srama

1998-01-01

309

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

310

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

311

Mass and energy balance of the cold Io torus  

NASA Technical Reports Server (NTRS)

A new model of the cold Io torus is described. Ions and energy are injected into the system by independent processes so that the mass balance is isolated from the energy balance. The primary source of energy is local ionization and acceleration of hot pickup ions resulting from charge exchange between thermal ions and an extended cloud of Iogenic sulfur and oxygen atoms. The primary energy loss mechanism of the plasma is collisionally excited line emission at optical wavelengths. The primary ion source is radial diffusion inward from the hot torus on a time scale of 140-710 days. The primary ion loss mechanism is a novel two-step enhanced recombination mechanism involving charge exchange between thermal ions and an extended cloud of neutral SO2 molecules, followed by rapid dissociative recombination of the resultant molecular ion. The model provides a self-consistent solution which reconciles a number of diverse observations with known physical processes.

Moreno, M. A.; Barbosa, D. D.

1986-01-01

312

REVIEW OF THE NATIONAL SPHERICAL TORUS EXPERIMENT RESEARCH RESULTS  

SciTech Connect

The National Spherical Torus Experiment (NSTX) produces plasmas, with toroidal aspect ratio as low as 1.25 and plasma currents up to 1.5 MA, which can be heated by up to 6 MW High-Harmonic Fast Waves and up to 7 MW of deuterium Neutral Beam Injection. With these capabilities, NSTX has already made considerable progress in advancing the scientific understanding of high performance plasmas needed for low-aspect-ratio reactor concepts and for ITER. In transport and turbulence research on NSTX, the role of magnetic shear is being elucidated in discharges in which electron energy transport barriers are observed. Scaling studies indicate a weaker dependence on plasma current than at conventional aspect ratio and a significant dependence on toroidal field (B{sub T}).

Mueller, D.; Menard, J. E.; Bell, M. G.; Bell, R. E.; Diem, S.; Fredrickson, E. D.; Gates, D. A.; Hill, K. W.; Hosea, J. C.; Kaye, S. M.; Kessel, C. E.; Kugel, H. W.; LeBlanc, B. P.; Mansfield, D. K.; Majeski, R. P.; Mazzucato, E.; Medley, S. S.; Myra, J. R.; Park, H. K.; Paul, S. F. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States)

2009-07-26

313

The astrophysical torus - Appearance and light curves  

NASA Astrophysics Data System (ADS)

It has been suggested (e.g., Madau, 1988) that there may exist a geometrically thick accretion torus at the center of active objects. This paper examines properties of a geometrically thick accretion torus, using photographs of an astrophysical torus taken by a distant observer, to calculate light curves during the primary eclipse of the torus in binary systems. The results were compared with observations of SS 433. The comparison indicated that the relativistic object in SS 433 is a black hole. This conclusion is consistent with the results of Antokhina and Cherepashchuk (1987), Stewart et al. (1987), and Kawai et al. (1989).

Fukue, Jun; Yamanaka, Koichi; Furukubo, Manabu

1992-10-01

314

Radio Sounding Techniques for the Galilean Icy Moons and their Jovian Magnetospheric Environment  

NASA Technical Reports Server (NTRS)

Radio sounding of the Earth's topside ionosphere and magnetosphere is a proven technique from geospace missions such as the International Satellites for Ionospheric Studies (ISIS) and the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE). Application of this technique to Jupiter's icy moons and the surrounding Jovian magnetosphere will provide unique remote sensing observations of the plasma and magnetic field environments and the subsurface conductivities, of Europa, Ganymede, and Callisto. Spatial structures of ionospheric plasma above the surfaces of the moons vary in response to magnetic-field perturbations from (1) magnetospheric plasma flows, (2) ionospheric currents from ionization of sputtered surface material, and (3) induced electric currents in salty subsurface oceans and from the plasma flows and ionospheric currents themselves. Radio sounding from 3 kHz to 10 MHz can provide the global electron densities necessary for the extraction of the oceanic current signals and supplements in-situ plasma and magnetic field measurements. While radio sounding requires high transmitter power for subsurface sounding, little power is needed to probe the electron density and magnetic field intensity near the spacecraft. For subsurface sounding, reflections occur at changes in the dielectric index, e.g., at the interfaces between two different phases of water or between water and soil. Variations in sub-surface conductivity of the icy moons can be investigated by radio sounding in the frequency range from 10 MHz to 50 MHz, allowing the determination of the presence of density and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts. The detection of subsurface oceans underneath the icy crusts of the Jovian moons is one of the primary objectives of the Jupiter Icy Moons Orbiter (JIMO) mission. Preliminary modeling results show that return signals are clearly distinguishable be&een an ice crust with a thickness of 7 km on 1) an ocean and 2) a layer of bedrock. Knowledge of the ionospheric contributions to the time delay of the low-frequency subsurface radar is shown to be important in obtaining accurate depth information.

Green, James L.; Markus, Thursten; Fung, Shing F.; Benson, Robert F.; Reinich, Bodo W.; Song, Paul; Gogineni, S. Prasad; Cooper, John F.; Taylor, William W. L.; Garcia, Leonard

2004-01-01

315

Effects of Jupiter's formation and migration: the Jovian Early Bombardment  

NASA Astrophysics Data System (ADS)

The first phase in the lifetime of the Solar System is that of the Solar Nebula, when the Solar System is constituted by a circumsolar disk of gas and dust particles where planetesimals and planetary embryos are forming. The giant planets should have formed during this phase, since the nebular gas represents the source material for their gaseous envelopes. Here we report the results of our investigation of the effects of Jupiter's formation on the planetesimals populating the Solar Nebula using Vesta and Ceres as case studies. Our results show that the formation of Jupiter triggered a brief yet intense phase of bombardment, which we called the Jovian Early Bombardment and whose intensity varies with the extent and the timescale of Jupiter's migration. The data that the Dawn mission will supply on Vesta and Ceres will allow us to test the Jovian Early Bombardment hypothesis and possibly gather information on the formation and the early dynamical evolution of Jupiter.

Turrini, D.; Coradini, A.; Magni, G.

2011-10-01

316

Particles, environments, and possible ecologies in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

The possible existence of indigenous Jovian organisms is investigated by characterizing the relevant physical environment of Jupiter, discussing the chromophores responsible for the observed coloration of the planet, and analyzing some permissible ecological niches of hypothetical organisms. Values of the eddy diffusion coefficent are estimated separately for the convective troposphere and the more stable mesosphere, and equilibrium condensation is studied for compounds containing Na, Cl, or both. The photoproduction of chromophores and nonequilibrium organic molecules is analyzed, and the motion of hypothetical organisms is examined along with the diffusion of metabolites and the consequent growth of organisms. Four kinds of organisms are considered: primary photosynthetic autotrophs ('sinkers'), larger autotrophs or heterotrophs that actively maintain their pressure level ('floaters'), organisms that seek out others ('hunters'), and organisms that live at almost pyrolytic depths ('scavengers'). It is concluded that ecological niches for sinkers, floaters, and hunters appear to exist in the Jovian atmosphere.

Sagan, C.; Salpeter, E. E.

1976-01-01

317

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

318

A CCD comparison of outer Jovian satellites and Trojan asteroids  

NASA Technical Reports Server (NTRS)

The eight small outer Jovian satellites are not as well known as the brighter, more illustrious Galilean satellites. They are divided into two groups, each containing four satellites; the inner group travels in prograde orbits while the outer group travels in retrograde orbits. From the distinct orbital characteristics of the two groups, most of the theories of their origin involve the capture and breakup of two planetesimals upon entry into the atmosphere of proto-Jupiter. Their proximity to the Trojans asteroids has led to conjectures of a link between them and the Trojans. However, Tholen and Zellner (1984) found no red spectrum among six of the satellites and postulated that they were all C-type objects; therefore, they were unlikely to be derivatives of the Trojan population. Charge-coupled device (CCD) photometry and spectroscopy of the eight outer Jovian satellites obtained from 1987 to 1989 and a comparison between these eight satellites and the Trojan asteroids are presented.

Luu, Jane X.

1991-01-01

319

Astronomical studies of the major planets, natural satellites and asteroids using the 2.24 m telescope  

NASA Technical Reports Server (NTRS)

Ground based detection of east-west asymmetries in the Jovian torus, three dimensional models of the plasma conditions in the Jovian torus, rotational variations in methane band images of Neptune, Io's rapid flickering, thermophysical models, the diameters and albedos of the satellites of Uranus from radiometric observations, the diameters of Pluto and Triton, standard stars are discussed.

Jefferies, J. T.

1982-01-01

320

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

321

Thermal shallow water models of geostrophic turbulence in Jovian atmospheres  

SciTech Connect

Conventional shallow water theory successfully reproduces many key features of the Jovian atmosphere: a mixture of coherent vortices and stable, large-scale, zonal jets whose amplitude decreases with distance from the equator. However, both freely decaying and forced-dissipative simulations of the shallow water equations in Jovian parameter regimes invariably yield retrograde equatorial jets, while Jupiter itself has a strong prograde equatorial jet. Simulations by Scott and Polvani [“Equatorial superrotation in shallow atmospheres,” Geophys. Res. Lett. 35, L24202 (2008)] have produced prograde equatorial jets through the addition of a model for radiative relaxation in the shallow water height equation. However, their model does not conserve mass or momentum in the active layer, and produces mid-latitude jets much weaker than the equatorial jet. We present the thermal shallow water equations as an alternative model for Jovian atmospheres. These equations permit horizontal variations in the thermodynamic properties of the fluid within the active layer. We incorporate a radiative relaxation term in the separate temperature equation, leaving the mass and momentum conservation equations untouched. Simulations of this model in the Jovian regime yield a strong prograde equatorial jet, and larger amplitude mid-latitude jets than the Scott and Polvani model. For both models, the slope of the non-zonal energy spectra is consistent with the classic Kolmogorov scaling, and the slope of the zonal energy spectra is consistent with the much steeper spectrum observed for Jupiter. We also perform simulations of the thermal shallow water equations for Neptunian parameter values, with a radiative relaxation time scale calculated for the same 25 mbar pressure level we used for Jupiter. These Neptunian simulations reproduce the broad, retrograde equatorial jet and prograde mid-latitude jets seen in observations. The much longer radiative time scale for the colder planet Neptune explains the transition from a prograde to a retrograde equatorial jet, while the broader jets are due to the deformation radius being a larger fraction of the planetary radius.

Warneford, Emma S., E-mail: emma.warneford@maths.ox.ac.uk; Dellar, Paul J., E-mail: dellar@maths.ox.ac.uk [OCIAM, Mathematical Institute, University of Oxford, Radcliffe Observatory Quarter, Oxford OX2 6GG (United Kingdom)

2014-01-15

322

Thermal shallow water models of geostrophic turbulence in Jovian atmospheres  

NASA Astrophysics Data System (ADS)

Conventional shallow water theory successfully reproduces many key features of the Jovian atmosphere: a mixture of coherent vortices and stable, large-scale, zonal jets whose amplitude decreases with distance from the equator. However, both freely decaying and forced-dissipative simulations of the shallow water equations in Jovian parameter regimes invariably yield retrograde equatorial jets, while Jupiter itself has a strong prograde equatorial jet. Simulations by Scott and Polvani ["Equatorial superrotation in shallow atmospheres," Geophys. Res. Lett. 35, L24202 (2008)] have produced prograde equatorial jets through the addition of a model for radiative relaxation in the shallow water height equation. However, their model does not conserve mass or momentum in the active layer, and produces mid-latitude jets much weaker than the equatorial jet. We present the thermal shallow water equations as an alternative model for Jovian atmospheres. These equations permit horizontal variations in the thermodynamic properties of the fluid within the active layer. We incorporate a radiative relaxation term in the separate temperature equation, leaving the mass and momentum conservation equations untouched. Simulations of this model in the Jovian regime yield a strong prograde equatorial jet, and larger amplitude mid-latitude jets than the Scott and Polvani model. For both models, the slope of the non-zonal energy spectra is consistent with the classic Kolmogorov scaling, and the slope of the zonal energy spectra is consistent with the much steeper spectrum observed for Jupiter. We also perform simulations of the thermal shallow water equations for Neptunian parameter values, with a radiative relaxation time scale calculated for the same 25 mbar pressure level we used for Jupiter. These Neptunian simulations reproduce the broad, retrograde equatorial jet and prograde mid-latitude jets seen in observations. The much longer radiative time scale for the colder planet Neptune explains the transition from a prograde to a retrograde equatorial jet, while the broader jets are due to the deformation radius being a larger fraction of the planetary radius.

Warneford, Emma S.; Dellar, Paul J.

2014-01-01

323

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

324

Relationship between Jovian Hectometric Attenuation Lanes And Io Volcanic Activity  

NASA Technical Reports Server (NTRS)

Within the Galileo plasma wave instrument data a narrow (in frequency) attenuation band is seen in the hectometric (HOM) emission that varies in frequency with system III longitude. This attenuation lane is believed to be the result of near-grazing incidence or coherent scattering of radio emission near the outer edge of the Io torus, i.e., when the ray path is nearly tangent to an L shell containing the Io flux tube. Such a process should, therefore, be enhanced when the Io volcanic activity is increased and the Io flux tube has enhanced density. We have performed a systematic study of the existing Galileo radio emission data in an effort to determine the phenomenology and frequency of occurrence of the attenuation lanes and the association, if any, with published volcanic activity of Io. Our results indicate that the attenuation lanes are present almost all of the time but are enhanced on occasion. The best examples of attenuation lanes occur when Galileo is within approximately 65 R(sub J) of Jupiter and thus are probably more apparent because of the increased signal-to-noise ratio of the radio receivers. The lack of continuous monitoring of Io activity and the lack of known activity on the anti-Earthward side of Io are problematic and make detailed correlation with radio emission very difficult at this time. Nevertheless, if the data are displayed for periods when the spacecraft is within 65 R(sub J) (i.e., for each perijove pass), then the highest-contrast lanes occur on most passes when the Io volcanic activity is also high for that pass. These results support our current understanding of attenuation lane formation and suggest that future efforts can be made to better understand the interaction of HOM emission with the Io flux tube.

Menietti, J. D.; Gurnett, D. A.; Spencer, J. R.; Stansberry, J. A.

2001-01-01

325

Jovian longitudinal control of Io-related radio emissions  

NASA Technical Reports Server (NTRS)

A theoretical model is proposed to explain the control of Io-related radio emissions by Jupiter's rotational phase. The model is based on the hypothesis that the radio emissions are generated by Birkeland currents flowing between Io and the Jovian ionosphere. Specifically, it is suggested that the precipitation of radiation-belt electrons within a certain range of Jovian longitudes produces a restricted region of enhanced ionization and correspondingly enhanced conductivity in Jupiter's ionosphere and that the Io-Jupiter Birkeland current and the associated radio emissions are dramatically increased when Io's flux tube encounters this sector of enhanced ionization in Jupiter's ionosphere. The magnitude of the current is found to be about 100,000 A at most Jovian longitudes because of ionospheric resistance. It is estimated that within the favored longitudinal sector electron precipitation produces an enhancement of this current by one to three orders of magnitude. The model predictions are compared with observations made during the Pioneer 10 and 11 flybys, and satisfactory agreement is obtained.

Dessler, A. J.; Hill, T. W.

1979-01-01

326

Dynamics of Charged Nano-Dust in the Jovian Rings  

NASA Astrophysics Data System (ADS)

The main ring of Jupiter with an outer edge at 1.806 RJ is maintained by the small satellite, Adrastea. After passing the orbit of Metis at 1,798 RJ a ring halo begins to take shape characterizied by extended vertical structure. According to Burns, Schaffer, Greenberg and Showalter (1985), this feature is related to the motion of the charged sub-micron dust grains under the influence of the Lorentz force. For charge-to-mass (q/m) ratio exceeds a certain value, the small dust grains could be injected into the Jovian atmosphere after following trajectories alighned with the magnetic field. This is likely the cause of the cutoff of the inner Jovian rings at the orbital position which coincident with the 2:1 Lorentz resonance. Because the JUNO spacecraft will move through the gap between the Jovian upper atmosphere and the 2:1 LR location, it is interesting to investigate to what extent would the charged nano-dust be able to from a three-dimensional cocoon/envelope surrounding Jupiter just providing an important opportunity to study the ring material by in-situ measurements. The same consideration can be applied to the nano-dust in the D-ring of Saturn which will be investigated intensively by the Cassini spacecraft in its Proximal Orbits Phase in 2017 before the end of the Cassini-Huygens mission.

Ip, W.; Liu, C.; Liu, Y.

2012-12-01

327

The relationship between Jovian electrons and solar wind stream structure  

NASA Technical Reports Server (NTRS)

Near-earth observations of above-0.22-MeV Jovian electrons by the APL/JHU experiments on IMP-7 and 8 during 1972-1975, a period of stable recurrent solar wind, reveals 19 of 26 events in good association with solar wind streams. This pattern of positive correlation with solar wind streams is also observed in 3-6 MeV data from 1965-1972 during well-defined electron events. During their pre-encounter periods Pioneers 10 and 11 were nearly radially aligned with Jupiter and direct magnetic connection was highly unlikely. Jovian electrons above about 5 MeV in the UCSD experiments on Pioneers 10 and 11 were anticorrelated with solar wind velocity from about 3-4 AU until encounter. Reconstructions of the large-scale interplanetary magnetic field suggest that the near-earth events result from direct connection with the Jovian magnetotail and corotation of quasi-trapped populations while for Pioneer events electrons propagate out from the magnetosphere to a solar wind stream interaction, in along the interaction, then in to Pioneer on undisturbed field lines.

Gold, R. E.; Krimigis, S. M.; Roelof, E. C.; Fillius, R. W.

1978-01-01

328

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 ± 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) ~ 1.4 ± 0.2, lower than the 1.6 ± 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

329

Temperature structure and emergent flux of the Jovian planets  

NASA Technical Reports Server (NTRS)

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 enough absorption to create a thermal inversion for each of the planets. The suite of emergent spectral fluxes and representative limb darkenings and brightenings are calculated for comparison with the Voyager infrared spectra. The temperature differences between Jovian belts and zones corresponds to a difference in the ammonia cirrus particle radii (1 to 3 micron in zones; 10 micron in belts). The Jovian tropopause is approximately at the 0.1 bar level. A thin ammonia cirrus haze should be distributed throughout the Saturnian troposphere; and NH3 gas must be slightly supersaturated or ammonia ice particles are carried upwards convectively in the upper troposphere of Saturn. Substantial methane clouds exist on both Uranus and Neptune. There is some evidence for almost isothermal structures in the deep atmospheres of these two planets.

Silvaggio, P.; Sagan, C.

1978-01-01

330

Particles, environments and possible ecologies in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

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 the Jovian tropopause. Candidate chromophore molecules must satisfy the condition that they are produced sufficiently rapidly that convective pyrolysis maintains the observed chromophore optical depth. The condition is satisfied if complex organic chromophores are produced with high quantum yield by NH3 photolysis at less than 2,300 A. Jovian photoautotrophs in the upper troposphere satisfy this condition well, even with fast circulation, assuming only biochemical properties of comparable terrestrial organisms. An organism in the form of a thin, gas filled balloon can grow fast enough to replicate if (1) it can survive at the low mesospheric temperatures, or if (2) photosynthesis occurs in the troposphere.

Sagan, C.; Salpeter, E. E.

1976-01-01

331

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

332

Superradiance in a torus magnetosphere around a black hole  

PubMed

The coalescence of a neutron star and a black hole in a binary system is believed to form a torus around a Kerr black hole. A similarly shaped magnetosphere then results from the remnant magnetic field of the neutron star. In the strong-field case, it contains a cavity for plasma waves located between the barrier of the gravitational potential and the surrounding torus. This cavity may be unstable to superradiance of electromagnetic waves. Superradiant amplification of such waves, initially excited by turbulence in the torus, should inflate into a bubble in a time as short as approximately 0.75 (1 percent/&cjs3539;epsilon&cjs3539;2)(M/7M middle dot in circle) seconds approximately 0.15 to 1.5 seconds, assuming an efficiency &cjs3539;epsilon&cjs3539;2 = 0.5 to 5 percent and a mass M = 7M middle dot in circle. These bubbles may burst and repeat, of possible relevance to intermittency in cosmological gamma-ray bursts. The model predicts gamma-ray bursts to be anticorrelated with their gravitational wave emissions. PMID:10102805

van Putten MH

1999-04-01

333

Torus elements used in effective shock absorber  

NASA Technical Reports Server (NTRS)

Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload.

Cunningham, P.; Platus, D. L.

1966-01-01

334

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.

335

A feasibility study for the spherical torus experiment  

SciTech Connect

Oak Ridge National Laboratory (ORNL) proposes to build the Spherical Torus Experiment (STX), a very low aspect ratio toroidal confinement device. This proposal concentrates on tokamak operation of the experiment; however, it can in principle be operated as a pinch or reversed-field pinch as well. As a tokamak, the spherical torus confines a plasma that is characterized by high toroidal beta, low poloidal beta, large natural elongation, high plasma current for a given edge q, and strong paramagnetism. These features combine to offer the possibility of a compact, low-field fusion device. The figure below shows that when compared to a conventional tokamak the spherical torus represents a major change in geometry. The primary goals of the experiment will be to demonstrate a capability for high beta (20%) in the first stability regime, to extend our knowledge of tokamak confinement scaling, and to test oscillating-field current drive. The experiment will operate in the high-beta, collisionless regime, which is achieved in STX at low temperatures because of the geometry. At a minimum, operation of STX will help to resolve fundamental questions regarding the scaling of beta and confinement in tokamaks. Complete success in this program would have a significant impact on toroidal fusion research in that it would demonstrate solutions to the problems of beta and steady-state operation in the tokamak. The proposed device has a major radius of 0.45 m, a toroidai field of 0.5 T, a plasma current of 900 kA, and heating by neutral beam injection. We estimate 30 months for design, construction, and assembly. The budget estimate, including contingency and escalation, is $6.8 million.

Lazarus, E [Oak Ridge National Laboratory (ORNL); Peng, Yueng Kay Martin [ORNL

1985-10-01

336

The Jovian magnetotail and its current sheet  

NASA Technical Reports Server (NTRS)

Analyses of Voyager magnetic field measurements have extended the understanding of the structural and temporal characteristics of Jupiter's magnetic tail. The magnitude of the magnetic field in the lobes of the tail is found to decrease with Jovicentric distance approximately as r to he-1.4, compared with the power law exponent of -1.7 found for the rate of decrease along the Pioneer 10 outbound trajectory. Voyager observations of magnetic field component variations with Jovicentric distance in the tail do not support the uniform radial plasma outflow model derived from Pioneer data. Voyager 2 has shown that the azimuthal current sheet which surrounds Jupiter in the inner and middle magnetosphere extends tailward (in the anti-Sun direction) to a distance of at least 100 R sub J. In the tail this current sheet consists of a plasma sheet and embedded neutral sheet. In the region of the tail where the sheet is observed, the variation of the magnetic field as a result of the sheet structure and its 10 hr periodic motion is the dominant variation seen.

Behannon, K. W.; Burlaga, L. F.; Ness, N. F.

1980-01-01

337

Simulations of field-aligned currents: Application of theory of thin filament motion to Io's plasma wake  

NASA Astrophysics Data System (ADS)

Io's plasma wake was treated as a tail of magnetic flux tubes perturbed by Io successively. The evolution of an Io-perturbed flux tube was studied numerically via magnetohydrodynamics (MHD) approach of a thin filament. 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 s, until a tilt angle of about 4° has been developed, before it is released downstream. A magnetic field depression forms downstream as a result of the continual departure of the flux tubes from Io, which in turn has significant influence on the motion of a flux tube. A perturbed flux tube would undergo a subcorotational motion in Io's plasma wake. This motion is inevitably modulated by Alfvén wave bouncing back and forth between the equatorial plane and the boundary of Io plasma torus. The scale of the subcorotation region is in the order of 1 Jovian radius (RJ). The distribution of the simulated field-aligned currents downstream is consistent with the observed wake aurora brightness profile; in particular, the periodic structure in the current distribution is in agreement with recent infrared and FUV observations showing the presence of secondary spots in the auroral emissions.

Chen, C. X.

2007-03-01

338

Physics Results from the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) produces plasmas with aspect ratio A {triple_bond} R/a = 0.85m/0.68m {approx} 1.25, at plasma currents up to 1.5 MA with vacuum toroidal magnetic field up to 0.6 T on axis. The plasmas are heated by up to 6 MW of High-Harmonic Fast Waves (HHFW) at a frequency 30 MHz and by 7 MW of deuterium Neutral Beam Injection (NBI) at an energy up to 100 keV. Since January 2004, NSTX has been operating, routinely at toroidal fields up to 0.45 T, with a new central conductor bundle in the toroidal field coil.

M.G. Bell for the NSTX Research Team

2004-07-08

339

The neutral cloud and heavy ion inner torus at Saturn  

NASA Technical Reports Server (NTRS)

Voyager plasma data are used in conjunction with laboratory data on water molecule sputter-yields and energy distributions to calculate the morphology of the Saturn neutral water molecule and dissociated water molecule-product torus coexisting with the E-ring and icy satellites of this planet. Plasma production rates determined for this cloud exhibit a structure with distance from Saturn as well as from the orbit plane; this suggests a lack of equilibrium for the heavy ion plasma at less than 7 planet radii. Attention is given to the possibility that the Saturn E-ring may be a precipitate of the neutral cloud that is initiated by low-energy ion-molecule reactions.

Johnson, R. E.; Pospieszalska, M. K.; Sittler, E. C., Jr.; Cheng, A. F.; Lanzerotti, L. J.

1989-01-01

340

Nonlinear Gyrokinetic Turbulence Simulations of the NSTX Spherical Torus  

NASA Astrophysics Data System (ADS)

Recent progress in the numerical simulation of plasma turbulence has led to a greater understanding of the mechanisms behind anomalous heat and particle losses in tokamaks. However, the source of turbulent transport in machines with smaller aspect ratios, such as the National Spherical Torus Experiment (NSTX), remains elusive. Leading contenders for explaining transport in spherical tori include turbulence driven by the Electron Temperature Gradient (ETG) mode and microtearing modes. We present here nonlinear GYROfootnotetextJ. Candy, R. E. Waltz et al., J. Phys. Conf. Ser. 78, 012008 (2007). simulations of microturbulence in a variety of NSTX discharges and make comparisons between numerically simulated and experimentally measured levels of electron-scale turbulence.

Peterson, J. L.; Hammett, G. W.; Mikkelsen, D.; Kaye, S.; Candy, J.; Waltz, R. E.

2009-11-01

341

Study of turbulent fluctuations driven by the electron temperature gradient in the National Spherical Torus  

E-print Network

Study of turbulent fluctuations driven by the electron temperature gradient in the National temperature gradient. To check whether this turbulence is present in plasmas of the National Spherical Torus by the electron temperature gradient. These turbulent fluctuations were not observed at the location

Mazzucato, Ernesto

342

An Inexpensive Ohmic Transformer Firing Circuit for the CDXU Spherical Torus  

E-print Network

1 An Inexpensive Ohmic Transformer Firing Circuit for the CDX­U Spherical Torus T. Munsat, R designed and modeled a simple, efficient circuit for delivering power to the CDX­U ohmic transformer, spherical tori) have traditionally driven plasma current by using the transformer action of a centrally

343

An Inexpensive Ohmic Transformer Firing Circuit for the CDX-U Spherical Torus  

E-print Network

1 An Inexpensive Ohmic Transformer Firing Circuit for the CDX-U Spherical Torus T. Munsat, R designed and modeled a simple, efficient circuit for delivering power to the CDX-U ohmic transformer, spherical tori) have traditionally driven plasma current by using the transformer action of a centrally

344

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

345

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

346

Studies for the Europagenic Plasma Source in Jupiter's Inner Magnetosphere during the Galileo Europa Mission  

NASA Technical Reports Server (NTRS)

Progress in research to understand the three-dimensional nature of the Europagenic plasma torus is summarized. Efforts to improve the plasma torus description near Europa's orbit have included a better understanding of Europa's orbit and an improved description of the planetary magnetic field. New plasma torus chemistry for molecular and atomic species has been introduced and implemented in Europa neutral cloud models. Preliminary three-dimensional model calculations for Europa's neutral clouds and their plasma sources are presented.

Smyth, William H.

2004-01-01

347

Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations  

NASA Astrophysics Data System (ADS)

We study the formation process of an oxygen torus during the 12-15 November 2012 magnetic storm, using the magnetic field and plasma wave data obtained by Van Allen Probes. We estimate the local plasma mass density (?L) and the local electron number density (neL) from the resonant frequencies of standing Alfvén waves and the upper hybrid resonance band. The average ion mass (M) can be calculated by M ˜ ?L/neL under the assumption of quasi-neutrality of plasma. During the storm recovery phase, both Probe A and Probe B observe the oxygen torus at L = 3.0-4.0 and L = 3.7-4.5, respectively, on the morning side. The oxygen torus has M = 4.5-8 amu and extends around the plasmapause that is identified at L˜3.2-3.9. We find that during the initial phase, M is 4-7 amu throughout the plasma trough and remains at ˜1 amu in the plasmasphere, implying that ionospheric O+ ions are supplied into the inner magnetosphere already in the initial phase of the magnetic storm. Numerical calculation under a decrease of the convection electric field reveals that some of thermal O+ ions distributed throughout the plasma trough are trapped within the expanded plasmasphere, whereas some of them drift around the plasmapause on the dawnside. This creates the oxygen torus spreading near the plasmapause, which is consistent with the Van Allen Probes observations. We conclude that the oxygen torus identified in this study favors the formation scenario of supplying O+ in the inner magnetosphere during the initial phase and subsequent drift during the recovery phase.

Nosé, M.; Oimatsu, S.; Keika, K.; Kletzing, C. A.; Kurth, W. S.; Pascuale, S. De; Smith, C. W.; MacDowall, R. J.; Nakano, S.; Reeves, G. D.; Spence, H. E.; Larsen, B. A.

2015-02-01

348

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

349

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

350

Clouds, aerosols, and photochemistry in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

An assessment is made of the development status of concepts for cloud and aerosol compositions, vertical and horizontal distributions, and microphysical properties, in the Jovian upper troposphere and stratosphere. Attention is given to several key photochemical species' relationships to aerosol formation as well as their transport process implications, treating photochemistry in the context of comparative planetology and noting differences and similarities among the outer planet atmospheres; since this approach emphasizes observational data, a variegated assortment of ground-based and spacecraft observations is assembled. Current views on the tropospheric distribution of clouds are challenged, and a rationale is presented for alternative accounts.

West, R. A.; Strobel, D. F.; Tomasko, M. G.

1986-01-01

351

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

352

Spoke wavenumbers and mode transitions in the NASA Lewis bumpy torus  

NASA Technical Reports Server (NTRS)

Waveforms of fluctuations of plasma potential, resulting from rotating electron and ion charge concentrations, were observed in a bumpy torus. Since these fluctuations were thought to be spoke rotations in the direction of the ExB drift, measuring the direction of spoke rotation should determine the direction of the electric fields over much of the plasma surface. A Langmuir probe was inserted into the plasma to measure the floating potential of the plasma, hence the direction of the electric field could be checked another way.

Gerdin, G. A.

1974-01-01

353

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

354

Methanol in the L1551 Circumbinary Torus  

E-print Network

We report observations of gaseous methanol in an edge-on torus surrounding the young stellar object L1551 IRS5. The peaks in the torus are separated by ~ 10,000 AU from L1551 IRS5, and contain ~ 0.03 earth masses of cold methanol. We infer that the methanol abundance increases in the outer part of the torus, probably as a result of methanol evaporation from dust grain surfaces heated by the shock luminosity associated with the shocks associated with the jets of an externally located x-ray source. Any methanol released in such a cold environment will rapidly freeze again, spreading methanol throughout the circumbinary torus to nascent dust grains, planitesimals, and primitive bodies. These observations probe the initial chemical conditions of matter infalling onto the disk.

Glenn J. White; C. W. M. Fridlund; P. Bergman; A. Beardsmore; Rene Liseau; R. R. Phillips

2006-09-25

355

FAST plasma scenarios and equilibrium configurations  

Microsoft Academic Search

In this paper we present the fusion advanced studies torus (FAST) plasma scenarios and equilibrium configurations, designed to reproduce the ITER ones (with scaled plasma current) and suitable to fulfil plasma conditions for integrated studies of plasma-wall interaction, burning plasma physics, ITER relevant operation problems and steady state scenarios. The attention is focused on FAST flexibility in terms of both

G. Calabrò; F. Crisanti; G. Ramogida; R. Albanese; A. Cardinali; A. Cucchiaro; G. Granucci; G. Maddaluno; M. Marinucci; S. Nowak; A. Pizzuto; V. Pericoli Ridolfini; A. Pironti; A. A. Tuccillo; F. Zonca

2009-01-01

356

SED Signatures of Jovian Planets Around White Dwarf Stars  

E-print Network

The problem of detecting Jovian-sized planets orbiting White Dwarf stars is considered. Significant IR excesses result from warm Jupiters orbiting a White Dwarf of $T_{\\rm eff}=10000$ K at a distance of $\\sim 10^3$ White Dwarf radii (corresponding to $\\sim 10^2$ Jupiter radii or a few tenths of an AU) with an orbital period of $\\sim 100$ days. Such a planet will have a 10 micron flux density at its Wien peak that is comparable to the emission of the White Dwarf at that wavelength. Although the White Dwarf is much hotter than the planet, the planet will have peak brightness at the IR, well into the Rayleigh-Jeans tail of the White Dwarf, plus Jovians are about 10 times larger than White Dwarfs, so there is a substantial gain in the planet to star brightness contrast as compared to planets around Main Sequence stars. In the solar neighborhood, there are 51 White Dwarf stars within 13 pc of the Sun. At 10 pc, the IR flux density of ``warm'' Jupiters (a few hundred Kelvin) will fall in the range 10--100 micro-Jansky which should be observable with {\\it SIRTF}.

R. Ignace

2001-06-28

357

Fine-scale structure of the Jovian magnetotail current sheet  

NASA Technical Reports Server (NTRS)

During the outbound leg of its passage through the Jovian magnetosphere in the Voyager 2 spacecraft observed 50 traversals of the magnetotail current sheet during a 10 day period at distances between 30 and 130 R sub j. Analysis of these observations shown that the Jovian tail sheet tends to lie approximately parallel to the ecliptic plane and to oscillate about the tail axis with the 10 hour planetary rotation period. The magnetic structure near and within the current sheet was variable with time and distance from Jupiter, but generally corresponded to one of the following: (1) simple rotation of field across the sheet, with an approximately southward direction in the sheet (generally northward beyond a distance from Jupiter of approximately 84 R sub j; (2) field having a southward component in a broad region near the sheet, but northward in a restricted region at the sheet itself; or (3) a clear bipolar variation of the sheet normal field component as the sheet was crossed (i.e., the field became northward and then southward, or vice versa, in crossing the sheet).

Behannon, K. W.

1983-01-01

358

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

359

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

360

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

361

Further observational support for the limited-latitude magnetodisc model of the outer Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

A distinction is made between the solar-wind-influenced limited-latitude magnetodisk and magnetic anomaly models of the outer Jovian magnetosphere, and an observational comparison of the two models is presented based on Pioneer and Voyager measurements. Predictions of the two models concerning the location of the current sheet as a function of Jovigraphic latitude, System III longitude and radial distance are contrasted, and it is shown that both models can satisfactorily explain the merging of the current sheep crossings by Voyager 1 and 2. Variations in the energetic particle intensities observed on the outbound pass of Voyager 1 and 2 are observed to correspond to scale heights for energetic particle latitudinal confinement consistent with MHD calculations and Pioneer 10 and Voyager magnetic observations only when the scale heights are calculated on the basis of the limited-latitude magnetodisk model. It is thus suggested that the solar wind must have a greater influence on magnetosphere structure than internal longitudinal plasma asymmetry.

Thomsen, M. F.; Goertz, C. K.

1981-01-01

362

Jovian Early Bombardment: planetesimal erosion in the inner asteroid belt  

E-print Network

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. 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 depen...

Turrini, Diego; Magni, Gianfranco

2012-01-01

363

Nonequilibrium radiative heating of a Jovian entry body  

NASA Technical Reports Server (NTRS)

The influence of nonlocal thermodynamic equilibrium (NLTE) radiative transfer on radiative and convective heating of a Jovian entry body is investigated. The flow in the shock layer is assumed to be axisymmetric, viscous, and in chemical equilibrium. The chemical species considered for the collisional deactivation processes are H2, H, H+. The NLTE radiative transfer equations are derived for multilevel energy transitions. The rotational and vibrational energy modes are assumed to be in local thermodynamic equilibrium. The results indicate that higher-level energy transitions have little influence on the overall NLTE results. The NLTE results, however, are found to be greatly influenced by the temperature distributions in the shock layer. The convective and radiative heating to the entry body are reduced significantly because of the NLTE conditions; the reduction in convective heating, however, is relatively small. The influence of NLTE is found to be greater at higher entry altitudes.

Tiwari, S. N.; Subramanian, S. V.

1979-01-01

364

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

365

Jovian radio emission below 5 mHz  

NASA Technical Reports Server (NTRS)

The GS2 and GS3 operational modes of the planetary radio astronomy experiment on the Voyager 1 spacecraft are described as well as the dynamic spectra obtained. Repeated pulses of unpolarized emission (P bursts) recorded by GS2 were studied and attempts were made to correlate their occurrences, which have sudden onset and conclusion, with features in the GS3 dynamic spectra. The influence of the phase of any of the Galilean satellites or the subspacecraft system 3 longitude on P bursts was also investigated. Tables show Voyage 1 GS2 frequencies, high quality Jovian P bursts, and the geometry and pulse repetition frequency of the P burst groups. Plotted bursts are included.

Evans, D. R.

1983-01-01

366

Performance of a 12-coil superconducting bumpy torus magnet facility  

NASA Technical Reports Server (NTRS)

The bumpy torus facility consists of 12 superconducting coils, each 19 cm i.d. and capable of 3.0 teslas on their axes. The coils are equally spaced around a toroidal array with a major diameter of 1.52 m, and are mounted with the major axis of the torus vertical in a single vacuum tank 2.6 m in diameter. Final shakedown tests of the facility mapped out its magnetic, cryogenic, vacuum, mechanical, and electrical performance. The facility is now ready for use as a plasma physics research facility. A maximum magnetic field on the magnetic axis of 3.23 teslas was held for a period of more than sixty minutes without a coil normalcy. The design field was 3.00 teslas. The steady-state liquid helium boil-off rate was 87 liters per hour of liquid helium without the coils charged. The coil array was stable when subjected to an impulsive loading, even with the magnets fully charged. When the coils were charged to a maximum magnetic field of 3.35 teslas, the system was driven normal without damage.

Roth, J. R.; Holmes, A. D.; Keller, T. A.; Krawczonek, W. M.

1972-01-01

367

Hopkins Ultraviolet Telescope determination of the Io torus electron temperature  

NASA Technical Reports Server (NTRS)

Sulfur ion emissions from the Io plasma torus observed by the Hopkins Ultraviolet Telescope (HUT) in 1990 December have been analyzed to determine the effective temperature of the exciting electrons. Spectra were obtained with a long slit that extended from 3.1 to 8.7 Jupiter radii R(sub J) on both dawn and dusk torus ansae. The average temperature of electrons exciting S(2+) emissions from the dawn ansa is (4800 +/- 2400) K lower than on the dusk ansa, a dawn-dusk asymmetry comparable in both sign and magnitude to that measured by the Voyager Ultraviolet Spectrograph (UVS) experiment. Emissions from S(2+) ions are generated in a source region with electron temperatures in the range 32,000-56,000 K; S(3+) ion emissions are excited by electrons that average 20,000-40,000 K hotter. This distinct difference suggests that the S(3+) emission source region is spatially separate from the S(2+) source region. Estimated relative aperture filling factors suggest that the S(3+) emissions originate from a region more extended out of the centrifugal plane than the S(2+) emissions.

Hall, D. T.; Bednar, C. J.; Durrance, S. T.; Feldman, P. D.; Mcgrath, M. A.; Moos, H. W.; Strobel, D. F.

1994-01-01

368

Engineering design of the National Spherical Torus Experiment  

SciTech Connect

NSTX is a proof-of-principle experiment aimed at exploring the physics of the ``spherical torus'' (ST) configuration, which is predicted to exhibit more efficient magnetic confinement than conventional large aspect ratio tokamaks, amongst other advantages. The low aspect ratio (R/a, typically 1.2--2 in ST designs compared to 4--5 in conventional tokamaks) decreases the available cross sectional area through the center of the torus for toroidal and poloidal field coil conductors, vacuum vessel wall, plasma facing components, etc., thus increasing the need to deploy all components within the so-called ``center stack'' in the most efficient manner possible. Several unique design features have been developed for the NSTX center stack, and careful engineering of this region of the machine, utilizing materials up to their engineering allowables, has been key to meeting the desired objectives. The design and construction of the machine has been accomplished in a rapid and cost effective manner thanks to the availability of extensive facilities, a strong experience base from the TFTR era, and good cooperation between institutions.

C. Neumeyer; P. Heitzenroeder; J. Spitzer, J. Chrzanowski; et al

2000-05-11

369

The Jovian Early Bombardment and the Primordial Evolution of Vesta and the Asteroid Belt  

NASA Astrophysics Data System (ADS)

The formation and migration of Jupiter in the Solar Nebula triggered a short but violent phase of primordial bombardment. Here we show the implications of this Jovian Early Bombardment for the collisional evolution of the asteroid belt and of Vesta.

Turrini, D.; Coradini, A.; Magni, G.

2012-05-01

370

Conjecture on the Appearance of the Galileo Probe's Entry and Descent in to the Jovian Atmosphere  

NASA Astrophysics Data System (ADS)

This paper gives the technical background for depiction of the Galileo Probes appearance during jovian entry. A clip from the planetarium show "Dark Universe" will be shown during the opening. session.

Park, C.; Arnold, J. O.; Green, M.; Witkowski, A.

2014-06-01

371

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

NASA Technical Reports Server (NTRS)

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 caused by multiple reflections of a standing Alfven wave current system excited by Io. Estimates of the reflection coefficient at the ionosphere and other damping processes show that a large number of reflections can occur, with the Alfven wave current system possibly extending completely around Jupiter. This source geometry can account for a number of otherwise puzzling characteristics of the Jovian decametric radiations,

Gurnett, D. A.; Goertz, C. K.

1981-01-01

372

Plasma wave turbulence at Jupiter's bow shock  

Microsoft Academic Search

Voyager 1 measurements of wave-particle interactions of Jupiter's bow shock are reported. Some of the wave phenomena detected during the spacecraft's third inbound passage are discussed. The results indicate that the Jovian magnetosheath was characterized by a virtual absence of detectable plasma wave turbulence after passage through the bow shock and that there were impulsive wave structures within the shock

F. L. Scarf; D. A. Gurnett; W. S. Kurth; R. L. Poynter

1979-01-01

373

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

374

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

375

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

SciTech Connect

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 ?{sub i}, and decorrelation times are about 5 a/c{sub s}. 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. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)] [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Bell, R. E.; Diallo, A.; Guttenfelder, W.; Kaye, S. M.; LeBlanc, B. P.; Podesta, M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2013-05-15

376

Measurement of Poloidal Velocity on the National Spherical Torus Experiment  

SciTech Connect

A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

Ronald E. Bell and Russell Feder

2010-06-04

377

Evolution of low-density Thomson scattering on ELMO Bumpy Torus  

Microsoft Academic Search

The ELMO Bumpy Torus (EBT) confines a low-density, steady-state, microwave-driven plasma. On the basis of favorable initial diagnostic results, major machine upgrades: increases in microwave power and magnetic field: were initiated, and the feasibility of Thomson scattering was considered. From the time of the first laser measurements, in which a two-point spectrum was integrated during 30 or more Q-switched pulses,

J. A. Cobble

1985-01-01

378

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

379

Ion beam testing of the Aerolor X-point dump plate for the Joint European Torus  

Microsoft Academic Search

The durability of a carbon-carbon composite, Aerolor A05, X-point divertor dump plate to thermal fatigue was evaluated for the Joint European Torus (JET) at Sandia's Plasma Material Test Facility. Of primary interest was the effect of thermal cycling on the carbon-carbon threads of the bolted attachment scheme for the Aerolor X-point divertor. This report describes the testing performed at the

J. C. Salmonson; J. G. Watkins; R. D. Watson; J. M. McDonald

1991-01-01

380

An investigation of density fluctuations and electron transport in the Madison Symmetric Torus reversed-field pinch  

E-print Network

by inductive current drive, both fluctuation amplitudes and the total radial electron flux are greatly reduced over the entire plasma cross section. © 2001 American Institute of Physics. DOI: 10.1063/1.1378328 IAn investigation of density fluctuations and electron transport in the Madison Symmetric Torus

Biewer, Theodore

381

Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus  

Microsoft Academic Search

New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented. The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating

Alessandro Casati; P. Mantica; D. van Eester; N. Hawkes; F. Imbeaux; E. Joffrin; A. Marinoni; F. Ryter; A. Salmi; T. Tala; P. de Vries; JET EFDA contributors

2007-01-01

382

Multiply reflected standing Alfven waves in the Io torus - Pioneer 10 observations  

NASA Technical Reports Server (NTRS)

Observations from the Voyager 1 pass by the Io flux tube strongly suggest that large amplitude standing Alfven waves are generated as Jovian plasma flows past Io. It has recently been proposed by Gurnett and Goertz (1981) that this Io generated standing Alfven wave system extends an appreciable way around the Io L-shell. Observations are presented here of magnetic perturbations found in the Pioneer 10 record as it crossed the Io L-shell. The field perturbations are found to be qualitatively consistent with the passage of the spacecraft through a standing Alfven wave pattern. The observations suggest an Alfven Mach number of 0.03, which is 1/5 the value inferred from Voyager 1 observations. This implies a lower plasma density at the time of the flyby of Pioneer 10.

Walker, R.; Kivelson, M.

1981-01-01

383

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

384

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

385

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

386

Galileo dust data from the jovian system: 1997 1999  

NASA Astrophysics Data System (ADS)

The dust detector system on board the Galileo spacecraft recorded dust impacts in circumjovian space during the craft's orbital mission about Jupiter. This is the eighth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January 1997-December 1999 when the spacecraft completed 21 revolutions about Jupiter. In this time interval data were obtained as high resolution realtime science data or recorded data during 449 days (representing 41% of the entire period), or via memory readouts during the remaining times. Because the data transmission rate of the spacecraft was very low, the complete data set (i.e. all parameters measured by the instrument during impact of a dust particle) of only 3% (7625) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data of 2883 particles detected during Galileo's interplanetary cruise and 5353 particles detected in the jovian system in 1996, complete data of 15 861 particles detected by the Galileo dust instrument from 1989 to 1999 are now available. The majority of the detected particles were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the highest impact rates exceeded 100min-1 (C21 orbit; 01 July 1999). With the new data set the times of onset, cessation and a 180? shift in the impact direction of the grains measured during 19 Galileo orbits about Jupiter are well reproduced by simulated 9 nm particles charged up to a potential of +3V, confirming earlier results obtained for only two Galileo orbits (Horányi, M., Grün, E., Heck, A., 1997. Modeling the Galileo dust measurements at Jupiter. Geophys. Res. Lett. 24, 2175-2178). Galileo has detected a large number of bigger particles mostly in the region between the Galilean moons. The average radius of 370 of these grains measured in the 1996-1999 period is about 2?m (assuming spherical grains with density 1gcm-3) and the size distribution rises steeply towards smaller grains. The biggest detected particles have a radius of about 10?m.

Krüger, H.; Bindschadler, D.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Moissl, R.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A.

2006-08-01

387

Jovian millisecond-bursts as markers of Alfvenic electron acceleration  

NASA Astrophysics Data System (ADS)

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tubes connecting Io's wake to Jupiter, triggered by electrons accelerated from Io to Jupiter. We present simulations of a hot electron population under the assumption of acceleration by Alfvén waves in the Io flux tube. Outside of limited acceleration regions where parallel electric field associated with Alfvén waves are found, the electrons have an adiabatic motion along the magnetic field lines. Electron distribution functions are computed at various altitudes and times (relatively to the propagation of the Alfvén wave). Near Jupiter, a loss cone appears in the magnetically mirrored electron population; it amplifies extraordinary (X) mode radio waves. The X-mode growth rate (depending on time and altitude) is computed, and a theoretical dynamic spectrum of the resulting Jovian radio emissions is built. This spectrum is compared with those made from observations.

Mottez, F.; Hess, S.; Zarka, P.

2007-12-01

388

Jovian Early Bombardment: Planetesimal Erosion in the Inner Asteroid Belt  

NASA Astrophysics Data System (ADS)

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.

2012-05-01

389

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

390

WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy  

E-print Network

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 be 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 50km shows that the D-type objects dominate both the leading cloud ($L_4$), with a fraction of 84%, and trailing cloud ($L_5$), 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 of these large objects, $L_4/L_5...

Grav, Tommy; Bauer, James M; Masiero, Joe R; Nugent, Carrie R

2012-01-01

391

Eddy processes in the general circulation of the Jovian atmospheres  

NASA Technical Reports Server (NTRS)

Two fundamentally different views of the general circulation of Jovian atmospheres have emerged. According to one view, the observed jet streams at the cloud tops are controlled by the vorticity transfers of small scale eddies generated by planetary wave instabilities within a shallow atmospheric layer. According to the alternate point of view, the zonal jets are surface manifestations of deep interior convection organized into cylindrical motion with axes parallel to the planetary rotation axis. Both approaches may be considered in the context of the very different roles assumed by the potential vorticity. A possible reconciliation of the two kinds of dynamical systems is considered in which the interior motion is overlaid with a statically stable cappling layer driven by turbulent energy injection from below. A simple model for the eddy driving of quasi-geostrophic dynamics in the capping layer is presented which is consistent with the tentative evidence for up-gradient momentum flux on Jupiter and IRIS observations of thermal contrast correlations with cyclonic and anticyclonic shear zones. Certain synoptic-scale cloud features in Jupiter's atmosphere are interpreted as breaking waves, which may also influence the lateral mixing of tracers such as the ortho-para hydrogen ratio.

Leovy, Conway

1986-01-01

392

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

393

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

NASA Technical Reports Server (NTRS)

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, D sub E, 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 D sub E, 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 D sub E 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, Lon L.

1993-01-01

394

Outer satellite atmospheres: Their extended nature and planetary interactions. [sodium cloud of Io, hydrogen torus of Titan, and comet atmospheres  

NASA Technical Reports Server (NTRS)

Highly developed numerical models are applied to interpret extended-atmosphere data for the sodium cloud of Io and the hydrogen torus of Titan. Solar radiation pressure was identified and verified by model calculations as the mechanism to explain two different east-west asymmetries observed in the sodium cloud. Analysis of sodium line profile data, suggesting that a Jupiter magnetospheric wind may be responsible for high speed sodium atoms emitted from Io, and preliminary modeling of the interaction of the Io plasma torus and Io's sodium cloud are also reported. Models presented for Titan's hydrogen torus are consistent both with the recent Pioneer 11 measurements and earlier Earth-orbiting observations by the Copernicus satellite. Progress is reported on developing models for extended gas and dust atmospheres of comets.

Smyth, W. H.

1980-01-01

395

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

396

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 RJ 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 ~1 miliWatt per meter squared. 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.

2008-12-01

397

TORUS: Radiation transport and hydrodynamics code  

NASA Astrophysics Data System (ADS)

TORUS is a flexible radiation transfer and radiation-hydrodynamics code. The code has a basic infrastructure that includes the AMR mesh scheme that is used by several physics modules including atomic line transfer in a moving medium, molecular line transfer, photoionization, radiation hydrodynamics and radiative equilibrium. TORUS is useful for a variety of problems, including magnetospheric accretion onto T Tauri stars, spiral nebulae around Wolf-Rayet stars, discs around Herbig AeBe stars, structured winds of O supergiants and Raman-scattered line formation in symbiotic binaries, and dust emission and molecular line formation in star forming clusters. The code is written in Fortran 2003 and is compiled using a standard Gnu makefile. The code is parallelized using both MPI and OMP, and can use these parallel sections either separately or in a hybrid mode.

Harries, Tim

2014-04-01

398

Advanced tokamak reactors based on the spherical torus (ATR/ST). Preliminary design considerations  

SciTech Connect

Preliminary design results relating to an advanced magnetic fusion reactor concept based on the high-beta, low-aspect-ratio, spherical-torus tokamak are summarized. The concept includes resistive (demountable) toroidal-field coils, magnetic-divertor impurity control, oscillating-field current drive, and a flowing liquid-metal breeding blanket. Results of parametric tradeoff studies, plasma engineering modeling, fusion-power-core mechanical design, neutronics analyses, and blanket thermalhydraulics studies are described. The approach, models, and interim results described here provide a basis for a more detailed design. Key issues quantified for the spherical-torus reactor center on the need for an efficient drive for this high-current (approx.40 MA) device as well as the economic desirability to increase the net electrical power from the nominal 500-MWe(net) value adopted for the baseline system. Although a direct extension of present tokamak scaling, the stablity and transport of this high-beta (approx.0.3) plasma is a key unknown that is resoluble only by experiment. The spherical torus generally provides a route to improved tokamak reactors as measured by considerably simplified coil technology in a configuration that allows a realistic magnetic divertor design, both leading to increased mass power density and reduced cost.

Miller, R.L.; Krakowski, R.A.; Bathke, C.G.; Copenhaver, C.; Schnurr, N.M.; Engelhardt, A.G.; Seed, T.J.; Zubrin, R.M.

1986-06-01

399

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

400

The interaction of Io's Alfven waves with the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

A numerical solution for the propagation of the Alfven waves produced by Io is presented. The waves are shown to interact strongly with the torus and magnetic-field inhomogeneities. Substantial reflection occurs from the magnetospheric medium, and only about a quarter of the wave power will reach the ionosphere on its first pass. It is concluded that both WKB and ray-tracing arguments are inappropriate, contrary to previous studies. A more realistic picture may be that of a whole field line or L shell resonating in an eigenmode. The Alfven structure behind Io and some possible features that it may exhibit are discussed. In particular, it may be possible to produce decametric arcs that are more closely spaced than ray tracing permits by exciting higher-harmonic eigenmodes of Io's L shell.

Wright, A. N.

1987-09-01

401

Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots  

NASA Technical Reports Server (NTRS)

Auroral emissions generated by the Jovian moons Io and Europa, originating at the foot of the magnetic flux tubes of the satellites, may be largely limited to longitudes where the planet's ionospheric conductivity is enhanced. The enhanced conductivity is produced by trapped energetic electrons that drift into the Jovian atmosphere in regions where the planet's magnetic field is anomalously weak. The most active auroral hot-spot emissions lie in a sector of the northern hemisphere defined by decametric radio emission. Weaker auroral hot spots are found in the southern hemisphere along a magnetic conjugate trace. The brightness and the longitude of the Jovian hot spots predicted in this paper are in agreement with observations reported by Atreya et al. (1977).

Dessler, A. J.; Chamberlain, J. W.

1979-01-01

402

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

403

Nonlinear Gyrokinetic Turbulence Simulations of the NSTX Spherical Torus  

NASA Astrophysics Data System (ADS)

The National Spherical Torus Experiment provides a unique environment for the study of electron turbulence and transport. We present nonlinear GYROootnotetextJ. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003). simulations of microturbulence in NSTX discharges and make comparisons between numerically simulated and experimentally measured levels of electron-scale turbulence. In particular we examine the effects of magnetic shear, ExB shearing and collisionality on turbulence driven by the Electron Temperature Gradient (ETG) mode, while paying attention to the roles of electromagnetic fluctuations, kinetic ions and realistic experimental NSTX parameters. We also investigate the interplay between electron turbulence and transport using the TGYROootnotetextJ. Candy et al., Phys. Plasmas 16, 060704 (2009). simulation suite. This work is supported by the SciDAC Center for the Study of Plasma Microturbulence, DOE Contract DE-AC02-09CH11466, and used the resources of the National Center for Computational Sciences at ORNL, under DOE Contract DE-AC05-00OR22725.

Peterson, J. Luc; Hammett, G. W.; Mikkelsen, D.; Kaye, S.; Mazzucato, E.; Bell, R.; Leblanc, B.; Yuh, H.; Smith, D.; Candy, J.; Waltz, R. E.; Belli, E. A.; Staebler, G. M.; Kinsey, J.

2010-11-01

404

Strike Point Control for the National Spherical Torus Experiment (NSTX)  

SciTech Connect

This paper presents the first control algorithm for the inner and outer strike point position for a Spherical Torus (ST) fusion experiment and the performance analysis of the controller. A liquid lithium divertor (LLD) will be installed on NSTX which is believed to provide better pumping than lithium coatings on carbon PFCs. The shape of the plasma dictates the pumping rate of the lithium by channeling the plasma to LLD, where strike point location is the most important shape parameter. Simulations show that the density reduction depends on the proximity of strike point to LLD. Experiments were performed to study the dynamics of the strike point, design a new controller to change the location of the strike point to desired location and stabilize it. The most effective PF coils in changing inner and outer strike points were identified using equilibrium code. The PF coil inputs were changed in a step fashion between various set points and the step response of the strike point position was obtained. From the analysis of the step responses, PID controllers for the strike points were obtained and the controller was tuned experimentally for better performance. The strike controller was extended to include the outer-strike point on the inner plate to accommodate the desired low outer-strike points for the experiment with the aim of achieving "snowflake" divertor configuration in NSTX.

E. Kolemen, D. A. Gates, C.W. Rowley, N. J. Kasdin, J. Kallman,S. Gerhardt, V. Soukhanovskii, D. Mueller

2010-07-09

405

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

406

Detection of Disruptions in the High-? Spherical Torus NSTX  

SciTech Connect

This paper describes the prediction of disruptions based on diagnostic data in the high-? spherical torus NSTX [M. Ono, et al., Nuclear Fusion 40 , 557 (2000)]. The disruptive threshold values on many signals are examined. In some cases, raw diagnostic data can be used as a signal for disruption prediction. In others, the deviations of the plasma data from simple models provides the signal used to determine the proximity to disruption. However, no single signal and threshold value can form the basis for disruption prediction in NSTX; thresholds that produce an acceptable false positive rate have too large a missed or late warning rate, while combinations that produce an acceptable rate of missed or late warnings have an unacceptable false positive rate. To solve this problem, a novel means of combining multiple threshold tests has been developed. After being properly tuned, this algorithm can produce a false positive rate of 2.8%, with a late warning rate of 3.7% when applied to a database of ~2000 disruptions collected from three run campaigns. Furthermore, many of these false positives are triggered by near-disruptive MHD events that might indeed be disruptive in larger plasmas with more stored energy. However, the algorithm is less efficient at detecting the MHD event that prompts the disruption process.

Gerhardt, S P; Bell, R E; LeBlanc, B P; Menard, J E; Mueller, D; Roquemore, A L; Sabbagh, S A

2013-01-16

407

Design of the new magnetic sensors for Joint European Torus  

SciTech Connect

A new magnetic diagnostics system has been designed for the 2005 Joint European Torus (JET) experimental campaigns onward. The new system, which adds to the existing sensors, aims to improve the JET safety, reliability, and performance, with respect to: (i) equilibrium reconstruction; (ii) plasma shape control; (iii) coil failures; (iv) VDEs; (v) iron modeling; and (vi) magnetohydrodynamics poloidal mode analysis. The system consists of in-vessel and ex-vessel sensors. The former are a set of 38 coil pairs (normal and tangential), located as near as possible to the plasma. Coils are generally grouped in rails, in order to ease remote handling in-vessel installation. The system includes: (i) two outer poloidal limiter arrays (2x7 coil pairs); (ii) two divertor region arrays (2x7 coil pairs); and (iii) two top coil arrays (2x5 coil pairs). Ex-vessel sensors, including discrete coils, Hall probes, and flux loops (26 in total) will be installed on the iron limbs, in order to provide experimental data for the treatment of iron in equilibrium codes. The design is accompanied by a software analysis, aiming to predict the expected improvement.

Coccorese, V.; Albanese, R.; Altmann, H.; Cramp, S.; Edlington, T.; Fullard, K.; Gerasimov, S.; Huntley, S.; Lam, N.; Loving, A.; Riccardo, V.; Sartori, F.; Marren, C.; McCarron, E.; Sowden, C.; Tidmarsh, J.; Basso, F.; Cenedese, A.; Chitarin, G.; DegliAgostini, F. [Consorzio CREATE, Associazione EURATOM-ENEA sulla Fusione, Via Claudio 21, I-80125 Naples (Italy); Association EURATOM-UKAEA Fusion, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); Asociacion EURATOM-CIEMAT para Fusion, Avenida Complutense 22, E-28040 Madrid (Spain)] [and others

2004-10-01

408

The chemistry of hydrocarbon ions in the Jovian ionosphere  

NASA Technical Reports Server (NTRS)

We have modeled the chemistry of hydrocarbon ions in the jovian ionosphere. We find that a layer of hydrocarbon ions is formed in the altitude range 300-400 km above the ammonia cloud tops, due largely to direct ionization of hydrocarbons by photons in the wings of the H2 absorption lines in the 912- to 1100-A region that penetrate to below the methane homopause. We have explicitly included in the model 156 ion-neutral reactions involving hydrocaron ions with up to two carbon atoms. Larger hydrocarbon ions are included as two pseudoions, C3Hn(+) and C4Hn(+). The model shows that 15 reactions of H(+), CH3(+), CH5(+), C2H3(+), C2H5(+), and C2H6(+) with hydrocarbon neutrals are the major processes that are responsible for the production and growth of C1-, C2- and C3- or C4-ions in the hydrocarbon ion layer. The model also shows that ions initially produced in the hydrocarbon ion layer are converted into hydrocarbon ions with more than two carbon atoms with very little loss by recombination. It is likely that successive hydrocarbon ion-neutral reactions continue to produce even larger hydrocarbon ions, so the terminal ions probably have more than three or four carbon atoms. In the auroral regions, the chemistry of hydrocarbon ions may modify the densities of neutral hydrocarbons, especially C2H2 in the upper mesosphere, and may play a major role in the production of polar haze particles.

Kim, Y. H.; Fox, J. L.

1994-01-01

409

Chandra ACIS Observations of Jovian X-Ray Emission  

NASA Technical Reports Server (NTRS)

On November 25 and 26, 1999, the Chandra X-ray spacecraft conducted a set of four 19,000 sec observations of Jupiter. The ACIS-S instrument configuration was used for its good low energy efficiency and spatial resolution. An anomalous response was obtained which was subsequently attributed to strong jovian infrared radiation penetrating the detector and piling up spurious events across the entire X-ray range. However, the pre-observation establishment of an offsetting bias field has allowed the recovery of data from that portion of Jupiter's disc which remained within the elevated portion of the bias field during the observation. This ranges from fewer than 3000 sec to the entire observing time for about 10% of the planet. Auroral emission is seen near both poles in each observation. The northern aurora ia overall more intense than the southern, consistent with prior Einstein and ROSAT Observatory results. The southern aurora shows more modulation with Jupiter's rotation than the northern. Spatial resolution has been improved by at least a factor of two over prior measurements but convincing evidence of structure has not been seen. Lower latitude emission, first observed by ROSAT, is confirmed with flux levels averaging more than a factor of five below peak auroral values. Pronounced variation in the observed emission has occurred over the observing period. The spectral response extends from 0.24 keV, below which noise dominates, to about 1.2 keV. For all four observations the spectrum is clearly enhanced between 0.45 and 0.85 keV. This is apparently unequivocal evidence that Jupiter's X-ray emission is the result of oxygen and perhaps sulfur ions precipitating into the planet's atmosphere, where they undergo charge exchange interactions. The identification of specific transitions lines in the spectrum is among the ongoing efforts. A bremsstrahlung component has not yet been identified.

Garmire, Gordon; Elsner, Ronald; Feigelson, Eric; Ford, Peter; Gladstone, G. Randall; Hurley, Kevin; Metzger, Albert; Waite, J. Hunter, Jr.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

410

About the structure of the high latitude Jovian aurorae  

NASA Astrophysics Data System (ADS)

In this study we determine of a 'reference main oval' for Jupiter's aurorae from a series of high resolution images taken with the FOC on board HST in the H2 Lyman bands near 1550 Å. We have focused on images taken when most of the north auroral oval was active, including at longitudes <= 170o where it is generally undetectable. Our reference main ovals are consistent in size and in general aspect with the footprints of 20-30 RJ VIP4 model ovals (Connerney et al. 1998). However, in the north it differs from the model (and from previous 'reference' main ovals) in that it exhibits a 'kidney-like' aspect with excursions toward low latitude in the SIII longitude range 190o-240o (an already reported feature), and toward high latitude in the poorly documented 120o-150o range. In the south, it is also shifted from a VIP4 model oval, toward low latitude and toward high latitude, in the longitudes ranges (110o-200o) and (310o-100o), respectively. The accurate definition of both main oval loci puts additional strong constraints on magnetic field models. By extrapolation of the north reference main oval, we define higher latitude 'reduced reference ovals', which we can fit both the polewardmost arc detected longward of longitude 170o and the high latitude edge of what we had previously named the 'transpolar emission' shortward of 170o. This indicates that these two features must in fact be part of a single, very high latitude auroral oval, connected to the outer magnetosphere. We suggest that, subject to solar wind condition variations, this oval indicates the approximate location of the northern polar cap boundary. Finally we study a bright spot located just equatorward of this oval, we establish that it remains fixed near magnetic noon, and we tentitatively identify it with the northern Jovian polar cusp.

Prangé, R.; Pallier, L.

2000-10-01

411

Direct currents generated by microwave heating in toroidal plasma  

Microsoft Academic Search

The existence of a direct toroidal current in a magnetized plasma torus heated by microwaves is established experimentally. The dependences of that electric current on microwave power and gas pressure are given. The experimental results are consistent with the theory of non-linear dragging of electrons by waves travelling along the torus

R. Klima; V. Kopecky; J. Musil; F. Zacek; P. Heymann; A. M. Ternopol

1978-01-01

412

Jovian electron propagation close to the sun /at about 0.5 AU/  

NASA Technical Reports Server (NTRS)

On the basis of interplanetary electron flux measurements in the energy range 0.7-25 MeV made on the Mariner 10 spacecraft launched in 1973 for successive encounters with planet Mercury (R approximately equal 0.5 AU), it is shown that the dominant interplanetary flux of electrons close to the sun is Jovian in origin (except for times of solar flares) and that these observations are consistent with a three-dimensional diffusion-convection model which describes Jovian electron propagation in the outer solar system.

Eraker, J. H.; Simpson, J. A.

1979-01-01

413

Significance of shock and body slip conditions on Jovian entry heating  

NASA Technical Reports Server (NTRS)

The influence of the body and shock slip conditions on the heating of a Jovian entry body is investigated. The flow in the shock layer is considered to be axisymmetric, steady, laminar, viscous, and in chemical equilibrium. Realistic thermophysical and step-function spectral models are employed and results are obtained by implicit finite-difference and iteractive procedures. The freestream conditions correspond to a typical Jovian entry trajectory point. The results indicate that the effect of the slip conditions is significant when the altitudes are higher than 225 km and that the contribution of a radiative heat-flux term in the energy equation should not be neglected at any altitude.

Tiwari, S. N.; Szema, K. Y.

1979-01-01

414

Organic synthesis in a simulated Jovian atmosphere. III - Synthesis of aminonitriles  

NASA Technical Reports Server (NTRS)

The products from spark and semicorona discharges through mixtures simulating the Jovian atmosphere were analyzed by gas chromatography combined with mass spectrometry. When the reaction was performed at -80 C, 3-ethylaminopropionitrile and a number of higher homologs were formed. On the other hand, at +20 C, higher molecular-weight material appeared which yielded aminonitrile-derived fragments on mass spectrometry. Although the spectra were not identical, there were notable similarities between these and the mass spectra of some compounds present in the Murray and Orgeuil meteorites. Aminonitriles may occur as minor constituents of the Jovian atmosphere and perhaps by cyclization may produce pyrimidines.

Molton, P. M.; Ponnamperuma, C.

1974-01-01

415

Responses of the Jovian Atmosphere to Cometary Particles and Photon Impacts  

NASA Technical Reports Server (NTRS)

Spectra of soft x-ray and EUV emissions of oxygen ions, precipitating into the Jovian atmosphere, are calculated, taking into account the dynamical character of the energy and charge distributions of the ions as they propagate. Monte-Carlo simulations are performed using experimental and theoretical cross sections of ion collisions with the atmospheric gases. The numbers of x-ray and EUV photons produced per precipitating oxygen ion are calculated as functions of the initial ion energy and charge. The energy and charge distribution functions are used to evaluate the intensities of characteristic x-ray and EUV spectral emission lines of oxygen ions in the Jovian aurora.

Dalgarno, A.

1998-01-01

416

Observations of low energy interplanetary electrons. [Jovian origin suggested by temporal behavior  

NASA Technical Reports Server (NTRS)

Observations of the temporal behavior of low energy (0.16-6 MeV) at 1 AU are reported. The electron intensity is found to vary by a factor of more than five from one quiet time to another, including short-term enhancements of the type reported at higher electron energies. Over a period of about four months, beginning with the time at which the interplanetary field line first connects earth and Jupiter, the magnitude and frequency of the increases grow abruptly and remain high. The observed longitudinal distribution of Jovian electrons could be the result of the interconnection of the interplanetary field with an extended Jovian magnetotail.

Mewaldt, R. A.; Stone, E. C.; Vogt, R. E.

1975-01-01

417

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'