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1

Remote sensing of the Io torus plasma ribbon using natural radio occultation of the Jovian radio emissions  

NASA Astrophysics Data System (ADS)

We study the Jovian hectometric (HOM) emissions recorded by the RPWS (Radio and Plasma Wave Science) experiment onboard the Cassini spacecraft during its Jupiter flyby. We analyze the attenuation band associated with the intensity extinction of HOM radiation. This phenomenon is interpreted as a refraction effect of the Jovian hectometric emission inside the Io plasma torus. This attenuation band was regularly observed during periods of more than 5 months, from the beginning of October 2000 to the end of March 2001. We estimate for this period the variation of the electron density versus the central meridian longitude (CML). We find a clear local time dependence. Hence the electron density was not higher than 5.0 × 104 cm-3 during 2 months, when the spacecraft approached the planet on the dayside. In the late afternoon and evening sectors, the electron density increases to 1.5 × 105 cm-3 and reach a higher value at some specific occasions. Additionally, we show that ultraviolet and hectometric wavelength observations have common features related to the morphology of the Io plasma torus. The maxima of enhancements/attenuations of UV/HOM observations occur close to the longitudes of the tip of the magnetic dipole in the southern hemisphere (20° CML) and in the northern hemisphere (200° CML), respectively. This is a significant indication about the importance of the Jovian magnetic field as a physical parameter in the coupling process between Jupiter and the Io satellite.

Boudjada, M. Y.; Galopeau, P. H. M.; Sawas, S.; Lammer, H.

2014-09-01

2

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

E-print Network

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect a 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 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 backgr...

Lipatov, A S; Paterson, W R; Sittler, E C; Hartle, R E; Simpson, D G

2012-01-01

3

Diffuse Jovian aurora influenced by plasma injection from Io  

NASA Technical Reports Server (NTRS)

The paper demonstrates that the broad band of whistler-mode waves observed within the high density torus surrounding Io is consistent with electron cyclotron generation. Cyclotron resonant instability of Jovian energetic electrons is enhanced due to the lower resonant electron energy within the equatorial high density plasma torus surrounding the orbit of Io. The higher energy resonant electron scattering and the corresponding energetic electron lifetimes indicate that an efficient local acceleration process is required to replenish the precipitating relativistic electrons. Calculated energy deposition into the Jovian atmosphere should provide a dominant source of middle atmospheric ionization and excite a continuous band of diffuse auroral emission. It is suggested that the diffuse Jovian aurora should be influenced by the variable volcanic activity on Io which is thought to be an important source of plasma, since the cyclotron scattering process is strongly influenced by the ambient equatorial thermal plasma density.

Thorne, R. M.; Tsurutani, B. T.

1979-01-01

4

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

5

Studies of Io's atmosphere and plasma torus  

SciTech Connect

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

Moreno, M.A.

1989-01-01

6

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

Microsoft Academic Search

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

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

1982-01-01

7

Departure from corotation of the Io plasma torus - Local plasma production  

NASA Technical Reports Server (NTRS)

The departure of the Jovian magnetosphere from rigid corotation is adequately explained by outward plasma transport at distances where L is greater than approximately 10. The departure of 5% observed in the Io plasma torus, however, is too large to be accounted for simply by plasma transport. Local plasma production is proposed as the main factor determining the corotation lag in the torus. The outward pick-up current provided by ionization of neutral atoms is calculated and related to the current produced in the ionosphere by the corotation lag. This leads to an expression giving the corotation lag of the torus as a function of radial distance. Charge transfer is found to be an important process, allowing the majority of the torus mass to be ejected from the magnetosphere in a neutral state. Thus, the mass loading rate is found to be several times that inferred from examination of the corotation lag associated with outward plasma transport.

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

1982-01-01

8

Titan's gas and plasma torus  

NASA Technical Reports Server (NTRS)

The implications of the Voyager observations for a steady state model of a torus of hydrogen and nitrogen neutral gas and plasma are assessed. Constraints are placed on the nitrogen neutral density, the neutral hydrogen and nitrogen escape fluxes (from Titan), and the diffusion rate in terms of observed or inferred quantities. The results obtained are consistent with the Voyager observations.

Eviatar, A.; Podolak, M.

1983-01-01

9

Ground based observations of Io plasma torus variability  

NASA Astrophysics Data System (ADS)

Jupiter is not only the largest planet in the Solar System, it also has the largest magnetosphere. Jupiter's innermost Galilean moon, Io, is the most volcanically active body in the Solar System. This volcanic activity produces tenuous atmosphere which escapes, creating the Io plasma torus, a ring of charged particles encircling Jupiter. The Io plasma torus is composed mainly of sulfur and oxygen ions. It is most dense around Io's orbit (5.6 Rj). It's observed in extreme ultraviolet (EUV) emission and in the optical. EUV emission arise from interactions between torus superthermal ("hot") electrons and ions. Optical emission comes from interaction between thermal electrons and sulfur ions. The optical emission trace the densest part of the torus, the EUV trace the hottest part of the torus. In early December, 2013, we observed the Io plasma torus at the McMath-Pierce Solar Telescope using a specially designed coronagraph in support of the JAXA EXtrem ultraviolet spectrosCope for ExophEric Dynamics (EXCEED) mission. EXCEED is observing the Io plasma torus in the EUV in a manner similar to that of the landmark observations made by the Cassini UVIS instrument in 2000. Our ground-based [SII] 6731 angstrom images provide context for the EXCEED observations. The analysis of the 2013 [SII] data is important preparation for analysis of a much larger set of observations recorded between 1997 and 2008. This large set of over 1000 images were recorded during the Galileo tour, the Cassini flyby, and the Ulysses flyby of Jupiter. The images provide context for in-situ observations, EUV images, and several new measurements of the mysterious and variable Jovian magnetospheric "system IV" period. In this work, we'll be presenting a comparison between our results and EXCEED's and the methodology which will be used for the 1000 images.

Pinho Magalhães, Fabíola; Echer, Ezequiel; Demétrio Gonzalez Alarcon, Walter; Lopes, Rosaly; Morgenthaler, Jeffrey; Echer, Mariza P. S.

10

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

11

Physics of Spherical Torus Plasmas  

SciTech Connect

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

Peng, Yueng Kay Martin [ORNL

2000-01-01

12

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

13

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

14

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

15

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

16

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

17

Simulations of the Effects of Jupiter's Plasma Torus on Io's Pele Plume  

NASA Astrophysics Data System (ADS)

Io’s plumes rise hundreds of kilometers above its surface and sublimation atmosphere, presenting large targets for incoming ions from Jupiter’s plasma torus. The direct simulation Monte Carlo method is used to model the gas plume at Pele and its interaction with the Jovian plasma torus. Chemical reactions resulting from ion impacts in a plume change its composition and energy from the impacts changes the plume’s structure (asymmetrically). The presence of non-condensible daughter species in a warmer plume canopy produces a more diffuse deposition ring on Io’s surface, compared to simulations without plasma. Energized molecules also escape from the plume, forming a diffuse cloud of fast particles above the plume’s canopy, which may function to resupply the plasma torus and which suggests a mechanism for lofting other species to very high altitudes.

McDoniel, William; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

2014-11-01

18

Jovian magnetospheric plasma effects at Europa and Ganymede (Invited)  

Microsoft Academic Search

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

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

2009-01-01

19

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

20

Characterization of Jovian plasma-embedded dust particles  

NASA Astrophysics Data System (ADS)

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.

Graps, Amara L.

2006-08-01

21

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

22

Longitudinal asymmetry of the Io plasma torus  

NASA Technical Reports Server (NTRS)

Remote observations of the Io plasma torus have revealed a persistent longitudinal asymmetry in the brightness of optical S(+) emission lines but not of ultraviolet S(2+) emission lines. The S(+) asymmetry (with respect to the corotating System III coordinates) has been attributed to an asymmetric plasma source; the question then arises, why do the higher ionization states of sulfur not reflect a similar asymmetry? The explanation proposed here is based on the fact that torus ions do not quite corotate at the System III rate because of mass loading. If the resulting System III drift period of the ions is intermediate between the ionization lifetimes of S(+) and S(2+), then the asymmetry of the source will be obscured by longitudinal drift for the relatively long-lived multiply-ionized sulfur ions, but not for short-lived S(+).

Hill, T. W.

1983-01-01

23

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

24

Diffusion in the Io plasma torus and its relation to the torus spatial structure  

SciTech Connect

This is a study of the plasma diffusion processes relevant to the physical nature of the Io plasma torus at Jupiter. The author examined physical properties that lead him to conclude that flux-tube interchange diffusion is not a valid mechanism in the plasma torus. The collisional nature of the hot torus plasma is seen through its observed EUV emissions which dominate the energy loss from the system. Further, the torus plasma parameters fall in the range of values satisfying the criteria for the use of collisional transport theory to derive a collisional diffusion coefficient. The collisional nature of the torus plasma is characterized in the long mean-free-path regime where classical transport theory breaks down. The Chapman-Enskog method of calculating the plasma diffusion coefficient from a solution of the Boltzmann equation is studied. The radical spatial structure and energetics of the plasma torus is modeled by employing the collisional diffusion coefficient in a computer model calculation of collisional ionization-diffusive equilibrium and energy branching. The computer model employs the known significant plasma reactions involving the torus sulfur and oxygen species, utilizing the most recently available atomic parameters.

Davis, E.W.

1991-01-01

25

Using a 2D Model of the Io Plasma Torus to Investigate the Effects of Density Variations on the Morphology and Intensity of the Io Footprint  

NASA Astrophysics Data System (ADS)

Io is the primary source of plasma in the Jovian magnetosphere, continuously releasing approximately 1 ton/s of SO2 from volcanic eruptions. The interaction of Io with Jupiter's magnetosphere is strongly influenced by the density structure of the resulting plasma torus and the position of Io relative to the center of the torus [Bonfond et al. 2008]. This unusual interaction produces a complex auroral feature on Jupiter's ionosphere known as the Io footprint. Hubble Space Telescope (HST) observations of Jupiter's far-UV aurora during spring 2007 showed an increased number of isolated auroral blobs along with a continuous expansion of Jupiter's main auroral oval over a few months. These blobs were associated with several large injections of hot plasma between 9 and 27 Jovian radii. These events coincided with a large volcanic eruption of the Tvashtar Paterae on Io, as observed by the New Horizons spacecraft [Spencer et al., 2007]. This, in turn, may have resulted in a significant increase in the plasma torus density. Besides, on June 7th, 2007, the Io footprint momentarily became so faint that it disappeared under a diffuse patch of emission remaining from an injection blob [Bonfond et al., 2012]. The goal of the present study is to examine the relationship between the increased density of the plasma torus and the dimming of the Io footprint. We implement a 2D model of the Io plasma torus that treats the variable-density torus as being composed of discrete layers of uniform density. As the co-rotating plasma in the plasma torus impinges on Io, Alfvén waves are launched at a pushback angle obtained from Gurnett and Goertz [1981]. The waves propagate inside the plasma torus through reflection and refraction at density discontinuities where they lose some of their initial energy. Using the above model, we can track the Alfvén wave fronts in the plasma torus and determine the longitude at which they exit the torus along with the corresponding remaining energy. Since Alfvén waves are capable of accelerating charged particles along magnetic field lines, we assume that the discrete Io footprint features are created at these longitudes, and that the intensity of each of these features is positively correlated to the energy transported by the wave front as it exits the plasma torus. Therefore, the model allows us to investigate both the effects of density changes and of Io's position in the plasma torus on the intensity and the morphology of the Io footprint. In this context, the model enables us to determine the density increase in the plasma torus required to explain the apparent disappearance of Io footprint given its position at that time.

Payan, A. P.; Rajendar, A.; Paty, C. S.; Bonfond, B.; Crary, F.

2012-12-01

26

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

Microsoft Academic Search

Angular distributions are presented of ion (approx.0.5--2 MeV) and electron (>10 Mev) fluxes measured during the Voyager 1 spacecraft passage through the inner regions of the Jovian magnetosphere (radial distances from the planet < or approx. =10 R\\/sub J\\/). In the regions of peak flux intensities, just outside the orbit of Io, the ion angular distributions are most sharply peaked

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

1981-01-01

27

Empirical model of the Io plasma torus: Voyager measurements  

Microsoft Academic Search

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

Fran Bagenal

1994-01-01

28

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

29

Dawn-dusk electric field asymmetry of the Io plasma torus  

NASA Astrophysics Data System (ADS)

The effects of a combined convection and corotation electric field across the Io plasma torus are considered. A dawn-to-dusk electric field EC will modify the orbits of charged particles shifting them toward dawn. The radial drift imposed by the perturbed orbits implies a local time-dependent modulation of low-energy ion and electron temperatures with particles hotter at dusk than at dawn. With EC approximately 4 mV/m, the orbits near 6 Jupiter radii would be shifted by approximately 0.2 Jupiter radius. Then the electron temperature would be 20% higher at dust than at dawn, an effect which could explain the local time asymmetry of EUV intensity found by the Voyager ultraviolet spectrometer. The source of the convection electric field is internal to the magnetosphere, and is attributed to the tailward escape of Iogenic and Jovian plasma beyond the Alfven surface.

Barbosa, D. D.; Kivelson, M. G.

1983-03-01

30

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

31

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

SciTech Connect

Angular distributions are presented of ion (approx.0.5--2 MeV) and electron (>10 Mev) fluxes measured during the Voyager 1 spacecraft passage through the inner regions of the Jovian magnetosphere (radial distances from the planet < or approx. =10 R/sub J/). In the regions of peak flux intensities, just outside the orbit of Io, the ion angular distributions are most sharply peaked at 90/sup 0/ local pitch angle, a configuration consistent with diffusion of the particles inward from larger radial distances. Inside the orbit of Io the lower-energy ions exhibit angular distributions depleted at 90/sup 0/ local pitch angles, suggesting the possiblity 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 equatiorial 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.

1981-09-30

32

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

33

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

34

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

35

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 soIn situ detection of interplanetary and Jovian nanodust with radio and plasma wave instruments Nicole Meyer-Vernet and Arnaud Zaslavsky Abstract Radio and plasma wave instruments in space can detect

Demoulin, Pascal

36

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

E-print Network

Voyager, despite the fact that neither the radio (Warwick et al., 1982) nor the plasma wave (Scarf et alIn situ detection of interplanetary and Jovian nanodust with radio and plasma wave instruments Nicole Meyer-Vernet and Arnaud Zaslavsky Abstract Radio and plasma wave instruments in space can detect

Demoulin, Pascal

37

Jovian magnetosphere: a post-Voyager view  

SciTech Connect

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

Hill, T.W.

1981-01-20

38

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

39

Plasma outflow and superrotation in the Jovian magnetosphere deduced from voyager observations  

SciTech Connect

Magnetometer and plasma science data from the Voyager 1 and Voyager 2 encounters of Jupiter are combined with earlier theoretical analysis by T.W. Hill and V.M. Vasyliunas to determine the total mass outflow rate and radial bulk velocity of the magnetospheric plasma in the Jovian plasma sheet, as well as the height integrated Pedersen conductivity of the Jovian ionosphere. The analysis requires accurate determination of the orientation of the plasma sheet using magnetometer data surrounding the plasma sheet crossing points. This analysis was applied to fifteen crossings of the Jovian plasma sheet on both the day side and the night side. Results obtained from this analysis are believed to be accurate within a factor of two, and confirm previous order-of-magnitude estimates. Evidence of an enhanced outflow of plasma in the active hemisphere of System III longitude is observed on the dayside. On the night side, evidence of plasma inflow and superrotation is seen in the inactive hemisphere. These two observations lend support to the corotating-hemisphere. These two observations lend support to the corotating-convection model of plasma transport in the Jovian magnetosphere.

Hairston, M.R.

1986-01-01

40

Drift wave instability in the Io plasma torus  

SciTech Connect

The authors present a lienar normal-mode analysis of low-frequency electrostatic drift waves in the Io plasma torus, providing a kinetic description of the centrifugal interchange instability of the torus regulated by coupling to Jupiter's ionosphere. They assume a periodic potential perturbation with azimuthal wavenumber m {much gt} 1 and solve a boundary value problem to obtain the wave dispersion relation and radial eigenfunction. For given m the growing mode is a standing wave in the corotating reference frame. If the outer torus boundary is taken as a discontinuity, the growth rate is proportional to m times the torus flux tube content times the ion drift frequency, divided by the Pedersen conductivity of Jupiter's ionosphere. The inner torus boundary has a modest stabilizing effect for azimuthal wavelengths greater than the radial thickness of the torus. The finite slope of the outer torus density profile has a more pronounced stabilizing effect, reducing the growth rate by the factor 2{beta}/m, where {beta}{approximately}2 is the exponent of the assumed power law decline of flux tube content with distance. Even so, the e-folding time is of the order of 1 hour, much less than the inferred residence time of torus ions. The growth rate can be further reduced dramatically by the stabilizing effect of an as-yet unobserved ring current distribution, the impoundment effect proposed by Siscoe et al. Various theoretical models of global radial transport in Jupiter's magnetosphere, including corotating convection, interchange diffusion, and transient flux tube convection, can be understood as plausible nonlinear evolutions of electrostatic drift waves. Further observations and/or numerical simulations are needed to ascertain the relative importance of these transport mechanisms.

Huang, T.S. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Hill, T.W. (Rice Univ., Houston, TX (United States))

1991-08-01

41

RF experiments on spherical torus plasmas  

SciTech Connect

Experimental operations are about to begin on the next generation of spherical torus (ST) devices-the National Spherical Torus eXperiment (NSTX) in the U.S. and the Mega-Amp Spherical Torus (MAST) in the U.K. The application of RF heating and current drive to these high beta, compact confinement devices is a challenging problem. The initial focus for NSTX had been on the High Harmonic Fast Wave (HHFW) regime. Although modeling of HHFW heating and current drive has been performed at ORNL, UCSD, MIT, and PPPL, there are few experiments in this frequency range. In conventional tokamaks, the DIII-D experiments at the 5{sup th}-7{sup th} cyclotron harmonic are the closest approach to the HHFW regime. In an ST, the only RF heating experiments to date have been performed at the 15{sup th} harmonic on the Current Drive eXperiment-Upgrade (CDX-U) at PPPL. General features of HHFW heating and current drive and the degree to which experimental confirmation of these features is available will be discussed. (c) 1999 American Institute of Physics.

Majeski, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Menard, J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Batchelor, D. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Bigelow, T. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Carter, M. D. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Finkenthal, M. [Johns Hopkins University, Baltimore, Maryland 21218 (United States); Jaeger, E. F. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Jones, B. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Kaita, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Mau, T. K. [University of California-San Diego, La Jolla, California 92093 (United States)] (and others)

1999-09-20

42

The transmission of Alfven waves through the Io plasma torus  

SciTech Connect

In this paper the authors study the nature of Alfven wave propagation through the Io plasma torus. A one-dimensional model is used with uniform magnetic field and exponential density decrease to a constant value. The solution can be expanded near the center of the torus and far away from the torus to give propagating Alfven waves. The time-averaged Poynting flux is independent of position and, in the near and far limits, is equivalent to the sum of Poynting fluxes carried by individual wave trains. In this fashion it is possible to calculate the fraction of energy that is transmitted or reflected by the change in Alfven speed through the torus, for a given wave train near Io. The solution is sensitive to the distant (or asymptotic) Alfven speed. A lower limit for this speed can be found from the density decrease alone. Using this value they find, in accord with previous work, that there is negligible wave reflection. A more realistic asymptotic Alfven speed takes into account the increase in field strength along the Io flux tube. This larger Alfven speed value yields a significant reflection coefficient, and the result is in good agreement with their previous numerical solution. The results imply that Io's Alfven waves may not propagate completely through the plasma torus, and thus WKB theory and ray tracing may not provide meaningful estimates of the energy transport.

Wright, A.N.; Schwartz, S.J. (Univ. of London (England))

1989-04-01

43

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

44

Nonideal momentum coupling between Iogenic plasma and the Jovian ionosphere  

Microsoft Academic Search

The interaction between Io and Jupiter was dramatically illustrated by recent ultraviolet and infrared imaging of the Io-induced Jovian aurora. Bright auroral emissions were observed at the base of Io's flux tube with emissions at the footprint of Io's wake extending large distances downstream (roughly 180 deg around Jupiter). The extended emission trail is poorly understood. We propose as a

P. A. Delamere; F. Bagenal; R. Ergun; Y. Su

2002-01-01

45

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

46

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

47

Magnetic Fluctuations in the Jovian Magnetosphere  

NASA Technical Reports Server (NTRS)

The engine that drives the jovian magnetosphere is the mass added to the Io ion torus, accelerated to corotational velocities by field-aligned currents that couple the Io torus to the jovian ionosphere. The mass of the torus builds up to an amount that the magnetic forces cannot contain and the plasma, first slowly and then more rapidly, drifts outward. Numerous authors have treated this problem based first on the observations of the Pioneer 10 and 11 flybys; then on Voyager 1 and 2, and Ulysses; and finally most recently the Galileo orbiter. The initial observations revealed the now familiar magnetodisk, in which the field above and below the magnetic equator became quite radial in orientation and much less dipolar. The Galileo observations show this transformation to occur on average at 24 R(sub J) and to often be quite abrupt. These observations are consistent with outward transport of magnetized plasma that moves ever faster radially until about 50 R(sub J) on the nightside where the field lines stretch to the breaking point, reconnection occurs, and plasma and field islands are transported down the tail ultimately removing the mass from the magnetosphere that Io had deposited deep in the inner torus. The reconnection process creates empty flux tubes connected to Jupiter that are buoyant and thought to float inward and replace the flux carried out with the torus plasma. As described above, the jovian magnetosphere could very well be in a state of steady laminar circulation, but indeed it is not. The process is very unsteady and the wave levels can be very intense. The existence of these waves in turn can lead to processes that compete with the radial circulation pattern in removing plasma from the system. These waves can scatter particles so that they precipitate into the ionosphere. This process should be important in the Io torus where the atmospheric loss cone is relatively large and becomes less important as the loss cone decreases in size with radial distance. However, the Io torus is relatively quiet compared to the region outside the torus and it is not obvious without studying this scattering carefully whether the loss in the torus or out of the torus is greater and whether it can act rapidly enough to compete with the radial transport of ions to the tail in the life cycle of the mass added at Io. Closer to Io the ion cyclotron waves are most intense and possibly are associated with the losses in the Io flux tube. The waves are also diagnostic of both the Io atmospheric composition and the size and strength of the massloading process.

Russell, Christopher T.

2002-01-01

48

Longitude variation of ion temperature in the Io plasma torus  

Microsoft Academic Search

The Io plasma torus shows an unanticipated variation of ion temperature as a function of System III (magnetic) longitude ?III. The simple expectation for the perpendicular temperature T$\\\\perp$, based on ion pick-up in a tilted dipole magnetic field, is a double-peaked function with two maxima and two minima per 360° of longitude, having an average value of ?480 eV for

T. W. Hill; A. J. Dessler

2004-01-01

49

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

50

Fluctuation spectra in the NASA Lewis bumpy-torus plasma  

NASA Technical Reports Server (NTRS)

The electrostatic potential fluctuation spectrum in the NASA Lewis bumpy-torus plasma was studied with capacitive probes in the low pressure (high impedance) mode and in the high pressure (low impedance) mode. Under different operating conditions, the plasma exhibited electrostatic potential fluctuations (1) at a set of discrete frequencies, (2) at a continuum of frequencies, and (3) as incoherent high-frequency turbulence. The frequencies and azimuthal wave numbers were determined from digitally implemented autopower and cross-power spectra. The azimuthal dispersion characteristics of the unstable waves were examined by varying the electrode voltage, the polarity of the voltage, and the neutral background density at a constant magnetic field strength.

Singh, C. M.; Krawczonek, W. M.; Roth, J. R.; Hong, J. Y.; Powers, E. J.

1978-01-01

51

Low energy ion distribution measurements in Madison Symmetric Torus plasmas  

NASA Astrophysics Data System (ADS)

Charge-exchange neutrals contain information about the contents of a plasma and can be detected as they escape confinement. The Florida A&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.; Mezonlin, E. D.; Johnson, J. A.

2014-06-01

52

Interaction of the Jovian magnetosphere with Europa: Constraints on the neutral atmosphere  

Microsoft Academic Search

A three-dimensional plasma model was developed to understand the sources and sinks that maintain Europa's neutral atmosphere and to study the interaction of the Jovian magnetosphere with this atmosphere and the formation of an ionosphere. The model includes self-consistently the feedback of the plasma action on the atmosphere through mass balance. Suprathermal torus ions with a contribution from thermal ions

J. Saur; D. F. Strobel; F. M. Neubauer

1998-01-01

53

Voyager observations of lower hybrid noise in the Io plasma torus and anomalous plasma heating rates  

Microsoft Academic Search

A study of Voyager 1 electric field measurements obtained by the plasma wave instrument in the Io plasma torus has been carried out. A survey of the data has revealed the presence of persistent peaks in electric field spectra in the frequency range 100-600 Hz consistent with their identification as lower hybrid noise for a heavy-ion plasma of sulfur and

D. D. Barbosa; F. V. Coroniti; W. S. Kurth; F. L. Scarf

1985-01-01

54

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

NASA Technical Reports Server (NTRS)

Research efforts in the second quarter have been focused upon a preliminary exploration of the likely impact of Europs's local atmospheres and neutral clouds on the plasma torus and the initiation of an assessment of the basic nature of the radial structure of the electron density in the plasma torus during the JO encounter of the Galileo spacecraft with Jupiter.

Smyth, William H.

2004-01-01

55

Negative specific heat of a magnetically self-confined plasma torus  

PubMed Central

It is shown that the thermodynamic maximum-entropy principle predicts negative specific heat for a stationary, magnetically self-confined current-carrying plasma torus. Implications for the magnetic self-confinement of fusion plasma are considered. PMID:12576553

Kiessling, Michael K.-H.; Neukirch, Thomas

2003-01-01

56

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

57

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

58

DEPLETED MAGNETIC FLUX TUBES AS PROBES OF THE IO TORUS PLASMA  

E-print Network

DEPLETED MAGNETIC FLUX TUBES AS PROBES OF THE IO TORUS PLASMA C. T. Russell1 , M. G. Kivelson1 , W spacecraft detected thin tubes of magnetic flux that had stronger fields than their surroundings indicating that they were depleted in their energy content. These tubes have not been seen on every return to the Io torus

Russell, Christopher T.

59

On the electromagnetic fields generated by a slowly moving conducting body in a magnetized plasma. Possible applications for the Io-Jovian system, spacecraft, and plasma probes  

Microsoft Academic Search

To explain self-consistently some energetic processes, radiation features, and the electromagnetic environment near the Io satellite moving in the Jovian magnetospheric plasma, as well as a spacecraft body or a plasma probe, we consider, by means of plasma kinetic theory, the process of electromagnetic interaction between a moving conducting body and the surrounding hot magnetized plasma described by the tensor

M. L. Khodachenko; V. M. Gubchenko; H. O. Rucker

1998-01-01

60

The Jovian magnetotail  

NASA Technical Reports Server (NTRS)

The current understanding of the plasma, magnetic field, and plasma wave characteristics of the near and distant Jovian magnetotail is discussed. The properties of these two regions are compared, with particular emphasis given to the data on the distant tail obtained by Voyager 2. The Jovian tail has many unusual properties, such as the large scale sausage-string shape of its outer boundary, but some of its properties resemble those of the earth's magnetotail, such as its central current sheet and a surrounding region resembling a plasma sheet consisting of hot ions. Data are presented that support the view that plasma in the Jovian tail plasma sheet comes from Jupiter.

Lepping, R. P.

1986-01-01

61

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

62

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

63

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

E-print Network

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{\\AA}-1912{\\AA}. 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 de...

Steffl, Andrew J; Stewart, A Ian F; 10.1016/j.icarus.2004.04.016

2013-01-01

64

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

65

Plasma depletions in the Jovian magnetosphere - Evidence of transport and solar wind interaction  

NASA Technical Reports Server (NTRS)

A series of plasma voids ('dropouts') was observed by the Plasma Science (PLS) experiment in Jupiter's magnetosphere during the Voyager 2 encounter with that planet. A reexamination of Voyager 2 data has led to the conclusion that the dropout phenomenon cannot be a manifestation of a plasma wake produced by Ganymede. Rather, the appearance of the dropouts is attributed to changes in the upstream solar wind conditions and the global state of the magnetosphere; the proximity of Voyager 2 to Ganymede at the time is considered to be coincidental. It is suggested that these dropouts are evidence of a state of 'bubbling' of the magnetosphere that alternates with 'laminar' states in which, as in the case of the Voyager 1 encounter with Jupiter, voids are not present and that these states correspond to different processes by which plasma is transported out of the system. The nature of these states is related to changes in the magnitude of the upstream solar wind ram pressure. In the bubbling state, this pressure is higher than in the laminar state and drives an intermittent instability. The analysis presented is one of the first attempts to introduce, in space physics, recently acquired theoretical notions of the physics of the finite-beta plasmas of which the Jovian magnetospheric plasma is an important example.

Mcnutt, Ralph L., Jr.; Coppi, Paolo S.; Selesnick, Richard S.; Coppi, Bruno

1987-01-01

66

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 Abstract: The Current Drive Experiment-Upgrade (CDX-U) device at the Princeton Plasma Physics Laboratory of this concept, key liquid lithium-plasma interaction questions are being addressed in the CDX-U device[2

California at Los Angeles, University of

67

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

68

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

Microsoft Academic Search

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

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

1979-01-01

69

On the electromagnetic fields generated by a slowly moving conducting body in a magnetized plasma. Possible applications for the Io-Jovian system, spacecraft, and plasma probes  

Microsoft Academic Search

To explain self-consistently some energetic processes, radiation features, and the electromagnetic environment near the Io\\u000a satellite moving in the Jovian magnetospheric plasma, as well as a spacecraft body or a plasma probe, we consider, by means\\u000a of plasma kinetic theory, the process of electromagnetic interaction between a moving conducting body and the surrounding\\u000a hot magnetized plasma described by the tensor?

M. L. Khodachenko; V. M. Gubchenko; H. O. Rucker

1998-01-01

70

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

71

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

72

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

73

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

NASA Technical Reports Server (NTRS)

Research efforts in the second quarterly period have been focused primarily upon reviewing and assessing the neutral-plasma reactions and the plasma-plasma reactions that are important in determining the production and loss rates for the primary heavy ion species S(+), S(++), S(+++), O(+), and O(++) in the plasma torus and in acquiring new and updating old cross sections for the important processes.

Smyth, William H.

2003-01-01

74

The magnetic-anomaly model of the Jovian magnetosphere - A post-Voyager assessment  

NASA Technical Reports Server (NTRS)

Predictions previously put forth (Dessler and Vasyliunas, 1979) as tests for the magnetic-anomaly model (in which the anomalously weak magnetic field region in the northern hemisphere of Jupiter influences the outer Jovian magnetosphere by one or more plasma interaction processes) are reexamined in the light of Voyager and other recent observations. With regard to the prediction of a restricted longitude range of enhanced interaction between Io and Jupiter's ionosphere, the longitudinal asymmetries seen both in ground-based observations of sulfur emissions from the Io torus and in Voyager observations of Jovian auroral emissions are found to agree well with the predicted asymmetries.

Vasyliunas, V. M.; Dessler, A. J.

1981-01-01

75

Statistics of low-frequency plasma fluctuations in a simple magnetized torus  

Microsoft Academic Search

Statistical analysis is performed on time series of plasma potential and electron pressure fluctuations for two particular plasma states in a simple magnetized torus. In spite of the occurrence of cyclic trends in the signals, the analysis demonstrates the existence of long-range dependence on much longer time-scales than the plasma confinement time, and both Gaussian and non-Gaussian self-affinity is demonstrated

K. Rypdal; S. Ratynskaia

2003-01-01

76

Plasma–lithium interaction in the CDX-U spherical torus  

Microsoft Academic Search

Results on the interaction between plasma in the current drive experiment-upgrade (CDX-U) spherical torus and a liquid lithium limiter are reported. It is observed that macroscopic lithium droplets detach from the limiter head and fall towards the plasma core. However, no disruptions occurred during these discharges despite the fact that relatively large-scale blobs are observed entering the confined plasma. A

G. Y. Antar; R. P. Doerner; R. Kaita; R. Majeski; J. Spaleta; T. Munsat; B. Jones; R. Maingi; V. Soukhanovskii; H. Kugel; J. Timberlake; S. I. Krasheninnikov; S. C. Luckhardt; R. W. Conn

2002-01-01

77

Effect of plasma torus density variations on the morphology and brightness of the Io footprint  

NASA Astrophysics Data System (ADS)

develop a 2-D-layered model of the Io plasma torus to study the apparent "shutoff" of the Io footprint in 2007, when it disappeared beneath a region of diffuse emissions, roughly coincident with a massive eruption of Tvashtar Paterae. First, we investigate the effects of Io's location in the plasma torus and validate our model results against Hubble UV observations of the Io footprint. We are able to qualitatively reproduce variations in the morphology of the footprint due to Io's changing latitudinal location with respect to the center of the plasma torus, capturing the bright leading spot and the dimmer tail. Then, we consider the effects of an increase in the local plasma density on the brightness and morphology of the Io footprint. Our results show a correlation between a local density increase in the plasma torus and the dimming of the Io footprint as observed in 2007. In particular, we find that a local density enhancement at Io of fivefold compared to the nominal value is sufficient to produce the observed shutoff of the footprint.

Payan, A. P.; Rajendar, A.; Paty, C. S.; Crary, F.

2014-05-01

78

Space and ground-based multi-wavelength observing campaign of Jupiter's aurora and the Io Plasma Torus  

NASA Astrophysics Data System (ADS)

The EXCEED EUV spectrograph (55 - 145 nm) on-board the Japanese mission Sprint-A, due for launch into low Earth orbit in August 2013, will be dedicated to the study of the tenuous plasma surrounding planets in our solar system. A target of special interest will be Jupiter and its environment, and the emission from the Io Plasma Torus (IPT) in particular. A systematic campaign of observations of Jupiter and the IPT is planned over the period Oct. 2013 - March 2014. This is a unique opportunity to explore the possible links between the IPT emission distribution, the strength and character of Jupiter's auroral emissions and the conditions of the solar wind. Hence, concurrently with the EXCEED observations, a large multi-wavelength campaign has been organised to exploit this unique opportunity of gathering important diagnostic data on the complex array of physical processes taking place in Jupiter's environment. This campaign includes (this is by no means a complete list) approved FUV imaging and spectroscopy of Jupiter's Northern aurora with HSTSTIS (PI: Sarah Badman), Kitt Peak 4m visible spectroscopy of the IPT (PI: Sarah Badman), Gemini observations of Jupiter H3+ (4 µm) aurora (PI: Melin), submitted proposals for HST-STIS FUV observations of Jupiter's Southern aurora, Io and Ganymede's footprints (PI: Bonfond), Chandra and XMM-Newton pointings of Jupiter and the IPT (PI: Kraft), Suzaku observations of diffuse X-rays from the Jovian inner magnetosphere (PI: Ezoe); in addition, ground based observations with IRTF, Subaru and other facilities are planned. This talk will review the motivation for this vaste coordinated observing campaign, and the science that we expect to draw from it: essentially a better understanding of how the Jupiter's system works.

Branduardi-Raymont, G.; Yoshikawa, I.; Badman, S.

2013-09-01

79

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

80

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

Microsoft Academic Search

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

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

2005-01-01

81

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

NASA Technical Reports Server (NTRS)

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.

1982-01-01

82

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

83

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

84

The source of Jovian auroral hiss observed by Voyager 1  

NASA Technical Reports Server (NTRS)

Observations of auroral hiss obtained from the Voyager 1 encounter with Jupiter have been reanalyzed. The Jovian auroral hiss was observed near the inner boundary of the warm Io torus and has a low-frequency cutoff caused by propagation near the resonance cone. A simple ray tracing procedure using an offset tilted dipole of the Jovian magnetic field is used to determine possible source locations. The results obtained are consistent with two sources located symmetrically with respect to the centrifugal equator along an L shell (L approximately = 5.59) that is coincident with the boundary between the hot and cold regions of the Io torus and is located just inward of the ribbon feature observed from Earth. The distance of the sources from the centrifugal equator is approximately 0.58 +/- 0.01 R(sub J). Based on the similarity to terrestrial auroral hiss, the Jovian is auroral hiss is believed to be generated by beams of low energy (approximately tens to thousands of eV) electrons. The low-frequency cutoff of the auroral hiss suggests that the electrons are accelerated near the inferred source region, possibly by parallel electric fields similar to those existing in the terrestrial auroral regions. A field-aligned current is inferred to exist at L shells just inward of the plasma ribbon. A possible mechanism for driving this current is discussed.

Morgan, D. D.; Gurnett, D. A.; Kurth, W. S.; Bagenal, F.

1994-01-01

85

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

86

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

87

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

88

SO/sub 2/ ionization and dissociation in the Io plasma torus  

SciTech Connect

Escape of SO/sub 2/ from Io may be driven by corotating ion impact and energy deposition by the Io flux tube current. The yield of O I per SO/sub 2/ is estimated in steady state ionization and dissociation of SO/sub 2/. An average SO/sub 2/ injection rate of 10/sup 28/ s/sup -1/ is found to be consistent with O I observations in the hot plasma torus. The average densities of S I and SO/sub 2/ are estimated, but the expected oxygen to sulfur ion ratios from SO/sub 2/ ionization and dissociation are uncertain. There is substantial loss of neutrals from charge exchange and electron impact on molecular and negative ions (Io plasma torus, mass injection, neutral densities).

Cheng, A.F.

1982-07-01

89

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

90

The probability distributions of S/+/ gyrospeeds in the Io torus  

NASA Technical Reports Server (NTRS)

The first detailed thermal speed probability distribution for a Jovian plasma ion is presented. The distribution of heavy ion thermal speeds appears to be highly significant for an evaluation of the processes by which the particle and energy budgets of the Io plasma torus are maintained. Attention is given to the measurement, reduction, and analysis procedures which yield the reported probability distribution. A kinetic energy inventory of the Jovian plasma heavy ion component can be obtained from high-resolution, high-precision spectrophotometry of emission lines. The current S(+) study finds that detection of the line wings results in a mean energy (approximately 60 eV) which is higher by a factor of approximately 10 than is implied by the line core. This illustrates that a dispersive measurement may provide only a lower limit to the kinetic energy content.

Brown, R. A.

1982-01-01

91

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

92

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

93

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

E-print Network

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 ratio of S II is 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 hours--1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System IV period defined by Brown (1995). 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 5-25% 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 ratio (minimum S IV mixing ratio) is aligned with a System III longitude of ~200 +/- 15 degrees, 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.

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

2005-08-01

94

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

95

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

SciTech Connect

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

Kugel, H. [Princeton Plasma Physics Laboratory (PPPL); Bell, M. [Princeton Plasma Physics Laboratory (PPPL); Ahn, J W [University of California, San Diego; Bush, C.E. [Oak Ridge National Laboratory (ORNL); Maingi, R. [Oak Ridge National Laboratory (ORNL)

2008-01-01

96

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

97

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

SciTech Connect

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

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

2008-05-15

98

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

99

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

100

National Spherical Torus Experiment Real Time Plasma Control Data Acquisition Hardware  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is currently providing researchers data on low aspect-ratio toroidal plasmas. NSTX's Plasma Control System adjusts the firing angles of thyristor rectifier power supplies, in real time, to control plasma position, shape and density. A Data Acquisition system comprised of off-the-shelf and custom hardware provides the magnetic diagnostics data required in calculating firing angles. This VERSAmodule Eurocard (VME) bus-based system utilizes Front Panel Data Port (FPDP) for high-speed data transfer. Data coming from physically different locations is referenced to several different ground potentials necessitating the need for a custom FPDP multiplexer. This paper discusses the data acquisition system configuration, the in-house designed 4-to-1 FPDP Input Multiplexing Module (FIMM), and future expansion plans.

R.J. Marsala; J. Schneider

2002-08-05

101

Modeling of Jovian Hectometric Radiation Source Locations: Ulysses Observations  

NASA Technical Reports Server (NTRS)

The Unified Radio and Plasma Wave (URAP) experiment on Ulysses has provided unique high latitude measurements of Jovian hectometric radiation (HOM) during its encounter with Jupiter in February 1992. URAP was the first radio instrument in the Jovian environment with radio direction-finding capability, which was previously used to determine the HOM source locations in the Jovian magnetosphere. These initial source location determinations were based on several assumptions, including the neglect of refractive effects, which may be tested. We have, for the first time, combined the measured incident ray-direction at the spacecraft with a model magnetosphere to directly trace the rays back to the HOM source. We concentrate on the observations of HOM from high northern latitudes when Ulysses was at distances less than 15 R(sub j). The three- dimensional ray-tracing calculations presented here indicate that the HOM sources probably lie on L shells in the range 3 less than or approximately equal to L less than 7 (tilted dipole magnetic field model) consistent with previous determinations that ignored the effects of refraction. The ray-tracing results, however, indicate that wave refraction due to the Io torus and the magnetic field can significantly influence the precise source location. We show that constraints on the locations imposed by the gyroemission mechanism suggest that the lo torus density may have experienced temporal and/or spatial fluctuations during the Ulysses observations of HOM. Finally, in the cold plasma approximation we demonstrate that even if the emission were nearly linearly polarized near the source region, almost circular polarization will be observed at Ulysses, in agreement with observations.

Menietti, J. D.; Reiner, M. J.

1996-01-01

102

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

103

First Studies of Pure Electron Plasmas in the Columbia Non-neutral Torus  

SciTech Connect

The first studies of pure electron plasmas confined on magnetic surfaces in the Columbia Non-neutral Torus are overviewed. The electron plasma is created by a thermionic emitter filament and similar filaments mounted on ceramic rods are used as Langmuir and emissive probes. The equilibrium density, temperature and potential profiles are experimentally measured. Numerical calculations of the equilibrium agree well with measurements and also predict a toroidal density variation of a factor of four. The confinement time is found to decrease with increased neutral pressure and emitter bias voltage, and it is presently limited to 20 ms by the insulated emitter and probe rods. A retractable electron emitter and external diagnostics will be used to determine the confinement time in the absence of rods. Ion driven instabilities are observed at high neutral pressure and low magnetic field strength. Further research of these instabilities will be carried out.

Berkery, J. W.; Pedersen, T. S.; Kremer, J. P.; Lefrancois, R. G.; Marksteiner, Q. R.; Boozer, A. H. [Dept. of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027 (United States); Mynick, H. E.; Pomphrey, N.; Reiersen, W.; Dahlgreen, F. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Himura, H. [Kyoto Institute of Technology, Kyoto (Japan); Sarasola, X. [CIEMAT, Madrid (Spain)

2006-10-18

104

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

105

Demonstration of low recycling on a spherical torus with lithium plasma facing components  

NASA Astrophysics Data System (ADS)

Plasma facing components (PFCs) play an important role in the performance of fusion research devices. In order to investigate the effects of liquid lithium plasma facing components on plasma performance, the Current Drive Experiment - Upgrade (CDX-U) spherical torus installed a toroidal liquid lithium tray limiter and an electron beam lithium evaporation system. Measurements of the effective particle confinement time, t*p , were performed by using transient gas puffing and observing the time dependence of the plasma density with microwave interferometry. A significant drop in t*p was observed in the discharges with liquid lithium PFCs, which is consistent with increased particle pump-put. Spectroscopic measurements also support an overall decrease in the particle flux to the plasma. In order to look at the global particle balance in the CDX-U discharges with liquid lithium PFCs, modeling of the plasma discharges with DEGAS2, a neutral particle transport code, has been performed. Utilizing the available spectroscopic data, this modeling allows a calculation of a global recycling coefficient ( R) for both standard discharges and ones with liquid lithium PFCs. The modeling shows a significant reduction in recycling, with R = 0.75 in the liquid lithium case. An analysis of the impact of light reflections on the spectroscopic measurements was also performed.

Gray, Timothy Garrett

106

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

107

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

108

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

SciTech Connect

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

Shaing, K. C.

2009-07-09

109

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

110

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

111

Effect of plasma shaping on performance in the national spherical torus experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving beta(t)similar to 40%. Precise plasma shape control has been achieved on NSTX using real-time equilibrium reconstruction. NSTX has simultaneously achieved elongation kappa similar to 2.8 and triangularity delta similar to 0.8. Ideal MHD theory predicts increased stability at high values of shaping factor S equivalent to q(95)I(p)/(aB(t)), which has been observed at large values of the S similar to 37[MA/(m center dot T)] on NSTX. The behavior of ELMs is observed to depend on plasma shape. A description of the ELM regimes attained as shape is varied will be presented. Increased shaping is predicted to increase the bootstrap fraction at fixed I-p. The achievement of strong shaping has enabled operation with 1 s pulses with I-p=1 MA, and for 1.6 s for I-p=700 kA. Analysis of the noninductive current fraction as well as empirical analysis of the achievable plasma pulse length as elongation is varied will be presented. Data are presented showing a reduction in peak divertor heat load due to increasing in flux expansion.

Gates, D. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL

2006-01-01

112

Two-fluid low-collisionality equilibrium model and application to spherical torus plasmas  

SciTech Connect

A two-fluid equilibrium model with low-collisionality is developed including a new flow-singularity condition. This description is applied to the rapidly rotating, high-performance National Spherical Torus eXperiment (NSTX) [Peng et al., Plasma Phys. Controlled Fusion 47, B263 (2005)]. The model replicates the primary features of an example equilibrium, such as the profiles of electron and ion temperatures, density, and toroidal flow of an example equilibrium. This is the first full-two-fluid computation of two-dimensional equilibrium with rapid ion flow near the thermal speed. In consequence several important features emerge: (1) the ion toroidal current exceeds the toroidal plasma current as a result of electron rotational flow reversal; (2) the ion flow in the core region is roughly parallel to the magnetic field, i.e., the ion fluid in the core is nearly force free; (3) E+u(i) x B differs considerably from zero, so that the E x B drift fails to describe the ion and electron flows perpendicular to the magnetic field. Simpler models of equilibrium, such as the static equilibrium or the one-fluid flowing model, cannot replicate these properties. These results suggest that the rapidly rotating, high-performance NSTX plasma may represent a new parameter regime of fusion plasmas.

Ishida, A. [Niigata University, Niigata, Japan; Steinhauer, Steinhauer L. C. [University of Washington; Peng, Yueng Kay Martin [ORNL

2010-01-01

113

Fusion engineering and plasma science conditions for a spherical torus component test facility  

SciTech Connect

A broadly based study of the fusion engineering and plasma science conditions of a Component Test Facility (CTF),1 using the Spherical Torus or Spherical Tokamak (ST) configuration,2 have been carried out. The chamber systems testing conditions in a CTF are characterized by high fusion neutron fluxes n > 4.4 1013 n/s/cm2, over size scales > 105 cm2 and depth scales > 50 cm, delivering > 3 accumulated displacement per atom (dpa) per year.3 The desired chamber conditions can be provided by a CTF with R0 = 1.2 m, A = 1.5, elongation ~ 3, Ip ~ 9 MA, BT ~ 2.5 T, producing a driven fusion burn using 36 MW of combined neutral beam and RF power. Relatively robust ST plasma conditions are adequate, which have been shown achievable4 without active feedback manipulation of the MHD modes. The ST CTF will test the single-turn, copper alloy center leg for the toroidal field coil without an induction solenoid and neutron shielding, and require physics data on solenoid-free plasma current initiation, ramp-up, and sustainment to multiple MA level. A new systems code that combines the key required plasma and engineering science conditions of CTF has been prepared and utilized as part of this study. The results show high potential for a family of lower-cost CTF devices to suit a variety of fusion engineering science test missions.

Peng, Yueng Kay Martin [ORNL

2005-01-01

114

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

115

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

E-print Network

We report the discovery of soft (0.25--2 keV) x-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (>10 keV) H, O, and S ions from the region of the IPT seems the likely source of the x-ray emission from the Galilean satellites. According to our estimates, fluorescent x-ray emission excited by solar x-rays, even during flares from the active Sun, charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora and cometary x-ray emission, and ion stripping by dust grains fail to account for the observed emission. On the other hand, bremsstrahlung emission of soft X-rays from non-thermal electrons in the few hundred to few thousand eV range may account for a substantial fraction of the observed x-ray flux from the IPT.

Elsner, R F; Waite, J H; Crary, F J; Howell, R R; Johnson, R E; Ford, P G; Metzger, A E; Hurley, K C; Feigelson, E D; Garmire, G P; Bhardwaj, A I; Grodent, D C; Majeed, T; Tennant, A F; Weisskopf, M C; Elsner, Ronald F.; Crary, Frank J.; Howell, Robert R.; Johnson, Robert E.; Ford, Peter G.; Metzger, Albert E.; Hurley, Kevin C.; Feigelson, Eric D.; Garmire, Gordon P.; Bhardwaj, Anil; Grodent, Denis C.; Majeed, Tariq; Tennant, Allyn F.; Weisskop, Martin C.

2002-01-01

116

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

E-print Network

We report the discovery of soft (0.25--2 keV) x-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (>10 keV) H, O, and S ions from the region of the IPT seems the likely source of the x-ray emission from the Galilean satellites. According to our estimates, fluorescent x-ray emission excited by solar x-rays, even during flares from the active Sun, charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora and cometary x-ray emission, and ion stripping by dust grains fail to account for the observed emission. On the other hand, bremsstrahlung emission of soft X-rays from non-thermal electrons in the few hundred to few thousand eV range may account for a substantial fraction of the observed x-ray flux from the IPT.

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

2002-02-14

117

Doppler line profiles measurement of the Jovian Lyman Alpha emission with OAO-C  

NASA Technical Reports Server (NTRS)

Observation of Jupiter made with the high resolution ultraviolet spectrometer of the Orbiting Astronomical Observatory copernicus in April and May, 1980, yield a Jovian Lyman alpha emission intensity of 7 + or 2.5 RR. This indicates a decrease by about a factor of two since the Voyager ultraviolet spectrometer measurements, nearly a year earlier. An unusually high column abundance of hydrogen atoms above the methane homopause at the Voyager epoch is indicated. Since the auroral charged particle bombardment of molecular hydrogen is expected to contribute significantly to the global population of the hydrogen atoms, it is suggested that at the time of the Voyager Jupiter encounter unusually high auroral activity existed, perhaps d to the high concentration of the Io plasma torus. The temporal variation of the Saturn lyman alpha emission, when contrasted with the Jovian data, reveals that the auroral processes are not nearly as important in determining the Saturn Lyman alpha intensity in the nonauroral region.

Barker, E. S.; Cochran, W. D.; Smith, H. J.

1982-01-01

118

An interpretation of the broadband VLF waves near the Io torus as observed by Ulysses  

NASA Technical Reports Server (NTRS)

The requirements for the Ulysses trajectory to attain high ecliptic latitudes using a Jovian gravitational assist resulted in a fortuitous passage through the Io torus region. Specifically, the spacecraft spent many hours at latitudes just above the torus. During this time the low-frequency cutoff of an ordinary mode (O mode) emission allowed a determination of the local electron plasma frequency (i.e., electron density) along the northern flank of the torus. Also, near a Jovian System III longitude of 100 deg, the spacecraft flew past a set of active field lines that have been previously identified to be associated with the hectometric generation region. During the passage, Ulysses observed a newly discovered O mode component and a whistler mode emission similar to that observed by Voyager 1 13 years previously. All of the broadband VLF emissions imply the presence of a particular population of electrons. We suggest that broadband VLF emissions can be used as a `particle detector' to qualitatively measure the electron plasma conditions in the torus region and identify active regions.

Farrell, W. M.; Macdowell, R. J.; Hess, R. A.; Kaiser, M. L.; Desch, M. D.; Stone, R. G.

1993-01-01

119

Characterization of the plasma current quench during disruptions in the National Spherical Torus Experiment  

SciTech Connect

A detailed analysis of the plasma current quench in the National Spherical Torus Experiment [M.Ono, et al Nuclear Fusion 40, 557 (2000)] is presented. The fastest current quenches are fit better by a linear waveform than an exponential one. Area-normalized current quench times down to .4 msec/m2 have been observed, compared to the minimum of 1.7 msec/m2 recommendation based on conventional aspect ratio tokamaks; as noted in previous ITPA studies, the difference can be explained by the reduced self-inductance at low aspect ratio and high-elongation. The maximum instantaneous dIp/dt is often many times larger than the mean quench rate, and the plasma current before the disruption is often substantially less than the flat-top value. The poloidal field time-derivative during the disruption, which is directly responsible for driving eddy currents, has been recorded at various locations around the vessel. The Ip quench rate, plasma motion, and magnetic geometry all play important roles in determining the rate of poloidal field change.

Gerhardt, S.P., Menard, J.E., and the NSTX Research Team

2008-12-17

120

High-harmonic fast magnetosonic wave coupling, propagation, and heating in a spherical torus plasma  

SciTech Connect

A novel rotatable two-strap antenna has been installed in the current drive experiment upgrade (CDX-U) [T. Jones, Ph.D. thesis, Princeton University (1995)] in order to investigate high-harmonic fast wave coupling, propagation, and electron heating as a function of strap angle and strap phasing in a spherical torus plasma. Radio-frequency-driven sheath effects are found to fit antenna loading trends at very low power and become negligible above a few kilowatts. At sufficiently high power, the measured coupling efficiency as a function of strap angle is found to agree favorably with cold plasma wave theory. Far-forward microwave scattering from wave-induced density fluctuations in the plasma core tracks the predicted fast wave loading as the antenna is rotated. Signs of electron heating during rf power injection have been observed in CDX-U with central Thomson scattering, impurity ion spectroscopy, and Langmuir probes. While these initial results appear promising, damping of the fast wave on thermal ions at high ion-cyclotron-harmonic number may compete with electron damping at sufficiently high ion {beta}{emdash}possibly resulting in a significantly reduced current drive efficiency and production of a fast ion population. Preliminary results from ray-tracing calculations which include these ion damping effects are presented. {copyright} {ital 1999 American Institute of Physics.}

Menard, J.; Majeski, R.; Kaita, R.; Ono, M.; Munsat, T. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Stutman, D.; Finkenthal, M. [Johns Hopkins University, Baltimore, Maryland 21205 (United States)] [Johns Hopkins University, Baltimore, Maryland 21205 (United States)

1999-05-01

121

Compact torus  

SciTech Connect

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

Furth, H.P.

1980-10-01

122

Depleted Flux Tubes in the Jovian Magnetosphere  

Microsoft Academic Search

Thin magnetic flux tubes with enhanced field strengths are found in the Io torus. The size of the increase in the magnetic field strength is comparable to that expected if the tubes contained no Io torus plasma. The tubes are found outside the orbit of Io but not inside. Since empty flux tubes should be buoyant in the Io torus

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

2003-01-01

123

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

124

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

SciTech Connect

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

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

2007-06-15

125

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

SciTech Connect

The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving {beta}{sub t}{approx}40%. Precise plasma shape control has been achieved on NSTX using real-time equilibrium reconstruction. NSTX has simultaneously achieved elongation {kappa}{approx}2.8 and triangularity {delta}{approx}0.8. Ideal MHD theory predicts increased stability at high values of shaping factor S{identical_to}q{sub 95}I{sub p}/(aB{sub t}), which has been observed at large values of the S{approx}37[MA/(m{center_dot}T)] on NSTX. The behavior of ELMs is observed to depend on plasma shape. A description of the ELM regimes attained as shape is varied will be presented. Increased shaping is predicted to increase the bootstrap fraction at fixed I{sub p}. The achievement of strong shaping has enabled operation with 1 s pulses with I{sub p}=1 MA, and for 1.6 s for I{sub p}=700 kA. Analysis of the noninductive current fraction as well as empirical analysis of the achievable plasma pulse length as elongation is varied will be presented. Data are presented showing a reduction in peak divertor heat load due to increasing in flux expansion.

Gates, D.A.; Menard, J.; Kaye, S.; Taylor, G.; Wilson, J.R.; Bell, M.G.; Bell, R.E.; Bernabei, S.; Biewer, T.; Blanchard, W.; Darrow, D.S.; Davis, W.; Diem, S.; Foley, J.; Fredrickson, E.D.; Hatcher, R.E.; Hill, K.; Hosea, J.C.; Johnson, D.W.; Kaita, R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] (and others)

2006-05-15

126

Fusion Engineering and Plasma Science Conditions of Spherical Torus Component Test Facility  

SciTech Connect

A broadly based study of the fusion engineering and plasma science conditions of a Component Test Facility (CTF), using the Spherical Torus or Spherical Tokamak (ST) configuration, have been carried out. The chamber systems testing conditions in a CTF are characterized by high fusion neutron fluxes {gamma}{sub n} > 4.4 x 10{sup 13} n/s/cm{sup 2}, over size scales > 10{sup 5} cm{sup 2} and depth scales > 50 cm, delivering > 3 accumulated displacement per atom (dpa) per year. The desired chamber conditions can be provided by a CTF with R{sub 0} 1.2 m, A = 1.5, elongation {approx} 3, I{sub p} {approx} 9 MA, B{sub T} {approx} 2.5 T, producing a driven fusion burn using 36 MW of combined neutral beam and RF power. Relatively robust ST plasma conditions are adequate, which have been shown achievable without active feedback manipulation of the MHD modes. The ST CTF will test the single-turn, copper alloy center leg for the toroidal field coil without an induction solenoid and neutron shielding, and require physics data on solenoid-free plasma current initiation, ramp-up, and sustainment to multiple MA level. A new systems code that combines the key required plasma and engineering science conditions of CTF has been prepared and utilized as part of this study. The results show high potential for a family of lower-cost CTF devices to suit a variety of fusion engineering science test missions.

Peng, Y.-K.M. [Oak Ridge National Laboratory (United States); Neumeyer, C.A. [Princeton Plasma Physics Laboratory (United States); Fogarty, P.J. [Oak Ridge National Laboratory (United States)] (and others)

2005-04-15

127

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

128

Plasma IMS Composition Measurements for Europa, Ganymede, and the Jovian System  

NASA Technical Reports Server (NTRS)

NASA and ESA are now planning a reduced version of the joint Europa Jupiter System Mission (EJSM), potentially including a radically descoped Jupiter Europa Orbiter (JEO) but still with magnetometer and plasma instruments. Similar field and plasma instrumentation would also reside on ESA's Jupiter Ganymede Orbiter (JGO), which conceivably could carry out multiple flybys of Europa before entering orbit at Ganymede. We are developing the 3D Ion Mass Spectrometer (IMS) designed to measure both major and minor ion species within the high radiation environment of Jupiter's magnetosphere and the icy Galilean moons. The IMS covers the energy range from 10 eV to 30 keY, wide field-of-view (FOV) capability and 10-60 sec time resolution for major ions. This instrument has two main goals: 1) measure the plasma interaction between Europa and Jupiter's magnetosphere and 2) infer the global surface composition to trace elemental and significant isotopic levels; these goals are also applicable for in-situ measurements at Ganymede and Callisto, and remotely everywhere via the iogenic plasma for 10. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa's sub-surface ocean, while the second goal gives information about transfer of material between the Galilean moons, e.g. mainly from 10 to the other moons, and further allows detection of oceanic materials emergent to the moon surfaces from subsurface layers putatively including salt water oceans. Outgassed exospheric materials are probed by the IMS by measuring pickup ions accelerated up to spacecraft altitudes of approximately 100-200 km in electric fields extending through the local magnetospheric environment and moon exosphere to the surface. Our 3D hybrid kinetic model of the moon-magnetosphere interaction is used to construct a global model of electric and magnetic fields for tracing of pickup ion trajectories back to the sources at approximate surface resolution of 100 km. We show that Europa's exospheric ionosphere is dominated by pickup ions with energies of 100-1000 eV. We also expect field aligned polar ion outflows driven by ionospheric electrons via the polarization electric field at Europa; the IMS will observe such outflows and thus sample the ionosphere below spacecraft orbit altitude approximately 100 km. Based on previous Ganymede studies, we also comment on IMS applications to a Ganymede orbiter. The IMS and the Europa interaction model are respectively being developed with support from NASA's Astrobiology Instrument Development (ASTID) and Outer Planets Research (OPR) programs.

Sittler, E. C., Jr.; Cooper, J. F.; Hartle, R. E.; Paterson, W. R.; Christian, E. R.; Lipatov, A. S.; Mahaffy, P R.; Paschalidis, N.; Sarantos, M.; Coplan, M. A.; Cassidy, T. A.; Wurz, P.

2011-01-01

129

Plasma IMS Composition Measurements for Europa, Ganymede, and the Jovian Systems  

NASA Technical Reports Server (NTRS)

NASA and ESA are now planning a reduced version of the joint Europa Jupiter System Mission (EJSM), potentially including a radically descoped Jupiter Europa Orbiter (JEO) but still with magnetometer and plasma instruments. Similar field and plasma instrumentation would also reside on ESA's Jupiter Ganymede Orbiter (JGO), which conceivably could carry out multiple flybys of Europa before entering orbit at Ganymede. We are developing the 3D Ion Mass Spectrometer (IMS) designed to measure both major and minor ion species within the high radiation environment of Jupiter s magnetosphere and the icy Galilean moons. The IMS covers the energy range from 10 eV to 30 keV, wide field-ofview (FOV) capability and 10-60 sec time resolution for major ions. This instrument has two main goals: 1) measure the plasma interaction between Europa and Jupiter s magnetosphere and 2) infer the global surface composition to trace elemental and significant isotopic levels; these goals are also applicable for in-situ measurements at Ganymede and Callisto, and remotely everywhere via the iogenic plasma for Io. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa's sub-surface ocean, while the second goal gives information about transfer of material between the Galilean moons, e.g. mainly from Io to the other moons, and further allows detection of oceanic materials emergent to the moon surfaces from subsurface layers putatively including salt water oceans. Outgassed exospheric materials are probed by the IMS by measuring pickup ions accelerated up to spacecraft altitudes of approximately 100-200 km in electric fields extending through the local magnetospheric environment and moon exosphere to the surface. Our 3D hybrid kinetic model of the moon-magnetosphere interaction is used to construct a global model of electric and magnetic fields for tracing of pickup ion trajectories back to the sources at approximate surface resolution of 100 km. We show that Europa's exospheric ionosphere is dominated by pickup ions with energies of 100-1000 eV. We also expect field aligned polar ion outflows driven by ionospheric electrons via the polarization electric field at Europa; the IMS will observe such outflows and thus sample the ionosphere below spacecraft orbit altitude approximately 100 km. Based on previous Ganymede studies, we also comment on IMS applications to a Ganymede orbiter. The IMS and the Europa interaction model are respectively being developed with support from NASA's Astrobiology Instrument Development (ASTID) and Outer Planets Research (OPR) programs.

Sittler, E.; Cooper, J.; Hartle, R.; Paterson ,W.; Christian, E.; Mahaffy, P.; Paschalidis, N.; Lipatov, A.; Sarantos, M.; Coplan, M.; Cassidy, T.; Wurz, P.

2011-01-01

130

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.

131

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

132

Low-energy charged particle observations in the 5-20 Jupiter-radius region of the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

Ion (greater than 0.5 MeV) and electron (greater than 30 keV) measurements made by the low-energy charged particle instrument during the Voyager 1 and 2 traversals of the 5-20 Jupiter-radius region of the Jovian magnetosphere are presented. The spatial morphology of particle intensities, energy spectra, and composition is emphasized. Diffusive radial transport is also discussed. The Jovian magnetosphere seemed to be much more disturbed during the Voyager 2 passage than during that of Voyager 1. Significant inbound-outbound asymmetries of the radial profiles of intensities are observed; an appropriate magnetic field model to provide closure has not been found. Low-energy electrons are not enhanced or depleted in the Io torus region except at the inner edge, about 5.2 Jupiter-radius, where they sharply decrease. This may be due to enhanced electron loss associated with a region of increased plasma density.

Armstrong, T. P.; Paonessa, M. T.; Brandon, S. T.; Krimigis, S. M.; Lanzerotti, L. J.

1981-01-01

133

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

134

Implications of depleted flux tubes in the Jovian magnetosphere  

Microsoft Academic Search

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

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

2000-01-01

135

On the nature of S II emission from Jupiter's hot plasma torus  

NASA Technical Reports Server (NTRS)

An effective electron temperature T(e) of 80,000 K is indicated by the Voyager 1 encounter Jupiter hot torus emission rates in the 6731, 1256, 911 and reclassified 765 A transitions of S II. A set of 53 measurements of the S II red line doublet obtained at 5.9 Jupiter radii shows strong, irregular fluctuations in intensity, but no variation in the line ratio. At this distance from Jupiter, the torus is found to be longitudinally uniform in density; this is consonant with Voyager UVS findings, but contrary to magnetic anomaly model predictions. It is suggested that presently unidentified ion-ion and/or iron-atom reactions are responsible for the S II component irregular variations, in view of the fact that electron properties are regular and variable only over a small range in the hot torus at 5.9 Jupiter radii.

Brown, R. A.; Shemansky, D. E.

1982-01-01

136

Interpretation of core localized Alfvén eigenmodes in DIII-D and Joint European Torus reversed magnetic shear plasmas  

NASA Astrophysics Data System (ADS)

Reversed shear Alfvén eigenmodes (RSAE) that were observed in the Joint European Torus (JET) [P. H. Rebut and B. E. Keen, Fusion Technol.11, 13 (1987)] and DIII-D [J. L. Luxon, Nucl. Fusion42, 614 (2002)] are studied with the ideal magnetohydrodynamic code NOVA-K [C. Z. Cheng, Phys. Rep.211, 1 (1992)]. It was found that the frequency behavior of the RSAEs can be described accurately by the NOVA-K code when plasma compressibility effects and toroidal plasma rotation are taken into account. For the mode activity on JET, the calculated drive exceeds the mode damping rate, consistent with experimental observations, while on DIII-D the growth rate from neutral beam ions for modes with high toroidal mode numbers is insufficient to account for the excitation of the modes and a major part of the drive comes from the background plasma.

Kramer, G. J.; Nazikian, R.; Alper, B.; de Baar, M.; Berk, H. L.; Fu, G.-Y.; Gorelenkov, N. N.; McKee, G.; Pinches, S. D.; Rhodes, T. L.; Sharapov, S. E.; Solomon, W. M.; van Zeeland, M. A.; Jet Efda Contributors

2006-05-01

137

Depleted magnetic flux tubes as probes of the Io torus plasma  

Microsoft Academic Search

On the initial pass by Io the Galileo spacecraft detected thin tubes of magnetic flux that had stronger fields than their surroundings indicating that they were depleted in their energy content. These tubes have not been seen on every return to the Io torus, only on the passes with the longest stretches of data. They are also not observed much

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

2001-01-01

138

Ion Heating and Containment in the NASA Lewis Bumpy Torus Plasma.  

National Technical Information Service (NTIS)

Experimental observations have been made during steady state operation of a torus experiment at input powers up to 150 kilowatts in deuterium and helium gas. The steady state ion heating method utilizes a modified Penning discharge operated in a bumpy tor...

J. R. Roth

1974-01-01

139

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

140

Single and multiple ionization of sulfur atoms by electron impact. [in Io plasma torus  

NASA Technical Reports Server (NTRS)

In 1979 significant concentrations of singly and multiply charged sulfur ions were observed in the Io torus. Attempts to model these observations revealed a need for new fundamental cross section data. In response, laboratory measurements of the cross-sections for single, double, triple and quadruple ionization of sulfur atoms by electron impact are presented for collision energies from threshold to 500 eV.

Ziegler, D. L.; Newman, J. H.; Goeller, L. N.; Smith, K. A.; Stebbings, R. F.

1982-01-01

141

The Jovian aurora: Electron or ion precipitation  

NASA Technical Reports Server (NTRS)

High signal-to-noise spectra of the Jovian aurora at UV wavelengths obtained using the International Ultraviolet Explorer Observatory (including the brightest Jovian aurora observed to date) set strigent upper limits for sulfur and oxygen emissions, which would be associated with the precipitation of energetic heavy ions in the upper Jovian atmosphere if they were solely responsible for Jovian auroral processes. Model calculations of heavy ion precipitation and corresponding estimates of the associated sulfur and oxygen UV emissions previously carried out suggest emission values for 1304 A OI emission that are at least 30 times larger than the upper limit values set by the IUE observations reported. On the other hand the observed (feature of SII at 1256 A of 2 kR) is quite comparable to the theoretically predicted emission intensity. Taken together these observations and calculations suggest that electron as well as ion precipitation play a role in Jovian auroral processes. In light of earlier X-ray observations and in-situ plasma observations that suggest energetic heavy ion precipitation in the Jovian auroral zone, a scenario is suggested where heavy ion auroral energy deposition is concentrated at altitudes below the homopause. Electrons with energies of 10 to 30 keV are responsible for the bulk of the observable UV and EUV emissions since they deposit their energy above the methane absorbing layer defined by the homopause.

Waite, J. H., Jr.; Clarke, J. T.; Cravens, T. E.

1986-01-01

142

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

143

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

SciTech Connect

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

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

2004-12-01

144

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

NASA Astrophysics Data System (ADS)

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

Xu, Y. H.; Jachmich, S.; Weynants, R. R.; Huber, A.; Unterberg, B.; Samm, U.

2004-12-01

145

The source location of certain Jovian decametric radio emissions  

NASA Technical Reports Server (NTRS)

Evidence is presented which supports the concept that certain of the Jovian decametric radio waves originate as northern hemisphere extraordinary mode cyclotron emissions. The wave signals received by Voyager 1 near 10 MHz shortly after the closest approach to Jupiter were found to exhibit cusps in the fringe pattern which can be attributed to Faraday rotation in the Io plasma torus. At nearly the same time, the wave polarization near 1 MHz was found to exhibit a sudden reversal of its rotation sense, indicating that the wave path for those frequencies had also become perpendicular to the magnetic field at the spacecraft. It was determined that the waves came from the northern hemisphere at progressively lower altitudes with increasing frequency, and if the source is assumed to be associated with an L = 6 field line, the emission appears to have occurred near the source cyclotron frequency somewhere in the local midnight sector. The evidence indicates that the source is at the Io flux tube and that the emitted wave mode must have been extraordinary. In addition, the emitted wave polarization must have been substantially noncircular which would require a low plasma density near the source, much like that which occurs with auroral kilometric radiation at the earth.

Calvert, W.

1983-01-01

146

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

NASA Astrophysics Data System (ADS)

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

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

1999-12-01

147

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

E-print Network

by Kurth et al. [1989] using the Voyager plasma wave wideband instrument [Scarf and Gurnett, 1977 of many Jovian plasma wave and radio emissions. One of these emissions is Jovian type III radio emissions); 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 6984 Radio Science: Waves in plasma

Gurnett, Donald A.

148

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

149

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

150

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

151

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

152

Effects of large area liquid lithium limiters on spherical torus plasmas  

NASA Astrophysics Data System (ADS)

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 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.; Majeski, 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. P.; Antar, G.; Doerner, R.; Luckhardt, S.; Baldwin, M.; Conn, R. W.; Maingi, R.; Menon, M.; Causey, R.; Buchenauer, D.; Ulrickson, M.; Jones, B.; Rodgers, D.

2005-03-01

153

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

154

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

155

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 analyse error fields, to measure error-field amplification and to detect resistive wall modes (RWMs) 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 favourable 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 the 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 x 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.

Menard, J. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Gates, D.A. [Princeton Plasma Physics Laboratory (PPPL); Gerhardt, S.P. [Princeton Plasma Physics Laboratory (PPPL); Park, J.-K. [Princeton Plasma Physics Laboratory (PPPL); Sabbagh, S. A. [Columbia University; Berkery, J.W. [Columbia University; Egan, A. [University of Pennsylvania; Kallman, J. [Princeton Plasma Physics Laboratory (PPPL); Kaye, S. M. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Liu, Y. Q. [Culham Science Center, Abington, UK; Sontag, Aaron C [ORNL; Swanson, D. [Princeton Plasma Physics Laboratory (PPPL); Yuh, H. [Nova Photonics; Zhu, W. [Credit Suisse, New York, NY

2010-01-01

156

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

157

Observations of Reduced Electron Gyro-scale Fluctuations in National Spherical Torus Experiment H-mode Plasmas with Large E × B Flow Shear  

SciTech Connect

Electron gyro-scale fluctuation measurements in National Spherical Torus Experiment (NSTX) H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temper- ature gradient (ETG) turbulence. Large toroidal rotation in NSTX plasmas with neutral beam injection generates E × B flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the E × B flow shear rate exceeds ETG linear growth rates. The observations indicate E × B flow shear can be an effective suppression mechanism for ETG turbulence.

Smith, D. R.; Kaye, S. M.; Lee, W.; Mazzucato, E.; Park, H. K.; Bell, R. E.; Domier, C. W.; LeBlanc, B. P.; Levinton, F. M.; Luhmann, Jr., N. C.; Menard, J. E.; Yu, H.

2009-02-13

158

Losing the Io plasma: Local time variations of magnetospheric structure and the development of the Jovian outer magnetospheric maelstrom  

Microsoft Academic Search

In comparisons of planetary magnetospheres, the dominant contribution of rotational stresses at Jupiter as contrasted with the dominant role of solar wind-driven interactions at Earth has been stressed repeatedly. Discussions of the outward transport of the plasma delivered at a rate of a ton per second to the magnetosphere of Jupiter from a source at Io, deep within the magnetosphere,

D. J. Southwood; M. G. Kivelson

2003-01-01

159

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

160

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

Microsoft Academic Search

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

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

2005-01-01

161

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

162

Jovian satellite nomenclature  

NASA Technical Reports Server (NTRS)

A brief review of the history of Jovian satellite nomenclature is given to indicate the background for the names proposed for the numbered satellites. The new names are consistent with established tradition and should cause minimal confusion with other named objects in the solar system.

Owen, T.

1976-01-01

163

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

164

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

165

Dual periodicity of the Jovian Magnetosphere  

SciTech Connect

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

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

1988-06-01

166

Triggered Jovian radio emissions  

NASA Technical Reports Server (NTRS)

Certain Jovian radio emissions seem to be triggered from outside, by much weaker radio waves from the sun. Recently found in the Voyager observations near Jupiter, such triggering occurs at hectometric wavelengths during the arrival of solar radio bursts, with the triggered emissions lasting sometimes more than an hour as they slowly drifted toward higher frequencies. Like the previous discovery of similar triggered emissions at the earth, this suggests that Jupiter's emissions might also originate from natural radio lasers.

Calvert, W.

1985-01-01

167

Jovian Auroral Chemistry  

NASA Astrophysics Data System (ADS)

Recent STIS data indicate that the jovian aurora occasionally deposits an energy flux of several W/m2 into the upper atmosphere, most of which penetrates the homopause into hydrocarbon-rich layers. The energetic electrons which carry this flux are thought to initiate the formation of complex hydrocarbons and soot-like aerosols which settle into and blanket the polar stratosphere. Because of the large number of important species and reactions involved, until recently there has been little attention paid to the problem of simulating jovian auroral chemistry. We have modified the Caltech/JPL KINETICS code for general atmospheric chemistry for the investigation of jovian auroral chemistry. Building on the recent work by Perry et al. (J. Geophys. Res., 104, 16,451, 1999), Wong et al. (Astrophys. J., 534, L215, 2000), and Moses et al. (Icarus, 143, 244, 2000; J. Geophys. Res., 105, 7013, 2000), we have updated and included several hundred neutral-neutral and ion-neutral reactions to provide a basis for studying the effects of energetic electron impact on the auroral region atmosphere of Jupiter. We present here the initial results from this study, concentrating on the main ion-neutral pathways for producing complex hydrocarbons, and examining the role of the simplest aromatic compound, c-C3H3+.

Gladstone, G. R.; Majeed, T.; Moses, J. I.; Waite, J. H., Jr.; Allen, M. A.; Yung, Y. L.; Pryor, W. R.

2000-10-01

168

Energetic particles in the jovian magnetotail.  

PubMed

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

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

2007-10-12

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

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

171

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

172

Reduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source  

SciTech Connect

A helicon based pre-ionization source has been developed and installed on the Helicity Injected Torus with Steady Inductance (HIT-SI) spheromak. The source initiates plasma breakdown by injecting impurity-free, unmagnetized plasma into the HIT-SI confinement volume. Typical helium spheromaks have electron density reduced from (2–3) × 10{sup 19} m{sup ?3} to 1 × 10{sup 19} m{sup ?3}. Deuterium spheromak formation is possible with density as low as 2 × 10{sup 18} m{sup ?3}. The source also enables HIT-SI to be operated with only one helicity injector at injector frequencies above 14.5 kHz. A theory explaining the physical mechanism driving the reduction of breakdown density is presented.

Hossack, Aaron C.; Jarboe, Thomas R.; Victor, Brian S. [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); Firman, Taylor; Prager, James R.; Ziemba, Timothy [Eagle Harbor Technologies, Inc., 119 W. Denny Way, Suite 210, Seattle, Washington 98119 (United States)] [Eagle Harbor Technologies, Inc., 119 W. Denny Way, Suite 210, Seattle, Washington 98119 (United States); Wrobel, Jonathan S. [979B West Moorhead Circle, Boulder, Colorado 80305 (United States)] [979B West Moorhead Circle, Boulder, Colorado 80305 (United States)

2013-10-15

173

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

174

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

175

Joule Heating of the Jovian Ionosphere by Corotation Enforcement Currents  

Microsoft Academic Search

A simple magnetodisk model is used to estimate the Joule heating rate, for several causes of departure from the corotation during whose enforcement heat is deposited on the Jovian magnetosphere. Following compression or expansion of the magnetosphere, the magnetospheric plasma sub- or super-rotates due to conservation of angular momentum and thermal energy is deposited in the ionosphere at a rate

Atsuhiro Nishida; Yukio Watanabe

1981-01-01

176

R t f N l C t T ti Di i GReport of Nuclear Component Testing Discussion Group National Spherical Torus ProgramNational Spherical Torus Program  

E-print Network

& National Spherical Torus ProgramNational Spherical Torus Program Martin Peng National Spherical Torus R, tokamak-CTF, ITER-EDA, SG2 leader MIT Peng, Martin ST, NCT DG Coordinator ORNL Baylor, Larry Plasma Sabbagh, Steve MHD Columbia U Sovenic, Carl Numerical fusion simulation U Wisc Tynan, George Plasma

177

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

178

Modeling the Jovian aurora  

NASA Technical Reports Server (NTRS)

The Jovian aurora is the most powerful aurora in the solar system, over 100 times more powerful than the Earth's aurora. These magnificent visual displays can provide important information about the planetary magnetosphere which is responsible for the acceleration of energetic particles that produce aurora at any planet. Similarities and differences in planetary auroral emissions are thus a viable means of classifying and studying both comparative atmospheric and magnetospheric processes. For instance, at Earth the solar wind is the primary source of auroral power while at Jupiter it is conjectured that the rotation of the planet is the major source of magnetospheric and auroral power. The purpose of this IR project was to develop a model: (1) for use in interpreting the existing set of multispectral observations of Jupiter's aurora; and (2) to design new experiments based on the findings to improve understanding of the underlying auroral processes.

Waite, J. Hunter, Jr.

1992-01-01

179

GEOLogic: Terrestrial and Jovian Planets  

NSDL National Science Digital Library

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

Guertin, Laura

180

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

181

The Jovian Moons  

NSDL National Science Digital Library

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

2007-07-09

182

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

183

New Possibilities of Radioastronomical Diagnostics of the Jovian Magnetosphere Using the Observed Polarization of its Decameter Radio Emission  

Microsoft Academic Search

We discuss possibilities of diagnostics of the Jovian magnetosphere based on the results of measurements of the polarization characteristics of the decameter radio emission. It is shown that the essentially elliptical polarization of that radiation and its generation at frequencies near the local electron gyrofrequency opens new possibilities for radioastronomical diagnostics of the Jovian magnetosphere. The plasma distribution can be

V. E. Shaposhnikov

2001-01-01

184

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

Microsoft Academic Search

A model for an explanation of far ultraviolet (FUV) emissions observed from the Io flux tube footprints at the Jovian ionosphere is presented. An acceleration of electrons and ions of the ionospheric plasma up to sufficient energies for an effective excitation of H2 Lyman and Werner bands is proposed. The neutral particles within the Jovian ionosphere are excited due to

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

2001-01-01

185

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

186

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

SciTech Connect

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

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

2012-01-01

187

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

SciTech Connect

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

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

2012-01-01

188

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

189

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

190

JOURNALOF GEOPHYSICALRESEARCH,VOL. 92, NO. A9, PAGES9963-9970, SEPTEMBER1, 1987 THE INTERACTION OF IO'S ALFVEN WAVES WITH THE JOVIAN  

E-print Network

observednear the Io produced behind Io in an effort to explain the arc spacing flux tube (IFT) by Voyager 1 OF IO'S ALFVEN WAVES WITH THE JOVIAN MAGNETOSPHERE Andrew N. Wright Theoretical Astronomy Unit, School densityseen by the wave as it propagatesthrough the torus the Alfv·n wavesproducedby Io is presented

Wright, Andrew N.

191

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

192

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

SciTech Connect

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

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

1997-05-01

193

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

194

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

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

195

Periodic amplitude variations in Jovian continuum radiation  

NASA Technical Reports Server (NTRS)

An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

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

1986-01-01

196

Jovian Dark Spot  

NASA Technical Reports Server (NTRS)

A recently discovered black spot in Jupiter's clouds is darker than any feature ever before observed on the giant planet. The spot may be the result of a downward spiraling wind that blows away high clouds and reveals deeper, very dark cloud layers. These three panels depict the same area of Jupiter's atmosphere. A map of Jovian temperatures near 250 millibar pressure (top) panel is derived from the photopolarimeter-radiometer instrument on NASA's Galileo Jupiter orbiter. This map is compared with maps derived from images of the same area in visible light (middle panel)and thermal radiation sensitive to cloud-top temperatures (bottom panel).

The single downward-pointing arrow in the top panel indicates the location of a warm area that corresponds to the position of a so-called 'black spot'(shown in the middle panel), a feature that is about a year old. Features this dark are rare on Jupiter. The bottom panel, sensitive to temperatures at Jupiter's cloud tops, shows this feature as a bright object, meaning that upper-level cold clouds are missing - allowing us to see deeper into Jupiter's warmer interior. The dark visible appearance of the feature than most likely represents the color of very deep clouds. The warm temperatures and cloud-free conditions imply that this feature is a region where dry upper-atmospheric gas is being forced to converge, is warmed up and then forced to descend, clearing out clouds. It is the opposite of wet, upwelling gas in areas such as Jupiter's Great Red Spot or white ovals. On the other hand, it is unlike the dry and relatively cloudless feature into which the Galileo probe descended in 1995, because that region had the same temperatures as its surroundings and did not appear nearly as dark as this new spot.

The temperatures sampled by the photopolarimeter radiometer are near the top of Jupiter's troposphere, where wind motions control the atmosphere. The top row of arrows shows the location of temperature waves in a warm region of the atmosphere. These types of waves have never been seen before. What is interesting about these waves is both that they are 'channeled' within the warm band at the top of the panel, and that they appear to have no counterpart in the visible cloud structure. Thermal waves have already been seen in Jupiter that are independent of the cloud structure, but those waves were much larger in size. This is the first time Jupiter's temperatures have been mapped at a spatial resolution better than 2,000 kilometers (1,243 miles), allowing these waves to be detected.

These maps include an area on Jupiter between approximately the equator and 40 degrees south latitude, covering about 60 degrees of longitude. They were taken in late September during the spacecraft's 17th orbit.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.

1998-01-01

197

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

198

Plasma pressure in the environment of Jupiter, inferred from Voyager 1 magnetometer observations  

NASA Technical Reports Server (NTRS)

A model combining the internal magnetic field with a self-consistent model of the Jovian magnetodisc was fitted to the Voyager 1 Jovian magnetic field data by means of a generalized inverse technique. The model parameters included the internal field spherical harmonic coefficients as well as with parameters describing the plasma distribution in the magnetosphere. Assuming that the pressure in the middle and outer magnetosphere is related to the unit flux tube volume V through PV exp gamma = const, the model fit yielded a value of 0.88 for gamma. If the hot (30 keV) plasma is transported adiabatically inward under the interchange instability triggered by centrifugal force of the heavy torus ions, losses are not sufficient to account for such a low value of gamma beyond L = 10. Closer to the planet, as the outer edge of the Io plasma torus is approached, PV exp gamma is found to decrease inward, as expected from the particle measurements, which identified an inner boundary of the particle fluxes in that region. With the present stage of the development of magnetodisc models, secular variations of the internal field still remain difficult to estimate.

Caudal, G.; Connerney, J. E. P.

1989-01-01

199

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

200

Modeling and investigative studies of Jovian low frequency emissions  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

201

Spherical Torus Pathway to Fusion Power  

Microsoft Academic Search

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

Martin Peng

1998-01-01

202

Statistics of depleted flux tubes in the jovian magnetosphere  

Microsoft Academic Search

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

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

2005-01-01

203

Statistics of Depleted Flux Tubes in the Jovian Magnetosphere  

Microsoft Academic Search

On many of its passes through the Io torus the Galileo spacecraft has detected the presence of thin magnetic flux tubes with fields somewhat higher than their surroundings. In these tubes the magnetic pressure is higher than in neighboring tubes to such an extent that it is possible that the plasma contribution to the pressure is insignificant. These tubes occupy

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

2003-01-01

204

Relationship between Jovian hectometric attenuation lanes and Io volcanic activity  

Microsoft Academic Search

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

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

2001-01-01

205

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

SciTech Connect

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

Carpenter, K.H.

1981-02-01

206

Jovian X-ray emissions  

NASA Technical Reports Server (NTRS)

The Einstein and Rosat observations of X-ray emissions from Jupiter are summarized. Jupiter's soft X-ray emission is observed to originate from the planet's auroral zones, and specifically, from its equatorial region. The processes responsible for these emissions are not established. The brightness distribution of the Jovian X-rays is characterized by the dependence on central meridian longitude and by north-south and morning-afternoon asymmetries. The X-rays observed during the impact of the comet Shoemaker-Levy 9 are believed to be impact-induced brightenings of the X-ray aurora.

Waite, J. H.; Lewis, W. S.; Gladstone, G. R.; Fabian, A. C.; Brandt, W. N.

1996-01-01

207

Charged particle modification of ices in the Saturnian and Jovian systems  

NASA Technical Reports Server (NTRS)

The modification by ion bombardment of the surfaces of icy objects in the Saturnian and Jovian systems is discussed. Chemical changes in ices are induced by breaking of bonds and by implantation of incident ions. Long-term irradiation by fast ions produces physical changes such as increasing the surface reflectivity and ability to scatter light. On large satellites, molecules which are ejected by ion bombardment are redistributed across the surfaces of large satellites. For small satellites and ring particles bombarded by ions, such as those of Saturn, most or all of the sputtered material is lost to space, forming a neutral torus in the locale of the satellite orbits and rings and supplying ions to the magnetosphere. Noting the existence of such a torus, the sputter erosion and possible stabilization of the E-ring of Saturn is discussed.

Johnson, R. E.; Barton, L. A.; Boring, J. W.; Jesser, W. A.; Brown, W. L.

1985-01-01

208

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

Microsoft Academic Search

An overview of the results obtained so far for the radiative I-mode regime on the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94) [Proceedings of the 16th IEEE Symposium on Fusion Engineering (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1995), Vol. 1, p. 470] is given. This regime is obtained under quasistationary conditions with edge neon seeding in a

A. M. Messiaen; J. Ongena; B. Unterberg; J. Boedo; G. Fuchs; R. Jaspers; L. Konen; H. R. Koslowski; G. Mank; J. Rapp; U. Samm; P. E. Vandenplas; G. van Oost; G. van Wassenhove; G. Waidmann; G. H. Wolf; G. Bertschinger; G. Bonheure; M. Brix; P. Dumortier; F. Durodie; K. H. Finken; B. Giesen; D. Hillis; P. Hutteman; R. Koch; A. Kramer-Flecken; A. Lyssoivan; Ph. Mertens; A. Pospieszczyk; A. Post-Zwicker; M. Sauer; B. Schweer; J. Schwelberger; G. Telesca; M. Z. Tokar; R. Uhlemann; M. Vervier; J. Winter

1997-01-01

209

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.

210

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

211

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

212

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

213

Jovian satellite eclipse study. 1: 1971 eclipses  

NASA Technical Reports Server (NTRS)

Observations of five Jovian satellite eclipses were obtained during February, March, and April 1971 with the 200-inch Hale telescope and multichannel spectrometer. Eclipse light curves in 20 wavelength bandpasses were obtained for each eclipse.

Greene, T. F.; Shorthill, R. W.; Despain, L. G.

1971-01-01

214

Design Innovations of the Next-Step Spherical Torus Experiment and Spherical Torus Development Path  

SciTech Connect

The spherical torus (ST) fusion energy development path is complementary to the tokamak burning plasma experiment such as ITER as it focuses toward the compact Component Test Facility (CTF) and higher toroidal beta regimes to improve the design of DEMO and a Power Plant. To support the ST development path, one option of a Next Step Spherical Torus (NSST) device is examined. NSST is a performance extension (PE) stage ST with a plasma current of 5 - 10 MA, R = 1.5, BT 2.7 T with flexible physics capability to 1) Provide a sufficient physics basis for the design of the 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, 3) Contribute to the general plasma / fusion science of high toroidal plasmas. The NSST facility is designed to utilize the TFTR site to minimize the cost and time required for the construction.

Ono, M. [Princeton Plasma Physics Laboratory (PPPL)] [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL] [ORNL

2004-01-01

215

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

216

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

Microsoft Academic Search

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

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

2008-01-01

217

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

218

Performance characterization of the Caltech corn act torus injector  

Microsoft Academic Search

A compact torus (CT), or spheromak, is a toroidal mag- netofluid configuration in which plasma is cot-dined by a nearly force-free field structure. This structure, formed by currents flowing in the plasma and in nearby conducting sur- faces, consists of a poloidal magnetic field wrapped around a toroidal magnetic field. CTs have recently gained attention in a variety of applications,

P. K. Loewenhardt; J. Yee; P. M. Bellan

219

Final report on the LLNL compact torus acceleration project  

Microsoft Academic Search

In this report, we summarize recent work at LLNL on the compact torus (CT) acceleration project. The CT accelerator is a novel technique for projecting plasmas to high velocities and reaching high energy density states. The accelerator exploits magnetic confinement in the CT to stably transport plasma over large distances and to directed kinetic energies large in comparison with the

J. Eddleman; J. Hammer; C. Hartman; H. McLean; A. Molvik

1995-01-01

220

The Jovian ionospheric E region  

NASA Technical Reports Server (NTRS)

A model of the Jovian ionosphere was constructed, that includes direct photoionization of hydrocarbon molecules. A high-resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N), and high-resolution cross sections for photoabsorption by H2 bands in the range 842 to 1116 A were constructed. Two strong solar lines and about 30 percent of the continuum flux between 912 and 1116 A penetrate below the methane homopause despite strong absorption by CH4 and H2. It is found that hydrocarbons (mainly C2H2 are ionized at a maximum rate of 55/cu cm per sec at 320 km above the ammonia cloud tops. The hydrocarbon ions produced are quickly converted to more complex hydrocarbon ions through reactions with CH4, C2H2, C2H6, and C2H4. It is found that a hydrocarbon ion layer is formed near 320 km that is about 50 km wide with a peak density in excess of 10,000/cu cm.

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

1991-01-01

221

The Helicity Injected Torus (HIT) Program  

NASA Astrophysics Data System (ADS)

The Helicity Injected Torus (HIT) program develops current drive techniques for low-aspect-ratio toroidal plasmas. The present HIT--II spherical tokamak device is capable of driving current using both Coaxial Helicity Injection (CHI) and Ohmic transformer drive. The HIT--II device is modestly sized (major radius of 0.3 m, minor radius of 0.2 m, with on-axis toroidal fields of up to 0.5 T), but has demonstrated toroidal plasma currents of up to 200 kA, using either CHI or Ohmic drive. Recent experiments have included exploration of current drive mixing scenarios, in addition to detailed studies of the physics of low-aspect-ratio Ohmic and CHI-driven plasmas. An overview of ongoing research on HIT--II plasmas will be presented, especially diagnostic data from multi-chord FIR interferometry, multi-point Thomson scattering and sets of triple Langmuir probes. In the near future, the HIT--II device will be replaced by the Helicity Injected Torus with Steady Inductive helicity injection (HIT--SI), a device capable of generating and sustaining a high-beta low-aspect-ratio toroidal plasma. The final design of the HIT--SI device, and construction milestones, will be presented.

Jarboe, T. R.; Gu, P.; Hamp, W. T.; Izzo, V. A.; Nelson, B. A.; O'Neill, R. G.; Raman, R.; Redd, A. J.; Sieck, P. E.; Smith, R. J.; Nagata, M.; Uyama, T.; Jain, K. K.

2002-11-01

222

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

Microsoft Academic Search

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

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

2007-01-01

223

Field-aligned Currents in Io's Plasma Wake  

NASA Astrophysics Data System (ADS)

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

Chen, Chuxin

2008-09-01

224

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

225

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

226

New upper limits on Jovian X rays  

NASA Technical Reports Server (NTRS)

The paper presents results of a comprehensive search for X-ray emission from the Jovian magnetosphere, using data obtained with an X-ray telescope aboard OSO 3. This satellite scanned Jupiter for 33 days from a distance of 4.4 AU during a maximum phase of solar activity. No transient X-ray fluxes were observed to accompany decameter-wave radio bursts, but upper limits on the steady X-ray emission over the energy range from 7.7 to 210 keV are estimated. These limits are shown to be consistent with the fluxes measured by Pioneer 10 as well as with the trapped-particle fluxes predicted by recent precise modeling of the Jovian trapped radiation. Upper limits are determined for the energy dissipated on Jupiter in bremsstrahlung-producing collisions and also for the electron loss rate. The energy limit is found to be approximately equal to the total solar radiant energy intercepted by the Jovian disk. It is concluded that Jovian X-rays are unlikely to be detected by near-earth observations with sensitivities currently conceivable.

Peterson, L. E.; Hudson, H. S.; Tsikoudi, V.

1976-01-01

227

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

228

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

229

Fast ion stabilization of the ion temperature gradient driven modes in the Joint European Torus hybrid-scenario plasmas: a trigger mechanism for internal transport barrier formation  

Microsoft Academic Search

Understanding and modelling turbulent transport in thermonuclear fusion plasmas are crucial for designing and optimizing the operational scenarios of future fusion reactors. In this context, plasmas exhibiting state transitions, such as the formation of an internal transport barrier (ITB), are particularly interesting since they can shed light on transport physics and offer the opportunity to test different turbulence suppression models.

M. Romanelli; A. Zocco; F. Crisanti; JET-EFDA Contributors

2010-01-01

230

International workshop on Time-Variable Phenomena in the Jovian System  

NASA Technical Reports Server (NTRS)

Many of the scientifically interesting phenomena that occur in the Jovian system are strongly time variable. Some are episodic (e.g., Io volcanism); some are periodic (wave transport in Jupiters atmosphere); and some are exceedingly complex (magnetosphere - Io - Torus-Auroral interactions) and possibly unstable. To investigate this class of phenomena utilizing Voyager data and, in the future, Galileo results, a coherent program of ground based and earth-orbital observations, and of theory that spans the time between the missions, is required. To stimulate and help define the basis of such a scientific program researchers organized an International Workshop on the subject with the intent of publishing the proceedings which would represent the state of knowledge in 1987.

Belton, Michael J. S.; West, R. A.

1988-01-01

231

A review of the Jovian magnetosphere based upon Pioneer 10 and 11  

NASA Technical Reports Server (NTRS)

Data derived from the plasma, magnetic field, and energetic particle experiments on the December, 1973 and December, 1974 Jupiter encounters are reviewed. A bow shock was discovered on the solar side of the planet, as predicted. However, a smaller magnetic field and larger fluxes of energetic electrons were found than anticipated. A ring current and current sheet in the Jovian plasmasphere are inferred from magnetic field measurements.

Trainor, J. H.

1975-01-01

232

Evidence for a distant \\/greater than 8,700 RJ\\/ Jovian magnetotail - Voyager 2 observations  

Microsoft Academic Search

A correlative survey of magnetometer (MAG) and Planetary Radio Astronomy (PRA) 1.2 kHz continuum radiation measurements from Voyager 2 provide evidence for at least eight distant Jovian magnetotail sightings occurring about once a month over the first 2\\/3 of 1981 at distances of approximately 5,000 to 9,000 RJ. The occurrences of these events are in good agreement with prior Plasma

R. P. Lepping; L. F. Burlaga; M. D. Desch; L. W. Klein

1982-01-01

233

Evidence for a distance (>8,700 R\\/sub j\\/) Jovian magnetotail: Voyager 2 observations  

Microsoft Academic Search

A correlative survey of Magnetometer (MAG) and Planetary Radio Astronomy (PRA) 1.2 kHz continuum radiation measurements from Voyager 2 provide evidence for at least eight distant Jovian magnetotail sightings occurring about once a month over the first 2\\/3 of 1981 at distances of approx.5,000 to approx.9,000 R\\/sub j\\/. The occurrences of these events are in good agreement with prior Plasma

R. P. Lepping; L. F. Burlaga; M. D. Desch; L. W. Klein

1982-01-01

234

Three-dimensional ray tracing of the Jovian magnetosphere in the low-frequency range  

Microsoft Academic Search

Three-dimensional ray tracing of the Jovian DAM emission has been performed utilizing the O-4 magnetic field model (Acuna and Ness, 1979) and a realistic plasma model. Minimal assumptions about the emission mechanism have been made that include radiation in the right-hand extraordinary mode, propagating nearly perpendicular to the field line at source points located just above the RX cutoff frequency

J. D. Menietti; J. L. Green; S. Gulkis

1984-01-01

235

Three-Dimensional Ray Tracing of the Jovian Magnetosphere in the Low-Frequency Range  

Microsoft Academic Search

Three-dimensional ray tracing of the Jovian DAM emission has been performed utilizing the 0-4 magnetic field model (Acuna and Ness, 1979) and a realistic plasma model. Minimal assumptions about the emission mechanism have been made that include radiation in the right-hand extraordinary mode, propagating nearly perpendicular to the field line at source points located just above the RX cutoff frequency

Ray Tracing

1984-01-01

236

Cassini ENA Observations of an Asymmetric Europa Torus with Indications of Magnetospheric Dynamics  

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. These observations have been demonstrated to be consistent with a neutral gas torus encircling Jupiter at Europa's orbit (Mauk et al., 2004). Here, we present a new, detailed analysis of the ENA images implying an asymmetric Europa neutral gas torus with indications of magnetospheric dynamics. The analysis uses images with a minimum integration time and background. A forward model using a parametric energetic ion model and a neutral gas model simulates ENA images through the instrument response function of INCA in order to determine the spatial distribution of the neutral gas.

Brandt, Pontus; Westlake, Joseph; Mauk, Barry; Mitchell, Donald

2014-05-01

237

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

238

Overview of the Helicity Injected Torus Program  

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

239

Spherical torus (ST) concept and its reactor implications  

SciTech Connect

A brief description of the spherical torus design is given. The design concept includes resistive demountable toroidal field coils, poloidal divertor for impurity control, oscillating-field current maintenance, RF initiation and ramp-up of the plasma current, and flowing liquid-metal breeding blanket. 4 refs., 6 figs. (WRF)

Peng, Y.K.M.; Lazarus, E.A.; Miller, R.L.; Carreras, B.A.; Hogan, J.T.; Krakowski, R.A.; Seed, T.J.; Zubrin, R.M.; Schnurr, N.M.

1986-01-01

240

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

241

Dust on the Outskirts of the Jovian System: What Might Galileo and Cassini See?  

NASA Astrophysics Data System (ADS)

The outer region of the jovian system beyond ~ 100 jovian radii might be a host of a retrograde dust population. Four outer tiny moons are orbiting Jupiter in retrograde orbits. These moons are subject to micrometeoroidal bombardment by interplanetary dust particles. Hypervelocity impacts create ejecta that are widely distributed in the circumjovian space. Submicrometer-sized grains are rapidly lost from the system due to the strong radiation pressure perturbations. Micrometer-sized particles form a huge halo bounded by the orbits of the source moons. Their number densities are less than those of the interplanetary dust background in that region, and they are not expected to contribute to the Galileo and Cassini dust detector datasets. However, larger ejecta, ~ 10 ?m in radius, keep confined to a torus-shaped cloud interior to the orbits of the parent moons, and they may dominate the number densities in this size regime over the interplanetary dust grains. Interestingly, the like-sized ejecta from the prograde outer moons are more vulnerable to the radiation pressure and are swept away from the system. We discuss the possibility for the dust detectors onboard Galileo and Cassini to detect the outer retrograde dust population.

Wardinski, I.; Krivov, A. V.; Spahn, F.

2000-12-01

242

Torus or black disk?  

E-print Network

We show that the interaction region of colliding protons looks completely absorptive (black) at the impact parameters up to 0.4 - 0.5 fm at the LHC energy 7 TeV. It is governed by the ratio of the elastic diffraction peak slope to the total cross section. The corresponding parameter is approximately equal to 1 at the LHC. The behavior of this ratio at higher energies will show if this region will evolve to the black disk or to the black torus. Recent fits at 7 TeV can not distinguish between these possibilities within the limits of experimental indefiniteness and of extrapolations in the regions of unmeasured transferred momenta.

I. M. Dremin

2014-04-16

243

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

Microsoft Academic Search

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

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

2004-01-01

244

Control System Development Plan for the National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) has as one of its primary goals the demonstration of the attractiveness of the spherical torus concept as a fusion power plant. Central to this goal is the achievement of high plasma {beta} ( = 2{micro}{sub 0}

/B{sup 2} a measure of the efficiency of a magnetic plasma confinement system). It has been demonstrated both theoretically and experimentally that the maximum achievable {beta} is a strong function of both local and global plasma parameters. It is therefore important to optimize control of the plasma. To this end a phased development plan for digital plasma control on NSTX is presented. The relative level of sophistication of the control system software and hardware will be increased according to the demands of the experimental program in a three phase plan. During Day 0 (first plasma), a simple coil current control algorithm will initiate plasma operations. During the second phase (Day 1) of plasma operations the control system will continue to use the preprogrammed algorithm to initiate plasma breakdown but will then change over to a rudimentary plasma control scheme based on linear combinations of measured plasma fields and fluxes. The third phase of NSTX plasma control system development will utilize the rtEFIT code, first used on DIII-D, to determine, in real-time, the full plasma equilibrium by inverting the Grad-Shafranov equation. The details of the development plan, including a description of the proposed hardware will be presented.

C. Neumeyer; D. Mueller; D.A. Gates; J.R. Ferron

1999-06-01

245

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

246

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

247

Dust from the Outer Jovian Satellites  

NASA Astrophysics Data System (ADS)

It is argued that the outer region of the jovian system between ~ 50 and 300 jovian radii from Jupiter harbors a previously unknown dust population. We analyzed the data of the dust detector aboard the Galileo spacecraft collected from December 1995 to April 2001 during Galileo's numerous traverses of the outer jovian system. About 100 individual events are found to be compatible with impacts of grains moving around Jupiter in bound orbits. These micrometer-sized grains have moderate eccentricities and a wide range of inclinations -- from prograde to retrograde ones. The radial profile of the dust number density is nearly flat between about 50 and 300 jovian radii, and the absolute number density level ( ~ 10km-3) surpasses by a factor of ten that of the interplanetary background. We identify the sources of the bound grains with outer irregular satellites of Jupiter. Six tiny moons orbiting the planet in prograde and fourteen in retrograde orbits should produce dust through continuous bombardment by interplanetary micrometeoroids. Our analytic and numerical study of the ejecta dynamics shows that micrometer-sized particles from both satellite families, although strongly perturbed by solar tidal gravity and radiation pressure, would stay in bound orbits for hundreds of thousands of years. The ejecta cloud would embrace the orbits of the parent moons and have substantial asymmetries created by the radiation pressure and solar gravity perturbations. Spatial location of the impacts, grains' orbital inclinations, mass distribution, speeds, and number density of dust derived from the data are all consistent with the dynamical model. This work was funded by Deutsches Zentrum für Luft- und Raumfahrt (DLR).

Krivov, A. V.; Wardinski, I.; Spahn, F.; Krüger, H.; Grün, E.

2001-11-01

248

Simultaneous multifrequency observations of Jovian S bursts  

Microsoft Academic Search

The millisecond component of the Jovian decameter emission has been studied at high resolution, in order to examine the short-term behavior of the S-burst drift rates and to define the drift rate spectrum at high frequencies. By using dynamic spectra having 300-..mu..s 3.3-KHz resolution and covering discrete frequency bands in the range 26--33 MHz, large systematic changes in the magnitude

R. S. Flagg; M. D. Desch

1979-01-01

249

Electron Bernstein Wave Research on the National Spherical Torus Experiment  

Microsoft Academic Search

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 â100 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

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

2005-01-01

250

Revisiting Jovian-Resonance Induced Chondrule Formation  

E-print Network

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 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 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, and that this is achieved around the 3:1 mean-motion resonance. The heating region is restricted to a relatively narrow band between 1.5 AU and 3.5 AU. Our res...

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

2014-01-01

251

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

252

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

253

A dawn to dusk electric field in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

It is shown that if Io-injected plasma is lost via a planetary wind-fixed Birkeland current system may result. This is due to the fact that the azimuthal centrifugal current flows across a density gradient produced by the loss of plasma through the planetary wind in the tail. The divergent centrifugal current is connected to field-aligned Birkeland currents which flow into the ionosphere at dawn and out of it at dusk. The closure currents in the ionosphere require a dawn to dusk electric field which at the orbit of Io is estimated to have a strength of 0.2 mV/m. However, the values of crucial parameters are not well known and the field at Io's orbit may well be significantly larger. Independent estimates derived from the local time asymmetry of the torus UV emission indicate a field of 1.5 mV/m.

Goertz, C. K.; Ip, W. I.

1983-01-01

254

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

255

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

256

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

257

Thermoelectric Rotating Torus for Fusion A. B. Hassam and Yi-Min Huang  

E-print Network

Thermoelectric Rotating Torus for Fusion A. B. Hassam and Yi-Min Huang Institute for Plasma power maintains the rotation and also heats the plasma. The thermoelectric effect from the resultingRevLett.91.195002 PACS numbers: 52.58.­c, 52.30.­q, 52.55.­s In magnetized plasma, thermoelectric currents

Hassam, Adil

258

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.

259

Analysis of Jovian Auroral H Ly-? Emission (1981–1991)  

Microsoft Academic Search

We present a new analysis of jovian auroral IUE spectra covering the period from 1981 to 1991. To extract integrated auroral H Ly-? emission from these spectra we have developed a new extraction method that bins signal with wavelength while preserving the spatial information provided by the IUE imaging spectrograph. This separates auroral emission from background sources including the jovian

Walter Harris; John T. Clarke; Melissa A. McGrath; Gilda E. Ballester

1996-01-01

260

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

261

Multiple frequency sounding of a Jovian cloud  

NASA Technical Reports Server (NTRS)

A thermal asymmetry displayed in Pioneer 10 45-micron IR radiometric data between the rising and setting limbs of the Jovian South Equatorial Belt (SEB) between -5.0 and -7.0 deg latitude is examined. A high correlation is found between the longitudinal asymmetry of the SEB at 45 microns and the appearance of Jupiter in 5-micron radiation. It is shown that there was a cooler 'obscuring' cloud within the SEB latitude region which correlates highly with the location of relatively reduced intensities at 45 microns. The cloud-top temperature is estimated on the basis of simultaneous 5- and 45-micron observations

Orton, G. S.; Terrile, R. J.

1978-01-01

262

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

263

Magnetic surfaces in an axisymmetric torus  

SciTech Connect

A method is developed for specifying the boundary equilibrium magnetic surface in an axially symmetric torus by using the absolute values of the magnetic field B = B{sub s}({theta}) and the gradient of the poloidal flux vertical bar vertical bar {nabla}{Psi} vertical bar = vertical bar {nabla}{Psi} vertical bar {sub s}({theta}) in a special flux coordinate system. By setting two surface constants (e.g., the safety factor q and dp/d{Psi}) and matching the absolute values of the magnetic field and the flux gradient on a closed magnetic surface, it is possible to find all equilibrium magnetic functions (including n {center_dot} {nabla} ln B and the local shear s) and all constants (including the toroidal current J and the shear d{mu}/d{Psi}) on this surface. Such a non-traditional formulation of the boundary conditions in solving the stability problem in an axisymmetric torus allows one to impose intentional conditions on plasma confinement and MHD stability at the periphery of the system.

Skovoroda, A. A., E-mail: skovorod@nfi.kiae.ru [National Research Centre Kurchatov Institute (Russian Federation)

2013-04-15

264

Overview of the Helicity Injected Torus Program  

NASA Astrophysics Data System (ADS)

The Helicity Injected Torus with Steady Inductive Helicity Injection (HIT-SI) spheromak experiment [Jarboe, Fus.Tech., v.36, p.85 (1999)] addresses critical research areas for spheromak formation and sustainment, including current drive, high-beta operation, confinement quality, and efficient steady-state operation. HIT-SI has a ``bow-tie'' shaped, axisymmetric confinement region with a major radius of 0.33 m, and an axial extent of 0.57 m. Attached to the confinement region are two half-torus helicity injectors, one mounted on each end of the flux conserver. HIT-SI has produced up to 30 kA of toroidal current in spheromaks generated using less than 4 MW of applied power, demonstrating that Steady Inductive Helicity Injection can create and sustain discharges with modest power requirements. HIT-SI has recently been repaired and upgraded, with an improved flux conserver, higher helicity and power injection, better diagnostic coverage, and an improved plasma-facing insulating surface. HIT-SI operational and diagnostic improvements, and corresponding physics studies, will be summarized.

Stewart, Bret Thomas; Redd, A. J.; Jarboe, T. R.; Aboulhosn, R. Z.; Akcay, C.; Hamp, W. T.; Marklin, G.; Nelson, B. A.; O'Neill, R. G.; Raman, R.; Sieck, P. E.; Smith, R. J.; Wrobel, J. S.

2007-11-01

265

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

266

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

267

Recent results in the Los Alamos compact torus program  

SciTech Connect

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

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

1983-01-01

268

Linear pinch driven by a moving compact torus  

SciTech Connect

In principle, a Z-pinch of sufficiently large aspect ratio can provide arbitrarily high magnetic field intensity for the confinement of plasma. In practice, however, achievable field intensities and timescales are limited by parasitic inductances, pulse driver power, current, voltage, and voltage standoff of nearby insulating surfaces or surrounding gas. Further, instabilities may dominate to prevent high fields (kink mode) or enhance them (sausage mode) but in a nonuniform and uncontrollable way. In this paper we discuss an approach to producing a high-field-intensity pinch using a moving compact torus. The moving torus can serve as a very high power driver and may be used to compress a pre-established pinch field, switch on an accelerating pinch field, or may itself be reconfigured to form an intense pinch. In any case, the high energy, high energy density, and high velocity possible with an accelerated compact torus can provide extremely high power to overcome, by a number of orders of magnitude, the limitations to pinch formation described earlier. In this paper we will consider in detail pinches formed by reconfiguration of the compact torus.

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

1984-04-25

269

Jovian narrow-band as generator of the Jovian millisecond radio bursts  

NASA Astrophysics Data System (ADS)

We report on the narrow-band emissions observed in the dynamic spectra of the Jovian decametric radio emissions. Such narrow-band emissions are infrequent phenomena and are related to the Jovian millisecond radio bursts (S-bursts). From the Riihimaa catalogue (Riihimaa 1991) we select narrow-band events observed in Oulu (Finland) with an acousto-optic spectrograph (AOS) with a high time resolution of about 7 ms. The AOS receiver gives the possibility to study the relationship between the S-bursts and the Jovian narrow-band emissions. For this we use the Riihimaa classification which shows sketches of millisecond radio bursts as they appear on the dynamic spectra and allows to distinguish one S-burst from another. The analysis of the temporal evolution of the Jovian narrow-band leads to a new interpretation of the Riihimaa structures. We show that each individual structure could be decomposed in one, two or three components and related to the narrow-band. It appears that the temporal evolution of the narrow-band involves the presence of fine structures, i.e. S-bursts, with a short time duration of about few tens of milliseconds. The individual S-burst duration and the short time scale of the gap in the narrow-band account for a mechanism totally intrinsic to the radio source. Taking into consideration our new results, we show that two models, the feedback model (Calvert 1982) and filamentary model (Louarn 1997) could explain part but not the global observed features of the narrow-band. According to the previous models the drift rate of the individual S-bursts seems to associate the combined effect of the source width with the refractive index or the geometry of the source relatively to the observer.

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

2000-11-01

270

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

271

Local Time Dependence of Jovian Radio Emissions Observed by Galileo  

NASA Technical Reports Server (NTRS)

Galileo has been in orbit around Jupiter since December 1995. All the orbits are equatorial and elliptical, with apogees between 60 R(sub J) - 142 R(sub J) and perigees from 8 - 12 R(sub J). Since orbit injection, the plasma wave instrument (PWS) has been collecting data over specific intervals of each of the orbits at all local times and a range of different radial distances. We present the results of a survey of the data for the frequency range 300 kHz to 5.6 MHz, which includes the hectometric (HOM) and low-frequency decametric (DAM) emissions. The results indicate that both the HOM and DAM emission are more intense and occur more frequently in the midnight sector of Jupiter. This is in analogy to Earth and consistent with a magnetic substorm source for a portion of the radio emissions in this frequency range. Another peak in the power levels is observed on the Jovian dayside in the local time range 11 hrs < LT < 12 hrs. This peak does not have a terrestrial counterpart. We speculate that this dayside peak may be a result of sampling near perigee, but we cannot rule out the possibility that this is not the case.

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

1999-01-01

272

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

Microsoft Academic Search

Various theories and numerical simulations support the conjecture that the ubiquitous problem of anomalous electron transport in tokamaks may arise from a short-scale turbulence driven by the electron temperature gradient. To check whether this turbulence is present in plasmas of the National Spherical Torus Experiment, measurements of turbulent fluctuations were performed with coherent scattering of electromagnetic waves. Results from plasmas

E. Mazzucato; R. E. Bell; Stephane Ethier; J. C. Hosea; S. M. Kaye; B. P. LeBlanc; W. W. Lee; P. M. Ryan; D. R. Smith; W. X. Wang; J. R. Wilson; H. Yuh

2009-01-01

273

Shapes and Densities of Jovian Trojan Objects  

NASA Astrophysics Data System (ADS)

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

Romanishin, William; Cooper, Erin

2008-08-01

274

Divine-garrett model and Jovian synchrotron emission  

NASA Technical Reports Server (NTRS)

Simulations of synchrotron emission from relativistic electrons trapped in Jupiter's magnetic field are used to evaluate the energetic electron distribution of the Divine-Garrett Jupiter radiation belt model at radial distances less than 4 Jovian radii.

Bolton, S.; Levin, S.; Gulkis, S.; Klein, M.; Sault, R.; Bhattacharya, B.; Thorne, R.; Dulk, G.; Leblanc, Y.

2001-01-01

275

Jovian Magnetospheric Impacts on Determination of Europa's Astrobiological Potential  

NASA Astrophysics Data System (ADS)

Astrobiological potential of Europa for potential habitability and life is governed by availability of liquid water, organic chemistry, and energy. Jovian magnetospheric interactions impact and can even enable surveys for these resources.

Cooper, J. F.; Sittler, E. C.

2014-02-01

276

Torus Grid Graph Kneser Graph  

E-print Network

,3) Torus Grid Graph {1,4} {3,4} {1,2} {2,5} {2,4} {2,3} {1,5} {4,5} {1,3} {3,5} Kneser Graph Considered the cheapest edge, {8, 9}. with weight 76 New Features of the GraphTheory Package Animations for Prim's and Kruskal's Algorithms Below we show some key frames from the commands: > G:=AntiPrismGraph(5,2): > G

277

AGN Torus Properties with WISE  

NASA Astrophysics Data System (ADS)

Beginning with an unbiased sample of unobscured QSOs (type 1 within AGN unification), we identify regions in the WISE color space that harbor the putative population of obscured type 2 counterparts. For the first time, we can predict the relation of their number vs. flux limits of a survey, applying knowledge from the CLUMPY torus models. This proceedings contribution is a preview of a forthcoming pair of papers (Nikkuta et al. 2014a,b).

Nikutta, R.; Nenkova, M.; Ivezi?, Ž.; Hunt-Walker, N.; Elitzur, M.

2014-10-01

278

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

279

A magnetohydrodynamic model of the interaction of the solar wind with the Jovian magnetosphere and a magnetohydrodynamic simulation of the interaction of the solar wind with the out flowing plasma from a comet  

NASA Technical Reports Server (NTRS)

A three-dimensional code for a rapidly rotating magnetosphere in which the MHD equations and the Maxwell equations were solved by using the two step Lax Endroff scheme, was developed. Preliminary results were presented at the Fall AGU meeting in San Francisco. The basic simulation model to study the solar wind interactions was adapted to other bodies in addition to Jupiter. Because of the recent comet flybys, a comet was chosen as the first model. The aim was to model the formation of the contact surface and the plasma tail. Later, work was begun on a three-dimensional model which would include the effects of mass loading. This model was designed to study the weak cometary bow shocks observed by the probes to comets Halley and Giacobini-Zinner. The model was successful in reproducing the position and shape of the bow shock which was determined by using observations from the Suisei spacecraft.

Walker, R. J.

1987-01-01

280

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

281

Multispectral observations of the Jovian aurora  

NASA Technical Reports Server (NTRS)

This paper presents and analyzes images of the Jovian aurora gathered by the Hubble Space Telescope Faint Object Camera (FOC) and the ROSAT Position Sensitive Proportional Counter (PSPC) to determine the function of energetic heavy ion precipitation in the inner magnetosphere and electron acceleration in the outer magnetosphere. Hubble data includes hydrogen auroral spectra and reduced images of Jupiter's north and south poles. One important result is that acceleration of electrons may be largely responsible for the discrete auroral emission features seen in the data set. ROSAT PSPC data presented includes a photon energy spectrum. A two line emission model is shown to produce the best fit to the data. The production of these emission lines occurs as a result of recombination lines that are produced from the slowing of the energetic ion beam as it enters the Jupiter upper atmosphere. It is noted that the observed energetic ion precipitation does not contain sufficient power to explain the observed ultraviolet aurora; it is therefore concluded that both electrons and ions play a role in the Jupiter auroral emissions, but that the bulk of the ultraviolet emissions comes from electron processes.

1992-01-01

282

Io-related Jovian decametric arcs  

SciTech Connect

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

Wilkinson, M.H.

1989-09-01

283

The ultraviolet spectra of the Jovian aurora  

SciTech Connect

The ultraviolet spectra of molecular hydrogen H{sub 2} due to electron impact excitation are calculated and compared with the high-resolution (0.56 A) spectra of the Jovian aurora obtained with the {ital Hubble} {ital Space} {ital Telescope} Goddard High-Resolution Spectrograph. All the observed features are reproduced by electron impact excitation emissions of H{sub 2}, and the predicted intensities agree well with the observed intensities. Accurate molecular parameters are used, and effects of secondary electrons are included. The auroral emissions are reproduced by energetic electron impact excitation of H{sub 2} with a temperature of 400{endash}600 K. Large temperature gradients occur with respect to altitude within the auroral emission regions. The auroral spectra contain a cascade contribution to the Lyman band emission from high-lying {ital E} and {ital F} states that are populated by the low-energy secondary electrons produced as the energetic auroral electrons slow down. {copyright} {ital 1996 The American Astronomical Society.}

Liu, W.; Dalgarno, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

1996-08-01

284

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

285

Prevalence of torus palatinus and torus mandibularis in the Split-Dalmatian County, Croatia.  

PubMed

Torus palatinus (TP) and torus mandibularis (TM) are non-pathological outgrowths of unclear etiology that develop from the jaw bone. The purpose of the present study was to report on the prevalence, shape and location of TP and TM in the population of the Central Dalmatian region, Croatia. The study comprised of 1679 subjects, 985 females and 694 males, age range from 9 to 99 years who were examined by clinical examination and analysis of the plaster casts. Torus palatinus was found in 42.9% subjects and torus mandibularis in 12.6% of the subjects. Spindle-shaped torus palatinus was the most frequent type (45.6%). The most frequent type of torus mandibularis was bilateral solitary torus mandibularis (35.4%). Furthermore, torus palatinus was found in 40.1% of the total number of females and in 46.8% of the total number of males, indicating a significantly higher prevalence in the male population (p = 0.006). Torus mandibularis was found in 11.3% of the female population and in 14.6% of the male population, again indicating significantly higher prevalence in the male population (p = 0.046). The results of this study show significantly higher prevalence of torus palatinus and torus mandibularis in the male subjects. Furthermore, no differences in the prevalence of either TM or TP regarding age were found. PMID:22053535

Simunkovi?, Sonja Kraljevi?; Bozi?, Matko; Alajbeg, Iva Z; Dulci?, Niksa; Boras, Vanja Vuci?evi?

2011-09-01

286

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

287

On the Infrared Properties of Dusty Torus  

E-print Network

We performed imaging on 49 type 2 Seyfert galaxies in 6 near- and mid-infrared bands (1-10$\\mu$m). We are separating the contribution of the torus from the host galaxy by radial profile fitting techniques and we will compare the observed spectral energy distributions with theoretical models of torus emission to constrain geometrical and physical parameters.

L. Videla; P. Lira; A. Alonso-Herrero; D. M. Alexander; M. Ward

2006-12-21

288

Three dimensional ray tracing of the Jovian magnetosphere in the low frequency range  

NASA Technical Reports Server (NTRS)

Ray tracing studies of Jovian low frequency emissions were studied. A comprehensive three-dimensional ray tracing computer code for examination of model Jovian decametric (DAM) emission was developed. The improvements to the computer code are outlined and described. The results of the ray tracings of Jovian emissions will be presented in summary form.

Menietti, J. D.

1984-01-01

289

AGN torus properties with WISE  

NASA Astrophysics Data System (ADS)

The Wide-field Infrared Survey Explorer (WISE) has scanned the entire sky with unprecedented sensitivity in four infrared bands, at 3.4, 4.6, 12, and 22 ?m. The WISE Point Source Catalog contains more than 560 million objects, among them hundreds of thousands of galaxies with Active Nuclei (AGN). While type 1 AGN, owing to their bright and unobscured nature, are easy to detect and constitute a rather complete and unbiased sample, their type 2 counterparts, postulated by AGN unification, are not as straightforward to identify. Matching the WISE catalog with known QSOs in the Sloan Digital Sky Survey we confirm previous identification of the type 1 locus in the WISE color space. Using a very large database of the popular Clumpy torus models, we find the colors of the putative type 2 counterparts, and also, for the first time, predict their number vs. flux relation that can be expected to be observed in any given WISE color range. This will allow us to put statistically very significant constraints on the torus parameters. Our results are a successful test of the AGN unification scheme.

Nikutta, Robert; Nenkova, Maia; Ivezi?, Željko; Hunt-Walker, Nicholas; Elitzur, Moshe

2014-07-01

290

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.

291

Multispectral observations of the Jovian aurora  

NASA Technical Reports Server (NTRS)

The upper atmospheres of the Earth and the outer planets form a screen on which precipitating charged particles, like the electron beam in a television, trace fleeting, but revealing patterns of visible, ultraviolet, infrared, and x ray emissions that offer valuable clues to processes occurring within the planetary magnetospheres. At Earth, years of in situ measurements, as well as ground based observations, have yielded a picture (still fuzzy) where the interaction of the solar wind with the magnetosphere of the Earth provides a complex path for the storage and release of energy during magnetic substorms; the ultimate manifestation of terrestrial auroral processes. More recent global imaging of substorm events from high above the Earth (greater than 3.5 R(sub e)) by Dynamics Explorer have made a unique contribution towards understanding the global and temporal evolution of such auroral events by providing a morphological perspective and by providing the crucial observational link that allows the separation of spatial and temporal variations inherent in the interpretation of in situ data. A similar role was played by the Hubble Space Telescope (HST) during the recent encounter of Ulysses with Jupiter in helping to define a new paradigm in Jovian auroral physics. The old paradigm portrayed Jupiter's magnetosphere as totally dominated by internal processes (i.e. Io related tori, heavy ions, etc.) where energetic heavy ion precipitation in the inner magnetosphere was solely responsible for the observed auroral phenomena. Ulysses and HST portray a more Earth-like paradigm where electron acceleration in the outer magnetosphere near the boundary with the solar wind plays a distinct role in the formation of auroral hot spots, yet energetic heavy ions also enter into the picture (similar to the role of the energetic ions from the terrestrial ring current during magnetic substorms). These heavy ions as a result of excitation during their transit through the atmosphere produce the x ray emissions observed in Roentgensatellit (ROSAT) x ray energy spectra.

1992-01-01

292

Wavelet Analysis of Jovian Stratospheric Temperatures  

NASA Astrophysics Data System (ADS)

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

Young, L. A.

2001-11-01

293

Brown dwarfs and Jovian planets: A comparison  

NASA Technical Reports Server (NTRS)

The recent detection of a subluminous companion to the M dwarf star VB8 has renewed interest in the characteristics of objects spanning the mass range from Jupiter to hydrogen burning stars. Atmospheric and interior models were constructed for objects in this mass regime, up to 30 Jupiter masses, with emphasis on understanding the relationship of brown dwarfs such as the VB8 companion to the better-studied Jovian planets. The atmospheric model solves the equation of radiative transfer assuming frequency dependent molecular opacity sources H2, He, H2O, CO, and CH4 which are important by virtue of the high cosmic abundance of their constituent atoms. Condensation of cosmochemically important materials, iron and silicates, in the atmosphere is possible, and the effect of such grains as opacity sources is assessed. The luminosity of the object is presumed due to degenerate cooling following a collapse phase and possibly deuterium burning and an interior model is constructed using as an outer boundary condition the temperature and pressure level at which the atmosphere becomes convective. The interior model is analogous to Jupiter, with a large liquid metallic-hydrogen core and a thinner molecular-hydrogen envelope. The oxidation state of carbon in the outer envelope of a brown dwarf of similar age to Jupiter is a function of the object's mass. This makes the wavelength dependence of the atmospheric opacity sensitive to the carbon to oxygen ratio, since the abundance of the primary source of molecular opacity, H2O, decreases as more oxygen is tied up as CO.

Lunine, J. I.; Hubbard, W. B.; Marley, M.

1986-01-01

294

On the proposed triggering of Jovian radio emissions  

NASA Astrophysics Data System (ADS)

Calvert (1985) has proposed that solar type III radio bursts can trigger the onset of certain Jovian hectometer wavelength emissions. The authors show, using the data obtained by the Voyager Planetary Radio Astronomy experiment, that this triggering hypothesis is not supported statistically. Furthermore, the authors question the causality of this proposed triggering 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.

1985-09-01

295

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

296

Collisional Evolution of Saturn's Neutral Torus  

NASA Astrophysics Data System (ADS)

We present a new DSMC (Direct Simulation Monte Carlo) model of Saturn's extended neutral torus. Previous models (e.g., Jurac and Richardson, 2005; Johnson et al. 2006) have attributed the cloud's observed breadth to plasma interaction. We found, instead, that neutral-neutral collisions could be as important in spreading the cloud. As suggested by Farmer (2008), a component of the cloud can spread like a stellar accretion disk: collisions impart a small fraction of the cloud with high energy and angular momentum, causing an expansion. This is compensated by an inward-moving component which, if not first ionized or accelerated to high energy by charge exchange, is lost to Saturn's rings or atmosphere. The substantial loss of H2O to Saturn's atmosphere, combined with the oxygen scattered from the ring atmosphere (Tseng et al., 2009) may provide the missing O source required by models of Saturn's stratosphere (Moses et al., 2002). The work may also help to explain new observations of the outer neutral cloud, which is broader than previously believed.

Cassidy, T. A.; Johnson, R. E.

2009-05-01

297

Response of the Jovian thermosphere to variations in solar EUV flux  

NASA Astrophysics Data System (ADS)

the response to solar extreme ultraviolet (EUV) radiation is an established diagnostic method used to understand the physics of planetary environments. In this study, we focus on the response of the Jovian thermosphere to variations in the solar EUV flux and discuss the consequences for the coupled thermosphere-ionosphere-magnetosphere system. We use a model that simulates both the thermospheric dynamics and the magnetospheric plasma velocity distribution under conditions of angular momentum transport between these regions. The simulations show that when the EUV flux increases by ~100% and 200%, the thermospheric neutral wind velocity at ~45° latitude increases by 16% and 22%, respectively. The short-term variation over a few Earth days causes an increased velocity at middle latitudes which are magnetically conjugate to the Jovian radiation belt. Increased heating due to solar EUV contributes to this velocity change. The other contribution arises ~30 planetary rotations after the initial solar EUV flux increase. This second ("delayed") effect is due to propagation of momentum from high latitudes (the auroral region), where Joule heating is dominant, and is related to the behavior of the ionospheric conductance and magnetosphere-ionosphere coupling currents. The modeled velocity enhancement is smaller than that required to explain the observed enhancement of the synchrotron emission by radial diffusion of the trapped energetic electrons. In this context, we discuss the sensitivity of the underlying thermosphere-ionosphere response to short-wavelength solar radiation and the ensuing three-dimensional wind fields.

Tao, Chihiro; Miyoshi, Yoshizumi; Achilleos, Nick; Kita, Hajime

2014-05-01

298

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

299

Ignition and burn criteria for D3He tokamak and spherical torus reactors  

Microsoft Academic Search

D sup 3 He ignition and burn criteria for tokamaks and spherical torus reactors are examined in a global analysis with profile corrections. Particle confinement and ash buildup effects are included with the power balance, which results in an increased sensitivity of the ignition criteria to losses via brehmsstrahlung and synchrotron radiation. Plasma beta scaling via an epsilon beta sub

J. D. Galambos; Y.-K. M. Peng

1989-01-01

300

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

301

Reactor assessments of advanced bumpy torus configurations  

SciTech Connect

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

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

1983-01-01

302

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

SciTech Connect

A spherical torus (ST) fusion energy development path which is complementary to the proposed tokamak burning plasma experiments such as ITER is described. The ST strategy focuses on a compact component test facility (CTF) and high performance advanced regimes leading to more attractive Demo and power plant scale reactors. To provide the physical basis for the CTF an intermediate step needs to be taken, which we refer to as the 'next-step spherical torus' (NSST) device and which we examine in some detail herein. NSST is a 'performance extension' stage ST with a plasma current of 5 10 MA, R = 1.5 m, BT 2.6 T and the possibility of varying physical parameters. The mission of NSST is to (1) provide a sufficient physical basis for the design of a CTF; (2) explore advanced operating scenarios with high bootstrap current fraction and high performance which can be utilized by CTF, Demo, and power plants; and (3) contribute to the general science of high toroidal plasmas. The NSST is designed to utilize a TFTR-like site to minimize the cost and time required for design and construction.

Ono, M. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL

2004-01-01

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

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

305

Corotation lag of the Jovian atmosphere, ionosphere, and magnetosphere  

Microsoft Academic Search

The authors modify the Jovian ionosphere-magnetosphere coupling model presented by Hill (1979) to include rotational slippage of the neutral atmosphere at ionospheric heights, relative to a frame of reference corotating rigidly with Jupiter. In the modified model, as altitude increases, the drift velocities of neutrals and ions relative to the corotating frame increase from zero at the bottom of the

T. S. Huang; T. W. Hill

1989-01-01

306

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

307

Structure of the Jovian Magnetodisk Current Sheet: Initial Galileo Observations  

NASA Technical Reports Server (NTRS)

The ten-degree tilt of the Jovian magnetic dipole causes the magnetic equator to move back and forth across Jupiter's rotational equator and tile Galileo orbit that lies therein. Beyond about 24 Jovian radii, the equatorial current sheet thins and tile magnetic structure changes from quasi-dipolar into magnetodisk-like with two regions of nearly radial but antiparallel magnetic field separated by a strong current layer. The magnetic field at the center of the current sheet is very weak in this region. Herein we examine tile current sheet at radial distances from 24 55 Jovian radii. We find that the magnetic structure very much resembles tile structure seen at planetary magnetopause and tail current sheet crossings. Tile magnetic field variation is mainly linear with little rotation of the field direction, At times there is almost no small-scale structure present and the normal component of the magnetic field is almost constant through the current sheet. At other times there are strong small-scale structures present in both the southward and northward directions. This small-scale structure appears to grow with radial distance and may provide the seeds for tile explosive reconnection observed at even greater radial distances oil tile nightside. Beyond about 40 Jovian radii, the thin current sheet also appears to be almost constantly in oscillatory motion with periods of about 10 min. The amplitude of these oscillations also appears to grow with radial distance. The source of these fluctuations may be dynamical events in tile more distant magnetodisk.

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

2001-01-01

308

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

309

Processes of Neutral Winds in the Jovian Thermosphere  

NASA Astrophysics Data System (ADS)

High-resolution infrared and far ultraviolet spectroscopy of the Jovian aurora indicates the pres-ence of high-speed (gt;2 km/s) winds in Jupiter's thermosphere. While existing 1-D models are useful for understanding global averages of the Jovian thermosphere, 3-D models can provide significant insight into the regional importance of various processes. We use our fully coupled 3-D Jupiter Thermosphere General Circulation Model (JTGCM) from 20 µbar (capturing hy-drocarbon cooling) to 10-4 nbar to interpret observations of neutral winds and their underlying processes on a global scale. Such general circulation models have been used to explain the global dynamical structure self-consistently with the thermal structure and compositions (ion and neutral) in the Jovian thermosphere. The coupling between ions in the Jovian auroral ovals and the corotating neutral atmosphere has been simulated. The heat sources that drive the thermospheric flow are due to solar EUV radiation and high-latitude auroral processes such as particle precipitation and Joule heating. Simulations of Jupiter's global thermospheric dy-namics indicate significant ion transport by high-speed winds. Strong neutral outflows develop mainly by auroral-region pressure gradients and temperatures up to 3000 K (depending on the magnitude of Joule heating). These outflows, characterized by wind speeds up to 1.3 km/s, is determined by various competing processes such as large pressure gradients, coriolis force, ion-drag process, and hydrodynamic advection. We will describe how these processes can be used to reasonably explain strong Jupiter winds generated in the auroral ovals. The models demonstrate that a significant amount of auroral energy is transported to equatorial latitudes by the Jovian wind system.

Majeed, Tariq; Bougher, Stephen; Waite, J. Hunter; Gladstone, Randy; Chaufray, Jean-Yves

310

Processes of Neutral Winds in the Jovian Thermosphere  

NASA Astrophysics Data System (ADS)

High-resolution infrared and far ultraviolet spectroscopy of the Jovian aurora indicates the presence of high-speed (>2 km/s) winds in Jupiter's thermosphere. While existing 1-D models are useful for understanding global averages of the Jovian thermosphere, 3-D models can provide significant insight into the regional importance of various processes. We use our fully coupled 3-D Jupiter Thermosphere General Circulation Model (JTGCM) from 20 ?bar (capturing hydrocarbon cooling) to 10-4 nbar to interpret observations of neutral winds and their underlying processes on a global scale. Such general circulation models have been used to explain the global dynamical structure self-consistently with the thermal structure and compositions (ion and neutral) in the Jovian thermosphere. The coupling between ions in the Jovian auroral ovals and the corotating neutral atmosphere has been simulated. The heat sources that drive the thermospheric flow are due to solar EUV radiation and high-latitude auroral processes such as particle precipitation and Joule heating. Simulations of Jupiter's global thermospheric dynamics indicate significant ion transport by high-speed winds. Strong neutral outflows develop mainly by auroral-region pressure gradients and temperatures up to 3000 K (depending on the magnitude of Joule heating). These outflows, characterized by wind speeds up to 1.3 km/s, is determined by various competing processes such as large pressure gradients, coriolis force, ion-drag process, and hydrodynamic advection. We will describe how these processes can be used to reasonably explain strong Jupiter winds generated in the auroral ovals. The models demonstrate that a significant amount of auroral energy is transported to equatorial latitudes by the Jovian wind system.

Majeed, T.; Waite, J. H.; Gladstone, G. R.; Bougher, S. W.; Chaufray, J.-Y.

2011-10-01

311

Modeling the Jovian subnebula. II. Composition of regular satellite ices  

NASA Astrophysics Data System (ADS)

We use an evolutionary turbulent model of Jupiter's subnebula to constrain the composition of ices incorporated in its regular icy satellites. We consider CO2, CO, CH4, N2, NH3, H2S, Ar, Kr and Xe as the major volatile species existing in the gas-phase of the solar nebula. All these volatile species, except CO2 which crystallized as a pure condensate, are assumed to be trapped by H2O to form hydrates or clathrate hydrates in the solar nebula. Once condensed, these ices were incorporated into the growing planetesimals produced in the feeding zone of proto-Jupiter. Some of these solids then flowed from the solar nebula to the subnebula, and may have been accreted by the forming Jovian regular satellites. We show that ices embedded in solids entering at early epochs into the Jovian subdisk were all vaporized. This leads us to consider two different scenarios of regular icy satellite formation in order to estimate the composition of the ices they contain. In the first scenario, icy satellites were accreted from planetesimals that have been produced in Jupiter's feeding zone without further vaporization, whereas, in the second scenario, icy satellites were accreted from planetesimals produced in the Jovian subnebula. In this latter case, we study the evolution of carbon and nitrogen gas-phase chemistries in the Jovian subnebula and we show that the conversions of N2 to NH3, of CO to CO2, and of CO to CH4 were all inhibited in the major part of the subdisk. Finally, we assess the mass abundances of the major volatile species with respect to H2O in the interiors of the Jovian regular icy satellites. Our results are then compatible with the detection of CO2 on the surfaces of Callisto and Ganymede and with the presence of NH3 envisaged in subsurface oceans within Ganymede and Callisto.

Mousis, O.; Alibert, Y.

2006-03-01

312

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

313

Noncommutative Torus from Fibonacci Chains via Foliation  

E-print Network

We classify the Fibonacci chains (F-chains) by their index sequences and construct an approximately finite dimensional (AF) $C^*$-algebra on the space of F-chains as Connes did on the space of Penrose tiling. The K-theory on this AF-algebra suggests a connection between the noncommutative torus and the space of F-chains. A noncommutative torus, which can be regarded as the $C^*$-algebra of a foliation on the torus, is explicitly embedded into the AF-algebra on the space of F-chains. As a counterpart of that, we obtain a relation between the space of F-chains and the leaf space of Kronecker foliation on the torus using the cut-procedure of constructing F-chains.

Hyeong-Chai Jeong; Eunsang Kim; Chang-Yeong Lee

2000-08-22

314

2D divertor design calculations for the national high-power advanced torus experiment  

Microsoft Academic Search

The national high-power advanced torus experiment is a concept for a new facility to address the FESAC theme of ‘taming the plasma-material interface’. This concept exploits the compactness and excellent access provided by low aspect ratio to achieve a high ratio of exhaust power to major radius in order to study the integration of high-performance, long-pulse plasmas with a reactor-relevant

John Canik; R. Maingi; Larry W Owen; J. Menard; R. Goldston; M. Kotschenreuther; P. Valanju; S. Mahajan

2009-01-01

315

Near-infrared Brightness of the Galilean Satellites Eclipsed in Jovian Shadow: A New Technique to Investigate Jovian Upper Atmosphere  

NASA Astrophysics Data System (ADS)

Based on observations from the Hubble Space Telescope and the Subaru Telescope, we have discovered that Europa, Ganymede, and Callisto are bright around 1.5 ?m even when not directly lit by sunlight. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was 10-6-10-7 of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 ?m, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 ?m by the Spitzer Space Telescope, but it was not detected, suggesting a significant wavelength dependence. It is still unknown why they are luminous even when in the Jovian shadow, but forward-scattered sunlight by hazes in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us with a new technique to investigate the Jovian atmospheric composition. Investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.

Tsumura, K.; Arimatsu, K.; Egami, E.; Hayano, Y.; Honda, C.; Kimura, J.; Kuramoto, K.; Matsuura, S.; Minowa, Y.; Nakajima, K.; Nakamoto, T.; Shirahata, M.; Surace, J.; Takahashi, Y.; Wada, T.

2014-07-01

316

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

317

Oxygen torus in the deep inner magnetosphere and its contribution to recurrent process of O+-rich ring current formation  

NASA Astrophysics Data System (ADS)

Using the magnetic field and plasma wave data obtained by the Combined Release and Radiation Effects Satellite (CRRES), we search for enhancements of O+ ion density in the deep inner magnetosphere known as "the oxygen torus". We examine 4 events on the dayside in which toroidal standing Alfvén waves appear clearly. From the frequency of the toroidal waves, the magnetospheric local mass density (?L) is estimated by solving the MHD wave equation for realistic models of the magnetic field and the field line mass distribution. We also estimate the local electron number density (neL) from the plasma wave spectrograms by identifying narrow-band emission at the upper-hybrid resonance frequency. Assuming the quasi-neutral condition of plasma, we infer the local average ion mass (ML) by ?L/neL. It is found that ML is approximately 3 amu in the plasma trough, while it shows an enhancement of >7 amu at L ˜ 4.5-6.5 that is close to the plasmapause at L ˜ 3.5-6.0. This indicates an existence of the oxygen torus in the vicinity of the plasmapause. The oxygen torus is found preferentially during the storm recovery phase. We interpret that these features of the oxygen torus (i.e., close relations with the plasmapause and the storm recovery phase) reflect its generation mechanism; that is, the ionospheric temperature is enhanced by heat conduction from high altitudes in the limited L range where the plasmasphere, because of its inflation during the recovery phase, encounters the ring current, and then the ionosphere has a larger scale height and supplies O+ ions to the inner magnetosphere, resulting in the oxygen torus. We also discuss the contribution of the oxygen torus to the formation of the O+-rich ring current. It is proposed that the O+-rich ring current is formed in a recurrent process, in which the oxygen torus, the plasmasphere, and the ring current interact with each other.

Nosé, M.; Takahashi, K.; Anderson, R. R.; Singer, H. J.

2011-10-01

318

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

319

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

320

Partially collisional model of the Titan hydrogen torus  

SciTech Connect

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

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

1988-02-01

321

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

322

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

323

Ultraviolet Emission from Oxygen Precipitating into Jovian Aurora  

SciTech Connect

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

Liu, Weihong; Schultz, D. R.

2000-02-10

324

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

325

Survival of common terrestrial microorganisms under simulated Jovian conditions.  

NASA Technical Reports Server (NTRS)

The microorganisms used in the experiments include Escherichia coli B, Serratia marcescens, Aerobacter aerogenes, and Bacillus subtilis. The survival of these microorganisms under simulated Jovian conditions indicates that there is a very real possibility of the contamination of Jupiter by a nonsterile spacecraft, provided that the planet can also permit growth of such contaminants. The apparent ease with which some very common organisms can survive for 24 hr suggests that, with adaptation, growth of anaerobic organisms may be a probability.-

Molton, P.; Ponnamperuma, C.

1972-01-01

326

Dust on the Outskirts of the Jovian System  

NASA Astrophysics Data System (ADS)

The outer region of the jovian system between ?50 and 300 jovian radii from the planet is found to be the host of a previously unknown dust population. We used the data from the dust detector aboard the Galileo spacecraft collected from December 1995 to April 2001 during Galileo's numerous traverses of the outer jovian system. Analyzing the ion amplitudes, calibrated masses and speeds of grains, and impact directions, we found about 100 individual events fully compatible with impacts of grains moving around Jupiter in bound orbits. These grains have moderate eccentricities and a wide range of inclinations-from prograde to retrograde ones. The radial number density profile of the micrometer-sized dust is nearly flat between about 50 and 300 jovian radii. The absolute number density level (?10 km-3 with a factor of 2 or 3 uncertainty) surpasses by an order of magnitude that of the interplanetary background. We identify the sources of the bound grains with outer irregular satellites of Jupiter. Six outer tiny moons are orbiting the planet in prograde and fourteen in retrograde orbits. These moons are subject to continuous bombardment by interplanetary micrometeoroids. Hypervelocity impacts create ejecta, nearly all of which get injected into circumjovian space. Our analytic and numerical study of the ejecta dynamics shows that micrometer-sized particles from both satellite families, although strongly perturbed by solar tidal gravity and radiation pressure, would stay in bound orbits for hundreds of thousands of years as do a fraction of smaller grains, several tenths of a micrometer in radius, ejected from the prograde moons. Different-sized ejecta remain confined to spheroidal clouds embracing the orbits of the parent moons, with appreciable asymmetries created by the radiation pressure and solar gravity perturbations. Spatial location of the impacts, mass distribution, speeds, orbital inclinations, and number density of dust derived from the data are all consistent with the dynamical model.

Krivov, Alexander V.; Wardinski, Ingo; Spahn, Frank; Krüger, Harald; Grün, Eberhard

2002-06-01

327

Formation of Jovian decametric S bursts by modulated electron streams  

Microsoft Academic Search

Jovian S bursts that are V shaped in the frequency-time domain have been reported by several observers. These can arise if an outward moving approx.2.5-keV electron beam in the Io flux tube is longitudinally modulated in velocity by approx.1 keV peak to peak, at a frequency of several hertz. Such modulation near the ionosphere could also explain the difference between

D. H. Staelin; P. W. Rosenkranz

1982-01-01

328

Formation of Jovian decametric S bursts by modulated electron streams  

Microsoft Academic Search

Jovian S bursts that are V shaped in the frequency-time domain have been reported by several observers. These can arise if an outward moving about 2.5-keV electron beam in the Io flux tube is longitudinally modulated in velocity by about keV peak to peak, at a frequency of several hertz. Such modulation near the ionosphere could also explain the difference

D. H. Staelin; P. W. Rosenkranz

1982-01-01

329

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

330

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

331

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

332

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

333

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

334

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

335

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

SciTech Connect

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 beta 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 l(i) similar to 0.4 with strong shaping (kappa similar to 2.7, delta similar to 0.8) with beta(N) approaching the with-wall beta-limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f(NI) similar to 71%. Instabilities driven by super-Alfvenic ions will be an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvenic. Linear toroidal Alfven 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 beta 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.

Biewer, T.M. [Oak Ridge National Laboratory (ORNL); Bigelow, Tim S [ORNL; Bush, C.E. [Oak Ridge National Laboratory (ORNL); Canik, John [ORNL; Carter, Mark Dwain [ORNL; Caughman, John B [ORNL; Hillis, D. L. [Oak Ridge National Laboratory (ORNL); Jaeger, Erwin Frederick [ORNL; Maingi, Rajesh [ORNL; Peng, Yueng Kay Martin [ORNL; Rasmussen, David A [ORNL; Ryan, Philip Michael [ORNL; Sontag, Aaron C [ORNL; Unterberg, Ezekial A [ORNL; Wilgen, John B [ORNL

2009-01-01

336

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

337

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

338

Physics and Engineering Assessments of Spherical Torus Component Test Facility  

SciTech Connect

A broadly based study of the fusion engineering and plasma science conditions of a Component Test Facility (CTF), using the Spherical Torus or Spherical Tokamak (ST) configuration, have been carried out. The chamber systems testing conditions in a CTF are characterized by high fusion neutron fluxes n > 4.4 1013 n/s/cm2, over size scales > 105 cm2 and depth scales > 50 cm, delivering > 3 accumulated displacement per atom (dpa) per year. The desired chamber conditions can be provided by a CTF with R0 = 1.2 m, A = 1.5, elongation ~ 3.2, Ip ~ 9 MA, BT ~ 2.5 T, producing a driven fusion burn using 36 MW of combined neutral beam and RF power. Relatively robust ST plasma conditions are adequate, which have been shown achievable [4] without active feedback manipulation of the MHD modes. The ST CTF will test the single-turn, copper alloy center leg for the toroidal field coil without an induction solenoid and neutron shielding, and require physics data on solenoid-free plasma current initiation, ramp-up, and sustainment to multiple MA level. A new systems code that combines the key required plasma and engineering science conditions of CTF has been prepared and utilized as part of this study. The results show high potential for a family of lowercost CTF devices to suit a variety of fusion engineering science test missions.

Peng, Yueng Kay Martin [ORNL] [ORNL; Fogarty, P. J. [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Strickler, Dennis J [ORNL] [ORNL; Burgess, Thomas W [ORNL] [ORNL; Tsai, C. C. [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Nelson, Brad E [ORNL] [ORNL

2004-01-01

339

Transient Transport Experiments in the CDX-U Spherical Torus  

SciTech Connect

Electron transport has been measured in the Current Drive Experiment-Upgrade (CDX-U) using two separate perturbative techniques. Gas modulation at the plasma edge was used to introduce cold-pulses which propagate towards the plasma center, providing time-of-flight information leading to a determination of chi(subscript e) as a function of radius. Sawteeth at the q=1 radius (r/a {approx} 0.15) induced heat-pulses which propagated outward towards the plasma edge, providing a complementary time-of-flight based chi(subscript e) profile measurement. This work represents the first localized measurement of chi(subscript e) in a spherical torus. It is found that chi(subscript e) = 1-2 meters squared per second in the plasma core (r/a < 1/3), increasing by an order of magnitude or more outside of this region. Furthermore, the chi(subscript e) profile exhibits a sharp transition near r/a = 1/3. Spectral and profile analyses of the soft X-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high chi(subscript e) region.

T. Munsat; P.C. Efthimion; B. Jones; R. Kaita; R. Majeski; D. Stutman; and G. Taylor

2001-06-12

340

Energetic Ion Behavior in the National Spherical Torus Experiment  

SciTech Connect

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

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

2003-06-26

341

Mass release at Jupiter: Substorm-like processes in the Jovian magnetotail  

Microsoft Academic Search

The Jupiter orbiting spacecraft Galileo has provided evidence that the Jovian magnetotail is subject to a periodic process with typical timescales of several days by which the Jovian system is presumably releasing its excess iogenic mass. The mass release process resembles a terrestrial substorm in the sense of a global reconfiguration of the magnetotail. During the initial “loading” phase the

E. A. Kronberg; J. Woch; N. Krupp; A. Lagg; K. K. Khurana; K.-H. Glassmeier

2005-01-01

342

Ignition and burn criteria for D-3He tokamak and spherical torus reactors  

Microsoft Academic Search

D-³He ignition and burn criteria for tokamaks and spherical torus reactors are examined in a global analysis with profile corrections. Particle confinement and ash buildup effects are included with the power balance, which results in an increased sensitivity of the ignition criteria to losses via brehmsstrahlung and synchrotron radiation. Plasma beta scaling via an {var_epsilon}{sub p} limit provides the needed

John D Galambos; Yueng Kay Martin Peng

1991-01-01

343

Transmutation of minor actinides in a spherical torus tokamak fusion reactor, FDTR  

Microsoft Academic Search

In this paper, a concept of transmutation minor actinide (MA) nuclear waste based on the spherical torus (ST) tokamak reactor, FDTR, was put forward. A set of plasma parameter was decided suitable for the ST transmutation nuclear waste blanket. Using the 2-D neutron transport code TWODANT, the 3-D Monte Carlo code MCNP-4B and the 1-D burn-up calculation code BISON3.0 and

K. M Feng; G. S Zhang; M. G Deng

2002-01-01

344

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

345

Modeling the excitation of global Alfvén modes by an external antenna in the Joint European Torus (JET)  

Microsoft Academic Search

The active excitation of global Alfven modes using the saddle coils in the Joint European Torus (JET) [{ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1984, Proceedings of the 10th International Conference, London (International Atomic Energy Agency, Vienna, 1985), Vol. 1, p. 11] as the external antenna, will provide information on the damping of

G. T. A. Huysmans; W. Kerner; D. Borba; H. A. Holties; J. P. Goedbloed

1995-01-01

346

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

347

Control of Jovian Radio Emission by Callisto  

NASA Technical Reports Server (NTRS)

Galileo has been in orbit around Jupiter since December 1995 and a large database has been collected. We present the results of a survey of the plasma wave data for the frequency range 2.0 MHz to 5.6 MHz, the low frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon lo is well known, and Ganymede control has been more recently indicated, we report that a small but significant portion of DAM emission is seen to be correlated with the orbital phase of Callisto. While the occurrence rate of emission controlled by Ganymede and Callisto is considerably less than for lo, the power levels can be nearly the same. We estimate the power of the Callisto-dependent emission to be approx. 70% of the Io-dependent radio emission and about the same as the Ganymede-dependent radio emission. This result indicates an Alfven current system associated with Callisto, and thus a significant interaction of the magnetosphere of Callisto with that of Jupiter as is believed to exist for both lo and Ganymede.

Menietti, J. D.; Gurnett, D. A.; Christopher, I.

2001-01-01

348

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

349

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

SciTech Connect

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

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

2009-11-26

350

Reversed-field pinch studies in the Madison Symmetric Torus  

SciTech Connect

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

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

1993-04-03

351

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

352

A Search for Jovian Planets around Hot White Dwarfs  

E-print Network

Current searches for extrasolar planets have concentrated on observing the reflex Doppler shift of solar-type stars. Little is known, however, about planetary systems around non-solar-type stars. We suggest a new method to extend planetary searches to hot white dwarfs. Near a hot white dwarf, the atmosphere of a Jovian planet will be photoionized and emit hydrogen recombination lines, which may be detected by high- dispersion spectroscopic observations. Multi-epoch monitoring can be used to distinguish between non-LTE stellar emission and planetary emission, and to establish the orbital parameters of the detected planets. In the future, high-precision astrometric measurements of the hot white dwarf will allow the masses of the detected planets to be determined. Searches for Jovian planets around hot white dwarfs will provide invaluable new insight on the development of planetary systems around stars more massive than the Sun and on how stellar evolution affects these systems. We present high-dispersion spectroscopic observations of the white dwarf Feige 34 to demonstrate the complexity and feasibility of the search method.

Y. -H. Chu; B. C. Dunne; R. A. Gruendl; W. Brandner

2000-10-24

353

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

354

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

355

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

356

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

357

Bifurcation scenarios for a 3D torus and torus-doubling  

NASA Astrophysics Data System (ADS)

Bifurcation transitions between a 1D invariant closed curve (ICC), corresponding to a 2D torus in vector fields, and a 2D invariant torus (IT), corresponding to a 3D torus in vector fields, have been the subjects of intensive research in recent years. An existing hypothesis involves the bifurcation boundary between a region generating an ICC and a region generating an IT. It asserts that an IT would be generated from a stable fixed point as a consequence of two Hopf (or two Neimark-Sacker) bifurcations. We assume that this hypothesis may puzzle many researchers because it is difficult to assess its validity, although it seems to be a reasonable bifurcation scenario at first glance. To verify this hypothesis, we conduct a detailed Lyapunov analysis for a coupled delayed logistic map that can generate an IT, and indicate that this hypothesis does not hold according to numerical results. Furthermore, we show that a saddle-node bifurcation of unstable periodic points does not coincide with the bifurcation boundary between an ICC and an IT. In addition, the bifurcation boundaries of torus doubling do not coincide with a period-doubling bifurcation of unstable periodic points. To conclude, torus bifurcations have no relation with the bifurcations of unstable periodic points. Additionally, we exactly derive a quasi-periodic Hopf bifurcation boundary introducing a double Poincaré map.

Inaba, Naohikio; Sekikawa, Munehisa; Shinotsuka, Yoshimasa; Kamiyama, Kyohei; Fujimoto, Ken'ichi; Yoshinaga, Tetsuya; Endo, Tetsuro

2014-02-01

358

The Torus as a Disk Outflow  

NASA Astrophysics Data System (ADS)

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

Elitzur, Moshe

2012-12-01

359

Near-infrared Brightness of the Galilean Satellites Eclipsed in Jovian Shadow: A New Technique to Investigate Jovian Upper Atmosphere  

E-print Network

We have discovered that Europa, Ganymede and Callisto are bright around 1.5 {\\mu}m even when not directly lit by sunlight, based on observations from the Hubble Space Telescope and the Subaru Telescope. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was $10^{-6}$-$10^{-7}$ of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 {\\mu}m, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 {\\mu}m by the Spitzer Space Telescope but it was not detected, suggesting a significant wavelength dependence. The reason why they are luminous even when in the Jovian shadow is still unknown, but forward-scattered sunlight by haze in the Jovian upper atmosphere is proposed as the most pla...

Tsumura, K; Egami, E; Hayano, Y; Honda, C; Kimura, J; Kuramoto, K; Matsuura, S; Minowa, Y; Nakajima, K; Nakamoto, T; Shirahata, M; Surace, J; Takahashi, Y; Wada, T

2014-01-01

360

Experimental demonstration of compact torus compression and acceleration  

SciTech Connect

Tests of compact torus (CT) compression on the RACE device (Phys. Rev. Lett. {bold 61}, 2843 (1988)) have successfully demonstrated stable compression by a factor of 2 in radius, field amplification by factors of 2--3 to 20 kG, and compressed densities exceeding 10{sup 16} cm{sup {minus}3}. The results are in good agreement with two-dimensional magnetohydrodynamic simulations of the CT dynamics. The CT is formed between a pair of coaxial conical conductors that serve as both a flux conserver for stable, symmetric formation and as electrodes for the compression and acceleration phases. The CT is compressed by {ital J}{times}{ital B} forces (poloidal current, toroidal field) when a 120 kV, 260 kJ capacitor bank is discharged across the electrodes. The CT reaches two-fold compression to a radius of 8 cm and a length of 20--30 cm near the time of peak current, 10 {mu}sec (many Alfven times) after the accelerator fire time, and is subsequently accelerated in a 150 cm straight coaxial section to velocities in the range 1.5--6.5{times}10{sup 7} cm/sec. A new set of acceleration/focusing electrodes 740 cm in length are projected to give an additional factor of 3 in radial compression with final velocities of 1--3{times}10{sup 8} cm/sec (similar to previously achieved on RACE) and incident power densities of a few {times}10{sup 11} W/cm{sup 2}. Compact torus accelerators scaled to multimegajoules have the potential to achieve unprecedented plasma velocities and power densities with many applications in high-energy-density physics.

Hammer, J.H.; Eddleman, J.L.; Hartman, C.W.; McLean, H.S.; Molvik, A.W. (Lawrence Livermore National Laboratory, Livermore, California 94526 (US))

1991-08-01

361

Multiply reflected standing Alfven waves in the IO torus: Pioneer 10 observations  

SciTech Connect

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

Walker, R.; Kivelson, M.

1981-12-01

362

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

363

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

364

Computing All Conic Sections in Torus and Natural Quadric Intersections  

Microsoft Academic Search

Conic sections embedded in a torus must be circles ofspecial types: (i) profile circles, (ii) cross-sectional circles,and (iii) Yvone-Villarceau circles. Based on thisclassification, we present efficient and robust geometricalgorithms that detect and compute all degenerateconic sections (circles) in torus\\/plane and torus\\/naturalquadricintersections.2 IntroductionSimple surfaces (such as planes, spheres, cylinders, cones,and tori) are important in conventional solid modelingsystems...

Ku-jin Kim; Myung-soo Kim Postech

1998-01-01

365

A convected kappa distribution model for hot ions in the Jovian magnetodisc  

NASA Technical Reports Server (NTRS)

Hot ion angular anisotropies measured by the Low Energy Charged Particle (LECP) instrument during the Voyager 2 encounter with the Jovian dayside outer magnetosphere (60-30 RJ) have been fitted to a 2 species convected kappa distribution function using a nonlinear least squares technique. The resulting parameters are well constrained by the data. The heavy ion species was assumed to be either sulfur or oxygen of unknown charge. The light species was assumed to be protons. The bulk flow speeds deduced from the model were found, contrary to some theories, to increase with increasing radial distance from Jupiter within the radial region addressed, remaining a substantial fraction (0.6) of the rigid corotation speed. Agreement with the averaged Voyager Plasma Science results was obtained near 30 RJ. The core Maxwellian temperature of the heavy ion distribution functions (30-100 keV) increased with increasing radial distance, following the trend anticipated from the corotation pickup of heavy ions. The proton temperature (20 keV) remained nearly constant.

Kane, M.; Mauk, B. H.; Keath, E. P.; Krimigis, S. M.

1992-01-01

366

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

367

Nonlocal neoclassical transport in tokamak and spherical torus experiments  

SciTech Connect

Large ion orbits can produce nonlocal neoclassical effects on ion heat transport, the ambipolar radial electric field, and the bootstrap current in realistic toroidal plasmas. Using a global {delta}f particle simulation, it is found that the conventional local, linear gradient-flux relation is broken for the ion thermal transport near the magnetic axis. With regard to the transport level, it is found that details of the ion temperature profile determine whether the transport is higher or lower when compared with the predictions of standard neoclassical theory. Particularly, this nonlocal feature is suggested to exist in the National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)], being consistent with NSTX experimental evidence. It is also shown that a large ion temperature gradient can increase the bootstrap current. When the plasma rotation is taken into account, the toroidal rotation gradient can drive an additional parallel flow for the ions and then additional bootstrap current, either positive or negative, depending on the gradient direction. Compared with the carbon radial force balance estimate for the neoclassical poloidal flow, our nonlocal simulation predicts a significantly deeper radial electric field well at the location of an internal transport barrier of an NSTX discharge.

Wang, W. X.; Rewoldt, G.; Tang, W. M.; Hinton, F. L.; Manickam, J.; Zakharov, L. E.; White, R. B.; Kaye, S. [Princeton Plasma Physics Laboratory, Princeton University P.O. Box 451, Princeton, New Jersey 08543 (United States)

2006-08-15

368

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

369

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

370

Ethane and acetylene abundances in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

The paper reports spectra of Jupiter in the spectral region from 755 to 850 kaysers, which covers the nu-9 fundamental of ethane and contains lines from the R branch of the nu-5 fundamental of acetylene. The monochromatic absorption coefficient of the central Q branch of the nu-9 fundamental of ethane, which was determined in the laboratory, is applied in a radiative-transfer calculation to evaluate the ethane mixing ratio in the Jovian atmosphere; the present data are also used to place an upper limit on the acetylene mixing ratio. For the radiative-transfer calculation, emission intensity is computed for the region above the 0.02-atm level assuming both an isothermal inversion layer and a previously reported temperature profile. The resulting maximum mixing ratios consistent with the observations are 0.00003 for ethane and 7.5 by 10 to the -8th power for acetylene.

Tokunaga, A.; Knacke, R. F.; Owen, T.

1976-01-01

371

Formation of Jovian decametric S bursts by modulated electron streams  

SciTech Connect

Jovian S bursts that are V shaped in the frequency-time domain have been reported by several observers. These can arise if an outward moving approx.2.5-keV electron beam in the Io flux tube is longitudinally modulated in velocity by approx.1 keV peak to peak, at a frequency of several hertz. Such modulation near the ionosphere could also explain the difference between the maximum observed frequencies of S burst and L burst emission. In order for this beam to produce the observed total S burst flux, a large part of the approx.5 x 10/sup 6/ A current observed in the Io flux tube must participate. In this case the observed duration of individual S bursts is consistent with magnetospheric ion densities greater than approx.15 cm/sup -3/. This ballistic model for S bursts also suggests an interpretation for the origin of L burst emission.

Staelin, D.H.; Rosenkranz, P.W.

1982-12-01

372

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

373

Is the Jovian auroral H3+ emission polarised?  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

374

Dynamical Analysis of the Reddening of Jovian Oval BA  

NASA Astrophysics Data System (ADS)

Over the past several years, the Jovian White Ovals of the Southern Temperate Belt have undergone significant changes. Three large vortices which emerged in the 1940's, BC, DE, and FA, gradually converged in latitude until BC and DE merged in 1998 to form the vortex BE. In 2000, BE and FA merged to form BA. In 2005, amateur astronomers began reporting a steady reddening of oval BA, becoming comparable in color to the Great Red Spot (GRS) in early 2006 (Naeye, R., 2006, Sky and Telescope, 111, No. 6, 18). The recent reddening of the oval BA marks an unprecedented event in the history of Jovian vortices. For the first time we see the long-term evolution of a large vortex whose color now qualitatively appears similar to the GRS. Some hypotheses advanced for this newly observed phenomenon postulate a change in the internal dynamics of the vortex, often involving a deeper convective base and increased peak wind speeds of the oval (e.g. Simon-Miller, A., et al., 2006, Icarus, submitted). To investigate dynamical changes associated with the oval interactions, we utilized images of oval BA from both pre-reddened (but post-merger) late 2000 Cassini ISS/NAC flyby imagery and post-reddened 2006 Hubble Space Telescope ACS/HRC images. Quantitative statistical analyses of the wind profile and vorticity are used to test the hypothesis that we are witnessing not merely a change in magnitude of wind speeds, but a transition of BA across geostrophic regimes (Williams, G.P., Yamagata, T., 1984, J. Atmos. Sci., 41, 453-478). Additionally, simulations of the oval BA were performed using the EPIC General Circulation Model (Dowling, T.E., et al., 1998, Icarus 132: 221-238) in an effort to study non-observational variables underlying the recent color change. This work was supported by NASA through award number NNG05GB45G.

Sussman, Michael; Chanover, N. J.; Simon-Miller, A. A.; Morales-Juberias, R.

2006-09-01

375

Low Energy Particle Oscillations and Correlations with Hydromagnetic Waves in the Jovian Magnetosphere: Ulysses Measurements  

NASA Technical Reports Server (NTRS)

We report on measurements of energetic particle modulations observed by the HI-SCALE instrument aboard the Ulysses Spacecraft that were associated with the only hydromagnetic wave event measured inside the Jovian magnetosphere by the Ulysses magnetometer investigation.

Krupp, N.; Tsurutani, B. T.; Lanzerotti, L. J.; Maclennan, C. G.

1996-01-01

376

International Workshop on Time-Variable Phenomena in the Jovian System. (Abstract Only),  

National Technical Information Service (NTIS)

Many of the scientifically interesting phenomena that occur in the Jovian system are strongly time variable. Some are episodic (e.g., Io volcanism); some are periodic (wave transport in Jupiter's atmosphere); and some are exceedingly complex (magnetospher...

M. J. S. Belton, R. A. West

1988-01-01

377

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

NASA Astrophysics Data System (ADS)

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.

1981-02-01

378

Er:YAG Laser: A New Technical Approach to Remove Torus Palatinus and Torus Mandibularis  

PubMed Central

Objective. The aim of this study was to assess the ability of Er:YAG laser to remove by excision torus mandibularis and to smooth torus palatinus exostosis. Materials and Methods. Torus mandibularis (TM) and torus palatinus (TP) were surgically eliminated via the Er:YAG laser using the following parameters: TM: output power ranging from 500 to 1000?mJ, frequency from 20 to 30?Hz, sapphire tips (diameter 0.8?mm), air-water spray (ratio 5/5), pulse duration 150??sec, fluence ranging from 99592?J/cm2 to 199044,586?J/cm2. TP: a peeling technique was used to eliminate TP, as excision by slicing being impossible here. Results. TM: excision was obtained after 12730 pulses. TP: smoothing technique took more time compared with excision. Once peeling was considered to be accomplished, the use of a surgical rasp was necessary to eliminate bone spicules that could delay the wound to heal in good conditions. Conclusion. Er:YAG excision (TM) or Er:YAG peeling (TP) are safe clinical techniques easy to practice even if the time required for excision or surface smoothing is more than the time required with bony burs and high speed instruments. PMID:22792500

Rocca, J. P.; Raybaud, H.; Merigo, E.; Vescovi, P.; Fornaini, C.

2012-01-01

379

Mapping a Luminous Seyfert 1 Dust Torus  

NASA Astrophysics Data System (ADS)

Ground-based reverberation mapping of the well-studied Seyfert 1 galaxy WPVS 48 has revealed that the near infrared J+K band variations lag those in the visible B band by ~72 days. The extremely sharp echo suggests a nearly face-on view of the ~1500 K hot dust torus and a surprisingly small apparent dust covering angle <20 deg. Additional ground-based monitoring is scheduled for 2013 November through 2014 May. Measurements will include photometry in visible (UBVRI) and NIR bands (JHK) at 2-day cadence along with spectroscopic monitoring with the 10-m South African Large Telescope. Adding Spitzer/IRAC 3.6 and 4.5 micron monitoring will reveal the echo of cooler (~800 K) dust and of deeply embedded hot dust expected in the optically thick case. The results will confirm or reject AGN models proposing 1) a concave dust torus geometry (by Kawaguchi & Mori); 2) a convex dust torus geometry optically thick at 2 micron (suggested by us), potentially with puffed-up inner rim to explain the 3 micron bump seen in the SEDs of type-1 AGN; and 3) a dust-related origin of the broad line region (by Elitzur & Shlosman and Czerny et al.). We therefore ask for 18 Spitzer visits during the 51-day visibility window in early 2014. Spitzer is needed because 1% photometric repeatability cannot be achieved from the ground in the L+M bands. We apply for DDT because our initial detections of the NIR echoes were made after the regular proposal deadline. Observations of WPVS 48 will complement the sole comparable Spitzer AGN dust reverberation mapping program by observing an object 25 times more luminous.

Willner, Steven; Ashby, Matthew; Haas, Martin; Pozo Nunez, Francisco

2013-11-01

380

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

SciTech Connect

The mission of 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 {beta} 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 confirm 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 fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance l{sub i} {approx} 0.4 with strong shaping ({kappa} {approx} 2.7, {delta} {approx} 0.8) with {beta}{sub N} approaching the with-wall beta limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f{sub NI} {approx} 71%. Instabilities driven by super-Alfvenic ions are an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvenic. Linear TAE thresholds and appreciable fast-ion loss during multi-mode bursts are measured and these results are compared to theory. RWM/RFA feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with {beta} above the no-wall limit. The impact of n > 1 error fields on stability is a important result for ITER. 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 CHI plasmas to OH ramp-up. These results advance the ST towards next step fusion energy devices such as NHTX and ST-CTF.

Gates, D; 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; Bozzer, 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; 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; Soloman, 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; Weland, A

2009-01-05

381

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. The system measures fluctuations with k{sub perpendicular}{rho}{sub e} < or approx. 0.6 and k{sub perpendicular} < or approx. 20 cm{sup -1}. 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.

Smith, D. R.; Mazzucato, E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Lee, W.; Park, H. K. [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Domier, C. W.; Luhmann, N. C. Jr. [Department of Applied Science, University of California at Davis, Davis, California 95616-8254 (United States)

2008-12-15

382

Progress towards Steady State at Low Aspect Ratio on the National Spherical Torus Experiment (NSTX)  

SciTech Connect

Modifications to the plasma control capabilities and poloidal field coils of the National Spherical Torus Experiment (NSTX) have enabled a significant enhancement in shaping capability which has led to the transient achievement of a record shape factor (S ? q95 (I?? ???)) of ?41 (MA m?1 ??1) simultaneous with a record plasma elongation of ? ? ? ? ? ? 3. This result was obtained using isoflux control and real-time equilibrium reconstruction. Achieving high shape factor together with tolerable divertor loading is an important result for future ST burning plasma experiments as exemplified by studies for future ST reactor concepts, as well as neutron producing devices, which rely on achieving high shape factors in order to achieve steady state operation while maintaining MHD stability. Statistical evidence is presented which demonstrates the expected correlation between increased shaping and improved plasma performance.

D.A. Gates, J. Menard, R. Maingi, S. Kaye, S.A. Sabbagh, S. Diem, J.R.Wilson, M.G. Bell, R.E. Bell, J. Ferron, E.D. Fredrickson, C.E. Kessel, B.P. LeBlanc, F. Levinton, J. Manickam, D. Mueller, R. Raman, T. Stevenson, D. Stutman, G. Taylor, K. Tritz, H. Yu, and the NSTX Research Team

2007-11-08

383

Sigma model BPS lumps on a torus  

NASA Astrophysics Data System (ADS)

We study doubly periodic Bogomol’nyi-Prasad-Sommerfield lumps in supersymmetric CPN-1 nonlinear sigma models on a torus T2. Following the philosophy of the Harrington-Shepard construction of calorons in Yang-Mills theory, we obtain the n-lump solutions on compact spaces by suitably arranging the n lumps on R2 at equal intervals. We examine the modular invariance of the solutions and find that there are no modular invariant solutions for n=1, 2 in this construction.

Nakamula, Atsushi; Sasaki, Shin

2012-09-01

384

The Enceladus Torus: Saturn's Vaporous Ring T. A. Cassidy  

E-print Network

The Enceladus Torus: Saturn's Vaporous Ring T. A. Cassidy Top-down view of water vapor ejected from) eject water vapor with escape speed, into Saturn orbit. (similar to how E-ring is formed) Most Our explanation for why the torus is so broad · Comparison to Saturn's solid rings Why are they so

385

Minimal Liouville Gravity on the Torus via Matrix Models  

E-print Network

In this paper we use recent results on resonance relations between the matrix models and the minimal Liouville gravity to compute the torus correlation numbers in (3,p) minimal Liouville gravity. Namely, we calculate the torus generating partition function of the (3,p) matrix models and use it to obtain the one- and two-point correlation numbers in the minimal Liouville gravity.

Spodyneiko, Lev

2014-01-01

386

The Molecular Torus and Ionized Gas in the Circinus Galaxy  

Microsoft Academic Search

In the current AGN paradigm, distributions of ionized gas in so-called `ionization cones' are believed to be produced by shadowing of the central source of ionizing radiation by a molecular torus. If this is indeed the case, there should be an excellent correspondence between the locations of the inner edge of the torus and the edge of the inner apex

Andrew Wilson

1997-01-01

387

Global Bifurcation Destroying The Experimental Torus T2  

E-print Network

We show experimentally the scenario of a two-frequency torus $T^2$ breakdown, in which a global bifurcation occurs due to the collision of a torus with an unstable periodic orbit, creating a heteroclinic saddle connection, followed by an intermittent behavior.

T. Pereira; M. S. Baptista; M. B. Reyes; I. L. Caldas; J. C. Sartorelli; J. Kurths

2007-06-22

388

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

389

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

390

High-spin torus isomers and their precession motions  

NASA Astrophysics Data System (ADS)

Background: In our previous study, we found that an exotic isomer with a torus shape may exist in the high-spin, highly excited states of Ca40. The z component of the total angular momentum, Jz=60?, of this torus isomer is constructed by totally aligning 12 single-particle angular momenta in the direction of the symmetry axis of the density distribution. The torus isomer executes precession motion with the rigid-body moments of inertia about an axis perpendicular to the symmetry axis. The investigation, however, has been focused only on Ca40. Purpose: We systematically investigate the existence of exotic torus isomers and their precession motions for a series of N =Z even-even nuclei from Si28 to Ni56. We analyze the microscopic shell structure of the torus isomer and discuss why the torus shape is generated beyond the limit of large oblate deformation. Method: We use the cranked three-dimensional Hartree-Fock method with various Skyrme interactions in a systematic search for high-spin torus isomers. We use the three-dimensional time-dependent Hartree-Fock method for describing the precession motion of the torus isomer. Results: We obtain high-spin torus isomers in Ar36,Ca40,Ti44,Cr48, and Fe52. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in Ca40. It is found that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value. Conclusions: The high-spin torus isomer of Ca40 is not an exceptional case. Similar torus isomers exist widely in nuclei from Ar36 to Fe52 and they execute the precession motion. The torus shape is generated beyond the limit of large oblate deformation by eliminating the 0s components from all the deformed single-particle wave functions to maximize their mutual overlaps.

Ichikawa, T.; Matsuyanagi, K.; Maruhn, J. A.; Itagaki, N.

2014-09-01

391

A comprehensive model of ion diffusion and charge exchange in the cold Io torus  

NASA Technical Reports Server (NTRS)

A comprehensive analytic model of radial diffusion in the cold Io torus is developed. The model involves a generalized molecular cloud theory of SO2 and its dissociation fragments SO, O2, S, and O, which are formed at a relatively large rate by solar UV photodissociation of SO2. The key component of the new theory is SO, which can react with S(+) through a near-resonant charge exchange process that is exothermic. This provides a mechanism for the rapid depletion of singly ionized sulfur in the cold torus and can account for the large decrease in the total flux tube content inward of Io's orbit. The model is used to demonstrate quantitatively the effects of radial diffusion in a charge exchange environment that acts as a combined source and sink for ions in various charge states. A detailed quantitative explanation for the O(2+) component of the cold torus is given, and insight is derived into the workings of the so-called plasma 'ribbon'.

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

1988-01-01

392

Radio and Plasma Wave Science Opportunities Afforded by the Jupiter Icy Moons Orbiter  

Microsoft Academic Search

The Galileo mission demonstrated the extensive and varied interactions between the Jovian magnetosphere and the icy Galilean satellites. In particular, the Galileo plasma wave investigation showed the surprisingly complex array of plasma and radio wave phenomena accompanying Ganymede's magnetosphere, evidence of an extensive magnetospheric interaction at Europa, and a weaker yet highly variable interaction at Callisto. The plasma wave observations

W. S. Kurth; D. A. Gurnett; W. M. Farrell; M. D. Desch; M. L. Kaiser; P. Zarka; A. Lecacheux; P. Canu; S. J. Bolton; J. E. Wahlund; L. G. Blomberg; S. D. Bale; M. Moncuquet

2003-01-01

393

Arithmetic functions in torus and tree networks  

DOEpatents

Methods and systems for performing arithmetic functions. In accordance with a first aspect of the invention, methods and apparatus are provided, working in conjunction of software algorithms and hardware implementation of class network routing, to achieve a very significant reduction in the time required for global arithmetic operation on the torus. Therefore, it leads to greater scalability of applications running on large parallel machines. The invention involves three steps in improving the efficiency and accuracy of global operations: (1) Ensuring, when necessary, that all the nodes do the global operation on the data in the same order and so obtain a unique answer, independent of roundoff error; (2) Using the topology of the torus to minimize the number of hops and the bidirectional capabilities of the network to reduce the number of time steps in the data transfer operation to an absolute minimum; and (3) Using class function routing to reduce latency in the data transfer. With the method of this invention, every single element is injected into the network only once and it will be stored and forwarded without any further software overhead. In accordance with a second aspect of the invention, methods and systems are provided to efficiently implement global arithmetic operations on a network that supports the global combining operations. The latency of doing such global operations are greatly reduced by using these methods.

Bhanot, Gyan (Princeton, NJ); Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton On Hudson, NY); Gara, Alan G. (Mount Kisco, NY); Giampapa, Mark E. (Irvington, NY); Heidelberger, Philip (Cortlandt Manor, NY); Steinmacher-Burow, Burkhard D. (Mount Kisco, NY); Vranas, Pavlos M. (Bedford Hills, NY)

2007-12-25

394

Applications of High Etendue Line-Profile Spectro-Polarimetry to the Study of the Atmospheric and Magnetospheric Environments of the Jovian Icy Moons  

NASA Technical Reports Server (NTRS)

Electrodynamic effects play a significant, global role in the state and energization of the Earth's ionosphere/magnetosphere, but even more so on Jupiter, where the auroral energy input is four orders of magnitude greater than on Earth. The Jovian magnetosphere is distinguished from Earth's by its rapid rotation rate and contributions from satellite atmospheres and internal plasma sources. The electrodynamic effects of these factors have a key role in the state and energization of the ionosphere-corona- plasmasphere system of the planet and its interaction with Io and the icy satellites. Several large scale interacting processes determine conditions near the icy moons beginning with their tenuous atmospheres produced from sputtering, evaporative, and tectonic/volcanic sources, extending out to exospheres that merge with ions and neutrals in the Jovian magnetosphere. This dynamic environment is dependent on a complex network of magnetospheric currents that act on global scales. Field aligned currents connect the satellites and the middle and tail magnetospheric regions to the Jupiter's poles via flux tubes that produce as bright auroral and satellite footprint emissions in the upper atmosphere. This large scale transfer of mass, momentum, and energy (e.g. waves, currents) means that a combination of complementary diagnostics of the plasma, neutral, and and field network must be obtained near simultaneously to correctly interpret the results. This presentation discusses the applicability of UV spatial heterodyne spectroscopy (SHS) to the broad study of this system on scales from satellite surfaces to Jupiter's aurora and corona.

Harris, Walter M.; Roesler, Fred L.; Jaffel, Lotfi Ben; Ballester, Gilda E.; Oliversen, Ronald J.; Morgenthaler, Jeffrey P.; Mierkiewicz, Edwin

2003-01-01

395

Gyrokinetic Turbulence Simulation Challenges in 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. The coupling of ITG and ETG turbulence complicates simulations in regular tokamaks. However, the flow-driven suppression of long wavelength modes in NSTX may reduce the resolution requirements for ETG simulations. Reduced ion models, which still include the enhancement of zonal flows on the ion gyroradius scale, may also speed up ETG simulations. Here we present some linear studies of microtearing and ETG modes for NSTX parameters using the GYRO nonlinear gyrokinetic code and some initial nonlinear studies of the resulting turbulence. J. Candy, R. E. Waltz et al., J. Phys. Conf. Ser. 78, 012008 (2007).

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

2008-11-01

396

High resolution Thomson scattering for Joint European Torus (JET)  

SciTech Connect

A Thomson scattering system is being developed for Joint European Torus with 15 mm spatial resolution and a foreseen accuracy for temperature better than 15% at a density of 10{sup 19} m{sup -3}. This resolution is required at the internal transport barrier and edge pedestal and it can not be fully achieved with the present light detection and ranging systems. The laser for this system is Nd:YAG, 5 Joule, 20 Hz. Scattering volumes from R=2.9 m to R=3.9 m are imaged onto 1 mm diameter fibers, with F/25 collection aperture. Two fibers are used per scattering volume. Using optical delay lines, three scattering volumes are combined in each of the 21 filter polychromators. The signals are recorded with transient digitizers, which allow the combined time delayed signals to be resolved. Knowledge of the time delay between signals allows the use of correlation techniques in determining signal levels. The ac output of the amplifier is used, which tolerates a higher level of background signal without affecting dynamic range. The noise resulting from plasma light is determined directly.

Pasqualotto, R.; Nielsen, P.; Gowers, C.; Beurskens, M.; Kempenaars, M.; Carlstrom, T.; Johnson, D. [EFDA-CSU Culham, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein (Netherlands); General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2004-10-01

397

Overview of Recent Results from the National Spherical Torus Experiment*  

NASA Astrophysics Data System (ADS)

Both spherical torus devices for fusion development and ITER require high energy confinement, sustained stability, and manageable first wall heat fluxes. NSTX research targets a predictive understanding of these needs. Low-k microtearing simulations predict lower collisionality, ?, to be nonlinearly stabilizing. Measured ion gyro-scale fluctuations transiently decrease after the H-mode transition, while high-k scattering shows electron gyro-scale fluctuations may increase at lower ?. Other channels for transport such as high frequency Alfvenic modes are examined. Increased RWM stability is expected at lower ? only if stabilizing precession drift/bounce resonance conditions are maintained. Improved RWM control now includes radial and poloidal field sensors, and state space feedback with a 3D conducting structure model. Non- inductive current fractions of 65-70% have been sustained. Divertor heat flux width strongly decreases as Ip increases but snowflake divertor studies have reduced the heat flux significantly. Beneficial effects due to lithium depend nearly continuously on the amount of pre-discharge Li evaporation. Mo divertor tiles have been installed to determine the impact of Li-coated metallic PFCs at strike point locations. Coaxial helicity injection has produced 0.37MA peak current and yielded a 40% inductive flux savings for ohmic startup to 1MA plasma current. *Work supported by U.S. DOE contract DE-AC02-09CH11466.

Sabbagh, S. A.

2011-11-01

398

Advanced tokamak reactors based on the spherical torus (ATR/ST)  

SciTech Connect

Results of a preliminary conceptual design of a magnetic fusion reactor based on the spherical torus (tokamak), characterized by high first-stability-regime beta values at low aspect ratio and moderate vertical elongation of the plasma, are described. The concept incorporates resistive (demountable) toroidal-field coils, a double-null poloidal-field magnetic divertor, and the potential for oscillating-field current drive to allow steady-state operation. The physics basis, design-point determination, and fusion-power-core engineering are summarized.

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

1986-11-01

399

Modeling the excitation of global Alfve´n modes by an external antenna in the Joint European Torus (JET)  

Microsoft Academic Search

The active excitation of global Alfve´n modes using the saddle coils in the Joint European Torus (JET) [PlasmaPhysicsandControlledNuclearFusionResearch 1984, Proceedings of the 10th International Conference, London (International Atomic Energy Agency, Vienna, 1985), Vol. 1, p. 11] as the external antenna, will provide information on the damping of global modes without the need to drive the modes unstable. For the modeling

G. T. A. Huysmans; W. Kerner; D. Borba; H. A. Holties; J. P. Goedbloed

1995-01-01

400

AGN torus emission for a homogeneous sample of bright FSRQs  

E-print Network

We have selected a complete sample of 80 flat-spectrum radio quasars (FSRQs) from the WMAP 7-yr catalog within the SDSS area, all with measured redshift, and have inspected their SEDs looking for evidence of an AGN torus emission. A SED fitting algorithm has found such evidence for seven objects and an uncertain indication for one more. These 8 FSRQs belong to the sub-sample of 55 sources showing the optical--ultraviolet bump interpreted as thermal emission from a standard accretion disc. Torus luminosities have been estimated for the eight objects whose torus was identified by the fitting algorithm. For the other 47 FSRQs in the sub-sample we have derived upper limits to the torus luminosity. Our analysis shows that the torus can show up clearly only under quite special conditions: low luminosity and preferentially low peak frequency of the beamed synchrotron emission from the jet; high torus luminosity, close to that of the accretion disc. This implies that the inferred ratios of torus to disc luminosity ar...

Castignani, Gianluca

2014-01-01

401

Progress towards high-performance, steady-state spherical torus  

SciTech Connect

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values beta(T) of up to 35% with a near unity central beta(T) have been obtained. NSTX will be exploring advanced regimes where beta(T) up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (similar to60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I-p similar to 500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Ono, M. [Princeton Plasma Physics Laboratory (PPPL); Peng, Yueng Kay Martin [ORNL

2003-01-01

402

Progress Towards High-Performance, Steady-State Spherical Torus  

SciTech Connect

Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fastwave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I{sub P} {approx}500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

Lawrence Livermore National Laboratory

2004-01-04

403

Progress Towards High Performance, Steady-state Spherical Torus  

SciTech Connect

Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction ({approx}60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip {approx} 500 kA. In parallel, start-up using radio-frequency current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.

M. Ono; M.G. Bell; R.E. Bell; T. Bigelow; M. Bitter; W. Blanchard; J. Boedo; C. Bourdelle; C. Bush; W. Choe; J. Chrzanowski; D.