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1

Numerical simulation of torus-driven plasma transport in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The Rice convection model has been modified for application to the transport of Io-generated plasma through the Jovian magnetosphere. The new code, called the RCM-J, has been used for several ideal-magnetohydrodynamic (MHD) numerical simulations to study how interchange instability causes an initially assumed torus configuration to break up. In simulations that start from a realistic torus configuration but include no energetic particles, the torus disintegrates too quickly (approximately 50 hours). By adding an impounding distribution of energetic particles to suppress the interchange instability, resonable lifetimes were obtained. For cases in which impoundment is insufficient to produce ideal-MHD stability, the torus breaks up predominantly into long fingers, unless the initial condition strongly favors some other geometrical form. If the initial torus has more mass on one side of the planet than the other, fingers form predominatly on the heavy side (which we associate with the active sector). Coriolis force bends the fingers to lag corotation. The simulation results are consistent with the idea that the fingers are formed with a longitudinal thickness that is roughly equal to the latitudinal distance over which the invariant density declines at the outer edges of the initial torus. Our calculations give an average longitudinal distance between plasma fingers of about 15 deg which corresponds to 20 to 30 minutes of rotation of the torus. We point to some Voyager and Ulysses data that are consistent with this scale of torus longitudinal irregularity.

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

1994-01-01

2

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

NASA Technical Reports Server (NTRS)

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa-moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo orbiter mission, and for planning flyby and orbital measurements, (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy etal.,2007;Shematovichetal.,2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyro radius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions).Non-thermal distributions of upstream plasma will be addressed in future work. Photoionization,electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider two models for background plasma:(a) with O(++) ions; (b) with O(++) and S(++) ions. The majority of O2 atmosphere is thermal with an extended cold population (Cassidyetal.,2007). A few first simulations already include an induced magnetic dipole; however, several important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work.

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

2010-01-01

3

Convective transport of plasma in the inner Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

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

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

1990-04-01

4

Ulysses plasma observations in the Jovian magnetosheath  

NASA Technical Reports Server (NTRS)

The solar wind plasma experiment aboard the Ulysses spacecraft, including separate ion and electron instruments, measured the plasma properties of the Jovian magnetosheath during the February 1992 encounter with Jupiter. Seven separate magnetosheath intervals were observed, as well as four bow shock crossings and numerous encounters with the magnetopause and its boundary layer. We present an overview of ion and electron bulk parameters and a sampling of distribution shapes for the magnetosheath and adjacent plasma regions. Plasma flows are generally appropriate for slowing and deflection of the solar wind flow about a relatively stationary obstacle, with the notable exception of the first inbound sheath transit, when an expanding magnetosphere resulted in sunward flow just above the magnetopause. The existence of a planetary depletion layer is suggested by trends in plasma density for some magnetopause encounters. The magnetopause boundary layer is characterized by a combination of sheathlike and magnetospheric distributions of both ions and electrons. The ion population in the sheath is observed to include a significant population of suprathermal protons. Electron distributions have a distinctive shape previously observed in the terrestrial magnetosheath, with fluxes parallel to the magnetic field dominating at thermal energies and perpendicular fluxes dominating at higher energies. Trends in electron temperature near the bow shock indicate that shock motion plays an important role in heating the electrons. In general, the plasma characteristics of the Jovian magnetosheath are quite similar to those in its terrestrial counterpart, but the compressible nature of the Jovian magnetosphere accentuates the importance of boundary motions.

Phillips, J. L.; Bame, S. J.; Thomsen, M. F.; Goldstein, Bruce E.; Smith, E. J.

1993-01-01

5

The Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

Research on Jovian magnetospheric physics from 1979 through 1982 is surveyed, with a focus on the observations of Voyagers 1 and 2. Jovian fields and plasmas are characterized in the order of their distance from the planet, and special emphasis is given to the Io plasma torus (IPT) in the 4.9-8-Jovian-radius region and to the extended Jovian magnetotail. Topics reviewed include synchrotron radiation, magnetic-field models, Na and S emissions in the IPT, aurora, the magnetic-anomaly model, IPT plasma diffusion-convection, Io-generated Alfven wave, plasma configuration beyond the IPT, low-energy charged particles, cosmic-ray-energy particles, particle acceleration, magnetic configuration, tail current sheet and plasma disc, magnetopause and magnetosheath, interplanetary ions of Jovian origin, and the Jovian magnetosphere at Saturnian distances.

Birmingham, T. J.

1983-01-01

6

The structure of Jupiter's Io plasma torus inferred from Ulysses radio occultation observations  

Microsoft Academic Search

The radio downlinks from Ulysses were monitored during the passage of the spacecraft through the Io plasma torus shortly after closest approach to Jupiter. The electron content of the Io torus was derived from the dispersive phase shift of the S-band (2.3 GHz) signal with respect to the X-band (8.4 GHz) signal. Corrections were applied for non-Jovian contributions to the

M. K. Bird; S. W. Asmar; P. Edenhofer; O. Funke; M. Pätzold; H. Volland

1993-01-01

7

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.

8

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

9

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

10

Ray tracing of Jovian kilometric radiation  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

11

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

12

Injection of Compact Torus into the HIST spherical torus plasmas  

NASA Astrophysics Data System (ADS)

The three-dimensional interaction of a spheromak-like compact torus (CT) plasma with spherical torus (ST) plasmas has been experimentally studied to understand magnetic reconnection, helicity current drive, particle fuelling and Alfvén wave excitation [1]. We have examined how the sign of helicity (Co-HI and Counter-HI) of the injected CT influences on the ST plasmas on HIST [2]. The dynamics of the CT have been identified to be significantly different between the both injection cases. Time-frequency analysis shows that the fluctuation induced in the co-HI case has the maximum spectral amplitude at around 300 -- 400 kHz that may indicate the magnetic reconnection. In this case, the CT particle is released quickly at a periphery region, but on the other hand, for the counter-HI case, the CT could penetrate deeply into the core region as accompanied by Alfvén wave due to no magnetic reconnection. [1] M. Nagata, et al., Nucl. Fusion 45, 1056 (2005) [2] M. Nagata, et al., Physics of Plasmas 10, 2932 (2003)

Sugawara, M.; Katsumoto, S.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2006-10-01

13

Stability of the Io plasma torus/atmosphere interaction  

NASA Technical Reports Server (NTRS)

The stability of the Io plasma torus-atmosphere interaction is examined. A simple plasma deflection model describes how transients in the plasma flux and the content of the atmosphere affect the ionospheric conductance, limiting the plasma bombardment and, hence, the supply of atmospheric species to the torus. The supply of the torus is seen to be determined by the thermal structure of the plasma, namely, the amount of low energy plasma producing atmospheric erosion vs. that which produces ionization, so that the torus supply rate is not simply proportional to the torus ion density.

Johnson, R. E.; Mcgrath, Melissa

1993-01-01

14

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

NASA Astrophysics Data System (ADS)

Plasma diffusion processes relevant to the physical nature of the Io plasma torus at Jupiter were studied. Centrifugally driven flux tube interchange instability, the only published theory of Io torus plasma diffusion, was examined and found to be an invalid mechanism in the plasma torus. The collisional nature of the hot torus plasma is observed through its extreme ultraviolet (EUV) emissions and is characterized in the long mean free path regime where classical transport theory breaks down. 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 Chapman Enskog method of calculating the plasma diffusion coefficient from a solution of the Boltzmann equation is used. Simplifying approximations of a fully ionized plasma dominated by Coulomb elastic charged particle collisions are made to derive an ad hoc nonclassical diffusion coefficient which results in slow differential diffusion rates for the various sulfur and oxygen ions in the plasma torus. The radial spatial structure and energetics of the plasma torus are modeled by employing the collisional diffusion coefficient in a computer model calculation of collisional ionization diffusive equilibrium and energy branching. The computer model uses the known significant plasma reactions involving the torus sulfur and oxygen species, utilizing the most recently available atomic parameters. Neutral Cloud Theory fails to adequately power the copious amounts of UV radiation emitted by the Io plasma torus. The radial plasma model was used to investigate this 'energy crisis'. The application of the plasma model to a proposed heterogeneous source of energetic electrons and a proposal of inward diffusing energetic outer magnetospheric O2 and S2 ions as ad hoc heat inputs to the plasma torus electrons in order to maintain a steady state energy balance, are investigated.

Davis, Eric Wesley

15

Longitudinal asymmetry in the Io plasma torus  

NASA Astrophysics Data System (ADS)

A clear inbound-outbound asymmetry is found in Voyager 1 low-energy charged particle (LECP) phase space densities near 6 Jupiter radii. The asymmetry is of the same sign and comparable magnitude for electrons and ions at several different energies. Ion phase space density profiles at three values of the first invariant are uniformly displaced to larger radius by 0.25 Jupiter radii during the inbound pass. Inbound-outbound asymmetries which are very similar for electrons and ions at many different energies can be accounted for naturally by a convection electric field in the plasma torus. If the asymmetry is attributed to a convection field fixed in local time, then the field has a component of 4 mV/m pointing toward 0120 LT, roughly orthogonal to the dawn-dusk electric field proposed to account for local time asymmetry in the plasma torus. On the other hand, the asymmetry can be attributed to a corotating convection field, such that plasma outflow occurs within lambda(III) = 170-300 deg at a velocity of 2 x 10 to the -6th Jupiter radii per second near L = 6. In this case the LECP observations would be consistent with the magnetic anomaly model.

Cheng, A. F.; Paonessa, M. T.; Maclennan, C. G.; Lanzerotti, L. J.; Armstrong, T. P.

1984-05-01

16

Effect of parallel electric fields on whistler mode waves in an anisotropic Jovian magnetospheric plasma  

Microsoft Academic Search

The effect of parallel electrostatic field on the amplification of whistler mode waves in an anisotropic bi-Maxwellian weakly ionized plasma for Jovian magnetospheric conditions has been carried out. The growth rate for different Jovian magnetospheric plasma parameters forL = 5.6Rj has been computed with the help of general dispersion relation for the whistler mode electromagnetic wave of a drifted bi-Maxwellian

M. M. Ahmad; Altaf Ahmad; Lalmani

1992-01-01

17

Evidence for short cooling time in the Io plasma torus  

Microsoft Academic Search

We present empirical evidence for a radiative cooling time for the Io plasma torus that is about a factor of ten less than presently accepted values. We show that brightness fluctuations of the torus in the extreme ultraviolet (EUV) at one ansa are uncorrelated with the brightness at the other ansa displaced in time by five hours, either later or

M. Volwerk; M. E. Brown; A. J. Dessler; B. R. Sandel

1997-01-01

18

Torus-Shaped Dust Clouds in Magnetized Anodic Plasmas  

SciTech Connect

The generation of a torus-shaped dust cloud in an anodic plasma is decribed. The confined dust particles perfom a rotational motion around the torus major axis. The structure of the cloud in dependence of the external parameters are observed and the rotation velocity of the particles was measured and compared with a simple estimate.

Pilch, I.; Reichstein, T.; Greiner, F.; Piel, A. [Institute for Experimental and Applied Physics, Christian-Albrechts University, D-24098 Kiel (Germany)

2008-09-07

19

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

20

On the energy crisis in the Io plasma torus  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

21

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

22

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

23

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

24

Alfven wave propagation in the Io plasma torus  

NASA Technical Reports Server (NTRS)

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

Bagenal, F.

1983-01-01

25

Electron Bernstein waves in spherical torus plasmas  

SciTech Connect

Propagation and absorption of the electron Bernstein waves (EBWs) in spherical tokamaks (STs) have been intensively discussed in recent years because the EBWs coupled with an externally launched electromagnetic beam seem to be the only opportunity for microwave plasma heating and current drive in the electron cyclotron (EC) frequency range in the STs. The whole problem of the electron Bernstein heating and current drive (EBWHCD) in spherical plasmas is naturally divided into three major parts: coupling of incident electromagnetic waves (EMWs) to the EBWs near the upper hybrid resonance (UHR) surface, propagation and absorption of the EBWs in the plasma interior and generation of noninductive current driven by the EBWs. The present paper is a brief survey of the most important theoretical and numerical results on the issue of EBWs.

Saveliev, A. N. [A.F.Ioffe Physico-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)

2006-11-30

26

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

27

Low energy ion distribution measurements in Madison Symmetric Torus plasmas  

SciTech Connect

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

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

2014-06-15

28

Cassini-plasma interactions in the Enceladus torus  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

29

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

NASA Astrophysics Data System (ADS)

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

Vasyliunas, V. M.

1994-03-01

30

High Performance Plasmas on the National Spherical Torus Experiment  

SciTech Connect

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

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

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

2001-07-10

31

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

32

Fluid properties of the distant Jovian magnetotail plasma using New Horizons Solar Wind Around Pluto (SWAP) instrument's observations  

NASA Astrophysics Data System (ADS)

Solar Wind Around Pluto (SWAP) instrument onboard New Horizons (NH), obtained in situ measurements of low energy plasma ions (35 eV to 7.5 keV) in the distant Jovian magnetosphere during its 2007 flyby. 16 magnetopause crossings were observed between 1654 and 2429 RJ (1 RJ = 1 Jovian Radii) that were identified by transitions between magnetotail, boundary layer and magnetosheath plasma. We have developed a forward model of SWAP instrument in order to derive the fluid properties of the plasma ions in the Jovian magnetosheath where the plasma flux seems to be invariable for relatively long period of time and much higher than it is inside the magnetotail. We present the magnetosheath plasma fluid properties as derived using our preliminary model. Our results can explain the observed magnetopause crossings due to the magnetotail movement and compression. In addition, a correlation between plasma density and temperature was found. Since the statistical noise is much higher in the magnetotail dataset we explain what modifications are needed in our model and technique in order to derive the fluid properties of plasma ions in this region. Among others, we demonstrate how we can estimate the statistical noise of the data and we explore how this noise can affect the estimation of different plasma parameters.

Nicolaou, G.; McComas, D. J.; Bagenal, F.; Elliott, H. A.

2013-12-01

33

Io’s Hot Plasma Torus—A Synoptic View from Voyager  

Microsoft Academic Search

A study of the morphology of Io's hot plasma torus has encompassed hundreds of Voyager UVS measurements of torus intensity. The long-term average stateøof the torus can be characterized by an axial asymmetry in the brightness of the prominent SIII 685-A feature manifested as an enhancement in brightness whose peak is fixed near 1900 local time. No long-term correlation of

B. R. Sandel; A. L. Broadfoot

1982-01-01

34

Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas  

NASA Astrophysics Data System (ADS)

As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.

Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira

2010-11-01

35

`Mass unloading along the inner edge of the Enceladus plasma torus W. M. Farrell,1  

E-print Network

`Mass unloading along the inner edge of the Enceladus plasma torus W. M. Farrell,1 M. L. Kaiser,1 D field lines near the Cassini gap. Citation: Farrell, W. M., M. L. Kaiser, D. A. Gurnett, W. S. Kurth, A

Gurnett, Donald A.

36

Energetic oxygen and sulfur in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Measurements made in the Jovian magnetosphere by the cosmic ray subsystem on Voyager 1 and 2 are reported. Energy spectra of oxygen ions in the energy range 1-20 MeV/nuc between 5 and 20 Jovian radii are presented, and phase space densities are calculated. A steep positive radial gradient in the phase space density of the energetic oxygen ions is observed, indicating an inward diffusive flow. The upper limit on the rate at which oxygen ions with greater than 400 MeV/nuc-G diffuse across 10 Jovian radii is calculated to be 5 x 10 to the 21st ions per second, indicating that about 10 to the -7th of the ions from Io are accelerated to over 400 MeV/nuc-G and diffuse to 10 Jovian radii. Observations also suggest that oxygen and sulfur ions in the Io plasma torus diffuse radially outward, are nonadiabatically accelerated in a region outside 17 Jovian radii, and diffuse inward and outward from the accelerated region.

Gehrels, N.; Stone, E. C.; Trainor, J. H.

1981-10-01

37

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

38

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

NASA Technical Reports Server (NTRS)

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 oxygen. Typical wave intensities are 0.1 mV/m, and the spectra also show significant Doppler broadening, Delta omega/omega approximately 1. A theoretical analysis of lower hybrid wave generation by a bump-on-tail ring distribution of ions is given. The model is appropriate for plasmas with a superthermal pickup ion population present. A general methodology is used to demonstrate that the maximum plasma heating rate possible through anomalous wave-particle heat exchange is less than approximately 10 to the -14th ergs per cu cm per s. Although insufficient to meet the power requirement of the EUV-emitting warm torus, the heating rate is large enough to maintain a low-density (0.01-0.1 percent) superthermal electron population of keV electrons, which may lead to a small but significant anomalous ionization effect.

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

1985-01-01

39

Source characteristics of Jovian narrow-band kilometric radio emissions  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

40

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

41

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

Microsoft Academic Search

Tritium transport in edge localized mode (ELM) high confinement (H-mode) plasmas is analyzed here as a function of density for discharges from the recent trace tritium experimental campaign performed on Joint European Torus. In this campaign small amounts of tritium have been puffed or injected (with neutral beam injectors) into deuterium plasmas [K.-D. Zastrow, J. M. Adams, Yu. Baranov et

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

2005-01-01

42

Ion heating and containment in the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Experimental observations have been made during steady-state operation of the NASA Lewis Bumpy Torus experiment at input powers up to 150 kilowatts in deuterium and helium gas. A steady-state ion heating method utilizes a Modified Penning discharge operated in a bumpy torus confinement geometry. The bumpy torus plasma is acted upon by a combination of strong electric and magnetic fields. In a deuterium plasma, electron temperatures from 14 to 140 electron volts and ion kinetic temperatures from 160 to 1785 electron volts were observed. At least two distinct operating regimes exist, each of which is associated with a characteristic range of background gas pressure and electron temperature. Experimental data show that the average ion residence time (ionization time) in the plasma is virtually independent of the magnetic field strength.

Roth, J. R.

1974-01-01

43

Ion heating and containment in the NASA Lewis bumpy torus plasma  

NASA Technical Reports Server (NTRS)

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 torus confinement geometry. The bumpy torus plasma is acted upon by a combination of strong electric and magnetic fields. In a deuterium plasma, electron temperatures from 14 to 140 electron volts and ion kinetic temperatures from 160 to 1785 electron volts were observed. At least two distinct operating regimes exist, each of which is associated with a characteristic range of background gas pressure and electron temperature. Experimental data show that the average ion residence time in the plasma is virtually independent of magnetic field strength.

Roth, J. R.

1974-01-01

44

Atomic clouds as distributed sources for the plasma torus  

NASA Technical Reports Server (NTRS)

Implications of recent developments for the neutral particle environment of Jupiter are considered. The first detection is reported of very hot S+ ions with gyrospeeds comparable to the corotations speed, a phenomenon which results from a neutral sulfur cloud. Evidence supports the hypothesis that extensive neutral clouds of oxygen and sulfur exist and are important sources of ions and energy for the Io torus.

Brown, R. A.; Ip, W. H.

1981-01-01

45

47The Io Plasma Torus The satellite of Jupiter, Io,  

E-print Network

-section of the cylinder is r 2 , and the height of the cylinder is the circumference of the torus which equals 2 R, so of the cross section to a point on the circumference is given by r 2 = x 2 + y 2 . The width of the washer (the

46

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

Microsoft Academic Search

Plasma torus peak density structure at three epochs is consistently understoodThe dawn-dusk electric field departs from the true dawn-dusk directionThe electron density at Io's position in the plasma torus varies significantly

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

2011-01-01

47

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

48

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

NASA Technical Reports Server (NTRS)

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

Roth, J. R.

1976-01-01

49

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

50

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

51

Plasma Response to Lithium-Coated Plasma-Facing Components in the National Spherical Torus Experiment  

SciTech Connect

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

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

2009-08-20

52

Narrowband Z-mode emissions interior to Saturn's plasma torus W. M. Farrell,1  

E-print Network

Narrowband Z-mode emissions interior to Saturn's plasma torus W. M. Farrell,1 W. S. Kurth,2 M. L the course of an hour. Citation: Farrell, W. M., W. S. Kurth, M. L. Kaiser, M. D. Desch, D. A. Gurnett, and P

Gurnett, Donald A.

53

Decametric modulation lanes as a probe for inner jovian magnetosphere  

NASA Astrophysics Data System (ADS)

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

Arkhypov, Oleksiy V.; Rucker, Helmut O.

2013-11-01

54

Formation of zebra pattern in low-frequency Jovian radio emission  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

55

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

SciTech Connect

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

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

2009-01-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

57

Properties of plasma ions in the distant Jovian magnetosheath using Solar Wind Around Pluto data on New Horizons  

NASA Astrophysics Data System (ADS)

Solar Wind Around Pluto (SWAP) instrument on New Horizons (NH) made in situ observations of ions in Jupiter's distant magnetotail and magnetosheath during its 2007 flyby. NH observed 16 magnetopause crossings between 1654 and 2429 RJ antisunward from Jupiter. We have developed a method to calculate the bulk properties of the plasma ions (density, velocity, and temperature) based on a forward model of the SWAP instrument response. We fit the observations using both Maxwell and kappa distributions. In this paper we describe our technique, which includes accounting for the detailed and asymmetric response of the SWAP electrostatic analyzer, and present the results for the distant Jovian magnetosheath. Finally, we discuss the characteristics of the derived bulk properties and compare these results to previously developed gas dynamic models for magnetospheres of giant planets.

Nicolaou, G.; McComas, D. J.; Bagenal, F.; Elliott, H. A.

2014-05-01

58

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

NASA Technical Reports Server (NTRS)

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

Richardson, R. W.

1974-01-01

59

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

60

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

61

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

62

Chandra X-Ray Observatory Observations of the Jovian System  

NASA Technical Reports Server (NTRS)

Chandra X-ray Observatory (CXO) and XMM-Newton observations of x-rays from the Jovian system have answered questions that arose from early observations with the Einstein and Rosat X-ray Observatories, but in the process of vastly increasing our knowledge of x-ray emission from Jupiter and its environs they have also raised new questions and point to new opportunities for future studies. We will review recent x-ray results on the Jovian system, from the point of view of the CXO, and discuss various questions that have arisen in the course of our studies. We will discuss prospects for more observations in the immediate future, and how they might address open questions. Finally we will briefly describe ways in which an imaging x-ray spectrometer in the vicinity of the Jovian system could provide a wealth of data and results concerning Jupiter's x-ray auroral and disk emission, elemental abundance measurements for the Galilean moons, and detailed studies of x-ray emission from the Io Plasma Torus.

Elsner, R. F.; Bhardwaj, A.; Gladstone, R.; Waite, J. H.; Ford, P.; Branduari-Raymont, G.

2005-01-01

63

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

64

Sustainment Study of Flipped Spherical Torus Plasmas on HIST  

NASA Astrophysics Data System (ADS)

We have discovered that helicity-driven ST plasmas relax toward the flipped state by decreasing the external toroidal field and reversing its sign in time [1]. From the viewpoint of coaxial helicity injection (CHI) current drive, it is conceivable that the flipped ST (F-ST), which consists of only closed flux surfaces, compares favorably with the normal ST. We have investigated the sustainment mechanism of the F-ST plasma. The helicity-driven relaxed theory shows that there exist the mixed states of ST and F-ST in the flux conserver. Helicity is transferred to F-ST through the ST with coupling with gun electrodes. It has been found that magnetic reconnection between the toroidal magnetic field plays important role in the sustainment of the F-ST. The magnetic field in the outer edge region shows regular oscillations which have a large amplitude of the n=1 mode. The core region of the F-ST seems to be relatively stable. [1] M. Nagata, et al., Phys. Rev. Lett. 90, 225001 (2003)

Takamiya, T.; Nagata, M.; Kawami, K.; Hasegawa, H.; Fukumoto, N.; Uyama, T.; Masamune, S.; Iida, M.; Katsurai, M.

2003-10-01

65

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

66

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

67

The proton concentration in the vicinity of the Io plasma torus  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

68

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

69

Low-frequency limit of Jovian radio emissions and implications on source locations and Io plasma wake  

Microsoft Academic Search

After deriving from Ulysses-URAP measurements the low-frequency limit of the Jovian hectometer emission spectrum (250±50kHz at the ?20dB level below the emission peak), and confirming the absence of Io's control on Jovian radio emission below ?1MHz, we propose a single common explanation for these low-frequency limits: both are well explained by the quenching of the generation mechanism (the cyclotron-maser instability)

Philippe Zarka; Julien Queinnec; Frank J. Crary

2001-01-01

70

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

71

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

SciTech Connect

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

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

2009-10-15

72

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

NASA Astrophysics Data System (ADS)

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.

Yi, M.; Thorne, R. M.

1991-02-01

73

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

74

Radial profiles of ion density and parallel temperature in the Io plasma torus during the Voyager 1 encounter  

Microsoft Academic Search

We have analyzed a moderately large set of Voyager 1 ultraviolet spectrometer preencounter scans of the Io warm plasma torus in order to deduce its three-dimensional spatial structure. The density distributions of the five ions O+, O++, S+, S++, and S+++ have been determined in order to deduce their scale heights and thus the ion kinetic temperature parallel to the

Floyd Herbert; B. R. Sandel

1995-01-01

75

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

76

Effect of plasma shaping on performance in the National Spherical Torus Experimenta)  

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

77

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

78

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

79

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

80

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

SciTech Connect

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

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

2006-01-01

81

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

82

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

83

Resistive wall mode stabilization of high-? plasmas in the National Spherical Torus Experimenta)  

NASA Astrophysics Data System (ADS)

The resistive wall mode (RWM) poses a limit to the maximum ? that can be sustained in magnetic fusion experiments. RWM stabilization physics at low aspect ratio is studied in high-? National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)] plasmas (?t up to 39%; ?N up to 6.8) to understand and alleviate this constraint. Plasmas with increased q in NSTX have been maintained with ? above the computed ideal no-wall ? limit for more than 20 wall times with no signs of RWM growth in cases where toroidal rotation ??>?A/4q2 across the entire plasma cross section. Plasmas that violate this stability criterion can suffer a RWM induced collapse within a few wall times. This critical rotation profile for stabilization is in agreement with drift-kinetic theory applied to low frequency magnetohydrodynamics modes [A. Bondeson and M. S. Chu, Phys. Plasmas 3, 3013 (1996)]. A toroidally symmetric array of internal sensors has been used to observe n =1-3 RWMs in NSTX. This array consists of Bp and Br sensors both above and below the midplane at 12 toroidal locations instrumented to detect toroidal mode numbers of n =1-3. RWM perturbations exceeding 30G have been measured with mode growth rates on the order of 5ms. Small modes (?B<10G) which cause minor drops in ?, with growth rates ˜1500 s-1 have been observed when ?N exceeds 6. Resonant field amplification of an externally applied error field by the stable RWM has been observed.

Sontag, Aaron C.; Sabbagh, S. A.; Zhu, W.; Bialek, J. M.; Menard, J. E.; Gates, D. A.; Glasser, A. H.; Bell, R. E.; LeBlanc, B. P.; Bell, M. G.; Bondeson, A.; Callen, J. D.; Chu, M. S.; Hegna, C. C.; Kaye, S. M.; Lao, L. L.; Liu, Y.; Maingi, R.; Mueller, D.; Shaing, K. C.; Stutman, D.; Tritz, K.

2005-05-01

84

Waves and coherent structures in the turbulent plasma of a simple magnetized torus  

NASA Astrophysics Data System (ADS)

A systematic analysis of electrostatic fluctuations by means of Beall's technique has been performed in a helium plasma of the simple magnetized torus Blaamann [Rypdal et al., Plasma Phys. Controlled Fusion 35, 1099 (1994)]. A comparison between the wave-like description furnished by Beall's technique and the method based on conditional sampling, has been carried out. In agreement with previous results in Blaamann using the conditional sampling technique, coherent structures of the vortex type have been identified and analyzed measuring the bicoherence and the phase between the density and potential fluctuations. Moreover, with Beall's technique it was also possible to analyze the role of coherent structures in particle transport and identify another instability driving collisional drift waves. Fluctuations can produce particle transport in the edge of the coherent structures but not in the core of the vortical structure. Also, drift modes were detected at high magnetic fields, for which the density gradient was more pronounced. In addition, it was observed that increased neutral pressure produced a decrease of the spatial and cross coherence leading to dissipation of coherent structures and to an increase of the particle transport.

Riccardi, Claudia; Fredriksen, A.?Shild

2001-01-01

85

Interaction of rotating helical magnetic field with the HIST spherical torus plasmas  

NASA Astrophysics Data System (ADS)

The physical mechanism of current drive by co-axial helicity injection (CHI) has been experimentally investigated on both spheromak and spherical torus (ST) configurations on the HIST device [1]. It has been observed that the n = 1 kink mode rotates toroidally with a frequency of 10-20 kHz in the ExB direction. It seems that the induced toroidal current by CHI strongly relates with the observed rotating kink mode. On the other hand, it is well known that MHD instabilities can be controlled or even suppressed by an externally applied helical magnetic field in tokamak devices. Therefore, we have started to install two sets of external helical coils in order to produce a rotating helical magnetic field on HIST. Mode structures of the generated rotating helical magnetic field and preliminary experimental results of the interaction of the rotating helical magnetic field with the HIST plasmas will be shown in the conference. [1] M. Nagata, et al., Physics of Plasmas 10, 2932 (2003)

Kikuchi, Yusuke; Sugahara, Masato; Yamada, Satoshi; Yoshikawa, Tatsuya; Fukumoto, Naoyuki; Nagata, Masayoshi

2006-10-01

86

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

87

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

NASA Astrophysics Data System (ADS)

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

Serio, Andrew W.; Clarke, John T.

2008-09-01

88

Measured improvement of global magnetohydrodynamic mode stability at high-beta, and in reduced collisionality spherical torus plasmas  

SciTech Connect

Global mode stability is studied in high-? National Spherical Torus Experiment (NSTX) plasmas to avoid disruptions. Dedicated experiments in NSTX using low frequency active magnetohydrodynamic spectroscopy of applied rotating n?=?1 magnetic fields revealed key dependencies of stability on plasma parameters. Observations from previous NSTX resistive wall mode (RWM) active control experiments and the wider NSTX disruption database indicated that the highest ?{sub N} plasmas were not the least stable. Significantly, here, stability was measured to increase at ?{sub N}?l{sub i} higher than the point where disruptions were found. This favorable behavior is shown to correlate with kinetic stability rotational resonances, and an experimentally determined range of measured E?×?B frequency with improved stability is identified. Stable plasmas appear to benefit further from reduced collisionality, in agreement with expectation from kinetic RWM stabilization theory, but low collisionality plasmas are also susceptible to sudden instability when kinetic profiles change.

Berkery, J. W.; Sabbagh, S. A.; Balbaky, A. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B. P.; Manickam, J.; Menard, J. E.; Podestà, M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)] [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

2014-05-15

89

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

90

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

91

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

92

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

93

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

NASA Astrophysics Data System (ADS)

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

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

1993-01-01

94

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

95

A 12 coil superconducting bumpy torus magnet facility for plasma research  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

96

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

SciTech Connect

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

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

2009-02-15

97

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

98

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

SciTech Connect

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

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

2014-02-15

99

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

PubMed

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

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

2014-02-01

100

The Jovian magnetosphere and magnetopause  

NASA Technical Reports Server (NTRS)

The characteristics of the planet Jupiter's inner magnetosphere are examined, taking into account the Pioneer 10 and 11 magnetometer data. Data on the reliability of spherical harmonic expansions are presented in a table. The properties of the Jovian magnetosheath and magnetopause are described. Bow shock and magnetopause crossings were securely identified in plasma data and were usually identified in plasma data and were usually identifiable in the magnetometer data. Explanations for the large number of observed crossings are discussed. It is pointed out that in the case of the outer magnetosphere the observed field strength is nearly an order of magnitude larger than would be expected from Jupiter's dipole moment. The distinguishing characteristics of the magnetic field in the middle magnetosphere are also considered.

Davis, L., Jr.; Smith, E. J.

1976-01-01

101

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

102

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

103

Observations of the Jovian System with the Chandra X-Ray Observatory  

NASA Technical Reports Server (NTRS)

The {\\sl Chandra X-ray Observatory) observed the Jovian system on 25-26 Nov 1999 with the Advanced CCD Imaging Spectrometer (ACIS), in support of the Galileo flyby of Io, and on 18 Dec 2000 with the imaging array of the High Resolution Camera (HRC-I), in support of the Cassini flyby of Jupiter. These sensitive, very high spatial-resolution X-ray observations have revealed that Jupiter's northern x-ray aurora originates at a spot fixed in a coordinate system rotating with the planet at latitude (60--70 deg north) and longitude (160--180 deg System III). Contrary to previous expectations, this location is poleward of the main FUV auroral oval and the foot of the Io Flux Tube, and is apparently connected magnetically to a region of the outer magnetosphere beyond $\\sim$30 Jupiter radii. The northern auroral x-ray emission varies with a period $\\sim$45 minute and has a an average power of $\\sim$1 GW. The earlier view that Jupiter's x-ray aurora resulted from the precipitation of heavy ions from the outer edge of the lo Plasma Torus is now in doubt. Jupiter's disk also emits x-rays with a power of $\\sim$2 GW, perhaps resulting from reprocessing of solar x-rays in its atmosphere. These observations reveal for the first time x-ray emission from the Io Plasma Torus, with a power of $\\sim$0.1 Gw. The origin of this emission is not currently understood, although bremmstrahlung from non-thermal electrons may play a significant role. Finally, we report the discovery of very faint ($\\sim$1--2 MW) soft x-ray emission from the Galilean satellites Io, Europa, and probably Ganymede, most likely as a result of bombardment of their surfaces by energetic ($ greater than $10 keV) H, O, and S ions from the region of the Io Plasma Torus.

Elsner, R. F.; Tennant, A. F.; Weisskopf, M. C.; Gladstone, G. R.; Waite, J. H.; Crary, F. J.; Grodent, D.; Howell, R. R.; Johnson, R. E.; Bhardwaj, A.; Six, N. Frank (Technical Monitor)

2002-01-01

104

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

105

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

106

The Ring-dust Plasma Torus as Observed by Cassini RPWS  

NASA Astrophysics Data System (ADS)

We present new results indicating that ring-dust is a major plasma source for the magnetosphere of Saturn. This study of the cold plasma near the ring plane of Saturn is based on observations by the Radio and Plasma Wave Science (RPWS) instruments on board the Cassini spacecraft. A dense dusty ring plasma was detected both during the inbound and outbound crossings of the ring plane. The Langmuir probe and plasma emission measurements indicated an increase of the plasma density up to 100 cm(-3), and the dense plasma was centred around the maximum count rate of impacting micrometer sized dust particles on the spacecraft. Furthermore, the Langmuir probe observations pointed toward a cold plasma population with electron temperatures around 0.5-1 eV and ion temperatures well below 100 eV. The ram current to the spherical probe indicated an average ion mass between 20-40 amu, which was confirmed by the INMS instrument that the dominant ion was molecular oxygen (O2+). The plasma density decreased to very low values when Cassini passed over (northward) the visible rings of Saturn, which suggest that the ring-plasma is most dense just outside the F ring. The visible rings presumably absorb magnetically mirrored charged particles on conjugate magnetic field lines, and hence the plasma density is low inside the F-ring. Except during the Saturn Orbit Injection (SOI) spacecraft burn, the spacecraft potential was determined under the rings. From the information of the thermal plasma and the spacecraft potential over the rings we make an attempt to infer the electric charge of dust particles in the rings themselves. The Langmuir probe measurements therefore may provide observational constraints on the problem how the co-rotating magnetosphere of the planet Saturn affect the dynamics and structure of ring-dust.

Wahlund, J.; Boström, R.; Eriksson, A. I.; Gustafsson, G.; Morooka, M.; Gurnett, D. A.; Kurth, W. S.; Desch, M.; Waite, H. J.; Yelle, R.; Muller-Wodarg, I.

2004-12-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

108

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

109

Ion cyclotron resonance frequency heating of deuterium plasmas in the Joint European Torus: Interpretation of measurements of minority hydrogen isotope ion distribution functions  

NASA Astrophysics Data System (ADS)

An iterative method for solving the hot-plasma dispersion relation and computing power deposition during multispecies minority ion cyclotron resonance frequency (ICRF) heating experiments has been presented in a companion paper [D. Testa, W.G.F.Core, and A.Gondhalekar, Phys. Plasmas (this issue)]. Here this method is further developed to model and validate the measurements of minority hydrogen isotope ion distribution functions during multispecies second harmonic ICRF heating of deuterium plasmas in the Joint European Torus [J.Wesson, Tokamaks (Clarendon, Oxford, 1997), pp. 581-603].

Testa, D.; Core, W. G. F.; Gondhalekar, A.

1999-09-01

110

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

111

The internal magnetic field structures and current density profiles in the Helicity Injected Spherical Torus plasma driven by coaxial helicity injection  

NASA Astrophysics Data System (ADS)

In the Helicity Injected Spherical Torus device [Nagata et al., Proceedings of the 17th International Atomic Energy Agency Fusion Energy Conference, Yokohama, 1998 (International Atomic Energy Agency, Vienna, 1998) CD-ROM, EXP4/10], internal magnetic field and current density structures of spherical torus (ST) plasmas sustained by coaxial helicity injection (CHI) have been revealed via intensive internal magnetic measurements. The internal magnetic configuration of the ST plasma formed by CHI is in good agreement with the results of numerical equilibrium fitting calculations. The generation of closed poloidal flux of ST has been verified by varying the external toroidal field strength in the same device. Interestingly, the transition of the current profile from hollow to peaked has been observed during the sustainment phase, which could be explained by inductive effects of currents on open field lines winding the central conductor.

Nagata, Masayoshi; Kanki, Takashi; Fukumoto, Naoyuki; Uyama, Tadao

2003-07-01

112

Dual periodicity of the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

Using data from the 1979 Voyager flybys of Jupiter and two sets of ground-based observations of the Io torus, this paper presents an extensive analysis concerning the nature of the second magnetospheric periodicity of the Jupiter's magnetic field, along with a definition of a new Jovian matching coordinate system (referred to as system IV). It is shown that available independent data sets covering a time interval of 4 years, which either drift or show no particular organization in system III, fit mutually consistent patterns in system IV. Provisional values are derived for a transformation between systems III and IV. It is emphasized that system IV needs to be tested against additional data before its durability is assured.

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

1988-01-01

113

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

114

Investigations of the magnetic structure and the decay of a plasma-gun-generated compact torus  

NASA Astrophysics Data System (ADS)

The results of a series of experimental measurements of compact toroidal (CT) plasmas produced by a magnetized coaxial plasma gun injecting into a flux-conserving metallic liner are reported. The experiments were performed on the Beta II facility at Lawrence Livermore National Laboratory. The magnetic equilibria are well described by a force-free eigenmode structure that results from an extension of Taylor's theory of the reversed-field pinch. Consideration of helicity conservation during relaxation of the composite plasma-gun flux-conserver system to the final state equilibrium yields theoretical expressions that are compared with the experiment. In particular the CT poloidal flux (?pol) and the overall electrical efficiency for producing the CT are predicted to be functions of the plasma gun inner-electrode flux (?gun) and the volt-seconds input to the gun discharge (??0 V dt). Away from a cutoff at too low values of ??0 V dt or too high values, ?gun ,?pol scales linearly with the square root of the product of ?gun and ??0 V dt, whereas the electrical efficiency equals about 13% for ??0 V dt/?gun ?10. For an electrical energy input Win =45 kJ, CT's are produced with poloidal plus toroidal field energy up to WB =8 kJ and toroidal plasma current Itor =330 kA. The chord-averaged plasma density is 2-4×1014 cm-3, and the plasma volume equals 150 liters. The radius of the flux conserver is 37.5 cm, and the axial length is 40 cm. If a bias flux ?b is superimposed on the flux conserver, n=1 tilting is observed when ?b/?pol exceeds a ratio of about 0.20 to 0.25. Impurity radiation measured by a pyroelectric detector accounts for all of the plasma magnetic energy if uniform volume emission of radiation is assumed. The dominant impurities observed are carbon and oxygen. Helium-like lines are not observed, indicating that the plasma has not ``burned through'' the low electron temperature radiation maxima. The experimentally observed decay times (defined by the e-folding time of plasma magnetic fields) are 80 to 160 ?sec—consistent with Zeff =2 and Te in the range 5-10 eV if classical resistivity is assumed. A zero-dimensional rate equation model of impurity radiation loss gives a reasonably good account of the experimental observations and predicts that the carbon concentration must be reduced to the level of a few percent to allow burnthrough of the low-Te carbon radiation barrier. Glow discharge cleaning of the gun electrodes and flux conserver resulted in a 20% increase of the e-folding time of plasma magnetic fields (from an average value 115 to 140 ?sec). The CT plasma density was observed to scale linearly with the electrical energy input to the gun discharge and to be only weakly dependent on the filling pressure and timing of pulsed deuterium gas valves. It seems likely that further improvements in increasing plasma lifetime can be made by improving the vacuum conditions and discharge cleaning methods and experimenting with the gun electrode materials.

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

1983-07-01

115

Studies of plasma flow past Jupiter's satellite Io  

NASA Technical Reports Server (NTRS)

We have investigated the interaction of Io, Jupiter's innermost Galilean satellite, with the Io plasma torus. The interaction of Io with the plasma surrounding it has been a subject of interest for almost 30 years, dating from the discovery by Bigg (1964) that radio emissions from the Jovian magnetosphere are controlled by Io's position. Since that time, both ground-based and spacecraft observations have shown that Io is a unique satellite that influences the Jovian magnetosphere in important ways. In particular, material from Io is a major source of plasma for the magnetosphere, and the energy that this plasma harnesses from Jupiter's co-rotating magnetic field is an important power source for the magnetosphere. It is apparent that the local interaction of the torus plasma with Io plays a key role in the formation, composition, and energetics of the Io torus; the interaction is also highly nonlinear. We have modeled this interaction using time-dependent three-dimensional magnetohydrodynamic (MHD) simulations. During this past year, we have used NASA support to develop a new MHD code to study the interaction. As part of the Galileo spacecraft's recent successful insertion into orbit around Jupiter, the spacecraft passed within 900 km of Io's surface. Our calculations have focused on using Galileo particles and fields data to examine a question that was not resolved by the Voyager observations: Does Io have an intrinsic magnetic field? In this progress summary, we describe our efforts on this problem to date.

Linker, Jon

1996-01-01

116

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

117

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

SciTech Connect

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

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

2014-08-15

118

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

119

Jovian type III radio bursts  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

120

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

121

International Jupiter Watch - A program to study the time variability of the Jovian system  

NASA Technical Reports Server (NTRS)

The International Jupiter Watch is a program for the encouragement and coordination of the study of temporal variations in the Jovian system. It consists of six discipline working groups concerned with: the Io torus under N. Schneider; the Jovian atmosphere under R. West; the magnetosphere and radio emissions under I. de Peter and M. Klein; aurora under J. Caldwell; the Galilean satellites under W. Sinton and J. Goguen; and laboratory measurement and theory under B. Lutz. To date the IJW has held two workshops and selected several Jupiter Watch periods for coordinated observations. The next Jupiter Watch workshop is tentatively scheduled for 1990 in association with the next COSPAR meeting.

Russell, C. T.; Caldwell, J. J.; De Pater, I.; Goguen, J.; Klein, M. J.

1990-01-01

122

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

123

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.

124

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

125

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

126

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma. [ion heating by Penning discharge in confinement geometry  

NASA Technical Reports Server (NTRS)

Spectroscopic measurements were carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.

Richardson, R. W.

1974-01-01

127

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

SciTech Connect

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

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

1993-07-01

128

Impact of the Ulysses velocity on the diagnosis of the electron density by the Unified Radio and Plasma Wave sounder in the outskirts of the Io torus  

NASA Astrophysics Data System (ADS)

The resonance spectra collected on February 8, 1992, in the outskirts of the Io plasma torus by the Unified Radio and Plasma wave (URAP) relaxation sounder on board the Ulysses spacecraft present significant differences from the active spectra gathered by earthbound spacecraft in similar plasma conditions. The most striking anomaly is the lack of resonances at the harmonics of the electron gyrofrequency, one of the most common signatures found in usual sounder spectra. These differences are interpreted, when computing the dispersion relation of the Bernstein modes triggered by the sounder, by taking into account the large frequency shift induced on the resonances by the high speed of the Ulysses spacecraft in the plasma. The frequency of the shifted resonances depends on the ratio Vsat/p/Vth of the spacecraft speed relative to the plasma and the thermal speed of the electrons. The observed resonances are all found to be in excellent agreement with the computed frequencies obtained in this way. Some predicted resonances are not observed on the Ulysses spectra, but it is suggested that they have too long a wavelength to be easily detected by the URAP antenna. As a by-product of the electron density diagnosis allowed by this analysis a rough estimate of the electron temperature can be deduced.

Le Sager, Philippe; Canu, Patrick; Cornilleau-Wehrlin, Nicole

1998-11-01

129

Modulation of the jovian ring current and magnetodisc due to impulsive volcanic activity 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. Using recent UV observations of the Io plasma torus (Yoneda et al., 2010) we use 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 find (negative) magnetic field perturbations with an amplitude of around 5 nT that persist for around 10 - 15 days which is consistent with the magnetic field observations presented by Russell et al. (2001). We conclude by commenting 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. A.; Guio, P.

2010-12-01

130

Jovian Planet Systems Are jovian planets all alike?  

E-print Network

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

Crenshaw, Michael

131

Ion cyclotron resonance frequency heating of deuterium plasmas in the Joint European Torus: Modeling of the resonant minority ion distribution function  

NASA Astrophysics Data System (ADS)

Experiments were carried out in JET, the Joint European Torus [J. Wesson, Tokamaks (Clarendon, Oxford, 1997), pp. 581-603], to heat deuterium plasmas using ion cyclotron resonance frequency (ICRF) heating at fundamental hydrogen and second harmonic deuterium frequencies. These plasmas contained two minority resonant ion species, protons, and nonthermal deuterons due to neutral beam injection (NBI). To determine the resonant ion energy distribution functions in such plasmas, an iterative method for solving the hot-plasma dispersion relation was developed using a complex perpendicular wave number in cylindrical geometry. The distribution function of ICRF-heated ions is strongly anisotropic and significantly hotter than that of nonresonating particles. Therefore thermal and overlapping cyclotron harmonics effects were considered in computing wave dispersion and absorption. The formal solution of the lowest-order Fokker-Planck equation is derived for the slowing-down NBI deuterons. In a companion paper these results are applied to interpretation of measurements of distribution functions of ICRF-heated ions in the JET.

Testa, D.; Core, W. G. F.; Gondhalekar, A.

1999-09-01

132

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

133

Source characteristics of Jovian narrow-band kilometric radio emissions  

Microsoft Academic Search

New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery

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

1993-01-01

134

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

135

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

136

Jovian magnetospheric neutral wind and auroral precipitation flux  

NASA Technical Reports Server (NTRS)

A theoretical model of the Jovian magnetosphere is used to describe the mechanism by which energy is transported from Jupiter's rotation into heavy ions precipitating into the atmosphere, and resulting in intense ultraviolet aurora. The flow and magnetic field configurations used in the model are drawn from data collected by the Voyager orbiter. It is shown that the observed Jovian auroral radiation power is supplied by the precipitation of heavy ions of Iogenic origin. The ions are created by a charge exchange between the Io torus and fly as neutrals to the outer magnetosphere. A small fraction of the ions are photoionized in the outer magnetosphere where they acquire a magnetic moment determined by the local corotation electric field and planetary magnetic field. As the ions diffuse inward they are energized adiabatically. A schematic drawing illustrating the evolution of this process is provided. It is also shown that Jupiter may be a significant source of heavy ions for the solar wind by means of photoionization of a neutral wind. Secondary charge exchange in the outer magnetosphere could supply a flux of minimum energy neutral atoms that may have been measured by the Voyager Low Energy Charged Particle detector (LECP).

Eviatar, A.; Barbosa, D. D.

1984-01-01

137

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

138

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

139

Fine spectral structures in Jovian decametric radio emission observed by ground-based radio telescope.  

NASA Astrophysics Data System (ADS)

Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radio emission in a wide frequency range. This emission is a result of a complicated interaction between the dynamic Jovian magnetosphere and energetic particles supplying the free energy from planetary rotation and the interaction between Jupiter and the Galilean moons. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from few MHz up to 40 MHz. This emission is generated via cyclotron maser mechanism in sources located along Jovian magnetic field lines. Depending on the time scales the Jovian DAMexhibits different complex spectral structures. We present the observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN- 2 (Poltava, Ukraine) operated in the decametric frequency range. This telescope is one of the largest low frequency telescopes in Europe equipped with high performance digital radio spectrometers. The antenna array of URAN-2 consists of 512 crossed dipoles with an effective area of 28 000m2 and beam pattern size of 3.5 x 7 deg. (at 25 MHz). The instrument enables continuous observations of the Jovian radio during long period of times. Jovian DAM was observed continuously since Sep. 2012 (depending on Jupiter visibility) with relatively high time-frequency resolution (4 kHz - 100ms) in the broad frequency range (8-32MHz). We have detected a big amount of the fine spectral structures in the dynamic spectra of DAM such as trains of S-bursts, quasi-continuous narrowband emission, narrow-band splitting events and zebra stripe-like patterns. We analyzed mainly the fine structures associated with non-Io controlled DAM. We discuss how the observed narrowband structures which most probably are related to the propagation of the decametric radiation in the Jupiter's ionosphere can be used to study the plasma parameters in the inner Jovian magnetosphere.

Panchenko, M.; Brazhenko, A. I.; Shaposhnikov, V. E.; Konovalenko, A. A.; Rucker, H. O.

2014-04-01

140

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

141

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

142

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

143

Dual periodicity of the Jovian Magnetosphere  

Microsoft Academic Search

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

B. R. Sandel; A. J. Dessler

1988-01-01

144

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

SciTech Connect

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

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

2014-04-15

145

Low-Energy Energetic Neutral Atom Imaging of Io Plasma and Neutral Tori  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

146

The magnetic anomaly model of the Jovian magnetosphere - Predictions for Voyager  

NASA Technical Reports Server (NTRS)

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, has been put forth to account for the various observed Jovian magnetospheric phenomena that show evidence of Jovian longitudinal asymmetry or planetary spin periodicity. From this model, normalized by empirical fitting to Pioneer 10 and 11 flyby data and to ground-based radio data, a series of predictions are made that are subject to test by the forthcoming flybys of Jupiter by Voyagers 1 and 2. These predictions cover: (1) the longitude range and time intervals of enhanced interaction between Io (and possibly Europa) and Jupiter's ionosphere, (2) plasma, energetic particle, and magnetic field periodicities in the outer magnetosphere, and (3) the sub-spacecraft System III longitude and the time, modulo 10 hours, of the first and subsequent magnetopause crossings.

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

1979-01-01

147

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

SciTech Connect

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

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

2011-01-15

148

Observations of the Jovian UV aurora by Voyager  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

149

Simultaneous Observation of Jovian Radio Emissions by Cassini and Wind  

NASA Technical Reports Server (NTRS)

During the Cassini instrument checkout interval in January 1999 as the spacecraft was making a distant (0.6 AU) swing by Earth, the radio and plasma wave receiver (RPWS) detected radio emission from the sun, Earth, and Jupiter, the latter including both the hectometric (HOM) and decametric (DAM) components. The WAVES experiment on the Wind spacecraft in orbit near Earth was also making observations of Jupiter at this same time. By combining the RPWS and WAVES data sets, we are able to provide some insight into the instantaneous beaming of Jovian radio emissions. As seen by Jupiter, Cassini and Wind were a few degrees apart during this period, yet the correlation between Jovian DAM arcs observed by the two spacecraft suggests that the beam width is even narrower and does not simultaneously illuminate both. The only earlier spacecraft capable, in principle, of making these observations were Voyager-1 and 2, but their sensitivity to DAM emissions was too limited to reliably measure the instantaneous beaming. The beam width implied by the RPWS-WAVES measurements is approximately the same as the angle through which Jupiter rotates while an arc (at a fixed frequency) is visible. The HOM Jovian emissions, on the other hand, seem similar as observed by RPWS and WAVES, consistent with earlier Wind-Ulysses measurements indicating a somewhat broader beam width.

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

1999-01-01

150

Radiation chemistry in the Jovian stratosphere: laboratory simulations.  

PubMed

Low-pressure continuous-flow laboratory simulations of plasma induced chemistry in H2/He/CH4/NH3 atmospheres show radiation yields of hydrocarbons and nitrogen-containing organic compounds that increase with decreasing pressure in the range 2-200 mbar. Major products of these experiments that have been observed in the Jovian atmosphere are acetylene (C2H2), ethylene (C2H4), ethane (C2H6), hydrogen cyanide (HCN), propane (C3H8), and propyne (C3H4). Major products that have not yet been observed on Jupiter include acetonitrile (CH3CN), methylamine (CH3NH2), propene (C3H6), butane (C4H10), and butene (C4H8). Various other saturated and unsaturated hydrocarbons, as well as other amines and nitriles, are present in these experiments as minor products. We place upper limits of 10(6)-10(9) molecules cm-2 sec-1 on production rates of the major species from auroral chemistry in the Jovian stratosphere, and calculate stratospheric mole fraction contributions. This work shows that auroral processes may account for 10-100% of the total abundances of most observed organic species in the polar regions. Our experiments are consistent with models of Jovian polar stratospheric aerosol haze formation from polymerization of acetylene by secondary ultraviolet processing. PMID:11540156

McDonald, G D; Thompson, W R; Sagan, C

1992-09-01

151

Energetic oxygen and sulfur ions in the Jovian magnetosphere. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Observations of 1 to 20 MeV/nuc oxygen, sodium, and sulfur ions in the Jovian magnetosphere are reported. Measurements made by the cosmic ray subsystem on Voyager 1 and 2 were used to calculate abundances and energy spectra in the region from 5 to 20 Jovian radii. The phase space density of the oxygen ions calculated from the spectra has a positive radial gradient between 6 and 17 Jovian radii, indicating an inward diffusive flow. The diffusion coefficient upper limit at 9 Jovian radii is approximately 10 to the -5 power/s. This limit, combined with the analysis of Voyager plasma observations by Siscoe et al.1981, implies an upper limit to the mass loading rate near Io of approximately 10 to the 28th power ions/s. The energetic oxygen lifetime is within an order of magnitude of the strong pitch-angle diffusion lifetime in this region, with the largest total number of particles lost between 7.5 and 12.5 Jovian radii. It is shown that the losses are not due to geometric absorption by Io, absorption by dust grains, or energy loss in the plasma of the inner magnetosphere, and it is therefore postulated that the primary loss mechanism is pitch-angle scattering into the loss cone.

Gehrels, N.

1981-01-01

152

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

153

Low-frequency fluctuation spectra and associated particle transport in the NASA Lewis bumpy-torus plasma  

NASA Technical Reports Server (NTRS)

The strong radial electric field associated with the Penning discharge and the strong toroidal magnetic field give rise to a diversity of E/B phenomena, such as rotating waves and spokes, which in turn manifest themselves as space-time fluctuations of the plasma density and potential. Work is done to further understand the nature and origin of the fluctuations and their connection with fluctuation-induced transport. The approach is to monitor the density and potential fluctuations; to digitize the data; and to generate, with the aid of a computer, various spectral properties by means of the fast fourier transform. Of particular interest is the computer-generated transport spectrum that indicates in a quantitative way which fluctuation spectral components contribute to transport and which do not. All experimental measurements of the spectral characteristics of the plasma are given in absolute units rather than as relative values. Preliminary measurements of the transport spectrum of the ion population are given, and it is shown that the fluctuation-induced transport is in order-of-magnitude agreement with that inferred from the steady state current flowing to the electrodes that generate the plasma.

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

1978-01-01

154

PARTIAL TORUS INSTABILITY  

SciTech Connect

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

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

2010-07-20

155

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

Microsoft Academic Search

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

T. W. Hill; F. C. Michel

1976-01-01

156

Direction finding study of Jovian hectometric and broadband kilometric radio emissions: Evidence for their auroral origin  

Microsoft Academic Search

Taking advantage if the direction finding capabilities of the Ulysses unified radio and plasma wave (URAP) experiment we derive the source locations and emission characteristics of the Jovian hectometric (HOM) and broadband kilometric (bKOM) emissions. Unlike previous studies we additionally determine the systematic error of the source direction due to the uncertainty of the antenna\\/receiver calibration parameters. To obtain maximum

H. P. Ladreiter; P. Zarka; A. Lacacheux

1994-01-01

157

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

158

Radiation chemistry in the Jovian stratosphere - Laboratory simulations  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

159

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

Microsoft Academic Search

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

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

2009-01-01

160

Wake flowfields for Jovian probe  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

161

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

162

Jupiter's magnetosphere: Plasma description from the Ulysses flyby  

SciTech Connect

Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating that similar processes are operating. A boundary layer populated by a varying mixture of solar wind and magnetospheric plasmas was found inside the magnetopause, again as at Earth. In the middle magnetosphere, large electron density excursions were detected with a 10-hour periodicity as planetary rotation carried the tilted plasma sheet past Ulysses. Deep in the magnetosphere, Ulysses crossed a region, tentatively described as magnetically connected to the Jovian polar cap on one end and to the interplanetary magnetic field on the other. In the inner magnetosphere and Io torus, where corotation plays a dominant role, measurements could not be made because of extreme background rates from penetrating radiation belt particles.

Bame, S.J.; Barraclough, B.L.; Feldman, W.C.; Gisler, G.R.; Gosling, J.T.; McComas, D.J.; Phillips, J.L.; Thomsen, M.F. (Los Alamos National Lab., NM (United States)); Goldstein, B.E.; Neugebauer, M. (California Inst. of Tech., Pasadena (United States))

1992-09-11

163

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

164

Mandibular torus morphology.  

PubMed

The morphology of the mandibular torus was examined, and comparisons were made between a Medieval Norse skeletal population from Greenland and a 14th to 17th century Greenland Eskimo skeletal series. Three parameters were analyzed: degree of development (on a 4-point scale), position and length, and surface morphology according to the number of knobs, or lobuli. It was found that the Eskimos have a high frequency of weakly developed tori and no cases of the extreme development, while over 20% of the Norsemen had tori in the "extreme" category. The Norse torus was generally found to be longer than that of the Eskimos, and both groups exhibited a slight asymmetry between the sides, the torus on the left side tending to be longer and more forward in position than the right. A great difference was found in surface morphology. The Norse torus is in general very irregular, while the Eskimo torus is rather smooth. These differences are believed to be genetically determined. PMID:7468791

Sellevold, B J

1980-11-01

165

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

166

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

167

A scenario for Jovian S-bursts  

Microsoft Academic Search

Jovian S-bursts are intense impulsive decameter radio spikes drifting in frequency in tens of milliseconds over several hundreds of kHz up to a few MHz. Their generation scenario has been much debated for 30 years. The automated analysis of an extensive set of digital radio observations at very high temporal and spectral resolutions is presented here. It strongly suggests that

Philippe Zarka; Thomas Farges; Boris P. Ryabov; Meil Abada-Simon; Laurent Denis

1996-01-01

168

Observations of Jovian Electrons at 1 AU  

Microsoft Academic Search

It has recently been suggested that electrons of Jovian origin are responsible for the 'quiet time increases' in the > 3-MeV electron intensity observed at I AU. Using data from the California Institute of Technology electron\\/isotope spectrometers on Imp 7 and 8, we have studied the temporal behavior of quiet time electrons at I AU over the period October 1972

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

1976-01-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

170

Rotation Properties of Three Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

171

Dust measurements in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Dust measurements have been obtained with the dust detector onboard the Galileo spacecraft inside a distance of about 60RJ from Jupiter (Jupiter radius, RJ = 71,492 km) during two periods of about 8 days around Galileo's closest approaches to Ganymede on 27 June and on 6 Sept 1996. The impact rate of submicrometer-sized particles fluctuated by a factor of several hundred with a period of about 10 hours, implying that their trajectories are strongly affected by the interaction with the Jovian magnetic field. Concentrations of small dust impacts were detected at the times of Ganymede closest approaches that could be secondary ejecta particles generated upon impact of other particles onto Ganymede's surface. Micrometer-sized dust particles, which could be on bound orbits about Jupiter, are concentrated in the inner Jovian system inside about 20RJ from Jupiter.

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

1997-09-01

172

Interplanetary scintillation and Jovian DAM emission  

NASA Astrophysics Data System (ADS)

The influence of interplanetary scintillations (IPS) on Jovian decametric (DAM) emission (10-40 MHz) is studied on broad-band dynamic spectra, for the whole range of solar elongations. L-bursts are confirmed to be the result of IPS, and it is shown that they are broad-band bursts. This implies that IPS are correlated on the whole frequency range of observation. It is concluded from observations at conjunction that the intrinsic time scale of Jovian emission is either some milliseconds (S-bursts) or some minutes (arcs). On the other hand, when the elongation is about 130 deg east, a clear decrease in scintillation appears, which has already been observed by Erskine (1976). It is shown that this is a permanent feature of IPS. It could be interpreted as an effect of the interplanetary magnetic field in IPS.

Genova, F.; Leblanc, Y.

1981-05-01

173

Forward and inverse modeling for jovian seismology  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

174

SL9 Dust in the Jovian System?  

NASA Astrophysics Data System (ADS)

The break up of the comet Shoemaker-Levy 9 (SL9) in 1992 shortly before the fragment train spectacularly crashed into Jupiter must have produced a copious amount of dust. It has been suggested (e.g., Horányi 1994, GRL 21, 1039--1042) that in about ten years following the SL9 disruption a fraction of material would settle in retrograde orbits well inside the jovian magnetosphere. In an attempt to find any evidence for the SL9 dust in the jovian system, we analyzed dust detector data of the Galileo spacecraft obtained from 1996 through 2001 between the orbits of the Galilean satellites. We have selected dust events probably caused by impacts of dust grains in retrograde orbits and derived yearly averages of the dust number density in that region. Our preliminary results seem to indicate a perceptible variation of the number density of the retrograde dust population with time, which might be attributed to the SL9 dust. Scarcity of the dataset prevents us from making firm conclusions, however. Furthermore, a direct comparison of the simulation results and the detector data is hampered by the fact that the theory and the measurements cover somewhat different time spans (2002 vs 1996--2001) and spatial regions (4--6 vs 6--30 jovian radii from the planet).

Krivov, A. V.; Krueger, H.; Horanyi, M.; Spahn, F.

2002-09-01

175

Radiation from Electron Phase Space Holes as a Possible Source of Jovian S-bursts  

NASA Astrophysics Data System (ADS)

Radio frequency short burst emissions (25 - 30 MHz), known as Jovian S-bursts, have been observed from the Jovian aurora for over fifty years. These emissions, associated with Io's motion, have a rapidly declining frequency and an extremely narrow bandwidth. While it is widely believed that S-bursts are generated by the electron cyclotron maser mechanism, the mechanism responsible for the rapidly declining frequency and narrow bandwidth is currently uncertain. Similar fine structure has been observed in Auroral Kilometric Radiation (AKR) by several auroral satellites. It was postulated by Mutel et al, [2007] that AKR emissions, created by the electron cyclotron maser, have enhanced growth in ion phase space holes. However, the implied speed (~20,000 km/s) of the structure creating the Jovian S-bursts is significantly faster than that creating the fine structure in AKR emissions (~100s of km/s) indicating that a faster structure is responsible for the fine structure in the radiation observed from Jupiter. We postulate that electron phase space holes radiate in the Jovian Aurora plasma environment and are a possible source of S-burst emission. Electron phase-space holes are ubiquitous in an auroral environment and travel at the implied speeds. This study shows that, under the conditions expected at Jupiter (strongly magnetized), electron phase space holes have enough energy content and can excite electro-magnetic waves. This finding implies that electron phase-space holes may be an important source of radiation from strongly magnetized or from relativistic astrophysical plasmas.

Goodrich, K.; Ergun, R.

2013-12-01

176

Observations of Short Term Variation of Jovian Synchrotron Radiation  

NASA Astrophysics Data System (ADS)

We have made detailed observations of Jovian decimetric radiation (DIM) from relativistic electrons in the Jovian radiation belt by using the Kashima 34 in antenna to seek the existence of DIM short-term variations. In these observations, the sky tipping method was used to correct the terrestrial atmospheric extinction effect. We also evaluated the background radio sources noise, which has caused serious problems in previous observations. As a result we showed for the first time that the Jovian synchrotron radiation has variations in intensity over a period of a few days. We then developed a model of Jovian synchrotron radiation based on the empirical models of Jovian magnetic field and the distribution of particles in the Jovian radiation belt derived from direct measurements made by past spacecraft. By comparing this model with the results of observations, we clarified that when the Jovian synchrotron radiation intensity is increasing, the spatial distribution of electrons in the Jovian radiation belt changes in such a way that the electrons concentrate at Jupiter's magnetic equatorial plane. Next, we developed and numerically tested a computer code relating to the transport of particles in the Jovian radiation belt. We showed that the observed flux increase of Jovian synchrotron radiation for a few days can be explained by a scenario in which the radial diffusion coefficient of electrons in the radiation belt increases. Furthermore, we performed a comparative analysis with the solar F10.7 observed on the earth during the same period, and we showed the possibility that this increase in the radial diffusion coefficient arises from heating of the Jovian ionosphere by solar UV/EUV radiation during the observation period.

Miyoshi, Yoshizumi; Misawa, Hiroaki; Morioka, Akira; Kondo, Tetsuro; Koyama, Yasuhiro; Nakajima, Junichi

2001-03-01

177

Computational compact torus experiment  

SciTech Connect

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

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

1980-12-24

178

Low energy ion distribution measurements in Madison Symmetric Torus plasmas J. B. Titus, E. D. Mezonlin, and J. A. Johnson III  

E-print Network

, Florida 32310, USA 2 Pyramid Plasmas LLC, Lawrenceville, Georgia 30043, USA (Received 8 May 2014; accepted are useful because they can diagnose the bulk ion temperature, the power lost due to charge

Wisconsin at Madison, University of

179

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

180

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

181

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

182

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

183

Cosmic ray ionization of the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic-ray-induced cascade may be especially important in ionizing the atmosphere at levels where the total number density exceeds 10 to the 19th per cu cm (well below the ionospheric layers produced by solar EUV). A model containing both positive and negative ion reactions has been employed to compute electron and ion number densities. Peak electron number densities of the order of 1000 per cu cm may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH4(+) and CnHm(+) cluster ions, with n at least 2; it is suggested that the absorption of galactic cosmic-ray energy at such relatively high pressures in the Jovian atmosphere (M about 10 to the 18th to 10 to the 20th per cu cm) and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.

Capone, L. A.; Dubach, J.; Whitten, R. C.; Prasad, S. S.

1979-01-01

184

A theory of Jovian decameter radiation  

NASA Astrophysics Data System (ADS)

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

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

1983-02-01

185

VOLUME54, NUMBER9 PHYSICAL REVIEW LETTERS 4 MARCH1985 Conversion of Wave Energy to Magnetic Field Energy in a Plasma Torus  

E-print Network

VOLUME54, NUMBER9 PHYSICAL REVIEW LETTERS 4 MARCH1985 Conversion of Wave Energy to Magnetic Field into plasma heating so that the conversion efficiency of rf energy to po- loidal field energy, given. Evidently, P,JP- 1. This points to a regime for efficient energy conversion except for two further effects

Karney, Charles

186

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

187

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

188

A Comprehensive Analysis of Io's Atmosphere and Torus  

Microsoft Academic Search

This final report describes the results of our NASA\\/Planetary Atmospheres program studying the atmosphere of Jupiter's moon Io and the plasma torus which it creates. Io is the most volcanically active body in the solar system, and it is embedded deep within the strongest magnetosphere of any planet. This combination of circumstances leads to a host of scientifically compelling phenomena,

Nicholas M. Schneider

1999-01-01

189

Parabolic torus transreflector antenna  

NASA Astrophysics Data System (ADS)

The possible scan rate of conventional radar antennas using parabolic dishes is limited to about 60 rev/min. This limitation is related to mechanical rotation requirements. Many radar applications require high data renewal rates, including short-range defense systems and systems for reduction of sea clutter. Faster scan rates can be obtained by using phased arrays and electronic scanning. However, the use of the required equipment introduces considerable complexity and cost. The present investigation is concerned with a novel form of antenna permitting high scan rates, taking into account a parabolic torus transreflector antenna. The feed horn illuminates one side of the radome with polarization parallel to the wires, which therefore reflect the radiation like a dish antenna. In the antenna considered, rotation of the beam is effected by mechanical rotation of the horn feed only, and this provides the potential for high scanning rates.

Diaz, L. M.; Smith, M. S.

1984-12-01

190

Jovian Chromophore Characteristics from Multispectral HST Images  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

191

The Orbits of the Regular Jovian Satellites  

NASA Astrophysics Data System (ADS)

At the conclusion of the Galileo Mission we produced ephemerides for the Galilean and four inner Jovian satellites, Amalthea, Thebe, Adrastea, and Metis [1]. The satellite orbits were determined by fitting a data set that included Earthbased astrometry through 2001 and data acquired by the Pioneer, Voyager, Ulysses, Cassini, and Galileo spacecraft. The spacecraft tracking data provided additional information on the Jovian system gravity parameters. In preparation for the Juno mission currently enroute to Jupiter, we have been developing new ephemerides from updated satellite orbits. As before, the orbits are determined through a comprehensive data fit which also redetermines the gravity parameters and spacecraft trajectories to be consistent with the revised satellite orbits. Our standard model for the orbits, both satellite and spacecraft, is a numerical integration of their equations of motion. We include the gravitational effects of the point mass mutual interactions of Jupiter, the Galilean satellites, and Amalthea (Thebe, Adrastea, and Metis are assumed to be massless), the effects of an oblate Jupiter, and perturbations from the Sun and planets. For our new orbits we also take into account the effects of tides raised on Jupiter by the satellites. Lainey et al. [4] have pointed out the importance of the tidal accelerations. The spacecraft are also affected by nongravitational forces, e.g., solar radiation pressure, trajectory correction maneuvers. These forces are discussed by several authors [2, 3, 5]. Our current data set is an expansion of that used previously. We have extended the Galilean satellite Earthbased astrometry back to 1891 and forward to 2013 and the inner satellite astrometry back to 1892 and forward to 2002. We added the Galilean satellite mutual events from 2003 and 2009, the Galilean satellite eclipse timings from 1878 to 2013, and the Earthbased radar ranges to Ganymede and Callisto measured in 1992. We also augmented our spacecraft data set with imaging acquired by the New Horizons spacecraft when it flew through the Jovian system in February 2007. In this paper we present the results of our latest determination of the satellite orbits and associated gravity parameters. We compare the orbits and gravity parameters to those that we found previously and our tidal parameters to those of Lainey et al.. We comment on possible future modifications and enhancements before our ephemeris delivery to the Juno Project for orbital operations.

Jacobson, R.

2014-04-01

192

A beaming model of the Io-independent Jovian decameter radiation based on multipole models of the Jovian magnetic field  

NASA Technical Reports Server (NTRS)

A geometrical model is presented in which the apparent source locations of the Io-independent decameter radiation are computed. The calculations assume that the radiation is produced by stably trapped electrons radiating near the electron gyrofrequency and that the emission is then beamed onto a conical surface. The maximum occurrence probability of noise storms is associated with regions in the Jovian magnetosphere where the axis of the emission cone is most inclined toward the Jovian equatorial plane. The calculations utilize and compare two of the octupole spherical harmonic expansions of the Jovian magnetic field constructed from data accumulated by the fluxgate and vector helium magnetometers on board Pioneer 11.

Goldstein, M. L.; Eviatar, A.; Thieman, J. R.

1978-01-01

193

Neutral cloud and heavy ion inner torus at Saturn  

Microsoft Academic Search

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

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

1989-01-01

194

Jovian large-scale stratospheric circulation  

NASA Astrophysics Data System (ADS)

An attempt is made to diagnose the annual-average mean meridional residual Jovian large-scale stratospheric circulation from observations of the temperature and reflected sunlight that reveal the morphology of the aerosol heating. The annual mean solar heating, total radiative flux divergence, mass stream function, and Eliassen-Palm flux divergence are shown. The stratospheric radiative flux divergence is dominated the high latitudes by aerosol absorption. Between the 270 and 100 mbar pressure levels, where there is no aerosol heating in the model, the structure of the circulation at low- to midlatitudes is governed by the meridional variation of infrared cooling in association with the variation of zonal mean temperatures observed by IRIS. The principal features of the vertical velocity profile found by Gierasch et al. (1986) are recovered in the present calculation.

West, R. A.; Friedson, A. J.; Appleby, J. F.

1992-11-01

195

Jovian Auroral Monitoring Coordinated with the IJW  

NASA Astrophysics Data System (ADS)

Jovian aurorae are complicated, time-dependent phenomena. Only recently has it been realized that they are observable from the Earth and infrared wavelengths (2 microns and 8 microns) as well as from space in the ultraviolet (120 nm - 160 nm). Comparison of multi-spectral observations uncoordinated in time would be meaningless because of the temporal variability. Under this proposal and one to be submitted to the NASA Infrared Telescope Facility in Hawaii, coordinated observations over the spectral range from 120 nm to 8 microns will be attempted for the first time. The geographic locations of these observatories ensures that interested observers in North and South America will be able to participate at the same time. This effort is part of the International Jupiter Watch.

Wagener, Richard

196

New periodicity in Jovian decametric radio emission M. Panchenko,1  

E-print Network

Jovian magnetic field lines [Zarka, 1998]. As a result of nonaxisymmetric magnetic field, nonisotropic; Queinnec and Zarka, 1998]. The nonIo component of the DAM, which is the subject of our study, appears

California at Berkeley, University of

197

Jovian Chromophore Characteristics from Multispectral HST Images  

NASA Astrophysics Data System (ADS)

Characterizing the chromophores responsible for coloring the Jovian atmosphere remains a challenging problem. Knowledge of their spectral shapes and 3-dimensional distributions can provide important clues as to their chemical identities. In this study, HST WFPC2 data were fit with radiative transfer models to find spectral shapes and vertical distributions of Jovian chromophores. The observations were made on 15 May, 28 June, and 8 July 2008, covering a passage of Oval BA and the Great Red Spot (GRS). Nine filters sampled the continuum (255, 343, 375, 390, 410, 437, 469, 502, and 673 nm), making this data set ideal for high spatial resolution color studies. One methane absorption filter (889 nm) provided first-order cloud height information. The radiative transfer code used was originally developed to analyze Galileo SSI data (Simon-Miller et al. 2001, Icarus 154, 459). Each model aerosol layer in the code was parameterized by a base pressure, an optical depth, a particle radius, and single-scattering albedos at the observed continuum wavelengths. Initial values for cloud structure parameters were taken from recent publications. The best-fit model parameters at a given planet location were found for each initial cloud structure, resulting in a spectrum of the chromophore component present in each aerosol layer. Results are presented for the GRS, Oval BA, a small red anticyclone that passed through the perimeter of the GRS, the Equatorial Zone, and the South Equatorial Belt. This work was supported by NASA's Planetary Atmospheres Program through grant number NNX08AF53A. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #GO/DD11498.

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

2009-09-01

198

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., v. 36, p. 85 (1999)] addresses critical issues for spheromaks, including current drive, high-beta operation, and confinement quality. HIT--SI features an optimized high-beta plasma shape and current profile, minimal plasma-wall interaction, and the long-term goal of steady-state operation. HIT--SI has a ``bow-tie'' shaped axisymmetric confinement region (major radius R=0.33m, axial extent of 0.57m) and two half-torus helicity injectors, one mounted on each end of the flux conserver. The flux and loop voltage in each helicity injector are varied sinusoidally and in phase, while the two injectors are 90 degrees out of phase with each other, producing a constant rate of helicity injection. The physical principles of SIHI and the HIT--SI device will be presented, along with descriptions of key experimental and computational results.

Redd, A. J.

2005-10-01

199

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

200

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

201

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

202

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

203

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

204

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

205

Torus Immersions and Transformations Carlo H. Squin  

E-print Network

1 Torus Immersions and Transformations Carlo H. Séquin CS Division, University of California, Berkeley E-mail: sequin@cs.berkeley.edu Abstract All possible immersions of a torus in 3D Euclidean space that opposite e

O'Brien, James F.

206

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

207

Cassini and Wind Stereoscopic Observations of Jovian Non-Thermal Radio Emissions  

NASA Technical Reports Server (NTRS)

During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January, the Jovian longitude difference between the two spacecraft was about 5 deg, whereas for the August-September Earth flyby of Cassini, the angle ranged from 0 deg to about 2.5 deg. With these separations, the instantaneous widths of the walls of the hollow conical radiation beams of some of the decametric arcs were measured suggesting that the typical width is approximately 2 deg. The conical beams seem to move at Io's revolution rate rather than with Jupiter's rotation rate. Additionally, some of the non-arc emissions have very narrow and quite peculiar beamwidths.

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

1999-01-01

208

Lorentz resonances and the structure of the Jovian ring  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

209

On the proposed triggering of Jovian radio emissions  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

210

Lump Scattering on a Torus  

E-print Network

Head-on collisions between two solitons in the pure $CP^1$ model on a flat torus are investigated via numerical simulations. The charge-two lumps, written out in terms of Weierstrass' elliptic $\\wp$-function, are found to scatter at 90$^{\\circ}$. The phenomenon of singularity formation is also seen.

RJ Cova

2001-09-02

211

Status of the control system on the National Spherical Torus Experiment (NSTX)  

E-print Network

#61 final Status of the control system on the National Spherical Torus Experiment (NSTX) D. A Abstract In 2003, the NSTX plasma control system was used for plasma shape control using real. More recently, the system has been upgraded to support feedback control of the resistive wall mode (RWM

Princeton Plasma Physics Laboratory

212

Particles, environments and possible ecologies in the Jovian atmosphere  

Microsoft Academic Search

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

C. Sagan; E. E. Salpeter

1976-01-01

213

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

214

Jovian Dust Streams Revisited - Cassini Dust Detector At Jupiter  

NASA Astrophysics Data System (ADS)

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

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

215

Solar Wind Magnetic Field Bending of Jovian Dust Trajectories  

Microsoft Academic Search

From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain

H. A. Zook; E. Grun; M. Baguhl; D. P. Hamilton; G. Linkert; J.-C. Liou; R. Forsyth; J. L. Phillips

1996-01-01

216

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

217

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

NASA Astrophysics Data System (ADS)

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 along Io flux tubes. Ray tracing has been performed in the frequency range from 2-35 MHz from successive Io flux tubes separated by ten degrees of central meridian longitude for a full circumference of northern hemisphere sources. The results show unusual complexity in model arc spectra that is displayed in a constant Io phase format with many similarities to the Voyager PRA data. The results suggest much of the variation in observed DAM spectral features is a result of propagation effects rather than emission process differences.

Menietti, J. D.; Green, J. L.; Gulkis, S.; Six, F.

1984-03-01

218

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

NASA Technical Reports Server (NTRS)

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 along Io flux tubes. Ray tracing has been performed in the frequency range from 2-35 MHz from successive Io flux tubes separated by ten degrees of central meridian longitude for a full circumference of northern hemisphere sources. The results show unusual complexity in model arc spectra that is displayed in a constant Io phase format with many similarities to the Voyager PRA data. The results suggest much of the variation in observed DAM spectral features is a result of propagation effects rather than emission process differences.

Menietti, J. D.; Green, J. L.; Gulkis, S.; Six, F.

1984-01-01

219

Performance of a 12-coil superconducting 'bumpy torus' magnet facility.  

NASA Technical Reports Server (NTRS)

The NASA-Lewis 'bumpy torus' facility consists of 12 superconducting coils, each 19 cm ID and capable of 3.0 tesla on their axes. The coils are equally spaced around a toroidal array with a major diameter of 1.52 m, and are mounted with the major axis of the torus vertical in a single vacuum tank 2.6 m in diameter. Final shakedown tests of the facility mapped out its magnetic, cryogenic, vacuum, mechanical, and electrical performance. The facility is now ready for use as a plasma physics research facility. A maximum magnetic field on the magnetic axis of 3.23 teslas has been held for a period of more than sixty minutes without a coil normalcy.

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

1972-01-01

220

Plasmadynamic hypervelocity dust injector for the National Spherical Torus Experiment  

SciTech Connect

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

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

2006-10-15

221

Review of the National Spherical Torus Experiment Research Results  

NASA Astrophysics Data System (ADS)

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

Mueller, D.; Menard, J. E.; Bell, M. G.; Bell, R. E.; Bialek, J. M.; Boedo, J. A.; Bush, C. E.; Crocker, N. A.; Diem, S.; Domier, C. W.; D'Ippolito, D. A.; Ferron, J. R.; Fredrickson, E. D.; Gates, D. A.; Hill, K. W.; Hosea, J. C.; Kaye, S. M.; Kessel, C. E.; Kubota, S.; Kugel, H. W.; LeBlanc, B. P.; Lee, K. C.; Levinton, F. M.; Luhmann, N. C.; Maingi, R.; Mansfield, D. K.; Majeski, R. P.; Maqueda, R. J.; Mazzucato, E.; Medley, S. S.; Myra, J. R.; Park, H. K.; Paul, S. F.; Peebles, W. A.; Raman, R.; Sabbagh, S. A.; Skinner, C. H.; Smith, D. R.; Sontag, A. C.; Soukhanovskii, V. A.; Stratton, B. C.; Stutman, D.; Taylor, G.; Tritz, K.; Wilson, J. R.; Yuh, H.; Zhu, W.; Zweben, S. J.

2009-07-01

222

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

NASA Technical Reports Server (NTRS)

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

Jefferies, J. T.

1982-01-01

223

Numerical model of long-lived Jovian vortices  

NASA Technical Reports Server (NTRS)

The extension of the measured zonal velocity profile into the adiabatic interior of Jupiter, while eddies and large oval structures are confined to a shallow stably-stratified upper layer, are assumed in a nonlinear numerical model of long-lived Jovian vortices. In agreement of the observed flows of Jupiter, each vortex is stationary with respect to the shear flow at a critical latitude that is close to the latitude of the vortex center. The solutions obtained are strongly nonlinear, in contrast to the solitary wave solutions that are the weakly nonlinear extensions of ultralong linear waves. The merging of two stable vortices upon collision, rather than the non-interaction predicted by solitary wave theory, is in keeping with Jovian vortex observations. It is suggested that long-lived vortices maintain themselves against dissipation by absorbing smaller vortices produced by convection.

Ingersoll, A. P.; Cuong, P. G.

1981-01-01

224

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

225

Theoretical predictions of deuterium abundances in the Jovian planets  

SciTech Connect

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

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

1980-01-01

226

A CCD comparison of outer Jovian satellites and Trojan asteroids  

NASA Technical Reports Server (NTRS)

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

Luu, Jane X.

1991-01-01

227

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

228

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

229

A Nuclear Ramjet Flyer for Exploration of Jovian Atmosphere  

NASA Astrophysics Data System (ADS)

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

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

2001-01-01

230

Thermal shallow water models of geostrophic turbulence in Jovian atmospheres  

SciTech Connect

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

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

2014-01-15

231

Flux, power, energy and polarization of Jovian S-bursts  

Microsoft Academic Search

The bandwidth, flux density, power, energy, and polarization of Jovian S-bursts are statistically analyzed from high-resolution dynamic spectral observations performed in Nançay using an acousto-optical spectrograph. Average values and ranges of variation are derived. The Io-Jupiter-observer configuration of our observations corresponds to S-bursts with dominant right-hand elliptical polarization. We obtain a bandwidth of 0.5–9 MHz, an average flux density of

Julien Queinnec; Philippe Zarka

2001-01-01

232

Galilean satellite eclipse studies. III - Jovian methane abundance  

NASA Technical Reports Server (NTRS)

The methane abundance in the lower Jovian stratosphere is measured using the Galilean satellite eclipse technique. The average mixing ratio at the locations measured is larger than the expected value for a solar abundance of carbon with the expected value for a solar abundance of carbon with the possibility of some zenographic variation. Observationally compatible values are found for the South Temperate Zone, the edge of the Great Red Spot and the South Tropical Zone, and the Great Red Spot.

Smith, D. W.; Greene, T. F.

1980-01-01

233

Temperature structure and emergent flux of the Jovian planets  

NASA Technical Reports Server (NTRS)

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

Silvaggio, P.; Sagan, C.

1978-01-01

234

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

235

Comparison of Jovian and Terrestrial lightning as observed from space.  

NASA Astrophysics Data System (ADS)

We compare the images of Jovian lightning taken by Galileo spacecraft with the images of terrestrial lightning observed by Lightning Imaging Spectrometer (LIS) onboard of the TERRA spacecraft. Both data sets have good spatial resolution: Galileo's pixel is 25 km, or about half the atmospheric scale height, LIS pixel is 3-6 km, also about half of the scale height. This good resolution allows us to see that both Jovian and terrestrial lightning spots look diffuse because of the scattering in the clouds above. Previously we used the appearance of the diffuse spots on Jupiter to model lightning depths and the opacity and shape of the overlying clouds (Dyudina and Ingersoll, 2000). The comparison with LIS data allowed us to verify that the model is valid for terrestrial lightning. The irregular shapes of large terrestrial lightning suggests 30-km scale horizontal bolts. On Jupiter the spots, projected onto the horizontal plane, are nearly circular suggesting that the large size of the spots is mostly due to the horizontal diffusion of the photons scattered in the clouds. Unlike the Galileo observations, LIS has fine temporal resolution of 2 ms, or about 250 frames per single lightning flash. We will discuss the temporal evolution of terrestrial flashes and its implications for Jupiter. U. A. Dyudina and A. P Ingersoll, ``Modeling of Jovian Lightning Imaged by Galileo SSI Camera", B.A.S.S. 32(3) 997, (2000)

Dyudina, U. A.; Ingersoll, A. P.; Boccippio, D.

2001-11-01

236

Dynamics of Charged Nano-Dust in the Jovian Rings  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

237

Relationship between Jovian Hectometric Attenuation Lanes And Io Volcanic Activity  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

238

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

239

Influence of azimuthal variations in the jovian magnetospheric field on global thermospheric energy inputs  

NASA Astrophysics Data System (ADS)

Jupiter's upper atmosphere is coupled to the magnetosphere via an electrical circuit in which current travels along the planetary magnetic field between these two regions, radially outwards in the magnetospheric equatorial plane, and equatorward through the ionosphere. Energy and momentum are communicated to the thermosphere by a combination of joule heating and ion drag. Together, these processes modify the local thermosphere, and produce a system of meridional and azimuthal winds, as well as localized heating. The driver for this current circuit is the radial transport of plasma outward through the planetary magnetosphere. Io ejects ~1000 kg/s neutral material, which then becomes partly ionized through electron impact and charge exchange, leaving ~500 kg/s plasma to be transported through the magnetosphere. As the remaining plasma moves outwards, it slows in its rotation to conserve angular momentum, bending back the planetary magnetic field lines that thread it. Field-aligned currents simultaneously develop to support this magnetic geometry, transporting angular momentum from the planet to the magnetospheric plasma. In the equatorial plane, a j x B force accelerates the plasma towards corotation with the planet. Axially symmetric models for the magnetic field and plasmasheet have been extensively applied to describe this process. Outside of ~20 RJ (jovian radii), however, the north-south component of the equatorial magnetic field varies significantly with azimuth (local time). Therefore, the magnitude of the current is also expected to change, in accordance with the corresponding variation in the radial profile of magnetospheric plasma angular velocity. Using the UCL JASMIN model, which describes the coupled thermosphere-ionosphere-magnetosphere system in 2.5 dimensions, we explore how these azimuthal variations in the equatorial magnetic field structure modify the ionospheric currents, and discuss the ensuing effects on the thermospheric heating and flows.

Ray, L. C.; Achilleos, N.; Yates, J. N.; Vogt, M. F.

2013-09-01

240

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

241

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

E-print Network

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

242

An Inexpensive Ohmic Transformer Firing Circuit for the CDXU Spherical Torus  

E-print Network

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

243

Electrodynamic interaction of Ganymede with the Jovian magnetosphere and the radial spread of wake-associated disturbances  

NASA Technical Reports Server (NTRS)

An investigation is conducted of the electrostatics of the interaction of Jupiter's satellite Ganymede with the Jovian plasma and the MHD stability of the resulting downstream cavity, taking into account an evaluation of the effect of distorted magnetic field models on the radial extent of the disturbances. The objective of the investigation is an understanding of the data which have been provided by Voyager 2 during its approach to Jupiter, giving attention to the Voyager 2 magnetometer experiment. It is concluded that the magnetic field distortion by itself is insufficient to explain the large radial extent of the observed wake encounters. Linear treatment of MHD equations showed that the Kelvin-Helmholtz instability is initiated at the plasma-cavity interface.

Tariq, G. F.; Armstrong, T. P.; Lowry, J. W.

1985-01-01

244

Electrodynamic interaction of Ganymede with the Jovian magnetosphere and the radial spread of wake-associated disturbances  

SciTech Connect

An investigation is conducted of the electrostatics of the interaction of Jupiter's satellite Ganymede with the Jovian plasma and the MHD stability of the resulting downstream cavity, taking into account an evaluation of the effect of distorted magnetic field models on the radial extent of the disturbances. The objective of the investigation is an understanding of the data which have been provided by Voyager 2 during its approach to Jupiter, giving attention to the Voyager 2 magnetometer experiment. It is concluded that the magnetic field distortion by itself is insufficient to explain the large radial extent of the observed wake encounters. Linear treatment of MHD equations showed that the Kelvin-Helmholtz instability is initiated at the plasma-cavity interface. 29 references.

Tariq, G.F.; Armstrong, T.P.; Lowry, J.W.

1985-05-01

245

Normality of Torus Orbit Closures in G=P  

E-print Network

Normality of Torus Orbit Closures in G=P James B. Carrell Alexandre Kurth Abstract. Suppose G asked whether or not all closures of torus orbits in the algebraic homogeneous space G=P are normal. In this paper, we describe all the normal torus orbit closures in G=P , and show, for example, that all torus

Carrell, Jim

246

Jovian magnetosphere-ionosphere current system characterized by diurnal variation of ionospheric conductance  

NASA Astrophysics Data System (ADS)

We developed a new numerical model of the Jovian magnetosphere-ionosphere coupling current system in order to investigate the effects of diurnal variation of ionospheric conductance. The conductance is determined by ion chemical processes that include the generation of hydrogen and hydrocarbon ions by solar EUV radiation and auroral electrons precipitation. The model solves the torque equations for magnetospheric plasma accelerated by the radial currents flowing along the magnetospheric equator. The conductance and magnetospheric plasma then change the field-aligned currents (FACs) and the intensity of the electric field projected onto the ionosphere. Because of the positive feedback of the ionospheric conductance on the FAC, the FAC is the maximum on the dayside and minimum just before sunrise. The power transferred from the planetary rotation is mainly consumed in the upper atmosphere on the dayside, while it is used for magnetospheric plasma acceleration in other local time (LT) sectors. Further, our simulations show that the magnetospheric plasma density and mass flux affect the temporal variation in the peak FAC density. The enhancement of the solar EUV flux by a factor of 2.4 increases the FAC density by 30%. The maximum density of the FAC is determined not only by the relationship between the precipitating electron flux and ionospheric conductance, but also by the system inertia, i.e., the inertia of the magnetospheric plasma. A theoretical analysis and numerical simulations reveal that the FAC density is in proportion to the planetary angular velocity on the dayside and to the square of the planetary angular velocity on the nightside. When the radial current at the outer boundary is fixed at values above 30 MA, as assumed in previous model studies, the peak FAC density determined at latitude 73°-74° is larger than the diurnal variable component. This result suggests large effects of this assumed radial current at the outer boundary on the system.

Tao, Chihiro; Fujiwara, Hitoshi; Kasaba, Yasumasa

2010-02-01

247

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

NASA Astrophysics Data System (ADS)

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

Hood, L. L.

1993-04-01

248

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

NASA Technical Reports Server (NTRS)

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

Smyth, William H.

2004-01-01

249

Evidence for a distant ( 8700 R sub J) Jovian magnetotail: Voyager 2 observations  

NASA Technical Reports Server (NTRS)

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 R sub J. The occurrences of these events are in good agreement with prior Plasma Wave Science and Plasma Science identifications. Observations of these distant magnetotail, or tail filament, encounters appear most prevalent in both MAC and PRA data sets when the spacecraft was closest to the Jupiter-Sun axis at approximately 6,500 R sub J from the planet; the PRA events are also most intense during those times. A specific tail encounter occurring in mid-February 1981 is analyzed and shown to possess a remarkably symmetric magnetic field signature and to have a bipolar field structure in the central region. The bipolarity is characteristic of most of the eight events.

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

1982-01-01

250

Limb-darkening and the structure of the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

By observing the transit of various cloud features across the Jovian disk, limb-darkening curves were constructed for three regions in the 4.6 to 5.1 mu cm band. Several models currently employed in describing the radiative or dynamical properties of planetary atmospheres are here examined to understand their implications for limb-darkening. The statistical problem of fitting these models to the observed data is reviewed and methods for applying multiple regression analysis are discussed. Analysis of variance techniques are introduced to test the viability of a given physical process as a cause of the observed limb-darkening.

Newman, W. I.; Sagan, C.

1978-01-01

251

The long-term motion of artificial Jovian satellites  

NASA Technical Reports Server (NTRS)

This paper is a description of a preliminary study aimed at the classification and establishment of realistic orbit design criteria of artificial satellites of Jupiter. The work is concentrated on investigation of the factors that will affect the long-term motion, and particularly the dynamic lifetime, of the first Jupiter orbiters. Included is a perturbation analysis describing the effects of the Jovian gravity, the Galilean satellites, and the solar gravitational perturbations. An unusual problem is identified in the great difficulty of avoiding near-collisions with the Galilean satellites. The results of the perturbation and dynamic lifetime analyses are used in brief discussions of some possible Jupiter orbit missions.

Uphoff, C.

1973-01-01

252

Coupling of acoustic waves to clouds in the jovian troposphere  

NASA Astrophysics Data System (ADS)

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

Gaulme, Patrick; Mosser, Benoît

2005-11-01

253

1979J2 - Discovery of a previously unknown Jovian satellite  

NASA Technical Reports Server (NTRS)

Detailed examination of imaging data of Jupiter taken by Voyager 1 reveals a previously unknown satellite 1979J2. Analysis of the image on the Jovian disk indicates that it is not an atmospheric feature or the shadow of any known satellite. The orbital period is calculated at 16 hours 11 minutes 21.25 seconds + or - 0.5 second and the semimajor axis is 3.1054 Jupiter radii. The observed profile is roughly circular with a diameter of 80 kilometers. An albedo of approximately 0.05 is reported, which is similar to Amalthea's. The geometry of the observational situation is illustrated.

Synnott, S. P.

1980-01-01

254

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

255

Initial Physics Results From the National Spherical Torus Experiment  

SciTech Connect

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

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

2001-01-03

256

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

257

A 3D Convective Model for the Jovian Wind Bands  

NASA Technical Reports Server (NTRS)

In an earlier paper, we proposed that Jupiter's alternating wind bands are a manifestation of the global interaction between rotation and convection in a shallow layer. The model, however, was obtained from linearization of the 2D equations of motions. At HKUST/Hong Kong, we are now trying to study this problem by rigorous numerical simulation. Using a three-dimensional spectral numerical code, we compute models for the outermost layer of Jupiter's convective envelope. Two cases have been studied. In one the atmospheric pressure varies from 1 to 23 bar, and in the other from 1 to 115 bar. The physical parameters (internal energy flux, rotation rate) are chosen to be close to those expected, but solar heating, chemistry, as well as dynamical influences from deeper layers are ignored. The models generate wind field patterns that contain alternating jet streams with resemblance to the Jovian bands. Instantaneous values of the mean zonal flow at the equator reach 80 m/sec. Yet the mean meridional flows are less than 1% of such value. The meridional temperature profile at the cloud top level also shows a double hump structure of a few degrees (as observed) in the subtropics. Though there is not complete quantitative agreement (caused perhaps by neglected effects like solar radiation), these models demonstrate, in principle, the feasibility of generating a Jovian type wind pattern through the interaction of fast rotation and convection in a thin shell.

Mayr, H. G.; Chan, K. L.

2004-01-01

258

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

NASA Technical Reports Server (NTRS)

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.

1990-01-01

259

Flow profile measurement with multi-Mach probes on the HIST spherical torus device  

NASA Astrophysics Data System (ADS)

Role of plasma flow during MHD relaxation and magnetic reconnection processes is still underlying physics. The HIST spherical torus can generate various spherical torus (ST) configurations by changing the external toroidal magnetic field. Especially, the flipped ST (F-ST) configuration has been for the first time found in the HIST device [1]. In the present study, plasma flow measurements were performed by multi-Mach probes in the ST and the F-ST configurations. In addition, the measured plasma flow was compared with that evaluated by an ion Doppler spectrometer (IDS) system and plasma images measured by a high-speed camera. As the result, it was shown that the toroidal plasma flow (˜ 20 km/s) at the location far from the plasma gun was clearly reversed after the transition from the ST to the F-ST. However, the direction of the toroidal flow was not changed near the plasma gun. Therefore, it can be considered that there are flipped and non-reversal regions in the plasma. The result agrees well with a magnetic configuration predicted by magnetic field measurements. The plasma images measured by the high-speed camera also indicated that a helically twisted structure appeared from the gun region, and it localized at the edge region. [1] M. Nagata et al., Phys. Rev. Lett. 90, pp. 225001-225004 (2003).

Hashimoto, S.; Nishioka, T.; Ando, K.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2008-11-01

260

Palatine torus in the Greenlandic Norse.  

PubMed

Physical anthropologists have long been intrigued by the distinctive oral tori expressed by the medieval Norse populations of Iceland and Greenland. To assess the temporal and spatial variation of one form of oral tori, palatine torus, observations were made on all available Greenlandic Norse skeletons, as well as on samples of medieval Icelanders and Norwegians. In terms of temporal variation, 12th to 14th century (medieval) Greenlanders from the Eastern and Western settlements exhibited higher frequencies and more pronounced expressions of palatine torus compared with early 11th century Greenlanders. The early Greenlandic sample closely approximated the medieval Icelandic and Norwegian samples for total torus frequency, although the Norwegians exhibited the trait to a less pronounced degree. As degree of expression is the most distinctive aspect of torus variation among the Norse, some combination of environmental factors, including increased masticatory stress and chronic undernutrition, probably accounts for most of the difference between settlement period and medieval Greenlanders. Although palatine torus may be hereditary in part, environmental factors play a significant role in the expression of this trait. PMID:1605314

Halffman, C M; Scott, G R; Pedersen, P O

1992-06-01

261

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

262

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

263

Electric discharge synthesis of HCN in simulated Jovian atmospheres  

NASA Technical Reports Server (NTRS)

Corona discharge is presently considered as a possible source of the HCN detected in the Jovian atmosphere at 2.2 x 10 to the -7th moles/sq cm column density, for the cases of gas mixtures containing H2, CH4, and NH3, with H2/CH4 ratios from 4.4 to 1585. A 3:1 ratio of corona discharge to lightning energy similar to that of the earth is applied to Jupiter. Depending on the lightning energy available on Jupiter and the eddy diffusion coefficients in the synthesis region, HCN column densities generated by corona discharge could account for about 10 percent of the HCN observed.

Stribling, Roscoe; Miller, Stanley L.

1987-01-01

264

Astrometry of the inner Jovian moons Thebe, Amalthea, and Metis  

NASA Astrophysics Data System (ADS)

The paper presents the results of the astrometric observations of the inner Jovian satellites Thebe, Amalthea, and Metis obtained with 2-m Zeiss RCC Telescope located at Peak Terskol Observatory. The 268 inter-satellite positions were gathered during the five-year period between 1998 and 2002. Comparison of the observed positions with those of JPL JUP203 ephemerides demonstrates high quality of the collected observations. The RMS errors of the differences between the observed and the theoretical positions are about 0.10, 0.15, and 0.30 arcsec for Amalthea, Thebe, and Metis, respectively. Thebe and Amalthea's mean residuals are about zero. The dispertion of the mean residuals derived from the data sets obtained in the different years does not exceed 0.04 arcsec. The brief description of the technique for the scattered light subtraction may be useful as an experience of the image processing of a faint object near the bright planet.

Kulyk, I.

2008-11-01

265

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

266

Performance of a 12-coil superconducting bumpy torus magnet facility  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

267

Jovian electron propagation in three dimensions of the heliosphere: The Ulysses investigations  

NASA Technical Reports Server (NTRS)

We report investigations of Jovian relativistic electrons in the interplanetary medium that provide new insights into both the physical processes by which the Jovian magnetosphere releases its trapped, relativistic electrons into the interplanetary medium, and the modes of their interplanetary propagation. These studies were dependent on the unique postencounter trajectory for Ulysses. The spacecraft remained close to the radial distance of Jupiter (approximately 5.2 AU) and moved southward on the duskside by only approximately 12 deg in heliographic latitude and less than 8 deg in the heliographic azimuth relative to Jupiter for the period of approximately 100 deg days of this study. During this period the nominal Parker spiral interplanetary magnetic field with its alternating polarities sector structure established direct magnetic field line connections frequently between Jupiter and the spacecraft. These unique conditions made it possible to investigate in detail, for approximately four solar rotations, both the Jovian electron burst phenomenon and the continuous, diffusive interplanetary propagation of Jovian electrons.

Simpson, J. A.; Smith, D. A.; Zhang, M.

1993-01-01

268

A 3D Convective Model for the Jovian Wind Bands  

NASA Astrophysics Data System (ADS)

In an earlier paper (Mayr et al. 1984, Earth, Moon, & Planets, 30, 245), we proposed that Jupiter's alternating wind bands are a manifestation of the global interaction between rotation and convection in a shallow layer. The model, however, was obtained from linearization of the 2D equations of motions. At HKUST/Hong Kong, we are now trying to study this problem by rigorous numerical simulation. Using a three-dimensional spectral numerical code, we compute models for the outermost layer of Jupiter's convective envelope. Two cases have been studied. In one the atmospheric pressure varies from 1 to 23 bar, and in the other from 1 to 115 bar. The physical parameters (internal energy flux, rotation rate) are chosen to be close to those expected, but solar heating, chemistry, as well as dynamical influences from deeper layers are ignored. The models generate wind field patterns that contain alternating jet streams with resemblance to the Jovian bands. Instantaneous values of the mean zonal flow at the equator reach 80 m/sec. Yet the mean meridional flows are less than 1% of such value. The meridional temperature profile at the cloud top level also shows a double hump structure of a few degrees (as observed) in the subtropics. Though there is not complete quantitative agreement (caused perhaps by neglected effects like solar radiation), these models demonstrate, in principle, the feasibility of generating a Jovian type wind pattern through the interaction of fast rotation and convection in a thin shell. KLC thanks RGC/Hong Kong for support.

Mayr, H. G.; Chan, K. L.

2004-11-01

269

Jupiter's magnetosphere: Plasma description from the Ulysses flyby  

Microsoft Academic Search

Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating that similar processes are operating. A

S. J. Bame; B. L. Barraclough; W. C. Feldman; G. R. Gisler; J. T. Gosling; D. J. McComas; J. L. Phillips; M. F. Thomsen; B. E. Goldstein; M. Neugebauer

1992-01-01

270

ULYSSES radio and plasma wave observations in the Jupiter environment  

Microsoft Academic Search

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded

R. G. Stone; B. M. Pedersen; C. C. Harvey; P. Canu; N. Cornilleau-Wehrlin; M. D. Desch; C. de Villedary; J. Fainberg; W. M. Farrell; K. Goetz; R. A. Hess; S. Hoang; M. L. Kaiser; P. J. Kellogg; A. Lecacheux; N. Lin; R. J. MacDowall; R. Manning; C. A. Meetre; N. Meyer-Vernet; M. Moncuquet; V. Osherovich; M. J. Reiner; A. Tekle; J. Thiessen; P. Zarka

1992-01-01

271

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

272

Design Features and Commissioning of the Versatile Experiment Spherical Torus (VEST) at Seoul National University  

NASA Astrophysics Data System (ADS)

A new spherical torus called VEST (Versatile Experiment Spherical Torus) is designed, constructed and successfully commissioned at Seoul National University. A unique design feature of the VEST is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, appropriate power supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEST is ready for tokamak plasma operation by completing and commissioning most of the designed components.

J. Chung, K.; H. An, Y.; K. Jung, B.; Y. Lee, H.; C., Sung; S. Na, Y.; S. Hahm, T.; S. Hwang, Y.

2013-03-01

273

Measurement of Poloidal Velocity on the National Spherical Torus Experiment  

SciTech Connect

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

Ronald E. Bell and Russell Feder

2010-06-04

274

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

275

Progress in the studies of passive heat removal in the next European torus under accident conditions  

Microsoft Academic Search

Within the framework of safety analysis for the next European torus, a decay heat hazards assessment is under way in Ispra. Undercooling accidents (loss-of-coolant and loss-of-flow accidents (LOCAs and LOFAs)) due to pump failure have been investigated assuming an automatic plasma shutdown in both cases. The passive heat removal mechanisms considered include radiation between components and residual cooling by the

A. Soria; V. Renda; L. Papa; F. Fenoglio

1989-01-01

276

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

277

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

SciTech Connect

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

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

1990-05-01

278

On the Virasoro constraints for torus knots  

NASA Astrophysics Data System (ADS)

We construct a Virasoro algebra of differential operators for the matrix model for torus knots. These operators generate various relations between Wilson loops. Then we discuss the operators constructed and corresponding relations in the stability limit. We also give a series of examples.

Dubinkin, Oleg

2014-12-01

279

Quantum Hall wave functions on the torus  

SciTech Connect

We present explicit expressions for a large set of hierarchy wave functions on the torus. Included are the Laughlin states, the states in the positive Jain series, and recently observed states at, e.g., {nu}=4/11. The techniques we use constitute a nontrivial extension of the conformal field theory methods developed earlier to construct the corresponding wave functions in disk geometry.

Hermanns, M.; Bergholtz, E. J.; Hansson, T. H.; Karlhede, A. [Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Suorsa, J. [Laboratory of Physics, Helsinki University of Technology, FIN-02015 HUT (Finland)

2008-03-15

280

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

NASA Astrophysics Data System (ADS)

During the flyby of Jupiter on its cruise to Saturn, the Cassini/Huygens spacecraft collected unique data with a broad assortment of instruments. The Magnetospheric Imaging Instrument (MIMI) measured in-situ energetic ions and electrons, performed charge and mass analysis of both interstellar pickup ions and Jovian source ions, and remotely imaged the Jovian magnetosphere in energetic neutral atom (ENA) emissions. The ENA images were measured with the Ion and Neutral Camera (INCA) [Mitchell et al., 1998]. INCA images ENA in the velocity range from about 1200 km/s to 8000 km/s, which for hydrogen corresponds to about 8 keV to about 350 keV. Jupiter, as expected based on Voyager measurements [Kirsch et al., 1981; Cheng 1986], is a weak ENA source. The expected INCA response was modeled by Mauk et al., 1998. The INCA sensor was run in a mode for which images were obtained only below about 80 keV/nucleon. The images obtained are quite close to the predictions of Mauk et al., both in conformation and in intensity. They are consistent with the source strength of the Jovian magnetosphere remaining essentially constant between 1979 and 2001. Rough inferences as to the composition of the ENA show that there is a mix of hydrogen as well as heavier atoms, most probably oxygen and sulfur. These first-ever images of Jupiter's magnetosphere provide a taste of what we can look forward to at Saturn, although the distance of this flyby (140 Rj) allows only hints of the magnetospheric structure to be resolved with this instrument, which is designed for a closer vantage point. Mitchell, D. G., A. F. Cheng, K. C. Hsieh, S. M. Krimigis, E. P. Keath, S. E. Jaskulek, B. H. Mauk, R. W. McEntire, E. C. Roelof, C. E. Schlemm, B. E. Tossman, and D. J. Williams, The ion neutral camera for the Cassini Mission to Saturn and Titan, Measurement Techniques in Space Plasmas, Fields, R. F. Pfaff, J. E. Borovsky, and D. T. Young, ed., Geophysical Monograph 103, p281, AGU, 1998. Kirsch, E., S. M. Krimigis, J. Johl, and E. Keath, Upper limits for X-ray and energetic neutral particle emission from Jupiter: Voyager 1 results, Geophys. Res. Lett., 8, 169, 1981. Mauk, B.H., S.M. Krimigis, D.G. Mitchell, and E.C. Roelof, Energetic neutral atom imaging of Jupiter's magnetosphere using the Cassini MIMI instrument, Adv. Space Res., 21, 1483, 1998.

Mitchell, D. G.; Krimigis, S. M.; Mauk, B. H.

2001-05-01

281

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

282

Torus Palatinus Osteonecrosis Related to Bisphosphonate: A Case Report  

PubMed Central

Introduction Osteonecrosis of the palate is a rare condition which is even rarer when occurring on a torus palatinus and associated with bisphosphonate (BP). Case Presentation We report an uncommon case of osteonecrosis of a torus palatinus. Our patient was a 67-year-old white female who presented with a painful intraoral ulcer associated with necrotic bone tissue of her torus palatinus, due to the chronic use of alendronate. Conclusion We point out the possible causative relationship of BPs and osteonecrosis on torus growth. It is very important to know that torus palatinus and the use of BPs are risk factors for osteonecrosis of the maxilla. PMID:23687490

Godinho, Mariana; Barbosa, Fabio; Andrade, Felipe; Cuzzi, Tullia; Ramos-e-Silva, Marcia

2013-01-01

283

Jovian auroral ovals inferred from infrared H3(+) images  

NASA Technical Reports Server (NTRS)

Detailed analyses have been carried out of infrared H3(+) images of Jupiter's polar regions observed with the ProtoCam camera on the Infrared Telescope Facility (IRTF) on March 3-6, 1992. The images were obtained at 3.5 microns, where H3(+) emission is strong and the jovian disk is dark. By carefully examining the H3(+) emission over the limb of the polar regions, we find that the H3(+) emission extended significantly above Jupiter's limb in the north polar region and to a lesser degree in the south polar region. This could be due to either a highly extended thermosphere or a broad energy spectrum of precipitating particles in the auroral regions. After we applied a new technique to the H3(+) images to remove limb brightening, we found auroral ovals in both polar regions. The northern oval appears to be close to the L = 30 footprint in the magnetospheric spot locations derived from previous analyses. One intrinsically bright area is found in the northern oval approximately at 150 deg longitude (System III) and 70 deg latitude, where the oval is also wider than elsewhere. The intensity of the bright area varies with a time scale as short as 50 min. The southern oval seems to occur at latitudes higer by a few degrees than the L = 30 footprint, although L = 30 is within the uncertainty of latitude determination. One or two localized intensity maxima are found in the southern oval between 0 deg and 70 deg longitude.

Kim, Y. H.; Kim, Sang, J.; Stuewe, J. A.; Caldwell, John; Herbst, Thomas M.

1994-01-01

284

WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy  

E-print Network

We present updated/new thermal model fits for 478 Jovian Trojan asteroids observed with the Wide-field Infrared Survey Explorer (WISE). Using the fact that the two shortest bands used by WISE, centered on 3.4 and $4.6\\mu$m, are dominated by reflected light, we derive albedos of a significant fraction of these objects in these bands. While the visible albedos of both the C-, P- and D-type asteroids are strikingly similar, the WISE data reveal that the albedo at $3.4\\mu$m is different between C-/P- and D-types. The albedo at 3.4$\\mu$m can be thus be used to classify the objects, with C-/P-types having values less than 10%, and D-types have values larger than 10%. Classifying all objects larger than 50km shows that the D-type objects dominate both the leading cloud ($L_4$), with a fraction of 84%, and trailing cloud ($L_5$), with a fraction of 71-80%. The two clouds thus have very similar taxonomic distribution for these large objects, but the leading cloud has a larger number of of these large objects, $L_4/L_5...

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

2012-01-01

285

Convective forcing of global circulations on the Jovian planets  

NASA Technical Reports Server (NTRS)

Examples of convection in rotating layers are presented to illustrate how convection can drive global circulations on the Jovian planets. For rapid rotation the convective motions become largely two-dimensional and produce Reynold stresses which drive large scale flows. The initial tendency is to produce a prograde equatorial jet and a meridional circulation which is directed toward the poles in the surface layers. Fully nonlinear numerical simulations for the slowly rotating solar convection zone show that the meridional circulation does not reach the poles. Instead a multicellular meridional circulation is produced which has a downward flowing branch in the mid-latitudes. For more rapidly rotating objects such as Jupiter and Saturn this meridional circulation may consist of a larger number of cells. Axisymmetric convective models then show that prograde jets form at the downflow latitudes. A nonlinear numerical simulation of convection in a prograde jet is presented to illustrate the interactions which occur between convection and these jets. Without rotation the convection removes energy and momentum from the jet. With rotation the convection feeds energy and momentum into the jet.

Hathaway, David H.

1986-01-01

286

JOVIAN EARLY BOMBARDMENT: PLANETESIMAL EROSION IN THE INNER ASTEROID BELT  

SciTech Connect

The asteroid belt is an open window on the history of the solar system, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions (SFDs). In this work, we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depends on the SFD of the primordial planetesimals. If the asteroid belt was dominated by planetesimals less than 100 km in diameter, the primordial bombardment would have caused the erosion of bodies smaller than 200 km in diameter. If the asteroid belt was instead dominated by larger planetesimals, the bombardment would have resulted in the destruction of bodies as big as 500 km.

Turrini, D.; Coradini, A.; Magni, G., E-mail: diego.turrini@ifsi-roma.inaf.it [Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, 00133, Rome (Italy)

2012-05-01

287

Jovian Vortices and Barges: HST observations 1994-1998  

NASA Astrophysics Data System (ADS)

We have used the HST-WFPC2 archived images of Jupiter in the period 1994-1998 to study the zonal and meridional distributions, long-term motions, lifetimes, interactions and other properties of the vortices larger than 2 degrees. The latitude range covered spans from +75 to -75 degrees. High-resolution images obtained with the 890nm, 410nm and 953nm wavelength filters allowed us to make a morphological classification based on their appearance in each filter. The vortices are anticyclones, and their long-term motions have been completed with ground-based images and are compared to the mean Jovian zonal wind profile. Significant differences are found between the vortex velocities and the mean zonal winds. Some vortices exhibited important drift changes in short period times. We analyze a possible correlation between their size and zonal wind velocity. On the other hand, the "barges" lie in the cyclone domains of the wind-profile and have been identified in several latitudes. Their latitudinal size is similar in all of them (typically 1.6 degrees) but their longitudinal size ranges from 1 to 32 degrees. We discuss the temporal evolution of some of these cyclonic regions. The Spanish team was supported by Gobierno Vasco PI 034/97. The French team was supported by the "Programme National de Planetologie." RM acknowledges a fellowship from Universidad Pais Vasco.

Morales, R.; Sanchez-Lavega, A.; Lecacheux, J.; Colas, F.; Miyazaki, I.

2000-10-01

288

Equatorial electron energy and number densities in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

A synchrotron model with a Maxwellian energy distribution of the form e to the (-E/E sub 0) power is used in a comparison with spatially resolved radio interferometric measurements of the Jovian emission. The observations of the decimeter radiation as a function of equatorial distance at 10.4 and 21 cm wavelength were reduced to source emission/cc of source electrons in each of 16 concentric rings. The peak energies for isotropically distributed electrons exceeded the maximum energy for flat orbiting electrons, and the peaks were generally located from 2.25 to 3 Jupiter radii. Beyond 3 radii, the order of magnitude on number density became a sensitive function of pitch angle distribution. The total equatorial intensities at 75 cm wavelength were computed for (E sub 0)(r) and n(r) at different values of B sub 0. The radiative half life for electrons of initial energy E sub 0 in a dipole field was calculated and found to be nearly constant at one year or less for altitudes at and below the position in peak energy.

Luthey, J. L.

1972-01-01

289

Q torus in N=2 supersymmetric QED  

SciTech Connect

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

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

2007-12-15

290

TORUS: Radiation transport and hydrodynamics code  

NASA Astrophysics Data System (ADS)

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

Harries, Tim

2014-04-01

291

A principle for ideal torus knots  

NASA Astrophysics Data System (ADS)

Using bent-helix embeddings, we investigate simple and knotted torus windings that are made of tubes of finite thickness. Knots which have the shortest rope length are often denoted as ideal structures. Conventionally, the ideal structures are found by rope shortening routines. It is shown that alternatively they can be directly determined as maximally twisted structures. In many cases these structures are also structures with zero strain-twist coupling, i.e. structures that neither rotate one or the other way under strain. We use this principle to implement rapid numerical calculations of the ideal structures and subsequently quantify them by their aspect ratio. The results are compared with the aspect ratios of biological torus molecules.

Olsen, Kasper W.; Bohr, Jakob

2013-08-01

292

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

293

A new equilibrium torus solution and GRMHD initial conditions  

NASA Astrophysics Data System (ADS)

Context. General relativistic magnetohydrodynamic (GRMHD) simulations are providing influential models for black hole spin measurements, gamma ray bursts, and supermassive black hole feedback. Many of these simulations use the same initial condition: a rotating torus of fluid in hydrostatic equilibrium. A persistent concern is that simulation results sometimes depend on arbitrary features of the initial torus. For example, the Bernoulli parameter (which is related to outflows), appears to be controlled by the Bernoulli parameter of the initial torus. Aims: In this paper, we give a new equilibrium torus solution and describe two applications for the future. First, it can be used as a more physical initial condition for GRMHD simulations than earlier torus solutions. Second, it can be used in conjunction with earlier torus solutions to isolate the simulation results that depend on initial conditions. Methods: We assume axisymmetry, an ideal gas equation of state, constant entropy, and ignore self-gravity. We fix an angular momentum distribution and solve the relativistic Euler equations in the Kerr metric. Results: The Bernoulli parameter, rotation rate, and geometrical thickness of the torus can be adjusted independently. Our torus tends to be more bound and have a larger radial extent than earlier torus solutions. Conclusions: While this paper was in preparation, several GRMHD simulations appeared based on our equilibrium torus. We believe it will continue to provide a more realistic starting point for future simulations.

Penna, Robert F.; Kulkarni, Akshay; Narayan, Ramesh

2013-11-01

294

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

295

New observations from Cassini and Ulysses of Jovian VLF radio M. L. Kaiser and W. M. Farrell  

E-print Network

New observations from Cassini and Ulysses of Jovian VLF radio emissions M. L. Kaiser and W. M observations of Jupiter's so-called reradiated VLF radio emission by the Cassini and Ulysses spacecraft confirm. Hospodarsky, and D. A. Gurnett (2004), New observations from Cassini and Ulysses of Jovian VLF radio emissions

Gurnett, Donald A.

296

Torus Knots and the Topological Vertex  

NASA Astrophysics Data System (ADS)

We propose a class of toric Lagrangian A-branes on the resolved conifold that is suitable to describe torus knots on S 3. The key role is played by the transformation, which generates a general torus knot from the unknot. Applying the topological vertex to the proposed A-branes, we rederive the colored HOMFLY polynomials for torus knots, in agreement with the Rosso and Jones formula. We show that our A-model construction is mirror symmetric to the B-model analysis of Brini, Eynard and Mariño. Compared to the recent proposal by Aganagic and Vafa for knots on S 3, we demonstrate that the disk amplitude of the A-brane associated with any knot is sufficient to reconstruct the entire B-model spectral curve. Finally, the construction of toric Lagrangian A-branes is generalized to other local toric Calabi-Yau geometries, which paves the road to study knots in other three-manifolds such as lens spaces.

Jockers, Hans; Klemm, Albrecht; Soroush, Masoud

2014-08-01

297

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

SciTech Connect

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

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

1986-06-01

298

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

SciTech Connect

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

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

2003-02-11

299

Jovian impact flashes and their implication to meteoroids in outer region of Solar System  

NASA Astrophysics Data System (ADS)

Optical flashes on the surface of Jupiter have been observed by amateur astronomers during 2010. These phenomena were thought to be impact flashes caused by the collision of small bodies of which size is a few to 10 m. They are bright fireballs happened in the Jovian atmosphere. If the frequency and the scale of these phenomena are systematically investigated, the size distribution of meteoroids can be derived down to meteoroids a few meters in size in the giant planet region because the brightness of such flashes depends only on their sizes in the case of Jupiter. We are trying to detect Jovian impact flashes by professional and amateur network over Japan, and to detect much fainter flashes by using larger telescopes. It is a unique method to utilize Jovian planets as natural impact detectors for the small bodies.

Watanabe, J.

2014-07-01

300

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

301

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

SciTech Connect

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

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

2010-07-09

302

Chandra ACIS Observations of Jovian X-Ray Emission  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

303

Retrievals of Jovian Tropospheric Phosphine from Cassini/CIRS  

NASA Technical Reports Server (NTRS)

On December 30th 2000, the Cassini-Huygens spacecraft reached the perijove milestone on its continuing journey to the Saturnian system. During an extended six-month encounter, the Composite Infrared Spectrometer (CIRS) returned spectra of the Jovian atmosphere, rings and satellites from 10-1400 cm(exp -1) (1000-7 microns) at a programmable spectral resolution of 0.5 to 15 cm(exp -1). The improved spectral resolution of CIRS over previous IR instrument-missions to Jupiter, the extended spectral range, and higher signal-to-noise performance provide significant advantages over previous data sets. CIRS global observations of the mid-infrared spectrum of Jupiter at medium resolution (2.5 cm(exp -1)) have been analysed both with a radiance differencing scheme and an optimal estimation retrieval model to retrieve the spatial variation of phosphine and ammonia fractional scale height in the troposphere between 60 deg S and 60 deg N at a spatial resolution of 6 deg. The ammonia fractional scale height appears to be high over the Equatorial Zone (EZ) but low over the North Equatorial Belt (NEB) and South Equatorial Belt (SEB) indicating rapid uplift or strong vertical mixing in the EZ. The abundance of phosphine shows a similar strong latitudinal variation which generally matches that of the ammonia fractional scale height. However while the ammonia fractional scale height distribution is to a first order symmetric in latitude, the phosphine distribution shows a North/South asymmetry at mid latitudes with higher amounts detected at 40 deg N than 40 deg S. In addition the data show that while the ammonia fractional scale height at this spatial resolution appears to be low over the Great Red Spot (GRS), indicating reduced vertical mixing above the approx. 500 mb level, the abundance of phosphine at deeper levels may be enhanced at the northern edge of the GRS indicating upwelling.

Irwin, P. G. J.; Parrish, P.; Fouchet, T.; Calcutt, S. B.; Taylor, F. W.; Simon-Miller, A. A.; Nixon, C. A.

2004-01-01

304

The chemistry of hydrocarbon ions in the Jovian ionosphere  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

305

Responses of the Jovian Atmosphere to Cometary Particles and Photon Impacts  

NASA Technical Reports Server (NTRS)

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

Dalgarno, A.

1998-01-01

306

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

307

Rossby autosoliton and stationary model of the Jovian Great Red SPOT  

NASA Astrophysics Data System (ADS)

A theory proposed about 10 years ago claimed that the jovian Great Red Spot (GRS) was a solitary wave vortex (Rossby soliton) kept stationary by counter-streaming zonal winds. The authors have attempted to verify this soliton theory experimentally. The jovian atmosphere is modelled by a rotating thin parabolic layer of fluid (shallow water) with a free surface in which counter-streaming (zonal) flows are excited mechanically. It is found that instability of these flows can generate a Rossby autosoliton, that is, an undamped stationary solitary vortex which is alone on the perimeter of the system. This result can be considered to support the soliton theory of the GRS.

Antipov, S. V.; Nezlin, M. V.; Snezhkin, E. N.; Trubnikov, A. S.

1986-09-01

308

A Determination of the Source of Jovian Hectometric Radiation via Occultation by Ganymede  

NASA Technical Reports Server (NTRS)

During the first Galileo flyby of Ganymede, Jovian radio emissions in the frequency range of 700 kHz to 5.6 MHz were completely occulted by the satellite. We take advantage of this serendipitous observation to determine the location of the radio emission source relative to Jupiter. The evidence suggests that the apparent source is along an L greater than or approximately equal to 7 magnetic field line near the central meridian longitude (approximately 160 deg) of the spacecraft and at 1 to 3 Jovian radii above the northern hemisphere of Jupiter. These results are consistent with a source located along either the Ganymede or Europa flux tube.

Kurth, W. S.; Bolton, S. J.; Gurnett, D. A.; Levin, S.

1997-01-01

309

The ~10 hour modulation of the relativistic electron spectrum as a result of the periodic motion of the Jovian outer magnetosphere layer: Ulysses observations  

NASA Astrophysics Data System (ADS)

We analyze relativistic (E>3 MeV) electron observations during the dayside inbound trajectory of Ulysses (day 33 to day 38, 1992) in the Jovian magnetosphere and we demonstrate that the continuous presence of a relativistic electron layer at higher north latitudes (Ulysses reached ~40° lat. during closest approach the planet). In particular, we evaluated the cross-B field anisotropy of relativistic (E>3 MeV) electrons intensity by the COSPIN/HET detector onboard Ulysses, and we found that between the times of plasma sheet crossings/approaches, when Ulysses was found far from the magnetodisc, at higher north latitudes, local increases in the relativistic electron intensity and intensity gradient in the northward direction were persistently observed. We also found that (1) the well known ~10 h separated relativistic electron spectral index peaks (spectral softening) and (2) the detection of relativistic electron intensity gradient in the northward direction are related phenomena. We infer that phenomenon 1 and 2 are explained by the ~10 h periodic upward-downward motion of the Jovian magnetosphere, and consequently of the outer magnetosphere relativistic electron layer. ?he above results extends earlier results for low energy electrons and energetic protons (Anagnostopoulos et al., 1998, 2001b) to relativistic electron phenomena, and provide strong evidence, for the first time, that the well known ~10 h rocking of the relativistic electron spectrum in the outer magnetosphere (the so called "clock phenomenon") is a spatial and not a temporal effect, as was earlier hypothesized (Simpson et al.,1992).

Anagnostopoulos, G. C.; Karanikola, I.; Marhavilas, P. K.

2013-08-01

310

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

311

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

312

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

313

Determination of Jupiter's electron density profile from plasma wave observations  

Microsoft Academic Search

This paper summarizes the electron density measurements obtained in the Jovian magnetosphere from the plasma wave instruments on the Voyager 1 and 2 spacecraft. Three basic techniques are discussed for determining the electron density: (1) local measurements from the low-frequency cutoff of continuum radiation, (2) local measurements from the frequency of upper hybrid resonance emissions, and (3) integral measurements from

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

1981-01-01

314

Locating sub-jovian planets and debris in exo-planetary systems  

Microsoft Academic Search

In the past decade, more than 100 jovian mass planets have been detected in orbit about sun-like stars in our galactic neighborhood; ten of these include systems with two or more planets. It is likely that these systems contain additional bodies that are presently below the detection threshold. Dynamical stability considerations can constrain or suggest the possible orbital configurations of

R. Malhotra

2004-01-01

315

Detailed study of FUV Jovian auroral features with the post-COSTAR HST faint object camera  

Microsoft Academic Search

A set of Hubble Space Telescope faint object camera images taken in the H2 bands near 1550 Å is used to infer the morphological properties of the steady state Jovian FUV aurorae. We focus on issues best addressed using the excellent spatial resolution available after correction of the spherical aberration, i.e., those related to high latitude or small auroral features.

Renée Prangé; Daniel Rego; Laurent Pallier; Jack Connerney; Philippe Zarka; Julien Queinnec

1998-01-01

316

Correlated variations of UV and radio emissions during an outstanding Jovian auroral event  

Microsoft Academic Search

During the period December 20 to 21, 1990, an exceptional event caused the FUV and the radio DAM auroral activity on Jupiter to vary simultaneously. This is the first time that a correlated variation in Jovian optical and radio aurorae has ever been observed. The authors analyzed in detail the longitudinal distributions of the FUV source and the corresponding variations

R. Prangé; P. Zarka; G. E. Ballester; T. A. Livengood; L. Denis; T. Carr; F. Reyes; S. J. Bame; H. W. Moos

1993-01-01

317

Lightning Generation in a Jovian Thundercloud: Results from an Axisymmetric Numerical Cloud Model  

Microsoft Academic Search

An axisymmetric cloud model with detailed microphysics was used to calculate the electrical development of a jovian water cloud. The charge separation mechanism was based on the noninductive interaction between ice crystals and graupel particles in the presence of supercooled liquid droplets. The results show that for plausible concentrations of cloud condensation and freezing nuclei in the atmosphere, the electric

Yoav Yair; Zev Levin; Shalva Tzivion

1995-01-01

318

Morphology and time variation of the Jovian far UV aurora: Hubble Space Telescope observations  

Microsoft Academic Search

Two groups of two high spectral resolution images of the far ultraviolet Jovian aurora have been obtained with the FOC on board the Hubble Space Telescope. The H2 Lyman band images confirm that the discrete aurora lies at the footprint of magnetotail field lines. The change of morphology from a narrow bright arc in the morning to a broad diffuse

Jean-Claude Gerard; Vincent Dols; Francesco Paresce; Renee Prange

1993-01-01

319

Simulation of the Morphology of the Jovian UV North Aurora Observed with the Hubble Space Telescope  

Microsoft Academic Search

A model simulating Earth views of UV auroral arcs and diffuse emissions in the Jovian north polar region is described. It assumes a Chapman profile of vertical brightness distribution and various horizontal structures. Simple geometric cases are described to illustrate the dependence on the altitude, atmospheric scale height, and central meridian planetary longitude (CML) of an idealized auroral morphology seen

D. Grodent; G. R. Gladstone; J. C. Gérard; V. Dols; J. H. Waite

1997-01-01

320

The morphology of the north Jovian ultraviolet aurora observed with the Hubble Space Telescope  

Microsoft Academic Search

A series of six images covering a complete rotation of the north polar region of Jupiter were obtained in February 1993 with the Faint Object Camera on board the Hubble Space Telescope (HST). These images provide the first global picture of the morphology of the Jovian ultraviolet aurora observed from Earth orbit. The camera passband was centered near 153 nm,

Jean-Claude Gerard; Vincent Dols; Renee Prange; Francesco Paresce

1994-01-01

321

Operations cost Reduction for a Jovian Science Mission Using CubeSats  

NASA Astrophysics Data System (ADS)

This paper proposes the operation of a mission architecture for jovian satellite tour, that uses small orbiter 6U CubeSats, airless body landers of the same order of 6U size and a mothership carrier that will act as a communication hub to DSN.

Rajguru, A.; Faler, A. C.

2014-06-01

322

RADON TRANSFORM ON THE TORUS AHMED ABOUELAZ AND FRANOIS ROUVIRE  

E-print Network

RADON TRANSFORM ON THE TORUS AHMED ABOUELAZ AND FRANÃ?OIS ROUVIÃ?RE Abstract. We consider the Radon-Ricci spaces etc. We consider here the n-dimensional (at) torus Tn = Rn=Zn and the Radon transform de will thus enter the picture, as in the case of Radon transforms on Zn already studied by the ...rst author

Rouvière, François

323

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

324

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 of this talk will be about what happens to the vapor as it orbits Saturn. 2 #12;3 Enceladus' torus is one

325

Information Spreading on Almost Torus Networks Antonia Maria Masucci 1  

E-print Network

Information Spreading on Almost Torus Networks Antonia Maria Masucci 1 and Alonso Silva 2 1 ETIS the spread of computer Email: antonia-maria.masucci@ensea.fr Email: alonso.silva@alcatel-lucent.com To whom's Blue Gene L [12, 13] and Blue Gene P [14]; Cray's XT and XT3 [15] systems use three-dimensional torus

326

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

327

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

328

Ideal magnetohydrodynamic equilibrium in a non-symmetric topological torus  

SciTech Connect

An alternative representation of an ideal magnetohydrodynamic equilibrium is developed. The representation is a variation of one given by A. Salat, Phys. Plasmas 2, 1652 (1995). The system of equations is used to study the possibility of non-symmetric equilibria in a topological torus, here an approximate rectangular parallelopiped, with periodicity in two of the three rectangular coordinates. An expansion is carried out in the deviation of pressure surfaces from planes. Resonances are manifest in the process. Nonetheless, provided the magnetic shear is small, it is shown that it is possible to select the magnetic fields and flux surfaces in such a manner that no singularities appear on resonant surfaces. One boundary surface of the parallelopiped is not arbitrary but is dependent on the equilibrium in question. A comparison of the solution sets of axisymmetric and non-axisymmetric equilibria suggests that the latter have a wider class of possible boundary shapes but more restrictive rotational transform profiles. No proof of convergence of the series is given.

Weitzner, Harold [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)] [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)

2014-02-15

329

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

330

Jovian decametric arcs - An estimate of the required wave normal angles from three-dimensional ray tracing.  

NASA Technical Reports Server (NTRS)

Three-dimensional ray tracing is applied to an analysis of variable radio wave normal angle effects on the associated decametric (DAM) arc structures in the Jovian magnetosphere. The analysis is bed on 1-40 MHz radio signature recorded during Voyage 1 and 2 passages. The frequencies considered are above the R-X cut-off, and several ratios of the emission frequency/source frequency. The ray tracing code is based on a cold plasma formula and integration of the Hasselgrove (1955) equations. It is assumed that the emission is in the R-X mode, the source lies at the foot of an Io flux tube, and the emission cone is hollow. Attention is focused on data for two intense, vertex-late, high curvature DAM arc. A possible source for the arcs is found to be doppler-shifted gyroemission from a beam of electrons with an energy of 10 keV. A value of 1.1 is set as the limit of the doppler shift of the DAM emissions.

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

1984-01-01

331

Imaging x-ray crystal spectrometers for the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

A new type of high-resolution x-ray imaging crystal spectrometers is described for implementation on the National Spherical Torus Experiment (NSTX) to provide spatially and temporally resolved data on the ion temperature, toroidal and poloidal plasma rotation, electron temperature, impurity ion-charge state distributions, and impurity transport. These data are derived from observations of the satellite spectra of heliumlike argon, Ar XVII, which is the dominant charge state for electron temperatures in the range from 0.4 to 3.0 keV and which is accessible to NSTX. Experiments at the Torus Experiment for Technology Oriented Research (TEXTOR) demonstrate that a throughput of 2×105 photons/s (corresponding to the count-rate limit of the present detectors) can easily be obtained with small, nonperturbing argon gas puffs of less than 1×10-3 Torr l/s, so that it is possible to record spectra with a small statistical error and a good time resolution (typically 50 and 1 ms in some cases). Employing a novel design, which is based on the imaging properties of spherically bent crystals, the spectrometers will provide spectrally and spatially resolved images of the plasma for all experimental conditions, which include ohmically heated discharges as well as plasmas with rf and neutral-beam heating. The conceptual design, experimental results on the focusing properties, and relevant spectral data from TEXTOR are presented.

Bitter, M.; Hill, K. W.; Roquemore, A. L.; Beiersdorfer, P.; Kahn, S. M.; Elliott, S. R.; Fraenkel, B.

1999-01-01

332

Ion flow measurements during the MHD relaxation processes in the HIST spherical torus device  

NASA Astrophysics Data System (ADS)

Plasma flow is one of the key roles in self-organization and magnetic reconnection processes of helicity-driven spherical torus (ST) and spheromak. The HIST spherical torus can form the standard ST and the flipped ST plasmas by utilizing the variation of the external toroidal field coil current. The flipped ST plasma can be generated by changing the polarity of the toroidal magnetic field during the standard ST discharge [1]. We have developed an ion Doppler spectrometer (IDS) system using a compact 16 channel photomultiplier tube (PMT) in order to measure the spatial profile of ion temperature and rotation velocity in the HIST device. The IDS system consists of a light collection system including optical fibers, 1 m-spectrometer and the PMT detector. As the results, it was observed that ion velocity was about 10 km/s in the same direction as the toroidal current and ExB direction in the standard ST discharge. The observed ion velocity agrees with Mach probe measurements. During the transition from the standard ST to the flipped ST state, the ion temperature was fluctuated and increased. The result implies an ion heating during magnetic reconnections. In addition, the toroidal direction of the ion flow was reversed. The detail physics of the observed phenomenon will be shown. [1] M. Nagata et al., Phys Rev. Lett. 90, pp. 225001-225004 (2003).

Nishioka, T.; Hashimoto, S.; Ando, K.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2008-11-01

333

Parametric dependence of fast-ion transport events on the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

This paper presents an empirical approach towards characterizing the stability boundaries for some common energetic-ion-driven instabilities as seen on the National Spherical Torus Experiment (NSTX). Understanding the conditions for which beam-driven instabilities arise, and the extent of the resulting perturbation to the fast-ion population, is important for predicting and eventually demonstrating non-inductive current ramp-up and sustainment in NSTX-U (Menard J. et al 2012 Nucl. Fusion 52 083015), as well as the performance of future fusion plasma experiments such as ITER. A database has been constructed, based on shots from the 2010 experimental campaign for which TRANSP runs were performed. Each shot was divided into 50 ms intervals and the dominant beam-driven activity was characterized, and plasma parameters were collected into a database. It is found that TAE avalanches are present for ?fast/?total > 0.3 and quiescent plasmas only for ?fast/?total < 0.3.

Fredrickson, E. D.; Gorelenkov, N. N.; Podesta, M.; Bortolon, A.; Gerhardt, S. P.; Bell, R. E.; Diallo, A.; LeBlanc, B.

2014-09-01

334

Formation of the Jovian and Saturnian Satellite Systems (Invited)  

NASA Astrophysics Data System (ADS)

The Jovian and Saturnian regular satellites likely formed within circumplanetary disks of gas (primarily hydrogen) and solids (rock and ice). Here I will focus on a model [1-3] in which gas giant satellites form within disks produced by the final stages of gas accretion by the planets [4]. Small solids carried into the disk by gas inflowing from solar orbit provide the raw material for accreting satellites. Each satellite can grow no larger than a critical mass, at which point its orbit spirals into the planet due to density wave interactions with the gas disk (Type I migration). This critical mass is comparable to those of the Galilean satellites and Titan. Multiple generations of satellites having this critical mass are predicted to form and be lost to collision with the planet. The final surviving satellites are those that form as gas inflow to the planet ends, the circumplanetary gas disk dissipates, and the satellite orbits stabilize. In this model, all the gas giant satellites accrete slowly, at a rate governed by the rate of delivery of solid material to the disk. This implies that the final large satellites form on a timescale comparable to the solar nebula dissipation timescale, which was likely ~ 10^6 yr. Such a slow accretion can allow large, outer ice-rock satellites to remain undifferentiated or to undergo only partial differentiation as they form [5-6]. The model produces final satellite systems having either several large satellites (like the Galilean satellites) or a single large satellite (like Saturn’s Titan) [2,7]. A Saturn-like system is produced when large, Titan-sized satellites orbiting interior to Titan spiral into the planet and are lost as gas inflow ends, leaving Titan as the sole large survivor [2]. As the final large satellite lost from the Saturn system spirals within the Roche limit, planetary tides preferentially strip material from its outer layers, producing a massive ice ring [8]. Such conditions offer a new explanation for the origin of Saturn’s main rings and the Saturnian ice-rich satellites interior to and including Tethys [8]. [1] Canup, R.M. & W.R. Ward, AJ, 124, 3404 (2002); [2] Canup, R.M. & W.R. Ward, Nature 441, 834 (2006). [3] Ward, W.R. & R.M. Canup, In Europa, Univ. Az. Press (2009). [4] Ward, W.R. & R.M. Canup, AJ, in press (2010); [5] Barr, A.C. & R.M. Canup, Icarus 198, 163 (2008); [6] Barr, A.C., Citron, R. & R.M. Canup, Icarus, in press (2010); [7] Sasaki, T., G.R. Stewart, & S. Ida. ApJ, 714, 1052 (2010). [8] Canup, R.M., Nature, submitted (2010). Support from NASA’s OPR and PGG programs is gratefully acknowledged.

Canup, R. M.

2010-12-01

335

The time-frequency structure of Jovian narrowband decametric radio emission as a probe of the ionosphere of Jupiter  

NASA Astrophysics Data System (ADS)

We consider the origin of the time-frequency structure of Jovian narrowband decametric radio emission as a consequence of propagation of radiation in the Jovian ionosphere with time varied parameters. Our laboratory and numerical experiments show that the time-frequency structure of dynamic spectra of an initially continuous signal can drastically vary as functions of the form of the magnetic field disturbance in the media where the radiation propagates. Structures similar to those observed in the real experiments, ranging from NB emission and quasiperiodic trains of S bursts to more complex structures, arise in the dynamic spectrum. Assuming the formation of the time-frequency structure of the Jovian narrowband decametric radio emission as a result of propagation of the radiation in the ionosphere and lower magnetosphere of the planet we can get the information about the conditions in the Jovian ionosphere and low magnetosphere.

Shaposhnikov, V.; Korobkov, S.; Gushchin, M.; Kostrov, A.; Rucker, H.; Litvinenko, G.

2012-09-01

336

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

NASA Astrophysics Data System (ADS)

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 ?T and ?N values of 17% and 5.7 (%m T MA-1), respectively. A newly available motional Stark effect diagnostic has enabled validation of current-drive sources and improved the understanding of NSTX 'hybrid'-like scenarios. In MHD research, ex-vessel radial field coils have been utilized to infer and correct intrinsic EFs, provide rotation control and actively stabilize the n = 1 resistive wall mode at ITER-relevant low plasma rotation values. In transport and turbulence research, the low aspect ratio and a wide range of achievable ? in the NSTX provide unique data for confinement scaling studies, and a new microwave scattering diagnostic is being used to investigate turbulent density fluctuations with wavenumbers extending from ion to electron gyro-scales. In energetic particle research, cyclic neutron rate drops have been associated with the destabilization of multiple large toroidal Alfven eigenmodes (TAEs) analogous to the 'sea-of-TAE' modes predicted for ITER, and three-wave coupling processes have been observed for the first time. In boundary physics research, advanced shape control has enabled studies of the role of magnetic balance in H-mode access and edge localized mode stability. Peak divertor heat flux has been reduced by a factor of 5 using an H-mode-compatible radiative divertor, and lithium conditioning has demonstrated particle pumping and results in improved thermal confinement. Finally, non-solenoidal plasma start-up experiments have achieved plasma currents of 160 kA on closed magnetic flux surfaces utilizing coaxial helicity injection.

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

2007-10-01

337

Progress Towards High Performance, Steady-state Spherical Torus  

SciTech Connect

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

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

2003-10-02

338

Progress towards high-performance, steady-state spherical torus  

NASA Astrophysics Data System (ADS)

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 (bgr), 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 bgrT of up to 35% with a near unity central bgrT have been obtained. NSTX will be exploring advanced regimes where bgrT 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 (~60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip ~ 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.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W.; Boedo, J.; Bourdelle, C.; Bush, C.; Choe, W.; Chrzanowski, J.; Darrow, D. S.; Diem, S. J.; Doerner, R.; Efthimion, P. C.; Ferron, J. R.; Fonck, R. J.; Fredrickson, E. D.; Garstka, G. D.; Gates, D. A.; Gray, T.; Grisham, L. R.; Heidbrink, W.; Hill, K. W.; Hoffman, D.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kaye, S. M.; Kessel, C.; Kim, J. H.; Kissick, M. W.; Kubota, S.; Kugel, H. W.; LeBlanc, B. P.; Lee, K.; Lee, S. G.; Lewicki, B. T.; Luckhardt, S.; Maingi, R.; Majeski, R.; Manickam, J.; Maqueda, R.; Mau, T. K.; Mazzucato, E.; Medley, S. S.; Menard, J.; Mueller, D.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ostrander, C. N.; Pacella, D.; Paoletti, F.; Park, H. K.; Park, W.; Paul, S. F.; Peng, Y.-K. M.; Phillips, C. K.; Pinsker, R.; Probert, P. H.; Ramakrishnan, S.; Raman, R.; Redi, M.; Roquemore, A. L.; Rosenberg, A.; Ryan, P. M.; Sabbagh, S. A.; Schaffer, M.; Schooff, R. J.; Seraydarian, R.; Skinner, C. H.; Sontag, A. C.; Soukhanovskii, V.; Spaleta, J.; Stevenson, T.; Stutman, D.; Swain, D. W.; Synakowski, E.; Takase, Y.; Tang, X.; Taylor, G.; Timberlake, J.; Tritz, K. L.; Unterberg, E. A.; Von Halle, A.; Wilgen, J.; Williams, M.; Wilson, J. R.; Xu, X.; Zweben, S. J.; Akers, R.; Barry, R. E.; Beiersdorfer, P.; Bialek, J. M.; Blagojevic, B.; Bonoli, P. T.; Carter, M. D.; Davis, W.; Deng, B.; Dudek, L.; Egedal, J.; Ellis, R.; Finkenthal, M.; Foley, J.; Fredd, E.; Glasser, A.; Gibney, T.; Gilmore, M.; Goldston, R. J.; Hatcher, R. E.; Hawryluk, R. J.; Houlberg, W.; Harvey, R.; Jardin, S. C.; Hosea, J. C.; Ji, H.; Kalish, M.; Lowrance, J.; Lao, L. L.; Levinton, F. M.; Luhmann, N. C.; Marsala, R.; Mastravito, D.; Menon, M. M.; Mitarai, O.; Nagata, M.; Oliaro, G.; Parsells, R.; Peebles, T.; Peneflor, B.; Piglowski, D.; Porter, G. D.; Ram, A. K.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Shaing, K.; Shiraiwa, S.; Sichta, P.; Stotler, D.; Stratton, B. C.; Vero, R.; Wampler, W. R.; Wurden, G. A.

2003-12-01

339

Torus CLAS12-Superconducting Magnet Quench Analysis  

SciTech Connect

The JLAB Torus magnet system consists of six superconducting trapezoidal racetrack-type coils assembled in a toroidal configuration. These coils are wound with SSC-36 Nb-Ti superconductor and have the peak magnetic field of 3.6 T. The first coil manufacturing based on the JLAB design began at FNAL. The large magnet system dimensions (8 m diameter and 14 MJ of stored energy) dictate the need for quench protection. Each coil is placed in an aluminum case mounted inside a cryostat and cooled by 4.6 K supercritical helium gas flowing through a copper tube attached to the coil ID. The large coil dimensions and small cryostat thickness drove the design to challenging technical solutions, suggesting that Lorentz forces due to transport currents and eddy currents during quench and various failure scenarios are analyzed. The paper covers the magnet system quench analysis using the OPERA3d Quench code.

Kashikhin, V. S.; Elouadhiri, L.; Ghoshal, P. K.; Kashy, D.; Makarov, A.; Pastor, O.; Quettier, L.; Velev, G.; Wiseman, M.

2014-06-01

340

Torus Knot Polynomials and Susy Wilson Loops  

NASA Astrophysics Data System (ADS)

We give, using an explicit expression obtained in (Jones V, Ann Math 126:335, 1987), a basic hypergeometric representation of the HOMFLY polynomial of ( n, m) torus knots, and present a number of equivalent expressions, all related by Heine's transformations. Using this result, the symmetry and the leading polynomial at large N are explicit. We show the latter to be the Wilson loop of 2d Yang-Mills theory on the plane. In addition, after taking one winding to infinity, it becomes the Wilson loop in the zero instanton sector of the 2d Yang-Mills theory, which is known to give averages of Wilson loops in = 4 SYM theory. We also give, using matrix models, an interpretation of the HOMFLY polynomial and the corresponding Jones-Rosso representation in terms of q-harmonic oscillators.

Giasemidis, Georgios; Tierz, Miguel

2014-12-01

341

A torus bifurcation theorem with symmetry  

NASA Technical Reports Server (NTRS)

Hopf bifurcation in the presence of symmetry, in situations where the normal form equations decouple into phase/amplitude equations is described. A theorem showing that in general such degeneracies are expected to lead to secondary torus bifurcations is proved. By applying this theorem to the case of degenerate Hopf bifurcation with triangular symmetry it is proved that in codimension two there exist regions of parameter space where two branches of asymptotically stable two-tori coexist but where no stable periodic solutions are present. Although a theory was not derived for degenerate Hopf bifurcations in the presence of symmetry, examples are presented that would have to be accounted for by any such general theory.

Vangils, S. A.; Golubitsky, M.

1989-01-01

342

Non-factorizable branes on the torus  

NASA Astrophysics Data System (ADS)

This work discusses string compactifications on the torus with optional Z×Z or Z×Z orbifold action from the perspective of matrix factorizations. The method is brought to a level where model building on these backgrounds is possible. Whereas branes discussed in the literature typically wrap factorizable cycles, that is, cycles in H(,Z)3?H(T,Z), branes studied here can be in generic homology classes, can have arbitrary position and Wilson line, have full complex structure respectively Kähler moduli dependence and can be subject to any consistent orientifold action. It is shown how any desired D-brane can be constructed systematically. Three-point correlators can be computed as is demonstrated at hand of an example. Their normalization is not discussed.

Omer, Harun

2010-07-01

343

A Megawatt-level 28z GHz Heating System For The National Spherical Torus Experiment Upgrade  

SciTech Connect

The National Spherical Torus Experiment Upgrade (NSTX-U) will operate at axial toroidal fields of < 1 T and plasma currents, Ip < 2 MA. The development of non-inductive (NI) plasmas is a major long-term research goal for NSTX-U. Time dependent numerical simulations of 28 GHz electron cyclotron (EC) heating of low density NI start-up plasmas generated by Coaxial Helicity Injection (CHI) in NSTX-U predict a significant and rapid increase of the central electron temperature (Te(0)) before the plasma becomes overdense. The increased Te(0) will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast wave heating and neutral beam injection. A megawatt-level, 28 GHz electron heating system is planned for heating NI start-up plasmas in NSTX-U. In addition to EC heating of CHI start-up discharges, this system will be used for electron Bernstein wave (EBW) plasma start-up, and eventually for EBW heating and current drive during the Ip flattop.

Taylor, Gary [PPPL

2014-04-01

344

Spectral mapping of the FUV Jovian aurora and electron energy distribution  

NASA Astrophysics Data System (ADS)

Observations have been made with the Hubble Space Telescope in the timetag mode using the UVIS long slit. During the 40 min of the observations, the slit spatially scanned the polar regions to build spectral maps of the jovian aurora. The emission is composed of the HI Lyman-alpha line and the H2 Lyman and Werner bands. The shorter wavelengths are partly absorbed by the methane layer overlying the bulk of the auroral emission. Since the CH4 absorption cross section drastically drop above 140 nm, the longer wavelengths are not absorbed and the intensity directly reflects the precipitated energy flux carried by the electrons. Maps of the intensity ratio of the two spectral regions will be presented, together with the associated auroral electron energy. These values will be compared with those expected from current magnetosphere-ionosphere model. They will provide input into 3-D modeling of the auroral heat source into the high-latitude Jovian upper atmosphere.

Gérard, J.-C.; Bonfond, B.; Grodent, D.; Gustin, J.; Radioti, A.; Clarke, J. T.; Gladstone, R. G.; Waite, J. H.

2014-04-01

345

Ray tracing of Jovian decametric radiation from Southern and Northern Hemisphere sources - Comparison with Voyager observations  

NASA Technical Reports Server (NTRS)

The Voyager 1 and 2 Planetary Radio Astronomy observations of Io-dependent decametric (DAM) radiation originating from the Southern Hemisphere of Jupiter were compared with the results of three-dimensional model ray tracing calculations of the DAM radiation. The ray trajectories for sources located at constant sub-Io longitudes of 260 and 300 deg were computed for both the Northern and the Southern Jovian Hemisphere sources. The model results of wave propagation agree with the Voyager observations obtained with Io located at 260 and 300 deg in Jovian system III longitude. The agreement between the Voyager observations and the model ray tracings allows identification of the origin of several of the emission components.

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

1987-01-01

346

Energetic ion losses near Io's orbit  

NASA Astrophysics Data System (ADS)

The interactions between Io and the Jovian particle population have been of considerable interest ever since the discovery that Io modulates Jupiter's decametric radiation. Voyager 1 observations established that a plasma torus around Io dominates the mass and energy budgets of the Jovian magnetosphere. This torus must then play a central role in the particle loss process around Io. The present investigation provides a picture for particle transport and energetic ion losses near Io's orbit which considers both low energy plasma data and energetic ion data. The approximate match between the energy needed to power the Jovian UV aurora and the 'missing' energy of the low energy charged particle (LECP) measured ions is consistent with the concept that significant precipitation of energetic ions into the Jovian atmosphere can maintain the Jovian aurora.

Cheng, A. F.; Maclennan, C. G.; Lanzerotti, L. J.; Paonessa, M. T.; Armstrong, T. P.

1983-05-01

347

Chandra X-ray Observations of Jovian Low-latitude Emissions: Morphological, Temporal, and Spectral Characteristics  

NASA Technical Reports Server (NTRS)

Chandra observed X-rays from Jupiter during 24-26 February 2003 for about 40 hours with the ACIS-S and HRC-I instruments. The analysis of Jovian low-latitude "disk" Xray emissions are presented and compared with the high-latitude "auroral" emissions. We report the first Chandra ACIS-S measured X-ray spectrum (0.3-2 keV) of Jupiter's low-latitude disk The disk X-ray emission is harder and extends to higher energies than the auroral spectrum. The temporal variation in the Jovian disk X-rays is on an average consistent with those in the solar X-rays observed by GOES, and TIMED/SSE. Contrary to the auroral X-rays, the disk emissions are uniformly distributed over Jupiter; no indication of longitudinal dependence or correlation with surface magneh field strength is visible. Also, unlike the approx. 40 +/- 20 min periodic oscillations seen in the auroral X-ray emissions, the disk emissions do not show any periodic oscillations. The disk spectrum seems to be consistent with resonant and fluorescent scattering of solar X-rays by the Jovian upper atmosphere. Jupiter's disk is found to be about 50% dimmer in soft X-rays in February 2003 compared that in December 2000, which is consistent with the decrease in solar activity. No evidence of lightning-induced X-rays is seen in the Chandra X-ray data. The Jovian disk spectra observed with Chandra-ACIS is stronger than that observed with XMM-Newton two months later during April 28-29, 2003. The XMM-Newton Xray image of Jupiter shows evidence of limb darkening on the anti-sunward side as seen from Earth, as well as an asymmetry with respect to the subsolar point: suggesting a solar driven process.

Bhardwaj, Anil; Elsner, Ronald F.; Gladstone, G. Randall; Cravens, Thomas E.; Waiate J. Hunter, Jr.; Branduardi-Raymont, Graziella; Ford, Peter

2004-01-01

348

Spectral Energy Distribution Signatures of Jovian Planets around White Dwarf Stars  

Microsoft Academic Search

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 Teff=10,000 K at a distance of ~103 white dwarf radii (corresponding to ~102 Jupiter radii or a few tenths of an AU) with an orbital period of ~100 days. Such a planet will have a 10

R. Ignace

2001-01-01

349

On the ortho-para equilibrium of H2 in the atmospheres of the Jovian planets  

NASA Technical Reports Server (NTRS)

The ratio for the equivalent widths for the unsaturated H2 quadrupole transitions observed in the Jovian planets is calculated and compared with a large number of observations. The comparison indicates that equilibrium hydrogen may be present in Jupiter and Saturn, while Uranus and Neptune exhibit ratios not in accord with equilibrium hydrogen. Observations which can differentiate among the possible states of H2 are proposed.

Smith, W. H.

1978-01-01

350

Retired A Stars and Their Companions. VII. 18 New Jovian Planets  

Microsoft Academic Search

We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 <= M sstarf\\/M &sun; <= 1.95, radii 2.5 <= R sstarf\\/R &sun; <= 8.7, and metallicities -0.46 <= [Fe\\/H] <=+0.30.

John Asher Johnson; Christian Clanton; Andrew W. Howard; Brendan P. Bowler; Gregory W. Henry; Geoffrey W. Marcy; Justin R. Crepp; Michael Endl; William D. Cochran; Phillip J. MacQueen; Jason T. Wright; Howard Isaacson

2011-01-01

351

Low-frequency Jovian emission and solar wind magnetic sector structure  

Microsoft Academic Search

The Earth, Jupiter and Saturn emit non-thermal low-frequency radiations with similar characteristics. For the Earth and Saturn, the radio emissions are known to fluctuate with a time scale of several days, correlated with variations of the solar wind or related phenomena at the planet1-4. Several studies of the jovian radiation at decametre wavelengths, from ground-based observations, suggest that the non-Io-controlled

P. Zarka; F. Genova

1983-01-01

352

What can we learn from the auroral footprints of the Jovian moons? (Invited)  

NASA Astrophysics Data System (ADS)

The signature of electromagnetic interaction between the moons Io, Europa and Ganymede and the Jovian magnetosphere can be observed on Jupiter’s polar ionosphere in the form of auroral footprints. The observation campaigns carried out during the past few years by the Hubble Space Telescope in the Far UV domain provided not only a high spatial and temporal resolution but also an unprecedented System III longitude coverage. Consequently, these recent observations of the morphology and the dynamics of the footprints proved to be very powerful tools to probe these interactions. For example, the locations of the satellite footprints have been used as a valuable constraint for building Jovian magnetic field models. Moreover, analysis of the multiplicity of the Io footprint spots as well as their relative motion lead to new conclusions on the electron acceleration processes. The altitude of the Io footprint has also been used to infer the typical energy of the impinging electrons. Finally, the study of the three-dimensional shape and of the brightness of the different sub-structures of the footprints provides important clues on the processes at play between Io and the Jovian ionosphere. On the theoretical side, considerable efforts have also been recently carried out in order to model the propagation of the Alfvén waves generated at Io and the subsequent acceleration of auroral electrons. Coupled with HST images, radio decametric measurements and in situ data from the Galileo spacecraft, these advances provide a brand new understanding of the satellite footprints.

Bonfond, B.

2010-12-01

353

New Observations of Europa's Surface Composition: Discovery of an Anti-Jovian Salty Region  

NASA Astrophysics Data System (ADS)

The surface composition of Europa is the best means available to probe its global chemical cycle and constrain the composition of its ocean. New observations of Europa's near-infrared reflectance spectra were obtained with the OSIRIS instrument on the Keck II telescope. Previous investigations of Europa's surface composition have mostly relied on Galileo NIMS infrared spectra; though NIMS measurements have high spatial resolution, they lack spectral resolution and span a limited spatial extent. Conversely, our observations comprise a near-global spectral map of Europa in the infrared H and K bands. At ~ 1 nm spectral resolution and ~ 100 km spatial resolution, these data reveal global distributions of key spectral features, enabling a more complete characterization of Europa's surface composition than previously possible. Simple linear spectral modelling of these data reproduces the global abundance distributions of water ice and sulfuric acid hydrate. In addition, this modelling reveals a suggestively "salty" region on Europa's anti-Jovian hemisphere. This region is spectrally distinct from both the trailing hemisphere bullseye and the spectrum of pure water ice, and shows a direct spatial correlation to an anti-Jovian chaos unit. Similar chaos regions show enhancements of saltier spectra as well, though to a lesser degree. We report three spectral end member regions on Europa's surface, represented by the trailing hemisphere bullseye, the leading hemisphere north polar "icy" region, and the anti-Jovian "salty" chaos unit. We present global compositional maps, and discuss the potential compositions of the three end member regions.

Fischer, Patrick D.; Brown, Michael E.; Hand, Kevin P.

2014-11-01

354

The morphology of the north Jovian ultraviolet aurora observed with the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

A series of six images covering a complete rotation of the north polar region of Jupiter were obtained in February 1993 with the Faint Object Camera on board the Hubble Space Telescope (HST). These images provide the first global picture of the morphology of the Jovian ultraviolet aurora observed from Earth orbit. The camera passband was centered near 153 nm, a region dominated by the H2 Lyman bands and continuum. The successive exposures, taken approximately 90 min apart, are used to construct a polar view of the auroral zone. It is found that the auroral emissions do not exactly follow the footprint of a constant L-shell although the size of the oval and its location agree best with the footprints of the approximately equal to 30 R(sub J) field line in the GSFC O6 model of the Jovian magnetic field. The displacement between the observed auroral zone and the theoretical oval may indicate a possible distortion of the Jovian magnetic field lines near the surface. A comparison with two images at the same wavelength obtained 8 months earlier shows that the main morphological features are persistent, in spite of changes in the detailed emission distribution. Small scale features with characteristic sizes of approximately 1000 km are observed along the auroral oval. The change of morphology observed as a function of the System 3 longitude appears as a persistent characteristic of the morphology of the north polar aurora.

Gerard, Jean-Claude; Dols, Vincent; Prange, Renee; Paresce, Francesco

1994-01-01

355

Development of rotating magnetic field coil system in the HIST spherical torus device  

NASA Astrophysics Data System (ADS)

Coaxial Helicity Injection (CHI) is one of most attractive methods to achieve non-inductive current drive in spherical torus devices. The current drive mechanism of CHI relies on MHD relaxation process of rotating kink behavior [1], so that there is a possibility to control the CHI by using an externally applied rotating magnetic field (RMF). We have recently started to develop a RMF coil system in the HIST spherical torus device. Eight coils are located above and below the midplane at four toroidal locations so that the RMF is resonant with n = 1 rotating kink mode driven by the CHI. In addition, the RMF coil set is installed inside a flux conserver of 5 mm thickness (cut-off frequency ˜ 170 Hz) so that the RMF penetrates into the plasma. The coil winding is made of 20 turns of enameled copper circular wires (1.5 mm^2 conductor cross section), covered with a thin stainless steal case of 0.5 mm thickness (cut-off frequency ˜ 710 kHz). The RMF system is driven by an IGBT inverter power supply (nominal current: 1 kA, nominal voltage: 1 kV) with an operating frequency band from 10 kHz to 30 kHz. The estimated amplitude of RMF neglecting effects of image current at the flux conserver is a few tens Gauss at around the magnetic axis. A preliminary experimental result will be shown in the conference. [1] M. Nagata, et al., Physics of Plasmas 10, 2932 (2003).

Yoshikawa, T.; Kikuchi, Y.; Yamada, S.; Hashimoto, S.; Nishioka, T.; Fukumoto, N.; Nagata, M.

2007-11-01

356

Mixing in milli torus reactor under aerated conditions  

Microsoft Academic Search

The present paper contributes to improve the understanding of two-phase flow hydrodynamics characteristics in milli torus reactor. To reach this goal, experiments were performed in a vertical milli torus reactor, having a capacity of 0.140l. The effect of the aeration numbers and the impeller rotation speeds has been studied. It was found that the homogenization of the tracer inside the

R. Rihani; J. Legrand; A. Bensmaili

2009-01-01

357

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment  

SciTech Connect

The National Spherical Torus Experiment (NSTX) has recently studied the use of a liquid lithium divertor (LLD). Divertor Langmuir probes have also been installed for making measurements of the local plasma conditions. A non-local probe interpretation method is used to supplement the classical probe interpretation and obtain measurements of the electron energy distribution function (EEDF) which show the occurrence of a hot-electron component. Analysis is made of two discharges within a sequence that exhibited changes in plasma fueling efficiency. It is found that the local electron temperature increases and that this increase is most strongly correlated with the energy contained within the hot-electron population. Preliminary interpretative modeling indicates that kinetic effects are likely in the NSTX.

Jaworski, M A; Gray, T K; Kaita, R; Kallman, J; Kugel, H; LeBlanc, B; McLean, A; Sabbagh, S A; Soukanovskii, V; Stotler, D P

2011-06-03

358

Simulation and design of feedback control on resistive wall modes in Keda Torus eXperiment  

NASA Astrophysics Data System (ADS)

The feedback control of resistive wall modes (RWMs) in Keda Torus eXperiment (KTX) (Liu et al., Plasma Phys. Controlled Fusion 56, 094009 (2014)) is investigated by simulation. A linear model is built to describe the growth of the unstable modes in the absence of feedback and the resulting mode suppression due to feedback, given the typical reversed field pinch plasma equilibrium. The layout of KTX with two shell structures (the vacuum vessel and the stabilizing shell) is taken into account. The feedback performance is explored both in the scheme of "clean mode control" (Zanca et al., Nucl. Fusion 47, 1425 (2007)) and "raw mode control." The discrete time control model with specific characteristic times will mimic the real feedback control action and lead to the favored control cycle. Moreover, the conceptual design of feedback control system is also presented, targeting on both RWMs and tearing modes.

Li, Chenguang; Liu, Wandong; Li, Hong

2014-12-01

359

Realizing "2001: A Space Odyssey": Piloted Spherical Torus Nuclear Fusion Propulsion  

NASA Technical Reports Server (NTRS)

A conceptual vehicle design enabling fast, piloted outer solar system travel was created predicated on a small aspect ratio spherical torus nuclear fusion reactor. The initial requirements were satisfied by the vehicle concept, which could deliver a 172 mt crew payload from Earth to Jupiter rendezvous in 118 days, with an initial mass in low Earth orbit of 1,690 mt. Engineering conceptual design, analysis, and assessment was performed on all major systems including artificial gravity payload, central truss, nuclear fusion reactor, power conversion, magnetic nozzle, fast wave plasma heating, tankage, fuel pellet injector, startup/re-start fission reactor and battery bank, refrigeration, reaction control, communications, mission design, and space operations. Detailed fusion reactor design included analysis of plasma characteristics, power balance/utilization, first wall, toroidal field coils, heat transfer, and neutron/x-ray radiation. Technical comparisons are made between the vehicle concept and the interplanetary spacecraft depicted in the motion picture 2001: A Space Odyssey.

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

2005-01-01

360

Jupiter plasma wave observations: an initial Voyager 1 overview  

Microsoft Academic Search

The Voyager 1 plasma wave instrument detected low-frequency radio emissions, ion acoustic waves, and electron plasma oscillations for a period of months before encountering Jupiter's bow shock. In the outer magnetosphere, measurements of trapped radio waves were used to derive an electron density profile. Near and within the Io plasma torus the instrument detected high-frequency electrostatic waves, strong whistler mode

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

1979-01-01

361

Advanced Plasma Propulsion for Human Missions to Jupiter  

NASA Technical Reports Server (NTRS)

This paper will briefly identify a promising fusion plasma power source, which when coupled with a promising electric thruster technology would provide for an efficient interplanetary transfer craft suitable to a 4 year round trip mission to the Jovian system. An advanced, nearly radiation free Inertial Electrostatic Confinement scheme for containing fusion plasma was judged as offering potential for delivering the performance and operational benefits needed for such high energy human expedition missions, without requiring heavy superconducting magnets for containment of the fusion plasma. Once the Jovian transfer stage has matched the heliocentric velocity of Jupiter, the energy requirements for excursions to its outer satellites (Callisto, Ganymede and Europa) by smaller excursion craft are not prohibitive. The overall propulsion, power and thruster system is briefly described and a preliminary vehicle mass statement is presented.

Donahue, Benjamin B.; Pearson, J. Boise

1999-01-01

362

Voids in Jovian magnetosphere revisited - Evidence of spacecraft charging  

NASA Technical Reports Server (NTRS)

The Voyager 2 Plasma Science Instrument (PLS) measuring cold plasma number density observed about a dozen 'voids', lasting from a few minutes to 20 min, in the vicinity of the Ganymede-orbit crossing, when the low-energy ion and electron fluxes recorded fell to very low levels. Original interpretations associated these 'voids' with Ganymede wake effects. In the present study, the PLS data are reexamined, in conjunction with data from the magnetic field experiment and the low-energy charged particle (LECP) experiment. The LECP data showed that the PLS voids were accompanied by large enhancements of the flux of energetic electrons and ions, while the magnetic data exhibited no systematic signatures. It is suggested that increased energetic electron fluxes in the void regions intermittently charged the spacecraft negatively to values between a few kV and a few tens of kV, and that spacecraft charging could have produce dropouts in the measured cold ion and electron fluxes and enhancements in the measured fluxes of hot particles consistent with the observations.

Khurana, K. K.; Kivelson, M. G.; Walker, R. J.; Armstrong, T. P.

1987-01-01

363

Princeton Plasma Physics Laboratory:  

SciTech Connect

This paper discusses progress on experiments at the Princeton Plasma Physics Laboratory. The projects and areas discussed are: Principal Parameters Achieved in Experimental Devices, Tokamak Fusion Test Reactor, Princeton Large Torus, Princeton Beta Experiment, S-1 Spheromak, Current-Drive Experiment, X-ray Laser Studies, Theoretical Division, Tokamak Modeling, Spacecraft Glow Experiment, Compact Ignition Tokamak, Engineering Department, Project Planning and Safety Office, Quality Assurance and Reliability, and Administrative Operations.

Phillips, C.A. (ed.)

1986-01-01

364

Disruption Design Criteria for Joint European Torus In-Vessel Components  

SciTech Connect

In view of the modification to the Joint European Torus (JET) plasma facing components foreseen for the 2004 shutdown, the disruption design criteria for in-vessel components have been updated building on the operational experience with divertor plasmas gained since the early 1990s. In fast disruptions the largest contribution to the electromechanical loads comes from currents induced by the poloidal field change. This is proportional to the plasma current decay rate, the maximum of which is observed to be linear with the predisruption plasma current, as if the current quench in the fastest events has a fixed duration, around 10 ms. Usually vertical displacement events (VDEs) take place on a longer timescale. In these cases halo currents determine the worst loading condition. Analysis of recent VDE data confirmed the previously observed magnitude of asymmetries: toroidal peaking factor times ratio of average poloidal halo to initial plasma current up to 0.42.Experimental evidence to justify the new criteria and procedures for applying them to JET are included. The revised design criteria are discussed and compared with those used for the components already present in the JET vessel.

Riccardo, Valeria T.G.; Andrew, Philip L.; Kaye, Alan Sandford; Knoll, Peter [United Kingdom Atomic Energy Authority-Euratom Association (United Kingdom)

2003-06-15

365

Dynamical Evolution of Pedestal Parameters in ELMy H-mode in the National Spherical Torus Experiment  

SciTech Connect

Characterizations of the pedestal parameter dynamics throughout the edge localized modes(ELM) cycles are performed on the National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]). A clear buildup of the pedestal height is observed between ELMs for three di erent plasma currents, which tends to saturate prior to the onset of ELM at low and medium plasma current. Similarly, the pedestal width increases with no clear evidence of saturation during an ELM cycle. The maximum pedestal gradient increases as a function of plasma current, reaches a nominal value after the ELM crash, and remains constant until the end of the ELM cycle. The pedestal height just prior to the onset of ELM is shown to increase quadratically with plasma current. The pedestal width ? is proportional to the square-root of the poloidal ? at the top of the pedestal. Coherent density uctuations strongly increasing at the plasma edge are observed to be maximum after the ELM crash and to decay during the rest of the ELM cycle. Finally, the pedestal parameters evolution during the ELM cycle as well as the scaling with Ip of the pedestal pressure prior to the onset ELM are found to be qualitatively consistent with the peeling ballooning theory.

Diallo, A; Kubota, S; Sontag, A; Osborne, T; Podesta, M; Bell, R E; LeBlanc, B P; Menard, J

2011-07-27

366

Dynamical Evolution of Pedestal Parameters in ELMy H-mode in the National Spherical Torus Experiment  

SciTech Connect

Characterizations of the pedestal parameter dynamics throughout the edge localized mode (ELM) cycles are performed on the National Spherical Torus Experiment (NSTX, (Ono et al 2000 Nucl. Fusion 40 557)). A clear buildup of the pedestal height between ELMs is observed for three different plasma currents. This buildup tends to saturate at low and medium plasma currents. Similarly, the pedestal width increases with no clear evidence of saturation during an ELM cycle. The maximum pedestal gradient increases as a function of plasma current, reaches a nominal value after the ELM crash, and remains constant until the end of the ELM cycle. The pedestal height just prior to the onset of ELM is shown to increase quadratically with plasma current. The pedestal width (Delta) scales as Delta = 0.17 root beta(ped)(theta). with the poloidal beta at the top of the pedestal. Coherent density fluctuations strongly increasing at the plasma edge are observed to be maximum after the ELM crash and to decay during the rest of the ELM cycle. Finally, the evolution of the pedestal height and width during the ELM cycle as well as the scaling with I(p) of the pedestal pressure prior to the onset ELM are found to be qualitatively consistent with the peeling-ballooning theory.

Diallo, A. [Princeton Plasma Physics Laboratory (PPPL); Maingi, Rajesh [ORNL; Kubota, S. [University of California, Los Angeles; Sontag, Aaron C [ORNL; Osborne, T. [General Atomics, San Diego; Podesta, M. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B. P. [Princeton Plasma Physics Laboratory (PPPL); Menard, J. [Princeton Plasma Physics Laboratory (PPPL); Sabbagh, S. A. [Columbia University

2011-01-01

367

Efficient Subtorus Processor Allocation in a Multi-Dimensional Torus  

SciTech Connect

Processor allocation in a mesh or torus connected multicomputer system with up to three dimensions is a hard problem that has received some research attention in the past decade. With the recent deployment of multicomputer systems with a torus topology of dimensions higher than three, which are used to solve complex problems arising in scientific computing, it becomes imminent to study the problem of allocating processors of the configuration of a torus in a multi-dimensional torus connected system. In this paper, we first define the concept of a semitorus. We present two partition schemes, the Equal Partition (EP) and the Non-Equal Partition (NEP), that partition a multi-dimensional semitorus into a set of sub-semitori. We then propose two processor allocation algorithms based on these partition schemes. We evaluate our algorithms by incorporating them in commonly used FCFS and backfilling scheduling policies and conducting simulation using workload traces from the Parallel Workloads Archive. Specifically, our simulation experiments compare four algorithm combinations, FCFS/EP, FCFS/NEP, backfilling/EP, and backfilling/NEP, for two existing multi-dimensional torus connected systems. The simulation results show that our algorithms (especially the backfilling/NEP combination) are capable of producing schedules with system utilization and mean job bounded slowdowns comparable to those in a fully connected multicomputer.

Weizhen Mao; Jie Chen; William Watson

2005-11-30

368

Fast ion absorption of the high harmonic fast wave in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

Ion absorption of the high harmonic fast wave in a spherical torus [Y.-K. M. Peng et al., Nucl. Fusion 26, 769 (1986)] is of critical importance to assessing the viability of the wave as a means of heating and driving current. Analysis of recent National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] shots has revealed that under some conditions when neutral beam and rf power are injected into the plasma simultaneously, a fast ion population with energy above the beam injection energy is sustained by the wave. In agreement with modeling, these experiments find the rf-induced fast ion tail strength and neutron rate at lower B-fields to be less enhanced, likely due to a larger ? profile, which promotes greater off-axis absorption where the fast ion population is small. Ion loss codes find the increased loss fraction with decreased B insufficient to account for the changes in tail strength, providing further evidence that this is a rf interaction effect. Though greater ion absorption is predicted with lower k?, surprisingly little variation in the tail was observed, along with a neutron rate enhancement with higher k?. Data from the neutral particle analyzer, neutron detectors, x-ray crystal spectrometer, and Thomson scattering are presented, along with results from the TRANSP [R. J. Hawryluk, Physics of Plasmas Close to Thermonuclear Conditions 1, 19 (1981); J. P. H. E. Ongena et al., Fusion Technol. 33, 181 (1998)] transport analysis code, ray-tracing codes HPRT [J. Menard et al., Phys. Plasmas 6, 2002 (1999)], and CURRAY [T. K. Mau et al., RF Power in Plasmas: 13th Topical Conference (1999), p. 148], full-wave code AORSA [E. F. Jaeger et al., RF Power in Plasmas: 14th Topical Conference, 2001, p. 369], quasilinear code CQL3D [R. W. Harvey et al., in Proceedings of the IAEA TCM on Advances in Simulation and Modeling of Thermonuclear Plasmas, 1992], and ion loss codes EIGOL [D. S. Darrow et al., in Proceedings of the 6th IAEA TCM on Energetic Particles in Magnetic Confinement Systems, 2000, p. 109] and CONBEAM [J. Egedal et al., Phys. Plasmas 10, 2372 (2003)].

Rosenberg, A. L.; Menard, J. E.; Wilson, J. R.; Medley, S. S.; Andre, R.; Phillips, C. K.; Darrow, D. S.; LeBlanc, B. P.; Redi, M. H.; Fisch, N. J.; NSTX Team, Harvey, R. W.; Mau, T. K.; Jaeger, E. F.; Ryan, P. M.; Swain, D. W.; Sabbagh, S. A.; Egedal, J.

2004-05-01

369

The Pioneer 11 radio occultation measurements of the Jovian ionosphere  

NASA Technical Reports Server (NTRS)

Radio occultation data obtained with the Pioneer 11 spacecraft are utilized to study Jupiter's ionosphere. The ingress measurements, which were conducted by using a stable earth-based frequency reference for the tracking link, yielded ionospheric data near the morning terminator at about 79 deg south latitude. Data were also taken during egress on the evening side near 20 deg north latitude. The latter measurements were conducted in the one-way mode; i.e., an on-board crystal oscillator was employed as a frequency reference for the downlink (spacecraft-to-earth) signal. These data confirm previous results obtained with Pioneer 10 and show that Jupiter has a multilayered ionosphere extending over an altitude range of more than 3000 km. The topside scale height near 79 deg south latitude was 540 + or - 60 km. Assuming a topside electron, H(+) distribution controlled by diffusion yields a plasma temperature of 850 + or - 100 K in this region. The radio data indicate that the upper atmosphere is either warmer or more dissociated into atomic hydrogen than previously anticipated.

Fjeldbo, G.; Kliore, A.; Seidel, B.; Sweetnam, D.; Woiceshyn, P.

1976-01-01

370

On the production and interaction of planetary solitary waves - Applications to the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

Further evidence is presented that strengthens the case for the interpretation of many features in the Jovian atmosphere as solitary Rossby waves (solitons). These include: a mechanism whereby such waves can evolve from the instability of the basic shear flows; further interpretation of the interaction between observed features, and comparison with calculations of the interaction between planetary solitons of a restricted class; and calculations of soliton morphology for a type of shear flow other than the type considered originally by Maxworthy and Redekopp (1976).

Maxworthy, T.; Redekopp, L. G.; Weidman, P. D.

1978-01-01

371

Near-infrared observations of the Jovian ring and small satellites  

NASA Technical Reports Server (NTRS)

The Jovian ring has been observed at 2.2 microns at a near-maximum opening angle of 3.2 deg and a phase angle of 2.2 deg. The 126,100 +/- 500 km ring radius at maximum brightness obtained is compatible with Voyager data at high phase angles. Circular orbital elements have also been obtained for the two small satellites (Metis and Adrastea) associated with the ring. A combination of these orbits with the Voyager imaging-based measurements of Synnott yields a substantial improvement in mean motion estimates.

Nicholson, Philip D.; Matthews, Keith

1991-01-01

372

Troposphere-stratosphere interactions in a one-dimensional model of Jovian photochemistry  

NASA Astrophysics Data System (ADS)

The case of a chemically unreactive species flowing downward through the stratosphere and troposphere with a constant flux is presently treated by a one-dimensional Jovian atmosphere model which encompasses the coupling between a rapidly mixed troposphere and a stagnant stratosphere, so that the contrast between the peak stratosphere and tropopause concentrations is reflective of the variation between the lower stratosphere and upper troposphere eddy diffusion coefficients. Numerical simulations of unreactive CO and C2H6 species indicate that upper troposphere abundances may possess a substantial photochemical contribution. The implications of these modeling results for higher spectral resolution observations are noted.

Landry, B.; Allen, M.; Yung, Y. L.

1991-02-01

373

Cascade of torus doubling bifurcations in a detuned laser  

SciTech Connect

By using a simplified system of Maxwell-Bloch equations (with the adiabatically excluded polarisation of the medium), we studied the processes proceeding in the cross section of a light wave propagating in a wide-aperture laser emitting at the frequency detuned from the transition-line centre. It is shown that in the model under study the passage to the chaotic regime during a change in the wave propagation velocity across the aperture occurs via the doubling bifurcations of an ergodic two-dimensional torus. The spectrum of Lyapunov exponents is found and it is established that at bifurcation points a structurally unstable three-dimensional torus is produced, which gives rise to a stable doubled ergodic torus. (nonlinear optical phenomena)

Krents, A A [S.P. Korolev Samara State Aerospace University, Samara (Russian Federation); Molevich, N E [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation)

2009-08-31

374

The magnetospheres of the outer planets  

SciTech Connect

Research on the magnetospheres of all of the outer planets including Jupiter, Uranus, Neptune, and Pluto is reviewed for the 1987-1990 time period. Particular attention is given to magnetospheric structure, plasma transport, Jovian aurora, Io and the plasma torus, Titan and its magnetospheric interactions, rings and dusty plasmas, magnetospheric convection, and satellite interactions.

Mcnutt, R.L., Jr. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

375

Modulation of Jovian middle magnetosphere currents and auroral precipitation by solar wind-induced compressions and expansions of the magnetosphere: initial response and steady state  

NASA Astrophysics Data System (ADS)

We present results from a theoretical model which has been used to investigate the modulation of the magnetosphere-ionosphere coupling currents in the Jovian middle magnetosphere by solar wind-induced compressions and expansions of the magnetosphere. We consider an initial system in which the current sheet field lines extend to 50 RJ in the equatorial plane, and where the iogenic plasma in the current sheet undergoes steady outward radial diffusion under the influence of the ionospheric torque which tends to maintain corotation with the planet. We show using typical Jovian parameters that the upward-directed field-aligned currents flowing throughout the middle magnetosphere region in this system peak at values requiring the existence of significant field-aligned voltages to drive them, resulting in large precipitating energy fluxes of accelerated electrons and bright 'main oval' UV auroras. We then consider the changes in these parameters which take place due to sudden expansions or compressions of the magnetosphere, resulting from changes in the solar wind dynamic pressure. Two cases are considered and compared, these being first the initial response of the system to the change, determined approximately from conservation of angular momentum of the radially displaced plasma and frozen-in field lines, and second the subsequent steady state of steady outward radial diffusion applied to the compressed or expanded system. We show that moderate inward compressions of the outer boundary of the current sheet field lines, e.g. from 50 to 40 RJ, are effective in significantly reducing the coupling currents and precipitation in the initial state, the latter then recovering, but only partly so, during the evolution to the steady state. Strong inward compressions, e.g. to 30 RJ cause significant super-corotation of the plasma and a reversal in sense of the current system in the initial state, such that bright auroras may then be formed poleward of the usual 'main auroral oval' due to the 'return' currents. The sense of the currents subsequently reverts back to the usual direction as steady-state conditions are restored, but they are weak, and so is the consequent electron precipitation. For outward expansions of the current sheet, however, the field-aligned currents and electron precipitation are strongly enhanced, particularly at the poleward border mapping to the outer weak field region of the current sheet. In this case there is little evolution of the parameters between the initial expansion and the subsequent steady state. Overall, the results suggest that the Jovian middle magnetosphere coupling currents and resulting 'main oval' auroral acceleration and precipitation will be strongly modulated by the solar wind dynamic pressure in the sense of anti-correlation, through the resulting compressions and expansions in the size of the magnetosphere.

Cowley, S. W. H.; Bunce, E. J.

2003-01-01

376

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

SciTech Connect

A pneumatic-based, hydrogen isotope pellet injector that was developed at the Oak Ridge National Laboratory for the plasma fueling application on the Joint European Torus (JET) was described at the last Symposium on Fusion Engineering (1987). The injector was installed on JET during 1987 and has since been used in plasma fueling experiments. The injector consists of three independent machine-gun-like mechanisms (nominal pellet sizes of 2.7, 4.0, and 6.0 mm in diameter), and it features repetitive operation (1-5 Hz) for quasi-steady-state conditions (>10 s). An extensive set of injector diagnostics permits evaluation of parameters for each pellet shot, including speed, mass, and integrity. Pellet speeds can be varied but typically range from 1.0 to 1.5 km/s. Over 5000 pellets have been fired with the equipment at JET, including about 2000 pellets shot for plasma fueling experiments. In recent experiments, the system performance has been outstanding, including excellent reproducibility in pellet speed and mass and a reliability of >98% in delivery of pellets to the plasma. 7 refs., 5 figs.

Combs, S.K.; Jernigan, T.C.; Baylor, L.R.; Milora, S.L.; Foust, C.R.; Kupschus, P.; Gadeberg, M.; Bailey, W. (Oak Ridge National Lab., TN (USA); Commission of the European Communities, Abingdon (UK). JET Joint Undertaking)

1989-01-01

377

Physics Design of a 28 GHz Electron Heating System for the National Spherical Torus Experiment Upgrade  

SciTech Connect

A megawatt-level, 28 GHz electron heating system is being designed to support non-inductive (NI) plasma current (I{sub p}) start-up and local heating and current drive (CD) in H-mode discharges in the National Spherical Torus Experiment Upgrade (NSTX-U). The development of fully NI I{sub p} start-up and ramp-up is an important goal of the NSTX-U research program. 28 GHz electron cyclotron (EC) heating is predicted to rapidly increase the central electron temperature (T{sub e}(0)) of low density NI plasmas generated by Coaxial Helicity Injection (CHI). The increased T{sub e}(0) will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast wave heating and neutral beam injection. Also 28 GHz electron Bernstein wave (EBW) heating and CD can be used during the I{sub p} flat top in NSTX-U discharges when the plasma is overdense. Ray tracing and Fokker-Planck numerical simulation codes have been used to model EC and EBW heating and CD in NSTX-U. This paper presents a pre-conceptual design for the 28 GHz heating system and some of the results from the numerical simulations.

none,

2013-07-09

378

MHD simulation of relaxation transition to a flipped relaxed state in spherical torus  

NASA Astrophysics Data System (ADS)

Recently, it has been demonstrated in the HIST device that in spite of the violation of the Kruskal-Shafranov stability condition, a normal spherical torus (ST) plasma has relaxed to a flipped ST state through a transient reversed-field pinch-like state when the vacuum toroidal field is decreased and its direction is reversed [1]. It has been also observed during this relaxation transition process that not only the toroidal field but also the poloidal field reverses polarity spontaneously and that the ion flow velocity is strongly fluctuated and abruptly increased up to > 50 km/s. The purpose of the present study is to investigate the plasma flows and the relevant MHD relaxation phenomena to elucidate this transition mechanism by using three-dimensional MHD simulations [2]. It is found from the numerical results that the magnetic reconnection between the open and closed field lines occurs due to the non-linear growth of the n=1 kink instability of the central open flux, generating the toroidal flow ˜ 60 km/s in the direction of the toroidal current. The n=1 kink instability and the plasma flows driven by the magnetic reconnection are consider to be responsible for the self-reversal of the magnetic fields. [1] M. Nagata el al., Phys. Rev. Lett. 90, 225001 (2003). [2] Y. Kagei el al., Plasma. Phys. Control. Fusion 45, L17 (2003).

Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

2008-11-01

379

Characterization of Disruption Halo Currents in the National Spherical Torus Experiment  

SciTech Connect

This paper describes the general characteristics of disruptions halo currents in the National Spherical Torus Experiment [M. Ono, et al. Nuclear Fusion 40, 557 (2000)]. The commonly observed types of vertical motion and resulting halo current patterns are described, and it is shown that plasma discharges developing between components can facilitate halo current flow. The halo current fractions and toroidal peaking factors at various locations in the device are presented. The maximum product of these two metrics for localized halo current measurements is always significantly less than the worst-case expectations from conventional aspect ratio tokamaks (which are typically written in terms of the total halo current). The halo current fraction and impulse is often largest in cases with the fastest plasma current quenches and highest quench rates. The effective duration of the halo current pulse is comparable to or shorter than the plasma current quench time. The largest halo currents have tended to occur in lower ? and lower elongation plasmas. The sign of the poloidal halo current is reversed when the toroidal field direction is reversed.

S.P. Gerhardt, J. Menard, S. Sabbagh and F. Scotti

2012-04-25

380

Physics design of a 28 GHz electron heating system for the National Spherical Torus experiment upgrade  

NASA Astrophysics Data System (ADS)

A megawatt-level, 28 GHz electron heating system is being designed to support non-inductive (NI) plasma current (Ip) start-up and local heating and current drive (CD) in H-mode discharges in the National Spherical Torus Experiment Upgrade (NSTX-U). The development of fully NI Ip start-up and ramp-up is an important goal of the NSTXU research program. 28 GHz electron cyclotron (EC) heating is predicted to rapidly increase the central electron temperature (Te(0)) of low density NI plasmas generated by Coaxial Helicity Injection (CHI). The increased Te(0) will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast wave heating and neutral beam injection. Also 28 GHz electron Bernstein wave (EBW) heating and CD can be used during the Ip flat top in NSTX-U discharges when the plasma is overdense. Ray tracing and Fokker-Planck numerical simulation codes have been used to model EC and EBW heating and CD in NSTX-U. This paper presents a pre-conceptual design for the 28 GHz heating system and some of the results from the numerical simulations.

Taylor, G.; Bertelli, N.; Ellis, R. A.; Gerhardt, S. P.; Harvey, R. W.; Hosea, J. C.; Poli, F.; Raman, R.; Smirnov, A. P.

2014-02-01

381

Diagnostics of ST Plasmas in NSTX: Challenges and Opportunities  

SciTech Connect

This paper will highlight some of the challenges and opportunities present in the diagnosis of spherical torus (ST) plasmas on the National Spherical Torus Experiment (NSTX) and discuss the corresponding diagnostic development that is presently underway. After a brief description of diagnostic systems currently installed, examples of ST-specific diagnostic challenges will be highlighted, as will another case, where the ST configuration offers opportunities for new measurements.

D. Johnson; P. Efthimion; J. Foley; B. Jones; E. Mazzucato; H. Park; G. Taylor; F. Levinton; N. Luhmann

2001-09-26

382

REGULARITY OF GAUSSIAN WHITE NOISE ON THE d-DIMENSIONAL TORUS  

E-print Network

REGULARITY OF GAUSSIAN WHITE NOISE ON THE d-DIMENSIONAL TORUS MARK VERAAR Abstract. In this paper we prove that a Gaussian white noise on the d- dimensional torus has paths in the Besov spaces B -d/2 that Gaussian white noise on the d-dimensional torus has paths in a the Fourier-Besov space ^b -d/p p, (Td

Veraar, Mark C.

383

Crewed Mission to Callisto Using Advanced Plasma Propulsion Systems  

NASA Technical Reports Server (NTRS)

This paper describes the engineering of several vehicles designed for a crewed mission to the Jovian satellite Callisto. Each subsystem is discussed in detail. Mission and trajectory analysis for each mission concept is described. Crew support components are also described. Vehicles were developed using both fission powered magneto plasma dynamic (MPD) thrusters and magnetized target fusion (MTF) propulsion systems. Conclusions were drawn regarding the usefulness of these propulsion systems for crewed exploration of the outer solar system.

Adams, R. B.; Statham, G.; White, S.; Patton, B.; Thio, Y. C. F.; Alexander, R.; Fincher, S.; Polsgrove, T.; Chapman, J.; Hopkins, R.

2003-01-01

384

EUV photochemical production of unsaturated hydrocarbons: implications to EUV photochemistry in Titan and Jovian planets.  

PubMed

The EUV photochemistry of methane is one of the dominant chemical processes in the upper atmospheres of Titan and Jovian planets. The dilution of CH(4) with N(2) significantly changes the subsequent hydrocarbon chemistry initiated by EUV photoionization. At wavelengths below 80 nm, the presence of the dominant N(2) species in a N(2)/CH(4) gas mixture (=95/5) selectively enhances the formation of unsaturated hydrocarbons, such as benzene and toluene, while pure CH(4) gas leads to a wide mixture of saturated/unsaturated hydrocarbon species. This enhanced formation of unsaturated hydrocarbons is most likely initiated by the generation of CH(3)(+) via a dissociative charge-transfer reaction between N(2)(+) and CH(4). This mechanism was further confirmed with the dilution of CH(4) with Ar, which shows similarly enhanced formation of unsaturated species from an Ar/CH(4) (=95/5) gas mixture. In contrast, the depleted generation of unsaturated species from a H(2)/CH(4) gas mixture (=95/5) suggests that the CH(5)(+) ion generated via a proton-transfer reaction is not an important precursor in the production of complex unsaturated hydrocarbons. Therefore, it is the dissociative charge-transfer reaction of CH(4) that initiates the formation of unsaturated complex hydrocarbons through production of C(2)H(5)(+) with subsequent dissociative recombination. Implications regarding photochemistry in the upper atmospheres of Titan and the Jovian planets are discussed. PMID:19673465

Imanaka, Hiroshi; Smith, Mark A

2009-10-22

385

The modulation of SiO maser polarization by Jovian planets  

E-print Network

Searching for planets in the atmosphere of AGB stars is difficult, due to confusion with the stellar wind and pulsations. The aim here is to provide a complementary strategy for planet search in such a dense environment. The polarization properties of SiO masers, especially their circular polarization, are, under certain conditions, good tracers for rapid magnetospheric events. A Jovian planet with a magnetosphere whose dipole axis is misaligned with its rotation axis, naturally provides such conditions. Here I present several models showing that the polarization will be periodically modulated. Single-dish monitoring with a sufficiently dense time sampling and a carefully calibrated polarimeter, in combination with VLBI observations, are suited to detect and locate a periodic modulation of the circular maser polarization due to a precessing Jovian magnetosphere. The phenomenon will be rare, because a favourable arrangement of maser and magnetosphere is needed, otherwise the polarization may be below the detection threshold, especially if the maser is unsaturated. Linear polarization, though exhibiting a qualitatively similar modulation, is likely to suffer more from confusion due to beam dilution, even in VLBI observations.

Helmut Wiesemeyer

2009-05-06

386

Lightning generation in a Jovian thundercloud: Results from an axisymmetric numerical cloud model.  

NASA Astrophysics Data System (ADS)

An axisymmetric cloud model with detailed microphysics was used to calculate the electrical development of a jovian water cloud. The charge separation mechanism was based on the noninductive interaction between ice crystals and graupel particles in the presence of supercooled liquid droplets. The results show that for plausible concentrations of cloud condensation and freezing nuclei in the atmosphere, the electric field in a jovian thundercloud builds rapidly and exceeds its breakdown value. Low concentrations of cloud condensation nuclei produced shallow clouds and did not separate enough charge to produce critical fields. We simulated the lightning discharge by assuming that a flash occurred wherever the electric field, which resulted from the obtained space charge configuration, exceeded the local breakdown value. A lightning flash was assumed to neutralize a 20-Km channel within the cloud. The calculated flash rate suggests that the 192-sec exposure time of Voyager 1 camera, may have captured several superimposed lightning flashes. The energy calculated for such a simulated lightning discharge was of the order of 10 12-10 13 J, which translates to 10 9-10 10 J in the optical energy range, in agreement with Voyager's observations of Jupiter's lightning.

Yair, Yoav; Levin, Zev; Tzivion, Shalva

1995-06-01

387

Spatial and temporal variability of infrared-observable properties of the Jovian atmosphere: A partial survey  

NASA Technical Reports Server (NTRS)

Examination of infrared characteristics of the Jovian atmosphere are made using Voyager IRIS mapping from 1979, groud based scanning from 1979-1983, and ground based mapping from 1983 to the present. In general, there is a strong correlation between tropospheric thermal properties and the visual cloud albedo for all observations. The Voyager IRIS maps show no strong evidence for day/night differences. Temperature differences diminish with depth in the troposphere. Temporal changes over several weeks indicate a high correlation between thermal and visual properties, although no changes in the distribution of para H2 and ortho H2 are seen. Stratospheric banded organization is different from the troposphere, and there is a temperature enhancement near the north magnetic pole. The spatial distributions of ammonia gas and ammonia ice absorption are different. Stratospheric temperatures exhibit seasonal hemispheric asymmetry. Other temperature changes at and below the 150-mb level correlate with changes in the Jovian visual structure. The stratospheric temperature field is uncorrelated with visual features or temperatures below the 150-mb level. Elevated temperatures are observed near both north and south magnetic pole positions. Both the meridional positions and the relative intensities of stratospheric banded organization change significantly, especially after 1982. Ground based mapping confirms a correlation between temperatures and various measures of cloud distribution. Complex and unexpected characteristics are observed in the stratospheric temperature field; these include dramatic temporal changes on short time scales.

Orton, Glenn S.

1986-01-01

388

Copernicus measurement of the Jovian Lyman-alpha emission and its aeronomical significance  

NASA Technical Reports Server (NTRS)

It is pointed out that the intensity of the Lyman-alpha emission is a good indicator of the principal aeronomical processes on the major planets. The high-resolution ultraviolet spectrometer aboard the Orbiting Astronomical Observatory Copernicus was used in 1980 April and May to detect the Jovian Lyman-alpha emission by spectroscopically discriminating it from other Doppler shifted Lyman-alpha emissions such as those of the geocorona, and the interplanetary medium. Taking into consideration the reported emission data, it appears that an unusually large energy input due to the particle precipitation in the auroral region must have been responsible for the large observed Lyman-alpha intensity during the Voyager encounter. At most other times, the observed Jovian Lyman-alpha intensity can be explained, within the range of statistical uncertainty, by a model that takes into consideration the solar EUV flux, the solar Lyman-alpha flux, the high exospheric temperature, and the eddy diffusion coefficient without energy input from the auroral sources.

Atreya, S. K.; Kerr, R. B.; Upson, W. L., II; Festou, M. C.; Donahue, T. M.; Barker, E. S.; Cochran, W. D.; Bertaux, J. L.

1982-01-01

389

Three dimensional ray tracing Jovian magnetosphere in the low frequency range  

NASA Technical Reports Server (NTRS)

Ray tracing of the Jovian magnetosphere in the low frequency range (1+40 MHz) has resulted in a new understanding of the source mechanism for Io dependent decametric radiation (DAM). Our three dimensional ray tracing computer code has provided model DAM arcs at 10 deg. intervals of Io longitude source positions for the full 360 deg of Jovian system III longitude. In addition, particularly interesting arcs were singled out for detailed study and modelling. Dependent decametric radiation arcs are categorized according to curvature--the higher curvature arcs are apparently due to wave stimulation at a nonconstant wave normal angle, psi. The psi(f) relationship has a signature that is common to most of the higher curvature arcs. The low curvature arcs, on the other hand, are adequately modelled with a constant wave normal angle of close to 90 deg. These results imply that for higher curvature arcs observed for from Jupiter (to diminish spacecraft motion effects) the electrons providing the gyroemission are relativistically beamed.

Menietti, J. D.

1982-01-01

390

The phase of the ten-hour modulation in the Jovian magnetosphere /Pioneers 10 and 11/  

NASA Technical Reports Server (NTRS)

The paper describes the study of the phase of the 10-hour modulation of energetic electrons seen by Pioneers 10 and 11 in the Jovian magnetosphere. Attention is given to the peaks rather than the valleys of each cycle because the peaks are where physically interesting features occur, such as particle acceleration, current sheets, etc. To identify the peaks, it is required that the instantaneous intensity be higher than the 5-hour running average and the 5-hour running average be greater than the 10-hour running average. These criteria select an interval rather than a point and it is determined that this interval is an appropriate estimate of the experimental uncertainty. When the phases of the peaks are plotted together, they create patterns which are discussed in terms of disk-like, clock-like, and rotating anomaly models of the magnetosphere. Each model fits some of the data, but no model explains all of the data convincingly. It is concluded that there is still no understanding of the configuration of the outer Jovian magnetosphere.

Fillius, W.; Knickerbocker, P.

1979-01-01

391

Statistical analysis of variations in impurity ion heating at reconnection events in the Madison Symmetric Torus  

NASA Astrophysics Data System (ADS)

The connection between impurity ion heating and other physical processes in the plasma is evaluated by studying variations in the amount of ion heating at reconnection events in the Madison Symmetric Torus (MST). Correlation of the change in ion temperature with individual tearing mode amplitudes indicates that the edge-resonant modes are better predictors for the amount of global ion heating than the core-resonant modes. There is also a strong correlation between ion heating and current profile relaxation. Simultaneous measurements of the ion temperature at different toroidal locations reveal, for the first time, a toroidal asymmetry to the ion heating in MST. These results present challenges for existing heating theories and suggest a stronger connection between edge-resonant tearing modes, current profile relaxation, and ion heating than has been previously thought.

Cartolano, M. S.; Craig, D.; Den Hartog, D. J.; Kumar, S. T. A.; Nornberg, M. D.

2014-01-01

392

Statistical analysis of variations in impurity ion heating at reconnection events in the Madison Symmetric Torus  

SciTech Connect

The connection between impurity ion heating and other physical processes in the plasma is evaluated by studying variations in the amount of ion heating at reconnection events in the Madison Symmetric Torus (MST). Correlation of the change in ion temperature with individual tearing mode amplitudes indicates that the edge-resonant modes are better predictors for the amount of global ion heating than the core-resonant modes. There is also a strong correlation between ion heating and current profile relaxation. Simultaneous measurements of the ion temperature at different toroidal locations reveal, for the first time, a toroidal asymmetry to the ion heating in MST. These results present challenges for existing heating theories and suggest a stronger connection between edge-resonant tearing modes, current profile relaxation, and ion heating than has been previously thought.

Cartolano, M. S.; Craig, D., E-mail: darren.craig@wheaton.edu [Wheaton College, Wheaton, Illinois 60187 (United States); Den Hartog, D. J.; Kumar, S. T. A.; Nornberg, M. D. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States) [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, Wisconsin 53706 (United States)

2014-01-15

393

Three-dimensional simulations of blob dynamics in a simple magnetized torus  

SciTech Connect

The propagation of blobs, structures of localized enhanced plasma pressure, is studied in global three-dimensional simulations of a simple magnetized torus. In particular, we carry out single-seeded blob simulations to explore the dependence of the blob velocity with respect to its size. It is found that the velocity scaling for two-dimensional blobs is satisfied in the parameter space where polarization currents are the dominant damping mechanism. On the other hand, three-dimensional blobs propagate faster than their two-dimensional counterparts in the parallel current damping regime. A detailed analysis of the charge and current balance reveals that, in fact, the difference in speed is due to an overestimation of the strength of the sheath current term in the two-dimensional model compared to the self-consistent three-dimensional model.

Halpern, Federico D., E-mail: federico.halpern@epfl.ch; Cardellini, Annalisa; Ricci, Paolo; Jolliet, Sébastien; Loizu, Joaquim; Mosetto, Annamaria [École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, CH-1015 Lausanne (Switzerland)] [École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, CH-1015 Lausanne (Switzerland)

2014-02-15

394

Prompt Loss of Energetic Ions during Early Neutral Beam Injection in the National Spherical Torus Experiment  

SciTech Connect

Early neutral-beam injection is used in the National Spherical Torus Experiment (NSTX) to heat the electrons and slow current penetration which keeps q(0) elevated to avoid deleterious MHD activity and at the same time reduces Ohmic flux consumption, all of which aids long-pulse operation. However, the low plasma current (I{sub p} {approx} 0.5 MA) and electron density (n{sub e} {approx} 1 x 10{sup 13} cm{sup -3}) attending early injection lead to elevated orbit and shine through losses. The inherent orbit losses are aggravated by large excursions in the outer gap width during current ramp-up. An investigation of this behavior using various energetic particle diagnostics on NSTX and TRANSP code analysis is presented.

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

2005-03-25

395

Structure and motion of edge turbulence in the National Spherical Torus Experiment and Alcator C-Moda)  

NASA Astrophysics Data System (ADS)

In this paper we compare the structure and motion of edge turbulence observed in L-mode vs. H-mode plasmas in the National Spherical Torus Experiment (NSTX) [M. Ono, M. G. Bell, R. E. Bell et al., Plasma Phys. Controlled Fusion 45, A335 (2003)]. The radial and poloidal correlation lengths are not significantly different between the L-mode and the H-mode in the cases examined. The poloidal velocity fluctuations are lower and the radial profiles of the poloidal turbulence velocity are somewhat flatter in the H-mode compared with the L-mode plasmas. These results are compared with similar measurements Alcator C-Mod [E. Marmar, B. Bai, R. L. Boivin et al., Nucl. Fusion 43, 1610 (2003)], and with theoretical models.

Zweben, S. J.; Maqueda, R. J.; Terry, J. L.; Munsat, T.; Myra, J. R.; D'Ippolito, D.; Russell, D. A.; Krommes, J. A.; LeBlanc, B.; Stoltzfus-Dueck, T.; Stotler, D. P.; Williams, K. M.; Bush, C. E.; Maingi, R.; Grulke, O.; Sabbagh, S. A.; White, A. E.

2006-05-01

396

Structure and motion of edge turbulence in the National Spherical Torus Experiment and Alcator C-Mod  

SciTech Connect

In this paper we compare the structure and motion of edge turbulence observed in L-mode vs. H-mode plasmas in the National Spherical Torus Experiment (NSTX) [M. Ono, M. G. Bell, R. E. Bell et al., Plasma Phys. Controlled Fusion 45, A335 (2003)]. The radial and poloidal correlation lengths are not significantly different between the L-mode and the H-mode in the cases examined. The poloidal velocity fluctuations are lower and the radial profiles of the poloidal turbulence velocity are somewhat flatter in the H-mode compared with the L-mode plasmas. These results are compared with similar measurements Alcator C-Mod [E. Marmar, B. Bai, R. L. Boivin et al., Nucl. Fusion 43, 1610 (2003)], and with theoretical models.

Zweben, S.J.; Maqueda, R.J.; Terry, J.L.; Munsat, T.; Myra, J.R.; D'Ippolito, D.; Russell, D.A.; Krommes, J.A.; LeBlanc, B.; Stoltzfus-Dueck, T.; Stotler, D.P.; Williams, K.M.; Bush, C.E.; Maingi, R.; Grulke, O.; Sabbagh, S.A.; White, A.E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Nova Photonics, Princeton, New Jersey 08540 (United States); MIT, Cambridge, Massachusetts 02139 (United States); Univ. Colorado, Boulder, Colorado 80309 (United States); Lodestar Research, Boulder, Colorado 80301 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); ORNL, Oak Ridge, Tennessee 37831 (United States); MPI for Plasma Physics, Euratom Association. Greifswald (Germany); Columbia University, New York, New York 10027 (United States); UCLA, Los Angeles, Calilfornia 90095 (United States)

2006-05-15

397

Measurements with magnetic field in the National Spherical Torus Experiment using the motional Stark effect with laser induced fluorescence diagnostic  

NASA Astrophysics Data System (ADS)

The motional Stark effect with laser-induced fluorescence diagnostic (MSE-LIF) has been installed and tested on the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Lab. The MSE-LIF diagnostic will be capable of measuring radially resolved profiles of magnetic field magnitude or pitch angle in NSTX plasmas. The system includes a diagnostic neutral hydrogen beam and a laser which excites the n = 2 to n = 3 transition. A viewing system has been implemented which will support up to 38 channels from the plasma edge to past the magnetic axis. First measurements of MSE-LIF signals in the presence of small applied magnetic fields in neutral gas are reported.

Foley, E. L.; Levinton, F. M.

2013-04-01

398

A Radiation Hard Multi-Channel Digitizer ASIC for Operation in the Harsh Jovian Environment  

NASA Technical Reports Server (NTRS)

In 1995, the Galileo spacecraft arrived at Jupiter to conduct follow-up experiments on pathfinder Pioneer and key Voyager discoveries especially at Io, Europa, Ganymede and Callisto. These new observations helped expand our scientific knowledge of the prominent Galilean satellites; studies revealed diversity with respect to their geology, internal structure, evolution and degree of past and present activity. Jupiter's diverse Galilean satellites, of which three are believed to harbor internal oceans, are central to understanding the habitability of icy worlds. Galileo provided for the first time compelling evidence of a near-surface global ocean on Europa. Furthermore, by understanding the Jupiter system and unraveling the history of its evolution from initial formation to the emergence of possible habitats and life, gives insight into how giant planets and their satellite systems form and evolve. Most important, new light is shed on the potential for the emergence and existence of life in icy satellite oceans. In 2009, NASA released a detailed Jupiter Europa Mission Study (EJSM) that proposed an ambitious Flagship Mission to understand more fully the satellites Europa and Ganymede within the context of the Jovian system. Key to EJSM is the NASA led Jupiter Europa Orbiter (JEO) and the ESA led Jupiter Ganymede Orbiter (JGO). JEO and JGO would execute a choreographed exploration of the Jovian system before settling into orbit around Europa and Ganymede, respectively. The National Academies Planetary Decadal Survey, 2011 has listed the NASA-led JEO as the second highest priority mission for the decade 2013-2022, and if chosen it would be launched in 2020 with arrival at Jupiter in 2025. If the JEO mission is not chosen it is anticipated that there will be opportunities in future decadal cycles. Jupiter Orbit Insertion (JOI) begins a 30-month Jovian system tour followed by nine months of science mapping after Europa Orbit Insertion (EOI) in July 2028. The orbiter will ultimately impact the surface of Europa after the mission is completed. The current JEO mission concept includes a range of instruments on the payload, to monitor dynamic phenomena (such as Io's volcanoes and Jupiters atmosphere), map the Jovian magnetosphere and its interactions with the Galilean satellites, and characterize water oceans beneath the ice shells of Europa and Ganymede. The payload includes a low mass (3.7 Kg) and low power (< 5 W) Thermal Instrument (TI) concept for measuring possible warm thermal anomalies on Europa s cold surface caused by recent (< 10,000 years) eruptive activity. Regions of anomalously high heat flow will be identified by thermal mapping using a nadir pointing, push-broom filter radiometer that provides far-IR imagery in two broad band spectral wavelength regions, 8-20 m and 20-100 m, for surface temperature measurements with better than a 2 K accuracy and a spatial resolution of 250 m/pixel obtained from a 100 Km orbit. The temperature accuracy permits a search for elevated temperatures when combined with albedo information. The spatial resolution is sufficient to resolve Europa's larger cracks and ridge axial valleys. In order to accomplish the thermal mapping, the TI uses sensitive thermopile arrays that are readout by a custom designed low-noise Multi-Channel Digitizer (MCD) ASIC that resides very close to the thermopile linear array outputs. Both the thermopile array and the MCD ASIC will need to show full functionality within the harsh Jovian radiation environment, operating at cryogenic temperatures, typically 150 K to 170 K. In the following, a radiation mitigation strategy together with a low risk Radiation-Hardened-By-Design (RHBD) methodology using commercial foundry processes is given for the design and manufacture of a MCD ASIC that will meet this challenge.

Aslam, Shahid; Aslam, S.; Akturk, A.; Quilligan, G.

2011-01-01

399

A disrupted circumstellar torus inside eta Carinae's Homunculus Nebula  

E-print Network

We present thermal infrared images of the bipolar nebula surrounding eta Carinae at six wavelengths from 4.8 to 24.5 microns. These were obtained with the MIRAC3 camera system at the Magellan Observatory. Our images reveal new intricate structure in the bright core of the nebula, allowing us to re-evaluate interpretations of morphology seen in images with lower resolution. Complex structures in the core might not arise from a pair of overlapping rings or a cool (110 K) and very massive dust torus, as has been suggested recently. Instead, it seems more likely that the arcs and compact knots comprise a warm (350 K) disrupted torus at the intersection of the larger polar lobes. Some of the arcs appear to break out of the inner core region, and may be associated with equatorial features seen in optical images. The torus could have been disrupted by a post-eruption stellar wind, or by ejecta from the Great Eruption itself if the torus existed before that event. Kinematic data are required to rule out either possib...

Smith, N; Hinz, P M; Hoffmann, W F; Mamajek, E E; Meyer, M R; Hora, J L; Smith, Nathan; Gehrz, Robert D.; Hinz, Phillip M.; Hoffmann, William F.; Mamajek, Eric E.; Meyer, Michael R.; Hora, Joseph L.

2002-01-01

400

A disrupted circumstellar torus inside eta Carinae's Homunculus Nebula  

E-print Network

We present thermal infrared images of the bipolar nebula surrounding eta Carinae at six wavelengths from 4.8 to 24.5 microns. These were obtained with the MIRAC3 camera system at the Magellan Observatory. Our images reveal new intricate structure in the bright core of the nebula, allowing us to re-evaluate interpretations of morphology seen in images with lower resolution. Complex structures in the core might not arise from a pair of overlapping rings or a cool (110 K) and very massive dust torus, as has been suggested recently. Instead, it seems more likely that the arcs and compact knots comprise a warm (350 K) disrupted torus at the intersection of the larger polar lobes. Some of the arcs appear to break out of the inner core region, and may be associated with equatorial features seen in optical images. The torus could have been disrupted by a post-eruption stellar wind, or by ejecta from the Great Eruption itself if the torus existed before that event. Kinematic data are required to rule out either possibility.

Nathan Smith; Robert D. Gehrz; Phillip M. Hinz; William F. Hoffmann; Eric E. Mamajek; Michael R. Meyer; Joseph L. Hora

2002-01-29

401

ELMO Bumpy Torus fusion-reactor design study  

SciTech Connect

A complete power plant design of a 1200-MWe ELMO Bumpy Torus Reactor (EBTR) is described that emphasizes those features that are unique to the EBT confinement concept, with subsystems and balance-of-plant items that are generic to magnetic fusion being adopted from past, more extensive tokamak reactor designs.

Bathke, C.G.; Krakowski, R.A.

1981-01-01

402

ENGINEERING DESIGN OF THE NATIONAL SPHERICAL TORUS EXPERIMENT  

E-print Network

1 ENGINEERING DESIGN OF THE NATIONAL SPHERICAL TORUS EXPERIMENT C. Neumeyer a , P. Heitzenroeder a , J. Spitzer a , J. Chrzanowski a , A. Brooks a , J. Bialek b , H. M. Fan a , G. Barnes a , M. Viola.2 ~ 2 in ST designs compared to 4 ~ 5 in conventional tokamaks) decreases the available cross sectional

403

Preliminary Design of JLAB Clas12 Large Superconducting Torus Magnet  

SciTech Connect

Hall B at Jefferson Laboratory (JLAB) will need a 6-coil Torus producing a required integral of B-dl for an upgrade 12 GeV beam. In Sept. 2009, Wang NMR was awarded a contract to design, fabricate, assemble, deliver, and test at JLAB this ex citing magnet. The preliminary design review was completed by Dec. 2009 and intermediate design review will be completed by July 2010. Proto type coil construction, production of soldered conductor with SSC cable and final design review will be completed in 2010. We shall describe preliminary design and intermediate design for coil/cryostat, Torus central cylinder (hub), 48 cold mass suspensions, two intercoil support rings, cryocontrol tower, and adapter to Torus coil, magnet quench protection, and charge/ discharge con trol, and the two parallel path cooling design using supercritical helium. Because of coil in-plane and out-of-plane EM forces over these huge thin coils in addition to vacuum load, gravity load, and cool down thermal stress, we shall present the finite element analyses (FEA) on coil structure, 48 cold mass supports, intercoil cold rings, coil/ cryostat vacuum vessel, cryotower cryostat, and Torus hub. Finally, we shall shows that all pressure/ vacuum vessels and its weldment has satisfied ASME code.

Wang, B; Taylor, C; Zbasnik, J; Dell& #x27; Orco, D; Ross, J; Chen, J; Xu, L; Chen, H; Wagner, B; McMullin, J; Pong, R; Juang, T; Wang, M; Carter, C; Quettier, L; Burkert, V; Elouadrhiri, L; Kashy, D; Leung, E

2011-06-01

404

Torus-Margo Pits Help Conifers Compete with Angiosperms  

E-print Network

Torus-Margo Pits Help Conifers Compete with Angiosperms Jarmila Pittermann, John S. Sperry,* Uwe G (Pinus longaeva). Just how handicapped is conifer xylem trans- port relative to that of angiosperms? We lower than the angiosperm average (Fig. 1C) (2). This compensates for short tracheid length and low pit

Hacke, Uwe

405

The microwave properties of the jovian clouds: A new model for the complex dielectric constant of aqueous ammonia  

NASA Astrophysics Data System (ADS)

A new model for the complex dielectric constant of aqueous ammonia (NH4OH) under conditions characteristic of the jovian clouds has been developed. The new model is based on laboratory measurements in the frequency range between 2 and 8.5 GHz for ammonia concentrations of 0-8.5% by volume and temperatures between 274 and 297 K. The new model is based on the Meissner and Wentz (Meissner, T., Wentz, F.J. [2004]. IEEE Trans. Geosci. Rem. Sens. 42, 1836-1849) model of the complex dielectric constant of pure water but contains corrections for dissolved ammonia. Assuming Raleigh scattering, these measurements are applied to a cloud attenuation model to calculate the range of opacity of the jovian aqueous ammonia clouds. These measurements will improve our understanding of the data collected by the Juno microwave radiometer (MWR) by better characterizing the absorption properties of the aqueous ammonia present in the jovian atmosphere. The new model has been validated for temperatures up to 313 K, and may be consistently used for the expected conditions for aqueous clouds in all of the outer planets. The model fits 60.26% of all laboratory measurements within 2-sigma uncertainty. Descriptions of the experimental setups, uncertainties associated with the laboratory measurements, the model fitting process, the new model, and its application to approximating jovian cloud opacity are provided.

Duong, Danny; Steffes, Paul G.; Noorizadeh, Sahand

2014-02-01

406

The Microwave Properties of Jovian Clouds: Laboratory Measurement of Aqueous Ammonia (NH4OH) Between 2-8.5 GHz  

NASA Astrophysics Data System (ADS)

Laboratory measurements of the complex dielectric properties of aqueous ammonia, under conditions characteristic of Jovian clouds, have been made in the 2-8.5 GHz range at temperatures ranging from 24-60 oC and concentrations of 0-8.5% ammonia (NH3) by volume. No previous laboratory experiments have been made to characterize the microwave dielectric properties of aqueous ammonia. Previous models of Jovian microwave emission (de Pater et al., Icarus, 2005) have assumed that for low concentrations of ammonia in solution, the dielectric properties of aqueous ammonia are approximately equal to those of water; however, these measurements suggest that even at concentrations as low as 0.5% NH3 by volume, there is a marked difference in the complex dielectric properties of aqueous ammonia. Assuming Raleigh scattering, these measurements are applied to a cloud attenuation model to calculate the opacity of the Jovian aqueous ammonia clouds. These measurements will improve our understanding of the data collected by the Juno microwave radiometer (MWR) by characterizing the absorption properties of the aqueous ammonia present in the Jovian atmosphere. This work was supported by NASA Contract NNM06AA75C from the Marshall Space Flight Center supporting the Juno Mission Science Team, under Subcontract 699054X from the South-west Research Institute.

Duong, Danny; Steffes, P. G.

2010-10-01

407

Observations and analysis of the Jovian spectrum in the 10-micron nu-2 band of NH3  

NASA Technical Reports Server (NTRS)

Observations of the nu-2 band of NH3 in the Jovian atmosphere have been made at resolutions varying from 4 per cm to 0.15 per cm. The observations have been interpreted by computation of synthetic atmospheric spectra. Derived atmospheric parameters include a pressure of 0.5 atm at 145 K and a minimum temperature of 118 K.

Lacy, J. H.; Larrabee, A. I.; Wollman, E. R.; Geballe, T. R.; Townes, C. H.; Bregman, J. D.; Rank, D. M.

1975-01-01

408

Density and beta limits in the Madison Symmetric Torus Reversed-Field Pinch  

NASA Astrophysics Data System (ADS)

Operational limits and the underlying physics are explored on the Madison Symmetric Torus (MST) Reversed-Field Pinch (RFP) using deuterium pellet fueling. The injection of a fast pellet provides a large source of fuel in the plasma edge upon impact with the vessel wall, capable of triggering density limit terminations for the full range of plasma current, up to 600 kA. As the pellet size and plasma density increase, approaching the empirical Greenwald limit, plasma degradation is observed in the form of current decay, increased magnetic activity in the edge and core, increased radiation and plasma cooling. The complete termination of the plasma is consistent with the Greenwald limit; however, a slightly smaller maximum density is observed in discharges without toroidal field reversal. The plasma beta is the ratio of the plasma pressure to the confining magnetic pressure. Beta limits are known to constrain other magnetic confinement devices, but no beta limit has yet been established on the RFP. On MST, the highest beta values are obtained in improved confinement discharges with pellet fueling. By using pellet injection to scan the plasma density during PPCD, we also achieve a scan of Ohmic input power due to the increase in plasma resistivity. We observe a factor of 3 or more increase in Ohmic power as we increase the density from 1*1019 to 3*10 19 m-3. Despite this increased Ohmic power, the electron contribution to beta is constant, suggesting a confinement limited beta for the RFP. The electrons and ions are classically well coupled in these cold, dense pellet fueled plasmas, so the increase in total beta at higher density is primarily due to the increased ion contribution. The interaction of pellet fueling and NBI heating is explored. Modeling of MST's neutral heating beam suggests an optimal density for beam power deposition of 2-3*1019 m-3. Low current, NBI heated discharges show evidence of an increased electron beta in this density range. Additionally, the fast ion population can enhance ablation as well as cause pellet deflection. Other exploratory experiments with the pellet injection system explore additional injection scenarios and expand the injector capabilities.

Caspary, Kyle Jonathan

409

Nonlinear MHD simulation of current drive by multi-pulsed coaxial helicity injection in spherical torus  

NASA Astrophysics Data System (ADS)

The dynamics of structures of magnetic field, current density, and plasma flow generated during multi-pulsed coaxial helicity injection in spherical torus is investigated by 3-D nonlinear MHD simulations. During the driven phase, the flux and current amplifications occur due to the merging and magnetic reconnection between the preexisting plasma in the confinement region and the ejected plasma from the gun region involving the n=1 helical kink distortion of the central open flux column (COFC). Interestingly, the diamagnetic poloidal flow which tends toward the gun region is then observed due to the steep pressure gradients of the COFC generated by ohmic heating through an injection current winding around the inboard field lines, resulting in the formation of the strong poloidal flow shear at the interface between the COFC and the core region. This result is consistent with the flow shear observed in the HIST. During the decay phase, the configuration approaches the axisymmetric MHD equilibrium state without flow because of the dissipation of magnetic fluctuation energy to increase the closed flux surfaces, suggesting the generation of ordered magnetic field structure. The parallel current density ? concentrated in the COFC then diffuses to the core region so as to reduce the gradient in ?, relaxing in the direction of the Taylor state.

Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

2011-11-01

410

Spectroscopic diagnostics for liquid lithium divertor studies on National Spherical Torus Experiment  

SciTech Connect

The use of lithium-coated plasma facing components for plasma density control is studied in the National Spherical Torus Experiment (NSTX). A recently installed liquid lithium divertor (LLD) module has a porous molybdenum surface, separated by a stainless steel liner from a heated copper substrate. Lithium is deposited on the LLD from two evaporators. Two new spectroscopic diagnostics are installed to study the plasma surface interactions on the LLD: (1) A 20-element absolute extreme ultraviolet (AXUV) diode array with a 6 nm bandpass filter centered at 121.6 nm (the Lyman-{alpha} transition) for spatially resolved divertor recycling rate measurements in the highly reflective LLD environment, and (2) an ultraviolet-visible-near infrared R=0.67 m imaging Czerny-Turner spectrometer for spatially resolved divertor D I, Li I-II, C I-IV, Mo I, D{sub 2}, LiD, CD emission and ion temperature on and around the LLD module. The use of photometrically calibrated measurements together with atomic physics factors enables studies of recycling and impurity particle fluxes as functions of LLD temperature, ion flux, and divertor geometry.

Soukhanovskii, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Roquemore, A. L.; Bell, R. E.; Kaita, R.; Kugel, H. W. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2010-10-15

411

Direct X-B mode conversion for high-? national spherical torus experiment in nonlinear regime  

SciTech Connect

Electron Bernstein wave (EBW) can be effective for heating and driving currents in spherical tokamak plasmas. Power can be coupled to EBW via mode conversion of the extraordinary (X) mode wave. The most common and successful approach to study the conditions for optimized mode conversion to EBW was evaluated analytically and numerically using a cold plasma model and an approximate kinetic model. The major drawback in using radio frequency waves was the lack of continuous wave sources at very high frequencies (above the electron plasma frequency), which has been addressed. A future milestone is to approach high power regime, where the nonlinear effects become significant, exceeding the limits of validity for present linear theory. Therefore, one appropriate tool would be particle in cell (PIC) simulation. The PIC method retains most of the nonlinear physics without approximations. In this work, we study the direct X-B mode conversion process stages using PIC method for incident wave frequency f{sub 0}?=?15?GHz, and maximum amplitude E{sub 0}?=?10{sup 5?}V/m in the national spherical torus experiment (NSTX). The modelling shows a considerable reduction in X-B mode conversion efficiency, C{sub modelling}?=?0.43, due to the presence of nonlinearities. Comparison of system properties to the linear state reveals predominant nonlinear effects; EBW wavelength and group velocity in comparison with linear regime exhibit an increment around ?36% and 17%, respectively.

Ali Asgarian, M., E-mail: maliasgarian@ph.iut.ac.ir, E-mail: maa@msu.edu [Physics Department, Isfahan University of Technology, Isfahan 84156 (Iran, Islamic Republic of); Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States); Parvazian, A.; Abbasi, M. [Physics Department, Isfahan University of Technology, Isfahan 84156 (Iran, Islamic Republic of); Verboncoeur, J. P. [Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States)

2014-09-15