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1

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

NASA Astrophysics Data System (ADS)

The hybrid kinetic model approach supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of the existing measurements for surface and atmospheric composition from previous missions and to planning of future missions. The simulations are based on recent models of the atmosphere of Europa [1,2]. The hybrid model allows us to take into account the finite gyroradius effect and to estimate correctly the ions velocity distribution and the fluxes along the magnetic field in opposite the MHD simulation with the Maxwellian velocity distribution for background and pickup ions. The hybrid model also allows us to investigate the effects of the electron pressure on plasma wake structure that was already done for Jovian torus Io interaction [3]. Photoionization, electron-impact ionization and charge exchange are included in our model. The temperature of the background electrons and pickup electrons was also included into the generalized Ohm's law. We also take into account the collisions between the ions and neutrals. The background plasma contains only the ions with SO++ (Model A) [4] and O++ and S++ (Model B) [5]. The pickup ions were created from the atmosphere. The majority of O2 atmosphere is thermal with an extended non-thermal population [1]. The moon is modeled in this initial work as a weakly conducting body. Important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work. In this report we discuss the first results of the hybrid kinetic simulation of Europa's environment, namely, the global plasma structures, e.g., the formation of the magnetic barrier, Alfvn wing, pickup ion tail etc., and the computed map for the ion flux on the surface of the moon. References [1] Cassidy, T.A., R.E. Johnson, M.A. McGrath, M.C. Wong, J.F. Cooper, The spatial morphology of Europa's near-surface O2 atmosphere, Icarus, 191, 755-764, 2007. [2] Shematovich, V.I., R.E. Johnson, J.F. Cooper, M.C. Wong, Surface-bounded atmosphere of Europa, Icarus, 173, 480-498, 2005. [3] Lipatov, A.S. and M.R. Combi, Effects of kinetic processes in shaping Io's global plasma environment: A 3D hybrid model, Icarus, 180, 412-427, 2006. [4] Kabin, K., et al., On Europa's magnetospheric interaction: A MHD simulation of the E4 Flyby, JGR, 104, 19983-19992, 1999. [5] Paterson, W.R. et al., Galileo plasma observations at Europa: Ion energy spectra and moments, JGR, 104, 22779-22791, 1999.

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

2009-12-01

2

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

3

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

4

Convective transport of plasma in the inner Jovian magnetosphere  

SciTech Connect

The authors investigate the transport of plasma in the inner Jovian magnetosphere according to the corotating convection model of Hill et al. (1981), emphasizing mathematical aspects of the theory. They employ a simplified but physically plausible boundary condition at the inner Io torus, representing a 5% density enhancement of S{sup +} ions in an active sector that is fixed in Jovian (system 3) longitude. They first investigate the convection electric field pattern resulting from this longitudinal mass anomaly alone, and then generalize the theory to include the effects of Coriolis force and plasma acceleration. They find that even a small ({approximately}5%) 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. (Rice Univ., Houston, TX (United States))

1990-04-01

5

New description of Io's cold plasma torus  

NASA Astrophysics Data System (ADS)

Despite more than 25 years of study of the Io plasma torus, its generation, dynamics, and even its spatial structure are still poorly understood, especially in the case of the inner, cold region of the torus. To remedy this lack, we analyzed ground-based coronagraphic images of the torus in S+ 6371 emission. We derived cold torus properties by modeling and removing these images' inherent line-of-sight integration and atmospheric blurring, using new deconvolution techniques, obtaining high-spatial-resolution estimates of the three-dimensional (3-D) S+ distributions. From these 3-D distributions, we discovered that the cold torus is washer-shaped, with a roughly constant vertical thickness ?0.25 Jovian radius (RJ), and a radial width that varies from 0.6 to 0.9 RJ. The cold torus is separated by a 0.1-0.2 RJ-wide low-density region, or "gap," from the "ribbon" region which lies just outside it. The small, approximately constant washer height implies an ion parallel temperature (T?) of 3 eV, compared with a ribbon T? that varies from about 20 to 50 eV as a function of Jovian magnetic longitude (?III). The washer has a distinct inner edge, not seen before, whose jovicentric distance varies with ?III so as to create the variable cold torus width. Thus this inner edge is concentric with neither Jupiter nor the rest of the torus. We also confirm the existence of a tilt between the midplanes of the ribbon and cold torus, with an orientation that cannot be produced by the magnetic mirror force acting on ion temperature anisotropy. The structure and composition of the gap and cold torus are best explained by a model in which a small amount of warm S+ plasma diffuses inwards while radiatively cooling. While still warm, its distribution over a large scale height keeps its density small, forming the gap. After sufficient cooling, it collapses to the centrifugal equator, where its higher density and continued inward diffusion make it more visible as the cold torus washer. However, its low electron temperature (probably ? T?) must be kept from further decline by a hitherto-unsuspected energy source that powers the observed visible wavelength radiation from the cold torus and fluctuates on timescales less than the plasma diffusion time. The formation of the abrupt cold torus inner edge might indicate the loss there of either this energy source or the plasma itself.

Herbert, Floyd; Schneider, Nicholas M.; Dessler, A. J.

2008-01-01

6

Discontinuities in Jovian sulphur plasma  

NASA Technical Reports Server (NTRS)

The radial distribution of the Jovian sulfur plasma is discussed. Spectra of the ionized sulfur in the Jovian magnetosphere indicate a sharp discontinuity in visible sulfur emission at a radial distance of six Jupiter radii (Io orbit), outside of which emission is greatly reduced and the plasma is observed not to be in corotation with the planet. Possible explanations of this phenomenon include an effect of Io on the electron temperature outside its orbit, leading to the suppression of S II emission by second ionization, and a current system in Jupiter's ionosphere which prevents plasma from diffusing outward and decouples it from the corotation field. This discontinuity also requires reconciliation with Pioneer observations of the radial and pitch-angle diffusion of energetic charged particles.

Mekler, Y.; Eviatar, A.; Siscoe, G. L.

1979-01-01

7

Mass-injection rate from Io into the Io plasma torus  

Microsoft Academic Search

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

A Dessler

1980-01-01

8

On Jovian plasma sheet structure  

NASA Astrophysics Data System (ADS)

Several models of Jovian plasma sheet structure are studied, focusing on the ways in which they organize aspects of the observed Voyager 2 magnetic field characteristics as a function of radial distance from Jupiter. A technique which locates the interfaces between the plasma sheet and the lobes from magnetic data is presented. This boundary location is used to test models of the magnetotail. Improved variations of the hinged-magnetodisk and the magnetic anomaly models are given in which the parameters are optimized by using structural information from observed magnetic equator and plasma-sheet-lobe boundary crossings.

Khurana, Krishan K.; Kivelson, Margaret G.

1989-09-01

9

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

SciTech Connect

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

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

1980-01-01

10

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

Microsoft Academic Search

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

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

1982-01-01

11

Observations of Plasmas in the Jovian Magnetosphere  

Microsoft Academic Search

Large intensities of low-energy protons were observed deep within the Jovian magnetosphere with the plasma instrumentation on Pioneer 10 during the encounter of this space probe with Jupiter. The energy range of the electrostatic analyzer was 108 eV to 4.80 keV during encounter. Inside the flux tubes of the Galilean moon Io is a 'plasmasphere' of protons with relatively high

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

1976-01-01

12

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. Ptzold; H. Volland

1993-01-01

13

Drift wave instability in the Io plasma torus  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

14

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

15

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

16

First evidence for a Europa plasma torus  

NASA Technical Reports Server (NTRS)

The evidence from the Pioneer 10 plasma analyzer that plasma derived from Europa was present in the Jovian magnetosphere in December 1973 is summarized. Plasma detected between 1900 UT and 2100 UT on December 3, 1973, reveals a number of significant phenomena near the expected position of Europa's L shell. Mass addition to the magnetospheric plasma is indicated by a local increase in density apparently superimposed on the density gradient of Iogenic plasma. This increase in plasma density is unlike any phenomenon observed when the spacecraft is near a lunar L shell. The density shows fluctuations that make possible an estimate of the net outflow speed of magnetospheric ions per Jovian rotation. A radial flow speed in 1973 of 0.37 km/s from the Pioneer data is made, together with an estimate of 1 km/s in 1979 from Voyager 2 data, thus indicating a significant change.

Intriligator, D. S.; Miller, W. D.

1982-01-01

17

Ray tracing of Jovian kilometric radiation  

SciTech Connect

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

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

1980-01-01

18

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

19

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

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

20

Structure of the Jovian magnetotail from plasma wave observations  

Microsoft Academic Search

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

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

1980-01-01

21

Io's interaction with the plasma torus  

Microsoft Academic Search

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

C. K. Goertz

1980-01-01

22

Cassini UVIS observations of the Io plasma torus  

Microsoft Academic Search

On January 14, 2001, shortly after the Cassini spacecraft's closest approach to Jupiter, the Ultraviolet Imaging Spectrometer (UVIS) made a radial scan through the midnight sector of Io plasma torus. The Io torus has not been previously observed at this local time. The UVIS data consist of 2-D spectrally dispersed images of the Io plasma torus in the wavelength range

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

2004-01-01

23

Structure of the Jovian magnetotail from plasma wave observations  

SciTech Connect

Plasma wave measurements from the outbound passes of Voyager 1 and 2 are used to study the plasma density and structure of the Jovian magnetotail. Two principal types of plasma waves are observed in the magnetotail, continuum radiation and narrowband emissions near the electron gyrofrequency. The low frequency cutoff of the continuum radiation can be used to determine the local electron density. Profiles of the electron density from the outbound passes of Voyager 1 and 2 provide evidence of a broad region of nearly uniform plasma density between the magnetopause and the inner corotating portion of the magnetosphere. We refer to this region as the boundary layer. Comparisons are made with other experimental and theoretical evidence for the existence of such a boundary layer inside the Jovian magnetosphere.

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

1980-01-01

24

Plasma wave characteristics of the Jovian magnetopause boundary layer: Relationship to the Jovian aurora?  

SciTech Connect

The Jovian magnetopause boundary layer (BL) plasma wave spectra from 10{sup {minus}3} to 10{sup 2}Hz have been measured for the first time. For one intense event the magnetic (B{prime}) and electric (E{prime}) spectra were 2{times}10{sup {minus}4}f{sup {minus}2.4}nT{sup 2}/Hz and 4{times}10{sup {minus}9}f{sup {minus}2.4}V{sup 2}/m{sup 2}Hz, respectively. Although no measurable wave amplitudes were detected above the electron gyrofrequency, {approximately}140Hz, this finding may be due to the low signal strength characteristic of this region. The B{prime}/E{prime} ratio is relatively frequency independent. It is possible that waves are obliquely propagating whistler mode waves. The B{prime} and E{prime} spectra are broadband with no obvious spectral peaks. The waves are sufficiently intense to cause cross-field diffusion of magnetosheath plasma to create the BL itself. A BL thickness of 10,700 km is predicted, consistent with past in situ measurements. The Jovian boundary layer wave properties are quite similar to the BL waves at Earth (however, the Jovian waves are orders of magnitude less intense). It appears that the solar wind/magnetosphere dynamos at the two planets are similar enough to be consistent with a common wave generation mechanism. The predicted ionospheric latitudinal width of the BL of {approximately}100{endash}200km is quite similar to the Jovian auroral high-latitude ring. The location of the BL at and inside the foot point of the last closed field line may place the boundary layer and the aurora on approximately the same magnetic field lines. The Jovian BL waves are sufficiently intense to cause strong pitch angle diffusion for {lt}5-keV electrons and 1-keV to 1-MeV protons. The estimated energy precipitation rate from this interaction {lt}1ergcm{sup {minus}2}s{sup {minus}1}, sufficient for a weak high-latitude auroral ring. This intensity is 2 to 3 orders of magnitude too low to cause the main aurora ring, however. (Abstract Truncated)

Tsurutani, B.T.; Arballo, J.K.; Goldstein, B.E.; Ho, C.M.; Lakhina, G.S.; Smith, E.J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States)] [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Cornilleau-Wehrlin, N. [Centre dEtude des Environnements Terrestre et Planetaires/Universite Versailles-Saint-Quentin, Velizy (France)] [Centre dEtude des Environnements Terrestre et Planetaires/Universite Versailles-Saint-Quentin, Velizy (France); Prange, R. [Institute d`Astrophysique Spatiale, University of Paris XI, Orsay (France)] [Institute d`Astrophysique Spatiale, University of Paris XI, Orsay (France); Lin, N.; Kellogg, P. [University of Minnesota, School of Physics and Astronomy, Minneapolis, Minnesota (United States)] [University of Minnesota, School of Physics and Astronomy, Minneapolis, Minnesota (United States); Phillips, J.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Balogh, A. [Blackette Laboratory, Imperial College of Science and Technology, London (England)] [Blackette Laboratory, Imperial College of Science and Technology, London (England); Krupp, N. [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)] [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany); Kane, M. [Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland (United States)] [Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland (United States)

1997-03-01

25

Observations of Plasmas in the Jovian Magnetosphere.  

National Technical Information Service (NTIS)

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

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

1975-01-01

26

Empirical model of the Io plasma torus: Voyager measurements  

Microsoft Academic Search

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

Fran Bagenal

1994-01-01

27

Ion Temperature Control of the Io Plasma Torus  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

28

Dawn-dusk electric field asymmetry of the Io plasma torus  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

29

On the energy crisis in the Io plasma torus  

NASA Astrophysics Data System (ADS)

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

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

1988-06-01

30

The Galileo Ultraviolet and Extreme Ultraviolet Spectrometers: Observations of the Jovian System  

Microsoft Academic Search

The Galileo Ultraviolet and Extreme Ultraviolet spectrometers observed the Jovian system in late June 1996 during the approach to perijove. In addition, the EUV spectrometer observed Io's plasma torus during October and November 1995 prior to Jupiter orbit insertion. The luminosity and spectrum of Io's torus will be discussed and compared with earlier observations, and other results will be presented.

A. I. F. Stewart; C. W. Hord; C. A. Barth; W. R. Pryor; W. E. McClintock; K. E. Simmons; J. M. Ajello; W. K. Tobiska; R. W. West; A. L. Broadfoot; D. M. Hunten; B. R. Sandel; D. E. Shemansky

1996-01-01

31

Modeling Variability of Plasma Conditions in the Io Torus  

NASA Technical Reports Server (NTRS)

Telescopic observations an in situ measurements of the Io plasma torus show the density, temperature and composition to vary over time, sometimes up to a factor of 2. While previous models of the physical and chemical processes in the Io plasma torus have reasonably modeled the conditions of the Voyager 1 era, their authors have not addressed the observed variability nor explored the sensitivity of torus conditions to input parameters. In this paper we present a homogeneous torus model parameterized by five variables (transport timescale, neutral source strength, ratio of oxygen sulfur to atoms in the source, fraction of superthermal electrons, temperature of these hot electrons). The model incorporates the most recent data for ionization, recombination, charge exchange and radiative energy losses for the major torus species (S, S(sup +), S(sup ++), S(sup +++), O, O(sup +), O(sup ++). We solve equations of conservation of mass and energy to find equilibrium conditions for a set of input parameters. We compare model plasma conditions with those observed by Voyager 1 Voyager 2, and Cassini. Furthermore, we explore the sensitivity of torus conditions to each parameter. We find that (1) torus conditions are distinctly different for the Voyager 1, Voyager 2 and Cassini eras, (2) unique torus input parameters for any given era are poorly constrained given the wide range of solution space that is consistent with the range of observed torus conditions, (3) ion composition is highly sensitive to the specification of a non-thermal electron distribution, (4) neutral O/S source ratio is highly variable with model values ranging between 1.7 for Cassini to 4.0 for Voyager 1 conditions, (5) transport times range between 23 days for Voyager 2 to 50 days for Voyager 1 and Cassini, (6) neutral source strengths range between 7 to 30 x 10(sup -4) cm (sup -3) s(sup -1) which corresponds to a net production of 0.4 to 1.3 tons/s for a torus volume of 1.4 x 10(sup 31) cm(sup 3), or 38 R(sub j)(sup 3).

Delamere, P. A.; Bagenal, F.

2003-01-01

32

Jovian magnetosphere: a post-Voyager view  

SciTech Connect

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

Hill, T.W.

1981-01-20

33

Energetic /approximately 100-keV/ tailward-directed ion beam outside the Jovian plasma boundary  

NASA Technical Reports Server (NTRS)

The hot plasma instrument on the Voyager-2 spacecraft measured a nearly monoenergetic (100 keV) ion beam several hours after crossing the Jovian plasma boundary on the nightside of the planet. The beam, deduced to consist primarily of heavy ions, persisted for about four hours and originated from the general direction of Jupiter. The energy density of the beam was about several times the energy density of the magnetic field (beta greater than 1). This beam, a product of an as yet not understood Jovian plasma acceleration mechanism, provides a dramatic example of the energetic dynamics of Jupiter's magnetosphere.

Krimigis, S. M.; Bostrom, C. O.; Armstrong, T. P.; Axford, W. I.; Fan, C. Y.; Gloeckler, G.; Hamilton, D. C.; Lanzerotti, L. J.; Zwickl, R. D.

1980-01-01

34

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

SciTech Connect

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

Hairston, M.R.

1986-01-01

35

Energetic (approx. 100keV) tailward-directed ion beam outside the Jovian plasma boundary  

Microsoft Academic Search

The hot plasma instrument on the Voyager-2 spacecraft measured a nearly monoenergetic (approx.100 keV) ion beam several hours after crossing the Jovian plasma boundary on the nightside of the planet. The beam, deduced to consist primarily of heavy ions, persisted for about four hours and originated from the general direction of Jupiter. The energy density of the beam was approx.

S. M. Krimigis; T. P. Armstrong; W. I. Axford; C. O. Bostrom; C. Y. Fan; G. Gloeckler; L.J. Lanzerotti; D. C. Hamilton; R. D. Zwickl

1980-01-01

36

Magnetic Fluctuations in the Jovian Magnetosphere.  

National Technical Information Service (NTIS)

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 th...

C. T. Russell

2002-01-01

37

Modeling the Jovian Current Sheet and Inner Magnetosphere  

Microsoft Academic Search

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

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

1981-01-01

38

Jovian plasma sheet density profile from low-frequency radio waves  

NASA Astrophysics Data System (ADS)

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

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

1989-04-01

39

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

40

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

41

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

42

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

Microsoft Academic Search

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

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

1998-01-01

43

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

44

Turbulent Parameter Evolution in Madison Symmetric Torus RFP Plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

45

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

46

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

47

Fluctuations and turbulence in an electric field Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Fluctuation characteristics of plasma number density and electrostatic potential below the ion plasma and ion cyclotron frequencies in an electric field Bumpy Torus plasma were investigated experimentally, using digitally implemented spectral analysis techniques. The toroidal plasma was biased to high potentials by applying positive or negative voltage to electrodes located in the midplanes of two sectors of the toroidal array. The plasma was observed to be biased to 80 or 90% of the potential on the midplane electrodes, regardless of polarity. The radial electric field exceeded 1 kV/cm at the plasma boundary and penetrated inward to at least one-half of the plasma radius. When the imposed radial electric fields reached values characteristic of the experiment, the E/B drift velocities were comparable to the particle thermal velocities. The amplitude statistics of both the density and the potential fluctuations were found to be Gaussian for the most part, with near-zero skewness and a kurtosis of about 3.0. The spectral index of the density and potential fluctuations ranged from 2 to 6. The higher frequency components were found to propagate faster than the E/B drift velocity, which is the characteristic speed of the lower-frequency components.

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

1981-01-01

48

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

NASA Astrophysics Data System (ADS)

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

Kagitani, Masato

2013-10-01

49

Jovian plasma sheet density profile from low-frequency radio waves  

SciTech Connect

By using planetary radio astronomy (PRA), plasma wave system (PWS), and Magnetometer (MAG) data from Voyager 1 and 2 (V1 and V2), essential features of the nightside Jovian plasma sheet are derived, and the density gradient of the corotating plasma structure in the middle Jovian magnetosphere is calculated. The PRA experiment gives information about the plasma wave polarization. To determine the density profile of the plasma sheet, the authors have derived the hinge point position of the plasma disc from MAG data and used the low-frequency cutoffs observed at three frequencies (562 Hz, 1 kHz, and 1.78 kHz) from the PWS experiment. They show that the hinge point position varies with the solar wind ram pressure, and the plasma disc thickness decreases with distance up to about 60 R{sub J}. The average thickness for an isodensity contour corresponding to 1 kHz is 3.29 R{sub J} for V1 and 3.16 R{sub J} for V2.

Rucker, H.O. (Space Research Institute, Graz (Austria)); Ladreiter, H.P. (Univ. of Graz (Austria)); LeBlanc, Y. (Observatoire de Paris, Meudon (France)); Jones, D. (Natural Environment Research Council, Cambridge (England)); Kurth, W.S. (Univ. of Iowa, Iowa City (USA))

1989-04-01

50

Negative specific heat of a magnetically self-confined plasma torus  

PubMed Central

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

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

2003-01-01

51

Ios Hot Plasma TorusA 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 stateof 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

52

Coupled low-energy - ring current plasma diffusion in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The outwardly diffusing Iogenic plasma and the simultaneously inwardly diffusing ring current plasma in the Jovian magnetosphere are described using a coupled diffusion model which incorporates the effects of the pressure gradient of the ring current into the cross-L diffusion coefficient. The coupled diffusion coefficient is derived by calculating the total energy available to drive the diffusion process. The condition is imposed that the diffusion coefficient takes on a local minimum value at some point in the region L = 7-8, at which point the gradient of the Io plasma density is specified as ramp value given by Siscoe et al. (1981). The hypothesis that the pressure gradient of the ring current causes the diminution of radial plasma transport is tested, and solution profiles for the Iogenic and ring current plasma densities are obtained which imply that the Io plasma ramp is caused by a high-density, low-energy component of the ring current hitherto unobserved directly.

Summers, D.; Siscoe, G. L.

1985-01-01

53

HST/STIS FUV Observations of the Io Plasma Torus  

NASA Astrophysics Data System (ADS)

We analyze 74 FUV (1150 <= ? <= 1720 ) HST/STIS observations of the dawn ansa of the Io plasma torus made during Galileo's C23, I24, and I27 encounters with Io. These data include G140L spectral scans from 6 HST orbits observing near System III longitudes 39, 149, 208, 267, 325, and 337, plus 2 undispersed images at ~90\\ from 1 additional orbit. Special problems include the faintness (<= 200 R) of the torus at these wavelengths and the presence of a spatially inhomogeneous dark-count background with intensity comparable to the signal. To minimize sensitivity to photon noise, we fit the data with a special constrained-nonnegative least squares fitting procedure [JGR 105:16035], using a simple plasma emission model integrated over the line of sight. This procedure inverts the line-of-sight density superposition (``peels the onion'') using the assumption of local azimuthal symmetry at the dawn ansa and estimates model parameter uncertainty by Monte Carlo noise simulation. The undispersed images show that the ``ribbon'' feature seen at visible wavelengths in ground-based observations [Science 226:337] is also clearly present in the FUV. Although the analysis is still in its first stages, the fits to the S+ 1256 , S++ 1297 , and S+++ 1410 multiplets in the spectral scans indicate that the S++ and S+++ densities peak ~0.1 R J further from Jupiter than does the S+ density. Moreover, the System III variation of torus scale height relative to the centrifugal equatorial plane that was first observed in ground-based images [Science 450:450, JGR 100:21683] also appears in our results. It also appears that the S+/S++ and S+/S+++criptstyle; ratios dropped by a factor of ~2 between the I24 and I27 epochs, a variability that has also been seen in EUVE observations [F. Herbert et al., JGR 106, in press]. We thank NASA and STScI for support under grant #s NAG5-8952, NAG5-6362, and NAG5-8051.

Herbert, F.; Hendrix, A.; Bagenal, F.; Schneider, N. M.

2001-11-01

54

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

NASA Technical Reports Server (NTRS)

High time resolution (60 ms) Voyager magnetometer and plasma wave measurements of a strong (fast Mach number 16), quasi-perpendicular Jovian bow shock reveal an abrupt change in the plasma wave spectrum at the leading edge of the shock foot. Upstream electron plasma waves terminate at the leading edge, and are replaced by a lower-frequency broadband spectrum of ion-acoustic-like waves, which terminates at the main shock ramp. The clear association with the foot region of the lower frequency component suggests that it is generated by reflected ions. If the upstream plasma waves are generated by an escaping electron heat flux, their termination at the leading edge suggests that electrons are heated by the low-frequency waves in the shock foot.

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

1985-01-01

55

Spatial and temporal studies of Jovian kilometric radiation  

SciTech Connect

Plasma wave measurements taken during the Voyager 1 and 2 Jupiter encounters are used as a basis for synoptic studies of Jovian kilometric radiation. The studies reveal the existence of a shadow zone near the magnetic equator within which kilometric radiation is seldom or weakly observed. This shadow is presumably cast by the Io plasma torus whose density is high enough to refract electromagnetic waves generated either near the torus or closer to Jupiter. At 56.2 kHz this shadow zone has a half width of about 10 /sup 0/. In addition to a latitudinal shadow zone, there occasionally appear to be long-lived longitudinal variations of kilometric radiation intensities. That is, individual features may reappear on successive rotations at nearly constant System III longitudes. This may imply longitudinally asymmetric structures in the kilometric source region or intervening magnetosphere such as the Io torus which corotate and have lifetimes of up to several days. Some of the features appear to drift to higher longitudes with increasing time suggesting deviations from corotation ranging up to a few percent. Gross changes in the character of Jovian kilometric radiation on time scales of a few days imply dramatic changes in the inner Jovian magnetosphere on the same time scale and may be indicative of magnetospheric substorms or changes in plasma injection rates from Io.

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

1980-01-01

56

Electron Gyro-scale Fluctuation Measurements in National Spherical Torus Experiment H-Mode Plasmas  

National Technical Information Service (NTIS)

A collective scattering system has measured electron gyro-scale fluctuations in National Spherical Torus Experiment (NSTX) H-mode plasmas to investigate electron temperature gradient (ETG) turbulence. Observations and results pertaining to fluctuation mea...

B. P. LeBlanc D. R. Smith E. Mazzucato S. M. Kaye W. Lee

2009-01-01

57

Modeling of Spherical Torus Plasmas for Liquid Lithium Wall Experiments  

SciTech Connect

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

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

2002-01-29

58

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

59

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

SciTech Connect

The low-energy charged particle (LECP) experiment on the Voyager 1 and 2 spacecraft made measurements of the intensity, energy spectra, angular distributions and composition of ions (30 keV< or approx. =E< or approx. = 150 MeV) and the electrons (14 keV< or approx. =E< or approx. =10 MeV) during encounters with the Jovian magnetosphere in 1979. Detailed analysis of the multicomponent (H, He, O, S) low-energy (approx.30 keV to approx.4 MeV) ion population reveals the Jovian environment to be dominated by magnetospheric ions to distances > or approx. =200 R/sub J/ upstream and > or approx. =350 R/sub J/ downstream from the planet. Inside the magnetosphere, ions move generally in the sense of corotation to the dayside magnetopause, and on the nightside to distances of approx.130--150 R/sub J/, beyond this distance, but inside the magnetopause, ion flow abruptly changes to an antisunward, antiJupiter direction and continues to large (>350 R/sub J/) radial distances outside the magnetosphere. The ion particle spectrum is characterized by a nonthermal power law (E/sup -gamma/) component for E> or approx. =200 keV, and a convected Maxwellian for E< or approx. =200 with characteristic temperatures (kT) of approx.20--45 keV. Temperature maxima generally coincide with crossings of the Jovian plasma sheet, while at higher energies spectra become softer at the equator. The ion spectra and composition are affected strongly by convective flows in all parts of the magnetosphere. By using the observed spectra and angular distributions, density and pressure profiles are produced for ions measured above the lowest LECP detector threshold (E> or approx. =30 keV) and are compared with reported ambient total electron densities and magnetic field pressures. The particle pressures are found to be comparable to magnetic field pressures to at least approx.10 R/sub J/, i.e., Jovian magnetosphere dynamics are determined by pressure variations in a high ..beta.. plasma.

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

1981-09-30

60

Microwave radiation measurements near the electron plasma frequency of the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Microwave emission near the electron plasma frequency of the NASA Lewis Bumpy Torus plasma has been observed, and its relation to the average electron density and the dc toroidal magnetic field was examined. The emission was detected using a spectrum analyzer and a 50-ohm miniature coaxial probe. The radiation appeared as a broad amplitude peak that shifted in frequency as the plasma parameters were varied. The observed radiation scanned an average plasma density ranging from 20 billion to 800 billion per cu cm. A linear relation was observed between the density calculated from the emission frequency and the average plasma density measured with a microwave interferometer. With the aid of a relative density profile measurement of the plasma, it was determined that the emissions occurred from the outer periphery of the plasma.

Mallavarpu, R.; Roth, J. R.

1978-01-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

62

Momentum Transport in Electron-Dominated Spherical Torus Plasmas  

SciTech Connect

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

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

2009-02-24

63

Low energy energetic neutral atom imaging in the Jovian system  

NASA Astrophysics Data System (ADS)

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

Futaana, Yoshifumi; Wieser, Martin; Barabash, Stas

2013-04-01

64

Atomic clouds as distributed sources for the Io plasma torus  

NASA Technical Reports Server (NTRS)

Several recent developments have implications for the neutral particle environment of Jupiter. Very hot sulfur ions have been detected in the Io torus with gyrospeeds comparable to the corotation speed, a phenomenon that would result from a neutral sulfur cloud. Current evidence supports the hypothesis that extensive neutral clouds of oxygen and sulfur exist in the Jupiter magnetosphere and that they are important sources of ions and energy for the Io torus.

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

1981-01-01

65

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

66

On the structure of the Io Torus  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

67

X-ray Probes of Magnetospheric Interactions with Jupiter's Auroral zones, the Galilean Satellites, and the Io Plasma Torus  

NASA Technical Reports Server (NTRS)

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the Jovian system is a source of x-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are powerful sources of x-ray emission. Chandra observations revealed x-ray emission from the Io Plasma Torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from these moons is certainly due to bombardment of their surfaces of highly energetic protons, oxygen and sulfur ions from the region near the Torus exciting atoms in their surfaces and leading to fluorescent x-ray emission lines. Although the x-ray emission from the Galilean moons is faint when observed fiom Earth orbit, an imaging x-ray spectrometer in orbit around these moons, operating at 200 eV and above with 150 eV energy resolution, would provide a detailed mapping (down to 40 m spatial resolution) of the elemental composition in their surfaces. Here we describe the physical processes leading to x-ray emission fiom the surfaces of Jupiter's moons and the instrumental properties, as well as energetic ion flux models or measurements, required to map the elemental composition of their surfaces. We discuss the proposed scenarios leading to possible surface compositions. For Europa, the two most extreme are (1) a patina produced by exogenic processes such as meteoroid bombardment and ion implantation, and (2) upwelling of material fiom the subsurface ocean. We also describe the characteristics of X - m , an imaging x-ray spectrometer under going a feasibility study for the JIM0 mission, with the ultimate goal of providing unprecedented x-ray studies of the elemental composition of the surfaces of Jupiter's icy moons and Io, as well as of Jupiter's auroral x-ray emission.

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

2004-01-01

68

Observation of auroral secondary electrons in the Jovian magnetosphere  

SciTech Connect

Localized enhancements in the flux of suprathermal electrons were observed by the Voyager 1 Plasma Science instrument near the outer boundary of the Io plasma torus between L {approximately}7.5 and L {approximately}10. This localization, which occurs within the general region of hot electrons noted by Sittler and Strobel (1987), and the spectral characteristics of the observed electrons are consistent with secondary (backscattered) electron production by intense Jovian auroral energetic particle precipitation and support the hypothesis that such electrons may contribute to the processes that heat the plasma in this region of the magnetosphere.

McNutt, R.L. Jr. (Massachusetts Institute of Technology, Cambridge (USA)); Bagenal, F. (Univ. of Colorado, Boulder (USA)); Thorne, R.M. (Univ. of California, Los Angeles (USA))

1990-03-01

69

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

70

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

71

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

72

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

73

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

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

75

Source characteristics of Jovian narrow-band kilometric radio emissions  

NASA Astrophysics Data System (ADS)

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

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

1993-07-01

76

Characteristics of the NASA Lewis Bumpy-Torus Plasma Generated with Positive Applied Potentials.  

National Technical Information Service (NTIS)

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 m...

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

1976-01-01

77

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

78

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

79

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

80

Characteristics of the NASA Lewis Bumpy Torus plasma generated with positive applied potentials  

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 kW in deuterium and helium gas, and with positive potentials applied to the midplane electrodes. This steady-state ion heating method utilizes a modified Penning discharge operated in a bumpy torus confinement geometry 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, each of which is associated with a characteristic range of background pressure and electron temperature. Experimental data show that the average ion residence time in the plasma is virtually independent of the magnetic field strength.

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

1976-01-01

81

Cassini UVIS Observations of the Io Plasma Torus. 4; Modeling Temporal and Azimuthal Variability  

NASA Technical Reports Server (NTRS)

In this fourth paper in a series, we present a model of the remarkable temporal and azimuthal variability of the Io plasma torus observed during the Cassini encounter with Jupiter. Over a period of three months, the Cassini Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variaton in the average torus composition. Superimposed on this long-term variation, is a 10.07-hour periodicity caused by azimuthal variation in plasma composition subcorotating relative to System III longitude. Quite surprisingly, the amplitude of the azimuthal variation appears to be modulated at the beat frequency between the System III period and the observed 10.07-hour period. Previously, we have successfully modeled the months-long compositional change by supposing a factor of three increase in the amount of material supplied to Io's extended neutral clouds. Here, we extend our torus chemistry model to include an azimuthal dimension. We postulate the existence of two azimuthal variations in the number of superthermal electrons in the torus: a primary variation that subcorotates with a period of 10.07 hours and a secondary variation that remains fixed in System III longitude. Using these two hot electron variations, our model can reproduce the observed temporal and azimuthal variations observed by Cassini UVIS.

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

2008-01-01

82

Modeling sensitivity of temporal and azimuthal variability in the Io plasma torus  

NASA Astrophysics Data System (ADS)

During Cassini's inbound approach to Jupiter, the Cassini UVIS data revealed that the Io Plasma torus exhibits azimuthal (e.g. composition) and temporal (e.g. brightness) variations. The azimuthal variations were found to be modulated by the System III and System IV periods via hot (i.e. 10s to 100s eV) electron chemistry. While the System III hot electrons are understood to be governed, in part, by the longitude-dependent magnetic mirror ratio, the mechanism for modulating the hot electron abundance at the System IV period is undetermined and therefore motivates this study. Using an improved azimuthal physical chemistry model for the Io plasma torus, we will present sensitivity studies of torus properties to variations in neutral source rate, System III and System IV hot electron abundance, and the radial transport and azimuthal subcorotation timescales. We will investigate the range of parameters that yield quasi-stable azimuthal variation in composition that is imposed by a variable neutral source (i.e. similar to the inferred volcanic eruption preceding the Cassini flyby in 2000). These studies are relevant to the on-going analysis of the outbound Cassini UVIS data acquired between January and March 2001 and future observations of torus variability such as the EXCEED mission.

Copper, M.; Delamere, P. A.; Steffl, A. J.

2013-12-01

83

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

NASA Technical Reports Server (NTRS)

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

Smyth, William H.

2003-01-01

84

Periodic bursts of Jovian non-Io decametric radio emission  

PubMed Central

During the years 20002011 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 12MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300 and 60 (via 360). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ?25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

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

2013-01-01

85

Periodic bursts of Jovian non-Io decametric radio emission.  

PubMed

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

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

2013-03-01

86

Ring Current Impoundment of the Io Plasma Torus  

Microsoft Academic Search

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

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

1981-01-01

87

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

88

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

NASA Technical Reports Server (NTRS)

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

Richardson, R. W.

1974-01-01

89

Jovian electrodynamic tether experiment  

NASA Technical Reports Server (NTRS)

A case is made for an electrodynamic tether scientific platform to be put into orbit around Jupiter as a follow-on to the present series of earth-based Tethered Satellite System (TSS) experiments. Preliminary system trades are made to bound the amount of power (assuming 100 percent plasma contactor efficiency) that can be obtained from the orbiting Jovian tether. With magnetic field strengths of roughly 4 to 7 Gauss, power levels of the order of 100 kilowatts can be obtained with a thin 500 km long tether. This should suffice to power a Jovian scientific experiment package. The electrodynamic tether also affords a loitering capability as it can be operated as a thruster in addition to a power generator. Further study and research is needed to characterize the Jovian tether as to its electrodynamic and dynamic performance potential. Hollow cathode plasma contactor operation needs to be verified in near earth space.

Hammond, Walter E.; Freeman, Scott E.; Nave, Mark J.; Rupp, Charles C.

1991-01-01

90

Dawn-dusk electric field asymmetry of the Io plasma torus  

Microsoft Academic Search

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

D. D. Barbosa; M. G. Kivelson

1983-01-01

91

Soft-x-ray emission, plasma equilibrium, and fluctuation studies on Madison Symmetric Torus  

Microsoft Academic Search

A miniature multichord soft-x-ray detection system has been installed on the Madison Symmetric Torus (MST) reversed-field pinch to study the plasma equilibrium and fluctuation properties of standard- and improved-confinement discharges. Because of the relatively flat MST density and temperature profiles, the spatial resolution is relatively poor along the line of sight. However, the system can resolve line-integrated-emissivity fluctuations which are

C. Xiao; P. Franz; B. E. Chapman; D. Craig; W. X. Ding; G. Gadani; L. Marrelli; P. Martin; R. Pasqualotto; G. Spizzo; J. S. Sarff; S. D. Terry

2003-01-01

92

Electron Gyro-scale Fluctuation Measurements in National Spherical Torus Experiment H-mode Plasmas  

SciTech Connect

A collective scattering system has measured electron gyro-scale fluctuations in National Spherical Torus Experiment (NSTX) H-mode plasmas to investigate electron temperature gradient (ETG) turbulence. Observations and results pertaining to fluctuation measurements in ETGstable regimes, the toroidal field scaling of fluctuation amplitudes, the relation between between fluctuation amplitudes and transport quantities, and fluctuation magnitudes and k-spectra are presented. Collectively, the measurements provide insight and guidance for understanding ETG turbulence and anomalous electron thermal transport.

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

2009-08-10

93

Measurements of Prompt and MHD-Induced Fast Ion Loss from National Spherical Torus Experiment Plasmas  

SciTech Connect

A range of effects may make fast ion confinement in spherical tokamaks worse than in conventional aspect ratio tokamaks. Data from neutron detectors, a neutral particle analyzer, and a fast ion loss diagnostic on the National Spherical Torus Experiment (NSTX) indicate that neutral beam ion confinement is consistent with classical expectations in quiescent plasmas, within the {approx}25% errors of measurement. However, fast ion confinement in NSTX is frequently affected by magnetohydrodynamic (MHD) activity, and the effect of MHD can be quite strong.

D.S. Darrow; S.S. Medley; A.L. Roquemore; W.W. Heidbrink; A. Alekseyev; F.E. Cecil; J. Egedal; V.Ya. Goloborod'ko; N.N. Gorelenkov; M. Isobe; S. Kaye; M. Miah; F. Paoletti; M.H. Redi; S.N. Reznik; A. Rosenberg; R. White; D. Wyatt; V.A. Yavorskij

2002-10-15

94

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

95

Ion densities and velocities in the inner plasma torus of Saturn  

NASA Astrophysics Data System (ADS)

We present plasma data from the Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP), mapping the ion density and velocity of Saturn's inner plasma torus. Data from 129 orbits, recorded during the period from the 1st of February 2005 to the 27th of June 2010, are used to map the extension of the inner plasma torus. The dominant part of the plasma torus is shown to be located in between 2.5 and 8 Saturn radii (1 RS=60,268 km) from the planet, with a north-southward extension of 2RS. The plasma disk ion density shows a broad maximum in between the orbits of Enceladus and Tethys. Ion density values vary between 20 and 125 cm-3 at the location of the density maximum, indicating considerable dynamics of the plasma disk. The equatorial density structure, |z|<0.5RS, shows a slower decrease away from the planet than towards. The outward decrease, from 5 RS, is well described by the relation neq=2.2104(1/R)3.63. The plume of the moon Enceladus is clearly visible as an ion density maximum of 105 cm-3, only present at the south side of the ring plane. A less prominent density peak, of 115 cm-3, is also detected at the orbit of Tethys, at 4.9RS. No density peaks are recorded at the orbits of the moons Mimas, Dione, and Rhea. The presented ion velocity v shows a clear general trend in the region between 3 and 7 RS, described by v=1.5R2-8.7R+39. The average v starts to deviate from corotation at around 3 RS, reaching 68% of corotation close to 5 RS.

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

2012-12-01

96

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

SciTech Connect

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

Bieniosek, F. M.

1981-01-01

97

Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma  

NASA Technical Reports Server (NTRS)

The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

Roth, J. R.

1978-01-01

98

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 nex 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

99

Investigation of possible lower hybrid emission from the NASA Lewis bumpy torus plasma  

NASA Technical Reports Server (NTRS)

Radio frequency emission has been detected near the power hybrid frequency of a bumpy torus plasma by using a responsive detection system that consists of a spectrum analyzer and a 50 ohm miniature coaxial antenna concentrically located in a re-entrant quartz tube. The frequency shift of a broad emission peak was monitored as a function of background pressure, electrode voltage, and the strength of the dc magnetic field. Simultaneous measurements of the average plasma density were made with a polarization diplexing microwave interferometer. The information derived from the experiment is discussed with particular reference to the following: (1) whether the emissions are dominated by atomic or molecular species of deuterium; (2) the strength of the dc magnetic field in the emitting region; (3) the geometric location of the emitting region of the plasma; (4) comparison of the lower hybrid plasma density with the average plasma density; and (5) relation of ion spoke geometry to lower hybrid emission.

Mallavarpu, R.; Roth, J. R.

1977-01-01

100

Investigation of possible lower hybrid emission from the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Radio frequency emission detected near the lower hybrid frequency of the NASA Lewis Bumpy Torus plasma is studied, using a simple detection system that consists of a spectrum analyzer and a 50-ohm miniature co-axial antenna concentrically located in a re-entrant quartz tube. The frequency shift of a broad emission peak is monitored as a function of the background pressure, electrode voltage, and the strength of the dc magnetic field. Simultaneous measurements of the average plasma density are made with a polarization diplexing microwave interferometer. Information from the experiment is discussed with particular reference to the role of atomic or molecular species of deuterium in the emissions, the strength of the dc magnetic field in the emitting region, the geometric location of the emitting region of the plasma, the lower hybrid plasma density as compared with the average plasma density, and the relation of the ion spoke geometry to the lower hybrid emission.

Mallavarpu, R.; Roth, J. R.

1977-01-01

101

Unified Ideal Stability Limits for Advanced Tokamak and Spherical Torus Plasmas  

SciTech Connect

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

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

2003-02-06

102

Spatial distribution of plasma in the Io Torus  

Microsoft Academic Search

In situ measurements of ion densities and temperatures have been analyzed to produce profiles of these plasma parameters along the Voyager 1 inbound trajectory between 7 and 5 R\\/sub J\\/. The temperature profile shows a sharp decrease by a factor of approx.50 between 5.8 and 5.2R\\/sub J\\/ corresponding to a temperature gradient of approx.7 x 10⁵ per R\\/sub J\\/. The

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

1980-01-01

103

Io and Its Plasma Environment  

Microsoft Academic Search

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

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

1980-01-01

104

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

Microsoft Academic Search

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

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

1981-01-01

105

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

SciTech Connect

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

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

2008-01-01

106

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

107

Implications of Depleted flux Tubes in the Jovian Magnetosphere  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

108

Modeling Temporal Variability of Plasma Conditions in the Io Torus during the Cassini Era  

NASA Technical Reports Server (NTRS)

Observations of ultraviolet (UV) emissions from the major ion species (S(sup +), S(sup ++), S(sup +++), O(sup +), O(sup ++) of the Io Plasma torus made during the Cassini flyby (October 2000 to March 2001) have revealed significant time variability. Using a homogenoeus model for mass and energy flow in the torus parameterized by five input variables (transport timescale, neutral source strength, ratio of oxygen to sulfur atoms in the source, fraction of superthermal electrons, and temperature of the hot electrons), we have investigated the time variability of the torus properties (density, composition, and temperature) during the Cassini era. In order to match the changes in emissions, the model suggests that a significant change in the neutral source occurred near the beginning of the observing period, decreasing from more than 1.8 tons/s to 0.7 tons/s. The changes in the neutral source appear to coincide with the declining phase of a dramatic (i.e., 2-3 order of magnitude) peak in iogenic dust emissions observed by Galileo prior to the Cassini era.

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

2004-01-01

109

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

110

Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas  

SciTech Connect

A collective scattering system has measured electron gyroscale fluctuations in National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] H-mode plasmas to investigate electron temperature gradient (ETG) turbulence. Observations and results pertaining to fluctuation measurements in ETG-stable regimes, the toroidal field scaling of fluctuation amplitudes, the relation between fluctuation amplitudes and transport quantities, and fluctuation magnitudes and k-spectra are presented. Collectively, the measurements provide insight and guidance for understanding ETG turbulence and anomalous electron thermal transport.

Smith, D. R.; Kaye, S. M.; Mazzucato, E.; Bell, R. E.; LeBlanc, B. P.; Menard, J. E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lee, W.; Park, H. K. [Pohang University of Science and Technology, 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 (United States); Levinton, F. M.; Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2009-11-15

111

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

112

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

113

Jovian magnetosphere  

SciTech Connect

This paper discusses the various regions of the Jovian magnetosphere roughly in the order of their distance from the planet. We first consider briefly the region <4.9 R/sub J/ Jovicentric (R/sub J/ = 71,372 km is the Jovian radius), inside the distance of closest approach of V-1. Here there has been no in situ exploration in the 1979--82 time frame but progress was made by Pioneer-based studies and radio-telescope observations from Earth.

Birmingham, T.J.

1983-03-01

114

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

115

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

NASA Astrophysics Data System (ADS)

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

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

2003-01-01

116

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

SciTech Connect

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

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

2005-04-15

117

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

SciTech Connect

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

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

2006-10-18

118

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

119

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

120

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

SciTech Connect

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

Shaing, K. C.

2009-07-09

121

Localized reconnection in the near jovian magnetotail  

PubMed

The oppositely directed magnetic field in the jovian magnetic tail is expected eventually to reconnect across the current sheet, allowing plasma produced deep inside the magnetosphere near Io's orbit to escape in the antisolar direction down the tail. The Galileo spacecraft found localized regions of strong northward and southward field components beyond about 50 jovian radii in the postmidnight, predawn sector of the jovian magnetosphere. These pockets of vertical magnetic fields can be stronger than the surrounding magnetotail and magnetodisk fields. They may result from episodic reconnection of patches of the near jovian magnetotail. PMID:9582116

Russell; Khurana; Huddleston; Kivelson

1998-05-15

122

Progress Toward Stabilization of Low Internal Inductance Spherical Torus Plasmas in NSTX  

NASA Astrophysics Data System (ADS)

Steady-state spherical torus plasmas for fusion applications, such as a component test facility or demonstration power plant, target operation with high non-inductive current fraction. These broad current profile targets have low values of plasma internal inductance, li, less than 0.4, near to the lower end of present NSTX operation. A key significance of this operation is that it approaches the purely current-driven ideal kink limit, which by definition exceeds the no-wall stability limit for all values of plasma normalized pressure (beta). In this regime, passive or active kink and resistive wall mode (RWM) stabilization is critical. Experiments on NSTX have recently approached this condition, evidenced by a significant reduction of the n = 1 no-wall stability limit computed by DCON. This limit drops from normalized beta of 4.2 -- 4.6 at li 0.6, to 3.4 at li 0.5, to below 2.8 for li 0.4. Nevertheless, passive and active RWM control has produced high toroidal beta up to 28 percent, and normalized beta up to 6.5 (nearly double the no-wall limit), closely following a record normalized beta to li ratio of 13 between li = 0.4 - 0.5. Non-inductive current fraction reaches 0.5 in these high normalized current plasmas. However, the disruption probability of these plasmas increases significantly, with about half of the discharges suffering terminating instabilities. Alteration of n = 1 RWM control system parameters, plasma rotation profile, and the role of beta feedback is examined to potentially improve mode stability. Ion precession drift and bounce frequency resonance stabilization is examined for these plasmas and compared to the identified stabilization reduction at intermediate plasma rotation and higher li.ootnotetextJ.W. Berkery, et al., Phys. Rev. Lett. 104, 035003 (2010).

Sabbagh, S. A.

2010-11-01

123

Fluctuation measurements using a five-pin triple probe in the Joint European Torus boundary plasma  

SciTech Connect

A multi-probe system has been developed to investigate the importance of electron temperature fluctuations turbulent transport in the Joint European Torus boundary plasma. The compact five-pin triple probe has been designed to reduce the phase delay of fluctuations due to the finite pin separation in the standard triple probe technique, while still avoiding the effects of probe shadowing. This probe has been found to have advantages over the standard triple probe in the region close to the separatrix (r-r{sub sep}<0.01 m), where the fluctuation wavelength is large. Importantly, results obtained with the probe support the standard estimation of cross-field particle flux, which ignores temperature fluctuations. They cannot be ignored, however, in the estimation of energy losses since measurements show that the conducted energy may be as large as the convected component.

Silva, C.; Goncalves, B.; Hidalgo, C.; Pedrosa, M. A.; Erents, K.; Matthews, G.; Pitts, R. A. [Associacao Euratom/IST, Centro de Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisbon (Portugal); Associacion Euratom/Ciemat, 28040 Madrid (Spain); Euratom/UKAEA Association, Culham Science Centre, Abingdon Oxon OX14 3DB (United Kingdom); Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015, Lausanne (Switzerland)

2004-10-01

124

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

NASA Astrophysics Data System (ADS)

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

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

125

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

126

The Columbia Nonneutral Torus: A New Experiment to Confine Nonneutral and Positron-Electron Plasmas in a Stellarator  

SciTech Connect

The Columbia Nonneutral Torus is a new stellarator experiment being built at Columbia University, New York, to study the confinement of nonneutral and electron-positron plasmas. It will be a two-period, ultralow aspect ratio classical stellarator configuration created from four circular coils. The theory of the confinement and transport of pure electron plasmas on magnetic surfaces is reviewed. The guiding principles behind the experimental design are presented, together with the actual experimental design configuration.

Pedersen, Thomas Sunn [Columbia University (United States); Boozer, Allen H. [Columbia University (United States); Kremer, Jason Paul [Columbia University (United States); Lefrancois, Remi G. [Columbia University (United States); Reiersen, Wayne T. [Princeton Plasma Physics Laboratory (United States); Dahlgren, Fred [Princeton Plasma Physics Laboratory (United States); Pomphrey, Neil [Princeton Plasma Physics Laboratory (United States)

2004-07-15

127

High-Harmonic Fast Wave Heating and Current Drive Results for Deuterium H-Model Plasmas in the National Spherical Torus Experiment.  

National Technical Information Service (NTIS)

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) predict tha...

B. P. LeBlanc C. K. Phillips E. F. Jaeger E. J. Valeo G. Taylor J. C. Hosea J. C. Wright J. R. Wilson P. M. Ryan P. T. Bonoli R. W. Harvey

2011-01-01

128

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

SciTech Connect

Observations of Jupiter made with the high-resolution ultraviolet spectrometer of the Orbiting Astronomical Observatory Copernicus in 1980 April and May yield the intensity of the Jovian Lyman-alpha emission to be 7 +- 2.5 kR. These measurements indicate that the Lyman-alpha intensity has decreased by about a factor of 2 from the time of the Voyager ultraviolet spectrometer measurements, nearly a year earlier. The Copernicus measurements, when combined with all other previous measurements of the Jovian Lyman-alpha emission, point to an unusually high column abundance of hydrogen atoms above the methane homopause at the Voyager epoch. Since the auroral charged particle bombardment of moelcular 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, and it was perhaps linked to the high concentration of the Io plasma torus. It should be pointed out that 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. The latest Copernicus observations also suggest an increase in the Jovian homopause value of the eddy mixing coefficient by about a factor of 5--10 since the Voyager epoch.

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

1982-11-01

129

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

130

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

SciTech Connect

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

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

2006-01-15

131

Progress in the Development of Advanced Spherical Torus Plasmas in NSTX  

NASA Astrophysics Data System (ADS)

Recent experiments in the National Spherical Torus Experiment have explored lithium conditioned, high-beta, high elongation plasmas over a range of q95. Notable achievements include a very low surface voltage of 130 mV sustained through the current flat-top and an NSTX record plasma stored energy of 440 kJ. In the absence of MHD activity, the current profile can be modeled as the sum of inductive currents, neoclassical pressure-driven currents, and neutral beam driven current with classical collisional processes only. However, when core MHD is present, anomalous fast ion diffusivity is required to match the current profile. Overall, cases with 65-70% of the current driven non-inductively are common at higher field and lower current. Thermal transport in these plasmas is comparable to that predicted by the standard ITER H-mode scaling, and shows stronger IP and weaker BT scaling than in NSTX experiments that did not benefit from lithium conditioning and such strong shaping. Many of these discharges exhibited very low internal inductance, leading to a reduced no-wall beta-limit and enhanced resistive wall instability. This work was funded by the U.S. DOE under contract DE-AC02-09CH11466.

Gerhardt, S.; Gates, D.; Menard, J.; Bell, M.; Bell, R.; Canik, J.; Kaye, S.; Kugel, H.; Fredrickson, E.; Leblanc, B.; Maingi, R.; Sabbagh, S.; Soukhanovskii, V.; Tritz, K.; Yuh, H.

2010-11-01

132

Injection and loss mechanisms for energetic ions in the inner Jovian magnetosphere  

SciTech Connect

The pronounced depletion of energetic ions observed by Voyager outside the orbit of Io can be understood as a steady state balance between particle loss and inward diffusion. For ions above 1 MeV/nuc (nucleon) G sweeping loss by Io itself is unimportant; rather the removal mechanisms involve processes associated with the extensive torus of neutral and ionized gas emanating from the satellite. There is compelling evidence to suggest that losses throughout an extended region in the outer torus, exterior to the orbit of Io, occur at a rate comparable to the upper limit imposed by strong pitch angle diffusion; although the plasma wves responsible for such scattering have yet to be detected. This is by far the dominant process for removing energy from the inner Jovian magnetosphere, and it also provides a viable energy source for exciting intense Jovian auroral emissions. Charge exchange removal of equatorially trapped lower-energy (< or approx. =10 MeV/nuc G) heavy ions (e.g., O/sup +/ or S/sup +/) can become significant over a limited region near and just inside the orbit of lo, but this process appears to have little overall effect on the energetics of the Jovian system. The trapped particle distribution function in fact exhibits little evidence for effective loss inside the orbit of lo, presumably due to the absence of intense plasma waves. An equilibrium solution for the ion phase space density requires a pronounced increase in the rate of radial diffusion between the orbit of lo and the outer torus (L>7). In contrast, the diffusion rate near Io is substantially slower, D/sub L/L(Lapprox. =6)roughly-equal2 x 10-/sup 7/R/sub J//sup 2//s.

Thorne, R.M.

1982-10-01

133

Bulk Flows of Hot Plasma in the Jovian Magnetosphere: a Model of Anisotropic Fluxes of Energetic Ions  

NASA Astrophysics Data System (ADS)

Since the Ulysses flyby of Jupiter in February 1992, attempts to understand the bulk flows of hot plasma in the planet's magnetosphere have not given a consistent picture. The present study reports a comprehensive analysis of energetic particle anisotropies from the Ulysses mission. An empirical model has been developed which separates particle flow from particle gradient anisotropies. The model employs a multidimensional minimization routine to fit 13 free parameters simultaneously, using 98 measurements. The large number of independent measurements is possible because the Ulysses HI-SCALE instrument has nearly full angular coverage at high time resolution and moderately high angular resolution. The model uses the full energy-range (~50-3000 keV/nuc) of the low energy magnetic spectrometers and also the pure proton channels of the composition aperture on the instrument. Flow results are presented for analysis periods which included both the inbound and outbound trajectories of the spacecraft. Results from the inbound pass, which occurred in the late morning sector, show a persistent radial flow away from Jupiter. The azimuthal velocity component is in the sense of planetary rotation but generally is belong rigid corotation. This corotational flow component is greater near the plasma current sheet than at higher magnetic latitudes. Outbound, the flows in the high latitude duskside magnetosphere as inferred from the particle anisotropies indicate, surprisingly, sunward flows opposite to planetary rotation. Evidence of gradient anisotropies have also been found; these gradient anisotropies are present throughout the Jovian magnetosphere, but the convected anisotropies dominate any density gradients. A picture is presented, consistent with the model results, in which the global magnetic field configuration and flows of hot plasma are dominated by subcorotation at low latitudes but by sunward flow at high latitudes.

Hawkins, Samuel Edward, III

1998-07-01

134

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

135

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

SciTech Connect

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

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

2007-06-15

136

Observations of Reduced Electron Guyro-Scale Fluctuations in National Spherical Torus Experiment H-mode Plasmas with Large E x B Flow Shear.  

National Technical Information Service (NTIS)

Electron gyro-scale fluctuation measurements in National Spherical Torus Experiment (NSTX) H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in NSTX plas...

D. R. Smith E. Mazzucato H. K. Park R. E. Bell S. M. Kaye W. Lee

2009-01-01

137

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 Alfvn 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., Grard, 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

138

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

139

Plasma mass loading from the extended neutral gas torus of Enceladus as inferred from the observed plasma corotation lag  

NASA Astrophysics Data System (ADS)

At Saturn, significant plasma mass loading and radial transport occur together throughout the extended neutral torus, both producing corotation lags. We present a theory that depends upon the ratio of two classes of process: those injecting new mass (simple ionization) and those effectively removing momentum without changing plasma mass density (elastic ion-neutral collisions, like-species charge exchange). Both induce ionospheric torques, but only the former increases total outward mass flux. From an observed angular velocity, our model calculates the distribution of mass loading with radial distance. We present solutions based on Cassini Plasma Spectrometer measurements and theoretical chemistry models for Saturn's magnetosphere. We find a pronounced interaction peak near Enceladus' orbit and a broad ionization region between 5 and 8 Saturn radii (Rs). The total mass outflux at 8Rs is 100 kg/s (?/0.1 S), where ? is Saturn's ionospheric Pedersen conductance. The reported decrease in lag beyond 8Rs requires that ? ? const or reducing the total mass outflux.

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

2009-12-01

140

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 {beta} 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, Z{sub eff}, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and q{sub min}>1.0. Simulations show that noninductive sustained plasmas can be reached at I{sub P}=800 kA, B{sub T}=0.5 T, {kappa}{approx_equal}2.5, {beta}{sub N}{<=}5, {beta}{<=}15%, f{sub NI}=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high {beta} plasmas can be reached at I{sub P}=1.0 MA, B{sub T}=0.35 T, {kappa}{approx_equal}2.5, {beta}{sub N}{<=}9, {beta}{<=}43%, f{sub NI}=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 I{sub P} and low T{sub e} 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.; Kaye, S.M.; LeBlanc, B.P.; Menard, J.E.; Phillips, C.K.; Synakowski, E.J.; Taylor, G.; Wilson, R.; Harvey, R.W.; Mau, T.K.; Ryan, P.M.; Sabbagh, S.A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); CompX, Del Mar, California (United States); University of California, San Diego, California (United States); Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States); Columbia University, New York, New York (United States)

2006-05-15

141

Microwave radiation measurements near the electron plasma frequency of the NASA Lewis bumpy torus plasma  

NASA Technical Reports Server (NTRS)

Microwave emission near the electron plasma frequency was observed, and its relation to the average electron density and the dc toroidal magnetic field was examined. The emission was detected using a spectrum analyzer and a 50 omega miniature coaxial probe. The radiation appeared as a broad amplitude peak that shifted in frequency as the plasma parameters were varied. The observed radiation scanned an average plasma density ranging from 10 million/cu cm to 8 hundred million/cu cm. A linear relation was observed betweeen the density calculated from the emission frequency and the average plasma density measured with a microwave interferometer. With the aid of a relative density profile measurement of the plasma, it was determined that the emissions occurred from the outer periphery of the plasma.

Mallavarpu, R.; Roth, J. R.

1978-01-01

142

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

143

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

NASA Technical Reports Server (NTRS)

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

Barbosa, D. D.

1994-01-01

144

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

145

Low-energy charged particle observation in the 5--20 R/sub J/ region of the Jovian magnetosphere  

SciTech Connect

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

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

1981-09-30

146

Thermal ion flow in Saturn's inner magnetosphere measured by the Cassini plasma spectrometer: A signature of the Enceladus torus?  

NASA Astrophysics Data System (ADS)

For the middle and outer magnetosphere of Saturn (>5.5 RS), Cassini plasma spectrometer ion counting data provides thermal ion moments by assuming Maxwellian phase space density distributions for each ion species. However, in the inner magnetosphere (<5.5 RS) within Saturn's extended neutral cloud and proposed Enceladus torus, there is fresh ion production via charge exchange, yielding a complex ion velocity distribution. In this study, ion flow velocities in the inner region are obtained using the assumption that the ion phase space distributions are gyrotropic. Significantly sub-corotating ion flow velocities (75% of corotation) are found in the vicinity of the Enceladus orbit and the radial extent of the sub-corotation is about 1.0 RS, in reasonable agreement with the simulated radial dimension of the Enceladus torus.

Wilson, R. J.; Tokar, R. L.; Henderson, M. G.

2009-12-01

147

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

148

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

149

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

150

[Torus palatinus and torus mandibularis].  

PubMed

Lesions in the oral cavity due to protuberant bone growths known as hyperostosis, which in the oral cavity are found at the palate: torus palatinus (TP) and in the jaw area torus mandibularis (TM). PMID:15614303

Meza Flores, Jos Luis

2004-01-01

151

Electrostatic waves in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Observations by the plasma wave receivers on Voyagers 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are detected between higher harmonics of the electron gyrofrequency. Inside of about 23 Jupiter radii, electron cyclotron harmonic emissions appear to be durable features of the inner Jovian magnetosphere and are extremely well confined to the Jovian magnetic equator. The cyclotron emissions extend from just above the local electron gyrofrequency to the upper hybrid resonance frequency.

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

1980-01-01

152

Electrostatic waves in the Jovian magnetosphere  

SciTech Connect

Observations by the plasma wave receivers on Voyager 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are detected between higher harmonics of the electron gyrofrequency. Inside of about 23 R/sub J/, electron cyclotron harmonic emissions appear to be durable features of the inner Jovian magnetosphere and are extremely well confined to the Jovian magnetic equator. The cyclotron emissions extend from just above the local electron gyrofrequency to the upper hybrid resonance frequency.

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

1980-01-01

153

Possible in situ detection of K(2+) in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

During the Voyager 1 and 2 encounters with Jupiter in 1979 the positive ion composition of the cold thermal plasma in the Jovian plasma sheet and cold Io torus could be obtained when the plasma Mach number in the spacecraft rest frame was sufficiently large. Clear indication of an ionic species with a mass-to-charge ratio between 16 (O(+) and/or S(2+)) and 23 Na(+) is present in two spectra were acquired during apparent crossings of the plasma sheet in the middle magnetosphere. One interpretation is that the most likely identification of the ion is K(2+), even though there is no evidence in the data for K(+). Such an ion presence would be consistent with reports of neutral potassium associated with the Jovian system and originating at Io as well as with the identification of an ion with a similar mass-to-charge ratio at higher energies in the Ulysses data. An alternative interpretation is that the ion is a singly ionized molecular species associated with water products sputtered from Europa, a scenario which may also be consistent with the Ulysses data. However, other species present in the data and the low temperature favor the Iogenic potassium hypothesis.

Mcnutt, Ralph L, Jr.

1993-01-01

154

Observations of Reduced Electron Gyroscale Fluctuations in National Spherical Torus Experiment H-Mode Plasmas with Large ExB Flow Shear  

SciTech Connect

Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB 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 ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.

Smith, D. R.; Kaye, S. M.; Mazzucato, E.; Bell, R. E.; LeBlanc, B. P.; Menard, J. E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lee, W.; Park, H. K. [Pohang University of Science and Technology, 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 (United States); Levinton, F. M.; Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2009-06-05

155

Chandra X-Ray Observations of the Jovian System  

NASA Technical Reports Server (NTRS)

High-spatial resolution Chandra x-ray observations have demonstrated that most of Jupiter's northern auroral x-rays come from a hot spot located significantly poleward of the latitudes connected to the inner magnetosphere. This hot spot appears fixed in magnetic latitude and longitude and coincides with a region exhibiting anomalous ultraviolet and infrared emissions. The hot spot also exhibited approximately 45 minute quasi-periodic oscillations, a period similar to those reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft. These results invalidate the idea that jovian auroral x-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the x-rays appear to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths. The Chandra observations also revealed for the first time x-ray emission (about 0.1 GW) from the Io Plasma Torus, as well as very faint x-ray emission (about 1-2 MW) from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is almost certainly due to Kalpha emission of surface atoms (and possibly impact atoms) excited by the impact of highly energetic protons, oxygen, and sulfur atoms and ions from the Torus. The Torus emission is less well understood at present, although bremsstrahlung from the non-thermal tail of the electron distribution may provide a significant fraction. In any case, further observations, already accepted and in the process of being planned, with Chandra, some with the moderate energy resolution of the CCD camera, together with simultaneous Hubble Space Telescope observations and hopefully ground-based IRTF observations should soon provide greater insight into these various processes.

Elsner, R. F.; Waite, J. H.; Crary, F.; Majeed, T.; Gladstone, G. R.; Lewis, W. S.; Ford, P. G.; Howell, R. R.; Johnson, R. E.; Bhardwaj, A.; Six, N. Frank (Technical Monitor)

2002-01-01

156

Electrodynamic-Tether Magnetosphere Interaction From Capture to Low Jovian Orbit of its Spacecraft  

NASA Astrophysics Data System (ADS)

An orbiting conductive tether provides a dissipative mechanism in planets that have magnetic field and ionosphere/magnetosphere. The Jovian system is a particularly appropriate place for use of an electrodynamic tether because the magnetic field is intense, the stationary orbit is close to the planet, and moon Io provides a dense plasma torus farther away. The interaction of the tether with the magnetized plasma is analyzed under a variety of conditions, since the spacecraft is captured into an equatorial, highly elliptical orbit with perijove inside the stationary orbit, till the spacecraft reaches a low circular orbit around Jupiter, below the radiation belts. The radiation dose accumulated as the apojove distance is reduced through of sequence of perijove passes, is studied.

Sanmartin, J. R.; Charro, M.; Lorenzini, E. C.; Bombardelli, C.; Bramanti, C.

2007-12-01

157

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma  

NASA Technical Reports Server (NTRS)

Spectroscopic measurements have been 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

158

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

159

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

160

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

161

The Jovian aurora: Electron or ion precipitation  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

162

Jovian aurora: electron or ion precipitation  

SciTech Connect

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

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

1986-01-01

163

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

164

Gravity field of the Jovian system from Pioneer and Voyager tracking data  

NASA Astrophysics Data System (ADS)

Data sets from the Voyager and Pioneer flybys of Jupiter and the Galilean satellites are employed to characterize the Jovian magnetic field and the effects of the Io torus on transmissions. Both optical and Doppler radio data are considered, except for periods when the Jovian radiation environment disturbed the oscillator stability of the radio transmitters. Account is taken of small accelerations of the spacecraft by tidal forces of a single rising satellite, density differences in the Great Red Spot producing a columnar gravitational change, and three unknown objects in the inner Jovian system. Correction parameters are developed for the effects on the S-band data induced by the Jovian plasmasphere inwards from the Io torus. Calculations are then made of the planet and satellite masses, gravity harmonic coefficients, and orientation of the rotational pole. Large reductions in the uncertainties in previous mass estimates are obtained.

Campbell, J. K.; Synnott, S. P.

1985-02-01

165

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

SciTech Connect

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

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

2006-12-15

166

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

SciTech Connect

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

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

2008-09-22

167

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

SciTech Connect

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

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

2004-12-01

168

Spherical torus fusion reactor  

DOEpatents

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

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

1989-01-01

169

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

SciTech Connect

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

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

1988-01-01

170

The impact of comet Shoemaker-Levy 9 on the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

By the time of the impact of comet P/Shoemaker-Levy 9 with Jupiter, the freshly-broken surfaces of the accompanying rubble will have been outgassing for about two years, and will have produced an expanding and co-moving cloud of gas hundreds of R(sub J) across. Much of this gas, escaping from the cometary fragments at low (equal to or less than 1 km/s) speed, will arrive in the Jovian magnetopshere contemporaneously with the comet and drift through the magnetosphere. This gas, as it is photoionized, will be picked up primarily in the outer magnetosphere and the resulting high-energy ions should intensify magnetospheric processes, such as Io plasma torus and auroral emissions, that are thought to be powered by outer magnetospheric mass loading. If the composition of the comet is similar to that of P/Halley, the power available from mass loading should be comparable to that driving the aurora (10(exp 14) W) and at least an order of magnitude larger than that exciting the plasma torus for several weeks or months. Measurement of these emissions during and after the cometary encounter may constrain the mechanisms for energization of magnetospheric charged particle populations and magnetospheric transport processes.

Herbert, Floyd

1994-01-01

171

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

NASA Astrophysics Data System (ADS)

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

Gerard, Jean-Claude

2012-07-01

172

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

173

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

174

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

175

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

National Technical Information Service (NTIS)

The low aspect ratio, low magnetic field, and wide range of plasma beta of NSTX plasmas provide new insight into the origins and effects of magnetic field errors. An extensive array of magnetic sensors has been used to analyze error fields, to measure err...

J. K. Park R. E. Bell S. P. Gerhardt

2010-01-01

176

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas.  

National Technical Information Service (NTIS)

Use of a large-area liquid lithium surface as a first wall has significantly improved the plasma performance in the Current Drive Experiment-Upgrade (CDX-U) at the Princeton Plasma Physics Laboratory. Previous CDX-U experiments with a partially-covered to...

R. Kaita R. Majeski M. Boaz P. Efthimion G. Gettelfinger

2004-01-01

177

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

178

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

179

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas  

SciTech Connect

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

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

2004-06-03

180

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas  

SciTech Connect

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

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

2004-06-07

181

Progress in understanding error-field physics in NSTX spherical torus plasmas  

SciTech Connect

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

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

2010-01-01

182

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

SciTech Connect

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.

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

1983-07-01

183

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

SciTech Connect

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

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

1986-08-22

184

Three-Barrel Repeating Pneumatic Pellet Injector for Plasma Fueling of the Joint European Torus.  

National Technical Information Service (NTIS)

Pellet fueling, the injection of frozen hydrogen isotope pellets at high velocity, has been used to improve plasma performance in various tokamak experiments. In one recent experiment, the repeating pneumatic hydrogen pellet injector was used on the Tokam...

S. K. Combs S. L. Milora L. R. Baylor C. R. Foust F. E. Gethers

1987-01-01

185

Effects of Large Area Liquid Lithium Limiters on Spherical Torus Plasmas  

Microsoft Academic Search

Use of a large-area liquid lithium surface as a first wall has significantly improved the plasma performance in the Current Drive Experiment-Upgrade (CDX-U) at the Princeton Plasma Physics Laboratory. Previous CDX-U experiments with a partially-covered toroidal lithium limiter tray have shown a decrease in impurities and the recycling of hydrogenic species. Improvements in loading techniques have permitted nearly full coverage

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

2004-01-01

186

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

SciTech Connect

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

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

2011-05-15

187

Use of activation techniques for the measurement of neutron yields from deuterium plasmas at the Joint European Torus  

SciTech Connect

This paper reports on the time dependence of the 2.5-MeV neutron emission from the Joint European Torus (JET) which is reliably measured using fission chambers. The absolute calibration of these chambers is required to an accuracy of 10% or better for a range of intensities that may cover six or more decades. At JET, this calibration is now achieved by use of activation techniques, the most convenient of which involves fissionable materials (thorium and uranium) and delayed neutron counting. Because delayed neutron counting is unfamiliar in the fusion community, particular care is taken to obtain confirmation of the results based on this method by comparison with measurements made using the conventional activation procedure (involving indium, nickel, and zinc as target materials). As the activation measurements can be influenced appreciably by the weak emission of 14-MeV neutrons, this contribution is measured separately using high threshold energy activation reactions (in copper and silicon). Neutron transport calculations are employed to relate the measured local fluences of both 2.5- and 14-MeV neutrons to the total yields from the plasma. Absolute calibration accuracies of 6 and 8% are claimed for 2.5- and 14-MeV neutron yields, respectively; the accuracy of the 14-MeV to 2.5-MeV yield ratios is 6%.

Jarvis, O.N.; Clipsham, E.W.; Hone, M.A.; Laundy, B.J.; Sadler, G.J.; van Belle, P. (JET Joint Undertaking, Abingdon (United Kingdom)); Pillon, M.; Rapisarda, M. (Associazione Euratom-ENEA, Nuclear Research Centre, Frascati (IT)); Verschuur, K.A. (ECN, Petten (NL))

1991-11-01

188

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

189

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

190

Stellar and Jovian vortices  

SciTech Connect

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

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

1990-12-01

191

Influence of plasma diagnostics and constraints on the quality of equilibrium reconstructions on Joint European Torus  

SciTech Connect

One of the main approaches to thermonuclear fusion relies on confining high temperature plasmas with properly shaped magnetic fields. The determination of the magnetic topology is, therefore, essential for controlling the experiments and for achieving the required performance. In Tokamaks, the reconstruction of the fields is typically formulated as a free boundary equilibrium problem, described by the Grad-Shafranov equation in toroidal geometry and axisymmetric configurations. Unfortunately, this results in mathematically very ill posed problems and, therefore, the quality of the equilibrium reconstructions depends sensitively on the measurements used as inputs and on the imposed constraints. In this paper, it is shown how the different diagnostics (Magnetics Measurements, Polarimetry and Motional Stark Effect), together with the edge current density and plasma pressure constraints, can have a significant impact on the quality of the equilibrium on JET. Results show that both the Polarimetry and Motional Stark Effect internal diagnostics are crucial in order to obtain reasonable safety factor profiles. The impact of the edge current density constraint is significant when the plasma is in the H-mode of confinement. In this plasma scenario the strike point positions and the plasma last closed flux surface can change even by centimetres, depending on the edge constraints, with a significant impact on the remapping of the equilibrium-dependent diagnostics and of pedestal physics studies. On the other hand and quite counter intuitively, the pressure constraint can severely affect the quality of the magnetic reconstructions in the core. These trends have been verified with several JET discharges and consistent results have been found. An interpretation of these results, as interplay between degrees of freedom and available measurements, is provided. The systematic analysis described in the paper emphasizes the importance of having sufficient diagnostic inputs and of properly validating the results of the codes with independent measurements.

Gelfusa, M.; Gaudio, P.; Peluso, E. [Associazione EURATOM-ENEA, University of Rome Tor Vergata, Roma (Italy)] [Associazione EURATOM-ENEA, University of Rome Tor Vergata, Roma (Italy); Murari, A.; Baruzzo, M. [Consorzio RFX-Associazione EURATOM ENEA per la Fusione, I-35127 Padova (Italy)] [Consorzio RFX-Associazione EURATOM ENEA per la Fusione, I-35127 Padova (Italy); Lupelli, I.; Hawkes, N.; Brix, M.; Drozdov, V.; Meigs, A.; Romanelli, M. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)] [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Craciunescu, T. [EURATOM-MEdC Association, NILPRP, Bucharest (Romania)] [EURATOM-MEdC Association, NILPRP, Bucharest (Romania); Schmuck, S.; Sieglin, B. [Max-Planck-Institut fr Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstr.1, 17491 Greifswald (Germany)] [Max-Planck-Institut fr Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstr.1, 17491 Greifswald (Germany); Collaboration: JET-EFDA Contributors

2013-10-15

192

An Overview of Electrodynamic Tether Performance in the Jovian System  

NASA Technical Reports Server (NTRS)

The Jovian magnetosphere with its strong magnetic field and the rapid rotation of the planet present new opportunities and challenges for the use of electrodynamic tethers. An overview of the basic plasma physics properties of an electrodynamic tether moving through the Jovian magnetosphere is examined. Tether use for both propulsion and power generation are considered. Close to the planet, tether propulsive forces are found to be as high as 50 Newtons and power levels as high as 1 million Watts.

Gallagher, D. L.; Bagenal, F.; Moore, J.; Johnson, L.

1998-01-01

193

An Overview of Electrodynamic Tether Performance in the Jovian System  

NASA Technical Reports Server (NTRS)

The Jovian magnetosphere with its strong magnetic field and rapid planetary rotation present new opportunities and challenges for the use of electrodynamic tethers. An overview of the basic plasma physics properties of an electrodynamic tether moving through the Jovian magnetosphere is examined. Tether use for both propulsion and power generation are considered. Close to the planet, tether propulsive forces are found to be as high as 50 Newtons and power levels as high as 1 million Watts.

Gallagher, Dennis; Johnson, Les; Bagenal, Fran; Moore, James

1998-01-01

194

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

NASA Technical Reports Server (NTRS)

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

Tan, A.

1990-01-01

195

The Jovian aurora: Electron or ion precipitation  

SciTech Connect

High signal-to-noise spectra of the Jovian aurora at UV wavelengths obtained using the International Ultraviolet Explorer Observatory (including the brightest Jovian aurora observed to date) are used to study the existence of sulfur and oxygen emissions which would be associated with the precipitation of energetic heavy ions in the upper Jovian atmosphere. Model calculations of heavy ion precipitation and corresponding estimates of the associated sulfur and oxygen UV emissions carried out in the preceding companion paper of Horanyi et al. suggest emission values for 1,304-{angstrom} O I emission that are at least 50 times larger than the upper limit values set by the IUE observations reported here. On the other hand a possible emission feature of S II at 1,256 {angstrom} is comparable to the theoretically predicted emission intensity. Earlier X ray observations and in situ plasma observations have indicated the existence of energetic heavy ion precipitation in the Jovian auroral zone. Based on the IUE observations reported here, the authors suggest a scenario where heavy ion auroral energy deposition is concentrated at altitudes below the homopause (i.e. > 300 keV/nucleon) and electrons with energies of 10 to 30 keV are responsible for the bulk of the observable UV and EUV emissions since they deposit their energy above the methane-absorbing layer defined by the homopause.

Waite, J.H., Jr. (NASA Marshall Space Flight Center, Huntsville, AL (USA)); Clarke, J.T. (NASA Goddard Space Flight Center, Greenbelt, MD (USA)); Cravens, T.E. (Univ. of Michigan, Ann Arbor (USA)); Hammond, C.M. (Univ. of California, Los Angeles (USA))

1988-07-01

196

Pioneer 10 and 11 (Jupiter and Saturn) magnetometer experiment. [interaction of a flowing plasma with Titan and the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The interaction of a flowing plasma with Titan was studied. A Monte carlo simulation method is planned for the determination of the average flow field and pressure/temperature variations about Titan. Jupiter's magnetic field was also studied. Polynomial expressions describing this magnetic field are discussed briefly.

Jones, D. E.

1984-01-01

197

Interplanetary modulation and transport of Jovian electrons  

Microsoft Academic Search

Simultaneous measurements by Pioneer 11 of the 3- to 6-MeV Jovian electron flux, interplanetary magnetic field magnitude, and solar wind speed during the pre-Jupiter encounter period reveal that electron transport across the average field direction was greatly inhibited in corotating interaction regions (CIR's) and enhanced in rarefaction regions. Since CIR's are regions of compressed solar wind plasma, these results suggest

T. F. Conlon

1978-01-01

198

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

199

Bulk flows of hot plasma in the Jovian magnetosphere: A model of anisotropic fluxes of energetic ions  

NASA Astrophysics Data System (ADS)

Since the Ulysses flyby of Jupiter in February 1992, a consistent picture of the bulk flows of hot plasma has yet to be formed. The present study reports a comprehensive analysis of energetic particle anisotropies from the Ulysses mission. We present an empirical model which separates flow from gradient anisotropies. The model employs a multidimensional minimization routine to fit simultaneously 13 free parameters using 98 measurements. The large number of independent measurements is possible because the Ulysses Heliosphere Instrument for Spectra, Composition, and Anisotropy at Low Energy (HI-SCALE) has nearly full angular coverage at high time resolution and moderately high angular resolution. The model uses the full energy range (~50-3000 keV) of the low-energy magnetic spectrometers and also the pure proton channels of the composition aperture on the instrument. We present flow results during the inbound pass of Ulysses in which the radial velocity component shows a persistent radial outflow. The azimuthal component is in the sense of planetary rotation but generally below rigid corotation, and the azimuthal velocity is greater near the plasma current sheet than at higher magnetic latitudes. Outbound, the flows in the high-latitude duskside magnetosphere inferred from the particle anisotropies indicate, surprisingly, sunward flows opposite to planetary rotation. We find evidence of gradient anisotropies especially near the magnetospheric current sheet on the dayside. We present a picture of the global magnetic field configuration and flows of hot plasma, consistent with our model results, dominated by subcorotation at low latitudes but by sunward flow at high latitudes.

Hawkins, S. Edward; Cheng, Andrew F.; Lanzerotti, Louis J.

1998-09-01

200

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

201

Energetic particles in the jovian magnetotail.  

PubMed

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

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

2007-10-12

202

Plasma waves and continuum radiation in planetary magnetospheres  

NASA Technical Reports Server (NTRS)

Observations of whistler and Bernstein waves at the earth, Jupiter, and Saturn are discussed, as well as nonthermal continuum radiation which is common to the magnetospheres of these planets. Whistler mode waves and electron cyclotron harmonic emissions are examined in detail, with the purpose of understanding the interaction of these waves with the dynamics of the plasma electrons. Emphasis is placed on the occurrence and characteristics of the Jovian whistler mode chorus and the interactions with the plasma in and near the Io torus.

Kurth, W. S.

1986-01-01

203

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

204

Jovian type III radio bursts  

SciTech Connect

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. (Univ. of Iowa, Iowa City (USA)); Scarf, F.L. (TRW Space and Technology Group, Redondo Beach, CA (USA))

1989-06-01

205

Energetic oxygen and sulfur in the Jovian magnetosphere  

SciTech Connect

This paper reports measurements made by the cosmic ray subsystem onboard Voyager 1 and 2 in the Jovian magnetosphere. Energy spectra of oxygen ions in the energy range 1--20 MeV/nuc between 5 and 20 R/sub J/ are presented and used to calculate phase space densities. There is a steep positive radial gradient in the phase space density of the energetic oxygen ions in this region, indicating an inward diffusive flow. Solutions of the diffusion equation assuming a diffusion coefficient D and loss lifetime tau of the forms D = D/sub 0/L/sup n/ and tau = tau/sub 0/L/sup m/, where D/sub 0/, tau/sub 0/, n, and m are constants, and L is the McIlwain parameter, are fit to the radial phase space density profile of oxygen ions with magnetic moments of 680 MeV/nuc-G. The best fits are found to have n+mroughly-equal6 and 3400 MeV/nuc-G diffuse inward across 10 R/sub J/ is 5 x 10/sup 21plus-or-minus1/ ions s/sup -1/. The observations suggest that oxygen and sulfur ions in the Io plasma torus diffuse radially outward, are nonadiabatically accelerated in some region outside 17 R/sub J/ and then diffuse inward and outward from the acceleration region.

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

1981-10-01

206

Time-variable phenomena in the Jovian system  

SciTech Connect

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, M.J.S.; West, R.A.; Rahe, J.; Pereyda, M.

1989-01-01

207

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

208

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

NASA Astrophysics Data System (ADS)

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) 1019 m-3 to 1 1019 m-3. Deuterium spheromak formation is possible with density as low as 2 1018 m-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.; Firman, Taylor; Jarboe, Thomas R.; Prager, James R.; Victor, Brian S.; Wrobel, Jonathan S.; Ziemba, Timothy

2013-10-01

209

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 (23) 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

210

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

211

Variability in the Io torus as observed by Cassini UVIS  

Microsoft Academic Search

We present observations of the Io torus made by the Cassini Ultraviolet Imaging Spectrograph (UVIS) during the first half (4-Oct-2000-14-Nov-2000) of the inbound leg of the Cassini Jupiter flyby. During this period, 49 rotations of the Jovian magnetosphere were observed, resulting in nearly 2000 spectra, covering a wavelength range of 561-1182. The UVIS field of view encompasses the entire Io

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

2003-01-01

212

Satellite Atmosphere and Io Torus Observations  

NASA Technical Reports Server (NTRS)

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

Schneider, Nicholas

2004-01-01

213

Energetic oxygen and sulfur ions in the Jovian magnetosphere  

SciTech Connect

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

214

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

215

Energetic particle bursts in the predawn Jovian magnetotail  

Microsoft Academic Search

From September to October 1996 the Galileo spacecraft crossed through the distant predawn tail region of the Jovian magnetosphere. The Energetic Particles Detector (EPD) onboard Galileo recorded a series of energetic particle flow bursts in the region beyond 80RJ to the apojove at 113RJ. The events are similar in nature to an event observed with the hot plasma instrument (LECP)

N. Krupp; J. Woch; A. Lagg; B. Wilken; S. Livi; D. J. Williams

1998-01-01

216

Electrodynamic Tethers for Jovian Exploration  

NASA Technical Reports Server (NTRS)

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

2004-01-01

217

Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation). Annual report No. 2  

SciTech Connect

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

Tan, A.

1990-10-01

218

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

219

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

SciTech Connect

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

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

1999-11-01

220

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

221

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

222

Jovian Aurora: Electron or Ion Precipitation.  

National Technical Information Service (NTIS)

High signal-to-noise spectra of the Jovian aurora at UV wavelengths obtained using the International Ultraviolet Explorer Observatory (including the brightest Jovian aurora observed to date) set strigent upper limits for sulfur and oxygen emissions, which...

J. H. Waite J. T. Clarke T. E. Cravens

1986-01-01

223

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

NASA Astrophysics Data System (ADS)

LAPLACE (ESA-JAXA joint mission for the Jovian system) was selected as one of future ESA scientific missions Cosmic Vision in October 2007. LAPLACE is a mission with three spacecrafts aiming at coordinated observations of Jovian satellites and the magnetosphere, atmosphere and interior of Jupiter. An orbiter around Europa or Ganymede is involved. There is a possibility that JAXA (Japan Aerospace Exploration Agency) will take a role on the magnetosphere spinner. Japanese scientists working on the origin and evolution of Jupiter, satellite evolution, and astrobiology have been participating in the LAPLACE working group in Japan. Detailed observation of Jovian satellites Europa, Ganymede, Callisto and Io as well as smaller satellites such as Amalthea would be important also for the study of the origin of Jovian system. Resurfacing processes on Europa and Ganymede should be studied to know the properties of the internal oceans. The processes can be investigated by infrared observation for salt minerals and amorphous/crystal ices. Not only the thickness of icy crust of Europa but also thickness of the ocean and its bottom topography should be important targets, which would be investigated by gravity and magnetism measurements. For both Europa and Ganymede, the surface layering and structure of icy crust should be an interesting geological target, which will be clarified by subsurface radar. In Japan, KAGUYA is observing the Moon, and Venus remote sensing mission (PLANET-C) and Mercury mission Bepi Colombo will be launched in 2011 and 2013, respectively. Several instruments such as cameras, spectrometers, a laser altimeter, a radar, a magnetometer, plasma instruments, and a dust detector should come from the heritage of instruments on board KAGUYA, PLANET-C, and BepiColombo.

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

224

The Jovian aurora: Electron or ion precipitation  

Microsoft Academic Search

High signal-to-noise spectra of the Jovian aurora at UV wavelengths obtained using the International Ultraviolet Explorer Observatory (including the brightest Jovian aurora observed to date) are used to study the existence of sulfur and oxygen emissions which would be associated with the precipitation of energetic heavy ions in the upper Jovian atmosphere. Model calculations of heavy ion precipitation and corresponding

Waite J. H. Jr; J. T. Clarke; T. E. Cravens; C. M. Hammond

1988-01-01

225

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

226

Catastrophies in the Elmo Bumpy Torus  

Microsoft Academic Search

Experimentally it is observed that the plasma in Elmo Bumpy Torus (EBT) shows discontinuous changes in the electron line density, electron and ion temperatures and fluctuation levels as the ambient gas pressure or electron cyclotron heating is varied continuously. We use the Point Model of Hedrick et al. for the toroidal core plasma in EBT. The Point Model is not

Alkesh Ramprakash Punjabi

1983-01-01

227

Ion anisotropies in the outer Jovian magnetosphere  

SciTech Connect

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

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

1981-09-30

228

Limit on Rotational Energy Available to Excite Jovian Aurora  

Microsoft Academic Search

There is a fundamental relationship between the power that is extracted from Jupiter's rotation to drive magnetospheric processes and the rate at which mass is injected into the Io plasma torus. Half of this power is consumed by bulk motion of the plasma and the other half represents an upper limit on the energy from rotation available for dissipation and

Aharon Eviatar; G. L. Siscoe

1980-01-01

229

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

230

The electromagnetic ion cyclotron instability in the Io torus  

SciTech Connect

The electromagnetic ion cyclotron waves which are expected to exist in the Jovian magnetosphere are investigated. The temperature anisotropy generated by the inward radial diffusion of hot ions gives rise to an instability of L mode waves in the off-equatorial region of the Io torus. The resulting pitch angle scattering has been suggested as the cause for the precipitation of ions into the loss cone and auroral excitation. The linear wave dispersion is first examined, and the nonlinear wave amplitude for the saturated state is studied. Two estimates of the wave saturation level are checked by performing an electromagnetic hybrid simulation. Estimated nonlinear saturation amplitudes are compared with those resulting from linear amplification in a finite length. The result shows that the waves in the Jovian magnetosphere produced by the hot protons are mostly in a linear regime.

Machida, S.; Goertz, C.K. (Univ. of Iowa, Iowa City (USA)); Hada, T. (Univ. of California, Los Angeles (USA))

1988-07-01

231

The electromagnetic ion cyclotron instability in the Io torus  

NASA Technical Reports Server (NTRS)

The electromagnetic ion cyclotron waves which are expected to exist in the Jovian magnetosphere are investigated. The temperature anisotropy generated by the inward radial diffusion of hot ions gives rise to an instability of L mode waves in the off-equatorial region of the Io torus. The resulting pitch angle scattering has been suggested as the cause for the precipitation of ions into the loss cone and auroral excitation. The linear wave dispersion is first examined, and the nonlinear wave amplitude for the saturated state is studied. Two estimates of the wave saturation level are checked by performing an electromagnetic hybrid simulation. Estimated nonlinear saturation amplitudes are compared with those resulting from linear amplification in a finite length. The result shows that the waves in the Jovian magnetosphere produced by the hot protons are mostly in a linear regime.

Machida, S.; Goertz, C. K.; Hada, T.

1988-01-01

232

The interplanetary modulation and transport of Jovian electrons  

NASA Technical Reports Server (NTRS)

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

Conlon, T. F.

1978-01-01

233

PARIS to Hektor, A Mission to the Jovian Trojan Asteroids  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

234

Models of Electron Energetics in the Enceladus Torus  

Microsoft Academic Search

The inner magnetosphere of Saturn contains a mixture of plasma and neutral gas, the dominant source of which is the icy satellite Enceladus. Water vapor and water dissociation products are present throughout the magnetosphere but they are particularly concentrated in a torus surrounding Saturn at the orbit of Enceladus. The Hubble Space Telescope observed OH in the torus and other

T. E. Cravens; N. Ozak; M. S. Richard; I. P. Robertson; M. E. Perry; M. E. Campbell

2010-01-01

235

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

PubMed

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. PMID:24784606

Cazzaniga, C; Sundn, E Andersson; Binda, F; Croci, G; Ericsson, G; Giacomelli, L; Gorini, G; Griesmayer, E; Grosso, G; Kaveney, G; Nocente, M; Cippo, E Perelli; Rebai, M; Syme, B; Tardocchi, M

2014-04-01

236

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

National Technical Information Service (NTIS)

The implementation of the rtEFIT-isoflux algorithm in the digital control system for NSTX has led to improved ability to control the plasma shape. In particular, it has been essential for good gap control for radio-frequency experiments, for control of dr...

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

2004-01-01

237

Quasi-periodic modulations of the Jovian magnetotail  

Microsoft Academic Search

Measurements with the Energetic Particles Detector (EPD) on Galileo orbit C9 in the Jovian magnetotail revealed the existence of distinct quasi-periodic variations of energetic ion intensities which are superimposed on the well-known 10-hour modulations due to the planetary rotation. The intensity variations are associated with changes of the particle energy spectra and the plasma flow pattern. They are clearly of

J. Woch; N. Krupp; A. Lagg; B. Wilken; S. Livi; D. J. Williams

1998-01-01

238

Periodic amplitude variations in Jovian continuum radiation  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

239

Periodic amplitude variations in Jovian continuum radiation  

SciTech Connect

An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both 5 and 10 hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by the position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude solar-wind alignment to the amplitude of the continuum radiation implies that the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clock-like modulation of energetic electron fluxes from Jupiter.

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

1986-12-01

240

National Spherical Torus Experiment (NSTX)  

SciTech Connect

The main aim of National Spherical Torus Experiment (NSTX) is to establish the fusion physics principles of the innovative spherical torus (ST) concept. Physics outcome of the NSTX research program is relevant to near-term applications such as the Volume Neutron Source (VNS) and burning plasmas, and future applications such as the pilot and power plants. The NSTX device began plasma operations in February 1999 and the plasma current was successfully ramped up to the design value of 1 million amperes (MA) on December 14, 1999. The CHI (Coaxial Helicity Injection) and HHFW (High Harmonic Fast Wave) experiments have also started. Stable CHI discharges of up to 133 kA and 130-msec duration have been produced using 20 kA of injected current. Using eight antennas connected to two transmitters, up to 2 MW of HHFW power was successfully coupled to the plasma. The Neutral-beam Injection (NBI) heating system and associated NBI-based diagnostics such as the Charge-exchange Recombination Spectrometer (CHERS) will be operational in October 2000.

Masayuki Ono

2000-04-22

241

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

242

Theory of the Io phase asymmetry of the Jovian decametric radiation  

SciTech Connect

We propose an explanation of an asymmetry in the occurrence probability of the Io-dependent Jovian decametric radiation. We find that this asymmetry arises because when Io is in the northern part of the torus, more intense Alfven waves are generated propagating southward than northward. These waves then cause the excitation of decametric radiation in the northern ionosphere after reflection from the southern ionosphere. The asymmetry then results from the propagation time of the Alfven wave and the bending of the magnetic field (Alfven wing) along this trajectory. The ray paths of the decametric radiation are calculated using a three-dimensional ray-tracing program in the Jovian ionosphere. Variations in the expected probability plots are computed for two models of the Jovian ionosphere and global magnetic field, as well as for several choices of the ratio of the radiated frequency to the X mode cutoff frequency. The dependence of the occurrence probability on the Jovian declination of the earth is also discussed in the context of this model.

Hashimoto, K.; Goldstein, M.L.

1983-03-01

243

Plasma waves and continuum radiation in planetary magnetospheres  

NASA Technical Reports Server (NTRS)

Voyager data on whistler mode waves and electron cyclotron harmonic emissions are analyzed to understand the interaction of the waves with the dynamics of the electrons. The occurrence and characteristics of Jovian whistler mode chorus and the interactions with the plasma in and near the Io torus are emphasized. Bernstein waves, especially those near the upper hybrid or plasma frequency are discussed to provide insight into an important plasma diagnostic tool and to compare the relevant portions of the electron distribution function at Earth, Jupiter, and Saturn. The nonthermal continuum radiation common to the magnetospheres of Earth, Jupiter, and Saturn is considered. Because of the very low frequency of these radio waves and their close association with upper hybrid resonance emissions, continuum radiation is often associated more closely with the plasma wave spectrum of a planetary magnetosphere than with the planet's radio spectrum.

Kurth, W. S.

1986-01-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

245

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

246

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

247

Hybrid simulation of comet Shoemaker-Levy 9 interaction with Jovian bow shock  

NASA Technical Reports Server (NTRS)

The interaction of the solar wind with comet Shoemaker-Levy 9 leading to the formation of the cometary magnetosphere and its interaction with the Jovian bow shock is simulated using a one dimensional hybrid code. The mass loading of the solar wind by the cometary ions leads to the formation of a bow shock behind which the plasma density is 2-3/cu cm and the electron temperature is 4 eV. The interaction of this system with the Jovian bow shock yields local enhancements of the magnetic field and the plasma density by factors of 4-5 and the electron temperature by 2-3.

Lipatov, A. S.; Sharma, A. S.

1994-01-01

248

Thin current sheets in the Jovian magnetotail  

NASA Astrophysics Data System (ADS)

In this paper we investigate the fine structure of the current sheet located at the dawn side (and the central region) of the Jovian magnetotail (magnetodisk). We consider observational data collected by Galileo spacecraft (our dataset includes 226 current sheet crossings). Measurements of spectra of electric field fluctuations allow us to estimate the electron density. The plasma temperature is estimated from the vertical stress balance in the current sheet. To determine the vertical structure of the current sheet we use magnetic field measurements and the model of the neutral plane vertical motion. The current sheet vertical structure includes two spatial scales: the thin current sheet with the thickness around two Larmor radii of thermal sulfur ions is embedded into the thick current sheet with the thickness around one Jupiter radius, RJ. The vertical stress balance in the thin current sheet can be partially supported by the local maximum of the shear magnetic field. The amplitude of the corresponding field-aligned current density is comparable with the amplitude of the total current density. The drop of the plasma (electron) density across the thick current sheet is about 50-80% of the density peak value. We investigate horizontal (along the tail) distributions of magnetic field amplitudes B0 measured at the boundary of the current sheet and magnitudes of the normal component measured in the vicinity of the central region, Bn0. For r>50RJ both B0 and Bn0 vary with the radial distance r as ~r-1, and the ratio Bn0/B0~0.05-0.2 is almost constant along the tail (up to 120RJ). The amplitude of the current density jm0 and the plasma (electron) density (averaged across the current sheet) decrease with the same rate ~r-1. Thus, the current bulk velocity vD=jm0/e?100 km/s is almost constant along the tail. We compare properties of the Jovian magnetotail current sheet with the corresponding properties of current sheets observed in the Earth?s magnetotail. Current sheet (CS) in the Jupiter magnetotail has been investigated. The magnetotail includes thin CS (thickness <0.25RJ) and thick CS (thickness ~1RJ). Thin CS thickness is only about two Larmor radius of thermal sulfur ions. Current density in thin CS cannot be described by diamagnetic currents.

Artemyev, A. V.; Vasko, I. Y.; Kasahara, S.

2014-06-01

249

Rotational anisotropy of the Jovian magnetosphere at high latitudes  

NASA Astrophysics Data System (ADS)

The Ulysses spacecraft passed through the Jovian system in February 1992. Its trajectory, determined by its interplanetary mission, directed the spacecraft to the previously unexplored high-latitude regions of the Jovian magnetosphere. Like Pioneers 10 and 11 and the two Voyagers, Ulysses entered the magnetosphere in the near equatorial morning sector, but unlike the previous spacecraft, Ulysses exited at high latitude near local dusk. This report considerably extends the work of Lanzerotti et al. (1993) by analyzing the extent of rotational anisotropy at high southern Jovigraphic latitudes attained by Ulysses during its outbound pass. Using data acquired by the Ulysses Heliosphere Instrument for Spectral, Composition, and Anisotropy at Low Energies (HI-SCALE), we report some evidence of corotational flow in the high-latitude duskside magnetosphere. On the inbound pass the Ulysses HI-SCALE instrument observed anisotropies indicating partial corotation and a corotation lag. These data are consistent with Voyager plasma and energetic particle results. This is the first report of flow in the corotational direction from 44-57 RJ in the duskside, high-latitude Jovian magnetosphere. There is strong evidence for a substantially reduced corotational anisotropy in this duskside region relative to a comparable radial distance range, 47-59 RJ, on the dayside.

Hawkins, S. E.; Cheng, A. F.; Lanzerotti, L. J.; Maclennan, C. G.

1995-08-01

250

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

251

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

252

Joule heating of the Jovian ionosphere by corotation enforcement currents  

SciTech Connect

Heat is deposited to the Jovian ionosphere in the course of enforcement of corotation to the outer magnetosphere. The Joule heating rate is estimated for several possible causes of departure from the corotation by making use of a simple model of the magnetodisc. Following compression or expansion of the magnetosphere, the magnetospheric plasma superrotates or subrotates in consequence of conservation of the angular momentum, and thermal energy is deposited in the ionosphere at a rate of the order of 10/sup 12/ W for about 10/sup 5/ s while rotational speed is adjusted toward the corotation with the planet. Outward diffisuion of the Iogenic plasma at a rate of 10/sup 29/ amu/s also causes ionospheric heating at a rate of 10/sup 13/ W as the ionosphere acts to drive the plasma toward the corotation. Day-night asymmetry in trajectory of rotational motion of plasma, owing to asymmetry in configuration of the magnetosphere, is also likely to produce energy dissipation of a similar magnitude as the rotational speed is adjusted continually. Thus the corotation enforcement current deposits as much heat as the dynamo current from Io and plays an important part in energetics and dynamics of the Jovian magnetosphere. The heating rate per unit area of the high-latitude ionosphere is more than approx.10 erg/cm/sup 2/ s, namely, orders of magnitude greater than the rate of the energy supply by the solar UV radiation. These numbers depend on the adopted height-integrated conductivity of 0.1 mho of the Jovian ionosphere.

Nishida, A.; Watanabe, Y.

1981-11-01

253

Theory of Jovian decameter radiation  

SciTech Connect

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, we make a random phase approximation 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.; Papadopoulos, K.; Ben-Ari, M.; Eviatar, A.

1983-02-01

254

Computation of Three Dimensional Tokamak and Spherical Torus Equilibria  

SciTech Connect

A nominally axisymmetric plasma con?guration, such as a tokamak or a spherical torus, is highly sensitive to non-axisymmetric magnetic perturbations due to currents outside of the plasma. The high sensitivity means that the primary interest is in the response of the plasma to very small perturbations, | ?(over) ?/?(over)? | ? 102 to 104, which can be calculated using the theory of perturbed equilibria. The Ideal Perturbed Equilibrium Code (IPEC) is described and applied to the study of the plasma response in a spherical torus to such external perturbations.

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

2007-05-07

255

Corotation lag of the Jovian atmosphere, ionosphere, and magnetosphere  

SciTech Connect

The authors modify the Jovian ionosphere-magnetosphere coupling model presented by Hill (1979) to include rotational slippage of the neutral atmosphere at ionospheric heights, relative to a frame of reference corotating rigidly with Jupiter. In the modified model, as altitude increases, the drift velocities of neutrals and ions relative to the corotating frame increase from zero at the bottom of the ionosphere to their respective maximum values at the top, and the corotation lag of the magnetosphere is enhanced for a given rate of mass loading of the magnetosphere. The height variations of the drift velocities of neutrals and ions in the ionosphere and the enhancement factor for the corotation lag of the magnetosphere are related to the atmospheric eddy diffusion coefficient at ionospheric heights. On the basis of ionospheric properties deduced from measurements of Pioneer 11, Voyager 1, and Voyager 2, they derive height profiles of ion and neutral drift speed for various possible values of the eddy diffusion coefficient. If they accept the ion injection rate from Io (10{sup 29} ions/s) and the ion transport rate through the Jovian magnetosphere (3 {times} 10{sup 28} ions/s), corresponding to the observed values of the corotation lag of the Io torus ({delta}{omega}{sub I} = 0.04{omega}{sub j}) and the critical distance for magnetospheric corotation (L{sub 0} = 20), respectively, the effective ionospheric conductance is reduced by a factor of the order of 10, resulting in an enhanced corotation lag, for a given rate of mass loading, by the same factor compared to earlier models. The eddy diffusion coefficient in the high-latitude ionosphere is inferred to be {approximately} 10{sup 13} n{sub n}{sup {minus}1/2}m{sup 1/2}/s, or about a factor of 20 larger than the value inferred from Voyager measurements at near-equatorial latitudes.

Huang, T.S.; Hill, T.W. (Rice Univ., Houston, TX (USA))

1989-04-01

256

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

257

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

258

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

259

The Magnetic-Anomaly Model of the Jovian Magnetosphere: A Post-Voyager Assessment  

Microsoft Academic Search

We reexamine the three predictions that we previously put forth 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), taking into account the Voyager and other recent observations. Concerning the prediction of a restricted longitude range of

V. M. Vasyliunas; A. J. Dessler

1981-01-01

260

Elmo Bumpy Torus Reactor.  

National Technical Information Service (NTIS)

In the Elmo Bumpy Torus Reactor (EBTR) study the feasibility of achieving a fusion power plant based on the EBT confinement concept was evaluated. If the present understanding of the physics can be extrapolated to reactor scale devices the reactor could o...

D. G. McAlees N. A. Uckan L. M. Lidsky

1976-01-01

261

Bumpy Torus Betatron.  

National Technical Information Service (NTIS)

The combination of a bumpy torus field and a conventional betatron field leads to an interesting strongly-focused, high-current accelerator configuration. The question of orbital stability of a test particle in such a device is discussed and it is shown t...

D. Chernin A. Mondelli C. Roberson

1984-01-01

262

Models of the Io torus  

NASA Astrophysics Data System (ADS)

The author presents the results of three-dimensional calculations that include variations in the torus plasma properties with longitude, latitude, and distance from Jupiter. These calculations are used to model and interpret the data described in Paper I (Morgan, 1985), to compare these spectroscopic data with Oliversen's [S II] images and with the in situ measurements made by Voyager 1, and to test the hypothesis that the optical east-west variations observed in Paper I are consistent with the convective motions suggested by Barbosa and Kivelson (1983) and Ip and Goertz (1983). In this paper, the author shows that the optical intensity asymmetry can be explained as a natural consequence of the suggested convective motions.

Morgan, J. S.

1985-08-01

263

Jovian Chromophore Characteristics from Multispectral HST Images.  

National Technical Information Service (NTIS)

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

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

2011-01-01

264

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

265

Model of Jovian F Region Ionosphere.  

National Technical Information Service (NTIS)

To date, seven electron density profiles of the Jovian ionosphere have been furnished by the radio occultation experiments aboard the Pioneer and Voyager space probes. The data correspond to various localities (latitudes and longitudes) and times (dawn an...

A. Tan

1988-01-01

266

Ultraviolet Spectrum of the Jovian Dayglow.  

National Technical Information Service (NTIS)

The ultraviolet spectra of molecular hydrogen H2 and HD due to solar fluorescence and photoelectron excitation are calculated and compared with the Jovian equatorial dayglow spectrum measured at 3 A resolution at solar maximum. The dayglow emission is acc...

W. Liu A. Dalgarno

1995-01-01

267

ConcepTest: Jovian Planet Characteristics  

NSDL National Science Digital Library

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

268

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

269

Jovian Temperatures--Highest Resolution  

NASA Technical Reports Server (NTRS)

This is the highest resolution image ever recorded of Jupiter's temperature field. It was obtained by NASA's Galileo mission, with its Photopolarimeter-Radiometer (PPR) experiment, during the seventh of its 10 orbits around Jupiter to date, in the vicinity of Jupiter's Great Red Spot. This image, shown on the bottom panel, indicates the forces powering Jovian winds, and differentiates between areas of strongest upwelling and downwelling winds in the upper part of the atmosphere where winds are strong. For reference, the upper panel shows the visible clouds in a Hubble Space Telescope Planetary Camera color composite image of the same part of the planet taken within 10 hours of the PPR observation.

Many of Galileo's atmospheric observations targeted specific Jovian cloud features, including the Great Red Spot. It is the planet's coldest region, indicating that winds are upwelling and forcing air to expand outward over its entire visible extent. The edges of the cold inner region of the Great Red Spot are close to the PPR's 1800-kilometer (1100-mile) spatial resolution. The largest temperature gradient is also seen between the cold 'inner' Great Red Spot and a region some 5000 kilometers (3000 miles) south which is more than 10 degrees warmer. This implies a strong eastward jet, consistent with cloud-tracked winds.

The southern central portion of the Great Red Spot is not as cold as the rest of the feature. This is consistent with the winds inside the Great Red Spot being more complicated than a simple counterclockwise rotation around the center.

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

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

270

ALBEDOS OF SMALL JOVIAN TROJANS  

SciTech Connect

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

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

2009-07-15

271

Model of Jovian F region ionosphere  

NASA Technical Reports Server (NTRS)

To date, seven electron density profiles of the Jovian ionosphere have been furnished by the radio occultation experiments aboard the Pioneer and Voyager space probes. The data correspond to various localities (latitudes and longitudes) and times (dawn and dusk) and phases of sunspot cycle (high and low). This renders comparative studies difficult. Nevertheless, the possibility of existence of diurnal variation, equatorial anomaly, and auroral particle precipitation in the Jovian ionosphere have been put forth. The grand magnitude and depth of the equatorial anomaly, in particular, is a matter of great interest and speculation. Correct interpretations of the data and the physical processes in the complex Jovian atmospheric environment will remain a major task for the Aeronomer for decades to come. Model studies of a Jovian ionosphere created by solar EUV radiation and subjected to model ExB drifts showed that equatorial anomaly similar to that in the terrestrial ionosphere can indeed be produced in the Jovian ionosphere. However, owing to the difference in size and rotation period of the two planets and the ionic compositions, much larger drift velocities are required to produce a comparable anomaly in the Jovian atmosphere.

Tan, A.

1988-01-01

272

On the formation of Ios inner torus  

NASA Astrophysics Data System (ADS)

In December 1995 and November 2002, the Galileo spacecraft traversed the inner Io plasma torus on the J0 and A34 passes, respectively. Observations of electron density showed a steep drop off at the inner boundary located between 4.5 RJ and 5 RJ on the two passes, and a much more gradual decrease in the outer torus. The [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243-26260, 2001] model of torus formation considers multiple ionization and neutralization stages for the pickup ions, and predicts an inner torus boundary location which depends on the local plasma velocity at Io. For an inner torus boundary at 4.7 RJ, ions are picked up into a plasma flowing at 37 km/s (74 km/s is the corotation velocity at 5.9 RJ). The steepness of the boundary and the double peaked density structure seen on the two Galileo passes is not reproduced by the [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243-26260, 2001] model, which considers the source of mass loading at Io to be uniformly distributed around the moon and does not include outward radial convection. Adding this convection to the model, as would be required to maintain a steady state magnetodisk, steepens the inner torus boundary, but does so over very long timescales. The different inner torus density structure observed on the J0 and A34 passes is not reproduced by either the [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243-26260, 2001] or outward radial convection models and indicates the possible occurrence of a large mass loading event in the 7 years between the passes or longitudinal asymmetry in the torus structure.

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

273

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

Microsoft Academic Search

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

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

2008-01-01

274

The Jovian ionospheric E region  

SciTech Connect

The authors have constructed a model of the Jovian ionosphere that includes direct photoionization of hydrocarbon molecules. A high resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N) and high resolution cross sections for photoabsorption by H{sub 2} bands in the range 842 to 1,116 {angstrom} were constructed. Two strong solar lines and about 30% of the continuum flux between 912 and 1,116 {angstrom} penetrate below the methane homopause despite strong absorption by CH{sub 4} and H{sub 2}. They find that hydrocarbons (mainly C{sub 2}H{sub 2}) are ionized at a maximum rate of 55 cm{sup {minus}3}sec{sup {minus}1} at 320 km above the ammonia cloud tops. The hydrocarbon ions produced are quickly converted to more complex hydrocarbon ions through reactions with CH{sub 4}, C{sub 2}H{sub 2}, C{sub 2}H{sub 6}, and C{sub 2}H{sub 4}. They find that a hydrocarbon ion layer is formed near 320 km that is about 50 km wide with a peak density in excess of 1 {times} 10{sup 4} cm{sup {minus}3}.

Kim, Y.H.; Fox, J.L. (State Univ. of New York, Stony Brook (USA))

1991-02-01

275

Jovian Planet Finder optical system  

NASA Astrophysics Data System (ADS)

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

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

2003-02-01

276

A New Asymptotic Formalism for Jovian Seismology  

NASA Astrophysics Data System (ADS)

In order to account for the core of the giant planets interior, a second order asymptotic formalism has been adapted to Jovian seismology, for low degree high frequency acoustic modes, starting from the work of Tassoul (1980). We consider a spherical non-rotating model of Jupiter presenting a strong discontinuity in density and sound speed at the core frontier. We exhibit a peculiar behavior of the pressure modes eigenfrequency pattern. Contrarily to the solar case, eigenfrequencies are not almost equidistant, and this has to be taken into account when interpreting an observed spectrum. A qualitative agreement with the frequencies computed from a planetary model is obtained. Therefore we use the asymptotic formalism to compare actual Jovian interior models. The formalism developed here is applicable to any non rotating object presenting a noncontinuous interior, provided the asymptotic constraints are fulfilled. The limit of validity of this formalism is discussed in the context of Jovian seismology.

Provost, J.; Mosser, B.; Berthomieu, G.

1993-07-01

277

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

NASA Astrophysics Data System (ADS)

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

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

1993-05-01

278

Simulation of Plasma Interaction with Io's Atmosphere  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

279

Models of Electron Energetics in the Enceladus Torus  

NASA Astrophysics Data System (ADS)

The inner magnetosphere of Saturn contains a mixture of plasma and neutral gas, the dominant source of which is the icy satellite Enceladus. Water vapor and water dissociation products are present throughout the magnetosphere but they are particularly concentrated in a torus surrounding Saturn at the orbit of Enceladus. The Hubble Space Telescope observed OH in the torus and other neutral species (mainly water) have been measured by the Ion and Neutral Mass Spectrometer (INMS) and the Ultraviolet Imaging Spectrometer (UVIS) onboard the Cassini spacecraft. Relatively cold plasma, dominated by water group ion species, was measured by instruments onboard both the Voyager and Cassini spacecraft. The electron distribution function in this torus appears to include both a colder thermal population (seen for example by the Cassini Radio and Plasma Wave Spectrometers Langmuir probe -- RPWS/LP) and hotter suprathermal populations (seen by the electron spectrometer part of the Cassini plasma analyzer -- CAPS/ELS). We present a model of electron energetics in the torus. One part of this model utilizes an electron energy deposition code to determine electron fluxes versus energy. The model includes photoelectron production from the absorption of solar radiation as well as electron impact collisional processes for water and other neutral species. Another part of the model consists of an energetics code for thermal electrons that generates electron temperatures. Heating from Coulomb collisions with photoelectrons and with hot pick-up ions was included, as was cooling due to electron impact collisions with water. We show that solar radiation is the dominant source of suprathermal electrons in the core neutral torus, in agreement with recently published CAPS-ELS data. We predict electron thermal energies of about 2 eV, which is somewhat low in comparison with recently published RPWS-LP data. The implications of these results for plasma densities in the torus will also be discussed.

Cravens, T. E.; Ozak, N.; Richard, M. S.; Robertson, I. P.; Perry, M. E.; Campbell, M. E.

2010-12-01

280

Lower hybrid emission diagnostics on the NASA Lewis bumpy torus  

NASA Technical Reports Server (NTRS)

The feasibility of using RF emission near the lower hybrid frequency of the NASA Lewis Bumpy Torus plasma for diagnostic purposes is examined. The emission is detected using a spectrum analyzer and a 50 omega miniature coaxial antenna that is sensitive to the polarization of the incoming signal. The frequency shift of the lower hybrid emission peak is monitored as a function of the background pressure, electrode voltage, electrode ring configuration and the strength of the toroidal dc magnetic field. Simultaneous measurements of the average plasma density are made with a polarization diplexing microwave interferometer. Data derived from the experiment are discussed with reference to the following: (1) the strength of the dc magnetic field in the emitting region; (2) comparison of the lower hybrid plasma density with the average plasma density; and (3) validity of the cold plasma lower hybrid resonance formula in the high density operating regime of the bumpy torus plasma.

Mallavarpu, R.

1977-01-01

281

Spherical torus center stack design  

SciTech Connect

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

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

2002-01-01

282

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

283

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

284

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

285

Next Step Spherical Torus Design Studies  

SciTech Connect

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

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

2002-11-08

286

An alternative to the compact torus ICF driver  

SciTech Connect

Plasma guns have been used in the Controlled Thermonuclear Reaction (CTR) Program to inject energetic deuterium-tritium plasma into a magnetic confinement machine, also for dense-plasma-focus devices to achieve fusion utilizing Z-pinches. In this report we propose another CTR application of a plasma gun: accelerating the plasma in a coaxial geometry to a speed in the neighborhood of a centimeter per shake with a total kinetic energy of about 20 MJ. The kinetic energy is efficiently converted to x-rays in a time of about a shake, and the x-ray pulse is used to implode an Inertial Confinement Fusion (ICF) capsule. As far as we know the plasma gun application we are proposing has not been explored before, but we observe that the LLNL Compact Torus Program hopes to accelerate a compact-torus-plasma to a comparable speed and energy and, in one of its applications, to generate x-rays for ICF purposes. In fact, the only difference between the LLNL Compact Torus Program and what we are proposing is that our plasma does not rely on imbedded magnetic fields and currents to minimize instabilities. We minimize instabilities by snowplowing the plasma to its required speed in a single shock. Which approach is better requires additional investigation.

Latter, A.L.; Martinelli, E.A.

1992-11-01

287

Studying the Jovian System with small telescopes  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

288

Global Magnetohydrodynamic Model of Jovian Magnetosphere.  

National Technical Information Service (NTIS)

The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pion...

R. J. Walker

2001-01-01

289

Energetic Electrons in the Jovian Magnetosphere  

Microsoft Academic Search

Detailed analysis of the University of Iowa Pioneer 10 data using several design features of the instrument to accomplish particle species identification shows that the observed counting rates within the magnetosphere of Jupiter were caused primarily by electrons, Ee > 0.06 MeV. This identification holds for the magnetodisc region (r > 20 Rj (Jovian radii)) as well as for the

D. N. Baker; J. A. Van Allen

1976-01-01

290

Global resonance in the Jovian radiation belts  

SciTech Connect

The oscillation regimes of cyclotron stability in the Jovian radiation belts are analyzed. It is shown that the eigenfrequencies of oscillations in the outer magnetosphere of Jupiter are independent of the magnetic shell L and coincide with the angular rotational velocity. The theoretical results are used to explain Pioneer observations of 10-hour modulation in the energetic electron flux of Jupiter. 7 references.

Bespalov, P.A.

1985-02-01

291

Measurements of the Jovian radiation belts  

Microsoft Academic Search

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

R. W. Fillius; C. E. McIlwain

1974-01-01

292

Energetic protons in the jovian magnetosphere  

Microsoft Academic Search

The time histories, angular distributions and energy spectra of energetic protons have been measured over an energy range extending from 0.2 to 20 MeV for the four passes of Pioneers 10 and 11 through the Jovian magnetosphere. The energetic particle data from these four passes are remarkably different. Azimuthal asymmetries appear to dominate with time variations also contributing to the

F. B. McDonald; A. W. Schardt; J. H. Trainor

1979-01-01

293

Raman scattering in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

294

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 Alfvn 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 Alfvn 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

295

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

NASA Astrophysics Data System (ADS)

From about December 2000 to January 2001 the Ion Neutral Camera (INCA) on board the Cassini spacecraft imaged Jupiter in Energetic Neutral Atoms (ENA) that are created when singly charged ions charge exchange with neutral gas atoms or molecules. The INCA observations were obtained from a distance of about 137-250 Jovian planetary radii (RJ) over an energy range from about 10 to 300 keV. These observations have been demonstrated to be consistent with a neutral gas torus encircling Jupiter at Europa's orbit (Mauk et al., 2004). Here, we present a new, detailed analysis of the ENA images implying an asymmetric Europa neutral gas torus with indications of magnetospheric dynamics. The analysis uses images with a minimum integration time and background. A forward model using a parametric energetic ion model and a neutral gas model simulates ENA images through the instrument response function of INCA in order to determine the spatial distribution of the neutral gas.

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

2014-05-01

296

Summary of US compact torus experiments  

SciTech Connect

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

Hartman, C.W.

1981-03-11

297

On the nature of the interaction of the Jovian magnetosphere with the icy Galilean satellites  

NASA Technical Reports Server (NTRS)

The effects of plasma and micrometeoroid bombardment of each satellite are considered in the case of interactions between the Jovian magnetosphere and Europa, Ganymede, and Callisto, in an attempt to understand the influences of these exogenic processes on the surface properties of each of the three moons. Sublimated and sputtered H2O results in a net O2 atmosphere on each of the three moons, and the effectiveness of such an atmosphere in preventing the Jovian plasma from reaching each satellite surface is considered for a variety of magnetospheric conditions. Also studied are the effects of possible satellite magnetic field magnitude and orientation, in order to estimate satellite magnetosphere properties, and the orbits of charged micrometeroids in the Jupiter magnetosphere, in order to determine the relative flux of these particles over the satellite surfaces.

Wolff, R. S.; Mendis, D. A.

1983-01-01

298

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

NASA Technical Reports Server (NTRS)

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

Trainor, J. H.

1975-01-01

299

Energetic oxygen and sulfur ions in the Jovian magnetosphere  

SciTech Connect

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 are used to calculate abundances and energy spectra in the region from 5 to 20 Jovian radii (R/sub J/). The phase space density of the oxygen ions calculated from the spectra has a positive radial gradient between 6 and 17 R/sub J/, indicating an inward diffusive flow. The diffusion coefficient upper limit at 9 R/sub J/ is approx. 10/sup -5/s/sup -1/. 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 lo of approx. 10/sup 28/ 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 numbers of particles lost between 7.5 and 12.5 R/sub J/. It is shown that the losses are not due to geometric absorption by lo, 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. The power delivered to the Jovian atmosphere by oxygen and sulfur ions with magnetic moments greater than 70 MeV/nuc-G (E greater than or equal to 0.3 MeV/nuc at 10 R/sub j/), scattered into the loss cone between 6 and 17 R/sub j/, is approx. 5 x 10/sup 12/ W; a power comparable to the approx. 1.2 x 10/sup 13/W required to produce the auroral emission observed by the ultraviolet spectrometer on Voyager. The measured dependence of the input power on magnetic moment threshold indicates that additional power is contributed by oxygen and sulfur ions with magnetic moments less than 70 meV/nuc-G.

Gehrels, N.

1982-01-01

300

Survey of Elmo Bumpy Torus.  

National Technical Information Service (NTIS)

Oak Ridge National Laboratory is pursuing an active experimental and theoretical program directed toward developing the Elmo Bumpy Torus (EBT) concept of a fusion reactor. ERDA has requested Science Applications, Inc. (SAI) to perform an independent surve...

N. A. Krall J. B. Bride G. W. Stuart

1975-01-01

301

Control System Development Plan for the National Spherical Torus Experiment  

SciTech Connect

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

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

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

1999-06-01

302

Relativistic wave-particle interaction in magnetospheric plasmas  

NASA Astrophysics Data System (ADS)

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

Xiao, Fuliang

2001-06-01

303

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

304

The Juno Jovian Auroral Distributions Experiment (JADE)  

NASA Astrophysics Data System (ADS)

The Jovian Auroral Distributions Experiment (JADE) is a part of the suite of instruments carried on Juno to directly explore, for the first time, Jupiter's polar magnetosphere in general and auroral processes, in particular. JADE comprises a single-head ion mass spectrometer (JADE-I) and three identical electron energy per charge (E/q) analyzers (JADE-E) to measure the full auroral electron and ion particle distributions. Together these three-dimensional distributions 1) determine the particle populations that precipitate into the auroral regions and produce the observed auroral emissions; 2) measure the leakage of Jovian ions out along the field; and 3) address the acceleration processes at work in the regions both around and below the spacecraft. This paper briefly summarizes the JADE scientific objectives, instrumentation, and capabilities.

Pollock, C.; Allegrini, F.; Crary, F.; Desai, M.; Louarn, P.; McComas, D.; Weidner, S.

2008-12-01

305

An Improved Model of the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

The Jovian magnetosphere is modulated by the solar wind and centrifugal force. The configuration of the magnetic field in the previous model of the magnetosphere including the centrifugal force is consistent with the observations at low magnetic latitude (? < 50), while there is a substantial difference between the results of the model and the observations at high magnetic latitude (? >= 50), especially in the distant magnetotail. Based on the previous model, a new configuration of the Jovian magnetosphere in the night side is suggested by a three-step transformation in this study. The new magnetosphere obtained by the transformation method is flattened in the z-direction and stretched in the x-direction in distant magnetotail, which agree with general knowledge.

Lu, Bin; Chen, Chu-Xin

2014-03-01

306

Distant asteroids and outer Jovian satellites  

NASA Technical Reports Server (NTRS)

Sixty percent of the sampled objects in the Hilda, Trojan and outer Jovian satellite locations belong to C-type and another 30% belong to a new group called RD-type (reddish and dark), sometimes referred to simply as D-type. Objects in this group have low albedo values between 2 and 4% and steep reflection spectra between 0.7 micron and 0.9 micron. Furthermore, 944 Hidalgo belongs to this group but shows color variation over its surface. Meteoritic minerals with similar optical reflection spectra are discussed. Trojans with sizes down to 15 km in the cloud preceding Jupiter are about 3.5 times more numerous than those in the following cloud. RD-type Trojans appear more often in the preceding cloud. There is a resemblance of spectrum, albedo and phase relation among the majority of Trojans and the outer Jovian satellites.

Degewij, J.; Van Houten, C. J.

1979-01-01

307

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

SciTech Connect

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 the dispersion of whistlers. The limitations and advantages of each technique are critically reviewed. In all cases the electron densities are unaffected by spacecraft charging or sheath effects, which makes these measurements of particular importance for verifying in situ plasma and low-energy charged particle measurments. In the outer regions of the dayside magnetosphere, beyond about 40 R/sub J/, the electron densities range from about 3 x 10/sup -3/ to 3 x 10/sup -2/ cm/sup -3/. On Voyager 2, several brief excursions apparently occurred into the low-density region north of the plasma sheet with densities less than 10/sup -3/ cm/sup -3/. Approaching the planet the electron density gradually increases, with the plasma frequency extending above the frequency range of the plasma wave instrument (56 kHz, or about 38 electrons cm/sup -3/) inside of about 8 R/sub J/. Within the high-density region of the Io plasma torus, whistlers provide measurements of the north-south scale height of the plasma torus, with scale heights ranging from about 0.9 to 2.5 R/sub J/.

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

1981-09-30

308

Models of the Jovian upper atmosphere  

Microsoft Academic Search

Recent developments in photochemical models of the upper atmosphere of Jupiter and Titan are reviewed. Measurements of the Jovian Lyman alpha airglow favor a homopause value of approximately 107 cm s?1 for the eddy diffusion coefficient. A relatively hot exosphere as implied by the electron density measurements results in an extended atmosphere of hydrogen. Larger than solar C\\/H and N\\/H

S. K. Atreya; T. M. Donahue

1979-01-01

309

Jovian decametric arcs as an interference pattern  

SciTech Connect

Is is proposed that the nested arc structures, observed in the decametric Jovian radio emission by the planetary radio astronomy experiment, are due to the interference of two rays from a single source at each frequency, the relative phase changing with rotation of the planet. This idea can explain at the same time the shape of the arcs and their repetitivity. But the nature of the two interfering rays is not understood yet.

Boischot, A.; Aubier, M.

1981-09-30

310

Ion anisotropies in the outer Jovian magnetosphere  

Microsoft Academic Search

We present results from the Voyager 1 and 2 low-energy charged particle measurement of ion anisotropies in the outer Jovian magnetosphere (R> or approx. =20 R\\/sub J\\/). Theses anisotropies represent the first observed from an instrument rotating in the spin plane of Jupiter. For the several ion species ivestigated the first-order anisotropies are all strongly in the corotational sense throughout

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

1981-01-01

311

Electron capture decay in Jovian planets  

SciTech Connect

Following the commonly acknowledged fact that the decay of K-40 substantially contributes to the heating of planetary interiors, an examination is made of the possibility that interior heat in the Jovian planets and stars, where interior pressures may exceed 45 Mbar, may be generated by the pressure-accelerated electron capture decay of a variety of isotopes. The isotopes considered encompass K-40, V-50, Te-123, La-138, Al-26, and Cl-36. 19 references.

Zito, R.R.; Schiferl, D.

1987-12-01

312

The Jovian Aurora - Electron or ion precipitation?  

NASA Technical Reports Server (NTRS)

High signal-to-noise spectra of the Jovian aurora obtained at 1200 to 1500 A by the IUE Observatory were examined for the existence of sulfur and oxygen emissions that would be expected if the UV emissions were produced by precipitating heavy ions. The results of these measurements and subsequent spectral modeling, using a model of heavy aurora constructed by Horanyi et al. (1988), showed mixed evidence of the oxygen and sulfur emissions. It was noted that only the UV emissions which are produced above the UV absorbing hydrocarbon layer were observed by the IUE and Voyager UV spectrometers. This fact, combined with the recent observations of the longitudinal distribution of the Jovian UV aurora, indicates that electrons as well as ions play a role in Jovian auroral processes. Based on the observations, it is suggested that heavy-ion auroral energy deposition is concentrated at altitudes below the homopause, while electrons with energies of 10 to 30 keV are responsible for the bulk of the observable UV and EUV emissions.

Waite, J. H., Jr.; Clarke, J. T.; Cravens, T. E.; Hammond, C. M.

1988-01-01

313

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

314

Satellite Atmosphere and Io Torus Observations  

NASA Technical Reports Server (NTRS)

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, including (1) an atmosphere out of proportion with such a small object, (2) a correspondingly large atmospheric escape rate, (3) a ring of dense plasma locked in a feedback loop with the atmosphere, and (4) a host of Io-induced emissions from radio bursts to UV auroral spots on Jupiter. This proposal seeks to continue our investigation into the physics connecting these phenomena, with emphasis on Io's atmosphere and plasma torus. The physical processes are clearly of interest for Io, and also other places in the solar system where they are important but not readily observable.

Schneider, Nicholas M.

2000-01-01

315

A summary of observational records on periodicities above the rotational period in the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

The Jovian magnetosphere is a very dynamic system. The plasma mass-loading from the moon Io and the fast planetary rotation lead to regular release of mass from the Jovian magnetosphere and to a change of the magnetic topology. These regular variations, most commonly on several (2.5-4) days scale, were derived from various data sets obtained by different spacecraft missions and instruments ranging from auroral images to in situ measurements of magnetospheric particles. Specifically, ion measurements from the Galileo spacecraft represent the periodicities, very distinctively, namely the periodic thinning of the plasma sheet and subsequent dipolarization, and explosive mass release occurring mainly during the transition between these two phases. We present a review of these periodicities, particularly concentrating on those observed in energetic particle data. The most distinct periodicities are observed for ions of sulfur and oxygen. The periodic topological change of the Jovian magnetosphere, the associated mass-release process and auroral signatures can be interpreted as a global magnetospheric instability with analogies to the two step concept of terrestrial substorms. Different views on the triggering mechanism of this magnetospheric instability are discussed.

Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.

2009-06-01

316

Modeling and investigative studies of Jovian low frequency emissions. Final report  

SciTech Connect

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

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

1986-08-01

317

Initial Diagnostics for the National Spherical Torus Experiment  

SciTech Connect

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

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

1999-06-01

318

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

NASA Astrophysics Data System (ADS)

The Jovian Auroral Distributions Experiment (JADE) on Juno provides the critical in situ measurements of electrons and ions needed to understand the plasma energy particles and processes that fill the Jovian magnetosphere and ultimately produce its strong aurora. JADE is an instrument suite that includes three essentially identical electron sensors (JADE-Es), a single ion sensor (JADE-I), and a highly capable Electronics Box (EBox) that resides in the Juno Radiation Vault and provides all necessary control, low and high voltages, and computing support for the four sensors. The three JADE-Es are arrayed 120? apart around the Juno spacecraft to measure complete electron distributions from 0.1 to 100 keV and provide detailed electron pitch-angle distributions at a 1 s cadence, independent of spacecraft spin phase. JADE-I measures ions from 5 eV to 50 keV over an instantaneous field of view of 270?90? in 4 s and makes observations over all directions in space each 30 s rotation of the Juno spacecraft. JADE-I also provides ion composition measurements from 1 to 50 amu with m/?m2.5, which is sufficient to separate the heavy and light ions, as well as O+ vs S+, in the Jovian magnetosphere. All four sensors were extensively tested and calibrated in specialized facilities, ensuring excellent on-orbit observations at Jupiter. This paper documents the JADE design, construction, calibration, and planned science operations, data processing, and data products. Finally, the Appendix describes the Southwest Research Institute [SwRI] electron calibration facility, which was developed and used for all JADE-E calibrations. Collectively, JADE provides remarkably broad and detailed measurements of the Jovian auroral region and magnetospheric plasmas, which will surely revolutionize our understanding of these important and complex regions.

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

2013-05-01

319

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

NASA Astrophysics Data System (ADS)

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

Cooper, J. F.

2002-05-01

320

A torus palatinus with a family history  

Microsoft Academic Search

Throughout history, different etiologies have been suggested for torus palatinus. In more recent years, however, torus palatinus has been attributed to heredity; a case which confirms this is presented. The relevant literature is reviewed.

A. Castro Sierra; I. T. Jackson

1992-01-01

321

Planetary circulations: 1. Barotropic representation of Jovian and terrestrial turbulence  

Microsoft Academic Search

We seek the formative processes of planetary circulations of Jupiter and Saturn. The study concentrates on examining whether processes known to control the terrestrial circulation, namely, two-dimensional turbulence and baroclinic instability, can produce Jovian circulations under Jovian conditions. The first numerical model involves a spherical barotropic vorticity equation subjected to a stochastic representation of baroclinic processes. The resulting solutions suggest

Gareth P. Williams

1978-01-01

322

Energetic particle population in the Jovian magnetosphere: a preliminary note  

Microsoft Academic Search

A preliminary account of the Jovian encounter as viewed by the Pioneer ; 10 particle detector systems of Goddard Space Flight Center and the Univ. of New ; Hampshire is given. The systems were designed to measure the charge, energy, and ; angular distribution of galactic and soiar cosmic rays as well as the energetic ; particles in the Jovian

J. H. Trainor; B. J. Teegarden; D. E. Stilwell; F. B. McDonald; E. C. Foelof; W. R. Webber

1974-01-01

323

Planetary spin period acceleration of particles in the Jovian magnetosphere  

Microsoft Academic Search

We describe a model for the acceleration of energetic protons and relativistic electrons in the Jovian magnetosphere, employing a four-step process in which ionospheric particles are (1) accelerated outward along field lines by the centrifugal force of corotation, (2) energized by magnetic field annihilation in the Jovian magnetospheric tail, (3) convected inward from the tail, thus experiencing adiabatic compression, and

J. F. Carbary; T. W. Hill; A. J. Dessler

1976-01-01

324

Location and shape of the Jovian magnetopause and bow shock  

Microsoft Academic Search

Following Galileo's arrival at Jupiter in fall 1995, a total of six spacecraft have now sampled the Jovian magnetosphere. Using these data sets to investigate the average location and shape of the Jovian boundaries, we fit ellipse profiles to the observations, allowing for the disk-like shape of the magnetosphere and taking account of variable solar wind pressure. We find that

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

1998-01-01

325

Outward diffusion of energetic particles from the Jovian radiation belt  

Microsoft Academic Search

It is suggested that energetic particles populating the Jovian outer magnetosphere and neighboring interplanetary space are flowing from the Jovian radiation belt by the outward diffusion process that violates both second and third adiabatic invariants. This cross-field diffusion process operates preferentially at low altitudes, and it does not cause serious degradation of particle energy. A model is constructed which combines

A. Nishida

1976-01-01

326

Bispectral analysis of low frequency fluctuations in a simple magnetised torus  

NASA Astrophysics Data System (ADS)

The turbulent equilibrium of a simple magntised torus, i.e. a plasma device with a purely toroidal magentic field without rotational transform, is investigated. The device can be operated with two different plasma sources, a heated tungsten filament and a helicon source. Long time series from Langmiur and emissive probes are obtained for the whole poloidal cross-section. From previous analysis of such data it is known, that the low frequency fluctuations are influenced by long living vortex stuctures, rotating poloidally around the plasma. Using bispectral analysis the role of three wave coupling on the plasma turbulence in a simple magnetised torus is investigated.

Greiner, Franko; Ramisch, Mirko; Grulke, Olaf; Piel, Alexander

2001-10-01

327

Catastrophies in the Elmo Bumpy Torus  

SciTech Connect

Experimentally it is observed that the plasma in Elmo Bumpy Torus (EBT) shows discontinuous changes in the electron line density, electron and ion temperatures, and fluctation levels as the ambient gas pressure or electron cyclotron heating is varied continuously. The Point Model of Hedrick et al. is used for the toroidal core plasma in EBT. The Point model is not a gradient dynamic system. Hence, the Elementary Catastrophe Theory is not directly applicable to the Point Model. Nonetheless, the Point Model equilibria is shown to exhibit properties quite akin to the canonical cusp catastrophe. The ambipolar electric field is taken as a control parameter. When electrons are nonresonant, the equilibrium surfaces show only one fold; but when ions are nonresonant, equilibrium surfaces may show single or multiple folds. In the former (electron) case, qualitative agreement with experiments is quite good. For the case of nonresonant ions, predictions are made as to the possible plasma behavior which, when ICRH heating is sufficiently intense, may be checked by experiments. The nonlinear time evolution of the Point Model equations shows that the plasma follows the Delay Convention. This simple model of the EBT plasma exhibits rich structure, i.e., equilibrium surfaces with single or multiple folds, attractors, repellors, appearance and disappearance of folds, reversal of direction on equilibrium trajectories, catastrophes, hysteresis, competition between multiple point attractors, and basins of attractors. This leads to the conclusion that a simple model of physical systems governed by external parameters can unravel general, complicated qualitative behavior of the system.

Punjabi, A.R.

1983-01-01

328

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

SciTech Connect

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

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

2009-10-21

329

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

330

IUE observations of the Jovian dayglow emission  

SciTech Connect

IUE spectra of Jupiter are examined in light of recent models put forward to explain the anomalously bright ultraviolet emissions seen from the upper atmospheres of the outer planets. Chi-squared fits of the IUE spectra with model spectra produced by two proposed excitation mechanisms, electron impact and fluorescence of solar radiation, result in consistently higher{chi}{sup 2} values for the solar fluorescence model. The authors find no conclusive evidence in the IUE data for the dominance of solar fluorescence over electron excitation in producing the Jovian dayglow emission.

McGarth, M.A.; Feldman, P.D.; Ballester, G.E.; Moos, H.W. (Johns Hopkins Univ., Baltimore, MD (USA))

1989-06-01

331

Infrared processes in the Jovian auroral zone  

SciTech Connect

In the present theoretical model of the Jovian auroral zone's CH/sub 4/ and H/sub 2/ vibrational excitation and deexitation processes, the calculation of the emission intensities of nu3 and nu4 bands of CH/sub 3/ assume that electrons are the bombarding particles. The most uncertain part of the model calculation involves the energy flux spectrum of incident electrons on the auroral zone. Comparisons with Voyager 1 IRIS observations indicate a domination of the nonthermal, directly or indirectly particle bombardment-derived emission by the thermal emission of the CH/sub 4/ band. 45 references.

Kim, S.J.

1988-09-01

332

The origin of chondrules at jovian resonances  

PubMed

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

Weidenschilling; Marzari; Hood

1998-01-30

333

Non-Circular Bumpy Torus.  

National Technical Information Service (NTIS)

A bumpy torus with noncircular coils is studied analytically and numerically with respect to the confinement of high energy passing particles. The minimum position r sub Jmin of the longitudinal invariant J, and the confinement area sP for passing particl...

A. Tsushima H. Tsuchidate T. Kamimura M. Fujiwara H. Ikegami

1982-01-01

334

Generalized Fuzzy Torus and its Modular Properties  

NASA Astrophysics Data System (ADS)

We consider a generalization of the basic fuzzy torus to a fuzzy torus with non-trivial modular parameter, based on a finite matrix algebra. We discuss the modular properties of this fuzzy torus, and compute the matrix Laplacian for a scalar field. In the semi-classical limit, the generalized fuzzy torus can be used to approximate a generic commutative torus represented by two generic vectors in the complex plane, with generic modular parameter ?. The effective classical geometry and the spectrum of the Laplacian are correctly reproduced in the limit. The spectrum of a matrix Dirac operator is also computed.

Schreivogl, Paul; Steinacker, Harold

2013-10-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

336

Linear pinch driven by a moving compact torus  

SciTech Connect

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

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

1984-04-25

337

Latitudinal structure within Jovian hectometric radiation  

NASA Astrophysics Data System (ADS)

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

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

1998-11-01

338

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

National Technical Information Service (NTIS)

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 descr...

W. H. Smyth

2004-01-01

339

Exploration of Spherical Torus Physics in the NSTX Device  

SciTech Connect

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

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

1998-11-01

340

Lower hybrid emission diagnostics on the NASA Lewis Bumpy Torus  

NASA Technical Reports Server (NTRS)

The feasibility of using RF emission near the lower-hybrid frequency of the NASA Lewis Bumpy Torus plasma for diagnostic purposes is examined. The emission is detected using a spectrum analyzer and a 50-ohm miniature coaxial antenna that is sensitive to the polarization of the incoming signal. The frequency shift of the lower-hybrid emission peak is monitored as a function of the background pressure, electrode voltage, electrode ring configuration, and the strength of the toroidal dc magnetic field. Simultaneous measurements of the average plasma density are made with a polarization diplexing microwave interferometer. The experimental results extend previous work to include negative electrode voltages and plasma densities up to 1 trillion per cu cm. The information derived from the experiment is discussed with reference to: (1) the strength of the dc magnetic field in the emitting region, (2) a comparison of the lower-hybrid plasma density with the average plasma density, and (3) the validity of the cold-plasma lower-hybrid resonance formula in the high-density operating regime of the bumpy-torus plasma.

Mallavarpu, R.

1977-01-01

341

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

342

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 local 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 octopole 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.; Thieman, J. R.; Eviatar, A.

1979-01-01

343

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

344

Current Algebra on the Torus  

Microsoft Academic Search

We derive the N-point one-loop correlation functions for the currents of an arbitrary affine Kac-Moody algebra. The one-loop\\u000a amplitudes, which are elliptic functions defined on the torus Riemann surface, are specified by group invariant tensors and\\u000a certain constant tau-dependent functions. We compute the elliptic functions via a generating function, and explicitly construct\\u000a the invariant tensor functions recursively in terms of

Louise Dolan; Peter Goddard

2009-01-01

345

Heavy ion dynamics and auroral arc formation in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

This paper gives a brief review of some of the current controversial issues surrounding the Jovian aurora. In particular, the manner of its excitation be it that of electron or heavy ion precipitation is examined critically in the context of proposed models for magnetospheric dynamics, particle energization, and auroral energy input. A model for the X-ray aurora based on bremsstrahlung by a primary electron beam and its ionization secondaries is high-lighted and the connection to the outward magnetospheric transport of heavy ion plasma from the satellite Io is made.

Barbosa, D. D.

1992-01-01

346

On the Origin of System III Asymmetries in the Io Torus  

NASA Technical Reports Server (NTRS)

The Io plasma torus exhibits several intriguing asymmetries which offer insights to the processes that transport mass and energy through the system. While these asymmetries are increasingly well described observationally, most still lack physical explanations. One important asymmetry is fixed in the coordinate system corotating with Jupiter's magnetic field. Space-based and ground-based observations have shown that torus ions are hotter and more highly ionized around System III 20 deg. Our simulations show that this type of torus asymmetry can be caused by enhanced pickup of fresh ions from Io's neutral clouds near these longitudes. The enhancement is caused primarily by the tilt and offset of the torus relative to the neutral clouds. We will report on the model parameters required to match the observed asymmetries, and offer predictions which will allow a test of this hypothesis.

Schneider, N. M.; Delamere, P. A.

2006-01-01

347

Retrievals of Jovian Tropospheric Phosphine from Cassini/CIRS.  

National Technical Information Service (NTIS)

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 atmos...

P. G. Irwin P. Parrish T. Foucher S. B. Calcutt F. W. Taylor

2004-01-01

348

Time-Variable Phenomena in the Jovian System.  

National Technical Information Service (NTIS)

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 ...

M. J. S. Belton R. A. West J. Rahe M. Pereyda

1989-01-01

349

Millimeter-Wave Spectra of the Jovian Planets.  

National Technical Information Service (NTIS)

The millimeter wave portion of the electromagnetic spectrum is critical for understanding the subcloud atmospheric structure of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune). This research utilizes a combination of laboratory measurements, com...

J. Joiner P. G. Steffes

1991-01-01

350

Ion phase space densities in the Jovian magnetosphere  

SciTech Connect

The authors have analyzed the Voyager Low-Energy Charged Particle (LECP) ion data from the Jovian magnetosphere to determine the phase-space densities of particles in the region 5-80 R{sub J}. They used data only from the Jovian current sheet crossings for locally mirroring particles. These are the first calculations of phase-space densities in the non-dipolar field region containing the Jovian magnetodisk current sheet. The profiles are consistent with lossy inward radial transport and a source in the outer magnetosphere. The inferred loss rate in a radial diffusion model measuring how quickly particles are scattered out of the neutral sheet exceeds the usual strong diffusion loss rate. The energetic particles lost from the neutral sheet do not necessarily precipitate into the Jovian atmosphere, but if a substantial fraction of these particles is actually precipitated, they contribute a large part of the total auroral luminosity.

Paranicas, C.P.; Cheng, A.F.; Mauk, B.H.; Krimigis, S.M. (Johns Hopkins Univ., Laurel, MD (USA)); Armstrong, T.P. (NASA Headquarters, Washington, DC (USA))

1990-12-01

351

Particles, Environments and Possible Ecologies in the Jovian Atmosphere.  

National Technical Information Service (NTIS)

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 whi...

C. Sagan E. E. Salpeter

1976-01-01

352

Magnetohydrodynamic Modeling of the Jovian Magnetosphere  

NASA Technical Reports Server (NTRS)

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

Walker, Raymond

2005-01-01

353

Energetic particles in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

A detailed account of the Pioneer 10 encounter with Jupiter is presented. Flux time histories of electrons and protons are given over a wide energy band. Proton and electron energy spectra are given at various Jovicentric distances. Proton spectra are shown to transform from a power law with indices in the 3-4.2 range to more nearly exponential forms in the inner regions. Extensive data are presented on the angular distributions of protons and electrons at various locations in the Jovicentric magnetosphere. In addition, a harmonic analysis of 1-2 MeV proton angular distributions was performed. Alpha/proton ratios are given as a function of Jovian radius and are compared to the earth and solar wind values.

Trainor, J. H.; Mcdonald, F. B.; Teegarden, B. J.; Webber, W. R.; Roelof, E. C.

1974-01-01

354

Current sheet interaction and particle acceleration in the Jovian magnetosphere  

SciTech Connect

The thin, rapidly rotating current sheet in Jupiter's magnetodisk can energize heavy ions by hundreds of keV. If the magnetic field lines are azimuthally swept back, energetic ions undergoing nonadiabatic current sheet interactions will step radially outward and be centrifugally energized. Estimated energization times can be comparable to the Jovian rotation period. Nonadiabatic interactions with the rotating Jovian current sheet may be an important energization mechanism for heavy ion, but are not effective for energizing electrons or light ions like protons.

Cheng, A.F. (Johns Hopkins Univ., Laurel, MD (United States))

1990-04-01

355

Jovian: a framework for optimizing parallel I\\/O  

Microsoft Academic Search

There has been a great deal of recent interest in parallel I\\/O. We discuss the design and implementation of the Jovian library, which is intended to optimize the I\\/O performance of multiprocessor architectures that include multiple disks or disk arrays. We also present preliminary performance measurements from benchmarking the Jovian I\\/O library on the IBM SP1 distributed memory parallel machine

Robert Bennett; Kelvin Bryant; Alan Sussman; Raja Das; Joel Saltz

1994-01-01

356

Final report on the LLNL compact torus acceleration project  

SciTech Connect

In this report, we summarize recent work at LLNL on the compact torus (CT) acceleration project. The CT accelerator is a novel technique for projecting plasmas to high velocities and reaching high energy density states. The accelerator exploits magnetic confinement in the CT to stably transport plasma over large distances and to directed kinetic energies large in comparison with the CT internal and magnetic energy. Applications range from heating and fueling magnetic fusion devices, generation of intense pulses of x-rays or neutrons for weapons effects and high energy-density fusion concepts.

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

1995-03-19

357

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

358

Mass and energy balance of the cold Io torus  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

359

The radiation impedance of electrodynamic tethers in a polar Jovian orbit  

NASA Astrophysics Data System (ADS)

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

Snchez-Torres, A.; Sanmartn, J. R.; Donoso, J. M.; Charro, M.

2010-04-01

360

ELMO Bumpy Torus data base  

SciTech Connect

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

Stanton, J.S.

1981-03-01

361

Torus elements used in effective shock absorber  

NASA Technical Reports Server (NTRS)

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

Cunningham, P.; Platus, D. L.

1966-01-01

362

Physics Basis for a Spherical Torus Power Plant  

SciTech Connect

The spherical torus, or low-aspect-ratio tokamak, is considered as the basis for a fusion power plant. A special class of wall-stabilized high-beta high-bootstrap fraction low-aspect-ratio tokamak equilibrium are analyzed with respect to MHD stability, bootstrap current and external current drive, poloidal field system requirements, power and particle exhaust and plasma operating regime. Overall systems optimization leads to a choice of aspect ratio A = 1:6, plasma elongation kappa = 3:4, and triangularity delta = 0:64. The design value for the plasma toroidal beta is 50%, corresponding to beta N = 7:4, which is 10% below the ideal stability limit. The bootstrap fraction of 99% greatly alleviates the current drive requirements, which are met by tangential neutral beam injection. The design is such that 45% of the thermal power is radiated in the plasma by Bremsstrahlung and trace Krypton, with Neon in the scrapeoff layer radiating the remainder.

C.E. Kessel; J. Menard; S.C. Jardin; T.K. Mau; et al

1999-11-01

363

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

364

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

NASA Technical Reports Server (NTRS)

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

Walker, R. J.

1987-01-01

365

Search for oxygen torus in the inner magnetosphere: Van Allen Probes observations  

NASA Astrophysics Data System (ADS)

The oxygen torus is found in the deep inner magnetosphere as enhancements of O+ ion density in a limited L range. It was first reported by Chappell [1982] who used the DE-1/RIMS instrument. Horwitz et al. [1984, 1986] showed that the O+ density sometimes becomes comparable to or exceeds the H+ density at L=3-4. Following studies revealed that the oxygen torus is observed just inside the plasmasphere at all local time with higher occurrence frequency in the late evening and morning sectors. A recent study by Nos et al. [2010] cast a new light on the oxygen torus as a one of essential factors of O+-rich ring current generation. They proposed that thermal O+ ions preexisting in the oxygen torus are locally and nonadiabatically accelerated by fluctuations associated with dipolarization in the deep inner magnetosphere and contribute to ring current O+ ions. Therefore investigation of the oxygen torus is important to understand the dynamics of ions of ionospheric origin in the inner magnetosphere. In this study we search for the oxygen torus, using the magnetic field and plasma wave data obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument onboard the Van Allen Probes. We examine a few events on the dawnside in which toroidal standing Alfvn waves appear clearly. From the frequency of the toroidal waves, the magnetospheric local mass density (?) is estimated by solving the MHD wave equation for realistic models of the magnetic field and the field line mass distribution. We also estimate the local electron number density (ne) from the plasma wave spectrograms by identifying narrow-band emission at the upper-hybrid resonance frequency. Assuming the quasi-neutral condition of plasma, we infer the local average ion mass (M) by ?/ne. It is found that M is generally less than 4 amu in the plasma trough, while it shows an enhancement of >6 amu near the plasmapause. This indicates an existence of the oxygen torus in the vicinity of the plasmapause. We will present the result and discuss possible formation mechanisms of the oxygen torus. Possible contribution of the oxygen torus to the formation of the O+-rich ring current will be also discussed.

Nose, M.; Satoshi, O.; Keika, K.; Kletzing, C.; Smith, C. W.; MacDowall, R. J.; Kurth, W. S.; De Pascuale, S.

2013-12-01

366

Superradiance in a torus magnetosphere around a black hole  

PubMed

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

van Putten MH

1999-04-01

367

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

368

The ultraviolet spectra of the Jovian aurora  

SciTech Connect

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

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

1996-08-01

369

Io-related Jovian decametric arcs  

SciTech Connect

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

Wilkinson, M.H.

1989-09-01

370

Idealized Voyager Jovian magnetosphere shape and field  

SciTech Connect

A magnetic field arising from the Jovian equatorial sheet current deduced from Voyager 1 and 2 observations has been added to a planetary dipole field to provide a model of magnetic field inside the magnetopause. This internal field was used to calculate the magnetopause surface in a cyclic process. During each cycle, the surface was calculated, and the resulting field due to currents on the magnetopause was calculated for inclusion in the total field used to calculate the next-order surface. The resulting magnetopause is, as anticipated, flatter in shape than one resulting primarily from a dipole internal field source, but not dissimilar in overall height-to-width configuration to that of the magnetopause calculated for the larger inflated magnetopause observed by Pioneer 10. An array of magnetic field values for locations internal and external to the magnetopause due to currents on the surface has been computed by integrating over the entire magnetopause. A model for the total magnetospheric field of this semi-inflated magnetosphere has been constructed by adding this latter contribution to the internal source fields to obtain a global model of a semi-inflated Jovianlike magnetospheric field. The magnitude of the contribution of the surface currents to the total magnetic field in the region of the orbits of the Galilean satellites is calculated to be considerably larger for this Voyager model than for the Pioneer model.

Engle, I.M. (US Naval Academy, Annapolis, MD (USA))

1991-05-01

371

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

372

Energetic oxygen and sulfur ions in the Jovian magnetosphere and their contribution to the auroral excitation  

SciTech Connect

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 are used to calculate abundances and energy spectra in the region from 5 to 20 Jovian radii (R/sub j/). The phase space density of the oxygen ins calculated from the spectra has a positive radial gradient between 6 and 17 R/sub J/, indicating an inward diffusive flow. The upper limit for the diffusion coefficient D at 9 R, is approx.10/sup -5/ s/sup -1/. This limit, combined with the analysis of Voyager plasma observations by Sisccoe et al (1981), implies an upper limit to the production rate of oxygen and sulfur ions from Io of approx.10/sup 28/ ions/s. If D(9 R/sub J/) is approx.4 x 10/sup -6/ s/sup -1/, then approx.2 x 10/sup 24/ oxygen and sulfur ions with >70 MeV/nuc-G are lost per second as they diffuse inward from 12 to 8 R/sub j/. Assuming these ions are scattered into the loss cone, they deliver approx.4 x 10/sup 12/ W to the Jovian atmosphere. Extrapolations to lower magnetic moments suggest that the 10/sup 13/-10/sup 14/ W required to produce the observed ultraviolet auroral emissins could result from the precipitation of approx.10/sup 26/ oxygen and sulfur ions/s with magnetic moments > or approx. =10 to 30 MeV/nuc-G (> or approx. =35 to 100 keV/nuc at 10 R/sub J/).

Gehrels, N.; Stone, E.C.

1983-07-01

373

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

Microsoft Academic Search

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

D. A. Gurnett; C. K. Goertz

1981-01-01

374

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

PubMed

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

Rzepa, Henry S

2009-03-01

375

Fast Waves and Electron Current Drive in the Irvine Torus.  

NASA Astrophysics Data System (ADS)

This work reports the results of experimental studies of the fast wave with frequencies near the mean gyro-frequency (omega ~ ~ (omega _{rm ci}omega_{ rm ce})^{1/2}) in magnetized, toroidal plasmas with comparison to theory. Experiments investigating fast wave dispersion and damping, and the use of unidirectional fast waves to drive steady-state electron currents were performed on the Irvine Torus. The wave was excited in the plasmas by a phased array antenna which allowed launching of uni - or bi-directional fast waves around the torus. Probe measurements of the angle of propagation of wave energy, radial wavelengths, and the direction and magnitude of radial wave phase velocities were found to be in good agreement with predictions from cold plasma theory. Measurements of fast wave damping showed the observed damping lengths to be anomalously short when compared to predictions for electron Landau damping, transit-time magnetic pumping, and collisional damping, but may be explained by effects due to fast wave scattering from drift wave density fluctuations. Steady-state electron currents were driven by uni-directional fast waves. Low power experiments (< 25W) generated up to 1.3 A of electron current with a peak efficiency of eta = INR _{rm o}/P ~eq 6 times 10^{-2}A/W (10 ^{13}cm^{-3 }) m. Up to 14% of the wave energy was converted to poloidal magnetic field energy. The maximum current observed was found to be in rough agreement with a prediction from quasi-linear theory. Electron currents generated by application of radio-frequency power applied to a loop coupler antenna designed to excite the fast wave were observed in the Princeton Large Torus.

Platt, Robert Croft

376

Microtearing Simulations in the Madison Symmetric Torus  

NASA Astrophysics Data System (ADS)

Recent studies of improved confinement discharges in reversed field pinch (RFP) plasmas have revealed the need for greater understanding of the role that microinstabilities may be playing in these devices. In this work, the gyrokinetic codes GYRO and GENE are used to investigate the characteristics of these instabilities in an RFP-type equilibrium. Microtearing is found to have large growth rates across a range of scales for the parameter regime of the Madison Symmetric Torus and may be especially relevant to high-beta PPCD discharges, where large scale tearing mode activity is suppressed and microturbulence is believed to play a greater role in transport. Important features of the mode, such as critical values for beta and electron temperature gradient, are studied for a number of geometric parameters, including flux surface radius and RFP ?. The dependence on collisionality, which plays an important role in this instability, is explored using a Lorentz operator. We find that the RFP microtearing mode is unstable across a range of collisional frequency, and parameter scans show different responses at low versus moderate/high collisionality, possible evidence for different physical drive mechanisms. The source of these drives is explored and compared with existing theory.

Carmody, Daniel; Pueschel, M. J.; Terry, P. W.

2012-10-01

377

Voyager 2 - Energetic ions and electrons in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The passage of Voyager 2 through the Jovian magnetosphere demonstrated that this magnetosphere is highly variable, even as close as 10 Jupiter radii from the planet. The cosmic-ray subsystem measured the flux, elemental composition, and anisotropy of energetic particles. Its high sensitivity was particularly valuable during the long passage through the magnetotail, where particle fluxes were orders of magnitude less than in the inner magnetosphere and approached interplanetary values. The new data confirm earlier observations that the Jovian magnetosphere is a giant accelerator of particles - electrons, protons, and heavy ions, including sulfur. Both spatial and temporal changes are observed in the magnetosphere as compared to prior observations with Pioneer 10 and 11 and Voyager 1. It is suggested that the 10-hr modulation of interplanetary Jovian electrons may be associated with the arrival at the dawn magnetopause of a rarefaction region each planetary rotation.

Vogt, R. E.; Cummings, A. C.; Garrard, T. L.; Gehrels, N.; Stone, E. C.; Trainor, J. H.; Schardt, A. W.; Conlon, T. F.; Mcdonald, F. B.

1979-01-01

378

Initial Results from the Jovian Electrodynamic Tether Systems (JETS) Study  

NASA Technical Reports Server (NTRS)

The Jovian system with its rapid planetary rotation and strong magnetic field presents exciting opportunities for the use of electrodynamic (EM) tethers in system applications on a Jovian spacecraft. Previous analysis for a radial, 10 km length tether demonstrated the possibility of propulsive forces as large as 50 N and power generation levels as high as 10(exp 6) W for low perijov passing trajectories. For orbital positions beyond approximately 2.5 Jovian radii, JETS can be used simultaneously for power and increases in the orbital altitude. Previous study demonstrated the physical feasibility of EM tether use at Jupiter, but did not address the issues of limited gravity gradient force for tether extension and power regulation needed before JETS can be implemented as a practical spacecraft system. This presentation will discuss these issues and current progress in an ongoing systems feasibility study.

Gallagher, D. L.; Garbe, G. P.; Moore, J.; Talley, C.

2001-01-01

379

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

380

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

381

High-order magnetic multipoles as a source of gross asymmetry in the distant Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The longitudinal asymmetry of the surface magnetic-field strength at Jupiter causes a longitudinal asymmetry in the equatorial plasma mass density within the Jovian magnetosphere. The rotation of these density variations with the planet causes a diurnal variation of the radial distance on the night side at which the centrifugal stress of the magnetospheric plasma exceeds the local magnetic-field tension. This is approximately the distance at which the magnetic field opens to interplanetary space; we estimate that the opening distance can vary by as much as 14% as a result of the observed surface field asymmetry. Such a diurnal variation of the boundary of the particle trapping region can account for the observed ten-hour modulation of relativistic electrons emitted from Jupiter into interplanetary space.

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

1975-01-01

382

Fast-wave current drive in the Irvine torus  

SciTech Connect

Steady-state electron currents were driven by fast waves with ..omega../sub c/i<<..omega..<<..omega../sub ce/ in an initially current-free plasma in the Irvine Torus. Current direction was controlled by the fast-wave phased-array antenna. Low power experiments (<25 W) generated up to 1.3 A of electron current with a peak effeciency of eta = InR/Papprox. =(6 x 10/sup -2/ A/W)(10/sup 13/ cm/sup -3/)m. Up to 14% of the wave energy was converted to poloidal magnetic field energy.

McWilliams, R.; Platt, R.C.

1986-02-24

383

Fast-wave current drive in the Irvine torus  

Microsoft Academic Search

Steady-state electron currents were driven by fast waves with omegaci<plasma in the Irvine Torus. Current direction was controlled by the fast-wave phased-array antenna. Low power experiments (<25 W) generated up to 1.3 A of electron current with a peak effeciency of eta=InR\\/P~=(610-2 A\\/W)(1013 cm-3)m. Up to 14% of the wave energy was converted to poloidal

R. McWilliams; R. C. Platt

1986-01-01

384

New Capabilities and Results for the National Spherical Torus Experiment  

SciTech Connect

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

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

2008-02-29

385

New capabilities and results for the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

386

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

Microsoft Academic Search

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

M. A. Jaworski; M. G. Bell; T. K. Gray; R. Kaita; J. Kallman; H. Kugel; B. LeBlanc; A. McLean; S. A. Sabbagh; V. Soukhanovskii; D. P. Stotler; V. Surla

2011-01-01

387

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

National Technical Information Service (NTIS)

The durability of a carbon-carbon composite, Aerolor A05, X-point divertor dump plate to thermal fatigue was evaluated for the Joint European Torus (JET) at Sandia's Plasma Material Test Facility. Of primary interest was the effect of thermal cycling on t...

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

1991-01-01

388

Wavelet Analysis of Jovian Stratospheric Temperatures  

NASA Astrophysics Data System (ADS)

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

Young, L. A.

2001-11-01

389

Physics Results from the National Spherical Torus Experiment  

SciTech Connect

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

M.G. Bell for the NSTX Research Team

2004-07-08

390

The neutral cloud and heavy ion inner torus at Saturn  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

391

Neutral cloud and heavy ion inner torus at Saturn  

SciTech Connect

Voyager plasma data are used in conjunction with laboratory data on water molecule sputter-yields and energy distributions to calculate the morphology of the Saturn neutral water molecule and dissociated water molecule-product torus coexisting with the E-ring and icy satellites of this planet. Plasma production rates determined for this cloud exhibit a structure with distance from Saturn as well as from the orbit plane; this suggests a lack of equilibrium for the heavy ion plasma at less than 7 planet radii. Attention is given to the possibility that the Saturn E-ring may be a precipitate of the neutral cloud that is initiated by low-energy ion-molecule reactions. 61 references.

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

1989-02-01

392

Monte Carlo simulation of energization of Jovian trapped electrons by recirculation  

SciTech Connect

The recirculation model for particle acceleration in the Jovian magnetosphere is studied by means of Monte Carlo simulation. The recirculation model combines the conventional radial and pitch angle diffusion processes with the essentially energy-conserving latitudinal diffusion in low altitudes and the pitch angle scattering in the plasma disc. This process has been proposed to explain the pitch angle and spectral characteristics of MeV electrons observed by Pioneer spacecraft in the Jovian magnetosphere. The simulation confirms that the dumbbell type anisotropy and the high-energy tail of the energy spectrum can be produced from the recirculation process if the rate of the low-altitude cross-L diffusion is comparable to that of the conventional radial diffusion. The required low-altitude diffusion rate corresponds to roughly 10{sup {minus}2} times the Bohm diffusion rate for 1-MeV electrons, and altitudes is responsible for this high diffusion rate. The dumbbell type anisotropy observed also for MeV range electrons in the Earth's and Saturnian magnetospheres could also be the consequence of the recirculation process.

Fujimoto, M.; Nishida, A. (Inst. of Space and Astronautical Science, Sagamihara (Japan))

1990-04-01

393

Response of the Jovian thermosphere to variations in solar EUV flux  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

394

Multifolded torus chaotic attractors: design and implementation.  

PubMed

This paper proposes a systematic methodology for creating multifolded torus chaotic attractors from a simple three-dimensional piecewise-linear system. Theoretical analysis shows that the multifolded torus chaotic attractors can be generated via alternative switchings between two basic linear systems. The theoretical design principle and the underlying dynamic mechanism are then further investigated by analyzing the emerging bifurcation and the stable and unstable subspaces of the two basic linear systems. A novel block circuit diagram is also designed for hardware implementation of 3-, 5-, 7-, 9-folded torus chaotic attractors via switching the corresponding switches. This is the first time a 9-folded torus chaotic attractor generated by an analog circuit has been verified experimentally. Furthermore, some recursive formulas of system parameters are rigorously derived, which is useful for improving hardware implementation. PMID:17411254

Yu, Simin; Lu, Jinhu; Chen, Guanrong

2007-03-01

395

Modeling the Interaction of Europa with the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

396

Homological mirror symmetry and torus fibrations  

Microsoft Academic Search

In this paper we discuss two major conjectures in Mirror Symmetry: Strominger-Yau-Zaslow conjecture about torus fibrations, and the homological mirror conjecture (about an equivalence of the Fukaya category of a Calabi-Yau manifold and the derived category of coherent sheaves on the dual Calabi-Yau manifold). Our point of view on the origin of torus fibrations is based on the standard differential-geometric

Maxim Kontsevich; Yan Soibelman

2000-01-01

397

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

Microsoft Academic Search

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

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

1998-01-01

398

Diffusive Mass and Angular Momentum Transport in an Euler Potential Model of the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

Radial profiles of plasma flux tube content are often modelled using diffusive plasma transport using an assumed source rate and diffusion coefficient. Independently, and not necessarily self-consistently, the radial profile of the plasma azimuthal velocity can be calculated using the Hill-Pontius equation, for the mathematically separable case where the source and transport regions are spatially distinct. These steady state profiles can be imposed into a magnetospheric model to understand the resulting fields and currents. In a non-steady state where the plasma source rate is varying, and/or the outflowing plasma is not in equilibrium, these solutions do not apply. Hence, important questions concerning time-dependent mass-loading in the jovian and saturnian magnetospheres cannot be adequately addressed using such models. In this paper we present a new approach where we solve the time-dependent equations for diffusive radial transport of both mass and angular momentum, thus allowing for time-dependent plasma sources and the motion of radial structures produced by such time-dependence. These time-dependent solutions are coupled to an Euler potential magnetospheric model to calculate time-dependent magnetospheric configurations. We present our modelling methodology and the first results from this coupled model.

Arridge, C. S.

2012-12-01

399

Similarities and Differences of Transport in the Terrestrial and Jovian Environments  

NASA Astrophysics Data System (ADS)

Jupiter's magnetosphere differs from the terrestrial magnetosphere in ways that critically modify the transport of plasma through the system. Of great consequence is the fact that Jupiter's moon Io provides a source of heavy ion plasma deep within the magnetosphere. The rapid rotation of the planet subjects the plasma to large rotational accelerations. Interchange instability is of little consequence at Earth but is identified at Jupiter and may be of critical importance in transporting Jovian plasma. Conservation of angular momentum causes the plasma to slow its angular speed with outward motion and this drives currents that couple the equatorial magnetosphere to the auroral zone, producing an aurora with very different sources from those familiar at Earth. The gargantuan scale of the magnetosphere affects the conservation of adiabatic invariants, with time scales of planetary rotation short or of order of the bounce time of thermal plasma. This feature of the magnetosphere results in strong local time-dependent structure. We will discuss these and other aspects of the comparison of the two magnetospheres.

Kivelson, M. G.

2001-12-01

400

Io as a source of the jovian dust streams  

Microsoft Academic Search

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

A. L. Graps; E. Grn; H. Svedhem; H. Krger; M. Hornyi; A. Heck; S. Lammers

2000-01-01

401

Near-Infrared Spectroscopy of Himalia An Irregular Jovian Satellite  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

402

A global magnetohydrodynamic simulation of the Jovian magnetosphere  

Microsoft Academic Search

We have developed a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and a rapidly rotating magnetosphere and applied it to Jupiter. For fixed solar wind dynamic pressure the rotating model Jovian magnetosphere extends farther toward the Sun and has greater extent in the east-west direction than a model without rotation but is little different in the

Tatsuki Ogino; Raymond J. Walker; Margaret G. Kivelson

1998-01-01

403

Corotation lag of the Jovian atmosphere, ionosphere, and magnetosphere  

Microsoft Academic Search

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

T. S. Huang; T. W. Hill

1989-01-01

404

A Time Dependent Model of the Jovian Current Sheet  

Microsoft Academic Search

From analysis of vector helium magnetometer measurements obtained during the Pioneer 10 outbound pass through the Jovian magnetosphere it is argued that the average location of the near-equatorial current sheet is a surface whose shape is determined by the veloc- ity at which the magnetic perturbations produced by a rotating tilted dipole propagate to large radial distances. The equation of

Margaret G. Kivelson; Paul J. Coleman; Lucien Froidevaux; Ronald L. Rosenberg

1978-01-01

405

Probabilistic models of the Jovian magnetopause and bow shock locations  

Microsoft Academic Search

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

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

406

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

407

Fine-Scale Structure of the Jovian Magnetotail Current Sheet.  

National Technical Information Service (NTIS)

During the outbound leg of its passage through the Jovian magnetosphere in the Voyager 2 spacecraft observed 50 traversals of the magnetotail current sheet during a 10 day period at distances between 30 and 130 R sub j. Analysis of these observations show...

K. W. Behannon

1983-01-01

408

Tangent Cylinder Effects in Jovian Convection  

NASA Astrophysics Data System (ADS)

Two properties of Jupiter's dynamics that are still not well understood are the extent and driving force of the zonal winds and the meridionally-independent heat loss. These may be linked by the presence of a tangent cylinder effect in the interior of the planet. A tangent cylinder could be formed by rotational constraints at the molecular to metallic hydrogen transition at ~0.8 jovian radii. Evidence for the existence of a tangent cylinder can be seen in pictures of Jupiter's northern hemisphere taken by the Cassini spacecraft en route to Saturn. At the latitude corresponding to the surface projection of the tangent cylinder, cloud motions are separated into a equatorial region with large scale zonal motions and a polar region with smaller scale, chaotic motions. To investigate tangent cylinder effects in Jupiter, we study a 3-D rotating thermal convection numerical simulation in a thin shell (rinner}/r{outer=0.75). Thermal convection solutions are obtained over a range of Rayleigh numbers Ra, for both rigid and free lower stress boundary conditions. The zonal winds and heat loss at the top of the shell and meridional flow throughout the shell are compared with observations. The numerical zonal winds recover some characteristics of observed winds on Jupiter, such as the large prograde equatorial zonal jet. Furthermore, at Ra>4E6, alternating jets appear poleward of the tangent cylinder, with wavelength similar to those seen in the Cassini image. Equatorial winds outside of the tangent cylinder are driven by the Reynold stresses from sloping fluid columns. Winds inside the tangent cylinder are non-geostrophic and require a different mechanism for their generation. Also at Ra>4E6, heat loss at the top of the shell is greater inside the tangent cylinder than outside. The tangent cylinder acts as a barrier to fluid motions, preventing meridional heat transfer and enhancing interior heat loss at the poles. This offers an explanation for why the total (interior + solar) heat loss from Jupiter is observed to be nearly independent of latitude.

Andreadis, S. J.; Olson, P.

2004-12-01

409

Ion partitioning in the hot Io torus - The influence of S2 outgassing  

NASA Technical Reports Server (NTRS)

An alternative time-independent model of the ion partitioning in the hot Io torus is proposed which introduces the ratio of sulfur to oxygen in the neutral source as a free parameter. Measurements of the ion abundances in the torus plasma are presented and discussed, noting some ambiguities and identifying the features that are well established. Physical processes important to the understanding of the ion partitioning calculation are reviewed. The results of the model are discussed in the context of observational constraints, and spectroscopic constraints are discussed. It is concluded that a bimodal source model, together with a small percentage of hot electrons and a relatively short diffusion time scale, can account for the principal observational features without invoking significant time variability. In particular, the O III deficiency observed in 1981 can be obtained in a model that produces other aspects of the torus ion partitioning measured during the Voyager 1 encounter.

Moreno, M. A.; Newman, W. I.; Kivelson, M. G.

1985-01-01

410

Preliminary discharge-cleaning and arcing studies in mini-torus  

NASA Astrophysics Data System (ADS)

Discharge cleaning was carried out in a small tokamak (Mini-Torus) with zero B ? and without limiter; the plasma contacted with the chamber wall closely. After 2000 shots the impurities consisting of water and other molecules were reduced by an order of magnitude. Probes of several materials placed close to the plasma acted as a kind of limiter. Unipolar arc tracks have been clearly observed with aluminum-coated glass probe. Arcing is closely related to initial electron bombardment.

Cao, J.; Chen, J.; Duan, W.; Fang, K.; Yan, D.; Yang, S.; Zhu, Y.

1980-10-01

411

Suprathermal ion transport in simple magnetized torus configurations  

SciTech Connect

Inspired by suprathermal ion experiments in the basic plasma experiment TORPEX, the transport of suprathermal ions in ideal interchange mode turbulence is theoretically examined in the simple magnetized torus configuration. We follow ion tracer trajectories as specified by ideal interchange mode turbulence imported from a numerical simulation of drift-reduced Braginskii equations. Using the variance of displacements, {sigma}{sup 2}(t){approx}t{sup {gamma}}, we find that {gamma} depends strongly on suprathermal ion injection energy and the relative magnitude of turbulent fluctuations. The value of {gamma} also changes significantly as a function of time after injection, through three distinguishable phases: ballistic, interaction, and asymmetric. During the interaction phase, we find the remarkable presence of three regimes of dispersion: superdiffusive, diffusive, and subdiffusive, depending on the energy of the suprathermal ions and the amplitude of the turbulent fluctuations. We contrast these results with those from a 'slab' magnetic geometry in which subdiffusion does not occur during the interaction phase. Initial results from TORPEX are consistent with data from a new synthetic diagnostic used to interpret our simulation results. The simplicity of the simple magnetized torus makes the present work of interest to analyses of more complicated contexts ranging from fusion devices to astrophysics and space plasma physics.

Gustafson, K.; Ricci, P.; Bovet, A.; Furno, I.; Fasoli, A. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-1015 Lausanne (Switzerland)

2012-06-15

412

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

413

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

414

WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy  

NASA Astrophysics Data System (ADS)

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 ?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 ?m is different between C-/P- and D-types. The albedo at 3.4 ?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 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 these large objects, L 4/L 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.; Mainzer, A. K.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R.

2012-11-01

415

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

416

Plasma conditions and the structure of the Jovian ring  

NASA Astrophysics Data System (ADS)

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

Hornyi, Mihly; Juhsz, Antal

2010-09-01

417

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

NASA Astrophysics Data System (ADS)

Based on observations from the Hubble Space Telescope and the Subaru Telescope, we have discovered that Europa, Ganymede, and Callisto are bright around 1.5 ?m even when not directly lit by sunlight. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was 106-107 of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 ?m, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 ?m by the Spitzer Space Telescope, but it was not detected, suggesting a significant wavelength dependence. It is still unknown why they are luminous even when in the Jovian shadow, but forward-scattered sunlight by hazes in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us with a new technique to investigate the Jovian atmospheric composition. Investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.

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

2014-07-01

418

Periodic amplitude variations in Jovian continuum radiation. Progress report for period ending February 1986  

SciTech Connect

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

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

1986-04-02

419

The sub-Alfvnic interaction of the Galilean satellites with the Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

Recent observations by the Galileo spacecraft and Earth-based techniques have motivated us to reconsider the sub-Alfvnic interaction between the Galilean satellites of Jupiter and the magnetosphere. (1) We show that the atomic processes causing the interaction between the magnetoplasma and a neutral atmosphere can be described by generalized collision frequencies with contributions from elastic collisions, ion pickup, etc. Thus there is no fundamental difference in the effect of these processes on the plasma dynamics claimed in the recent literature. For a magnetic field configuration including possible internal fields, we show that the sub-Alfvnic, low-beta interaction can be described by an anisotropically conducting atmosphere joined to an Alfvn wing as one extreme case and the Jovian ionosphere as the other extreme case. (2) The addition of a small magnetic field of internal origin does not modify the general Alfvn wing model qualitatively but only quantitatively. All magnetic moments discussed in the literature for Io are small in this sense. For an aligned internal dipole and ambient Jovian magnetic field the interaction will be enhanced by focusing of the electric field. (3) A qualitative change occurs by the additional occurrence of closed magnetic field lines for larger internal magnetic fields as in the case of Ganymede. Here the focusing is even enhanced. (4) The first discussion of nonstationary plasma flows at the satellites shows that electromagnetically induced magnetic fields may play an important role if the satellite interiors are highly conducting. From the point of view of the external excitation, induction effects may be strong for Callisto, Io, Europa, and Ganymede in order of decreasing importance. The magnetic field observations at the first Callisto encounter can be explained by these effects.