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Plasma Science, IEEE Transactions on

Issue 6 • Date Dec 1992

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Displaying Results 1 - 25 of 67
  • The development of discrete active auroral forms

    Publication Year: 1992 , Page(s): 764 - 769
    Cited by:  Papers (1)
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    Using analytical and numerical methods, it is shown that all the basic forms of the active arcs can be described within the framework of a nonlinear Alfven wave model. The auroral forms are then considered as nonlinear two-dimensional Alfven vortex structures that are uniform along the ambient magnetic field. They can exist in a cold inhomogeneous plasma, e.g., the Earth's ionosphere. Large-scale spirals and folds can recover the initial form of a typical arc. In the case of a small solitary disturbance of the current density or a sharp bending of the current sheets, vortex chains are formed in the spirals and the folds View full abstract»

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  • Inequality conditions for critical velocity ionization space experiments

    Publication Year: 1992 , Page(s): 770 - 777
    Cited by:  Papers (2)
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    A compilation is given of various parametric conditions for the critical ionization velocity (CIV) process to occur in the ionosphere. The most important and salient aspects of CIV are discussed, including beam velocity, Townsend's criterion, magnetic-field strength, beam width, pitch angle, mixture of species, metastable states, and mass loading View full abstract»

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  • A comparison between laboratory and space experiments on Alfven's CIV effect

    Publication Year: 1992 , Page(s): 778 - 786
    Cited by:  Papers (2)
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    Laboratory experiments on Alfven's critical ionization velocity (CIV) effect have established the reality of the CIV effect and determined the parameter limits within which the effect can be expected in the laboratory for different combinations of plasma and neutral gas species: velocity, magnetic field strength, and neutral gas and plasma density. However, in the laboratory experiments there are always walls and usually electrodes present, and the available parameter regime is such that the details inside the CIV process are difficult to study. Such studies can better be made in ionospheric release experiments, where waves and particle spectra can be directly measured inside the interaction region. Injection experiments are also better suited to study the momentum exchange process between the CIV region and a larger surrounding plasma View full abstract»

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  • Unification of gravitational, electrical, and strong forces by a virtual plasma theory

    Publication Year: 1992 , Page(s): 939 - 943
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    It was demonstrated in previous papers that a virtual plasma theory of physical forces unifies all forces as `fluid' or `Magnus' forces generated by vortex structures (particles) in the virtual plasma gas. The theory generates gravitational fields. It generates the electrostatic field in the atom, explains the form and action of the Schrodinger equation, and generates the appropriate Bohr orbits in the hydrogen atom. It is demonstrated that the general form of the strong nuclear forces is also generated by the theory. An extension of the concept of planetary formation to this virtual plasma also predicts the mass spectrum for the leptons and hadrons View full abstract»

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  • Three fluid transport models by particle-in-cell method for RF glow discharges

    Publication Year: 1992 , Page(s): 1000 - 1014
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    Three self-consistent fluid transport models, simulated by the particle-in-cell simulation method (PIC/FE), have been developed for parallel-plate RF glow discharges. The electron transport is modeled by the equilibrium single-moment and nonequilibrium two- and three-moment fluid equations. In the equilibrium single-moment model, the α and γ discharges are underestimated and the nonlocal γ-discharge behavior is difficult to measure. On the other hand, the nonequilibrium three-moment model can clearly demonstrate the distinct α- and γ-discharge effects similar to self-consistent Monte Carlo model results. Moreover, the three-moment model can describe the transition of plasma density, sheath width, and bulk mean energy from the α regime to the γ regime and verify the transition boundary between α and γ regimes which are all consistent with experimental results. The results of the three-fluid models are presented, analyzed, and compared with each other in terms of the plasma density, electric field, average velocity, current density, mean energy, and ionization rate View full abstract»

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  • The role of self-consistency in double layer calculations

    Publication Year: 1992 , Page(s): 695 - 700
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    In a number of calculations involving nonlinear structures such as double layers and solitons, the Korteweg-de Vries theory is applied beyond its range of validity or approximations are made which are not self-consistent. Some situations arising in the theory of double layers in fluid multispecies plasmas are pointed out and attention is drawn to arbitrary-amplitude numerical calculations which yield results that are physically very different from those of the approximate theories. In particular, severe restrictions on the occurrence of ion-acoustic double layers in negative-ion plasmas and of electron-acoustic double layers in two-electron-component plasmas are found View full abstract»

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  • Effects of higher order nonlinearity on the propagation of solitary waves in relativistic ion drift plasma

    Publication Year: 1992 , Page(s): 1015 - 1022
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    The effects of higher-order nonlinearity, relativistically drifting ions, and negative ions on the ion-acoustic solitons in a plasma having isothermal electrons are investigated theoretically. By applying the reductive perturbation technique to the basic system of equations, a modified Korteweg-de Vries equations and a linear inhomogeneous wave equation have been derived. Moreover, stationary solutions of the coupled field equations have been obtained. A scenario is presented where the higher-order perturbed terms containing relativistic effects change the behavior of the solitons drastically. Results have been compared with those evaluated earlier for plasmas without negative ions and higher-order nonlinearity View full abstract»

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  • Transport of time-varying plasma currents by whistler wave packets

    Publication Year: 1992 , Page(s): 787 - 796
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    In a large laboratory plasma the properties of time-varying current systems have been studied experimentally. The parameter regime of interest involves magnetized electrons and unmagnetized ions. In the laboratory complete measurements of three-dimensional, time-varying vector fields of the total current density are obtained from magnetic probe measurements. Pulsed currents are observed to propagate at the speed of whistler wave packets. Their field structure forms flux-rope-like configurations which are electromagnetically force-free. Moving sources induce eddy currents which excite waves and form Cerenkov-like whistler wings. The radiation patterns of moving magnetic antennas and electrodynamic tethers have been investigated. The current closure between tethered electrodes across B&oarr;0 has been mapped. Nonlinear effects of large-amplitude, antenna-launched whistler pulses have been observed. These involve a new modulational instability in which a channel of high conductivity is formed which permits the wave/currents to penetrate deeply into a collisional plasma View full abstract»

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  • A global magnetohydrodynamic simulation of the magnetosheath and magnetosphere when the interplanetary magnetic field is northward

    Publication Year: 1992 , Page(s): 817 - 828
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1068 KB)  

    A new high-resolution global magnetohydrodynamic simulation model is used to investigate the configuration of the magnetosphere when the interplanetary magnetic field (IMF) is northward. For northward IMF the magnetospheric configuration is dominated by magnetic reconnection at the tail lobe magnetopause tailward of the polar cusp. This results in a local thickening of the plasma sheet equatorward of the region of reconnection and the establishment of a convection system with two cells in each lobe. In the magnetosheath the plasma density and pressure decrease near the subsolar magnetopause, forming a depletion region. Along the flanks of the magnetosphere the magnetosheath flow is accelerated to values larger than the solar wind velocity. The magnetopause shape from the simulations is consistent with the empirically determined shape View full abstract»

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  • Nonlinear interactions between electrons and RF waves in crossed electric and magnetic fields

    Publication Year: 1992 , Page(s): 659 - 662
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A laboratory experiment has been initiated to study nonlinear electron-wave interactions. In this experiment, the interaction between a guided RF wave and an electron beam is investigated using a large crossed field amplifier. The electron beam is injected through externally imposed crossed electric and magnetic fields. The large-amplitude RF wave is guided by a serpentine slow wave structure and travels at a phase velocity approximately equal to the average velocity of the electron beam. The formation of long-wavelength density structures has been proposed to affect the emission characteristics of the RF wave itself. Possible applications of the experiment in space plasmas are discussed View full abstract»

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  • Equilibrium of intergalactic currents

    Publication Year: 1992 , Page(s): 891 - 892
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    The plasma Universe approach to the structure of the Universe considers space to be filled with a network of currents which can undergo pinch compression. The equilibrium structures of such currents are treated in the same way as the structure in laboratory pinches. The difference, for the galactic case, is that gravitational interaction forces between the particles must be included in the analysis. A simple and straightforward way of achieving this is illustrated View full abstract»

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  • Two-stream and gravitational instabilities in a grain plasma

    Publication Year: 1992 , Page(s): 922 - 928
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    If the massive component of a two-component plasma consists of weakly charged solid grains, electrostatic and gravitational instabilities can operate on similar spatial and temporal scales. In particular, when the grain charge-to-mass ratio is on the order of the square root of the gravitational constant, the electrostatic two-stream (or Buneman) instability can seed the Jeans gravitational instability, selecting a scale for the resulting condensation. Using particle-in-cell simulations, the behavior of each of these instabilities acting alone in the appropriate limits is verified, and it is shown that when both act in concert a grand equipartition among all available stores of energy is achieved View full abstract»

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  • On finite ion Larmor radius MHD equations

    Publication Year: 1992 , Page(s): 1023 - 1025
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    The finite ion Larmor radius effects in magnetohydrodynamic equations are formulated without imposing plasma incompressibility. The result is in agreement with the gyrokinetic formulation View full abstract»

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  • Wave-particle interaction at the plasmasphere-ring current interface

    Publication Year: 1992 , Page(s): 829 - 832
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    During the plasmasphere filling process following geomagnetic storms, an outward density decrease of the cold plasma at L=3-4 is typically observed. When this structure overlaps with the sharp inner edge of the ring current, wave activity is detected at linearly stable phase velocities. The excitation of these waves around the lower hybrid frequency and their effects on the heating of thermal ions is analyzed. It is found that lower hybrid drift waves are most effective at heating lower mass ions, e.g., plasmaspheric H+, versus He+, which may be heated more effectively by electromagnetic ion cyclotron waves driven unstable by the ring current loss cone View full abstract»

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  • Current loop models for the circumstellar matter in SN 1987A

    Publication Year: 1992 , Page(s): 874 - 876
    Cited by:  Papers (1)
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    Some properties of current-loop models are explored, and some implications are discussed. The elliptical ring observed to be centered on the supernova can be interpreted as light from ions trapped in the magnetic field of a circular current loop. The current is 1.5×10 12 A for a model where gravitational force on 0.03 solar masses of trapped matter balances the electrodynamic expansion of the loop. The magnetic energy of the loop is 2×1041 erg. Consideration of the magnetized clouds in the solar wind as an analogous source for such a loop leads to the conclusion that the loop formed over the lifetime of the progenitor star View full abstract»

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  • Sounding rocket measurements of suprathermal ion acceleration

    Publication Year: 1992 , Page(s): 705 - 714
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    Transverse ion acceleration has been observed at rocket altitudes between 500 and 1000 km due to the injection of 100-200-eV argon plasma, auroral electron precipitation, and the injection of electromagnetic waves. Field-aligned currents necessary to neutralize the plasma injection payloads and those naturally occurring in the aurora could be responsible for the ions observed in the first two observations. Associated with the aurora, both bulk heating and tail heating are observed, sometimes simultaneously. In this case, either different masses are accelerated and/or different mechanisms are responsible. The bulk heating is closely correlated with the aurora structure while tail heating is not so well correlated. High-time-resolution rocket ion data have revealed that the transverse acceleration process is of very short duration (~100 ms) and occurs in a very limited volume (a few hundred kilometers along B and on the order of the ion gyrodiameter across B). Such impulse acceleration events are correlated with waves near the lower hybrid resonance. Wave injections of electromagnetic waves near the lower hybrid frequency result in the transverse acceleration of ambient ions View full abstract»

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  • Internal dynamics of a plasma propelled across a magnetic field

    Publication Year: 1992 , Page(s): 672 - 677
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    When a plasma is pushed across a magnetic field by some nonelectromagnetic force, ions and electrons get turned in opposite directions by the magnetic field. This creates an internal current as well as sheaths at the plasma surfaces and results in an electric field which allows the plasma to maintain some, or even most of its initial momentum in the form of E&oarr;×B&oarr; drift. An exact analysis of that process is presented for the internal region of the plasma. The energy provided by the initial push is used, in part, to create some gyrations inside the plasma. When the rest energy density of the plasma exceeds twice the magnetic energy density (or when the Alfven speed is less than c), there will be enough energy to spare for the plasma to continue across the magnetic field at half its initial momentum. Two cases are considered: an impulsive start and a gentle push such as provided by gravity. The amplitude of the resulting internal gyrations becomes small in the second case. The frequencies of the gyrations are those of extraordinary modes of very long spatial wavelength View full abstract»

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  • Carbon cathode spot plasma flux distributions in low pressures of hydrogen: some evidence for the C++H2→CH++H reaction

    Publication Year: 1992 , Page(s): 1053 - 1059
    Cited by:  Papers (2)
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    Measurements of the wall current collected from the expanding cathodic arc plasma are reported as a function of angle to cathode plane normal, with hydrogen gas pressure in the arc chamber varying between 10 -4 torr and 10 torr and distance R to the cathode varying between 10 and 80 mm. The angular distribution of the collected current is not seen to be affected by the gas pressure in the chamber. This flux decreases with distance to the cathode as R-(1.4) in vacuum and R-4 in the 1-10 torr pressure domain. Flux intensity evaluated as a function of NR, where N is the number density of hydrogen in the chamber, leads to an evaluation of an effective collision cross section, σe, of 0.2×10-16 cm2 for the C+-ion/H2 molecule interaction. This value can be attributed to the reaction C++H2→CH+ +H and agrees with a velocity of the C+ ions following a shock wave interaction model View full abstract»

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  • Test-ion diffusion in a magnetized plasma

    Publication Year: 1992 , Page(s): 655 - 658
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    Cross-field transport of barium test ions is studied in a Q-machine plasma. Test particles are produced and tracked in their motion by an optical tagging method. The comparison between the measured tag signal and a simple theoretical simulation yields an evaluation of the ion diffusivity. Diffusion is supported by classical mechanisms. The injection of different noble buffer gases modifies the plasma parameters in such a way that the diffusion remains classical but its magnitude is reduced View full abstract»

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  • Fiber theory and cosmic plasmas

    Publication Year: 1992 , Page(s): 893 - 897
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    The fiber theory of plasmas has been developed as an alternative description to conventional MHD, and some of its aspects are reviewed. Cosmic plasmas described in terms of the fiber theory have very different properties from those predicted by traditional methods. For example, cosmic current filaments can store magnetic energy internally, so that intense electric activity is not necessarily observable in terms of a magnetic field View full abstract»

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  • Physics issues associated with low-β plasma generators

    Publication Year: 1992 , Page(s): 644 - 650
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    Kinetic aspects of MHD generators are explored by examining the propagation of dense, low-β streams of plasma. Three situations are considered: the basic principles of plasma-stream propagation, the propagation of plasma streams into vacuum, and the propagation of plasma streams into ambient plasmas. These three situations are analogous to plasma generators, plasma generators with vacuum loads, and plasma generators with plasma loads. Kinetic (microphysics) aspects include oscillations of the generator plasma, the effects of diocotron instabilities, the acceleration of particles, the starvation of current systems, and plasma-wave production View full abstract»

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  • Unification of gravity and electromagnetism in the plasma universe

    Publication Year: 1992 , Page(s): 944 - 957
    Cited by:  Papers (1)
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    The basic arguments and results of the gravity-electromagnetism (GEM) theory are presented. This theory unifies gravity and electromagnetism using simple models and concepts and is based on two postulates: (1) gravity is a spatially varying Poynting field that defines the geometry of space such that ultrastrong fields are self-canceling and (2) the splitting or separation of characteristics of gravity and EM are mirrored in the splitting of protons and electrons and these quantities merge at the Planck level to give one field and one particle type. Consequently, it is shown that two highly accurate formulas can be derived: (1) G=e2/(4πε0mp me) αexp(-2R1/2), where mp and me are the proton and electron masses respectively, α is the fine structure constant, and R=mp/me, and (2) α-1=R2/3-R1/3 -2/3/(1+4/(3R)). It is found that the GEM theory is consistent with a flat open cosmos and predicts the value of the cosmic background temperature to high accuracy and the Hubble time to reasonable agreements with current estimates View full abstract»

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  • Some aspects of dust-plasma interactions in the cosmic environment

    Publication Year: 1992 , Page(s): 929 - 934
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    A brief, critical review of dust-plasma interactions in the cosmic environment is presented, with emphasis on certain results. Both single-particle (e.g., gravitoelectrodynamics) and collective (e.g., appearance of new wave models) effects are discussed and some areas in which further research is needed are pointed out. The pressing need for laboratory studies, both to provide the necessary data for the theoretical studies and to test the predictions of these theories, is emphasized View full abstract»

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  • Day-side auroral signatures based on simultaneous, coordinated observations at Svalbard and Greenland

    Publication Year: 1992 , Page(s): 726 - 739
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    The height distribution of the dayside cusp aurora and the relation between optical emissions and net downward electron energy flux are discussed. These two important characteristics of day-side cusp aurora are still unknown. It is instructive to compare particle flux and optical luminosity because these two quantities should be proportional if the cusp aurora is caused by electron impact, as has been found for nighttime aurora in the oval. Furthermore, there should then be a direct relation between auroral altitudes and particle energy. Based on coordinated auroral observations at Svalbard and Greenland, together with simultaneous, overhead F-9 satellite measurements, these quantities have been evaluated View full abstract»

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  • Magnetic suppression of arc blowout in a model arc furnace

    Publication Year: 1992 , Page(s): 1026 - 1035
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    The two most likely causes of electromagnetic instability in electric furnace arcs are shown to be the kink and the fire-hose instabilities. Stabilization by an externally imposed axially magnetic field is analyzed, and experimental results are presented demonstrating stabilization of a small, pulsed test arc by this method View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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