By Topic

Plasma Science, IEEE Transactions on

Issue 6 • Date Dec 1992

Filter Results

Displaying Results 1 - 25 of 67
  • A comparison between laboratory and space experiments on Alfven's CIV effect

    Publication Year: 1992 , Page(s): 778 - 786
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of higher order nonlinearity on the propagation of solitary waves in relativistic ion drift plasma

    Publication Year: 1992 , Page(s): 1015 - 1022
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On finite ion Larmor radius MHD equations

    Publication Year: 1992 , Page(s): 1023 - 1025
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 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)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Physics issues associated with low-β plasma generators

    Publication Year: 1992 , Page(s): 644 - 650
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Acoustic double layers in multispecies plasma

    Publication Year: 1992 , Page(s): 745 - 755
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    Particle simulation in a one-dimensional bounded system is used to examine the formation of acoustic double layers in the presence of two ion species. Double-layer formation depends critically on the details of the distribution functions of the supporting ion populations, and their relative drifts with respect to the electrons. The effect of having two ion components, an H+ and an O+ beam, on double-layer evolution from ion acoustic turbulence driven by an electron drift relative to the H+ beam of ≈0.5u e, where uue is the electron thermal speed, is examined. The ratio of ion drifts is taken to be consistent with acceleration by a quasi-static auroral potential drop (i.e. V H/VO=√MO/ MH=4.0). Acoustic double layers form in either ion species on the time scale τ≈100ωps-1, where ωps is the ion plasma frequency for species `s' and s=H or O, and for drifts relative to the electrons lower than that required for double layer formation in simulations of single ion component plasma View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Manifestations of electric currents in interstellar molecular clouds

    Publication Year: 1992 , Page(s): 867 - 873
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    Attention is drawn to filamentary structures in molecular clouds and the existence of subfilaments of sinusoidal shape and also of helix-like structures is pointed out. For two dark clouds, the Lynds 204 complex and the Sandqvist 187-188 complex (the Norma `sword'), a detailed study of such shapes is made, and the possible existence of helices wound around the main filaments is found. All these features suggest the existence of electric currents and magnetic fields in these clouds. On the basis of a generalization of the Bennett pinch model, the magnitudes of the currents expected to flow in the filaments are derived. Values of column densities, magnetic field strengths, and directions of the fields are derived from observations. Magnetic fields with both toroidal and axial components are considered. This study shows that axial currents on the order of a few times 1013 A are necessary for the clouds to be in equilibrium View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evolution of particle clouds around ablating pellets in magnetically confined hot plasmas

    Publication Year: 1992 , Page(s): 663 - 668
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Cryogenic hydrogen isotope pellets are being used for introducing fuel particles into the plasma interior in magnetic confinement fusion experiments. The spatial and the time evolution of the initially low-temperature, high-density particle clouds forming around such pellets are considered, with particular attention given to such physical processes as heating of the clouds by the energy fluxes carried by incident plasma particles, gas-dynamic expansion with j× B-produced deceleration in the transverse direction, finite-rate ionization and recombination processes, and magnetic field convection and diffusion. While the dynamic processes associated with the ionization and radial confinement processes are characterized by the relatively short Alfven time scale (μs range), the subsequent phase of axial expansion is associated with a notably larger hydrodynamic time scale defined by the heat input and gas-dynamic expansion rates (ms range). Data stemming from experimental measurements in toroidal confinement machines are compared with results of model calculations. Some similarities with extraterrestrial plasma scenarios, such as the earlier magnetospheric barium release experiments, are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Plasma diffusion through multidipole magnetic fields

    Publication Year: 1992 , Page(s): 988 - 995
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The diffusion of a cold plasma through multidipole fields of a magnetic picket fence is presented. The ion diffusion and trapping are determined by electric potentials inside the multidipole fields. The electron diffusion is regulated by an anomalous transport process driven by low-frequency fluctuations inside the magnetic sheath. Particles drifting with velocities above the ion acoustic speed generate high-amplitude turbulent waves responsible for an anomalous diffusion process View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Velocity space diffusion in Q-machine plasmas

    Publication Year: 1992 , Page(s): 651 - 654
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    Measurements of test particle diffusion in velocity space are reported. Test particles are created and examined using the method of optical tagging, an extension of laser-induced fluorescence. In quiet plasma conditions (δn/n⩽0.01%) results show diffusion to be linear with density in agreement with classical theory. Measurements taken in the presence of drift waves (δn/n≃6%) show resonant particle interactions. Applications to magnetospheric phenomena are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experiments on the interaction of current channels in a laboratory plasma: relaxation to the force-free state

    Publication Year: 1992 , Page(s): 614 - 621
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    A series of experiments on the dynamic interaction of two current channels has been performed in the large plasma device, a laboratory device at UCLA. The two current channels are formed by coating the cathode source nonuniformly and then biasing it with respect to an anode 10 m away. The experiment consists of two phases, one in which a net current is drawn through the plasma, and one in which the net current is zero. The current channels twist about each other, merge, and evolve toward a force-free state when a net current is drawn through the plasma. When the net current is zero the interaction between the channels is greatly reduced. The dynamics of the system are dominated by electron pressure and associated electrostatic fields. However, as the currents twist, a small amount of magnetic helicity is generated. The helicity and its temporal rate of change are computed and found to compare within experimental uncertainty to the predicted rate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The cosmological constant and the red shift of quasars

    Publication Year: 1992 , Page(s): 958 - 964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    How the cosmological constant that is used in Einstein's model has an equivalent in the Big Bang model is discussed; gravitational fields are also considered. That model requires a critical density of matter that leads to the problem of dark matter. It is shown that data on new cosmological structures and on a non-Doppler red-shift mechanism lead to an unlimited and ageless Universe. It is also explained why quasars appear to be unusual objects and have a large red shift while being physically much closer to us than usually claimed. One can see that their luminosity is about the same as standard galaxies and not as millions of galaxies as believed previously. One can also explain why the luminosity-distance relationship observed in galaxies is not observed in quasars View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of strongly dissipative MHD structures

    Publication Year: 1992 , Page(s): 882 - 890
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The formation of compact magnetic structures by advection of an initial magnetic seed due to the motion of the plasma, and the intensification of the field due to line stretching are discussed. It is shown that when the plasma is squeezed locally by external agents, so that an inflow-outflow near a stagnation point is generated by the pinching, large amounts of Joule heating are obtained in a short time when the magnetic Reynolds number is large View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Alfven's programme in solar system physics

    Publication Year: 1992 , Page(s): 577 - 589
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1448 KB)  

    Hannes Alfven's research program in solar system physics provides a valuable case study for the historians and philosophers of science. The response of the scientific community to his remarkable contributions is a severe test of widely held views about how science is or should be done. Seven of those contributions are examined, in the light of two doctrines of scientific methodology, those of Karl Popper (1959) and Imre Lakatos (1978). The seven are: application of the magnetic braking concept to the origin of the solar system; magnetohydrodynamic waves; field-aligned (`Birkeland') currents; critical ionization velocity and the existence of planetary rings; jet streams; electrostatic double layers; and partial corotation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Observation of closed loops in high-voltage discharges: a possible precursor of magnetic flux trapping

    Publication Year: 1992 , Page(s): 669 - 671
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    In multimegavolt electrostatic generators, the accidental sparkover discharges change in character as the voltage and stored energy increase. The usual forked, unidirectional discharges are replaced by complex discharges containing numerous closed loops. It is suggested that this is an example of the formation of closed-current loops that generate magnetic fields in astrophysics View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulations of second-order Fermi acceleration of electrons: solving the injection problem

    Publication Year: 1992 , Page(s): 917 - 921
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The boosting of electrons from a Maxwellian distribution into a suprathermal power-law tail is studied, using a test-particle simulation code, following the full equations of motion of tens of thousands of electrons chosen from a thermal population as they move through general time-dependent magnetic fields. This distinguishes between bulk heating of the electron population or boosting of selected electrons. Which of these occurs is found to depend on the size of the swarm thermal speed compared with the electron thermal speed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laboratory experiment on kinetic Alfven waves in connection with phenomena in space plasmas

    Publication Year: 1992 , Page(s): 622 - 625
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A laboratory experiment has been performed in connection with interesting phenomena in space plasmas such as geomagnetic pulsations in the magnetosphere or particle acceleration by the kinetic Alfven wave in field-aligned currents of the auroral circuit. Fast waves or MHD surface waves in a cylindrical finite-β plasma have been observed to be mode converted into kinetic Alfven waves at the Alfven resonance layer. The surface waves were excited using small loop antennas located at the edge of the inhomogeneous plasma to simulate those on the magnetosphere or plasmapause View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cosmological implications of a massive neutrino

    Publication Year: 1992 , Page(s): 965 - 966
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    The Alfven cosmic plasma model of the Universe is shown to be consistent with the cosmic background radiation, which is taken to be the radiation from neutrino-antineutrino annihilation. The mass of the neutrino is found to be 6.2×10-4 eV, which is consistent with other experimental observations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Unification of gravitational, electrical, and strong forces by a virtual plasma theory

    Publication Year: 1992 , Page(s): 939 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Equilibrium of intergalactic currents

    Publication Year: 1992 , Page(s): 891 - 892
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sounding rocket measurements of suprathermal ion acceleration

    Publication Year: 1992 , Page(s): 705 - 714
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Day-side auroral signatures based on simultaneous, coordinated observations at Svalbard and Greenland

    Publication Year: 1992 , Page(s): 726 - 739
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1332 KB)  

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generation of coherent structures caused by ionospheric heating

    Publication Year: 1992 , Page(s): 803 - 809
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    The thermal parametric instability excited by powerful high-frequency (HF) radio waves in the F region of the ionosphere is investigated. The HF radio waves, propagating through this inhomogeneous, magnetized plasma, are transformed into large-amplitude electrostatic plasma waves, which in turn couple to pseudo-three-dimensional nonlinear low-frequency density disturbances. This scenario is described by a system of equations consisting of the nonlinear Schrodinger equation for the HF plasma wave envelope, and the nonlinear equations for the electron density and temperature fluctuations, which are reinforced by the nonlinear terms associated with the pondermotive force and the differential Joule heating of the electrons. The formation of three-dimensional density striation structures is analyzed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
Santa Fe, NM  87505  87505  USA
tps-editor@ieee.org
Phone:505-988-5751
Fax:505-988-5751 (call first)