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Sample records for plasma sheet electrons

  1. Spatial distribution of energetic plasma sheet electrons.

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Farley, T. A.

    1972-01-01

    The spatial distribution of energetic plasma sheet electrons (E greater than 50 keV) out to a radial distance of 24 earth radii using data from electron spectrometer and fluxgate magnetometer experiments on Ogo 5 is presented. A comparison of distributions in geocentric solar magnetospheric coordinates (GSM) prepared with and without the use of a neutral sheet model indicates that the use of such a model facilitates organization of plasma sheet data. The percentage of flux occurrence above a given flux threshold falls off rapidly with distance from the neutral sheet. Contours of constant percentage of occurrence diverge slightly from the neutral sheet at local times away from midnight. This effect decreases with increasing flux threshold.

  2. Observations of electron vorticity in the inner plasma sheet

    NASA Astrophysics Data System (ADS)

    Gurgiolo, C.; Goldstein, M. L.; Viñas, A. F.; Matthaeus, W. H.; Fazakerley, A. N.

    2011-09-01

    From a limited number of observations it appears that vorticity is a common feature in the inner plasma sheet. With the four Cluster spacecraft and the four PEACE instruments positioned in a tetrahedral configuration, for the first time it is possible to directly estimate the electron fluid vorticity in a space plasma. We show examples of electron fluid vorticity from multiple plasma sheet crossings. These include three time periods when Cluster passed through a reconnection ion diffusion region. Enhancements in vorticity are seen in association with each crossing of the ion diffusion region.

  3. Observations of Electron Vorticity in the Inner Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Gurgiolo, C.; Goldstein, M. L.; Vinas, A. F.; Matthaeus, W. H.; Fazakerley, A. N.

    2011-01-01

    From a limited number of observations it appears that vorticity is a common feature in the inner plasma sheet. With the four Cluster spacecraft and the four PEACE instruments positioned in a tetrahedral configuration, for the first time it is possible to directly estimate the electron fluid vorticity in a space plasma. We show examples of electron fluid vorticity from multiple plasma sheet crossings. These include three time periods when Cluster passed through a reconnection ion diffusion region. Enhancements in vorticity are seen in association with each crossing of the ion diffusion region.

  4. Experimental investigation of a 1 kA/cm2 sheet beam plasma cathode electron gun

    NASA Astrophysics Data System (ADS)

    Kumar, Niraj; Narayan Pal, Udit; Kumar Pal, Dharmendra; Prajesh, Rahul; Prakash, Ram

    2015-01-01

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ˜1 kA/cm2 from pseudospark based argon plasma for pulse length of ˜200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

  5. Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

    PubMed

    Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

    2015-01-01

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field. PMID:25638082

  6. Graphene sheets embedded carbon film prepared by electron irradiation in electron cyclotron resonance plasma

    SciTech Connect

    Wang Chao; Diao Dongfeng; Fan Xue; Chen Cheng

    2012-06-04

    We used a low energy electron irradiation technique to prepare graphene sheets embedded carbon (GSEC) film based on electron cyclotron resonance plasma. The particular {pi} electronic structure of the GSEC film similar to bilayer graphene was verified by Raman spectra 2D band analyzing. The phase transition from amorphous carbon to GSEC was initiated when electron irradiation energy reached 40 eV, and the growth mechanism of GSEC was interpreted as inelastic scattering of low energy electrons. This finding indicates that the GSEC film obtained by low energy electron irradiation can be excepted for widely applications with outstanding electric properties.

  7. Thin Current Sheets and Associated Electron Heating in Turbulent Space Plasma

    NASA Astrophysics Data System (ADS)

    Chasapis, A.; Retinò, A.; Sahraoui, F.; Vaivads, A.; Khotyaintsev, Yu. V.; Sundkvist, D.; Greco, A.; Sorriso-Valvo, L.; Canu, P.

    2015-05-01

    Intermittent structures, such as thin current sheets, are abundant in turbulent plasmas. Numerical simulations indicate that such current sheets are important sites of energy dissipation and particle heating occurring at kinetic scales. However, direct evidence of dissipation and associated heating within current sheets is scarce. Here, we show a new statistical study of local electron heating within proton-scale current sheets by using high-resolution spacecraft data. Current sheets are detected using the Partial Variance of Increments (PVI) method which identifies regions of strong intermittency. We find that strong electron heating occurs in high PVI (>3) current sheets while no significant heating occurs in low PVI cases (<3), indicating that the former are dominant for energy dissipation. Current sheets corresponding to very high PVI (>5) show the strongest heating and most of the time are consistent with ongoing magnetic reconnection. This suggests that reconnection is important for electron heating and dissipation at kinetic scales in turbulent plasmas.

  8. Electron generation of electrostatic waves in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Onsager, T. G.; Thomsen, M. F.; Elphic, R. C.; Gosling, J. T.; Anderson, R. R.; Kettmann, G.

    1993-01-01

    Broadband electrostatic noise (BEN) has been shown to occur in conjunction with ion beams; extensive investigations of possible ion beam-related instabilities that could generate the observed wave spectra have been conducted. It has also been demonstrated that unstable electron distribution functions are sometimes measured in the plasma sheet boundary layer. We present simultaneous observations of ion and electron distribution functions and electric field wave spectra measured by ISEE 1 and ISEE 2 in the Earth's magnetotail. As the spacecraft moved from the tail lobe toward the plasma sheet, the fast indication of boundary layer plasma was seen in the electron distributions, followed some minutes later by the detection of boundary layer ions. The onset of large-amplitude electrostatic waves at frequencies up to the electron plasma frequency was coincident with the onset of the boundary layer electrons, suggesting that broadband electrostatic waves may often be generated by unstable electron distributions in the plasma sheet boundary layer, particularly the higher frequency portion of the wave spectrum. The observed changes in the electron distribution functions indicate that the plasma was not heated locally by the waves.

  9. In Situ Observations of Ion Scale Current Sheets and Associated Electron Heating in Turbulent Space Plasmas

    NASA Astrophysics Data System (ADS)

    Chasapis, A.; Retino, A.; Sahraoui, F.; Greco, A.; Vaivads, A.; Khotyaintsev, Y. V.; Sundkvist, D. J.; Canu, P.

    2014-12-01

    We present a statistical study of ion-scale current sheets in turbulent space plasma. The study was performed using in situ measurements from the Earth's magnetosheath downstream of the quasi-parallel shock. Intermittent structures were identified using the Partial Variance of Increments method. We studied the distribution of the identified structures as a function of their magnetic shear angle, the PVI index and the electron heating. The properties of the observed current sheets were different for high (>3) and low (<3) values of the PVI index. We observed a distinct population of high PVI (>3) structures that accounted for ~20% of the total. Those current sheets have high magnetic shear (>90 degrees) and were observed mostly in close proximity to the bow shock with their numbers reducing towards the magnetopause. Enhancement of the estimated electron temperature within these current sheets suggest that they are important for local electron heating and energy dissipation.

  10. Inner Magnetospheric Superthermal Electron Transport: Photoelectron and Plasma Sheet Electron Sources

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Liemohn, M. W.; Kozyra, J. U.; Moore, T. E.

    1998-01-01

    Two time-dependent kinetic models of superthermal electron transport are combined to conduct global calculations of the nonthermal electron distribution function throughout the inner magnetosphere. It is shown that the energy range of validity for this combined model extends down to the superthermal-thermal intersection at a few eV, allowing for the calculation of the en- tire distribution function and thus an accurate heating rate to the thermal plasma. Because of the linearity of the formulas, the source terms are separated to calculate the distributions from the various populations, namely photoelectrons (PEs) and plasma sheet electrons (PSEs). These distributions are discussed in detail, examining the processes responsible for their formation in the various regions of the inner magnetosphere. It is shown that convection, corotation, and Coulomb collisions are the dominant processes in the formation of the PE distribution function and that PSEs are dominated by the interplay between the drift terms. Of note is that the PEs propagate around the nightside in a narrow channel at the edge of the plasmasphere as Coulomb collisions reduce the fluxes inside of this and convection compresses the flux tubes inward. These distributions are then recombined to show the development of the total superthermal electron distribution function in the inner magnetosphere and their influence on the thermal plasma. PEs usually dominate the dayside heating, with integral energy fluxes to the ionosphere reaching 10(exp 10) eV/sq cm/s in the plasmasphere, while heating from the PSEs typically does not exceed 10(exp 8) eV/sq cm/s. On the nightside, the inner plasmasphere is usually unheated by superthermal electrons. A feature of these combined spectra is that the distribution often has upward slopes with energy, particularly at the crossover from PE to PSE dominance, indicating that instabilities are possible.

  11. SHEET PLASMA DEVICE

    DOEpatents

    Henderson, O.A.

    1962-07-17

    An ion-electron plasma heating apparatus of the pinch tube class was developed wherein a plasma is formed by an intense arc discharge through a gas and is radially constricted by the magnetic field of the discharge. To avoid kink and interchange instabilities which can disrupt a conventional arc shortiy after it is formed, the apparatus is a pinch tube with a flat configuration for forming a sheet of plasma between two conductive plates disposed parallel and adjacent to the plasma sheet. Kink instabilities are suppressed by image currents induced in the conductive plates while the interchange instabilities are neutrally stable because of the flat plasma configuration wherein such instabilities may occur but do not dynamically increase in amplitude. (AEC)

  12. Experimental investigation of a 1 kA/cm{sup 2} sheet beam plasma cathode electron gun

    SciTech Connect

    Kumar, Niraj Narayan Pal, Udit; Prajesh, Rahul; Prakash, Ram; Kumar Pal, Dharmendra

    2015-01-15

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm{sup 2} from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

  13. Electron distributions observed with Langmuir waves in the plasma sheet boundary layer

    SciTech Connect

    Hwang, Junga; Rha, Kicheol; Seough, Jungjoon; Yoon, Peter H.

    2014-09-15

    The present paper investigates the Langmuir turbulence driven by counter-streaming electron beams and its plausible association with observed features in the Earth's plasma sheet boundary layer region. A one-dimensional electrostatic particle-in-cell simulation code is employed in order to simulate broadband electrostatic waves with characteristic frequency in the vicinity of the electron plasma frequency ω/ω{sub pe}≃1.0. The present simulation confirms that the broadband electrostatic waves may indeed be generated by the counter-streaming electron beams. It is also found that the observed feature associated with low energy electrons, namely quasi-symmetric velocity space plateaus, are replicated according to the present simulation. However, the present investigation only partially succeeds in generating the suprathermal tails such that the origin of observed quasi power-law energetic population formation remains outstanding.

  14. The relationship between diffuse auroral and plasma sheet electron distributions near local midnight

    SciTech Connect

    Schumaker, T.L. ); Gussenhoven, M.S. ); Hardy, D.A.; Carovillano, R.L.

    1989-08-01

    A study of the relationship between diffuse auroral and plasma sheet electron distributions in the energy range from 50 eV to 20 keV in the midnight region was conducted using data from the P78-1 and SCATHA satellites. From 1 1/2 years of data, 14 events were found where the polar-orbiting P78-1 satellite and the near-geosynchronous SCATHA satellite were approximately on the same magnetic field line simultaneously, with SCATHA in the plasma sheet and P78-1 in the diffuse auroral region. For all cases the spectra from the two satellites are in good quantitative agreement. For 13 of the 14 events the pitch angle distribution measured at P78-1 was isotropic for angles mapping into the loss cone at the SCATHA orbit. For one event the P78-1 electron flux decreased with pitch angle toward the field line direction. At SCATHA the distributions outside the loss cone were most commonly butterfly or pancake, although distributions peaked toward the field line were sometimes observed at energies below 1 keV. Electron distributions, as measured where there is isotropy within the loss cone but anisotropy outside the loss cone, are inconsistent with current theories for the scattering of cone for the distribution measured at SCATHA, the electron precipitation lifetimes were calculated for the 14 events. Because the distributions are anisotropic at pitch angles away from the loss cone, the calculated lifetimes significantly exceed the lifetimes in the limit when the flu is isotropic at all pitch angles. The computed precipitation lifetimes are found to be weakly dependent on magnetic activity. The average lifetimes exceed those for the case of isotropy at all pitch angles by a factor between 2 and 3 for {ital Kp}{le}2 and approximately 1.5 for {ital Kp}{gt}2. {copyright} American Geophysical Union 1989

  15. Energetic electron bursts in the plasma sheet and their relation with BBFs

    NASA Astrophysics Data System (ADS)

    Duan, A. Y.; Cao, J. B.; Dunlop, M.; Wang, Z. Q.

    2014-11-01

    We studied energetic electron bursts (EEBs) (40-250 keV) in the plasma sheet (PS) and their relation to bursty bulk flows (BBFs) using the data recorded by Cluster from 2001 to 2009. The EEBs in the PS can be classified into four types. Three types of EEBs are dispersionless, including EEBs accompanied with BBFs (V > 250 km/s) but without dipolarization front (DF); EEBs accompanied with both dipolarization front (DF) and BBF; and EEBs accompanied with DF and fast flow with V < 250 km/s. One type of EEB, i.e., EEBs not accompanied with BBFs and DFs, is dispersed. The energetic electrons (40-130 keV) can be easily transported earthward by BBFs due to the strong dawn-dusk electric field embedded in BBFs. The DFs in BBFs can produce energetic electrons (40 to 250 keV). For the EEBs with DF and BBFs, the superposed epoch analyses show that the increase of energetic electron flux has two phases: gradual increase phase before DF and rapid increase phase concurrent with DF. In the PS around x = -18 RE, 60%-70% of EEBs are accompanied with BBFs, indicating that although hitherto there have been various acceleration mechanisms of energetic electrons, most of the energetic electrons in the PS are related with magnetic reconnection, and they are produced either directly by magnetic reconnection or indirectly by the DFs within BBFs. In the BBF's braking region of -12 RE < x < -10 RE, 20% of EEBs are accompanied with BBFs. The corresponding ratio between EEBs and BBFs shows a dawn-dusk asymmetry.

  16. Sheet electron beam tester

    NASA Astrophysics Data System (ADS)

    Spear, Alexander Grenbeaux

    The DARPA HiFIVE project uses a pulsed electron sheet beam gun to power a traveling wave tube amplifier operating at 220 GHz. Presented is a method for characterizing the high current density 0.1 mm by 1 mm sheet electron beam. A tungsten tipped probe was scanned through the cross section of the sheet electron beam inside of a vacuum vessel. The probe was controlled with sub-micron precision using stepper motors and LabView computer control while boxcar averaging hardware sampled the pulsed beam. Matlab algorithms were used to interpret the data, calculate beam dimensions and current density, and create 2-dimensional cross section images. Full characterization of two separate HiFIVE sheet electron guns was accomplished and is also presented.

  17. Probing the Plasma Membrane Structure of Immune Cells Through the Analysis of Membrane Sheets by Electron Microscopy

    PubMed Central

    Lillemeier, Björn F.; Davis, Mark M.

    2013-01-01

    This chapter describes a method to generate plasma membrane sheets that are large enough to visualize the membrane architecture and perform quantitative analyses of protein distributions. This procedure places the sheets on electron microscopy grids, parallel to the imaging plane of the microscope, where they can be characterized by transmission electron microscopy. The basic principle of the technique is that cells are broken open (“ripped”) through mechanical forces applied by the separation of two opposing surfaces sandwiching the cell, with one of the surfaces coated onto an EM grid. The exposed inner membrane surfaces can then be visualized with electron dense stains and specific proteins can be detected with gold conjugated probes. PMID:21701974

  18. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-01-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  19. Effect of an MLT dependent electron loss rate on the inner magnetosphere electrodynamics and plasma sheet penetration to the ring current region

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Wang, C.; Wing, S.; Lyons, L. R.; Wolf, R. A.; Hsu, T.

    2012-12-01

    Transport of plasma sheet particles into the ring current region is strongly affected by the penetrating convection electric field, which is the result of the large-scale magnetosphere-ionosphere (M-I) electromagnetic coupling. One of the main factors controlling this coupling is the ionospheric conductance. As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and precipitate to the ionosphere, producing auroral conductance. Realistic electron loss is thus important for modeling the (M-I) coupling and penetration of plasma sheet into the inner magnetosphere. To evaluate the significance of electron loss rate, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. The plasma sheet ion and electron sources for the simulations are based on the Geotail observations. Two major rates are used: different portions of i) strong pitch-angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that the dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. Electrons trapped inside L ~ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Compared with the strong rate, the remaining electrons under the MLT rate cause higher conductance at lower latitudes, allowing for less efficient electric field shielding to convection enhancement, thus further earthward penetration of the plasma sheet into the inner magnetosphere. Therefore, our simulation results indicate that the electron loss rate can significantly affect the electrodynamics of the ring current region. Development of a more realistic electron loss rate model for the inner magnetosphere is thus much needed and will become feasible with new observations from the upcoming RBSP mission.

  20. Observations of energetic electrons /E no less than about 200 keV/ in the earth's magnetotail - Plasma sheet and fireball observations

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Stone, E. C.

    1977-01-01

    An earlier paper by the authors (1976) has reported on energetic electron anisotropies observed in conjunction with the acceleration regions identified by Frank et al., (1976). The present paper gives more detailed analyses of observations in the distant plasma sheet, including specific features of intensities, energy spectra, and pitch angle distributions of the very energetic electrons associated with intense plasma particle events, with energies ranging between 50 eV and 45 keV, detected with an electron/isotope spectrometer aboard the earth-orbiting spacecraft Imp 8. Two domains are considered: the plasma sheet and the regions near and within the localized magnetotail acceleration regions known as the fireball regions. The instrumentation used offered a number of observational advantages over many previous studies, including inherently low background, large geometric factors, excellent species identification, good angular distribution measurement capability, and availability of high resolution of differential intensities.

  1. Statistics of plasma sheet convection

    NASA Astrophysics Data System (ADS)

    Juusola, L.; Østgaard, N.; Tanskanen, E.

    2011-08-01

    Determining the characteristics of plasma sheet convection and their response to changes in various solar wind parameters is important for understanding the energy and mass transport, as well as disturbance propagation, through geospace. We use 15 years of data obtained by Geotail, Cluster, and THEMIS to study statistically the characteristics of plasma sheet flows and the effect of the interplanetary magnetic field (IMF) on the convection. We find that plasma sheet convection is dominated by slow speed (<100 km/s) flows that circulate around Earth on both sides toward the dayside. With increasing flow speed the sunward component of the flow velocity becomes more pronounced such that flows with V > 500 km/s are directed almost purely sunward. Both IMF By and IMF Bz are observed to penetrate the plasma sheet. During southward IMF conditions, a channel of increased Bz is created in the nightside around the aberrated midnight axis. We suggest that the channel is caused by dipolarization and magnetic flux pileup related to fast flows. The nightside region of highest mean flow speed is located more duskward during dawnward IMF conditions than during duskward IMF conditions. For plasma sheet flows with speeds higher than 100 km/s, we find that the orientation of IMF (clock angle) controls the speeds, while the magnitude of the solar wind electric field plays a minor role. The increasing speed indicates that energy transfer per unit length of the nightside X line increases as IMF turns southward.

  2. MHD Ballooning Instability in the Plasma Sheet

    SciTech Connect

    C.Z. Cheng; S. Zaharia

    2003-10-20

    Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.

  3. Duskside auroral undulations observed by IMAGE and their possible association with large-scale structures on the inner edge of the electron plasma sheet

    NASA Astrophysics Data System (ADS)

    Lewis, W. S.; Burch, J. L.; Goldstein, J.; Horton, W.; Perez, J. C.; Frey, H. U.; Anderson, P. C.

    2005-12-01

    On February 6, 2002 large-scale undulations along the equatorward edge of the afternoon/dusk auroral oval were observed with the IMAGE FUV/Wideband Imaging Camera (WIC) during the late expansion/recovery phase of a substorm. The undulations are similar to others previously reported, but occur at higher than usual latitudes and map to the outer duskside magnetosphere, 1 to 2 RE beyond a plasmaspheric drainage plume. The mapping suggests that the undulations result from large-scale fluctuations on the inner edge of the electron plasma sheet. 2.5-D simulations using representative plasma parameters for this region indicate that such large-scale coherent structures can be created by a kinetic drift wave driven by the ion pressure gradient in the destabilizing curvature and grad B drift of the plasma sheet ions.

  4. Storm-time Injection of Plasma Sheet Electrons into the Radiation Belt During the March~31, 2001 Geomagnetic StormOuter

    NASA Astrophysics Data System (ADS)

    Elkington, S. R.; Baker, D. N.; Li, X.; Hudson, M. K.; Wiltberger, M. J.

    2001-12-01

    A fundamental problem in understanding the physics of the outer radiation belts is the very origin of the energetic particles comprising them [Li et al., GRL~24, 923, 1997]. Several sources have been suggested, e.g., injection of particles from the cusp [Sheldon et al., GRL 25, 1825, 1998], local heating of inner magnetospheric plasmas [e.g. Summers & Ma, JGR 105, 15887, 2000], or through the transport of plasma sheet particles into the stable trapping region of the inner magnetosphere via convective or substorm injection. In general, the latter may occur when time-varying electric and magnetic fields alter the position of the Alfvén layer, the energy- and field-dependent separatrix between those particles whose gradient-curvature drift keeps them on closed orbits within the magnetosphere, and those particles whose drift paths intersect the magnetopause. In this work, we use global MHD simulations of the March~31, 2001 magnetic storm to investigate the transport of energetic (keV) electrons from the plasma sheet into the stable trapping region. We examine trapping efficiency both under the influence of strong, time-varying magnetospheric convection, such as characterized the main phase of this storm, as well as during periods of substantial magnetotail reconfiguration, such as may be associated with the dramatic 0630 substorm observed during this event.

  5. Transport phenomena in the Earth's plasma sheet

    NASA Astrophysics Data System (ADS)

    Angelopoulos, Vassilis

    1993-01-01

    We present a series of studies that utilize observation and modeling in order to characterize transport in the earth's plasma sheet out to distances of 23 R(sub E). After a brief description of the dissertation's goals in Chapter 1, we analyze in Chapter 2 representative cases of high speed flows in the inner central plasma sheet along with the concurrent behavior of the plasma and magnetic field. We argue that such flows are organized in 10 min. time scale entities of convection enhancements that we term bursty bulk flow (BBF) events. BBF's have a substructure that is on a 1 min time scale, referred to as 'flow bursts'. BBF's represent intervals of enhanced, predominantly earthward transport of mass energy and magnetic flux. In Chapter 3, we use an algorithm to automatically detect BBF's and study their statistical properties. BBF's cause the plasma sheet to be in a more dipolarized, higher temperature state for a long time after their subsidence. Despite their short duration, BBF's can account for most of the measured earthward transport of particles, energy, and magnetic flux in the plasma sheet. The concept of BBF's as a particular state of transport in the plasma sheet is applied in Chapter 4 to the study of the non-BBF, quiet state of the inner plasma sheet. We construct the average ion velocity pattern in the quiet inner plasma sheet. We show that a semi-empirical magnetic field model of the magnetotail along with the inferred cross tail electric field and the measured average density reproduce the observed velocity averages assuming that the flow is the sum of corrotation, an E x B flow, and a model-derired diamagnetic drift Despite the qualitative agreement of the average flow pattern with our model calculations, the flow exhibits variability much larger than its average. The non-BBF flow is highly irregular and fundamentally unsteady, a reason why convection in the quiet state of the plasma sheet may be able to avoid a pressure balance inconsistency with the lobes. Chapter 5 explores whether a segregation of plasma sheet states similar to the one applied to the inner plasma sheet can also be extended to the outer plasma sheet.

  6. Magnetic field at geosynchronous orbit during high-speed stream-driven storms: Connections to the solar wind, the plasma sheet, and the outer electron radiation belt

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.; Denton, Michael H.

    2010-08-01

    Superposed-epoch analysis is performed on magnetic field measurements from five GOES spacecraft in geosynchronous orbit during 63 high-speed stream-driven storms in 1995-2005. The field strength and the field stretching angle are examined as functions of time and local time, and these quantities are compared with the properties of the solar wind, the plasma sheet, and the outer electron radiation belt. Compression of the dayside magnetosphere coincides with an increased solar wind ram pressure commencing before the arrival of the corotating interaction region (CIR). Stretching of the nightside magnetosphere occurs in two phases: a strong-stretching phase early in the storm followed by a modest-stretching phase lasting for days. The strong-stretching phase coincides with the occurrence of the superdense plasma sheet, implying that ion pressure causes the strong stretching. This nightside strong-stretching perturbation corresponds to a ˜25% contribution to Dst*. The relativistic electron flux at geosynchronous orbit has a dropout recovery temporal profile that matches the strong-stretching temporal profile; however, the number density dropout and recovery of the electron radiation belt has a profile that leads the stretching profile. A comparison of geosynchronous field strengths and magnetopause field strengths indicates that magnetopause shadowing plays a role in the radiation belt dropout. Temporal fluctuations of the geosynchronous magnetic field are examined via 1 min changes of the GOES magnetic field vectors. Fluctuation amplitudes increase at all local times at storm onset and then slowly decay during the storms. The amplitude is linearly related to the Kp, PCI, and MBI indices, except during the strong-stretching phase of the storms.

  7. Systematic study of plasma flow during plasma sheet thinnings

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.; Frank, L. A.; Ackerson, K. L.; Meng, C.-I.; Akasofu, S.-I.

    1977-01-01

    On the basis of a study of Imp 6 measurements of plasma flow, it is concluded that there is no clear indication of a predominance of tailward plasma flow beyond about X = -15 R sub E in the midnight sector of the plasma sheet during the expansive phase of a substorm. In fact, it is shown statistically that sunward plasma flow is more frequently observed in the midnight sector within about 30 R sub E from the earth than in any other direction during plasma sheet thinning at the substorm expansion. This result supports the conclusion that there is no definite evidence for the formation of a reconnection neutral line in the near-earth plasma sheet during most substorms.

  8. Heliospheric current sheet and plasma sheet crossings associated with heatflux dropouts: A statistical survey using STEREO observations

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Galvin, A. B.; Popecki, M.; Simunac, K.; Kistler, L. M.; Farrugia, C. J.; Moebius, E.; Jian, L.; Opitz, A.; Luhmann, J. G.

    2010-12-01

    We investigate the heliospheric current sheet (HCS) crossing events and the related heliospheric plasma sheet (HPS) on both STEREO spacecraft from Mar, 1, 2008 to Dec, 31, 2008. Observed plasma sheets are categorized into two types based on their relative position to the current sheets. Type I plasma sheets straddle the current sheets, and type II plasma sheets are located on one side of the current sheets. The electron heat flux dropouts (HFD) are also documented for each type of plasma sheets. Initially, the investigation was limited to 39 ideal HCS crossings. Among the initial 39 HCS crossings in our study, 4 have no HPS, 21 have a type I HPS, and 13 a Type II HPS. Most of the Type II HCSs don’t show a HFD, but a large portion of type I HPSs show a HFD. Later, the study is generalized to all HCS events for which we can determine the actual time and properties of the HPS. This conclusion still holds when all the identifiable HPS are included in the study. Schematic plots summing the different magnetic field configurations are presented, and the potential origin of plasmas forming the two types of HPS is discussed.

  9. Plasma sheet turbulence observed by Cluster II

    NASA Technical Reports Server (NTRS)

    Weygand, James M.; Kivelson, M. G.; Khurana, K. K.; Schwarzl, H. K.; Thompson, S. M.; McPherron, R. L.; Balogh, A.; Kistler, L. M.; Goldstein, M. L.; Borovsky, J.

    2005-01-01

    Cluster fluxgate magnetometer (FGM) and ion spectrometer (CIS) data are employed to analyze magnetic field fluctuations within the plasma sheet during passages through the magnetotail region in the summers of 2001 and 2002 and, in particular, to look for characteristics of magnetohydrodynamic (MHD) turbulence. Power spectral indices determined from power spectral density functions are on average larger than Kolmogorov's theoretical value for fluid turbulence as well as Kraichnan's theoretical value for MHD plasma turbulence. Probability distribution functions of the magnetic fluctuations show a scaling law over a large range of temporal scales with non-Gaussian distributions at small dissipative scales and inertial scales and more Gaussian distribution at large driving scales. Furthermore, a multifractal analysis of the magnetic field components shows scaling behavior in the inertial range of the fluctuations from about 20 s to 13 min for moments through the fifth order. Both the scaling behavior of the probability distribution functions and the multifractal structure function suggest that intermittent turbulence is present within the plasma sheet. The unique multispacecraft aspect and fortuitous spacecraft spacing allow us to examine the turbulent eddy scale sizes. Dynamic autocorrelation and cross correlation analysis of the magnetic field components allow us to determine that eddy scale sizes fit within the plasma sheet. These results suggest that magnetic field turbulence is occurring within the plasma sheet resulting in turbulent energy dissipation.

  10. Thermomechanical processing of plasma sprayed intermetallic sheets

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  11. Trajectories of Electrons and Protons in the Reconnecting Current Sheet

    NASA Astrophysics Data System (ADS)

    Lin, J.

    In the framework of the catastrophe model of solar eruptions a current sheet forms separating two magnetic fields of opposite polarity as the magnetic structure loses the equilibrium and stretches the closed magnetic field lines severely Magnetic fields and plasma near the sheet are driven toward the current sheet and magnetic reconnection converts the magnetic energy into the other types of energy In this process an electric field in the current sheet is induced by the reconnection inflow Both theories and observations show that this electric field could be of a few V cm at maximum The electric field of such strength is able to accelerate any charged particles especially electrons and protons This work investigates motions of electrons and protons in the 3D reconnecting current sheets via the test particle approach The collisionless environment in the current sheet allows us to ignore collisions among particles Our results indicate that motions of individual particles are confined within certain places We find that these particles either gather together around the X-point along the z -axis or shoot out of the current sheet along the separatrices and that they may leave the current sheet along any separatrix So their motions do not yield extra electric current

  12. Theoretical modeling of the plasma-assisted catalytic growth and field emission properties of graphene sheet

    NASA Astrophysics Data System (ADS)

    Sharma, Suresh C.; Gupta, Neha

    2015-12-01

    A theoretical modeling for the catalyst-assisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbon-clusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations.

  13. Birkeland currents in the plasma sheet

    SciTech Connect

    Tsyganeko, N.A.; Stern, D.P.; Kaymaz, Z.

    1993-11-01

    A search was conducted for the signatures of Birkeland currents in the Earth`s magnetic tail, using observed values of B{sub x} and B{sub y} from large sets of spacecraft data. The data were binned by x and y for {minus}10 > x{sub GSM} > {minus}35 and {vert_bar}y{sub GSM}{vert_bar} {<=} 20 R{sub E} ({<=}30 R{sub E} for x{sub GSM} {<=} {minus}25 R{sub E}) and in each bin their distribution in the (B{sub x}, B{sub y}) plane was fitted by least squares to a piecewise linear function. That gave average x-y distributions of the flaring angle between B{sub xy} and the x direction, as well as that angle`s variation across the thickness of the plasma sheet. Angles obtained in the central plasma sheet differed from those derived near the lobe boundary. That is the expected signature if earthward or tailward Birkeland current sheets are embedded in the plasma sheet, and from this difference the authors derived the dawn-dusk profiles of the tail Birkeland currents for several x{sub GMS} intervals. It was found that (1) the Birkeland currents have the sense of region 1 currents, when mapped to the ionosphere; (2) both the linear current density (kiloamperes/R{sub E}) and the net magnitude of the field-aligned currents decrease rapidly down the tail; (3) the total Birkeland current x{approximately} {minus}10 R{sub E} equals {approximately}500-700 kA, which is {approx}30% of the net region 1 current observed at ionospheric altitudes, in agreement with model mapping results; and (4) the B{sub z} and B{sub y} components of the interplanetary magnetic field influence the distribution of Birkeland currents in the tail. 27 refs., 11 figs.

  14. Birkeland currents in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Tsyganenko, Nikolai A.; Stern, David P.; Kaymaz, Zerefsan

    1993-01-01

    A search was conducted for the signatures of Birkeland currents in the Earth's magnetic tail, using observed values of B(sub x) and B(sub y) from large sets of spacecraft data. The data were binned by x and y for -10 greater than x(sub GSM) greater than -35 and absolute value of y(sub GSM) less than or equal to 20 R(sub E) (less than or equal to 30 R(sub E) for x(sub GSM) less than or equal to -25 R(sub E)) and in each bin their distribution in the (B(sub x), B(sub y)) plane was fitted by least squares to a piecewise linear function. That gave average x-y distributions of the flaring angle between B(sub xy) and the x direction, as well as that angle's variation across the thickness of the plasma sheet. Angles obtained in the central plasma sheet differed from those derived near the lobe boundary. That is the expected signature if earthward or tailward Birkeland current sheets are embedded in the plasma sheet, and from this dfiference we derived the dawn-dusk profiles of the tail Birkeland currents for several x(sub GSM) intervals. It was found that (1) the Birkeland currents have the sense of region 1 currents, when mapped to the ionosphere; (2) both the linear current density (kiloamperes/R(sub E)) and the net magnitude of the field-aligned currents decrease rapidly down the tail; (3) the total Birkeland current at x approximately equals -10 R(sub E) equals approximately equals 500-700 kA, which is approx. 30% of the net region 1 current observed at ionospheric altitudes, in agreement with model mapping results; and (4) the B(sub z) and B(sub y) components of the interplanetary magnetic field influence the distribution of Birkeland currents in the tail.

  15. The State of the Plasma Sheet and Atmosphere at Europa

    NASA Astrophysics Data System (ADS)

    Shemansky, D. E.; Yung, Y. L.; Liu, X.; Yoshii, J.; Hansen, C. J.; Hendrix, A.; Esposito, L. W.

    2014-12-01

    The Hall et al. (1995) report announcing the discovery of atomic oxygen FUV emission from Europa included a conclusion that the atmosphere was dominated by O2. Over the following 20 years publications referencing the atmosphere accepted this conclusion, and calculations of rates, particularly mass loading of the magnetosphere depended on a composition that was of order 90% O2. Analysis of the Europa emission spectrum in the present work, leads to the conclusion that the O I emission properties were misinterpreted. The interpretation of the source process depends on the ratio of the O I 1356 and 1304 A multiplet emissions (R(4:5) = (I(1356)/I(1304)). The value of R(4:5) never reaches the lower limit for electron impact dissociation of O2 for any of the 7 recorded disk averaged measurements between 1994 and 2013. Analysis of the Cassini UVIS exposures show the 1304 A multiplet to be optically thick, and the emissions are modeled as direct electron and solar photon excitation of O I. The result is a model atmosphere dominated by O I and O II, with neutral density a factor of 100 below the original O2 model. Other considerations show incompatibility with an O2 atmosphere. Deep exposures using the Cassini UVIS EUV spectrograph provide the state of the plasma sheet at Europa. The ion species are identified as mainly outwardly diffused mass from the Io plasma torus with a minor contribution from Europa. Plasma time-constants are of the order of 200 days. Neutral species in the plasma sheet are not measureable. The energy flux in the magnetosphere L-shells are mainly responsible for energy deposition maintaining the plasma sheet. The energy content in the Io and Europa L-shells, as measured, is similar, but the mean radiative cooling rate in the Io plasma torus at the time of the Cassini encounter was 565 femtoergs cm-3 s-1, compared to 7.3 at Europa, reflecting the difference between an active and inactive planetary satellite, particularly considering the fact that most of the radiation at the Europa plasma sheet is from ions that originated at the orbit of Io. The stochastic observational evidence in disk averaged Europa oxygen emission obtained over the 1994 to 2012 period shows no indication of transient events. A significant neutral transient injection in the Europa plasma sheet would take of order year time-scales to relax to steady state

  16. A pincer-shaped plasma sheet at Uranus

    SciTech Connect

    Hammond, C.M.; Walker, R.J.; Kivelson, M.G. )

    1990-09-01

    A model from Voigt et al. (1987) and an MHD simulation from Walker et al. (1989) both show that the curvature of the plasma sheet at Uranus changes as the dipole tilt varies between 38{degree} and 22{degree}. The models suggest that one of the two partial traversals of the uranian plasma sheet made during the outbound trajectory of Voyager 2 can be explained as an entry into the highly curved plasma sheet that develops when Uranus is near the maximum dipole tilt value of 38{degree}; previously both partial traversals have been explained as anomalous. The spacecraft would have reversed its motion relative to the plasma sheet as the continued rotation diminished the dipole tilt and the retreating plasma sheet uncurled. As the dipole tilt approached its minimum value, spacecraft motion towards the neutral sheet resumed and the traversal of the plasma sheet was completed. Evidence from the PWS plasma wave detector suggests that the spacecraft trajectory skimmed the plasma sheet boundary layer for several hours prior to the partial immersion. The plasma sheet of the Voigt et al. model was not located near the spacecraft during this time interval. On the other hand, the MHD simulation reveals a plasma sheet that is more curved than in the Boigt et al. model; near maximum dipole tilt, the plasma sheet is pincer-shaped. The unusual geometry implies that Voyager 2 remained near the plasma sheet boundary layer during the period suggested by the PWS data. Thus the simulation accounts easily for the first of the plasma sheet encounters previously called anomalous. The second partial immersion remains anomalous, having previously been related to substorm activity, and thus is not discussed here. The stagnation distances of the earth and Uranus at the nose of the magnetopause were used to scale the Walker et al. (1989) simulation of the terrestrial magnetosphere to represent the uranian magnetosphere.

  17. Plasma processes driven by current sheets and their relevance to the auroral plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1986-01-01

    Plasma processes dealing with ac and dc electric fields, the formation of ion beams and conics, and electron acceleration are considered, and similarities between simulation results and satellite-based observations are discussed. Electrostatic shock-type electric fields are found to occur near the current sheet edges, and double layers having upward electric fields form inside the sheet and are distinguishable from the large perpendicular electric fields only in wide sheets with thicknesses much greater than the ion Larmor radius. It is found that the most energetic ions have pitch angles near 90 deg, indicating a large perpendicular acceleration of the ions, and that the downward accelerating electrons inside the sheet are neither monoenergetic nor perfectly field aligned.

  18. Electric fields and current sheet structure in magnetospheric plasmas

    NASA Astrophysics Data System (ADS)

    Cully, C. M.

    The electric currents of the central plasma sheet play a pivotal role in the dynamics of the Earth's magnetosphere. I describe new instrumentation developed for measuring its properties, and analyze data from existing instruments. The analysis shows the structure and physical current-carrying mechanisms of the quiescent central plasma sheet in new detail. Electric field observations are critical for this work. I discuss two aspects of space-based double-probe electric field experiments: the probe design and the signal processing. I develop a numerical model that self-consistently solves for the interaction between the probes and the nearby plasma environment, including the effects of the spacecraft and its attendant photoelectrons. I also describe the signal processing hardware developed for the 5-satellite THEMIS mission, known as the Digital Fields Boards (DFB). THEMIS was launched in February 2007, and all 5 DFBs are working as intended. Since THEMIS is only recently launched, I analyze data from the 4-satellite Cluster mission, which has similar instrumentation. With Cluster data, the position of the current sheet relative to the satellite can be determined, allowing direct comparisons between observations and models. To encompass the wide variety of possible current-carrying mechanisms, I develop a kinetic model based on the quasi-isotropic formalism of Schindler and Birn [2002]. The model fits many of the observed sheets well. The observations reveal a wide variety of current-carrying mechanisms. Some of the thinnest currents consist entirely of a pair of electron Hall currents which together form a bifurcated current sheet driven by strong inward-pointing electric fields.

  19. Plasma Relaxation Dynamics Moderated by Current Sheets

    NASA Astrophysics Data System (ADS)

    Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho

    2014-10-01

    Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.

  20. Kinetic Theory of Dawson Plasma Sheet Model

    NASA Astrophysics Data System (ADS)

    Sano, Mitsusada M.; Kitahara, Kazuo

    2011-08-01

    A kinetic theory of one-dimensional plasma sheet model (Dawson model) is developed. The Vlasov equation, the Landau equation, and the Balescu--Lenard equation corresponding to this model are derived. For the Vlasov equation, it is shown that the linearized Vlasov equation exhibits a typical behavior of plasmas as in the three-dimensional space. The Landau collision term and the Balescu--Lenard collision term are identically zero. The fact of the vanishing collision term agrees with the behavior of generic one-dimesional systems. In an approximation that the system is in a thermal bath, the derived Landau equation and Balescu--Lenard equation are transformed into the Fokker--Planck equations. Some physical quantities such as thermal conductivity, relaxation rate, etc., are estimated. A discussion on physical meaning of these results, in particular, the zero collision terms, will be given.

  1. Plasma Sheet Source and Loss Processes

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    2000-01-01

    Data from the TIMAS ion mass spectrometer on the Polar satellite, covering 15 ev/e to 33 keV/e in energy and essentially 4(pi) in view angles, are used to investigate the properties of earthward (sunward) field-aligned flows of ions, especially protons, in the plasma sheet-lobe transition region near local midnight. A total of 142 crossings of this region are analyzed at 12-sec time resolution, all in the northern hemisphere, at R(SM) approx. 4 - 7 R(sub E), and most (106) in the poleward (sunward) direction. Earthward proton flows are prominent in this transition region (greater than 50% of the time), typically appearing as sudden "blasts" with the most energetic protons (approx. 33 keV) arriving first with weak flux, followed by protons of decreasing energy and increasing flux until either: (1) a new "blast" appears, (2) the flux ends at a sharp boundary, or (3) the flux fades away within a few minutes as the mean energy drops to a few keV. Frequent step-like changes (less than 12 sec) of the flux suggest that perpendicular gradients on the scale of proton gyroradii are common. Peak flux is similar to central plasma sheet proton flux (10(exp 5) - 10(exp 6)/[cq cm sr sec keV/e] and usually occurs at E approx. 4 - 12 keV. Only the initial phase of each "blast" (approx. 1 min) displays pronounced field-alignment of the proton velocity distribution, consistent with the time-of-flight separation of a more or less isotropic source distribution with df/d(nu) less than 0. The dispersive signatures are often consistent with a source at R(SM) less than or equal to 30 R(sub E). No systematic latitudinal velocity dispersion is found, implying that the equatorial plasma source is itself convecting. In short, the proton "blasts" appear as sudden local expansions of central plasma sheet particles along reconfigured ("dipolarized") magnetic field lines.

  2. Thin current sheets in collisionless plasma: Equilibrium structure, plasma instabilities, and particle acceleration

    SciTech Connect

    Zelenyi, L. M.; Malova, H. V.; Artemyev, A. V.; Popov, V. Yu.; Petrukovich, A. A.

    2011-02-15

    The review is devoted to plasma structures with an extremely small transverse size, namely, thin current sheets that have been discovered and investigated by spacecraft observations in the Earth's magnetotail in the last few decades. The formation of current sheets is attributed to complicated dynamic processes occurring in a collisionless space plasma during geomagnetic perturbations and near the magnetic reconnection regions. The models that describe thin current structures in the Earth's magnetotail are reviewed. They are based on the assumption of the quasi-adiabatic ion dynamics in a relatively weak magnetic field of the magnetotail neutral sheet, where the ions can become unmagnetized. It is shown that the ion distribution can be represented as a function of the integrals of particle motion-the total energy and quasi-adiabatic invariant. Various modifications of the initial equilibrium are considered that are obtained with allowance for the currents of magnetized electrons, the contribution of oxygen ions, the asymmetry of plasma sources, and the effects related to the non-Maxwellian particle distributions. The theoretical results are compared with the observational data from the Cluster spacecraft mission. Various plasma instabilities developing in thin current sheets are investigated. The evolution of the tearing mode is analyzed, and the parameter range in which the mode can grow are determined. The paradox of complete stabilization of the tearing mode in current sheets with a nonzero normal magnetic field component is thereby resolved based on the quasi-adiabatic model. It is shown that, over a wide range of current sheet parameters and the propagation directions of large-scale unstable waves, various modified drift instabilities-kink and sausage modes-can develop in the system. Based on the concept of a turbulent electromagnetic field excited as a result of the development and saturation of unstable waves, a mechanism for charged particle acceleration in turbulent current sheets is proposed and the energy spectra of the accelerated particles are obtained.

  3. Bright subcycle extreme ultraviolet bursts from a single dense relativistic electron sheet.

    PubMed

    Ma, W J; Bin, J H; Wang, H Y; Yeung, M; Kreuzer, C; Streeter, M; Foster, P S; Cousens, S; Kiefer, D; Dromey, B; Yan, X Q; Meyer-ter-Vehn, J; Zepf, M; Schreiber, J

    2014-12-01

    Double-foil targets separated by a low density plasma and irradiated by a petawatt-class laser are shown to be a copious source of coherent broadband radiation. Simulations show that a dense sheet of relativistic electrons is formed during the interaction of the laser with the tenuous plasma between the two foils. The coherent motion of the electron sheet as it transits the second foil results in strong broadband emission in the extreme ultraviolet, consistent with our experimental observations. PMID:25526132

  4. ISEE observations of the plasma sheet boundary, plasma sheet, and neutral sheet. I - Electric field, magnetic field, plasma, and ion composition

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.; Hones, E. W., Jr.; Anderson, R. R.; Sharp, R. D.

    1986-01-01

    The first simultaneous study of dc and ac electric and magnetic fields, E x B velocity, plasma flows, ratio of plasma to magnetic field pressure, total energy density, energetic particles, and ion composition from the ISEE satellites and ground and interplanetary magnetic fields has been made to determine (1) the relationship of the previously observed electric fields at the plasma sheet boundary and at the neutral sheet to plasma parameters, and (2) whether the phenomena occurring during quiet and active times were consistent with the formation of a near-earth neutral line during substorms or with the boundary layer model. Five observations made during the study of two substorms were seen to be in agreement with the neutral-line model. The observations are consistent with the satellite being located at varying distances from the neutral line and diffusion region where reconnection and plasma acceleration were occurring. Although the z component (into or out of the ecliptic plane) of E x B convection was generally toward the neutral sheet, there were examples when it was consistent with the inferred motion of the plasma sheet past the satellite. A synthesis of previous reports on large electric fields at the plasma sheet boundary and variable fields at the neutral sheet including the associated plasma flows is also described.

  5. Observations of double layers in earth's plasma sheet.

    PubMed

    Ergun, R E; Andersson, L; Tao, J; Angelopoulos, V; Bonnell, J; McFadden, J P; Larson, D E; Eriksson, S; Johansson, T; Cully, C M; Newman, D N; Goldman, M V; Roux, A; LeContel, O; Glassmeier, K-H; Baumjohann, W

    2009-04-17

    We report the first direct observations of parallel electric fields (E_{ parallel}) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E_{ parallel} signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet. PMID:19518640

  6. Observations of Double Layers in Earth's Plasma Sheet

    SciTech Connect

    Ergun, R. E.; Tao, J.; Andersson, L.; Eriksson, S.; Johansson, T.; Angelopoulos, V.; Bonnell, J.; McFadden, J. P.; Larson, D. E.; Cully, C. M.; Newman, D. N.; Goldman, M. V.; Roux, A.; LeContel, O.; Glassmeier, K.-H.; Baumjohann, W.

    2009-04-17

    We report the first direct observations of parallel electric fields (E{sub parallel}) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E{sub parallel} signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet.

  7. A pincer-shaped plasma sheet at Uranus

    NASA Technical Reports Server (NTRS)

    Hammond, C. Max; Walker, Raymond J.; Kivelson, Margaret G.

    1990-01-01

    An MHD simulation of the terrestrial magnetosphere, rescaled to represent the Uranian magnetotail, is carried out. The 3p immersion can be explained in terms of possible extreme departures from average plasma sheet shapes in the Uranian magnetosphere. The orientation of the Uranian dipole and rotation axes produce a dynamically curved plasma sheet which is an unusual feature of the Uranian magnetosphere.

  8. Magnetic turbulence in the plasma sheet

    NASA Astrophysics Data System (ADS)

    VöRöS, Z.; Baumjohann, W.; Nakamura, R.; Volwerk, M.; Runov, A.; Zhang, T. L.; Eichelberger, H. U.; Treumann, R.; Georgescu, E.; Balogh, A.; Klecker, B.; RéMe, H.

    2004-11-01

    Small-scale magnetic turbulence observed by the Cluster spacecraft in the plasma sheet is investigated by means of a wavelet estimator suitable for detecting distinct scaling characteristics even in noisy measurements. The spectral estimators used for this purpose are affected by a frequency-dependent bias. The variances of the wavelet coefficients, however, match the power-law shaped spectra, which makes the wavelet estimator essentially unbiased. These scaling characteristics of the magnetic field data appear to be essentially nonsteady and intermittent. The scaling properties of bursty bulk flow (BBF) and non-BBF associated magnetic fluctuations are analyzed with the aim of understanding processes of energy transfer between scales. Small-scale (˜0.08-0.3 s) magnetic fluctuations having the same scaling index α ˜ 2.6 as the large-scale (˜0.7-5 s) magnetic fluctuations occur during BBF-associated periods. During non-BBF associated periods the energy transfer to small scales is absent, and the large-scale scaling index α ˜ 1.7 is closer to Kraichnan or Iroshnikov-Kraichnan scalings. The anisotropy characteristics of magnetic fluctuations show both scale-dependent and scale-independent behavior. The former can be partly explained in terms of the Goldreich-Sridhar model of MHD turbulence, which leads to the picture of Alfvénic turbulence parallel and of eddy turbulence perpendicular to the mean magnetic field direction. Nonetheless, other physical mechanisms, such as transverse magnetic structures, velocity shears, or boundary effects can contribute to the anisotropy characteristics of plasma sheet turbulence. The scale-independent features are related to anisotropy characteristics which occur during a period of magnetic reconnection and fast tailward flow.

  9. Early results of microwave transmission experiments through an overly dense rectangular plasma sheet with microparticle injection

    SciTech Connect

    Gillman, Eric D.; Amatucci, W. E.

    2014-06-15

    These experiments utilize a linear hollow cathode to create a dense, rectangular plasma sheet to simulate the plasma layer surrounding vehicles traveling at hypersonic velocities within the Earth's atmosphere. Injection of fine dielectric microparticles significantly reduces the electron density and therefore lowers the electron plasma frequency by binding a significant portion of the bulk free electrons to the relatively massive microparticles. Measurements show that microwave transmission through this previously overly dense, impenetrable plasma layer increases with the injection of alumina microparticles approximately 60 μm in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

  10. Early results of microwave transmission experiments through an overly dense rectangular plasma sheet with microparticle injection

    NASA Astrophysics Data System (ADS)

    Gillman, Eric D.; Amatucci, W. E.

    2014-06-01

    These experiments utilize a linear hollow cathode to create a dense, rectangular plasma sheet to simulate the plasma layer surrounding vehicles traveling at hypersonic velocities within the Earth's atmosphere. Injection of fine dielectric microparticles significantly reduces the electron density and therefore lowers the electron plasma frequency by binding a significant portion of the bulk free electrons to the relatively massive microparticles. Measurements show that microwave transmission through this previously overly dense, impenetrable plasma layer increases with the injection of alumina microparticles approximately 60 μm in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

  11. Plasma processes driven by current sheets and their relevance to the auroral plasma

    SciTech Connect

    Singh, N.; Thiemann, H.; Schunk, R.W.

    1986-12-01

    Satellite and rocket observations have revealed a host of auroral plasma processes, including large dc perpendicular electric fields (E /sub perpendicular/) associated with electrostatic shocks, relatively weak parallel electric fields (E /sub parallel/) associated with double layers, upflowing ions in the form of beams and conics, downflowing and upflowing accelerated electron beams, several wave modes such as the electrostatic ion-cyclotron (EIC), lower hybrid (LH), very low frequency (VLF), extremely low frequency (ELF), and high-frequency waves and associated non-linear phenomena. Recently, the authors have attempted to simulate the various processes using a two-dimensional particle-in-cell code in which the plasma is driven by current sheets of a finite thickness. Striking similarities between the observed auroral plasma processes and those seen in the simulations are found. In this paper they give a review of the plasma processes dealing with dc and ac electric fields, formation of ion beams and conics, and electron acceleration.

  12. A two satellite study of nightside flux transfer events in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Sergeev, V. A.; Elphic, R. C.; Mozer, F. S.; Saint-Marc, A.; Sauvaud, J. A.

    1992-01-01

    The short-term (about 1 min) events during two consecutive substorms on March 23 1979 have been studied using high time resolution measurements of magnetic and electric fields and of the kiloelectronvolt electron flux at X about -21 R(e). Data obtained make it possible to describe the localized magnetic structures transported or propagated within the plasma sheet and to identify these events as plasma sheet nightside magnetic flux transfer events (NFTEs). The best examples of the NFTEs found so far are all observed in a thin portion of plasma sheet where the contraction of the reconnected field lines dominates over the oppositely directed pressure gradient force. Systematic differences in the magnetic variations observed at ISEE-1 and 2 indicate current concentration at the outer plasma sheet boundary during the passage of a NFTE.

  13. Electric fields in the plasma sheet and plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Pedersen, A.; Knott, K.; Cattell, C. A.; Mozer, F. S.; Falthammar, C.-G.; Lindqvist, P.-A.; Manka, R. H.

    1985-01-01

    Results obtained by Forbes et al. (1981) on the basis of time delay measurements between ISEE 1 and ISEE 2 imply that the plasma flow and the boundary contracting velocity were nearly the same, whereas the expanding boundary velocity was not accompanied by any significant plasma sheet plasma motion. In the present study, this observation is discussed in conjunction with electric field data. The study is based on electric field data from the spherical double probe experiment on ISEE 1. Electric field data from GEOS 2 are used to some extent to monitor the electric fields near the geostationary orbit during the considered eve nts. Electric field data during CDAW 6 events are discussed, taking into account positions of ISEE 1/ISEE 2 and GEOS 2; March 22, 0600-1300 UT; and March 22, UT; and March 31, 1400-2400 UT.

  14. Energy spectra of plasma sheet ions and electrons from about 50 eV/e to about 1 MeV during plamsa temperature transitions

    NASA Technical Reports Server (NTRS)

    Christon, S. P.; Mitchell, D. G.; Williams, D. J.; Frank, L. A.; Huang, C. Y.; Eastman, T. E.

    1988-01-01

    ISEE-1 charged-particle measurements obtained during eight plasma temperature transitions (PTTs) in 1978-1979 are compiled in tables and graphs and analyzed in detail, comparing the ion and electron differential energy spectra with the predictions of theoretical models. PTTs are defined as approximately 1-h periods of low bulk plasma velocity and steadily increasing or decreasing thermal energy. A Maxwellian distribution is found to be inadequate in describing the PTT energy spectra, but velocity-exponential and kappa distributions are both successful, the latter especially at higher energies. The power-law index kappa varies from PTT to PTT, but the high-energy spectral index and overall shape of the distribution remain constant during a PTT; both spatial and temporal effects are observed.

  15. Plasma Sheet Dynamics Imposed by Bursty Bulk Flows

    NASA Astrophysics Data System (ADS)

    Panov, E. V.

    2009-04-01

    On 17 March 2008 around 9:12 UT the five Themis spacecraft were located in the plasma sheet no more than 1 hour MLT apart and cover ed radial distances from 15 Re (THB) to about 10 Re (THA). We found that all the spacecraft consecutively observed a bursty bulk flow traveling first earthward, slowing down between THB and THA from 400 km/s to 50 km/s, and then changing toward the opposite direction. We found that the most tailward located spacecraft, THB and THC, detected thinning and then thickening of the plasma sheet around the time of the flow direction change. The plasma sheet thinning propagated from THB to THC at about the Alfvén velocity in the plasma sheet boundary layer. Both spacecraft showed signatures of crossing the reconnection separatrix. On the other hand, we found that the THA, THD and THE spacecraft, which were located in a more dipolar region, indicated first plasma sheet thickening and then thinning. The five spacecraft observations can well be explained as the observation of the reconnected magnetic flux, which first moved toward a more dipolar field region close to the Earth, and then bounced tailward. Finally, we discuss the Pi2 pulsations observed by ground based magnetometers during these space observations, and also the non-adiabatic heating of particles inside the plasma sheet found after the sheet's thinning-thickening motion.

  16. Multiple crossings of a very thin plasma sheet in the Earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Hones, E. W., Jr.; Meng, C. I.

    1981-01-01

    High resolution magnetic field, plasma and energetic particle data from the IMP-8 spacecraft were studied for multiple crossings of the Earth's magnetotail plasma sheet when it becomes thin during magnetospheric substorms. Traversals recur on a time scale of several minutes and they are associated with high velocity plasma flows that are usually directed tailward but are occasionally directed earthward for brief intervals. Observations are explained by rapid oscillations of a plasma sheet that is only a few thousand km thick, a dimension comparable to the gyroradius of energetic protons. Differences in the angular distributions of the two energies indicate that the higher energy protons are preferentially located on field lines deeper in the tail lobe. A neutral line acceleration model is supported tailward streaming energetic electrons which are occasionally present at the lobe plasma sheet interface.

  17. Particle drift in the Earth's plasma sheet

    NASA Technical Reports Server (NTRS)

    Wolf, R. A.; Pontius, D. H., Jr.

    1993-01-01

    We generalize the derivation of the average gradient/curvature-drift for a flux tube filled with an isotropic distribution of particles at specified kinetic energy. The present treatment is restricted to a two-dimensional magnetic field with zero electric field, but it includes all chaotic and Speiser orbits, which do not correspond to the simple picture of gradient/curvature drift. We assume that particles are evenly distributed throughout the regions of phase space allowed by their energy and canonical momentum. This assumption is closely related but not exactly equivalent to the assumption of isotropic pitch-angle distribution. Our derivation assumes that the maximum Larmor radius is small compared to the scale length for equatorial variations in the flux tube volume, but it does not involve any restrictions on the curvature of the field line. The resulting expression for the drift rate is valid for situations where the particle drift velocity is comparable to the thermal speed in some regions. The apparent implication of this generalized treatment is that the existence of very complex non-adiabatic particle trajectories in the plasma sheet may not invalidate previous estimates of the average rate of particle drift out the sides of the tail, estimates that were made under the assumption of simple guiding-center drifts.

  18. Azimuthal flow bursts in the inner plasma sheet and possible connection with SAPS and plasma sheet earthward flow bursts

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Nishimura, Y.; Gallardo-Lacourt, B.; Nicolls, M. J.; Chen, S.; Hampton, D. L.; Bristow, W. A.; Ruohoniemi, J. M.; Nishitani, N.; Donovan, E. F.; Angelopoulos, V.

    2015-06-01

    We have combined radar observations and auroral images obtained during the Poker Flat Incoherent Scatter Radar Ion Neutral Observations in the Thermosphere campaign to show the common occurrence of westward moving, localized auroral brightenings near the auroral equatorward boundary and to show their association with azimuthally moving flow bursts near or within the subauroral polarization stream (SAPS) region. These results indicate that the SAPS region, rather than consisting of relatively stable proton precipitation and westward flows, can have rapidly varying flows, with speeds varying from ~100 m/s to ~1 km/s in just a few minutes. The auroral brightenings are associated with bursts of weak electron precipitation that move westward with the westward flow bursts and extend into the SAPS region. Additionally, our observations show evidence that the azimuthally moving flow bursts often connect to earthward (equatorward in the ionosphere) plasma sheet flow bursts. This indicates that rather than stopping or bouncing, some flow bursts turn azimuthally after reaching the inner plasma sheet and lead to the bursts of strong azimuthal flow. Evidence is also seen for a general guiding of the flow bursts by the large-scale convection pattern, flow bursts within the duskside convection being azimuthally turned to the west, and those within the dawn cell being turned toward the east. The possibility that the SAPS region flow structures considered here may be connected to localized flow enhancements from the polar cap that cross the nightside auroral poleward boundary and lead to flow bursts within the plasma sheet warrants further consideration.

  19. Escape of O+ through the distant tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Kistler, L. M.; Galvin, A. B.; Popecki, M. A.; Simunac, K. D. C.; Farrugia, C.; Moebius, E.; Lee, M. A.; Blush, L. M.; Bochsler, P.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Opitz, A.; Sauvaud, J.-A.; Thompson, B.; Russell, C. T.

    2010-11-01

    In February 2007, the STEREO-B spacecraft encountered the magnetosheath, plasma sheet and plasma sheet boundary layer from about 200 RE to 300 RE downtail. This time period was during solar minimum, and there was no storm activity during this month. Using data from the PLASTIC instrument, we find that even during quiet times, O+ is a constant feature of the deep magnetotail, with an O+ density of about 15% of the O+ density in the near-earth plasma sheet for similar conditions. The tailward flux of the O+ is similar to the flux of O+ beams that have been observed in the lobe/mantle region of the deep tail. The total outflow rate of the O+ down the plasma sheet is 1.1 × 1024 ions/s, which is 10% of the total outflow rate of 1 × 1025 ions/s, and of the same order as the estimated loss from dayside transport.

  20. Escape of O+ Through the Distant Tail Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Kistler, L. M.; Galvin, A. B.; Popecki, M.; Simunac, K. D.; Farrugia, C. J.; Moebius, E.; Lee, M. A.; Blush, L. M.; Bochsler, P. A.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Opitz, A.; Sauvaud, J.; Russell, C. T.

    2010-12-01

    During the early orbit phase of the STEREO mission, in February, 2007, the STEREO-B spacecraft went down the deep magnetotail, and encountered the magnetosheath, plasma sheet and plasma sheet boundary layer from about 200 Re to 300 Re downtail, before finally exiting to the solar wind. This time period was during solar minimum, and there was no storm activity during this month. We have used the ion composition data from the PLASTIC instrument to determine how much ionospheric O+ is in the deep tail plasma sheet, and to calculate the loss rate through this path. Surprisingly, we find that during this solar and geomagnetically quiet time, O+ is a constant feature of the deep magnetotail. We find that the O+ density is about 15% of the density in the near-earth plasma sheet for similar conditions. The tailward flux of the O+ is similar to the flux of O+ beams that have been observed in the lobe/mantle region of the deep tail. The observations provide a consistent picture that some O+ is transported into the distant tail in the lobe/mantle region, and then enters the plasma sheet tailward of the distant neutral line. The total outflow of the O+ down the plasma sheet is a rate of 1.1x1024 ions/s, which is 10% of the total outflow rate of 1x 1025 ions/s, and of the same order as the estimated loss from dayside transport.

  1. Experimental study of plasma compression into the sheet in three-dimensional magnetic fields with singular X lines

    SciTech Connect

    Frank, Anna G.; Bogdanov, Sergey Yu.; Markov, Vladimir S.; Ostrovskaya, Galya V.; Dreiden, Galina V.

    2005-05-15

    The formation and evolution of the plasma sheets resulting from the plasma compression in diversified three-dimensional (3D) magnetic configurations with singular X lines are reported on. The research was focused on the correlation between the structure of a plasma sheet and the topology of the initial 3D magnetic configuration, especially on the impact of the guide field aligned with the X line. It has been demonstrated experimentally that plasma compression and formation of extended plasma sheets can take place in configurations with the X lines in the presence of a strong guide field. The electron density distributions in the plasma sheets were found to be rather sensitive to the magnetic field topology. The experiments revealed the effect of progressive decrease of the plasma compression ratio in response to increasing guide field. This effect has two basic manifestations: a decrease of the maximum plasma density and an enlargement of the sheet thickness. Based on the experimental data we advanced a concept that the deterioration of plasma compression into the sheet is due to enhancement of the guide field inside the sheet over its initial value, and due to excitation of additional currents in the plane perpendicular to the singular X line and to the original current in the sheet.

  2. Average electric wave spectra across the plasma sheet and their relation to ion bulk speed

    NASA Technical Reports Server (NTRS)

    Baumjohann, W.; Treumann, R. A.; Labelle, J.; Anderson, R. R.

    1989-01-01

    Using 4 months of tail data obtained by the ELF/MF spectrum analyzer of the wave experiment and the three-dimensional plasma instrument on board the AMPTE/IRM satellite, a statistical survey on the electric wave spectral density in the earth's plasma sheet has been conducted. More than 50,000 10-s-averaged electric wave spectra were analyzed with respect to differences between their values in the inner and outer central plasma sheet and the plasma sheet boundary layer as well as their dependence on radial distance and ion bulk speed. High-speed flows are dominated by broadband electrostatic noise with highest spectral densities in the plasma sheet boundary, where broadband electrostatic noise also exists during periods of low-speed flows. The broadband electrostatic noise has a typical spectral index of about -2. During low-speed flows the spectra in the central plasma sheet show distinct emissions at the electron cyclotron odd half-harmonic and upper hybrid frequency. Wave intensities during episodes of fast perpendicular flows are higher than those associated with fast parallel flows.

  3. On the plasma sheet dependence on solar wind and substorms and its role in magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Sergeev, V. A.; Dmitrieva, N. P.; Stepanov, N. A.; Sormakov, D. A.; Angelopoulos, V.; Runov, A. V.

    2015-12-01

    Recently, it was argued that Hall conductivity and peak intensity of equivalent ionospheric currents are sensitive to the amount of field-aligned acceleration of plasma sheet (PS) electrons, which in turn depends on the plasma sheet parameters T e and N e (electron temperature and density) proportionally to the quantity eTN = ( T e)1/2/ N e. Here we extend these studies using data from six tail seasons of THEMIS observations to show statistically that the behavior of these PS electron parameters, measured in the middle of the nightside plasma sheet at ~10 RE distance, depends in a very different way on two basic processes: the solar wind state and substorms. We confirm previous work that slow/dense (fast/tenuous) solar wind provides cold/dense (hot/tenuous) plasma sheet conditions. However, we find that electron temperature and pressure parameters ( T e and P e) behave differently from the proton ones ( T p and P p), indicating a strong decoupling between temperature variations of auroral protons and electrons in the central plasma sheet (CPS): electrons are more sensitive to the substorm-related acceleration in the magnetotail than protons. Our superposed epoch study of plasma sheet parameter variations during substorms as well as our analysis of plasma acceleration at dipolarization fronts shows that during the substorm expansion phase a new (accelerated and plasma-depleted) population comes into the inner CPS with the flow bursts, showing an average increase of electron temperature and eTN parameter roughly by a factor of 2 above its background values for both cold/dense and hot/tenuous plasma sheet states. Preferential electron heating in the flow bursts is also statistically confirmed.

  4. Central Plasma Sheet Ion Properties as Inferred from Ionospheric Observations

    NASA Technical Reports Server (NTRS)

    Wing, Simon; Newell, Patrick T.

    1998-01-01

    A method of inferring central plasma sheet (CPS) temperature, density, and pressure from ionospheric observations is developed. The advantage of this method over in situ measurements is that the CPS can be studied in its entirely, rather than only in fragments. As a result, for the first time, comprehensive two-dimensional equatorial maps of CPS pressure, density, and temperature within the isotropic plasma sheet are produced. These particle properties are calculated from data taken by the Special Sensor for Precipitating Particles, version 4 (SSJ4) particle instruments onboard DMSP F8, F9, F10, and F11 satellites during the entire year of 1992. Ion spectra occurring in conjunction with electron acceleration events are specifically excluded. Because of the variability of magnetotail stretching, the mapping to the plasma sheet is done using a modified Tsyganenko [1989] magnetic field model (T89) adjusted to agree with the actual magnetotail stretch at observation time. The latter is inferred with a high degree of accuracy (correlation coefficient -0.9) from the latitude of the DMSP b2i boundary (equivalent to the ion isotropy boundary). The results show that temperature, pressure, and density all exhibit dawn-dusk asymmetries unresolved with previous measurements. The ion temperature peaks near the midnight meridian. This peak, which has been associated with bursty bulk flow events, widens in the Y direction with increased activity. The temperature is higher at dusk than at dawn, and this asymmetry increases with decreasing distance from the Earth. In contrast, the density is higher at dawn than at dusk, and there appears to be a density enhancement in the low-latitude boundary layer regions which increases with decreasing magnetic activity. In the near-Earth regions, the pressure is higher at dusk than at dawn, but this asymmetry weakens with increasing distance from the Earth and may even reverse so that at distances X less than approx. 10 to -12 R(sub E), depending on magnetic activity, the dawn sector has slightly higher pressure. The temperature and density asymmetries in the near-Earth region are consistent with the ion westward gradient/curvature drift as the ions ExB convect earthward. When the solar wind dynamic pressure increases, CPS density and pressure appear to increase, but the temperature remains relatively constant. Comparison with previously published work indicates good agreement between the inferred pressure, temperature, and density and those obtained from in situ data. This new method should provide a continuous mechanism to monitor the pressure, temperature, and density in the magnetotail with unprecedented comprehensiveness.

  5. Simultaneous measurements of energetic ion (50 keV and above) and electron (220 keV and above) activity upstream of earth's bow shock and inside the plasma sheet - Magnetospheric source for the November 3 and December 3, 1977 upstream events

    NASA Technical Reports Server (NTRS)

    Sarris, E. T.; Anagnostopoulos, G. C.; Krimigis, S. M.

    1987-01-01

    Simultaneous observations of energetic ions and electrons by the IMP 7 and 8 spacecraft are used here to separate temporal variations from spatial variations during the upstream ion events observed on December 3, 1977 and November 2-3, 1977, in order to determine the source of these particles. Analysis of the observations and comparison with theory shows that: (1) for each of the observed upstream enhancements, energetic ions and electrons were simultaneously present inside the plasma sheet; (2) the low-energy ion intensity profile inside the plasma sheet was relatively flat, while at higher energies there was considrable variability; (3) relativistic electron bursts were seen inside the plasma sheet and also upstream of the shock but at substantially reduced intensities; (4) the ion energy spectrum for the December 3 event, extended to energies of about 2 MeV, was identical in form with the plasma sheet and upstream of the shock; (5) ion anisotropies exhibited typically large dawn-dusk or dusk-dawn gradients and large field-aligned streaming away from the bow shock.

  6. Plasma sheet flow damping by oscillatory flow braking

    NASA Astrophysics Data System (ADS)

    Panov, Evgeny V.; Leontyeva, Olga S.; Baumjohann, Wolfgang; Nakamura, Rumi; Amm, Olaf; Angelopoulos, Vassilis; Glassmeier, Karl-Heinz; Kubyshkina, Marina V.; Petrukovich, Anatoli A.; Sergeev, Victor A.; Weygand, James M.

    2015-04-01

    Using simultaneous observations in the near-Earth plasma sheet by five Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes, conjugate ground all-sky camera observations from Canada, and magnetometer networks over North America, we show that auroral bulge dynamics is modulated by a recently discovered process known as oscillatory flow braking, which occurs at about 10 Earth radii down the Earth's magnetotail. In oscillatory flow breaking, plasma sheet flows oscillating with different periods at various distances collide, producing pressure forces that exert shear stresses on the magnetic field, transiently amplifying the vertical magnetic field component. Sporadic fast relief of these stresses through significant particle precipitations causes damping of plasma sheet fast flows.

  7. Properties and origin of subproton-scale magnetic holes in the terrestrial plasma sheet

    NASA Astrophysics Data System (ADS)

    Sundberg, T.; Burgess, D.; Haynes, C. T.

    2015-04-01

    Electron-scale magnetic depressions in the terrestrial plasma sheet are studied using Cluster multispacecraft data. The structures, which have an observed duration of ~5-10 s, are approximately 200-300 km wide in the direction of propagation, and they show an average reduction in the background magnetic field of 10-20%. A majority of the events are also associated with an increase in the high-energy high pitch angle electron flux, which indicates that the depressions are presumably generated by electrons with relatively high velocity perpendicular to the background magnetic field. Differences in the recorded electron spectra in the four spacecraft indicates a possible nongyrotropic structure. Multispacecraft measurements show that a subset of events are cylindrical, elongated along the magnetic field, and with a field-parallel scale size of at a minimum 500 km. Other events seem to be better described as electron-scale sheets, about 200-300 km thick. We find that no single formation mechanism can explain this variety of events observed. Instead, several processes may be operating in the plasma sheet, giving rise to similar magnetic field structures in the single-spacecraft data, but with different 3-D structuring. The cylindrical structures have several traits that are in agreement with the electron vortex magnetic holes observed in 2-D particle-in-cell simulations of turbulent relaxation, whereas the sheets, which show nearly identical signatures in the multispacecraft data, are better explained by propagating electron solitary waves.

  8. Space Charge Effect in the Sheet and Solid Electron Beam

    NASA Astrophysics Data System (ADS)

    Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

    1998-11-01

    We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.

  9. Cold plasma heating in the plasma sheet boundary layer - Theory and simulations

    NASA Technical Reports Server (NTRS)

    Schriver, David; Ashour-Abdalla, Maha

    1990-01-01

    Satellite observations in recent years have confirmed that the plasma sheet boundary layer is a permanent feature of the earth's magnetotail located between the lobe and central plasma sheet during both quiet and active magnetic periods. Distinct features of the boundary layer include field aligned ion beams and intense electrostatic emissions known as broadband electrostatic noise. Since the plasma sheet boundary layer is a spatial feature of the magnetotail, within it will occur thermal mixing of the resident warm boundary layer plasma with inflowing (convecting) cold ionospheric plasma. A theoretical study involving linear theory and nonlinear numerical particle simulations is presented which examines ion beam instabilities in the presence of a thermally mixed hot and cold background plasma. It is found that the free energy in the ion beams can heat the cool ionospheric plasma to ambient plasma sheet boundary layer temperatures via broadband electrostatic noise. These results, along with recent observational reports that ionospheric outflow can account for measured plasma sheet densities, suggest that the ionospheric role in plasma sheet dynamics and content may be as large as the solar wind.

  10. Plasma flows and magnetic field vectors in the plasma sheet during substorms

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.; Frank, L. A.; Ackerson, K. L.; Meng, C.-I.; Akasofu, S.-I.

    1978-01-01

    A detailed study of the plasma flow and the magnetic field vector in the plasma sheet during magnetospheric substorms is made to determine whether plasma flows are field-aligned or crossfield. It is shown that there is generally a large magnetic field-aligned component in the rapid plasma flow observed in the plasma sheet during substorms. In particular, the larger the observed flow speed, the closer the observed flow direction is aligned with the magnetic field line. There is no clear association between the plasma flow direction and the sign of the Bz component of the magnetic field during plasma sheet thinnings at substorms. The rapid plasma flows observed in the magnetotail are predominantly magnetic field-aligned.

  11. Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Lau, Matthew

    2011-01-01

    The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

  12. The inner edge of the plasma sheet and the diffuse aurora

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Vinas, A. F.

    1983-01-01

    Three dimensional measurements from the ISEE-1 low energy electron spectrometer are used to map the location of the inner edge of the plasma sheet and study the anisotropies in the electron distribution function associated with this boundary. Lower energy plasma sheet electrons have inner edges closer to the Earth than higher energies with the separations at different energies being larger near dawn and after dusk than at midnight. Lowest energy inner edges are frequently located adjacent to the plasmapause in the dawn hemisphere but are often separated from it in the dusk hemisphere by a gap of at least several Re. The energy dispersion is minimal in the afternoon quadrant where the inner edge is near the magnetopause and frequently oscillating on a time scale of minutes. The location of the inner edge is probably determined primarily by the motion of electrons in the existing electric and magnetic fields rather than by strong diffusion as has sometimes been supposed.

  13. Preliminary characterization of a laser-generated plasma sheet

    NASA Astrophysics Data System (ADS)

    Keiter, P. A.; Malamud, G.; Trantham, M.; Fein, J.; Davis, J.; Klein, S. R.; Drake, R. P.

    2015-12-01

    We present the results from recent experiments to create a flowing plasma sheet. Two groups of three laser beams with nominally 1.5 kJ of energy per group were focused to separate pointing locations, driving a shock into a wedge target. As the shock breaks out of the wedge, the plasma is focused on center, creating a sheet of plasma. Measurements at 60 ns indicate the plasma sheet has propagated 2825 microns with an average velocity of 49 microns/ns. These experiments follow previous experiments [Krauland et al. 2013], which are aimed at studying similar physics as that found in the hot spot region of cataclysmic variables. Krauland et al. created a flowing plasma, which represents the flowing plasma from the secondary star. This flow interacted with a stationary object, which represented the disk around the white dwarf. A reverse shock is a shock formed when a freely expanding plasma encounters an obstacle. Reverse shocks can be generated by a blast wave propagating through a medium. They can also be found in binary star systems where the flowing gas from a companion star interacts with the accretion disk of the primary star.

  14. Kinetic theory of the electron bounce instability in two dimensional current sheets-Full electromagnetic treatment

    NASA Astrophysics Data System (ADS)

    Tur, A.; Fruit, G.; Louarn, P.; Yanovsky, V.

    2014-03-01

    In the general context of understanding the possible destabilization of a current sheet with applications to magnetospheric substorms or solar flares, a kinetic model is proposed for studying the resonant interaction between electromagnetic fluctuations and trapped bouncing electrons in a 2D current sheet. Tur et al. [A. Tur et al., Phys. Plasmas 17, 102905 (2010)] and Fruit et al. [G. Fruit et al., Phys. Plasmas 20, 022113 (2013)] already used this model to investigate the possibilities of electrostatic instabilities. Here, the model is completed for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly strechted current, undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet half thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in ? = Bz/Blobes, the mode becomes explosive with typical growth rate of a few tens of seconds. The free energy contained in the bouncing motion of the electrons may trigger an electromagnetic instability able to disrupt the cross-tail current in a few seconds. This new instability-electromagnetic electron-bounce instability-may explain fast and global scale destabilization of current sheets as required to describe substorm phenomena.

  15. Auroral wave structures and ballooning instabilities in the plasma sheet

    NASA Astrophysics Data System (ADS)

    Xing, Xiaoyan; Liang, Jun; Spanswick, Emma; Lyons, Larry; Angelopoulos, Vassilis

    2013-10-01

    wavelike structures extended in the east-west direction along preexisting arcs are often observed to precede the auroral poleward expansions initiated along that arc. These wave structures are suggested to be the manifestation of ballooning/interchange instabilities in the near-Earth plasma sheet that may play crucial roles in leading to substorm expansion. The triggering and the development of the ballooning instability in the MHD regime can be evaluated with theory and numerical simulations; however, observations have never shown how these instabilities are initiated in the plasma sheet. In order to examine the instability triggering, we take advantage of the THEMIS ground all-sky-imagers and NORSTAR-NASCAM multiwavelength imagers together with a multi-spacecraft conjunction to identify the auroral wave structures and to examine the dynamics in the plasma sheet. We show in a case study that the MHD ballooning instability criterion is violated near X = -11 RE in the plasma sheet starting about 1.5 min prior to the initiation of the auroral wave structures. The estimated Alfvnic transit time is slightly larger than 1 min, indicating that the observed auroral signatures are correlated with the ballooning instability developing in the plasma sheet and propagating to the ionosphere along field lines. Magnetic field wavelet analysis shows the initiation of the perpendicular disturbances between 0.01 and 0.02 Hz correlated with the calculated onset of the instability perturbations at the same location, supporting the identification of the localized ballooning instability. At the more tailward region of X ~ -13 RE, enhanced earthward transport toward the unstable region are observed several minutes prior to the instability initiation, which may have modified the pressure spatial distribution and magnetic field topology in the near-Earth region, leading to the violation of the instability criterion. The further development of the instability may play a crucial role for the aurora explosive expansion.

  16. Entropy Properties of Bubble Penetration in the Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Sanchez, E. R.; Wing, S.; Spanswick, E. L.

    2010-12-01

    A longstanding question exists about how transport in the plasma sheet proceeds to avoid pressure imbalance. Various mechanisms have been proposed to explain how pressure is relieved. One mechanism involves rapid earthward convection of flux tubes of under-dense, cold plasma (“bubbles”). Quantifying the conservation of specific and total entropy along the bubble trajectory provides a direct assessment of the validity of entropy assumptions used by global MHD models, which are fundamental building blocks of the Geospace General Circulation Model (GGCM). The paramount objective of this study is to quantify the contribution of inertial effects to releasing pressure in the plasma sheet. The study follows individual bubble/streamer trajectories with ionospheric and magnetospheric observations to determine whether the total entropy (S) and specific entropy (s) are conserved along the bubble trajectories. If entropy is not conserved, the objective then is to determine whether s and S vary randomly, or whether they depend on location, solar wind or magnetic conditions, temperature, or density. We identify the plasma properties of bubbles in the magnetosphere with THEMIS and in the ionosphere with FAST, DMSP and all-sky imagers in order to address the following two questions: (1) Is penetration of bubbles controlled by entropy equalization in the plasma sheet? (2) Can bubbles contribute in a non-negligible way to reducing the entropy of the plasma sheet? We estimate s and S along the trajectory of the flux tubes during THEMIS major tail alignments and observed auroral streamer propagation. Instances are identified during weakly driven geomagnetic conditions where bubble penetration conserved total entropy. For the cases analyzed thus far, the entropy of the bubbles in the farthest region of the plasma sheet is typically ~67% smaller than the average entropy of the ambient plasma sheet. In some cases the entropy reduction was found to be as much as ~95%. At the closest sampled distance, the bubble entropy is only ~10% smaller. Entropy equalization does appear to apply in most cases. A profile of S versus radial distance calculated from three examples shows that S(bubble)/S(ambient) drops more rapidly between THEMIS-B and THEMIS-C than between THEMIS-C and THEMIS-D,-E.

  17. In situ observations of ion scale current sheet and associated electron heating in Earth's magnetosheath turbulence

    NASA Astrophysics Data System (ADS)

    Chasapis, Alexandros; Retinò, Alessandro; Sahraoui, Fouad; Greco, Antonella; Vaivads, Andris; Sundkvist, David; Canu, Patrick

    2014-05-01

    Magnetic reconnection occurs in thin current sheets that form in turbulent plasmas. Numerical simulations indicate that turbulent reconnection contributes to the dissipation of magnetic field energy and results in particle heating and non-thermal acceleration. Yet in situ measurements are required to determine its importance as a dissipation mechanism at those scales. The Earth's magnetosheath downstream of the quasi-parallel shock is a turbulent near-Earth environment that offers a privileged environment for such a study. Here we present a study of the properties of thin current sheets by using Cluster data. We studied the distribution of the current sheets as a function of their magnetic shear angle, the PVI index and the electron heating. The properties of the observed current sheets were different for high shear (θ > 90 degrees) and low shear current sheets (θ < 90 degrees). These high-shear current sheets account for about ˜ 20% of the total and have an average thickness comparable to the ion inertial length. Enhancement of electron temperature within these current sheets suggest that they are important for local electron heating and energy dissipation.

  18. Enhancement mechanism of H- production and suitable configurations for materials processing in a magnetized sheet plasma

    NASA Astrophysics Data System (ADS)

    Ramos, Henry J.; Villamayor, Michelle Marie S.; Mella, Aubrey Faith M.; Salamania, Janella Mae R.; Villanueva, Matthew Bryan P.; Viloan, Rommel Paulo B.

    2014-08-01

    A magnetized sheet plasma ion source was developed for steady state high density plasma with strong density and high temperature gradients. This feature provides efficient formation of negative hydrogen (H-) ions over a wide beam extraction area through the electron volume process. A hexapole confinement at the cathode, addition of argon and magnesium seeding led to the increase of H- yield. The device configuration is suitable for plasma based materials processing namely, synthesis of TiN, SiH, SnO2, and the formation of advanced MAX phase materials Ti2AlC, Ti2CdC and NbAlC.

  19. Substorm Evolution in the Near-Earth Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Erickson, Gary M.

    2004-01-01

    This grant represented one-year, phase-out funding for the project of the same name (NAG5-9110 to Boston University) to determine precursors and signatures of local substorm onset and how they evolve in the plasma sheet using the Geotail near-Earth database. We report here on two accomplishments: (1) Completion of an examination of plasma velocity signature at times of local onsets in the current disruption (CD) region. (2) Initial investigation into quantification of near-Earth flux-tube contents of injected plasma at times of substorm injections.

  20. Comparison of plasma sheet ion composition with the IMF and solar wind plasma

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.

    1988-01-01

    Plasma sheet energetic ion data (0.1- to 16 keV/e) obtained by the Plasma Composition Experiment on ISEE-1 between 10 and 23 earth radii are compared with concurrent IMF and solar wind plasma data. The densities of H(+) and He(++) ions in the plasma sheet are found to be the highest, and the most nearly proportional to the solar wind density, when the IMF B(z) is not northward. The density of terrestrial O(+) ions increases strongly with increasing magnitude of the IMF, in apparent agreement with the notion that the IMF plays a fundamental role in the electric coupling between the solar wind and the ionosphere.

  1. The effect of plasma modification on the sheet resistance of nylon fabrics coated with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Johnson, Les; Silva, S. Ravi P.; Lei, M. K.

    2012-08-01

    Low-pressure oxygen and argon plasmas were used to pre-treat nylon fabrics, and the modified fabrics, together with the raw fabrics, were subsequently coated with single walled carbon nanotubes (SWCNTs) by a dip-drying process. Scanning electron microscopy (SEM) and Raman spectroscopy analyses indicated the attachment of SWCNTs onto nylon fabrics. After the coating with SWCNTs, the plasma modified fabrics exhibited sheet resistance of as low as 2.0 kΩ/sq. with respect to 4.9 kΩ/sq. of the raw fabrics, presumably owing to the increase of fibre surface roughness incurred by the plasma modification, which is evidenced by SEM analyses. Fourier transform infrared spectroscopy (FTIR) analysis indicates the incorporation of oxygen functionalities on fibre surfaces in the plasma modification. This is responsible for the variation of the electrical conductance of SWCNT-coated fabrics with the type of plasma and the duration of plasma ablation.

  2. Earthward and tailward flows in the plasma sheet

    NASA Astrophysics Data System (ADS)

    Zhang, L. Q.; Wang, J. Y.; Baumjohann, W.; Rème, H.; Dunlop, M. W.

    2015-06-01

    Utilizing C3/Cluster satellite observations from the year of 2001 to 2006, we investigated the earthward flow (EF) and tailward flow (TF) at Bz > 0 in the plasma sheet. We found that the EF and the TF have similar spatial distributions. Both characteristics are independent of the distance beyond 14 RE. Both flows are deflected while closer to the Earth. Statistical results further showed that the EF/TF occur in the central plasma sheet as well as the plasma sheet boundary layer and can be observed during quiet times and periods of geomagnetic activity. A typical event reveals that the EF and the TF have different plasma population. A transition region (TR) can be formed at the interface between the EF and TF. Very significant duskward components appeared in bulk velocities for both populations. It appears that the vortical-like structure can be formed near the TR. The magnetic field within the TR is twisted and strongly fluctuates. No clear magnetic flux pileups are observed inside the TR.

  3. On the nature of the plasma sheet boundary layer

    SciTech Connect

    Hones, E.W. Jr. Los Alamos National Lab., NM )

    1990-01-01

    The regions of the plasma sheet adjacent to the north and south lobes of the magnetotail have been described by many experimenters as locations of beams of energetic ions and fast-moving plasma directed primarily earthward and tailward along magnetic field lines. Measurements taken as satellites passed through one or the other of these boundary layers have frequently revealed near-earth mirroring of ions and a vertical segregation of velocities of both earthward-moving and mirroring ions with the fastest ions being found nearest the lobe-plasma sheet interface. These are features expected for particles from a distant tail source {bar E} {times} {bar B} drifting in a dawn-to-dusk electric field and are consistent with the source being a magnetic reconnection region. The plasma sheet boundary layers are thus understood as separatrix layers, bounded at their lobeward surfaces by the separatrices from the distant neutral line. This paper will review the observations that support this interpretation. 10 refs., 7 figs.

  4. Spatial Distribution of Dense Plasma in the Near-Earth Plasma Sheet and its Transport Into the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Izutsu, T.; Nishino, M. N.; Fujimoto, M.; Lavraud, B.; Hasegawa, H.; Angelopoulos, V.; McFadden, J. P.; Larson, D.; Auster, U.; Saito, Y.; Thomsen, M. F.

    2008-12-01

    We investigate the cold-dense plasma sheet (CDPS) on November 12 and 13, 2007 by using THEMIS, Geotail, and LANL satellite. During the last extend period of northward IMF, 2-component CDPS in the duskside plasma sheet (PS), single component CDPS in the dawnside PS, and hot-dense ions (HDIs) at the inner edge of the PS on the dawnside were observed by Geotail, THC, and THA simultaneously. Then, super-dense plasma sheet (SDPS) was detected near the midnight region at geosynchronous orbit (GEO) (i) 1 hour after the southward turning of the IMF and (ii) at the rapid enhancement of the solar wind density (4 hours after (i)). Focusing on (i), duskward moving HDIs and earthward fast flow were encountered by Geotail in the pre-midnight PS. The appearance of SDPS and energetic electrons was in good association with this fast flow. We suggest that HDIs on the dawnside moved to the pre-midnight PS and they were pushed into GEO by the fast flow. After both observations of SDPS, the dense plasma was not seen on the dawnside where THA had detected HDIs (X < ~-5 Re), while it existed earthward of the region. Although these periods were front parts of corotating interaction region (CIR), geomagnetic activity was very weak. We discuss the transport mechanism and the geoeffectiveness of the dense plasma.

  5. Plasma electron analysis: Voyager plasma science experiment

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.

    1983-01-01

    The Plasma Science Experiment (PLS) on the Voyager spacecraft provide data on the plasma ions and electrons in the interplanetary medium and the magnetospheres of the giant planets Jupiter and Saturn. A description of the analysis used to obtain electron parameters (density, temperature, etc.) from the plasma science experiment PLS electron measurements which cover the energy range from 10 eV to 5950 eV is presented. The electron sensor (D cup) and its transmission characteristics are described. A derivation of the fundamental analytical expression of the reduced distribution function F(e) is given. The electron distribution function F(e), used in the moment integrations, can be derived from F(e). Positive ions produce a correction current (ion feedthrough) to the measured electron current, which can be important to the measurements of the suprathermal electron component. In the case of Saturn, this correction current, which can either add to or subtract from the measured electron current, is less than 20% of the measured signal at all times. Comments about the corrections introduced by spacecraft charging to the Saturn encounter data, which can be important in regions of high density and shadow when the spacecraft can become negatively charged are introduced.

  6. Current sheet in plasma as a system with a controlling parameter

    SciTech Connect

    Fridman, Yu. A. Chukbar, K. V.

    2015-08-15

    A simple kinetic model describing stationary solutions with bifurcated and single-peaked current density profiles of a plane electron beam or current sheet in plasma is presented. A connection is established between the two-dimensional constructions arising in terms of the model and the one-dimensional considerations by Bernstein−Greene−Kruskal facilitating the reconstruction of the distribution function of trapped particles when both the profile of the electric potential and the free particles distribution function are known.

  7. Current sheet in plasma as a system with a controlling parameter

    NASA Astrophysics Data System (ADS)

    Fridman, Yu. A.; Chukbar, K. V.

    2015-08-01

    A simple kinetic model describing stationary solutions with bifurcated and single-peaked current density profiles of a plane electron beam or current sheet in plasma is presented. A connection is established between the two-dimensional constructions arising in terms of the model and the one-dimensional considerations by Bernstein-Greene-Kruskal facilitating the reconstruction of the distribution function of trapped particles when both the profile of the electric potential and the free particles distribution function are known.

  8. On the plasma-based growth of ‘flowing’ graphene sheets at atmospheric pressure conditions

    NASA Astrophysics Data System (ADS)

    Tsyganov, D.; Bundaleska, N.; Tatarova, E.; Dias, A.; Henriques, J.; Rego, A.; Ferraria, A.; Abrashev, M. V.; Dias, F. M.; Luhrs, C. C.; Phillips, J.

    2016-02-01

    A theoretical and experimental study on atmospheric pressure microwave plasma-based assembly of free standing graphene sheets is presented. The synthesis method is based on introducing a carbon-containing precursor (C2H5OH) through a microwave (2.45 GHz) argon plasma environment, where decomposition of ethanol molecules takes place and carbon atoms and molecules are created and then converted into solid carbon nuclei in the ‘colder’ nucleation zones. A theoretical model previously developed has been further updated and refined to map the particle and thermal fluxes in the plasma reactor. Considering the nucleation process as a delicate interplay between thermodynamic and kinetic factors, the model is based on a set of non-linear differential equations describing plasma thermodynamics and chemical kinetics. The model predictions were validated by experimental results. Optical emission spectroscopy was applied to detect the plasma emission related to carbon species from the ‘hot’ plasma zone. Raman spectroscopy, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS) techniques have been applied to analyze the synthesized nanostructures. The microstructural features of the solid carbon nuclei collected from the colder zones of plasma reactor vary according to their location. A part of the solid carbon was deposited on the discharge tube wall. The solid assembled from the main stream, which was gradually withdrawn from the hot plasma region in the outlet plasma stream directed to a filter, was composed by ‘flowing’ graphene sheets. The influence of additional hydrogen, Ar flow rate and microwave power on the concentration of obtained stable species and carbon-dicarbon was evaluated. The ratio of sp3/sp2 carbons in graphene sheets is presented. A correlation between changes in C2 and C number densities and sp3/sp2 ratio was found.

  9. Vertical plasma motions in prominence sheets observed by Hinode

    NASA Astrophysics Data System (ADS)

    Panasenco, Olga; Velli, Marco; Berger, Thomas

    We analyze the approximately vertical motions inside prominence plasma observed by Hinode on 25 April 2007 in Hα line and 30 November 2006 in CaH line. Well-established observational facts are that all filaments (prominences on the limb) are composed of fine threads of similar dimensions, rooted in the photosphere and presumably tracing magnetic field lines, and that continuous counter-streaming motions occur along threads. We take into account the geometry of the prominence sheet and the viewing angle to reduce possible projection effect and more correctly interpret the nature of observational downward flows of denser and cooler plasma as well as the upward flow of hotter plasma which appears dark in the Hα and CaH spectral lines. The dark upflows exhibit turbulent flow properties such as vortex formation and shedding that are consistent with the properties of thermal starting plumes. Sometimes an illusion of dark upward motion is generated by rarefactions in the plasma sheet caused by the cooler denser downward flows. On both dates, we suspect there is probably more filament mass in the prominence that is visible in either the Hα or CaH lines. The source of the downward moving plasma may be located either higher above the visible upper edge of the prominence or on the far end of the prominence spine. The bright downward motions of the more cool and dense plasma may be partly due to the counter-streaming motion along the magnetic fields lines, or it may be due to the presence of rayleigh-taylor type or ballooning/interchange instabilities in the upper regions of the prominence, which are then stabilized lower down where the magnetic field is stronger and the plasma beta lower.

  10. Thin filament simulations for Earth's plasma sheet: Interchange oscillations

    NASA Astrophysics Data System (ADS)

    Wolf, R. A.; Chen, C. X.; Toffoletto, F. R.

    2012-02-01

    This paper presents a quantitative theory of “interchange oscillations,” which occur as an earthward-moving low-entropy plasma bubble slows and eventually comes to rest. Our theoretical picture is based on an idealized situation where an ideal-MHD magnetic filament moves without friction through a stationary background that represents the plasma sheet. If the relevant region of the background plasma sheet is interchange stable, then the filament usually executes a damped oscillation about an equilibrium position, where its entropy parameter matches the local background. The oscillations are typically dramatic only if the equatorial plasma beta is greater than about one. We derive an approximate analytic formula for the oscillation period, which is not simply related to slow- or intermediate-wave travel times. For an oscillation that Panov and collaborators carefully studied using THEMIS data, our simple theory, though based on an unrealistic 2D background magnetic field, predicted an oscillation period that agrees with the observations within about 40%. The simulations suggest that the ionospheric oscillation should lag behind the magnetospheric one by between 40 and 90 degrees. Ionospheric conductance affects the damping rate, which maximizes for an auroral zone conductance ˜2 S. Adding a friction force acting between the filament and the background increases the decay rate of the oscillation.

  11. MESSENGER Observations of Magnetic Flux Ropes in Mercury's Plasma Sheet

    NASA Astrophysics Data System (ADS)

    DiBraccio, Gina A.; Slavin, James A.; Imber, Suzanne M.; Gershman, Daniel J.; Raines, Jim M.; Boardsen, Scott A.; Anderson, Brian J.; Korth, Haje; Zurbuchen, Thomas H.; McNutt, Ralph L., Jr.; Solomon, Sean C.

    2014-05-01

    MESSENGER orbital observations provide a new opportunity to investigate magnetic reconnection in the cross-tail current sheet of Mercury's magnetotail. Here we use measurements collected by the Magnetometer and Fast Imaging Plasma Spectrometer (FIPS) during 'hot seasons,' when the orbital periapsis is on Mercury's dayside and MESSENGER crosses the plasma sheet at distances of ~1.5 to 3 RM (where RM is Mercury's radius, or 2440 km). These data frequently contain signatures of large-scale magnetic reconnection in the form of plasmoid-type magnetic flux ropes and southward magnetic fields in the post-plasmoid plasma sheet. In the cross-tail current sheet, which separates the north and south lobes of the magnetotail, flux ropes are formed by reconnection at two or more X-lines and are then transported either toward or away from the planet by the Alfvénic flow emanating from the X-lines. Here we present a survey of 49 plasmoid-type flux ropes identified during seven MESSENGER 'hot seasons,' for which minimum variance analysis indicates that the spacecraft passed near the central axis of the structure. The locations of the selected flux ropes range between 1.7 and 2.8 RM down the tail from the center of the planet. With FIPS measurements, we determined an average proton density of 2.55 cm-3 in the adjacent plasma sheet surrounding the flux ropes, implying an Alfvén speed of ~450 km s-1. Under the assumption that the flux ropes are moving at the local Alfvén speed, we used the mean duration of 0.74 ± 0.15 s to calculate a typical diameter of ~0.14 RM, or ~340 km. We have modeled the plasmoids as force-free flux ropes in order to confirm this result. A superposed epoch analysis demonstrates that the magnetic structure of the flux ropes is similar to what is observed at Earth, but the timescales are 40 times faster at Mercury. The results of this flux rope survey indicate that intense magnetic reconnection occurs frequently in the cross-tail current layer of this small but extremely dynamic magnetosphere.

  12. On the 3-dimensional structure of plasmoids. [in near-earth plasma sheets

    NASA Technical Reports Server (NTRS)

    Hughes, W. J.; Sibeck, D. G.

    1987-01-01

    The hypothesis that the IMF penetrates plasmoids causing them to be three- rather than two-dimensional is tested by comparing observations of By within plasmoids and related tail structures to upstream IMF By data. The magnetic topologies that result from the mergings of closed plasma sheet flux tubes and open tail lobe flux tubes at a near-earth neutral line, and merging near the tail flanks are described and studied. The particle signals and isotropic electron distributions are examined. It is observed that the IMF By penetrates plasmoids and that their structure is three-dimensional. In the three-dimensional model of plasmoids the reconnected plasma sheet field lines form a magnetic flux-ropelike structure. The three-dimensional model is utilized to analyze stagnant, slowly moving and earthward moving structures.

  13. Plasma convection and ion beam generation in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.; Smith, R. A.

    1991-01-01

    Because of the dawn-dusk electric field E(dd), plasma in the magnetotail convects from the lobe toward the central plasma sheet (CPS). In the absence of space or velocity diffusion due to plasma turbulence, convection would yield a steady state distribution function f = V exp (-2/3) g(v exp 2 V exp 2/3), where V is the flux tube volume. Starting with such a distribution function and a plasma beta which varies from beta greater than 1 in the CPS to beta much smaller than 1 in the lobe, the evolution of the ion distribution function was studied considering the combined effects of ion diffusion by kinetic Alfven waves (KAW) in the ULF frequency range (1-10 mHz) and convection due to E(dd) x B drift in the plasma sheet boundary layer (PSBL) and outer central plasma sheet (OCPS). The results show that, during the early stages after launching the KAWs, a beamlike ion distribution forms in the PSBL and at the same time the plasma density and temperature decrease in the OCPS. Following this stage, ions in the beams convect toward the CPS resulting in an increase of the plasma temperature in the OCPS.

  14. Electron cyclotron resonance plasma photos

    SciTech Connect

    Racz, R.; Palinkas, J.; Biri, S.

    2010-02-15

    In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

  15. A new stationary analytical model of the heliospheric current sheet and the plasma sheet

    NASA Astrophysics Data System (ADS)

    Kislov, Roman A.; Khabarova, Olga V.; Malova, Helmi V.

    2015-10-01

    We develop a single-fluid 2-D analytical model of the axially symmetric thin heliospheric current sheet (HCS) embedded into the heliospheric plasma sheet (HPS). A HCS-HPS system has a shape of a relatively thin plasma disk limited by separatrices that also represent current sheets, which is in agreement with Ulysses observations in the aphelion, when it crossed the HCS perpendicular to its plane. Our model employs a differential rotation of the solar photosphere that leads to unipolar induction in the corona. Three components of the interplanetary magnetic field (IMF), the solar wind speed, and the thermal pressure are taken into account. Solar corona conditions and a HCS-HPS system state are tied by boundary conditions and the "frozen-in" equation. The model allows finding spatial distributions of the magnetic field, the speed within the HPS, and electric currents within the HCS. An angular plasma speed is low within the HPS due to the angular momentum conservation (there is no significant corotation with the Sun), which is consistent with observations. We found that the HPS thickness L decreases with distance r, becoming a constant far from the Sun (L ~2.5 solar radii (R0) at 1 AU). Above the separatrices and at large heliocentric distances, the solar wind behavior obeys Parker's model, but the magnetic field spiral form may be different from Parker's one inside the HPS. At r ≤ 245 R0, the IMF spiral may undergo a turn simultaneously with a change of the poloidal current direction (from sunward to antisunward).

  16. Ion Kinetic Properties in Mercury's Pre-Midnight Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Gershman, Daniel J.; Slavin, James A.; Raines, Jim M.; Zurbuchen, Thomas H.; Anderson, Brian J.; Korth, Haje; Baker, Daniel N.; Solomon, Sean C.

    2014-01-01

    With data from the Fast Imaging Plasma Spectrometer sensor on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, we demonstrate that the average distributions for both solar wind and planetary ions in Mercury's pre-midnight plasma sheet are well-described by hot Maxwell-Boltzmann distributions. Temperatures and densities of the H(+)-dominated plasma sheet, in the ranges is approx. 1-10 cm(exp -3) and is approx. 5-30MK, respectively, maintain thermal pressures of is approx.1 nPa. The dominant planetary ion, Na(+), has number densities about 10% that of H(+). Solar wind ions retain near-solar-wind abundances with respect to H(+) and exhibit mass-proportional ion temperatures, indicative of a reconnection-dominated heating in the magnetosphere. Conversely, planetary ion species are accelerated to similar average energies greater by a factor of is approx. 1.5 than that of H(+). This energization is suggestive of acceleration in an electric potential, consistent with the presence of a strong centrifugal acceleration process in Mercury's magnetosphere.

  17. Large-Area Plasmas Formed by Magnetically Confined Electron Beams

    NASA Astrophysics Data System (ADS)

    Fernsler, Richard; Meger, Robert; Lampe, Martin; Manheimer, Wallace; Murphy, Donald; Pechacek, Robert

    1998-10-01

    Magnetically confined electron beams can create plasmas in gas with less heating and greater control and uniformity than sources that produce ionization by heating the plasma electrons. Control is greater because the beam is generated separate from the plasma and steered using an external magnetic field. Uniformity is high because the beam current is constant along the propagation direction and confined magnetically in the transverse direction. And last, heating is reduced because energetic beam electrons ionize efficiently. That is, beam electrons typically require 30 eV of discharge energy per plasma electron formed, whereas conventional plasma sources require 100 eV and often much more. Based on these concepts, a Large Area Plasma Processing System (LAPPS) reactor has recently been built at the Naval Research Laboratory.(R. A. Meger et al., this conference) This reactor utilizes a long hollow-cathode glow discharge to generate a sheet electron beam of several keV in energy, and this beam produces planar plasmas up to 60 cm on a side by 2 cm thick with densities as high as 5x10^12 cm-3 in 30 mtorr of oxygen. Various aspects of beam-produced plasmas will be discussed including confinement and stability, efficiency of ionization and dissociation, cathode operation, and the effects of a low and adjustable plasma electron temperature.

  18. Increases in plasma sheet temperature with solar wind driving during substorm growth phases

    PubMed Central

    Forsyth, C; Watt, C E J; Rae, I J; Fazakerley, A N; Kalmoni, N M E; Freeman, M P; Boakes, P D; Nakamura, R; Dandouras, I; Kistler, L M; Jackman, C M; Coxon, J C; Carr, C M

    2014-01-01

    During substorm growth phases, magnetic reconnection at the magnetopause extracts ∼1015 J from the solar wind which is then stored in the magnetotail lobes. Plasma sheet pressure increases to balance magnetic flux density increases in the lobes. Here we examine plasma sheet pressure, density, and temperature during substorm growth phases using 9 years of Cluster data (>316,000 data points). We show that plasma sheet pressure and temperature are higher during growth phases with higher solar wind driving, whereas the density is approximately constant. We also show a weak correlation between plasma sheet temperature before onset and the minimum SuperMAG AL (SML) auroral index in the subsequent substorm. We discuss how energization of the plasma sheet before onset may result from thermodynamically adiabatic processes; how hotter plasma sheets may result in magnetotail instabilities, and how this relates to the onset and size of the subsequent substorm expansion phase. PMID:26074645

  19. Two types of energy-dispersed ion structures at the plasma sheet boundary

    NASA Astrophysics Data System (ADS)

    Sauvaud, J.-A.; Kovrazhkin, R. A.

    2004-12-01

    We study two main types of ion energy dispersions observed in the energy range ˜1 to 14 keV on board the Interball-Auroral (IA) satellite at altitudes 2-3 RE at the poleward boundary of the plasma sheet. The first type of structure is named velocity dispersed ion structures (VDIS). It is known that VDIS represent a global proton structure with a latitudinal width of ˜0.7-2.5°, where the ion overall energy increases with latitude. IA data allow to show that VDIS are made of substructures lasting for ˜1-3 min. Inside each substructure, high-energy protons arrive first, regardless of the direction of the plasma sheet boundary crossing. A near-continuous rise of the maximal and minimal energies of consecutive substructures with invariant latitude characterizes VDIS. The second type of dispersed structure is named time-of-flight dispersed ion structures (TDIS). TDIS are recurrent sporadic structures in H+ (and also O+) with a quasi-period of ˜3 min and a duration of ˜1-3 min. The maximal energy of TDIS is rather constant and reaches ≥14 keV. During both poleward and equatorward crossings of the plasma sheet boundary, inside each TDIS, high-energy ions arrive first. These structures are accompanied by large fluxes of upflowing H+ and O+ ions with maximal energies up to 5-10 keV. In association with TDIS, bouncing H+ clusters are observed in quasi-dipolar magnetic field tubes, i.e., equatorward from TDIS. The electron populations generally have different properties during observations of VDIS and TDIS. The electron flux accompanying VDIS first increases smoothly and then decreases after Interball-Auroral has passed through the proton structure. The average electron energy in the range ˜0.5-2 keV is typical for electrons from the plasma sheet boundary layer (PSBL). The electron fluxes associated with TDIS increases suddenly at the polar boundary of the auroral zone. Their average energy, reaching ˜5-8 keV, is typical for CPS. A statistical analysis shows that VDIS are observed mainly during magnetically quiet times and during the recovery phase of substorms, while sporadic and recurrent TDIS are observed during the onset and main phases of substorms and magnetic storms and, although less frequently, during substorm recovery phases. From the slope of the (velocity)-1 versus time dispersions of TDIS, we conclude that they have a sporadic source located at the outer boundary of the central plasma sheet, at distances from 8 to 40 RE in the equatorial plane. The disappearance of the PSBL associated with TDIS can be tentatively linked to a reconfiguration of the magnetotail, which disconnects from the Earth the field lines forming the "quiet" PSBL. We show that VDIS consist of ion beams ejected from an extended current sheet at different distances. These ion beams could be formed in the neutral sheet at distance ranging from ˜30 RE to ˜100 RE from the Earth. Inside each substructure the time-of-flight dispersion of ions generally dominate over any latitudinal dispersion induced by a dawn-dusk electric field. These two main types of energy-dispersed ion structures reflect probably two main states of the magnetotail, quiet and active. Finally, it must be stressed that only ˜49% (246 over 501) of the Interball-Auroral auroral zone-polar cap boundary crossings can be described as VDIS or TDIS. On the other 51% of the crossings of the plasma sheet boundary, no well-defined ion dispersed structures were observed.

  20. Stability analysis of the plasma sheet using Hall magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Lee, D.-Y.

    1999-09-01

    Linear stability analysis of the plasma sheet configuration is performed using Hall magnetohydrodynamics, which is more appropriate than the strict ideal MHD for the stressed current sheet during the substorm growth phase. By adding the Hall term in Ohm's law we study the impact of the error involved in assuming perfect conductivity on the stability. The ballooning-like mode with large perpendicular wavenumber is considered, and its basic eigenmode equations are derived. The ballooning instability is currently one of the strong candidates for causing the substorm onset. Numerical computations of the eigenmode equations are carried out for some model equilibria. It is found that the Hall-MHD effect is not so significant in determining the ballooning stability, as the result is not much different from that of ideal MHD: (1) The ballooning instability is rather easily triggered in the model where the field lines are not too much stretched but the plasma beta still exceeds some critical value, which depends on the situation; (2) The ballooning mode, however, seems to be stabilized in the very stretched field models and is not destabilized by adding the Hall-MHD effect in such models. The result implies that the ballooning stability in the plasma sheet seems to be much more dependent on equilibrium properties such as the field shape than on the physical formulation. It is further suggested that extensive field modeling and subsequent tests for the ballooning mode are a high priority in future in order to establish a firm connection between ballooning instability and the substorm onset.

  1. Three dimensional instabilities of an electron scale current sheet in collisionless magnetic reconnection

    SciTech Connect

    Jain, Neeraj; Bchner, Jrg

    2014-06-15

    In collisionless magnetic reconnection, electron current sheets (ECS) with thickness of the order of an electron inertial length form embedded inside ion current sheets with thickness of the order of an ion inertial length. These ECS's are susceptible to a variety of instabilities which have the potential to affect the reconnection rate and/or the structure of reconnection. We carry out a three dimensional linear eigen mode stability analysis of electron shear flow driven instabilities of an electron scale current sheet using an electron-magnetohydrodynamic plasma model. The linear growth rate of the fastest unstable mode was found to drop with the thickness of the ECS. We show how the nature of the instability depends on the thickness of the ECS. As long as the half-thickness of the ECS is close to the electron inertial length, the fastest instability is that of a translational symmetric two-dimensional (no variations along flow direction) tearing mode. For an ECS half thickness sufficiently larger or smaller than the electron inertial length, the fastest mode is not a tearing mode any more and may have finite variations along the flow direction. Therefore, the generation of plasmoids in a nonlinear evolution of ECS is likely only when the half-thickness is close to an electron inertial length.

  2. Variation of the Plasma Sheet in the Near-Earth Magnetotail by the Impact of an Interplanetary Shock

    NASA Astrophysics Data System (ADS)

    Lee, E.; Parks, G. K.; Lin, N.; Kim, K.; Lee, D.; SEON, J.; Jin, H.

    2012-12-01

    It has been reported that Earth's magnetosphere is compressed by the impact of an interplanetary shock. ULF waves or pulses of electric fields are induced in the inner magnetosphere by the impact, which can energize radiation belt particles. In this study we report the observations of the plasma sheet in the near-Earth magnetotail around ~-17 RE by the Cluster spacecraft when an interplanetary shock impacts Earth's magnetosphere. On 24 August 2005 an interplanetary shock impacted Earth's magnetosphere and induced a storm sudden commencement (SSC) and a magnetic storm. After the SSC both the density and temperature of plasmas in the near-Earth magnetotail significantly increased. The current density in the plasma sheet also increased, which implies that the plasma sheet was compressed. The increase of the particle fluxes of ions and electrons was measured predominantly for E > ~30 keV up to ~100 keV, which is much lower than the energies of the particles observed in the radiation belt. The flux enhancement was more prominent for electrons than ions, which suggests that the energization is more efficient for electrons than ions. These observations show that the plasma sheet in the near-Earth magnetotail is affected by the impact of an interplanetary shock, but some aspects are different from those observed in the inner magnetosphere.

  3. Survey of the plasma electron environment of Jupiter: A view from Voyager

    NASA Technical Reports Server (NTRS)

    Scudder, J. D.; Sittler, E. C., Jr.; Bridge, H. S.

    1980-01-01

    The plasma environment within Jupiter's bow shock is considered in terms of the in situ, calibrated electron plasma measurements made between 10 eV and 5.95 keV by the Voyager plasma science experiment (PLS). Measurements were analyzed and corrected for spacecraft potential variations; the data were reduced to nearly model independent macroscopic parameters of the local electron density and temperature. It is tentatively concluded that the radial temperature profile within the plasma sheet is caused by the intermixing of two different electron populations that probably have different temporal histories and spatial paths to their local observation. The cool plasma source of the plasma sheet and spikes is probably the Io plasma torus and arrives in the plasma sheet as a result of flux tube interchange motions or other generalized transport which can be accomplished without diverting the plasma from the centrifugal equator. The hot suprathermal populations in the plasma sheet have most recently come from the sparse, hot mid-latitude "bath" of electrons which were directly observed juxtaposed to the plasma sheet.

  4. Electron velocity distributions and plasma waves associated with the injection of an electron beam into the ionosphere

    SciTech Connect

    Frank, L. A.; Paterson, W. R.; Ashour-Abdalla, M.; Schriver, D.; Kurth, W. S.; Gurnett, D. A.

    1989-06-01

    An electron beam was injected into Earth's ionosphere on August 1, 1985, the flight of the space shuttle /ital Challenger/ as part of the objectives of the Spacelab 2 mission. In the wake of the space shuttle a magnetically aligned sheet of electrons returning from the direction of propagation of the beam was detected with the free-flying plasma Diagnostics Package. The thickness of this sheet of returning electrons was about 20 m. Large intensifications of broadband electrostatic noise were also observed within this sheet of electrons. A numerical simulation of the interaction of the electron beam with the ambient ionospheric plasmas is employed to show that the electron beam excites electron plasma oscillations and that it is possible for the ion ascoustic instability to provide a returning flux of hot electorns by means of quasi-linear diffusion. /copyright/ American Geophysical Union 1989

  5. A Gridded Electron Gun for a Sheet Beam Klystron

    SciTech Connect

    Read, M.E.; Miram, G.; Ives, R.L.; Ivanov, V.; Krasnykh, A.; /SLAC

    2008-04-25

    This paper describes the development of an electron gun for a sheet beam klystron. Initially intended for accelerator applications, the gun can operate at a higher perveance than one with a cylindrically symmetric beam. Results of 2D and 3D simulations are discussed.

  6. The origins of the plasma in the distant plasma sheet

    NASA Technical Reports Server (NTRS)

    Sharp, R. D.; Lennartsson, W.; Peterson, W. K.; Shelley, E. G.

    1982-01-01

    It is pointed out that ion mass spectrometers operating in the keV range have recently begun to provide a new class of information on magnetospheric processes. One of the principal motivations for the development of energetic ion mass spectrometers has been to investigate the origins of the hot plasma populations of the magnetosphere. Peterson et al. (1981) were able to estimate the fractional ion density of ionospheric origin in five intervals by intercomparing the He(++) and H(+) spectra and assuming the excess low-energy H(+) ions were from the ionosphere. They obtained values in the range from 0.1 to 0.65. The present investigation is concerned with an expansion of the previous study. A substantially larger data base is utilized, and a different set of assumptions is considered to infer the relative fractions of solar and ionospheric H(+) and to look for systematic changes in the relative source strengths with magnetic activity.

  7. Association of plasma sheet variations with auroral changes during substorms

    SciTech Connect

    Hones, E.W. Jr.; Craven, J.D.; Frank, L.A.; Parks, G.K.

    1988-01-01

    Images of the southern auroral oval taken by the University of Iowa auroral imaging instrumentation on the Dynamics Explorer 1 satellite during an isolated substorm are correlated with plasma measurements made concurrently by the ISEE 1 satellite in the magnetotail. Qualitative magnetic field configuration changes necessary to relate the plasma sheet boundary location to the latitude of the auroras are discussed. Evidence is presented that the longitudinal advances of the auroras after expansive phase onset are mappings of a neutral line lengthening across the near-tail. We observe a rapid poleward auroral surge, occurring about 1 hour after expansive phase onset, to coincide with the peak of the AL index and argue that the total set of observations at that time is consistent with the picture of a /open quotes/poleward leap/close quotes/ of the electrojet marking the beginning of the substorm's recovery. 9 refs. 3 figs.

  8. Kinetic electron bounce instability in a 2D current sheet - Implication for substorm dynamics

    NASA Astrophysics Data System (ADS)

    Fruit, G.; Tur, A.; Louarn, P.

    2013-12-01

    In the general context of understanding the possible destabilization of the magnetotail before a substorm, we propose a kinetic model for electromagnetic ballooning-type instabilities in resonant interaction with trapped bouncing electrons in a 2D current sheet. Tur et al. 2010 and Fruit et al. 2013 already used this model to investigate the possibilities of electrostatic instabilities. Here, we generalize the model for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly stretched current sheet (Bz > 0.1 Blobes) undamped and stable modes oscillate at typical electron bounce frequency with wavelength (in y) of the order of the plasma sheet thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in epsilon=Bz/Blobes < 0.05 typically, the mode becomes explosive (pure imaginary frequency) with typical growing rate of a few tens of seconds. The free energy contained in the electron bouncing motion could thus trigger and drive an electromagnetic instability able to disrupt the cross-tail current in a few seconds. The role of the temperature ratio Te/Ti is also evaluated.

  9. Dense attosecond electron sheets from laser wakefields using an up-ramp density transition.

    PubMed

    Li, F Y; Sheng, Z M; Liu, Y; Meyer-ter-Vehn, J; Mori, W B; Lu, W; Zhang, J

    2013-03-29

    Controlled electron injection into a laser-driven wakefield at a well defined space and time is reported based on particle-in-cell simulations. Key novel ingredients are an underdense plasma target with an up-ramp density profile followed by a plateau and a fairly large laser focus diameter that leads to an essentially one-dimensional (1D) regime of laser wakefield, which is different from the bubble (complete blowout) regime occurring for tightly focused drive beams. The up-ramp profile causes 1D wave breaking to occur sharply at the up-ramp-plateau transition. As a result, it generates an ultrathin (few nanometer, corresponding to attosecond duration), strongly overdense relativistic electron sheet that is injected and accelerated in the wakefield. A peaked electron energy spectrum and high charge (∼nC) distinguish the final sheet. PMID:23581329

  10. Electron acceleration in the turbulent reconnecting current sheets in solar flares

    NASA Astrophysics Data System (ADS)

    Wu, G. P.; Huang, G. L.

    2009-07-01

    Context: We investigate the nonlinear evolution of the electron distribution in the presence of the strong inductive electric field in the reconnecting current sheets (RCS) of solar flares. Aims: We aim to study the characteristics of nonthermal electron-beam plasma instability and its influence on electron acceleration in RCS. Methods: Including the external inductive field, the one-dimensional Vlasov simulation is performed with a realistic mass ratio for the first time. Results: Our principal findings are as follows: 1) the Buneman instability can be quickly excited on the timescale of 10-7 s for the typical parameters of solar flares. After saturation, the beam-plasma instabilities are excited due to the non-Maxwellian electron distribution; 2) the final velocity of the electrons trapped by these waves is of the same order as the phase speed of the waves, while the untrapped electrons continue to be accelerated; 3) the inferred anomalous resistance of the current sheet and the energy conversion rate are basically of the same order as those previously estimated, e.g., “the analysis of Martens”. Conclusions: The Buneman instability is excited on the timescale of 10-7 s and the wave-particle resonant interaction limits the low-energy electrons to be further accelerated in RCS.

  11. Fermi I electron acceleration by magnetic reconnection exhausts on closely stacked current sheets near the heliopause

    NASA Astrophysics Data System (ADS)

    Czechowski, A.; Grzedzielski, S.; Strumik, M.

    2010-03-01

    Recent observations (up to 32 AU) of solar wind reconnection exhausts suggest fairly frequent occurrence of such events on current sheets associated with the ICME fronts and on the heliospheric current sheet (HCS). Comparison of relevant plasma β values and magnetic field strengths with conditions in the heliosheath indicates that reconnection may also take place in the heliosheath, especially towards the heliopause where the folds of HCS are expected to be pressed together by the slowing of solar plasma flow. We propose a Fermi I type acceleration mechanism in which particles gain energy by random collisions reconnection exhausts expanding typically with local Alfven speed. The most probable place for this process is a (several wide) region of tightly folded HCS near the nose of heliopause. The process may in particular provide the mechanism of accelerating the electrons needed for generation of 2-3 kHz heliospheric emissions.

  12. SOIS Support for Onboard Device Virtualisation and the Use of Electronic Data Sheets

    NASA Astrophysics Data System (ADS)

    Fowell, Stuart D.; Melvin, Richard; Mendham, Peter; Torelli, Felice; Taylor, Chris

    2014-08-01

    This paper describes the motivation for, current status of prototyping, and planned standardisation of SOIS Electronic Data Sheets. This is based upon the recent "Adoption of Electronic Data Sheets for Device Virtualisation for Onboard Devices" TRP project for ESA.

  13. Electric fields in the plasma sheet and plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Pedersen, A.; Cattell, C. A.; Faelthammar, C. G.; Knott, K.; Lindqvist, P. A.; Manka, R. H.; Mozer, F. S.

    1984-01-01

    Data from the spherical double probe electric-field experiment on ISEE-1 were used to study plasmasheet/lobe boundary crossings during substorms, identified by plasma measurements and by using the electric field probes as a reference for measurements of the spacecraft potential. There are strong electric fields, with a dominant dawn-to-dusk component, throughout the boundary layer outside the plasmasheet for contracting and expanding motions of the plasmasheet and for different magnetic field directions. Characteristic amplitudes and durations are 5 to 10 mV/m and 5 to 15 min. The corresponding E x B vectors are always towards the plasmasheet.

  14. Preliminary empirical model of inner boundary of ion plasma sheet

    NASA Astrophysics Data System (ADS)

    Cao, J. B.; Zhang, D.; Reme, H.; Dandouras, I.; Sauvaud, J. A.; Fu, H. S.; Wei, X. H.

    2015-09-01

    The penetration of the plasma sheet into the inner magnetosphere is important to both ring current formation and spacecraft charging at geosynchronous orbit. This paper, using hot ion data recorded by HIA of TC-1/DSP, establishes an empirical model of the inner boundary of ion plasma sheet (IBIPS) on the near equatorial plane. All IBIPS are located inside geocentric radial distance of 9 RE. We divided local times (LT) into eight local time bins and found that during quiet times (Kp ⩽ 2-), the IBIPS is closest to the Earth on the pre-midnight side (LT = 1930-2130) and farthest on the dawn side (LT = 0430-0730), which differs from previous spiral models. The geocentric radius of IBIPS in each local time bin can be described by a linear fitting function: Rps = A + Bkp · Kp. The changing rate Bkp of the radius of IBIPS relative to Kp index on the midnight side (LT = 2230-0130) and post-night side (LT = 0130-0430) are the two largest (0.66 and 0.67), indicating that the IBIPS on the night side (LT = 2230-0430) moves fastest when Kp changes. Since the IBIPSs in different local times bins have different changing rates, both the size and shape of IBIPS change when Kp varies. The correlation coefficients between the radius of IBIPS and the instantaneous Kp increase with the increase of ΔT (the time difference between IBIPS crossing time and preceding Kp interval), which suggests that with the increase of ΔT, the radius of IBIPS is more and more controlled by instantaneous Kp, and the influence of preceding Kp becomes weaker. The response time of IBIPS to Kp is between 80 and 95 min. When ΔT > 95 min, the correlation coefficient basically keeps unchanged and only has a weak increase, suggesting that the IBIPS is mainly determined by the convection electric field represented by instantaneous Kp.

  15. Validity of closed periodic magnetic focusing for sheet electron beams

    SciTech Connect

    Zhao Ding

    2009-11-15

    Theoretical analyses and numerical calculations have demonstrated that a closed periodic cusped magnetic (PCM) field can effectively confine a sheet electron beam in two transverse directions (i.e., in the wide and narrow dimensions, simultaneously) for stable long distance transport in which the sizes of the beam cross section are set by referring to the present state of the art. Moreover, the method for matching the transverse magnetic focusing force and the inner space charge force in the wide dimension of the sheet electron beam is given, and the longitudinal periodic length and the cross sectional shape of the closed PCM focusing structure can be determined. Calculations also demonstrate that the optimum focusing state can be attained by adjusting the wide dimension on the transverse section of the closed PCM structure independently. The work presented in this paper indicates that the closed PCM structure is very promising for the confinement of the sheet electron beam, and it can be helpful for guiding practical engineering design.

  16. Magnetic reconnection at the solar wind current sheets as a possible cause of strahl electrons acceleration and SEP dropouts

    NASA Astrophysics Data System (ADS)

    Khabarova, O.; Zharkova, V. V.

    2014-12-01

    According to the shape of the electron velocity distribution function, there are two populations of suprathermal electrons: halo and strahls (beams). The halo electrons are omni-directional, and strahls are magnetic field aligned beams of electrons that predominantly move in the anti-sunward direction. Properties of strahls represent a great interest, because this population is most energetic, but its origination is still unclear. Usually, it is supposed that strahls is a focused part of halo electrons, non-scattered during their propagation from the Sun. We demonstrate a possibility to better understand nature of strahls if to suggest their acceleration directly in the solar wind due to a magnetic reconnection, occurring at current sheets. We use results of our PIC-simulation of particles behaviour at reconnecting current sheets (Zharkova, Khabarova, ApJ, 2012) in order to explain such effects as:- mismatches between a position of suprathermal electrons pitch-angle changes and real crossing of the heliospheric current sheet,- correlation between heat flux/solar energetic particles dropouts and high plasma beta,- occurrence of counterstreaming electrons at the ICME front and at corotating shocks at r > 2 AU,- radial evolution of strahls/halo density.Multi-spacecraft observations (STEREO, ACE, Ulysses) of properties of suprathermal electrons attributed to crossings of the heliospheric current sheet as well as smaller-scale current sheets during SEP events and CME-CIR interactions will be discussed.

  17. Observation of the plasma boundary layer at lunar distances - Direct injection of plasma into the plasma sheet

    NASA Technical Reports Server (NTRS)

    Sanders, G. D.; Maher, L. J.; Freeman, J. W.

    1980-01-01

    The paper presents observational evidence from the Apollo suprathermal ion detector experiments that the injection of magnetosheath particles at the low-latitude magnetopause operates at lunar distances as well. An interface between the magnetosheath and the plasma sheet, termed the plasma sheet boundary layer (PSBL), is identified and believed to be the extension of the magnetospheric boundary layer (also called the plasma boundary layer) observed on the dayside. Using measurements of the PSBL's thickness, magnetic field, and plasma velocity the average electric potential drop across the PSBL is estimated at 4.2 kV and compared with the potential drop which is needed to insure that the magnetopause is an equipotential for a closed magnetosphere. It was concluded though that the magnetosphere is open since this drop is much larger than 4.2 kV.

  18. Restructured graphene sheets embedded carbon film by oxygen plasma etching and its tribological properties

    NASA Astrophysics Data System (ADS)

    Guo, Meiling; Diao, Dongfeng; Yang, Lei; Fan, Xue

    2015-12-01

    An oxygen plasma etching technique was introduced for improving the tribological properties of the graphene sheets embedded carbon (GSEC) film in electron cyclotron resonance plasma processing system. The nanostructural changing in the film caused by oxygen plasma etching was examined by transmission electron microscope, Raman spectroscopy and X-ray photoelectron spectroscopy, showing that the 3 nm thick top surface layer was restructured with smaller graphene nanocrystallite size as well as higher sp3 bond fraction. The surface roughness, mechanical behavior and tribological properties of the original GSEC and oxygen plasma treated GSEC films were compared. The results indicated that after the oxygen plasma treatment, the average roughness decreased from 20.8 ± 1.1 nm to 1.9 ± 0.1 nm, the hardness increased from 2.3 ± 0.1 GPa to 2.9 ± 0.1 GPa, the nanoscratch depth decreased from 64.5 ± 5.4 nm to 9.9 ± 0.9 nm, and the wear life increased from 930 ± 390 cycles to more than 15,000 frictional cycles. The origin of the improved tribological behavior was ascribed to the 3 nm thick graphene nanocrystallite film. This finding can be expected for wide applications in nanoscale surface engineering.

  19. Optimized H - extraction in an argon-magnesium seeded magnetized sheet plasma

    NASA Astrophysics Data System (ADS)

    Noguera, Virginia R.; Blantocas, Gene Q.; Ramos, Henry J.

    2008-06-01

    The enhancement and optimization of H- extraction through argon and magnesium seeding of hydrogen discharges in a magnetized sheet plasma source are reported. The paper first presents the modification of the production chamber into a hexapole multicusp configuration resulting in decreased power requirements, improved plasma confinement and longer filament lifetime. By this, a wider choice of discharge currents for sustained quiescent plasmas is made possible. Second, the method of adding argon to the hydrogen plasma similar to the scheme in Abate and Ramos [Y. Abate, H. Ramos, Rev. Sci. Instr. 71 (10) (2000) 3689] was performed to find the optimum conditions for H- formation and extraction. Using an E × B probe, H- yields were investigated at varied argon-hydrogen admixtures, different discharge currents and spatial points relative to the core plasma. The optimum H- current density extracted at 3.0 cm from the plasma core using 3.0 A plasma current with 10% argon seeding increased by a factor of 2.42 (0.63 A/m2) compared to the measurement of Abate and Ramos [Y. Abate, H. Ramos, Rev. Sci. Instr. 71 (10) (2000) 3689]. Third, the argon-hydrogen plasma at the extraction chamber is seeded with magnesium. Mg disk with an effective area of 22 cm2 is placed at the extraction region's anode biased 175 V with respect to the cathode. With Mg seeding, the optimum H- current density at the same site and discharge conditions increased by 4.9 times (3.09 A/m2). The enhancement effects were analyzed vis-à-vis information gathered from the usual Langmuir probe (electron temperature and density), electron energy distribution function (EEDF) and the ensuing dissociative attachment (DA) reaction rates at different spatial points for various plasma discharges and gas ratios. Investigations on the changes in the effective electron temperature and electron density indicate that the enhancement is due to increased density of low-energy electrons in the volume, conducive for DA reactions. With Mg, the density of electrons with electron temperature of about 3 eV increased 3 orders of magnitude from 2.76 × 1012 m-3 to 2.90 × 1015m-3.

  20. A new approach to nanoporous graphene sheets via rapid microwave-induced plasma for energy applications.

    PubMed

    Odedairo, Taiwo; Ma, Jun; Gu, Yi; Zhou, Wei; Jin, Jian; Zhao, X S; Zhu, Zhonghua

    2014-12-12

    We developed a novel approach to the fabrication of three-dimensional, nanoporous graphene sheets featuring a high specific surface area of 734.9 m(2) g(-1) and an ultrahigh pore volume of 4.1 cm(3) g(-1) through a rapid microwave-induced plasma treatment. The sheets were used as electrodes for supercapacitors and for the oxygen reduction reaction (ORR) for fuel cells. Argon-plasma grown sheets exhibited a 44% improvement of supercapacitive performance (203 F g(-1)) over the plasma grown sheets (141 F g(-1)). N-doped sheets with Co3O4 showed an outstanding ORR activity evidenced from the much smaller Tafel slope (42 mV/decade) than that of Pt/C (82 mV/decade), which is caused by the high electrical conductivity of the graphene sheets, the planar N species content and the nanoporous morphology. PMID:25410325

  1. Poleward arcs of the auroral oval during substorms and the inner edge of the plasma sheet

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2009-06-01

    An analytical model for the connection between the near-Earth edge of the plasma sheet at substorm onset and the auroral arcs at the poleward edge of the auroral oval is presented. The connection is established through the existence of a Boström type I current system. Its generator is assumed to be constituted by a narrow high-beta plasma layer located at the interface between the near-Earth plasma sheet and the outer edge of the near-dipolar field of the magnetosphere. The energy balance between the downward Poynting flux and the energy conversion in the auroral acceleration region and ionosphere provides a relation for the electric fields as a function of the upward field-aligned current. Only the upward current region is being considered in this work. An interesting effect, incorporated in the energy balance, is the feedback of the auroral electrojet on the magnetospheric plasma by dragging the latter eastward from below under the action of a Hall generator. Thereby a relation arises between the westward electric field, tangential to the arc, and the equatorward polarization field. Quantitative solution of the energy equation is achieved by using the empirical relations between auroral energy flux and electron energy and the integrated Hall and Pedersen conductivities. Accommodation of the downward energy flux requires the existence of a minimum arc length. The resulting quantities are consistent with typical auroral data sets. Relating the downward energy flux to the parameters of the generator reveals a strong dependence of polarization electric field, overall energy dissipation, and total current strength on the plasma beta of the generator. The dumping of excess energy from the high-beta plasma layer into the auroral arc(s) allows the stretched tail field lines to transform into dipolar field lines. It opens, so-to-speak, the gate into the outer magnetosphere.

  2. Bursty bulk flows in the inner central plasma sheet

    NASA Technical Reports Server (NTRS)

    Angelopoulos, V.; Baumjohann, W.; Kennel, C. F.; Coronti, F. V.; Kivelson, M. G.; Pellat, R.; Walker, R. J.; Luehr, H.; Paschmann, G.

    1992-01-01

    High-speed flows in the inner central plasma sheet (first reported by Baumjohann et al. (1990) are studied, together with the concurrent behavior of the plasma and magnetic field, by using AMPTE/IRM data from about 9 to 19 R(E) in the earth magnetotail. The conclusions drawn from the detailed analysis of a representative event are reinforced by a superposed epoch analysis applied on two years of data. The high-speed flows organize themselves in 10-min time scale flow enhancements called here bursty-bulk flow (BBF) events. Both temporal and spatial effects are responsible for their bursty nature. The flow velocity exhibits peaks of very large amplitude with a characteristic time scale of the order of a minute, which are usually associated with magnetic field dipolarizations and ion temeperature increases. The BBFs represent intervals of enhanced earthward convection and energy transport per unit area in the y-z GSM direction of the order of 5 x 10 exp 19 ergs/R(E-squared).

  3. Bursty bulk flows in the inner central plasma sheet

    SciTech Connect

    Angelopoulos, V.; Kennel, C.F.; Coroniti, F.V.; Kivelson, M.G.; Pellat, R.; Walker, R.J. ); Baumjohann, W.; Paschmann, G. ); Luehr, H. )

    1992-04-01

    High speed flow in the inner central plasma sheet are studied, together with the concurrent behavior of the plasma and magnetic field, by using AMPTE/IRM data from {approx} 9 to 19 R{sub E} in the Earth's magnetotail. The conclusions drawn from the detailed analysis of a representative event are reinforced by a superposed epoch analysis on 2 years of data. The high-speed flows organize themselves in 10-min time scale flow enhancements which they call bursty bulk flow (BBF) events. Both temporal and spatial effects are responsible for their bursty nature. The flow velocity exhibits peaks of very large amplitude with a characteristic time scale of the order of a minute, which are usually associated with magnetic field dipolarizations and ion temperatures increases. The BBFs represent intervals of enhanced earthward convection and energy transport per unit area in the y-z GSM direction of the order of 5 {times} 10{sup 19} ergs/R{sub E}{sup 2}.

  4. A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

    SciTech Connect

    Lennartsson, O.W.

    1994-04-01

    Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

  5. A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1994-01-01

    Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

  6. Optical plasma torch electron bunch generation in plasma wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Wittig, G.; Karger, O.; Knetsch, A.; Xi, Y.; Deng, A.; Rosenzweig, J. B.; Bruhwiler, D. L.; Smith, J.; Manahan, G. G.; Sheng, Z.-M.; Jaroszynski, D. A.; Hidding, B.

    2015-08-01

    A novel, flexible method of witness electron bunch generation in plasma wakefield accelerators is described. A quasistationary plasma region is ignited by a focused laser pulse prior to the arrival of the plasma wave. This localized, shapeable optical plasma torch causes a strong distortion of the plasma blowout during passage of the electron driver bunch, leading to collective alteration of plasma electron trajectories and to controlled injection. This optically steered injection is more flexible and faster when compared to hydrodynamically controlled gas density transition injection methods.

  7. Communication through a plasma sheet around a fast moving vehicle

    NASA Astrophysics Data System (ADS)

    Sotnikov, V. I.; Mudaliar, S.; Genoni, T.; Rose, D.; Oliver, B. V.; Mehlhorn, T. A.

    2011-10-01

    Investigation of the complicated problem of scattering of electromagnetic waves on turbulent pulsations induced by a sheared flow inside a plasma sheath is important for many applications including communication with hypersonic and re-entry vehicles. Theoretical and computational work aimed at improving the understanding of electromagnetic wave scattering processes in such turbulent plasmas is presented. We analyze excitation of low frequency ion-acoustic type oscillations in a compressible plasma flow with flow velocity shear and influence of such turbulent pulsations on scattering of high frequency electromagnetic waves used for communication purposes. We have appropriately included in our analysis the presence of electron and ion collisions with neutrals as well as electron - ion collisions. Results of numerical solutions for plasma density and electric field perturbations for different velocity profiles have been used in the derived expressions for scattered wave energy and scattering cross section. Work supported by the Air Force Research Laboratory and Air Force Office Of Scientific Research Sandia is a multiprogram laboratory operated by Sandia Corporation, A Lockheed Martin Company, under contract DE-AC04-94AL85000.

  8. A statistical analysis of heliospheric plasma sheets, heliospheric current sheets, and sector boundaries observed in situ by STEREO

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.-M.; Huang, J.; Wang, C.; Klecker, B.; Galvin, A. B.; Simunac, K. D. C.; Popecki, M. A.; Kistler, L.; Farrugia, C.; Lee, M. A.; Kucharek, H.; Opitz, A.; Luhmann, J. G.; Jian, Lan

    2014-11-01

    The heliocentric orbits of STEREO A and B with a separation in longitude increasing by about 45° per year provide the unique opportunity to study the evolution of the heliospheric plasma sheet (HPS) on a time scale of up to ~2 days and to investigate the relative locations of HPSs and heliospheric current sheets (HCSs). Previous work usually determined the HCS locations based only on the interplanetary magnetic field. A recent study showed that a HCS can be taken as a global structure only when it matches with a sector boundary (SB). Using magnetic field and suprathermal electron data, it was also shown that the relative location of HCS and SB can be classified into five different types of configurations. However, only for two out of these five configurations, the HCS and SB are located at the same position and only these will therefore be used for our study of the HCS/HPS relative location. We find that out of 37 SBs in our data set, there are 10 suitable HPS/HCS event pairs. We find that an HPS can either straddle or border the related HCS. Comparing the corresponding HPS observations between STEREO A and B, we find that the relative HCS/HPS locations are mostly similar. In addition, the time difference of the HPSs observations between STEREO A and B match well with the predicted time delay for the solar wind coming out of a similar region of the Sun. We therefore conclude that HPSs are stationary structures originating at the Sun.

  9. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-01-01

    The auroral motions and geomagnetic changes the characterize the substorm's expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  10. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-05-01

    The auroral motions and geomagnetic changes the characterize the substorm`s expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  11. Multiple harmonic ULF waves in the plasma sheet boundary layer observed by Cluster

    NASA Astrophysics Data System (ADS)

    Engebretson, M. J.; Kahlstorf, C. R. G.; Posch, J. L.; Keiling, A.; Walsh, A. P.; Denton, R. E.; Broughton, M. C.; Owen, C. J.; FornaçOn, K.-H.; RèMe, H.

    2010-12-01

    The passage of the Cluster satellites in a polar orbit through Earth's magnetotail has provided numerous observations of harmonically related Pc 1-2 ULF wave events, with the fundamental near the local proton cyclotron frequency Ωcp. Broughton et al. (2008) reported observations by Cluster of three such events in the plasma sheet boundary layer, and used the wave telescope technique to determine that their wave vectors k were nearly perpendicular to B. This paper reports the results of a search for such waves throughout the 2003 Cluster tail passage. During the 4 month period of July-October 2003, 35 multiple-harmonic wave events were observed, all in the plasma sheet boundary layer (PSBL). From the first observed event (22 July) to the last (28 October), 13 of Cluster's 42 tail passes had at least one event. The wave events were rather evenly distributed from XGSE = -7 RE out to the Cluster apogee distance of -18 RE, with one event observed at -4 RE. ZGSE for these events ranged from -10 to -3 RE and +3 to +7 RE (i.e., there were no events for ∣Z∣ < 3 RE). The wave events, with durations from ˜1 to 50 min, were consistently associated with signatures of the PSBL: elevated fluxes of counterstreaming ions with energies ranging from ˜3 to 30 keV, and elevated fluxes of electrons with energies ranging from 0.25 to ˜5 keV. Analysis of plasma parameters suggests that although waves occurred only when the ion beta exceeded 0.1 (somewhat larger than typical for the PSBL), ion particle pressure may be of more physical importance in controlling wave occurrence. Electron distributions were more isotropic in pitch angles than the ion distributions, but some evidence of counterstreaming electrons was detected in 83% of the events. The ions also showed clear signatures of shell-like or ring-like distributions; i.e., with reduced fluxes below the energy of maximum flux. The suprathermal ion fluxes were asymmetric in all events studied, with more ions streaming earthward (for events both north and south of the central plasma sheet). Good agreement between the observed frequency of the fundamental harmonic and the local Ωcp suggests that the waves were observed near the region of their origin and did not propagate along B, consistent with the wave telescope analysis.

  12. Tearing instabilities driven by nonideal effects in the tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Sundaram, A. K.

    2008-05-01

    Using an extended magnetohydrodynamic description, the excitation of tearing modes is analytically investigated in the tail plasma sheet region that includes the magnetic field components B0x(x,z) and B0z(x,z). Taking electron inertia and the Hall effect into account, a generalized technique is displayed for obtaining the tearing solutions near the singular layer, where the B0x(x,z) field reverses sign at z =0. In two-dimensional tail geometry for scale lengths of order c /ωpe, it is shown that a localized tearing mode as well as a mode with broad spatial extent (Δ'-driven mode) is excited near the field reversal region and these modes are mainly driven by electron inertia. For appropriate current sheet parameters, it is found that the localized mode becomes unstable in a couple of minutes while the mode with broad spatial width grows faster in 10s. For three-dimensional perturbations wherein kx,ky≠0, the combined effects of the Hall term and the electron inertia are shown to excite new localized tearing modes with considerably enhanced growth rates (γ>ωci).

  13. Ion beams in the plasma sheet boundary layer

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.; Runov, A.; Zhou, X.-Z.

    2015-09-01

    We explore characteristics of energetic particles in the plasma sheet boundary layer associated with dipolarization events, based on simulations and observations. The simulations use the electromagnetic fields of an MHD simulation of magnetotail reconnection and flow bursts as basis for test particle tracing. They are complemented by self-consistent fully electrodynamic particle-in-cell (PIC) simulations. The test particle simulations confirm that crescent-shaped earthward flowing ion velocity distributions with strong perpendicular anisotropy can be generated as a consequence of near-tail reconnection, associated with earthward flows and propagating magnetic field dipolarization fronts. Both PIC and test particle simulations show that the ion distribution in the outflow region close to the reconnection site also consist of a beam superposed on an undisturbed population, which, however, does not show strong perpendicular anisotropy. This suggests that the crescent shape is created by quasi-adiabatic deformation from ion motion along the magnetic field toward higher field strength. The simulation results compare favorably with "Time History of Events and Macroscale Interactions during Substorms" observations.

  14. Substorm Evolution in the Near-Earth Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Erickson, Gary M.

    2003-01-01

    The goal of this project is to determine precursors and signatures of local substorm onset and how they evolve in the plasma sheet using the Geotail near-Earth database. This project is part of an ongoing investigation involving this PI, Nelson Maynard (Mission Research Corporation), and William Burke (AFRL) toward an empirical understanding of the onset and evolution of substorms. The first year began with dissemination of our CRRES findings, which included an invited presentation and major publication. The Geotail investigation began with a partial survey of onset signature types at distances X less than 15 R(sub E) for the first five months (March-July 1995) of the Geotail near-Earth mission. During the second year, Geotail data from March 1995 to present were plotted. Various signatures at local onset were catalogued for the period through 1997. During this past year we performed a survey of current-disruption-like (CD-like) signatures at distances X less than or equal to 14 R(sub E) for the three years 1995-1997.

  15. Plasmoid ejection and secondary current sheet generation from magnetic reconnection in laser-plasma interaction.

    PubMed

    Dong, Quan-Li; Wang, Shou-Jun; Lu, Quan-Ming; Huang, Can; Yuan, Da-Wei; Liu, Xun; Lin, Xiao-Xuan; Li, Yu-Tong; Wei, Hui-Gang; Zhong, Jia-Yong; Shi, Jian-Rong; Jiang, Shao-En; Ding, Yong-Kun; Jiang, Bo-Bin; Du, Kai; He, Xian-Tu; Yu, M Y; Liu, C S; Wang, Shui; Tang, Yong-Jian; Zhu, Jian-Qiang; Zhao, Gang; Sheng, Zheng-Ming; Zhang, Jie

    2012-05-25

    Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson et al. [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fanlike electron outflow region including three well-collimated electron jets appears. The (>1 MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS. PMID:23003270

  16. Relationship between wave-like auroral arcs and Pi2 pulsations in plasma sheet during substorms

    NASA Astrophysics Data System (ADS)

    Chang, T. F.; Cheng, C. Z.

    2014-12-01

    The observations of substorm onset phenomena in the magnetosphere and ionosphere are examined to investigate their correlation and to understand the substorm onset mechanism. In particular, we examine the Pi2 wave structure, propagation, frequency in the magnetosphere observed by the THEMIS satellites in the near-Earth plasma sheet and the structure and propagation of the substorm auroral onset arcs. The azimuthal mode number values of the wave-like substorm arcs are found to be in the range of ~ 100 - 260 and decrease with increasing geomagnetic latitude of the substorm auroral arc location. The wave-like arc brightness structures on the substorm auroral arcs tend to move azimuthally westward, but with a few exceptions of eastward movement, during tens of seconds prior to the substorm onset. The movement of the wave-like arc brightness structure is linearly correlated with the phase velocity of the Pi2 δBy pulsations in the near-Earth plasma sheet region. The result suggests that the Pi2 transverse δBy disturbances are related to the intensifying wave-like substorm onset arcs. One plausible explanation of the observations is the kinetic ballooning instability, which has high azimuthal mode number due to the ion gyro-radius effect and finite parallel electric field that accelerates electrons into the ionosphere to produce the wave-like arc structure.

  17. On the generation of field-aligned plasma flow at the boundary of the plasma sheet

    NASA Technical Reports Server (NTRS)

    Schindler, K.; Birn, J.

    1987-01-01

    A possible cause of the large plasma flow velocities parallel to the magnetic field (which were observed in spacecraft experiments) near the boundary of the plasma sheet in the earth's magnetotail is considered in the framework of a magnetohydrodynamic model. It is shown for steady-state configurations that high parallel flow velocities can be expected to exist on field lines connecting to a region of weak magnetic field. The physical mechanism causing large values of the parallel velocity component can be visualized as a strong imbalance of perpendicular mass flux into and out of magnetic flux tubes passing through regions where the magnetic field is weak and inhomogeneous. The value of the parallel velocity component is evaluated, and it is found that it can substantially exceed the perpendicular velocity (by as much as a factor of 40). The results are applied to the earth's magnetotail; it is found that this mechanism is able to explain the parallel flow velocities near the boundary of the plasma sheet in the range of several hundreds of km/s.

  18. A production mechanism of negative hydrogen ions in Uramoto-type sheet-plasma at Kyoto III.

    NASA Astrophysics Data System (ADS)

    Jimbo, K.

    1996-11-01

    Spin functions for three electrons have two distinct s = 1/2 doublets. We apply these two doublets to the plasma in the cold region of the sheet plasma type negative ion source. If liberated electrons have proper energies, the degenerate two ground states are considered to be in a kind of equilibrium; [ e + e + H rightarrow e + H^- ;;. ] Then, we obtain the following one dimensional Saha equation.^1 [ n_e^1/3 fracn_0n^- = frac4λ exp ( - fracɛ - eV_sTe ) ] where λ [cm] = frach√2 π m Te = 6.94 × 10-8 frac1√Te [eV], and frac1n_e^1/3 = int dx, Vs is the plasma potential, ɛ is the electron affinity, h is the plank constant, n0 is the density of H atom and n^- is the density of H^- ion. In the sheet plasma experiment, a relation between negative hydrogen ion currents and plasma potentials is well explained by this equation. 1. K. Jimbo: J. Phys. Soc. Jpn. 65, to be published (1996).

  19. Energetic particle beams in the plasma sheet boundary layer following substorm expansion - Simultaneous near-earth and distant tail observations

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Baker, D. N.; Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.; Klecker, B.; Terasawa, T.; Tsurutani, B. T.

    1986-01-01

    Simultaneous observations of ions and electron beams in the near-earth and deep magnetotail following the onset of substorm are analyzed in terms of the substorm neutral line model. The observations were collected on March 20, 1983 with ISSE 1 and 3. Energy fluxes and intensity-time profiles of protons and electrons are studied. The data reveal that the reconnection at the near-earth neutral line produces ions and electrons for the plasma sheet boundary layer. The maximum electric potential along the neutral line is evaluated.

  20. Electronic, phononic, and thermoelectric properties of graphyne sheets

    SciTech Connect

    Sevinçli, Hâldun; Sevik, Cem

    2014-12-01

    Electron, phonon, and thermoelectric transport properties of α-, β-, γ-, and 6,6,12-graphyne sheets are compared and contrasted with those of graphene. α-, β-, and 6,6,12-graphynes, with direction dependent Dirac dispersions, have higher electronic transmittance than graphene. γ-graphyne also attains better electrical conduction than graphene except at its band gap. Vibrationally, graphene conducts heat much more efficiently than graphynes, a behavior beyond an atomic density differences explanation. Seebeck coefficients of the considered Dirac materials are similar but thermoelectric power factors decrease with increasing effective speeds of light. γ-graphyne yields the highest thermoelectric efficiency with a thermoelectric figure of merit as high as ZT = 0.45, almost an order of magnitude higher than that of graphene.

  1. Comparative studies of multi-scale convective transport through the Earth's plasma sheet

    NASA Astrophysics Data System (ADS)

    Guild, Timothy Bryan

    In this dissertation we explore multi-scale, convective transport through the Earth's plasma sheet using in situ observations and global terrestrial magnetospheric simulations. We statistically test the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model with observations from the Geotail spacecraft at a variety of spatial and temporal scales within the plasma sheet. These comparisons, in addition to quantifying the LFM range of validity, illuminate model shortcomings and highlight the additional physics necessary to resolve data/model discrepancies. First, we perform the first ever comprehensive validation of the LFM in the plasma sheet. We show that the LFM largely reproduces global, long-term average plasma sheet properties and variability, but we also identify and characterize its systematic deficiencies. We find that the LFM overestimates the average plasma sheet velocity, and show that a portion of this overestimate is reflected in excessive LFM ionospheric transpolar potential (15%), and a portion of it is due to insufficient simulation resolution (15%). By characterizing the LFM plasma sheet velocity distribution as a function of simulation resolution, we find that increased resolution inherently changes the nature of the dynamics and transport within the LFM plasma sheet, bringing it into closer agreement with magnetotail observations containing fast, localized bulk flows. To perform the data/model comparisons described thus far, we construct one of the largest central plasma sheet data set of Geotail observations to date. Using this comprehensive data set, we investigate the equatorial distributions of fast, convective flows and infer that the Earthward extent of the average neutral line, the most likely location of near-Earth reconnection, is convex relative to the Earth and offset toward dusk. Due to the importance of these fast flows to mass, momentum, and energy transport in both the observed and simulated plasma sheets, we use the LFM to establish that locally-reconnecting magnetic lobe field lines initiate simulated "flow channels", explore the instability governing their subsequent evolution, and examine their similarity to observations of bursty bulk flows. This dissertation demonstrates the fruitful augmentation of sparse, statistical plasma sheet data sets with global MHD models, thereby enabling further exploration of the multi-scale nature of convective transport within the global, time-dependent plasma sheet.

  2. THEMIS observation of Kinetic Ballooning/Interchange Waves in the High Bz Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Panov, Evgeny V.; Nakamura, Rumi; Kubyshkina, Marina V.; Baumjohann, Wolfgang; A, Sergeev, Victor

    2015-04-01

    Using THEMIS observations of plasma sheet oscillations with kinetic ballooning/interchange instability (BICI) signatures, we investigate the properties of the waves when a high background plasma sheet Bz is seen. We find that such waves are in a better agreement with the existing kinetic simulations. Using adapted Tsyganenko models, we also show conjugate all-sky camera observations in the course of the development of the waves.

  3. Geotail observations of spiky electric fields and low-frequency waves in the plasma sheet and plasma sheet boundary

    NASA Technical Reports Server (NTRS)

    Cattell, C.; Mozer, F.; Tsuruda, K.; Hayakawa, H.; Nakamura, M.; Okada, T.; Kokubun, S.; Yamamoto, T.

    1994-01-01

    Electric field data from the Geotail spacecraft provide an opportunity to extend the observations of spiky fields made by International Sun Earth Explorer-1 (ISEE-1) to a region of the magnetosphere where quasistatic electric field measurements have not previously been msde, to examine their possible importance in the dynamics of the middle and distant tail, and to test some hypotheses about their formation. In this paper, examples of large fields in the plasma sheet and its boundary at radial distances up to approximately 90 R(sub E) are presented. It is shown that three different types of large electric fields can occur: (1) spiky fields; (2) 'DC' fields; and (3) waves at frequencies comparable to the lower hybrid frequency. There is usually a gradation between (1) and (3), and often large electric field spikes are embedded in regions of lower amplitude waves. The waves tend to occur in short (few to 10's of seconds) packets whose start and stop times are not always correlated with changes in the magnetic field and/or density (as indicated by the spacecraft potential). The peak frequency is often less than but comparable to the lower hybrid frequency in agreement with theories of lower hybrid drift waves in the magnetotail. The largest spikes are not always associated with the largest changes in the spacecraft potential and/or magnetic field. It is suggested that the spiky fields may represent the nonlinear development of the waves.

  4. Electromagnetic ELF wave intensification associated with fast earthward flows in mid-tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Liang, J.; Ni, B.; Cully, C. M.; Donovan, E. F.; Thorne, R. M.; Angelopoulos, V.

    2012-03-01

    In this study we perform a statistical survey of the extremely-low-frequency wave activities associated with fast earthward flows in the mid-tail central plasma sheet (CPS) based upon THEMIS measurements. We reveal clear trends of increasing wave intensity with flow enhancement over a broad frequency range, from below fLH (lower-hybrid resonant frequency) to above fce (electron gyrofrequency). We mainly investigate two electromagnetic wave modes, the lower-hybrid waves at frequencies below fLH, and the whistler-mode waves in the frequency range fLH < f < fce. The waves at f < fLH dramatically intensify during fast flow intervals, and tend to contain strong electromagnetic components in the high-plasma-beta CPS region, consistent with the theoretical expectation of the lower-hybrid drift instability in the center region of the tail current sheet. ULF waves with very large perpendicular wavenumber might be Doppler-shifted by the flows and also partly contribute to the observed waves in the lower-hybrid frequency range. The fast flow activity substantially increases the occurrence rate and peak magnitude of the electromagnetic waves in the frequency range fLH < f < fce, though they still tend to be short-lived and sporadic in occurrence. We also find that the electron pitch-angle distribution in the mid-tail CPS undergoes a variation from negative anisotropy (perpendicular temperature smaller than parallel temperature) during weak flow intervals, to more or less positive anisotropy (perpendicular temperature larger than parallel temperature) during fast flow intervals. The flow-related electromagnetic whistler-mode wave tends to occur in conjunction with positive electron anisotropy.

  5. Dawn-dusk asymmetries in plasma sheet particle distributions and the average behaviour of magnetotail current systems

    NASA Astrophysics Data System (ADS)

    Walsh, A. P.; Forsyth, C.; Owen, C. J.; Fazakerley, A. N.; Dandouras, I. S.

    2011-12-01

    We present the results of a survey of Cluster PEACE and CIS-CODIF data taken in the 2001-2006 tail seasons, building on the work of Walsh et al. (GRL, 2011). We examine the average pitch angle distributions of protons and electrons in the magnetotail as a function of proton plasma beta, restricted to times when the magnetosphere was exposed to steady (on a 3 hour timescale) IMF conditions and focussing in particular on dawn-dusk asymmetries. We confirm that, on average, the 2 component proton plasma sheet exists duskward of the noon-midnight meridian under steady northward IMF. An associated population of cold electrons is also observed. Dawnward of the noon-midnight meridian there are no significant fluxes of the cold component of protons and much reduced fluxes of the cold electron component, implying transport across the dusk magnetopause is the dominant formation mechanism of the two component plasma sheet for both protons and electrons. Under southward IMF, dawn-dusk asymmetries in the protons are controlled by the Y component of the IMF. For the electrons higher fluxes of high energy, field-aligned, particles are observed at dusk than at dawn. This suggests a link to a duskward offset of the tail neutral line and the preferential observation of substorm-related tail signatures in the premidnight sector. We also consider the relationship between the observed particle populations and the average behaviour of the large-scale magnetotail current systems as revealed by the Curlometer.

  6. Substorm-related plasma sheet motions as determined from differential timing of plasma changes at the ISEE satellites

    NASA Technical Reports Server (NTRS)

    Forbes, T. G.; Hones, E. W., Jr.; Bame, S. J.; Asbridge, J. R.; Paschmann, G.; Sckopke, N.; Russell, C. T.

    1981-01-01

    From an ISEE survey of substorm dropouts and recoveries during the period February 5 to May 25, 1978, 66 timing events observed by the Los Alamos Scientific Laboratory/Max-Planck-Institut Fast Plasma Experiments were studied in detail. Near substorm onset, both the average timing velocity and the bulk flow velocity at the edge of the plasma sheet are inward, toward the center. Measured normal to the surface of the plasma sheet, the timing velocity is 23 + or - 18 km/s and the proton flow velocity is 20 + or - 8 km/s. During substorm recovery, the plasma sheet reappears moving outward with an average timing velocity of 133 + or - 31 km/s; however, the corresponding proton flow velocity is only 3 + or - 7 km/s in the same direction. It is suggested that the difference between the average timing velocity for the expansion of the plasma sheet and the plasma bulk flow perpendicular to the surface of the sheet during substorm recovery is most likely the result of surface waves moving past the position of the satellites.

  7. Spectroscopic measurements of the electron and ion temperatures and effective ion charge in current sheets formed in two- and three-dimensional magnetic configurations

    SciTech Connect

    Voronov, G. S.; Kyrie, N. P.; Markov, V. S.; Ostrovskaya, G. V.; Frank, A. G.

    2008-12-15

    The spatial distributions of the electron temperature and density, the effective and average ion charges, and the thermal and directed ion velocities in current sheets formed in two-dimensional magnetic fields and three-dimensional magnetic configurations with an X line were studied using spectroscopic and interference holographic methods. The main attention was paid to studying the time evolution of the intensities of spectral lines of the working-gas (argon) and impurity ions under different conditions. Using these data, the electron temperature was calculated with the help of an original mathematical code based on a collisional-radiative plasma model incorporating the processes of ionization and excitation, as well as MHD plasma flows generated in the stage of the current-sheet formation. It is shown that the electron temperature depends on the longitudinal magnetic field, whereas the ion temperature is independent of it. The effective ion charge of the current-sheet plasma was determined for the first time.

  8. Experiments on a reflex-type sheet plasma negative-ion source

    SciTech Connect

    Ando, A.; Kuroda, T.; Oka, Y.; Kaneko, O.; Karita, A.; Kawamoto, T. )

    1990-01-01

    Negative hydrogen ions are extracted from a reflex-type sheet plasma. Electron density and temperature profiles are measured with changing the filling gas pressure, and they are optimized to the H{sup {minus}} production at the optimum gas pressure. The optimum gas pressure is 5 mTorr for the discharge current {ital I}{sub {ital d}} =2 A. As the discharge current {ital I}{sub {ital d}} increases, H{sup {minus}} current increases linearly corresponding to the density increase in the center region, but saturates above {ital I}{sub {ital d}} =40 A. The maximum extracted H{sup {minus}} current density of 4 mA/cm{sup 2} is obtained at {ital I}{sub {ital d}}=100 A.

  9. The double layers in the plasma sheet boundary layer during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Guo, J.; Yu, B.

    2014-11-01

    We studied the evolutions of double layers which appear after the magnetic reconnection through two-dimensional electromagnetic particle-in-cell simulation. The simulation results show that the double layers are formed in the plasma sheet boundary layer after magnetic reconnection. At first, the double layers which have unipolar structures are formed. And then the double layers turn into bipolar structures, which will couple with another new weak bipolar structure. Thus a new double layer or tripolar structure comes into being. The double layers found in our work are about several ten Debye lengths, which accords with the observation results. It is suggested that the electron beam formed during the magnetic reconnection is responsible for the production of the double layers.

  10. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    NASA Astrophysics Data System (ADS)

    Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  11. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    SciTech Connect

    Haynes, Christopher T. Burgess, David; Sundberg, Torbjorn; Camporeale, Enrico

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  12. Review of Solar Wind Entry into and Transport Within the Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Wing, S.; Johnson, J. R.; Chaston, C. C.; Echim, M.; Escoubet, C. P.; Lavraud, B.; Lemon, C.; Nykyri, K.; Otto, A.; Raeder, J.; Wang, C.-P.

    2014-11-01

    The plasma sheet is populated in part by the solar wind plasma. Four solar entry mechanisms are examined: (1) double cusp or double lobe reconnection, (2) Kelvin-Helmholtz Instability (KHI), (3) Kinetic Alfvén waves (KAW), and (4) Impulsive Penetration. These mechanisms can efficiently fill the plasma sheet with cold dense ions during northward interplanetary magnetic field (IMF). The solar wind ions appear to have been heated upon entry along the plasma sheet dawn flank. The cold-component (solar wind origin) ion density is higher on the dawn flank than the dusk flank. The asymmetric evolution of the KAW and magnetic reconnection in association with the KHI at the dawn and dusk flank magnetopause may partly produce the dawn-dusk temperature and density asymmetries. Solar wind that crosses the magnetopause lowers the specific entropy ( s= p/ ρ γ ) of the plasma sheet along the flanks. Subsequent transport of the cold ions from the flanks to the midnight meridian increases s by a factor of 5. T i , T e , s i , and s e increase when the solar wind particles are transported across the magnetopause, but T i / T e is roughly conserved. Within the magnetotail, E× B and curvature and gradient drifts play important roles in the plasma transport and can explain the large features seen in the plasma sheet. Turbulence can also play a significant role, particularly in the cold plasma transport from the flanks to the midnight meridian. Total entropy ( S= pV γ ) conservation provides important constraints on the plasma sheet transport, e.g., fast flows.

  13. Low sheet resistance titanium nitride films by low-temperature plasma-enhanced atomic layer deposition using design of experiments methodology

    SciTech Connect

    Burke, Micheal Blake, Alan; Povey, Ian M.; Schmidt, Michael; Petkov, Nikolay; Carolan, Patrick; Quinn, Aidan J.

    2014-05-15

    A design of experiments methodology was used to optimize the sheet resistance of titanium nitride (TiN) films produced by plasma-enhanced atomic layer deposition (PE-ALD) using a tetrakis(dimethylamino)titanium precursor in a N{sub 2}/H{sub 2} plasma at low temperature (250 °C). At fixed chamber pressure (300 mTorr) and plasma power (300 W), the plasma duration and N{sub 2} flow rate were the most significant factors. The lowest sheet resistance values (163 Ω/sq. for a 20 nm TiN film) were obtained using plasma durations ∼40 s, N{sub 2} flow rates >60 standard cubic centimeters per minute, and purge times ∼60 s. Time of flight secondary ion mass spectroscopy data revealed reduced levels of carbon contaminants in the TiN films with lowest sheet resistance (163 Ω/sq.), compared to films with higher sheet resistance (400–600 Ω/sq.) while transmission electron microscopy data showed a higher density of nanocrystallites in the low-resistance films. Further significant reductions in sheet resistance, from 163 Ω/sq. to 70 Ω/sq. for a 20 nm TiN film (corresponding resistivity ∼145 μΩ·cm), were achieved by addition of a postcycle Ar/N{sub 2} plasma step in the PE-ALD process.

  14. Average patterns of precipitation and plasma flow in the plasma sheet flux tubes during steady magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Sergeev, V. A.; Lennartsson, W.; Pellinen, R.; Vallinkoski, M.; Fedorova, N. I.

    1990-01-01

    Average patterns of plasma drifts and auroral precipitation in the nightside auroral zone were constructed during a steady magnetospheric convection (SMC) event on February 19, 1978. By comparing these patterns with the measurements in the midtail plasma sheet made by ISEE-1, and using the corresponding magnetic field model, the following features are inferred: (1) the concentration of the earthward convection in the midnight portion of the plasma sheet (convection jet); (2) the depleted plasma energy content of the flux tubes in the convection jet region; and (3) the Region-1 field-aligned currents generated in the midtail plasma sheet. It is argued that these three elements are mutually consistent features appearing in the process of ionosphere-magnetosphere interaction during SMC periods. These configurational characteristics resemble the corresponding features of substorm expansions (enhanced convection and 'dipolarized' magnetic field within the substorm current wedge) and appear to play the same role in regulating the plasma flow in the flux tubes connected to the plasma sheet.

  15. ATS-5 observations of plasma sheet particles before the expansion-phase onset, appendix C.. [plasma-particle interactions, magnetic storms and auroras

    NASA Technical Reports Server (NTRS)

    Fujii, K.; Nishida, A.; Sharp, R. D.; Shelley, E. G.

    1975-01-01

    Behavior of the plasma sheet around its earthward edge during substorms was studied by using high resolution (every 2.6 sec) measurements of proton and electron fluxes by ATS-5. In the injection region near midnight the flux increase at the expansion-phase onset is shown to lag behind the onset of the low-latitude positive bay by several minutes. Depending upon the case, before the above increase (1) the flux stays at a constant level, (2) it gradually increases for some tens of minutes, or (3) it briefly drops to a low level. Difference in the position of the satellite relative to the earthward edge and to the high-latitude boundary of the plasma sheet is suggested as a cause of the above difference in flux variations during the growth phase of substorms. Magnetograms and tables (data) are shown.

  16. Nonlinear electron oscillations in a warm plasma

    SciTech Connect

    Sarkar, Anwesa; Maity, Chandan; Chakrabarti, Nikhil

    2013-12-15

    A class of nonstationary solutions for the nonlinear electron oscillations of a warm plasma are presented using a Lagrangian fluid description. The solution illustrates the nonlinear steepening of an initial Gaussian electron density disturbance and also shows collapse behavior in time. The obtained solution may indicate a class of nonlinear transient structures in an unmagnetized warm plasma.

  17. Preliminary interpretation of plasma electron observations at the third encounter of Mariner 10 with Mercury

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Ogilvie, K. W.; Scudder, J. D.; Bridge, H. S.; Siscoe, G. L.; Lazarus, A. J.; Vasyliunas, V. M.; Yeates, C. M.

    1975-01-01

    Plasma electron count observations made during the first and third encounters of Mariner 10 with Mercury (i.e., during Mercury I and III) are reported. They provide detailed information on the magnetosphere of Mercury, especially those from Mercury III. A low-flux region was observed about closest approach (CA) of Mercury III, whereas no such region was detected by the lower-latitude Mercury I; a hot plasma sheet was measured on the outgoing (and near-equator) trajectory of Mercury I, while only cool plasma sheets were observed in the magnetosphere by Mercury III. Findings are similar, on a reduced scale, to models of the earth's magnetosphere and magnetosheath.

  18. Electron "bite-outs" in Dusty Plasmas

    NASA Astrophysics Data System (ADS)

    Horanyi, M.; Hsu, S.; Kempf, S.

    2012-12-01

    The study of dusty plasmas is still an emerging new field that bridges a number of traditionally separate subjects, including for example, celestial mechanics, and plasma physics. Dust particles immersed in plasmas and UV radiation collect electrostatic charges and respond to electromagnetic forces in addition to all the other forces acting on uncharged grains. Simultaneously, dust can alter its plasma environment. Dust particles in plasmas are unusual charge carriers. They are many orders of magnitude heavier than any other plasma particles, and they can have many orders of magnitude larger (negative or positive) time-dependent charges. Dust particles can communicate non-electromagnetic effects (gravity, drag, radiation pressure) to the plasma that can represent new free energy sources. Their presence can influence the collective plasma behavior, for example, by altering the traditional plasma wave modes and by triggering new types of waves and instabilities. Dusty plasmas represent the most general form of space, laboratory, and industrial plasmas. Interplanetary space, comets, planetary rings, asteroids, the Moon, aerosols in the atmosphere, are all examples where electrons, ions, and dust particles coexist. This talk will focus on "electron bite-outs", the apparent reduction of the electron density due to dust charging in a plasma comprised of electrons, ions and dust particles We will compare the recent observations of the plasma conditions near Enceladus at Saturn to the decades old measurements in the Earth's mesosphere. We present model calculations of dust charging in a region where plasma is maintained by UV radiation, and present the time-dependent charge distribution of grains as function of dust density and size distribution. We will also make estimates for possible dusty plasma wave activities as function of the magnitude of the electron "bite-outs".

  19. Hierarchical regrowth of flowerlike nanographene sheets on oxygen-plasma-treated carbon nanowalls

    NASA Astrophysics Data System (ADS)

    Shimoeda, Hironao; Kondo, Hiroki; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2014-04-01

    Cauliflorous nanographene sheets were hierarchically regrown on the spearlike structures of carbon nanowalls (CNWs) produced by O2-plasma etching. The spears on the CNWs acted as a stem for the growth of flowerlike flaky nanographene sheets, where the root of the nanoflower was located at a defect or disordered site. The defects on the graphitic structures were induced by irradiation with oxygen-related radicals and ions in the O2-based plasmas and acted as sites for the nucleation of flowerlike nanographene. The porous carbon nanostructures regrown after O2-plasma treatment have a relatively higher surface area and are thus promising materials for electrochemical applications.

  20. Low-frequency waves in the near-Earth plasma sheet

    SciTech Connect

    Bauer, T.M.; Baumjohann, W.; Treumann, R.A.

    1995-06-01

    The authors present an analysis of plasma wave measurements in the plasma sheet in the frequency range from 0.1 mHz to 8 Hz. They compute power spectra in several different bands, and look at this data against location in the plasma sheet, magnetic field, and magnetospheric activity. In general the power spectra increase with decreasing frequency over the full range. Wave power is enhanced during periods of enhanced activity, or substorms. Fluctuations are in the range of nanotesla, and tend to be stronger along X{sub GSM} as opposed to the two orthogonal directions.

  1. The lobe to plasma sheet boundary layer transition - Theory and observations

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Treumann, R.; Nakamura, M.; Kistler, L. M.

    1990-01-01

    The lobe and the plasma sheet boundary layer in the earth's magnetotail are regions of different plasma conditions and share a common interface. The transition from the lobe to the plasma sheet boundary layer is examined here using AMPTE/IRM data. When the satellite crossed from the lobe to the plasma sheet boundary layer, intense narrow-banded wave bursts at 1 kHz were observed and broadband electrostatic noise (BEN) immediately followed. Simultaneous with the onset of BEN, high energy earthward streaming proton beams at more than 40 keV (more than 2700 km/s) were detected. These results are used as input into a numerical simulation to study ion beam instabilities in the PSBL.

  2. Shape of the terrestrial plasma sheet in the near-Earth magnetospheric tail as imaged by the Interstellar Boundary Explorer

    SciTech Connect

    Dayeh, M. A.; Fuselier, S. A.; Funsten, H. O.; McComas, D. J.; Ogasawara, K.; Petrinec, S. M.; Schwadron, N. A.; Valek, P.

    2015-04-11

    We present remote, continuous observations from the Interstellar Boundary Explorer of the terrestrial plasma sheet location back to -16 Earth radii (RE) in the magnetospheric tail using energetic neutral atom emissions. The time period studied includes two orbits near the winter and summer solstices, thus associated with large negative and positive dipole tilt, respectively. Continuous side-view images reveal a complex shape that is dominated mainly by large-scale warping due to the diurnal motion of the dipole axis. Superposed on the global warped geometry are short-time fluctuations in plasma sheet location that appear to be consistent with plasma sheet flapping and possibly twisting due to changes in the interplanetary conditions. We conclude that the plasma sheet warping due to the diurnal motion dominates the average shape of the plasma sheet. Over short times, the position of the plasma sheet can be dominated by twisting and flapping.

  3. Shape of the terrestrial plasma sheet in the near-Earth magnetospheric tail as imaged by the Interstellar Boundary Explorer

    DOE PAGESBeta

    Dayeh, M. A.; Fuselier, S. A.; Funsten, H. O.; McComas, D. J.; Ogasawara, K.; Petrinec, S. M.; Schwadron, N. A.; Valek, P.

    2015-04-11

    We present remote, continuous observations from the Interstellar Boundary Explorer of the terrestrial plasma sheet location back to -16 Earth radii (RE) in the magnetospheric tail using energetic neutral atom emissions. The time period studied includes two orbits near the winter and summer solstices, thus associated with large negative and positive dipole tilt, respectively. Continuous side-view images reveal a complex shape that is dominated mainly by large-scale warping due to the diurnal motion of the dipole axis. Superposed on the global warped geometry are short-time fluctuations in plasma sheet location that appear to be consistent with plasma sheet flapping andmore » possibly twisting due to changes in the interplanetary conditions. We conclude that the plasma sheet warping due to the diurnal motion dominates the average shape of the plasma sheet. Over short times, the position of the plasma sheet can be dominated by twisting and flapping.« less

  4. Electronic and Magnetic Properties of Metal-Doped BN Sheet: A First-Principles Study

    SciTech Connect

    Zhou, Yungang; Xiao-Dong, J.; Wang, Zhiguo; Xiao, Haiyan Y.; Gao, Fei; Zu, Xiaotao T.

    2010-07-21

    Electronic and magnetic properties of BN sheet doped with 3d transition metals (Fe, Co and Ni) have been investigated using ab initio calculations. Our calculations show many interesting physical properties in metal-doped BN sheet. Fe-doped BN sheet is a half-metal with the magnetic moment of 2.0 μB, and Co-doped BN sheet becomes a narrow-gap semiconductor with the magnetic moment of 1.0 μB. However, no magnetic moment is induced on Ni-doped BN sheet, which has the same band gap as pristine BN sheet. Furthermore, Fe atom is easy to form isolated particle on BN sheet, while Ni and Co atoms are likely to form sheet-supported metal nanotemplate. These results are useful for spintronics application and could help in the development of magnetic nanotructures and metallic nanotemplate at room temperature.

  5. A Gridded Electron Gun for a Sheet Beam Klystron

    NASA Astrophysics Data System (ADS)

    Read, M. E.; Miram, G.; Ives, R. L.; Ivanov, V.; Krasnykh, A.

    2003-12-01

    Calabazas Creek Research, Inc.(CCR) is developing rectangular, gridded, thermionic, dispenser-cathode guns for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the electron beam limit the amount of current that can be transmitted at a given voltage. The options are to increase the beam voltage, leading to problems with X-Ray shielding and modulator and power supply design, or to develop new techniques for lowering the space charge forces in the electron beam. In this device, the beam has a rectangular cross section. The thickness is constrained as it would in a normal, cylindrically symmetric klystron with a Pierce gun. However, the width of the beam is many times the thickness, and the resulting cross sectional area is much larger than in the conventional device. This allows much higher current and/or a lower voltage before space charge forces become too high. The current program addresses issues related to beam formation at the emitter surface, design and implementation of shadow and control grids in a rectangular geometry. It is directed toward a robust, cost-effective, and reliable mechanical design. A prototype device will be developed that will operate at 415 kV, 250 A for an 80 MW, X-Band, sheet-beam klystron. The cathode will have 100 cm2 of cathode area with an average cathode current loading of 2.5 A/cm2. For short pulse formation, the use of a grid was chosen. The gun has been designed with a combination of 2-D and 3-D codes. 2-D codes were used to determine the starting point for the electrodes to produce the compression (which is in only 1 direction.) These results showed that a very high quality beam could be achieved even in the presence of the shadow grid. 3-D results have shown that the quality can be maintained for the actual geometry. Final designs of the gun are being completed, and fabrication is expected to begin in the spring of 2003. Details of the design will be reported.

  6. Structured plasma sheet thinning observed by Galileo and 1984-129

    NASA Technical Reports Server (NTRS)

    Reeves, G. D.; Belian, R. D.; Fritz, T. A.; Kivelson, M. G.; Mcentire, R. W.; Roelof, E. C.; Wilken, B.; Williams, D. J.

    1993-01-01

    On December 8, 1990, the Galileo spacecraft used the Earth for a gravity assist on its way to Jupiter. Its trajectory was such that it crossed geosynchronous orbit at approximately local midnight between 1900 and 2000 UT. At the same time, spacecraft 1984-129 was also located at geosynchronous orbit near local midnight. Several flux dropout events were observed when the two spacecraft were in the near-Earth plasma sheet in the same local time sector. Flux dropout events are associated with plasma sheet thinning in the near-profile of the near-Earth plasma sheet while 1984-129 provided an azimuthal profile. With measurements from these two spacecraft we can distinguish between spatial structures and temporal change. Our observations confirm that the geosynchronous flux dropout events are consistent with plasma sheet thinning which changes the spacecraft's magnetic connection from the trapping region to the more distant plasma sheet. However, for this period, thinning occurred on two spatial and temporal scales. The geosynchronous dropouts were highly localized phenomena of 30 min duration superimposed on a more global reconfiguration of the tail lasting approximately 4 hours.

  7. Structured plasma sheet thinning observed by Galileo and 1984-129

    SciTech Connect

    Reeves, G.D.; Belian, R.D.; Fritz, T.A.

    1993-12-01

    On December 8, 1990, the Galileo spacecraft used the Earth for a gravity assist on its way to Jupiter. Its trajectory was such that is crossed geosynchronous orbit at approximately local midnight between 1900 and 2000 UT. At the same time, spacecraft 1984-129 was also located at geosynchronous orbit near local midnight. Several flux dropout events were observed when the two spacecraft were in the near-Earth plasma sheet in the same local time sector. Flux dropout events are associated with plasma sheet thinning in the near-Earth tail during the growth phase of substorms. This period is unique in that Galileo provided a rapid radial profile of the near-Earth plasma sheet while 1984-129 provided an azimuthal profile. With measurements from these two spacecraft the authors can distinguish between spatial structures and temporal changes. Their observations confirm that the geosynchronous flux dropout events are consistent with plasma sheet thinning which changes the spacecraft`s magnetic connection from the trapping region to the more distant plasma sheet. However, for this period, thinning occurred on two spatial and temporal scales. The geosynchronous dropouts were highly localized phenomena of 30 min duration superimposed on a more global reconfiguration of the tail lasting approximately 4 hours. 28 refs., 10 figs.

  8. Fast magnetic reconnection in thin current sheets: effects of different current profiles and electron inertia in Ohm's law.

    NASA Astrophysics Data System (ADS)

    Pucci, Fulvia; Del Sarto, Daniele; Tenerani, Anna; Velli, Marco

    2015-04-01

    By examining sheets with thicknesses scaling as different powers of the Lundquist number S, we previously showed (Pucci and Velli, 2014) that the growth rate of the tearing mode increases as current sheets thin and, once the inverse aspect ratio reaches a scaling a/L = S-1/3, the time-scale for the instability to develop becomes of the order of the Alfvén time. That means that a fast instability sets in well before Sweet-Parker type current sheets can form. In addition, such an instability produces many islands in the sheet, leading to fast nonlinear evolution and most probably a turbulent disruption of the sheet itself. This has fundamental implications for magnetically driven reconnection throughout the corona, and in particular for coronal heating and the triggering of coronal mass ejections. Here we extend the study of reconnection instabilities to magnetic fields of grater complexity, displaying different current structures such as, for example, multiple or asymmetric current layers. We also consider the possibility of a Δ' dependence on wave-number k-p for different values of p, studying analogies and variations of the trigger scaling relation a/L ~ S-1/3 with respect to the Harris current sheet equilibrium. At large Lundquist numbers in typical Heliospheric plasmas kinetic effects become more important in Ohm's law: we consider the effects of electron skin depth reconnection, showing that we can define a trigger relation similar to the resistive case. The results are important to the transition to fast reconnection in the solar corona, solar wind, magnetosphere as well as laboratory plasmas. F. Pucci and M. Velli, "Reconnection of quasi-singular current sheets: the 'ideal" tearing mode" ApJ 780:L19, 2014.

  9. Relativistic plasma and electron bunches in plasma synchrotrons of GYRAC

    NASA Astrophysics Data System (ADS)

    Andreev, V. V.; Umnov, A. M.

    1999-08-01

    A review of experimental research performed on installations of GYRAC-type based on the synchrotron gyromagnetic autoresonance (SGA) phenomenon is presented. It is shown that the SGA-regime can be used to obtain relativistic plasma as well as a controlled bunch of relativistic electrons. GYRAC-produced plasma is of interest for applied plasma physics as a source of particles and different kinds of radiation (synchrotron radiation and bremsstrahlung).

  10. Observation of a current-driven plasma instability at the outer zone-plasma sheet boundary.

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.; Fredricks, R. W.; Russell, C. T.; Kivelson, M.; Neugebauer, M.; Chappell, C. R.

    1973-01-01

    Several spacecraft experimenters have reported on the detection of large temporal variations in trapped electron fluxes near L = 5 to 6 at midlatitudes in the night hemisphere. In this report we describe in detail the particle, wave, and field changes measured when Ogo 5 traversed an outer-zone trapping boundary of this type on September 7, 1968. It is shown that thermal proton concentrations and E greater than 50-keV electron fluxes abruptly decreased when electrons with (1-4) keV mean energy were detected. It is also shown that currents flowed along the average geomagnetic field direction near the plasma boundaries and that these were accompanied by intense VLF electrostatic waves. It is proposed that turbulent resistivity produced by current-driven plasma instabilities allows parallel dc electric fields to develop along this boundary.

  11. Coupling between electron plasma waves in laser-plasma interactions

    NASA Astrophysics Data System (ADS)

    Everett, M. J.; Lal, A.; Clayton, C. E.; Mori, W. B.; Joshi, C.; Johnston, T. W.

    1996-05-01

    A Lagrangian fluid model (cold plasma, fixed ions) is developed for analyzing the coupling between electron plasma waves. This model shows that a small wave number electron plasma wave (?2,k2) will strongly affect a large wave number electron plasma wave (?1,k1), transferring its energy into daughter waves or sidebands at (?1+n?2,k1+nk2) in the lab frame. The accuracy of the model is checked via particle-in-cell simulations, which confirm that the energy in the mode at (?1,k1) can be completely transferred to the sidebands at (?1+n?2,k1+nk2) by the presence of the electron plasma mode at (?2,k2). Conclusive experimental evidence for the generation of daughter waves via this coupling is then presented using time- and wave number-resolved spectra of the light from a probe laser coherently Thomson scattered by the electron plasma waves generated by the interaction of a two-frequency CO2 laser with a plasma.

  12. Plasma behavior during energetic electron streaming events further evidence for substorm-associated magnetic reconnection

    NASA Technical Reports Server (NTRS)

    Bieber, J. W.; Stone, E. C.; Hones, E. W., Jr.; Baker, D. N.; Bame, S. J.

    1982-01-01

    A recent study showed that streaming energetic (more than 200 keV) electrons in earth's magnetotail are statistically associated with southward magnetic fields and with enhancements of the AE index. It is shown here that the streaming electrons characteristically are preceded by an approximately 15-minute period of tailward plasma flow and followed by a dropout of the plasma sheet, thus demonstrating a clear statistical association between substorms and the classical signatures of magnetic reconnection and plasmoid formation. Additionally, a brief upward surge of mean electron energy preceded plasma dropout in several of the events studied, providing direct evidence of localized, reconnection-associated heating processes.

  13. Suprathermal plasma flows in current sheets formed in two- and three-dimensional magnetic configurations

    SciTech Connect

    Kyrie, N. P.; Markov, V. S.; Frank, A. G.

    2010-04-15

    Dynamics of the thermal and directed motions of argon plasma ions in current sheets formed in various magnetic configurations was investigated experimentally Measurements in three-dimensional magnetic configurations with an X line were carried out for the first time. The results of these measurements were compared with the data obtained in experiments with two-dimensional magnetic configurations. The ion temperature and the energies and velocities of directed plasma flows within the current sheet were determined by analyzing the shapes of argon ion spectral lines broadened due to the Doppler effect. It is found that, under the given experimental conditions, the axial magnetic field does not affect the ion temperature and plasma acceleration in the sheet.

  14. Ballooning instability of the earth's plasma sheet region in the presence of parallel flow

    NASA Technical Reports Server (NTRS)

    Lakhina, G. S.; Hameiri, E.; Mond, M.

    1990-01-01

    Stability of the plasma sheet and plasma sheet boundary layer against the ballooning mode instability is investigated. The equilibrium state of a two-dimensional plasma sheet configuration with parallel sheared flow is modeled. This equilibrium is shown to be ballooning unstable when delta-W is not positive definite, where delta-W is the potential energy. The eigenmode structure of the ballooning mode is found by imposing the boundary conditions that the waves are totally reflected from the ionosphere, and that no waves are coming in from infinity. The eigenmode structure of the unstable balloning modes is highly oscillatory, extending beyond about 100 R(E). The ballooning modes are thus a possible candidate for explaining the MHD waves and other dynamical events observed in the magnetotail by ISEE 3 and other spacecraft.

  15. Structural and electronic properties of a single layered α-tetragonal B50 sheet

    NASA Astrophysics Data System (ADS)

    Kah, Cherno; Yu, Ming; Jayanthi, Chakram S.; Wu, Shiyu

    Ultrathin single-crystalline boron nanosheets with α-tetragonal B50 symmetry (α-t-B50) have recently been synthesized. In this presentation, the relaxed structure of this new type of boron sheet is determined using a robust self-consistent and environment-dependent semi-empirical Hamiltonian developed within the LCAO framework that includes MD and power quenching schemes. Upon relaxation, the sheet symmetry is broken and the icosahedral B12 units in the sheet are found to be distorted. This stability of the sheet was investigated through a calculation of the vibrational frequencies. The sheet electronic density of states exhibits no energy gap at the Fermi level, suggesting a metallic character similar to that of the bulk α-t-B50. Finally, the cohesive energy of the α-t-B50 sheet is found to be higher than that of the recently reported icosahedral B12-δ6 sheet.

  16. Multispacecraft observations of the electron current sheet, neighboring magnetic islands, and electron acceleration during magnetotail reconnection

    SciTech Connect

    Chen Lijen; Bessho, Naoki; Bhattacharjee, Amitava; Lefebvre, Bertrand; Vaith, Hans; Puhl-Quinn, Pamela; Torbert, Roy; Asnes, Arne; Fazakerley, Andrew; Khotyaintsev, Yuri; Daly, Patrick

    2009-05-15

    Open questions concerning structures and dynamics of diffusion regions and electron acceleration in collisionless magnetic reconnection are addressed based on data from the four-spacecraft mission Cluster and particle-in-cell simulations. Using time series of electron distribution functions measured by the four spacecraft, distinct electron regions around a reconnection layer are mapped out to set the framework for studying diffusion regions. A spatially extended electron current sheet (ecs), a series of magnetic islands, and bursts of energetic electrons within islands are identified during magnetotail reconnection with no appreciable guide field. The ecs is collocated with a layer of electron-scale electric fields normal to the ecs and pointing toward the ecs center plane. Both the observed electron and ion densities vary by more than a factor of 2 within one ion skin depth north and south of the ecs, and from the ecs into magnetic islands. Within each of the identified islands, there is a burst of suprathermal electrons whose fluxes peak at density compression sites [L.-J. Chen et al., Nat. Phys. 4, 19 (2008)] and whose energy spectra exhibit power laws with indices ranging from 6 to 7.3. These results indicate that the in-plane electric field normal to the ecs can be of the electron scale at certain phases of reconnection, electrons and ions are highly compressible within the ion diffusion region, and for reconnection involving magnetic islands, primary electron acceleration occurs within the islands.

  17. Dynamic Harris current sheet thickness from Cluster current density and plasma measurements

    NASA Technical Reports Server (NTRS)

    Thompson, S. M.; Kivelson, M. G.; Khurana, K. K.; McPherron, R. L.; Weygand, J. M.; Balogh, A.; Reme, H.; Kistler, L. M.

    2005-01-01

    We use the first accurate measurements of current densities in the plasma sheet to calculate the half-thickness and position of the current sheet as a function of time. Our technique assumes a Harris current sheet model, which is parameterized by lobe magnetic field B(o), current sheet half-thickness h, and current sheet position z(sub o). Cluster measurements of magnetic field, current density, and plasma pressure are used to infer the three parameters as a function of time. We find that most long timescale (6-12 hours) current sheet crossings observed by Cluster cannot be described by a static Harris current sheet with a single set of parameters B(sub o), h, and z(sub o). Noting the presence of high-frequency fluctuations that appear to be superimposed on lower frequency variations, we average over running 6-min intervals and use the smoothed data to infer the parameters h(t) and z(sub o)(t), constrained by the pressure balance lobe magnetic field B(sub o)(t). Whereas this approach has been used in previous studies, the spatial gnuhen& now provided by the Cluster magnetometers were unavailable or not well constrained in earlier studies. We place the calculated hdf&cknessa in a magnetospheric context by examining the change in thickness with substorm phase for three case study events and 21 events in a superposed epoch analysis. We find that the inferred half-thickness in many cases reflects the nominal changes experienced by the plasma sheet during substorms (i.e., thinning during growth phase, thickening following substorm onset). We conclude with an analysis of the relative contribution of (Delta)B(sub z)/(Delta)X to the cross-tail current density during substorms. We find that (Delta)B(sub z)/(Delta)X can contribute a significant portion of the cross-tail c m n t around substorm onset.

  18. An Evaluation of Motions Found in Multiple Supra-Arcade Plasma Sheets with Local Correlation Tracking

    NASA Astrophysics Data System (ADS)

    Freed, Michael; McKenzie, David Eugene

    2016-05-01

    Plasma sheets can be seen in the corona above arcade loops that form shortly after the eruption phase of a solar flare. These structures are considered to be the location where current sheets can form, which are a key component for magnetic reconnection to take place. The objective of this study is to quantify the motion seen in these plasma sheets and to determine how these characteristics might vary over multiple length scales. We use contrast-enhanced EUV observations of five different plasma sheets to construct velocity maps of plasma motion — in the plane of the sky — via a Fourier local correlation tracking program. These derived velocities were then used to calculate angle-integrated power spectral density of intensity, kinetic energy, and enstrophy to determine if any self-similarity exists. The derived velocity fields also allowed for measurements of the kinetic energy density, enstrophy density, and magnetic diffusivity. We will also present the first reported observational evidence of Kelvin-Helmholtz instabilities forming at the interface of supra-arcade downflows (SADs) and the surrounding supra-arcade plasma.

  19. Survey of 0. 1- to 16-keV/e plasma sheet ion composition

    SciTech Connect

    Lennartsson, W.; Shelley, E.G.

    1986-03-01

    A large statistical survey of the 0.1- to 16-keV/e plasma sheet ion composition has been carried out using data obtained by the Plasma Composition Experiment on ISEE 1 between 10 and 23 R/sub E/ during 1978 and 1979. This survey includes more than 10 times the quantity of data used in earlier studies of the same topic and makes it possible to investigate in finer detail the relationship between the ion composition and the substorm activity. The larger data base also makes it possible for the first time to study the spatial distribution of the principal ion species. As found in previous studies, the ion composition has a large variance at any given value of the AE index, but a number of distinct trends emerge when the data are averaged at each activity level. During quiet conditions the plasma sheet is dominated by ions of solar origin (H/sup +/ and He/sup + +/), as found in earlier studies, and these ions are most numerous during extended periods of very low activity (AE< or approx. =30 ..gamma..). The quiet time density of these ions is particularly large in the flanks of the plasma sheet (GSM Yapprox. +- 10 R/sub E/), where it is about twice as large as it is near the central axis of the plasma sheet (Y = Z = 0). In contrast, the energy of these ions peaks near the central axis.

  20. Development of plasma cathode electron guns

    NASA Astrophysics Data System (ADS)

    Oks, Efim M.; Schanin, Peter M.

    1999-05-01

    The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

  1. Identification of the Electron Diffusion Region during Magnetic Reconnection in a Laboratory Plasma

    SciTech Connect

    Ren, Yang; Yamada, Masaaki; Ji, Hantao; Gerhardt, Stefan; Kulsrud, Russell

    2008-06-26

    We report the first identification of the electron diffusion region, where demagnetized electrons are accelerated to super-Alfvenic speed, in a reconnecting laboratory plasma. The electron diffusion region is determined from measurements of the out-of-plane quadrupole magnetic field in the neutral sheet in the Magnetic Reconnection Experiment. The width of the electron diffusion region scales with the electron skin depth (~ 5.5-7.5c=ωpi) and the peak electron outflow velocity scales with the electron Alfven velocity (~ 0.12 - 0.16VeA), independent of ion mass.

  2. Plasma interaction with electron-emitting surfaces

    NASA Astrophysics Data System (ADS)

    Campanell, Michael D.

    Electron emission from surfaces occurs in many plasma systems. Several types including secondary, thermionic and photon-induced emissions are intense under certain conditions. Understanding the effects of emission on the "sheaths" that govern plasma-surface interaction is important. This dissertation predicts some emitting sheath phenomena that were not reported in past studies. For example, most previous theoretical models assumed that an emitting sheath potential is always negative and that ions always accelerate into the wall. We show when the emission is intense that the sheath potential can become positive, fundamentally changing how the plasma and wall interact. In this "inverse sheath" state, ions are repelled, suggesting for instance that (a) no presheath exists in the plasma interior, (b) emitting walls could be used in applications to stop sputtering. Another topic considered is the "transit" of emitted electrons across the plasma to other surfaces, which is possible in low collisionality plasma systems. When transit occurs, the flux balance is a complex global problem where the sheaths at opposite surfaces are coupled through their exchange of emitted electrons. We also show that secondary emission can trigger a variety of sheath instability phenomena that change the state of the plasma-wall system or cause oscillations preventing steady state. Lastly, we analyze a mechanism where emitted electrons return to the same surface and knock out secondaries, which return and knock out more secondaries, etc., feedback amplifying the emission intensity. The four phenomena will be analyzed theoretically and verified with particle-in-cell simulations: (a) inverse sheath, (b) sheath coupling via transiting electrons, (c) sheath instabilities, (d) returning electron amplification. Consequences of these processes on the sheath potentials, wall heating, loss rate of charge, and cross field transport (near-wall conductivity) are discussed throughout. Possible implications are suggested for fusion machines, plasma propulsion engines, probes, dusty plasmas, RF discharges, and surfaces in space.

  3. Plasma wave instability in gated collisionless two-dimensional electron gas

    SciTech Connect

    Dmitriev, A. P.; Kachorovskii, V. Yu.; Shur, M. S.

    2001-08-13

    We present the solution of the Boltzmann equation for relatively low density gated two-dimensional electron gas where electron--electron collisions are not significant. This solution describes the plasma waves with the same dispersion law as for a high electron sheet density. In both cases, the plasma waves become instable in a short channel field effect transistor with asymmetric boundary conditions at small channel currents (provided that the scattering by phonons and impurity is sufficiently small). Our analysis also shows that for realistic values of the device parameters, the Landau damping is small. {copyright} 2001 American Institute of Physics.

  4. Electronic Broadening operator for relativistic plasmas

    SciTech Connect

    Meftah, M. T.; Naam, A.

    2008-10-22

    In this work we review some aspects of the semiclassical dipole impact approximation for isolated ion lines in relativistic plasma. Mainly we focuss our work on the collision operator for relativistic electrons. In this case, the electron trajectory around a positive charge in the plasma differs drastically from those known earlier as hyperbolic. The effect of this difference on the collision operator is discussed with respect the various plasma conditions. Some theoretical and practical aspects of lines -shape calculations are discussed. Detailed calculations are performed for the collision operator in the semiclassical (dipole) impact approximation.

  5. Recombinative plasma in electron runaway discharge

    SciTech Connect

    Kuznetsov, Yu.K.; Galvao, R.M.O.; Usuriaga, O.C.; Krasheninnikov, S.I.; Soboleva, T.K.; Tsypin, V.S.; Fonseca, A.M.M.; Ruchko, L.F.; Sanada, E.K.

    2005-07-15

    Cold recombinative plasma is the basic feature of the new regime of runaway discharges recently discovered in the Tokamak Chauffage Alfven Bresilien tokamak [R. M. O. Galvao et al., Plasma Phys. Controlled Fusion 43, 1181 (2001)]. With low plasma temperature, the resistive plasma current and primary Dreicer process of runaway generation are strongly suppressed at the stationary phase of the discharge. In this case, the runaway avalanche, which has been recently recognized as a novel important mechanism for runaway electron generation in large tokamaks, such as International Thermonuclear Experimental Reactor, during disruptions, and for electric breakdown in matter, is the only mechanism responsible for toroidal current generation and can be easily observed. The measurement of plasma temperature by the usual methods is a difficult task in fully runaway discharges. In the present work, various indirect evidences for low-temperature recombinative plasma are presented. The direct observation of recombinative plasma is obtained as plasma detachment from the limiter. The model of cold recombinative plasma is also supported by measurements of plasma density and H{sub {alpha}} emission radial profiles, analysis of time variations of these parameters due to the relaxation instability, estimations of plasma resistivity from voltage spikes, and energy and particle balance calculations.

  6. Recombinative plasma in electron runaway discharge

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Yu. K.; Galvão, R. M. O.; Usuriaga, O. C.; Krasheninnikov, S. I.; Soboleva, T. K.; Tsypin, V. S.; Fonseca, A. M. M.; Ruchko, L. F.; Sanada, E. K.

    2005-07-01

    Cold recombinative plasma is the basic feature of the new regime of runaway discharges recently discovered in the Tokamak Chauffage Alfvén Brésilien tokamak [R. M. O. Galvão et al., Plasma Phys. Controlled Fusion 43, 1181 (2001)]. With low plasma temperature, the resistive plasma current and primary Dreicer process of runaway generation are strongly suppressed at the stationary phase of the discharge. In this case, the runaway avalanche, which has been recently recognized as a novel important mechanism for runaway electron generation in large tokamaks, such as International Thermonuclear Experimental Reactor, during disruptions, and for electric breakdown in matter, is the only mechanism responsible for toroidal current generation and can be easily observed. The measurement of plasma temperature by the usual methods is a difficult task in fully runaway discharges. In the present work, various indirect evidences for low-temperature recombinative plasma are presented. The direct observation of recombinative plasma is obtained as plasma detachment from the limiter. The model of cold recombinative plasma is also supported by measurements of plasma density and Hα emission radial profiles, analysis of time variations of these parameters due to the relaxation instability, estimations of plasma resistivity from voltage spikes, and energy and particle balance calculations.

  7. Proton beam-electron plasma interactions

    NASA Astrophysics Data System (ADS)

    Pollock, R. E.; Ellsworth, Jennifer; Muterspaugh, M. W.; Todd, D. S.

    1999-12-01

    Stored, cooled proton beams of 200 MeV with intensities up to 3 mA pass along the axis of a Penning-Malmberg trap containing a nonneutral plasma of 1010 electrons. The plasma is maintained in a warmed steady state by injecting energy and angular momentum; the elevated temperature giving weak ionization to replenish lost electrons. Comparing charge density wave velocity with diocotron mode frequency gives continual non-destructive monitoring of plasma radius and density. The beam is observed to cause an increase in plasma radius indicating a torquing mechanism not yet understood. The effect is weakly sensitive to shifts in beam position or angle. Monitoring power input shows either "cooling" (increased electron loss rate) or heating depending on regulation method. Extension of these studies to higher containment fields will be described.

  8. Proton beam-electron plasma interactions

    SciTech Connect

    Pollock, R. E.; Ellsworth, Jennifer; Muterspaugh, M. W.; Todd, D. S.

    1999-12-10

    Stored, cooled proton beams of 200 MeV with intensities up to 3 mA pass along the axis of a Penning-Malmberg trap containing a nonneutral plasma of 10{sup 10} electrons. The plasma is maintained in a warmed steady state by injecting energy and angular momentum; the elevated temperature giving weak ionization to replenish lost electrons. Comparing charge density wave velocity with diocotron mode frequency gives continual non-destructive monitoring of plasma radius and density. The beam is observed to cause an increase in plasma radius indicating a torquing mechanism not yet understood. The effect is weakly sensitive to shifts in beam position or angle. Monitoring power input shows either 'cooling' (increased electron loss rate) or heating depending on regulation method. Extension of these studies to higher containment fields will be described.

  9. Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Hau, L.-N.; Erickson, G. M.

    1995-01-01

    There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

  10. Investigation of the Neutral Sheet Profile during Magnetic Reconnection in a Laboratory Plasma

    NASA Astrophysics Data System (ADS)

    Yamada, Masaaki

    1999-11-01

    Recent detailed data from laboratory plasma experiments, satellite observations, theoretical analyses, and computer simulations have contributed significantly to the understanding of magnetic reconnection both in space and laboratory plasmas. As magnetic field lines break and reconnect around the neutral region, a neutral sheet current is generated. This current then heats the plasma, and the opposing magnetic fields form a stationary equilibrium with the plasma thermal pressure. This region is a focal point of reconnection since it requires proper treatment of local non-MHD effects in a plasma which is highly conductive globally (with large Lundquist number S). Particularly, the profile of the neutral sheet current is a very good indicator of the nature of reconnection. In this talk, we focus on the diverse and very intriguing features of the neutral sheet in driven magnetic reconnection experiments on MRX(M. Yamada et al., Phys. Rev. Lett. 78), 3117 (1997); M. Yamada et al., Phys. Plasmas 4, 1936 (1997)., which was built to investigate the fundamental physics of magnetic reconnection. The MHD approximation (S >> 1, ρi << L, v_A<< c) is satisfied globally in MRX plasmas. In recent MRX experiments, the magnetic field profile of the neutral sheet was measured precisely by magnetic probes with a spatial resolution of 0.25-0.5ρ_i, and B(x) data fit excellently to the Harris profile(E. G. Harris, Il Nuovo Cimento 23), 115 (1962); S. M. Mahajan, Phys. Fluids B 1, 43 (1989). B(x) ~ tanh[(x-x_0)/δ], indicating the formation of a stable, axisymmetric neutral sheet. The sheet thickness δ is found to be equal to the ion skin depth c/ω_pi, which is in very good agreement with recent numerical simulations(J. F. Drake et al., Geophys. Res. Lett. 24), 2921 (1997); D. Biskamp et al., Phys. Rev. Lett. 75, 3850 (1995); R. Horiuchi and T. Sato, Phys. Plasmas 4, 277 (1997).. These data are also consistent with space observations both in the geotail region and the magnetopause. The detailed study of various additional local features of the reconnection region will be presented, along with further study of a generalized Sweet-Parker model(H. Ji et al., Phys. Rev. Lett. 80), 3256 (1998); H. Ji et al., Phys. Plasmas 6, 1743 (1999)., measurements of enhanced resistivity, and studies of ion acceleration and heating. The relationship of MRX data to recent space observations and numerical simulations also will be discussed.

  11. Electronic and magnetic properties of Fe and Mn doped two dimensional hexagonal germanium sheets

    SciTech Connect

    Soni, Himadri R. Jha, Prafulla K.

    2014-04-24

    Using first principles density functional theory calculations, the present paper reports systematic total energy calculations of the electronic properties such as density of states and magnetic moment of pristine and iron and manganese doped two dimensional hexagonal germanium sheets.

  12. Theoretical predictions on the electronic structure and charge carrier mobility in 2D phosphorus sheets.

    PubMed

    Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

    2015-01-01

    We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (?-P, ?-P,?-P and ?-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that ?-P, ?-P and ?-P are indirect gap semiconductors, while ?-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3 10(5) cm(2)V(-1)s(-1), which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, ?-P, ?-P and ?-P sheets can be considered as n-type semiconductors, and ?-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

  13. Electronic and magnetic properties of substituted BN sheets: A density functional theory study

    SciTech Connect

    Zhou, Yungang; Yang, Ping; Wang, Zhiguo; Zu, Xiaotao T.; Xiao, Hai Yan; Sun, Xin; Khaleel, Mohammad A.; Gao, Fei

    2011-04-15

    Using density functional calculations, we investigate the geometries, electronic structures and magnetic properties of hexagonal BN sheets with 3d transition metal (TM) and nonmetal atoms embedded in three types of vacancies: VB, VN, and VB+N. We show that some embedded configurations, except TM atoms in VN vacancy, are stable in BN sheet and yield interesting phenomena. For instance, the band gaps and magnetic moments of BN sheet can be tuned depending on the embedded dopant species and vacancy type. In particular, embedment such as Cr in VB+N, Co in VB, and Ni in VB leads to half-metallic BN sheets interesting for spin filter applications. From the investigation of Mn-chain (CMn) embedments, a regular 1D structure can be formed in BN sheet as an electron waveguide, a metal nanometer wire with a single atom thickness.

  14. The structure of the plasma sheet-lobe boundary in the Earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Candidi, M.; Formisano, V.; Balsiger, H.; Ghielmetti, A.; Ogilvie, K. W.

    1982-01-01

    The structure of the magnetotail plasma sheet-plasma lobe boundary was studied by observing the properties of tailward flowing O+ ion beams, detected by the ISEE 2 plasma experiment inside the boundary during three time periods. The computed value of the north-south electric field component as well as the O+ parameters are shown to change at the boundary. The results are related to other observations made in this region. The O+ parameters and the Ez component behavior are shown to be consistent with that expected from the topology of the electric field lines in the tail as mapped from the ionosphere.

  15. Compressible turbulence with slow-mode waves observed in the bursty bulk flow of plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Tieyan; Cao, Jinbin; Fu, Huishan; Meng, Xuejie; Dunlop, M.

    2016-03-01

    In this paper, we report the evidence of compressible turbulence with slow-mode waves in a bursty bulk flow of plasma sheet. This compressible turbulence is characterized by a multiscale (1-60 s) anticorrelation between plasma density and magnetic field strength. Besides, the magnetic compressibility spectrum stays nearly constant at all the measured frequencies. Furthermore, the turbulence energy distributions are anisotropic with k⊥ > k//, and the dispersion relation is consistent with slow-mode prediction. The fluctuations of density and magnetic field have similar double slope spectrum and kurtosis. These results suggest that the slow waves are involved in the intermittent turbulence cascade from MHD to ion kinetic scales, which may have significant implications for the energy transfer in the plasma sheet.

  16. Multifluid MHD simulation of Saturn's magnetosphere: Dynamics of mass- and momentum-loading, and seasonal variation of the plasma sheet

    NASA Astrophysics Data System (ADS)

    Rajendar, A.; Paty, C. S.; Arridge, C. S.; Jackman, C. M.; Smith, H. T.

    2013-12-01

    Saturn's magnetosphere is driven externally, by the solar wind, and internally, by the planet's strong magnetic field, rapid rotation rate, and the addition of new plasma created from Saturn's neutral cloud. Externally, the alignment of the rotational and magnetic dipole axes, combined with Saturn's substantial inclination to its plane of orbit result in substantial curvature of the plasma sheet during solstice. Internally, new water group ions are produced in the inner regions of the magnetosphere from photoionization and electron-impact ionization of the water vapor and OH cloud sourced from Enceladus and other icy bodies in Saturn's planetary system. In addition to this, charge-exchange collisions between the relatively fast-moving water group ions and the slower neutrals results in a net loss of momentum from the plasma. In order to study these phenomena, we have made significant modifications to the Saturn multifluid model. This model has been previously used to investigate the external triggering of plasmoids and the interchange process using a fixed internal source rate. In order to improve the fidelity of the model, we have incorporated a physical source of mass- and momentum-loading by including an empirical representation of Saturn's neutral cloud and modifying the multifluid MHD equations to include mass- and momentum-loading terms. Collision cross-sections between ions, electrons, and neutrals are calculated as functions of closure velocity and energy at each grid point and time step, enabling us to simulate the spatially and temporally varying plasma-neutral interactions. In addition to this, by altering the angle of incidence of the solar wind relative to Saturn's rotational axis and applying a realistic latitudinally- and seasonally-varying ionospheric conductivity, we are also able to study seasonal effects on Saturn's magnetosphere. We use the updated multifluid simulation to investigate the dynamics of Saturn's magnetosphere, focusing specifically on the production of new plasma, the resulting radial outflow, and corotation lag profiles. The simulation has produced well-defined interchange fingers, regions of cold inner-magnetosphere plasma that lag corotation and move radially outwards, which are balanced by the inward flow of hot tenuous plasma from the outer magnetosphere. We quantify the rate of interchange finger production, and from these calculate the net outward rate of plasma flow. We then compare simulation output with observational data from the Cassini spacecraft to validate the new physics that we have incorporated. In addition to internal mass production and corotation, we also investigate external driver effects, in particular the seasonal variation of curvature of the plasma sheet.

  17. Spectroscopic Diagnostics of Electric Fields in the Plasma of Current Sheets

    NASA Astrophysics Data System (ADS)

    Gavrilenko, Valeri; Kyrie, Natalya P.; Frank, Anna G.; Oks, Eugene

    2004-11-01

    Spectroscopic measurements of electric fields (EFs) in current sheet plasmas were performed in the CS-3D device. The device is intended to study the evolution of current sheets and the magnetic reconnection phenomena. We used the broadening of spectral lines (SLs) of HeII ions for diagnostics of EFs in the current sheet middle plane, and the broadening of SLs of HeI atoms for detection of EFs in the current sheet peripheral regions. For detection of EFs in current sheet plasma, we used SLs of HeII ions at 468.6; 320.3 and 656.0 nm, as well as SLs of HeI atoms at 667.8; 587.6; 492.2 and 447.1 nm. The latter two lines are of a special interest since their profiles include the dipole-forbidden components along with the allowed components. The experimental data have been analyzed by using the numerical calculations based on the Model Microfield Method. The maximum plasma density in the middle of the sheet was in the range (2-8) × 10^16 cm-3, the density in the peripheral regions was (1-2)×10^15 cm-3, and the strength of the quasi-one-dimensional anomalous electric fields in the peripheral regions reached the value of 100 kV/cm. Supported by CRDF, grant RU-P1-2594-MO-04; by the RFBR, grant 03-02-17282; and by the ISTC, project 2098.

  18. Ion and electron heating during magnetic reconnection in weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Numata, Ryusuke; Loureiro, N. F.

    2015-04-01

    Magnetic reconnection and associated heating of ions and electrons in strongly magnetized, weakly collisional plasmas are studied by means of gyrokinetic simulations. It is shown that an appreciable amount of the released magnetic energy is dissipated to yield (irreversible) electron and ion heating via phase mixing. Electron heating is mostly localized to the magnetic island, not the current sheet, and occurs after the dynamical reconnection stage. Ion heating is comparable to electron heating only in high-? plasmas, and results from both parallel and perpendicular phase mixing due to finite Larmor radius (FLR) effects; in space, ion heating is mostly localized to the interior of a secondary island (plasmoid) that arises from the instability of the current sheet.

  19. Ballooning Instabilities in the Plasma Sheet in Conjunction with Auroral Wave Structures

    NASA Astrophysics Data System (ADS)

    Xing, X.; Liang, J.; Spanswick, E.; Lyons, L. R.; Angelopoulos, V.

    2014-12-01

    Ballooning instability in the near-Earth plasma sheet transition region has been suggested to be a plausible trigger leading to azimuthally-aligned auroral wave structures (auroral beading) and subsequent substorm onset expansion. Previous observational studies on ballooning instability have been focused on the subsequent particle and field oscillations. However, the initiation of the instability has never been validated, and its connection to the auroral beading is also to be evaluated observationally. We take advantage of the THEMIS multi-spacecraft and ground All-Sky-Imager and Multi-Spectrum-Imager observation conjunctions to examine whether the plasma and field conditions in the transition region prior to the substorm/pseudo-breakup onset is unstable against ballooning mode within MHD regime. The instability criterion is calculated using observations from radially aligned THEMIS probes in the near-Earth plasma sheet. We found that the ballooning instability criterion is violated locally in the transition region about one Alfvenic transit time prior to the auroral beading initiation. The instability is associated with enhanced field-aligned currents (FAC) on top of the background currents, which provides energy source for the auroral brightening. These observations support the idea that the ballooning instability in the near-Earth plasma sheet is a plausible trigger for the auroral beading. We also found evidence in some cases that earthward moving flow channels from middle tail to the near-Earth region precedes the instability, indicating that the earthward penetrating plasma may lead to the violation of the instability criterion. The observed magnetic field profile prior to the instability initiation provides an initial condition for the numerical simulations, which may assist further understanding of the plasma sheet conditions leading to instability for every event.

  20. Ion precipitation from the inner plasma sheet due to stochastic diffusion

    NASA Technical Reports Server (NTRS)

    Zelenyi, L.; Galeev, A.; Kennel, C. F.

    1990-01-01

    Plasma sheet ions do not conserve their first adiabatic invariant when the magnetic field is appreciably tail-like. They do conserve a different adiabatic invariant but only to linear, rather than exponential, accuracy in the appropriate small parameter. Thus significant stochastic diffusion can occur for particles crossing the separatrix dividing the segments of orbits on which the particles cross and do not cross the tail midplane. Such ions can escape the plasma sheet and precipitate into the atmosphere. Stochastic scattering is strongest from those field lines where the ion's Larmor period in the normal component of the neutral sheet magnetic field approximately equals its bounce period. By comparing the rates of stochastic ion loss and convection in the tail, it is possible to estimate the location and thickness of the inner edge of the ion plasma sheet created by stochastic ion loss. Ions of different masses precipitate into the atmosphere at slightly different locations. Since wave particle interactions are not needed, this precipitation will always occur and should be particularly evident during quiet geomagnetic conditions, when it is less likely to be masked by other precipitation mechanisms.

  1. Magnetized relativistic electron-ion plasma expansion

    NASA Astrophysics Data System (ADS)

    Benkhelifa, El-Amine; Djebli, Mourad

    2016-03-01

    The dynamics of relativistic laser-produced plasma expansion across a transverse magnetic field is investigated. Based on a one dimensional two-fluid model that includes pressure, enthalpy, and rest mass energy, the expansion is studied in the limit of λD (Debye length) ≤RL (Larmor radius) for magnetized electrons and ions. Numerical investigation conducted for a quasi-neutral plasma showed that the σ parameter describing the initial plasma magnetization, and the plasma β parameter, which is the ratio of kinetic to magnetic pressure are the key parameters governing the expansion dynamics. For σ ≪ 1, ion's front shows oscillations associated to the break-down of quasi-neutrality. This is due to the strong constraining effect and confinement of the magnetic field, which acts as a retarding medium slowing the plasma expansion.

  2. Characterization of electron cyclotron resonance hydrogen plasmas

    SciTech Connect

    Outten, C.A. . Dept. of Nuclear Engineering); Barbour, J.C.; Wampler, W.R. )

    1990-01-01

    Electron cyclotron resonance (ECR) plasmas yield low energy and high ion density plasmas. The characteristics downstream of an ECR hydrogen plasma were investigated as a function of microwave power and magnetic field. A fast-injection Langmuir probe and a carbon resistance probe were used to determine plasma potential (V{sub p}), electron density (N{sub e}), electron temperature (T{sub e}), ion energy (T{sub i}), and ion fluence. Langmuir probe results showed that at 17 cm downstream from the ECR chamber the plasma characteristics are approximately constant across the center 7 cm of the plasma for 50 Watts of absorbed power. These results gave V{sub p} = 30 {plus minus} 5 eV, N{sub e} = 1 {times} 10{sup 8} cm{sup {minus}3}, and T{sub e} = 10--13 eV. In good agreement with the Langmuir probe results, carbon resistance probes have shown that T{sub i} {le} 50 eV. Also, based on hydrogen chemical sputtering of carbon, the hydrogen (ion and energetic neutrals) fluence rate was determined to be 1 {times} 10{sup 16}/cm{sup 2}-sec. at a pressure of 1 {times} 10{sup {minus}4} Torr and for 50 Watts of absorbed power. 19 refs.

  3. 30-cm electron cyclotron plasma generator

    NASA Technical Reports Server (NTRS)

    Goede, Hank

    1987-01-01

    Experimental results on the development of a 30-cm-diam electron cyclotron resonance plasma generator are presented. This plasma source utilizes samarium-cobalt magnets and microwave power at a frequency of 4.9 GHz to produce a uniform plasma with densities of up to 3 x 10 to the 11th/cu cm in a continuous fashion. The plasma generator contains no internal structures, and is thus inherently simple in construction and operation and inherently durable. The generator was operated with two different magnetic geometries. One used the rare-earth magnets arranged in an axial line cusp configuration, which directly showed plasma production taking place near the walls of the generator where the electron temperature was highest but with the plasma density peaking in the central low B-field regions. The second configuration had magnets arranged to form azimuthal line cusps with approximately closed electron drift surfaces; this configuration showed an improved electrical efficiency of about 135 eV/ion.

  4. Survey of low energy plasma electrons in Saturn's magnetosphere: Voyagers 1 and 2

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.; Ogilvie, K. W.; Scudder, J. D.

    1983-01-01

    The low energy plasma electron environment within Saturn's magnetosphere was surveyed by the Plasma Science Experiment (PLS) during the Voyager encounters with Saturn. Over the full energy range of the PLS instrument (10 eV to 6 keV) the electron distribution functions are clearly non-Maxwellian in character; they are composed of a cold (thermal) component with Maxwellian shape and a hot (suprathermal) non-Maxwellian component. A large scale positive radial gradient in electron temperature is observed, increasing from less than 1 eV in the inner magnetosphere to as high as 800 eV in the outer magnetosphere. Three fundamentally different plasma regimes were identified from the measurements: (1) the hot outer magnetosphere, (2) the extended plasma sheet, and (3) the inner plasma torus.

  5. Tamm states in electron plasma

    NASA Astrophysics Data System (ADS)

    2013-11-01

    Researchers have fabricated a voltage-tunable plasmonic crystal in a two-dimensional electron gas that operates at terahertz frequencies. Nature Photonics spoke to Eric Shaner, Greg Dyer and Greg Aizin about the observation of Tamm states at the crystal's edge.

  6. Magnetosonic rogons in electron-ion plasma

    NASA Astrophysics Data System (ADS)

    El-Awady, E. I.; Rizvi, H.; Moslem, W. M.; El-Labany, S. K.; Raouf, A.; Djebli, M.

    2014-01-01

    Magnetosonic rogue waves (rogons) are investigated in an electron-ion plasma by deriving the nonlinear Schrdinger (NLS) equation for low frequency limit. The first- and second-order rogue wave solutions of the NLS equation are obtained analytically and examined numerically. It is found that for dense plasma and stronger magnetic field the nonlinearity decreases, which causes the rogon amplitude becomes shorter. However, the electron temperature pumping more energy to the background waves which are sucked to create rogue waves with taller amplitudes.

  7. Pure electron plasmas in asymmetric traps*

    NASA Astrophysics Data System (ADS)

    Chu, R.; Wurtele, J. S.; Notte, J.; Peurrung, A. J.; Fajans, J.

    1993-07-01

    Pure electron plasmas are routinely confined within cylindrically symmetric Penning traps. In this paper the static and dynamic properties of plasmas confined in traps with applied electric field asymmetries are investigated. Simple analytical theories are derived and used to predict the shapes of the stable noncircular plasma equilibria observed in experiments. Both analytical and experimental results agree with those of a vortex-in-cell simulation. For an l=1 diocotron mode in a cylindrically symmetric trap, the plasma rotates as a rigid column in a circular orbit. In contrast, plasmas in systems with electric field asymmetries are shown to have an analog to the l=1 mode in which the shape of the plasma changes as it rotates in a noncircular orbit. These bulk plasma features are studied with a Hamiltonian model. It is seen that, for a small plasma, the area enclosed by the orbit of the center of charge is an invariant when electric field perturbations are applied adiabatically. This invariant has been observed experimentally. The breaking of the invariant is also studied. The dynamic Hamiltonian model is also used to predict the shape and frequency of the large amplitude l=1 and l=2 diocotron modes in symmetric traps.

  8. Plasma-loaded free-electron laser with thermal electron beam and background plasma

    NASA Astrophysics Data System (ADS)

    Babaei, S.; Maraghechi, B.

    2008-01-01

    Thermal properties of a plasma-loaded free-electron laser are studied with the aid of a dispersion relation obtained from the kinetic theory. The electron beam and the background plasma are assumed to have, respectively, small and finite momentum spread in the axial direction, using water-bag distribution functions. Thermal effects of the beam electrons are found to be stronger than those of the plasma. The maximum growth rate rises and falls as the momentum spread of the plasma is increased over a wide interval. In the Compton regime, with the high-energy and low-density electron beam, the plasma and its momentum spread have almost no effects on the growth rate.

  9. ELF wave intensification in conjunction with fast earthward flow in the mid-tail plasma sheet ------- A THEMIS survey

    NASA Astrophysics Data System (ADS)

    Liang, J.; Ni, B.; Cully, C. M.; Donovan, E. F.; Thorne, R. M.; Themis Team

    2010-12-01

    A number of recent studies have revealed a close association between the fast earthward flows and dipolarization fronts in the magnetotail and the plasma wave intensifications in the ELF/VLF range, including the lower-hybrid waves, whistler-mode and electron cyclotron waves. Those waves may play crucial roles in the acceleration and pitch-angle scattering of the plasma sheet electrons, and in turn produce a macroscopic effect accompanying the fast flows. In this study, we perform a statistical survey of the THEMIS B/C data over the 2008 and 2009 tail seasons, and select ~110 fast earthward flow intervals in which the probes were mostly located in the mid-tail central plasma sheet (CPS) region. We investigate the filterbank (FBK) dataset of the electric field instrument (EFI) and search coil magnetometer (SCM) during the collected fast flow intervals, and identify an unambiguous trend of increasing ELF wave intensities with the convective flow enhancement. Notwithstanding the relatively wide bandwidth of FBK data we may still distinguish the existence of the lower-hybrid waves, the whistler-mode waves, and the electrostatic waves at f>f_ce. On a further examining of the flow-associated whistler-mode waves we notice a mixture of the quasi-electrostatic and electromagnetic wave modes, implying a broad distribution of the wave normal angles. We tentatively suggest that the energetic electron beam originated from the reconnection site and/or the local dipolarizatoin front might be the main driving mechanism of the flow-associated ELF wave intensifications.

  10. On the contribution of plasma sheet bubbles to the storm time ring current

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Toffoletto, Frank R.; Wolf, Richard A.; Sazykin, Stanislav

    2015-09-01

    Particle injections occur frequently inside 10 Re during geomagnetic storms. They are commonly associated with bursty bulk flows or plasma sheet bubbles transported from the tail to the inner magnetosphere. Although observations and theoretical arguments have suggested that they may have an important role in storm time dynamics, this assertion has not been addressed quantitatively. In this paper, we investigate which process is dominant for the storm time ring current buildup: large-scale enhanced convection or localized bubble injections. We use the Rice Convection Model-Equilibrium (RCM-E) to model a series of idealized storm main phases. The boundary conditions at 14-15 Re on the nightside are adjusted to randomly inject bubbles to a degree roughly consistent with observed statistical properties. A test particle tracing technique is then used to identify the source of the ring current plasma. We find that the contribution of plasma sheet bubbles to the ring current energy increases from ~20% for weak storms to ~50% for moderate storms and levels off at ~61% for intense storms, while the contribution of trapped particles decreases from ~60% for weak storms to ~30% for moderate and ~21% for intense storms. The contribution of nonbubble plasma sheet flux tubes remains ~20% on average regardless of the storm intensity. Consistent with previous RCM and RCM-E simulations, our results show that the mechanisms for plasma sheet bubbles enhancing the ring current energy are (1) the deep penetration of bubbles and (2) the bulk plasma pushed ahead of bubbles. Both the bubbles and the plasma pushed ahead typically contain larger distribution functions than those in the inner magnetosphere at quiet times. An integrated effect of those individual bubble injections is the gradual enhancement of the storm time ring current. We also make two predictions testable against observations. First, fluctuations over a time scale of 5-20 min in the plasma distributions and electric field can be seen in the central ring current region for the storm main phase. We find that the plasma pressure and the electric field EY there vary over about 10%-30% and 50%-300% of the background values, respectively. Second, the maximum plasma pressure and magnetic field depression in the central ring current region during the main phase are well correlated with the Dst index.

  11. Electron density measurements for plasma adaptive optics

    NASA Astrophysics Data System (ADS)

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  12. Effect of Electron Beam Irradiation on the Tensile Properties of Carbon Nanotubes Sheets and Yarns

    NASA Technical Reports Server (NTRS)

    Williams, Tiffany S.; Miller, Sandi G.; Baker, James S.; McCorkle, Linda S.; Meador, Michael A.

    2013-01-01

    Carbon nanotube sheets and yarns were irradiated using electron beam (e-beam) energy to determine the effect of irradiation dose on the tensile properties. Results showed that a slight change in tensile strength occurred after irradiating as-received CNT sheets for 20 minutes, and a slight decrease in tensile strength as the irradiation time approached 90 minutes. On the other hand, the addition of small molecules to the CNT sheet surface had a greater effect on the tensile properties of e-beam irradiated CNT sheets. Some functionalized CNT sheets displayed up to a 57% increase in tensile strength following 90 minutes of e-beam exposure. In addition, as-received CNT yarns showed a significant increase in tensile strength as the irradiation time increased.

  13. On the diamagnetic effect of the plasma sheet near 60 earth radii.

    NASA Technical Reports Server (NTRS)

    Meng, C.-I.; Mihalov, J. D.

    1972-01-01

    The two-dimensional (YZ plane) spatial distribution of magnetic field magnitudes in the geomagnetic tail at the lunar distance is given in both the solar magnetospheric and the neutral-sheet coordinate systems by using three years of data from the Ames magnetometer on Explorer 35. The effect of changes in geomagnetic activity is also presented. In the magnetotail near 60 earth radii, a broad region in which the magnetic field intensity is relatively weak in comparison with that in the other region of the tail is located adjacent to the solar magnetospheric equatorial plane and the calculated neutral sheet. This depression of the field due to the diamagnetic effect of the plasma sheet is more evident during times of minimum geomagnetic activity.-

  14. Rapid variations of the plasma bulk flow direction observed in the plasma sheet at X[sub GSE [approximately

    SciTech Connect

    Saito, Yoshifumi; Mukai, Toshifumi; Nishida, Atsuhiro ); Machida, Shinobu ); Hirahara, Masafumi; Terasawa, Toshio )

    1994-03-01

    The authors report data observed by the Low Energy Particle (LEP) diagnostic on the GEOTAIL satellite. At a location of X[sub GSE][approx][minus]60R[sub e], the diagnostic observed variations in the bulk plasma flow in the plasma sheet. This variation could be broken down into a slowly, and rapidly varying component. The slowly varying component seems related to the direction of the magnetic field. The more rapidly varying component is not so simply explained, and the authors discuss several possible explanations for its behavior.

  15. Dynamic trapping of electrons in space plasmas

    NASA Astrophysics Data System (ADS)

    Brenning, N.; Bohm, M.; Faelthammar, Carl-Gunne

    1989-12-01

    The neutralization of positive space charge is studied in a case where heavy positive ions are added to a limited region of length in a collisionfree magnetized plasma. It is found that electrons which become accelerated towards the positive space charge can only achieve a partial neutralization: they overshoot, and the positive region becomes surrounded by negative space charges which screen the electric field from the surroundings. The process is studied both analytically and by computer simulations with consistent results: large positive potentials can be built up with respect to the surrounding plasma. In the process in growth, the potential maximum traps electrons in transit so that quasineutrality is maintained. The potential is proportional to the ambient electron temperature and the square of the plasma density increase, but independent of both the ion injection rate and the length. The process explains several features of the Porcupine xenon beam injection experiment. It could also have importance for the electrodynamic coupling between plasmas of different densities, e.g., the injection of neutral clouds in the ionosphere of species that becomes rapidly photoionized, or penetration of dense plasma clouds from the solar wind into the magnetosphere.

  16. Using PEACE Data from the four CLUSTER Spacecraft to Measure Compressibility, Vorticity, and the Taylor Microscale in the Magnetosheath and Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.; Parks, George; Gurgiolo, C.; Fazakerley, Andrew N.

    2008-01-01

    We present determinations of compressibility and vorticity in the magnetosheath and plasma sheet using moments from the four PEACE thermal electron instruments on CLUSTER. The methodology used assumes a linear variation of the moments throughout the volume defined by the four satellites, which allows spatially independent estimates of the divergence, curl, and gradient. Once the vorticity has been computed, it is possible to estimate directly the Taylor microscale. We have shown previously that the technique works well in the solar wind. Because the background flow speed in the magnetosheath and plasma sheet is usually less than the Alfven speed, the Taylor frozen-in-flow approximation cannot be used. Consequently, this four spacecraft approach is the only viable method for obtaining the wave number properties of the ambient fluctuations. Our results using electron velocity moments will be compared with previous work using magnetometer data from the FGM experiment on Cluster.

  17. The Giotto electron plasma experiment

    NASA Technical Reports Server (NTRS)

    Reme, H.; Cotin, F.; Cros, A.; Medale, J. L.; Sauvaud, J. A.

    1987-01-01

    The RPA-Copernic experiment aboard Giotto is described. The experiment is designed to measure the three-dimensional distributions of electrons between 10 eV and 30 keV (by the RPA-1 EESA spectrometer) and the composition and distribution, close to the comet, of thermal positive ions in the mass range 10-213 amu (by the RPA-2 PICCA electrostatic mass analyzer). Three microprocessors interface RPA-1 EESA with RPA-2 PICCA and with the spacecraft and perform extensive onboard data processing. The experiment was operated successfully aboard the spacecraft in September 1985 during the encounter of Giotto with the comet Halley. The results provided by the EESA-1 indicate that the solar wind interaction with the comet Halley forms a well-defined bow shock with features quite different from the features of the comet Giacobini-Zinner bow shock; the data also showed a presence of accelerated keV electrons at the cometary bow shock, upstream and in the transition region.

  18. Nonquasineutral electron vortices in nonuniform plasmas

    SciTech Connect

    Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W.; Ottinger, P. F.

    2014-11-15

    Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds V{sub ϕ} close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λ{sub B}=|B|/4πen and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λ{sub B}. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.

  19. Nonquasineutral electron vortices in nonuniform plasmas

    NASA Astrophysics Data System (ADS)

    Angus, J. R.; Richardson, A. S.; Ottinger, P. F.; Swanekamp, S. B.; Schumer, J. W.

    2014-11-01

    Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds Vϕ close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λB=|B |/4 πe n and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λB. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.

  20. Electron beam-plasma interaction in a dusty plasma with excess suprathermal electrons

    SciTech Connect

    Danehkar, A.; Saini, N. S.; Hellberg, M. A.; Kourakis, I.

    2011-11-29

    The existence of large-amplitude electron-acoustic solitary structures is investigated in an unmagnetized and collisionless two-temperature dusty plasma penetrated by an electron beam. A nonlinear pseudopotential technique is used to investigate the occurrence of stationary-profile solitary waves, and their parametric dependence on the electron beam and dust perturbation is discussed.

  1. Solar-wind control of plasma sheet dynamics

    NASA Astrophysics Data System (ADS)

    Myllys, M.; Kilpua, E.; Pulkkinen, T.

    2015-07-01

    The purpose of this study is to quantify how solar-wind conditions affect the energy and plasma transport in the geomagnetic tail and its large-scale configuration. To identify the role of various effects, the magnetospheric data were sorted according to different solar-wind plasma and interplanetary magnetic field (IMF) parameters: speed, dynamic pressure, IMF north-south component, epsilon parameter, Auroral Electrojet (AE) index and IMF ultra low-frequency (ULF) fluctuation power. We study variations in the average flow speed pattern and the occurrence rate of fast flow bursts in the magnetotail during different solar-wind conditions using magnetospheric data from five Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission spacecraft and solar-wind data from NASA's OMNIWeb. The time interval covers the years from 2008 to 2011 during the deep solar minimum between cycles 23 and 24 and the relatively quiet rising phase of cycle 24. Hence, we investigate magnetospheric processes and solar-wind-magnetospheric coupling during a relatively quiet state of the magnetosphere. We show that the occurrence rate of the fast (|Vtail| > 100 km s-1) sunward flows varies under different solar-wind conditions more than the occurrence of the fast tailward flows. The occurrence frequency of the fast tailward flows does not change much with the solar-wind conditions. We also note that the sign of the IMF BZ has the most visible effect on the occurrence rate and pattern of the fast sunward flows. High-speed flow bursts are more common during the slow than fast solar-wind conditions.

  2. High conductivity magnetic tearing instability. [of neutral plasma sheets

    NASA Technical Reports Server (NTRS)

    Cross, M. A.; Van Hoven, G.

    1976-01-01

    Linearized equations of magnetohydrodynamics are used to investigate the tearing mode, for arbitrary values of the conductivity, through a consideration of the additional effect of the electron-inertia contribution to Ohm's law. A description is provided of the equilibrium and subsequent instability in the magnetohydrodynamic approximation. A method for solving the perturbation equations in the linear approximation is discussed and attention is given to the results in the high conductivity limit.

  3. Electric and magnetic components of ballooning perturbations in the magnetotail plasma sheet before breakup

    NASA Astrophysics Data System (ADS)

    Kogai, T. G.; Golovchanskaya, I. V.; Kornilov, I. A.; Kornilova, T. A.; Fedorenko, Y. V.

    2016-01-01

    Using data from THEMIS spacecraft we investigated transverse to the magnetic field mutually perpendicular electric and magnetic components of ballooning type perturbations with periods 60-240 s, which are observed in the magnetospheric plasma sheet during the period preceding substorm onset. With applying Hilbert transform, we analyzed the phase relations between them. It is shown that the perturbations are dominated by radial electric and azimuthal magnetic (that is, toroidal) components which are usually in phase or out-of-phase. Along with them, approximately 2.5 times less intense azimuthal electric and radial magnetic components are present, which are more often phase-shifted by π/2. It is concluded that the observed perturbations are not a simple consequence of the development of plasma sheet ballooning instability, leading to the growth of strongly elongated along the magnetotail ballooning structures. It is pointed out that this conclusion is confirmed by simultaneous ground-based observations of magnetically conjugate auroral structures.

  4. Plasma sheet access to the inner magnetosphere during bursty bulk flows

    NASA Astrophysics Data System (ADS)

    Elkington, S. R.; Wiltberger, M. J.; Jaynes, A. N.; Malaspina, D.

    2014-12-01

    Energetic particles in the plasma sheet and near-Earth magnetotail can be transported sunward by large-scale magnetospheric convective processes, allowing some populations to be trapped inside the 'Alfven Layer' on close drift paths in the inner magnetosphere. These newly-trapped particles may contribute directly to the seed populations that are subsequently heated to ring current and radiation belt energies, and may also provide a source of free energy for the generation of electromagnetic waves that affect the dynamic variations of the outer radiation belts. In this work, we examine the access of plasma sheet particles to the inner magnetosphere using a combination of global MHD/test particle simulations and observations from geosynchronous, THEMIS, and the Van Allen probes. We focus in particular on transient events associated with substorm activity and bursty bulk flows, and contrast particle access to geosynchronous orbit during these events with that observed during steady driving of the magnetosphere.

  5. Graphene electron cannon: High-current edge emission from aligned graphene sheets

    SciTech Connect

    Liu, Jianlong; Li, Nannan; Guo, Jing; Fang, Yong; Deng, Jiang; Zeng, Baoqing; Wang, Wenzhong; Li, Jiangnan; Hao, Chenchun

    2014-01-13

    High-current field emitters are made by graphene paper consist of aligned graphene sheets. Field emission luminance pattern shows that their electron beams can be controlled by rolling the graphene paper from sheet to cylinder. These specific electron beams would be useful to vacuum devices and electron beam lithograph. To get high-current emission, the graphene paper is rolled to array and form graphene cannon. Due to aligned emission array, graphene cannon have high emission current. Besides high emission current, the graphene cannon is also tolerable with excellent emission stability. With good field emission properties, these aligned graphene emitters bring application insight.

  6. GEOTAIL observation of ring-shaped ion distribution functions in the plasma sheet-lobe boundary

    SciTech Connect

    Saito, Yoshifumi; Mukai, Toshifumi; Nishida, Atsuhiro; Yamamoto, Tatsundo; Hirahara, Masafumi; Terasawa, Toshio; Machida, Shinobu; Kokubun, Susumu

    1994-12-15

    The authors present an analysis of the observations made of ring shaped distribution functions of ion velocities observed in the boundary between the plasma sheet and lobe in regions near X{sub GSM} approximately {minus}70 or {minus} 170 R{sub E}. Data was collected by a particle analyzer configured to observe distribution functions, and the magnetic field instrumentation. The ions were observed to be moving tailward, and the normal to the ring was almost parallel with the magnetic field vector.

  7. Cluster observation of magnetohydrodynamic turbulence in the plasma sheet boundary layer

    NASA Astrophysics Data System (ADS)

    Narita, Y.

    2016-04-01

    Measurement of turbulent magnetic field is presented from the Earth magnetotail crossing of the Cluster spacecraft on August 25, 2006, as an ideal case study of magnetohydrodynamic turbulence in the plasma sheet boundary layer on a spatial scale of about 10,000 km. The fluctuation energy of the magnetic field is evaluated in both the frequency and wavevector domains. The observed plasma sheet turbulence event shows anisotropy in the wavevector domain with a spectral extension perpendicular to the mean magnetic field. The analyses of the dispersion relation and phase speed diagrams indicate that the coherent wave components should be regarded as a set of the linear-mode waves and the other fluctuation components in magnetohydrodynamics. Although the magnetic field fluctuation amplitudes are sufficiently small compared to the large-scale field strength, there is no clear indication of the linear-mode dominance in the plasma sheet. As a lesson, magnetohydrodynamic turbulence must be modeled by including both linear-mode waves and nonlinear wave components such as sideband waves.

  8. Polytropic index of central plasma sheet ions based on MHD Bernoulli integral

    NASA Astrophysics Data System (ADS)

    Pang, Xuexia; Cao, Jinbin; Liu, Wenlong; Ma, Yuduan; Lu, Haoyu; Yang, Junying; Li, Liuyuan; Liu, Xu; Wang, Jing; Wang, Tieyan; Yu, Jiang

    2015-06-01

    This paper uses the data of Cluster from 2001 to 2009 to study the polytropic processes of central plasma sheet (CPS) ions. We first adopt the approach of MHD Bernoulli integral (MBI) to identify homogeneous streamflow tubes (quasi-invariant MBI regions) and then calculate the polytropic index of ions for those streamflow tubes whose outward electromagnetic energy ratios δ < 0.05. The central plasma sheet is actually a complicated system, which comprises many streamflow tubes with different polytropic relations and the transition layers in between. The polytropic indexes of the CPS ions range from 0.1 to 1.8 and have a quasi-Gaussian distribution. The median polytropic index is 0.93 for AE < 200 nT and 0.91 for AE ≥ 200 nT. Thus, there is no obvious difference between the polytropic indexes of the quiet time and the substorm time CPS ions, which suggests that the thinning and thickening processes of plasma sheet during substorm times do not change obviously the polytropic relation of the CPS ions. The statistical analysis using different δ (δ < 0.05, 0.025, and 0.01) shows that the outward emission of electromagnetic energy is an effective cooling mechanism and can make the polytropic index to decrease and shift toward isobaric. It is inferred that the CPS ions as a whole much likely behave in a way between isobaric and isothermal.

  9. Hinode/XRT Measurements of Turbulent Velocities in Flare Plasma Sheets

    NASA Astrophysics Data System (ADS)

    McKenzie, David; Freed, Michael

    2015-04-01

    The turbulent, dynamic motions that we observe in the hot plasma surrounding current sheets very likely distort the embedded magnetic fields, resulting in reduced length scales and locally augmented resistivities. These conditions may help to accelerate and/or prolong the reconnection in solar flares. Although we cannot as yet measure directly the magnetic fields in the corona, the velocity fields within the flare plasma sheets provide a means to study the conditions that control the spatial and temporal scales of reconnection, in the locations and at the times that are relevant to structuring the magnetic fields.The plasma sheets are observable in many flares in soft X-ray and EUV wavelengths, due to their high temperatures. For two recent flares observed with the Hinode X-Ray Telescope (XRT), we have analyzed the velocity fields with a local correlation tracking technique, and compared to measurements from the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA).This work is supported by NASA under contract NNM07AB07C with the Smithsonian Astrophysical Observatory, and by grant NNX14AD43G.

  10. Silicone Coating on Polyimide Sheet

    NASA Technical Reports Server (NTRS)

    Park, J. J.

    1985-01-01

    Silicone coatings applied to polyimide sheeting for variety of space-related applications. Coatings intended to protect flexible substrates of solar-cell blankets from degradation by oxygen atoms, electrons, plasmas, and ultraviolet light in low Earth orbit and outer space. Since coatings are flexible, generally useful in forming flexible laminates or protective layers on polyimide-sheet products.

  11. Electron Scattering in Hot/Warm Plasmas

    SciTech Connect

    Rozsnyai, B F

    2008-01-18

    Electrical and thermal conductivities are presented for aluminum, iron and copper plasmas at various temperatures, and for gold between 15000 and 30000 Kelvin. The calculations are based on the continuum wave functions computed in the potential of the temperature and density dependent self-consistent 'average atom' (AA) model of the plasma. The cross sections are calculated by using the phase shifts of the continuum electron wave functions and also in the Born approximation. We show the combined effect of the thermal and radiative transport on the effective Rosseland mean opacities at temperatures from 1 to 1000 eV. Comparisons with low temperature experimental data are also presented.

  12. Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Bonds, Kevin W.; Emsellem, Gregory D.

    2011-01-01

    Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration that accompanies the radial compression of the plasma in conical theta pinches.

  13. Hydromagnetic equilibrium and instabilities in the convectively driven near-Earth plasma sheet

    NASA Astrophysics Data System (ADS)

    Wu, C.-C.; Pritchett, P. L.; Coroniti, F. V.

    1998-06-01

    Recent particle simulations have suggested that the convectively driven near-Earth plasma sheet can develop a structure in which a thin current sheet is embedded within the much thicker plasma sheet and that finite-ky modes with the character of kink and interchange modes can be excited in this system. Here the ideal magnetohydrodynamic (MHD) equations are used to investigate the equilibrium and linear stability properties of such a system. It is shown that the embedded current sheet configuration satisfies the conditions of pressure balance and represents an approximate two-dimensional (x,z) MHD equilibrium state. The stability analysis, in which the boundary conditions are imposed in terms of MHD characteristic waves, indicates that two types of pressure-driven modes are unstable. One mode is associated with the presence of a tailward gradient in the equatorial magnetic field profile. As the wavelength of this mode is made shorter, the mode becomes localized on the field lines crossing the region of increasing field and has the character of an interchange/ballooning mode. A second mode is associated with the existence of a magnetic island and is localized within the island; it has a structure similar to that of the classical kink mode for a plasma column. While the MHD growth rates continue to increase at short wavelengths, at longer wavelengths determined by the ion gyroradius (kyρi<~1, where ρi is computed in the local equatorial field) they are comparable to those for the dominant nonlinear modes observed in the kinetic simulations.

  14. Detection of Steel Fatigue Cracks with Strain Sensing Sheets Based on Large Area Electronics

    PubMed Central

    Yao, Yao; Glisic, Branko

    2015-01-01

    Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM) of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm) were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs. PMID:25853407

  15. Detection of steel fatigue cracks with strain sensing sheets based on large area electronics.

    PubMed

    Yao, Yao; Glisic, Branko

    2015-01-01

    Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM) of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm) were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs. PMID:25853407

  16. Ion mixing in the plasma sheet boundary layer by drift instabilities

    NASA Technical Reports Server (NTRS)

    Horton, W.; Dong, J. Q.; Su, X. N.; Tajima, T.

    1993-01-01

    The linear stability properties of collisionless drift instabilities are analyzed in a Harris equilibrium model of the plasma sheet boundary layer (PSBL). The strearmng ions with drift-type instabilities driven in the PSBL are considered. The fluid approximation leads to growth but predicts that the mode width approaches the gyroradius of the energetic ions. Thus an integral equation theory for the modes is developed taking into account that in the PSBL the curvature drift is weak compared with the grad-B drift. The exact wave particle resonance is kept in the nonlocal response functions. Plasma density, temperature, and magnetic gradient drift motions are taken into account. The drift modes produce an anomalous cross-field momentum transport mixing the PSBL ions on the time scale of tens of seconds. A nonlinear simulation is performed which shows the coalescence of the small scale, fast growing modes into large-scale vortices. The relation between these collective modes and plasma sheet transport phenomena is discussed including the comparison with the competing plasma mixing from single-particle stochasticity.

  17. Investigating the role of the entropy parameter in plasma sheet dynamics

    NASA Astrophysics Data System (ADS)

    Yang, J.; Toffoletto, F.; Wolf, R. A.; Sazykin, S.; Hu, B.; Raeder, J.

    2011-12-01

    Representing a combination of mass and entropy, the entropy parameter PV5/3 is approximately conserved for plasma sheet flux tubes and proves very useful for understanding plasma sheet dynamics. (Here P is plasma pressure and V is the volume of a flux tube containing one unit of magnetic flux). Under quasi-static-equilibrium conditions, PV5/3 determines Birkeland currents and interchange instability. It is consequently a key parameter for physical interpretation of results from RCM and RCM-E. The appropriate generalization of PV5/3 for conditions when P is not constant along a field line is the 5/3 power of the flux-tube integral of P3/5. That parameter is conserved in ideal MHD and is useful in physical interpretation of MHD simulations of the magnetosphere. We present recent computer experiments to investigate how the values of PV5/3 in the plasma sheet can affect the plasma transport and field configuration during various geomagnetic active times. A comparative study of RCM-E simulations shows that persistent steady magnetospheric convection during strong polar cap potential drops is possible if the flux tubes in the magnetotail are substantially depleted along a sector with very wide local times; otherwise, the magnetic field will gradually become highly stretched if the inner magnetosphere is fed with relatively high entropy plasma, resembling the substorm growth phase. In the end of the growth phase, resistive MHD simulations using OpenGGCM indicate that the violation of frozen-in-flux condition can give rise to the formation of a bubble (lower PV5/3 than its neighbors) earthward of a blob (higher PV5/3 than its neighbors). Both OpenGGCM and RCM-E results show that the earthward motion of the bubble and the tailward motion of the blob lead to a reduction of the normal magnetic field between them, which thins the current sheet rapidly. Substorm injection simulations are carried out using RCM-E by placing bubbles on the tailward boundary for both non-storm and storm times. A variety of aspects associated with the bubble injections will be discussed, including the classic substorm injection boundary problem, the reconfiguration of large-scale current systems and the magnetic disturbance in ground magnetograms.

  18. Electron kinetics in a cooling plasma

    SciTech Connect

    Helander, P.; Smith, H.; Fueloep, T.; Eriksson, L.-G.

    2004-12-01

    The distribution function of suprathermal electrons in a slowly cooling plasma is calculated by an asymptotic expansion in the cooling rate divided by the collision frequency. Since the collision frequency decreases with increasing velocity, a high-energy tail forms in the electron distribution function as the bulk population cools down. Under certain simplifying assumptions (slow cooling, constant density, Born approximation of cross sections), the distribution function evolves to a self-similar state where the tail is inversely proportional to the cube of the velocity. Its practical consequences are discussed briefly.

  19. Sensing sheets based on large area electronics for fatigue crack detection

    NASA Astrophysics Data System (ADS)

    Yao, Yao; Glisic, Branko

    2015-03-01

    Reliable early-stage damage detection requires continuous structural health monitoring (SHM) over large areas of structure, and with high spatial resolution of sensors. This paper presents the development stage of prototype strain sensing sheets based on Large Area Electronics (LAE), in which thin-film strain gauges and control circuits are integrated on the flexible electronics and deposited on a polyimide sheet that can cover large areas. These sensing sheets were applied for fatigue crack detection on small-scale steel plates. Two types of sensing-sheet interconnects were designed and manufactured, and dense arrays of strain gauge sensors were assembled onto the interconnects. In total, four (two for each design type) strain sensing sheets were created and tested, which were sensitive to strain at virtually every point over the whole sensing sheet area. The sensing sheets were bonded to small-scale steel plates, which had a notch on the boundary so that fatigue cracks could be generated under cyclic loading. The fatigue tests were carried out at the Carleton Laboratory of Columbia University, and the steel plates were attached through a fixture to the loading machine that applied cyclic fatigue load. Fatigue cracks then occurred and propagated across the steel plates, leading to the failure of these test samples. The strain sensor that was close to the notch successfully detected the initialization of fatigue crack and localized the damage on the plate. The strain sensor that was away from the crack successfully detected the propagation of fatigue crack based on the time history of measured strain. Overall, the results of the fatigue tests validated general principles of the strain sensing sheets for crack detection.

  20. Mechanisms for Generating Finite Cross-Tail Jets in the Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Pritchett, P. L.

    2014-12-01

    In the magnetotail, brief periods of fast plasma flow (``bursty bulk flows''--BBFs) provide much of the sunward transport of mass, energy, and magnetic flux. Although usually interpreted as resulting from magnetic reconnection acting in the mid- or more-distant tail, the precise generation mechanism for these flows has never been clearly established. Observationally, a key feature of these flow fronts or jets is that their full cross-tail width in the plasma sheet is of the order of 1--3 RER_E. The present work examines the relative ability of reconnection and ballooning/interchange (BICI) processes to produce such finite-width fronts. 3D particle-in-cell simulations are used to initiate reconnection in finite-width regions of the plasma sheet and to generate BICI heads from regions of the plasma sheet containing a tailward-decreasing entropy profile. For the reconnection jets, the front is observed to expand duskward (in the ion diamagnetic drift direction) to form a structure some 15 did_i wider than the initial localization width. The BICI heads have a comparable extent. Both types of jets feature abrupt increases in the equatorial BzB_z field and both tend to break up in yy due to a secondary interchange instability on a scale of 1--2 did_i. A distinguishing feature between the two types of jets is that the BICI fronts are preceded by an off-equatorial signal involving wave activity near the ion cyclotron frequency that involves intense (30--50 mV/m) electric fields and magnetic perturbations of the order of 10% of the ambient main field. The possibility of producing repeated jets by these mechanisms will be discussed as well.

  1. Transition in Electron Physics of Magnetic Reconnection in Weakly Collisional Plasma

    NASA Astrophysics Data System (ADS)

    Le, A.; Roytershteyn, V.; Karimabadi, H.; Daughton, W. S.; Egedal, J.; Forest, C.

    2013-12-01

    Using self-consistent fully kinetic simulations with a Monte-Carlo treatment of the Coulomb collision operator, we explore the transition between collisional and kinetic regimes of magnetic reconnection in high-Lundquist-number current sheets. Recent research in collisionless reconnection has shown that electron kinetic physics plays a key role in the evolution. Large-scale electron current sheets may form, leading to secondary island formation and turbulent flux rope interactions in 3D. The new collisional simulations demonstrate how increasing collisionality modifies or eliminates these electron structures in the kinetic regimes. Additional basic questions that are addressed include how the reconnection rate and the release of magnetic energy into electrons and ions vary with collisionality. The numerical study provides insight into reconnection in dense regions of the solar corona, the solar wind, and upcoming laboratory experiments at MRX (Princeton) and MPDX (UW-Madison). The implications of these results for studies of turbulence dissipation in weakly collisional plasmas are discussed.

  2. Unzipped Nanotube Sheet Films Converted from Spun Multi-Walled Carbon Nanotubes by O2 Plasma.

    PubMed

    Jangr, Hoon-Sik; Jeon, Sang Koo; Shim, Dae Seob; Lee, Nam Hee; Nahm, Seung Hoon

    2015-11-01

    Large-scale graphene or carbon nanotube (CNT) films are good candidates for transparent flexible electrodes, and the strong interest in graphene and CNT films has motivated the scalable production of a good-conductivity and an optically transmitting film. Unzipping techniques for converting CNTs to graphene are especially worthy of notice. Here, we performed nanotube unzipping of the spun multi-walled carbon nanotubes (MWCNTs) to produce networked graphene nanoribbon (GNR) sheet films using an 02 plasma etching method, after which we produced the spun MWCNT film by continually pulling MWCNTs down from the vertical well aligned MWCNTs on the substrate. The electrical resistance was slightly decreased and the optical transmittance was significantly increased when the spun MWCNT films were etched for 20 min by O2 plasma of 100 mA. Plasma etching for the optimized time, which does not change the thickness of the spun MWCNT films, improved the electrical resistance and the optical transmittance. PMID:26726645

  3. Temperature limit in ECH hot electron plasmas

    SciTech Connect

    Uckan, N.A.

    1982-06-01

    During the last two decades the production of high-beta, hot electron plasmas with electron cyclotron heating (ECH) has been amply demonstrated in open and closed geometries. A wide variety of conditions was present in these experiments with a factor of 2 change in device dimensions and more than an order of magnitude change in magnetic fields (approx. 1 to 10 kG), ECH frequencies (approx. 6 to 55 GHz), and hot electron temperatures (approx. 50 to 1200 keV). An analysis of the data from all the experiments that used single ECH frequency indicates that the hot electron temperatures do increase with magnetic field strength (or, equivalently, ECH frequency) and scale length. In particular, they all obey rho/L approx. = constant (approx. 5 to 6 x 10/sup -2/) scaling, where rho and L are the hot electron gyroradius (relativistic) and the magnetic field scale length, respectively. This is roughly the value at which conservationof the adiabatic invariant ..mu.. begins to break down and suggests that the hot electron temperatures are probably limited by nonadiabatic particle behavior. Results, primarily from hot electron ring experiments (ELMO, EBT, NBT, etc.), are discussed, and projections for future experiments are given. It is shown that although in all previous experiments the ring temperature is determined by the rho/L criterion EBT-P will be the first experiment unconstrained by this limit.

  4. A research of W-band folded waveguide traveling wave tube with elliptical sheet electron beam

    SciTech Connect

    Guo Guo; Wei Yanyu; Yue Lingna; Gong Yubin; Zhao Guoqing; Huang Minzhi; Tang Tao; Wang Wenxiang

    2012-09-15

    Folded waveguide (FWG) traveling wave tube (TWT), which shows advantages in high power capacity, moderate bandwidth, and low-cost fabrication, has become the focus of vacuum electronics recently. Sheet electron beam devices are better suited for producing radiation sources with large power in millimeter wave spectrum due to their characteristics of relatively low space charge fields and large transport current. A FWG TWT with elliptical sheet beam working in W-band is presented in this paper, with the analysis of its dispersion characteristics, coupling impedance, transmission properties, and interaction characteristics. A comparison is also made with the traditional FWG TWT. Simulation results lead to the conclusion that the FWG TWT with elliptical sheet beam investigated in this paper can make full use of relatively large electric fields and thus generate large output power with the same electric current density.

  5. Extreme energetic particle decreases near geostationary orbit - A manifestation of current diversion within the inner plasma sheet

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Mcpherron, R. L.

    1990-01-01

    A qualitative model of magnetic field reconfiguration as might result from neutral line formation in the central plasma sheet late in a substorm growth phase is considered. It is suggested that magnetic reconnection probably begins before the substorm expansion phase and that cross-tail current is enhanced across the plasma sheet both earthward and tailward of a limited region near the neutral line. Such an enhanced cross-tail current earthward of the original X line region may contribute to thinning the plasma sheet substantially, and this would in turn affect the drift currents in that location, thus enhancing the current even closer toward the earth. In this way a redistribution and progressive diversion of normal cross-tail current throughout much of the inner portion of the plasma sheet could occur. The resulting intensified current, localized at the inner edge of the plasma sheet, would lead to a very thin plasma confinement region. This would explain the very taillike field and extreme particle dropouts often seen late in substorm growth phases.

  6. Increased tensile strength of carbon nanotube yarns and sheets through chemical modification and electron beam irradiation.

    PubMed

    Miller, Sandi G; Williams, Tiffany S; Baker, James S; Sol, Francisco; Lebron-Colon, Marisabel; McCorkle, Linda S; Wilmoth, Nathan G; Gaier, James; Chen, Michelle; Meador, Michael A

    2014-05-14

    The inherent strength of individual carbon nanotubes (CNTs) offers considerable opportunity for the development of advanced, lightweight composite structures. Recent work in the fabrication and application of CNT forms such as yarns and sheets has addressed early nanocomposite limitations with respect to nanotube dispersion and loading and has pushed the technology toward structural composite applications. However, the high tensile strength of an individual CNT has not directly translated into that of sheets and yarns, where the bulk material strength is limited by intertube electrostatic attractions and slippage. The focus of this work was to assess postprocessing of CNT sheets and yarns to improve the macro-scale strength of these material forms. Both small-molecule functionalization and electron-beam irradiation were evaluated as means to enhance the tensile strength and Young's modulus of the bulk CNT materials. Mechanical testing revealed a 57% increase in tensile strength of CNT sheets upon functionalization compared with unfunctionalized sheets, while an additional 48% increase in tensile strength was observed when functionalized sheets were irradiated. Similarly, small-molecule functionalization increased tensile strength of yarn by up to 25%, whereas irradiation of the functionalized yarns pushed the tensile strength to 88% beyond that of the baseline yarn. PMID:24720450

  7. Analysis of an extended period of earthward plasma sheet flow at @220 R sub E : CDAW 8

    SciTech Connect

    Schindler, K. ); Baker, D.N. NASA Goddard Space Flight Center, Greenbelt, MD ); Birn, J.; Hones, E.W. Jr. ); Slavin, J.A. NASA Headquarters, Washington, DC ); Galvin, A.B. )

    1989-11-01

    Statistical studies of the ISEE 3 deep magnetic tail data (r {approx gt} 120 R{sub E}) show that the bulk electron plasma flow is virtually always tailward during both quiet and geomagnetically active times. This aspect of the magnetotail data has been interpreted as suggesting that ISEE 3 is nearly always tailward of the distant neutral line when the spacecraft is at distances {approx gt} 120 R{sub E}. During an extended period ({approximately}0900 to {approximately}1230 UT) on January 29, 1983, however, ISEE 3 observed substantial earthward plasma flows while located in the distant plasma sheet at X{sub GSM} = {minus}217 R{sub E}. The authors have analyzed the distant neutral line location within the context of the distant tail, geostationary orbit, auroral zone, and solar wind data for this case based on an extension of the Coroniti and Kennel (1972) flaring tail theory. They conclude from known solar wind conditions that for a typical neutral line location at {approximately}135 R{sub E}, an {approximately}30% increase of the near-Earth lobe field strength would be required to cause the distant neutral line to move tailward beyond 220 R{sub E}. The available data suggest that this is quite plausible and that, therefore, the earthward flow episode is due to an exceptionally distant neutral line position. The question of why substorms did not terminate the growth phase earlier is also addressed.

  8. Fact Sheet for KM200 Front-end Electronics

    SciTech Connect

    Ianakiev, Kiril Dimitrov; Iliev, Metodi; Swinhoe, Martyn Thomas

    2015-07-08

    The KM200 device is a versatile, configurable front-end electronics boards that can be used as a functional replacement for Canberra’s JAB-01 boards based on the Amptek A-111 hybrid chip, which continues to be the preferred choice of electronics for large number of the boards in junction boxes of multiplicity counters that process the signal from an array of 3He detectors. Unlike the A-111 chip’s fixed time constants and sensitivity range, the shaping time and sensitivity of the new KM200 can be optimized for demanding applications such as spent fuel, and thus could improve the safeguards measurements of existing systems where the A-111 or PDT electronics does not perform well.

  9. Possible role of ionospheric oxygen in the initiation and development of plasma sheet instabilities

    SciTech Connect

    Baker, D.N.; Hones, E.W. Jr.; Young, D.T.; Birn, J.

    1982-12-01

    We relate measurements made during substorm growth and expansion to available plasma compositional observations and propose that asymmetries in the distribution of enhanced densities of O/sup +/ (of ionospheric origin) may define regions of the plasma sheet in which tearing mode growth rates are increased and the instability threshold is lowered. We make qualitative estimates of the growth rates of the linear ion tearing mode using statistical models of the dusk-dawn and earthward-tailward distributions of O/sup +/. The theoretical results predict maximum ion tearing growth rate in the range X/sub GSM/ = -10 to -15 R/sub E/ and Y/sub GSM/approx.5 R/sub E/. These values are in reasonable accord with substorm observations since many asymmetries in particle and field phenomena associated with substorms favor the interpretation that substorm onset occurs in the dusk sector of the near-earth plasma sheet. Present results therefore suggest that substorm initiation and development may be closely related to distribution patterns of ionospheric ions.

  10. Study of the turbulent transport in the plasma sheet related to eddy-diffusion using THEMIS satellite data

    NASA Astrophysics Data System (ADS)

    L'Huissier, P.; Pinto, V. A.; Stepanova, M. V.; Antonova, E. E.; Valdivia, J. A.

    2011-12-01

    Recent studies of the turbulent processes in the central plasma sheet have shown that the instantaneous profiles of the diagonal terms of eddy-diffusion coefficients tensor show an increase with distance from the Earth in the tailward direction [Pinto et al. 2011,Stepanova et al. 2011], which agree with previous statistical studies. In this study we analyzed the relevance of the off-diagonal terms of the eddy-diffusion coefficients tensor in the plasma transport in the plasma sheet as a function of the distance into the magnetic tail

  11. Probing Runaway Electrons with Nanoparticle Plasma Jet

    NASA Astrophysics Data System (ADS)

    Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.

    2014-10-01

    The injection of C60/C nanoparticle plasma jet (NPPJ) into tokamak plasma during a major disruption has the potential to probe the runaway electrons (REs) during different phases of their dynamics and diagnose them through spectroscopy of C ions visible/UV lines. A C60/C NPPJ of ~75 mg, high-density (>1023 m-3), hyper-velocity (>4 km/s), and uniquely fast response-to-delivery time (~1 ms) has been demonstrated on a test bed. It can rapidly and deeply deliver enough mass to increase electron density to ~2.4 × 1021 m-3, ~60 times larger than typical DIII-D pre-disruption value. We will present the results of our investigations on: 1) C60 fragmentation and gradual release of C atoms along C60 NPPJ penetration path through the RE carrying residual cold plasma, 2) estimation of photon emissivity coefficient for the lines of the C ions, and 3) simulation of C60/C PJ penetration to the RE beam location in equivalent conditions to the characteristic ~1 T B-field of DIII-D. The capabilities of this injection technique provide a unique possibility in understanding and controlling the RE beam, which is a critical problem for ITER. Work supported by US DOE DE-SC0011864 Grant.

  12. Electron-helium scattering in Debye plasmas

    SciTech Connect

    Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor; Janev, R. K.

    2011-11-15

    Electron-helium scattering in weakly coupled hot-dense (Debye) plasma has been investigated using the convergent close-coupling method. The Yukawa-type Debye-Hueckel potential has been used to describe plasma Coulomb screening effects. Benchmark results are presented for momentum transfer cross sections, excitation, ionization, and total cross sections for scattering from the ground and metastable states of helium. Calculations cover the entire energy range up to 1000 eV for the no screening case and various Debye lengths (5-100 a{sub 0}). We find that as the screening interaction increases, the excitation and total cross sections decrease, while the total ionization cross sections increase.

  13. Plasma treatment for producing electron emitters

    DOEpatents

    Coates, Don Mayo; Walter, Kevin Carl

    2001-01-01

    Plasma treatment for producing carbonaceous field emission electron emitters is disclosed. A plasma of ions is generated in a closed chamber and used to surround the exposed surface of a carbonaceous material. A voltage is applied to an electrode that is in contact with the carbonaceous material. This voltage has a negative potential relative to a second electrode in the chamber and serves to accelerate the ions toward the carbonaceous material and provide an ion energy sufficient to etch the exposed surface of the carbonaceous material but not sufficient to result in the implantation of the ions within the carbonaceous material. Preferably, the ions used are those of an inert gas or an inert gas with a small amount of added nitrogen.

  14. Whistler-mode phenomena in electron MHD plasmas

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.

    2003-12-01

    While the linear properties of plane whistler waves are well known, many new phenomena of bounded wavepackets and nonlinear effects are worth to describe. The present talk will review laboratory observations of whistler filaments, whistler vortices, whistler wings, whistler-sound modes in high-beta plasmas, nonlinear whistlers forming magnetic null points, and magnetic reconnection in EMHD plasmas. The time-varying magnetic field of a spatially bounded whistler wave packet consists of 3-D vortices. Each vortex can be decomposed into linked toroidal and poloidal field components. The self-helicity is positive for propagation along the field, negative for opposite propagation. Helicity injection from a suitable source produces unidirectional propagation. Magnetic helicity changes sign, i.e., is not conserved, when the propagation direction along B changes, for example due to reflection or propagation through a magnetic null point. In ideal EMHD the electric and magnetic forces on the electrons are equal, -n e E +J x B=0, i.e., the electron fluid is not compressed. Force-free vortices do not interact during collisions. Vortices are excited with pulsed magnetic antennas or pulsed electrodes. Both transient currents and fields can form vortices that propagate in the whistler mode. Moving dc magnets or dc current systems can also induce whistler modes in a magnetized plasma. These form a Cherenkov-like radiation pattern, a ``whistler wing.'' Nonlinear phenomena arise from wave-induced modifications of the electron temperature, density and magnetic field. In collisional plasmas electrons are heated by strong whistlers. Modifications of the classical conductivity leads to current filamentation. On a slower time scale density modifications arise from ambipolar fields associated with electron heating. In a filamentation instability a strong whistler wave is ducted along a narrow field-aligned density depression. The ion density is also modified by the ac electric field of low-frequency whistlers in high-beta plasmas. Pressure-gradient driven instabilities near the lower hybrid frequency produce coupled density and magnetic perturbations that propagate at the sound speed nearly across the field, forming a new whistler-sound mode. The net magnetic field is modified when the whistler magnetic field exceeds the background magnetic field. A field-reversed configuration (FRC) with two 3-D null points is produced. This EMHD structure does not propagate in the whistler mode. It elongates and precesses, which are manifestations of magnetic fields frozen into the electron fluid flow. The free magnetic energy is converted into electron heat by field line annihilation in the toroidal current sheet. No reconnection is seen at the 3-D spiral nulls. The energy dissipation is anomalously fast due to current-driven ion sound turbulence. In contrast to linear vortices, two FRCs do interact and merge into a single one. These basic properties of EMHD fields will be applied to cases of interest in space plasmas such as reconnection, strong turbulence, and possible active experiments. Work performed in collaboration with J.~M. Urrutia, M.~C. Griskey, and K.~D. Strohmaier with support from NSF PHY.

  15. Quantification of ridging in ferritic stainless steel sheets by electron backscattered diffraction R-value maps.

    PubMed

    Lee, Kye-Man; Park, Jieon; Kim, Sangseok; Park, Sooho; Huh, Moo-Young

    2013-08-01

    In ferritic stainless steel (FSS), undesirable surface defects of ridging appear during deep drawing. The formation of these defects is attributed to the inhomogeneous distribution of orientations of individual grains. In the present work, a new electron backscattered diffraction R(α)-value map was introduced, and the dependence of the tensile directions on the formation of ridging in an FSS sheet was discussed using this map. The results showed that large grain colonies in the R(α)-value maps lead to the formation of severe ridging in an FSS sheet. PMID:23920166

  16. Electron Recombination in a Dense Hydrogen Plasma

    SciTech Connect

    Jana, M.R.; Johnstone, C.; Kobilarcik, T.; Koizumi, G.M.; Moretti, A.; Popovic, M.; Tollestrup, A.V.; Yonehara, K.; Leonova, M.A.; Schwarz, T.A.; Chung, M.; /Unlisted /IIT, Chicago /Fermilab /MUONS Inc., Batavia /Turin Polytechnic

    2012-05-01

    A high pressure hydrogen gas filled RF cavity was subjected to an intense proton beam to study the evolution of the beam induced plasma inside the cavity. Varying beam intensities, gas pressures and electric fields were tested. Beam induced ionized electrons load the cavity, thereby decreasing the accelerating gradient. The extent and duration of this degradation has been measured. A model of the recombination between ionized electrons and ions is presented, with the intent of producing a baseline for the physics inside such a cavity used in a muon accelerator. Analysis of the data taken during the summer of 2011 shows that self recombination takes place in pure hydrogen gas. The decay of the number of electrons in the cavity once the beam is turned off indicates self recombination rather than attachment to electronegative dopants or impurities. The cross section of electron recombination grows for larger clusters of hydrogen and so at the equilibrium of electron production and recombination in the cavity, processes involving H{sub 5}{sup +} or larger clusters must be taking place. The measured recombination rates during this time match or exceed the analytic predicted values. The accelerating gradient in the cavity recovers fully in time for the next beam pulse of a muon collider. Exactly what the recombination rate is and how much the gradient degrades during the 60 ns muon collider beam pulse will be extrapolated from data taken during the spring of 2012.

  17. Plasma heating by a relativistic electron beam

    SciTech Connect

    Janssen, G.C.A.M.; Bonnie, J.H.M.; Granneman, E.H.A.; Krementsov, V.I.; Hopman, H.J.

    1984-03-01

    Reported are measurements on the interaction between a relativistic electron beam (REB) with the parameters 800 kV, 6 kA, 50--150 nsec, and a plasma with a density of n/sub e/ = 1.0 x 10/sup 19/ m/sup -3/--1.0 x 10/sup 20/ m/sup -3/. The electron temperature during and after the beam pulse is obtained by means of Thomson scattering. Also measured is the angular distribution of the beam electrons as a function of time and position. By varying the angular spread of the beam it is possible to pass from a kinetic to a quasihydrodynamic interaction. In both regimes measurements are compared with the appropriate theoretical model. Energy transfer is largest in the quasihydrodynamic regime and amounts to 2.5 x 10/sup 3/ J/m/sup 3/ or 2.2 x 10/sup 16/ eV/cm/sup 3/. The electron temperature reaches values of 150 eV and appears limited by the electron heat conduction along the magnetic field.

  18. Energy Measurements of Trapped Electrons from a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neal; Auerbach, David; Berry, Melissa; Blumenfeld, Ian; Clayton, Christopher E.; Decer, Franz-Josef; Hogan, Mark J.; Huang, Chengkun; Ischebeck, Rasmus; Iverson, Richard; Johnson, Devon; Joshi, Chadrashekhar; Katsouleas, Thomas; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; Muggli, Patric; Oz, Erdem; Siemann, Robert H.; Walz, Dieter; Zhou, Miaomiao; /SLAC /UCLA /Southern California U.

    2007-01-03

    Recent electron beam driven plasma wakefield accelerator experiments carried out at SLAC indicate trapping of plasma electrons. More charge came out of than went into the plasma. Most of this extra charge had energies at or below the 10 MeV level. In addition, there were trapped electron streaks that extended from a few GeV to tens of GeV, and there were mono-energetic trapped electron bunches with tens of GeV in energy.

  19. Observations of a nonthermal ion layer at the plasma sheet boundary during substorm recovery

    NASA Technical Reports Server (NTRS)

    Moebius, E.; Scholer, M.; Hovestadt, D.; Klecker, B.; Ipavich, F. M.; Gloeckler, G.

    1980-01-01

    Measurements of the energy and angular distributions of energetic protons and alpha particles (not less than 30 keV/charge) in the geomagnetic tail are presented. The measurements were made during the recovery phase of a geomagnetic substorm on Apr. 19, 1978, with the Max-Planck-Institut/University of Maryland sensor system on the Isee 1 satellite. The measurements were also correlated with plasma observations made by the LASL/MPE instrument on Isee 1. The data reveal the presence of a thin nonthermal layer of protons and alpha particles at the plasma sheet boundary. The particles have their maximum flux at 60 keV/charge and are streaming highly collimated in the earthward direction. The alpha particle layer is confined within the proton layer. Many aspects of the observations are in agreement with an acceleration model near the neutral line proposed by Jaeger and Speiser (1974)

  20. An exact collisionless equilibrium for the Force-Free Harris Sheet with low plasma beta

    SciTech Connect

    Allanson, O. Neukirch, T. Wilson, F. Troscheit, S.

    2015-10-15

    We present a first discussion and analysis of the physical properties of a new exact collisionless equilibrium for a one-dimensional nonlinear force-free magnetic field, namely, the force-free Harris sheet. The solution allows any value of the plasma beta, and crucially below unity, which previous nonlinear force-free collisionless equilibria could not. The distribution function involves infinite series of Hermite polynomials in the canonical momenta, of which the important mathematical properties of convergence and non-negativity have recently been proven. Plots of the distribution function are presented for the plasma beta modestly below unity, and we compare the shape of the distribution function in two of the velocity directions to a Maxwellian distribution.

  1. Status of Plasma Electron Hose Instability Studies in FACET

    SciTech Connect

    Adli, Erik; England, Robert Joel; Frederico, Joel; Hogan, Mark; Li, Selina Zhao; Litos, Michael Dennis; Nosochkov, Yuri; An, Weiming; Mori, Warren; /UCLA

    2011-12-13

    In the FACET plasma-wakefield acceleration experiment a dense 23 GeV electron beam will interact with lithium and cesium plasmas, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons may lead to a fast growing electron hose instability. By using optics dispersion knobs to induce a controlled z-x tilt along the beam entering the plasma, we investigate the transverse behavior of the beam in the plasma as function of the tilt. We seek to quantify limits on the instability in order to further explore potential limitations on future plasma wakefield accelerators due to the electron hose instability. The FACET plasma-wakefield experiment at SLAC will study beam driven plasma wakefield acceleration. A dense 23 GeV electron beam will interact with lithium or cesium plasma, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons drives the electron hose instability, as first studied by Whittum. While Ref. [2] indicates the possibility of a large instability growth rate for typical beam and plasma parameters, other studies including have shown that several physical effects may mitigate the hosing growth rate substantially. So far there has been no quantitative benchmarking of experimentally observed hosing in previous experiments. At FACET we aim to perform such benchmarking by for example inducing a controlled z-x tilt along the beamentering the plasma, and observing the transverse behavior of the beam in the plasma as function. The long-term objective of these studies is to quantify potential limitations on future plasma wakefield accelerators due to the electron hose instability.

  2. Fractal structure of low-temperature plasma of arc discharge as a consequence of the interaction of current sheets

    NASA Astrophysics Data System (ADS)

    Smolanov, N. A.

    2016-01-01

    The structure of the particles deposited from the plasma arc discharge were studied. The flow of plasma spreading from the cathode spot to the walls of the vacuum chamber. Electric and magnetic fields to influence the plasma flow. The fractal nature of the particles from the plasma identified by small-angle X-ray scattering. Possible cause of their formation is due to the instability of the growth front and nonequilibrium conditions for their production - a high speed transition of the vapor-liquid-solid or vapor - crystal. The hypothesis of a plasma arc containing dust particles current sheets was proposed.

  3. Stability of two-dimensional PN monolayer sheets and their electronic properties.

    PubMed

    Ma, ShuangYing; He, Chaoyu; Sun, L Z; Lin, Haiping; Li, Youyong; Zhang, K W

    2015-12-21

    Three two-dimensional phosphorus nitride (PN) monolayer sheets (named as α-, β-, and γ-PN, respectively) with fantastic structures and properties are predicted based on first-principles calculations. The α-PN and γ-PN have a buckled structure, whereas β-PN shows puckered characteristics. Their unique structures endow these atomic PN sheets with high dynamic stabilities and anisotropic mechanical properties. They are all indirect semiconductors and their band gap sensitively depends on the in-plane strain. Moreover, the nanoribbons patterned from these three PN monolayers demonstrate a remarkable quantum size effect. In particular, the zigzag α-PN nanoribbon shows size-dependent ferromagnetism. Their significant properties show potential in nano-electronics. The synthesis of the three phases of the PN monolayer sheet is proposed theoretically, which is deserving of further study in experiments. PMID:26573995

  4. Relationship between wave-like auroral arcs and Pi2 disturbances in plasma sheet prior to substorm onset

    NASA Astrophysics Data System (ADS)

    Chang, Tzu-Fang; Cheng, Chio-Zong

    2015-12-01

    Wave-like substorm arc features in the aurora and Pi2 magnetic disturbances observed in the near-Earth plasma sheet are frequently, and sometimes simultaneously, observed around the substorm onset time. We perform statistical analyses of the THEMIS ASI auroral observations that show wave-like bright spot structure along the arc prior to substorm onset. The azimuthal mode number values of the wave-like substorm arcs are found to be in the range of ~100-240 and decrease with increasing geomagnetic latitude of the substorm auroral arc location. We suggest that the azimuthal mode number is likely related to the ion gyroradius and azimuthal wave number. We also perform correlation study of the pre-onset wave-like substorm arc features and Pi2 magnetic disturbances for substorm dipolarization events observed by THEMIS satellites during 2008-2009. The wave-like arc brightness structures on the substorm auroral arcs tend to move azimuthally westward, but with a few exceptions of eastward movement, during tens of seconds prior to the substorm onset. The movement of the wave-like arc brightness structure is linearly correlated with the phase velocity of the Pi2 ? B y disturbances in the near-Earth plasma sheet region. The result suggests that the Pi2 transverse ? B y disturbances are related to the intensifying wave-like substorm onset arcs. One plausible explanation of the observations is the kinetic ballooning instability, which has high azimuthal mode number due to the ion gyroradius effect and finite parallel electric field that accelerates electrons into the ionosphere to produce the wave-like arc structure.

  5. Nonnuclear nearly free electron conduction channels induced by doping charge in nanotube-molecular sheet composites.

    PubMed

    Zhao, Jin; Zheng, Qijing; Petek, Hrvoje; Yang, Jinlong

    2014-09-01

    Nearly free electron (NFE) states with density maxima in nonnuclear (NN) voids may have remarkable electron transport properties ranging from suppressed electron-phonon interaction to Wigner crystallization. Such NFE states, however, usually exist near the vacuum level, which makes them unsuitable for transport. Through first principles calculations on nanocomposites consisting of carbon nanotube (CNT) arrays sandwiched between boron nitride (BN) sheets, we describe a stratagem for stabilizing the NN-NFE states to below the Fermi level. By doping the CNTs with negative charge, we establish Coulomb barriers at CNTs walls that, together with the insulating BN sheets, define the transverse potentials of one-dimensional (1D) transport channels, which support the NN-NFE states. PMID:24401149

  6. Electron temperature dynamics of TEXTOR plasmas

    NASA Astrophysics Data System (ADS)

    Udintsev, Victor Sergeevich

    2003-11-01

    To study plasma properties in the presence of large and small MHD modes, new high-resolution ECE diagnostics have been installed at TEXTOR tokamak, and some of the already existing systems have been upgraded. Two models for the plasma transport properties inside large m/n = 2/1 MHD islands have been found to give estimations for the heat diffusivities, which are much lower than the global plasma heat diffusivity, which is in agreement with previous measurements in different tokamaks. The 3D-reconstruction of large m/n = 2/1 modes in TEXTOR with the help of all available ECE diagnostics allows modelling the island as a structure with closed flux surfaces. The main plasma heat flux flows through the X-point area probably along stochastic magnetic field lines. The confinement is improved within the magnetic island, compared to the background plasma. This is confirmed by a temperature profile flattening and sometimes even a secondary peaking inside the island, compared to the X-point. Making use of the mode rotation, assumed to be a rigid rotor, it has been possible to obtain information on the topology of the m = 1 precursor mode leading to sawtooth collapses. It becomes clear that this precursor cannot be described by an m = 1 cold tearing mode island but by a hot crescent wrapped around a cold high-density bubble. In the future multi-chord ECE-imaging will allow this mode reconstruction without the assumption of the rotation to be rigid. From the measurements of the broadband temperature and density fluctuations one can conclude that the turbulent structures inside the q = 1 surface are separated from the turbulence outside the q = 1 surface. This fits nicely with the observation that q = 1 surface acts as a barrier for the thermal transport. Correlation length and time measured inside q = 1 are in agreement with the observed turbulent heat diffusivity. Qualitative studies of non-thermal electrons at different heating regimes (ECRH and Ohmic) at TEXTOR were done with the help of the combined 2nd -3rd harmonic X-mode ECE radiometer. It has been found that the lower energetic non-thermal electrons are directly responsive to small density changes, in contrast to the highly energetic runaways with energy up to 20 MeV. Those are only affected by a substantial density ramp up.

  7. Nonlinear stability of the near-Earth plasma sheet during substorms: 9 February 1995 event

    NASA Astrophysics Data System (ADS)

    Dobias, P.; Wanliss, J. A.; Samson, J. C.

    2006-12-01

    It has been previously demonstrated that several minutes prior to an onset of a magnetospheric substorm the near-Earth plasma sheet becomes unstable to resonance-type perturbations. The next logical step, examined here, is an assumption that the velocity shear in the resonance would lead to a development of a Kelvin-Helmholtz (KH) instability. Using a Grad-Shafranov equilibrium constrained by CANOPUS data, we analyze the stability properties of the near-Earth plasma sheet in the presence of a field-line resonance-generated KH instability at around 10 Earth radii. The results of the analysis are in general agreement with observations and computer modeling of substorms. As a part of the analysis, we discuss the importance of the proper distinction between the stability properties of the magnetotail, and the trigger mechanism responsible for the instability. While these two aspects of a substorm may be (and likely are) related, it is possible that they involve different types of processes that work in a complementary fashion.

  8. Multiscale Auroral Emission Statistics as Evidence of Turbulent Reconnection in Earth's Midtail Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Klimas, Alex; Uritsky, Vadim; Donovan, Eric

    2010-01-01

    We provide indirect evidence for turbulent reconnection in Earth's midtail plasma sheet by reexamining the statistical properties of bright, nightside auroral emission events as observed by the UVI experiment on the Polar spacecraft and discussed previously by Uritsky et al. The events are divided into two groups: (1) those that map to absolute value of (X(sub GSM)) < 12 R(sub E) in the magnetotail and do not show scale-free statistics and (2) those that map to absolute value of (X(sub GSM)) > 12 R(sub E) and do show scale-free statistics. The absolute value of (X(sub GSM)) dependence is shown to most effectively organize the events into these two groups. Power law exponents obtained for group 2 are shown to validate the conclusions of Uritsky et al. concerning the existence of critical dynamics in the auroral emissions. It is suggested that the auroral dynamics is a reflection of a critical state in the magnetotail that is based on the dynamics of turbulent reconnection in the midtail plasma sheet.

  9. Nonlinear impact of plasma sheet density on the storm-time ring current

    NASA Astrophysics Data System (ADS)

    Ebihara, Y.; Fok, M.-C.; Wolf, R. A.; Thomsen, M. F.; Moore, T. E.

    2005-02-01

    We investigated the nonlinear impact of the plasma sheet density on the total energy of the storm-time ring current by means of a numerical simulation that self-consistently solves the kinetic equation of ring current protons and the closure of the electric current between the magnetosphere and ionosphere. Results of the simulation indicate that when the convection electric field is self-consistently coupled with the ring current, the total energy of the ring current ions trapped by the Earth's magnetic field is roughly proportional to Nps1/2, where Nps is the plasma sheet density. This nonlinear response results from the strengthened shielding electric field with increasing Nps. The total energy is almost proportional to Nps when using an empirical convection electric field, which is independent of the condition of the simulated ring current. An empirical relationship between Nps and the solar wind density was used to estimate time-dependent Nps. The result shows that the calculated Dst* tends to overshoot the observed one when the non-self-consistent electric field is employed. A better agreement was obtained with the self-consistent electric field. We suggest that the nonlinear response of the ring current to Nps is one of the mechanisms that impedes the growth of the storm-time ring current. Another mechanism is probably the saturation of the polar cap potential drop for high solar wind electric field.

  10. THEMIS two-point measurements of the cross-tail current density: A thick bifurcated current sheet in the near-Earth plasma sheet

    NASA Astrophysics Data System (ADS)

    Saito, Miho

    2015-08-01

    The basic properties of the near-Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail-like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets.

  11. 3-D Gyrokinetic Electron and Fully Kinetic Ion Simulation of Current Sheet Instabilities

    NASA Astrophysics Data System (ADS)

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2014-10-01

    Instability of a Harris current sheet is investigated using a 3-D linearized (δf) electromagnetic gyrokinetic electron and fully kinetic ion (GeFi) particle simulation code. The equilibrium magnetic field consists of an asymptotic anti-parallel component Bx 0 and a guide field BG, with the current sheet normal in the z direction. The simulation is performed for cases with a broad range of BG. The eigenmode structure, real frequency, and the growth rate of instabilities are calculated as a function of wave numbers kx and ky. In the cases with a small kyρe , tearing mode is found to dominate, with peak growth rate at kx L = 0 . 4 -0.5, where L is the half-width of the current sheet. On the other hand, in the cases with a small kxρe <= 0 . 1 , there exist two unstable modes: a quasi-electrostatic mode at the current sheet edge with wave number 0 . 3 <=kyρe <= 0 . 6 and frequency around the lower-hybrid frequency ωLH and an electromagnetic mode with kyρe <= 0 . 2 at the sheet center under a guide field BG /Bx 0 = 0 . 1 . The transition from the tearing-like instability to the ky-dominant instabilities is presented by scanning through the (kx ,ky) space. The complete 3-D profile of instabilitie.

  12. Flute-interchange stability in a hot electron plasma

    SciTech Connect

    Dominguez, R.R.

    1980-01-01

    Several topics in the kinetic stability theory of flute-interchange modes in a hot electron plasma are discussed. The stability analysis of the hot-electron, curvature-driven flute-interchange mode, previously performed in a slab geometry, is extended to a cylindrical plasma. The cold electron concentration necessary for stability differs substantially from previous criteria. The inclusion of a finite temperature background plasma in the stability analysis results in an ion curvature-driven flute-interchange mode which may be stabilized by either hot-electron diamagnetic effects, hot-electron plasma density, or finite (ion) Larmor radius effects.

  13. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    NASA Astrophysics Data System (ADS)

    Sydorenko, D.; Kaganovich, I. D.; Chen, L.; Ventzek, P. L. G.

    2015-12-01

    Generation of anomalously energetic suprathermal electrons was observed in simulation of a high-voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in the discharge via a two-stream instability. The energy transfer from the beam to the plasma electrons is ensured by the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The waves with short wavelength near the anode accelerate plasma bulk electrons to suprathermal energies. The sheath near the anode reflects some of the accelerated electrons back into the plasma. These electrons travel through the plasma, reflect near the cathode, and enter the accelerating area again but with a higher energy than before. Such particles are accelerated to energies much higher than after the first acceleration. This mechanism plays a role in explaining earlier experimental observations of energetic suprathermal electrons in similar discharges.

  14. High and low frequency instabilities driven by counter-streaming electron beams in space plasmas

    SciTech Connect

    Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.

    2014-05-15

    A four-component plasma composed of a drifting (parallel to ambient magnetic field) population of warm electrons, drifting (anti-parallel to ambient magnetic field) cool electrons, stationary hot electrons, and thermal ions is studied in an attempt to further our understanding of the excitation mechanisms of broadband electrostatic noise (BEN) in the Earth's magnetospheric regions such as the magnetosheath, plasmasphere, and plasma sheet boundary layer (PSBL). Using kinetic theory, beam-driven electrostatic instabilities such as the ion-acoustic, electron-acoustic instabilities are found to be supported in our multi-component model. The dependence of the instability growth rates and real frequencies on various plasma parameters such as beam speed, number density, temperature, and temperature anisotropy of the counter-streaming (relative to ambient magnetic field) cool electron beam are investigated. It is found that the number density of the anti-field aligned cool electron beam and drift speed play a central role in determining which instability is excited. Using plasma parameters which are closely correlated with the measurements made by the Cluster satellites in the PSBL region, we find that the electron-acoustic and ion-acoustic instabilities could account for the generation of BEN in this region.

  15. Electron Acceleration in a Dynamically Evolved Current Sheet Under Solar Coronal Conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Shaohua; Du, A. M.; Feng, Xueshang; Cao, Xin; Lu, Quanming; Yang, Liping; Chen, Gengxiong; Zhang, Ying

    2014-05-01

    Electron acceleration in a drastically evolved current sheet under solar coronal conditions is investigated via the combined 2.5-dimensional (2.5D) resistive magnetohydrodynamics (MHD) and test-particle approaches. Having a high magnetic Reynolds number (105), the long, thin current sheet is torn into a chain of magnetic islands, which grow in size and coalesce with each other. The acceleration of electrons is explored in three typical evolution phases: when several large magnetic islands are formed (phase 1), two of these islands are approaching each other (phase 2), and almost merging into a "monster" magnetic island (phase 3). The results show that for all three phases electrons with an initial Maxwell distribution evolve into a heavy-tailed distribution and more than 20 % of the electrons can be accelerated higher than 200 keV within 0.1 second and some of them can even be energized up to MeV ranges. The lower-energy electrons are located away from the magnetic separatrices and the higher-energy electrons are inside the magnetic islands. The most energetic electrons have a tendency to be around the outer regions of the magnetic islands or to appear in the small secondary magnetic islands. It is the trapping effect of the magnetic islands and the distributions of E p that determine the acceleration and spatial distributions of the energetic electrons.

  16. Electron Beam Emission Characteristics from Plasma Focus Devices

    SciTech Connect

    Zhang, T.; Patran, A.; Wong, D.; Hassan, S.M.; Springham, S.V.; Tan, T.L.; Lee, P.; Lee, S.; Rawat, R.S.

    2006-01-05

    In this paper we observed the characteristics of the electron beam emission from our plasma focus machine filling neon, argon, helium and hydrogen. Rogowski coil and CCD based magnetic spectrometer were used to obtain temporal and energy distribution of electron emission. And the preliminary results of deposited FeCo thin film using electron beam from our plasma focus device were presented.

  17. Electron energy distribution in a dusty plasma: analytical approach.

    PubMed

    Denysenko, I B; Kersten, H; Azarenkov, N A

    2015-09-01

    Analytical expressions describing the electron energy distribution function (EEDF) in a dusty plasma are obtained from the homogeneous Boltzmann equation for electrons. The expressions are derived neglecting electron-electron collisions, as well as transformation of high-energy electrons into low-energy electrons at inelastic electron-atom collisions. At large electron energies, the quasiclassical approach for calculation of the EEDF is applied. For the moderate energies, we account for inelastic electron-atom collisions in the dust-free case and both inelastic electron-atom and electron-dust collisions in the dusty plasma case. Using these analytical expressions and the balance equation for dust charging, the electron energy distribution function, the effective electron temperature, the dust charge, and the dust surface potential are obtained for different dust radii and densities, as well as for different electron densities and radio-frequency (rf) field amplitudes and frequencies. The dusty plasma parameters are compared with those calculated numerically by a finite-difference method taking into account electron-electron collisions and the transformation of high-energy electrons at inelastic electron-neutral collisions. It is shown that the analytical expressions can be used for calculation of the EEDF and dusty plasma parameters at typical experimental conditions, in particular, in the positive column of a direct-current glow discharge and in the case of an rf plasma maintained by an electric field with frequency f=13.56MHz. PMID:26465570

  18. Electron plasma dynamics during autoresonant excitation of the diocotron mode

    SciTech Connect

    Baker, C. J. Danielson, J. R. Hurst, N. C. Surko, C. M.

    2015-02-15

    Chirped-frequency autoresonant excitation of the diocotron mode is used to move electron plasmas confined in a Penning-Malmberg trap across the magnetic field for advanced plasma and antimatter applications. Plasmas of 10{sup 8} electrons, with radii small compared to that of the confining electrodes, can be moved from the magnetic axis to ≥90% of the electrode radius with near unit efficiency and reliable angular positioning. Translations of ≥70% of the wall radius are possible for a wider range of plasma parameters. Details of this process, including phase and displacement oscillations in the plasma response and plasma expansion, are discussed, as well as possible extensions of the technique.

  19. Effects of emitted electron temperature on the plasma sheath

    SciTech Connect

    Sheehan, J. P.; Kaganovich, I. D.; Wang, H.; Raitses, Y.; Sydorenko, D.; Hershkowitz, N.

    2014-06-15

    It has long been known that electron emission from a surface significantly affects the sheath surrounding that surface. Typical fluid theory of a planar sheath with emitted electrons assumes that the plasma electrons follow the Boltzmann relation and the emitted electrons are emitted with zero energy and predicts a potential drop of 1.03T{sub e}/e across the sheath in the floating condition. By considering the modified velocity distribution function caused by plasma electrons lost to the wall and the half-Maxwellian distribution of the emitted electrons, it is shown that ratio of plasma electron temperature to emitted electron temperature significantly affects the sheath potential when the plasma electron temperature is within an order of magnitude of the emitted electron temperature. When the plasma electron temperature equals the emitted electron temperature the emissive sheath potential goes to zero. One dimensional particle-in-cell simulations corroborate the predictions made by this theory. The effects of the addition of a monoenergetic electron beam to the Maxwellian plasma electrons were explored, showing that the emissive sheath potential is close to the beam energy only when the emitted electron flux is less than the beam flux.

  20. Nonnuclear Nearly Free Electron Conduction Channels Induced by Doping Charge in Nanotube–Molecular Sheet Composites

    SciTech Connect

    Zhao, Jin; Zheng, Qijing; Petek, Hrvoje; Yang, Jinlong

    2014-09-04

    Nearly free electron (NFE) states with density maxima in nonnuclear (NN) voids may have remarkable electron transport properties ranging from suppressed electron–phonon interaction to Wigner crystallization. Such NFE states, however, usually exist near the vacuum level, which makes them unsuitable for transport. Through first principles calculations on nanocomposites consisting of carbon nanotube (CNT) arrays sandwiched between boron nitride (BN) sheets, we describe a stratagem for stabilizing the NN-NFE states to below the Fermi level. By doping the CNTs with negative charge, we establish Coulomb barriers at CNTs walls that, together with the insulating BN sheets, define the transverse potentials of one-dimensional (1D) transport channels, which support the NN-NFE states.

  1. Electron collisions with excited molecules in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Celiberto, Roberto; Laporta, Vincenzo

    2015-01-01

    State-to-state vibrationally resolved cross sections for electron-impact processes involving vibrationally excited molecules are reviewed, with particular emphasis on atmospheric and fusion plasma applications.

  2. Etching with electron beam generated plasmas

    SciTech Connect

    Leonhardt, D.; Walton, S.G.; Muratore, C.; Fernsler, R.F.; Meger, R.A.

    2004-11-01

    A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen-argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to 220 nm/min at 100 eV), with reasonable anisotropic pattern transfer above 50 eV. Little change in etch rate was seen as gas composition went from pure oxygen to 70% argon, implying the resist removal mechanism in this system required the additional energy supplied by the ions. With silicon substrates at room temperature, mixtures of argon and sulfur hexafluoride etched approximately seven times faster (1375 nm/min) than mixtures of oxygen and sulfur hexafluoride ({approx}200 nm/min) with 200 eV ions, the difference is attributed to the passivation of the silicon by involatile silicon oxyfluoride (SiO{sub x}F{sub y}) compounds. At low incident ion energies, the Ar-SF{sub 6} mixtures showed a strong chemical (lateral) etch component before an ion-assisted regime, which started at {approx}75 eV. Etch rates were independent of the 0.5%-50% duty factors studied in this work.

  3. Observations at the planet Mercury by the plasma electron experiment, Mariner 10

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Scudder, J. D.; Vasyliunas, V. M.; Hartle, R. E.; Siscoe, G. L.

    1976-01-01

    Plasma electron observations made onboard Mariner 10 are reported. Three encounters with the planet Mercury show that the planet interacts with the solar wind to form a bow shock and a permanent magnetosphere. The observations provide a determination of the dimensions and properties of the magnetosphere, independently of and in general agreement with magnetometer observations. The magnetosphere of Mercury appears to be similar in shape to that of the Earth but much smaller in relation to the size of the planet. Electron populations similar to those found in the Earth's magnetotail, within the plasma sheet and adjacent regions, were observed at Mercury; both their spatial location and the electron energy spectra within them bear qualitative and quantitative resemblance to corresponding observations at the Earth. The magnetosphere of Mercury resembles to a marked degree a reduced version of that of the Earth, with no significant differences of structure.

  4. Electron acceleration by magnetic islands in a dynamically evolved coronal current sheet

    NASA Astrophysics Data System (ADS)

    Zhang, Shaohua; Feng, Xueshang; Wang, Bin; Yang, Liping; Meng, Lifei

    2016-03-01

    This work simulated the electron acceleration by magnetic islands in a drastically evolved solar coronal current sheet via the combined 2.5-dimensional (2.5D) resistive Magnetohydrodynamics (MHD) and guiding-center approximation test-particle methods. With high magnetic Reynolds number of 105, the long-thin current sheet is evolved into a chain of magnetic islands, growing in size and coalescing with each other, due to tearing instability. The acceleration of electrons is studied in one typical phase when several large magnetic islands are formed. The results show that the electrons with an initial Maxwell distribution evolve into a heavy-tailed distribution and more than 20% of the electrons can be accelerated higher than 200 keV within 0.1 second and some of them can even be energized up to MeV ranges. The most energetic electrons have a tendency to be around the outer regions of the magnetic islands or to be located in the small secondary magnetic islands. We find that the acceleration and spatial distributions of the energetic electrons is caused by the trapping effect of the magnetic islands and the distributions of the parallel electric field Ep.

  5. Holographic interferometry study of two-fluid properties of the plasma in current sheets formed in heavy noble gases

    SciTech Connect

    Bogdanov, S. Yu.; Dreiden, G. V.; Markov, V. S.; Ostrovskaya, G. V.; Frank, A. G.

    2007-11-15

    Two-exposure holographic interferometry was used to study the structure of current sheets formed in three-dimensional magnetic configurations with a singular X line in heavy noble gases (Ar, Kr, and Xe). It is found that, in the presence of a longitudinal magnetic field B{sub Z} directed along the X line, plasma sheets take on an unusual shape: they are titled and asymmetric. Their asymmetry becomes more pronounced as the mass of a plasma ion increases-a manifestation of the two-fluid properties of the plasma. The observed effects can be attributed to additional forces arising due to the interaction of the longitudinal magnetic field B{sub Z} with Hall currents excited in a plane perpendicular to the X line. A qualitative model describing plasma dynamics with allowance for the Hall effect and accounting for most of the experimentally observed effects is proposed.

  6. Thermal and suprathermal protons and alpha particles in the earth's plasma sheet

    NASA Technical Reports Server (NTRS)

    Ipavich, F. M.; Scholer, M.

    1983-01-01

    Detailed proton energy spectra in the quasi-stable distant plasma sheet over the energy range from approximately 13 keV to approximately 130 keV are presented. These spectra are compared with spectra of simultaneously measured alpha particles in the energy range from approximately 30 keV/Q to approximately 130 keV/Q. The proton spectra are then extended into the higher energy range up to approximately 1 MeV, thereby supplementing the study of Sarris et al. (1981). The temporal behavior of the spectra in the higher energy range is discussed. It is found that below about 16 keV the proton spectra can be represented by a Maxwellian distribution; above this level, a suprathermal tail is found that cannot be represented by a single power law.

  7. Simulation of sheet-shaped lithium beam probe performance for two-dimensional edge plasma measurement

    SciTech Connect

    Tsuchiya, H.; Morisaki, T.; Komori, A.; Motojima, O.

    2006-10-15

    A sheet-shaped thermal lithium beam probe has been developed for two-dimensional density measurements in the edge region of the torus plasma. A numerical simulation was carried out to confirm the validity of the diagnostics for fast and transient phenomena such as edge localized modes or blobs, etc., where the velocity of blobs is faster than that of the probe beam. It was found in the simulation that the density of the blob itself is reconstructed to be low and unexpected ghosts appear in the reconstructed density profile near the blob, if the conventional reconstruction method is employed. These results invite our attention to the numerical errors in the density reconstruction process. On the other hand, the errors can be corrected by using the simulation results.

  8. Energy transport by kinetic-scale electromagnetic waves in fast plasma sheet flows

    NASA Astrophysics Data System (ADS)

    Chaston, C. C.; Bonnell, J. W.; Clausen, L.; Angelopoulos, V.

    2012-09-01

    We report observations from the THEMIS spacecraft characterizing the nature and importance of low frequency electromagnetic fluctuations on kinetic scales embedded within fast flows in the Earth's plasma sheet. A consideration of wave property variations with frequency and flow speed suggest that for spacecraft frame frequencies satisfying |vf|/ñi ≤ ùsc ≤ 100|vf|/ñi (or 0.2 ≲ fsc ≲ 20 Hz) these fluctuations can generally be described as kinetic Alfvén waves. Here vf is the flow speed, ñi the ion gyroradius, and ùsc and fsc are the angular and cyclical frequencies respectively in the spacecraft frame. The statistics of energy transport via Poynting flux (S) in these fluctuations and ion energy flux (å) in the flow follow log normal distributions with mean values of = 101.1 ± 0.7 and <ɛ> = 102.4 ± 0.4 mW/m2 respectively where the values are ‘mapped’ to a reference magnetic field at 100 km altitude. Here the indices following ‘ ± ’ correspond to one standard deviation. We find that = 10-1.3 ± 0.7 or that kinetic Alfvén waves on average transport ˜5% of the total energy transport in the flow but note that the values larger than 25% are within one standard deviation of the mean. Our observations show that these waves are continually radiated outward from the flow toward the auroral oval, low latitude boundary layer or lobes and that over several Earth-radii the integrated energy loss from the flow channel can be comparable to the total energy content of the flow itself. We find that this plasma sheet energy loss process is particularly effective within |XGSE| ≤ 15 RE.

  9. The 3 DLE instrument on ATS-5. [plasma electron counter

    NASA Technical Reports Server (NTRS)

    Deforest, S. E.

    1973-01-01

    The performance and operation of the DLE plasma electron counter on board the ATS 5 are described. Two methods of data presentation, microfilm line plots and spectrograms, are discussed along with plasma dynamics, plasma flow velocity, electrostatic charging, and wave-particle interactions.

  10. Vortices, Reconnection and Turbulence in High Electron-Beta Plasmas

    SciTech Connect

    Stenzel, R. L.

    2004-08-31

    Plasmas in which the kinetic energy exceeds the magnetic energy by a significant factor are common in space and in the laboratory. Such plasmas can convect magnetic fields and create null points in whose vicinity first the ions become unmagnetized, then the electrons. This project focuses on the detailed study of the transition regime of these plasmas.

  11. Vortex stabilized electron beam compressed fusion grade plasma

    SciTech Connect

    Hershcovitch, Ady

    2014-03-19

    Most inertial confinement fusion schemes are comprised of highly compressed dense plasmas. Those schemes involve short, extremely high power, short pulses of beams (lasers, particles) applied to lower density plasmas or solid pellets. An alternative approach could be to shoot an intense electron beam through very dense, atmospheric pressure, vortex stabilized plasma.

  12. Long-term variations in the plasma sheet ion composition and substorm occurrence over 23 years

    NASA Astrophysics Data System (ADS)

    Nosé, Masahito

    2016-12-01

    The Geotail satellite has been operating for almost two solar cycles (~23 years) since its launch in July 1992. The satellite carries the energetic particle and ion composition (EPIC) instrument that measures the energetic ion flux (9.4-212 keV/e) and enables the investigation of long-term variations of the ion composition in the plasma sheet for solar cycles 22-24. From the statistical analysis of the EPIC data, we find that (1) the plasma ion mass ( M) is approximately 1.1 amu during the solar minimum, whereas it increases to 1.5-2.7 amu during the solar maximum; (2) the increases in M seem to have two components: a raising of the baseline levels (~1.5 amu) and a large transient enhancement (~1.8-2.7 amu); (3) the baseline level change of M correlates well with the Mg II index, which is a good proxy for the solar extreme ultraviolet (EUV) or far ultraviolet (FUV) irradiance; and (4) the large transient enhancement of M is caused by strong magnetic storms. We also study the long-term variations of substorm occurrences in 1992-2015 that are evaluated with the number of Pi2 pulsations detected at the Kakioka observatory. The results suggest no clear correlation between the substorm occurrence and the Mg II index. Instead, when the substorms are classified into externally triggered events and non-triggered events, the number of the non-triggered events and the Mg II index are negatively correlated. We interpret these results that the increase in the solar EUV/FUV radiation enhances the supply of ionospheric ions (He+ and O+ ions) into the plasma sheet to increase M, and the large M may suppress spontaneous plasma instabilities initiating substorms and decrease the number of the non-triggered substorms. The present analysis using the unprecedentedly long-term dataset covering ~23 years provides additional observational evidence that heavy ions work to prevent the occurrence of substorms.

  13. ISEE-1 and 2 observations of magnetic flux ropes in the magnetotail: FTE's in the plasma sheet

    SciTech Connect

    Elphic, R.C.; Russel, C.T.; Cattell, C.A.; Takahashi, K.; Bame, S.J.

    1986-07-01

    Magnetic field observations on ISEE-1 and 2 in and near the neutral sheet about 20 Re down the near-Earth magnetotail reveal the occurrence of structures resembling magnetic flux ropes. Both electric field and fast plasma data show that these structures convect across the spacecraft at speeds of 200--600 km/s, and that they have scale sizes of roughly 3--5 Re. The rope axis orientation is across the tail, approximately in the -Y GSM direction. Their magnetic structure is strikingly similar to magnetic flux ropes observed in the Venus ionosphere, and to flux transfer events observed at the dayside magnetopause. The total field-aligned current within these ropes may approach a million amps. These structures may arise because of patchy reconnection within the plasma sheet, or may be tearing islands formed when the plasma sheet magnetic field has a cross-tail component. Plasma sheet flux ropes are not a common feature at ISEE orbital altitudes; this suggests that near-Earth neutral line formation within ISEE apogee (22 Re) may be equally rare.

  14. ISEE-1 and 2 observations of magnetic flux ropes in the magnetotail - FTE's in the plasma sheet?

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Russell, C. T.; Cattell, C. A.; Takahasi, K.; Bame, S. J.

    1986-01-01

    Magnetic field observations on ISEE-1 and 2 in and near the neutral sheet about 20 Re down the near-earth magnetotail reveal the occurrence of structures resembling magnetic flux ropes. Both electric field and fast plasma data show that these structures convect across the spacecraft at speeds of 200 - 600 km/s, and that they have scale sizes of roughly 3 5 Re. The rope axis orientation is across the tail, approximately in the -Y GSM direction. Their magnetic structure is strikingly similar to magnetic flux ropes observed in the Venus ionosphere, and to flux transfer events observed at the dayside magnetopause. The total field-aligned current within these ropes may approach a million amps. These structures may arise because of patchy reconnection within the plasma sheet, or may be tearing islands formed when the plasma sheet magnetic field has a cross-tail component. Plasma sheet flux ropes are not a common feature at ISEE orbital altitudes; this suggests that near-earth neutral line formation within ISEE apogee (22 Re) may be equally rare.

  15. Effects of nonthermal electrons on plasma expansion into vacuum

    SciTech Connect

    Bennaceur-Doumaz, D. Bara, D.; Benkhelifa, E.; Djebli, M.

    2015-01-28

    The expansion of semi-infinite plasma into vacuum is analyzed with a hydrodynamic model for cold ions assuming electrons modelled by a kappa-type distribution. Similarly to Mora study of a plasma expansion into vacuum [P. Mora, Phys. Rev. Lett. 90, 185002 (2003)], we formulated empirical expressions for the electric field strength, velocity, and position of the ion front in one-dimensional nonrelativistic, collisionless isothermally expanding plasma. Analytic expressions for the maximum ion energy and the spectrum of the accelerated ions in the plasma were derived and discussed to highlight the electron nonthermal effects on enhancing the ion acceleration in plasma expansion into vacuum.

  16. Pulse propagation and electron acceleration in a corrugated plasma channel.

    PubMed

    Palastro, J P; Antonsen, T M; Morshed, S; York, A G; Milchberg, H M

    2008-03-01

    A preformed plasma channel provides a guiding structure for laser pulses unbound by the intensity thresholds of standard waveguides. The recently realized corrugated plasma channel [Layer, Phys. Rev. Lett. 99, 035001 (2007)] allows for the guiding of laser pulses with subluminal spatial harmonics. These spatial harmonics can be phase matched to high energy electrons, making the corrugated plasma channel ideal for the acceleration of electrons. We present a simple analytic model of pulse propagation in a corrugated plasma channel and examine the laser-electron beam interaction. Simulations show accelerating gradients of several hundred MeV/cm for laser powers much lower than required by standard laser wakefield schemes. PMID:18517531

  17. Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Gallagher, D. L.

    1999-01-01

    The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies.

  18. Solitary waves in asymmetric electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Lu, Ding; Li, Zi-Liang; Xie, Bai-Song

    2015-10-01

    > By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron-positron plasma and/or electron-positron-ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions' mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron-positron plasmas and decrease also with ion concentration.

  19. Novel spin-electronic properties of BC{sub 7} sheets induced by strain

    SciTech Connect

    Xu, Lei; Dai, ZhenHong Sui, PengFei; Sun, YuMing; Wang, WeiTian

    2014-11-01

    Based on first-principles calculations, the authors have investigated the electronic and magnetic properties of BC{sub 7} sheets with different planar strains. It is found that metal–semiconductor transition appears at the biaxial strain of 15.5%, and the sheets are characteristic of spin-polarized semiconductor with a zero band-gap. The band-gap rapidly increases with strain, and reaches a maximum value of 0.60 eV at the strain of 20%. Subsequently, the band-gap decreases until the strain reaches up to 22% and shows a semiconductor-half metal transformation. It will further present metal properties until the strain is up to the maximum value of 35%. The magnetic moments also have some changes induced by biaxial strain. The numerical analysis shows that the two-dimensional distortions have great influences on the magnetic moments. The novel spin-electronic properties make BC{sub 7} sheets have potential applications in future spintronic nanodevices.

  20. Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source

    NASA Astrophysics Data System (ADS)

    Christy, Larry

    Field emission (FE) properties of carbon nanotube (CNT) fibers from Rice University and the University of Cambridge have been studied for use within a high current electron source for a directed energy weapon. Upon reviewing the performance of these two prevalent CNT fibers, cathodes were designed with CNT fibers from the University of Cincinnati Nanoworld Laboratory. Cathodes composed of a single CNT fiber, an array of three CNT fibers, and a nonwoven CNT sheet were investigated for FE properties; the goal was to design a cathode with emission current in excess of 10 mA. Once the design phase was complete, the cathode samples were fabricated, characterized, and then analyzed to determine FE properties. Electrical conductivity of the CNT fibers was characterized with a 4-probe technique. FE characteristics were measured in an ultra-high vacuum chamber at Wright-Patterson Air Force Base. The arrayed CNT fiber and the enhanced nonwoven CNT sheet emitter design demonstrated the most promising FE properties. Future work will include further analysis and cathode design using this nonwoven CNT sheet material to increase peak current performance during electron emission.

  1. Electron acceleration by a laser pulse in a plasma

    SciTech Connect

    McKinstrie, C.J.; Startsev, E.A.

    1996-08-01

    The acceleration of an electron by a circularly polarized laser pulse in a plasma is studied. It appears possible to increase significantly the energy of a preaccelerated electron. Although the pulse tends to generate a plasma wake, to which it loses energy, one can eliminate the wake by choosing the duration of the pulse judiciously. {copyright} {ital 1996 The American Physical Society.}

  2. Terahertz rectification by periodic two-dimensional electron plasma

    SciTech Connect

    Popov, V. V.; Saratov State University, Saratov 410012

    2013-06-24

    The physics of terahertz rectification by periodic two-dimensional electron plasma is discussed. Two different effects yielding terahertz rectification are studied: the plasmonic drag and plasmonic ratchet. Ultrahigh responsivity of terahertz rectification by periodic two-dimensional electron plasma in semiconductor heterostructures and graphene is predicted.

  3. Influence of the renormalization plasma screening on the electron-atom collision in partially ionized plasmas

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2012-02-13

    The renormalization plasma screening effects on the elastic electron-atom collision are investigated in partially ionized dense hydrogen plasmas using the eikonal method. It is found that the renormalization plasma screening suppresses the eikonal phase shift and cross section for the elastic electron-atom collision in partially ionized plasmas. It is also found that the renormalization plasma screening effect on the elastic electron-atom collision process increases with an increasing impact parameter. In addition, it is found that the maximum position of the differential cross section is receded from the center of the atom with an increase of the Debye length.

  4. Electron transfer from sulfate-reducing becteria biofilm promoted by reduced graphene sheets

    NASA Astrophysics Data System (ADS)

    Wan, Yi; Zhang, Dun; Wang, Yi; Wu, Jiajia

    2012-01-01

    Reduced graphene sheets (RGSs) mediate electron transfer between sulfate-reducing bacteria (SRB) and solid electrodes, and promote the development of microbial fuel cells (MFC). We have investigated RSG-promoted electron transfer between SRB and a glassy carbon (GC) electrode. The RGSs were produced at high yield by a chemical sequence involving graphite oxidation, ultrasonic exfoliation of nanosheets, and N2H4 reduction. Cyclic voltammetric testing showed that the characteristic anodic peaks (around 0.3 V) might arise from the combination of bacterial membrane surface cytochrome c3 and the metabolic products of SRB. After 6 d, another anodic wave gradually increased to a maximum current peak and a third anodic signal became visible at around 0 V. The enhancements of two characteristic anodic peaks suggest that RSGs mediate electron-transfer kinetics between bacteria and the solid electrode. Manipulation of these recently-discovered electron-transport mechanisms will lead to significant advances in MFC engineering.

  5. Paper-like electronic displays: Large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks

    PubMed Central

    Rogers, John A.; Bao, Zhenan; Baldwin, Kirk; Dodabalapur, Ananth; Crone, Brian; Raju, V. R.; Kuck, Valerie; Katz, Howard; Amundson, Karl; Ewing, Jay; Drzaic, Paul

    2001-01-01

    Electronic systems that use rugged lightweight plastics potentially offer attractive characteristics (low-cost processing, mechanical flexibility, large area coverage, etc.) that are not easily achieved with established silicon technologies. This paper summarizes work that demonstrates many of these characteristics in a realistic system: organic active matrix backplane circuits (256 transistors) for large (≈5 × 5-inch) mechanically flexible sheets of electronic paper, an emerging type of display. The success of this effort relies on new or improved processing techniques and materials for plastic electronics, including methods for (i) rubber stamping (microcontact printing) high-resolution (≈1 μm) circuits with low levels of defects and good registration over large areas, (ii) achieving low leakage with thin dielectrics deposited onto surfaces with relief, (iii) constructing high-performance organic transistors with bottom contact geometries, (iv) encapsulating these transistors, (v) depositing, in a repeatable way, organic semiconductors with uniform electrical characteristics over large areas, and (vi) low-temperature (≈100°C) annealing to increase the on/off ratios of the transistors and to improve the uniformity of their characteristics. The sophistication and flexibility of the patterning procedures, high level of integration on plastic substrates, large area coverage, and good performance of the transistors are all important features of this work. We successfully integrate these circuits with microencapsulated electrophoretic “inks” to form sheets of electronic paper. PMID:11320233

  6. Probing the electronic structure of graphene sheets with various thicknesses by scanning transmission X-ray microscopy

    SciTech Connect

    Bai, Lili; Liu, Jinyin; Zhao, Guanqi; Gao, Jing; Sun, Xuhui E-mail: jzhong@suda.edu.cn; Zhong, Jun E-mail: jzhong@suda.edu.cn

    2013-12-16

    The electronic structure of an aggregation of graphene sheets with various thicknesses was probed by scanning transmission X-ray microscopy. A uniform oxidation of the graphene sheets in the flat area was observed regardless of the thickness, while in the folded area the result could be strongly affected by the geometry. Moreover, thick parts of the aggregation showed strong angle-dependence to the incident X-ray, while thin parts showed less angle-dependence, which might be related to the surface wrinkles and ripples. The electronic structure differences due to the geometry and thickness suggest a complicated situation in the aggregation of graphene sheets.

  7. Electromagnetic solitons in degenerate relativistic electron-positron plasma

    NASA Astrophysics Data System (ADS)

    Berezhiani, V. I.; Shatashvili, N. L.; Tsintsadze, N. L.

    2015-06-01

    The existence of soliton-like electromagnetic (EM) distributions in a fully degenerate electron-positron plasma is studied applying relativistic hydrodynamic and Maxwell equations. For a circularly polarized wave it is found that the soliton solutions exist both in relativistic as well as nonrelativistic degenerate plasmas. Plasma density in the region of soliton pulse localization is reduced considerably. The possibility of plasma cavitation is also shown.

  8. Physics of laser-driven plasma-based electron accelerators

    SciTech Connect

    Esarey, E.; Schroeder, C. B.; Leemans, W. P.

    2009-07-15

    Laser-driven plasma-based accelerators, which are capable of supporting fields in excess of 100 GV/m, are reviewed. This includes the laser wakefield accelerator, the plasma beat wave accelerator, the self-modulated laser wakefield accelerator, plasma waves driven by multiple laser pulses, and highly nonlinear regimes. The properties of linear and nonlinear plasma waves are discussed, as well as electron acceleration in plasma waves. Methods for injecting and trapping plasma electrons in plasma waves are also discussed. Limits to the electron energy gain are summarized, including laser pulse diffraction, electron dephasing, laser pulse energy depletion, and beam loading limitations. The basic physics of laser pulse evolution in underdense plasmas is also reviewed. This includes the propagation, self-focusing, and guiding of laser pulses in uniform plasmas and with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Experiments demonstrating key physics, such as the production of high-quality electron bunches at energies of 0.1-1 GeV, are summarized.

  9. Experimental evidence of warm electron populations in magnetron sputtering plasmas

    SciTech Connect

    Sahu, B. B. Han, Jeon G.; Kim, Hye R.; Ishikawa, K.; Hori, M.

    2015-01-21

    This work report on the results obtained using the Langmuir probe (LP) measurements in high-power dc magnetron sputtering discharges. Data show clear evidence of two electron components, such as warm and bulk electrons, in the sputtering plasma in a magnetic trap. We have also used optical emission spectroscopy diagnostic method along with LP to investigate the plasma production. Data show that there is a presence of low-frequency oscillations in the 23?MHz range, which are expected to be generated by high-frequency waves. Analysis also suggests that the warm electrons, in the plasmas, can be formed due to the collisionless Landau damping of the bulk electrons.

  10. Electrostatic turbulence in the earth's central plasma sheet produced by multiple-ring ion distributions

    NASA Technical Reports Server (NTRS)

    Huba, J. D.; Chen, J.; Anderson, R. R.

    1992-01-01

    Attention is given to a mechanism to generate a broad spectrum of electrostatic turbulence in the quiet time central plasma sheet (CPS) plasma. It is shown theoretically that multiple-ring ion distributions can generate short-wavelength (less than about 1), electrostatic turbulence with frequencies less than about kVj, where Vj is the velocity of the jth ring. On the basis of a set of parameters from measurements made in the CPS, it is found that electrostatic turbulence can be generated with wavenumbers in the range of 0.02 and 1.0, with real frequencies in the range of 0 and 10, and with linear growth rates greater than 0.01 over a broad range of angles relative to the magnetic field (5-90 deg). These theoretical results are compared with wave data from ISEE 1 using an ion distribution function exhibiting multiple-ring structures observed at the same time. The theoretical results in the linear regime are found to be consistent with the wave data.

  11. Plasma response to electron energy filter in large volume plasma device

    NASA Astrophysics Data System (ADS)

    Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K.

    2013-12-01

    An electron energy filter (EEF) is embedded in the Large Volume Plasma Device plasma for carrying out studies on excitation of plasma turbulence by a gradient in electron temperature (ETG) described in the paper of Mattoo et al. [S. K. Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. In this paper, we report results on the response of the plasma to the EEF. It is shown that inhomogeneity in the magnetic field of the EEF switches on several physical phenomena resulting in plasma regions with different characteristics, including a plasma region free from energetic electrons, suitable for the study of ETG turbulence. Specifically, we report that localized structures of plasma density, potential, electron temperature, and plasma turbulence are excited in the EEF plasma. It is shown that structures of electron temperature and potential are created due to energy dependence of the electron transport in the filter region. On the other hand, although structure of plasma density has origin in the particle transport but two distinct steps of the density structure emerge from dominance of collisionality in the source-EEF region and of the Bohm diffusion in the EEF-target region. It is argued and experimental evidence is provided for existence of drift like flute Rayleigh-Taylor in the EEF plasma.

  12. Plasma response to electron energy filter in large volume plasma device

    SciTech Connect

    Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K.

    2013-12-15

    An electron energy filter (EEF) is embedded in the Large Volume Plasma Device plasma for carrying out studies on excitation of plasma turbulence by a gradient in electron temperature (ETG) described in the paper of Mattoo et al. [S. K. Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. In this paper, we report results on the response of the plasma to the EEF. It is shown that inhomogeneity in the magnetic field of the EEF switches on several physical phenomena resulting in plasma regions with different characteristics, including a plasma region free from energetic electrons, suitable for the study of ETG turbulence. Specifically, we report that localized structures of plasma density, potential, electron temperature, and plasma turbulence are excited in the EEF plasma. It is shown that structures of electron temperature and potential are created due to energy dependence of the electron transport in the filter region. On the other hand, although structure of plasma density has origin in the particle transport but two distinct steps of the density structure emerge from dominance of collisionality in the source-EEF region and of the Bohm diffusion in the EEF-target region. It is argued and experimental evidence is provided for existence of drift like flute Rayleigh-Taylor in the EEF plasma.

  13. Cold streams of ionospheric oxygen in the plasma sheet during the CDAW-6 event of March 22, 1979

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Amata, E.; Candidi, M.; Balsiger, H.; Stokholm, M.; Huang, C. Y.; Lennartsson, W.; Lindqvist, P. A.

    1983-01-01

    During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near Earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the Earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

  14. Comparative simulation studies of plasma cathode electron (PCE) gun

    NASA Astrophysics Data System (ADS)

    Prajapati, Jitendra; Pal, U. N.; Kumar, Niraj; Verma, D. K.; Prakash, Ram; Srivastava, V.

    2012-05-01

    Pseudospark discharge based plasma cathode has capability to provide high current density electron beam during discharge process. In this paper an effort has been made to simulate the breakdown processes in the pseudospark discharge based plasma cathode electron gun. The two-dimensional plasma simulation codes VORPAL and OOPIC-Pro have been used and results are compared. The peak discharge current in the plasma cathode electron gun is found to be dependent on aperture size, hollow cathode dimensions, anode voltage and seed electrons energy. The effect of these design parameters on the peak anode current has been analysed by both the codes and results matches well within 10% variation. For the seed electron generation an electron beam trigger source is used to control the discharge process in the hollow cathode cavity. The time span of trigger source has been varied from 1-100 ns to analyze the effect on the peak anode current.

  15. Dry etch damage in GaAs metal-semiconductor field-effect transistors exposed to inductively coupled plasma and electron cyclotron resonance Ar plasmas

    SciTech Connect

    Ren, F.; Lee, J.W.; Abernathy, C.R.; Pearton, S.J.; Constantine, C.; Barratt, C.; Shul, R.J.

    1997-07-01

    The effects of Ar plasma exposure on transconductance, channel sheet resistance, output resistance, and gate contact ideality factor of GaAs metal-semiconductor field-effect transistors (MESFETs) were investigated using two different high-density plasma sources, namely inductively coupled plasma and electron resonance plasma. Ion-induced damage is found to be reduced at moderate source powers ({approximately}200W) because of the reduction in cathode dc self-bias and hence ion energy, but at higher source powers the increase in ion flux produces significant deterioration of the device performance. Careful attention must be paid to both ion flux and ion energy in order to minimize ion-induced damage. Due to their relatively low channel doping levels, MESFETs are found to be more sensitive to plasma damage than devices with very heavily doped component layers such as heterojunction bipolar transistors. {copyright} {ital 1997 American Vacuum Society.}

  16. Nonlinear evolution of three-dimensional instabilities of thin and thick electron scale current sheets: Plasmoid formation and current filamentation

    SciTech Connect

    Jain, Neeraj; Büchner, Jörg

    2014-07-15

    Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =d{sub e}=c/ω{sub pe}), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ∼5 d{sub e}), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow.

  17. Determination of Plasma Electron Density from Optical Measurements

    NASA Astrophysics Data System (ADS)

    Neiswander, Brian; Matlis, Eric; Corke, Thomas

    2009-11-01

    Plasma has been shown to be effective in many flow control applications, but now may also find use in adaptive optics. Plasma's index of refraction is coupled with it's electron density which may be adjusted for adaptive control. An experimental setup to verify the relation between plasma electron density, pressure, and voltage is presented. A non-thermal DBD plasma cell is created by evacuating air and applying a voltage potential between two conducting glass slides. Plasma forms in the chamber between the glass and the applied voltage potential controls the electron density. A HeNe laser is passed through the plasma cell and then focused onto a duo-lateral position sensing device (PSD). The plasma cell is oriented at an angle to the laser's beam and so changes in the plasma's index of refraction produce lateral translations in the beam position. Differences in the PSD output with and without plasma provides for the calculation of the electron density averaged over the beam spot area. The data from this experiment will be used to further develop an adaptive plasma lens for wavefront aberration corrections.

  18. Public Data Set: Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup

    DOE Data Explorer

    Hinson, Edward T. [University of Wisconsin-Madison; Barr, Jayson L. [University of Wisconsin-Madison] (ORCID:0000000177685931); Bongard, Michael W. [University of Wisconsin-Madison] (ORCID:0000000231609746); Burke, Marcus G. [University of Wisconsin-Madison] (ORCID:0000000176193724); Fonck, Raymond J. [University of Wisconsin-Madison] (ORCID:0000000294386762); Perry, Justin M. [University of Wisconsin-Madison] (ORCID:0000000171228609)

    2016-05-12

    This data set contains openly-documented, machine readable digital research data corresponding to figures published in E.T. Hinson et al., 'Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup,' accepted for publication by Physics of Plasmas.

  19. Progress toward positron-electron pair plasma experiments

    NASA Astrophysics Data System (ADS)

    Stenson, E. V.; Saitoh, H.; Stanja, J.; Niemann, H.; Hergenhahn, U.; Pedersen, T. Sunn; Marx, G. H.; Schweikhard, L.; Danielson, J. R.; Surko, C. M.; Hugenschmidt, C.

    2015-06-01

    Electron-positron plasmas have been of theoretical interest for decades, due to the unique plasma physics that arises from all charged particles having precisely identical mass. It is only recently, though, that developments in non-neutral plasma physics (both in linear and toroidal geometries) and in the flux of sources for cold positrons have brought the goal of conducting electron-positron pair plasma experiments within reach. The APEX/PAX collaboration is working on a number of projects in parallel toward that goal; this paper provides an overview of recent, current, and upcoming activities.

  20. Multifunctional bulk plasma source based on discharge with electron injection.

    PubMed

    Klimov, A S; Medovnik, A V; Tyunkov, A V; Savkin, K P; Shandrikov, M V; Vizir, A V

    2013-01-01

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings. PMID:23387642

  1. Multifunctional bulk plasma source based on discharge with electron injection

    SciTech Connect

    Klimov, A. S.; Medovnik, A. V.; Tyunkov, A. V.; Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V.

    2013-01-15

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.

  2. Level shifts and inelastic electron scattering in dense plasmas

    NASA Technical Reports Server (NTRS)

    Davis, J.; Blaha, M.

    1982-01-01

    A completely quantum mechanical formalism has been developed to describe the high density plasma effects on fundamental atomic parameters. Both the bound and free electrons are treated by a method which in principle is similar to Hartree's self-consistent field method. The free plasma electrons' wavefunction is obtained from the Schroedinger equation with the effective potential representing the spherically averaged Coulomb interaction with bound and free electrons. Results are given for level shifts, coefficients of transition probabilities, and electron collision cross sections of Ne(9+) for temperatures of 200 and 500 eV for an electron density range of 1-6 x 10 to the 24th per cu cm.

  3. Electron acoustic shock waves in a collisional plasma.

    PubMed

    Dutta, Manjistha; Ghosh, Samiran; Chakrabarti, Nikhil

    2012-12-01

    A nonlinear analysis for the finite amplitude electron acoustic wave (EAW) is considered in a collisional plasma. The fluid model is used to describe the two-temperature electron species in a fixed ion background. In general, in electron-ion plasma, the presence of wave nonlinearity, dispersion, and dissipation (arising from fluid viscosity) give rise to the Korteweg-de Vries Burgers (KdVB) equation which exhibits shock wave. In this work, it is shown that the dissipation due to the collision between electron and ion in the presence of collective phenomena (plasma current) can also introduce an anomalous dissipation that causes the Burgers term and thus leads to the generation of electron acoustic shock wave. Both analytical and numerical analysis show the formation of transient shock wave. Relevance of the results are discussed in the context of space plasma. PMID:23368060

  4. Solitary and shock waves in magnetized electron-positron plasma

    SciTech Connect

    Lu, Ding; Li, Zi-Liang; Abdukerim, Nuriman; Xie, Bai-Song

    2014-02-15

    An Ohm's law for electron-positron (EP) plasma is obtained. In the framework of EP magnetohydrodynamics, we investigate nonrelativistic nonlinear waves' solutions in a magnetized EP plasma. In the collisionless limit, quasistationary propagating solitary wave structures for the magnetic field and the plasma density are obtained. It is found that the wave amplitude increases with the Mach number and the Alfvén speed. However, the dependence on the plasma temperature is just the opposite. Moreover, for a cold EP plasma, the existence range of the solitary waves depends only on the Alfvén speed. For a hot EP plasma, the existence range depends on the Alfvén speed as well as the plasma temperature. In the presence of collision, the electromagnetic fields and the plasma density can appear as oscillatory shock structures because of the dissipation caused by the collisions. As the collision frequency increases, the oscillatory shock structure becomes more and more monotonic.

  5. Potential applications of an electron cyclotron resonance multicusp plasma source

    SciTech Connect

    Tsai, C.C.; Berry, L.A.; Gorbatkin, S.M.; Haselton, H.H.; Roberto, J.B.; Stirling, W.L.

    1989-01-01

    An electron cyclotron resonance (ECR) multicusp plasmatron has been developed by feeding a multicusp bucket arc chamber with a compact ECR plasma source. This novel source produced large (about 25-cm-diam), uniform (to within {plus minus}10%), dense (>10{sup 11}-cm{sup -3}) plasmas of argon, helium, hydrogen, and oxygen. It has been operated to produce an oxygen plasma for etching 12.7-cm (5-in.) positive photoresist-coated silicon wafers with uniformity within {plus minus}8%. Results and potential applications of this new ECR plasma source for plasma processing of thin films are discussed. 21 refs., 10 figs.

  6. Association of an auroral surge with plasma sheet recovery and the retreat of the substorm neutral line

    SciTech Connect

    Hones, E.W. ); Elphinstone, R.; Murphree, J.S. . Dept. of Physics); Galvin, A.B. . Dept. of Space Physics); Heinemann, N.C. . Dept. of Physics); Parks, G.K. ); Rich, F.J. (Air Force Geophysics Lab., Hanscom AFB, MA

    1990-01-01

    One of the periods being studied in the PROMIS CDAW (CDAW-9) workshops is the interval 0000-1200 UT on May 3, 1986, designated Event 9C.'' A well-defined substorm, starting at 0919 UT, was imaged by both DE 1 over the southern hemisphere and Viking over the northern hemisphere. The images from Viking, at 80-second time resolution, showed a surge-like feature forming at about 0952 UT at the poleward edge of the late evening sector of the oval. The feature remained relatively stationary until about 1000 UT when it seemed to start advancing westward. ISEE 1 and 2 were closely conjugate to the surge as mapped from both the DMSP and Viking images. We conclude that the plasma sheet recovery was occasioned by the arrival at ISEE 1,2 of a westward traveling wave of plasma sheet thickening, the wave itself being formed by westward progression of the substorm neutral line's tailward retreat. The westward traveling surge was the auroral manifestation of this nonuniform retreat of the neutral line. We suggest that the upward field aligned current measured by DMSP F7 above the surge head was driven by plasma velocity shear in the plasma sheet at the duskward kink'' in the retreating neutral line. By analogy with this observation we propose that the westward traveling surges and the current wedge field aligned currents that characterize the expanding auroral bulge during substorm expansive phase are manifestations of (and are driven by) velocity shear in the plasma sheet near the ends of the extending substorm neutral line.

  7. Electron plasma wave propagation in external-electrode fluorescent lamps

    SciTech Connect

    Cho, Guangsup; Kim, Jung-Hyun; Jeong, Jong-Mun; Hong, Byoung-Hee; Koo, Je-Huan; Choi, Eun-Ha; Verboncoeur, John P.; Uhm, Han Sup

    2008-01-14

    The optical propagation observed along the positive column of external electrode fluorescent lamps is shown to be an electron plasma wave propagating with the electron thermal speed of (kT{sub e}/m){sup 1/2}. When the luminance of the lamp is 10 000-20 000 cd/m{sup 2}, the electron plasma temperature and the plasma density in the positive column are determined to be kT{sub e}{approx}1.26-2.12 eV and n{sub o}{approx}(1.28-1.69)x10{sup 17} m{sup -3}, respectively.

  8. Electron plasma oscillations associated with type 3 radio emissions and solar electrons

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Frank, L. A.

    1975-01-01

    An extensive study of the IMP-6 and IMP-8 plasma and radio wave data was performed to try to find electron plasma oscillations associated with type III radio noise bursts and low-energy solar electrons. It is shown that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare the electric field strength is relatively small. Electromagnetic radiation, believed to be similar to the type III radio emission, is observed coming from the region of the more intense electron plasma oscillations upstream. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation.

  9. Energy exchange in strongly coupled plasmas with electron drift

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.; Ghorbanalilu, M.

    2015-11-01

    In this paper, the generalized viscoelastic collisional quantum hydrodynamic model is employed in order to investigate the linear dielectric response of a quantum plasma in the presence of strong electron-beam plasma interactions. The generalized Chandrasekhar's relativistic degeneracy pressure together with the electron-exchange and Coulomb interaction effects are taken into account in order to extend current research to a wide range of plasma number density relevant to big planetary cores and astrophysical compact objects. The previously calculated shear viscosity and the electron-ion collision frequencies are used for strongly coupled ion fluid. The effect of the electron-beam velocity on complex linear dielectric function is found to be profound. This effect is clearly interpreted in terms of the wave-particle interactions and their energy-exchange according to the sign of the imaginary dielectric function, which is closely related to the wave attenuation coefficient in plasmas. Such kinetic effect is also shown to be in close connection with the stopping power of a charged-particle beam in a quantum plasma. The effect of many independent plasma parameters, such as the ion charge-state, electron beam-velocity, and relativistic degeneracy, is shown to be significant on the growing/damping of plasma instability or energy loss/gain of the electron-beam.

  10. Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

    SciTech Connect

    Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

    2009-08-11

    Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test and benchmark for a 2-D Harris current sheet against tearing mode and other instabilities in linear theories/models. More importantly, we have, for the first time, carried out simulation of linear instabilities in a 2-D Harris current sheet with a broad range of guide field BG and the realistic mi/me, and obtained important new results of current sheet instabilities in the presence of a finite BG. Indeed the code has accurately reproduced waves of interest here, such as kinetic Alfven waves, compressional Alfven/whistler wave, and lower-hybrid/modified two-stream waves. Moreover, this simulation scheme is capable of investigating collisionless kinetic physics relevant to magnetic reconnection in the fusion plasmas, in a global scale system for a long-time evolution and, thereby, produce significant new physics compared with both full-particle and hybrid codes. The results, with mi/me=1836 and moderate to large BG as in the real laboratory devices, have not been obtained in previous theory and simulations. The new simulation model will contribute significantly not only to the understanding of fundamental fusion (and space) plasma physics but also to DOE's SciDAC initiative by further pushing the frontiers of simulating realistic fusion plasmas.

  11. Relativistic electromagnetic waves in an electron-ion plasma

    NASA Technical Reports Server (NTRS)

    Chian, Abraham C.-L.; Kennel, Charles F.

    1987-01-01

    High power laser beams can drive plasma particles to relativistic energies. An accurate description of strong waves requires the inclusion of ion dynamics in the analysis. The equations governing the propagation of relativistic electromagnetic waves in a cold electron-ion plasma can be reduced to two equations expressing conservation of energy-momentum of the system. The two conservation constants are functions of the plasma stream velocity, the wave velocity, the wave amplitude, and the electron-ion mass ratio. The dynamic parameter, expressing electron-ion momentum conversation in the laboratory frame, can be regarded as an adjustable quantity, a suitable choice of which will yield self-consistent solutions when other plasma parameters were specified. Circularly polarized electromagnetic waves and electrostatic plasma waves are used as illustrations.

  12. Field electron emission characteristics of plasma treated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Koinkar, Pankaj M.; Yonekura, Daisuke; Murakami, Ri-Ichi; Moriga, Toshihiro; More, Mahendra A.

    2015-03-01

    This paper reports the effect of hydrogen (H2) plasma treatment on field emission property of double walled carbon nanotubes (DWCNTs) synthesized by using chemical vapor deposition method. The hydrogen plasma treatment was carried out for various duration. The DWCNTs films were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that the field emission properties of DWCNTs were influenced with increasing plasma treatment duration. The Raman spectra of samples clearly show structural defects after hydrogen plasma treatment. It is observed that the change in the field emission characteristics of DWCNTs is attributed to the structural defects due to the H2 plasma and depends on the plasma treatment duration.

  13. Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

    NASA Astrophysics Data System (ADS)

    Culfa, O.; Tallents, G. J.; Rossall, A. K.; Wagenaars, E.; Ridgers, C. P.; Murphy, C. D.; Dance, R. J.; Gray, R. J.; McKenna, P.; Brown, C. D. R.; James, S. F.; Hoarty, D. J.; Booth, N.; Robinson, A. P. L.; Lancaster, K. L.; Pikuz, S. A.; Faenov, A. Ya.; Kampfer, T.; Schulze, K. S.; Uschmann, I.; Woolsey, N. C.

    2016-04-01

    An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (1020W cm-2 ) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are evaluated. 2D EPOCH PIC code simulations are found to be in agreement with measurements of the electron energy spectra showing that laser filamentation in plasma preformed by a prepulse is important with longer plasma scale lengths (>8 μ m ).

  14. Cluster electric current density measurements within a magnetic flux rope in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.; Lepping, R. P.; Gjerloev, J.; Goldstein, M. L.; Fairfield, D. H.; Acuna, M. H.; Balogh, A.; Dunlop, M.; Kivelson, M. G.; Khurana, K.

    2003-01-01

    On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a magnetic flux rope in the tail. The flux rope encounter took place in the central plasma sheet, Beta(sub i) approx. 1-2, near the leading edge of a bursty bulk flow. The "time-of-flight" of the flux rope across the 4 spacecraft yielded V(sub x) approx. 700 km/s and a diameter of approx.1 R(sub e). The speed at which the flux rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The magnetic field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free flux rope model. The results indicated that the center of the flux rope passed northward (above) s/c 3, but southward (below) of s/c 1, 2 and 4. The peak electric currents along the central axis of the flux rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster magnetic field measurements provide a second means to determine the electric current density without any assumption regarding flux rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft magnetic field observations and yielded a peak current density of 17 nA/m2 near the central axis of the rope. However, the curlometer results also showed that the flux rope was not force-free with the component of the current density perpendicular to the magnetic field exceeding the parallel component over the forward half of the rope, perhaps due to the pressure gradients generated by the collision of the BBF with the inner magnetosphere. Hence, while the single-spacecraft models are very successful in fitting flux rope magnetic field and current variations, they do not provide a stringent test of the force-free condition.

  15. Modeling the Self-organized Critical Behavior of Earth's Plasma Sheet Reconnection Dynamics

    NASA Technical Reports Server (NTRS)

    Klimas, Alexander J.

    2006-01-01

    Analyses of Polar UVI auroral image data show that bright night-side high-latitude W emissions exhibit so many of the key properties of systems in self-organized criticality that an alternate interpretation has become virtually impossible. These analyses will be reviewed. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the magnetotail plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques (and more) that have been applied to the auroral image data have also been applied to this Poynting flux. New results will be presented showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. A strong correlation between these key properties of the model and those of the auroral UV emissions will be demonstrated. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

  16. Modeling the Self-organized Critical Behavior of the Plasma Sheet Reconnection Dynamics

    NASA Technical Reports Server (NTRS)

    Klimas, Alex; Uritsky, Vadim; Baker, Daniel

    2006-01-01

    Analyses of Polar UVI auroral image data reviewed in our other presentation at this meeting (V. Uritsky, A. Klimas) show that bright night-side high-latitude UV emissions exhibit so many of the key properties of systems in self-organized criticality (SOC) that an alternate interpretation has become virtually impossible. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques, and more, that have been applied to the auroral image data have also been applied to this Poynting flux. Here, we report new results showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. Further, we find a strong correlation between these key properties of the model and those of the auroral UV emissions. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

  17. Quantum tunneling resonant electron transfer process in Lorentzian plasmas

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2014-08-15

    The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed.

  18. Acceleration of electrons in strong beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1984-01-01

    The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

  19. Electron beam transport analysis of W-band sheet beam klystron

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Xun; Barnett, Larry R.; Luhmann, Neville C.; Shin, Young-Min; Humphries, Stanley

    2010-04-01

    The formation and transport of high-current density electron beams are of critical importance for the success of a number of millimeter wave and terahertz vacuum devices. To elucidate design issues and constraints, the electron gun and periodically cusped magnet stack of the original Stanford Linear Accelerator Center designed W-band sheet beam klystron circuit, which exhibited poor beam transmission (≤55%), have been carefully investigated through theoretical and numerical analyses taking advantage of three-dimensional particle tracking solvers. The re-designed transport system is predicted to exhibit 99.76% (cold) and 97.38% (thermal) beam transmission, respectively, under space-charge-limited emission simulations. The optimized design produces the required high aspect ratio (10:1) sheet beam with 3.2 A emission current with highly stable propagation. In the completely redesigned model containing all the circuit elements, more than 99% beam transmission is experimentally observed at the collector located about 160 mm distant from the cathode surface. Results are in agreement of the predictions of two ray-tracing simulators, CST PARTICLE STUDIO and OMNITRAK which also predict the observed poor transmission in the original design. The quantitative analysis presents practical factors in the modeling process to design a magnetic lens structure to stably transport the elliptical beam along the long drift tube.

  20. Electron backscatter diffraction applied to lithium sheets prepared by broad ion beam milling.

    PubMed

    Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

    2015-01-01

    Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be <50 nm. Despite the fact that the IM process generates an increase of temperature at the specimen surface, it was assumed that the milling parameters were sufficient to minimize the heating effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. PMID:25280344

  1. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  2. Effect of Time Dependent Bending of Current Sheets in Response to Generation of Plasma Jets and Reverse Currents

    NASA Astrophysics Data System (ADS)

    Frank, Anna

    Magnetic reconnection is a basis for many impulsive phenomena in space and laboratory plasmas accompanied by effective transformation of magnetic energy. Reconnection processes usually occur in relatively thin current sheets (CSs), which separate magnetic fields of different or opposite directions. We report on recent observations of time dependent bending of CSs, which results from plasma dynamics inside the sheet. The experiments are carried out with the CS-3D laboratory device (Institute of General Physics RAS, Moscow) [1]. The CS magnetic structure with an X line provides excitation of the Hall currents and plasma acceleration from the X line to both side edges [2]. In the presence of the guide field By the Hall currents give rise to bending of the sheet: the peripheral regions located away from the X line are deflected from CS middle plane (z=0) in the opposite directions ±z [3]. We have revealed generation of reverse currents jy near the CS edges, i.e. the currents flowing in the opposite direction to the main current in the sheet [4]. There are strong grounds to believe that reverse currents are generated by the outflow plasma jets [5], accelerated inside the sheet and penetrated into the regions with strong normal magnetic field component Bz [4]. An impressive effect of sudden change in the sign of the CS bend has been disclosed recently, when analyzing distributions of plasma density [6] and current away from the X line, in the presence of the guide field By. The CS configuration suddenly becomes opposite from that observed at the initial stage, and this effect correlates well with generation of reverse currents. Consequently this effect can be related to excitation of the reverse Hall currents owing to generation of reverse currents jy in the CS. Hence it may be concluded that CSs may exhibit time dependent vertical z-displacements, and the sheet geometry depends on excitation of the Hall currents, acceleration of plasma jets and generation of reverse currents. The work was supported in part by the Program (OFN-15) “Plasma Processes in Space and Laboratory” of the Division of Physical Sciences of the Russian Academy of Sciences. 1. Frank A.G., Bogdanov S.Yu., Markov V.S. et al. // Phys. Plasmas 2005. 12, 052316(1-11). 2. Frank A.G., Bugrov S.G., Markov V.S. // Phys. Plasmas 2008. 15, 092102 (1-10). 3. Frank A.G., Bogdanov S.Yu., Dreiden G.V. et al. // Phys. Lett. A 2006. 348, 318-325. 4. Frank A.G., Kyrie N.P., Satunin S.N. // Phys. Plasmas 2011. 18, 111209 (1-9). 5. Kyrie N.P., Markov V.S., Frank A.G. // Plasma Phys. Reports 2010. 36, 357-364; JETP Lett. 2012. 95, 14-19. 6. Ostrovskaya G.V., Frank A.G. // Plasma Phys. Reports 2014. 40, 21-33.

  3. Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions

    NASA Technical Reports Server (NTRS)

    Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.

    2011-01-01

    The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+ -to -H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+ -to -H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+ -to -H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near ]Earth region rather than through the distant tail.

  4. Field-aligned current signatures in the near-tail region. I - ISEE observations in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Ohtani, S.; Kokubun, S.; Elphic, R. C.; Russell, C. T.

    1988-01-01

    Field-aligned currents in the near-tail region are examined using ISEE magnetometer data. Two substorms (the 1054 UT and the 1436 UT substorms on March 22, 1979) were examined, demonstrating the consistency of the current polarity and intensity with observations at lower altitudes, which suggests that field-aligned currents in the plasma sheet boundary layer are parts of the large-scale current system, the region-1 system. An examination of the steplike changes of the magnetic field direction, which correspond to the spacecraft crossing of a net field-aligned current, showed that the field-aligned currents in the plasma sheet boundary layer have the same polarity as the region-1 system.

  5. Controlling electron injection in laser plasma accelerators using multiple pulses

    SciTech Connect

    Matlis, N. H.; Geddes, C. G. R.; Plateau, G. R.; Esarey, E.; Schroeder, C.; Bruhwiler, D.; Cormier-Michel, E.; Chen, M.; Yu, L.; Leemans, W. P.

    2012-12-21

    Use of counter-propagating pulses to control electron injection in laser-plasma accelerators promises to be an important ingredient in the development of stable devices. We discuss the colliding pulse scheme and associated diagnostics.

  6. Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas

    SciTech Connect

    V. I. Geyko; Fraiman, G. M.; Dodin, I. Y.; Fisch, N. J.

    2009-02-01

    The oscillation-center Hamiltonian is derived for a relativistic electron injected with an arbitrary momentum in a linearly polarized laser pulse propagating in tenuous plasma, assuming that the pulse length is smaller than the plasma wavelength. For hot electrons generated at collisions with ions under intense laser drive, multiple regimes of ponderomotive acceleration are identified and the laser dispersion is shown to affect the process at plasma densities down to 1017 cm-3. Assuming a/Υg << 1, which prevents net acceleration of the cold plasma, it is also shown that the normalized energy Υ of hot electrons accelerated from the initial energy Υo < , Γ does not exceed Γ ~ aΥg, where a is the normalized laser field, and Υg is the group velocity Lorentz factor. Yet Υ ~ Γ is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted.

  7. Recent measurements of electron density profiles of plasmas in PLADIS I, a plasma disruption simulator

    SciTech Connect

    Bradley, J. III; Sharp, G.; Gahl, J.M. Kuznetsov, V.; Rockett, P.; Hunter, J.

    1995-12-31

    Tokamak disruption simulation experiments are being conducted at the University of New Mexico (UNM) using the PLADIS I plasma gun system. PLADIS I is a high power, high energy coaxial plasma gun configured to produce an intense plasma beam. First wall candidate materials are placed in the beam path to determine their response under disruption relevant energy densities. An optically thick vapor shield plasma has been observed to form above the target surface in PLADIS I. Various diagnostics have been used to determine the characteristics of the incident plasma and the vapor shielding plasma. The cross sectional area of the incident plasma beam is a critical characteristic, as it is used in the calculation of the incident plasma energy density. Recently, a HeNe interferometer in the Mach-Zehnder configuration has been constructed and used to probe the electron density of the incident plasma beam and vapor shield plasma. The object beam of the interferometer is scanned across the plasma beam on successive shots, yielding line integrals of beam density on different chords through the plasma. Data from the interferometer is used to determine the electron density profile of the incident plasma beam as a function of beam radius. This data is then used to calculate the effective beam area. Estimates. of beam area, obtained from other diagnostics such as damage targets, calorimeter arrays and off-axis measurements of surface pressure, will be compared with data from the interferometer to obtain a better estimate of the beam cross sectional area.

  8. Alfvenic Solitons in Ultrarelativistic Electron-Position Plasmas

    NASA Technical Reports Server (NTRS)

    Verheest, G. S. Lakhina F.

    1997-01-01

    In electron-positron plasmas some of the plasma modes are decoupled due to the equal charge-to-mass ratio of both species. We derive the dispersion law for a low-frequency, generalized X-mode, which exists at all angles of propagation with respect to the static magnetic field.

  9. Negative plasma potential relative to electron-emitting surfaces.

    PubMed

    Campanell, M D

    2013-09-01

    Most works on plasma-wall interaction predict that with strong electron emission, a nonmonotonic "space-charge-limited" (SCL) sheath forms where the plasma potential is positive relative to the wall. We show that a fundamentally different sheath structure is possible where the potential monotonically increases toward a positively charged wall that is shielded by a single layer of negative charge. No ion-accelerating presheath exists in the plasma and the ion wall flux is zero. An analytical solution of the "inverse sheath" regime is demonstrated for a general plasma-wall system where the plasma electrons and emitted electrons are Maxwellian with different temperatures. Implications of the inverse sheath effect are that (a) the plasma potential is negative, (b) ion sputtering vanishes, (c) no charge is lost at the wall, and (d) the electron energy flux is thermal. To test empirically what type of sheath structure forms under strong emission, a full plasma bounded by strongly emitting walls is simulated. It is found that inverse sheaths form at the walls and ions are confined in the plasma. This result differs from past particle-in-cell simulation studies of emission which contain an artificial "source sheath" that accelerates ions to the wall, leading to a SCL sheath at high emission intensity. PMID:24125367

  10. Electron-hole plasma generation in gallium nitride

    NASA Astrophysics Data System (ADS)

    Cingolani, R.; Ferrara, M.; Lugarà, M.

    1986-12-01

    The electron-hole plasma has been studied in both epitaxial and needle GaN. The threshold and the stability of the plasma are also discussed. The observed different behaviour of the samples we studied is interpreted in terms of growth technique.

  11. Structural Stability and Electronic Structures of a Curved Graphene Sheet on Stepped SiC(0001) Surface

    NASA Astrophysics Data System (ADS)

    Ono, Youky; Nara, Jun; Ohno, Takahisa

    2016-03-01

    The structural stabilities and electronic structures of graphene sheets laid on stepped SiC(0001) surfaces are theoretically investigated by density functional theory calculations. To precisely estimate the van der Waals (vdW) binding energy between graphene sheets and SiC surfaces, the vdW density functional (vdW-DF) was used. We have found that a graphene sheet put over a stepped SiC surface has a curved structure bridging the upper and lower terraces without making any bonds to the atoms of the step. This bridging curved structure of the graphene sheet is mainly stabilized by the vdW attraction force. With respect to the electronic structure, the original sp2 network is maintained in the curved graphene sheet. By comparing the local density of states (LDOS) of carbon atoms in the curved graphene sheet, we also found that the electronic structure of each carbon atom largely depends on the distance between the carbon atom and the surface.

  12. The Role of Self-Organized Criticality in the Substorm Phenomenon and its Relation to Localized Reconnection in the Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Klimas, A. J.; Vassiliadis, D.; Valdivia, J. A.; Baker, D. N.; Hesse, M.

    1999-01-01

    Recent observations of the magnetotail plasma sheet have shown it to be a dynamic and turbulent region. Research has found strong turbulence in the plasma sheet at approximately 20 Earth's Radius tailward of Earth; the turbulence is observed at all activity levels. The existence of strong turbulence in the plasma sheet in the region associated with substorm onset might be thought difficult to reconcile with the coherence and repeatability of the substorm cycle. We review a variety of evidence that strongly suggests the magnetotail is driven, through magnetic flux transfer, into a state of "self-organized criticality" (SOC). It is an important property of physical systems that evolve into SOC that they self-organize into a unique, global dynamic state. This global state is inevitable, and repeatable. In this state, however, small-spatiotemporal-scale system fluctuations are unpredictable and can be only described statistically. This is the basis, we think, for the global coherence and repeatability of the substorm phenomenon in the turbulent plasma sheet. At, or near, substorm onset the plasma sheet can be described by a global SOC state containing significant small scale turbulence. In several recent studies, "sandpile" models were driven into SOC and then shown to reproduce various measures of substorm activity. We discuss the plasma physical foundation of these sandpile models. The evolution of simple continuum plasma sheet models into SOC-like states of many small reconnection events in the turbulent plasma sheet under the will be demonstrated. We view the substorm phenomenon as an avalanche assumption that the plasma sheet is in a SOC state.

  13. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  14. Properties of Trapped Electron Bunches in a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neil; /SLAC

    2009-10-30

    Plasma-based accelerators use the propagation of a drive bunch through plasma to create large electric fields. Recent plasma wakefield accelerator (PWFA) experiments, carried out at the Stanford Linear Accelerator Center (SLAC), successfully doubled the energy for some of the 42 GeV drive bunch electrons in less than a meter; this feat would have required 3 km in the SLAC linac. This dissertation covers one phenomenon associated with the PWFA, electron trapping. Recently it was shown that PWFAs, operated in the nonlinear bubble regime, can trap electrons that are released by ionization inside the plasma wake and accelerate them to high energies. These trapped electrons occupy and can degrade the accelerating portion of the plasma wake, so it is important to understand their origins and how to remove them. Here, the onset of electron trapping is connected to the drive bunch properties. Additionally, the trapped electron bunches are observed with normalized transverse emittance divided by peak current, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/kA. A theoretical model of the trapped electron emittance, developed here, indicates that the emittance scales inversely with the square root of the plasma density in the non-linear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m and multi-kA peak currents. These properties make the trapped electrons a possible particle source for next generation light sources. This dissertation is organized as follows. The first chapter is an overview of the PWFA, which includes a review of the accelerating and focusing fields and a survey of the remaining issues for a plasma-based particle collider. Then, the second chapter examines the physics of electron trapping in the PWFA. The third chapter uses theory and simulations to analyze the properties of the trapped electron bunches. Chapters four and five present the experimental diagnostics and measurements for the trapped electrons. Next, the sixth chapter introduces suggestions for future trapped electron experiments. Then, Chapter seven contains the conclusions. In addition, there is an appendix chapter that covers a topic which is extraneous to electron trapping, but relevant to the PWFA. This chapter explores the feasibility of one idea for the production of a hollow channel plasma, which if produced could solve some of the remaining issues for a plasma-based collider.

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

    NASA Technical Reports Server (NTRS)

    Mallavarpu, R.; Roth, J. R.

    1978-01-01

    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.

  16. Bulk and shear viscosities of the two-dimensional electron liquid in a doped graphene sheet

    NASA Astrophysics Data System (ADS)

    Principi, Alessandro; Vignale, Giovanni; Carrega, Matteo; Polini, Marco

    2016-03-01

    Hydrodynamic flow occurs in an electron liquid when the mean free path for electron-electron collisions is the shortest length scale in the problem. In this regime, transport is described by the Navier-Stokes equation, which contains two fundamental parameters, the bulk and shear viscosities. In this paper, we present extensive results for these transport coefficients in the case of the two-dimensional massless Dirac fermion liquid in a doped graphene sheet. Our approach relies on microscopic calculations of the viscosities up to second order in the strength of electron-electron interactions and in the high-frequency limit, where perturbation theory is applicable. We then use simple interpolation formulas that allow to reach the low-frequency hydrodynamic regime where perturbation theory is no longer directly applicable. The key ingredient for the interpolation formulas is the "viscosity transport time" τv, which we calculate in this paper. The transverse nature of the excitations contributing to τv leads to the suppression of scattering events with small momentum transfer, which are inherently longitudinal. Therefore, contrary to the quasiparticle lifetime, which goes as -1 /[T2ln(T /TF) ] , in the low-temperature limit we find τv˜1 /T2 .

  17. Electron Beam Transport in Advanced Plasma Wave Accelerators

    SciTech Connect

    Williams, Ronald L

    2013-01-31

    The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams were generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.

  18. Measuring ionospheric electron density using the plasma frequency probe

    SciTech Connect

    Jensen, M.D.; Baker, K.D. )

    1992-02-01

    During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

  19. Initiation of Ballooning Instability by Reconnection in Near-Earth Plasma Sheet: Analysis of a THEMIS Event

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Raeder, J.; Bhattacharjee, A.; Germaschewski, K.; Hegna, C. C.

    2008-05-01

    This study explores the scenario in which a robust ballooning instability is initiated from its linear stage by reconnection process in the near-Earth plasma sheet leading to a substorm onset. Previous analyses based on the near-tail configurations obtained from 2D Hall MHD simulations of substorm onset process found that the near-tail region becomes most ballooning unstable in the so-called impulsive growth phase. Recently, we analyzed the ballooning properties of the near-Earth plasma sheet in the presence of magnetospheric convection during the March 23, 2007 THEMIS substorm event. Using the solar wind data from WIND observations for the substorm event as an input at dayside in OpenGGCM simulations, we have reconstructed a sequence of global magnetospheric configurations around substorm onset, matching closely the observation in terms of onset timing. An approximate local dispersion relation for ballooning instability in the presence of flow is evaluated for the tail region when the configuration attains quasi steady-state conditions. Our analysis of the near-Earth tail region evolution during this substorm event starts to reveal the correlation between the breaching of the ballooning stability condition and the substorm onset, in both time and location. The analysis also indicates that the magnetospheric convection appears to have little direct effect on the ballooning instability itself; rather it plays a profound role by engaging the interaction between reconnection and ballooning instability in the plasma sheet. Research supported by U.S. NSF Grant No. ATM-0542954.

  20. Hybrid Simulation of Laser-Plasma Interactions and Fast Electron Transport in Inhomogeneous Plasma

    SciTech Connect

    Cohen, B I; Kemp, A; Divol, L

    2009-05-27

    A new framework is introduced for kinetic simulation of laser-plasma interactions in an inhomogenous plasma motivated by the goal of performing integrated kinetic simulations of fast-ignition laser fusion. The algorithm addresses the propagation and absorption of an intense electromagnetic wave in an ionized plasma leading to the generation and transport of an energetic electron component. The energetic electrons propagate farther into the plasma to much higher densities where Coulomb collisions become important. The high-density plasma supports an energetic electron current, return currents, self-consistent electric fields associated with maintaining quasi-neutrality, and self-consistent magnetic fields due to the currents. Collisions of the electrons and ions are calculated accurately to track the energetic electrons and model their interactions with the background plasma. Up to a density well above critical density, where the laser electromagnetic field is evanescent, Maxwell's equations are solved with a conventional particle-based, finite-difference scheme. In the higher-density plasma, Maxwell's equations are solved using an Ohm's law neglecting the inertia of the background electrons with the option of omitting the displacement current in Ampere's law. Particle equations of motion with binary collisions are solved for all electrons and ions throughout the system using weighted particles to resolve the density gradient efficiently. The algorithm is analyzed and demonstrated in simulation examples. The simulation scheme introduced here achieves significantly improved efficiencies.

  1. Simulation of laser-plasma interactions and fast-electron transport in inhomogeneous plasma

    SciTech Connect

    Cohen, B.I. Kemp, A.J.; Divol, L.

    2010-06-20

    A new framework is introduced for kinetic simulation of laser-plasma interactions in an inhomogeneous plasma motivated by the goal of performing integrated kinetic simulations of fast-ignition laser fusion. The algorithm addresses the propagation and absorption of an intense electromagnetic wave in an ionized plasma leading to the generation and transport of an energetic electron component. The energetic electrons propagate farther into the plasma to much higher densities where Coulomb collisions become important. The high-density plasma supports an energetic electron current, return currents, self-consistent electric fields associated with maintaining quasi-neutrality, and self-consistent magnetic fields due to the currents. Collisions of the electrons and ions are calculated accurately to track the energetic electrons and model their interactions with the background plasma. Up to a density well above critical density, where the laser electromagnetic field is evanescent, Maxwell's equations are solved with a conventional particle-based, finite-difference scheme. In the higher-density plasma, Maxwell's equations are solved using an Ohm's law neglecting the inertia of the background electrons with the option of omitting the displacement current in Ampere's law. Particle equations of motion with binary collisions are solved for all electrons and ions throughout the system using weighted particles to resolve the density gradient efficiently. The algorithm is analyzed and demonstrated in simulation examples. The simulation scheme introduced here achieves significantly improved efficiencies.

  2. Transition of electron kinetics in weakly magnetized inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Kim, Young-Cheol; Chung, Chin-Wook

    2013-10-01

    Transition of the electron kinetics from nonlocal to local regime was studied in weakly magnetized solenoidal inductively coupled plasma from the measurement of the electron energy probability function (EEPF). Without DC magnetic field, the discharge property was governed by nonlocal electron kinetics at low gas pressure. The electron temperatures were almost same in radial position, and the EEPFs in total electron energy scale were radially coincided. However, when the DC magnetic field was applied, radial non-coincidence of the EEPFs in total electron energy scale was observed. The electrons were cooled at the discharge center where the electron heating is absent, while the electron temperature was rarely changed at the discharge boundary with the magnetic field. These changes show the transition from nonlocal to local electron kinetics and the transition is occurred when the electron gyration diameter was smaller than the skin depth. The nonlocal to local transition point almost coincided with the calculation results by using nonlocal parameter and collision parameter.

  3. Nonlocal collisionless and collisional electron transport in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor

    2009-10-01

    The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and A. Smolyakov, Phys. Plasmas 14, 057104 (2007). [0pt] [3] V.I. Demidov, C.A. DeJoseph, and A.A. Kudryavtsev, Phys. Rev. Lett. 95, 215002 (2005); V.I. Demidov, C.A. DeJoseph, J. Blessington, and M.E. Koepke, Europhysics News, 38, 21 (2007).

  4. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  5. Plasma parameters and electron energy distribution functions in a magnetically focused plasma

    SciTech Connect

    Samuell, C. M.; Blackwell, B. D.; Howard, J.; Corr, C. S.

    2013-03-15

    Spatially resolved measurements of ion density, electron temperature, floating potential, and the electron energy distribution function (EEDF) are presented for a magnetically focused plasma. The measurements identify a central plasma column displaying Maxwellian EEDFs at an electron temperature of about 5 eV indicating the presence of a significant fraction of electrons in the inelastic energy range (energies above 15 eV). It is observed that the EEDF remains Maxwellian along the axis of the discharge with an increase in density, at constant electron temperature, observed in the region of highest magnetic field strength. Both electron density and temperature decrease at the plasma radial edge. Electron temperature isotherms measured in the downstream region are found to coincide with the magnetic field lines.

  6. Secondary-electrons-induced cathode plasma in a relativistic magnetron

    SciTech Connect

    Queller, T.; Gleizer, J. Z.; Krasik, Ya. E.

    2012-11-19

    Results of time- and space-resolved spectroscopic studies of cathode plasma during a S-band relativistic magnetron operation and a magnetically insulated diode having an identical interelectrode gap are presented. It was shown that in the case of the magnetron operation, one obtains an earlier, more uniform plasma formation due to energetic electrons' interaction with the cathode surface and ionization of desorbed surface monolayers. No differences were detected in the cathode's plasma temperature between the magnetron and the magnetically insulated diode operation, and no anomalous fast cathode plasma expansion was observed in the magnetron at rf power up to 350 MW.

  7. Thermal conduction by electrons in hot dense plasmas

    SciTech Connect

    Khalfaoui, A.H.; Bennaceur, D.

    1997-03-01

    Based on a quantum collective approach, electron conduction opacity is analyzed, taking into account several nonideality effects such as electron-electron (e-e) collisions in addition to electron-ion collisions, dynamic shielding, electron partial degeneracy, and ion coupling. The collision process is based on electron wave functions interacting with the continuum oscillations (plasma waves). The e-e collisions, the main nonideal effect, contribute to the thermal conductivity calculation in the intermediate coupling regime. Hence, the extensively used Lorentz gas approximation cannot be justified for plasma of astrophysical interest. The present results are compared to existing theories of electron conduction in stellar matter. {copyright} {ital 1997} {ital The American Astronomical Society}

  8. Measurements of beat wave accelerated electrons in a toroidal plasma

    SciTech Connect

    Rogers, J.H.; Hwang, D.W. |

    1992-06-01

    Electrons are accelerated by large amplitude electron plasma waves driven by counter-propagating microwaves with a difference frequency approximately equal to the electron plasma frequency. Energetic electrons are observed only when the phase velocity of the wave is in the range 3v{sub e} < v{sub ph} < 7v{sub e} (v{sub ph} was varied 2v{sub e} < v{sub ph} < 10v{sub e}), where v{sub e} is the electron thermal velocity, (kT{sub e}/m{sub e}){sup {1/2}}. As the phase velocity increases, fewer electrons are accelerated to higher velocities. The measured current contained in these accelerated electrons has the power dependence predicted by theory, but the magnitude is lower than predicted.

  9. Hydrated Electrons at the Plasma-Water Interface

    NASA Astrophysics Data System (ADS)

    Graves, David; Gopalakrishnan, Ranga; Kawamura, Emi; Lieberman, Michael

    2015-09-01

    When atmospheric pressure plasma interacts with liquid water surfaces, complex processes involving both charged and neutral species generally occur but the details of the processes are not well understood. One plasma-generated specie of considerable interest that can enter an adjacent liquid water phase is the electron. Hydrated electrons are well known to be important in radiation chemistry as initiating precursors for a variety of other reactive compounds. Recent experimental evidence for hydrated electrons near the atmospheric pressure plasma-water interface was reported by Rumbach et al.. We present results from a model of a dc argon plasma coupled to an anodic adjacent water layer that aims to simulate this experiment. The coupled plasma-electrolyte model illustrates the nature of the plasma-water interface and reveals important information regarding the self-consistent electric fields on each side of the interface as well as time- and space-resolved rates of reaction of key reactive species. We suggest that the reducing chemistry that results from electron hydration may be useful therapeutically in countering local excess oxidative stress. Supported by the Department of Energy, Office of Fusion Science Plasma Science Center

  10. Electron plasma oscillations associated with type III radio emissions and solar electrons

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Frank, L. A.

    1975-01-01

    Results of an extensive search for electron plasma oscillations associated with type III radio noise bursts are presented which were obtained by analyzing 87 type III bursts detected in plasma-wave and charged-particle measurements carried out by IMP 6, 7, and 8. Only one case is found for which plasma oscillations were associated with electrons of solar origin; at least eight events are identified in which no plasma oscillations were detected even though electrons from solar flares were clearly evident. The type III emissions are compared with similar radiation coming from upstream of earth's bow shock at the harmonic of the local electron plasma frequency, and quantitative calculations of the rate of conversion from plasma oscillatory energy to electromagnetic radiation are performed. The results show that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU and that neither the type III emissions nor the radiation from upstream of the bow shock can be adequately explained by a current model for the coupling of electron plasma oscillations to electromagnetic radiation. Several possible explanations are considered for this discrepancy between theory and observations.

  11. Non-thermal plasma mills bacteria: Scanning electron microscopy observations

    NASA Astrophysics Data System (ADS)

    Lunov, O.; Churpita, O.; Zablotskii, V.; Deyneka, I. G.; Meshkovskii, I. K.; Jäger, A.; Syková, E.; Kubinová, Š.; Dejneka, A.

    2015-02-01

    Non-thermal plasmas hold great promise for a variety of biomedical applications. To ensure safe clinical application of plasma, a rigorous analysis of plasma-induced effects on cell functions is required. Yet mechanisms of bacteria deactivation by non-thermal plasma remain largely unknown. We therefore analyzed the influence of low-temperature atmospheric plasma on Gram-positive and Gram-negative bacteria. Using scanning electron microscopy, we demonstrate that both Gram-positive and Gram-negative bacteria strains in a minute were completely destroyed by helium plasma. In contrast, mesenchymal stem cells (MSCs) were not affected by the same treatment. Furthermore, histopathological analysis of hematoxylin and eosin-stained rat skin sections from plasma-treated animals did not reveal any abnormalities in comparison to control ones. We discuss possible physical mechanisms leading to the shred of bacteria under non-thermal plasma irradiation. Our findings disclose how helium plasma destroys bacteria and demonstrates the safe use of plasma treatment for MSCs and skin cells, highlighting the favorability of plasma applications for chronic wound therapy.

  12. External Control of Electron Temperature in Ultra-Cold Plasmas

    NASA Astrophysics Data System (ADS)

    Wilson, Roy O.; Tate, Duncan A.

    2008-03-01

    We discuss our progress towards achieving external control of the electron temperature and the Coulomb coupling parameter of ultra-cold plasmas. Using a Littman dye laser, we create the plasma by partially photoionizing a dense, cold sample of rubidium atoms in a magneto-optical trap (MOT). At a controllable time delay, we excite neutral atoms in the plasma to a specific Rydberg state using a narrow bandwidth pulsed laser. We have made very qualitative measurements of the electron temperature as a function of delay from the exciting laser pulses. Some of our results suggest that the plasma is stabilized by the presence of the Rydberg atoms, with a longer lifetime and slower expansion rate than a plasma that evolves directly from a dense Rydberg sample.

  13. Formation and evolution of high-plasma-pressure region in the near-Earth plasma sheet: Precursor and postcursor of substorm expansion onset

    NASA Astrophysics Data System (ADS)

    Yao, Y.; Ebihara, Y.; Tanaka, T.

    2015-08-01

    Cause of substorm expansion onset is one of the major problems in the magnetospheric study. On the basis of a global magnetohydrodynamic (MHD) simulation, Tanaka et al. (2010) suggested that formation and evolution of a high-pressure region (HPR) in the near-Earth plasma sheet could result in sudden intensification of the Region 1 field-aligned current and the westward auroral electrojet. In this sense, the formation and evolution of the HPR are a key in understanding the cause of the onset. On 5 April 2009, three probes of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) were located at XGSM~-11 Re around the equator, which provide unique opportunity to investigate the spatial-temporal evolution of the HPR near the substorm expansion onset. Just before the onset, a positive excursion of the plasma pressure appeared at the outermost probe first, followed by the inner ones. Just after the onset, the opposite sequence took place. A positive excursion of the Y component of the current density was observed near the onset by the THEMIS probes and followed by a decrease trend. A similar variation was also found in the MHD simulation. All these features are consistent with the simulation result that a squeeze of the plasma from the plasma sheet results in the formation of the HPR before the onset and that the accumulated plasma spreads outward after the onset. The HPR is shown to be important for the dynamics of the magnetosphere during a substorm.

  14. Ionization-Induced Electron Trapping inUltrarelativistic Plasma Wakes

    SciTech Connect

    Oz, E.; Deng, S.; Katsouleas, T.; Muggli, P.; Barnes, C.D.; Blumenfeld, I.; Decker, F.J.; Emma, P.; Hogan, M.J.; Ischebeck, R.; Iverson, R.H.; Kirby, N.; Krejcik, P.; O'Connell, C.; Siemann, R.H.; Walz, D.; Auerbach, D.; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; /UCLA

    2007-04-06

    The onset of trapping of electrons born inside a highly relativistic, 3D beam-driven plasma wake is investigated. Trapping occurs in the transition regions of a Li plasma confined by He gas. Li plasma electrons support the wake, and higher ionization potential He atoms are ionized as the beam is focused by Li ions and can be trapped. As the wake amplitude is increased, the onset of trapping is observed. Some electrons gain up to 7.6 GeV in a 30.5 cm plasma. The experimentally inferred trapping threshold is at a wake amplitude of 36 GV/m, in good agreement with an analytical model and PIC simulations.

  15. Effect of secondary electron emission on the plasma sheath

    SciTech Connect

    Langendorf, S. Walker, M.

    2015-03-15

    In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 10{sup 12} m{sup −3} at a pressure of 10{sup −4} Torr-Ar, with a 1%–16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (∼1 T{sub e}), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

  16. Electron energy distributions in a magnetized inductively coupled plasma

    SciTech Connect

    Song, Sang-Heon E-mail: Sang-Heon.Song@us.tel.com; Yang, Yang; Kushner, Mark J.

    2014-09-15

    Optimizing and controlling electron energy distributions (EEDs) is a continuing goal in plasma materials processing as EEDs determine the rate coefficients for electron impact processes. There are many strategies to customize EEDs in low pressure inductively coupled plasmas (ICPs), for example, pulsing and choice of frequency, to produce the desired plasma properties. Recent experiments have shown that EEDs in low pressure ICPs can be manipulated through the use of static magnetic fields of sufficient magnitudes to magnetize the electrons and confine them to the electromagnetic skin depth. The EED is then a function of the local magnetic field as opposed to having non-local properties in the absence of the magnetic field. In this paper, EEDs in a magnetized inductively coupled plasma (mICP) sustained in Ar are discussed with results from a two-dimensional plasma hydrodynamics model. Results are compared with experimental measurements. We found that the character of the EED transitions from non-local to local with application of the static magnetic field. The reduction in cross-field mobility increases local electron heating in the skin depth and decreases the transport of these hot electrons to larger radii. The tail of the EED is therefore enhanced in the skin depth and depressed at large radii. Plasmas densities are non-monotonic with increasing pressure with the external magnetic field due to transitions between local and non-local kinetics.

  17. Kinetic Alfven wave in the presence of kappa distribution function in plasma sheet boundary layer

    SciTech Connect

    Shrivastava, G. Ahirwar, G.; Shrivastava, J.

    2015-07-31

    The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of kinetic Alfven wave. Expressions are found for the dispersion relation, damping/growth rate and associated currents in the presence of kappa distribution function. Kinetic effect of electrons and ions are included to study kinetic Alfven wave because both are important in the transition region. It is found that the ratio β of electron thermal energy density to magnetic field energy density and the ratio of ion to electron thermal temperature (T{sub i}/T{sub e}), and kappa distribution function affect the dispersion relation, damping/growth rate and associated currents in both cases(warm and cold electron limit).The treatment of kinetic Alfven wave instability is based on assumption that the plasma consist of resonant and non resonant particles. The resonant particles participate in an energy exchange process, whereas the non resonant particles support the oscillatory motion of the wave.

  18. Numerical model of the plasma formation at electron beam welding

    SciTech Connect

    Trushnikov, D. N.; Mladenov, G. M.

    2015-01-07

    The model of plasma formation in the keyhole in liquid metal as well as above the electron beam welding zone is described. The model is based on solution of two equations for the density of electrons and the mean electron energy. The mass transfer of heavy plasma particles (neutral atoms, excited atoms, and ions) is taken into account in the analysis by the diffusion equation for a multicomponent mixture. The electrostatic field is calculated using the Poisson equation. Thermionic electron emission is calculated for the keyhole wall. The ionization intensity of the vapors due to beam electrons and high-energy secondary and backscattered electrons is calibrated using the plasma parameters when there is no polarized collector electrode above the welding zone. The calculated data are in good agreement with experimental data. Results for the plasma parameters for excitation of a non-independent discharge are given. It is shown that there is a need to take into account the effect of a strong electric field near the keyhole walls on electron emission (the Schottky effect) in the calculation of the current for a non-independent discharge (hot cathode gas discharge). The calculated electron drift velocities are much bigger than the velocity at which current instabilities arise. This confirms the hypothesis for ion-acoustic instabilities, observed experimentally in previous research.

  19. A reflex electron beam discharge as a plasma source for electron beam generation

    SciTech Connect

    Murray, C.S.; Rocca, J.J.; Szapiro, B. )

    1988-10-01

    A reflex electron beam glow discharge has been used as a plasma source for the generation of broad-area electron beams. An electron current of 120 A (12 A/cm/sup 2/) was extracted from the plasma in 10 ..mu..s pulses and accelerated to energies greater than 1 keV in the gap between two grids. The scaling of the scheme for the generation of multikiloamp high-energy beams is discussed.

  20. Revisiting plasma hysteresis with an electronically compensated Langmuir probe.

    PubMed

    Srivastava, P K; Singh, S K; Awasthi, L M; Mattoo, S K

    2012-09-01

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 μA, allowing plasma measurements to be done with ion saturation current of the order of hundreds of μA. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of ≤45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as δT(pk-pk) changes by ~30%. The developed technique with swept rate ≤100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering ≤50 kHz. PMID:23020373

  1. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, Donald; Esarey, Eric; Kim, Joon K.

    1997-01-01

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

  2. Revisiting plasma hysteresis with an electronically compensated Langmuir probe

    SciTech Connect

    Srivastava, P. K.; Singh, S. K.; Awasthi, L. M.; Mattoo, S. K.

    2012-09-15

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 {mu}A, allowing plasma measurements to be done with ion saturation current of the order of hundreds of {mu}A. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of {<=}45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as {delta}T{sub pk-pk} changes by {approx}30%. The developed technique with swept rate {<=}100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering {<=}50 kHz.

  3. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, D.; Esarey, E.; Kim, J.K.

    1997-06-10

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

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

    NASA Technical Reports Server (NTRS)

    Mallavarpu, R.; Roth, J. R.

    1978-01-01

    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.

  5. Theory and Simulations of Auroral Undulations Associated with Instabilities in the Dusk Sector Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Perez, J. C.; Horton, W.; Lewis, W. S.; Burch, J.; Goldstein, J.; Frey, H.; Anderson, P.

    2005-12-01

    Ion drift wave theory and simulations of large-scale auroral undulations are presented for the observations in Lewis et al (2005). These undulations are identified as a nonlinear stage of the drift balloning-interchange mode in the presence of a sheared E×B flow for high Richardson's number in the dusk sector of the plasma sheet. The system is ideal MHD stable. Theoretical density, temperature and pressure profiles are constructed and constrained from data and used as input for a 2-1/2 D nonlinear Chebyshev-Fourier-tau pseudospectral code which reproduces the undulation structure to a good degree. Undulations were observed on February 6, 2002 along the equatorward edge of the auroral oval with the Far-Ultraviolet Wideband Imaging Camera on NASA's IMAGE satellite during the recovery phase of a moderate magnetic storm. The undulations occurred in the 18.5-14.5 magnetic local time sector between 63° and 71° magnetic latitude. Their wavelength and crest-to-base length averaged 292~km and 224~km, respectively; and they propagated westward with an average speed of 0.90±0.06~km/s. Such undulations are a relatively uncommon auroral phenomenon, and the mechanism that produce them and the magnetospheric conditions under which they occur are not well understood. Work supported by the National Science Foundation. [1] W.~S. Lewis, J.~L. Burch, J. Goldstein, W. Horton, J.~C. Perez, H.~U. Frey and P.~C. Anderson, submitted to GRL (2005).

  6. A high current density plasma cathode electron gun

    SciTech Connect

    Fu Wenjie; Yan Yang; Li Wenxu; Li Xiaoyun; Wu Jianqiang

    2010-02-15

    The design, performance, and characteristics of a plasma cathode electron gun are presented. The plasma cathode is based on a hollow cathode direct current discharge, and the electron beam is accelerated by pulse voltage. By discharging at high gas pressure and operating at low gas pressure, both the maximum accelerating voltage and maximum emitting current could be increased. Utilizing argon, with the accelerating voltage up to 9 kV and gas pressure down to 52 mPa, the gun is able to generate an electron beam of about 4.7 A, and the corresponding emitting current density is about 600 A/cm{sup 2}.

  7. Kinetic description of electron plasma waves with orbital angular momentum

    SciTech Connect

    Mendonca, J. T.

    2012-11-15

    We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.

  8. Suprathermal electrons produced by beam-plasma-discharge

    NASA Technical Reports Server (NTRS)

    Sharp, W. E.

    1982-01-01

    Experiments conducted with a low energy plasma lens, HARP, in the electron beam of the large vacuum chamber at Johnson Space Center indicate that an enhanced population of 50 to 300 volt electrons appear when the beam goes into the Beam-Plasma Discharge (BPD) mode. Below the BPD instability the electron distribution appears to be characterized as non-energized single particle scattering and energy loss. At 100 cm from the beam core in the BPD mode the fluxes parallel to the beam are reduced by a factor of 20 with respect to the fluxes at 25 cm. Some evidence for isotropy near the beam core is presented.

  9. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    NASA Astrophysics Data System (ADS)

    Sydorenko, Dmytro

    2015-11-01

    Electrons emitted by electrodes surrounding or immersed in the plasma are accelerated by the sheath electric field and become electron beams penetrating the plasma. In plasma applications where controlling the electron velocity distribution function (EVDF) is crucial, these beams are an important factor capable of modifying the EVDF and affecting the discharge properties. Recently, it was reported that an EVDF measured in a dc-rf discharge with 800 V dc voltage has not only a peak of 800 eV electrons emitted from the dc-biased electrode, but also a peak of suprathermal electrons with energy up to several hundred eV. Initial explanation of the suprathermal peak suggested that the fast long plasma waves excited by the beam decay parametrically into ion acoustic waves and short plasma waves with much lower phase velocity which accelerate bulk electrons to suprathermal energies. Particle-in-cell simulation of a dc beam-plasma system, however, reveals that the short waves appear not due to the parametric instability, but due to the plasma nonuniformity. Moreover, the acceleration may occur in two stages. Plasma waves excited by the beam in the middle of the system propagate towards the anode and enter the density gradient area where their wavelength and phase speed rapidly decrease. Acceleration of thermal electrons by these waves is the first stage. Some of the accelerated electrons reflect from the anode sheath, travel through the plasma, reflect near the cathode, and enter the accelerating area again but with the energy higher than before. The acceleration that occurs now is the second stage. The energy of a particle after the second acceleration exceeds the initial thermal energy by an order of magnitude. This two-stage mechanism plays a role in explaining previous observations of energetic suprathermal electrons in similar discharges. The study is performed in collaboration with I. D. Kaganovich (PPPL), P. L. G. Ventzek and L. Chen (Tokyo Electron America).

  10. Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 2. Hall dynamics, mass and momentum transfer

    NASA Astrophysics Data System (ADS)

    Savin, S.; Amata, E.; Andre, M.; Dunlop, M.; Khotyaintsev, Y.; Decreau, P. M. E.; Rauch, J. L.; Trotignon, J. G.; Buechner, J.; Nikutowski, B.; Blecki, J.; Skalsky, A.; Romanov, S.; Zelenyi, L.; Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Song, P.; Reme, H.; Volosevich, A.; Alleyne, H.; Panov, E.

    2006-08-01

    Proceeding with the analysis of Amata et al. (2005), we suggest that the general feature for the local transport at a thin magnetopause (MP) consists of the penetration of ions from the magnetosheath with gyroradius larger than the MP width, and that, in crossing it, the transverse potential difference at the thin current sheet (TCS) is acquired by these ions, providing a field-particle energy exchange without parallel electric fields. It is suggested that a part of the surface charge is self-consistently produced by deflection of ions in the course of inertial drift in the non-uniform electric field at MP. Consideration of the partial moments of ions with different energies demonstrates that the protons having gyroradii of roughly the same size or larger than the MP width carry fluxes normal to MP that are about 20% of the total flow in the plasma jet under MP. This is close to the excess of the ion transverse velocity over the cross-field drift speed in the plasma flow just inside MP (Amata et al., 2005), which conforms to the contribution of the finite-gyroradius inflow across MP. A linkage through the TCS between different plasmas results from the momentum conservation of the higher-energy ions. If the finite-gyroradius penetration occurs along the MP over ~1.5 RE from the observation site, then it can completely account for the formation of the jet under the MP. To provide the downstream acceleration of the flow near the MP via the cross-field drift, the weak magnetic field is suggested to rotate from its nearly parallel direction to the unperturbed flow toward being almost perpendicular to the accelerated flow near the MP. We discuss a deceleration of the higher-energy ions in the MP normal direction due to the interaction with finite-scale electric field bursts in the magnetosheath flow frame, equivalent to collisions, providing a charge separation. These effective collisions, with a nonlinear frequency proxy of the order of the proton cyclotron one, in extended turbulent zones are a promising alternative in place of the usual parallel electric fields invoked in the macro-reconnection scenarios. Further cascading towards electron scales is supposed to be due to unstable parallel electron currents, which neutralize the potential differences, either resulted from the ion- burst interactions or from the inertial drift. The complicated MP shape suggests its systematic velocity departure from the local normal towards the average one, inferring domination for the MP movement of the non-local processes over the small-scale local ones. The measured Poynting vector indicates energy transmission from the MP into the upstream region with the waves triggering impulsive downstream flows, providing an input into the local flow balance and the outward movement of the MP. Equating the transverse electric field inside the MP TCS by the Hall term in the Ohm's law implies a separation of the different plasmas primarily by the Hall current, driven by the respective part of the TCS surface charge. The Hall dynamics of TCS can operate either without or as a part of a macro-reconnection with the magnetic field annihilation.

  11. Electron trapping and acceleration across a parabolic plasma density profile.

    PubMed

    Kim, J U; Hafz, N; Suk, H

    2004-02-01

    It is known that as a laser wakefield passes through a downward density transition in a plasma some portion of the background electrons are trapped in the laser wakefield and the trapped electrons are accelerated to relativistic high energies over a very short distance. In this study, by using a two-dimensional (2D) particle-in-cell (PIC) simulation, we suggest an experimental scheme that can manipulate electron trapping and acceleration across a parabolic plasma density channel, which is easier to produce and more feasible to apply to the laser wakefield acceleration experiments. In this study, 2D PIC simulation results for the physical characteristics of the electron bunches that are emitted from the parabolic density plasma channel are reported in great detail. PMID:14995568

  12. Electron temperature and density measurements of laser induced germanium plasma

    NASA Astrophysics Data System (ADS)

    Shakeel, Hira; Arshad, Saboohi; Haq, S. U.; Nadeem, Ali

    2016-05-01

    The germanium plasma produced by the fundamental harmonics (1064 nm) of Nd:YAG laser in single and double pulse configurations have been studied spectroscopically. The plasma is characterized by measuring the electron temperature using the Boltzmann plot method for neutral and ionized species and electron number density as a function of laser irradiance, ambient pressure, and distance from the target surface. It is observed that the plasma parameters have an increasing trend with laser irradiance (9-33 GW/cm2) and with ambient pressure (8-250 mbar). However, a decreasing trend is observed along the plume length up to 4.5 mm. The electron temperature and electron number density are also determined using a double pulse configuration, and their behavior at fixed energy ratio and different interpulse delays is discussed.

  13. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3 Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  14. Bremsstrahlung neutrinos from electron-electron scattering in a relativistic degenerate electron plasma

    SciTech Connect

    Jaikumar, Prashanth; Gale, Charles; Page, Dany

    2005-12-15

    We present a calculation of neutrino pair bremsstrahlung due to electron-electron scattering in a relativistic degenerate plasma of electrons. Proper treatment of the in-medium photon propagator, i.e., inclusion of Debye screening of the longitudinal part and Landau damping of the transverse part, leads to a neutrino emissivity which is several orders of magnitude larger than when Debye screening is imposed for the tranverse part. Our results show that this in-medium process can compete with other sources of neutrino radiation and can, in some cases, even be the dominant neutrino emission mechanism. We also discuss the natural extension to quark-quark bremsstrahlung in gapped and ungapped quark matter.

  15. Modulating electronic, magnetic and chemical properties of MoS2 monolayer sheets by substitutional doping with transition metals

    NASA Astrophysics Data System (ADS)

    Ma, Dongwei; Ju, Weiwei; Li, Tingxian; Zhang, Xiwei; He, Chaozheng; Ma, Benyuan; Tang, Yanan; Lu, Zhansheng; Yang, Zongxian

    2016-02-01

    Based on first-principles calculations, the effects of substitutional doping with transition-metal (TM) atoms (Co, Ni, Ru, Rh, Pd, Ir, Pt and Au) were investigated on the electronic structure, magnetic property and chemical activity of the molybdenum disulfide (MoS2) monolayer sheet. It is found that all the considered TM atoms are strongly bonded to the sulfur defects. The magnetic properties of MoS2 monolayer sheets can be modulated by embedding TM atoms. The introduced spin magnetic moments are 1.00, 1.00, 1.00, 0.99, and 2.00μB, respectively, for Ir, Rh, Co, Au and Ru doping. The electronic properties of MoS2 monolayer sheets are also significantly changed due to the induced impurity states in the band gap. The chemical activity of the TM-doped MoS2 monolayer sheet (TM-MoS2) is significantly enhanced compared with the undoped sheet. Most TM-MoS2 can strongly adsorb and thus effectively activate the adsorbed O2. It is proposed that the partially occupied d orbitals of the doped TM atoms localized in the vicinity of the Fermi level play a crucial role in adsorbing and activating the adsorbed O2. The adsorption of O2 can in turn modify the electronic structures and magnetic properties of TM-MoS2.

  16. Non-thermal plasma mills bacteria: Scanning electron microscopy observations

    SciTech Connect

    Lunov, O. Churpita, O.; Zablotskii, V.; Jäger, A.; Dejneka, A.; Deyneka, I. G.; Meshkovskii, I. K.; Syková, E.; Kubinová, Š.

    2015-02-02

    Non-thermal plasmas hold great promise for a variety of biomedical applications. To ensure safe clinical application of plasma, a rigorous analysis of plasma-induced effects on cell functions is required. Yet mechanisms of bacteria deactivation by non-thermal plasma remain largely unknown. We therefore analyzed the influence of low-temperature atmospheric plasma on Gram-positive and Gram-negative bacteria. Using scanning electron microscopy, we demonstrate that both Gram-positive and Gram-negative bacteria strains in a minute were completely destroyed by helium plasma. In contrast, mesenchymal stem cells (MSCs) were not affected by the same treatment. Furthermore, histopathological analysis of hematoxylin and eosin–stained rat skin sections from plasma–treated animals did not reveal any abnormalities in comparison to control ones. We discuss possible physical mechanisms leading to the shred of bacteria under non-thermal plasma irradiation. Our findings disclose how helium plasma destroys bacteria and demonstrates the safe use of plasma treatment for MSCs and skin cells, highlighting the favorability of plasma applications for chronic wound therapy.

  17. dc-plasma-sprayed electronic-tube device

    DOEpatents

    Meek, T.T.

    1982-01-29

    An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  18. Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas

    SciTech Connect

    Kim, Young-Cheol; Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook

    2013-05-15

    A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing.

  19. Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas.

    PubMed

    Kim, Young-Cheol; Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook

    2013-05-01

    A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing. PMID:23742549

  20. Plasma-wall interaction in an electrostatic sheath of plasma containing a monoenergetic electron beam

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Zhao, Xiaoyun; Gan, Chunyun

    2016-04-01

    The plasma-wall interaction in the presence of a monoenergetic electron beam has been studied by taking into account the self-consistency among plasma transport in a collisionless electrostatic sheath, deposited energy flux at the wall and material thermal response for carbon and tungsten as wall materials. The variations of the potential drop across the sheath, ion velocity at the sheath edge, and surface temperature of material as a function of electron beam flux are explored in the presence of the electron emission. It is found that when electron beam does not dominate the sheath, potential drop across the sheath depends strongly on the material properties due to the impact of electron emission while the surface temperature of material shows monotonic variation. In the case of carbon wall, the electron beam may dominate the sheath at a certain electron beam concentration or energy. Under this circumstance, both the potential drop across the sheath and surface temperature of material demonstrate the sharp increasing transition. The development of local hot spot on the plasma facing material is caused by the enhanced ion energy flux instead of the electron beam energy flux. If the electron emission is not taken into account, as a smaller electron beam flux, both the potential drop across the sheath and surface temperature of material display the significant change and then it may be easier to develop for the local hot spot on the plasma facing material.

  1. Proton Beam Tests of an Electron Plasma Target

    NASA Astrophysics Data System (ADS)

    Pollock, R.; Stoller, D.; Sarrazine, A.; Gerberich, H.; Sloan, T.

    1996-11-01

    Stored protons of 45 MeV striking a non-neutral electron plasma have shown the stability of a beam-target system. The plasma had a length of 0.5 m, with 10^10 electrons maintained in a steady state by torque from a rotating electric quadrupole field and thermal energy from a noise source. A plasma temperature of a few eV allowed ionization of background gas to regulate electron number. Proton beam currents up to 0.2 mA were used, either coasting (no time structure) or bunched (rf cavity and electron cooling) to form narrow pulses. Coasting beam was observed to heat the electron plasma consistent with energy transfer via particle collisions, limiting the luminosity to about 10^24cm-2s-1, useful for atomic physics research. A higher trap B field with radiation cooling would raise this limit. Bunched beam gave extra heating, which varied with plasma length, indicating a resonance of a standing density wave with a harmonic of the 1.03 MHz orbit frequency. Increased radial transport was observed after exposure to the proton beam, probably caused by patchy-charge deposits on trap surfaces, and alleviated by raising the wall temperature.

  2. Effects of Electron Emission on Plasma-Surface Interaction

    NASA Astrophysics Data System (ADS)

    Campanell, Michael; Wang, Hongyue; Khrabrov, Alexander; Kaganovich, Igor

    2013-10-01

    Most models of sheaths facing emitting surfaces invoke assumptions that the sheath is time-independent, the wall potential is negative, ions enter the sheath at Bohm velocity, the presheath is weakly affected, and one wall is considered. We present theory and PIC simulations showing that these assumptions can break down in practice. When emission is strong, the sheath potential can become positive, repelling ions from the wall. Emitted electrons entering the plasma can drastically affect the presheath structure too. If their mean-free-path is large, emitted electrons can transit the plasma and impact the opposite wall; hence wall charging becomes a complex global problem. Secondary emission can trigger sheath instabilities preventing plasma-wall systems from reaching steady state. Implications are discussed for tokamaks, Hall thrusters, dusty plasmas, hot cathodes, RF discharges and spacecraft. This work was supported by the U.S. DOE under contract no. DE-AC02-09CH11466, and by AFOSR.

  3. Terahertz spectroscopy of plasma waves in high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Nouvel, P.; Marinchio, H.; Torres, J.; Palermo, C.; Gasquet, D.; Chusseau, L.; Varani, L.; Shiktorov, P.; Starikov, E.; Gruinskis, V.

    2009-07-01

    We report on systematic measurements of resonant plasma waves oscillations in several gate-length InGaAs high electron mobility transistors (HEMTs) and compare them with numerical results from a specially developed model. A great concern of experiments has been to ensure that HEMTs were not subject to any spurious electronic oscillation that may interfere with the desired plasma-wave spectroscopy excited via a terahertz optical beating. The influence of geometrical HEMTs parameters as well as biasing conditions is then explored extensively owing to many different devices. Plasma resonances up to the terahertz are observed. A numerical approach, based on hydrodynamic equations coupled to a pseudo-two-dimensional Poisson solver, has been developed and is shown to render accurately from experiments. Using a combination of experimental results and numerical simulations all at once, a comprehensive spectroscopy of plasma waves in HEMTs is provided with a deep insight into the physical processes that are involved.

  4. Decays of electron Bernstein waves near plasma edge

    SciTech Connect

    Xiang Nong; Cary, John R.

    2011-12-15

    Nonlinear wave-wave couplings near the upper hybrid resonance are studied via particle-in-cell simulations. It is found that the decay of an electron Bernstein wave (EBW) depends on the ratio of the incident frequency and electron cyclotron frequency. For ratios less than two, parametric decay into a lower hybrid wave (or an ion Bernstein wave) and EBWs at a lower frequency is observed. For ratios larger than two, the daughter waves could be an electron cyclotron quasi-mode and another EBW or an ion wave and EBW. For sufficiently high incident power, the former process may dominate. Because of the electron cyclotron quasi-mode, electrons can be strongly heated by nonlinear Landau damping. As a result, the bulk of the incident power can be absorbed near plasma edge at high power. The increase in number of decay channels with frequency implies that the allowable power into the plasma must decrease with frequency.

  5. Plasma properties in electron-bombardment ion thrusters

    SciTech Connect

    Matossian, J.N.; Beattie, J.R.

    1987-05-01

    The paper describes a technique for computing volume-averaged plasma properties within electron-bombardment ion thrusters, using spatially varying Langmuir-probe measurements. Average values of the electron densities are defined by integrating the spatially varying Maxwellian and primary electron densities over the ionization volume, and then dividing by the volume. Plasma properties obtained in the 30-cm-diameter J-series and ring-cusp thrusters are analyzed by the volume-averaging technique. The superior performance exhibited by the ring-cusp thruster is correlated with a higher average Maxwellian electron temperature. The ring-cusp thruster maintains the same fraction of primary electrons as does the J-series thruster, but at a much lower ion production cost. The volume-averaged predictions for both thrusters are compared with those of a detailed thruster performance model. 20 references.

  6. Plasma properties in electron-bombardment ion thrusters

    NASA Technical Reports Server (NTRS)

    Matossian, J. N.; Beattie, J. R.

    1987-01-01

    The paper describes a technique for computing volume-averaged plasma properties within electron-bombardment ion thrusters, using spatially varying Langmuir-probe measurements. Average values of the electron densities are defined by integrating the spatially varying Maxwellian and primary electron densities over the ionization volume, and then dividing by the volume. Plasma properties obtained in the 30-cm-diameter J-series and ring-cusp thrusters are analyzed by the volume-averaging technique. The superior performance exhibited by the ring-cusp thruster is correlated with a higher average Maxwellian electron temperature. The ring-cusp thruster maintains the same fraction of primary electrons as does the J-series thruster, but at a much lower ion production cost. The volume-averaged predictions for both thrusters are compared with those of a detailed thruster performance model.

  7. Direct Acceleration of Electrons in a Corrugated Plasma Channel

    SciTech Connect

    Palastro, J. P.; Antonsen, T. M.; Morshed, S.; York, A. G.; Layer, B.; Aubuchon, M.; Milchberg, H. M.; Froula, D. H.

    2009-01-22

    Direct laser acceleration of electrons provides a low power tabletop alternative to laser wakefield accelerators. Until recently, however, direct acceleration has been limited by diffraction, phase matching, and material damage thresholds. The development of the corrugated plasma channel [B. Layer et al., Phys. Rev. Lett. 99, 035001 (2007)] has removed all of these limitations and promises to allow direct acceleration of electrons over many centimeters at high gradients using femtosecond lasers [A. G. York et al., Phys Rev. Lett 100, 195001 (2008), J. P. Palastro et al., Phys. Rev. E 77, 036405 (2008)]. We present a simple analytic model of laser propagation in a corrugated plasma channel and examine the laser-electron beam interaction. Simulations show accelerating gradients of several hundred MeV/cm for laser powers much lower than required by standard laser wakefield schemes. In addition, the laser provides a transverse force that confines the high energy electrons on axis, while expelling low energy electrons.

  8. The functionalization of graphene using electron-beam generated plasmas

    SciTech Connect

    Baraket, M.; Walton, S. G.; Lock, E. H.; Robinson, J. T.; Perkins, F. K.

    2010-06-07

    A plasmas-based, reversible functionalization of graphene is discussed. Using electron-beam produced plasmas, oxygen and fluorine functionalities have been added by changing the processing gas mixtures from Ar/O{sub 2} to Ar/SF{sub 6}, respectively. The reversibility of the functionalization was investigated by annealing the samples. The chemical composition and structural changes were studied by x-ray photoelectron spectroscopy and Raman spectroscopy.

  9. Collisionless Reconnection in an Electron-Positron Plasma

    SciTech Connect

    Bessho, N.; Bhattacharjee, A.

    2005-12-09

    Electromagnetic particle-in-cell simulations of fast collisionless reconnection in a two-dimensional electron-positron plasma (without an equilibrium guide field) are presented. A generalized Ohm's law in which the Hall current cancels out exactly is given. It is suggested that the key to fast reconnection in this plasma is the localization caused by the off-diagonal components of the pressure tensors, which produce an effect analogous to a spatially localized resistivity.

  10. Collisionless reconnection in an electron-positron plasma.

    PubMed

    Bessho, N; Bhattacharjee, A

    2005-12-01

    Electromagnetic particle-in-cell simulations of fast collisionless reconnection in a two-dimensional electron-positron plasma (without an equilibrium guide field) are presented. A generalized Ohm's law in which the Hall current cancels out exactly is given. It is suggested that the key to fast reconnection in this plasma is the localization caused by the off-diagonal components of the pressure tensors, which produce an effect analogous to a spatially localized resistivity. PMID:16384388

  11. Kinetic Theory of Vortex Crystal Formation in Electron Plasmas

    NASA Astrophysics Data System (ADS)

    Kono, M.; Pécseli, H. L.; Trulsen, J.

    Vortex-like structures in two dimensional strongly magnetized plasmas are studied by use of a point vortex description. A model equation describing the dynamics of point vortices under the influence of fluctuations is derived, and by a numerical solution it is demonstrated that it has self-organizing properties. The numerical results have many similarities with experimental observations of crystal-like structures found in strongly magnetized electron plasmas.

  12. Anomalous skin effects in a weakly magnetized degenerate electron plasma

    SciTech Connect

    Abbas, G. Sarfraz, M.; Shah, H. A.

    2014-09-15

    Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring the ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].

  13. Modeling Evaporative Electron Cooling in an Ultracold Neutral Plasma

    NASA Astrophysics Data System (ADS)

    Witte, Craig; Roberts, Jacob

    2015-11-01

    Ultracold plasmas (UCPs) are formed by photoionizing a collection of laser cooled atoms. Once formed, these plasmas expand, cooling over the course of their expansion. In theory, further cooling should be obtainable by forcibly inducing electron evaporation by applying DC electric fields to extract electrons. However, this cooling is difficult to quantify experimentally. Any attempt to obtain such a measurement requires a firm knowledge of evaporation dynamics in the system. For UCPs, electron mean free paths are smaller than the width of the plasma, resulting in significant transport effects that are not included in standard evaporation treatments. We have developed a simple Monte Carlo model that incorporates these effects. This talk will discuss this model, and how it can be utilized to measure evaporation and cooling in UCPs. This work was supported by the Air Force Office of Scientific Research.

  14. Linear and nonlinear modes in nonrelativistic electron-positron plasmas

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; Greaves, R. G.

    1995-06-01

    A comprehensive two-fluid model is developed for collective modes in a nonrelativistic electron-positron plasma. Longitudinal and transverse electrostatic and electromagnetic modes, both in the presence and absence of a magnetic field, are studied. Wave properties are discussed in terms of dispersion relations, wave normal surfaces, and cylindrical mirror analyzer clemmow-Mullaly-Allis diagrams. The results are extended to include the two-stream instability and ion acoustic solitary waves. For the two-stream instability, a similar result is found as in the electron-ion plasma. For ion acoustic solitary waves, only subsonic solutions are found to exist. Furthermore, their width is proportional to their amplitude, unlike the electron-ion plasma case, where the speed is proportional to the amplitude.

  15. Strongly turbulent stabilization of electron beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Haber, I.; Palmadesso, P.; Papadopoulos, K.

    1980-01-01

    The stabilization of electron beam interactions due to strongly turbulent nonlinearities is studied analytically and numerically for a wide range of plasma parameters. A fluid mode coupling code is described in which the effects of electron and ion Landau damping and linear growth due to the energetic electron beam are included in a phenomenological manner. Stabilization of the instability is found to occur when the amplitudes of the unstable modes exceed the threshold of the oscillating two-stream instability. The coordinate space structure of the turbulent spectrum which results clearly shows that soliton-like structures are formed by this process. Phenomenological models of both the initial stabilization and the asymptotic states are developed. Scaling laws between the beam-plasma growth rate and the fluctuations in the fields and plasma density are found in both cases, and shown to be in good agreement with the results of the simulation.

  16. Magnetoacoustic solitons in dense astrophysical electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Mahmood, S.; Mushtaq, A.

    2013-08-01

    Nonlinear magnetoacoustic waves in dense electron-positron-ion plasmas are investigated by using three fluid quantum magnetohydrodynamic model. The quantum mechanical effects of electrons and positrons are taken into account due to their Fermionic nature (to obey Fermi statistics) and quantum diffraction effects (Bohm diffusion term) in the model. The reductive perturbation method is employed to derive the Korteweg-de Vries (KdV) equation for low amplitude magnetoacoustic soliton in dense electron-positron-ion plasmas. It is found that positron concentration has significant impact on the phase velocity of magnetoacoustic wave and on the formation of single pulse nonlinear structure. The numerical results are also illustrated by taking into account the plasma parameters of the outside layers of white dwarfs and neutron stars/pulsars.

  17. Two-dimensional studies of relativistic electron beam plasma instabilities in an inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Shukla, Chandrasekhar; Das, Amita; Patel, Kartik

    2015-11-01

    Relativistic electron beam propagation in plasma is fraught with several micro instabilities like two stream, filamentation, etc., in plasma. This results in severe limitation of the electron transport through a plasma medium. Recently, however, there has been an experimental demonstration of improved transport of Mega Ampere of electron currents (generated by the interaction of intense laser with solid target) in a carbon nanotube structured solid target [G. Chatterjee et al., Phys. Rev. Lett. 108, 235005 (2012)]. This then suggests that the inhomogeneous plasma (created by the ionization of carbon nanotube structured target) helps in containing the growth of the beam plasma instabilities. This manuscript addresses this issue with the help of a detailed analytical study and 2-D Particle-In-Cell simulations. The study conclusively demonstrates that the growth rate of the dominant instability in the 2-D geometry decreases when the plasma density is chosen to be inhomogeneous, provided the scale length 1/ks of the inhomogeneous plasma is less than the typical plasma skin depth (c/?0) scale. At such small scale lengths channelization of currents is also observed in simulation.

  18. Electronic and magnetic properties of monolayer SiC sheet doped with 3d-transition metals

    NASA Astrophysics Data System (ADS)

    Bezi Javan, Masoud

    2016-03-01

    We theoretically studied the electronic and magnetic properties of the monolayer SiC sheet doped by 3d transition-metal (TM) atoms. The structural properties, induced strain, electronic and magnetic properties were studied for cases that a carbon or silicon of the SiC sheet replaced with TM atoms. We found that the mount of induced strain to the lattice structure of the SiC sheet with substituting TM atoms is different for Si (TMSi) and C (TMC) sites as the TMSi structures have lower value of the strain. Also the TM atoms can be substituted in the lattice of the SiC sheet with different binding energy values for TMSi and TMC structures as the TMSi structures have higher value of the binding energies. Dependent to the structural properties, the TM doped SiC sheets show magnetic or nonmagnetic properties. We found that some structures such as MnSi, CuSi and CoC configurations have significant total magnetic moment about 3 μB.

  19. External control of electron temperature in ultra-cold plasmas

    NASA Astrophysics Data System (ADS)

    Tate, Duncan; Wilson, Roy; Martei, Margaret; Wood, Anders

    2007-06-01

    In this presentation, we will discuss our progress towards achieving external control of the electron temperature and Coulomb coupling parameter of ultra-cold plasmas. The plasma is created by partial photoionization of a dense, cold sample of rubidium atoms in a MOT using a Littman dye laser (Rb density ˜4 x10^10 cm-3, temperature 100 μK). At a controllable time delay, neutral atoms embedded in the plasma are excited to a specific Rydberg state by a narrow bandwidth pulsed laser. We measure the plasma electron energy spectrum as a function of delay between the lasers, as a function of the Rydberg state populated by the second laser, and as a function of Rydberg atom density. We have made progress towards quantifying and maximizing the Rydberg atom density that can be achieved by using mm-wave spectroscopy to control the evolution of a cold, dense Rydberg sample to plasma. We have also begun preliminary investigation of plasma electron temperature measurements. We are also investigating the use of a dark SPOT to increase the Rydberg density.

  20. Numerical study of a dust-contaminated electron plasma

    NASA Astrophysics Data System (ADS)

    Maero, Giancarlo; Romé, Massimiliano; Lepreti, Fabio; Cavenago, Marco

    2014-10-01

    The collective behaviour of dusty plasmas is heavily affected by the presence of a small fraction of micrometric or sub-micrometric dust particles which collect a large surface charge. While dusty plasmas under study are usually quasi-neutral, we propose here an investigation on a magnetized nonneutral plasma (a situation found for example in Penning traps) where a conventional plasma with a single sign of charge (e.g. electrons) is contaminated by a dust population. We simulate the two-dimensional dynamics of such a plasma in the plane orthogonal to a homogeneous magnetic field with a tailored Particle-In-Cell code implementing a mass-less fluid (drift-Poisson) approximation for electrons and a kinetic description for the dust component, including gravity effects. Simulations with a range of initial conditions are performed to observe the influence of dust on the diocotron instability developing in the electron plasma. The early stage of the growth of diocotron modes is analyzed by Fourier decomposition. The fully non-linear evolution is studied by means of a statistical analysis of probability density functions and flatness of spatial vorticity increments in order to characterize the intermittency properties of the turbulence. Contribution to the Topical Issue "Theory and Applications of the Vlasov Equation", edited by Francesco Pegoraro, Francesco Califano, Giovanni Manfredi and Philip J. Morrison.

  1. On thermalization of electron-positron-photon plasma

    NASA Astrophysics Data System (ADS)

    Siutsou, I. A.; Aksenov, A. G.; Vereshchagin, G. V.

    2015-12-01

    Recently a progress has been made in understanding thermalization mechanism of relativistic plasma starting from a non-equilibrium state. Relativistic Boltzmann equations were solved numerically for homogeneous isotropic plasma with collision integrals for two- and three-particle interactions calculated from the first principles by means of QED matrix elements. All particles were assumed to fulfill Boltzmann statistics. In this work we follow plasma thermalization by accounting for Bose enhancement and Pauli blocking in particle interactions. Our results show that particle in equilibrium reach Bose-Einstein distribution for photons, and Fermi-Dirac one for electrons, respectively.

  2. Analysis of electron beam damage of exfoliated MoS₂ sheets and quantitative HAADF-STEM imaging.

    PubMed

    Garcia, Alejandra; Raya, Andres M; Mariscal, Marcelo M; Esparza, Rodrigo; Herrera, Miriam; Molina, Sergio I; Scavello, Giovanni; Galindo, Pedro L; Jose-Yacaman, Miguel; Ponce, Arturo

    2014-11-01

    In this work we examined MoS₂ sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS₂ sheets has been controlled at 80 kV according a theoretical calculation based on the inelastic scattering of the electrons involved in the interaction electron-matter. The threshold energy for the MoS₂ material has been found and experimentally verified in the microscope. At energies higher than the energy threshold we show surface and edge defects produced by the electron beam irradiation. Quantitative analysis at atomic level in the images obtained at 80 kV has been performed using the experimental images and via STEM simulations using SICSTEM software to determine the exact number of MoS2₂ layers. PMID:24929924

  3. Analysis of electron beam damage of exfoliated MoS2 sheets and quantitative HAADF-STEM imaging

    PubMed Central

    Garcia, A.; Raya, A.M.; Mariscal, M.M.; Esparza, R.; Herrera, M.; Molina, S.I.; Scavello, G.; Galindo, P.L.; Jose-Yacaman, M.; Ponce, A.

    2014-01-01

    In this work we examined MoS2 sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS2 sheets has been controlled at 80 kV according a theoretical calculation based on the inelastic scattering of the electrons involved in the interaction electron-matter. The threshold energy for the MoS2 material has been found and experimentally verified in the microscope. At energies higher than the energy threshold we show surface and edge defects produced by the electron beam irradiation. Quantitative analysis at atomic level in the images obtained at 80 kV has been performed using the experimental images and via STEM simulations using SICSTEM software to determine the exact number of MoS2 layers. PMID:24929924

  4. Improved plasma uniformity in a discharge system with electron injection

    SciTech Connect

    Vizir, A. V.; Tyunkov, A. V.; Shandrikov, M. V.

    2009-02-15

    We present the results of experiments leading to improvement in bulk plasma uniformity of a constricted-arc discharge system with electron injection. The steady-state discharge was in argon, at a gas pressure of 0.5 mTorr, and operated with a main discharge voltage between 20 and 100 V and current between 3 and 15 A. The radial plasma distribution was measured with a movable Langmuir probe. We find that geometric modification of the intermediate electrode exit aperture and the main discharge cathode add little to the plasma uniformity. Improved bulk plasma uniformity is observed when a special distributing grid electrode is used and the main discharge voltage is less than 20-30 V. The application of a weakly divergent magnetic field in the region of the intermediate electrode exit aperture decreases the plasma nonuniformity from 20% to 14% over a radial distance of 30 cm. The plasma uniformity was further improved by compensating the magnetic self-field of the injected electron beam by a reverse magnetic field produced with a special electrode compensator. It is shown that an increase in discharge current causes a proportional increase in back current in the distributing electrode. The approach allows a decrease in plasma nonuniformity from 20% to 13% over a radial distance of 30 cm.

  5. CURRENT SHEET REGULATION OF SOLAR NEAR-RELATIVISTIC ELECTRON INJECTION HISTORIES

    SciTech Connect

    Agueda, N.; Sanahuja, B.; Vainio, R.; Dalla, S.; Lario, D.

    2013-03-10

    We present a sample of three large near-relativistic (>50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes (>60 Degree-Sign ) and close to 2 AU. Despite the large latitudinal distance between the two spacecraft, electrons injected near the Sun reached both heliospheric locations. All three events were associated with large solar flares, strong decametric type II radio bursts and accompanied by wide (>212 Degree-Sign ) and fast (>1400 km s{sup -1}) coronal mass ejections (CMEs). We use advanced interplanetary transport simulations and make use of the directional intensities observed in situ by the spacecraft to infer the electron injection profile close to the Sun and the interplanetary transport conditions at both low and high latitudes. For the three selected events, we find similar interplanetary transport conditions at different heliolatitudes for a given event, with values of the mean free path ranging from 0.04 AU to 0.27 AU. We find differences in the injection profiles inferred for each spacecraft. We investigate the role that sector boundaries of the heliospheric current sheet (HCS) have on determining the characteristics of the electron injection profiles. Extended injection profiles, associated with coronal shocks, are found if the magnetic footpoints of the spacecraft lay in the same magnetic sector as the associated flare, while intermittent sparse injection episodes appear when the spacecraft footpoints are in the opposite sector or a wrap in the HCS bounded the CME structure.

  6. Nonlinear interactions between electromagnetic waves and electron plasma oscillations in quantum plasmas.

    PubMed

    Shukla, P K; Eliasson, B

    2007-08-31

    We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schrödinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed. PMID:17931024

  7. Nonlinear Interactions between Electromagnetic Waves and Electron Plasma Oscillations in Quantum Plasmas

    SciTech Connect

    Shukla, P. K.; Eliasson, B.

    2007-08-31

    We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schroedinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed.

  8. Thermal effects on the electron density fluctuations in ICF plasmas

    NASA Astrophysics Data System (ADS)

    Rozmus, Wojciech; Chapman, T.; Berger, R.; Brantov, A.; Bychenkov, V.; Tzoufras, M.

    2013-10-01

    We have examined modifications of the electron distribution functions (EDF) due to thermal gradients in the ignition-scale ICF plasmas. In particular, given the high background temperatures of such plasmas the heat-carrying electrons have energies (20 - 40 keV) that are close to kinetic energies of the electrons that are resonant with Langmuir waves produced by parametric instabilities, such as stimulated Raman scattering. We have found that under these conditions the modifications of the EDF introduce anisotropy in the plasma response that manifests itself in the significant reduction (increase) of the Landau damping of Langmuir waves propagating along (against) the temperature gradient. Similarly there is strong anisotropy in the fluctuation spectra of the electron plasma waves that modifies Thomson scattering cross-section. The EDF have been calculated and compared using the standard Spitzer-Harm theory, numerical solutions to the Fokker-Planck equations and analytical solutions of the kinetic equation. An impact of this theory on the observations of scattering instabilities and Thomson scattering experiments in ICF plasmas will be discussed.

  9. Effect of electron extraction from a grid plasma cathode on the generation of emission plasma

    NASA Astrophysics Data System (ADS)

    Devyatkov, V. N.; Koval, N. N.

    2014-11-01

    The paper describes the operating mode of a plasma electron source based on a low- pressure arc discharge with grid stabilization of the plasma emission boundary which provides a considerable (up to twofold) increase in discharge and beam currents at an Ar pressure in the vacuum chamber p = 0.02-0.05 Pa, accelerating voltages of up to U = 10 kV, and longitudinal magnetic field of up to Bz = 0.1 T. The discharge and beam currents are increased on electron extraction from the emission plasma through meshes of a fine metal grid due to the energy of a high-voltage power supply which ensures electron emission and acceleration. The electron emission from the plasma cathode and arrival of ions from the acceleration gap in the discharge changes the discharge plasma parameters near the emission grid, thus changing the potential of the emission grid electrode with respect to the discharge cathode. The load is not typical and changes the voltage polarity of the electrode gap connected to the discharge power supply, which is to be taken into account in its calculation and design. The effect of electron emission from the plasma cathode on the discharge system can not only change the discharge and beam current pulse shapes but can also lead to a breakdown of the acceleration gap and failure of semiconductor elements in the discharge power supply unit.

  10. Plasma effects on the free-electron laser gain with a plasma wave undulator

    NASA Astrophysics Data System (ADS)

    Hedayati, R.; Jafari, S.; Batebi, S.

    2015-08-01

    Employing a magnetized plasma medium in the interaction region of a free-electron laser (FEL) offers the possibility of generating short wavelengths using moderate energy beams. Plasma in the presence of static magnetic field supports right and left circularly polarized electromagnetic modes. By superposition of these two modes, a linearly polarized electromagnetic mode is generated which can be employed as a plasma undulator in a FEL. This configuration has a higher tunability by controlling the plasma density on top of the γ -tubability of the conventional FELs. The roles of the axial magnetic field and plasma on the laser gain and the electron trajectories of an e-beam propagating through the plasma medium have been studied and new orbits of group (I, II, and III) have been found. Moreover, the stability of these orbits for different values of plasma frequencies has been investigated. It is shown that by increasing the axial guide magnetic field strength, the gain for orbits of group I trivially increase, while a decrease in gain has been obtained for orbits of group II and group III. In addition, it is found that with increasing the plasma frequency (or plasma density) the gain for orbits of group I and group II trivially decreases and shift to the lower cyclotron frequencies, while an increase in gain has been obtained for orbits of group III.

  11. Electronic properties of Boron Nitride sheet and nanotube in the presence of transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Rezania, H.; Aghaiimanesh, Z.

    2015-09-01

    We study the effects of a transverse magnetic field on the electronic properties of both Boron-Nitride monolayer and zigzag nanotubes in the context of Hubbard model at the antiferromagnetic sector. In particular, the behavior of density of states and temperature dependence of specific heat have been investigated. Mean field approximation has been employed in order to obtain the electronic spectrum of the system. Our results show the band gap in the density of states broadens with an increase of Hubbard parameter. Whereas the band gap width decreases with magnetic field. Also specific heat of Boron Nitride sheet is found to be exponentially increasing behavior with temperature at low values of it and for all the magnetic field values. However specific heat reaches its maximum value at finite temperature and specific heat starts to decrease upon more increase of temperature. Furthermore the effect of magnetic field and Hubbard interaction on the density of states and specific heat of Boron Nitride nanotubes has been studied.

  12. Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

    NASA Astrophysics Data System (ADS)

    Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

    2014-11-01

    The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

  13. Influence of electron injection into 27 cm audio plasma cell on the plasma diagnostics

    SciTech Connect

    Haleem, N. A.; Ragheb, M. S.; Zakhary, S. G.; El Fiki, S. A.; Nouh, S. A.; El Disoki, T. M.

    2013-08-15

    In this article, the plasma is created in a Pyrex tube (L = 27 cm, φ= 4 cm) as a single cell, by a capacitive audio frequency (AF) discharge (f = 10–100 kHz), at a definite pressure of ∼0.2 Torr. A couple of tube linear and deviating arrangements show plasma characteristic conformity. The applied AF plasma and the injection of electrons into two gas mediums Ar and N{sub 2} revealed the increase of electron density at distinct tube regions by one order to attain 10{sup 13}/cm{sup 3}. The electrons temperature and density strengths are in contrast to each other. While their distributions differ along the plasma tube length, they show a decaying sinusoidal shape where their peaks position varies by the gas type. The electrons injection moderates electron temperature and expands their density. The later highest peak holds for the N{sub 2} gas, at electrons injection it changes to hold for the Ar. The sinusoidal decaying density behavior generates electric fields depending on the gas used and independent of tube geometry. The effect of the injected electrons performs a responsive impact on electrons density not attributed to the gas discharge. Analytical tools investigate the interaction of the plasma, the discharge current, and the gas used on the electrodes. It points to the emigration of atoms from each one but for greater majority they behave to a preferred direction. Meanwhile, only in the linear regime, small percentage of atoms still moves in reverse direction. Traces of gas atoms revealed on both electrodes due to sheath regions denote lack of their participation in the discharge current. In addition, atoms travel from one electrode to the other by overcoming the sheaths regions occurring transportation of particles agglomeration from one electrode to the other. The electrons injection has contributed to increase the plasma electron density peaks. These electrons populations have raised the generated electrostatic fields assisting the elemental ions emigration to a preferred electrode direction. Regardless of plasma electrodes positions and plasma shape, ions can be departed from one electrode to deposit on the other one. In consequence, as an application the AF plasma type can enhance the metal deposition from one electrode to the other.

  14. Thin current sheets in the deep geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Pulkkinen, T. I.; Baker, D. N.; Owen, C. J.; Gosling, J. T.; Murphy, N.

    1993-01-01

    The International Sun-Earth Explorer 3 (ISEE-3) magnetic field and plasma electron data from Jan - March 1983 have been searched to study thin current sheets in the deep tail region. 33 events were selected where the spacecraft crossed through the current sheet from lobe to lobe within 15 minutes. The average thickness of the observed current sheets was 2.45 R(sub E), and in 24 cases the current sheet was thinner than 3.0 R(sub E); 6 very thin current sheets (thickness lambda less than 0.5 R(sub E) were found. The electron data show that the very thin current sheets are associated with considerable temperature anisotropy. On average, the electron gradient current was about 17% of the total current, whereas the current arising from the electron temperature anisotropy varied between 8-45% of the total current determined from the lobe field magnitude.

  15. Inelastic electron-ion scattering in a dense plasma

    SciTech Connect

    Hatton, G.J.; Lane, N.F.; Weisheit, J.C.

    1981-04-01

    The Born approximation was used to investigate the influence of a dense plasma on the inelastic scattering of electrons by one-electron ions. Scaled collision strengths Z/sup 2/Q for 1s ..-->.. 2s, 1s ..-->.. 2p and 2s ..-->.. 2p transitions in an ion of arbitrary nuclear charge Z were computed for a Debye-Hueckel model of the screened Coulomb interaction. Over a wide range of screening lengths, the effect of the plasma environment is to appreciably reduce cross sections just above threshold.

  16. Analytical theory of a current sheet formed between the magnetized and nonmagnetized plasmas with arbitrary energy distribution of particles

    NASA Astrophysics Data System (ADS)

    Martyanov, Vladimir; Kocharovsky, Vladimir; Kocharovsky, Vitaly

    We present analytical description of a self-consistent stationary boundary layer formed between the magnetized and nonmagnetized collisionless plasmas with arbitrary energy distribution of particles. Various spatial profiles of the current and respective particle distributions in the neutral current sheets are found on the basis of the self-consistency equation of the Grad-Shafranov type, which takes into account a homogeneous external magnetic field. The solutions are obtained due to development of the method of invariants of particle motion (Astron. Lett. 36, 396 (2010)) and provide, for the first time, a detailed description of various transition domains in the magnetospheres of stars and planets, in particular, boundary regions formed by an interaction of a solar wind with an interstellar medium or Earth magnetosphere. We restrict ourselves to the shearless magnetic field configurations and consider four special dependencies of particle distribution function on momentum parallel to current direction, which make it possible to detail the relations between the magnetic field profile, plasma density, and particle anisotropy gradient, including both thin and thick (with respect to a particle gyroradius) layers. Special attention is paid to the cases of an utmost sharp boundary between the magnetized and nonmagnetized plasmas and to the cases where there are sections of a boundary current sheet with magnetic field energy density exceeding kinetic energy density of plasma particles. The kinetic instabilities and reconnection phenomena are also discussed, especially the ones related to the Weibel instability in the weakly magnetized parts of the boundary layer. These analytical results are applied to the analysis of the spacecraft observations of the magnetized-nonmagnetized boundaries in cosmic plasma.

  17. Potential and electron density calculated for freely expanding plasma by an electron beam

    SciTech Connect

    Ho, C. Y.; Tsai, Y. H.; Ma, C.; Wen, M. Y.

    2011-07-01

    This paper investigates the radial distributions of potential and electron density in free expansion plasma induced by an electron beam irradiating on the plate. The region of plasma production is assumed to be cylindrical, and the plasma expansion is assumed to be from a cylindrical source. Therefore, the one-dimensional model in cylindrical coordinates is employed in order to analyze the radial distributions of the potential and electron density. The Runge-Kutta method and the perturbation method are utilized in order to obtain the numerical and approximate solutions, respectively. The results reveal that the decrease in the initial ion energy makes most of the ions gather near the plasma production region and reduces the distribution of the average positive potential, electron, and ion density along the radial direction. The oscillation of steady-state plasma along the radial direction is also presented in this paper. The ions induce a larger amplitude of oscillation along the radial direction than do electrons because the electrons oscillate around slowly moving ions due to a far smaller electron mass than ion mass. The radial distributions of the positive potential and electron density predicted from this study are compared with the available experimental data.

  18. Influence of electron evaporative cooling on ultracold plasma expansion

    SciTech Connect

    Wilson, Truman; Chen, Wei-Ting; Roberts, Jacob

    2013-07-15

    The expansion of ultracold neutral plasmas (UCP) is driven primarily by the thermal pressure of the electron component and is therefore sensitive to the electron temperature. For typical UCP spatial extents, evaporative cooling has a significant influence on the UCP expansion rate at lower densities (less than 10{sup 8}/cm{sup 3}). We studied the effect of electron evaporation in this density range. Owing to the low density, the effects of three-body recombination were negligible. We modeled the expansion by taking into account the change in electron temperature owing to evaporation as well as adiabatic expansion and found good agreement with our data. We also developed a simple model for initial evaporation over a range of ultracold plasma densities, sizes, and electron temperatures to determine over what parameter range electron evaporation is expected to have a significant effect. We also report on a signal calibration technique, which relates the signal at our detector to the total number of ions and electrons in the ultracold plasma.

  19. Characterization of Secondary Electron Emission Properties of Plasma Facing Materials

    NASA Astrophysics Data System (ADS)

    Patino, Marlene I.; Capece, Angela M.; Raitses, Yevgeny; Koel, Bruce E.

    2015-11-01

    The behavior of wall-bounded plasmas is significantly affected by the plasma-wall interactions, including the emission of secondary electrons (SEE) from the wall materials due to bombardment by primary electrons. The importance of SEE has prompted previous investigations of SEE properties of materials especially with applications to magnetic fusion, plasma thrusters, and high power microwave devices. In this work, we present results of measurements of SEE properties of graphite and lithium materials relevant for the divertor region of magnetic fusion devices. Measurements of total SEE yield (defined as the number of emitted secondary electrons per incident primary electron) for lithium are extended up to 5 keV primary electron energy, and the energy distributions of secondary electrons are provided for graphite and lithium. Additionally, the effect of contamination on the total SEE yield of lithium was explored by exposing the material to water vapor. Auger electron spectroscopy (AES) was used to determine surface composition and temperature programmed desorption (TPD) was used to determine lithium film thickness. Results show an order of magnitude increase in total SEE yield for lithium exposed to water vapor. This work was supported by DOE contract DE-AC02-09CH11466; AFOSR grants FA9550-14-1-0053, FA9550-11-1-0282, and AF9550-09-1-0695; and DOE Office of Science Graduate Student Research Program.

  20. Nonlocal electron transport in magnetized plasmas with arbitrary atomic number

    SciTech Connect

    Bennaceur-Doumaz, D.; Bendib, A.

    2006-09-15

    The numerical solution of the steady-state electron Fokker-Planck equation perturbed with respect to a global equilibrium is presented in magnetized plasmas with arbitrary atomic number Z. The magnetic field is assumed to be constant and the electron-electron collisions are described by the Landau collision operator. The solution is derived in the Fourier space and in the framework of the diffusive approximation which captures the spatial nonlocal effects. The transport coefficients are deduced and used to close a complete set of nonlocal electron fluid equations. This work improves the results of A. Bendib et al. [Phys. Plasmas 9, 1555 (2002)] and of A. V. Brantov et al. [Phys. Plasmas 10, 4633 (2003)] restricted to the local and nonlocal high-Z plasma approximations, respectively. The influence of the magnetic field on the nonlocal effects is discussed. We propose also accurate numerical fits of the relevant transport coefficients with respect to the collisionality parameter {lambda}{sub ei}/L and the atomic number Z, where L is the typical scale length and {lambda}{sub ei} is the electron-ion mean-free-path.

  1. Relativistic ponderomotive effect on the propagation of rippled laser beam and the excitation of electron plasma wave in collisionless plasma

    NASA Astrophysics Data System (ADS)

    Priyanka; Chauhan, Prashant; Purohit, Gunjan

    2013-01-01

    This paper presents an investigation of the propagation of rippled laser beam in a collisionless plasma and its effect on and the excitation of electron plasma wave and particle acceleration, when relativistic and ponderomotive nonlinearities are simultaneously operative. Electron plasma wave (EPW) coupling with rippled laser beam arises on account of the relativistic change in the electron mass and the modification of the background electron density due to ponderomotive nonlinearity. When the electron plasma wave gets coupled to the rippled laser beam, a large fraction of the pump energy gets transferred to EPW and this excited EPW can accelerate the electrons. Analytical expressions for the growth rate of the laser spike in plasma, beam width of the rippled laser beam and excited electron plasma wave have been obtained using paraxial ray approximation. These coupled equations are solved analytically and numerically to study the growth of laser spike in plasma and its effect on the self focusing of rippled laser beam in plasma, amplitude of the excited electron plasma wave and particle acceleration. The result shows that the effect of including ponderomotive nonlinearity significantly affects the growth of laser spike in plasma, excitation of electron plasma wave as well as the number of energetic electrons in particle acceleration process. The results are presented for typical laser plasma parameters.

  2. Experimental study of hot electrons in LECR2M plasma

    SciTech Connect

    Zhao, H. Y.; Zhao, H. W.; Ma, X. W.; Wang, H.; Zhang, X. Z.; Sun, L. T.; Ma, B. H.; Li, X. X.; Sha, S.; Zhu, Y. H.; Lu, W.; Shang, Y.

    2008-02-15

    In order to investigate the hot electron component in electron cyclotron resonance (ECR) plasmas, the volume bremsstrahlung spectra in the x-ray photon energy range were measured with a high-purity germanium detector on Lanzhou ECR Ion Source No. 2 Modified (LECR2M). A collimation system similar to Bernhardi's was used to focus at the central part of the plasma. The ion source was operated under various source conditions with argon; sometimes oxygen was added to enhance high charge state ion beam intensities. The spectral temperature of hot electrons T{sub spe} was derived from the measured bremsstrahlung spectra. The evolution of the deduced temperature of hot electrons T{sub spe} with the ion source parameters, such as the rf frequency, power, and the magnetic confinement configuration, was investigated.

  3. Beltrami–Bernoulli equilibria in plasmas with degenerate electrons

    SciTech Connect

    Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.

    2015-02-15

    A new class of Double Beltrami–Bernoulli equilibria, sustained by electron degeneracy pressure, is investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami–Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars, etc.

  4. Modulational instability in a plasma with suprathermal electrons

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Smith, R. A.; Papadopoulos, K.; Palmadesso, P.

    1981-01-01

    The consequences of the presence of suprathermal electrons on the linear stage of modulational instabilities are investigated for a range of parameters appropriate to both laboratory and astrophysical plasmas. Substantial modification to the growth rate and secondary spectrum are found to occur for instabilities driven by large amplitude Langmuir waves in the dipole limit due to the kinetic effects of the suprathermal electrons. In particular, for reasonable choices of pump amplitude and suprathermal energy density, additional modes become unstable.

  5. Low Energy Electrons in the Mars Plasma Environment

    NASA Technical Reports Server (NTRS)

    Link, Richard

    2001-01-01

    The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (< 4 keV) electrons will be modeled using the two-stream electron transport code of Link. The code models both external (solar wind) and internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

  6. Double tearing mode induced by parallel electron viscosity in tokamak plasmas

    SciTech Connect

    He Zhixiong; Dong, J. Q.; Long, Y. X.; Mou, Z. Z.; He, H. D.; Liu, F.; Shen, Y.; Gao Zhe

    2010-11-15

    The linear behaviors of the double tearing mode (DTM) mediated by parallel electron viscosity in cylindrical plasmas with reversed magnetic shear and thus two resonant rational flux surfaces is numerically investigated. The distance between the two surfaces is found to play an important role for modes with poloidal mode number m>1. Two modes, one of which is centered at the inner rational surface and the other is located between the two surfaces, are simultaneously unstable and the growth rates show the standard single tearing mode (STM) scaling as {gamma}{proportional_to}R{sup -1/3} when the distance is large (here, the Reynolds number R{identical_to}{tau}{sub {upsilon}/{tau}h}, {tau}{sub {upsilon},} and {tau}{sub h} are, respectively, the viscosity penetration time of the magnetic field and the Alfven time for a plasma sheet of width a). The latter is unstable only and the growth rate transits to the standard DTM scaling as {gamma}{proportional_to}R{sup -1/5} for low-m (e.g., m<4) modes and keeps the STM scaling {gamma}{proportional_to}R{sup -1/3} for high-m (e.g., m{approx}10) modes, which are found dominant, when the distance is decreased. In contrast, two unstable modes extending from plasma center to the two rational surfaces, respectively, coexist and the growth rates always show the scaling of {gamma}{proportional_to}R{sup -1/5}, independent of the distance, when the poloidal mode number m=1. The DTMs mediated by electron viscosity are enhanced by plasma resistivity of the range where the growth rate of the mode induced by the latter alone is comparable with that mediated by the former alone and vice versa. Otherwise, the growth rate of the mode is equal to the higher of the modes mediated by resistivity or electron viscosity alone when both of them are taken into account.

  7. ISEE observations of low frequency waves and ion distribution function evolution in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Gary, S. P.

    1990-01-01

    This paper describes ISEE plasma and magnetic fluctuation observations during two crossings of the plasma sheet boundary layer (PSBL) in the earth's magnetotail. Distribution function observations show that the counterstreaming ion components undergo pitch-angle scattering and evolve into a shell distribution in velocity space. This evolution is correlated with the development of low frequency, low amplitude magnetic fluctuations. However, the measured wave amplitudes are insufficient to accomplish the observed degree of ion pitch-angle scatttering locally; the near-earth distributions may be the result of processes occurring much farther down the magnetotail. Results show a clear correlation between the ion component beta and the relative streaming speed of the two components, suggesting that electromagnetic ion/ion instabilities do play an important role in the scattering of PSBL ions.

  8. Fizeau interferometer for measurement of plasma electron current

    SciTech Connect

    Brower, D.L.; Ding, W.X.; Deng, B.H.; Mahdavi, M.A.; Mirnov, V.; Prager, S.C.

    2004-10-01

    A high-resolution, vertically viewing far-infrared polarimeter-interferometer system is currently used on the Madison symmetric torus (MST) reversed-field pinch (RFP) to measure the plasma electron density and toroidal current density via Faraday rotation. In this article, we propose a scheme to measure the well-known Fizeau effect, whereby through modest modification of the existing apparatus, the line-integrated poloidal current density can also be directly measured. This parameter is important, since the RFP toroidal magnetic field is largely determined by currents flowing within the plasma. The Fizeau effect is a phase shift of an electromagnetic wave associated with movement of a dielectric medium. This motion can be related directly to the plasma electron current. Determining the Fizeau effect involves measurement of the phase shift between two collinear, orthogonally polarized, counterpropagating laser beams. Estimates indicate a phase shift of {approx}2 deg. is expected for typical MST parameters, well within the existing system resolution.

  9. Magnetically Controlled Optical Plasma Waveguide for Electron Acceleration

    SciTech Connect

    Pollock, B. B.; Davis, P.; Divol, L.; Glenzer, S. H.; Palastro, J. P.; Price, D.; Froula, D. H.; Tynan, G. R.

    2009-01-22

    In order to produce multi-Gev electrons from Laser Wakefield Accelerators, we present a technique to guide high power laser beams through underdense plasma. Experimental results from the Jupiter Laser Facility at the Lawrence Livermore National Laboratory that show density channels with minimum plasma densities below 5x10{sup 17} cm{sup -3} are presented. These results are obtained using an external magnetic field (<5 T) to limit the radial heat flux from a pre-forming laser beam. The resulting increased plasma pressure gradient produces a parabolic density gradient which is tunable by changing the external magnetic field strength. These results are compared with 1-D hydrodynamic simulations, while quasi-static kinetic simulations show that for these channel conditions 90% of the energy in a 150 TW short pulse beam is guided over 5 cm and predict electron energy gains of 3 GeV.

  10. Magnetically Controlled Optical Plasma Waveguide for Electron Acceleration

    SciTech Connect

    Pollock, B B; Froula, D H; Tynan, G R; Divol, L; Davis, P; Palastro, J P; Price, D; Glenzer, S H

    2008-08-28

    In order to produce multi-Gev electrons from Laser Wakefield Accelerators, we present a technique to guide high power laser beams through underdense plasma. Experimental results from the Jupiter Laser Facility at the Lawrence Livermore National Laboratory that show density channels with minimum plasma densities below 5 x 10{sup 17} cm{sup -3} are presented. These results are obtained using an external magnetic field (<5 T) to limit the radial heat flux from a pre-forming laser beam. The resulting increased plasma pressure gradient produces a parabolic density gradient which is tunable by changing the external magnetic field strength. These results are compared with 1-D hydrodynamic simulations, while quasi-static kinetic simulations show that for these channel conditions 90% of the energy in a 150 TW short pulse beam is guided over 5 cm and predict electron energy gains of 3 GeV.

  11. Characterization of electron kinetics regime with electron energy probability functions in inductively coupled hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Kim, June Young; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-02-01

    Electron kinetics regime is characterized with the evolution of electron energy probability functions (EEPFs) in inductively coupled hydrogen plasmas. Measurements on EEPFs are carried out with a radio-frequency-compensated single Langmuir probe at the center of a planar-type hydrogen plasma driven by 13.56 MHz wave frequency. Measured EEPFs deviate considerably from the Maxwellian distribution only at relatively high pressures (15-40 mTorr), and the effective electron temperature steeply decreases as the gas pressure increases. Such evolution of the EEPF shapes with pressures is discussed in the consideration of the electron energy relaxation length and various characteristic frequencies. It is found that the EEPFs show locally depleted electron energy distribution where the electron-molecule vibrational collision frequency exceeds the electron-electron collision frequency at the local kinetics regime, while the measured EEPF is not dependent on the vibrational collision frequency at the non-local kinetics regime. Variation of the EEPF shape with distance from the heating region at the local kinetics regime is also well explained in the context of the energy relaxation length and electron-molecule collision frequencies. This study indicates that the control of electron energy distribution should be carried out in the consideration of electron kinetic regime depending on the energy relaxation length for various hydrogen plasma sources.

  12. Electron impact excitation coefficients for laboratory and astrophysical plasmas

    NASA Technical Reports Server (NTRS)

    Davis, J.; Kepple, P. C.; Blaha, M.

    1976-01-01

    Electron impact excitation rate coefficients have been obtained for a number of transitions in highly ionized ions of interest to astrophysical and laboratory plasmas. The calculations were done using the method of distorted waves. Results are presented for various transitions in highly ionized Ne, Na, Al, Si, A, Ca, Ni and Fe.

  13. Experimental Studies of Self Organization with Electron Plasmas

    SciTech Connect

    Matthaeus, William H.

    2011-04-11

    During the period of this grant we had a very active research effort in our group on the topic of 2D electron plasmas, relaxation, 2D Navier Stokes turbulence, and related issues. The project also motivated other studies we carried out such as a study of 2D turbulence with two-species vorticity.

  14. Low radio frequency biased electron cyclotron resonance plasma etching

    NASA Astrophysics Data System (ADS)

    Samukawa, Seiji; Toyosato, Tomohiko; Wani, Etsuo

    1991-03-01

    A radio frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology has been developed to realize an efficient ion acceleration in high density and uniform ECR plasma for accurate Al-Si-Cu alloy film etching. In this technology, the substrate is located at the ECR position (875 G position) and the etching is carried out with a 400 kHz rf bias power. This Al-Si-Cu etching technology achieves a high etching rate (more than 5000 A/min), excellent etching uniformity (within ±5%), highly anisotropic etching, and Cu residue-free etching in only Cl2 gas plasma. These etching characteristics are accomplished by the combination of the dense and uniform ECR plasma generation at the ECR position with the efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.

  15. The solvation of electrons by an atmospheric-pressure plasma

    PubMed Central

    Rumbach, Paul; Bartels, David M.; Sankaran, R. Mohan; Go, David B.

    2015-01-01

    Solvated electrons are typically generated by radiolysis or photoionization of solutes. While plasmas containing free electrons have been brought into contact with liquids in studies dating back centuries, there has been little evidence that electrons are solvated by this approach. Here we report direct measurements of solvated electrons generated by an atmospheric-pressure plasma in contact with the surface of an aqueous solution. The electrons are measured by their optical absorbance using a total internal reflection geometry. The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer. We estimate an average penetration depth of 2.5±1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination. Reactions with various electron scavengers including H+, NO2−, NO3− and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis. PMID:26088017

  16. Plasma heating, plasma flow and wave production around an electron beam injected into the ionosphere

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Erickson, K. N.

    1986-01-01

    A brief historical summary of the Minnesota ECHO series and other relevant electron beam experiments is given. The primary purpose of the ECHO experiments is the use of conjugate echoes as probes of the magnetosphere, but beam-plasma and wave studies were also made. The measurement of quasi-dc electric fields and ion streaming during the ECHO 6 experiment has given a pattern for the plasma flow in the hot plasma region extending to 60m radius about the ECHO 6 electron beam. The sheath and potential well caused by ion orbits is discussed with the aid of a model which fits the observations. ELF wave production in the plasma sheath around the beam is briefly discussed. The new ECHO 7 mission to be launched from the Poker Flat range in November 1987 is described.

  17. Sheet Size-Induced Evaporation Behaviors of Inkjet-Printed Graphene Oxide for Printed Electronics.

    PubMed

    Kim, Haena; Jang, Jeong In; Kim, Hyun Ho; Lee, Geon-Woong; Lim, Jung Ah; Han, Joong Tark; Cho, Kilwon

    2016-02-10

    The size of chemically modified graphene nanosheets is a critical parameter that affects their performance and applications. Here, we show that the lateral size of graphene oxide (GO) nanosheets is strongly correlated with the concentration of graphite oxide present in the suspension as graphite oxide is exfoliated by sonication. The size of the GO nanosheets increased from less than 100 nm to several micrometers as the concentration of graphite oxide in the suspension was increased up to a critical concentration. An investigation of the evaporation behavior of the GO nanosheet solution using inkjet printing revealed that the critical temperature of formation of a uniform film, Tc, was lower for the large GO nanosheets than for the small GO nanosheets. This difference was attributed to the interactions between the two-dimensional structures of GO nanosheets and the substrate as well as the interactions among the GO nanosheets. Furthermore, we fabricated organic thin film transistors (OTFTs) using line-patterned reduced GO as electrodes. The OTFTs displayed different electrical performances, depending on the graphene sheet size. We believe that our new strategy to control the size of GO nanosheets and our findings about the colloidal and electrical properties of size-controlled GO nanosheets will be very effective to fabricate graphene based printed electronics. PMID:26824166

  18. Electron tomography of early melanosomes: Implications for melanogenesis and the generation of fibrillar amyloid sheets

    PubMed Central

    Hurbain, Ilse; Geerts, Willie J. C.; Boudier, Thomas; Marco, Sergio; Verkleij, Arie J.; Marks, Michael S.; Raposo, Graç

    2008-01-01

    Melanosomes are lysosome-related organelles (LROs) in which melanins are synthesized and stored. Early stage melanosomes are characterized morphologically by intralumenal fibrils upon which melanins are deposited in later stages. The integral membrane protein Pmel17 is a component of the fibrils, can nucleate fibril formation in the absence of other pigment cell-specific proteins, and forms amyloid-like fibrils in vitro. Before fibril formation Pmel17 traffics through multivesicular endosomal compartments, but how these compartments participate in downstream events leading to fibril formation is not fully known. By using high-pressure freezing of MNT-1 melanoma cells and freeze substitution to optimize ultrastructural preservation followed by double tilt 3D electron tomography, we show that the amyloid-like fibrils begin to form in multivesicular compartments, where they radiate from the luminal side of intralumenal membrane vesicles. The fibrils in fully formed stage II premelanosomes organize into sheet-like arrays and exclude the remaining intralumenal vesicles, which are smaller and often in continuity with the limiting membrane. These observations indicate that premelanosome fibrils form in association with intralumenal endosomal membranes. We suggest that similar processes regulate amyloid formation in pathological models. PMID:19033461

  19. Electron Plasma Oscillations and Related Effects Observed By Voyager 1 in the Interstellar Plasma during 2014

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.; Kurth, W. S.; Stone, E. C.; Cummings, A. C.; Krimigis, S. M.; Decker, R. B.; Ness, N. F.; Burlaga, L. F.

    2014-12-01

    It is now well known that the Voyager 1 spacecraft crossed the heliopause into interstellar space in late August 2012. A key observation supporting this conclusion was the detection of electron plasma oscillations in October-November 2012, and again in April-May 2013. These observations showed the local electron density was consistent with the expected density of the local interstellar plasma. Such plasma oscillations are believed to be excited by electron beams originating from shocks associated with global merged interaction regions (GMIRs) propagating outward from the Sun. Now, another series of plasma oscillation events has been observed starting in early February 2014, and continuing to the present time (late July 2014). These events show a clear association with changes in the cosmic ray intensities and anisotropies that are suggestive of a solar disturbance propagating outward through the interstellar plasma. The interpolated radial density profile inferred from these and the previous plasma oscillations shows that after crossing the heliopause the electron density increased rapidly from 0.055 cm-3 in late October 2012, at 122 AU, to a broad maximum of about 0.090 to 0.095 cm-3 in July-August 2013, at about 125 AU, followed by a slow decrease to about 0.085 cm-3 in the most recent data, at 128 AU. This density profile is consistent with a large-scale compression (i.e., pileup) of the interstellar plasma near the nose of the heliosphere, together with a smaller scale plasma depletion layer immediately adjacent to the heliopause, as suggested by Fuselier and Cairns [2013].

  20. PECVD of SiOC Films Using a Sheet-type Atmospheric Pressure Plasma Jet

    NASA Astrophysics Data System (ADS)

    Nakajima, Kouta; Tanaka, Kenji; Shirafuji, Tatsuru

    2015-09-01

    Packaging industries have used SiOC thin films for gas barrier coatings on the membranes for packaging foods, drug, and so on. PECVD is the most extensively employed method for preparing the SiOC films. However, PECVD is a process performed at a low pressure in general and requires expensive vacuum systems, especially in the case of large area coatings. Atmospheric pressure PECVD is a candidate to overcome this issue. If we simply apply atmospheric pressure plasma to CVD processes, however, we will encounter the problem of particle formation because of the high collision frequency in the environment of atmospheric pressure. In this work, we have developed a reactor that utilizes a unique gas-flow scheme for avoiding the particle formation. We have successfully deposited SiOC films by using this reactor, in which the source material is hexamethyldisiloxane and discharge/carrier gas is He. XPS measurements on the SiOC films have revealed that the films contain relatively higher concentrations of unfavorable methyl groups that reduce gas barrier performances. However, no particulates are involved in and on the deposited films as long as characterizing the films with eye observation and with transmission electron microscopy.

  1. Effects of target plasma electron-electron collisions on correlated motion of fragmented protons.

    PubMed

    Barriga-Carrasco, Manuel D

    2006-02-01

    The objective of the present work is to examined the effects of plasma target electron-electron collisions on H2 + protons traversing it. Specifically, the target is deuterium in a plasma state with temperature Te=10 eV and density n=10(23) cm(-3), and proton velocities are vp=vth, vp=2vth, and vp=3vth, where vth is the electron thermal velocity of the target plasma. Proton interactions with plasma electrons are treated by means of the dielectric formalism. The interactions among close protons through plasma electronic medium are called vicinage forces. It is checked that these forces always screen the Coulomb explosions of the two fragmented protons from the same H2 + ion decreasing their relative distance. They also align the interproton vector along the motion direction, and increase the energy loss of the two protons at early dwell times while for longer times the energy loss tends to the value of two isolated protons. Nevertheless, vicinage forces and effects are modified by the target electron collisions. These collisions enhance the calculated self-stopping and vicinage forces over the collisionless results. Regarding proton correlated motion, when these collisions are included, the interproton vector along the motion direction overaligns at slower proton velocities (vp=vth) and misaligns for faster ones (vp=2vth, vp=3vth). They also contribute to a great extend to increase the energy loss of the fragmented H2 + ion. This later effect is more significant in reducing projectile velocity. PMID:16605459

  2. Spatial distributions of ion pitch angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Ping; Zaharia, Sorin G.; Lyons, Larry R.; Angelopoulos, Vassilis

    2013-01-01

    We have quantified anisotropy of ion pitch angle distributions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and determined statistically how anisotropy varies with particle energy, as well as spatial distributions and dependences on geomagnetic activity. In the tail plasma sheet, ions from a few keV to a few tens of keV are mostly isotropic. The locations and energy ranges for these isotropic ions and their changes with Dst are consistent with ions being isotropized by current sheet scattering predicted using empirical magnetic field models. Ions of a few hundreds of keV in the tail have cigar-shaped or unidirectional pitch angle distribution (PAD) and are likely a result of Speiser motion. The majority of ions in the near-Earth magnetosphere are expected to conserve their first and second adiabatic invariants as they move with pitch angle dependent drift. This gives drift shell splitting, which plays an important role in generating pancake-shaped PAD observed from ~1 keV up to hundreds of keV. The magnetic local time of the pancake PAD rotates with increasing energy. Loss of near 90° ions due to magnetopause shadowing can further explain the butterfly-shaped PAD observed at the postmidnight sector at energies above 30 keV. For ions below a few hundreds of eV in the tail plasma sheet and the near-Earth magnetosphere, their PAD is dominantly bidirectional, which is likely due to ionosphere outflow. High-energy ions on the dayside become less anisotropic during higher AE, when pitch angle scattering by electromagnetic ion cyclotron waves may play an important role.

  3. Kinetics of transient plasmas generated by accelerated electrons and protons

    SciTech Connect

    Seval`nikov, A.Yu.; Skvortsov, V.A.

    1994-12-31

    The aim of the work was to carry out numerical studies and comparative analysis of plasmochemical effects of electron and proton beams in atomic and molecular gases such as nitrogen and air. The questions of transient beam plasma heating and charge kinetics were considered. Calculations were made using the SKIF model taking into account more than 200 plasmochemical and elementary processes including those with the participation of non-Maxwellian electrons generated by the processes of gas molecule ionization by beam particles. We used a simplified analytical model for the calculation of the distribution function of these electrons that allowed us to reduce computational expenses considerably. 26 refs., 6 figs.

  4. Electron beam generated whistler emissions in a laboratory plasma

    NASA Astrophysics Data System (ADS)

    Van Compernolle, B.; An, X.; Bortnik, J.; Thorne, R. M.; Pribyl, P.; Gekelman, W.

    2015-12-01

    Naturally occurring whistler mode emissions in the magnetosphere, are important since they are responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Recently, we reported on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced [1]. A beam of energetic electrons is launched into a cold plasma and excites both chirping whistler waves and broadband waves. Here we extend our previous analysis by comparing the properties of the broadband waves with linear theory.

  5. Electron-acoustic plasma waves: oblique modulation and envelope solitons.

    PubMed

    Kourakis, I; Shukla, P K

    2004-03-01

    Theoretical and numerical studies are presented of the amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, Boltzmann distributed hot electrons, and stationary ions. Perturbations oblique to the carrier EAW propagation direction have been considered. The stability analysis, based on a nonlinear Schrödinger equation, reveals that the EAW may become unstable; the stability criteria depend on the angle theta between the modulation and propagation directions. Different types of localized EA excitations are shown to exist. PMID:15089419

  6. Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

    NASA Technical Reports Server (NTRS)

    Jung, Young-Dae

    1993-01-01

    Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

  7. Turbulence and transport in two-dimensional magnetized electron plasmas

    SciTech Connect

    Shaikh, Dastgeer; Shukla, P. K.

    2008-04-15

    Electron plasmas confined by an external magnetic field exhibit variations in a two-dimensional plane orthogonal to the confining magnetic field. A nonlinear fluid simulation code to investigate the properties of 2D electron plasma wave turbulence in a nonuniform magnetoplasma has been developed. It is found that the presence of the density gradient convection by mean electric fields considerably influence the characteristic nonlinear interaction processes, such as the energy cascades and the cross-field electron transport. The initial random turbulent state evolves towards an intermittent state where forward cascade of vorticity coexists with an inverse cascade of electric potential fluctuations. The latter lead to the formation of large scale entities in 2D electron plasmas and can be alternatively understood by seeking exact nonlinear coherent vortex solutions in the form of a dipolarlike configuration. The energy cascades are governed typically by the Kolmogorov-type k{sup -5/3} spectrum. In agreement with the experimental observations, we find that the electron transport is improved significantly by the application of an externally imposed electric field.

  8. Stability of hot electron plasma in the ELMO bumpy torus

    NASA Astrophysics Data System (ADS)

    Tsang, K. T.; Cheng, C. Z.

    The stability of a hot electron plasma in the ELMO Bumpy Torus was investigated using two different models. In the first model, where the hot electron distribution function is assumed to be a delta function in the perpendicular velocity, a stability boundary in addition to those discussed by Nelson and by Van Dam and Lee is found. In the second model, where the hot electron distribution function is assumed to be a Maxwellian in the perpendicular velocity, stability boundaries significantly different from those of the first model are found. Coupling of the Nelson-Van Dam-Lee mode to the compressional Alfven mode is now possible. This leads to a higher permissible core plasma beta value for stable operation.

  9. Plasma source for ion and electron beam lithography

    SciTech Connect

    Lee, Y.; Gough, R.A.; Leung, K.N.; Vujic, J.; Williams, M.D.; Zahir, N.; Fallman, W.; Tockler, M.; Bruenger, W.

    1998-11-01

    A new plasma source configuration, coaxial source, has been developed at the Lawrence Berkeley National Laboratory suitable for ion and electron beam lithography applications. The axial ion energy spread and electron temperature of the multicusp ion source have been reduced considerably from 2 and 0.3 eV to a record low of 0.6 eV by employing a coaxial source arrangement. Results of ion projection lithographic exposure at the Fraunhofer Institute demonstrate that feature size less than 65 nm can be achieved by using a filter-equipped multicusp ion source. Langmuir probe measurements also show that very low energy spread electron beams can be obtained with the multicusp plasma generator. {copyright} {ital 1998 American Vacuum Society.}

  10. Nonextensive statistical mechanics approach to electron trapping in degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Mebrouk, Khireddine; Gougam, Leila Ait; Tribeche, Mouloud

    2016-06-01

    The electron trapping in a weakly nondegenerate plasma is reformulated and re-examined by incorporating the nonextensive entropy prescription. Using the q-deformed Fermi-Dirac distribution function including the quantum as well as the nonextensive statistical effects, we derive a new generalized electron density with a new contribution proportional to the electron temperature T, which may dominate the usual thermal correction (∼T2) at very low temperatures. To make the physics behind the effect of this new contribution more transparent, we analyze the modifications arising in the propagation of ion-acoustic solitary waves. Interestingly, we find that due to the nonextensive correction, our plasma model allows the possibility of existence of quantum ion-acoustic solitons with velocity higher than the Fermi ion-sound velocity. Moreover, as the nonextensive parameter q increases, the critical temperature Tc beyond which coexistence of compressive and rarefactive solitons sets in, is shifted towards higher values.

  11. Electron energy spectrum in circularly polarized laser irradiated overdense plasma

    NASA Astrophysics Data System (ADS)

    Liu, C. S.; Tripathi, V. K.; Shao, Xi; Kumar, Pawan

    2014-10-01

    A circularly polarized laser normally impinged on an overdense plasma thin foil target is shown to accelerate the electrons in the skin layer towards the rear, converting the quiver energy into streaming energy exactly if one ignores the space charge field. The energy distribution of electrons is close to Maxwellian with an upper cutoff ɛmax=m c2(1 +a02) 1 /2-1 ] , where a02=(1 +(2 ω2/ωp2)|ai n|2) 2-1 , |ai n| is the normalized amplitude of the incident laser of frequency ω, and ωp is the plasma frequency. The energetic electrons create an electrostatic sheath at the rear and cause target normal sheath acceleration of protons. The energy gain by the accelerated ions is of the order of ɛmax .

  12. Resonant scattering of central plasma sheet protons by multiband EMIC waves and resultant proton loss timescales

    NASA Astrophysics Data System (ADS)

    Cao, Xing; Ni, Binbin; Liang, Jun; Xiang, Zheng; Wang, Qi; Shi, Run; Gu, Xudong; Zhou, Chen; Zhao, Zhengyu; Fu, Song; Liu, Jiang

    2016-02-01

    This is a companion study to Liang et al. (2014) which reported a "reversed" energy-latitude dispersion pattern of ion precipitation in that the lower energy ion precipitation extends to lower latitudes than the higher-energy ion precipitation. Electromagnetic ion cyclotron (EMIC) waves in the central plasma sheet (CPS) have been suggested to account for this reversed-type ion precipitation. To further investigate the association, we perform a comprehensive study of pitch angle diffusion rates induced by EMIC wave and the resultant proton loss timescales at L = 8-12 around the midnight. Comparing the proton scattering rates in the Earth's dipole field and a more realistic quiet time geomagnetic field constructed from the Tsyganenko 2001 (T01) model, we find that use of a realistic, nondipolar magnetic field model not only decreases the minimum resonant energies of CPS protons but also considerably decreases the limit of strong diffusion and changes the proton pitch angle diffusion rates. Adoption of the T01 model increases EMIC wave diffusion rates at > ~ 60° equatorial pitch angles but decreases them at small equatorial pitch angles. Pitch angle scattering coefficients of 1-10 keV protons due to H+ band EMIC waves can exceed the strong diffusion rate for both geomagnetic field models. While He+ and O+ band EMIC waves can only scatter tens of keV protons efficiently to cause a fully filled loss cone at L > 10, in the T01 magnetic field they can also cause efficient scattering of ~ keV protons in the strong diffusion limit at L > 10. The resultant proton loss timescales by EMIC waves with a nominal amplitude of 0.2 nT vary from a few hours to several days, depending on the wave band and L shell. Overall, the results demonstrate that H+ band EMIC waves, once present, can act as a major contributor to the scattering loss of a few keV protons at lower L shells in the CPS, accounting for the reversed energy-latitude dispersion pattern of proton precipitation at low energies (~ keV) on the nightside. The pitch angle coverage for H+ band EMIC wave resonant scattering strongly depends on proton energy, L shell, and field model. He+ and O+ band EMIC waves tend to cause efficient scattering loss of protons at higher energies, thereby importantly contributing to the isotropic distribution of higher energy (> ~ 10 keV) protons at higher L shells on the nightside where the geomagnetic field line is highly stretched. Our results also suggest that scattering by H+ band EMIC waves may significantly contribute to the formation of the reversed-type CPS proton precipitation on the dawnside where both the wave activity and occurrence probability is statistically high.

  13. Feedback control of plasma electron density and ion energy in an inductively coupled plasma etcher

    SciTech Connect

    Lin Chaung; Leou, K.-C.; Huang, H.-M.; Hsieh, C.-H.

    2009-01-15

    Here the authors report the development of a fuzzy logic based feedback control of the plasma electron density and ion energy for high density plasma etch process. The plasma electron density was measured using their recently developed transmission line microstrip microwave interferometer mounted on the chamber wall, and the rf voltage was measured by a commercial impedance meter connected to the wafer stage. The actuators were two 13.56 MHz rf power generators which provided the inductively coupled plasma power and bias power, respectively. The control system adopted the fuzzy logic control algorithm to reduce frequent actuator action resulting from measurement noise. The experimental results show that the first wafer effect can be eliminated using closed-loop control for both poly-Si and HfO{sub 2} etching. In particular, for the HfO2 etch, the controlled variables in this work were much more effective than the previous one where ion current was controlled, instead of the electron density. However, the pressure disturbance effect cannot be reduced using plasma electron density feedback.

  14. Theoretical Studies of Pure Electron Plasmas in Asymmetric Traps.

    NASA Astrophysics Data System (ADS)

    Chu, Ronson Yiu-Yuen

    Pure electron plasmas are routinely confined within cylindrically symmetric Penning traps by static electric and magnetic fields. However, the azimuthal symmetry can be broken by applied perturbations. In this thesis, the static and dynamic properties of plasmas confined in traps with such applied electric field asymmetries are investigated. The shapes of the non-circular plasma equilibria are studied both analytically and numerically. A simple analytic model for the boundary of a uniform density asymmetric plasma is derived, and it agrees well with vortex-in-cell simulations. Both the analytical results and numerical simulations agree with the shapes observed in experiments. Furthermore, an energy principle is used to prove that these asymmetric plasmas are stable to {bf E }times{bf B} drift perturbations, when the asymmetries are small. For an l = 1 diocotron mode in a cylindrically symmetric trap, the plasma rotates as a rigid column in a circular orbit. In contrast, plasmas in systems with electric field asymmetries are shown to have an analog to the l = 1 mode in which the shape of the plasma changes as it rotates in a non-circular orbit. These bulk plasma features are studied with a Hamiltonian model, in which elliptical plasma shapes are assumed. Equations for the motion of the center of the plasma, its ellipticity, and its orientation are derived. It is seen that, for a small plasma, the evolution of the plasma shape and orientation has little effect on the center of charge motion, and the area enclosed by the center of charge orbit is an invariant when electric field perturbations are applied adiabatically. This invariant has been observed experimentally. Detailed studies are made of the breaking of the invariant when perturbations are rapidly applied. The dynamic Hamiltonian model is also used to predict the shape and frequency of the large amplitude l = 1 and l = 2 diocotron modes in symmetric traps, and good agreement with experimental results is obtained. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  15. Electron Densities Near Io from Galileo Plasma Wave Observations

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Persoon, A. M.; Kurth, W. S.; Roux, A.; Bolton, S. J.

    2001-01-01

    This paper presents an overview of electron densities obtained near Io from the Galileo plasma wave instrument during the first four flybys of Io. These flybys were Io, which was a downstream wake pass that occurred on December 7, 1995; I24, which was an upstream pass that occurred on October 11, 1999; I25, which was a south polar pass that occurred on November 26, 1999; and I27, which was an upstream pass that occurred on February 22, 2000. Two methods were used to measure the electron density. The first was based on the frequency of upper hybrid resonance emissions, and the second was based on the low-frequency cutoff of electromagnetic radiation at the electron plasma frequency. For three of the flybys, Io, I25, and I27, large density enhancements were observed near the closest approach to Io. The peak electron densities ranged from 2.1 to 6.8 x 10(exp 4) per cubic centimeters. These densities are consistent with previous radio occultation measurements of Io's ionosphere. No density enhancement was observed during the I24 flyby, most likely because the spacecraft trajectory passed too far upstream to penetrate Io's ionosphere. During two of the flybys, I25 and I27, abrupt step-like changes were observed at the outer boundaries of the region of enhanced electron density. Comparisons with magnetic field models and energetic particle measurements show that the abrupt density steps occur as the spacecraft penetrated the boundary of the Io flux tube, with the region of high plasma density on the inside of the flux tube. Most likely the enhanced electron density within the Io flux tube is associated with magnetic field lines that are frozen to Io by the high conductivity of Io's atmosphere, thereby enhancing the escape of plasma along the magnetic field lines that pass through Io's ionosphere.

  16. Simulation studies on stability of hot electron plasma

    NASA Astrophysics Data System (ADS)

    Ohsawa, Y.

    1985-03-01

    Stability of a hot electron plasma in a NBT(EBT)-like geometry is studied, using a 2-1/2 dimensional relativistic, electromagnetic particle code. In the simulation model, spatial variation is allowed only in the x- and y- directions, with the z-direction being an ignorable coordinate, although the particles have three velocity components (u sub x, v sub y, v sub z). The system is periodic in the y-direction and is bounded in the x-direction with total grid size L sub x xL sub y=128d x 128d, where d is the grid spacing. The external magnetic field B sub 0 is formed by an external current J sub 0 which is rigid and not influenced by the plasma. The external magnetic field B sub 0 points in the z-direction, and its strength decreases with x as 1/(x-Lx-2+R), where the constant R is a measure of the magnetic field gradient. The initial plasma density also decreases with x. All quantities are constant in the y-direction in the equilibrium state. Because both the external magnetic field and the plasma density (pressure) decreases with x, the plasma can be interchange unstable if there is no hot electron layer.

  17. Growth in Electron Plasma Radius Caused By Fast Proton Beam*

    NASA Astrophysics Data System (ADS)

    Pollock, R. E.; Ellsworth, Jennifer; Muterspaugh, M. W.; Todd, D. S.

    1999-11-01

    A slightly warmed nonneutral electron plasma is stabilized in a long-lived state with slow particle loss to the trap wall balanced by weak ionization of background gas. Sub-nanowatt power is input by noise, or a line source tuned below a resonance, while a rotating electric field provides compressional torque. From line charge density, extracted from the diocotron frequency, and plasma potential, extracted from a G-T mode frequency, a non-destructive measure of the plasma radius is obtained. When the plasma is bombarded by 0.2 GeV protons in the IUCF storage ring, this radius is observed to increase with proton current. The effect is insensitive to changes in beam position or angle relative to the plasma symmetry axis. Torque estimated from proton-electron Coulomb scatter is orders of magnitude too small to explain the observations. The mechanism for beam-induced radial growth remains unexplained. Progress toward torque calibration, and containment with higher magnetic field, will be described. *Work supported by US DOE (DE FG0297 ER 54433) & US NSF (PHY 96-02872, 94-23896).

  18. Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams.

    PubMed

    van Tilborg, J; Steinke, S; Geddes, C G R; Matlis, N H; Shaw, B H; Gonsalves, A J; Huijts, J V; Nakamura, K; Daniels, J; Schroeder, C B; Benedetti, C; Esarey, E; Bulanov, S S; Bobrova, N A; Sasorov, P V; Leemans, W P

    2015-10-30

    Compact, tunable, radially symmetric focusing of electrons is critical to laser-plasma accelerator (LPA) applications. Experiments are presented demonstrating the use of a discharge-capillary active plasma lens to focus 100-MeV-level LPA beams. The lens can provide tunable field gradients in excess of 3000 T/m, enabling cm-scale focal lengths for GeV-level beam energies and allowing LPA-based electron beams and light sources to maintain their compact footprint. For a range of lens strengths, excellent agreement with simulation was obtained. PMID:26565471

  19. Concept of a laser-plasma-based electron source for sub-10-fs electron diffraction

    NASA Astrophysics Data System (ADS)

    Faure, J.; van der Geer, B.; Beaurepaire, B.; Gallé, G.; Vernier, A.; Lifschitz, A.

    2016-02-01

    We propose a new concept of an electron source for ultrafast electron diffraction with sub-10-fs temporal resolution. Electrons are generated in a laser-plasma accelerator, able to deliver femtosecond electron bunches at 5 MeV energy with a kilohertz repetition rate. The possibility of producing this electron source is demonstrated using particle-in-cell simulations. We then use particle-tracking simulations to show that this electron beam can be transported and manipulated in a realistic beam line, in order to reach parameters suitable for electron diffraction. The beam line consists of realistic static magnetic optics and introduces no temporal jitter. We demonstrate numerically that electron bunches with 5-fs duration and containing 1.5 fC per bunch can be produced, with a transverse coherence length exceeding 2 nm, as required for electron diffraction.

  20. Vacuum laser acceleration of relativistic electrons using plasma mirror injectors

    NASA Astrophysics Data System (ADS)

    Thévenet, M.; Leblanc, A.; Kahaly, S.; Vincenti, H.; Vernier, A.; Quéré, F.; Faure, J.

    2016-04-01

    Accelerating particles to relativistic energies over very short distances using lasers has been a long-standing goal in physics. Among the various schemes proposed for electrons, vacuum laser acceleration has attracted considerable interest and has been extensively studied theoretically because of its appealing simplicity: electrons interact with an intense laser field in vacuum and can be continuously accelerated, provided they remain at a given phase of the field until they escape the laser beam. But demonstrating this effect experimentally has proved extremely challenging, as it imposes stringent requirements on the conditions of injection of electrons in the laser field. Here, we solve this long-standing experimental problem by using a plasma mirror to inject electrons in an ultraintense laser field, and obtain clear evidence of vacuum laser acceleration. With the advent of petawatt lasers, this scheme could provide a competitive source of very high charge (nC) and ultrashort relativistic electron beams.

  1. Suprathermal Electrons in the Plasma Environments of Mars and Venus

    NASA Astrophysics Data System (ADS)

    Brain, D. A.

    2014-12-01

    Suprathermal electrons have been measured in situ at every planet in the solar system, as well as at many smaller solar system bodies. They are hallmarks of heating, acceleration, or non-equilibrium processes occurring in any plasma, and planets are no exception. After introducing the many planetary measurements that have been made over time, this presentation will focus on a subset of electron measurements from Mars and Venus made over the last decade. At Mars, suprathermal electrons are used as diagnostics of auroral acceleration in small-scale crustal fields, and the magnetic topology of the crustal fields. At Venus, electron energy distributions are used to map the ionosphere, revealing previously unknown asymmetries. The presentation will close with a brief discussion of prospects for future and ongoing planetary electron measurements.

  2. Calculation of electronic transport coefficients of Ag and Au plasma.

    PubMed

    Apfelbaum, E M

    2011-12-01

    The thermoelectric transport coefficients of silver and gold plasma have been calculated within the relaxation-time approximation. We considered temperatures of 10-100 kK and densities of ρ plasma composition was calculated using a corresponding system of coupled mass action laws, including the atom ionization up to +4. For momentum cross sections of electron-atom scattering we used the most accurate expressions available. The results of our modeling have been compared with other researchers' data whenever possible. PMID:22304204

  3. Kinetic modelling of runaway electron avalanches in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Peysson, Y.; Granetz, R. S.; Saint-Laurent, F.; Vlainic, M.

    2015-09-01

    Runaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runaway electrons mainly through knock-on collisions (Hender et al 2007 Nucl. Fusion 47 S128-202), where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of runaway electrons. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. For this purpose, a bounce-averaged knock-on source term is derived. The generation of runaway electrons from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a solver of the 3D linearized bounce-averaged relativistic electron Fokker-Planck equation (Decker and Peysson 2004 DKE: a fast numerical solver for the 3D drift kinetic equation Report EUR-CEA-FC-1736, Euratom-CEA), through the calculation of the response of the electron distribution function to a constant parallel electric field. The model, which has been successfully benchmarked against the standard Dreicer runaway theory now describes the runaway generation by knock-on collisions as proposed by Rosenbluth (Rosenbluth and Putvinski 1997 Nucl. Fusion 37 1355-62). This paper shows that the avalanche effect can be important even in non-disruptive scenarios. Runaway formation through knock-on collisions is found to be strongly reduced when taking place off the magnetic axis, since trapped electrons can not contribute to the runaway electron population. Finally, the relative importance of the avalanche mechanism is investigated as a function of the key parameters for runaway electron formation, namely the plasma temperature and the electric field strength. In agreement with theoretical predictions, the LUKE simulations show that in low temperature and electric field the knock-on collisions becomes the dominant source of runaway electrons and can play a significant role for runaway electron generation, including in non-disruptive tokamak scenarios.

  4. Thin Film Deposition of MAX Phase Nb-Al-C Compounds on Stainless Steel Substrates Using a Magnetized Sheet Plasma Source

    NASA Astrophysics Data System (ADS)

    Salamania, Janella Mae; Ramos, Henry

    2013-09-01

    Thin films of the Nb-Al-C system were deposited on stainless steel substrates through the magnetron sputtering mode of the Magnetized Sheet Plasma Facility from elemental source of Nb, Al metals and reactive gas CH4. Niobium and aluminum targets were first sputtered using argon plasma and were deposited together with CH4 gas onto the substrates. Various parameters such as target bias, time, filling pressure and extraction current were varied. Synthesized thin films were then characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX) and Raman Spectroscopy. XRD spectra of the samples show that MAX phases of the Nb-Al-C family are present on the films, specifically, the 413 phase (Nb4AlC3) . EDX and Raman spectra confirm the presence of the elemental niobium, aluminum and carbon in the films. Raman spectra show that excess carbon formed fine graphite crystallites. SEM surface images show that the resulting films follow the contours of the SS substrate. The cross-sectional images show micron scale thickness deposited above the SS substrates. We would like to thank the Department of Science and Technology for the funding of this project.

  5. Dense electron-positron plasmas generated by 10PW lasers in the QED-plasma regime

    NASA Astrophysics Data System (ADS)

    Ridgers, C. P.; Brady, C. S.; Kirk, J. G.; Blackburn, T.; Arber, T. D.; Bell, A. R.

    2013-05-01

    Electron-positron plasmas are a prominent feature of the high energy Universe. In the relativistic winds from pulsars and black holes it is thought that non-linear quantum electrodynamics (QED) processes cause electromagnetic energy to cascade into an e-e+ plasma. We show that next-generation 10PW lasers, available in the next few years, will generate such a high density of pairs that they create a micro-laboratory for the first experimental study of a similarly generated e-e+ plasma. In the first simulations of a 10PW laser striking a solid we demonstrate the production of a pure electron-positron plasma of density 1026m-3. This is seven orders of magnitude denser than currently achievable in the laboratory and is comparable to the critical density for commonly used lasers, marking a step change to collective e-e+ plasma behaviour. Furthermore, a new ultraefficient laser-absorption mechanism converts 35% of the laser energy to a burst of gamma-rays of intensity 1022Wcm-2, potentially the most intense gamma-ray source available in the laboratory. This absorption results in a strong feedback between both pair and gamma-ray production and classical plasma physics leading to a new physical regime of QED-plasma physics. In this new regime the standard particle-in-cell (PIC) simulation approach, which has been the dominant kinetic simulation tool in plasma physics for 50 years, is inadequate. We have developed a new approach (QED-PIC) which will provide a powerful new modelling tool essential to the future advancement of the field of high intensity laser-plasma interactions.

  6. Cleaning of Glass Disk in Oxygen Plasma by Using Compact Electron-Beam-Excited Plasma Source

    NASA Astrophysics Data System (ADS)

    Tada, Shigekazu; Ito, Masafumi; Hamagaki, Manabu; Hori, Masaru; Goto, Toshio

    2002-11-01

    We have applied a compact electron-bean-excited plasma (EBEP) source to the cleaning process for a glass disk. Since the EBEP enables us to control the ion sheath bias on the floating substrate by changing the electron-beam energy, the substrate ion bombardment energy to perform a reactive ion etching (RIE) can be determined without applying additional bias power supply such as RF. The source system has been modified in several ways so that it can be reliably used in the O2 plasma for a long time. In order to evaluate the cleaning capability of the source system, the etch performance of carbon film was investigated. It was found that the etching rate increased with electron-beam current and electron acceleration voltage. The etch rate of 4 nm/s was obtained at Va of 100 V and Ia of 2.5 A.

  7. A laser-plasma accelerator producing monoenergetic electron beams.

    PubMed

    Faure, J; Glinec, Y; Pukhov, A; Kiselev, S; Gordienko, S; Lefebvre, E; Rousseau, J-P; Burgy, F; Malka, V

    2004-09-30

    Particle accelerators are used in a wide variety of fields, ranging from medicine and biology to high-energy physics. The accelerating fields in conventional accelerators are limited to a few tens of MeV m(-1), owing to material breakdown at the walls of the structure. Thus, the production of energetic particle beams currently requires large-scale accelerators and expensive infrastructures. Laser-plasma accelerators have been proposed as a next generation of compact accelerators because of the huge electric fields they can sustain (>100 GeV m(-1)). However, it has been difficult to use them efficiently for applications because they have produced poor-quality particle beams with large energy spreads, owing to a randomization of electrons in phase space. Here we demonstrate that this randomization can be suppressed and that the quality of the electron beams can be dramatically enhanced. Within a length of 3 mm, the laser drives a plasma bubble that traps and accelerates plasma electrons. The resulting electron beam is extremely collimated and quasi-monoenergetic, with a high charge of 0.5 nC at 170 MeV. PMID:15457253

  8. Requirement for coenzyme Q in plasma membrane electron transport.

    PubMed Central

    Sun, I L; Sun, E E; Crane, F L; Morré, D J; Lindgren, A; Löw, H

    1992-01-01

    Coenzyme Q is required in the electron transport system of rat hepatocyte and human erythrocyte plasma membranes. Extraction of coenzyme Q from the membrane decreases NADH dehydrogenase and NADH:oxygen oxidoreductase activity. Addition of coenzyme Q to the extracted membrane restores the activity. Partial restoration of activity is also found with alpha-tocopherylquinone, but not with vitamin K1. Analogs of coenzyme Q inhibit NADH dehydrogenase and oxidase activity and the inhibition is reversed by added coenzyme Q. Ferricyanide reduction by transmembrane electron transport from HeLa cells is inhibited by coenzyme Q analogs and restored with added coenzyme Q10. Reduction of external ferricyanide and diferric transferrin by HeLa cells is accompanied by proton release from the cells. Inhibition of the reduction by coenzyme Q analogs also inhibits the proton release, and coenzyme Q10 restores the proton release activity. Trans-plasma membrane electron transport stimulates growth of serum-deficient cells, and added coenzyme Q10 increases growth of HeLa (human adenocarcinoma) and BALB/3T3 (mouse fibroblast) cells. The evidence is consistent with a function for coenzyme Q in a trans-plasma membrane electron transport system which influences cell growth. PMID:1454789

  9. Requirement for Coenzyme Q in Plasma Membrane Electron Transport

    NASA Astrophysics Data System (ADS)

    Sun, I. L.; Sun, E. E.; Crane, F. L.; Morre, D. J.; Lindgren, A.; Low, H.

    1992-12-01

    Coenzyme Q is required in the electron transport system of rat hepatocyte and human erythrocyte plasma membranes. Extraction of coenzyme Q from the membrane decreases NADH dehydrogenase and NADH:oxygen oxidoreductase activity. Addition of coenzyme Q to the extracted membrane restores the activity. Partial restoration of activity is also found with α-tocopherylquinone, but not with vitamin K_1. Analogs of coenzyme Q inhibit NADH dehydrogenase and oxidase activity and the inhibition is reversed by added coenzyme Q. Ferricyanide reduction by transmembrane electron transport from HeLa cells is inhibited by coenzyme Q analogs and restored with added coenzyme Q10. Reduction of external ferricyanide and diferric transferrin by HeLa cells is accompanied by proton release from the cells. Inhibition of the reduction by coenzyme Q analogs also inhibits the proton release, and coenzyme Q10 restores the proton release activity. Trans-plasma membrane electron transport stimulates growth of serum-deficient cells, and added coenzyme Q10 increases growth of HeLa (human adenocarcinoma) and BALB/3T3 (mouse fibroblast) cells. The evidence is consistent with a function for coenzyme Q in a trans-plasma membrane electron transport system which influences cell growth.

  10. Excitation of Plasma Waves in Aurora by Electron Beams

    NASA Technical Reports Server (NTRS)

    daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.

    1996-01-01

    In this paper, we study numerically the excitation of plasma waves by electron beams, in the auroral region above 2000 km of altitude. We have solved the fully kinetic dispersion relation, using numerical method and found the real frequency and the growth rate of the plasma wave modes. We have examined the instability properties of low-frequency waves such as the Electromagnetic Ion Cyclotron (EMIC) wave as well as Lower-Hybrid (LH) wave in the range of high-frequency. In all cases, the source of free energy are electron beams propagating parallel to the geomagnetic field. We present some features of the growth rate modes, when the cold plasma parameters are changed, such as background electrons and ions species (H(+) and O(+)) temperature, density or the electron beam density and/or drift velocity. These results can be used in a test-particle simulation code, to investigate the ion acceleration and their implication in the auroral acceleration processes, by wave-particle interaction.

  11. Collimated fast electron beam generation in critical density plasma

    SciTech Connect

    Iwawaki, T. Habara, H.; Morita, K.; Tanaka, K. A.; Baton, S.; Fuchs, J.; Chen, S.; Nakatsutsumi, M.; Rousseaux, C.; Filippi, F.; Nazarov, W.

    2014-11-15

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 10{sup 14 }W/cm{sup 2}, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 10{sup 14 }W/cm{sup 2}, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  12. Synchrotron radiation from electron beams in plasma-focusing channels.

    PubMed

    Esarey, E; Shadwick, B A; Catravas, P; Leemans, W P

    2002-05-01

    Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma-focusing channel is analyzed, and applications to plasma wake-field accelerator experiments and to the ion-channel laser (ICL) are discussed. Important similarities and differences between a free electron laser (FEL) and an ICL are delineated. It is shown that the frequency of spontaneous radiation is a strong function of the betatron strength parameter a(beta), which plays a role similar to that of the wiggler strength parameter in a conventional FEL. For a(beta) > or approximately 1, radiation is emitted in numerous harmonics. Furthermore, a(beta) is proportional to the amplitude of the betatron orbit, which varies for every electron in the beam. The radiation spectrum emitted from an electron beam is calculated by averaging the single-electron spectrum over the electron distribution. This leads to a frequency broadening of the radiation spectrum, which places serious limits on the possibility of realizing an ICL. PMID:12059723

  13. Electron acoustic solitons in magneto-rotating electron-positron-ion plasma with nonthermal electrons and positrons

    NASA Astrophysics Data System (ADS)

    Jilani, K.; Mirza, Arshad M.; Iqbal, J.

    2015-02-01

    The propagation of electron acoustic solitary waves (EASWs) in a magneto-rotating electron-positron-ion (epi) plasma containing cold dynamical electrons, nonthermal electrons and positrons obeying Cairns' distribution have been explored in the stationary background of massive positive ions. Through the linear dispersion relation (LDR) the effects of nonthermal components, magnetic field and rotation have been analyzed, wherein, various limiting cases have been deduced from the LDR. For nonlinear analysis, Korteweg-de Vries (KdV) equation is obtained using the reductive perturbation technique. It is found that in the presence of nonthermal positrons both hump and dip type solitons appear to excite, the structural properties of these solitary waves change drastically with magneto-rotating effects. The present work may be employed to explore and to understand the formation of electron acoustic solitary structures in the space and laboratory plasmas with nonthermal electrons and positrons under magneto-rotating effects.

  14. Observations of underdense plasma lens focusing of relativistic electron beams

    SciTech Connect

    Thompson, M.C.; Badakov, H.; Rosenzweig, J.B.; Travish, G.; Fliller, R.; Kazakevich, G.M.; Piot, P.; Santucci, J.; Li, J.; Tikhoplav, R.; /Rochester U.

    2007-06-01

    Focusing of a 15 MeV, 19 nC electron bunch by an underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in experiments at the Fermilab NICADD Photoinjector Laboratory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam-envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Correlations between the beam charge and the properties of the beam focus corroborate this conclusion.

  15. Plasma Wakefield Acceleration Simulations with Multiple Electron Bunches

    NASA Astrophysics Data System (ADS)

    Kallos, Efthymios; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Park, Jangho; Babzien, Marcus; Lichtl, Adam

    2008-11-01

    In the multibunch plasma wakefield accelerator, a train of electron bunches is utilized to excite a high gradient wakefield in a plasma which can be sampled by a trailing short witness bunch. We show that for five drive bunches with 150 pC total charge which can be generated in the Accelerator Test Facility of the Brookhaven National Lab, a wakefield of 140 MV/m can be generated if the plasma density is matched to the bunch train period. In addition, the possibility of ramping the charge per bunch in order to achieve high transformer ratios (>5) is examined, a scenario that is of great interest for a future afterburner collider. The work was supported by the US Department of Energy.

  16. Possible excitation of solitary electron holes in a laboratory plasma

    SciTech Connect

    Kar, S.; Mukherjee, S.; Ravi, G.; Saxena, Y. C.

    2010-10-15

    Plasma response to a fast rising high positive voltage pulse is experimentally studied in a uniform and unmagnetized plasma. The pulse is applied to a metallic disk electrode immersed in a low pressure argon plasma (n{sub p{approx}}10{sup 9} cm{sup -3} and T{sub e{approx}}0.5-2 eV) with the pulse magnitude U{sub 0}>>kT{sub e}/e, where T{sub e} is the electron temperature. Experiments have been carried out for various applied pulse widths {tau}{sub p} ranging from less than 3f{sub i}{sup -1} to greater than 3f{sub i}{sup -1}, where f{sub i} is the ion plasma frequency. For pulse widths less than 3f{sub i}{sup -1}, potential disturbances are observed to propagate in two opposite directions from a location different from the actual exciter (metal disk electrode), indicating the presence of a virtual source. For pulse widths equal or greater than 3f{sub i}{sup -1}, there is no indication of such virtual source. These disturbances propagate with two phase speeds, i.e., v{sub p}/v{sub e}=1.36{+-}0.11 and 0.4{+-}0.15, where v{sub e} is the electron thermal speed. It is also observed that by increasing plasma density, the speed of these disturbances increases, whereas the speed is independent of pulse magnitude. Analysis of these disturbances indicates the excitation of solitary electron holes.

  17. Electron trajectories and growth rates of the plasma wave pumped free-electron laser

    NASA Astrophysics Data System (ADS)

    Jafari, S.; Jafarinia, F.; Nilkar, M.; Amiri, M.

    2014-12-01

    A theory for a plasma wave wiggler has been described which employs the plasma whistler wave for producing laser radiation in a free-electron laser (FEL). While electromagnetically pumped FELs have been proven to be an effective means generating short wavelengths, practical difficulties occur in the design of these wigglers. For this reason, it is found that a plasma wave wiggler can be employed in concept with an electromagnetic wave wiggler due to both higher tunability and holding the focus of pump wave and e-beam over a significant distance to achieve a suitable amplification. Plasma in the presence of static magnetic field supports a plasma whistler wave. The plasma wiggler period can be tuned by varying the plasma density and/or ambient magnetic field. Electron trajectories have been analyzed using single particle dynamics and regimes of orbital stability have been demonstrated. A polynomial dispersion relation for electromagnetic and space-charge waves has then been derived, analytically. Numerical studies of the dispersion relation reveal that the growth rates are sensitive functions of the cyclotron frequency. It has been shown that by increasing the axial magnetic field strength (or cyclotron frequency), the growth rate for groups I and III orbits increases, while a growth decrement has been obtained for groups II and IV orbits.

  18. Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Erickson, K. N.

    1990-01-01

    The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

  19. Electron heating in capacitively coupled RF plasmas: a unified scenario

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf Peter

    2016-02-01

    Electron heating in radio-frequency capacitively coupled plasmas (RF-CCP) is studied from first principles. The starting points are the electron equations of continuity and motion, with ionization neglected but electric and pressure forces and elastic collisions with the neutral background taken into account. Poisson’s equation self-consistently calculates the electric field; the ion density is assumed as a given. Postulating that the Debye length {λ\\text{D}} is small compared to the sheath length scale l and the applied frequency {ω\\text{RF}} is small compared to the electron plasma frequency {ω\\text{pe}} , an asymptotic expansion in the smallness parameter ε ={λ\\text{D}}/l∼ {ω\\text{RF}}/{ω\\text{pe}} is conducted. As has been demonstrated before (Brinkmann 2015 Plasma Sources Sci. Technol. 24 064002), this ansatz gives an expression—the smooth step model (SSM)—which yields (i) the space charge field in the unipolar region, (ii) the generalized Ohmic field in the ambipolar region, and (iii) a smooth interpolation for the rapid transition in between. Using the SSM and formulas for the electron density and the electron flux, expressions for the electric force and the electric power density are established which hold up to O≤ft(ε \\right) . Integrating over the sheath and taking the phase average, a representation for the total dissipated power is found as a sum of four physically distinct contributions. All terms correspond to electron heating mechanisms which are (explicitly or implicitly) already known but were so far discussed only within mutually incompatible frameworks.

  20. Modeling Plasmas with a Kappa Electron Energy Distribution

    NASA Astrophysics Data System (ADS)

    Hahn, Michael; Savin, Daniel Wolf

    2016-05-01

    Nonthermal kappa electron energy distributions have been observed in the Earth's magnetosphere and the solar wind, and are likely also present in the solar corona and in solar flares. In order to model the spectra of these plasmas, it is necessary to obtain the appropriate collision rate coefficients. We show that this can be done simply by summing appropriately weighted Maxwellian rate coefficients. The resulting data have similar or better accuracies than are obtained with other approaches. Summing Maxwellians has the additional advantages of being easy to implement and extendable to many different collision processes. We apply this technique to modeling the charge state distribution (CSD) of kappa-distribution plasmas. In particular, we examine the influence of electron impact multiple ionization on the equilibrium CSD and calculate the time variation of the CSD during a solar flare.