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1

Spatial distribution of energetic plasma sheet electrons.  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

2

Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study  

E-print Network

Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail and the solar wind, as well as >2 MeV geosynchronous electrons, is investigated using plasma sheet measurements from Cluster (2001­2005) and Geotail (1998­2005) and concurrent solar wind measurements from ACE

Li, Xinlin

3

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

4

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

SciTech Connect

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.

Wang Chao; Diao Dongfeng; Fan Xue; Chen Cheng [Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, 710049 Xi'an (China)

2012-06-04

5

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

NASA Astrophysics Data System (ADS)

We used a low energy electron irradiation technique to prepare graphene sheets embedded carbon (GSEC) film based on electron cyclotron resonance plasma. The particular ? 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.

Wang, Chao; Diao, Dongfeng; Fan, Xue; Chen, Cheng

2012-06-01

6

Electromagnetic electron temperature anisotropy instability in the earth's magnetotail plasma sheet  

NASA Astrophysics Data System (ADS)

The electromagnetic fire hose instability driven by an electron temperature anisotropy is considered for parallel propagating waves as a possible explanation for the observations of magnetic noise bursts in the central plasma sheet of the geomagnetic tail. The approximative condition for instability is given. The fire hose instability could generate a wave frequency spectrum up to 3Hz with a maximum growth rate at 1Hz in the central plasma sheet.

Nikutowski, B.

1989-01-01

7

Electron generation of electrostatic waves in the plasma sheet boundary layer  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

8

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

NASA Technical Reports Server (NTRS)

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 entire 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.

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

1998-01-01

9

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

10

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

SciTech Connect

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 ?/?{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.

Hwang, Junga [Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Department of Astronomy and Space Science, University of Science and Technology, Daejeon (Korea, Republic of); Rha, Kicheol [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Seough, Jungjoon [Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Yoon, Peter H. [School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States)

2014-09-15

11

Plasma sheet boundary layer  

Microsoft Academic Search

The plasma sheet boundary layer is a temporally variable transition region located between the magnetotail lobes and the central plasma sheet. We have made a survey of these regions by using particle spectra and three-dimensional velocity-space distributions sampled by the ISEE 1 LEPEDEA. Ion composition measurements obtained by the Lockhead ion mass spectrometers indicate that ionospheric ions play a crucial

T. E. Eastman; L. A. Frank; W.K. Peterson; W. Lennartsson

1984-01-01

12

The Inner Edge of the Plasma Sheet, REGION-2 Currents, and Electron Precipitation: Plasma Observations from ISEE 1.  

NASA Astrophysics Data System (ADS)

On 17 April, 29 April, and 4 June of 1978 the ISEE 1 spacecraft encountered the inner edge of the plasma sheet on the dusk side of Earth at radial distances of 6 to 9 R_{rm E}. Measurements obtained with a plasma analyzer aboard this spacecraft are examined in an effort to determine the source of Region -2 Birkeland currents. Near the inner edge it is found that the distributions of both electrons and positive ions have low-energy field-aligned components that apparently originate at low altitudes. In two cases it is also found that the low-energy electrons carry a current that is consistent in direction and magnitude with Region-2 currents observed at low altitude. Positive ions with energies per charge _sp{~}{<}1 kV also stream along the field and sometimes provide a current that is comparable in magnitude but opposite in direction to the electron current. The low-energy electrons are counterstreaming and appear to be backscattered secondaries produced by precipitation of keV plasma sheet electrons into the atmosphere. The source of low-energy ions is not determined but is probably related to the electron flow, possibly by wave-particle interactions. An analysis of electron distributions indicates that the inner edge is a drift boundary separating open and closed flow trajectories. However, shielding there is found to be more localized than the shielding assumed in standard convection models. This shielding may be provided by the low-energy field-aligned plasmas. It is also found that the electron distributions at the inner edge are strongly modified, apparently by pitch-angle diffusion which drives keV electrons into the loss cone and scatters secondary electrons out of the source cone, and modification of the distributions by pitch-angle diffusion may also play a role in producing the field-aligned currents. Thus, it is found that precipitation and pitch -angle diffusion play important roles in determining the structure of the inner magnetosphere and may serve to couple apparently diverse phenomena such as diffuse aurora, Region -2 currents, and formation of the inner edge.

Paterson, William Russell

1990-01-01

13

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

SciTech Connect

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

Schumaker, T.L. (Physics Department, Boston College, Chestnut Hill, Massachusetts (US)); Gussenhoven, M.S. (Physics Department, Boston College, Chestnut Hill, Massachusetts (US)); Hardy, D.A. (Air Force Geophysics Laboratory, Hanscom Air Force Base, Massachusetts); Carovillano, R.L. (Physics Department, Boston College, Chestnut Hill, Massachusetts)

1989-08-01

14

Observations of correlated broadband electrostatic noise and electron-cyclotron emissions in the plasma sheet. Technical report  

SciTech Connect

Electric field wave observations in the central plasma sheet of the earth's magnetosphere show the correlated occurrence of broadband electrostatic noise and electrostatic electron cyclotron harmonic emissions. A model is proposed in which the broadband emissions are electron acoustic waves generated by an observed low energy electron beam, and the cyclotron emissions are generated by the hot electron loss cone instability. The high degree of correlation between the two emissions is provided in the model by the presence of the cold electron beam population, which allows both of the plasma instabilities to grow.

Roeder, J.L.; Angelopoulos, V.; Baumjohann, W.; Anderson, R.R.

1991-11-15

15

Average plasma properties in the central plasma sheet  

Microsoft Academic Search

A statistical study on the behaviors of ion and electron moments in the central plasma sheet was carried out using tail data obtained by the three-dimensional plasma instrument on board the AMPTE\\/IRM satellite in 1986. Results show that the ion temperature increases with increasing magnetic activity and the ion density decreases during disturbed intervals, except in the neutral sheet neighborhood

W. Baumjohann; G. Paschmann; C. A. Cattell

1989-01-01

16

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

PubMed Central

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

Lillemeier, Björn F.; Davis, Mark M.

2013-01-01

17

Sheet electron beam tester  

NASA Astrophysics Data System (ADS)

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.

Spear, Alexander Grenbeaux

18

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)

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.

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

2012-12-01

19

Heliospheric plasma sheets N. U. Crooker,1  

E-print Network

sheet (HPS) encasing the heliospheric current sheet shows a high degree of variability. A study of 52 that only half concur with both high-beta plasma and current sheets, as required for an HPS. The remaining et al. [1990a] designated the heliospheric plasma sheet (HPS) as the equatorial solar wind sandwiched

California at Berkeley, University of

20

MHD Ballooning Instability in the Plasma Sheet  

SciTech Connect

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.

C.Z. Cheng; S. Zaharia

2003-10-20

21

Microwave reflections from a vacuum ultraviolet laser produced plasma sheet  

E-print Network

) is the plasma frequency, m is the mass of the electron, is the permittivity of free space, is the microwaveMicrowave reflections from a vacuum ultraviolet laser produced plasma sheet K. L. Kelly, J. E and two-body recombination coefficient are measured by means of microwave backscatter plasma reflectivity

Scharer, John E.

22

Plasma sheet expansion: Statistical characteristics  

NASA Astrophysics Data System (ADS)

The present study addresses the cause of plasma sheet expansion by statistically comparing the characteristics of lobe-to-plasma sheet (LB-to-PS) and PS-to-LB crossings observed by the Geotail satellite. Whereas the flapping motion of the magnetotail causes both types of crossing, the PS expansion (thinning) can be associated only with the LB-to-PS (PS-to-LB) crossing. Thus any systematic difference between the two types of crossing should reflect the difference between the PS expansion and thinning. Geotail observed more LB-to-PS crossings (744 events) than PS-to-LB crossings (640 events), and the preferred occurrence of the LB-to-PS crossing is more manifest closer to the Earth. It is found that at the PS-to-LB crossing, the plasma moves in the same direction as the boundary motion. At the LB-to-PS crossing, in contrast, the plasma often moves in the opposite direction to the boundary motion, indicating that there is a finite electric field in the frame of the boundary motion associated with the PS expansion. The PS expansion is therefore considered to be a manifestation of magnetic reconnection. That is, the PS expands because new PS flux tubes are added onto the preexisting PS. In the course of the PS expansion, the total pressure decreases, which may be interpreted in terms of the replacement of the preexisting PS plasma with new low-pressure plasma originating from the tail lobe. The PS expansion is also characterized by relaxation (dipolarization) of the local magnetic field, which is inferred to be a direct consequence of reconnection. On the basis of recent reports of the lack of a one-to-one correspondence between reconnection and substorm onset, it is suggested that the PS expansion cannot be uniquely associated with a specific substorm phase.

Ohtani, S.; Mukai, T.

2006-05-01

23

Distant plasma sheet ion distributions during reconnection  

NASA Astrophysics Data System (ADS)

Previous models of the plasma sheet following reconnection and current sheet acceleration predict ’lima-bean’ ion distributions. These are inconsistent with observational constraints. We postulate that following initial interaction with the current sheet, a fraction of outflow ions are backscattered and re-encounter the current sheet. Fermi acceleration processes then generate an additional high-energy outflow population. In the backscatter region these ions form a complete shell in velocity space, providing sufficient pressure to support weak fields. Further from the current sheet, where backscatter is less efficient, a hemispherical shell of ions moves away from the current sheet, and field strengths are nearer the external lobe value. The fastest ions stream ahead of the bulk population to form the plasma sheet boundary layer. This model predicts a multi-layered plasma sheet structure, consistent with recent GEOTAIL observations.

Owen, C. J.; Mist, R. T.

24

Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows  

NASA Astrophysics Data System (ADS)

the interval ~07:45:36-07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (~3.2-95 keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (XGSM ~ -17.25 RE). However, the fluxes of the higher-energy electrons (?128 keV) and energetic ions (10-160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30°electrons, the low-energy electrons (~0.073-2.1 keV) have initially a field-aligned pitch angle distribution (0°???30° and 150°???180°) in the absence of whistler mode waves, and their loss in field-aligned directions is accompanied by their increase in quasi-perpendicular directions in the wave growth regions, but the loss of the low-energy electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

Li, L. Y.; Yu, J.; Cao, J. B.; Zhang, D.; Wei, X. H.; Rong, Z. J.; Yang, J. Y.; Fu, H. S.

2013-11-01

25

Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows  

NASA Astrophysics Data System (ADS)

During the interval 07:45:36- 07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (3.2- 95keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (X _{GSM}= -17.25 R _{E}). However, the fluxes of the higher-energy electrons (>128keV) and energetic ions (10- 160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30(°) electrons, the low-energy electrons (0.073- 2.1keV) have initially a field-aligned pitch angle distribution (0(°) electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

Li, L. Y.; Yu, J.; Cao, J. B.

26

Plasma sheet behavior during substorms  

SciTech Connect

Auroral or magnetic substorms are periods of enhanced auroral and geomagnetic activity lasting one to a few hours that signify increased dissipation of energy from the magnetosphere to the earth. Data acquired during the past decade from satellites in the near-earth sector of the magnetotail have suggested that during a substorm part of the plasma sheet is severed from earth by magnetic reconnection, forming a plasmoid, i.e., a body of plasma and closed magnetic loops, that flows out of the tail into the solar wind, thus returning plasma and energy that have earlier been accumulated from the solar wind. Very recently this picture has been dramatically confirmed by observations, with the ISEE 3 spacecraft in the magnetotail 220 R/sub E/ from earth, of plasmoids passing that location in clear delayed response to substorms. It now appears that plasmoid release is a fundamental process whereby the magnetosphere gives up excess stored energy and plasma, much like comets are seen to do, and that the phenomena of the substorm seen at earth are a by-product of that fundamental process.

Hones, E.W. Jr.

1983-01-01

27

The driving of the plasma sheet by the solar wind  

Microsoft Academic Search

The coupling of the plasma sheet to the solar wind is studied statistically using measurements from various satellite pairs: one satellite in the solar wind and one in either the magnetotail central plasma sheet or the near-Earth plasma sheet. It is found that the properties of the plasma sheet are highly correlated with the properties of the solar wind: specifically

Joseph E. Borovsky; Michelle F. Thomsen; Richard C. Elphic

1998-01-01

28

Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale  

Microsoft Academic Search

Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale. Theoretical investigations, in situ spacecraft and rocket missions, and laboratory studies form an essential triad for understanding the variety of current sheet phenomena found in space plasmas. In the Large Plasma Device (LAPD) at UCLA, the formation dynamics, equilibrium state, and wave-mediated disruptions of current sheets can be studied

S. Vincena; W. Gekelman

2005-01-01

29

The ripple's enhancement in graphene sheets by spark plasma sintering  

NASA Astrophysics Data System (ADS)

This paper introduces a simple and effective process of directly enhancing the ripple formation of graphene sheets by using spark plasma sintering (SPS) system. The morphology, microstructure and surface property of the pristine and SPS treated graphene sheets were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and contact angle meter. The results reveal that: 1) A large amount of ripples can be induced in graphene sheets after SPS treatment at 1300 °C, and the pristine graphene surfaces change from smoothness into roughness with the patterns; 2) There are three kinds of graphene ripples with different structures after SPS treatment; (3) After the formation of ripples, the SPS-treated graphene sheets become hydrophobicity. In addition, the formation mechanism of the graphene ripples was also discussed in this paper.

Cao, Bing; Yu, Guannan; Pan, Chunxu

2011-09-01

30

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

NASA Astrophysics Data System (ADS)

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.

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

31

Plasma sheet turbulence observed by Cluster II  

NASA Technical Reports Server (NTRS)

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.

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

32

CURRENT SHEETS AND COLLISIONLESS DAMPING IN KINETIC PLASMA TURBULENCE  

SciTech Connect

We present the first study of the formation and dissipation of current sheets at electron scales in a wave-driven, weakly collisional, three-dimensional kinetic turbulence simulation. We investigate the relative importance of dissipation associated with collisionless damping via resonant wave-particle interactions versus dissipation in small-scale current sheets in weakly collisional plasma turbulence. Current sheets form self-consistently from the wave-driven turbulence, and their filling fraction is well correlated to the electron heating rate. However, the weakly collisional nature of the simulation necessarily implies that the current sheets are not significantly dissipated via Ohmic dissipation. Rather, collisionless damping via the Landau resonance with the electrons is sufficient to account for the measured heating as a function of scale in the simulation, without the need for significant Ohmic dissipation. This finding suggests the possibility that the dissipation of the current sheets is governed by resonant wave-particle interactions and that the locations of current sheets correspond spatially to regions of enhanced heating.

TenBarge, J. M.; Howes, G. G., E-mail: jason-tenbarge@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2013-07-10

33

Excitation of slow EM waves in a waveguide having a thin, annular plasma sheet  

Microsoft Academic Search

A thin, annular plasma sheet in a waveguide slows down the phase velocity of electromagnetic modes in a plasma density window for frequencies below the electron cyclotron frequency via Cerenkov interaction. At lower densities, the plasma is not effective enough to reduce the phase velocity of the EM wave below c. At higher densities the plasma expels the radiation field,

Lalita; V. K. Tripathi

1993-01-01

34

Current sheet collapse in a plasma focus.  

NASA Technical Reports Server (NTRS)

Collapse of the current sheets in a plasma focus has been recorded simultaneously through slits parallel and perpendicular to the symmetry axis in the streak mode. The dark period following the collapse is due to the plasma moving out of the field of view. Microdensitometric measurements of intensity variation also support this conclusion. A large anisotropy is also found in the x-ray radiation pattern. Effects of different vacuum vessels were investigated.

Jalufka, N. W.; Lee, J. H.

1972-01-01

35

Visualization of Current Sheet Canting in a Pulsed Plasma Accelerator  

E-print Network

Visualization of Current Sheet Canting in a Pulsed Plasma Accelerator T.E. Markusic and E and propagation of current sheets in a rectangular-geometry pulsed plasma accelerator was observed using high to the performance of pulsed plasma thrusters. Photographs of the light emitted from the current sheet during

Choueiri, Edgar

36

Plasma Synthesis of Nitrogen Clusters on Carbon Nanotube Sheets  

NASA Astrophysics Data System (ADS)

The radio frequency plasma synthesis of nitrogen clusters stabilized on carbon nanotube sheets has been demonstrated under various conditions. Characterization of the samples produced has been carried out using micro-Raman and attenuated total reflectance-Fourier transform infrared spectroscopy. Initial investigations of the sample morphologies and compositions have also been performed using scanning electron microscopy combined with energy-dispersive x-ray analysis and transmission electron microscopy. The spectroscopic results, together with density functional theory calculations, suggest that a linear chain nitrogen cluster is formed under the plasma conditions employed and is stabilized most likely inside the walls of the carbon nanotubes that are used as substrates during the synthesis.

Benchafia, El Mostafa; Yu, Chi; Sosnowski, Marek; Ravindra, N. M.; Iqbal, Zafar

2014-04-01

37

Thermomechanical processing of plasma sprayed intermetallic sheets  

DOEpatents

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.

Hajaligol, Mohammad R. (Midlothian, VA); Scorey, Clive (Cheshire, CT); Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Midlothian, VA); Fleischhauer, Grier (Midlothian, VA); Lilly, Jr., A. Clifton (Chesterfield, VA); German, Randall M. (State College, PA)

2001-01-01

38

Current Sheets in the Earth Magnetotail: Plasma and Magnetic Field Structure with Cluster Project Observations  

NASA Astrophysics Data System (ADS)

Thin current sheets having kinetic scales are an important plasma structure, where the magnetic energy dissipation and charged particle acceleration are the most effective. It is believed that such current sheets are self-consistently formed by the specific nonadiabatic dynamics of charged particles and play a critical role in many space plasma and astrophysical objects. Current sheets in the near-Earth plasma environment, e.g., the magnetotail current sheet, are readily available for in-situ investigations. The dedicated multi-spacecraft Cluster mission have revealed basic properties of this current sheet, which are presented in this review: typical spatial profiles of magnetic field and current density, distributions of plasma temperature and density, role of heavy ions and electron currents, etc. Being important for the Earth magnetosphere physics, the new knowledge also could provide the basis for advancement in general plasma physics as well as in plasma astrophysics.

Petrukovich, Anatoli; Artemyev, Anton; Vasko, Ivan; Nakamura, Rumi; Zelenyi, Lev

2015-02-01

39

A pincer-shaped plasma sheet at Uranus  

SciTech Connect

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.

Hammond, C.M.; Walker, R.J.; Kivelson, M.G. (Univ. of California, Los Angeles (USA))

1990-09-01

40

Birkeland currents in the plasma sheet  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

41

Measurement of Hydrogen Negative Ions in Sheet Plasma  

NASA Astrophysics Data System (ADS)

Measurements of the hydrogen negative ion current by using omegatron mass analyzer were carried out in hydrogen sheet plasma with a hydrogen gas puff. Under a secondary hydrogen gas supply entering into the plasma, the peak position of the H- ion current IH- is localized in the periphery of the sheet plasma.

Matsumoto, Satoki; Kawada, Yukinobu; Iijima, Takaaki; Kobayashi, Hiroaki; Tonegawa, Akira; Sato, Kohnosuke; Kawamura, Kazutaka

42

The transport of plasma sheet material from the distant tail to geosynchronous orbit  

Microsoft Academic Search

Several aspects of mass transport in the Earth's plasma sheet are exam- ined. The evolution of plasma sheet material as it moves earthward is examined by sta- tistically comparing plasma sheet properties at three different downtail distances: near- Earth plasma sheet properties obtained from measurements by 1989-046 near the geo- magnetic equator near midnight at 6.6 RE, midtail plasma sheet

Joseph E. Borovsky; Michelle F. Thomsen; Richard C. Elphic; Thomas E. Cayton; David J. McComas

1998-01-01

43

Plasma-sheet dynamics induced by plasma mantle  

SciTech Connect

Is the magnetic field in the Earth's magnetotail static If yes, why if not, what causes the magnetic field to change and how does it evolve with time Although significant progress has been made in this area of research, a consensus still does not exist. This thesis approaches the problem from the most fundamental basis - Faraday's law relating the curl of the electric field to the time variation of the magnetic field. If we can reach an independent theory that relates the electric field to the magnetic field, the whole problem can, at least in principle, be solved. This thesis pursues the problem both physically and mathematically. Answers to the questions listed at the beginning are: (1) the magnetic field is generally not static; (2) the change is powered by the energy transfer from the solar wind to the magnetosphere, the agent that effects the change is plasma injection from the high-latitude plasma mantle; (3) the time-dependence is closely related to the velocity distribution of the mantle plasma; A decrease of B{sub z} in the near tail and a flux buildup at the farther end of tail are two primary features of the time evolution; (4) a dense, drifting plasma mantle causes an intensive reconfiguration in the plasma sheet and is likely to lead to plasma sheet instability.

Liu, W.W.

1988-01-01

44

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

PubMed

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

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

45

CURRENT SHEET MASS LEAKAGE IN A PULSED PLASMA ACCELERATOR  

E-print Network

CURRENT SHEET MASS LEAKAGE IN A PULSED PLASMA ACCELERATOR John W. Berkery A DISSERTATION PRESENTED a current sheet accelerates a propellant gas through the j Ã? B force density. In the ideal case all of the gas is entrained and acceler- ated by the sheet. An observed departure from this ideality is current

Choueiri, Edgar

46

Bursty escape fluxes in plasma sheets of Mars and Venus  

NASA Astrophysics Data System (ADS)

High resolution measurements of plasma in the plasma sheets of Mars and Venus performed by almost identical plasma instruments ASPERA-3 on the Mars Express spacecraft and ASPERA-4 on Venus Express reveal similar features of bursty fluxes of escaping planetary ions. A period of bursts lasts about 1-2 min. Simultaneous magnetic field measurements on Venus Express show that these burst-like features arise due to flapping motions of the plasma sheet. Their occurrence can be related to large-amplitude waves propagating on the plasma sheet surface and launched by reconnection in the magnetic tails.

Dubinin, E.; Fraenz, M.; Woch, J.; Zhang, T. L.; Wei, J.; Fedorov, A.; Barabash, S.; Lundin, R.

2012-01-01

47

Observations pertaining to the dynamics of the plasma sheet  

Microsoft Academic Search

Plasmas on the surface of the plasma sheet at its interface with the high-latitude lobes are studied at approx. 30-40 earth radii (R\\/sub e\\/) in the tail of the earth's magnetosphere with Lepedea plasma instrumentation on board the earth-orbiting Imp 7 and Imp 8 satellites. Ten of the twenty cases studied exhibit plasma sheet cooling. Simultaneous magnetotail crossings by Imp

R. J. DeCoster; L. A. Frank

1979-01-01

48

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

NASA Astrophysics Data System (ADS)

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 ?m in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

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

2014-06-01

49

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

SciTech Connect

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 ?m in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

Gillman, Eric D., E-mail: eric.gillman.ctr@nrl.navy.mil [National Research Council Postdoctoral Associate at the U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Amatucci, W. E. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

2014-06-15

50

Observations of Double Layers in Earth's Plasma Sheet  

SciTech Connect

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.

Ergun, R. E.; Tao, J. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309 (United States); Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309 (United States); Andersson, L.; Eriksson, S.; Johansson, T. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309 (United States); Angelopoulos, V. [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90055 (United States); Bonnell, J.; McFadden, J. P.; Larson, D. E. [Space Sciences Laboratory, University of California, Berkeley, California, 94720 (United States); Cully, C. M. [Swedish Institute of Space Physics, Uppsala (Sweden); Newman, D. N.; Goldman, M. V. [Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80309 (United States); Roux, A.; LeContel, O. [Centre d'etude des Environnements Terrestre et Planetaires, Velizy (France); Glassmeier, K.-H. [TUBS, Braunschweig, D-38106 (Germany); Baumjohann, W. [Space Research Institute, Austrian Academy of Sciences, A-8042 Graz (Austria)

2009-04-17

51

Observations of double layers in earth's plasma sheet.  

PubMed

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

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

52

Plasma Sheet Source and Loss Processes  

NASA Technical Reports Server (NTRS)

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.

Lennartsson, O. W.

2000-01-01

53

A pincer-shaped plasma sheet at Uranus  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

54

Multi-spacecraft observations of the heliospheric plasma sheet  

NASA Astrophysics Data System (ADS)

The heliospheric plasma sheet (HPS) has been described both as quasi-stationary and transient in nature. In order to better quantify the temporal and spatial scales under which each description is appropriate we have compared observations of the HPS from the two STEREO observatories and Wind. Identification criteria of the HPS included a change in magnetic sector from "towards" to "away" (or vice versa, identified using electron pitch angle distributions), an increase in proton density, and minima in the proton specific entropy argument (T/n?-1) and alpha to proton number density ratio. Following the technique of Liu et al. (2010), we have classified each plasma sheet as leading, following, straddling, or absent from the heliospheric current sheet. We find the configuration of the HPS agrees between the three spacecraft when longitudinal separation between observation points is 10 degrees or less (temporal separation of less than 1 day). Preliminary results show that in some cases the HPS is quasi-stationary over longitudinal scales of at least 25 degrees.

Simunac, K. D. C.; Galvin, A. B.; Farrugia, C. J.; Liu, Y. C.-M.; Luhmann, J. G.

2013-06-01

55

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

56

Generation of Large Area, Sheet Plasma Mirrors for Redirecting High Frequency Microwave Beams  

Microsoft Academic Search

Large area, planar, sheet plasma mirrors have been generated with electron densities high enough to reflect X-band microwave beams. The 50 cm×60 cm negative glow plasmas operate in air and other gases at ~100 mTorr. These plasmas are immersed in an axial magnetic field of moderate strength (150-250 G), and they may be capable of being rapidly steered. The cathode

J. Mathew; R. F. Fernsler; R. A. Meger; J. A. Gregor; D. P. Murphy; R. E. Pechacek; W. M. Manheimer

1996-01-01

57

Electric fields in the plasma sheet and plasma sheet boundary layer  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

58

Plasmoid observations in the distant plasma sheet boundary layer  

SciTech Connect

Substorm associated large amplitude bipolar magnetic events occurred when ISEE 3 was in the distant geotail's plasma sheet boundary layer (PSBL). The characteristics of these events, their substorm association and their possible source mechanisms are examined. We propose that these PSBL events are signatures of a passing plasmoid in the plasma sheet, analogous to the traveling compression region model in the geomagnetic lobes. 20 refs.

Moldwin, M.B.; Hughes, W.J. (Boston Univ., MA (United States))

1992-10-01

59

Upper Hybrid Resonance of Microwaves with a Large Magnetized Plasma Sheet  

NASA Astrophysics Data System (ADS)

A large magnetized plasma sheet with size of 60 cm × 60 cm × 2 cm was generated by a linear hollow cathode discharge under the confinement of a uniform magnetic field generated by a Helmholtz Coil. The microwave transmission characteristic of the plasma sheet was measured for different incident frequencies, in cases with the electric field polarization of the incident microwave either perpendicular or parallel to the magnetic field. In this measurement, parameters of the plasma sheet were changed by varying the discharge current and magnetic field intensity. In the experiment, upper hybrid resonance phenomena were observed when the electric field polarization of the incident wave was perpendicular to the magnetic field. These resonance phenomena cannot be found in the case of parallel polarization incidence. This result is consistent with theoretical consideration. According to the resonance condition, the electron density values at the resonance points are calculated under various experimental conditions. This kind of resonance phenomena can be used to develop a specific method to diagnose the electron density of this magnetized plasma sheet apparatus. Moreover, it is pointed out that the operating parameters of the large plasma sheet in practical applications should be selected to keep away from the upper hybrid resonance point to prevent signals from polarization distortion.

Huo, Wenqing; Guo, Shijie; Ding, Liang; Xu, Yuemin

2013-10-01

60

Particle drift in the Earth's plasma sheet  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

61

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

NASA Technical Reports Server (NTRS)

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.

Schriver, David; Ashour-Abdalla, Maha

1990-01-01

62

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

NASA Technical Reports Server (NTRS)

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.

Nawaz, Anuscheh; Lau, Matthew

2011-01-01

63

Slow Mode Waves in the Heliospheric Plasma Sheet  

NASA Technical Reports Server (NTRS)

We report the results of a search for waves/turbulence in the Heliospheric Plasma Sheet (HPS) surrounding the Heliospheric Current Sheet (HCS). The HPS is treated as a distinctive heliospheric structure distinguished by relatively high Beta, slow speed plasma. The data used in the investigation are from a previously published study of the thicknesses of the HPS and HCS that were obtained in January to May 2004 when Ulysses was near aphelion at 5 AU. The advantage of using these data is that the HPS is thicker at large radial distances and the spacecraft spends longer intervals inside the plasma sheet. From the study of the magnetic field and solar wind velocity components, we conclude that, if Alfven waves are present, they are weak and are dominated by variations in the field magnitude, B, and solar wind density, NP, that are anti-correlated.

Smith, Edward. J.; Zhou, Xiaoyan

2007-01-01

64

On the interaction of a charge with a thin plasma sheet  

E-print Network

The interaction of the electromagnetic field with a two dimensional plasma sheet intended to describe the pi-electrons of a carbon nano-tube or a $C_{60}$ molecule is investigated. By integrating out first the displacement field of the plasma or first the electromagnetic field different representations for quantities like the Casimir energy are derived which are shown to be consistent with one another. Starting from the covariant gauge for the electromagnetic field it is shown that the matching conditions to which the presence of the plasma sheet can be reduced are different from the commonly used ones. The difference in the treatments does not show up in the Casimir force between two parallel sheets, but it is present in the Casimir-Polder force between a charge or a neutral atom and a sheet. At once, since the plasma sheet is a regularization of the conductor boundary conditions, this sheds light on the difference in physics found earlier in the realization of conductor boundary conditions as 'thin' or 'thick' boundary conditions in Phys.Rev.D70(2004)085010.

M. Bordag

2007-04-29

65

Ultrarelativistic Electron-Positron Plasma  

E-print Network

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.

Markus H. Thoma

2008-10-06

66

Plasma sheet fast flows observations during substorm: a case study  

NASA Astrophysics Data System (ADS)

INTERBALL-1 observations of a substorm development in the mid-tail are compared with the auroral dynamics and with the observations performed by adjacent spacecraft. It was shown that in the mid plasma sheet, the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. When active auroras moved poleward of the INTERBALL-1 projection, earthward bursty bulk flows (BBFs) were observed. This confirms the concept that flow reversal region is the source of auroras forming the poleward edge of the auroral bulge. The comparison of the fast flows directions obtained by nearby satellites in the plasma sheet during the substorm was done.

Borodkova, N. L.; Yahnin, A. G.; Sauvaud, J.-A.; Lutsenko, V. N.

2003-04-01

67

Space Charge Effect in the Sheet and Solid Electron Beam  

NASA Astrophysics Data System (ADS)

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.

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

1998-11-01

68

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

NASA Astrophysics Data System (ADS)

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.

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

69

Bursty bulk flows in the inner central plasma sheet  

Microsoft Academic Search

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

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

1992-01-01

70

On a possible connection between the longitudinally propagating near-Earth plasma sheet and auroral arc waves: A reexamination  

NASA Astrophysics Data System (ADS)

propagating low-frequency waves (or wavy structures) often occur in a localized region of the near-Earth plasma sheet and auroral arc immediately prior to auroral breakup. Although both are believed to be magnetospheric and ionospheric manifestations of a plasma sheet instability that may lead to substorm onset, the fundamental coupling processes behind their relationship are not yet understood. To address this question, we reexamined in detail a fortuitous conjunction event of prebreakup near-Earth plasma sheet and auroral arc waves, initially reported by Uritsky et al. (2009) using the Time History of Events and Macroscale Interactions during Substorms space-ground observations. The event exhibited a morphological one-to-one association between longitudinally propagating arc wave (LPAW) in the ionosphere and Pi2/Pc4 range wave activity in the plasma sheet. Our analysis revealed that (1) the LPAW was the periodic luminosity modulation of the growth phase arc by faint, diffuse, green line-dominated auroral patches propagating westward along/near the arc, rather than some type of small-scale arc structuring, such as auroral beads/rays/undulations; and (2) the plasma sheet wave, which had a diamagnetic nature, propagated duskward with accompanying coincident modulation of field-aligned fluxes of 0.1-30 keV electrons. These findings suggest that the LPAW was likely connected to the plasma sheet wave via modulated diffuse precipitation of hard plasma sheet electrons (> ~1 keV), not via filamentary field-aligned currents, as expected from the ballooning instability regime. Another potential implication is that such prebreakup low-frequency wave activity in the near-Earth plasma sheet is not necessarily guaranteed to initiate prebreakup auroral arc structuring.

Motoba, T.; Ohtani, S.; Donovan, E. F.; Angelopoulos, V.

2015-01-01

71

Kinetic theory of the electron bounce instability in two dimensional current sheets—Full electromagnetic treatment  

SciTech Connect

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 ??=?B{sub z}/B{sub lobes}, 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.

Tur, A.; Fruit, G.; Louarn, P. [Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS UMR5277/Université Paul Sabatier, Toulouse (France)] [Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS UMR5277/Université Paul Sabatier, Toulouse (France); Yanovsky, V. [Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkov 61001 (Ukraine)] [Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkov 61001 (Ukraine)

2014-03-15

72

Rapid flux transport in the central plasma sheet  

Microsoft Academic Search

On the basis of several years of Geotail data we performed a comprehensive statistical analysis of rapid convective transport in the neartail and midtail central plasma sheet. We chose a new approach by using flux transport and not ion bulk velocity as the threshold parameter for the identification of rapid flows. This criterion for rapid convection is independent of the

R. Schödel; W. Baumjohann; R. Nakamura; V. A. Sergeev; T. Mukai

2001-01-01

73

Geotail observations of magnetic flux ropes in the plasma sheet  

Microsoft Academic Search

Examination of Geotail measurements in the near-tail (X > ?30 RE) has revealed the presence of small flux ropes in the plasma sheet. A total of 73 flux rope events were identified in the Geotail magnetic field measurements between November 1998 and April 1999. This corresponds to an estimated occurrence frequency of ?1 flux rope per 5 hours of central

J. A. Slavin; R. P. Lepping; J. Gjerloev; D. H. Fairfield; M. Hesse; C. J. Owen; M. B. Moldwin; T. Nagai; A. Ieda; T. Mukai

2003-01-01

74

Tail plasma sheet models derived from Geotail particle data  

Microsoft Academic Search

Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and interplanetary magnetic field (IMF) parameters, at distances between 10 and 50 RE. The models are based on a large set of

N. A. Tsyganenko; T. Mukai

2003-01-01

75

Plasma electron analysis: Voyager plasma science experiment  

NASA Technical Reports Server (NTRS)

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.

Sittler, E. C., Jr.

1983-01-01

76

Excitation of an electrostatic wave by a cold electron current sheet of finite thickness  

NASA Technical Reports Server (NTRS)

Calculations for the threshold of current-driven instabilities and the growth rates of ion acoustic and electrostatic ion cyclotron instabilities in a magnetized plasma driven a current sheet with a finite width are presented. Maxwellian equations are employed to model the velocity distributions of electrons and ions in a direction perpendicular to the sheet. A dispersion relation is defined for the regions of instability, and boundary conditions are characterized in order to obtain a set of eigenvalue equations. Thresholds are delineated for various regions, including ducted mode solutions where only ion-acoustic waves are excited in areas where the frequency range significantly exceeds the ion cyclotron frequency. When a constant electron drift velocity is present, a thick current sheet is more unstable than a thin one. Fewer modes become unstable with a thinner sheet.

Hwang, K. S.; Fontheim, E. G.; Ong, R. S. B.

1983-01-01

77

Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale  

NASA Astrophysics Data System (ADS)

Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale. Theoretical investigations, in situ spacecraft and rocket missions, and laboratory studies form an essential triad for understanding the variety of current sheet phenomena found in space plasmas. In the Large Plasma Device (LAPD) at UCLA, the formation dynamics, equilibrium state, and wave-mediated disruptions of current sheets can be studied with great spatial and temporal resolution using a variety of probes as well as non-invasive laser induced fluorescence and other optical diagnostics. The LAPD is aptly suited for studying current sheets flowing in a magnetized background plasma which is capable of supporting Alfvén waves. The cylindrical device is 20m long and one meter in diameter with a solenoidal magnetic field as high as 3000 Gauss. For the parameters in this experiment, the plasma column is ten shear Alfvén wavelengths along the field and 100 electron inertial lengths (?e) (or 200 ?i) in the perpendicular direction. An electron current sheet is created in the plasma by placing a thin copper plate in the plasma column at one end of the device and pulsing this plate positive with respect to the chamber wall. The current sheet extends for the length of the device and has an initial cross-field size of roughly 45 ?e by 0.5?e. A parallel flow of ions is observed with similar dimensions and moves in the same direction as the electrons in the current sheet with a velocity of 0.2 times the ion sound speed. A much weaker sheared perpendicular flow is also measured. Cross-sections of the ion flow are measured at several axial locations over a distance of six meters. Second, as the ion flow increases in magnitude, a much broader (8?i) density depletion (n=0.25nO) develops around the flow. The gradient scale length of the depletion shortens until the spontaneous growth of drift waves occurs. This disrupts the electron current and ion flow, and leads to cross-field transport of plasma and a relaxation of the density gradient. The process of steepening and disruption repeats during the bias pulse. Detailed two-dimensional correlation measurements reveal the density and magnetic field propagation of the waves and statistics on the wave fluctuations.

Vincena, S.; Gekelman, W.

2005-12-01

78

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

NASA Astrophysics Data System (ADS)

An electron beam was injected into earth's ionosphere on August 1, 1985, during the flight of the Space Shuttle 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 acoustic instability to provide a returning flux of hot electrons by means of quasi-linear diffusion.

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

1989-06-01

79

On the nature of the plasma sheet boundary layer  

SciTech Connect

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.

Hones, E.W. Jr. (Mission Research Corp., Los Alamos, NM (USA) Los Alamos National Lab., NM (USA))

1990-01-01

80

Acceleration of O+ from the cusp to the plasma sheet  

NASA Astrophysics Data System (ADS)

Heavy ions from the ionosphere that are accelerated in the cusp/cleft have been identified as a direct source for the hot plasma in the plasma sheet. However, the details of the acceleration and transport that transforms the originally cold ions into the hot plasma sheet population are not fully understood. The polar orbit of the Cluster satellites covers the main transport path of the O+ from the cusp to the plasma sheet, so Cluster is ideal for tracking its velocity changes. However, because the cusp outflow is dispersed according to its velocity as it is transported to the tail, due to the velocity filter effect, the observed changes in beam velocity over the Cluster orbit may simply be the result of the spacecraft accessing different spatial regions and not necessarily evidence of acceleration. Using the Cluster Ion Spectrometry/Composition Distribution Function instrument onboard Cluster, we compare the distribution function of streaming O+ in the tail lobes with the initial distribution function observed over the cusp and reveal that the observations of energetic streaming O+ in the lobes around -20 RE are predominantly due to the velocity filter effect during nonstorm times. During storm times, the cusp distribution is further accelerated. In the plasma sheet boundary layer, however, the average O+ distribution function is above the upper range of the outflow distributions at the same velocity during both storm and nonstorm times, indicating that acceleration has taken place. Some of the velocity increase is in the direction perpendicular to the magnetic field, indicating that the E × B velocity is enhanced. However, there is also an increase in the parallel direction, which could be due to nonadiabatic acceleration at the boundary or wave heating.

Liao, J.; Kistler, L. M.; Mouikis, C. G.; Klecker, B.; Dandouras, I.

2015-02-01

81

Equilibrium structure of the plasma sheet boundary layer-lobe interface  

NASA Technical Reports Server (NTRS)

Observations are presented which show that plasma parameters vary on a scale length smaller than the ion gyroradius at the interface between the plasma sheet boundary layer and the lobe. The Vlasov equation is used to investigate the properties of such a boundary layer. The existence, at the interface, of a density gradient whose scale length is smaller than the ion gyroradius implies that an electrostatic potential is established in order to maintain quasi-neutrality. Strongly sheared (scale lengths smaller than the ion gyroradius) perpendicular and parallel (to the ambient magnetic field) electron flows develop whose peak velocities are on the order of the electron thermal speed and which carry a net current. The free energy of the sheared flows can give rise to a broadband spectrum of electrostatic instabilities starting near the electron plasma frequency and extending below the lower hybrid frequency.

Romero, H.; Ganguli, G.; Palmadesso, P.; Dusenbery, P. B.

1990-01-01

82

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

83

Canted Current Sheet Mass Leakage and its Impact on Pulsed Plasma Thruster Performance  

E-print Network

Canted Current Sheet Mass Leakage and its Impact on Pulsed Plasma Thruster Performance J.W. Berkery An analytical model of the leakage of the current sheet in a parallel plate pulsed electromagnetic accelerator observed: current sheet canting and plasma leakage. Figure 1 shows a photograph that illustrates these two

Choueiri, Edgar

84

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

SciTech Connect

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

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

1989-06-01

85

Electron cyclotron resonance plasma photos  

SciTech Connect

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.

Racz, R.; Palinkas, J. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary); University of Debrecen, H-4010 Debrecen, Egyetem ter 1 (Hungary); Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary)

2010-02-15

86

Retarding field energy analyzer for the characterization of negative glow sheet plasmas in a magnetic field  

SciTech Connect

A retarding field energy analyzer has been developed for diagnosing 300 {mu}s duration, 60 cm{times}60 cm negative glow, sheet plasmas immersed in a 150{endash}250 G axial magnetic field. The electron density in these 4.5 kV, 13 A, 120 mTorr discharges in air and other gases, is high enough to reflect {ital X}-band microwaves. The presence of the magnetic field makes the suppression of secondary electrons from the Faraday collector surface more difficult. The approach taken here is to bias the entire collection circuit and the amplifiers 90 V positive with respect to the data acquisition room. The differentially pumped analyzer is designed to accept electrons with a large range of perpendicular velocities, and it measures the parallel velocity distribution function of the discharge electrons entering a 0.64-mm-diam hole in the anode plate. It gives valuable information about the energy spectrum of the energetic beam electrons emitted from the cathode, and the effect of energy loss and scattering processes on this propagating beam component. Additionally, since the analyzer sampling hole is offset from the anode-cathode axis, the current density profile can be measured for different bias voltages on the retarding grid, by rotating the linear cathode about the vertical anode-cathode axis. These profiles give the sheet thickness for the beam and plasma components of the negative glow discharge. It also gives useful information about the scattering induced beam spreading and its effects on the plasma sheet thickness and electron density. {copyright} {ital 1996 American Institute of Physics.}

Mathew, J.; Meger, R.A.; Fernsler, R.F. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5346 (United States)] [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5346 (United States); Gregor, J.A. [Institute for Plasma Physics, University of Maryland, College Park, Maryland 20742 (United States)] [Institute for Plasma Physics, University of Maryland, College Park, Maryland 20742 (United States)

1996-08-01

87

A statistical study on correlations between plasma sheet and solar wind based on DSP explorations  

NASA Astrophysics Data System (ADS)

By using the data of two spacecraft TC-1 and ACE Advanced Composition Explorer a statistical study on the correlations between plasma sheet and solar wind has been carried out The results obtained shows that the plasma sheet at geocentric distances of about 9 sim 13 4 Re has apparent driving relationship with solar wind It is found that 1 There is a positive correlation between the duskward component of interplanetary magnetic field IMF and the duskward component of geomagnetic field in plasma sheet with a proportionality constant of about 1 09 It indicates that the duskward component of the IMF can effectively penetrate into the near earth plasma sheet and can be amplified by sunward convection in the corresponding region at geocentric distances of about 9 sim 13 4 Re 2 The increase of the density or the dynamic pressure of the solar wind will generally lead to the increase of the density of the plasma sheet 3 The ion thermal pressure in the near earth plasma sheet is significantly controlled by the dynamic pressure of solar wind 4 Under the northward IMF condition the ion temperature and ion thermal pressure in plasma sheet decrease as the solar wind speed increases This feature indicates that plasmas in the near earth plasma sheet can come from magnetosheath through LLBL Northward IMF is one important condition for the transport of the cold plasmas of magnetosheath into plasma sheet through LLBL and fast solar wind will enhance such transport process

Yan, G. Q.; Shen, C.; Liu, Z. X.; Carr, C. M.; Rème, H.; Zhang, T. L.

88

Role of Plasma Sheet Source Population in Ring Current Dynamics (Invited)  

NASA Astrophysics Data System (ADS)

Understanding the dynamics of ring current particles during disturbed conditions remains a long-standing challenge, moreover these particles represent a seed population for the hazardous radiation belts. The formation of the storm-time ring current depends on two main factors: 1) the plasma sheet as a reservoir supplying particles that are transported earthward, and 2) the electric field as a mechanism that energizes them. To investigate ring current development on a global scale, we use our four-dimensional (4-D) ring current-atmosphere interactions model (RAM-SCB) [Jordanova et al., 2010; Zaharia et al., 2010] which solves the kinetic equation for H+, O+, and He+ ions and electrons using a self-consistently calculated magnetic field in force balance with the anisotropic ring current plasma pressure. The model boundary was recently expanded from geosynchronous orbit to 9 RE, where the plasma boundary conditions are specified from the empirical plasma sheet model TM03 [Tsyganenko and Mukai, 2003] based on Geotail data. We simulate the transport, acceleration, and loss of energetic particles from the magnetotail to the inner magnetosphere during several geomagnetic storms that occurred since the launch of the Van Allen Probes in August 2012. We compare our results with simultaneous plasma and field observations from the Energetic particle, Composition, and Thermal plasma (ECT) [Spence et al., 2013] and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) [Kletzing et al., 2013] investigations on the Van Allen Probes. We investigate the role of the plasma sheet source population in global ring current simulations considering various boundary conditions and electric field formulations. An improved understanding of the highly coupled inner magnetosphere system is provided.

Jordanova, V.; Yu, Y.; Reeves, G. D.; Kletzing, C.; Spence, H.; Sazykin, S. Y.

2013-12-01

89

Plasma sheet oscillations and their relation to substorm development: Cluster and double star TC1 case study  

E-print Network

Plasma sheet oscillations and their relation to substorm development: Cluster and double star TC1 2007 Abstract We examined two consecutive plasma sheet oscillation and dipolarization events observed-tail current lead to current sheet thinning and plasma sheet oscillations of 3­5 min periods, while the pseudo

California at Berkeley, University of

90

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

NASA Astrophysics Data System (ADS)

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.

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

91

Characterization of electron cyclotron resonance hydrogen plasmas  

Microsoft Academic Search

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 ({ital V}{sub {ital p}} ), electron density ({ital N}{sub {ital e}} ), electron

C. A. Outten; J. C. Barbour; W. R. Wampler

1991-01-01

92

Study of plasma flow reversal in the near-Earth plasma sheet using numerical computations  

NASA Astrophysics Data System (ADS)

Tailward flow in the near-Earth plasma sheet associated with a rebound of the earthward bursty bulk flow (BBF) is investigated using three-dimensional magnetohydrodynamics simulations of magnetic reconnection in the magnetotail on the basis of the spontaneous fast reconnection model. In order to investigate the properties of this tailward flow, virtual satellites are located at different positions in the plasma sheet within the simulation region, so that we can directly observe the temporal variations of plasma quantities in accordance with the growth and preceding the flow reversal associated with the magnetic reconnection. The time profile of the plasma flow velocity in the course of the BBF depends on the satellite position. Furthermore, the time profile of the magnetic field strength in the course of the reverse flow depends on the satellite position in the dawn-dusk direction. As a result of the rebound of the earthward flow, the accumulation of the plasma density and the plasma pressure is observed at any position in the plasma sheet during the interval between the BBF and the reverse flow.

Kondoh, Koji; Shimizu, Tohru

2014-12-01

93

The quiet evening auroral arc and the structure of the growth phase near-Earth plasma sheet  

NASA Astrophysics Data System (ADS)

The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening auroral arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the electron precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling auroral streamers and their associated earthward traveling dipolarization fronts.

Coroniti, F. V.; Pritchett, P. L.

2014-03-01

94

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

SciTech Connect

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.

Jain, Neeraj; Büchner, Jörg [Max Planck/Princeton Center for Plasma Physics, Göttingen (Germany); Max Planck Institute for Solar System Research, Justus-Von-Liebig-Weg-3, Göttingen (Germany)

2014-06-15

95

Ion kinetic properties in Mercury's pre-midnight plasma sheet  

NASA Astrophysics Data System (ADS)

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 ~1-10 cm-3 and ~5-30 MK, respectively, maintain thermal pressures of ~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 ~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.

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

2014-08-01

96

Azimuthal plasma pressure gradient in quiet time plasma sheet L. R. Lyons,1  

E-print Network

-aligned currents peak in the vicinity of midnight and decrease towards dusk and dawn, perhaps approaching zero near studies have found a dawn-dusk asymmetric pressure profile for the near-Earth plasma sheet (r % 10$20 RE gradient toward dusk in the dawn and dusk sectors and a gradient toward dawn near midnight. The high

California at Berkeley, University of

97

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

PubMed

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

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

2013-03-29

98

Electromagnetic Particle Code With Adaptive Mesh Refinement Technique: Application to the Plasma Sheet  

NASA Astrophysics Data System (ADS)

It is widely believed that magnetic reconnection plays an important role in the magnetospheric substorm and solar flares. However, physical processes around the diffusion region are not well understood. Recently, it has been suggested that multi-scale coupling process should be important in the reconnection triggering and the anomalous plasma heating and acceleration around the diffusion region. It is necessary to conduct a self-consistent large-scale simulation including phenomena with various scales to describe multi-scale coupling. However, a realization of such a simulation with an ordinary PIC technique is still difficult because electron-scale phenomena are very localized and embedded in an ion-scale or MHD-scale system. To overcome this difficulty, we made a new 2-1/2 dimensional electromagnetic particle code with adaptive mesh refinement (AMR) technique. The AMR technique dynamically subdivides the cells that satisfy a refinement criterion and effectively achieves high-resolution simulations. In fact, it is only in the vicinity of the central current sheet where high-resolution simulations are required and we can reduce the number of cells in the lobe region where plasma density is low so that both the electron Debye length and a characteristic scale length are large. Though conventional AMR algorithm has been unsuitable to the parallel computation, our code is improved by adopting the fully threaded tree (FTT) algorithm developed by Khokhlov (1998), which facilitates to modify the cell structure in parallel. The AMR technique is expected to be one of the promising methods to realize self-consistent multi-scale simulations. In this paper, we report the results of some test simulations and discuss the limitations of our code, especially the reflections at the boundaries of the refined regions. We also report the results on the time developing Harris plasma sheet and show that the hierarchical cell structure is automatically reconstructed and fine cells are produced in the central plasma sheet, especially around the X-type neutral line.

Fujimoto, K.; Machida, S.

2004-12-01

99

Topological Features of a Compressible Plasma Vortex Sheet: 6 Cases  

NSDL National Science Digital Library

The Voyager and Pioneer Spacecraft have detected large-scale quasi-periodic plasma fluctuations in the outer heliosphere beyond 20 AU. A plasma vortex sheet model can explain these fluctuations and the observed correlations between various physical variables. The large scale outer heliosphere is modeled by solving the 3-D compressible magnetohydrodynamic equations involving three interacting shear layers. Computations were done on a Cray computer at the NASA Center for Computational Sciences. Six cases are animated: Weak magnetic field and strong magnetic field, each at three values of tau, the vortex street characteristic time. Contours of density are shown as dark transparent tubes. Critical points of the velocity field are represented by Glyphs. Vortex cores are shown in orange and blue.

Cindy Starr

1993-12-17

100

Association of plasma sheet variations with auroral changes during substorms  

SciTech Connect

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.

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

1988-01-01

101

Relationship of the Plasma Sheet, Ring Current, Trapping Boundary, and Plasmapause near the Magnetic Equator and Local Midnight  

Microsoft Academic Search

pause position in the pre-midnight sector. An electron 'trough' characterized by relatively low, constant electron energy densities lies between the plasmapause and the inner boundary of the earthward edge of the plasma sheet in the pre-midnight sector. The plasmapause is within the region of the proton ring current. The near-earth termination of proton ring current is usually at 0.5 to

L. A. Frank

1971-01-01

102

Association of conductivity and geomagnetic activity in the plasma sheet of geomagnetotail.  

NASA Astrophysics Data System (ADS)

Computes the specific conductivity ? of the plasma sheet for the selected 22 substorm events which occurred in the maximum solar activity year 1978-9 and finds variations with plasma ?-parameter (ratio of plasma pressure to magnetic pressure) and geomagnetic activity indices. The dependence of the correlation coefficient Rm between the planetary index Kp and sunspot number ? on the specific conductivity of the plasma sheet is studied. The effect of storm index Dst on specific conductivity is found. As the Dst level increases, specific conductivity falls and this reveals an anticorrelation between the storm index and the geomagnetic activity in the plasma sheet.

Prince, P. R.; Bindu, S.; Renuka, G.; Sindhu, M. S.; Venugopal, C.

1997-10-01

103

Generation of Microwave Free-Electron Laser Radiation Using Sheet Electron Beam and Planar Electromagnet Wiggler  

Microsoft Academic Search

An experimental study of sheet electron beam propagation through a planar electromagnet and generation of microwave radiation by free-electron laser action has been carried out. The space charge dominated sheet electron beam of energy 100-200 keV, current 50-150 A, and pulsewidth of 100-150 ns was propagated through a 20-period planar electromagnet wiggler. Significant enhancement in the beam transmission through the

K. K. Jain; K. K. Mohandas; A. V. Ravikumar

1999-01-01

104

Generation of Microwave Free-Electron Laser Radiation Using Sheet Electron Beam and Planar Electromagnet Wiggler  

Microsoft Academic Search

An experimental study of sheet electron beam propagation through a planar electromagnet and generation of microwave radiation by free-electron laser action has been carried out. The space charge dominated sheet electron beam of energy 100-200 keV, current 50-150 A, and pulsewidth of 100-150 ns was propagated through a 20-period planar electromagnet wiggler. Significant enhancement in the beam transmission through the

K. K. Jain

2002-01-01

105

Generation of microwave free-electron laser radiation using sheet electron beam and planar electromagnetic wiggler  

Microsoft Academic Search

An experimental study of sheet electron beam propagation through a planar electromagnetic wiggler and generation of microwave radiation by free-electron laser action has been carried out. The space charge dominated sheet electron beam of energy ~100-200 keV, current 50-150 A, and pulsewidth of 100-150 ns was propagated through a 20-period planar electromagnetic wiggler. Significant enhancement in the beam transmission through

A. V. Ravi Kumar; K. K. Mohandas; K. K. Jain

1998-01-01

106

Electronic and optical properties of silicon based porous sheets.  

PubMed

Si based sheets have attracted tremendous attention due to their compatibility with the well-developed Si-based semiconductor industry. On the basis of state-of-the-art theoretical calculations, we systematically study the stability, electronic and optical properties of Si based porous sheets including g-Si4N3, g-Si3N4, g-Si3N3 and g-Si3P3. We find that the g-Si3N3 and g-Si3P3 sheets are thermally stable, while the g-Si4N3 and g-Si3N4 are unstable. Different from the silicene-like sheets of SiN and Si3N which are nonplanar and metallic, both the porous g-Si3N3 and g-Si3P3 sheets are planar and nonmetallic, and the former is an indirect band gap semiconductor with a band gap of 3.50 eV, while the latter is a direct band gap semiconductor with a gap of 1.93 eV. Analysis of the optical absorption spectrum reveals that the g-Si3P3 sheet may have applications in solar absorbers owing to its narrow direct band gap and wide range optical absorption in the visible light spectrum. PMID:25005914

Guo, Yaguang; Zhang, Shunhong; Wang, Qian

2014-08-21

107

A Gridded Electron Gun for a Sheet Beam Klystron  

SciTech Connect

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.

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

2008-04-25

108

Compressional wave events in the dawn plasma sheet observed by Interball-1  

E-print Network

Compressional wave events in the dawn plasma sheet observed by Interball-1 O. Verkhoglyadova1 , A in October 1995 and October 1996 in the dawn plasma sheet at Ã?30 i XGSM and jZGSMj 10 i are con- sidered

Paris-Sud XI, Université de

109

Properties of a vacuum ultraviolet laser created plasma sheet for a microwave reflector  

E-print Network

has attractive properties for a microwave agile mirror. 0 1995 American Institute of Physics. 1 illustrate that a plasma sheet generated using a linear hollow cathode immersed in a magnetic field yieldsProperties of a vacuum ultraviolet laser created plasma sheet for a microwave reflector W. Shen, J

Scharer, John E.

110

Response of the inner magnetosphere and the plasma sheet to a sudden R. Nakamura,1  

E-print Network

Response of the inner magnetosphere and the plasma sheet to a sudden impulse K. Keika,1 R. Nakamura caused a sudden compression of the magnetosphere between 0900 UT and 0915 UT on 24 August 2005) and Tan Ce 2 (TC2) in the inner magnetosphere and by the Cluster spacecraft in the dawnside plasma sheet

California at Berkeley, University of

111

Plasma sheet crossings at Jupiter: Energetic particle observations with the Galileo spacecraft  

E-print Network

1 Plasma sheet crossings at Jupiter: Energetic particle observations with the Galileo spacecraft L in the outer Jovian magnetosphere by the Energetic Particles Detector (EPD) onboard the Galileo space- craft conditions are a more likely explanation of their origin. Keywords: Plasma sheet; Galileo; Jupiter

112

Magnetized electron-positron plasmas  

E-print Network

Electrostatic oscillations in cold electron-positron plasmas can be coupled to a propagating electromagnetic mode if the background magnetic field is inhomogeneous. Previous work considered this coupling in the quasi-linear regime, successfully simulating the electromagnetic mode. Here we present a stability analysis of the non-linear problem, perturbed from dynamical equilibrium, in order to gain some insight into the modes present in the system.

C. R. Stark; D. A. Diver; A. A. da Costa

2006-12-22

113

Microwave emission from plasmas produced by magnetically confined-electron beams  

Microsoft Academic Search

Microwave emission, in the x-band frequency range (8.2-12.4 GHz), from a thin, large, rectangular sheet plasma has been measured. The plasma electron density was such that the plasma frequency was within or just above this frequency range. The plasma was immersed in an external magnetic field from a set of Helmholz coils. The magnetic field was oriented parallel to the

Donald P. Murphy; Richard F. Fernsler; Robert E. Pechacek; Robert A. Meger

2002-01-01

114

Undriven periodic plasma oscillation in electron cyclotron resonance Ar plasma  

Microsoft Academic Search

We report experimental observation of periodic oscillation in a steady state electron cyclotron resonance argon plasma that is not driven by extra periodic forces. We interpret the oscillation according to the predator-prey model, which is a nonlinear plasma-neutral coupling in the plasma production region. The oscillation is observed in a narrow plasma parameter window and is evidence for neutral density

Pyung-Woo Lee; Sang-Won Lee; Hong-Young Chang

1996-01-01

115

Energy efficiency of electron plasma emitters  

SciTech Connect

Electron emission influence from gas-discharge plasma on plasma emitter energy parameters is considered. It is shown, that electron emission from plasma is accompanied by energy contribution redistribution in the gas-discharge from plasma emitter supplies sources-the gas-discharge power supply and the accelerating voltage power supply. Some modes of electron emission as a result can be realized: 'a probe measurements mode,' 'a transitive mode,' and 'a full switching mode.'.

Zalesski, V. G., E-mail: V.Zalesski@mail.ru [Polotsk State University (Belarus)

2011-12-15

116

Characterization of electron cyclotron resonance hydrogen plasmas  

Microsoft Academic Search

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

C. A. Outten; J. C. Barbour; W. R. Wampler

1990-01-01

117

A statistical study on the correlations between plasma sheet and solar wind based on DSP explorations  

NASA Astrophysics Data System (ADS)

By using the data of two spacecraft, TC-1 and ACE (Advanced Composition Explorer), a statistical study on the correlations between plasma sheet and solar wind has been carried out. The results obtained show that the plasma sheet at geocentric distances of about 9~13.4 Re has an apparent driving relationship with the solar wind. It is found that (1) there is a positive correlation between the duskward component of the interplanetary magnetic field (IMF) and the duskward component of the geomagnetic field in the plasma sheet, with a proportionality constant of about 1.09. It indicates that the duskward component of the IMF can effectively penetrate into the near-Earth plasma sheet, and can be amplified by sunward convection in the corresponding region at geocentric distances of about 9~13.4 Re; (2) the increase in the density or the dynamic pressure of the solar wind will generally lead to the increase in the density of the plasma sheet; (3) the ion thermal pressure in the near-Earth plasma sheet is significantly controlled by the dynamic pressure of solar wind; (4) under the northward IMF condition, the ion temperature and ion thermal pressure in the plasma sheet decrease as the solar wind speed increases. This feature indicates that plasmas in the near-Earth plasma sheet can come from the magnetosheath through the LLBL. Northward IMF is one important condition for the transport of the cold plasmas of the magnetosheath into the plasma sheet through the LLBL, and fast solar wind will enhance such a transport process.

Yan, G. Q.; Shen, C.; Liu, Z. X.; Carr, C. M.; Rème, H.; Zhang, T. L.

2005-11-01

118

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

NASA Astrophysics Data System (ADS)

We developed a novel approach to the fabrication of three-dimensional, nanoporous graphene sheets featuring a high specific surface area of 734.9 m2 g?1 and an ultrahigh pore volume of 4.1 cm3 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.

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

2014-12-01

119

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

PubMed

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

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

2014-12-12

120

Plasma Wave Wigglers for Free Electron Lasers  

Microsoft Academic Search

We explore the possibility of using relativistic plasma density waves as wigglers for producing free electron laser radiation. Two possi- ble wave and beam geometries are explored. In the first, the wiggler is a purely electric wiggler with frequency ma (plasma frequency) but (approximately) zero wavenumber k,. If an electron beam is injected parallel to a wide plasma wave wavefront,

C. Joshi; F. F. Chen; J. M. Dawson; T. Katsouleas; Y. T. Yan

1987-01-01

121

Electron plasma orbits from competing diocotron drifts.  

PubMed

The perpendicular dynamics of a pure electron plasma column are investigated when the plasma spans two Penning-Malmberg traps with noncoinciding axes. The plasma executes noncircular orbits described by competing image-charge electric-field (diocotron) drifts from the two traps. A simple model is presented that predicts a set of nested orbits in agreement with observed plasma trajectories. PMID:25062198

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

2014-07-11

122

Electron Plasma Orbits from Competing Diocotron Drifts  

NASA Astrophysics Data System (ADS)

The perpendicular dynamics of a pure electron plasma column are investigated when the plasma spans two Penning-Malmberg traps with noncoinciding axes. The plasma executes noncircular orbits described by competing image-charge electric-field (diocotron) drifts from the two traps. A simple model is presented that predicts a set of nested orbits in agreement with observed plasma trajectories.

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

2014-07-01

123

Experimental Investigation of Electron-Acoustic Waves in Electron Plasmas  

E-print Network

.3 fbnc. Thus, such drive causes significant bulk plasma heating due to bounce resonances [3], which waves. time. Plasma heating then adjusts the thermal velocity and EAW phase velocity to be in resonanceExperimental Investigation of Electron-Acoustic Waves in Electron Plasmas Andrey A. Kabantsev , F

California at San Diego, University of

124

Interaction of an interplanetary shock with the heliospheric plasma sheet  

NASA Technical Reports Server (NTRS)

Interplanetary shocks often propagate along the heliospheric plasma sheet (HPS) where the interplanetary magnetic field (IMF) changes its polarity. This problem is investigated by the time-dependent 2.5-D MHD numerical model in the meridional plane. An example of computation is shown in the figure using density (log) contours and IMF vectors. Values of plasma parameters along the HPS fluctuate in time due to the Kelvin-Helmholtz instability. The HPS with its decreased intensity of the IMF as well as with its increased mass density causes a dimple in the shock structure (relatively weak for the forward shock, significant for the reverse shock, and very large for the contact discontinuity). Beyond the forward shock, the HPS is slightly compressed due to the post-shock increase of the azimuthal IMF component. Then follows expansion of the HPS surrounded by the highly-deformed contact discontinuity. A significant draping of IMF lines occurs around this structure that increases the meridional component of the IMF. This can cause a favorable condition for initiation of a geomagnetic storm.

Odstrcil, D.; Dryer, M.; Smith, Z.

1995-01-01

125

Bursty bulk flows in the inner central plasma sheet  

NASA Technical Reports Server (NTRS)

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).

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

126

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

SciTech Connect

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.

Hones, E.W.

1992-05-01

127

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

SciTech Connect

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.

Hones, E.W.

1992-01-01

128

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

NASA Astrophysics Data System (ADS)

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 ?cp. 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 ?cp suggests that the waves were observed near the region of their origin and did not propagate along B, consistent with the wave telescope analysis.

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

129

Scaling of the energy of ion beams in the low-altitude plasma sheet boundary layer  

NASA Astrophysics Data System (ADS)

The scaling of the energy of ion beams (beamlets) in resonance regions of the low-altitude plasma sheet boundary layer has been analyzed using the measurements made on the Interball-2 and Cluster satellites at distances of 3.0 to 6.0 Earth's radii and numerical simulations of the acceleration of ions in the current sheet of the Earth's magnetotail. The experimental test of the previously theoretically predicted scaling W N ˜ N A (where W N is the energy at the Nth resonance and A ˜ 1.33) shows that the real scaling of resonance energies varies in a wide range A ? [0.61, 1.75] and is independent of the geomagnetic indices K p and AE. Model calculations with allowance for an electric field E z perpendicular to the current sheet are in good agreement with the experimental data. They indicate that the scaling increases in the case of the dominance of the ion current and decreases in the case of the dominance of the electron current ( A > 1.33 and A < 1.33, respectively).

Kovrazhkin, R. A.; Dolgonosov, M. S.; Sauvaud, J.-A.

2012-05-01

130

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

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

131

New observations of plasma vortices and insights into their interpretation. [in magnetotail plasma sheet  

NASA Technical Reports Server (NTRS)

Two- and three-dimensional plasma measurements and three-dimensional magnetic field measurements made with the ISEE 1 and 2 satellites during sixteen plasma vortex occurrences in the magnetotail plasma sheet are used to develop a fuller description of the vortex phenomenon than has existed heretofore. The phase and energy propagation properties of the vortex waves was studied in particular. The rotation period of the vortices (T = 10 + or - 5 minutes) is apparently independent of location, while the wavelength (lambda not less than several Re) increases with increasing distance down the tail, pointing to a global mode of propagation in which effects of inhomogeneous equilibrium are important. The flow rotation can be explained by propagation of surface waves or resonant waves in a uniform medium. Other observed features, however, require a nonuniform model: nonuniform propagation properties and differences of the phase propagation speed calculated from different components of velocity or magnetic field.

Hones, E. W., Jr.; Birn, J.; Bame, S. J.; Russell, C. T.

1983-01-01

132

528 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 33, NO. 2, APRIL 2005 Visualization of Current Sheet Evolution in a Pulsed  

E-print Network

528 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 33, NO. 2, APRIL 2005 Visualization of Current Sheet of current sheets in a pulsed plasma accelerator. Magnetic field mea- surements complement photographic to create high speed jets of plasma, and are used in many basic plasma science experiments [1], as well

Choueiri, Edgar

133

Controllable formation of graphene and graphene oxide sheets using photo-catalytic reduction and oxygen plasma treatment  

NASA Astrophysics Data System (ADS)

Au/SiO2/Si interdigital electrodes with thickness of 1 ?m were created on silicon substrate. Graphene oxide (GO) sheets hanging from these electrodes were obtained by spin coating of chemically synthesized GO dispersed in water. We used UV-light-induced photo-catalytic activity of titanium oxide nanoparticles to reduce the GO layer. Effects of the photo-induced chemical reduction on the conductivity of the GO were investigated. Also, low power DC plasma was used for oxidation of the sheets. Oxygen bombardment leads to sheets with low electrical conductivity. Measurements show that graphene and GO sheets with the controlled electrical conductivity were obtained by these processes. Scanning electron and atomic force microscopy were used to study the morphology of the TiO2/GO and graphene structures. X-ray diffraction and Raman scattering analysis were used to verify the structural characteristics of the prepared sheets. Analysis showed a gradual increase in the number of C-O bonds on the surface of the graphene layer as a result of increasing the time of plasma bombardment. Based on the Raman spectroscopy, the photo-catalytic activity of TiO2 nanoparticles resulted in a decrease in the number of C-O bonds.

Ostovari, Fatemeh; Abdi, Yaser; Ghasemi, Foad

2012-12-01

134

The thermal and plasma-physical evolution of laminar current sheets formed in the solar atmosphere by emerging flux  

NASA Technical Reports Server (NTRS)

A time-dependent analysis of emerging flux is carried out, and the time evolution of both the current sheet energetics and the plasma state is calculated. This evolution is determined in two different regimes. In the first case the width of the current sheet is assumed to be independent of the sheet thermodynamics and is fixed by the initial conditions. In the second, the width of the current sheet is a function of the resistivity and is allowed to decrease to its minimum given by the electron gyroradius. In both cases the resistivity is computed according to the marginal stability hypothesis. In each case the thermodynamic evolution is found to be quite rapid, with the temperature increasing from 10,000 to 1,000,000 K in a second or less. In contrast to previous studies, it is found that the resistivity is not significantly enhanced by the current-driven plasma wave turbulence. It is concluded that a laminar current sheet cannot be responsible for the activity associated with emerging flux.

Larosa, T. N.

1992-01-01

135

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

NASA Astrophysics Data System (ADS)

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.

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

136

Electron vortex magnetic holes: A nonlinear coherent plasma structure  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

137

Characteristics of high-speed ion flows in the plasma sheet  

Microsoft Academic Search

The occurrence rates and typical characteristics of high-speed ion flows with velocities of 400-600 km\\/s are determined on the basis of the analysis of a large quantity of ion moments and magnetic field measurements acquired from the AMTE\\/IRM satellite data. It is determined that the occurrence rates in the plasma sheet boundary layer, the outer central plasma sheet and the

Wolfgang Baumjohann; Goetz Paschmann; Hermann Luehr

1990-01-01

138

Plasma sheet and (nonstorm) ring current formation from solar and polar wind sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and geosynchronous region (nonstorm) ring current in the framework of collisionless test particle motions in three-dimensional magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft during 2001 and 2002. Many particles were initiated in two regions representative of the

T. E. Moore; M.-C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2005-01-01

139

Plasma Sheet and (non-storm) Ring Current Formation from Solar and Polar Wind Sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and geosynchronous region (non-storm) ring current in the framework of collisionless test particle motions in 3D magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft, during 2001 and 2002. Many particles were initiated in two regions representative of the

T. E. Moore; M. C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2004-01-01

140

Plasma Sheet and Ring Current Formation from Solar and Polar Wind Sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and quiet ring current in the framework of collisionless test particle motions in 3D magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft, during 2001 and 2002. Many particles were initiated in two regions representative of the solar wind

T. E. Moore; M. C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2004-01-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

142

Electron Cyclotron Resonance (ECR) Plasma Thruster Research  

Microsoft Academic Search

A study is being made on an electric propulsion system (EICR Plasma Thruster) which can generate plasma with ECRH (Electron Cyclotron Resonance Heating), accelerate ions with ICRFH (Ion Cyclotron Range of Frequency Heating) via antenna, and adopts a gradient in magnetic field to obtain thrust. The plasma thruster could achieve high power density and long lifetime since this system does

H. Nakashima; Y. Takao; Y. Mori; K. Uemura; T. Gouda; T. Miyamoto; T. Esaki; T. Maeyama; T. Muranaka

2000-01-01

143

The effect of local magnetic fields on the lunar photoelectron layer while the moon is in the plasma sheet  

NASA Technical Reports Server (NTRS)

Data from the Charged Particle Lunar Environment Experiment (CPLEE), at the Apollo 14 site, are used to investigate the interactive properties of the plasma sheet and the lunar photoelectron layer. It is shown that the predictions of the Guernsey-Fu model are compatible with SIDE but not CPLEE observations. The apparent contradiction is resolved by fitting the remanent magnetic field to that of a dipole buried about 1.1 km beneath the surface. In this case a charge separation layer must form above the instrument due to the different rigidities of plasma sheet electrons and protons. The qualitative properties of the charge separation layer needed to reconcile CPLEE and SIDE observations are presented.

Burke, W. J.; Reiff, P. H.; Reasoner, D. L.

1975-01-01

144

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

SciTech Connect

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??/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??/sq.), compared to films with higher sheet resistance (400–600??/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??/sq. to 70??/sq. for a 20?nm TiN film (corresponding resistivity ?145 ??·cm), were achieved by addition of a postcycle Ar/N{sub 2} plasma step in the PE-ALD process.

Burke, Micheal, E-mail: micheal.burke@tyndall.ie; Blake, Alan; Povey, Ian M.; Schmidt, Michael; Petkov, Nikolay; Carolan, Patrick; Quinn, Aidan J., E-mail: aidan.quinn@tyndall.ie [Tyndall National Institute, University College Cork, Cork (Ireland)

2014-05-15

145

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

146

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)

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.

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

1975-01-01

147

Thinning and functionalization of few-layer graphene sheets by CF4 plasma treatment  

PubMed Central

Abstract Structural changes of few-layer graphene sheets induced by CF4 plasma treatment are studied by optical microscopy and Raman spectroscopy, together with theoretical simulation. Experimental results suggest a thickness reduction of few-layer graphene sheets subjected to prolonged CF4 plasma treatment while plasma treatment with short time only leads to fluorine functionalization on the surface layer by formation of covalent bonds. Raman spectra reveal an increase in disorder by physical disruption of the graphene lattice as well as functionalization during the plasma treatment. The F/CF3 adsorption and the lattice distortion produced are proved by theoretical simulation using density functional theory, which also predicts p-type doping and Dirac cone splitting in CF4 plasma-treated graphene sheets that may have potential in future graphene-based micro/nanodevices. PACS 81.05.ue; 73.22.Pr; 52.40.Hf. PMID:22625875

2012-01-01

148

Io plasma torus electrons - Voyager 1  

NASA Technical Reports Server (NTRS)

A thermal Maxwellian component of the electron distribution function, together with a suprathermal, non-Maxwellian one, are featured in the present analysis of in situ plasma electron observations made by the Voyager 1 plasma science experiment in the Io plasma torus. A large difference in the hot electron pressure P(H) is noted between the inbound and the outbound data; this is interpreted as a latitudinal gradient, with P(H) being maximum at the magnetic equator. The presence of a neutral corona around Io is inferred from the observed decrease and symmetry with respect to Io of the cold electron temperature.

Sittler, E. C., Jr.; Strobel, Darrell F.

1987-01-01

149

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

150

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

151

Intense Sheet Electron Beam Transport in a Uniform Solenoidal Magnetic Field  

Microsoft Academic Search

In this paper, the transport of intense sheet electron beams in a uniform solenoidal magnetic field in high-power vacuum electronic devices is theoretically examined with the 3-D beam optics code MICHELLE. It is shown that a solenoidal magnetic field can be an effective transport mechanism for sheet electron beams, provided the beam tunnel is matched to the beam shape, and

Khanh T. Nguyen; John A. Pasour; Thomas M. Antonsen; Paul B. Larsen; John J. Petillo; Baruch Levush

2009-01-01

152

Energy Spectra and Angular Distributions of Particles in the Plasma Sheet and Their Comparison with Rocket Measurements over the Auroral Zone  

Microsoft Academic Search

This paper presents examples of electron and proton differential energy spectra between ~100 ev and 18 key measured with hemispherical plate electrostatic analyzers on the Vela satellites at a geocentric distance of ~18 Rr in the magnetotail plasma sheet. The spectra were obtained under several conditions of geomagnetic activity' (a) during very quiet conditions, (b) during the expansive phase of

E. W. Hones; J. R. Asbridge; S. J. Bame; Sidney Singer

1971-01-01

153

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

NASA Astrophysics Data System (ADS)

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/ ? ? ) 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 ? ) conservation provides important constraints on the plasma sheet transport, e.g., fast flows.

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

154

Tail plasma sheet models derived from Geotail particle data  

NASA Astrophysics Data System (ADS)

Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and interplanetary magnetic field (IMF) parameters, at distances between 10 and 50 RE. The models are based on a large set of data of the Low-Energy Particle (LEP) and Magnetic Field (MGF) instruments, taken by Geotail spacecraft between 1994 and 1998, comprising 7234 1-min average values of the CPS temperature and density. Concurrent solar wind and IMF data were provided by the Wind and IMP 8 spacecraft. The accuracy of the models was gauged by the correlation coefficient (c.c.) R between the observed and predicted values of a parameter. The CPS ion density N is controlled mostly by the solar wind proton density and by the northward component of the IMF. Being the least stable characteristic of the CPS, it yielded the lowest c.c. RN = 0.57. The CPS temperature T, controlled mainly by the solar wind speed V and the IMF Bz, gave a higher c.c. RT = 0.71. The CPS ion pressure P was best controlled by the solar wind ram pressure Psw and by an IMF-related parameter F = B??, where B? is the perpendicular component of the IMF and ? is its clock angle. In a striking contrast with N and T, the model pressure P revealed a very high c.c. with the data, RP = 0.95, an apparent consequence of the force balance between the CPS and the tail lobe magnetic field. No significant dawn-dusk asymmetry of the CPS was found beyond the distance 10 RE, in line with the observed symmetry of the tail lobe magnetic field. The plasma density N is lowest at midnight and increases toward the tail's flanks. Larger (smaller) solar wind ion densities and northward (southward) IMF Bz result in larger (smaller) N in the CPS. In contrast to the density N, the temperature T peaks at the midnight meridian and falls off toward the dawn/dusk flanks. Faster (slower) solar wind flow and southward (northward) IMF Bz result in a hotter (cooler) CPS. The CPS ion pressure P is essentially a function of only XGSM in the midtail (20-50 RE); at closer distances the isobars gradually bend to approximately follow the contours of constant geomagnetic field strength. For northward IMF conditions combined with a slow solar wind, the isobars remain quasi-circular up to larger distances, reflecting a weaker tail current and, hence, more dipole-like magnetic field.

Tsyganenko, N. A.; Mukai, T.

2003-03-01

155

THEMIS Observation of Plasma Sheet Evolution Leading To a Substorm Onset  

NASA Astrophysics Data System (ADS)

We investigate THEMIS observations on 28 February 2008 between 7:00 and 8:00 UT. Using the AM-03 adapted Tsyganenko model we found that the change in the Z-component of the solar wind velocity between 7:09 and 7:24 UT forced stronger bending of the Earth's magnetotail in the positive ZGSM-direction downtail from 9 Re. The final bend angle reached 30 degrees. The bending appeared to be the reason for the negative gradient in the ZGSM-component of the magnetic field (dBZ/dX) in the plasma sheet. The negative dBZ/dX can be a free energy source for the drift-kink and ballooning/interchange instabilities in the plasma sheet, which can be seen as plasma sheet flapping. Indeed, the plasma sheet started to exhibit flapping oscillations near the bending point at the radial distance 11 Re. The amplitude of the oscillations has grown substantially with larger bending angles after 7:12 UT. The value of the dBZ/dX continued becoming more negative up to 7:38 UT. At 7:30 UT the region of the plasma sheet flapping extended to 16 Re downtail. Between 7:30 and 7:39 UT THEMIS observed gradual vanishing of the pressure gradient between 11 Re and 16 Re, Finally, at 7:39 UT THEMIS detected earthward plasma flows at the radial distance 11 Re and tailward plasma flows at 16 to 29 Re downtail. Simultaneously, at the footpoints of the field lines leading to the THEMIS spacecraft, the THEMIS all-sky camera array observed a substorm breakup arc. We discuss the possible relationship between the current sheet bending and the evolution of the current sheet instability that may relate to the substorm onset.

Panov, E.; Nakamura, R.; Baumjohann, W.; Artemyev, A.; Kubyshkina, M.; Sergeev, V. A.; Petrukovich, A. A.; Angelopoulos, V.; Glassmeier, K.; McFadden, J. P.; Larson, D. E.

2011-12-01

156

Creating standardized electronic data sheets for applications and devices  

NASA Astrophysics Data System (ADS)

The Air Force Research Laboratory (AFRL) continues to develop infrastructure to enable the modular construction of satellites using an open network architecture and off-the-shelf avionics for space systems. Recent efforts have included the refinement of an ontology to formalize a standard language for the exchange of data and commands between components, including hardware and software, which is still evolving. AFRL is also focusing effort on creating standard interfaces using electronic data sheets based on this recently defined ontology. This paper will describe the development of standard interfaces that are documented in terms of an electronic datasheet for a specific application. The datasheet will identify the standard interfaces between hardware devices and software applications that are needed for a specific satellite function, in this case, a spacecraft guidance, navigation, and control (GN& C) application for Sun pointing. Finally, the benefits of using standardized interfaces will be discussed.

Hansen, L. J.; Lanza, D.

157

Responses of different ion species to fast plasma flows and local dipolarization in the plasma sheet  

NASA Astrophysics Data System (ADS)

investigate the responses of different ion species (H+, He+, He++, and O+) to fast plasma flows and local dipolarization in the plasma sheet in terms of energy density. We use energetic (9-210 keV) ion composition measurements made by the Geotail satellite at r = 10~31 RE. The results are summarized as follows: (1) whereas the O+-to-H+ ratio decreases with earthward flow velocity, it increases with tailward flow velocity with steeper Vx dependence for perpendicular flows than for parallel flows; (2) for fast earthward flows, the energy density of each ion species increases without any clear preference for heavy ions; (3) for fast tailward flows, the ion energy density initially increases, then it decreases to below the preceding levels except for O+; (4) the O+-to-H+ ratio does not increase through local dipolarization irrespective of dipolarization amplitude, background Bz, X distance, and Vx; (5) in general, the H+ and He++ ions behave similarly. Result (1) can be attributed to radial transport in the presence of the earthward gradient of the background O+-to-H+ ratio. Results (2) and (4) suggest that ion energization at local dipolarization is not mass dependent in the energy range of our interest because the ions are not magnetized irrespective of species. Result (3) can be attributed to the thinning of the plasma sheet and the preferable field-aligned escape of the H+ ions on the tailward side of the reconnection site. Result (5) suggests that the solar wind is the primary source of the high-energy H+ ions.

Ohtani, S.; Nosé, M.; Miyashita, Y.; Lui, A. T. Y.

2015-01-01

158

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

159

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

SciTech Connect

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=?pi) and the peak electron outflow velocity scales with the electron Alfven velocity (? 0.12 - 0.16VeA), independent of ion mass.

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

2008-06-26

160

Electron kinetic theory in laser heated plasmas  

NASA Astrophysics Data System (ADS)

Since the formulation of the linearized nonlocal hydrodynamic equations [Phys. Rev. Lett. 75, 4405 (1995)] our studies of collisional thermal processes in laser produced plasmas have led to better understanding of the electron transport, plasma fluctuations, electron distribution functions, and parametric instabilities. This talk will discuss some of these advances. The linear nonlocal theory of electron transport is derived from the solution to the Fokker-Planck (FP) equation and provides plasma description, which is valid in the entire range of electron collisionality. Numerical studies involving FP and collisional particle-in-cell codes have confirmed our analytical theories and provided more general results in a nonlinear regime of large perturbations. A nonlinear expression has been proposed for the thermal transport coefficient, which explains numerical results. The nonlocal hydrodynamic equations have been used as the framework for the theoretical description of thermal stimulated Brillouin scattering, filamentation instability, return current instability and hydrodynamical fluctuations. Results from laser plasma interaction and Thomson scattering experiments are consistent with theoretical scenarios involving nonlocal thermal effects. New nonequilibrium electron distribution functions have been found. They occur in laser heated plasmas due to competing effects of strong laser field, inverse bremsstrahlung absorption, electron-electron collisions and plasma inhomogeneity. In addition to well known flattening of the low velocity part, these distribution functions usually display superthermal tails of fast electrons.

Rozmus, Wojciech

2001-10-01

161

A Modified Porous Titanium Sheet Prepared by Plasma-Activated Sintering for Biomedical Applications  

PubMed Central

This study aimed to develop a contamination-free porous titanium scaffold by a plasma-activated sintering within an originally developed TiN-coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN-coated carbon graphite mold. This modified plasma-activated sintering with the TiN-coated graphite mold would be useful to fabricate a contamination-free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair. PMID:21350650

Tamaki, Yukimichi; Lee, Won Sik; Kataoka, Yu; Miyazaki, Takashi

2010-01-01

162

Three-dimensional analyses of electric currents and pressure anisotropies in the plasma sheet  

E-print Network

suggests that the net effect of chaotic ion motion near the neutral sheet is to create a weak source cone by an electric field with a parallel component near the neutral sheet. The parallel electric field is small but is required to maintain charge neutrality in the region containing guiding center electron and nonguiding

Kaufmann, Richard L.

163

Electron-cyclotron-resonance (ECR) plasma acceleration  

NASA Technical Reports Server (NTRS)

A research effort directed at analytically and experimentally investigating electron-cyclotron-resonance (ECR) plasma acceleration is outlined. In addition, relevant past research is reviewed. Also, the prospects for application of ECR plasma acceleration to spacecraft propulsion are described. It is shown that previously unexplained losses in converting microwave power to directed kinetic power via ECR plasma acceleration can be understood in terms of diffusion of energized plasma to the physical walls of the accelerator. It is also argued that line radiation losses due to electron-ion and electron-atom inelastic collisions should be less than estimated in past research. Based on this new understanding, the expectation now exists that very efficient ECR plasma accelerators can be designed for application to high-specific-impulse spacecraft propulsion.

Sercel, Joel C.

1987-01-01

164

Structured plasma sheet thinning observed by Galileo and 1984-129  

SciTech Connect

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.

Reeves, G.D.; Belian, R.D.; Fritz, T.A. [Los Alamos National Lab., NM (United States)] [and others

1993-12-01

165

Plasma diagnostics using electron paramagnetic resonance  

NASA Astrophysics Data System (ADS)

Methods giving absolute concentrations of various species in the plasma are of utmost importance to plasma research. Besides currently prevalent laser methods, a method based on microwave absorption—electron paramagnetic resonance—can be successfully used for plasma diagnostics. It is able to detect many atoms, molecules and radicals in the ground or excited states. In this paper we give an overview of the method and several practical examples.

Kudrle, V.; Vašina, P.; Tálský, A.; Mrázková, M.; Štec, O.; Jan?a, J.

2010-03-01

166

Investigation of a staged plasma-focus apparatus. [pinch construction and current sheet dynamics investigation  

NASA Technical Reports Server (NTRS)

A new staged plasma-focus geometry combining two Mather-type plasma-focus guns was constructed, and the current-sheet dynamics were investigated. The production of simultaneous pairs of plasma foci was achieved. The intensities of X-ray and fusion-neutron emission were measured and found to agree with the scaling law for a plasma focus. Advantages of this new geometry include the possibility of using plasma-focus type pinches in multiple arrays at power levels beyond the validity regime of the current scaling law for a single gun.

Lee, J. H.; Mcfarland, D. R.; Harries, W. L.

1978-01-01

167

Plasma effects in a free electron laser  

Microsoft Academic Search

The introduction of a plasma and a strong guide magnetic field in a free electron laser (FEL) slows down the phase velocity of radiation, significantly reducing the requirements on beam energy for generating frequencies below the electron-cyclotron frequency (?1≲?c). Around plasma resonance (?1~?p), the FEL mode couples to two-stream instability (TSI), attaining a large growth rate, comparable to that of

VIPIN K. TRIPATHI; CHUAN SHENG LIU

1990-01-01

168

Development of plasma cathode electron guns  

NASA Astrophysics Data System (ADS)

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.

Oks, Efim M.; Schanin, Peter M.

1999-05-01

169

Plasma interaction with electron-emitting surfaces  

NASA Astrophysics Data System (ADS)

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.

Campanell, Michael D.

170

The motion and magnetic structure of the plasma sheet near 30 earth radii  

NASA Technical Reports Server (NTRS)

Data taken by the NASA-GSFC magnetometer aboard the Explorer 34 satellite are analyzed in an effort to ascertain the average motion and magnetic field structure of the plasma sheet near 30 earth radii. It is found that the flapping motion of the plasma sheet in the solar ecliptic Z-coordinate is characterized by a typical speed of 90 km/sec and an amplitude of plus or minus 2 earth radii. Results suggest that there exists a layer of nearly uniform cross-tail current density in the central region of the plasma sheet approximately 2.3-2.6 earth radii thick within which the solar-magnetospheric X-component of the magnetic field changes from 10 gamma to -10 gamma.

Bowling, S. B.; Wolf, R. A.

1974-01-01

171

Vortex and ULF wave structures in the plasma sheet of the Earth magnetosphere  

NASA Astrophysics Data System (ADS)

We studied the ULF wave packet propagation in the Earth plasma sheet making use of the magnetic field measurements from FGM detector and plasma properties from CORRAL detector aboard the Interball-Tail spacecraft. The MHD vortex structures were observed simultaneously with the Pc5 ULF waves. The vortex spatial scale was found to be about 1200-3600 km and the velocity is 4-16 km/s transverse to the background magnetic field. We studied numerically the dynamics of the initial vortex perturbations in the plasma system with parameters observed in the Earth plasma sheet. The system with the vector nonlinearity was processed making use of the full reduction scheme. The good agreement of the experimental value of the vortex structure velocity with numerical results was obtained. The velocity was found to be close to the local plasma drift velocity.

Saliuk, D. A.; Agapitov, O. V.

2013-08-01

172

Multiple harmonic ULF waves in the plasma sheet boundary layer: Instability analysis  

NASA Astrophysics Data System (ADS)

Multiple-harmonic electromagnetic waves in the ULF band have occasionally been observed in Earth's magnetosphere, both near the magnetic equator in the outer plasmasphere and in the plasma sheet boundary layer (PSBL) in Earth's magnetotail. Observations by the Cluster spacecraft of multiple-harmonic electromagnetic waves with fundamental frequency near the local proton cyclotron frequency, ?cp, were recently reported in the plasma sheet boundary layer by Broughton et al. (2008). A companion paper surveys the entire magnetotail passage of Cluster during 2003, and reports 35 such events, all in the PSBL, and all associated with elevated fluxes of counterstreaming ions and electrons. In this study we use observed pitch angle distributions of ions and electrons during a wave event observed by Cluster on 9 September 2003 to perform an instability analysis. We use a semiautomatic procedure for developing model distributions composed of bi-Maxwellian components that minimizes the difference between modeled and observed distribution functions. Analysis of wave instability using the WHAMP electromagnetic plasma wave dispersion code and these model distributions reveals an instability near ?cp and its harmonics. The observed and model ion distributions exhibit both beam-like and ring-like features which might lead to instability. Further instability analysis with simple beam-like and ring-like model distribution functions indicates that the instability is due to the ring-like feature. Our analysis indicates that this instability persists over an enormous range in the effective ion beta (based on a best fit for the observed distribution function using a single Maxwellian distribution), ?', but that the character of the instability changes with ?'. For ?' of order unity (for instance, the observed case with ?' ˜ 0.4), the instability is predominantly electromagnetic; the fluctuating magnetic field has components in both the perpendicular and parallel directions, but the perpendicular fluctuations are larger. If ?' is greatly decreased to about 5 × 10-4 (by increasing the magnetic field), the instability becomes electrostatic. On the other hand, if ?' is increased (by decreasing the magnetic field), the instability remains electromagnetic, but becomes predominantly compressional (magnetic fluctuations predominantly parallel) at ?' ˜ 2. The ?' dependence we observe here may connect various waves at harmonics of the proton gyrofrequency found in different regions of space.

Denton, R. E.; Engebretson, M. J.; Keiling, A.; Walsh, A. P.; Gary, S. P.; DéCréAu, P. M. E.; Cattell, C. A.; RèMe, H.

2010-12-01

173

Electronic structures of graphene/boron nitride sheet superlattices  

NASA Astrophysics Data System (ADS)

Single-sheet graphene/boron nitride superlattices (SLs) are studied by a first-principles density functional theory approach to form a basic understanding for engineering a graphene band gap. The formation energy and electronic properties of SLs with different orientations (armchair or zigzag boundary) and stripe widths (2.16-14.80 Å) are studied. The trends of the formation energy with respect to the stripe widths and orientations are explained by the differences in bond energies and simple coulombic forces between ions. Regarding the electronic properties, it is found that not all SLs have a nonzero band gap. The band gap size and band edge locations can be explained by the Brillouin zone folding, the symmetry of SLs, and the effects from the graphene/boron nitride edges. The factors that cause the band gap opening and those that lift it are analyzed and discussed. The detailed electronic states near the band edges of each SL group are analyzed by directly plotting the charge densities, as well as utilizing a simple tight-binding model to resolve their characteristics.

Jungthawan, Sirichok; Limpijumnong, Sukit; Kuo, Jer-Lai

2011-12-01

174

Current Sheet Permeability in Electromagnetic Pulsed Plasma Thrusters  

E-print Network

of Scientific Re- search and the Program of Plasma Science and Technology at Princeton University. Graduate on the same device employed in our work, found evidence of a plasma wake as well through photographic

Choueiri, Edgar

175

Plasma sheet instability related to the westward traveling surge  

SciTech Connect

The detailed analysis of an isolated dispersionless substorm is performed on the basis of field and particle data collected in situ by the geostationary satellite GEOS 2 and of data from ground-based instruments installed close to the GEOS 2 magnetic footprint. These data give evidence for (1) quasi-periodic variations of the magnetic field configuration, which is alternatively taillike and dipolelike, (2) in-phase oscillations of the flux of energetic electrons, which is high when the configuration is dipolelike and vice versa, (3) a gradient in the flux of energetic ions, which is, on the average, earthward but undergoes large fluctuations around this average direction, and (4) large transient fluctuations of the quasi-dc electric field, which reverses its direction from eastward to westward. It is shown that these results are consistent with the development of an instability which leads to a westward propagating wave. The source of the instability is the differential drift of energetic electrons and ions in a highly stressed magnetic field configuration (in a high {beta} plasma). Evidence is given for a system of localized field-aligned currents flowing alternately earthward and equatorward at the leading and trailing edges of the westward propagating wave. This current system resulting from the temporal development of the instability produces the so-called Pi 2 pulsations, at the ionospheric level. The closure of this current system in the equatorial region leads to a current antiparallel to the tail current, and therefore to its reduction or cancellation. This reduction/cancellation of the tail current restores the dipole magnetic field (dipolarization) and generates a large westward directed induced electric field (injection).

Roux, A.; Perraut, S.; Robert, P.; Morane, A. (Centre National d'Etudes des Telecommunications, Issy-les-Moulineaux (France)); Pedersen, A. (European Space Research and Technology Centre, Noordwijk (Netherlands)); Korth, A.; Kremser, G. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (West Germany)); Aparicio, B. (Swedish Inst. of Space Physics, Kiruna (Sweden)); Rodgers, D. (University College, London (England)); Pellinen, R. (Finnish Meteorological Inst., Helsinki (Finland))

1991-10-01

176

Reconnection AND Bursty Bulk Flow Associated Turbulence IN THE Earth'S Plasma Sheet  

NASA Astrophysics Data System (ADS)

Reconnection related fast flows in the Earth's plasma sheet can be associated with several accompanying phenomena, such as magnetic field dipolarization, current sheet thinning and turbulence. Statistical analysis of multi-scale properties of turbulence facilitates to understand the interaction of the plasma flow with the dipolar magnetic field and to recognize the remote or nearby temporal and spatial characteristics of reconnection. The main emphasis of this presentation is on differentiating between the specific statistical features of flow associated fluctuations at different distances from the reconnection site.

Voros, Z.; Nakamura, R.; Baumjohann, W.; Runov, A.; Volwerk, M.; Jankovicova, D.; Balogh, A.; Klecker, B.

2006-12-01

177

Electron density measurements in magnetized complex plasmas  

Microsoft Academic Search

This contribution introduces a new experiment for the investigation of magnetized complex plasmas. Its basic features are discussed and first experiments on free-falling dust particles are presented. By means of Langmuir probes and the resonance cone technique, the influence of dust particles on the free electron density is studied. With both methods, significant electron density reductions are observed.

Thomas Trottenberg; Björn Brede; Dietmar Block; Alexander Piel

2004-01-01

178

Magnetic Reconnection and the Deduced Properties of Plasma inside the CME/Flare Current Sheet  

NASA Astrophysics Data System (ADS)

In the present work, we display our results of studying and analyzing the observational data from UVCS and other remote sensing instruments for three CME/flare events that obviously developed a long current sheet during the eruptions. These results include the thickness of the current sheets, magnetic diffusivities and electrical conductivities (resistivities) of the plasma inside the current sheets. This is the first time that the electrical conductivity (resistivity) within magnetic reconnection region during the real eruptive processes has been deduced since the theory of magnetic reconnection was applied to the solar eruptions about 6 decades ago. The thickness of the current sheet developed during the January 8, 2002 event varies from 7 × 104 km to 2.2 × 105 km for altitudes between 2.5 R? and 5.5 R?, with the average thickness of 1.4× 105 km, and the speed of magnetic reconnection inflow near the current sheet is about 10 km s-1. These results suggest a magnetic diffusivity of the plasma inside the current sheet to be 0.7 × 1012 m2 s-1 (compared to the classical value for the quiet corona of 1 m2 s-1, and to the corresponding value for the "turbulent plasma" of 3.4× 106 m2 s-1). For the event occurring on November 18, 2003, the data from UVCS indicate that the upper limit of the current sheet thickness at altitude of 1.7 R? is about 2.8 × 104 km, and that the velocity of magnetic reconnection inflow near the current sheet ranges from 10.5 km s-1 to 106 km s-1. Combining these results yields a range of magnetic diffusivity from 1.4× 1011 m2 s-1 to 1.4× 1012 m2 s-1. During the event observed on March 23, 1998, the upper limit of the thickness of the current sheet in the wake of a CME is about 105 km according to data from UVCS. No data for the velocity of the magnetic reconnection near the current sheet in this event were obtained. Considering the fact that this event was more gradual than the other two cases, we assume the inflow speed in this event to be 5 km s-1. So, we obtain that the magnetic diffusivity of the plasma inside the current sheet has an upper limit of 2.5× 1011 m2 s-1. We notice that values of magnetic diffusivity deduced for three different events are within the range of magnitude.

Lin, J.; Li, J.; Forbes, T. G.; Ko, Y.; Raymond, J. C.; van Ballegooijen, A. A.

2005-05-01

179

Ion and electron heating during magnetic reconnection in weakly collisional plasmas  

NASA Astrophysics Data System (ADS)

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.

Numata, Ryusuke; Loureiro, N. F.; Loureiro

2015-04-01

180

Time-Variability of Plasma Sheet Particle Precipitation as Seen in ENA Observations  

NASA Astrophysics Data System (ADS)

The dynamics of energetic particles (ring current energies) in the inner magnetosphere is a well studied topic. The study of the plasma sheet in the same region (primarily the inner edge of the plasma sheet) is possibly less intense. For one, the observation of plasma sheet dynamics in the inner magnetosphere is made harder by the slower bulk plasma motion. Particles with a few keV energy do respond to geomagnetic activity and events (e.g., storms, substorms). However, their motion is primarily driven on the relatively slow time scales of electrically induced convection, and it is much slower compared to the particle motion typical for ring current energies. Nevertheless, the plasma sheet does respond measurably on a variety of time scales, from geomagnetic storms (several hours to days) down to substorm time scales (~3 hours). Recently, there has been increased focus on remote sensing ion precipitation into the atmosphere using low altitude energetic neutral atom (ENA) emissions (so-called LAEs). These emissions are created primarily when energetic plasma precipitates into Earth's atmosphere and encounters the oxygen exobase, where there is a sudden increase in neutral (oxygen) density that results in a drastically increased ENA production. Current studies focus on the relationship between ion precipitation and geomagnetic storm phase, primarily studying the intensity, location, and extent of LAEs in relation with geomagnetic activity. We are expanding this work and investigate specifically the response of LAE (and thus, the amount of measured ion precipitation) on shorter time scales down to typical substorm durations (~ 3 hours across a complete substorm cycle). We are bringing the analysis techniques developed for storms studies to bear, correlating LAE emissions during the last solar maximum with Kp (which has proven to be a good measure of the location of the inner edge of the plasma sheet), and with substorm activity (auroral indices, geosynchronous ion injections, and ion precipitation induced UV signatures of auroral substorms).

Jahn, J.; Mackler, D. A.; Pollock, C. J.

2012-12-01

181

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

182

Substorm-associated explosive magnetic field stretching near the earthward edge of the plasma sheet  

NASA Astrophysics Data System (ADS)

report a detailed analysis of explosive local magnetic field line stretching just before dipolarization observed by one of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites during the pseudo-breakup followed by local substorm of 6 January 2008. At the end of the substorm growth phase, this satellite (THEMIS-C) was located at r ~ 6.3 RE near the convection boundary of 10 keV electrons. Penetration of the hot electron plasma sheet to the region of trapped energetic ions was a precondition for the substorm onset in the premidnight sector. Observed oscillations of fields and particles with period 50-60 s are consistent with the ballooning mode in the near-Earth magnetotail and with the near-Earth initiation current disruption model. Basing on the simple line-current model, the explosive stretching and following dipolarization observed by THEMIS-C satellite are interpreted as a manifestation of the magnetospheric generator of the 3-D meridional current system with the driving electric field in the meridional direction during nonlinear growth of ballooning instability when non-MHD processes are also turning on.

Kozelova, T. V.; Kozelov, B. V.

2013-06-01

183

A Gridded Electron Gun for a Sheet Beam Klystron  

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

184

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

NASA Technical Reports Server (NTRS)

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).

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

1995-01-01

185

Particle pitch angle diffusion due to nonadiabatic effects in the plasma sheet  

Microsoft Academic Search

In order to understand certain aspects of the plasma sheet dynamics, a numerical study of the nonadiabatic behavior of particles in a model field geometry is performed. The particle's magnetic moment as a function of time is calculated for various initial parameters, corresponding to various particle energies and degrees of field curvature. It is shown that the magnetic moment changes

P. C. Gray; L. C. Lee

1982-01-01

186

Characterization of electron cyclotron resonance hydrogen plasmas  

SciTech Connect

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.

Outten, C.A. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Nuclear Engineering); Barbour, J.C.; Wampler, W.R. (Sandia National Labs., Albuquerque, NM (USA))

1990-01-01

187

Characterization of electron cyclotron resonance hydrogen plasmas  

SciTech Connect

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 ({ital V}{sub {ital p}} ), electron density ({ital N}{sub {ital e}} ), electron temperature ({ital T}{sub {ital e}} ), ion energy ({ital T}{sub {ital 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 W of absorbed power. These results gave {ital V}{sub {ital p}} =30{plus minus}5 eV, {ital N}{sub {ital e}} =1{times}10{sup 8} cm{sup {minus}3}, and {ital T}{sub {ital e}} =10--13 eV. In good agreement with the Langmuir probe results, carbon resistance probes have shown that {ital T}{sub {ital 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} s at a pressure of 1{times}10{sup {minus}4} Torr and for 50 W of absorbed power.

Outten, C.A. (Department of Nuclear Engineering, University of Michigan, Ann Arbor, Michigan 48109 (USA)); Barbour, J.C.; Wampler, W.R. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (USA))

1991-05-01

188

ELECTRON CYCLOTRON HEATING OF AN ANISOTROPIC PLASMA J. C. SPROTT  

E-print Network

ELECTRON CYCLOTRON HEATING OF AN ANISOTROPIC PLASMA by J. C. SPROTT December 4, 1969 PLP No. 322 professor. Plasma Studies University of Wisconsin #12;Electron Cyclotron Heating of an Anisotropic Plasma, and multipole confined plasmas also exhibit a degree of anisotropy at high energies when electron cyclotron 1

Sprott, Julien Clinton

189

Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.  

PubMed

We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet. PMID:25666919

Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

2015-03-01

190

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)

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.

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

2013-12-01

191

Fundamentals and Applications of a Plasma Processing System Based on Electron Beam Ionization  

NASA Astrophysics Data System (ADS)

Electron beam (e-beam) ionization has been shown to be both efficient at producing plasma and scalable to large area (square meters). NRL has developed a number of advanced research tools culminating in a ``Large Area Plasma Processing System'' (LAPPS) based on an e-beam sheet geometry. We have demonstrated that the beam ionization process is fairly independent of gas composition and capable of producing low temperature plasma electrons (<0.5 eV in molecular gases) in high densities (10^9-10^12 cm-3). This system can offer increased control of plasma-to-surface fluxes and the ability to modify materials' surface properties uniformly over large areas. The systems to be discussed consist of continuous and pulsed planar plasma distributions generated by a magnetically collimated sheet of 2-3kV, < 1 mA/cm^2 electrons injected into a neutral gas background (oxygen, nitrogen, sulfur hexafluoride, argon). Typical operating pressures range from 20-150 mTorr with beam-collimating magnetic fields (100-200 Gauss) for plasma localization. The attributes of beam-generated plasmas make them ideal for many materials applications. These systems have been investigated for a broad range of applications, including surface activation, line edge roughening, and anisotropic etching of polymers, electron-ion and ion-ion plasma etching, low-temperature metal nitriding and thin film deposition (reactive sputtering and plasma enhanced chemical vapor deposition). Details of some of these applications will be discussed in terms of the critical plasma physics and chemistry, with complementary time-resolved in situ plasma diagnostics (Langmuir probes, microwave transmission, energy-resolved mass spectrometry and laser spectroscopy).

Leonhardt, Darrin

2006-10-01

192

Electron density measurements for plasma adaptive optics  

NASA Astrophysics Data System (ADS)

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.

Neiswander, Brian W.

193

Plasma sheet fast flows and auroral dynamics during substorm: a case study  

NASA Astrophysics Data System (ADS)

Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL). It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region) is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs), described by Angelopolous et al. (1992). These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i) tailward/earthward flows were superimposed on a very strong duskward flow, and (ii) wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.

Borodkova, N. L.; Yahnin, A. G.; Liou, K.; Sauvaud, J.-A.; Fedorov, A. O.; Lutsenko, V. N.; Nozdrachev, M. N.; Lyubchich, A. A.

2002-03-01

194

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

195

Electron transport in a nondegenerate dense plasma  

NASA Astrophysics Data System (ADS)

A physical model is developed which describes the conductivity and electron heat conductivity of an equilibrium plasma in the density range from gaseous to solid-state and at any temperature above the free-electron degeneracy limit. The model assumes local thermodynamic equilibrium, and the semiclassical theory is considered. The conductivity and degree of ionization of NaCl are calculated for different densities and temperatures.

Ermakov, V. V.; Kalitkin, N. N.

1979-05-01

196

Kink-like mode of a double gradient instability in a compressible plasma current sheet  

PubMed Central

A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet. PMID:22053125

Korovinskiy, D.B.; Ivanova, V.V.; Erkaev, N.V.; Semenov, V.S.; Ivanov, I.B.; Biernat, H.K.; Zellinger, M.

2011-01-01

197

The relationship between fluctuating plasma sheet and substorm development: Cluster and Double Star TC1 case study  

NASA Astrophysics Data System (ADS)

During magnetospheric substorms the magnetic field configuration in the near-Earth tail often changes drastically from tail-like to a more dipolar configuration This dipolarization seems to be caused by the disruption of cross-tail currents in the near-Earth tail or by bursty bulk flows BBFs in the midtail Around the disturbances it is also known that the plasma sheet sometimes fluctuates strongly magnetotail flapping kink-like motion or sausage modes The relationship between such a fluctuating plasma sheet and BBFs dipolarization is still unknown In this study conjunction events of Cluster in the midtail region and Double Star TC1 in near-Earth tail are investigated We present two global dipolarization events observed by Cluster and TC1 on Sep 3 2004 that were preceded by a fluctuating plasma sheet Dipolarization took place associated with a global onset and a fluctuating plasma sheet was observed during periods of pseudo-breakup In the first case a fluctuation of plasma sheet kink-like preceded an auroral brightening In the second case a fluctuating plasma sheet kink-like and sausage mode followed the auroral brightening In both cases the following substorm expands globally and both spacecraft observe the propagating dipolarization front We discuss how the fluctuating plasma sheet relates to localized activation during the growth phase and leads to a large scale onset of the substorm

Takada, T.; Nakamura, R.; Zhang, T. L.; Asano, Y.; Baumjohann, W.; Klecker, B.; Reme, H.; Balogh, A.; Carr, C. M.; Frey, H. U.

198

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)

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.

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

2008-01-01

199

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

SciTech Connect

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.

Soni, Himadri R., E-mail: himadri.soni@gmail.com; Jha, Prafulla K., E-mail: himadri.soni@gmail.com [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364001 (India)

2014-04-24

200

Gyro-kinetic Electron and Fully-Kinetic Ion Particle Simulation of Tearing Mode Instability in a Harris Current Sheet  

NASA Astrophysics Data System (ADS)

Two-dimensional simulations are carried out using our gyro-kinetic electron and fully-kinetic ion (GeFi, formerly GKe/FKi [1]) particle simulation model to investigate the collisionless tearing mode instability in a Harris current sheet in the presence of a finite guide field, under a realistic ion-to-electron mass ratio m^i/m^e. The simulation is performed in the plane that contains the anti-parallel magnetic field B^x and the current sheet normal B^z. First, results based on the linearized delta-f scheme are compared with the eigenfunction and linear growth rate obtained from the drift kinetic eigenmode theory as well as the asymptotic matching results of Drake and Lee [2]. Effect of the electron-to-ion temperature ratio T^e/T^i, beta values, and the half-width of the current sheet are investigated. Second, the physics of saturation is studied using the nonlinear simulation scheme. [4pt] [1] Lin, Y., X. Y. Wang, Z. Lin, and L. Chen, Plasma Phys. Controlled Fusion, 47, 657 ,2005. [0pt] [2] Drake, J.F, and Y.C.Lee, Phys.Fluids, 20, 1341, 1977

Lu, Xiang; Wang, Xueyi; Lin, Yu; Wei, Kong; Liu, Chen

2010-11-01

201

The superdense plasma sheet in the magnetosphere during high-speed-stream-driven storms: Plasma transport timescales  

Microsoft Academic Search

The superdense plasma sheet in the Earth's magnetosphere is studied via a superposition of multispacecraft data collected during 124 high-speed-stream-driven storms. The storm onsets tend to occur after the passage of the IMF sector reversal and before the passage of the stream interface, and the storms continue on for days during the passage of the high-speed stream. The superdense phase

Michael H. Denton; Joseph E. Borovsky

2009-01-01

202

The Giotto electron plasma experiment  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

203

Turbulent electron thermal transport in fusion plasmas  

NASA Astrophysics Data System (ADS)

Electron heat transport at the scale of electron gyroradius are investigated via numerical simulation of a fluid model and a role of E x B shear flow with intermediate E x B shearing rate is explored in Euler's equation. The anomalous transport, enhanced transport due to turbulent electromagnetic fields caused by plasma instabilities, has been a focus of the international fusion research communities. Among the instabilities, the drift-type instabilities from the pressure-gradient universal in magnetic fusion devices are considered responsible for the anomalous transport. In the current status of wide use of wave heating on electrons and subsequent high core electron temperature, the turbulent heat loss through electrons has one of the most important science element in preventing the large fusion tokamaks from reaching breakeven in the past decade. The Electron Temperature Gradient fluid model consists of electrostatic potential, toroidal magnetic flux function and electron temperature (or pressure) describing electron drift waves. The fluid model proves to be highly useful to electron heat flux analysis in fusion machines. We analyze the discharges in National Spherical Tokamak eXperiment(NSTX) and Tokamak Configuration Variable (TCV) and found that the electron thermal diffusivities can be explained in terms of the mixing length argument based on electron gyroradius, linear theory and our nonlinear fluid simulation. The nonlinear fluid model predicts reasonable heat flux observed in the experiments. Based on the analysis, we investigate the dependences of the dynamics on the ratio of electron and ion temperature Te/Ti and plasma beta betae . The nonlinear dynamics such as saturation mechanism of the ETG turbulence and the electromagnetic dynamics in terms of micro-tearing at the scale of electron gyroradius are discussed briefly. In most of plasma confinement devices, the equilibrium radial electric field exists and the turbulence-generated electric field is observed. The coherent structure, called as zonal flow, has been know to be effective to suppress the micro-turbulence. But at intermediate E x B shear, where the vortex eddy turn-over time is comparable to E x B shearing rate, the suppression is weak and the flow shear can leads to vortex amplification through interaction of nonlinear dynamics and shear flow.

Kim, Juhyung

204

Particle Acceleration and Magnetic Dissipation in Relativistic Current Sheet of Pair Plasmas  

E-print Network

We study linear and nonlinear development of relativistic and ultrarelativistic current sheets of pair plasmas with antiparallel magnetic fields. Two types of two-dimensional problems are investigated by particle-in-cell simulations. First, we present the development of relativistic magnetic reconnection, whose outflow speed is an order of the light speed c. It is demonstrated that particles are strongly accelerated in and around the reconnection region, and that most of magnetic energy is converted into "nonthermal" part of plasma kinetic energy. Second, we present another two-dimensional problem of a current sheet in a cross-field plane. In this case, the relativistic drift kink instability (RDKI) occurs. Particle acceleration also takes place, but the RDKI fast dissipates the magnetic energy into plasma heat. We discuss the mechanism of particle acceleration and the theory of the RDKI in detail. It is important that properties of these two processes are similar in the relativistic regime of T > mc^2, as long as we consider the kinetics. Comparison of the two processes indicates that magnetic dissipation by the RDKI is more favorable process in the relativistic current sheet. Therefore the striped pulsar wind scenario should be reconsidered by the RDKI.

S. Zenitani; M. Hoshino

2007-10-11

205

Hinode/XRT Measurements of Turbulent Velocities in Flare Plasma Sheets  

NASA Astrophysics Data System (ADS)

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.

McKenzie, David; Freed, Michael

2015-04-01

206

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

207

Density effect on relativistic electron beams in a plasma fiber  

SciTech Connect

Intense short-petawatt-laser driven relativistic electron beams in a hollow high-Z plasma fiber embedded in low-Z plasmas of different densities are studied. When the plasma is of lower density than the hollow fiber, resistive filamentation of the electron beam is observed. It is found that the electron motion and the magnetic field are highly correlated with tens of terahertz oscillation frequency. Depending on the material property around the hollow fiber and the plasma density, the beam electrons can be focused or defocused as it propagates in the plasma. Relativistic electron transport and target heating are also investigated.

Zhou, C. T.; He, X. T. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Wang, X. G. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Cai, H. B. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Wang, F. [Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)

2010-11-15

208

High conductivity magnetic tearing instability. [of neutral plasma sheets  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

209

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

SciTech Connect

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.

Liu, Jianlong; Li, Nannan; Guo, Jing; Fang, Yong; Deng, Jiang [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zeng, Baoqing, E-mail: bqzeng@uestc.edu.cn [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices Zhongshan Lab, Department of Electronic Engineering, University of Electronic Science and Technology of China Zhongshan Institute, Zhongshan 528402 (China); Wang, Wenzhong; Li, Jiangnan; Hao, Chenchun [School of Science, Minzu University of China, Beijing 100081 (China)

2014-01-13

210

Residual stresses in polycrystalline silicon sheet and their relation to electron-hole lifetime  

Microsoft Academic Search

This letter summarizes research on the characterization of residual stresses and electron-hole lifetimes of polycrystalline silicon sheet for photovoltaic applications. Full-field polariscopy, scanning room temperature photoluminescence, and surface photovoltage are used to characterize the polycrystalline silicon sheet. An orientation dependent stress-optic coefficient has been developed and used to extract the in-plane residual stresses from analysis of transmitted near-infrared light. The

S. He; S. Danyluk; I. Tarasov; S. Ostapenko

2006-01-01

211

Effect of Electron Beam Irradiation, EPDM and Azodicarbonamide on the Foam Properties of LDPE Sheet  

Microsoft Academic Search

The effect of electron beam irradiation, EPDM blending, and Azodicarbonamide (ACA) concentration on the foaming properties of LDPE sheet was investigated. The studied properties are foaming degree, cell densities, mechanical properties and thermal decomposition properties. The data showed that the increasing of foaming agent (ACA) concentration reduces the mechanical properties and increases the gel content. Also, electron beam irradiation has

Magdy M. Senna; Hussein A. Youssef; Hannan M. Eyssa

2007-01-01

212

High average power CW FELS (Free Electron Laser) for application to plasma heating: Designs and experiments  

NASA Astrophysics Data System (ADS)

A short period wiggler (period approximately 1 cm), sheet beam free electron laser (FEL) has been proposed as a low-cost source of high average power (1 MW) millimeter-wave radiation for plasma heating and space-based radar applications. Recent calculation and experiments have confirmed the feasibility of this concept in such critical areas as RF wall heating, intercepted beam current, and high voltage (0.5 to 1 MV) sheet beam generation and propagation. Results of preliminary low-gain sheet beam FEL oscillator experiments using a field emission diode and pulse line accelerator have verified that lasing occurs at the predicted FEL frequency. Measured start oscillation currents also appear consistent with theoretical estimates. Finally, we consider the possibilities of using a short-period, superconducting planar wiggler for improved beam confinement, as well as access to the high gain, strong pump Compton regime with its potential for highly efficient FEL operation.

Booske, J. H.; Granatstein, V. L.; Radack, D. J.; Antonsen, T. M., Jr.; Bidwell, S.; Carmel, Y.; Destler, W. W.; Latham, P. E.; Levush, B.; Mayergoyz, I. D.

213

Ion mixing in the plasma sheet boundary layer by drift instabilities  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

214

Production of large-area plasmas by electron beams  

Microsoft Academic Search

An analysis is presented for the production of weakly ionized plasmas by electron beams, with an emphasis on the production of broad, planar plasmas capable of reflecting X-band microwaves. Considered first in the analysis is the ability of weakly ionized plasmas to absorb, emit and reflect electromagnetic radiation. Following that is a determination of the electron beam parameters needed to

R. F. Fernsler; W. M. Manheimer; R. A. Meger; J. Mathew; D. P. Murphy; R. E. Pechacek; J. A. Gregor

1998-01-01

215

New aspects of plasma sheet dynamics MHD and kinetic theory Institut fu r Astronomie und Astrophysik, Ludwig-Maximilians-Universita t Mu nchen, Scheinerstr. 1, D-81679 Munich, Germany  

E-print Network

New aspects of plasma sheet dynamics ± MHD and kinetic theory H. Wiechen Institut fu� r Astronomie reconnection is a process of funda- mental importance for the dynamics of the Earth's plasma sheet. In this context, the development of thin current sheets in the near-Earth plasma sheet is a topic of special

Boyer, Edmond

216

Status of Plasma Electron Hose Instability Studies in FACET  

SciTech Connect

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.

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

2011-12-13

217

Plasma treatment for producing electron emitters  

DOEpatents

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.

Coates, Don Mayo (Santa Fe, NM); Walter, Kevin Carl (Los Alamos, NM)

2001-01-01

218

Electron Capture in a Fully Ionized Plasma  

E-print Network

Properties of fully ionized water plasmas are discussed including plasma charge density oscillations and the screening of the Coulomb law especially in the dilute classical Debye regime. A kinetic model with two charged particle scattering events determines the transition rate per unit time for electron capture by a nucleus with the resulting nuclear transmutations. Two corrections to the recent Maiani et al. calculations are made: (i) The Debye screening length is only employed within its proper domain of validity. (ii) The WKB approximation employed by Maiani in the long De Broglie wave length limit is evidently invalid. We replace this incorrect approximation with mathematically rigorous Calogero inequalities in order to discuss the scattering wave functions. Having made these corrections, we find a verification for our previous results based on condensed matter electro-weak quantum field theory for nuclear transmutations in chemical batteries.

A. Widom; J. Swain; Y. N. Srivastava

2014-09-17

219

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

220

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

SciTech Connect

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.

Mbuli, L. N. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200, Republic of South Africa (South Africa); University of the Western Cape, Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa); Maharaj, S. K. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200, Republic of South Africa (South Africa); Bharuthram, R. [University of the Western Cape, Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa)

2014-05-15

221

The model of plasma-electronic technology of producing electricity from electron beams  

NASA Astrophysics Data System (ADS)

The article obtains the main results of the research on plasma- electronic technology for producing electricity from electronic beams, based on the electrical properties of electrons and their combination in the form of electron beams. The functional diagram of the experimental setup implementing plasma-electronic technology that proves the possibility of electricity generation by electrical installations, based on plasma-electronic technology is described.

Ryzhov, D. R.; Kazmin, B. N.; Trifanov, I. V.

2015-01-01

222

Electron distribution of the degenerate electron gas of a plasma in a strong electromagnetic field  

NASA Astrophysics Data System (ADS)

The paper determines the electron energy distribution function for the degenerate electron gas of a dense plasma in an intense electromagnetic field. The analysis is applicable to conditions in solid state plasmas.

Ablekov, V. K.; Babaev, Iu. N.; Frolov, A. M.

1980-01-01

223

Flute-interchange stability in a hot electron plasma  

SciTech Connect

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.

Dominguez, R.R.

1980-01-01

224

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

PubMed

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

Yao, Yao; Glisic, Branko

2015-01-01

225

Electron Recombination in a Dense Hydrogen Plasma  

SciTech Connect

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.

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

2012-05-01

226

[Electron cyclotron resonance (ECR) plasma film deposition  

SciTech Connect

During the third quarter of 1995, an electron cyclotron resonance (ECR) plasma film deposition facility was constructed at the University of New Mexico. This work was conducted in support of the Los Alamos/Tycom CRADA agreement to pursue methods of improving drill bit lifetime. Work in the fourth quarter will center on the coating of drill bits and the treating and testing of various test samples. New material systems as well as treatment techniques will be attempted during this period. The following is a brief description of the various subsystems of the film deposition facility. Particular emphasis is placed on the slotted waveguide system as requested.

NONE

1999-04-01

227

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

E-print Network

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. Efficient 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 short waves 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 i...

Sydorenko, D; Chen, L; Ventzek, P L G

2015-01-01

228

Survey of 0.1- to 16-keV/e plasma sheet ion composition  

NASA Technical Reports Server (NTRS)

An analysis is performed of all plasma sheet data collected in 1978-79 in order to discern statistical trends in the data. Attention is focused on the bulk parameters of 0.1-16 keV/e plasma sheet ions detected by the Plasma Composition Experiment on the ISEE 1 satellite. The data were collected at 10-23 earth radii, and are averaged for various levels of activity in the AE index. Solar H(+) and He(2+) ions dominate during quiet periods and possess energies similar to those of the solar wind when the quiet period lasts several hours. Increasing AE index values eventually lead to a replacement of the solar ions with terrestrial ions, particularly O(+), which can have an average energy density of 3-4 keV/e at every activity level. The solar ions, however, increase in energy as their density decreases. The O(+) density is highest near the local midnight and becomes the most numerous during highly disturbed conditions. Finally, the O(+) density was observed to increase by a factor of three over the monitoring period, possibly due to enhanced solar EUV radiation.

Lennartsson, W.; Shelley, E. G.

1986-01-01

229

Plasma Sheet Fast Flows and Auroral Dynamics During Substorm: A Case Study  

NASA Astrophysics Data System (ADS)

INTERBALL-1 observations of a substorm development in the mid-tail are compared to the auroral dynamics obtained from the POLAR UV imager. Using these data the relationship between the plasma flow directions in the tail and the location of the au- roral activation is examined. It is unambiguously shown that in the mid plasma sheet, the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved pole- ward of the INTERBALL- 1 projection, earthward fast flow bursts were observed. This confirms the concept that the Near Earth Neutral Line (or flow reversal region) is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBF). These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail- ward of INTERBALL-1. In addition, some non-typically phenomena observed in the plasma sheet during this substorm are discussed.

Borodkova, N. L.; Yahnin, A. G.; Liou, K.; Sauvaud, J.-A.; Fedorov, A. O.; Lutsenko, V. N.; Nozdrachev, M. N.

230

Nonlocal electron kinetics in collisional gas discharge plasmas  

Microsoft Academic Search

Nonlocal phenomena in electron kinetics of collisional gas discharge plasmas, their kinetic treatment by a nonlocal approach, and relevant experimental results are reviewed in this paper. Using the traditional two-term approximation for the electron distribution function, a general method to analyze electron kinetics in nonuniform plasmas in DC and RF fields for atomic gases is presented for the nonlocal case,

Vladimir I. Kolobov; Valery A. Godyak

1995-01-01

231

Thermal Field Theory in a layer: Applications of Thermal Field Theory methods to the propagation of photons in a two-dimensional electron sheet  

E-print Network

We apply the Thermal Field Theory methods to study the propagation of photons in a plasma layer, that is a plasma in which the electrons are confined to a two-dimensional plane sheet. We calculate the photon self-energy and determine the appropriate expression for the photon propagator in such a medium, from which the properties of the propagating modes are obtained. The formulas for the photon dispersion relations and polarization vectors are derived explicitly in some detail for some simple cases of the thermal distributions of the charged particle gas, and appropriate formulas that are applicable in more general situations are also given.

Jos'e F. Nieves

2012-01-09

232

Thermal field theory in a layer: Applications of thermal field theory methods to the propagation of photons in a two-dimensional electron sheet  

SciTech Connect

We apply the thermal field theory methods to study the propagation of photons in a plasma layer, that is a plasma in which the electrons are confined to a two-dimensional plane sheet. We calculate the photon self-energy and determine the appropriate expression for the photon propagator in such a medium, from which the properties of the propagating modes are obtained. The formulas for the photon dispersion relations and polarization vectors are derived explicitly in some detail for some simple cases of the thermal distributions of the charged particle gas, and appropriate formulas that are applicable in more general situations are also given.

Nieves, Jose F. [Laboratory of Theoretical Physics, Department of Physics, P.O. Box 23343, University of Puerto Rico, Rio Piedras, 00931-3343 (Puerto Rico)

2010-04-01

233

Modeling of ionization composition in argon plasma with fast electrons  

Microsoft Academic Search

Discharge and laser produced plasmas often have non-equilibrium electron distributions containing fast electrons that may\\u000a have a profound effect on the ionization balance. The influence of high energy electrons on the ionization balance in the\\u000a collisional-radiative equilibrium model for optically thin plasma is considered forthwith. A nonmaxwellian electron distribution\\u000a with fast electrons at energies and concentrations is used for calculating

V. S. Zakharov; V. G. Novikov

2009-01-01

234

Multiple-satellite studies of magnetospheric substorms - Plasma sheet recovery and the poleward leap of auroral zone activity  

NASA Technical Reports Server (NTRS)

Particle observations from pairs of satellites (OGO 5 and Vela 4A and 5A) during 28 plasma sheet thickening events indicate that thickening of the nighttime plasma sheet during substorms occurs in two main stages. The early stage involves single or multiple expansions of the near-earth plasma sheet at the onset of substorm expansions (Pi 2 bursts) on the ground, while the later stage of plasma sheet recovery starts near the time of maximum auroral zone bay activity. This stage is characterized by a large-scale thickening toward higher latitudes that occurs over a broad azimuthal scale and at heights that range from the ionosphere to beyond the Vela orbit. A detailed analysis of two-satellite observations during eight plasma sheet recoveries is presented, and events that occurred within 5 min in widely separated locations at small distances from the tail's midplane as well as events that occurred concurrently in the Vela orbit and at high latitudes in the near-earth region are revealed.

Pytte, T.; Mcpherron, R. L.; Kivelson, M. G.; West, H. I., Jr.; Hones, E. W., Jr.

1978-01-01

235

Nonlinear drift waves in electron-positron-ion plasmas  

NASA Astrophysics Data System (ADS)

It is suggested that low-frequency drift waves can play an important role in the dynamics of electron-positron plasmas comprising some concentration of ions. In the electromagnetic case the drift wave couples with the shear Alfvén wave in an electron-positron-ion plasma. The drift wave frequency can be very low in such plasmas depending on the concentration and density scale lengths of the plasma components. In the nonlinear regime these waves can give rise to dipolar vortices in both electrostatic and electromagnetic limits. The velocity of the nonlinear structure turns out to be different compared to the case of an electron-ion plasma.

Saleem, H.; Haque, Q.; Vranjes, J.

2003-05-01

236

Electron plasma dynamics during autoresonant excitation of the diocotron mode  

NASA Astrophysics Data System (ADS)

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 108 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.

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

2015-02-01

237

Small Scale Plasmoids in the Post-Plasmoid Plasma Sheet: Origin of MHD Turbulence?  

NASA Astrophysics Data System (ADS)

A variety of MHD turbulence can be observed in the Earth's magnetotail, but the origin of the turbulence is still a long-standing problem. We study the small-scale fluctuations excited in coll-sionless magnetic reconnection by using a two-dimensional, particle-in-cell numerical simulation, and propose that the magnetic diffusion region of reconnection may be one of the possible regions to excite a strong MHD turbulence. The magnetic field turbulence observed in the post-plasmoid plasma sheet is compared with the fluctuations obtained in the computer simulation.

Hoshino, M.

238

Evolution of the heliospheric plasma sheet observed in situ by 3 spacecraft over 4 solar rotations  

NASA Astrophysics Data System (ADS)

We present in situ observations of the heliospheric plasma sheet (HPS) from 3 observatories (STEREO-A, STEREO-B, and WIND) over 4 solar rotations: Carrington rotations (CR) 2054 through 2057. At least one interplanetary coronal mass ejection (ICME) occurred during CR 2056, which leads to reorganization of the HPS from its previous quasi-stationary structure. The HPS crossings were identified using criteria including reversal of the interplanetary magnetic field, increased proton density, and local minima in proton entropy and in the alpha to proton density ratio. We also find an enhancement of the average iron charge state at the HPS.

Simunac, K.; Galvin, A. B.; Kistler, L. M.; Kucharek, H.; Lazarus, A. J.; Liu, Y.; Luhmann, J. G.; Ogilvie, K. W.; Opitz, A.; Popecki, M.; Wang, S.

2010-12-01

239

Effects of emitted electron temperature on the plasma sheath  

SciTech Connect

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.

Sheehan, J. P., E-mail: sheehanj@umich.edu [Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Kaganovich, I. D.; Wang, H.; Raitses, Y. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Sydorenko, D. [Physics Department, University of Alberta, Edmonton, Alberta T6G 2E9 (Canada); Hershkowitz, N. [Department of Engineering Physics, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)

2014-06-15

240

PHYSICAL REVIEW B 87, 035404 (2013) Electronic structure of boron nitride sheets doped with carbon from first-principles calculations  

E-print Network

PHYSICAL REVIEW B 87, 035404 (2013) Electronic structure of boron nitride sheets doped with carbon quasiparticle (GW) approach, we study the electronic structure of hexagonal boron nitride (h-BN) sheets, both and doped h-BN and should further help to optimize the postsynthesis doping of boron nitride nanostructures

Krasheninnikov, Arkady V.

241

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

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

242

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

243

Field Theoretic Description of Ultrarelativistic Electron-Positron Plasmas  

E-print Network

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.

Markus H. Thoma

2009-07-06

244

Topological Features of a Compressible Plasma Vortex Sheet - a Model of the Outer Heliospheric Wind  

NSDL National Science Digital Library

The Voyager and Pioneer Spacecraft have detected large-scale quasi-periodic plasma fluctuations in the outer heliosphere beyond 20 AU. A plasma vortex sheet model can explain these fluctuations and the observed correlations between various physical variables. The large scale outer heliosphere is modeled by solving the 3-D compressible magnetohydrodynamic equations involving three interacting shear layers. Computations were done on a Cray computer at the NASA Center for Computational Sciences. Six cases are animated: Weak magnetic field and strong magnetic field, each at three values of tau, the vortex street characteristic time. Contours of density are shown as dark transparent tubes. Critical points of the velocity field are represented by Glyphs. Vortex cores are shown in orange and blue.

Cindy Starr

1993-12-17

245

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

NASA Technical Reports Server (NTRS)

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)

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

1980-01-01

246

Forced magnetic reconnection in a plasma sheet with localized resistivity profile excited by lower hybrid drift type instability  

NASA Technical Reports Server (NTRS)

A forced magnetic reconnection process with a temporal evolution of resistivity is studied for a plasma sheet with a nonuniform resistivity profile based on the nonlocal mode structure of the lower hybrid drift type instability. The growth rate of the mode found is almost independent of the resistivity at the neutral sheet, but depends on the resistivity of the region of maximum density gradient away from the neutral sheet. This is studied by using both a nonlinear numerical MHD simulation and a linear theory. The mode may be relevant to the prevalent theoretical concept of MHD reconnection and the localized anomalous resistivity profile based on the lower hybrid drift instability.

Hoshino, M.

1991-01-01

247

Cluster view of the plasma sheet boundary layer and bursty bulk flow connection  

NASA Astrophysics Data System (ADS)

The high-latitude boundaries of the plasma sheet (PSBL) are dynamic latitude zones of recurring and transient (minutes to tens of minutes) earthward and magnetic field-aligned bursts of plasma, each being more or less confined in longitude as well, whose ionic component is dominated by protons with flux, energies and density that are consistent with a central plasma sheet (CPS) source at varying distance (varying rates of energy time dispersion), sometimes as close as the ~19 RE Cluster apogees, or closer still. The arguably most plausible source consists of so called "bursty bulk flows" (BBFs), i.e. proton bulk flow events with large, positive and bursty GSE vx. Known mainly from CPS observations made at GSE x>-30 RE, the BBF type events probably take place much further downtail as well. What makes the BBFs an especially plausible source are (1) their earthward bulk flow, which helps explain the lack of distinctive latitudinal PSBL energy dispersion, and (2) their association with a transient strong increase of the local tail Bz component ("local dipolarization"). The enhanced Bz provides intermittent access to higher latitudes for the CPS plasma, resulting in local density reductions in the tail midplane, as illustrated here by proton data from the Cluster CIS CODIF instruments. Another sign of kinship between the PSBL bursts and the BBFs is their similar spatial fine structure. The PSBL bursts have prominent filaments aligned along the magnetic field with transverse flux gradients that are often characterized by local ~10 keV proton gyroradii scale size (or even smaller), as evidenced by Cluster measurements. The same kind of fine structure is also found during Cluster near-apogee traversals of the tail midplane, as illustrated here and implied by recently published statistics on BBFs obtained with Cluster multipoint observations at varying satellite separations. Altogether, the Cluster observations described here mesh rather well with theories about so called plasma sheet "bubbles," i.e. earthward drifting closed magnetic flux tubes with reduced particle pressure and enhanced magnetic field strength at their apex. It is argued that such bubbles may be initiated by localized diamagnetic instabilities.

Lennartsson, O. W.; Kistler, L. M.; Rème, H.

2009-04-01

248

Use of a Plasma Cathode Electron (PCE) source in an Electron Beam Integrated Thruster (EBIT)  

Microsoft Academic Search

The electron Beam Integrated Thruster (EBIT) plasma propulsion concept centers around the use of an electron beam to ionize a propellant; a more efficient ionization mechanism than conventional electric propulsion concepts. In this paper we outline the EBIT concept, in particular, the generation of the electron beam in a Plasma Cathode Electron (PCE) source. The PCE beam source utilizes a

Max Light; Tsitsi Madziwa-Nussinov; Pat Colestock; Ron Kashuba; Rick Faehl

2006-01-01

249

Beam-plasma instabilities and nonlinear electron waves in a helical-beam, magnetic mirror plasma  

Microsoft Academic Search

The possibility of using the plasma produced by a helical electron beam in a magnetic mirror geometry to study large amplitude electron plasma waves was investigated in the Allis mode. Results indicate that the helical-beam system is not suitable for nonlinear electron wave studies. Suggestions are made for certain modification on the apparatus so that it could be used to

E. P. Scannell

1976-01-01

250

Theoretical study of the adsorption of CHO radicals on hexagonal boron nitride sheet: Structural and electronic changes  

NASA Astrophysics Data System (ADS)

It is well known that pristine hexagonal boron nitride sheet (h-BN sheet) exhibits large insulating band gap, thus hindering its application to some extent. In this regard, surface chemisorption of certain groups on h-BN sheet is shown to be the most popular method to tune its band gap and thus modify its electronic properties. In the present work, we performed density functional theory (DFT) calculations to study the adsorption of CHO radicals with different coverages on h-BN sheet. Particular attention is paid to explore the effects of CHO adsorption on the geometrical structures and electronic properties of h-BN sheet. The results indicate that the adsorption of a single CHO radical on pristine h-BN sheet is very weak with a negligible adsorption energy (-0.09 eV). In contrast, upon adsorption of more CHO radicals on h-BN sheet, these adsorbates prefer to adsorb in pairs on the B and the nearest N atoms from both sides of h-BN sheet. An energy diagram of the average adsorption energy of CHO radicals on h-BN sheet as a function of its coverage indicates that up to 20 CHO radicals (40%) can be attached to h-BN sheet with the adsorption energy of -0.29 eV. More importantly, the adsorption of CHO radicals can induce certain impurity states within the band gap of h-BN sheet, thus reducing the band gap and enhancing its electrical conductivity.

Tian, Yu; Pan, Xiao-fan; Liu, Yue-jie; Zhao, Jing-xiang

2014-03-01

251

Cold-dense plasma sheet and hot-dense ions in the inner-magnetosphere  

NASA Astrophysics Data System (ADS)

Cold-dense plasma sheet (CDPS) is known to appear during extended northward IMF periods. Its appearance suggests enhanced entry of the solar wind into the magnetosphere during the times when it is supposed to be most closed, in a manner totally different from active times, and that on to closed field lines. To understand the CDPS formation mechanism, which still remains open, anatomy of CDPS is performed in this study. By inspecting the ion spectrum characteristics CDPS is classified into three categories. Dawn-dusk asymmetry is revealed as the spatial distributions of the three categories are plotted separately, which indicates that different heating/transport processes are operative on different sides of the magnetotail. On dawnside a group of data characterized by the highest temperature from one of the CDPS categories is distributed at the plasma sheet inner-edge and is connected to the hot-dense ions (HDIs) at the further inner region. An independent analysis indicates that HDIs not associated with elevated solar wind dynamic pressure appear in the dawnside inner-magnetosphere during extended northward IMF. Both studies points to the idea that HDIs are the inner-magnetosphere extension of dawnside CDPS and that there is significant dawn-dusk asymmetry in heating and transport in the magnetotail under northward IMF.

Fujimoto, M.; Mukai, T.; Kokubun, S.

252

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

NASA Technical Reports Server (NTRS)

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.

Klimas, Alex; Uritsky, Vadim; Donovan, Eric

2010-01-01

253

Vortices, Reconnection and Turbulence in High Electron-Beta Plasmas  

SciTech Connect

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.

Stenzel, R. L.

2004-08-31

254

Heating of the relativistic electron plasma in a levitated spherator  

Microsoft Academic Search

Noncyclotron resonant microwave heating preferentially heats relativistic electrons in a plasma. In the FM-1 device, a levitated spherator, plasma may be produced by cyclotron resonant microwave heating at a base pressure of 3 × 10?8 Torr in helium. Under these conditions, plasma lifetimes are of the order of 100 sec. Nonresonant microwave heating at power levels of up to 1.5

J. L. Shohet; K. Chen; M. Okabayashi

1973-01-01

255

A plasma mirror for electronic microwave beam steering  

Microsoft Academic Search

Summary form only given. A planar plasma may be used as a reflector for microwaves if the plasma frequency (at the angle of incidence) is greater than the microwave frequency. If this plasma mirror can be repositioned electronically, it could have the capability of redirecting microwave beams on a very fast time scale, and as such it could have important

R. Meger; J. Mathew; W. Manheimer; R. Fernsler; J. Gregor; D. Murphy; M. Myers; R. Pechacek

1997-01-01

256

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

NASA Technical Reports Server (NTRS)

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.

Deforest, S. E.

1973-01-01

257

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

SciTech Connect

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.

Hong, Woo-Pyo [Department of Electronics Engineering, Catholic University of Daegu, Hayang 712-702 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2012-02-13

258

Generation And Applications Of Electron-Beam Plasma Flows  

NASA Astrophysics Data System (ADS)

Plasma flows generated by continuous or interrupted injection of an electron beam into subsonic or supersonic gaseous streams are considered. Liquid and powder spraying by the electron-beam plasma (EBP) flows is studied as a technique of the aerosol plasma generation. A number of experimental setups generating both free plasma jets and plasma flows in channels are described. Examples of the EBP flows applications for industrial and aerospace technologies are given. The applications are shown to be based on unique properties of the EBP and its stability within very wide ranges of the plasma generation conditions. Some applications of the Hybrid Plasma (HP) generated by combined action of the electron beam (EB) and intermittent gas discharge on flows of gaseous mixtures and aerosols are presented as well.

Vasiliev, M. N.; Tun Win, Aung

2015-03-01

259

Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

260

Microstability of Magnetically Confined Electron-Positron Plasmas  

NASA Astrophysics Data System (ADS)

It is shown that magnetically confined electron-positron plasmas can enjoy remarkable stability properties. Many of the microinstabilities driving turbulence and transport in electron-ion plasmas are absent if the density is so low that the Debye length is significantly larger than the gyroradius. In some magnetic configurations, almost complete linear stability may be attainable in large parts of the parameter space.

Helander, P.

2014-09-01

261

Interaction of a rotating relativistic electron beam with plasma  

Microsoft Academic Search

Results of an experimental study of the interaction of a rotating relativistic electron beam with plasma confined in a mirror field are presented. The rotating relativistic electron beam has been propagated up to a distance of 150 cm in a metal tube containing plasma. Net axial and azimuthal currents are observed. The azimuthal currents last for periods much longer than

K. K. Jain; P. I. John

1984-01-01

262

Microwave heating and cyclotron instability of hot electron plasmas  

Microsoft Academic Search

A relativistic theory of electron heating to high energies by narrow-band microwaves directed into a spatially limited region of plasma is formulated. A novel feature of the analysis is its prediction regarding the motion of electrons along field lines. Specifically, the phase space of trapped electrons is found to be divided into two parts. In one, as an electron gains

B. Hafizi; R. E. Aamodt

1986-01-01

263

A plasma flow velocity boundary at Mars from the disappearance of electron plasma oscillations  

E-print Network

echo due to vertical reflection from the horizontally stratified ionosphere is measured (Gurnett et al sounding mode, the sounder transmitter excites electrostatic electron plasma oscillations at the local

Gurnett, Donald A.

264

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

PubMed

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

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

2014-09-01

265

Electron energy distribution function control in gas discharge plasmas  

SciTech Connect

The formation of the electron energy distribution function (EEDF) and electron temperature in low temperature gas discharge plasmas is analyzed in frames of local and non-local electron kinetics. It is shown, that contrary to the local case, typical for plasma in uniform electric field, there is the possibility for EEDF modification, at the condition of non-local electron kinetics in strongly non-uniform electric fields. Such conditions “naturally” occur in some self-organized steady state dc and rf discharge plasmas, and they suggest the variety of artificial methods for EEDF modification. EEDF modification and electron temperature control in non-equilibrium conditions occurring naturally and those stimulated by different kinds of plasma disturbances are illustrated with numerous experiments. The necessary conditions for EEDF modification in gas discharge plasmas are formulated.

Godyak, V. A. [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)] [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)

2013-10-15

266

Plasma response to electron energy filter in large volume plasma device  

SciTech Connect

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.

Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K. [Institute for Plasma Research, Gandhinagar, 382 428 Gujarat (India)] [Institute for Plasma Research, Gandhinagar, 382 428 Gujarat (India)

2013-12-15

267

Experimental evidence of warm electron populations in magnetron sputtering plasmas  

NASA Astrophysics Data System (ADS)

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 2-3 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.

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

2015-01-01

268

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

269

Electron interactions with plasma processing gases – Progress of magnetized electron-impact total cross section measurement system(ELECS-1)  

Microsoft Academic Search

Electron-impact cross sections for molecular targets, including their radicals, are important in developing plasma reactors and testing various plasma processing gases. However, we suffer from lack of theoretical and experimental electron-impact cross section data for plasma processing gas, such as plasma etching and deposition processes. Thus, in this work, the total cross sections for electron scattering from plasma processing gases

Dae Chul Kim; Mi-Young Song; Yonghyun Kim; Young-Woo Kim; Young Rock Choi; Jung-Sik Yoon; Hyck Cho

270

Electron energy distribution function and plasma parameters across magnetic filters  

SciTech Connect

The electron energy distribution function (EEDF) is measured across a magnetic filter in inductively coupled plasmas. The measured EEDFs are found to be Maxwellian in the elastic energy range with the corresponding electron temperature monotonously decreasing along the positive gradient of the magnetic field. At the maximum of the magnetic field, the electron temperature reaches its minimum and remains nearly constant in the area of the negative gradient of the field, where the plasma density distribution exhibits a local minimum.

Aanesland, A.; Bredin, J.; Chabert, P. [Laboratoire de Physique des Plasmas, CNRS--Ecole Polytechnique, 91128 Palaiseau Cedex (France); Godyak, V. [RF Plasma Consulting, Brookline, Massachusetts 02446 (United States)

2012-01-23

271

Correction to ``Three-dimensional analyses of electric currents and pressure anisotropies in the plasma sheet'' by Richard L. Kaufmann,  

E-print Network

Correction to ``Three-dimensional analyses of electric currents and pressure anisotropies. Paterson, and L. A. Frank, Correction to ``Three-dimensional analyses of electric currents and pressure] In the paper ``Three-dimensional analyses of electric currents and pressure anisotropies in the plasma sheet

Kaufmann, Richard L.

272

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

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

273

Plasma density profiles and finite bandwidth effects on electron heating  

SciTech Connect

Intense, p-polarized microwaves are incident on an inhomogeneous plasma in a cylindrical waveguide. Microwaves are mainly absorbed by resonant absorption near the critical surface (where the plasma frequency, ..omega../sub pe/, equals the microwave frequency, ..omega../sub o/). The localized plasma waves strongly modify the plasma density. Step-plateau density profiles or a cavity are created depending on the plasma flow speed. Hot electron production is strongly affected by the microwave bandwidth. The hot electron temperature varies as T/sub H/ is proportional to (..delta.. ..omega../..omega..)/sup -0/ /sup 25/. As the hot electron temperature decreases with increasing driver bandwidth, the hot electron density increases. This increase is such that the heat flux into the overdense region (Q is proportional to eta/sub H/T/sub H//sup 3/ /sup 2/) is nearly constant.

Spielman, R.B.; Mizuno, K.; DeGroot, J.S.; Bollen, W.M.; Woo, W.

1980-01-01

274

Multifunctional bulk plasma source based on discharge with electron injection  

SciTech Connect

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.

Klimov, A. S.; Medovnik, A. V. [Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Tyunkov, A. V. [Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Institute of High Current Electronics, Tomsk 634055 (Russian Federation); Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V. [Institute of High Current Electronics, Tomsk 634055 (Russian Federation)

2013-01-15

275

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

NASA Astrophysics Data System (ADS)

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 = 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.

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

2012-09-01

276

Collisional Cooling of Pure Electron Plasmas W. Bertsche  

E-print Network

Collisional Cooling of Pure Electron Plasmas Using CO2 W. Bertsche and J. Fajans Physics Department, U. C. Berkeley Abstract. Inelastic collisions with CO2 buffer gas cool a pure electron gas in a Penning-Malmberg trap at low magnetic fields. 0.6 eV electrons are cooled by down to 30% of their original

Fajans, Joel

277

Towards a free electron laser based on laser plasma accelerators  

NASA Astrophysics Data System (ADS)

The recent advances in developing compact laser plasma accelerators that deliver high quality electron beams in a more reliable way offer the possibility to consider their use in designing a compact free electron laser (FEL). Because of the particularity of these beams (especially concerning the divergence and the energy spread), specific electron beam handling is proposed in order to achieve FEL amplification.

Couprie, M. E.; Loulergue, A.; Labat, M.; Lehe, R.; Malka, V.

2014-12-01

278

Plasma Chemistry and Plasma Processing, Vol. 22, No. 2, June 2002 ( 2002) Electron Density and Energy Distributions in  

E-print Network

Plasma Chemistry and Plasma Processing, Vol. 22, No. 2, June 2002 ( 2002) Electron Density in the corona plasma is required to quantify the chemical processes. In this paper, the electron density- ness of the plasma and the electron energy distribution are not affected. Smaller electrodes produce

Chen, Junhong

279

Solitary and shock waves in magnetized electron-positron plasma  

SciTech Connect

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.

Lu, Ding; Li, Zi-Liang; Abdukerim, Nuriman; Xie, Bai-Song, E-mail: bsxie@bnu.edu.cn [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, and College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China)] [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, and College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China)

2014-02-15

280

Solitary and shock waves in magnetized electron-positron plasma  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

281

Nonneutral Electron Plasmas Confined in a Compact Magnetic Mirror Trap  

NASA Astrophysics Data System (ADS)

With a new compact magnetic mirror trap, it was demonstrated that the confinement time of 2×107 electrons in a simple magnetic mirror can be longer than 40 ms and that electrostatic oscillations of the plasma can be detected with a multiring electrode configuration. Also, a solitary wave was excited and detected for a mirror-confined nonneutral electron plasma. Obtained results suggest that the new compact magnetic mirror trap will make it possible to investigate electron-positron plasmas experimentally, which have never been conducted so far.

Higaki, Hiroyuki; Sakurai, Shota; Ito, Kiyokazu; Okamoto, Hiromi

2012-10-01

282

Potential applications of an electron cyclotron resonance multicusp plasma source  

SciTech Connect

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.

Tsai, C.C.; Berry, L.A.; Gorbatkin, S.M.; Haselton, H.H.; Roberto, J.B.; Stirling, W.L.

1989-01-01

283

Plasma wave electronics: terahertz detectors and sources using two dimensional electronic fluid in high electron mobility transistors  

Microsoft Academic Search

We discuss applications of plasma waves in high electron mobility transistors for detectors and sources operating in millimeter and submillimeter range. A short channel high electron mobility transistor (HEMT) has a resonance response to electromagnetic radiation at the plasma oscillation frequencies of the two dimensional electrons in the device. The devices, which use this resonance response should operate at much

M. I. Dyakonov; M. S. Shur

1997-01-01

284

Langmuir probe interpretation for plasmas with secondary electrons from the wall  

Microsoft Academic Search

Summary form only given. In a low-pressure hot-filament discharge, the primary electrons induce the emission of secondary electrons from the walls of the plasma chamber. The generation rate of these secondary electrons typically exceeds the rate of ionization. The plasma thus has three electron components: fast electrons from the filament, secondary electrons from the walls, and plasma electrons confined in

S. Robertson; Zoltan Sternovsky

2004-01-01

285

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

286

Electron Acceleration in a Dynamically Evolved Current Sheet of Solar Coronal Conditions  

NASA Astrophysics Data System (ADS)

Electron acceleration in a drastically evolved current sheet of solar coronal conditions is investigated via the combined resistive Magnetohydrodynamics (MHD) and test particle approaches. With high magnetic Reynolds number, the long-thin current sheet is tearing into a chain of magnetic islands, which grow in size and coalesce together. The acceleration of electrons are explored in three typical evolvement phases: when several large magnetic islands are formed (phase1), two of them are approaching each other (phase2) and almost merging into a "monster" magnetic island (phase3). The results show that for all the three phases electrons with an initially Maxwellian 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. Most of the energetic electrons move around the magnetic islands in clockwise direction (anti-parallel to the magnetic field lines), drifting in the -Z direction. The energetic electrons with 10 keV < Ek < 200 keV are located outside the magnetic separatrices, where parallel electric field (Ep) is small. The electrons with 200 keV < Ek < 5000 keV are distributed inside the magnetic islands where Ep is moderate large but have complex structures. The electrons with Ek > 5000 keV are located around the outer regions of the magnetic islands or at the core regions of the magnetic islands. Some of the most energetic electrons even appear in the small secondary magnetic islands that are embedded in the diusion regions in between the magnetic islands. It is the trapping eect of the magnetic islands and the distributions of Ep that determine the acceleration processes and space distribution of the energetic electrons.

Shaohua, Z.; Du, A.; Feng, X.

2012-12-01

287

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 94, NO. A6, PAGES 6995-7001, JUNE 1, 1989 Electron Velocity Distributions and Plasma Waves Associated With  

E-print Network

and inclination 49.5ø on the space shuttle Challenger on July 29, 1985.During August 1the Plasma.In the wake of the space shuttle a magneticallyaligned sheet of electrons returning from the direction, andthe ambientionosphere. The PDP provided observationsout to a distanceof--·400 m from the space shuttle

Gurnett, Donald A.

288

Relativistic electromagnetic waves in an electron-ion plasma  

NASA Technical Reports Server (NTRS)

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.

Chian, Abraham C.-L.; Kennel, Charles F.

1987-01-01

289

Dynamical Casimir effect for TE and TM modes in a resonant cavity bisected by a plasma sheet  

E-print Network

Parametric photon creation via the dynamical Casimir effect (DCE) is evaluated numerically, in a three-dimensional rectangular resonant cavity bisected by a semiconductor diaphragm (SD), which is irradiated by a pulsed laser with frequency of GHz order. The aim of this paper is to determine some of the optimum conditions required to detect DCE photons relevant to a novel experimental detection system. We expand upon the thin plasma sheet model [Crocce et al., Phys. Rev. A 70 033811 (2004)] to estimate the number of photons for both TE and TM modes at any given SD position. Numerical calculations are performed considering up to 51 inter-mode couplings by varying the SD location, driving period and laser power without any perturbations. It is found that the number of photons created for TE modes strongly depends on SD position, where the strongest enhancement occurs at the midpoint (not near the cavity wall); while TM modes have weak dependence on SD position. Another important finding is the fact that significant photon production for TM$_{111}$ modes still takes place at the midpoint even for a low laser power of 0.01 micro J/pulse, although the number of TE$_{111}$ photons decreases almost proportionately with laser power. We also find a relatively wide tuning range for both TE and TM modes that is correlated with the frequency variation of the instantaneous mode functions caused by the interaction between the cavity photons and conduction electrons in the SD excited by a pulsed laser.

Wade Naylor; S. Matsuki; Tomoaki Nishimura; Yoshiaki Kido

2010-01-18

290

Self-consistent theory of the multiscale and split current sheets in collisionless non-Maxwellian plasma  

NASA Astrophysics Data System (ADS)

In view of a large number of the observational and theoretical indications of the complicated non-Maxwellian plasma configurations in the magnetospheres of planets and stars, we develop an analytical approach to the description of the stationary planar neutral current sheets in a collisionless multicomponent plasma, relativistic or not. It is based on the method of the invariants of particle motion and admits a functional freedom in the choice of the particle distribution functions and spatial profiles of current density and corresponding magnetic field. Using a general theory (Phys. Rev. Lett. 104, 215002 (2010)) and a variety of novel examples, we show that splitting of the current sheets is typical for the non-Maxwellian distributions of particles and the multiscale current sheets might exist in plasma with essentially different anisotropies of the particle species. The examples of splitting include the self-consistent sheets with two or three separate components of current density with either parallel or antiparallel directions of the current which may be formed by one or several particle species. The examples of the multiscale sheets include two or three current components, embedded in one another and formed by one, two or three particle species. We describe general properties of the split and multiscale sheets for a wide class of the particle distribution functions with the polynomial and/or exponential dependences on a momentum directed along the current. We investigate in detail possible interrelation of the spatial scales and magnitudes of the magnetic field, anisotropy, and density of particles of different species. In particular, we apply these results to the description of the current structures in the Earth’s magnetotail using observational data from the Cluster spacecraft mission. We compare our analytical results with the known numerical analysis and qualitative estimates of multiscale properties and splitting effects in the magnetospheric current structures.

Kocharovsky, Vladimir; Martyanov, Vladimir; Kocharovsky, Vitaly

291

Quantum tunneling resonant electron transfer process in Lorentzian plasmas  

SciTech Connect

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.

Hong, Woo-Pyo [Department of Electronics Engineering, Catholic University of Daegu, Hayang 712-702 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States); Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2014-08-15

292

Electron density measurements in the ITER fusion plasma  

NASA Astrophysics Data System (ADS)

The operation of ITER requires high-quality estimates of the plasma electron density over multiple regions in the plasma for plasma evaluation, plasma control and machine protection purposes. Although the density regimes of ITER are not very different from those of existing tokamaks (1018-1021 m-3), the severe conditions of the fusion plasma environment present particular challenges to implementing these density diagnostics. In this paper we present an overview of the array of ITER electron density diagnostics designed to measure over the entire ITER domain: plasma core, pedestal, edge, scrape-off layer and divertor. It will focus on the challenges faced in making these measurements, and the technical solutions of the current designs.

Watts, Christopher; Udintsev, Victor; Andrew, Philip; Vayakis, George; Van Zeeland, Michael; Brower, David; Feder, Russell; Mukhin, Eugene; Tolstyakov, Sergey

2013-08-01

293

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

SciTech Connect

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.

Bai, Lili; Liu, Jinyin; Zhao, Guanqi; Gao, Jing; Sun, Xuhui, E-mail: xhsun@suda.edu.cn, E-mail: jzhong@suda.edu.cn; Zhong, Jun, E-mail: xhsun@suda.edu.cn, E-mail: jzhong@suda.edu.cn [Soochow University-Western University Centre for Synchrotron Radiation Research, Institute of Functional Nano and Soft Materials Laboratory (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123 (China)] [Soochow University-Western University Centre for Synchrotron Radiation Research, Institute of Functional Nano and Soft Materials Laboratory (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123 (China)

2013-12-16

294

Effect of plasma-? on the onset of plasmoid instability in Sweet-Parker current sheets  

NASA Astrophysics Data System (ADS)

A numerical study of magnetic reconnection in two-dimensional resistive magnetohydrodynamics for Sweet-Parker current sheets that are subject to plasmoid instability is carried out. The effect of the initial upstream plasma-? on the critical Lundquist number Sc for the onset of plasmoid instability is studied. Our results indicate a weak dependence, with a value of Sc ~= 1.5 × 104 in the limit of zero ?, and a value of Sc ~= 1 × 104 in the opposite high ? regime (? >> 1). A similar dependence was previously obtained (Ni et al. 2012 Phys. Plasm. 19, 072902), but with a somewhat much larger variation, that can be largely attributed to the different configuration setup used in their study, and also to the definition of the Lundquist number. This conclusion does not depend significantly on the equilibrium used, i.e. both initial configurations with either plasma density or temperature spatial variations lead to very similar results. Finally, we show that the inner plasmoid structure appears as an under-dense hotted magnetic island, with a local temperature increase that is noticeably strengthened for low ? cases.

Baty, H.; Baty

2014-10-01

295

Self-injected petawatt laser-driven plasma electron acceleration in 1017 cm-3 plasma  

NASA Astrophysics Data System (ADS)

We report production of a self-injected, collimated (8 mrad divergence), 600 pC bunch of electrons with energies up to 350 MeV from a petawatt laser-driven plasma accelerator in a plasma of electron density ne = 1017 cm-3, an order of magnitude lower than previous self-injected laser-plasma accelerators. The energy of the focused drive laser pulse (150 J, 150 fs) was distributed over several hot spots. Simulations show that these hot spots remained independent over a 5 cm interaction length, and produced weakly nonlinear plasma wakes without bubble formation capable of accelerating pre-heated (~1 MeV) plasma electrons up to the observed energies. The required pre-heating is attributed tentatively to pre-pulse interactions with the plasma.

Wang, X.; Zgadzaj, R.; Yi, S. A.; Khudik, V.; Henderson, W.; Fazel, N.; Chang, Y.-Y.; Korzekwa, R.; Tsai, H.-E.; Pai, C.-H.; Li, Z.; Gaul, E.; Martinez, M.; Dyer, G.; Quevedo, H.; Bernstein, A.; Donovan, M.; Shvets, G.; Ditmire, T.; Downer, M. C.; Downer

2012-08-01

296

Plasma actuator electron density measurement using microwave perturbation method  

SciTech Connect

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.

Mirhosseini, Farid; Colpitts, Bruce [Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)

2014-07-21

297

Electromagnetic solitary pulses in a magnetized electron-positron plasma  

SciTech Connect

A theory for large amplitude compressional electromagnetic solitary pulses in a magnetized electron-positron (e-p) plasma is presented. The pulses, which propagate perpendicular to the external magnetic field, are associated with the compression of the plasma density and the wave magnetic field. Here the solitary wave magnetic field pressure provides the restoring force, while the inertia comes from the equal mass electrons and positrons. The solitary pulses are formed due to a balance between the compressional wave dispersion arising from the curl of the inertial forces in Faraday's law and the nonlinearities associated with the divergence of the electron and positron fluxes, the nonlinear Lorentz forces, the advection of the e-p fluids, and the nonlinear plasma current densities. The compressional solitary pulses can exist in a well-defined speed range above the Alfven speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas composed of electrons and positrons.

Shukla, P. K. [RUB International Chair, International Centre for Advanced Studies in Physical Sciences, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Eliasson, B. [Institut fuer Theoretische Physik, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Stenflo, L. [Department of Physics, Linkoeping University, SE-58183 Linkoeping (Sweden)

2011-03-15

298

Electromagnetic solitary pulses in a magnetized electron-positron plasma.  

PubMed

A theory for large amplitude compressional electromagnetic solitary pulses in a magnetized electron-positron (e-p) plasma is presented. The pulses, which propagate perpendicular to the external magnetic field, are associated with the compression of the plasma density and the wave magnetic field. Here the solitary wave magnetic field pressure provides the restoring force, while the inertia comes from the equal mass electrons and positrons. The solitary pulses are formed due to a balance between the compressional wave dispersion arising from the curl of the inertial forces in Faraday's law and the nonlinearities associated with the divergence of the electron and positron fluxes, the nonlinear Lorentz forces, the advection of the e-p fluids, and the nonlinear plasma current densities. The compressional solitary pulses can exist in a well-defined speed range above the Alfvén speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas composed of electrons and positrons. PMID:22060541

Shukla, P K; Eliasson, B; Stenflo, L

2011-09-01

299

Controlling electron injection in laser plasma accelerators using multiple pulses  

NASA Astrophysics Data System (ADS)

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.

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.

2012-12-01

300

Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas  

SciTech Connect

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/?g << 1, which prevents net acceleration of the cold plasma, it is also shown that the normalized energy ? of hot electrons accelerated from the initial energy ?o < , ? does not exceed ? ~ a?g, where a is the normalized laser field, and ?g is the group velocity Lorentz factor. Yet ? ~ ? is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted.

V.I. Geyko and G.M. Fraiman, I.Y. Dodin and N.J. Fisch

2009-02-17

301

Alfvenic Solitons in Ultrarelativistic Electron-Position Plasmas  

NASA Technical Reports Server (NTRS)

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.

Verheest, G. S. Lakhina F.

1997-01-01

302

Pure electron plasmas in a stellarator: Theory and experiment  

NASA Astrophysics Data System (ADS)

The confinement of non-neutral plasmas by magnetic surfaces, such as those of a tokamak or a stellarator, is a new area of plasma research. The theory of such plasmas, which range from single component to quasi-neutral, has had a rapid development in recent years. The primary focus has been on pure electron plasmas, in particular the properties of low density electron plasma equilibria. The equilibrium equation is a Poisson-Boltzmann equation for the electrostatic potential which has been solved numerically in realistic three-dimensional geometries. Pure electron plasmas confined on magnetic surfaces are now being studied in several experiments, including the recently operational Columbia Non-neutral Torus (CNT). CNT is an ultralow aspect ratio stellarator at Columbia University, which is devoted to the study of plasma confinement on magnetic surfaces over the full range of plasma neutrality: single component to quasi-neutral. These experiments have already confirmed one theoretical prediction: The existence of macroscopically stable equilibria. We will report on theoretical predictions and experimental measurements of equilibrium, stability, and confinement, and will discuss work in progress on the inclusion of a finite ion fraction and the effects of high electron densities. In collaboration with Allen H. Boozer, Remi G. Lefrancois, Jason P. Kremer, Quinn R. Marksteiner, and John Berkery, Columbia University.

Pedersen, Thomas Sunn

2006-04-01

303

Accessibillity of Electron Bernstein Modes in Over-Dense Plasma  

SciTech Connect

Mode-conversion between the ordinary, extraordinary and electron Bernstein modes near the plasma edge may allow signals generated by electrons in an over-dense plasma to be detected. Alternatively, high frequency power may gain accessibility to the core plasma through this mode conversion process. Many of the tools used for ion cyclotron antenna de-sign can also be applied near the electron cyclotron frequency. In this paper, we investigate the possibilities for an antenna that may couple to electron Bernstein modes inside an over-dense plasma. The optimum values for wavelengths that undergo mode-conversion are found by scanning the poloidal and toroidal response of the plasma using a warm plasma slab approximation with a sheared magnetic field. Only a very narrow region of the edge can be examined in this manner; however, ray tracing may be used to follow the mode converted power in a more general geometry. It is eventually hoped that the methods can be extended to a hot plasma representation. Using antenna design codes, some basic antenna shapes will be considered to see what types of antennas might be used to detect or launch modes that penetrate the cutoff layer in the edge plasma.

Batchelor, D.B.; Bigelow, T.S.; Carter, M.D.

1999-04-12

304

Rarefaction ion acoustic solitons in two-electron-temperature plasma  

Microsoft Academic Search

This paper shows that rarefaction ion acoustic solitons appear in a two-electron-temperature plasma. It also presents general conditions and physical mechanism for existence of the rarefaction solitons. It is found that finite amplitude rarefaction and compression solitons coexist in a plasma within a certain parameter region.

Katsunobu Nishihara; Masayoshi Tajiri

1981-01-01

305

Ion-acoustic solitons in electron-positron-ion plasmas  

Microsoft Academic Search

The ion-acoustic solitons are investigated in three-component plasmas, whose constituents are electrons, positrons, and singly charged ions. It is found that the presence of the positron component in such a multispecies plasma can result in reduction of the ion-acoustic soliton amplitudes.

S. I. Popel; S. V. Vladimirov; P. K. Shukla

1995-01-01

306

Electron-temperature evolution in expanding ultracold neutral plasmas.  

PubMed

We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elastic-collision regime at low initial Gamma(e), which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma(e) in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and we experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas. PMID:17930904

Gupta, P; Laha, S; Simien, C E; Gao, H; Castro, J; Killian, T C; Pohl, T

2007-08-17

307

Study on electron beam in a low energy plasma focus  

SciTech Connect

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.

Khan, Muhammad Zubair, E-mail: mzubairkhan-um76@yahoo.com [Plasma Technology Research Center, Department of Physics, Faculty of Science, University Malaya, 50603 Kuala Lumpur, Malaysia and Department of Physics, Federal Urdu University of Arts, Science and Technology, 45320 Islamabad (Pakistan); Ling, Yap Seong; San, Wong Chiow [Plasma Technology Research Center, Department of Physics, Faculty of Science, University Malaya, 50603 Kuala Lumpur (Malaysia)

2014-03-05

308

High efficiency nonequilibrium air plasmas sustained by high energy electrons  

Microsoft Academic Search

The Air Plasma Ramparts MURI goal is to sustain a volume-filling, nonequilibrium plasma with an electron number density of 1013 electrons\\/cm3 in atmospheric pressure air at temperatures at or below 2000 K, with the minimum expenditure of power. That minimum depends directly on the energy cost of ionization. In this paper, approaches to minimize the cost of ionization are examined.

R. B. Miles; S. O. Macheret; M. N. Shneider

2001-01-01

309

Energy transfer of a relativistic electron beam to a plasma  

Microsoft Academic Search

The energy loss of a relativistic electron beam and the accompanying plasma heating have been measured in an experiment where an electron beam of 500 keV, 0.5 kA, and 20-ns pulse duration was injected into a plasma of density between 100 billion and 1 trillion per cu cm confined in a magnetic mirror trap with 0.2 T in the homogeneous

B. Jurgens; H. J. Hopman; P. de Haan; P. C. de Jagher; J. Kistemaker

1977-01-01

310

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

SciTech Connect

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.

Xu, Lei; Dai, ZhenHong, E-mail: zhdai@ytu.edu.cn; Sui, PengFei; Sun, YuMing; Wang, WeiTian [Computational Physics Laboratory, Institute of Opto-Electronic Information Science and Technology, Yantai University, Yantai 264005 (China)

2014-11-01

311

Simulation of laser-plasma interactions and fast-electron transport in inhomogeneous plasma  

SciTech Connect

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.

Cohen, B.I. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States)], E-mail: bcohen@llnl.gov; Kemp, A.J.; Divol, L. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States)

2010-06-20

312

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

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

313

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

PubMed Central

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 ?m) 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

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

314

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

PubMed

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 ( approximately 5 x 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 ( approximately 1 microm) 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 ( approximately 100 degrees 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

Rogers, J A; Bao, Z; Baldwin, K; Dodabalapur, A; Crone, B; Raju, V R; Kuck, V; Katz, H; Amundson, K; Ewing, J; Drzaic, P

2001-04-24

315

Oscillating plasma bubbles. III. Internal electron sources and sinks  

SciTech Connect

An internal electron source has been used to neutralize ions injected from an ambient plasma into a spherical grid. The resultant plasma is termed a plasma 'bubble.' When the electron supply from the filament is reduced, the sheath inside the bubble becomes unstable. The plasma potential of the bubble oscillates near but below the ion plasma frequency. Different modes of oscillations have been observed as well as a subharmonic and multiple harmonics. The frequency increases with ion density and decreases with electron density. The peak amplitude occurs for an optimum current and the instability is quenched at large electron densities. The frequency also increases if Langmuir probes inside the bubble draw electrons. Allowing electrons from the ambient plasma to enter, the bubble changes the frequency dependence on grid voltage. It is concluded that the net space charge density in the sheath determines the oscillation frequency. It is suggested that the sheath instability is caused by ion inertia in an oscillating sheath electric field which is created by ion bunching.

Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

2012-08-15

316

Electron Beam Transport in Advanced Plasma Wave Accelerators  

SciTech Connect

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.

Williams, Ronald L

2013-01-31

317

Secondary electron enhanced discharges in plasma source ion implantation  

SciTech Connect

The first published measurements of a plasma discharge enhanced by secondary electrons during plasma source ion implantation are presented. The ion implantation target consists of 1000 aluminum, automotive piston surrogates mounted on four racks; total surface area is over 16 m{sup 2}. The four racks are positioned parallel to each other, 0.25 m apart, in an 8 m{sup 3} vacuum chamber. The racks of pistons are immersed in a capacitive radio frequency plasma, with an argon gas pressure of 20{endash}65 mPa. Each plasma ion implanted into the target results in the emission of multiple secondary electrons. Langmuir probe measurements indicate that at high enough gas pressures, the energy of the secondary electrons can couple to the plasma, increasing the rate of ionization. Two different coupling mechanisms are observed. In the first, the secondary electrons directly ionize the background gas. In the second, the secondary electrons couple to the thermal electrons through a beam-plasma instability. Measurements of the instabilities are in agreement with two-dimensional particle-in-cell simulations.

Cluggish, B.P.; Munson, C.P. [MS-E526, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [MS-E526, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1998-12-01

318

Transition of electron kinetics in weakly magnetized inductively coupled plasmas  

NASA Astrophysics Data System (ADS)

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.

Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Kim, Young-Cheol; Chung, Chin-Wook

2013-10-01

319

Transition of electron kinetics in weakly magnetized inductively coupled plasmas  

SciTech Connect

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.

Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)] [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Young-Cheol [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)] [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2013-10-15

320

Linear analysis of a rectangular waveguide cyclotron maser with a sheet electron beam  

SciTech Connect

A linear theory for a rectangular waveguide cyclotron maser with a sheet electron beam is developed by using the Laplace transformation approach. This theory can be applied to any TE{sub mn} rectangular waveguide mode. The corresponding equations for the TM{sub mn} mode in the rectangular waveguide are also derived as a useful reference. Especially, the effect from the coupling between degenerate modes, which is induced by the nonideal rectangular waveguide walls, on the dispersion relation is considered in order to provide a more accurate model for the real devices. Through numerical calculations, the linear growth rate, launching loss, and spontaneous oscillations (caused by the absolute instability and backward wave oscillation) of this new structure can be analyzed in detail. It is worthwhile to point out that the operation at higher power levels of the rectangular waveguide sheet beam system is possible.

Zhao Ding; Ding Yaogen; Wang Yong; Ruan Cunjun [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

2010-11-15

321

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

SciTech Connect

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/?{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.

Jain, Neeraj; Büchner, Jörg [Max Planck/Princeton Center for Plasma Physics, Göttingen (Germany); Max Planck Institute for Solar System Research, Justus-Von-Liebig-Weg-3, Göttingen (Germany)

2014-07-15

322

Association of an auroral surge with plasma sheet recovery and the retreat of the substorm neutral line  

SciTech Connect

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.

Hones, E.W. (Mission Research Corp., Los Alamos, NM (USA)); Elphinstone, R.; Murphree, J.S. (Calgary Univ., AB (Canada). Dept. of Physics); Galvin, A.B. (Maryland Univ., College Park, MD (USA). Dept. of Space Physics); Heinemann, N.C. (Boston Coll., Chestnut Hill, MA (USA). Dept. of Physics); Parks, G.K. (Washington Univ., Seattle, WA (USA)); Rich, F.J. (Air Force Geophysics Lab., Hanscom AFB, MA

1990-01-01

323

Thomson scattering and diamagnet loop studies of a relativistic electron beam-heated plasma  

Microsoft Academic Search

The plasma heating resulting from the interaction of a relativistic electron beam and a pre-ionized plasma column confined in hard vacuum by a 2:1 magnetic mirror field was investigated to determine the mechanism by which electron beam energy is coupled to plasma perpendicular energy, and the partitioning of this plasma perpendicular energy among the plasma species with time after electron

J. D. Sethian

1976-01-01

324

Nonlocal collisionless and collisional electron transport in low temperature plasmas  

NASA Astrophysics Data System (ADS)

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).

Kaganovich, Igor

2009-10-01

325

The plasma environment during particle beam injection into space plasmas. 1. Electron beams  

SciTech Connect

A new isolated-system, two-dimensional electrostatic simulation model is used to investigate the plasma environment in the vicinity of a spacecraft during the injection of electron beams. The propagation of the electron beam and the plasma response to the beam injection are found to vary dramatically depending on the ratio of the ambient plasma density to the beam density. When the ambient plasma density is low, most of the beam electrons are drawn back into the spacecraft by the electric field associated with the charging of the spacecraft. Return currents are associated with field-aligned flow of the ambient electrons and result in regions of charge imbalance away from the spacecraft. The resulting space-charge fields produce strong perpendicular heating of the ions on a time scale of the ion plasma period, resulting in conical distributions. As the ambient plasma density is increased, the response time of the plasma to the electric fields associated with the beam injection is decreased. The beam is then increasingly neutralized, the interaction of the beam with the spacecraft is correspondingly reduced. The fraction of the beam particles that propagate away from the vicinity of the spacecraft is increased. When the ambient plasma density is much larger than the beam density, the beam is able to propagate freely into the plasma. Coherent wave structures are produced in the beam near the spacecraft, while further downstream the beam becomes increasingly turbulent.

Pritchett, P.L. (Univ. of California, Los Angeles (United States)); Winglee, R.M. (Univ. of Colorado, Boulder (United States))

1987-07-01

326

Femtosecond laser-induced electronic plasma at metal surface  

SciTech Connect

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.

Chen Zhaoyang; Mao, Samuel S. [Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720 (United States)

2008-08-04

327

Thermal conduction by electrons in hot dense plasmas  

SciTech Connect

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}

Khalfaoui, A.H.; Bennaceur, D. [Laboratoire Interaction Laser-Matiere, CDTA, 2 Bd. Frantz Fanon, BP 1017, Alger-gare 16000 (Algeria)] [Laboratoire Interaction Laser-Matiere, CDTA, 2 Bd. Frantz Fanon, BP 1017, Alger-gare 16000 (Algeria)

1997-03-01

328

Pure electron plasmas confined for 90 ms in a stellarator without electron sources or internal objects  

SciTech Connect

We report on the creation and up to 90 ms sustainment of pure electron plasmas confined in a stellarator without internal objects. Injection of positrons into such plasmas is expected to lead to the creation of the first electron-positron plasma experiments. These newly created plasmas will also allow a study of pure electron plasmas without the perturbing presence of internal objects. The plasmas were created by thermionic emission of electrons from a heated, biased filament that was retracted in 20 ms. The confinement of these transient plasmas is different from that of steady state plasmas with internal objects and emissive filaments, and is generally shorter, limited by ion buildup. The decay time is increased by lowering the neutral pressure, lowering the electron plasma temperature, or operating with neutrals with high ionization energies (helium). These findings are all consistent with ion accumulation being the cause for the shorter than expected confinement times. The magnetic field strength also moderately increases the decay times. The deleterious effect of ions is not expected to imply a similar deleterious effect when introducing positrons, but it implies that ion accumulation must be avoided also in an electron-positron experiment.

Brenner, P. W.; Sunn Pedersen, T.

2012-05-15

329

The Model of Gas-Discharge Nonneutral Electron Plasma  

E-print Network

The model of gas-discharge nonneutral electron plasma has been considered, in which the electron density is limited by non-linear processes initiated by diocotron instability and it does not depend on the mechanism of electron transport across the magnetic field. The model describes well the characteristics of electron sheath and the current characteristics of discharge both, in magnetron geometry and in the geometry of inversed magnetron, and it allows us to describe quantitatively the influence of anode misalignment on the discharge electron sheath for the first time. The scope of applicability of the proposed model, as well as its relation with other models of electron sheath is studied.

Kervalishvili, N A

2013-01-01

330

Secondary-electrons-induced cathode plasma in a relativistic magnetron  

SciTech Connect

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.

Queller, T.; Gleizer, J. Z.; Krasik, Ya. E. [Physics Department, Technion, Haifa 32000 (Israel)

2012-11-19

331

Electron cyclotron wave resonance plasma assisted deposition of cubic boron nitride thin films  

E-print Network

Electron cyclotron wave resonance plasma assisted deposition of cubic boron nitride thin films Z. X-pressure plasma source. The electron-cyclotron-wave resonance ECWR plasma served both to sputter the hBN target

Zexian, Cao

332

Non-thermal plasma mills bacteria: Scanning electron microscopy observations  

NASA Astrophysics Data System (ADS)

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.

Lunov, O.; Churpita, O.; Zablotskii, V.; Deyneka, I. G.; Meshkovskii, I. K.; Jäger, A.; Syková, E.; Kubinová, Š.; Dejneka, A.

2015-02-01

333

Ionization-induced electron trapping in ultrarelativistic plasma wakes.  

PubMed

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. PMID:17359103

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; Lu, W; Marsh, K A; Mori, W B; Zhou, M

2007-02-23

334

Three-wave coupling in electron-positron-ion plasmas  

SciTech Connect

The three-wave coupling processes in electron-positron-ion plasmas are investigated. The non-linear dispersion relation is derived along with the non-linear growth rate in both resonant and non resonant processes. It is shown that the inclusion of positron affects the dielectric properties of the plasma as well as the nonlinear growth rates of parametric processes. As one increases the positron density to electron density ratio from 0 to 1, maintaining quasi neutrality of the plasma, the growth rates of stimulated Raman, Brillouin, and Compton scattering processes in an isothermal plasma tend to zero due to the ponderomotive forces acting on electrons and positrons due the pump and scattered waves being equal.

Tinakiche, N.; Annou, R. [Faculty of Physics, U.S.T.H.B. Algiers 16111 (Algeria); Tripathi, V. K. [Physics Department, I.T.T Delhi, New-Delhi 16 (India)

2012-07-15

335

Ionization-Induced Electron Trapping inUltrarelativistic Plasma Wakes  

SciTech Connect

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.

Oz, E.; Deng, S.; Katsouleas, T.; Muggli, P.; /UCLA; Barnes, C.D.; Blumenfeld, I.; Decker, F.J.; Emma, P.; Hogan, M.J.; Ischebeck, R.; Iverson, R.H.; Kirby, N.; Krejcik,; O'Connell, C.; Siemann, R.H.; Walz, D.; /SLAC; Auerbach, D.; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; /UCLA

2007-04-06

336

Electron energy distributions in a magnetized inductively coupled plasma  

NASA Astrophysics Data System (ADS)

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.

Song, Sang-Heon; Yang, Yang; Chabert, Pascal; Kushner, Mark J.

2014-09-01

337

Electron energy distributions in a magnetized inductively coupled plasma  

SciTech Connect

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.

Song, Sang-Heon, E-mail: ssongs@umich.edu, E-mail: Sang-Heon.Song@us.tel.com [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, Michigan 48109-2104 (United States); Yang, Yang, E-mail: yang-yang@amat.com [Applied Materials Inc., 974 E. Arques Avenue, M/S 81312, Sunnyvale, California 94085 (United States); Chabert, Pascal, E-mail: pascal.chabert@lpp.polytechnique.fr [LPP, CNRS, Ecole Polytechnique, UPMC, Paris XI, 91128 Palaiseau (France); Kushner, Mark J., E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109-2122 (United States)

2014-09-15

338

Numerical model of the plasma formation at electron beam welding  

NASA Astrophysics Data System (ADS)

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.

Trushnikov, D. N.; Mladenov, G. M.

2015-01-01

339

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

Microsoft Academic Search

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

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

1981-01-01

340

Coupled electron and ion nonlinear oscillations in a collisionless plasma  

SciTech Connect

Dynamics of coupled electrostatic electron and ion nonlinear oscillations in a collisionless plasma is studied with reference to a kinetic description. Proceeding from the exact solution of Vlasov-Maxwell equations written as a function of linear functions in the electron and ion velocities, we arrive at the two coupled nonlinear equations which describe the evolution of the system.

Karimov, A. R. [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)] [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)

2013-05-15

341

Multi electron species and shielding potentials in plasmas  

SciTech Connect

The phenomenon of Debye shielding is investigated in electron ion plasmas using the approach of two temperature electrons. We get different profiles of potential for different parameters and observe that the potentials fall very slowly than the standard Coulomb and Debye potentials. The importance of work is pointed out in the introduction.

Khan, Arroj A.; Murtaza, G. [Salam Chair in Physics, Government College University, Lahore 54000 (Pakistan); Rasheed, A.; Jamil, M. [Department of Physics, Government College University, Faisalabad 38000 (Pakistan)

2012-11-15

342

Fundamental processes in pair plasmas. [electron-positron relativistic plasmas in quasars and active galaxies  

NASA Technical Reports Server (NTRS)

The various processes that produce and destroy electron-positron pairs are reviewed, and the timescales of these processes are compared to thermalization, accretion, and cooling timescales. The various radiation spectra produced by relativistic, thermal plasmas are considered. Recent results for the equilibria available to finite, thermal relativistic plasmas with and without embedded magnetic fields are reviewed. Such plasmas, in steady state, have maximum temperatures, luminosities, and field strengths, useful diagnostics for interpreting quasars and active galaxies.

Lightman, A. P.

1983-01-01

343

Revisiting plasma hysteresis with an electronically compensated Langmuir probe.  

PubMed

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 ?A, allowing plasma measurements to be done with ion saturation current of the order of hundreds of ?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 ?T(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

Srivastava, P K; Singh, S K; Awasthi, L M; Mattoo, S K

2012-09-01

344

Method for generating a plasma wave to accelerate electrons  

DOEpatents

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.

Umstadter, D.; Esarey, E.; Kim, J.K.

1997-06-10

345

Energetic Electron Transport In An Inhomogeneous Plasma Medium  

SciTech Connect

A review of the work carried out at IPR on energetic electron transport through an inhomogeneous plasma medium is presented in this article. A Generalized Electron Magnetohydrodynamic (G-EMHD) fluid model has been developed and employed for such studies. Novel observations such as (i) the trapping of electron current pulse structure in a high density plasma region, (ii) the formation of sharp magnetic field shock structures at the inhomogeneous plasma density layer (iii) and intense energy dissipation at the shock layer even in the collisionless limit are reported. The intense energy dissipation of the electron current pulse at the shock layer provides a mechanism whereby highly energetic electrons which are essentially collision-less can also successfully deposit their energy in a local region of the plasma. This is specially attractive as it opens up the possibility of heating a localized region of an overdense plasma (where lasers cannot penetrate) by highly energetic collision-less electrons. A direct application of this mechanism to Fast Ignition (FT) experiments is discussed.

Das, Amita [Institute for Plasma Research, Bhat Gandhinagar-382428 (India)

2010-11-23

346

Microwave heating of electrons of a dense plasma column at frequencies higher than electron cyclotron frequency  

Microsoft Academic Search

In this experimental study the absorption of plasma waves, excited in a dense plasma column, was investigated and the localization of the regions of efficient heating of electrons were determined in a broad range of parameters: 1>Oce\\/O>0·1, 0·3n\\/nUH-5v\\/O-3. The heating of electrons near the second electron cyclotron harmonic was investigated in greater detail.

J. ?atlov; L. Kryška; V. N. Budnikov

1973-01-01

347

Formation of stable, high-beta, relativistic-electron plasmas using electron cyclotron heating  

Microsoft Academic Search

A one-dimensional, steady-state, relativistic Fokker-Planck model of electron cyclotron heating (ECH) is used to analyse the heating kinetics underlying the formation of the two-component hot-electron plasmas characteristic of ECH in magnetic mirror configurations. The model is first applied to the well diagnosed plasmas obtained in SM-1 and is then used to simulate the effective generation of relativistic electrons by upper

G. E. Guest; R. L. Miller

1988-01-01

348

Kinetic description of electron plasma waves with orbital angular momentum  

SciTech Connect

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.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2012-11-15

349

Mechanical and electronic properties of pristine and Ni-doped Si, Ge, and Sn sheets.  

PubMed

Silicene, a graphene analogue of silicon, has been generating immense interest due to its potential for applications in miniaturized devices. Unlike planar graphene, silicene prefers a buckled structure. Here we explore the possibility of stabilizing the planar form of silicene by Ni doping using first principles density functional theory based calculations. It is found that planar as well as buckled structure is stable for Ni-doped silicene, but the buckled sheet has slightly lower total energy. The planar silicene sheet has unstable phonon modes. A comparative study of the mechanical properties reveals that the in-plane stiffness of both the pristine and the doped planar silicene is higher compared to that of the buckled silicene. This suggests that planar silicene is mechanically more robust. Electronic structure calculations of the planar and buckled Ni-doped silicene show that the energy bands at the Dirac point transform from linear behavior to parabolic dispersion. Furthermore, we extend our study to Ge and Sn sheets that are also stable and the trends of comparable mechanical stability of the planar and buckled phases remain the same. PMID:24322985

Manjanath, Aaditya; Kumar, Vijay; Singh, Abhishek K

2014-01-28

350

RESEARCH NOTE: Parameters of plasma produced by an electron cyclotron resonance heating plasma gun  

Microsoft Academic Search

Plasma parameters of a plasma produced by a slotted cylindrical microwave cavity are investigated experimentally, and two components of electron temperature are observed. When the neutral gas pressure is decreased, both the temperature of the hot component and the energy density increase. The electron temperature rises at a rate of approximately 2 to 4·5 MeV s?1. This suggests that the

Masataka Masuda; Yuji Tanaka; Takayoshi Okuda

1972-01-01

351

Modeling the Self-organized Critical Behavior of Earth's Plasma Sheet Reconnection Dynamics  

NASA Technical Reports Server (NTRS)

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.

Klimas, Alexander J.

2006-01-01

352

Modeling the Self-organized Critical Behavior of the Plasma Sheet Reconnection Dynamics  

NASA Technical Reports Server (NTRS)

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.

Klimas, Alex; Uritsky, Vadim; Baker, Daniel

2006-01-01

353

The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations  

NASA Astrophysics Data System (ADS)

In this paper we present in situ observations of the heliospheric plasma sheet (HPS) from STEREO-A, Wind, and STEREO-B over four solar rotations in the declining phase of Solar Cycle 23, covering late March through late June 2007. During this time period the three spacecraft were located in the ecliptic plane, and were gradually separating in heliographic longitude from about 3 degrees to 14 degrees. Crossings of the HPS were identified using the following criteria: reversal of the interplanetary magnetic field sector, enhanced proton density, and local minima in both the proton specific entropy argument and in the alpha particle-to-proton number density ratio ( N a/ N p). Two interplanetary coronal mass ejections (ICMEs) were observed during the third solar rotation of our study period, which disrupted the HPS from its quasi-stationary state. We find differences in the in situ proton parameters at the HPS between the three spacecraft despite temporal separations of less than one day. We attribute these differences to both small separations in heliographic latitude and radial evolution of the solar wind leading to the development of compression regions associated with stream interaction regions (SIRs). We also observed a modest enhancement in the density of iron ions at the HPS.

Simunac, K. D. C.; Galvin, A. B.; Farrugia, C. J.; Kistler, L. M.; Kucharek, H.; Lavraud, B.; Liu, Y. C.-M.; Luhmann, J. G.; Ogilvie, K. W.; Opitz, A.; Popecki, M. A.; Sauvaud, J.-A.; Wang, S.

2012-11-01

354

Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions  

NASA Technical Reports Server (NTRS)

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.

Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.

2011-01-01

355

Negative ion measurements in electron cyclotron resonance plasmas  

SciTech Connect

Electrically confined negative ions are known as the precursors of particle formation in low pressure processing plasmas. The presence of negative ions can cause various negative aspects during the process: contamination of wafers, limitations of the manufacturing productivity and device reliability in microelectronics production. Various negative ions were detected in low-pressure, high-density Electron Cyclotron Resonance plasmas (H{sub 2}, O{sub 2}, CF{sub 4}, and Cl{sub 2}) by an omegatron mass spectrometer. Preliminary results show H{sup {minus}} and H{sub 2}{sup {minus}} in H{sub 2} plasmas, O{sup {minus}} in O{sub 2} plasmas, F{sup {minus}} and CF{sup {minus}} in CF{sub 4} plasmas. Two other techniques were employed for the verifications of the observed negative ions: photo-detachment and a Langmuir probe in magnetized plasmas. (1) For photodetachment, a pulsed Nitrogen laser ({approximately}4 mJ, 50 nsec) was used to detach the electrons from H{sup {minus}} and Cl{sup {minus}}, and a cylindrical probe, positively biased above the plasma potential, was used to collect the additional electrons. (2) A Langmuir probe theory was developed and employed for various ECR plasmas (H{sub 2}, He, N{sub 2}, O{sub 2}, Ar, and CF{sub 4}). The theory, adapted to magnetized, partially ionized, low temperature processing plasmas, was based on radial diffusion into the depleted flux tube unlike earlier work by Stangeby in fusion plasmas where Bohm diffusion dominates.

Koo, B.W.; Hershkowitz, N.; Buhr, B.

1999-07-01

356

Formation of High-Beta Plasma and Stable Confinement of Toroidal Electron Plasma in RT-1  

NASA Astrophysics Data System (ADS)

The Ring Trap 1 (RT-1) device is a laboratory magnetosphere generated by a levitated superconducting magnet. The goals of RT-1 are to realize stable formation of ultra high-beta plasma suitable for burning advanced fusion fuels, and confinement of toroidal non-neutral plasmas including antimatter particles. RT- 1 has produced high-beta plasma in the magnetospheric configuration. The effects of coil levitation and geomagnetic field compensation [Y. Yano et al., Plasma Fusion Res. 4, 039] resulted drastic improvements of the plasma properties, and a maximum local beta value exceeded 70%. Because plasma is generated by electron cyclotron resonance heating (ECH) in the present experiment, the plasma pressure is mainly due to hot electrons, whose bremsstrahlung was observed with an x-ray CCD camera. The pressure profiles have rather steep gradient near the superconducting coil in the strong field region. The decay rates of magnetic probe and interferometer signals have different time constants, suggesting multiple temperature components. The energy confinement time estimated from the input RF power and stored magnetic energy is on the order of 1s, which is comparable to the decay time constant of the density of hot electron component. Pure electron plasma experiments are also conducted in RT-1. Radial profiles of electrostatic potential and electron density showed that the plasma rigidly rotates in the toroidal direction in the stable confinement phase. Long time confinement of toroidal non- neutral plasma for more than 300s and inward particle diffusion to strong field regions, caused by the activation of the diocotron (Kelvin-Helmholtz) instability, have been realized [Z. Yoshida et al., Phys. Rev. Lett. 104, 235004].

Saitoh, Haruhiko

2010-11-01

357

Numerical studies on three-dimensional earthward fast plasma flows in the near-Earth plasma sheet by the spontaneous fast reconnection model  

NASA Astrophysics Data System (ADS)

The spontaneous fast reconnection model is applied to the earthward fast flow events observed in the near-Earth plasma sheet. Here, the earthward fast flow events include both of bursty bulk flow events and flow burst events. In order to apply it directly to actual observations, virtual probes are located in the plasma sheet region in the three-dimensional simulation domain so that we can directly observe the temporal variations of plasma quantities in accordance with the growth and proceeding of the fast reconnection. In this model, magnetic reconnection drastically evolves and Alfvénic fast plasma jet flows in the very restricted narrow channel, and a large-scale plasmoid is formed ahead of the fast plasma jet. The results of virtual observation of these evolutions are found to be in good agreement with actual satellite observations. At the same time, in the lobe region, travelling compression regions (TCRs) are observed in connection with the fast flow events. The temporal profiles of magnetic fields detected by the virtual probes are also in good agreement with actual satellite observations. It is concluded that the earthward fast flow events and earthward TCR events result from the fast reconnection mechanism.

Kondoh, K.; Ugai, M.

2008-03-01

358

Separation of finite electron temperature effect on plasma polarimetry.  

PubMed

This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, ?, and ellipticity angle, ?, of polarization state have different dependency on the electron density, n(e), and the electron temperature, T(e), and that the separation of n(e) and T(e) from ? and ? is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10(20) m(-3), and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I(p), is known and when I(p) is unknown, the profiles of plasma current density, j(?), n(e), and T(e) are successfully reconstructed. The reconstruction of j(?) without the information of I(p) indicates the new method of I(p) measurement applicable to steady state operation of tokamak. PMID:23277987

Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori

2012-12-01

359

Applications of plasma cleaning for electron microscopy  

Microsoft Academic Search

Summary form only given. Specimen contamination and amorphous irradiation damage severely limit the ability to perform accurate electron microscope analysis of materials, especially as specimen areas of interest decrease in size. To analyze smaller areas of interest, electron probe sizes have decreased, while probe currents have increased. The combination of these two factors results in an increase in the amount

T. C. Isabell; P. E. Fischione; E. A. Fischione

1998-01-01

360

PEACE: A Plasma Electron and Current Experiment  

NASA Astrophysics Data System (ADS)

An electron analyzer to measure the three dimensional velocity distribution of electrons on the multispacecraft Cluster mission is described, and the steps taken to meet the special requirements imposed by the novel character of the mission are explained. The onboard data processing unit is described and the telemetry outputs are addressed. The mass, power consumption, and calibration of the equipment is addressed.

Johnstone, A. D.; Alsop, C.; Carter, P. J.; Coates, A. J.; Coker, A. J.; Gowen, R. A.; Hancock, B. K.; Kennedy, T. E.; Sheather, P. H.; Woodliffe, R. D.

1993-03-01

361

Electron temperature and density fluctuations during improved confinement plasmas  

NASA Astrophysics Data System (ADS)

We plan to present initial results of Thomson scattering measurements of Te and ne fluctuations associated with electrostatic transport during improved confinement plasmas (PPCD). Recent upgrades to the MST Thomson scattering diagnostic have allowed detailed measurements of electron temperature fluctuations in a variety of plasmas. For example, previous studies have mapped temperature fluctuations to magnetic perturbations, observing remnant island structures between sawteeth events in standard plasmas. Electron temperature fluctuations have also been shown to decrease significantly during PPCD plasmas and it is thought that electrostatic fluctuations may dominate transport. Further upgrades to the Thomson diagnostic may enable absolute density measurements, and the planned addition of a fast laser system will improve maximum time resolution from 25 kHz to 250 kHz. These capabilities will allow investigations into correlated Te and ne fluctuations associated with electrostatic transport. This work supported by the USDoE.

Parke, E.; Stephens, H. D.; den Hartog, D. J.; Reusch, J. A.; Yang, Y. M.; Harris, W. S.; Falkowski, A. F.; Kasten, C. P.

2010-11-01

362

Nonlocal electron kinetics in a weakly ionized plasma  

NASA Astrophysics Data System (ADS)

Electron dynamics in a time dependent inhomogeneous electric field in a weakly ionized plasma with elastic electron-neutral collisions is analyzed. We consider the most general ordering when the electron mean free path vTe/?e is arbitrary with respect to the characteristic length scale k-1 of the electric field, and frequency ? of the electric field is arbitrary with respect to the electron collisional frequency ?e ?~?e~kvt. In this case the standard two-term approximation is not valid and higher order spherical harmonics in the perturbed electron distribution function should be taken into account. This results in an infinite hierarchy of coupled equations for angular harmonics that can be solved in the form of the infinite continued fraction. This method is easily generalized for a wide class of scattering cross sections with angular dependencies. The developed approach uniformly describes both local (strongly collisional) and nonlocal regimes. As an example, a closed form of the perturbed electron distribution function is found for the argon gas with nonmonotic dependence of the collisional cross section as function of energy (Ramsauer effect). The conductivity and surface impedance of a semi-infinite plasma are calculated in different collisionality regimes, and anomalous penetration of the electric field into such plasma is analyzed. The nonmonotonous behavior of the amplitude of the external electric field inside of a plasma has been recovered for the nonlocal case (?>1).

Furkal, E.; Smolyakov, A.; Hirose, A.

1998-07-01

363

Effect of electron extraction from a grid plasma cathode on the generation of emission plasma  

NASA Astrophysics Data System (ADS)

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.

Devyatkov, V. N.; Koval, N. N.

2014-11-01

364

Stochastic heating of plasma electrons using microwave noise  

Microsoft Academic Search

A mirror-contained hydrogen plasma of approximately 1 1. volume, 1*1011 cm-3 density and 1 keV temperature is produced using 100 W broadband microwave noise at the electron cyclotron resonance. In contrast to the single frequency heating, noise heating generates a stable, reproducible plasma more efficiently. The use of Ioffe bars is found to be indispensable in suppressing the low-frequency instabilities

S. Puri

1974-01-01

365

Electron cyclotron heating of currentless plasmas in stellarators  

Microsoft Academic Search

This paper presents a review of experiments on the production and heating of currentless plasmas by electron cyclotron (EC) waves in the Heliotron-E, Wendelstein VII-A, and L-2 stellarators, in wide ranges of the magnetic field (1.0 - 2.5 T), frequency (28 - 70 GHz) and microwave power (100 - 500 kW). EC heating of low and high-density currentless plasmas as

L M Kovrizhnykh; I S Spigel

1987-01-01

366

Collisionless Reconnection in an Electron-Positron Plasma  

SciTech Connect

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.

Bessho, N.; Bhattacharjee, A. [Space Science Center and Center for Magnetic Self-Organization, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2005-12-09

367

Collisionless reconnection in an electron-positron plasma.  

PubMed

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

Bessho, N; Bhattacharjee, A

2005-12-01

368

Heating of the solar flare plasma by high energy electrons.  

NASA Technical Reports Server (NTRS)

Discussion of the heating of the ambient plasma by high-energy electrons in solar flares. It is shown that for large flares the heating is enough to produce a thermal plasma with a temperature up to 10 to the 7th K rapidly in the initial phase of the flares. Thus thermal bremsstrahlung in addition to nonthermal bremsstrahlung should be considered for the X-ray emission of solar flares in the initial phase.-

Cheng, C.-C.

1972-01-01

369

Electron backscatter diffraction applied to lithium sheets prepared by broad ion beam milling.  

PubMed

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

Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

2015-01-01

370

Influence of electron injection into 27 cm audio plasma cell on the plasma diagnostics  

SciTech Connect

In this article, the plasma is created in a Pyrex tube (L = 27 cm, ?= 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.

Haleem, N. A.; Ragheb, M. S.; Zakhary, S. G. [Accelerators Department, Nuclear Research Center, AEA, Cairo 13759 (Egypt)] [Accelerators Department, Nuclear Research Center, AEA, Cairo 13759 (Egypt); El Fiki, S. A.; Nouh, S. A. [Faculty of Science, Ain Shams University, Cairo 11566 (Egypt)] [Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); El Disoki, T. M. [Faculty of Girls, Ain Shams University, Cairo 11566 (Egypt)] [Faculty of Girls, Ain Shams University, Cairo 11566 (Egypt)

2013-08-15

371

Anomalous skin effects in a weakly magnetized degenerate electron plasma  

SciTech Connect

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].

Abbas, G., E-mail: gohar.abbas@gcu.edu.pk; Sarfraz, M. [Department of Physics, GC University Lahore, Katchery Road, Lahore 54000 (Pakistan); Shah, H. A. [Forman Christian College University, Farozpur Road, Lahore 54600 (Pakistan)

2014-09-15

372

Anomalous skin effects in a weakly magnetized degenerate electron plasma  

NASA Astrophysics Data System (ADS)

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].

Abbas, G.; Sarfraz, M.; Shah, H. A.

2014-09-01

373

Electron-cyclotron-resonance (ECR) plasma thruster research  

NASA Technical Reports Server (NTRS)

An experimental apparatus to scientifically investigate the process of Electron-Cyclotron-Resonance (ECR) plasma acceleration has been tested. The apparatus consists of a vacuum facility, a 20 kW microwave power supply, and an argon ECR plasma thruster. Present instrumentation allows measurement of microwave input power, reflected power, propellant flow rate, and static pressure in the vacuum tank. In initial tests, an argon ECR plasma has been initiated repeatably at power levels ranging from 0.3 to 7.0 kW. The ECR plasma appears to diverge and separate from the applied magnetic field as predicted by theory. These tests suggest that the ECR plasma acceleration concept can be studied scientifically in the new apparatus.

Sercel, Joel C.

1988-01-01

374

Numerical study of a dust-contaminated electron plasma  

NASA Astrophysics Data System (ADS)

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.

Maero, Giancarlo; Romé, Massimiliano; Lepreti, Fabio; Cavenago, Marco

2014-10-01

375

Magnetic field effect on electron emission from plasma  

Microsoft Academic Search

The influence of external magnetic field on the significant parameters of electrons from laser induced plasma (LIP) is investigated. A Q-switched Nd:YAG laser (1064nm, 9–14ns, 10mJ, 1.1MW) is focused on annealed, 4N pure (99.99%) Silver target (2×2×0.2cm3) for production of plasma under vacuum ?10?3torr. Temperature, density and energy measurements for electrons were made by self fabricated Langmuir probe both in

M. Khaleeq-ur-Rahman; K. A. Bhatti; M. S. Rafique; A. Latif; K. T. Chaudhary

2009-01-01

376

Electron-cyclotron maser instability in relativistic plasmas  

NASA Technical Reports Server (NTRS)

The electron-cyclotron maser instability is studied for the case of an anisotropic electron velocity distribution in the regime where the relativistic corrections to the wave dispersion are significant. Solution of the linear dispersion relation reveals that when the plasma frequency-gyrofrequency ratio is less than v(te)/c, the instability is localized just below k(perpendicular)c/Omega(e) = 1. The growth rate is then strongly peaked for emission at 90 deg to the magnetic field and is considerably larger than would be the case if the cold-plasma dispersion theory were valid. These features are confirmed by EM particle simulations.

Pritchett, P. L.

1986-01-01

377

Electron dynamics in a plasma focus. [electron acceleration  

NASA Technical Reports Server (NTRS)

Results are presented of a numerical integration of the three-dimensional relativistic equations of motion of electrons subject to given electric and magnetic fields deduced from experiments. Fields due to two different models are investigated. For the first model, the fields are those due to a circular distribution of axial current filaments. As the current filaments collapse toward the axis, large azimuthal magnetic and axial electric fields are induced. These fields effectively heat the electrons to a temperature of approximately 8 keV and accelerate electrons within the radius of the filaments to high axial velocities. Similar results are obtained for the current-reduction phase of focus formation. For the second model, the fields are those due to a uniform current distribution. Both the current-reduction and the compression phases were studied. These is little heating or acceleration of electrons during the compression phase because the electrons are tied to the magnetic field. However, during the current-reduction phase, electrons near the axis are accelerated toward the center electrode and reach energies of 100 keV. A criterion is obtained which limits the runaway electron current to about 400 A.

Hohl, F.; Gary, S. P.; Winters, P. A.

1977-01-01

378

Microwave heating of electrons of a dense plasma column at frequencies higher than the electron cyclotron frequency. Part I  

Microsoft Academic Search

The absorption of plasma waves excited in a dense plasma column was ; investigated and the localization of the regions of efficient electron heating ; was determined in a broad range of plasma parameters. The heating of electrons ; near the second electron cyclotron harmonic was investigated in more detail. ; (auth);

J. Datlov; L. Kryska; V. N. Budnikov

1972-01-01

379

Influence of electron evaporative cooling on ultracold plasma expansion  

SciTech Connect

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.

Wilson, Truman; Chen, Wei-Ting; Roberts, Jacob [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States)] [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States)

2013-07-15

380

Electron-acoustic solitary waves in a magnetized plasma with hot electrons featuring Tsallis distribution  

NASA Astrophysics Data System (ADS)

Nonlinear dynamics of electron-acoustic solitary waves in a magnetized plasma whose constituents are cold magnetized electron fluid, hot electrons featuring Tsallis distribution, and stationary ions are examined. The nonlinear evolution equation (i.e., Zakharov-Kuznetsov (ZK) equation), governing the propagation of EAS waves in such plasma is derived and investigated analytically and numerically, for parameter regimes relevant to the dayside auroral zone. It is revealed that the amplitude, strength and nature of the nonlinear EAS waves are extremely sensitive to the degree of the hot electron nonextensivity. Furthermore, the obtained results are in good agreement with the observations made by the Viking satellite.

Tribeche, Mouloud; Sabry, Refaat

2012-10-01

381

Mechanisms of plasma disruption and runaway electron losses in tokamaks  

E-print Network

Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak mechanisms of the formation of runaway electron beams and their losses are proposed. The plasma disruption is caused by strong stochastic magnetic field formed due to nonlinearly excited low-mode number MHD modes. It is hypothesized that the runaway electron beam is formed in the central plasma region confined inside the intact magnetic surface located between $q=1$ and the closest low--order rational [$q=4/3$ or $q=3/2$] magnetic surfaces. The thermal quench time caused by the fast electron transport in a stochastic magnetic field is calculated using the collisional transport model. The current decay stage is due to the ambipolar particle transport in a stochastic magnetic field. The runaway electron beam in the confined plasma region is formed due to their acceleration the inductive toroidal electric field. The runaway electron beam current is modeled as a sum of toroidally symmetric part and a ...

Abdullaev, S S; Wongrach, K; Tokar, M; Koslowski, H R; Willi, O; Zeng, L

2015-01-01

382

Investigation of Nitrogen Atoms in Low-Pressure Nitrogen Plasmas Using a Compact Electron-Beam-Excited Plasma Source  

NASA Astrophysics Data System (ADS)

We developed a new compact electron-beam-excited plasma (EBEP) source with a multihole grid. The source can be reliably operated under low-pressure conditions by controlling the electron-beam current and electron-beam energy independently. In this study, we applied the compact EBEP source to the generation of nitrogen plasma. The absolute nitrogen (N) atom densities in the plasma were evaluated using vacuum ultraviolet absorption spectroscopy (VUVAS) with a high-pressure microdischarge hollow cathode (MHCL) as a light source. The electron density and electron temperature were measured using a Langmuir probe. The behavior of N atom densities and electron densities in the plasma are discussed.

Tada, Shigekazu; Takashima, Seigou; Ito, Masafumi; Hamagaki, Manabu; Hori, Masaru; Goto, Toshio

2002-07-01

383

Electron Acoustic Solitary Waves in Magnetized Quantum Plasma with Relativistic Degenerated Electrons  

NASA Astrophysics Data System (ADS)

A model for the nonlinear properties of obliquely propagating electron acoustic solitary waves in a two-electron populated relativistically quantum magnetized plasma is presented. By using the standard reductive perturbation technique, the Zakharov-Kuznetsov (ZK) equation is derived and this equation gives the solitary wave solution. It is observed that the relativistic effects, the ratio of the cold to hot electron unperturbed number density and the magnetic field normalized by electron cyclotron frequency significantly influence the solitary structures.

Zhu, Zhenni; Wu, Zhengwei; Li, Chunhua; Yang, Weihong

2014-11-01

384

Slant Slot Antenna-Type Electron Cyclotron Resonance Plasma Source  

NASA Astrophysics Data System (ADS)

A new compact electron cyclotron resonance (ECR) plasma source, which is termed slant-slot antenna-type ECR plasma source, is presented. Using this plasma source an ion saturation current density Iis of 6.2 mA/cm2±5.2% was obtained over a diameter of 300 mm under ambient conditions of Cl2 gas at 0.7 Pa. The features of the plasma source are an independent circular TM011 mode cavity resonator and slot antennas mounted in the shape of a ring at a constant slant angle to the surface current flowing at the bottom of the cavity resonator. As the result, microwaves of TE01 mode and others having a ring-shaped the electric field distribution can be introduced into the reaction chamber with high stability. This plasma source can generate a plasma with a ring-shaped Iis distribution stably, and it can control the Iis distribution by means of both the configuration of the magnetic field and the pattern of slot antennas. Therefore, the plasma source can generate a uniform plasma under a wide range of discharge conditions.

Watanabe, Seiichi; Tamura, Hitoshi; Sumiya, Masahiro; Furuse, Muneo; Kawasaki, Sunao

1998-09-01

385

Electron kinematics in a plasma focus  

NASA Technical Reports Server (NTRS)

The results of numerical integrations of the three-dimensional relativistic equations of motion of electrons subject to given electric and magnetic fields are presented. Fields due to two different models are studied: (1) a circular distribution of current filaments, and (2) a uniform current distribution; both the collapse and the current reduction phases are studied in each model. Decreasing current in the uniform current model yields 100 keV electrons accelerated toward the anode and, as for earlier ion computations, provides general agreement with experimental results.

Hohl, F.; Gary, S. P.

1977-01-01

386

Effects of plasma composition on backscatter, hot electron production, and propagation in underdense plasmas  

NASA Astrophysics Data System (ADS)

A series of underdense laser plasma interaction experiments performed on the Helen laser [M. J. Norman et al., Appl. Opt. 41, 3497 (2002)] at the Atomic Weapons Establishment (AWE), U.K., using 2? light have uncovered a strong dependence of laser backscatter and hot electron production on plasma composition. Using low-Z materials, we find a behavior familiar from previous 3? work, the interchange of stimulated Raman scattering for Brillouin scattering as we change from gases that have high ion wave damping (e.g., C5H12) to gases with low ion wave damping (e.g., CO2). However, as Z is increased, we find that Brillouin scattering drops while Raman scattering remains low. For gases with Z greater than 18, it is possible to have long scalelength, underdense plasmas with both low Brillouin and Raman backscatter losses. Complementary measurements of hot electron production show efficient production of hot electrons in C5H12 plasmas approaching 0.25ncr, but changing the plasma composition can greatly suppress the hot electron production, even near 0.25ncr. Additional experiments indicate that by adding small amounts of high Z dopant, significant changes to the backscatter and hot electron production in C5H12 targets may be produced.

Stevenson, R. M.; Suter, L. J.; Oades, K.; Kruer, W.; Slark, G. E.; Fournier, K. B.; Meezan, N.; Kauffman, R.; Miller, M.; Glenzer, S.; Niemann, C.; Grun, J.; Davis, J.; Back, C.; Thomas, B.

2004-05-01

387

Sudden pressure enhancement and tailward retreat in the near-Earth plasma sheet: THEMIS observation and MHD simulation  

NASA Astrophysics Data System (ADS)

enhancement of the plasma pressure in the near-Earth plasma sheet is one of the common manifestations of substorms and is thought to play an important role in relevant disturbances in the magnetosphere and ionosphere. On 1 March 2008, four of the Time History of Events and Macroscale Interactions during Substorms probes observed the sudden enhancement of the plasma pressure around 15:40 UT. The four probes were almost aligned along the Sun-Earth line, which was suitable for investigating spatial-temporal evolution of the near-Earth plasma sheet around the substorm onset. The four probes were located off the equatorial plane, according to a magnetic field model. The plasma pressure suddenly increased at the innermost probe first (at ~7.2 Re), followed by the outer probes (at ~7.5, ~8.3, and ~10.4 Re), that could be seen as a tailward propagation (or retreat) of high-pressure region (HPR). After comparing with results of a global magnetohydrodynamic simulation, we found that only the tailward propagation of the HPR could be seen at off equator. Near the equatorial plane, the HPR propagates earthward from the magnetotail region, then it retreats tailward. In the course of the tailward retreat, the HPR also propagates away from the equatorial plane. As a consequence, the innermost probe observed the pressure enhancement first, followed by the outer probes. The propagation of the HPR in the ZGSM direction is understood to be a combination of the convergence of the plasma flow (the divergence of bulk velocity along the ZGSM axis) and the pressure gradient force.

Yao, Y.; Ebihara, Y.; Tanaka, T.

2015-01-01

388

Beltrami-Bernoulli equilibria in plasmas with degenerate electrons  

NASA Astrophysics Data System (ADS)

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.

Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.

2015-02-01

389

Whistler-Mode Electron Cyclotron Emission in a Mirror Plasma  

NASA Astrophysics Data System (ADS)

Measurements of electron cyclotron emission in the whistler mode have been made on the Maryland mirror machine and the results are compared with hot-plasma theory. Good agreement is obtained, demonstrating, in particular, that the emission attains black-body levels for a wide range of conditions. It is concluded that this emission is a promising candidate to measure axial variations of the electron temperature in tandem mirror devices.

Ellis, R. F.; Tsakiris, G. D.; Boyd, D. A.

1982-01-01

390

Development of a locally electron-heated plasma source  

Microsoft Academic Search

A new type high-density plasma source has been developed. It employs a 2.45-GHz microwave in combination with permanent magnets which surround microwave ports located in the chamber sidewall. Electron–cyclotron resonance regions are formed locally in front of the microwave ports. High-energy electrons are produced which diffuse into the center of the chamber along the lines of magnetic force. A cusp

H. Seki; S. Kitazawa; Y. Ueno; N. Wada; S. Takemori; T. Sato; S. Uchikawa; E. Setoyama

2000-01-01

391

Low Energy Electrons in the Mars Plasma Environment  

NASA Technical Reports Server (NTRS)

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.

Link, Richard

2001-01-01

392

Electron plasma waves upstream of the earth's bow shock  

NASA Technical Reports Server (NTRS)

Electrostatic waves are observed around the plasma frequency fpe in the electron foreshock, together with electrons backstreaming from the bow shock. Using data from the sounder aboard ISEE 1, it is shown that this noise, previously understood as narrow band Langmuir waves more or less widened by Doppler shift or nonlinear effects, is in fact composed of two distinct parts: one is a narrow band noise, emitted just above fpe, and observed at the upstream boundary of the electron foreshock. This component has been interpreted as Langmuir waves emitted by a beam-plasma instability. It is suggested that it is of sufficiently large amplitude and monochromatic enough to trap resonant electrons. The other is a broad band noise, more impulsive than the narrow band noise, observed well above and/or well below fpe, deeper in the electron foreshock. The broad band noise has an average spectrum with a typical bi-exponential shape; its peak frequency is not exactly equal to fpe and depends on the Deybe length. This peak frequency also depends on the velocity for which the electron distribution has maximum skew. An experimental determination of the dispersion relation of the broad band noise shows that this noise, as well as the narrow band noise, may be due to the instability of a hot beam in a plasma.

Lacombe, C.; Mangeney, A.; Harvey, C. C.; Scudder, J. D.

1985-01-01

393

Plasma heating, plasma flow and wave production around an electron beam injected into the ionosphere  

NASA Technical Reports Server (NTRS)

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.

Winckler, J. R.; Erickson, K. N.

1986-01-01

394

Atmospheric pressure plasma and electron cyclotron resonance plasma and their applications  

NASA Astrophysics Data System (ADS)

Based on a capacitively coupled electrical discharge scheme, an array of plasma torches is generated to form a dense plasma layer in the open air. In order to use a single power source to supply several torches simultaneously, capacitors are used as ballasting impedances coupling all the torches together. Several diagnostics are performed on a single plasma torch to find its temperature, dimensions, and plasma density. To ease constructing an atmospheric pressure plasma source, a modular system is then presented. The design and construction of the plasma torch module is described. The electrical characteristics of the module is studied for the case of a single module and two capacitively coupled modules. For understanding the plasma torch, each is represented by a parallel RC circuit, in which both R and C are time dependent due to the plasma. The dynamics of the plasma is described by the rate equations for the various plasma species. Numerical simulations have been performed to determine the parameter space for efficient generation of the plasma. Scattering (and absorption) of electromagnetic waves by the plasma torches in a rectangular waveguide is studied experimentally and theoretically. By changing the number of torches appearing in the waveguide, the dependence of the microwave power loss on the plasma volume is determined. ECR plasma-assisted chemical vapor deposition (PACVD) is a technique currently receiving much interest because the ECR plasma system offers a more complex parameter space than the conventional PACVD process. Moreover, a unique feature of the ECR plasma is the production of an energetic electron tail, establishing a large sheath potential on the substrate surface for energizing the bombarding ions, which enhances the nucleation rate. An ECR system for PACVD of diamond film on silicon substrates is designed and built. After surface treatment by the ECR produced energetic ions, the low pressure ECR plasma operation is switched, in situ, to a moderate pressure microwave plasma. The process of PACVD of diamond film was then continued. Structural information on the film was obtained using x-ray diffraction. The 76o scattering peak from the diamond (220) crystalline was measured.

Koretzky, Edward Van

1999-03-01

395

Plasma electron collection through biased slits in a dielectric  

NASA Technical Reports Server (NTRS)

A large number of experimental and analytical efforts have been directed toward understanding the plasma sheath growth and discharge phenomena which lead to high-voltage solar array/space plasma interactions. An important question which has not been addressed is how the voltage gradient in the plasma sheath near the surface of such an array may affect these interactions. The purpose of the experimental study described in this paper is to examine the merging of the sheaths around biased slits in a dielectric and how this affects the collection of electrons through these slits. The data, which are obtained by emissive probes and direct measurement of the current collected through the slits, indicate that when the sheaths merge the current collection by the slits is significantly altered with the most positive slit collecting more electrons than it otherwise would. Therefore, the effect of a voltage gradient in the sheath around a solar array should be considered when evaluating solar array performance.

Carruth, M. R., Jr.

1987-01-01

396

Thermalization of a nonequilibrium electron-positron-photon plasma  

E-print Network

Starting from a nonequilibrium configuration we analyse the essential role of the direct and the inverse binary and triple interactions in reaching an asymptotic thermal equilibrium in a homogeneous isotropic electron-positron-photon plasma. We focus on energies in the range 0.1--10 MeV. We numerically integrate the integro-partial differential relativistic Boltzmann equation with the exact QED collisional integrals taking into account all binary and triple interactions in the plasma. We show that first, when detailed balance is reached for all binary interactions on a timescale $t_{k}\\lesssim10^{-14}$sec, photons and electron-positron pairs establish kinetic equilibrium. Successively, when triple interactions fulfill the detailed balance on a timescale $t_{eq}\\lesssim10^{-12}$sec, the plasma reaches thermal equilibrium. It is shown that neglecting the inverse triple interactions prevents reaching thermal equilibrium. Our results obtained in the theoretical physics domain also find application in astrophysics and cosmology.

A. G. Aksenov; R. Ruffini; G. V. Vereshchagin

2007-07-22

397

Plasma electron flood for a scanned beam implanter  

Microsoft Academic Search

Recently, charging damage has been observed even in relatively low dose implantation on medium current ion implanters, especially in the case of wafers coated with photoresist patterns. To suppress the charging damage in implantation, a plasma electron flood system has been developed for the medium current ion implanter, NV-MC3, which has an electrostatic beam scanning system and accommodates up to

Makoto Sano; Mitsuaki Kabasawa; Fumiaki Sato; Michiro Sugitani

2002-01-01

398

Ion accumulation in an electron plasma confined on magnetic surfaces  

NASA Astrophysics Data System (ADS)

Accumulation of ions can alter and may destabilize the equilibrium of an electron plasma confined on magnetic surfaces. An analysis of ion sources and ion content in the Columbia Non-neutral Torus (CNT) [T.S. Pedersen, J.P. Kremer, R.G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is presented. In CNT ions are created preferentially at locations of high electron temperature, near the outer magnetic surfaces. A volumetric integral of ne?iz gives an ion creation rate of 2.8×1011ions/s. This rate of accumulation would cause neutralization of a plasma with 1011 electrons in about half a second. This is not observed experimentally, however, because currently in CNT ions are lost through recombination on insulated rods. From a steady-state balance between the calculated ion creation and loss rates, the equilibrium ion density in a 2×10-8Torr neutral pressure, 7.5×1011m-3 electron density plasma in CNT is calculated to be ni=6.2×109m-3, or 0.8%. The ion density is experimentally measured through the measurement of the ion saturation current on a large area probe to be about 6.0×109m-3 for these plasmas, which is in good agreement with the predicted value.

Berkery, John W.; Marksteiner, Quinn R.; Pedersen, Thomas Sunn; Kremer, Jason P.

2007-08-01

399

Extraction of electron plasma energy distribution function using distortion meters  

Microsoft Academic Search

A new method for direct evaluation of the electron energy distribution function in plasmas is suggested, which involves the use of audio frequencies distortion factor meters. The amount of distortion suffered by a Langmuir probe AC current produced by superimposing a clean AC voltage on the DC probe voltage is measured. Although such distortions are proportional to the second derivative

A. A. Azooz

2006-01-01

400

Permanent magnet electron cyclotron resonance plasma source with remote window  

Microsoft Academic Search

An electron cyclotron resonance (ECR) plasma has been used in conjunction with a solid metal sputter target for Cu deposition over 200 mm diameters. The goal is to develop a deposition system and process suitable for filling submicron, high-aspect ratio ULSI features. The system uses a permanent magnet for creation of the magnetic field necessary for ECR, and is significantly

Lee A. Berry; S. M. Gorbatkin

1995-01-01

401

Experimental Studies of Self Organization with Electron Plasmas  

SciTech Connect

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.

Matthaeus, William H. [University of Delaware] [University of Delaware

2011-04-11

402

Electron Cyclotron Resonance Ion Sources and ECR Plasmas  

Microsoft Academic Search

Let me say from the start that opening this book on electron cyclotron resonance ion sources (ECRIS) and ECR plasmas is a real pleasure. The book is written by a well known recognized expert in the field, an inquisitive experimentalist with a solid theoretical background. During the many years that Geller has worked in the field, he has clearly accumulated

A Pochelon

1997-01-01

403

Particle acceleration in axisymmetric pulsar current sheets  

NASA Astrophysics Data System (ADS)

The equatorial current sheet in pulsar magnetospheres is often regarded as an ideal site for particle acceleration via relativistic reconnection. Using 2D spherical particle-in-cell simulations, we investigate particle acceleration in the axisymmetric pulsar magnetosphere as a function of the injected plasma multiplicity and magnetization. We observe a clear transition from a highly charge-separated magnetosphere for low plasma injection with little current and spin-down power, to a nearly force-free solution for high plasma multiplicity characterized by a prominent equatorial current sheet and high spin-down power. We find significant magnetic dissipation in the current sheet, up to 30 per cent within 5 light-cylinder radii in the high-multiplicity regime. The simulations unambiguously demonstrate that the dissipated Poynting flux is efficiently channelled to the particles in the sheet, close to the Y-point within about 1-2 light-cylinder radii from the star. The mean particle energy in the sheet is given by the upstream plasma magnetization at the light cylinder. The study of particle orbits shows that all energetic particles originate from the boundary layer between the open and the closed field lines. Energetic positrons always stream outwards, while high-energy electrons precipitate back towards the star through the sheet and along the separatrices, which may result in auroral-like emission. Our results suggest that the current sheet and the separatrices may be the main source of high-energy radiation in young pulsars.

Cerutti, Benoît; Philippov, Alexander; Parfrey, Kyle; Spitkovsky, Anatoly

2015-03-01

404

Anti-bias voltage electron-Kondo transport in a quantum dot device driven by a graphene sheet  

NASA Astrophysics Data System (ADS)

We theoretically investigate the manipulation of electron-Kondo transport through a single-quantum dot (QD) two-electrode device by introducing a side-coupled graphene sheet. It is shown that with increase of coupling strength between the QD and the zero-potential graphene sheet, the anti-bias voltage capability of the QD-electrode Kondo resonance is improved obviously. This causes a high-conductance QD-electrode channel to be opened up for electron transport within a wide bias voltage range. Moreover, the conductance/current of the Kondo channel can be accurately controlled by adjusting the potential of the graphene sheet. These results may be useful for the observation of nonequilibrium Kondo effect and the design of high-conductance control device.

Chen, Xiongwen; Shi, Zhengang; Zhang, Shunru; Song, Kehui; Zhou, Guanghui

2015-01-01

405

Ion and electron-acoustic solitons in two-electron temperature space plasmas  

Microsoft Academic Search

Properties of ion- and electron-acoustic solitons are investigated in an unmagnetized multicomponent plasma system consisting of cold and hot electrons and hot ions using the Sagdeev pseudopotential technique. The analysis is based on fluid equations and the Poisson equation. Solitary wave solutions are found when the Mach numbers exceed some critical values. The critical Mach numbers for the ion-acoustic solitons

G. S. Lakhina; A. P. Kakad; S. V. Singh; F. Verheest

2008-01-01

406

Trajectories of high energy electrons in a plasma focus  

NASA Technical Reports Server (NTRS)

Measurements are made of high-energy electron trajectories in a plasma focus as functions of position, time, energy, and angle of emission. The spatial resolution of the X-ray emission shows that low-energy X-rays are emitted from the anode surface. It is also suggested that the highest energy X-rays originate from a small region on the axis. The so-called shadow technique shows that the electron beam is perpendicular to the anode surface. Polar diagrams of medium and high-energy X-rays agree with the bremsstrahlung emission from a relativistic electron beam, the current of which is several 100 A.

Harries, W. L.; Lee, J. H.; Mcfarland, D. R.

1978-01-01

407

Noncollisional heating and electron energy distributions in magnetically enhanced inductively coupled and helicon plasma sources  

E-print Network

Noncollisional heating and electron energy distributions in magnetically enhanced inductively enhanced inductively coupled plasma MEICP and helicon plasma sources are being developed for their high coupled and helicon plasma sources Ronald L. Kindera) and Mark J. Kushnerb) Department of Electrical

Kushner, Mark

408

Electron energy spectrum in circularly polarized laser irradiated overdense plasma  

SciTech Connect

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 ?{sub max}=mc{sup 2}[(1+a{sub 0}{sup 2}){sup 1/2}?1], where a{sub 0}{sup 2}=(1+(2?{sup 2}/?{sub p}{sup 2})|a{sub in}|{sup 2}){sup 2}?1, |a{sub in}| is the normalized amplitude of the incident laser of frequency ?, and ?{sub p} 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 ?{sub max}.

Liu, C. S.; Tripathi, V. K.; Shao, Xi [Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742 (United States); Kumar, Pawan, E-mail: kumarpawan-30@yahoo.co.in [Department of Physics, Raj Kumar Goel Institute of Technology, Ghaziabad 201003, UP (India)

2014-10-15

409

Electron Densities Near Io from Galileo Plasma Wave Observations  

NASA Technical Reports Server (NTRS)

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.

Gurnett, D. A.; Persoon, A. M.; Kurth, W. S.; Roux, A.; Bolton, S. J.

2001-01-01

410

A new 122 mm electromechanical drill for deep ice-sheet coring (DISC): 3. Control, electrical and electronics design  

Microsoft Academic Search

The deep ice-sheet coring (DISC) drill developed by Ice Coring and Drilling Services under contract to the US National Science Foundation is an electromechanical drill designed to take 122 mm ice cores to depths of 4000 m. Electronic, electrical and control systems are major aspects of the DISC drill. The drill sonde, the down-hole portion of the drill system, requires

Nicolai B. Mortensen; Paul J. Sendelbach; Alexander J. Shturmakov

2007-01-01

411

Electron velocity-space diffusion in a microunstable electron cyclotron resonance heated mirror plasma  

Microsoft Academic Search

An experimental study of the velocity-space diffusion of electrons in an electron cyclotron resonance heated (ECRH) mirror plasma, in the presence of microunstable whistler radio frequency (rf) emission, is presented. The dominant loss mechanism for hot electrons, with temperatures Th ?400 keV, is end loss produced by rf diffusion into the mirror loss cone. In a case with 4.5 kW

S. A. Hokin; R. S. Post; D. L. Smatlak

1989-01-01

412

Electron velocity-space diffusion in a microunstable electron cyclotron resonance heated mirror plasma  

Microsoft Academic Search

An experimental study of the velocity-space diffusion of electrons in an electron cyclotron resonance heated (ECRH) mirror plasma, in the presence of microunstable whistler radio frequency (rf) emission, is presented. The dominant loss mechanism for hot electrons, with temperatures T\\/sub h\\/ approx.400 keV, is end loss produced by rf diffusion into the mirror loss cone. In a case with 4.5

S. A. Hokin; R. S. Post; D. L. Smatlak

1989-01-01

413

Analysis of electron beam damage of exfoliated MoS? sheets and quantitative HAADF-STEM imaging.  

PubMed

In this work we examined MoS? sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS? 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 MoS? 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

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

414

Towards laboratory produced relativistic electron-positron pair plasmas  

NASA Astrophysics Data System (ADS)

We review recent experimental results on the path to producing electron-positron pair plasmas using lasers. Relativistic pair-plasmas and jets are believed to exist in many astrophysical objects and are often invoked to explain energetic phenomena related to Gamma Ray Bursts and Black Holes. On earth, positrons from radioactive isotopes or accelerators are used extensively at low energies (sub-MeV) in areas related to surface science positron emission tomography and basic antimatter science. Experimental platforms capable of producing the high-temperature pair-plasma and high-flux jets required to simulate astrophysical positron conditions have so far been absent. In the past few years, we performed extensive experiments generating positrons with intense lasers where we found that relativistic electron and positron jets are produced by irradiating a solid gold target with an intense picosecond laser pulse. The positron temperatures in directions parallel and transverse to the beam both exceeded 0.5 MeV, and the density of electrons and positrons in these jets are of order 10 16 cm -3 and 10 13 cm -3, respectively. With the increasing performance of high-energy ultra-short laser pulses, we expect that a high-density, up to 10 18 cm -3, relativistic pair-plasma is achievable, a novel regime of laboratory-produced hot dense matter.

Chen, Hui; Meyerhofer, D. D.; Wilks, S. C.; Cauble, R.; Dollar, F.; Falk, K.; Gregori, G.; Hazi, A.; Moses, E. I.; Murphy, C. D.; Myatt, J.; Park, J.; Seely, J.; Shepherd, R.; Spitkovsky, A.; Stoeckl, C.; Szabo, C. I.; Tommasini, R.; Zulick, C.; Beiersdorfer, P.

2011-12-01

415

Thermal equilibrium of a cryogenic magnetized pure electron plasma  

NASA Technical Reports Server (NTRS)

The thermal equilibrium correlation properties of a magnetically confined pure electron plasma (McPEP) are related to those of a one-component plasma (OCP). The N-particle spatial distribution rho sub s and the Helmholtz free energy F are evaluated for the McPEP to O(lambda sub d-squared/a-squared), where lambda sub d is the thermal de Broglie wavelength and is an interparticle spacing. The electron gyromotion is allowed to be fully quantized while the guiding center motion is quasi-classical. The distribution rho sub s is shown to be identical to that of a classical OCP with a slightly modified potential. To O(lambda sub d-squared/a-squared) this modification does not affect that part of F that is caused by correlations, as long as certain requirements concerning the size of the plasma are met. This theory is motivated by a current series of experiments that involve the cooling of a magnetically confined pure electron plasma to the cryogenic temperature range.

Dubin, D. H. E.; Oneil, T. M.

1986-01-01

416

Dusty plasma diagnostics methods for charge, electron temperature, and ion density  

E-print Network

Dusty plasma diagnostics methods for charge, electron temperature, and ion density Bin Liu,1 J Q and two plasma parameters, electron temperature Te, and ion density ni, in the main plasma region of a dusty plasma. Using video microscopy to track microparticles yields a resonance frequency, which along

Goree, John

417

Injection of a relativistic electron beam into an inhomogeneous magnetized plasma  

Microsoft Academic Search

Experiment and theory are described for a scheme of relativistic electron beam plasma heating in which increased beam energy is deposited by having the beam electrons reenter the plasma. This is done by reflecting them from a virtual cathode that they create at the plasma-vacuum boundary. In order to accomplish this, the plasma column must not be in contact with

P. Sunka; K. Jungwirth; I. Kovac; V. Piffl; J. Stockel; J. Ullschmied

1977-01-01

418

Electron Heating in a Relativistic, Weibel-Unstable Plasma  

E-print Network

The dynamics of two initially unmagnetized relativistic counter-streaming homogeneous ion-electron plasma beams are simulated in two dimensions using the particle-in-cell (PIC) method. It is shown that current filaments, which form due to the Weibel instability, develop a large scale longitudinal electric field in the direction opposite to the current carried by the filaments as predicted by theory. Fast moving ions in the current filaments decelerate due to this longitudinal electric field. The same longitudinal electric field, which is partially inductive and partially electrostatic, is identified as the main source of acceleration of electrons in the current filaments. The transverse electric field, though larger than the longitudinal one, is shown to play a smaller role in heating electrons, contrary to previous claims. It is found that, in 1D, the electrons become strongly magnetized and are \\textit{not} accelerated beyond their initial kinetic energy. Rather, the heating of the electrons is enhanced by ...

Kumar, Rahul; Gedalin, Michael

2015-01-01

419

Electron temperature and average density in spherical laser-produced plasmas - Ultraviolet plasma spectroscopy  

Microsoft Academic Search

The average values of the electron temperature Te and the electron density Ne in the corona plasmas of spherically irradiated high-Z targets have been estimated. Targets composed of the elements Cu through Br, Rb, and Mo were irradiated using the fundamental (1.06 microns) and the frequency-tripled (351 nm) output of the Omega laser system. Spectra were recorded in the wavelength

Samuel Goldsmith; J. F. Seely; U. Feldman; W. E. Behring; Leonard Cohen

1985-01-01

420

Investigation of Nitrogen Atoms in Low-Pressure Nitrogen Plasmas Using a Compact Electron-Beam-Excited Plasma Source  

Microsoft Academic Search

We developed a new compact electron-beam-excited plasma (EBEP) source with a multihole grid. The source can be reliably operated under low-pressure conditions by controlling the electron-beam current and electron-beam energy independently. In this study, we applied the compact EBEP source to the generation of nitrogen plasma. The absolute nitrogen (N) atom densities in the plasma were evaluated using vacuum ultraviolet

Shigekazu Tada; Seigou Takashima; Masafumi Ito; Manabu Hamagaki; Masaru Hori; Toshio Goto

2002-01-01

421

ISEE observations of low frequency waves and ion distribution function evolution in the plasma sheet boundary layer  

NASA Technical Reports Server (NTRS)

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.

Elphic, R. C.; Gary, S. P.

1990-01-01

422

Wind survey of high-speed bulk flows and field-aligned beams in the near-Earth plasma sheet  

NASA Astrophysics Data System (ADS)

We have surveyed all high-speed (>250 km/s) flows detected by Wind during its 17 perigee passes across the near-Earth (xGSE = -25 to 0 RE) plasma sheet in the period between 1995 and 1997. By classifying high-speed flow events based on their ion distribution characteristics rather than their plasma moments or the regions in which these flows were detected, we found that most (if not all) high-speed flow ion distributions fall into two distinct categories: bulk flows and field-aligned beams. We show that bulk flows are not simply the low-latitude counterparts of field-aligned beams. Field-aligned beams have sharp cutoffs at low energies, occur within relatively steady magnetic field and plasma conditions, and are detected more often away from the neutral sheet. On the other hand, high-speed bulk flows are well represented by a single drifting population and have their peak occurrence rate at the neutral sheet. Bulk flows are generally accompanied by large magnetic field fluctuations and sudden increase of energetic (up to 0.5 MeV) particle fluxes. They are often (but not always) associated with magnetic field dipolarization and plasma temperature enhancements. Little or no temperature enhancements are observed in cases where the spacecraft resides near the neutral sheet before the arrival of bursty bulk flows, suggesting that temperature enhancements seen in other bulk flow events may in part be a spatial effect instead of true heating of the plasma. Bulk flows are perpendicular to the magnetic field when detected at the neutral sheet but have a large field-aligned component at higher magnetic latitudes. Field-aligned bulk flows and field-aligned beams are similar in terms of their velocity moments and may occur at the same magnetic latitudes but are easily distinguishable based on their ion distributions. We have used our categorization of bulk flow and field-aligned beam events to search for the optimal moment-based selection criteria to distinguish bulk flows from beams. We found that no single moment-based parameter or threshold can serve to cleanly separate beam from bulk flow distributions because a range of values of these parameters exists where both types of fast flows are observed. We found perpendicular flow speed v? > 250 km/s and plasma ?xy (based on the x and y components of the magnetic field) > 2 to be the optimal moment-based bulk flow selection criteria because they eliminate ˜95% of beam events while retaining ˜60% of bulk flow events. Finally, a previously reported dawn-dusk asymmetry in the occurrence of bursty bulk flows, with most events occurring in the premidnight sector, is confirmed by our survey. Field-aligned beams, on the other hand, have no dawn-dusk bias.

Raj, Arjun; Phan, Tai; Lin, Robert P.; Angelopoulos, V.

2002-12-01

423

Secondary electron induced asymmetry in capacitively coupled plasmas  

NASA Astrophysics Data System (ADS)

Using a simple analytical model, together with a 1D particle-in-cell simulation, we show that it is possible to generate an asymmetric plasma response in a sinusoidally excited, geometrically symmetric, capacitively coupled plasma (CCP). The asymmetric response is produced using rf electrodes of differing materials, and hence different secondary electron emission coefficients. This asymmetry in the emission coefficients can produce a significant, measurable dc bias voltage (Vbias/Vrf ˜ 0-0.2), together with an asymmetry in the plasma density profiles and ion flux to each electrode. The dc bias formation can be understood from a particle-flux balance applied to each electrode, and results from two main effects: (1) the larger effective ion flux at each electrode due to the emission of secondary electrons and (2) ion-flux multiplication within the sheath due to ionization from these emitted secondary electrons. By making use of an empirical fit to the simulation data, the possibility of non-invasively estimating secondary electron emission coefficients in CCP systems is discussed.

Lafleur, T.; Chabert, P.; Booth, J. P.

2013-04-01

424

Self-consistent electron transport in collisional plasmas  

SciTech Connect

A self-consistent scheme has been developed to model electron transport in evolving plasmas of arbitrary classical collisionality. The electrons and ions are treated as either multiple donor-cell fluids, or collisional particles-in-cell. Particle suprathermal electrons scatter off ions, and drag against fluid background thermal electrons. The background electrons undergo ion friction, thermal coupling, and bremsstrahlung. The components move in self-consistent advanced E-fields, obtained by the Implicit Moment Method, which permits ..delta..t >> ..omega../sub p//sup -1/ and ..delta..x >> lambda/sub D/ - offering a 10/sup 2/ - 10/sup 3/-fold speed-up over older explicit techniques. The fluid description for the background plasma components permits the modeling of transport in systems spanning more than a 10/sup 7/-fold change in density, and encompassing contiguous collisional and collisionless regions. Results are presented from application of the scheme to the modeling of CO/sub 2/ laser-generated suprathermal electron transport in expanding thin foils, and in multi-foil target configurations.

Mason, R.J.

1982-01-01

425

Langmuir probe measurement of electron temperature in high-pressure plasmas  

Microsoft Academic Search

The effect upon measurements of electron temperature in high-pressure plasmas of the cooling of the plasma electrons by the inherently cold layer of gas surrounding the probe has been investigated. Theoretical considerations indicate that while cooling effects can be substantial, accurate electron temperature measurements can be obtained if the probe is sufficiently small or is moved through the plasma at

R. M. Clements; P. R. Smy

1973-01-01

426

Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a)  

E-print Network

Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a) V. I. Kolobov are derived. In many cases, even though in a semi-infinite plasma heating exists, in a bounded plasma plasma CCP ,1 this mechanism is now widely discussed in application to inductively coupled plasmas ICP ,2

Kaganovich, Igor