Reactions of BBr(n)(+) (n = 0--2) at fluorinated and hydrocarbon self-assembled monolayer surfaces: observations of chemical selectivity in ion--surface scattering.

Science.gov (United States)

Wade, N; Shen, J; Koskinen, J; Cooks, R G

2001-07-01

Ion-surface reactions involving BBr(n)(+) (n = 0--2) with a fluorinated self-assembled monolayer (F-SAM) surface were investigated using a multi-sector scattering mass spectrometer. Collisions of the B(+) ion yield BF(2)(+) at threshold energy with the simpler product ion BF(+)* appearing at higher collision energies and remaining of lower abundance than BF(2)(+) at all energies examined. In addition, the reactively sputtered ion CF(+) accompanies the formation of BF(2)(+) at low collision energies. These results stand in contrast with previous data on the ion-surface reactions of atomic ions with the F-SAM surface in that the threshold and most abundant reaction products in those cases involved the abstraction of a single fluorine atom. Gas-phase enthalpy data are consistent with BF(2)(+) being the thermodynamically favored product. The fact that the abundance of BF(2)(+) is relatively low and relatively insensitive to changes in collision energy suggests that this reaction proceeds through an entropically demanding intermediate at the vacuum--surface interface, one which involves interaction of the B(+) ion simultaneously with two fluorine atoms. By contrast with the reaction of B(+), the odd-electron species BBr(+)* reacts with the F-SAM surface to yield an abundant single-fluorine abstraction product, BBrF(+). Corresponding gas-phase ion--molecule experiments involving B(+) and BBr(+)* with C(6)F(14) also yield the products BF(+)* and BF(2)(+), but only in extremely low abundances and with no preference for double fluorine abstraction. Ion--surface reactions were also investigated for BBr(n)(+) (n = 0-2) with a hydrocarbon self-assembled monolayer (H-SAM) surface. Reaction of the B(+) ion and dissociative reactions of BBr(+)* result in the formation of BH(2)(+), while the thermodynamically less favorable product BH(+)* is not observed. Collisions of BBr(2)(+) with the H-SAM surface yield the dissociative ion-surface reaction products, BBrH(+) and BBrCH(3

EVOLUTION OF THE RELATIONSHIPS BETWEEN HELIUM ABUNDANCE, MINOR ION CHARGE STATE, AND SOLAR WIND SPEED OVER THE SOLAR CYCLE

International Nuclear Information System (INIS)

Kasper, J. C.; Stevens, M. L.; Korreck, K. E.; Maruca, B. A.; Kiefer, K. K.; Schwadron, N. A.; Lepri, S. T.

2012-01-01

The changing relationships between solar wind speed, helium abundance, and minor ion charge state are examined over solar cycle 23. Observations of the abundance of helium relative to hydrogen (A He ≡ 100 × n He /n H ) by the Wind spacecraft are used to examine the dependence of A He on solar wind speed and solar activity between 1994 and 2010. This work updates an earlier study of A He from 1994 to 2004 to include the recent extreme solar minimum and broadly confirms our previous result that A He in slow wind is strongly correlated with sunspot number, reaching its lowest values in each solar minima. During the last minimum, as sunspot numbers reached their lowest levels in recent history, A He continued to decrease, falling to half the levels observed in slow wind during the previous minimum and, for the first time observed, decreasing even in the fastest solar wind. We have also extended our previous analysis by adding measurements of the mean carbon and oxygen charge states observed with the Advanced Composition Explorer spacecraft since 1998. We find that as solar activity decreased, the mean charge states of oxygen and carbon for solar wind of a given speed also fell, implying that the wind was formed in cooler regions in the corona during the recent solar minimum. The physical processes in the coronal responsible for establishing the mean charge state and speed of the solar wind have evolved with solar activity and time.

A-type Stellar Abundances: A Corollary to Herschel Observations of Debris Disks

Science.gov (United States)

Draper, Zachary H.; Matthews, Brenda; Venn, Kim; Lambert, David; Kennedy, Grant; Sitnova, Tatyana

2018-04-01

In order to assess the relationship between metallicity and exoplanetary systems, we compare the abundances of AF-type main-sequence stars with debris disk properties assessed using Herschel observations of an unbiased survey of nearby stars. Hot stars are not as commonly observed, given their unique constraints in data reduction, lack of metal lines, and “astrophysical noise” from rotation speed. Here, we address that deficiency using new and archival spectra of 83 AF-type stars. We measure the abundances of a few species in addition to Fe in order to classify the stars with Ap/Am or Lambda Boo signatures. Lambda Boo stars have a chemical signature of solar-abundant volatile species and sub-solar refractory abundances that is hypothesized to be altered by the pollution of volatiles. Overall, we see no correlation between debris disks and metallicity, primarily because the sample size is cut significantly when using only reliable fits to the spectroscopic data. The abundance measured from the Mg II 4481 blend is a useful diagnostic because it can be reliably measured at large v·sin(i) and is found to be lower around stars with bright debris disks. We find that Lambda Boo stars have brighter debris disks compared to a bias-free sample of AF stars. The trend with disk brightness and Mg abundances suggests pollution effects can be significant and used as a marker for the stability of planetary systems. We explore trends with other species, such as with the C/O ratios, but are significantly limited by the low number of reliable detections.

Observation of ion-acoustic rarefaction solitons in a multicomponent plasma with negative ions

International Nuclear Information System (INIS)

Ludwig, G.O.; Ferreira, J.L.; Nakamura, Y.

1984-01-01

The propagation of ion-acoustic solitons in a plasma with negative ions has been observed. For sufficiently large concentration of negative ions, applied rarefactive (negative) voltage pulses break up into solitons, whereas compressive pulses evolve into wave trains, with exactly the opposite behavior as that for a plasma composed only of positive ions. There is a critical value of the negative-ion concentration for which a finite-amplitude pulse propagates without steepening

Structure and dynamics of highly charged heavy ions studied with the electron beam ion trap in Tokyo

International Nuclear Information System (INIS)

Nakamura, Nobuyuki; Hu, Zhimin; Watanabe, Hirofumi; Li, Yueming; Kato, Daiji; Currell, Fred J.; Tong Xiaomin; Watanabe, Tsutomu; Ohtani, Shunsuke

2011-01-01

In this paper, we present the structure and the dynamics of highly charged heavy ions studied through dielectronic recombination (DR) observations performed with the Tokyo electron beam ion trap. By measuring the energy dependence of the ion abundance ratio in the trap at equilibrium, we have observed DR processes for open shell systems very clearly. Remarkable relativistic effects due to the generalized Breit interaction have been clearly shown in DR for highly charged heavy ions. We also present the first result for the coincidence measurement of two photons emitted from a single DR event.

Ion cyclotron waves: Direct compariosn between ground-based measurements and observations in the source region

International Nuclear Information System (INIS)

Perraut, S.; Gendrin, R.; Roux, A.; de Villedary, C.

1984-01-01

Simultaneous measurements of ion cyclotron waves (ICW's) were performed on GEOS spacecraft and in the vicinity of their magnetic footprints with the French Mobile station. The detailed comparison between the two sets of data shown that while ICW's having F + gyrofrequency at the equator, generally propagate to the ground, only 50% of those generated above F/sub He/ can reach the ground station. It is shown that these results are in good agreement with the conclusions that Rauch and Roux [1982] drew on the basis of measurements reported by Young et al 1981]. In an He + -rich plasma, ICW's with F>F/sub He/ suffer a reflection where the frequency locally matches the local bi-ion hybrid frequency. We extend the calculations of Rauch and Roux and calculate, as a function of the He + concentration, the tunneling of ICW's through the stopband induced by the presence of minor He + ions. It is shown that the transmission coefficient strongly depends upon the wave frequency for a given He + abundance ratio. The results obtained are shown to be supported by existing observations

Observations of Two-Stream Ion Wave Instability

DEFF Research Database (Denmark)

Christoffersen, G.B.; Prahm, L.P.

1973-01-01

A double‐humped ion velocity distribution function is produced in a Q‐machine cesium plasma. When the plasma becomes unstable, a growing wave amplitude and a characteristic change in the phase velocity of a grid‐excited ion‐acoustic wave are observed.......A double‐humped ion velocity distribution function is produced in a Q‐machine cesium plasma. When the plasma becomes unstable, a growing wave amplitude and a characteristic change in the phase velocity of a grid‐excited ion‐acoustic wave are observed....

Helicon plasma ion temperature measurements and observed ion cyclotron heating in proto-MPEX

Science.gov (United States)

Beers, C. J.; Goulding, R. H.; Isler, R. C.; Martin, E. H.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Kafle, N.; Rapp, J.

2018-01-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) linear plasma device is a test bed for exploring and developing plasma source concepts to be employed in the future steady-state linear device Material Plasma Exposure eXperiment (MPEX) that will study plasma-material interactions for the nuclear fusion program. The concept foresees using a helicon plasma source supplemented with electron and ion heating systems to reach necessary plasma conditions. In this paper, we discuss ion temperature measurements obtained from Doppler broadening of spectral lines from argon ion test particles. Plasmas produced with helicon heating alone have average ion temperatures downstream of the Helicon antenna in the range of 3 ± 1 eV; ion temperature increases to 10 ± 3 eV are observed with the addition of ion cyclotron heating (ICH). The temperatures are higher at the edge than the center of the plasma either with or without ICH. This type of profile is observed with electrons as well. A one-dimensional RF antenna model is used to show where heating of the plasma is expected.

Terrestrial aurora: astrophysical laboratory for anomalous abundances in stellar systems

Directory of Open Access Journals (Sweden)

I. Roth

2014-02-01

Full Text Available The unique magnetic structure of the terrestrial aurora as a conduit of information between the ionosphere and magnetosphere can be utilized as a laboratory for physical processes at similar magnetic configurations and applied to various evolutionary phases of the solar (stellar system. The most spectacular heliospheric abundance enhancement involves the 3He isotope and selective heavy elements in impulsive solar flares. In situ observations of electromagnetic waves on active aurora are extrapolated to flaring corona in an analysis of solar acceleration processes of 3He, the only element that may resonate strongly with the waves, as well as heavy ions with specific charge-to-mass ratios, which may resonate weaker via their higher gyroharmonics. These results are applied to two observed anomalous astrophysical abundances: (1 enhanced abundance of 3He and possibly 13C in the late stellar evolutionary stages of planetary nebulae; and (2 enhanced abundance of the observed fossil element 26Mg in meteorites as a decay product of radioactive 26Al isotope due to interaction with the flare-energized 3He in the early solar system.

Positive and negative ion mode comparison for the determination of DNA/peptide noncovalent binding sites through the formation of "three-body" noncovalent fragment ions.

Science.gov (United States)

Brahim, Bessem; Tabet, Jean-Claude; Alves, Sandra

2018-02-01

Gas-phase fragmentation of single strand DNA-peptide noncovalent complexes is investigated in positive and negative electrospray ionization modes.Collision-induced dissociation experiments, performed on the positively charged noncovalent complex precursor ions, have confirmed the trend previously observed in negative ion mode, i.e. a high stability of noncovalent complexes containing very basic peptidic residues (i.e. R > K) and acidic nucleotide units (i.e. Thy units), certainly incoming from the existence of salt bridge interactions. Independent of the ion polarity, stable noncovalent complex precursor ions were found to dissociate preferentially through covalent bond cleavages of the partners without disrupting noncovalent interactions. The resulting DNA fragment ions were found to be still noncovalently linked to the peptides. Additionally, the losses of an internal nucleic fragment producing "three-body" noncovalent fragment ions were also observed in both ion polarities, demonstrating the spectacular salt bridge interaction stability. The identical fragmentation patterns (regardless of the relative fragment ion abundances) observed in both polarities have shown a common location of salt bridge interaction certainly preserved from solution. Nonetheless, most abundant noncovalent fragment ions (and particularly three-body ones) are observed from positively charged noncovalent complexes. Therefore, we assume that, independent of the preexisting salt bridge interaction and zwitterion structures, multiple covalent bond cleavages from single-stranded DNA/peptide complexes rely on an excess of positive charges in both electrospray ionization ion polarities.

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

Energy Technology Data Exchange (ETDEWEB)

Nilsson, H.; Waara, M.; Arvelius, S.; Yamauchi, M.; Lundin, R. [Inst. of Space Physics, Kiruna (Sweden); Marghitu, O. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); Inst. for Space Sciences, Bucharest (Romania); Bouhram, M. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); CETP-CNRS, Saint-Maur (France); Hobara, Y. [Inst. of Space Physics, Kiruna (Sweden); Univ. of Sheffield, Sheffield (United Kingdom); Reme, H.; Sauvaud, J.A.; Dandouras, I. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France); Balogh, A. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom); Kistler, L.M. [Univ. of New Hampshire, Durham (United States); Klecker, B. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); Carlson, C.W. [Space Science Lab., Univ. of California, Berkeley (United States); Bavassano-Cattaneo, M.B. [Ist. di Fisica dello Spazio Interplanetario, Roma (Italy); Korth, A. [Max-Planck-Inst. fuer Sonnensystemforschung, Katlenburg-Lindau (Germany)

2006-07-01

The results of a statistical study of oxygen ion outflow using cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H{sup +}) and oxygen ions (O{sup +}) from 3 years (2001-2003) of spring orbits (January to May) have been used. The altitudes covered were mainly in the range 5-12 R{sub E} geocentric distance. It was found that O{sup +} is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O{sup +} parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O{sup +} parallel bulk velocities in excess of 60 km s{sup -1} were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O{sup +} the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H{sup +} and O{sup +} was found to typically be close to the same throughout the observation interval when the H{sup +} bulk velocity was calculated for all pitch-angles. When the H{sup +} bulk velocity was calculated for upward moving particles only the H{sup +} parallel bulk velocity was typically higher than that of O{sup +}. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O{sup +} ions dominates. The thermal velocity of O{sup +} was always well below that of H{sup +}. Thus perpendicular energization that is more effective for O{sup +} takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

Directory of Open Access Journals (Sweden)

H. Nilsson

2006-05-01

Full Text Available The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H+ and oxygen ions (O+ from 3 years (2001-2003 of spring orbits (January to May have been used. The altitudes covered were mainly in the range 5–12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s-1 were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel acceleration. In particular centrifugal acceleration of the outflowing ions, which may

Observation of distorted Maxwell-Boltzmann distribution of epithermal ions in LHD

Science.gov (United States)

Ida, K.; Kobayashi, T.; Yoshinuma, M.; Akiyama, T.; Tokuzawa, T.; Tsuchiya, H.; Itoh, K.; LHD Experiment Group

2017-12-01

A distorted Maxwell-Boltzmann distribution of epithermal ions is observed associated with the collapse of energetic ions triggered by the tongue shaped deformation. The tongue shaped deformation is characterized by the plasma displacement localized in the toroidal, poloidal, and radial directions at the non-rational magnetic flux surface in toroidal plasma. Moment analysis of the ion velocity distribution measured with charge exchange spectroscopy is studied in order to investigate the impact of tongue event on ion distribution. A clear non-zero skewness (3rd moment) and kurtosis (4th moment -3) of ion velocity distribution in the epithermal region (within three times of thermal velocity) is observed after the tongue event. This observation indicates the clear evidence of the distortion of ion velocity distribution from Maxwell-Boltzmann distribution. This distortion from Maxwell-Boltzmann distribution is observed in one-third of plasma minor radius region near the plasma edge and disappears in the ion-ion collision time scale.

Ion hole formation and nonlinear generation of electromagnetic ion cyclotron waves: THEMIS observations

Science.gov (United States)

Shoji, Masafumi; Miyoshi, Yoshizumi; Katoh, Yuto; Keika, Kunihiro; Angelopoulos, Vassilis; Kasahara, Satoshi; Asamura, Kazushi; Nakamura, Satoko; Omura, Yoshiharu

2017-09-01

Electromagnetic plasma waves are thought to be responsible for energy exchange between charged particles in space plasmas. Such an energy exchange process is evidenced by phase space holes identified in the ion distribution function and measurements of the dot product of the plasma wave electric field and the ion velocity. We develop a method to identify ion hole formation, taking into consideration the phase differences between the gyromotion of ions and the electromagnetic ion cyclotron (EMIC) waves. Using this method, we identify ion holes in the distribution function and the resulting nonlinear EMIC wave evolution from Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. These ion holes are key to wave growth and frequency drift by the ion currents through nonlinear wave-particle interactions, which are identified by a computer simulation in this study.

Ion-molecule reactions in alkynes

International Nuclear Information System (INIS)

Lifshitz, C.; Weiss, M.

1980-01-01

Fragment ions from 1,5-hexadiyne are trapped in an electron space charge and allowed to react with the neutral 1,5-hexadiyne present. The reactivities are similar to those of ions of the same elementary formulae in the benzene system. Secondary ions of major abundance observed are, in decreasing order of importance: C 10 H + 8 , C 9 H + 7 , C 12 H + 8 , C 12 H + 9 and C 7 H + 7 . In contrast to the benzene system, the ion C 12 H + 11 is of minor importance. (orig.)

Paul Trapping of Radioactive 6He+ Ions and Direct Observation of Their β Decay

International Nuclear Information System (INIS)

Flechard, X.; Lienard, E.; Mery, A.; Rodriguez, D.; Ban, G.; Durand, D.; Duval, F.; Herbane, M.; Labalme, M.; Mauger, F.; Naviliat-Cuncic, O.; Velten, Ph.; Thomas, J. C.

2008-01-01

We demonstrate that abundant quantities of short-lived β unstable ions can be trapped in a novel transparent Paul trap and that their decay products can directly be detected in coincidence. Low energy 6 He + (807 ms half-life) ions were extracted from the SPIRAL source at GANIL, then decelerated, cooled, and bunched by means of the buffer gas cooling technique. More than 10 8 ions have been stored over a measuring period of six days, and about 10 5 decay coincidences between the beta particles and the 6 Li ++ recoiling ions have been recorded. The technique can be extended to other short-lived species, opening new possibilities for trap assisted decay experiments

HERSCHEL OBSERVATIONS REVEAL ANOMALOUS MOLECULAR ABUNDANCES TOWARD THE GALACTIC CENTER

Energy Technology Data Exchange (ETDEWEB)

Sonnentrucker, P. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Neufeld, D. A.; Indriolo, N. [Physics and Astronomy Department, Johns Hopkins University, Baltimore, MD 21218 (United States); Gerin, M.; De Luca, M. [LERMA-LRA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure, UPMC and UCP, 24 rue Lhomond, F-75231, Paris Cedex 05 (France); Lis, D. C. [Astronomy Department, California Institute of Technology, Pasadena, CA 91125 (United States); Goicoechea, J. R., E-mail: sonnentr@stsci.edu [Centro de Astrobiologia, CSIC/INTA, E-28850, Madrid (Spain)

2013-01-20

We report the Herschel detections of hydrogen fluoride (HF) and para-water (p-H{sub 2}O) in gas intercepting the sight lines to two well-studied molecular clouds in the vicinity of the Sgr A complex: G-0.02-0.07 (the {sup +}50 km s{sup -1} cloud{sup )} and G-0.13-0.08 (the {sup +}20 km s{sup -1} cloud{sup )}. Toward both sight lines, HF and water absorption components are detected over a wide range of velocities covering {approx}250 km s{sup -1}. For all velocity components with V{sub LSR} > -85 km s{sup -1}, we find that the HF and water abundances are consistent with those measured toward other sight lines probing the Galactic disk gas. The velocity components with V{sub LSR} {<=} -85 km s{sup -1}, which are known to trace gas residing within {approx}200 pc of the Galactic center, however, exhibit water vapor abundances with respect to HF at least a factor three higher than those found in the Galactic disk gas. Comparison with CH data indicates that our observations are consistent with a picture where HF and a fraction of the H{sub 2}O absorption arise in diffuse molecular clouds showing Galactic disk-like abundances while the bulk of the water absorption arises in warmer (T {>=} 400 K) diffuse molecular gas for V{sub LSR} {<=} -85 km s{sup -1}. This diffuse Interstellar Medium (ISM) phase has also been recently revealed through observations of CO, HF, H{sup +}{sub 3}, and H{sub 3}O{sup +} absorption toward other sight lines probing the Galactic center inner region.

Ion spectral structures observed by the Van Allen Probes

Science.gov (United States)

Ferradas, C.; Zhang, J.; Spence, H. E.; Kistler, L. M.; Larsen, B.; Reeves, G. D.; Skoug, R. M.; Funsten, H. O.

2015-12-01

During the last decades several missions have recorded the presence of dynamic spectral features of energetic ions in the inner magnetosphere. Previous studies have reported single "nose-like" structures occurring alone and simultaneous nose-like structures (up to three). These ion structures are named after the characteristic shapes of energy bands or gaps in the energy-time spectrograms of in situ measured ion fluxes. They constitute the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. The HOPE mass spectrometer onboard the Van Allen Probes measures energetic hydrogen, helium, and oxygen ions near the inner edge of the plasma sheet, where these ion structures are observed. We present a statistical study of nose-like structures, using 2-years measurements from the HOPE instrument. The results provide important details about the spatial distribution (dependence on geocentric distance), spectral features of the structures (differences among species), and geomagnetic conditions under which these structures occur.

Abundance patterns in the interstellar medium of early-type galaxies observed with Suzaku

International Nuclear Information System (INIS)

Konami, Saori; Matsushita, Kyoko; Tamagawa, Toru; Nagino, Ryo

2014-01-01

We have analyzed 17 early-type galaxies, 13 ellipticals and 4 S0 galaxies, observed with Suzaku, and investigated metal abundances (O, Mg, Si, and Fe) and abundance ratios (O/Fe, Mg/Fe, and Si/Fe) in the interstellar medium (ISM). The emission from each on-source region, which is four times the effective radius, r e , is reproduced with one-temperature (1T) or two-temperature (2T) thermal plasma models as well as a multi-temperature model, using APEC plasma code version 2.0.1. The multi-temperature model gave almost the same abundances and abundance ratios with the 1T or 2T models. The weighted averages of the O, Mg, Si, and Fe abundances of all the sample galaxies derived from the multi-temperature model fits are 0.83 ± 0.04, 0.93 ± 0.03, 0.80 ± 0.02, and 0.80 ± 0.02 solar, respectively, in solar units according to the solar abundance table by Lodders in 2003. These abundances show no significant dependence on the morphology and environment. The systematic differences in the derived metal abundances between versions 2.0.1 and 1.3.1 of the APEC plasma codes were investigated. The derived O and Mg abundances in the ISM agree with the stellar metallicity within an aperture with a radius of one r e derived from optical spectroscopy. From these results, we discuss the past and present Type Ia supernova rates and star formation histories in early-type galaxies.

Observations of transverse ion acceleration in the topside auroral ionosphere

International Nuclear Information System (INIS)

Garbe, G.P.; Arnoldy, R.L.; Moore, T.E.; Kintner, P.M.; Vago, J.L.

1992-01-01

Data obtained from a sounding rocket flight which reached an apogee of 927 km and passed through several auroral arcs are reported. During portions of the flight when the rocket was not in an energetic auroral structure, the ion data are fit to a Maxwellian function which yields the plasma parameters. Throughout the middle portion of the flight when above 700 km altitude, ion distributions having a superthermal tail were measured. These ion distributions generally coexisted with a cold thermal core distribution and peaked at pitch angles slightly greater than 90 degree, which identifies them as conic distributions. These ions can be modeled using a bi-Maxwellian distribution function with a perpendicular (to B) temperature about 10 times greater than the parallel temperature of 0.15 eV. When the rocket was immersed in energetic auroral electron precipitation, two other ion distributions were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed continuously in these arcs. The characteristic perpendicular energy of the transversely bulk heated ions reached as high as 3 eV compared to typically less than 0.4 eV during nonauroral times. Cold ions flowing down the magnetic field were also continuously observed when the rocket was immersed in auroral electron precipitation and had downward speeds between 3 and 5 km/s. If one balances electric and collisional forces, these speeds translate to an electric field pointing into the atmosphere of magnitude 0.01 mV/m. A close correlation between auroral electron precipitation, measured electrostatic oxygen cyclotron waves, cold downflowing ions and transversely bulk heated ions will be shown

Inner Source Pickup Ions Observed by Ulysses

Science.gov (United States)

Gloeckler, G.

2016-12-01

The existence of an inner source of pickup ions close to the Sun was proposed in order to explain the unexpected discovery of C+ in the high-speed polar solar wind. Here I report on detailed analyses of the composition and the radial and latitudinal variations of inner source pickup ions measured with the Solar Wind Ion Composition Spectrometer on Ulysses from 1991 to 1998, approaching and during solar minimum. We find that the C+ intensity drops off with radial distance R as R-1.53, peaks at mid latitudes and drops to its lowest value in the ecliptic. Not only was C+ observed, but also N+, O+, Ne+, Na+, Mg+, Ar+, S+, K+, CH+, NH+, OH+, H2O+, H3O+, MgH+, HCN+, C2H4+, SO+ and many other singly-charged heavy ions and molecular ions. The measured velocity distributions of inner source pickup C+ and O+ indicate that these inner source pickup ions are most likely produced by charge exchange, photoionization and electron impact ionization of neutrals close to the Sun (within 10 to 30 solar radii). Possible causes for the unexpected latitudinal variations and the neutral source(s) producing the inner source pickup ions as well as plausible production mechanisms for inner source pickup ions will be discussed.

Rare earth element abundances in presolar SiC

Science.gov (United States)

Ireland, T. R.; Ávila, J. N.; Lugaro, M.; Cristallo, S.; Holden, P.; Lanc, P.; Nittler, L.; Alexander, C. M. O'D.; Gyngard, F.; Amari, S.

2018-01-01

Individual isotope abundances of Ba, lanthanides of the rare earth element (REE) group, and Hf have been determined in bulk samples of fine-grained silicon carbide (SiC) from the Murchison CM2 chondrite. The analytical protocol involved secondary ion mass spectrometry with combined high mass resolution and energy filtering to exclude REE oxide isobars and Si-C-O clusters from the peaks of interest. Relative sensitivity factors were determined through analysis of NIST SRM reference glasses (610 and 612) as well as a trace-element enriched SiC ceramic. When normalised to chondrite abundances, the presolar SiC REE pattern shows significant deficits at Eu and Yb, which are the most volatile of the REE. The pattern is very similar to that observed for Group III refractory inclusions. The SiC abundances were also normalised to s-process model predictions for the envelope compositions of low-mass (1.5-3 M⊙) AGB stars with close-to-solar metallicities (Z = 0.014 and 0.02). The overall trace element abundances (excluding Eu and Yb) appear consistent with the predicted s-process patterns. The depletions of Eu and Yb suggest that these elements remained in the gas phase during the condensation of SiC. The lack of depletion in some other moderately refractory elements (like Ba), and the presence of volatile elements (e.g. Xe) indicates that these elements were incorporated into SiC by other mechanisms, most likely ion implantation.

Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

Directory of Open Access Journals (Sweden)

H. Nilsson

2006-05-01

Full Text Available The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H⁺ and oxygen ions (O⁺ from 3 years (2001-2003 of spring orbits (January to May have been used. The altitudes covered were mainly in the range 5–12 R_E geocentric distance. It was found that O⁺ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O⁺ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O⁺ parallel bulk velocities in excess of 60 km s^-1 were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O⁺ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H⁺ and O⁺ was found to typically be close to the same throughout the observation interval when the H⁺ bulk velocity was calculated for all pitch-angles. When the H⁺ bulk velocity was calculated for upward moving particles only the H⁺ parallel bulk velocity was typically higher than that of O⁺. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O⁺ ions dominates. The thermal velocity of O⁺ was always well below that of H⁺. Thus perpendicular energization that is more effective for O⁺ takes place, but this is not enough to explain the close to similar parallel velocities. Further

In-situ observation system for dual ion irradiation damage

International Nuclear Information System (INIS)

Furuno, Shigemi; Hojou, Kiichi; Otsu, Hitoshi; Sasaki, T.A.; Izui, Kazuhiko; Tukamoto, Tetsuo; Hata, Takao.

1992-01-01

We have developed an in-situ observation and analysis system during dual ion beam irradiation in an electron microscope. This system consists of an analytical electron microscope of JEM-4000FX type equipped with a parallel EELS and an EDS attachments and linked with two sets of ion accelerators of 40 kV. Hydrogen and helium dual-ion beam irradiation experiments were performed for SiC crystals. The result of dual-ion beam irradiation was compared with those of helium and hydrogen single ion irradiations. It is clearly seen that the dual-ion irradiation has the effect of suppressing bubble formation and growth in comparison with the case of single helium ion irradiation. (author)

Interstellar abundances in dense, moderately reddened lines of sight. I. Observational evidence for density-dependent depletion

International Nuclear Information System (INIS)

Joseph, C.L.; Snow, T.P. Jr.; Seab, C.G.; Crutcher, R.M.; NASA, Ames Research Center, Moffett Field, CA; Illinois Univ., Urbana)

1986-01-01

The nature of dust-gas interactions, which are capable of modifying the size distribution of interstellar grains and thus causing changes in the selective extinction curve, are investigated through depletion studies. The gaseous abundances of 15 elements have been determined for several lines of sight toward moderately reddened stars, each having an anomalous extinction curve and a large abundance of cyanogen (CN). The basic result of this study is that certain elements appear to deplete preferentially in interstellar clouds having a large abundance of CN. Since CN is a sensitive indicator of the interstellar spatial density, the data might suggest that the unique pattern of enhanced depletion observed here represents the best observational evidence of accretion. 107 references

Composition of heavy ions in solar energetic particle events

International Nuclear Information System (INIS)

Fan, C.Y.; Gloeckler, G.

1983-01-01

Recent advances in determining the elemental, charge state, and isotopic composition of approximatelt 1 to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations. Average values of relative abundances measured in a large number of SEP events were found to be roughly energy independent in the approx. 1 to approx. 20 MeV per nucleon range, and showed a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs revealed the surprisingly common presence of energetic He(+) along with heavy ion with typically coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events showed these to be consistent with the universal composition except for the puzzling overabundance of the SEP(22)Ne/(20)Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of (3)He rich, heavy ion rich and carbon poor SEP events, along with direct measurements of the ionization states of SEPs provided essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production

Cometary pick-up ions observed near Giacobini-Zinner

Science.gov (United States)

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

1986-01-01

The number and energy density of cometary water-group ions observed near Comet Giacobini-Zinner are derived using the rest-frame distribution functions. The data reveal that density profiles of inbound and outbound passes and their shape correlate with pick-up ion production model predictions. The lose rate and production rate of water-group cometary molecules calculated from predicted and measured density profiles are 2 x 10 to the -6th/sec and 2.6 x 10 to the 28th/sec respectively. The shapes of the distribution functions are examined to study the solar wind/cometary ions interaction process.

MESSENGER observations of the composition of Mercury's ionized exosphere and plasma environment.

Science.gov (United States)

Zurbuchen, Thomas H; Raines, Jim M; Gloeckler, George; Krimigis, Stamatios M; Slavin, James A; Koehn, Patrick L; Killen, Rosemary M; Sprague, Ann L; McNutt, Ralph L; Solomon, Sean C

2008-07-04

The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 +/- 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 +/- 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere.

Ion Demagnetization in the Magnetopause Current Layer Observed by MMS

Science.gov (United States)

Wang, Shan; Chen, Li-Jen; Hesse, Michael; Gershman, Daniel J.; Dorelli, John; Giles, Barbara; Torbert, Roy B.; Pollock, Craig J.; Lavraud, Benoit; Strangeway, Robert;

Infinite-Dimensional Boundary Observer for Lithium-Ion Battery State Estimation

DEFF Research Database (Denmark)

Hasan, Agus; Jouffroy, Jerome

2017-01-01

This paper presents boundary observer design for state-of-charge (SOC) estimation of lithium-ion batteries. The lithium-ion battery dynamics are governed by thermal-electrochemical principles, which mathematically modeled by partial differential equations (PDEs). In general, the model is a reaction......-diffusion equation with time-dependent coefficients. A Luenberger observer is developed using infinite-dimensional backstepping method and uses only a single measurement at the boundary of the battery. The observer gains are computed by solving the observer kernel equation. A numerical example is performed to show...

A new type of ion injection event observed by Viking

International Nuclear Information System (INIS)

Yamauchi, M.; Lundin, R.; Woch, J.; Shapshak, M.; Elphinstone, R.

1993-01-01

The authors report on the observation of a new type of ion injection event observed by Viking spacecraft several degrees equatorward of the cusp. Its signature seems considerably different than previously reported events such as flux transfer events or impulsive or transient magnetosheath plasma injection events. It consists of low energy ions, as the pattern drops sharply above 100 to 200 eV

Novel Faraday cup for the simultaneous observation and measurement of ion-beam currents

International Nuclear Information System (INIS)

Wei, C.; Seidman, D.N.

1977-01-01

A novel Faraday cup is described which allows the simultaneous observation and measurement of ion-beam currents. The Faraday cup is constructed around a Galileo channel electron multiplier array (CEMA), which serves as the basis of an internal image intensification system (a gain of >10 4 ) for the observation of the ion beam; the CEMA also acts as a collector for the ion current which is measured by a Keithley 602 electrometer. The ion current is integrated by a simple and inexpensive dosimeter; the electronic circuit for the dosimeter is described. The application of the Faraday cup to the observation and measurement of a 30-keV Ar + ion beam is presented as an illustrative example. We have also employed this Faraday cup to observe and measure 30-keV Cr + , Mo + , or W + , and 18-keV Au + ion beams employed for the in situ irradiation of field-ion microscope specimens

Product ion isotopologue pattern: A tool to improve the reliability of elemental composition elucidations of unknown compounds in complex matrices.

Science.gov (United States)

Kaufmann, A; Walker, S; Mol, G

2016-04-15

Elucidation of the elemental compositions of unknown compounds (e.g., in metabolomics) generally relies on the availability of accurate masses and isotopic ratios. This study focuses on the information provided by the abundance ratio within a product ion pair (monoisotopic versus the first isotopic peak) when isolating and fragmenting the first isotopic ion (first isotopic mass spectrum) of the precursor. This process relies on the capability of the quadrupole within the Q Orbitrap instrument to isolate a very narrow mass window. Selecting only the first isotopic peak (first isotopic mass spectrum) leads to the observation of a unique product ion pair. The lighter ion within such an isotopologue pair is monoisotopic, while the heavier ion contains a single carbon isotope. The observed abundance ratio is governed by the percentage of carbon atoms lost during the fragmentation and can be described by a hypergeometric distribution. The observed carbon isotopologue abundance ratio (product ion isotopologue pattern) gives reliable information regarding the percentage of carbon atoms lost in the fragmentation process. It therefore facilitates the elucidation of the involved precursor and product ions. Unlike conventional isotopic abundances, the product ion isotopologue pattern is hardly affected by isobaric interferences. Furthermore, the appearance of these pairs greatly aids in cleaning up a 'matrix-contaminated' product ion spectrum. The product ion isotopologue pattern is a valuable tool for structural elucidation. It increases confidence in results and permits structural elucidations for heavier ions. This tool is also very useful in elucidating the elemental composition of product ions. Such information is highly valued in the field of multi-residue analysis, where the accurate mass of product ions is required for the confirmation process. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Cluster observations of trapped ions interacting with magnetosheath mirror modes

Directory of Open Access Journals (Sweden)

J. Soucek

2011-06-01

Full Text Available Mirror modes are among the most intense low frequency plasma wave phenomena observed in the magnetosheaths of magnetized planets. They appear as large amplitude non-propagating fluctuations in the magnetic field magnitude and plasma density. These structures are widely accepted to represent a non-linear stage of the mirror instability, dominant in plasmas with large ion beta and a significant ion temperature anisotropy T⊥/T∥>1. It has long been recognized that the mirror instability both in the linear and non-linear stage is a kinetic process and that the behavior of resonant particles at small parallel velocities is crucial for its development and saturation. While the dynamics of the instability and the effect of trapped particles have been studied extensively in theoretical models and numerical simulations, only spurious observations of the trapped ions were published to date. In this work we used data from the Cluster spacecraft to perform the first detailed experimental study of ion velocity distribution associated with mirror mode oscillations. We show a conclusive evidence for the predicted cooling of resonant ions at small parallel velocities and heating of trapped ions at intermediate pitch angles.

An automated single ion hit at JAERI heavy ion microbeam to observe individual radiation damage

International Nuclear Information System (INIS)

Kamiya, Tomihiro; Sakai, Takuro; Naitoh, Yutaka; Hamano, Tsuyoshi; Hirao, Toshio

1999-01-01

Microbeam scanning and a single ion hit technique have been combined to establish an automated beam positioning and single ion hit system at the JAERI Takasaki heavy ion microbeam system. Single ion irradiation on preset points of a sample in various patterns can be performed automatically in a short period. The reliability of the system was demonstrated using CR-39 nuclear track detectors. Single ion hit patterns were achieved with a positioning accuracy of 2 μm or less. In measurement of single event transient current using this system, the reduction of the pulse height by accumulation of radiation damages was observed by single ion injection to the same local areas. This technique showed a possibility to get some quantitative information about the lateral displacement of an individual radiation effect in silicon PIN photodiodes. This paper will give details of the irradiation system and present results from several experiments

Novel Faraday cup for the simultaneous observation and measurement of ion-beam currents

International Nuclear Information System (INIS)

Wei, C.Y.; Seidman, D.N.

1977-07-01

The Faraday cup is constructed around a Galileo channel electron multiplier array (CEMA) which serves as the basis of an internal image intensification system (a gain of greater than 10 4 ) for the observation of the ion beam; the CEMA also acts as a collector for the ion cured by a Keithley 602 electrometer. The ion current is integrated by a simple and inexpensive dosimeter; the electronic circuit for the dosimeter is described. The application of the Faraday cup to the observation and measurement of a 30 keV Ar + ion beam is presented as an illustrative example. This Faraday cup was also employed to observe and measure 30 keV Cr + , Mo + or W + and 18 keV Au + ion beams employed for the in-situ irradiation of field-ion microscope specimens

Characteristics of solar and heliospheric ion populations observed near earth

International Nuclear Information System (INIS)

Gloeckler, G.

1984-01-01

The composition and spectra of ions in solar-energetic-particle and energetic-storm-particle events, of diffuse ions upstream of the earth bow shock, and of ions in deep-geomagnetic-tail plasmoids are characterized in a summary of in situ observations. Data are presented in graphs and tables, and remarkable similarities are noted in the distribution functions of the heliospheric ion populations. The solar wind, acting through acceleration mechanisms associated with shocks and turbulence, is identified as the major plasma source of suprathermal and energetic particles. 33 references

Temporal Evolution of Ion Spectral Structures During a Geomagnetic Storm: Observations and Modeling

Science.gov (United States)

Ferradas, C. P.; Zhang, J.-C.; Spence, H. E.; Kistler, L. M.; Larsen, B. A.; Reeves, G. D.; Skoug, R. M.; Funsten, H. O.

2018-01-01

Using the Van Allen Probes/Helium, Oxygen, Proton, and Electron mass spectrometer, we perform a case study of the temporal evolution of ion spectral structures observed in the energy range of 1 to 50 keV throughout the geomagnetic storm of 2 October 2013. The ion spectral features are observed near the inner edge of the plasma sheet and are signatures of fresh transport from the plasma sheet into the inner magnetosphere. We find that the characteristics of the ion structures are determined by the intensity of the convection electric field. Prior to the beginning of the storm, the plasma sheet inner edge exhibits narrow nose spectral structures that vary little in energy across L values. Ion access to the inner magnetosphere during these times is limited to the nose energy bands. As convection is enhanced and large amounts of plasma are injected from the plasma sheet during the main phase of the storm, ion access occurs at a wide energy range, as no nose structures are observed. As the magnetosphere recovers from the storm, single noses and then multiple noses are observed once again. We use a model of ion drift and losses due to charge exchange to simulate the ion spectra and gain insight into the main observed features.

Molecular Ions in Ion Upflows and their Effects on Hot Atomic Oxygen Production

Science.gov (United States)

Foss, V.; Yau, A. W.; Shizgal, B.

2017-12-01

We present new direct ion composition observations of molecular ions in auroral ion upflows from the CASSIOPE Enhanced Polar Outflow Probe (e-POP). These observed molecular ions are N2+, NO+, and possibly O2+, and are found to occur at all e-POP altitudes starting at about 400 km, during auroral substorms and the different phases of magnetic storms, sometimes with upflow velocities exceeding a few hundred meters per second and abundances of 5-10%. The dissociative recombination of both O2+ and NO+ was previously proposed as an important source of hot oxygen atoms in the topside thermosphere [Hickey et al., 1995]. We investigate the possible effect of the observed molecular ions on the production of hot oxygen atoms in the storm and substorm-time auroral thermosphere. We present numerical solutions of the Boltzmann equation for the steady-state oxygen energy distribution function, taking into account both the production of the hot atoms and their subsequent collisional relaxation. Our result suggests the formation of a hot oxygen population with a characteristic temperature on the order of 0.3 eV and constituting 1-5% of the oxygen density near the exobase. We discuss the implication of this result in the context of magnetosphere-ionosphere-thermosphere coupling.

ISEE/IMP Observations of simultaneous upstream ion events

International Nuclear Information System (INIS)

Mitchel, D.G.; Roelof, E.C.; Sanderson, T.R.; Reinhard, R.; Wenzel, K.

1983-01-01

Propagation of upstream energetic (50--200 keV) ions is analyzed in sixteen events observed simulataneously by solid state detectors on ISEE 3 at approx.200 R/sub E/ and on IMP 8 at approx.35 R/sub E/ from the earth. Conclusions are based on comparisons of the pitch angle distributions observed at the two spacecraft and transformed into the solar wind frame. They are beamlike at ISEE 3 and are confined to the outward hemisphere. When IMP 8 is furtherest from the bow shock, they are also usually beamlike, or hemispheric. However, when IMP 8 is closer to the bow shock, pancakelike distributions are observed. This systematic variation in the IMP 8 pitch angle distributions delimits a scattering region l< or approx. =14 R/sub E/ upstream of the earth's bow shock (l measured along the interplanetary magnetic field) that dominates ion propagation, influences the global distribution of fluxes in the foreshock, and may play a role in acceleration of the ions. When IMP 8 is beyond lapprox.15 R/sub E/, the propagation appears to be essentially scatter-free between IMP 8 and ISEE 3; this is deduced from the absence of earthward fluxes at IMP 8 as well as the tendency for the spin-averaged fluxes to be comparable at the two spacecraft

Auroral ion acceleration from lower hybrid solitary structures: A summary of sounding rocket observations

Science.gov (United States)

Lynch, K. A.; Arnoldy, R. L.; Kintner, P. M.; Schuck, P.; Bonnell, J. W.; Coffey, V.

In this paper we present a review of sounding rocket observations of the ion acceleration seen in nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two-point measurements of the Amicist mission. From this collection of observations we will demonstrate the following characteristics of transverse acceleration of ions (TAI) in lower hybrid solitary structures (LHSS). The ion acceleration process is narrowly confined to 90° pitch angle, in spatially confined regions of up to a few hundred meters across B. The acceleration process does not affect the thermal core of the ambient distribution and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. This precludes observation with these data of any nonlinear feedback between the ion acceleration and the existence or evolution of the density irregularities on which these LHSS events grow. Within the LHSS region the acceleration process creates a high-energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases, the pitch angles of the accelerated tail ions are elevated above perpendicular; that is, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: its altitude dependence can be modeled with the parameter B2/ne, and it is highest in regions of intense VLF activity. The cumulative ion outflow from these LHSS TAI is

Ion acoustic waves and related plasma observations in the solar wind

International Nuclear Information System (INIS)

Gurnett, D.A.; Marsch, E.; Pilipp, W.; Schwenn, R.; Rosenbauer, H.

1979-01-01

This paper presents an investigation of solar wind ion acoustic waves and their relationship to the macroscopic and microscopic characteristics of the solar wind plasma. Comparisons with the overall solar wind corotational structure show that the most intense ion acoustic waves usually occur in the low-velocity regions ahead of high-speed solar wind streams. Of the detailed plasma parameters investigated, the ion acoustic wave intensities are found to be most closely correlated with the electron to proton temperature ratio T/sub e//T/sub p/ and with the electron heat flux. Investigations of the detailed electron and proton distribution functions also show that the ion acoustic waves usually occur in regions with highly non-Maxwellian distributions characteristic of double-proton streams. The distribution functions for the double-proton streams are usually not resolved into two clearly defined peaks, but rather they appear as a broad shoulder on the main proton distribution. Two main mechanisms, an electron heat flux instability and a double-ion beam instability, are considered for generating the ion-acoustic-like waves observed in the solar wind. Both mechanisms have favorable and unfavorable features. The electron heat flux mechanism can account for the observed waves at moderate to large ratios of T/sub e//T/sub p/ but has problems when T/sub e//T/sub p/ is small, as sometimes occurs. The ion beam instability appears to provide more flexibility on the T/sub e//T/sub p/ ratio; however detailed comparisons using observed distribution functions indicate that the ion beam mode is usually stable. Possible resolutions of these difficulties are discussed

Observation of multiphoton detachment of the H/sup -/ ion

International Nuclear Information System (INIS)

Tang, C.Y.; Harris, P.G.; Mohagheghi, A.H.; Los Alamos National Laboratory, Los Alamos, New Mexico 87545; Cohen Mechanical Design, Broomall, Pennsylvania 19008; The University of Connecticut, Storrs, Connecticut 06268; Western Washington University, Bellingham, Washington 98225)

1989-01-01

We have observed nonresonant multiphoton electron detachment of H/sup -/ ions in moderately intense (a few tens of GW/cm 2 ) laser fields. A well-collimated beam of H/sup -/ ions with an energy of 581 MeV was intersected by focused 10.6-μm radiation from a pulsed CO 2 laser. The center-of-mass photon energy was tuned using the relativistic Doppler shift so that the minimum number of simultaneous photons required for electron detachment ranged from three to sixteen. Definite signals were observed for the minimum photon number ranging from three to eight. Our preliminary results show evidence for structure in the relative total cross section

Observational restrictions on sodium and aluminium abundance variations in evolution of the galaxy

Science.gov (United States)

Menzhevitski, V. S.; Shimanskaya, N. N.; Shimansky, V. V.; Sakhibullin, N. A.

2013-07-01

In this paper we construct and analyze the uniform non-LTE distributions of the aluminium ([Al/Fe]-[Fe/H]) and sodium ([Na/Fe]-[Fe/H]) abundances in the sample of 160 stars of the disk and halo of our Galaxy with metallicities within -4.07 ≤ [Fe/H] ≤ 0.28. The values of metallicity [Fe/H] and microturbulence velocity ξ turb indices are determined from the equivalent widths of the Fe II and Fe I lines. We estimated the sodium and aluminium abundances using a 21-level model of the Na I atom and a 39-level model of the Al I atom. The resulting LTE distributions of [Na/Fe]-[Fe/H] and [Al/Fe]-[Fe/H] do not correspond to the theoretical predictions of their evolution, suggesting that a non-LTE approach has to be applied to determine the abundances of these elements. The account of non-LTE corrections reduces by 0.05-0.15 dex the abundances of sodium, determined from the subordinate lines in the stars of the disk with [Fe/H] ≥ -2.0, and by 0.05-0.70 dex (with a strong dependence on metallicity) the abundances of [Na/Fe], determined by the resonance lines in the stars of the halo with [Fe/H] ≤ -2.0. The non-LTE corrections of the aluminium abundances are strictly positive and increase from 0.0-0.1 dex for the stars of the thin disk (-0.7 ≤ [Fe/H] ≤ 0.28) to 0.03-0.3 dex for the stars of the thick disk (-1.5 ≤ [Fe/H] ≤ -0.7) and 0.06-1.2 dex for the stars of the halo ([Fe/H] ≤ -2.0). The resulting non-LTE abundances of [Na/Fe] reveal a scatter of individual values up to Δ[Na/Fe] = 0.4 dex for the stars of close metallicities. The observed non-LTE distribution of [Na/Fe]-[Fe/H] within 0.15 dex coincides with the theoretical distributions of Samland and Kobayashi et al. The non-LTE aluminium abundances are characterized by a weak scatter of values (up to Δ[Al/Fe] = 0.2 dex) for the stars of all metallicities. The constructed non-LTE distribution of [Al/Fe]-[Fe/H] is in a satisfactory agreement to 0.2 dex with the theoretical data of Kobayashi et al., but

Abundance analysis from the UV spectrum of the He-w star HR 6000

International Nuclear Information System (INIS)

Castelli, F.; Cornachin, M.; Morossi, C.; Hack, M.

1984-01-01

A high resolution spectrum of the He-w star HR 6000, covering the SW and LW regions, has been analysed. A fully line-blanketed model atmosphere with parameters Tsub(e) = 14000 K, log g = 4, microturbulence xi = 2 km.s -1 has been adopted. This model is in agreement with the photometric data and yields the same abundance for the Fe II and Fe III ions. By using the synthetic spectrum method we compared the observed lines with the computed ones. We find an underabundance of C, Al Si, Mg, S, Sc, Co, Ni, Zn and an overabundance of Be, P, Cl, Ti, Mn, Fe, Ga. B, O, Cr have nearly solar abundances. Circumstellar (or interstellar) shortward-shifted components affect the strong resonance lines of the following ions: C II(1) lambda 1334.535, O I(2) lambda 1302.074,Mg II(1) lambda 2795.523, lambda 2802.698, Si II(3) lambda 1304.369, Fe II(1) lambda 2599.395

The abundance determination in a stellar atmosphere. Pt. 1

International Nuclear Information System (INIS)

Dumont, S.; Heidmann, N.; Pecker, J.C.; Jefferies, J.T.

1975-01-01

It is shown that the classical LTE analysis of an atomic spectrum of a solar-like star leads to values of the abundance A which may be different from the real values. Various uncertainties affect the results derived from neutral lines. However, proper selection of the observational data, for instance use of ion lines, can lead, in similar cases at least, to good values of A. These conclusions concern the solar-like case; however, they emphasize that, in all cases, the effect of departures from LTE needs very careful discussion. (orig.) [de

Fragmentation of organic ions bearing fixed multiple charges observed in MALDI MS.

Science.gov (United States)

Lou, Xianwen; Li, Bao; de Waal, Bas F M; Schill, Jurgen; Baker, Matthew B; Bovee, Ralf A A; van Dongen, Joost L J; Milroy, Lech-Gustav; Meijer, E W

2018-01-01

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) was used to analyze a series of synthetic organic ions bearing fixed multiple charges. Despite the multiple intrinsic charges, only singly charged ions were recorded in each case. In addition to the pseudo-molecular ions formed by counterion adduction, deprotonation and electron capture, a number of fragment ions were also observed. Charge splitting by fragmentation was found to be a viable route for charge reduction leading to the formation of the observed singly charged fragment ions. Unlike multivalent metal ions, organic ions can rearrange and/or fragment during charge reduction. This fragmentation process will evidently complicate the interpretation of the MALDI MS spectrum. Because MALDI MS is usually considered as a soft ionization technique, the fragment ion peaks can easily be erroneously interpreted as impurities. Therefore, the awareness and understanding of the underlying MALDI-induced fragmentation pathways is essential for a proper interpretation of the corresponding mass spectra. Due to the fragment ions generated during charge reduction, special care should be taken in the MALDI MS analysis of multiply charged ions. In this work, the possible mechanisms by which the organic ions bearing fixed multiple charges fragment are investigated. With an improved understanding of the fragmentation mechanisms, MALDI TOF MS should still be a useful technique for the characterization of organic ions with fixed multiple charges. Copyright © 2017 John Wiley & Sons, Ltd.

Observations of heavy ions in the auroral region during magnetic storms

International Nuclear Information System (INIS)

Gotselyuk, Yu.V.; Kuznetsov, S.N.; Kudela, K.

1984-01-01

The distribution and dynamics of precipitating protons, α-particles and C-, N-, O nuclei during the strong geomagnetic storms of October 27 and December 2, 1977 is studied from the data of polar ''Interkosmos-17'' satillite. The observed heavy ion fluxes are compared with the data obtained with ''Explorer-45'' and ''S3-3'' satellites. The scattering mechanism is suggested which enables one to explain the heavy ions observations at low altitudes

Benchmarking of the Oxford Nanopore MinION sequencing for quantitative and qualitative assessment of cDNA populations.

Science.gov (United States)

Oikonomopoulos, Spyros; Wang, Yu Chang; Djambazian, Haig; Badescu, Dunarel; Ragoussis, Jiannis

2016-08-24

To assess the performance of the Oxford Nanopore Technologies MinION sequencing platform, cDNAs from the External RNA Controls Consortium (ERCC) RNA Spike-In mix were sequenced. This mix mimics mammalian mRNA species and consists of 92 polyadenylated transcripts with known concentration. cDNA libraries were generated using a template switching protocol to facilitate the direct comparison between different sequencing platforms. The MinION performance was assessed for its ability to sequence the cDNAs directly with good accuracy in terms of abundance and full length. The abundance of the ERCC cDNA molecules sequenced by MinION agreed with their expected concentration. No length or GC content bias was observed. The majority of cDNAs were sequenced as full length. Additionally, a complex cDNA population derived from a human HEK-293 cell line was sequenced on an Illumina HiSeq 2500, PacBio RS II and ONT MinION platforms. We observed that there was a good agreement in the measured cDNA abundance between PacBio RS II and ONT MinION (rpearson = 0.82, isoforms with length more than 700bp) and between Illumina HiSeq 2500 and ONT MinION (rpearson = 0.75). This indicates that the ONT MinION can sequence quantitatively both long and short full length cDNA molecules.

Observations of two distinct populations of bow shock ions in the upstream solar wind

International Nuclear Information System (INIS)

Gosling, J.T.; Asbridge, J.; Bame, S.J.; Paschmann, G.; Sckopke, N.

1978-01-01

Observations upstream of the earth's bow shock with the LASL/MPI fast plasma experiments on ISEE 1 and 2 reveal the presence of two distinct and mutually exclusive populations of low energy (< or approx. =40keV) ions apparently accelerated at the bow shock. The first of these, the ''reflected'' population, is characterized by 1) sharply peaked spectra seldom extending much above approx. 10 keV/ion and 2) relatively collimated flow coming from the direction of the shock. On the other hand, the ''diffuse'' ions are distinguished by relatively flat energy spectra above approx. 10 keV and broad angular distributions. They are by far the most commonly observed upstream ion event. A close causal association is suggested between the diffuse ion population in the upstream solar wind and energetic plasma ions observed within the magnetosheath

Dual ion beam irradiation system for in situ observation with electron microscope

International Nuclear Information System (INIS)

Tsukamoto, Tetuo; Hojou, Kiiti; Furuno, Sigemi; Otsu, Hitosi; Izui, Kazuhiko.

1993-01-01

We have developed a new in situ observation system for dynamic processes under dual ion beam irradiation. The system consists of a modified 400 keV analytical electron microscope (JEOL, JEM-4000FX) and two 40 kV ion beam accelerators. This system allows evaluation of microscopic changes of structure and chemical bonding state of materials in the dynamic processes under two kinds of ion beam irradiations, that is required for the simulation test of the first wall of nuclear fusion reactors onto which He + , H + , and H 2 + ions are irradiated simultaneously. These two ion accelerators were equipped symmetrically both sides of the electron microscope and individually controlled. Each ion beam extracted from a duo-plasmatron ion gun is bent downward by an angle of 30deg with a mass-separating magnet, and introduced into specimen chamber of the electron microscope. Inside the specimen chamber the beam is deflected again by an angle of 30deg with an electrostatic prism so as to be incident on the specimen surface. Finally, two ion beams from both side are incident on the specimen surface at an angle of 60deg. The maximum ion current density of helium is more than 250μA/cm 2 at the specimen at an ion energy of 17 keV. Images of the electron microscope during dual ion beam irradiation are observed through a TV camera and recorded with a VTR. (author)

Bi-Abundance Ionisation Structure of the Wolf-Rayet Planetary Nebula PB 8

Science.gov (United States)

Danehkar, A.

2018-01-01

The planetary nebula PB 8 around a [WN/WC]-hybrid central star is one of planetary nebulae with moderate abundance discrepancy factors (ADFs 2-3), which could be an indication of a tiny fraction of metal-rich inclusions embedded in the nebula (bi-abundance). In this work, we have constructed photoionisation models to reproduce the optical and infrared observations of the planetary nebula PB 8 using a non-LTE stellar model atmosphere ionising source. A chemically homogeneous model initially used cannot predict the optical recombination lines. However, a bi-abundance model provides a better fit to most of the observed optical recombination lines from N and O ions. The metal-rich inclusions in the bi-abundance model occupy 5.6% of the total volume of the nebula, and are roughly 1.7 times cooler and denser than the mean values of the surrounding nebula. The N/H and O/H abundance ratios in the metal-rich inclusions are 1.0 and 1.7 dex larger than the diffuse warm nebula, respectively. To reproduce the Spitzer spectral energy distribution of PB 8, dust grains with a dust-to-gas ratio of 0.01 (by mass) were also included. It is found that the presence of metal-rich inclusions can explain the heavy element optical recombination lines, while a dual-dust chemistry with different grain species and discrete grain sizes likely produces the infrared continuum of this planetary nebula. This study demonstrates that the bi-abundance hypothesis, which was examined in a few planetary nebulae with large abundance discrepancies (ADFs > 10), could also be applied to those typical planetary nebulae with moderate abundance discrepancies.

The MOSDEF Survey: Direct Observational Constraints on the Ionizing Photon Production Efficiency, ξ ion, at z ∼ 2

Science.gov (United States)

Shivaei, Irene; Reddy, Naveen A.; Siana, Brian; Shapley, Alice E.; Kriek, Mariska; Mobasher, Bahram; Freeman, William R.; Sanders, Ryan L.; Coil, Alison L.; Price, Sedona H.; Fetherolf, Tara; Azadi, Mojegan; Leung, Gene; Zick, Tom

2018-03-01

We combine Hα and Hβ spectroscopic measurements and UV photometry for a sample of 673 galaxies from the MOSDEF survey to constrain hydrogen-ionizing photon production efficiencies ({ξ }ion}) at z = 1.4–2.6. We find = 25.06 (25.34), assuming the Calzetti (SMC) curve for the UV dust correction and a scatter of 0.28 dex in the {ξ }ion} distribution. After accounting for observational uncertainties and variations in dust attenuation, we conclude that the remaining scatter in {ξ }ion} is likely dominated by galaxy-to-galaxy variations in stellar populations, including the slope and upper-mass cutoff of the initial mass function, stellar metallicity, star formation burstiness, and stellar evolution (e.g., single/binary star evolution). Moreover, {ξ }ion} is elevated in galaxies with high ionization states (high [O III]/[O II]) and low oxygen abundances (low [N II]/Hα and high [O III]/Hβ) in the ionized ISM. However, {ξ }ion} does not correlate with the offset from the z ∼ 0 star-forming locus in the BPT diagram, suggesting no change in the hardness of the ionizing radiation accompanying the offset from the z ∼ 0 sequence. We also find that galaxies with blue UV spectral slopes ( =-2.1) have {ξ }ion} elevated by a factor of ∼2 relative to the average {ξ }ion} of the sample ( =-1.4). If these blue galaxies are similar to those at z > 6, our results suggest that a lower Lyman-continuum escape fraction is required for galaxies to maintain reionization, compared to the canonical {ξ }ion} predictions from stellar population models. Furthermore, we demonstrate that even with robustly dust-corrected Hα, the UV dust attenuation can cause on average a ∼0.3 dex systematic uncertainty in {ξ }ion} calculations.

Solar Ion Processing of Itokawa Grains: Reconciling Model Predictions with Sample Observations

Science.gov (United States)

Christoffersen, Roy; Keller, L. P.

2014-01-01

Analytical TEM observations of Itokawa grains reported to date show complex solar wind ion processing effects in the outer 30-100 nm of pyroxene and olivine grains. The effects include loss of long-range structural order, formation of isolated interval cavities or "bubbles", and other nanoscale compositional/microstructural variations. None of the effects so far described have, however, included complete ion-induced amorphization. To link the array of observed relationships to grain surface exposure times, we have adapted our previous numerical model for progressive solar ion processing effects in lunar regolith grains to the Itokawa samples. The model uses SRIM ion collision damage and implantation calculations within a framework of a constant-deposited-energy model for amorphization. Inputs include experimentally-measured amorphization fluences, a Pi steradian variable ion incidence geometry required for a rotating asteroid, and a numerical flux-versus-velocity solar wind spectrum.

A unique airborne observation. [Martian atmospheric temperature and abundances from occultation of Epsilon Geminorum

Science.gov (United States)

Elliot, J. L.; Dunham, E.; Church, C.

1976-01-01

The occultation of 3rd magnitude Epsilon Geminorum by Mars was observed using a 36-inch telescope equipped with a photoelectric photometer at the bent Cassegrain focus, carried aboard the Kuiper Airborne Observatory at altitudes up to 45,000 feet. Scintillation from the earth's atmosphere was greatly reduced in comparison with ground observations. The observations clearly show the central flash, caused by the symmetrical refraction of light by the atmosphere of Mars. The data are being analyzed to obtain temperature profiles and to assess the relative abundance of argon and carbon dioxide in the atmosphere of the planet.

Composition of heavy ions in solar energetic particle events

International Nuclear Information System (INIS)

Fan, C.Y.; Gloeckler, G.

1983-01-01

The elemental, charge state, and isotopic composition of approximately 1 to 20 MeV per nucleon ions in solar energetic particle (SEP) events was determined and current understanding of the nature of solar and interplanetary processes which may explain the observations are outlined. The composition within individual SEP events may vary both with time and energy, and will in general be different from that in other SEP events. Average values of relative abundances measured in a large number of SEP events, however are found to be roughly energy independent in the approximately 1 to approximately 20 MeV per nucleon range, and show a systematic deviation from photospheric abundances which seem to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs have revealed the surprisingly common presence of energetic He(+) along with heavy ions with typical coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events show these to be consistent with the universal composition except for the puzzling overabundance of the SEP Ne-22 relative to this isotopes ratio in the solar wind

The Observational Determination of the Primordial Helium Abundance: a Y2K Status Report

Science.gov (United States)

Skillman, Evan D.

I review observational progress and assess the current state of the determination of the primordial helium abundance, Yp. At present there are two determinations with non-overlapping errors. My impression is that the errors have been under-estimated in both studies. I review recent work on errors assessment and give suggestions for decreasing systematic errors in future studies.

Effects of Solvent and Ion Source Pressure on the Analysis of Anabolic Steroids by Low Pressure Photoionization Mass Spectrometry.

Science.gov (United States)

Liu, Chengyuan; Zhu, Yanan; Yang, Jiuzhong; Zhao, Wan; Lu, Deen; Pan, Yang

2017-04-01

Solvent and ion source pressure were two important factors relating to the photon induced ion-molecule reactions in low pressure photoionization (LPPI). In this work, four anabolic steroids were analyzed by LPPI mass spectrometry. Both the ion species present and their relative abundances could be controlled by switching the solvent and adjusting the ion source pressure. Whereas M •+ , MH + , [M - H 2 O] + , and solvent adducts were observed in positive LPPI, [M - H] - and various oxidation products were abundant in negative LPPI. Changing the solvent greatly affected formation of the ion species in both positive and negative ion modes. The ion intensities of the solvent adduct and oxygen adduct were selectively enhanced when the ion source pressure was elevated from 68 to 800 Pa. The limit of detection could be decreased by increasing the ion source pressure. Graphical Abstract ᅟ.

Effects of Solvent and Ion Source Pressure on the Analysis of Anabolic Steroids by Low Pressure Photoionization Mass Spectrometry

Science.gov (United States)

Liu, Chengyuan; Zhu, Yanan; Yang, Jiuzhong; Zhao, Wan; Lu, Deen; Pan, Yang

2017-04-01

Solvent and ion source pressure were two important factors relating to the photon induced ion-molecule reactions in low pressure photoionization (LPPI). In this work, four anabolic steroids were analyzed by LPPI mass spectrometry. Both the ion species present and their relative abundances could be controlled by switching the solvent and adjusting the ion source pressure. Whereas M•+, MH+, [M - H2O]+, and solvent adducts were observed in positive LPPI, [M - H]- and various oxidation products were abundant in negative LPPI. Changing the solvent greatly affected formation of the ion species in both positive and negative ion modes. The ion intensities of the solvent adduct and oxygen adduct were selectively enhanced when the ion source pressure was elevated from 68 to 800 Pa. The limit of detection could be decreased by increasing the ion source pressure.

Observations on abundance of bluntnose sixgill sharks, Hexanchus griseus, in an urban waterway in Puget Sound, 2003-2005.

Science.gov (United States)

Griffing, Denise; Larson, Shawn; Hollander, Joel; Carpenter, Tim; Christiansen, Jeff; Doss, Charles

2014-01-01

The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed but poorly understood large, apex predator. Anecdotal reports of diver-shark encounters in the late 1990's and early 2000's in the Pacific Northwest stimulated interest in the normally deep-dwelling shark and its presence in the shallow waters of Puget Sound. Analysis of underwater video documenting sharks at the Seattle Aquarium's sixgill research site in Elliott Bay and mark-resight techniques were used to answer research questions about abundance and seasonality. Seasonal changes in relative abundance in Puget Sound from 2003-2005 are reported here. At the Seattle Aquarium study site, 45 sixgills were tagged with modified Floy visual marker tags, along with an estimated 197 observations of untagged sharks plus 31 returning tagged sharks, for a total of 273 sixgill observations recorded. A mark-resight statistical model based on analysis of underwater video estimated a range of abundance from a high of 98 sharks seen in July of 2004 to a low of 32 sharks seen in March of 2004. Both analyses found sixgills significantly more abundant in the summer months at the Seattle Aquarium's research station.

Recording of heavy ion tracks in silicates. Application to the determination of the abundance of ultra-heavy elements in old solar cosmic radiation

International Nuclear Information System (INIS)

Duraud, J.-P.

1978-12-01

The aim of this thesis is to determine the abundance A(Z) and energy spectrum of the elements of atomic number Z present in cosmic radiation, by means of fossil traces recorded in moon and meteorite minerals. The difficulties due amongst other things to natural annealing are examined in detail in part one, of this paper, the outcome being a thorough study of the processes responsible for the formation, chemical attack and annealing of heavy ion tracks. Part two describes an original approach used here and consisting of a combined analysis as a function of annealing for a given track, of the microscopic structure of the latent track and its attack rate. Part three uses the new rules established beforehand to propose a new method of studying the UH ion (Z>30) to VH ion (20 [fr

Observation of large-amplitude ion acoustic wave in microwave-plasma interaction experiments

International Nuclear Information System (INIS)

Yugami, Noboru; Nishida, Yasushi

1997-01-01

Large amplitude ion acoustic wave, which is not satisfied with a linear dispersion relationship of ion acoustic wave, is observed in microwave-plasma interaction experiments. This ion acoustic wave is excited around critical density layer and begins to propagate to underdense region with a phase velocity one order faster than sound velocity C s , which is predicted by the linear theory, the phase velocity and the wave length of the wave decreases as it propagates. Finally, it converges to C s and strongly dumps. Diagnostic by the Faraday cup indicates that this ion acoustic wave is accompanied with a hot ion beam. (author)

Simulations and observations of plasma depletion, ion composition, and airglow emissions in two auroral ionospheric depletion experiments

International Nuclear Information System (INIS)

Yau, A.W.; Whalen, B.A.; Harris, F.R.; Gattinger, R.L.; Pongratz, M.B.; Bernhardt, P.A.

1985-01-01

In an ionospheric depletion experiment where chemically reactive vapors such as H 2 O and CO 2 are injected into the O + dominant F region to accelerate the plasma recombination rate and to reduce the plasma density, the ion composition in the depleted region is modified, and photometric emissions are produced. We compare in situ ion composition, density, and photometric measurements from two ionospheric depletion experiments with predictions from chemical modeling. The two injections, Waterhole I and III, were part of an auroral perturbation experiment and occurred in different ambient conditions. In both injections a core region of greater than fivefold plasma depletion was observed over roughly-equal5-km diameter within seconds of the injection, surrounded by an outer region of less drastic and slower depletion. In Waterhole I the plasma density was depleted tenfold over a 30-km diamter region after 2 min. The ambient O + density was drastically reduced, and the molecular O + 2 abundance was enhanced fivehold in the depletion region. OH airglow emission associated with the depletion was observed with a peak emission intensity of roughly-equal1 kR. In Waterhole III the ambient density was a decade lower, and the plasma depletion was less drastic, being twofold over 30 km after 2 min. The airglow emissions were also much less intense and below measurement sensitivity (30 R for the OH 306.4-nm emission; 50 R for the 630.0-nm emission)

Possibilities for direct optical observation of negative hydrogen ions in ion beam plasma sources via Rayleigh or Thomson scattering

International Nuclear Information System (INIS)

Burgess, D.D.

1985-01-01

The possibilities of applying optical scattering techniques to the determination of H - concentrations in plasma sources relevant to negative ion beam generation are considered. Rayleigh scattering measurements for incident wavelengths just below the H - photoionization limit appear to be only just feasible experimentally. A more promising possibility is observation of the modification in a plasma containing negative ions of the collective ion-feature in Thomson scattering. Numerical predictions of the effects of H - concentration on the spectral distribution of the ion-feature are presented. (author)

Case Study of Ion Beams Observed By Cluster At Perigee

Science.gov (United States)

Sergeev, V.; Sauvaud, J.-A.; Perigee Beam Team

During substorms the short beams of ions in the keV-to-tens keV energy range are injected into the auroral flux tubes from the magnetotail (sometimes extending up to >100 keV energy) carrying the information on the source distance, scale-size and temporal history of plasma acceleration. We present observations with the CLUSTER crossing inward the auroral zone flux tubes at ~4Re distance near its perigee during the substorm activity on February 14, 2001. The ion beams cover the same region (poleward half) of the auroral oval where the low-energy ions are extracted from the ionosphere, and where the small-scale transient transverse Alfven waves are observed which carry predominantly the downward parallel Poynting flux into the ionosphere. The multiple beams were basically confirmed to be the transient effects, although some effects including the (spatial) velocity filter and the parallel electric fields (im- posed by quasineutrality requirement) may complicate the interpretation. The gener- ation region of ion beams is not limited to most poleward, newly-reconnected flux tubes; the beam generation region could extend across magnetic field inward by as much as >100km (if mapped to the ionosphere). Surprising variety of injection dis- tances observed nearly simultaneously (ranging between >60 Re and ~10 Re) have been inferred when using the full available energy and time resolution, with shorter injection distances be possibly associated with the flow braking process. The beam multiplicity often displays the apparent ~3 min quasiperiodicity inherent to the basic dissipation process, it was not yet explained by any substorm theory.

Stellar Oxygen Abundances

Science.gov (United States)

King, Jeremy

1994-04-01

This dissertation addresses several issues concerning stellar oxygen abundances. The 7774 {\\AA} O I triplet equivalent widths of Abia & Rebolo [1989, AJ, 347, 186] for metal-poor dwarfs are found to be systematically too high. I also argue that current effective temperatures used in halo star abundance studies may be ~150 K too low. New color-Teff relations are derived for metal-poor stars. Using the revised Teff values and improved equivalent widths for the 7774A O I triplet, the mean [O/Fe] ratio for a handful of halo stars is found to be +0.52 with no dependence on Teff or [Fe/H]. Possible cosmological implications of the hotter Teff scale are discussed along with additional evidence supporting the need for a higher temperature scale for metal-poor stars. Our Teff scale leads to a Spite Li plateau value of N(Li)=2.28 +/- 0.09. A conservative minimal primordial value of N(Li)=2.35 is inferred. If errors in the observations and models are considered, consistency with standard models of Big Bang nucleosynthesis is still achieved with this larger Li abundance. The revised Teff scale raises the observed B/Be ratio of HD 140283 from 10 to 12, making its value more comfortably consistent with the production of the observed B and Be by ordinary spallation. Our Teff values are found to be in good agreement with values predicted from both the Victoria and Yale isochrone color-Teff relations. Thus, it appears likely that no changes in globular cluster ages would result. Next, we examine the location of the break in the [O/Fe] versus [Fe/H] plane in a quantitative fashion. Analysis of a relatively homogeneous data set does not favor any unique break point in the range -1.7 /= -3), in agreement with the new results for halo dwarfs. We find that the gap in the observed [O/H] distribution, noted by Wheeler et al. [1989, ARAA, 27, 279], persists despite the addition of more O data and may betray the occurrence of a hiatus in star formation between the end of halo formation and

Observations of interplanetary energetic ion enhancements near magnetic sector boundaries

International Nuclear Information System (INIS)

Briggs, P.R.; Armstrong, T.P.

1984-01-01

We have examined all energetic medium nuclei (carbon, nitrogen, and oxygen) flux increases observed all the satellites IMP 7 and IMP 8 at 1 AU during Bartels rotations 1906-1974. After removing flare-related increases, the remaining 14 ''events'' were compared to interplanetary magnetic field and solar wind parameters. We have discovered a class of flux enhancements in which the ion increases occur close to the onset of magnetic sector boundary crossings. We interpret this observation as a facilitated access to 1 AU of energetic ions from the corona or chromopshere via the magnetic sector structure. It appears that this access is more significant for medium than for lighter nuclei, ''suggesting a possible charge- or rigidity-dependent transport mechanism

Feasibility of Observing and Characterizing Single Ion Strikes in Microelectronic Components

International Nuclear Information System (INIS)

Dingreville, Remi Philippe Michel; Hattar, Khalid Mikhiel; Bufford, Daniel Charles

2015-01-01

The transient degradation of semiconductor device performance under irradiation has long been an issue of concern. A single high-energy charged particle can degrade or permanently destroy the microelectronic component, potentially altering the course or function of the systems. Disruption of the the crystalline structure through the introduction of quasi-stable defect structures can change properties from semiconductor to conductor. Typically, the initial defect formation phase is followed by a recovery phase in which defect-defect or defect-dopant interactions modify the characteristics of the damaged structure. In this LDRD Express, in-situ ion irradiation transmission microscopy (TEM) in-situ TEM experiments combined with atomistic simulations have been conducted to determine the feasibility of imaging and characterizing the defect structure resulting from a single cascade in silicon. In-situ TEM experiments have been conducted to demonstrate that a single ion strike can be observed in Si thin films with nanometer resolution in real time using the in-situ ion irradiation transmission electron microscope (I 3 TEM). Parallel to this experimental effort, ion implantation has been numerically simulated using Molecular Dynamics (MD). This numerical framework provides detailed predictions of the damage and follow the evolution of the damage during the first nanoseconds. The experimental results demonstrate that single ion strike can be observed in prototypical semiconductors.

Observations of strong ion-ion correlations in dense plasmas

Energy Technology Data Exchange (ETDEWEB)

Ma, T.; Fletcher, L.; Pak, A.; Chapman, D. A.; Falcone, R. W.; Fortmann, C.; Galtier, E.; Gericke, D. O.; Gregori, G.; Hastings, J.; Landen, O. L.; Le Pape, S.; Lee, H. J.; Nagler, B.; Neumayer, P.; Turnbull, D.; Vorberger, J.; White, T. G.; Wünsch, K.; Zastrau, U.; Glenzer, S. H.; Döppner, T.

2014-05-01

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ~3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4k=4Å-1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are however in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. We have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.

In-situ observations of the development of heavy-ion damage in semiconductors

International Nuclear Information System (INIS)

Jenkins, M.L.; Chandler, T.J.; Robertson, I.M.; Kirk, M.A.

1985-01-01

In-situ observations on ion-beam induced amorphisation of GaAs, GaP and Si are reported. Direct-impact amorphisation was found to occur in GaAs irradiated with 100-keV Xe + ions to low doses at low temperature (approx. 40K) in contrast to previous room temperature irradiations. In GaP and in silicon, where heavy projectiles do cause direct impact amorphisation at room temperature, the evolution of the damage structure with ion-dose was studied. The defect yield both in GaP irradiated with 100-keV Kr + ions and in Si irradiated with 100-keV Xe + ions was found to decrease monotonically with increasing dose over the dose range 10 15 to 10 17 ions m -2

Observations of Metallic Species in Mercury's Exosphere

Science.gov (United States)

Killen, Rosemary M.; Potter, Andrew E.; Vervack, Ronald J., Jr.; Bradley, E. Todd; McClintock, William E.; Anderson, Carrie M.; Burger, Matthew H.

2010-01-01

From observations of the metallic species sodium (Na), potassium (K), and magnesium (Mg) in Mercury's exosphere, we derive implications for source and loss processes. All metallic species observed exhibit a distribution and/or line width characteristic of high to extreme temperature - tens of thousands of degrees K. The temperatures of refractory species, including magnesium and calcium, indicate that the source process for the atoms observed in the tail and near-planet exosphere are consistent with ion sputtering and/or impact vaporization of a molecule with subsequent dissociation into the atomic form. The extended Mg tail is consistent with a surface abundance of 5-8% Mg by number, if 30% of impact-vaporized Mg remains as MgO and half of the impact vapor condenses. Globally, ion sputtering is not a major source of Mg, but locally the sputtered source can be larger than the impact vapor source. We conclude that the Na and K in Mercury's exosphere can be derived from a regolith composition similar to that of Luna 16 soil (or Apollo 17 orange glass), in which the abundance by number is 0.0027 (0.0028) for Na and 0.0006 (0.0045) for K.

The composition of heavy ions in solar energetic particle events

International Nuclear Information System (INIS)

Fan, C.Y.

1984-01-01

The composition within individual SEP events may vary both with time and energy, and will in general be different from that in other SEP events. Average values of relative abundances measured in a large number of SEP events, however, are found to be roughly energy independent in the proportional1 to proportional20 MeV per nucleon range, and show a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs have revealed the surprisingly common presence of energetic He + along with heavy ions with typically coronal ionization states. High-resolution measurements of isotopic abundance ratios in a small number of SEP events show these to be consistent with the universal composition except for the puzzling overabundance of the SEP 22 Ne/ 20 Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of 3 He-rich, heavy-ion rich and carbon-poor SEP events, along with direct measurements of the ionization states of SEPs provide essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production. (orig./HM)

Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations

International Nuclear Information System (INIS)

Shukla, Anil; Bogdanov, Bogdan

2015-01-01

Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry (collision-induced dissociation with N 2 ). Singly as well as multiply charged clusters were formed in both positive and negative ion modes with the general formulae, (HCOOLi) n Li + , (HCOOLi) n Li m m+ , (HCOOLi) n HCOO − , and (HCOOLi) n (HCOO) m m− . Several magic number cluster (MNC) ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi) 3 Li + being the most abundant and stable cluster ion. Fragmentations of singly charged positive clusters proceed first by the loss of a dimer unit ((HCOOLi) 2 ) followed by the loss of monomer units (HCOOLi) although the former remains the dominant dissociation process. In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi) 3 Li + as the most abundant fragment ion at higher collision energies which then fragments further to dimer and monomer ions at lower abundances. In the negative ion mode, however, singly charged clusters dissociated via sequential loss of monomer units. Multiply charged clusters in both positive and negative ion modes dissociated mainly via Coulomb repulsion. Quantum chemical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the central lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhanced stability

MMS Observations of Ion-Scale Magnetic Island in the Magnetosheath Turbulent Plasma

Science.gov (United States)

Huang, S. Y.; Sahraoui, F.; Retino, A.; Contel, O. Le; Yuan, Z. G.; Chasapis, A.; Aunai, N.; Breuillard, H.; Deng, X. H.; Zhou, M.;

Comparison of Depletion Strategies for the Enrichment of Low-Abundance Proteins in Urine.

Science.gov (United States)

Filip, Szymon; Vougas, Konstantinos; Zoidakis, Jerome; Latosinska, Agnieszka; Mullen, William; Spasovski, Goce; Mischak, Harald; Vlahou, Antonia; Jankowski, Joachim

2015-01-01

Proteome analysis of complex biological samples for biomarker identification remains challenging, among others due to the extended range of protein concentrations. High-abundance proteins like albumin or IgG of plasma and urine, may interfere with the detection of potential disease biomarkers. Currently, several options are available for the depletion of abundant proteins in plasma. However, the applicability of these methods in urine has not been thoroughly investigated. In this study, we compared different, commercially available immunodepletion and ion-exchange based approaches on urine samples from both healthy subjects and CKD patients, for their reproducibility and efficiency in protein depletion. A starting urine volume of 500 μL was used to simulate conditions of a multi-institutional biomarker discovery study. All depletion approaches showed satisfactory reproducibility (n=5) in protein identification as well as protein abundance. Comparison of the depletion efficiency between the unfractionated and fractionated samples and the different depletion strategies, showed efficient depletion in all cases, with the exception of the ion-exchange kit. The depletion efficiency was found slightly higher in normal than in CKD samples and normal samples yielded more protein identifications than CKD samples when using both initial as well as corresponding depleted fractions. Along these lines, decrease in the amount of albumin and other targets as applicable, following depletion, was observed. Nevertheless, these depletion strategies did not yield a higher number of identifications in neither the urine from normal nor CKD patients. Collectively, when analyzing urine in the context of CKD biomarker identification, no added value of depletion strategies can be observed and analysis of unfractionated starting urine appears to be preferable.

Primordial helium abundance from CMB: A constraint from recent observations and a forecast

International Nuclear Information System (INIS)

Ichikawa, Kazuhide; Sekiguchi, Toyokazu; Takahashi, Tomo

2008-01-01

We studied a constraint on the primordial helium abundance Y p from current and future observations of CMB. Using the currently available data from WMAP, ACBAR, CBI, and BOOMERANG, we obtained the constraint as Y p =0.25 -0.07 +0.10 at 68% confidence level. We also provide a forecast for the Planck experiment using the Markov chain Monte Carlo approach. In addition to forecasting the constraint on Y p , we investigate how assumptions for Y p affect constraints on the other cosmological parameters.

Dense ion clouds of 0.1 − 2 keV ions inside the CPS-region observed by Astrid-2

Directory of Open Access Journals (Sweden)

O. Norberg

Full Text Available Data from the Astrid-2 satellite taken between April and July 1999 show several examples of dense ion clouds in the 0.1–2 keV energy range inside the inner mag-netosphere, both in the northern and southern hemispheres. These inner magnetospheric ion clouds are found predomi-nantly in the early morning sector, suggesting that they could have originated from substorm-related ion injections on the night side. However, their location and density show no cor-relation with Kp, and their energy-latitude dispersion is not easily reproduced by a simple particle drift model. There-fore, these ion clouds are not necessarily caused by substorm-related ion injections. Alternative explanations for the ion clouds are the direct solar wind injections and up-welling ions from the other hemisphere. These explanations do not, however, account for all of the observations.Key words. Magnetospheric physics (energetic particles, trapped; magnetospheric configuration and dynamics; storm and substorms

Pitch Angle Dependence of Drift Resonant Ions Observed by the Van Allen Probes

Science.gov (United States)

Rankin, R.; Wang, C.; Wang, Y.; Zong, Q. G.; Zhou, X.

2017-12-01

Acceleration and modulation of ring current ions by poloidal mode ULF waves is investigated. A simplified MHD model of ULF waves in a dipole magnetic field is presented that includes phase mixing to perpendicular scales determined by the ionospheric Pedersen conductivity. The wave model is combined with a full Lorentz force test particle code to study drift and drift bounce resonance wave-particle interactions. Ion trajectories are traced backward-in-time to an assumed form of the distribution function, and Liouville's method is used to reconstruct the phase space density response (PSD) poloidal mode waves observed by the Van Allen Probes. In spite of its apparent simplicity, simulations using the wave and test particle models are able to explain the acceleration of ions and energy dispersion observed by the Van Allen Probes. The paper focuses on the pitch angle evolution of the initial PSD as it responds to the action of ULF waves. An interesting aspect of the study is the formation of butterfly ion distributions as ions make periodic radial oscillations across L. Ions become trapped in an effective potential well across a limited range of L and follow trajectories that cause them to surf along constant phase fronts. The impications of this new trapping mechanism for both ions and electrons is discussed.

Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun

Science.gov (United States)

Fu, Hui; Madjarska, M. S.; Li, Bo; Xia, LiDong; Huang, ZhengHua

2018-05-01

Two main models have been developed to explain the mechanisms of release, heating and acceleration of the nascent solar wind, the wave-turbulence-driven (WTD) models and reconnection-loop-opening (RLO) models, in which the plasma release processes are fundamentally different. Given that the statistical observational properties of helium ions produced in magnetically diverse solar regions could provide valuable information for the solar wind modelling, we examine the statistical properties of the helium abundance (AHe) and the speed difference between helium ions and protons (vαp) for coronal holes (CHs), active regions (ARs) and the quiet Sun (QS). We find bimodal distributions in the space of AHeand vαp/vA(where vA is the local Alfvén speed) for the solar wind as a whole. The CH wind measurements are concentrated at higher AHeand vαp/vAvalues with a smaller AHedistribution range, while the AR and QS wind is associated with lower AHeand vαp/vA, and a larger AHedistribution range. The magnetic diversity of the source regions and the physical processes related to it are possibly responsible for the different properties of AHeand vαp/vA. The statistical results suggest that the two solar wind generation mechanisms, WTD and RLO, work in parallel in all solar wind source regions. In CH regions WTD plays a major role, whereas the RLO mechanism is more important in AR and QS.

Determination of helium and oxygen abundances in gaseous nebulae

International Nuclear Information System (INIS)

Pronik, V.I.

1975-01-01

A new method of determining the abudance of helium and oxygen is proposed. It is based on the statement that functions of atomic distribution with states of ionization may be determined to the sufficient precision by the amount of atoms in two states of ionization. The abudance of helium atoms in nebulae is determined with most probability, since of three possible states of ionization two states with the overwhelming majority atoms may be directly observed. The amount of He++ ions is determined from He 2 recombination lines, and the amount of He+ ions is from He1 lines. The total abudance of He atoms can be found from the observed ratios of I(4686)/I(Hsub(β)) and I(4471)/I(Hsub(β)) at any degree of ionization. These ratios slightly depend on the electron temperature. For oxygen, unlike helium, the observed ratios depend on the electron temperature of gas, and at high densities they also depend on the density of electrons (it is necessary to take account of deactivation of the excited level by electron impacts). Constructed are curves of equal abundance He/H=const for determining He/H according to the ratios observed I(4686)/I(Hsub(β)) and I(4471)/I(Hsub(β)) and curves of equal abudance O/H=const for determining O/H according to the ratios observed I(3727)/I(Hsub(/b)) and I(Nsub(1)+Nsub(2))/I(Hsub(β)), corrected preliminarily for density and temperature

In situ EELS and TEM observation of Al implanted with nitrogen ions

International Nuclear Information System (INIS)

Hojou, K.; Furuno, S.; Kushita, K.N.; Otsu, H.; Izui, K.

1995-01-01

Formation processes of Aluminum nitride (AIN) in Aluminum (AI) implanted with nitrogen were examined by in situ EELS and TEM observations during nitrogen ion implantation in an electron microscope at room temperature and 400 deg C. AIN phase was identified both by EDP and EELS after nitrogen ion implantation to 6 x 10 20 (N + )/m 2 . The observed peak (20.8 eV) in EELS spectra was identified as plasmon loss peak of AIN formed in AI. The binding energy of N ls in AI was found to shift by about 4 eV to the lower side with increasing nitrogen-ion fluence. Unreacted AI was also found to remain in the AIN films after high fluence implantation both at room temperature and 400 deg C. (authors). 11 refs., 5 figs., 2 tabs

Tuning Li2MO3 phase abundance and suppressing migration of transition metal ions to improve the overall performance of Li- and Mn-rich layered oxide cathode

Science.gov (United States)

Zhang, Shiming; Tang, Tian; Ma, Zhihua; Gu, Haitao; Du, Wubing; Gao, Mingxia; Liu, Yongfeng; Jian, Dechao; Pan, Hongge

2018-03-01

The poor cycling stability of Li- and Mn-rich layered oxide cathodes used in lithium-ion batteries (LIBs) has severely limited their practical application. Unfortunately, current strategies to improve their lifecycle sacrifice initial capacity. In this paper, we firstly report the synergistic improvement of the electrochemical performance of a Li1.2Ni0.13Co0.13Mn0.54O2 (LNCMO) cathode material, including gains for capacity, cycling stability, and rate capability, by the partial substitution of Li+ ions by Mg2+ ions. Electrochemical performance is evaluated by a galvanostatic charge and discharge test and electrochemical impedance spectroscopy (EIS). Structure and morphology are characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Compared with the substitution of transition metal (TM) ions with Mg2+ ions reported previously, the substitution of Li+ ions by Mg2+ ions not only drastically ameliorates the capacity retention and rate performance challenges of LNCMO cathodes but also markedly suppresses their voltage fading, due to the inhibition of the migration of TM ions during cycling, while also increasing the capacity of the cathode due to an increased abundance of the Li2MO3 phase.

Observation of the Antimatter Nuclei in Relativistic Heavy Ion Collisions

International Nuclear Information System (INIS)

Yoo, I.-K.

2013-01-01

Recently antimatter hyper-triton nuclei ( 3 Λ¯ H ¯) and antimatter helium nuclei ( 4 2 He ¯ ) are discovered with the Solenoidal Tracker At RHIC detector in relativistic heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) (STAR Collaboration in Science 328(5974):58-62, 2010; STAR Collaboration in Nature 473:353-356, 2011). In this presentation, discoveries of antimatter particle are historically scanned and the recent observations at RHIC are reported in details as well as potential possibilities of discovery of antimatter nuclei at ALICE. (author)

Direct observation of interaction between plasma ions and grid-excited pulses in a Q-machine

DEFF Research Database (Denmark)

Andersen, S.A.; Jensen, Vagn Orla; Michelsen, Poul

1970-01-01

The change in velocity-distribution function caused by interaction between ions and density pulses in a Q-machine is observed experimentally.......The change in velocity-distribution function caused by interaction between ions and density pulses in a Q-machine is observed experimentally....

Quiet-time 0.04 - 2 MeV/nucleon Ions at 1 AU in Solar Cycles 23 and 24

Science.gov (United States)

Zeldovich, M. A.; Logachev, Y. I.; Kecskeméty, K.

2018-01-01

The fluxes of 3He, 4He, C, O, and Fe ions at low energies (about 0.04 - 2 MeV/nucleon) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using data from the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section 2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysis of the ion energy spectra and their relative abundances shows that their behavior is governed by their first-ionization potential. Substantial differences in the ion energy spectra in two consecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxes are divided into three distinct types according to the {˜} 80 - 320 keV/nucleon Fe/O ratio. Our results confirm the earlier observation that these types of suprathermal particles have different origins, that is, they represent different seed populations that are accelerated by different processes. Except for the solar activity minimum, the Fe/O ratio during quiet-time periods correspond either to the abundances of ions in particle fluxes accelerated in impulsive solar flares or to the mean abundances of elements in the solar corona. At the activity minimum, this ratio takes on values that are characteristic for the solar wind. These results indicate that the background fluxes of low-energy particles in the ascending, maximum, and decay phases of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal energies and ions accelerated in small impulsive solar flares rich in Fe, while the contribution of remnants from earlier SEP events cannot be excluded. The comparison of suprathermal ion abundances during the first five years of SC 23 and SC 24 suggests that the quiet-time and non-quiet fluxes of Fe and 3He were lower in SC 24.

Metal-poor dwarf galaxies in the SIGRID galaxy sample. I. H II region observations and chemical abundances

International Nuclear Information System (INIS)

Nicholls, David C.; Dopita, Michael A.; Sutherland, Ralph S.; Jerjen, Helmut; Kewley, Lisa J.; Basurah, Hassan

2014-01-01

In this paper we present the results of observations of 17 H II regions in thirteen galaxies from the SIGRID sample of isolated gas-rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [O III] 4363 Å line, from which we calculate the electron temperature, T e , and gas-phase oxygen abundance. Five of the objects are blue compact dwarf galaxies, of which four have not previously been analyzed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [N II] λλ 6548,6584 Å lines, suggesting a particularly low metallicity (< Z ☉ /30). We compare the electron temperature based abundances with those derived using eight of the new strong-line diagnostics presented by Dopita et al. Using a method derived from first principles for calculating total oxygen abundance, we show that the discrepancy between the T e -based and strong-line gas-phase abundances have now been reduced to within ∼0.07 dex. The chemical abundances are consistent with what is expected from the luminosity-metallicity relation. We derive estimates of the electron densities and find them to be between ∼5 and ∼100 cm –3 . We find no evidence for a nitrogen plateau for objects in this sample with metallicities 0.5 > Z ☉ > 0.15.

Metal-poor dwarf galaxies in the SIGRID galaxy sample. I. H II region observations and chemical abundances

Energy Technology Data Exchange (ETDEWEB)

Nicholls, David C.; Dopita, Michael A.; Sutherland, Ralph S.; Jerjen, Helmut; Kewley, Lisa J. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston ACT 2611 (Australia); Basurah, Hassan, E-mail: David.Nicholls@anu.edu.au [Astronomy Department, King Abdulaziz University, P.O. Box 80203 Jeddah (Saudi Arabia)

2014-05-10

In this paper we present the results of observations of 17 H II regions in thirteen galaxies from the SIGRID sample of isolated gas-rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [O III] 4363 Å line, from which we calculate the electron temperature, T{sub e} , and gas-phase oxygen abundance. Five of the objects are blue compact dwarf galaxies, of which four have not previously been analyzed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [N II] λλ 6548,6584 Å lines, suggesting a particularly low metallicity (< Z {sub ☉}/30). We compare the electron temperature based abundances with those derived using eight of the new strong-line diagnostics presented by Dopita et al. Using a method derived from first principles for calculating total oxygen abundance, we show that the discrepancy between the T{sub e} -based and strong-line gas-phase abundances have now been reduced to within ∼0.07 dex. The chemical abundances are consistent with what is expected from the luminosity-metallicity relation. We derive estimates of the electron densities and find them to be between ∼5 and ∼100 cm{sup –3}. We find no evidence for a nitrogen plateau for objects in this sample with metallicities 0.5 > Z {sub ☉} > 0.15.

Direct observation of cascade defect formation at low temperatures in ion-irradiated metals

International Nuclear Information System (INIS)

Muroga, T.; Hirooka, K.; Ishino, S.

1984-01-01

Direct transmission electron microscopy observations of cascade defect formation have been carried out in gold, Type 316 stainless steel, and aluminum irradiated by Al + , Ar - , and Xe + ions with energies between 80 and 400 keV. By utilizing a link of an ion accelerator to an electron microscope, in situ observations at low temperature (-150 0 C) have become possible. In gold, subcascade structures are clearly observed in all cases. Obvious dependence on projectile mass and energy is observed for cascade structure and vacancy clustering efficiency in gold and for defect visibility in aluminum and Type 316 stainless steel. A computer simulation calculation using MARLOWE shows subcascade distributions a little smaller in size and larger in number than the present observation

Sodium Pick-Up Ion Observations in the Solar Wind Upstream of Mercury

Science.gov (United States)

Jasinski, J. M.; Raines, J. M.; Slavin, J. A.; Regoli, L. R.; Murphy, N.

2018-05-01

We present the first observations of sodium pick-up ions upstream of Mercury’s magnetosphere. From these observations we infer properties of Mercury’s sodium exosphere and implications for the solar wind interaction with Mercury’s magnetosphere.

Neon Abundances from a Spitzer/IRS Survey of Wolf-Rayet Stars

NARCIS (Netherlands)

Ignace, R.; Cassinelli, J.P.; Tracy, G.; Churchwell, E.B.; Lamers, H.J.G.L.M.

2007-01-01

We report on neon abundances derived from Spitzer high resolution spectral data of eight Wolf-Rayet (WR) stars using the forbidden line of [Ne III] 15.56 μm. Our targets include four WN stars of subtypes 4-7, and four WC stars of subtypes 4-7. We derive ion fraction abundances γ of Ne2+ for the

Hot magnetospheric O+ and cold ion behavior in magnetopause reconnection: Cluster observations

Science.gov (United States)

Wang, S.; Kistler, L. M.; Mouikis, C. G.; Liu, Y.; Genestreti, K. J.

2014-12-01

In reconnection, the presence of heavy ions like O+ increases the ion mass density reducing the fluid's Alfvén speed. In addition, it may modify the reconnection structure, which can also change the reconnection rate. However, because O+ ions have a larger Larmor radii than H+ ions at the same velocity, they may not be fully entrained in the reconnection flow and may have kinetic effects other than just increasing the mass density. In this study, for the first time, the ion velocity distribution functions of H+ and O+ from one magnetopause reconnection event with a strong guide field are analyzed to determine in detail the behavior of the different ion populations. We show that the hot magnetospheric O+ ions, along with the hot magnetospheric H+ ions almost fully participate in the reconnection exhaust flows. Finite Larmor radius effects are also apparent and control how far the ions extend on the magnetosheath side. Ion signatures consistent with heating after being picked up in the reconnection exhaust flow are observed in the H+ and O+ distribution functions. The dynamics of the cold magnetospheric ions depends on where they enter the reconnection region. If they enter the reconnection region at the downstream separatrix, they will be taken away by the magnetic field in an adiabatic way as analyzed by Drake et al. (2009a); if they enter close to the diffusion region, they behave as pick-up ions.

Magnetospheric Multiscale (MMS) Observations of Energetic Ion Response to Magnetotail Dipolarization Events

Science.gov (United States)

Cohen, I. J.; Mauk, B.; Anderson, B. J.; Sitnov, M. I.; Motoba, T.; Ohtani, S.; Gkioulidou, M.; Fuselier, S. A.; Giles, B. L.; Strangeway, R. J.; Torbert, R. B.; Burch, J. L.

2017-12-01

Observations from the Energetic Ion Spectrometer (EIS) instruments aboard MMS have shown angular (pitch, elevation, azimuthal) asymmetries of energetic (>10s of keV) ions corresponding to dipolarization events in the near-Earth and distant magnetotail. In particular, EIS distinguishes the species composition of these ions (protons, helium, oxygen) and reveals apparent species-based differences in their response. This study presents analysis of the dynamic injection and mass-dependent response of energetic ions that likely result from the kinetic response of the ions to the time-varying electric and magnetic fields associated with injection process. Analysis is focused on discriminating between truly kinetic responses to the dynamics and the features that arise from large gyro-radii particles in the vicinity of strong spatial gradients. The study will focus on EIS measurements and include supplementary data from the FIELDS, FPI, and HPCA instruments.

Probing the possibility of a 12C13C abundance gradient from observations of interstellar CH+

International Nuclear Information System (INIS)

Hawkins, I.

1987-01-01

I have performed high signal-to-noise (SN /equals/ 300 to 500) observations of interstellar CH/sup /plus// at Lick Observatory and at CTIO of the reddened, early-type stars HD 183143, HD 24432, and HD 157038 in an effort to probe the existence of a 12 C 13 C abundance gradient in our Galaxy

Silicene for Na-ion battery applications

KAUST Repository

Zhu, Jiajie; Schwingenschlö gl, Udo

2016-01-01

Na-ion batteries are promising candidates to replace Li-ion batteries in large scale applications because of the advantages in natural abundance and cost of Na. Silicene has potential as the anode in Li-ion batteries but so far has not received

Observing giant panda habitat and forage abundance from space

NARCIS (Netherlands)

Wang, T.

2009-01-01

Giant pandas are obligate bamboo grazers. The bamboos favoured by giant
pandas are typical forest understorey plants. Therefore, the availability and
abundance of understorey bamboo is a key factor in determining the quantity
and quality of giant panda food resources. However,

Kinetic modeling of auroral ion outflows observed by the VISIONS sounding rocket

Science.gov (United States)

Albarran, R. M.; Zettergren, M. D.

2017-12-01

The VISIONS (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) sounding rocket was launched on Feb. 7, 2013 at 8:21 UTC from Poker Flat, Alaska, into an auroral substorm with the objective of identifying the drivers and dynamics of the ion outflow below 1000km. Energetic ion data from the VISIONS polar cap boundary crossing show evidence of an ion "pressure cooker" effect whereby ions energized via transverse heating in the topside ionosphere travel upward and are impeded by a parallel potential structure at higher altitudes. VISIONS was also instrumented with an energetic neutral atom (ENA) detector which measured neutral particles ( 50-100 eV energy) presumably produced by charge-exchange with the energized outflowing ions. Hence, inferences about ion outflow may be made via remotely-sensing measurements of ENAs. This investigation focuses on modeling energetic outflowing ion distributions observed by VISIONS using a kinetic model. This kinetic model traces large numbers of individual particles, using a guiding-center approximation, in order to allow calculation of ion distribution functions and moments. For the present study we include mirror and parallel electric field forces, and a source of ion cyclotron resonance (ICR) wave heating, thought to be central to the transverse energization of ions. The model is initiated with a steady-state ion density altitude profile and Maxwellian velocity distribution characterizing the initial phase-space conditions for multiple particle trajectories. This project serves to advance our understanding of the drivers and particle dynamics in the auroral ionosphere and to improve data analysis methods for future sounding rocket and satellite missions.

Solar-wind minor ions: recent observations

International Nuclear Information System (INIS)

Bame, S.J.

1982-01-01

During the years following the Solar Wind Four Conference at Burghausen our knowledge of the solar wind ion composition and dynamics has grown. There have been some surprises, and our understanding of the evolution of the solar wind has been improved. Systematic studies have shown that the minor ions generally travel with a common bulk speed and have temperatures roughly proportional to their masses. It has been determined that the 3 He ++ content varies greatly; 3 He ++ / 4 He ++ ranges from as high as 10 2 values to below 2 x 10 - 4 . In some solar wind flows which can be related to energetic coronal events, the minor ions are found in unusual ionization states containing Fe 16 + as a prominent ion, showing that the states were formed at unusually high temperatures. Unexpectedly, in a few flows substantial quantities of 4 He + have been detected, sometimes with ions identifiable as O 2 + and O 3 + . Surprisingly, in some of these examples the ionization state is mixed showing that part of the plasma escaped the corona without attaining the usual million-degree temperatures while other parts were heated more nearly in the normal manner. Additionally, detailed studies of the minor ions have increased our understanding of the coronal expansion. For example, such studies have contributed to identifying near equatorial coronal streamers as the source of solar wind flows between high speed streams

The heavy ion diffusion region in magnetic reconnection in the Earth's magnetotail

Science.gov (United States)

Liu, Y. H.; Mouikis, C. G.; Kistler, L. M.; Wang, S.; Roytershteyn, V.; Karimabadi, H.

2015-05-01

While the plasma in the Earth's magnetotail predominantly consists of protons and electrons, there are times when a significant amount of oxygen is present. When magnetic reconnection occurs, the behavior of these heavy ions can be significantly different from that of the protons, due to their larger gyroradius. In this study, we investigate the heavy ion distribution functions in the reconnection ion diffusion region from a 2.5D three-species particle-in-cell numerical simulation and compare those with Cluster observations from the near-Earth magnetotail. From the simulation results, we find that the heavy ions are demagnetized and accelerated in a larger diffusion region, the heavy ion diffusion region. The ion velocity distribution functions show that, inside the heavy ion diffusion region, heavy ions appear as counterstreaming beams along z in the GSM x-z plane, while drifting in y, carrying cross-tail current. We compare this result with Cluster observations in the vicinity of reconnection regions in the near-Earth magnetotail and find that the simulation predictions are consistent with the observed ion distribution functions in the ion diffusion region, as well as the inflow, exhaust, and separatrix regions. Based on the simulation and observation results, the presence of a multiscale diffusion region model, for O+ abundant reconnection events in the Earth's magnetotail, is demonstrated. A test particle simulation shows that in the diffusion region, the H+ gains energy mainly through Ex, while the O+ energy gain comes equally from Ex and Ey.

Experimental observations of anomalous potential drops over ion density cavities

International Nuclear Information System (INIS)

Bohm, M.

1991-08-01

Experiments are reported showing the plasma potential response when a step voltage is applied over the plasma column between the two plasma sources in a triple plasma machine. The time resolution is sufficient to resolve potential variations caused essentially by the electron motion, and two independent probe methods are used to obtain this time resolution. Depending on the initial conditions two different responses were observed on the time scale of the electron motion. When the initial ion density varies along the plasma column and has a local minimum (that is, forms an ion density cavity), the applied potential drop becomes distributed over the cavity after a few electron transit times. Later the profile steepens to a double layer on the time scale of the ion motion. The width of the cavity is comparable to the length of the plasma column. When the initial density is axially uniform, most of the potential drop instead concentrates to a narrow region at the low potential end of the plasma column after a few electron transit times. On the time scale of the ion motion this potential drop begins to propagate into the plasma as a double layer. The results obtained are consistent with those from numerical simulations with similar boundary conditions. Further experiments are necessary to get conclusive insight into the voltage supporting capability of an ion density cavity. (au) (34 refs.)

Hydrolysis of VX on concrete: rate of degradation by direct surface interrogation using an ion trap secondary ion mass spectrometer.

Science.gov (United States)

Groenewold, Gary S; Williams, John M; Appelhans, Anthony D; Gresham, Garold L; Olson, John E; Jeffery, Mark T; Rowland, Brad

2002-11-15

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate) is lethal at very low levels of exposure, which can occur by dermal contact with contaminated surfaces. Hence, behavior of VX in contact with common urban or industrial surfaces is a subject of acute interest. In the present study, VX was found to undergo complete degradation when in contact with concrete surfaces. The degradation was directly interrogated at submonolayer concentrations by periodically performing secondary ion mass spectrometry (SIMS) analyses after exposure of the concrete to VX. The abundance of the [VX + H]+ ion in the SIMS spectra was observed to decrease in an exponential fashion, consistent with first-order or pseudo-first-order behavior. This phenomenon enabled the rate constant to be determined at 0.005 min(-1) at 25 degrees C, which corresponds to a half-life of about 3 h on the concrete surface. The decrease in [VX + H]+ was accompanied by an increase in the abundance of the principal degradation product diisopropylaminoethanethiol (DESH), which arises by cleavage of the P-S bond. Degradation to form DESH is accompanied by the formation of ethyl methylphosphonic acid, which is observable only in the negative ion spectrum. A second degradation product was also implicated, which corresponded to a diisopropylvinylamine isomer (perhaps N,N-diisopropyl aziridinium) that arose via cleavage of the S-C bond. No evidence was observed for the formation of the toxic S-2-diisopropylaminoethyl methylphosphonothioic acid. The degradation rate constants were measured at four different temperatures (24-50 degrees C), which resulted in a linear Arrhenius relationship and an activation energy of 52 kJ mol(-1). This value agrees with previous values observed for VX hydrolysis in alkaline solutions, which suggests that the degradation of submonolayer VX is dominated by alkaline hydrolysis within the adventitious water film on the concrete surface.

Orion A helium abundance

International Nuclear Information System (INIS)

Tsivilev, A.P.; Ershov, A.A.; Smirnov, G.T.; Sorochenko, R.L.

1986-01-01

The 22.4-GHz (H,He)66-alpha and 36.5-GHz (H,He)56-alpha radio recombination lines have been observed at several Jaffe-Pankonin positions in the central part of the Orion A source. The measured relative abundance of ionized helium increases with distance, averaging 11.6 percent at peripheral points. The observed behavior is interpreted by a blister-type model nebula, which implies that Orion A has a true He abundance of 12 percent, is moving with a radial velocity of 5 km/sec, and is expanding. 18 references

Do stellar and nebular abundances in the Cocoon nebula agree?

Science.gov (United States)

García-Rojas, J.; Simón-Díaz, S.; Esteban, C.

2015-05-01

The Cocoon nebula is an apparently spherical Galactic HII region ionized by a single star (BD+46 3474). This nebula seems to be appropriate to investigate the chemical behavior of oxygen and other heavy elements from two different points of view: a detailed analysis of the chemical content of the ionized gas through nebular spectrophotometry and a detailed spectroscopic analysis of the spectrum of the ionizing star using the state-of-the-art stellar atmosphere modelling. In this poster we present the results from a set of high-quality observations, from 2m-4m class telescopes, including the optical spectrum of the ionizing star BD+46 3474, along with long-slit spatially resolved spectroscopy of the nebula. We have used state-of-the-art stellar atmosphere codes to determine stellar parameters and the chemical content of several heavy elements. Traditional nebular techniques along with updated atomic data have been used to compute gaseous abundances of O, N and S in the Cocoon nebula. Thanks to the low ionization degree of the nebula, we could determine total abundances directly from observable ions (no ionization correction factors were needed) for three of the analyzed elements (O, S, and N). The derived stellar and nebular abundances are compared and the influence of the possible presence of the so-called temperature fluctuations on the nebula is discussed. The results of this study are presented in more detail in García-Rojas, Simón-Díaz & Esteban 2014, A&A, 571, A93.

Thick Escaping Magnetospheric Ion Layer in Magnetopause Reconnection with MMS Observations

Science.gov (United States)

Nagai, T.; Kitamura, N.; Hasagawa, H.; Shinohara, I.; Yokota, S.; Saito, Y.; Nakamura, R.; Giles, B. L.; Pollock, C.; Moore, T. E.;

Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

Directory of Open Access Journals (Sweden)

M. Endo

2000-02-01

Full Text Available We have determined the MLT distribution and KP dependence of the ion upflow and downflow of the thermal bulk oxygen ion population based on a data analysis using the EISCAT VHF radar CP-7 data obtained at Tromsø during the period between 1990 and 1996: (1 both ion upflow and downflow events can be observed at any local time (MLT, irrespective of dayside and nightside, and under any magnetic disturbance level, irrespective of quiet and disturbed levels; (2 these upflow and downflow events are more frequently observed in the nightside than in the dayside; (3 the upflow events are more frequently observed than the downflow events at any local time except midnight and at any KP level and the difference of the occurrence frequencies between the upflow and downflow events is smaller around midnight; and (4 the occurrence frequencies of both the ion upflow and downflow events appear to increase with increasing KP level, while the occurrence frequency of the downflow appears to stop increasing at some KP level.Key words: Ionosphere (particle acceleration; plasma waves and instabilities - Space plasma physics (transport processes

Observation of fast-ion Doppler-shifted cyclotron resonance with shear Alfven waves

International Nuclear Information System (INIS)

Zhang Yang; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Vincena, S.; Carter, T. A.; Gekelman, W.; Leneman, D.; Pribyl, P.

2008-01-01

The Doppler-shifted cyclotron resonance (ω-k z v z =Ω f ) between fast ions and shear Alfven waves is experimentally investigated (ω, wave frequency; k z , axial wavenumber; v z , fast-ion axial speed; Ω f , fast-ion cyclotron frequency). A test particle beam of fast ions is launched by a Li + source in the helium plasma of the LArge Plasma Device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)], with shear Alfven waves (SAW) (amplitude δ B/B up to 1%) launched by a loop antenna. A collimated fast-ion energy analyzer measures the nonclassical spreading of the beam, which is proportional to the resonance with the wave. A resonance spectrum is observed by launching SAWs at 0.3-0.8ω ci . Both the magnitude and frequency dependence of the beam-spreading are in agreement with the theoretical prediction using a Monte Carlo Lorentz code that launches fast ions with an initial spread in real/velocity space and random phases relative to the wave. Measured wave magnetic field data are used in the simulation.

Ion Mobility Mass Spectrometry Direct Isotope Abundance Analysis

International Nuclear Information System (INIS)

Manard, Manuel J.; Weeks, Stephan; Kyle, Kevin

2010-01-01

The nuclear forensics community is currently engaged in the analysis of illicit nuclear or radioactive material for the purposes of non-proliferations and attribution. One technique commonly employed for gathering nuclear forensics information is isotope analysis. At present, the state-of-the-art methodology for obtaining isotopic distributions is thermal ionization mass spectrometry (TIMS). Although TIMS is highly accurate at determining isotope distributions, the technique requires an elementally pure sample to perform the measurement. The required radiochemical separations give rise to sample preparation times that can be in excess of one to two weeks. Clearly, the nuclear forensics community is in need of instrumentation and methods that can expedite their decision making process in the event of a radiological release or nuclear detonation. Accordingly, we are developing instrumentation that couples a high resolution IM drift cell to the front end of a MS. The IM cell provides a means of separating ions based upon their collision cross-section and mass-to-charge ratio (m/z). Two analytes with the same m/z, but with different collision cross-sections (shapes) would exit the cell at different times, essentially enabling the cell to function in a similar manner to a gas chromatography (GC) column. Thus, molecular and atomic isobaric interferences can be effectively removed from the ion beam. The mobility selected chemical species could then be introduced to a MS for high-resolution mass analysis to generate isotopic distributions of the target analytes. The outcome would be an IM/MS system capable of accurately measuring isotopic distributions while concurrently eliminating isobaric interferences and laboratory radiochemical sample preparation. The overall objective of this project is developing instrumentation and methods to produce near real-time isotope distributions with a modular mass spectrometric system that performs the required gas-phase chemistry and

Solitary waves in dusty plasmas with weak relativistic effects in electrons and ions

Energy Technology Data Exchange (ETDEWEB)

Kalita, B. C., E-mail: bckalita123@gmail.com [Gauhati University, Department of Mathematics (India); Choudhury, M., E-mail: choudhurymamani@gmail.com [Handique Girls’ College, Department of Mathematics (India)

2016-10-15

Two distinct classes of dust ion acoustic (DIA) solitary waves based on relativistic ions and electrons, dust charge Z{sub d} and ion-to-dust mass ratio Q’ = m{sub i}/m{sub d} are established in this model of multicomponent plasmas. At the increase of mass ratio Q’ due to increase of relativistic ion mass and accumulation of more negative dust charges into the plasma causing decrease of dust mass, relativistic DIA solitons of negative potentials are abundantly observed. Of course, relativistic compressive DIA solitons are also found to exist simultaneously. Further, the decrease of temperature inherent in the speed of light c causes the nonlinear term to be more active that increases the amplitude of the rarefactive solitons and dampens the growth of compressive solitons for relatively low and high mass ratio Q’, respectively. The impact of higher initial streaming of the massive ions is observed to identify the point of maximum dust density N{sub d} to yield rarefactive relativistic solitons of maximum amplitude.

Statistics of high-altitude and high-latitude O+ ion outflows observed by Cluster/CIS

Directory of Open Access Journals (Sweden)

A. Korth

2005-07-01

Full Text Available The persistent outflows of O+ ions observed by the Cluster CIS/CODIF instrument were studied statistically in the high-altitude (from 3 up to 11 RE and high-latitude (from 70 to ~90 deg invariant latitude, ILAT polar region. The principal results are: (1 Outflowing O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location; (2 at 6-8 RE geocentric distance, the latitudinal distribution of O+ ion outflow is consistent with velocity filter dispersion from a source equatorward and below the spacecraft (e.g. the cusp/cleft; (3 however, at 8-12 RE geocentric distance the distribution of O+ outflows cannot be explained by velocity filter only. The results suggest that additional energization or acceleration processes for outflowing O+ ions occur at high altitudes and high latitudes in the dayside polar region. Keywords. Magnetospheric physics (Magnetospheric configuration and dynamics, Solar wind-magnetosphere interactions

Abundances, Ionization States, Temperatures, and FIP in Solar Energetic Particles

Science.gov (United States)

Reames, Donald V.

2018-04-01

The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in {}3He/{}4He from resonant wave-particle interactions in the small "impulsive" SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio A/Q, rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in solar jets. In contrast, in the largest SEP events, the "gradual" events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of solar coronal abundances, but A/Q-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states Q show coronal temperatures of 1-2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of Q are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of A/Q, we can use abundances to deduce the probable Q-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs

Observations of Heavy Ions in the Magnetosphere

Science.gov (United States)

Kistler, L. M.

2017-12-01

There are two sources for the hot ions in the magnetosphere: the solar wind and the ionosphere. The solar wind is predominantly protons, with about 4% He++ and less than 1% other high charge state heavy ions. The ionospheric outflow is also predominantly H+, but can contain a significant fraction of heavy ions including O+, N+, He+, O++, and molecular ions (NO+, N2+, O2+). The ionospheric outflow composition varies significantly both with geomagnetic activity and with solar EUV. The variability in the contribution of the two sources, the variability in the ionospheric source itself, and the transport paths of the different species are all important in determining the ion composition at a given location in the magnetosphere. In addition to the source variations, loss processes within the magnetosphere can be mass dependent, changing the composition. In particular, charge exchange is strongly species dependent, and can lead to heavy ion dominance at some energies in the inner magnetosphere. In this talk we will review the current state of our understanding of the composition of the magnetosphere and the processes that determine it.

An ICR study of ion-molecule reactions of PH(n)+ ions. [of importance to interstellar chemistry, using ion cyclotron resonance techniques

Science.gov (United States)

Thorne, L. R.; Anicich, V. G.; Huntress, W. T.

1983-01-01

The reactions of PH(n)+ ions (n = 0-3) were examined with a number of neutrals using ion-cyclotron-resonance techniques. The reactions examined have significance for the distribution of phosphorus in interstellar molecules. The results indicate that interstellar molecules containing the P-O bond are likely to be more abundant than those containing the P-H bond.

Observation of the backward electrostatic ion-cyclotron wave

International Nuclear Information System (INIS)

Goree, J.; Ono, M.; Wong, K.L.

1985-01-01

The backward branch of the electrostatic ion-cyclotron wave has been observed for the first time. The wave, which was driven by a phased antenna structure inserted in a neon plasma, exists in the parameter ranges 2T/sub i//m/sub i/ 2 or approx. =T/sub i/, and ω/sub p/i > Ω/sub i/. Double-tip probe interferometry data agree with the theoretical dispersion relation. The antenna couples into the wave more readily on the side of the antenna where it has its smallest wavenumber

In-Situ atomic force microscopic observation of ion beam bombarded plant cell envelopes

International Nuclear Information System (INIS)

Sangyuenyongpipat, S.; Yu, L.D.; Brown, I.G.; Seprom, C.; Vilaithong, T.

2007-01-01

A program in ion beam bioengineering has been established at Chiang Mai University (CMU), Thailand, and ion beam induced transfer of plasmid DNA molecules into bacterial cells (Escherichia coli) has been demonstrated. However, a good understanding of the fundamental physical processes involved is lacking. In parallel work, onion skin cells have been bombarded with Ar + ions at energy 25 keV and fluence1-2 x 10 15 ions/cm 2 , revealing the formation of microcrater-like structures on the cell wall that could serve as channels for the transfer of large macromolecules into the cell interior. An in-situ atomic force microscope (AFM) system has been designed and installed in the CMU bio-implantation facility as a tool for the observation of these microcraters during ion beam bombardment. Here we describe some of the features of the in-situ AFM and outline some of the related work

Selective observation of charge storing ions in supercapacitor electrode materials.

Science.gov (United States)

Forse, Alexander C; Griffin, John M; Grey, Clare P

2018-02-01

Nuclear magnetic resonance (NMR) spectroscopy has emerged as a useful technique for probing the structure and dynamics of the electrode-electrolyte interface in supercapacitors, as ions inside the pores of the carbon electrodes can be studied separately from bulk electrolyte. However, in some cases spectral resolution can limit the information that can be obtained. In this study we address this issue by showing how cross polarisation (CP) NMR experiments can be used to selectively observe the in-pore ions in supercapacitor electrode materials. We do this by transferring magnetisation from 13 C nuclei in porous carbons to nearby nuclei in the cations ( 1 H) or anions ( 19 F) of an ionic liquid. Two-dimensional NMR experiments and CP kinetics measurements confirm that in-pore ions are located within Ångströms of sp 2 -hybridised carbon surfaces. Multinuclear NMR experiments hold promise for future NMR studies of supercapacitor systems where spectral resolution is limited. Copyright © 2017 University of Cambridge. Published by Elsevier Inc. All rights reserved.

MUSE observations of M87: radial gradients for the stellar initial-mass function and the abundance of Sodium

Science.gov (United States)

Sarzi, Marc; Spiniello, Chiara; Barbera, Francesco La; Krajnović, Davor; Bosch, Remco van den

2018-05-01

Based on MUSE integral-field data we present evidence for a radial variation at the low-mass end of the stellar initial-mass function (IMF) in the central regions of the giant early-type galaxy NGC 4486 (M87). We used state-of-the-art stellar population models and the observed strength of various IMF-sensitive absorption-line features to solve for the best low-mass tapered "bimodal" form of the IMF, while accounting also for variations in stellar metallicity, the overall α-elements abundance and the abundance of individual elements such as Ti, O, Na and Ca. Our analysis reveals a strong negative IMF gradient corresponding to an exceeding fraction of low-mass stars compared to the case of the Milky Way toward the center of M87, which drops to nearly Milky-way levels by 0.4 Re. Such IMF variations correspond to over a factor two increase in stellar mass-to-light M/L ratio compared to the case of a Milky-way IMF, consistent with independent constraints on M/L radial variations in M87 from dynamical models. We also looked into the abundance of Sodium in M87, which turned up to be super-Solar over the entire radial range of our MUSE observations and to exhibit a considerable negative gradient. These findings suggest an additional role of metallicity in boosting the Na-yields in the central, metal-rich regions of M87 during its early and brief star-formation history. Our work adds M87 to the few objects that presently have radial constraints on their IMF or [Na/Fe] abundance, while also illustrating the accuracy that MUSE could bring to this kind of investigations.

Nuclear abundances and evolution of the interstellar medium

International Nuclear Information System (INIS)

Wannier, P.G.

1980-01-01

Observations of molecular and elemental abundances in the interstellar medium (ISM) are reviewed, with special attention given to isotope ratios. The derivation of molecular isotope abundances for the ISM is discussed, along with H and C fractionation. Millimeter- and centimeter-wave spectra of giant clouds are examined with respect to isotope abundances of C, O, N, Si, S, and D. Evidence for the current enrichment of the ISM by mass loss from evolved stars is considered, together with chemical abundance gradients in H II regions and planetary nebulae. Cosmic-ray observations pertaining to abundances in the ISM are summarized, with emphasis on available results for Ne, Mg, Si, Fe, and Ni. The observations reviewed are shown to support arguments in favor of: (1) the cosmological production of D and He-3 (2) the production of the CNO elements by hydrostatic hydrogen burning (3) the nucleosynthesis of Ne, Mg, Si, S, Fe, and Ni as a result of He burning (4) solar abundances of interstellar S, Fe, and Ni and (5) a direct association between observed inhomogeneities in the ISM and mass loss from evolved stellar objects

Ion Thermalization and Electron Heating across Quasi-Perpendicular Shocks Observed by the MMS Mission

Science.gov (United States)

Chen, L. J.; Wilson, L. B., III; Wang, S.; Bessho, N.; Figueroa-Vinas, A.; Lai, H.; Russell, C. T.; Schwartz, S. J.; Hesse, M.; Moore, T. E.; Burch, J.; Gershman, D. J.; Giles, B. L.; Torbert, R. B.; Ergun, R.; Dorelli, J.; Strangeway, R. J.; Paterson, W. R.; Lavraud, B.; Khotyaintsev, Y. V.

2017-12-01

Collisionless shocks often involve intense plasma heating in space and astrophysical systems. Despite decades of research, a number of key questions concerning electron and ion heating across collisionless shocks remain unanswered. We `image' 20 supercritical quasi-perpendicular bow shocks encountered by the Magnetospheric Multiscale (MMS) spacecraft with electron and ion distribution functions to address how ions are thermalized and how electrons are heated. The continuous burst measurements of 3D plasma distribution functions from MMS reveal that the primary thermalization phase of ions occurs concurrently with the main temperature increase of electrons as well as large-amplitude wave fluctuations. Approaching the shock from upstream, the ion temperature (Ti) increases due to the reflected ions joining the incoming solar wind population, as recognized by prior studies, and the increase of Ti precedes that of the electrons. Thermalization in the form of merging between the decelerated solar wind ions and the reflected component often results in a decrease in Ti. In most cases, the Ti decrease is followed by a gradual increase further downstream. Anisotropic, energy-dependent, and/or nongyrotropic electron energization are observed in association with large electric field fluctuations in the main electron temperature (Te) gradient, motivating a renewed scrutiny of the effects from the electrostatic cross-shock potential and wave fluctuations on electron heating. Particle-in-cell (PIC) simulations are carried out to assist interpretations of the MMS observations. We assess the roles of instabilities and the cross-shock potential in thermalizing ions and heating electrons based on the MMS measurements and PIC simulation results. Challenges will be posted for future computational studies and laboratory experiments on collisionless shocks.

MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

Science.gov (United States)

Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

2017-12-01

Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

Observations of neutral beam and ICRF tail ion losses due to Alfven modes in TFTR

International Nuclear Information System (INIS)

Darrow, D.S.; Zweben, S.J.; Chang, Z.

1996-04-01

Fast ion losses resulting from MHD modes at the Alfven frequency, such as the TAE, have been observed in TFTR. The modes have been driven both by neutral beam ions, at low B T , and by H-minority ICRF tail ions at higher B T . The measurements indicate that the loss rate varies linearly with the mode amplitude, and that the fast ion losses during the mode activity can be significant, e.g. up to 10% of the input power is lost in the worst case

Observations of ions of ionospheric origin in the storm-time ring current

International Nuclear Information System (INIS)

Johnson, R.G.; Sharp, R.D.; Shelley, E.G.

1977-01-01

O + , He + , and H + ions in the energy range 0.5 to 16 keV have been observed in the storm-time ring current with an energetic ion mass spectrometer aboard the polar-orbiting S3-3 satellite. During the main phases of the 29 December 1976, 6 April 1977, and 19 April 1977 magnetic storms, the O + number density within the instrument energy range in the inner ring current (L=2.8--4.0) was larger than the H + density in the altitude range from about 5000--7000 km. At two days after the main phase of the 29 December 1976 storm, O + was still the dominant ion at MLT=14.5 hours in the L=2.6--3.4 range at altitudes near 6000 km

Spontaneous emission of heavy-ions from uranium

International Nuclear Information System (INIS)

Carvalho, H.G. de; Martins, J.B.; Souza, I.O. de; Tavares, O.A.P.

1974-09-01

The experimental evidences that 238 U, and perhaps other heavy nuclei, besides undergoing spontaneous fission, are also emitters of ions in the mass-range from 20 to 70. Estimates obtained by means of the WKB method indicate half-lifes of 10 15 to 10 18 years for some of these processes, which agree with our findings. Our results are supported by a systematic observation of neon and argon with abnormal isotopic abundance in both radioactive minerals and helium-bearing natural gases

Modeling and Observation of Interstellar He+ Pickup Ions in the Inner Heliosphere

Science.gov (United States)

Chen, Junhong

Interstellar pickup ions constitute a charged particle population that originates from interstellar neutrals inside the heliosphere. They are produced by photoionization, charge exchange with solar wind ions, and electron impact ionization (EI). Once ionized, they are picked up by the interplanetary magnetic field (IMF) and rapidly swept outward with the solar wind. Typically, pickup ion distributions have been described in terms of a velocity distribution function that evolves through fast pitch angle scattering followed by adiabatic cooling during radial transport in the reference frame of the solar wind [e.g., Vasyliunas & Siscoe, 1976, VS76 hereafter]. In the VS76 model, the slope of the isotropic velocity distributions is controlled by the combination of the ionization rate and the cooling process. Thus far, for the cooling index that relates the slope of the velocity distribution to the radial transport and expansion of the pickup ions a constant value of 3/2 has been widely used. The implicit assumptions to arrive at this value are immediate PUI isotropization due to pitch angle scattering and solar wind expansion with the square of the distance from the Sun. Any experimental determination of the cooling index depends on the knowledge of the ionization rate and its spatial variation, as well as solar wind and interplanetary conditions. In this thesis, we study their influences on the PUI cooling index and separate them by making use of the two complementary helium PUI data sets from SWICS instrument on the ACE spacecraft, and PLASTIC instrument on STEREO spacecraft. We use the pickup ion observations from ACE SIWCS in the last solar cycle to determine the cooling index, and the possible effects of the electron impact ionization on the determination of the cooling index. With pickup ion observations from STEREO PLASTIC, we determine how solar wind expansion patterns affect the cooling index. We find that the cooling index varies substantially with solar

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He²⁺ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the

Experimental observation of current generation by asymmetrical heating of ions in a tokamak plasma

International Nuclear Information System (INIS)

Gahl, J.; Ishihara, O.; Wong, K.L.; Kristiansen, M.; Hagler, M.

1986-01-01

The first experimental observation of current generation by asymmetrical heating of ions is reported. Ions were asymmetrically heated by a unidirectional fast Alfven wave launched by a slow wave antenna inside a tokamak. Current generation was detected by measuring the asymmetry of the toroidal plasma current with probes at the top and bottom of the toroidal plasma column

Noncollinear cluster ferromagnetism in manganite-lanthanum perovskites in manganese abundance

International Nuclear Information System (INIS)

Zubov, Eh.E.; D'yakonov, V.P.; Szymczak, H.

2002-01-01

The theoretical substantiation of the noncollinear spin structure realization in the weakly doped subsystem on the LaMnO 3 basis, which is observed in the compounds with the manganese abundance (La 1-y Ca y ) 1-x Mn 1+x O 3 , where y = 0.03 and x = 0-0.4, is carried out. It is shown experimentally, that the samples with x > 0.1 manifest anomalous magnetization at T 200 E increases. It is assumed, that this is connected with origination of the sloped phase in the clusters of the manganese heterovalent ions. It is shown, that the account for the spin quanta properties leads to essential modification of the thermodynamic behavior of the magnetic with collectivized electrons [ru

Coherent structures at ion scales in fast and slow solar wind: Cluster observations

Science.gov (United States)

Perrone, D.; Alexandrova, O.; Zouganelis, Y.; Roberts, O.; Lion, S.; Escoubet, C. P.; Walsh, A. P.; Maksimovic, M.; Lacombe, C.

2017-12-01

Spacecraft measurements generally reveal that solar wind electromagnetic fluctuations are in a state of fully-developed turbulence. Turbulence represents a very complex problem in plasmas since cross-scale coupling and kinetic effects are present. Moreover, the intermittency phenomenon, i.e. the manifestation of the non-uniform and inhomogeneous energy transfer and dissipation in a turbulent system, represents a very important aspect of the solar wind turbulent cascade. Here, we study coherent structures responsible for solar wind intermittency around ion characteristic scales. We find that, in fast solar wind, intermittency is due to Alfvén vortex-like structures and current sheets. In slow solar wind, we observe as well compressive structures like magnetic solitons, holes and shocks. By using high-time resolution magnetic field data of multi-point measurements of Cluster spacecraft, we characterize the observed coherent structures in terms of topology and propagation speed. We show that all structures around ion characteristic scales, both in fast and slow solar wind, are characterized by a strong wave-vector anisotropy in the perpendicular direction with respect to the local magnetic field. Moreover, some of them propagate in the plasma rest frame in the direction perpendicular to the local field. Finally, a further analysis on the electron and ion velocity distributions shows a high variability; in particular, close to coherent structures the electron and ion distribution functions appear strongly deformed and far from the thermodynamic equilibrium. Possible interpretations of the observed structures and their role in the heating process of the plasma are also discussed.

Observations of the Evolution of Ion Outflow During a Sawtooth Event

Science.gov (United States)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Frey, H. U.

2015-12-01

Sawtooth oscillations are one of several convection modes known to exist in the magnetosphere. Recent simulations have suggested that O+^+ ions transported from the high-latitude ionosphere to the magnetotail can drive sawtooth events. We present observational case studies of sawtooth events using data from FAST near the noon-midnight meridional plane, Cluster in the magnetotail, GOES and LANL energetic particle sensors at geosynchronous orbit, and ACE solar wind data to investigate the evolution of ion outflow during sawtooth events and the question of whether O+^+ outflow from one tooth helps to drive subsequent teeth. We find that oxygen enters the tail from the lobes after each tooth onset, the oxygen fraction in the magnetotail often increases after a tooth onset, and that the oxygen fraction of outflowing ions increases after a tooth event both in the cusp and on the nightside. However, a significant amount of low energy oxygen (≲1 keV) can end up in the dayside inner magnetosphere.

Conical pitch angle distributions of very-low energy ion fluxes observed by ISEE 1

International Nuclear Information System (INIS)

Horowitz, J.L.; Baugher, C.R.; Chappell, C.R.; Shelley, E.G.; Young, D.T.

1982-01-01

Observations of low-energy ionospheric ions by the plasma composition experiment abroad ISEE 1 often show conical pitch angle distributions, that is, peak fluxes between 0 0 and 90 0 to the directions parallel or antiparallel to the magnetic field. Frequently, all three primary ionospheric ion species (H + , He + , and O + ) simultaneously exhibit conical distributions with peak fluxes at essentially the same pitch angle. A distinction is made here between unidirectional, or streaming, distributions, in which ions are traveling essentially from only one hemisphere, and symmetrical distributions, in which significant fluxes are observed traveling from both hemispheres. The orbital coverage for this survey was largely restricted to the night sector, approximately 2100--0600 LT, and moderate geomagnetic latitudes of 20 0 --40 0 . Also, lack of complete pitch angle coverage at all times may have reduced detection for conics with small cone angles. However, we may conclude that the unidirectional conical distributions observed in the northern hemisphere are always observed to be traveling from the northern hemisphere and that they exhibit the following characteristics relative to the symmetric distributions, in that they (1) are typically observed on higher L shells (that is, higher geomagnetic latitudes or larger geocentric distances or both), (2) tend to have significantly larger cone angles, and (3), are associated with higher magnetic activity levels

Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

Science.gov (United States)

Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J

2013-12-12

The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena.

Metallic ions in the upper atmosphere

International Nuclear Information System (INIS)

Kumar, S.

1979-01-01

During the past 20 years considerable progress has been made in establishing the presence of metallic ions in the sporadic E layers at mid latitudes and as discrete patches at high altitudes in the equatorial ionosphere. The E-region observations have been based on rocket flights, which represent local conditions faithfully. But the global distribution of metallic ions and variations relating to changes in season, local time, magnetic activity, etc., which require satellite data, have been largely unexamined. This work presents a few aspects of this missing global distribution over an altitude range of 100 to 1000 km, using the data from AE-C, AE-D, and OGO-6 satellites and the rocket flights 18.117 and 18.118 from Wallops Island on July 12 and 13, 1971. The rocket data provide a day-night pair of vertical profiles that include altitudes not covered by the satellites. Results are presented for Mg + , Al + , Si + and Fe + ions in terms of their detection probabilities, median concentrations and relative abundances with respect to Mg + ions as a function of significant geophysical parameters. Na + and K + ions have been excluded from this study because alkali metal ions driven off the spacecraft hamper the measurement of ambient Na + and K + ions. This study has indicated that in general different metallic ions appear together in comparable concentrations except for Al + , which is an order of magnitude smaller than the others

Constraints on the Primordial Black Hole Abundance from the First Advanced LIGO Observation Run Using the Stochastic Gravitational-Wave Background

Science.gov (United States)

Wang, Sai; Wang, Yi-Fan; Huang, Qing-Guo; Li, Tjonnie G. F.

2018-05-01

Advanced LIGO's discovery of gravitational-wave events is stimulating extensive studies on the origin of binary black holes. Assuming that the gravitational-wave events can be explained by binary primordial black hole mergers, we utilize the upper limits on the stochastic gravitational-wave background given by Advanced LIGO as a new observational window to independently constrain the abundance of primordial black holes in dark matter. We show that Advanced LIGO's first observation run gives the best constraint on the primordial black hole abundance in the mass range 1 M⊙≲MPBH≲100 M⊙, pushing the previous microlensing and dwarf galaxy dynamics constraints tighter by 1 order of magnitude. Moreover, we discuss the possibility to detect the stochastic gravitational-wave background from primordial black holes, in particular from subsolar mass primordial black holes, by Advanced LIGO in the near future.

Constraints on the Primordial Black Hole Abundance from the First Advanced LIGO Observation Run Using the Stochastic Gravitational-Wave Background.

Science.gov (United States)

Wang, Sai; Wang, Yi-Fan; Huang, Qing-Guo; Li, Tjonnie G F

2018-05-11

Advanced LIGO's discovery of gravitational-wave events is stimulating extensive studies on the origin of binary black holes. Assuming that the gravitational-wave events can be explained by binary primordial black hole mergers, we utilize the upper limits on the stochastic gravitational-wave background given by Advanced LIGO as a new observational window to independently constrain the abundance of primordial black holes in dark matter. We show that Advanced LIGO's first observation run gives the best constraint on the primordial black hole abundance in the mass range 1M_{⊙}≲M_{PBH}≲100M_{⊙}, pushing the previous microlensing and dwarf galaxy dynamics constraints tighter by 1 order of magnitude. Moreover, we discuss the possibility to detect the stochastic gravitational-wave background from primordial black holes, in particular from subsolar mass primordial black holes, by Advanced LIGO in the near future.

Void structure of O+ ions in the inner magnetosphere observed by the Van Allen Probes

Science.gov (United States)

Nakayama, Y.; Ebihara, Y.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Tanaka, T.

2016-12-01

The Van Allen Probes Helium Oxygen Proton Electron instrument observed a new type of enhancement of O+ ions in the inner magnetosphere during substorms. As the satellite moved outward in the premidnight sector, the flux of the O+ ions with energy 10 keV appeared first in the energy-time spectrograms. Then, the enhancement of the flux spread toward high and low energies. The enhanced flux of the O+ ions with the highest energy remained, whereas the flux of the ions with lower energy vanished near apogee, forming what we call the void structure. The structure cannot be found in the H+ spectrogram. We studied the generation mechanism of this structure by using numerical simulation. We traced the trajectories of O+ ions in the electric and magnetic fields from the global magnetohydrodynamics simulation and calculated the flux of O+ ions in the inner magnetosphere in accordance with the Liouville theorem. The simulated spectrograms are well consistent with the ones observed by Van Allen Probes. We suggest the following processes. (1) When magnetic reconnection starts, an intensive equatorward and tailward plasma flow appears in the plasma lobe. (2) The flow transports plasma from the lobe to the plasma sheet where the radius of curvature of the magnetic field line is small. (3) The intensive dawn-dusk electric field transports the O+ ions earthward and accelerates them nonadiabatically to an energy threshold; (4) the void structure appears at energies below the threshold.

Model and observations of Schottky-noise suppression in a cold heavy-ion beam.

Science.gov (United States)

Danared, H; Källberg, A; Rensfelt, K-G; Simonsson, A

2002-04-29

Some years ago it was found at GSI in Darmstadt that the momentum spread of electron-cooled beams of highly charged ions dropped abruptly to very low values when the particle number decreased to 10 000 or less. This has been interpreted as an ordering of the ions, such that they line up after one another in the ring. We report observations of similar transitions at CRYRING, including an accompanying drop in Schottky-noise power. We also introduce a model of the ordered beam from which the Schottky-noise power can be calculated numerically. The good agreement between the model calculation and the experimental data is seen as evidence for a spatial ordering of the ions.

Radial transport of high-energy oxygen ions into the deep inner magnetosphere observed by Van Allen Probes

Science.gov (United States)

Mitani, K.; Seki, K.; Keika, K.; Gkioulidou, M.; Lanzerotti, L. J.; Mitchell, D. G.; Kletzing, C.

2017-12-01

It is known that proton is main contributor of the ring current and oxygen ions can make significant contribution during major magnetic storms. Ions are supplied to the ring current by radial transport from the plasma sheet. Convective transport of lower-energy protons and diffusive transport of higher-energy protons were reported to contribute to the storm-time and quiet-time ring current respectively [e.g., Gkioulidou et al., 2016]. However, supply mechanisms of the oxygen ions are not clear. To characterize the supply of oxygen ions to the ring current during magnetic storms, we studied the properties of energetic proton and oxygen ion phase space densities (PSDs) for specific magnetic moment (μ) during the April 23-25, 2013, geomagnetic storm observed by the Van Allen Probes mission. We here report on radial transport of high-energy (μ ≥ 0.5 keV/nT) oxygen ions into the deep inner magnetosphere during the late main phase of the magnetic storm. Since protons show little change during this period, this oxygen radial transport is inferred to cause the development of the late main phase. Enhancement of poloidal magnetic fluctuations is simultaneously observed. We estimated azimuthal mode number ≤5 by using cross wavelet analysis with ground-based observation of IMAGE ground magnetometers. The fluctuations can resonate with drift and bounce motions of the oxygen ions. The results suggest that combination of the drift and drift-bounce resonances is responsible for the radial transport of high-energy oxygen ions into the deep inner magnetosphere. We also report on the radial transport of the high-energy oxygen ions into the deep inner magnetosphere during other magnetic storms.

Electron impact ionization of highly charged lithiumlike ions

International Nuclear Information System (INIS)

Wong, K.L.

1992-10-01

Electron impact ionization cross sections can provide valuable information about the charge-state and power balance of highly charged ions in laboratory and astrophysical plasmas. In the present work, a novel technique based on x-ray measurements has been used to infer the ionization cross section of highly charged lithiumlike ions on the Livermore electron beam ion trap. In particular, a correspondence is established between an observed x ray and an ionization event. The measurements are made at one energy corresponding to approximately 2.3 times the threshold energy for ionization of lithiumlike ions. The technique is applied to the transition metals between Z=22 (titanium, Ti 19+ ) and Z=26 (iron, Fe 23+ ) and to Z=56 (barium, Ba 53+ ). The results for the transition metals, which have an estimated 17-33% uncertainty, are in good overall agreement with a relativistic distorted-wave calculation. However, less good agreement is found for barium, which has a larger uncertainty. Methods for properly accounting for the polarization in the x-ray intensities and for inferring the charge-state abundances from x-ray observations, which were developed for the ionization measurements, as well as an x-ray model that assists in the proper interpretation of the data are also presented

Formation and fragmentation of quadruply charged molecular ions by intense femtosecond laser pulses.

Science.gov (United States)

Yatsuhashi, Tomoyuki; Nakashima, Nobuaki

2010-07-22

We investigated the formation and fragmentation of multiply charged molecular ions of several aromatic molecules by intense nonresonant femtosecond laser pulses of 1.4 mum with a 130 fs pulse duration (up to 2 x 10(14) W cm(-2)). Quadruply charged states were produced for 2,3-benzofluorene and triphenylene molecular ion in large abundance, whereas naphthalene and 1,1'-binaphthyl resulted only in up to triply charged molecular ions. The laser wavelength was nonresonant with regard to the electronic transitions of the neutral molecules, and the degree of fragmentation was strongly correlated with the absorption of the singly charged cation radical. Little fragmentation was observed for naphthalene (off-resonant with cation), whereas heavy fragmentation was observed in the case of 1,1'-binaphthyl (resonant with cation). The degree of H(2) (2H) and 2H(2) (4H) elimination from molecular ions increased as the charge states increased in all the molecules examined. A striking difference was found between triply and quadruply charged 2,3-benzofluorene: significant suppression of molecular ions with loss of odd number of hydrogen was observed in the quadruply charged ions. The Coulomb explosion of protons in the quadruply charged state and succeeding fragmentation resulted in the formation of triply charged molecular ions with an odd number of hydrogens. The hydrogen elimination mechanism in the highly charged state is discussed.

Abundances of Neutral and Ionized PAH Along The Lines-of-Sight of Diffuse and Translucent Interstellar Clouds

Science.gov (United States)

Salama, Farid; Galazutdinov, Gazinur; Krewloski, Jacek; Biennier, Ludovic; Beletsky, Yuri; Song, In-Ok

2013-01-01

The spectra of neutral and ionized PAHs isolated in the gas phase at low temperature have been measured in the laboratory under conditions that mimic interstellar conditions and are compared with a set of astronomical spectra of reddened, early type stars. The comparisons of astronomical and laboratory data provide upper limits for the abundances of neutral PAH molecules and ions along specific lines-of-sight. Something that is not attainable from infrared observations. We present the characteristics of the laboratory facility (COSmIC) that was developed for this study and discuss the findings resulting from the comparison of the laboratory data with high resolution, high S/N ratio astronomical observations. COSmIC combines a supersonic jet expansion with discharge plasma and cavity ringdown spectroscopy and provides experimental conditions that closely mimic the interstellar conditions. The column densities of the individual PAH molecules and ions probed in these surveys are derived from the comparison of the laboratory data with high resolution, high S/N ratio astronomical observations. The comparisons of astronomical and laboratory data lead to clear conclusions regarding the expected abundances for PAHs in the interstellar environments probed in the surveys. Band profile comparisons between laboratory and astronomical spectra lead to information regarding the molecular structures and characteristics associated with the DIB carriers in the corresponding lines-of-sight. These quantitative surveys of neutral and ionized PAHs in the optical range open the way for quantitative searches of PAHs and complex organics in a variety of interstellar and circumstellar environments.

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron CaptureAbundance Gradients

Science.gov (United States)

O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

2017-06-01

The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

Visual Observation of Dissolution of Copper Ions from a Copper Electrode

Science.gov (United States)

Ikemoto, Isao; Saitou, Kouichi

2013-01-01

During electrolysis, to visually observe the conversion of a metal to its cation, either the cation or its complex ion should have a distinct color while the electrolyte solution must be colorless and transparent. A demonstration is described in which copper is used as the electrodes and sodium polyacrylate (a superabsorbent polymer) solution is…

Discovery of energetic molecular ions (NO+ and O2+) in the storm time ring current

International Nuclear Information System (INIS)

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

1986-01-01

A few hours after the onset of a large geomagnetic storm on September 4, 1984, energetic molecular ions in the mass range 28--32, predminantly NO + and O 2 + , have been discovered in the outer ring current at L--7. The data have been obtained with the time-of-flight spectrometer SULEICA on the AMPTE/IRM spacecraft. We find at 160 keV/e a mean abundance ratio of the molecular ions relative to O + ions of 0.031 +- 0.004. During quiet times no molecular ions are observed, the 1 sigma upper limit of the ratio derived by averaging over several quiet periods is 0.003. The observations demonstrate the injection of ionospheric plasma into the storm time ring current and the subsequent acceleration to energies of several hundred keV on a time scale of a few hours after the onset of the magnetic storm

Energy time dispersion of a new class of magnetospheric ion events observed near the Earth's bow shock

Directory of Open Access Journals (Sweden)

G. C. Anagnostopoulos

2000-01-01

Full Text Available We have analyzed high time resolution (\\geq6 s data during the onset and the decay phase of several energetic (\\geq35 keV ion events observed near the Earth's bow shock by the CCE/AMPTE and IMP-7/8 spacecraft, during times of intense substorm/geomagnetic activity. We found that forward energy dispersion at the onset of events (earlier increase of middle energy ions and/or a delayed fall of the middle energy ion fluxes at the end of events are often evident in high time resolution data. The energy spectra at the onset and the decay of this kind of events show a characteristic hump at middle (50-120 keV energies and the angular distributions display either anisotropic or broad forms. The time scale of energy dispersion in the ion events examined was found to range from several seconds to \\sim1 h depending on the ion energies compared and on the rate of variation of the Interplanetary Magnetic Field (IMF direction. Several canditate processes are discussed to explain the observations and it is suggested that a rigidity dependent transport process of magnetospheric particles within the magnetosheath is most probably responsible for the detection of this new type of near bow shock magnetospheric ion events. The new class of ion events was observed within both the magnetosheath and the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks

Thorium molecular negative ion production in a cesium sputter source at BARC-TIFR pelletron accelerator ion source test set up

International Nuclear Information System (INIS)

Gupta, A.K.; Mehrotra, N.; Kale, R.M.; Alamelu, D.; Aggarwal, S.K.

2005-01-01

Ion source test set up at Pelletron Accelerator facility has been utilized extensively for the production and characterization of negative ions, with particular emphasis being place at the species of experimental users interest. The attention have been focussed towards the formation of rare earth negative ions, due to their importance in the ongoing accelerator mass spectroscopy program and isotopic abundance measurements using secondary negative ion mass spectrometry

An assessment of oceanic seabird abundance and distribution off the southern Brazilian coast using observations obtained during deep-water fishing operations.

Science.gov (United States)

Branco, J O; Fracasso, H A A; Pérez, J A A; Rodrigues-Filho, J L

2014-08-01

The use of discarded fish over baited hooks used in longline fishery, and fish caught in gillnets, as a food source for gulls, albatrosses and petrels has been intensively studied in northern and southern oceans. This study describes the occurrence and abundance of seabirds observed from 20 foreign vessels which operated during the period between July 2001 and May 2005, off the southeastern and southern Brazilian coast. A total of 353,557 seabirds were observed; comprising eight families and 28 species. The most abundant species was Procellaria conspicillata followed by Daption capense, Puffinus gravis, Thalassarche melanophrys and Oceanites oceanicus. Ten species of seabirds (392 individual birds) were incidentally captured in gillnets; and 122 birds (9 species) by longline hooks, with P. gravis, D. capense and Procellaria aequinoctialis having the largest capture rates.

VOYAGER OBSERVATIONS OF MAGNETIC WAVES DUE TO NEWBORN INTERSTELLAR PICKUP IONS: 2–6 au

International Nuclear Information System (INIS)

Aggarwal, Poornima; Taylor, David K.; Smith, Charles W.; Joyce, Colin J.; Fisher, Meghan K.; Isenberg, Philip A.; Vasquez, Bernard J.; Schwadron, Nathan A.; Cannon, Bradford E.; Richardson, John D.

2016-01-01

We report observations by the Voyager 1 and 2 spacecraft of low-frequency magnetic waves excited by newborn interstellar pickup ions H + and He + during 1978–1979 when the spacecraft were in the range from 2 to 6.3 au. The waves have the expected association with the cyclotron frequency of the source ions, are left-hand polarized in the spacecraft frame, and have minimum variance directions that are quasi-parallel to the local mean magnetic field. There is one exception to this in that one wave event that is excited by pickup H + is right-hand polarized in the spacecraft frame, but similar exceptions have been reported by Cannon et al. and remain unexplained. We apply the theory of Lee and Ip that predicts the energy spectrum of the waves and then compare growth rates with turbulent cascade rates under the assumption that turbulence acts to destroy the enhanced wave activity and transport the associated energy to smaller scales where dissipation heats the background plasma. As with Cannon et al., we find that the ability to observe the waves depends on the ambient turbulence being weak when compared with growth rates, thereby allowing sustained wave growth. This analysis implies that the coupled processes of pitch-angle scattering and wave generation are continuously associated with newly ionized pickup ions, despite the fact that the waves themselves may not be directly observable. When waves are not observed, but wave excitation can be argued to be present, the wave energy is simply absorbed by the turbulence at a rate that prevents significant accumulation. In this way, the kinetic process of wave excitation by scattering of newborn ions continues to heat the plasma without producing observable wave energy. These findings support theoretical models that invoke efficient scattering of new pickup ions, leading to turbulent driving in the outer solar wind and in the IBEX ribbon beyond the heliopause.

VOYAGER OBSERVATIONS OF MAGNETIC WAVES DUE TO NEWBORN INTERSTELLAR PICKUP IONS: 2–6 au

Energy Technology Data Exchange (ETDEWEB)

Aggarwal, Poornima [Electrical Engineering Department, Cooper Union, New York, NY 10003 (United States); Taylor, David K. [Rensselaer Polytechnic Institute, Troy, NH 12180 (United States); Smith, Charles W.; Joyce, Colin J.; Fisher, Meghan K.; Isenberg, Philip A.; Vasquez, Bernard J.; Schwadron, Nathan A. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 (United States); Cannon, Bradford E. [Physics Department, Florida State University, Tallahassee, FL 32306 (United States); Richardson, John D., E-mail: neema2000@gmail.com, E-mail: daves@orol.org, E-mail: Charles.Smith@unh.edu, E-mail: cjl46@wildcats.unh.edu, E-mail: mkl54@wildcats.unh.edu, E-mail: Phil.Isenberg@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: N.Schwadron@unh.edu, E-mail: bc13h@my.fsu.edu, E-mail: jdr@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 37-655, Cambridge, MA 02139 (United States)

2016-05-10

We report observations by the Voyager 1 and 2 spacecraft of low-frequency magnetic waves excited by newborn interstellar pickup ions H{sup +} and He{sup +} during 1978–1979 when the spacecraft were in the range from 2 to 6.3 au. The waves have the expected association with the cyclotron frequency of the source ions, are left-hand polarized in the spacecraft frame, and have minimum variance directions that are quasi-parallel to the local mean magnetic field. There is one exception to this in that one wave event that is excited by pickup H{sup +} is right-hand polarized in the spacecraft frame, but similar exceptions have been reported by Cannon et al. and remain unexplained. We apply the theory of Lee and Ip that predicts the energy spectrum of the waves and then compare growth rates with turbulent cascade rates under the assumption that turbulence acts to destroy the enhanced wave activity and transport the associated energy to smaller scales where dissipation heats the background plasma. As with Cannon et al., we find that the ability to observe the waves depends on the ambient turbulence being weak when compared with growth rates, thereby allowing sustained wave growth. This analysis implies that the coupled processes of pitch-angle scattering and wave generation are continuously associated with newly ionized pickup ions, despite the fact that the waves themselves may not be directly observable. When waves are not observed, but wave excitation can be argued to be present, the wave energy is simply absorbed by the turbulence at a rate that prevents significant accumulation. In this way, the kinetic process of wave excitation by scattering of newborn ions continues to heat the plasma without producing observable wave energy. These findings support theoretical models that invoke efficient scattering of new pickup ions, leading to turbulent driving in the outer solar wind and in the IBEX ribbon beyond the heliopause.

Observations of upflowing ionospheric ions in the mid-altitude cusp/cleft region with the Viking satellite

International Nuclear Information System (INIS)

Thelin, B.; Aparicio, B.; Lundin, R.

1990-01-01

Measurements of positive ions (0.1-10 keV) from the polar-orbiting Viking satellite have been obtained in the cusp/cleft region and have been tabulated in MLT versus invariant latitude plots to get a synoptic picture of the occurrence of upgoing auroral positive ions. A distinction was made between ion distributions with peak fluxes along B (ion beam) and those exhibiting flux maxima that are not field-aligned (conics). Both beams and conics are shown to be common auroral phenomena, whose frequencies of occurrence in MLT, invariant latitude, and altitude were studied. During the period of study (March-June 1986) the ion beams were more frequenty (about a factor of 2) in the dusk sector than in the dawn sector. This effect seemed to increase with magnetic activity but was mostly unchanged with the sign of the interplanetary magnetic field B y component. An investigation was also made of the invariant latitude dependence for beams and conics, where the dawn sector beams have a tendency to be lcoated toward higher invariant latitudes for both positive and negative B y components. The ion beams were observed primarily above 5,000 km with a frequency of occurrence increasing with altitude up to the satellite apogee at about 13,500 km. The ion conics were observed from above 7,000 km to be steadily increasing in altitude

Remote sensing of electron density and ion composition using nonducted whistler observations on OGO 1 and Van Allen Probes

Science.gov (United States)

Sonwalkar, V. S.; Butler, J.; Reddy, A.

2017-12-01

We present a new method to remotely measure magnetospheric electron density and ion composition using lightning generated nonducted whistlers observed on a satellite. Electron and ion densities play important roles in magnetospheric processes such as wave-particle interactions in the equatorial region and ion-neutral dynamics in the ionosphere, and are important for calculating space weather effects such as particle precipitation, GPS scintillations, and satellite drag. The nonducted whistler resulting from a single lightning appears on a spectrogram as a series of magnetospherically reflected traces with characteristic dispersion (time delay versus frequency) and upper and lower cut off frequencies. Ray tracing simulations show that these observed characteristics depend on the magnetospheric electron density and ion composition. The cut off frequencies depend on both electron density and ion composition. The dispersion depends strongly on electron density, but weakly on ion composition. Using an iterative process to fit the measured dispersion and cutoff frequencies to those obtained from ray tracing simulations, it is possible to construct the electron and ion density profiles of the magnetosphere. We demonstrate our method by applying it to nonducted whistlers observed on OGO 1 and Van Allen probe satellites. In one instance (08 Nov 1965), whistler traces observed on OGO 1 (L = 2.4, λm = -6°) displayed a few seconds of dispersion and cutoff frequencies in the 1-10 kHz range. Ray tracing analysis showed that a diffusive equilibrium density model with the following parameters can reproduce the observed characteristics of the whistler traces: 1900 el/cc at L=2.4 and the equator, 358,000 el/cc at F2 peak (hmF2 = 220 km), the relative ion concentrations αH+ = 0.2, αHe+ = 0.2, and αO+ = 0.6 at 1000 km, and temperature 1600 K. The method developed here can be applied to whistlers observed on the past, current, and future magnetospheric satellite missions carrying

Cluster observations of ion dispersion discontinuities in the polar cusp

Science.gov (United States)

Escoubet, C. P.; Berchem, J.; Pitout, F.; Richard, R. L.; Trattner, K. J.; Grison, B.; Taylor, M. G.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.

2009-12-01

The reconnection between the interplanetary magnetic field (IMF) and the Earth’s magnetic field is taking place at the magnetopause on magnetic field lines threading through the polar cusp. When the IMF is southward, reconnection occurs near the subsolar point, which is magnetically connected to the equatorward boundary of the polar cusp. Subsequently the ions injected through the reconnection point precipitate in the cusp and are dispersed poleward. If reconnection is continuous and operates at constant rate, the ion dispersion is smooth and continuous. On the other hand if the reconnection rate varies, we expect interruption in the dispersion forming energy steps or staircase. Similarly, multiple entries near the magnetopause could also produce steps at low or mid-altitude when a spacecraft is crossing subsequently the field lines originating from these multiple sources. In addition, motion of the magnetopause induced by solar wind pressure changes or erosion due to reconnection can also induce a motion of the polar cusp and a disruption of the ions dispersion observed by a spacecraft. Cluster with four spacecraft following each other in the mid-altitude cusp can be used to distinguish between these “temporal” and “spatial” effects. We will present a cusp crossing with two spacecraft, separated by around two minutes. The two spacecraft observed a very similar dispersion with a step in energy in its centre and two other dispersions poleward. We will show that the steps could be temporal (assuming that the time between two reconnection bursts corresponds to the time delay between the two spacecraft) but it would be a fortuitous coincidence. On the other hand the steps and the two poleward dispersions could be explained by spatial effects if we take into account the motion of the open-closed boundary between the two spacecraft crossings.

Can occupancy-abundance models be used to monitor wolf abundance?

Directory of Open Access Journals (Sweden)

M Cecilia Latham

Full Text Available Estimating the abundance of wild carnivores is of foremost importance for conservation and management. However, given their elusive habits, direct observations of these animals are difficult to obtain, so abundance is more commonly estimated from sign surveys or radio-marked individuals. These methods can be costly and difficult, particularly in large areas with heavy forest cover. As an alternative, recent research has suggested that wolf abundance can be estimated from occupancy-abundance curves derived from "virtual" surveys of simulated wolf track networks. Although potentially more cost-effective, the utility of this approach hinges on its robustness to violations of its assumptions. We assessed the sensitivity of the occupancy-abundance approach to four assumptions: variation in wolf movement rates, changes in pack cohesion, presence of lone wolves, and size of survey units. Our simulations showed that occupancy rates and wolf pack abundances were biased high if track surveys were conducted when wolves made long compared to short movements, wolf packs were moving as multiple hunting units as opposed to a cohesive pack, and lone wolves were moving throughout the surveyed landscape. We also found that larger survey units (400 and 576 km2 were more robust to changes in these factors than smaller survey units (36 and 144 km2. However, occupancy rates derived from large survey units rapidly reached an asymptote at 100% occupancy, suggesting that these large units are inappropriate for areas with moderate to high wolf densities (>15 wolves/1,000 km2. Virtually-derived occupancy-abundance relationships can be a useful method for monitoring wolves and other elusive wildlife if applied within certain constraints, in particular biological knowledge of the surveyed species needs to be incorporated into the design of the occupancy surveys. Further, we suggest that the applicability of this method could be extended by directly incorporating some of its

Abundances of neon, sulfur, and argon in planetary nebulae

International Nuclear Information System (INIS)

Beck, S.C.; Lacy, J.H.; Townes, C.H.; Geballe, T.R.; Baas, F.

1981-01-01

Infrared observations of [Ne II], [S IV], and [Ar III] are used with optical observations to discuss the abundances of Ne, S, and Ar in 18 planetary nebulae. In addition, infrared observations of 18 other nebulae are presented. The derived abundances of S and Ar are each slightly enhanced relative to previous studies

Analysis of Solar Wind Precipitation on Mars Using MAVEN/SWIA Observations of Spacecraft-Scattered Ions

Science.gov (United States)

Lue, C.; Halekas, J. S.

2017-12-01

Particle sensors on the MAVEN spacecraft (SWIA, SWEA, STATIC) observe precipitating solar wind ions during MAVEN's periapsis passes in the Martian atmosphere (at 120-250 km altitude). The signature is observed as positive and negative particles at the solar wind energy, traveling away from the Sun. The observations can be explained by the solar wind penetrating the Martian magnetic barrier in the form of energetic neutral atoms (ENAs) due to charge-exchange with the Martian hydrogen corona, and then being reionized in positive or negative form upon impact with the atmosphere (1). These findings have elucidated solar wind precipitation dynamics at Mars, and can also be used to monitor the solar wind even when MAVEN is at periapsis (2). In the present study, we focus on a SWIA instrument background signal that has been interpreted as spacecraft/instrument-scattered ions (2). We aim to model and subtract the scattered ion signal from the observations including those of reionized solar wind. We also aim to use the scattered ion signal to track hydrogen ENAs impacting the spacecraft above the reionization altitude. We characterize the energy spectrum and directional scattering function for solar wind scattering off the SWIA aperture structure, the radome and the spacecraft body. We find a broad scattered-ion energy spectrum up to the solar wind energy, displaying increased energy loss and reduced flux with increasing scattering angle, allowing correlations with the solar wind direction, energy, and flux. We develop models that can be used to predict the scattered signal based on the direct solar wind observations or to infer the solar wind properties based on the observed scattered signal. We then investigate deviations to the models when the spacecraft is in the Martian atmosphere and evaluate the plausibility of that these are caused by ENAs. We also perform SIMION modeling of the scattering process and the resulting signal detection by SWIA, to study the results from

Ion implantation artifacts observed in depth profiling boron in silicon by secondary ion mass spectrometry

International Nuclear Information System (INIS)

Chi, P.; Simons, D.S.

1987-01-01

A comparison study of depth profiling by secondary ion mass spectrometry (SIMS) and neutron depth profiling (NDP) was recently conducted. The specimens were portions of 5 cm diameter single crystal silicon slices in which B-10 had been implanted at various fluences and energies. NDP measurements were made on a 13 mm diameter area at the center of the wafers. SIMS measurements were taken from a 60 μm diameter area approximately 16 mm from the center of the wafer. One observation that emerged from this work was an apparent discrepancy between the profiles of B-10 measured by DNP and SIMS. The peaks of the SIMS profiles were typically deeper than those of NDP by as much as 30 nm, which is 10% of the projected range for a 70 keV implant. Moreover, the profiles could not be made to coincide by either a constant shift or a proportional change of one depth scale with respect to the other. The lateral inhomogeneity of boron that these experiments have demonstrated arises from the variable contribution of ion channeling during implantation

Nitrogen abundance in Comet Halley

International Nuclear Information System (INIS)

Wyckoff, S.; Tegler, S.C.; Engel, L.

1991-01-01

Data on the nitrogen-containing compounds that observed spectroscopically in the coma of Comet Halley are summarized, and the elemental abundance of nitrogen in the Comet Halley nucleus is derived. It is found that 90 percent of elemental nitrogen is in the dust fraction of the coma, while in the gas fraction, most of the nitrogen is contained in NH3 and CN. The elemental nitrogen abundance in the ice component of the nucleus was found to be deficient by a factor of about 75, relative to the solar photosphere, indicating that the chemical partitioning of N2 into NH3 and other nitrogen compounds during the evolution of the solar nebula cannot account completely for the low abundance ratio N2/NH3 = 0.1, observed in the comet. It is suggested that the low N2/NH3 ratio in Comet Halley may be explained simply by physical fractionation and/or thermal diffusion. 88 refs

THE ABUNDANCES OF LIGHT NEUTRON-CAPTURE ELEMENTS IN PLANETARY NEBULAE. III. THE IMPACT OF NEW ATOMIC DATA ON NEBULAR SELENIUM AND KRYPTON ABUNDANCE DETERMINATIONS

Energy Technology Data Exchange (ETDEWEB)

Sterling, N. C. [Department of Physics, University of West Georgia, 1601 Maple Street, Carrollton, GA 30118 (United States); Porter, R. L. [Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, GA 30602 (United States); Dinerstein, Harriet L., E-mail: nsterlin@westga.edu, E-mail: ryanlporter@gmail.com, E-mail: harriet@astro.as.utexas.edu [Department of Astronomy, University of Texas, 2515 Speedway, C1400, Austin, TX 78712-1205 (United States)

2015-06-22

The detection of neutron(n)-capture elements in several planetary nebulae (PNe) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. However, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. Recently, photoionization (PI) and recombination data were determined for Se and Kr, the two most widely detected n-capture elements in nebular spectra. We have incorporated these new data into the photoionization code Cloudy. To test the atomic data, numerical models were computed for 15 PNe that exhibit emission lines from multiple Kr ions. We found systematic discrepancies between the predicted and observed emission lines that are most likely caused by inaccurate PI and recombination data. These discrepancies were removed by adjusting the Kr{sup +}–Kr{sup 3+} PI cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. From grids of models spanning the physical conditions encountered in PNe, we derive new, broadly applicable ionization correction factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs were applied to our previous survey of near-infrared [Kr iii] and [Se iv] emission lines in 120 PNe. The revised Se and Kr abundances are 0.1–0.3 dex lower than former estimates, with average values of [Se/(O, Ar)] = 0.12 ± 0.27 and [Kr/(O, Ar)] = 0.82 ± 0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. We also find a tendency for high-velocity PNe that can be associated with the Galactic thick disk to exhibit larger s-process enrichments than low-velocity PNe belonging to the thin-disk population.

Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

Science.gov (United States)

Hermanspahn; Haffner; Kluge; Quint; Stahl; Verdu; Werth

2000-01-17

We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Detailed Age and Abundance Gradients using DR12

Science.gov (United States)

Frinchaboy, Peter M.; Thompson, Benjamin A.; O'Connell, Julia; Meyer, Brianne; Donor, John; Majewski, Steven R.; Holtzman, Jon A.; Zasowski, Gail; Beers, Timothy C.; Beaton, Rachael; Cunha, Katia M. L.; Hearty, Fred; Nidever, David L.; Schiavon, Ricardo P.; Smith, Verne V.; Hayden, Michael R.

2015-01-01

We present detailed abundance results for Galactic open clusters as part of the Open Cluster Chemical Abundances and Mapping (OCCAM) Survey, which is based primarily on data from the Sloan Digital Sky Survey/ Apache Point Observatory Galactic Evolution Experiment. Using 100 open clusters from the uniformly observed complete SDSS-III/APOGEE-1 DR12 dataset, we present age and multi-element abundance gradients for the disk of the Milky Way.This work is supported by an NSF AAG grant AST-1311835.

Ulysses observations of magnetic waves due to newborn interstellar pickup ions. II. Application of turbulence concepts to limiting wave energy and observability

Energy Technology Data Exchange (ETDEWEB)

Cannon, Bradford E. [Physics Department, Florida State University, Tallahassee, FL 32306 (United States); Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Joyce, Colin J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 (United States); Murphy, Neil [Jet Propulsion Laboratory, Mail Stop 180-600, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Nuno, Raquel G., E-mail: bc13h@my.fsu.edu, E-mail: Charles.Smith@unh.edu, E-mail: Phil.Isenberg@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: cjl46@wildcats.unh.edu, E-mail: Neil.Murphy@jpl.nasa.gov, E-mail: raquel.nuno@asu.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)

2014-06-01

The low-frequency magnetic waves that arise from the isotropization of newborn interstellar pickup ions (PUIs) are reasonably well described by linear and quasi-linear kinetic theory in so far as those theories predict the wave frequency and polarization in the spacecraft frame. Those theories fail to describe the scarce observability of the waves. Quasilinear theory predicts that the wave power should accumulate over long periods of time as the relatively weak kinetic instability slowly adds power to the observed spectrum. At the same time it has been argued that the same wave energy must serve as a secondary source of thermal ion heating in the outer heliosphere once the initial turbulence is depleted. To the extent that turbulent transport of the wave energy acts against the spectrally confined accumulation of wave energy, turbulence should be a limiting factor in observability. We argue that turbulence does limit the observability of the waves and we use turbulence theory to predict the observed wave energy. We compare this prediction against a database of 502 wave observations attributed to newborn interstellar PUIs observed by the Ulysses spacecraft.

Ulysses observations of magnetic waves due to newborn interstellar pickup ions. II. Application of turbulence concepts to limiting wave energy and observability

International Nuclear Information System (INIS)

Cannon, Bradford E.; Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Joyce, Colin J.; Murphy, Neil; Nuno, Raquel G.

2014-01-01

The low-frequency magnetic waves that arise from the isotropization of newborn interstellar pickup ions (PUIs) are reasonably well described by linear and quasi-linear kinetic theory in so far as those theories predict the wave frequency and polarization in the spacecraft frame. Those theories fail to describe the scarce observability of the waves. Quasilinear theory predicts that the wave power should accumulate over long periods of time as the relatively weak kinetic instability slowly adds power to the observed spectrum. At the same time it has been argued that the same wave energy must serve as a secondary source of thermal ion heating in the outer heliosphere once the initial turbulence is depleted. To the extent that turbulent transport of the wave energy acts against the spectrally confined accumulation of wave energy, turbulence should be a limiting factor in observability. We argue that turbulence does limit the observability of the waves and we use turbulence theory to predict the observed wave energy. We compare this prediction against a database of 502 wave observations attributed to newborn interstellar PUIs observed by the Ulysses spacecraft.

Cosmological evolution of the nitrogen abundance

Science.gov (United States)

Vangioni, Elisabeth; Dvorkin, Irina; Olive, Keith A.; Dubois, Yohan; Molaro, Paolo; Petitjean, Patrick; Silk, Joe; Kimm, Taysun

2018-06-01

The abundance of nitrogen in the interstellar medium is a powerful probe of star formation processes over cosmological time-scales. Since nitrogen can be produced both in massive and intermediate-mass stars with metallicity-dependent yields, its evolution is challenging to model, as evidenced by the differences between theoretical predictions and observations. In this work, we attempt to identify the sources of these discrepancies using a cosmic evolution model. To further complicate matters, there is considerable dispersion in the abundances from observations of damped Lyα absorbers (DLAs) at z ˜ 2-3. We study the evolution of nitrogen with a detailed cosmic chemical evolution model and find good agreement with these observations, including the relative abundances of (N/O) and (N/Si). We find that the principal contribution of nitrogen comes from intermediate-mass stars, with the exception of systems with the lowest N/H, where nitrogen production might possibly be dominated by massive stars. This last result could be strengthened if stellar rotation which is important at low metallicity can produce significant amounts of nitrogen. Moreover, these systems likely reside in host galaxies with stellar masses below 108.5 M⊙. We also study the origin of the observed dispersion in nitrogen abundances using the cosmological hydrodynamical simulations Horizon-AGN. We conclude that this dispersion can originate from two effects: difference in the masses of the DLA host galaxies, and difference in their position inside the galaxy.

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Science.gov (United States)

Testa, D.; Albergante, M.

2012-08-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium-tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

International Nuclear Information System (INIS)

Testa, D.; Albergante, M.

2012-01-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium–tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the

Ion acceleration at the earth's bow shock: A review of observations in the upstream region

International Nuclear Information System (INIS)

Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.

1979-01-01

Positive ions are accelerated at or near the earth's bow shock and propagate into the upstream region. Two distinctly different population of these ions, distinguished by their greatly different spectral and angular widths, can be identified there. The type of ion population observed in the upstream region is strongly correlated with the presence or absence of long-period compresive waves in the solar wind. Very few ions are accelerated in the vicinity of the shock to energies much above about 100 keV. It is not yet clear whether the most energetic ions (i.e. those near 100 keV) are accelerated at the shock or in the broad disturbed region upstream from the shock. In either case stochastic acceleration by turbulent electrostatic fields seems to be the most viable candidate for the acceleration of the most energetic particles

Ion acceleration at the earth's bow shock: a review of observations in the upstream region

International Nuclear Information System (INIS)

Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.

1979-01-01

Positive ions are accelerated at or near the earth's bow shock and propagate into the upstream region. Two distinctly different populations of these ions, distinguished by their greatly different spectral and angular widths, can be identified there. The type of ion population observed in the upstream region is strongly correlated with the presence or absence of long-period compressive waves in the solar wind. Very few ions are accelerated in the vicinity of the shock to energies much above about 100 keV. It is not yet clear whether the most energetic ions (i.e., those near 100 keV) are accelerated at the shock or in broad disturbed region upstream from the shock. In either case stochastic acceleration by turbulent electrostatic fields seems to be the most viable candidate for the acceleration of the most energetic particles

Observation and Modeling of the Generation Mechanism of Ion Upflow during Sudden Commencement

Science.gov (United States)

Zou, S.; Ozturk, D. S.; Li, C.; Varney, R. H.; Reimer, A.

2017-12-01

Sudden commencement (SC) induced by solar wind pressure enhancement can produce significant global impact on the coupled magnetosphere-ionosphere (MI) system, and its effects have been studied extensively using ground magnetometers and coherent scatter radars. However, very limited observations have been reported about the effects of SC on the ionospheric plasma. We study the ionosphere response to the SC using the Poker Flat incoherent scatter radar (PFISR) and numerical simulations. A detailed case study of SC during the 17 March 2015 storm was conducted. PFISR observed lifting of the F region ionosphere, transient field-aligned ion upflow, prompt but short-lived ion temperature increase, subsequent F region density decrease, and persistent electron temperature increase. A global magnetohydrodynamic (MHD) simulation has been carried out to characterize the SC-induced current, convection, and magnetic perturbations. Simulated magnetic perturbations at Poker Flat show a satisfactory agreement with observations. The simulation provides a global context for linking localized PFISR observations to large-scale dynamic processes in the MI system. Following the case study, we also perform a statistical study of the effects of SC on the ionosphere focusing on the magnetic local time and latitudinal asymmetries using PFISR and GPS TEC.

Heavy element abundances of Nova Cygni 1975

International Nuclear Information System (INIS)

Ferland, G.J.; Shields, G.A.

1978-01-01

McDonald observations of the nebular phase of the outburst of Nova Cygni 1975 are analyzed to measure the abundances of several heavy elements. A new analytical procedure is used to derive the electron density and temperature from the emission line intensities of [O III], [Ne III], and He I observed between days 40 and 120. These physical conditions are used to derive the abundances. We find that Fe has approximately a solar abundance, whereas C, N, O, and Ne are enhanced by factors approx.20 to 100. The enhanced abundance of neon was theoretically unexpected.The derived physical conditions and line intensities are compared with predictions of an equilibrium photoionization model. The model successfully predicts the intensities of He I, [O III], and [Ne III]; but it underestimates the strength of [Ne V] and [Fe VII], which may originate in a mechanically heated ''subcoronal'' line region

Dependence of simulated positron emitter yields in ion beam cancer therapy on modeling nuclear fragmentation

DEFF Research Database (Denmark)

Lühr, Armin; Priegnitz, Marlen; Fiedler, Fine

2014-01-01

In ion beam cancer therapy, range verification in patients using positron emission tomography (PET) requires the comparison of measured with simulated positron emitter yields. We found that (1) changes in modeling nuclear interactions strongly affected the positron emitter yields and that (2) Monte...... Carlo simulations with SHIELD-HIT10A reasonably matched the most abundant PET isotopes 11C and 15O. We observed an ion-energy (i.e., depth) dependence of the agreement between SHIELD-HIT10A and measurement. Improved modeling requires more accurate measurements of cross-section values....

Investigation into the behavior of metal-argon polyatomic ions (MAr+) in the extraction region of inductively coupled plasma-mass spectrometry

International Nuclear Information System (INIS)

Ebert, Chris H.; Witte, Travis M.; Houk, R.S.

2012-01-01

The abundances of metal-argon polyatomic ions (MAr + ) are determined in inductively coupled plasma-mass spectrometry (ICP-MS). The ratios of MAr + abundance to that for M + ions are measured experimentally. These ratios are compared to expected values, calculated for typical plasma conditions using spectroscopic data. For all metals studied (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn), the measured ratios are significantly lower than the calculated ratios. Increasing the plasma potential (and thereby increasing the ion kinetic energy) by means of a homemade guard electrode with a wide gap further reduces the MAr + /M + ratio. Implementing a skimmer cone designed for high transmission of light ions increases the MAr + abundance. Considering this evidence, the scarcity of MAr + ions is attributed to collision induced dissociation (CID), likely due to a shock wave at the tip of or in the throat of the skimmer cone. - Highlights: ► MAr + ions are less abundant in the mass spectrum than expected from the ICP. ► Increasing the plasma potential reduces their abundance further. ► The extraction lens voltage does not greatly affect the MAr + abundances. ► The weakly-bound MAr + ions are probably dissociated by collisions during extraction.

An algorithm to correct saturated mass spectrometry ion abundances for enhanced quantitation and mass accuracy in omic studies

Energy Technology Data Exchange (ETDEWEB)

Bilbao, Aivett; Gibbons, Bryson C.; Slysz, Gordon W.; Crowell, Kevin L.; Monroe, Matthew E.; Ibrahim, Yehia M.; Smith, Richard D.; Payne, Samuel H.; Baker, Erin S.

2018-04-01

The mass accuracy and peak intensity of ions detected by mass spectrometry (MS) measurements are essential to facilitate compound identification and quantitation. However, high concentration species can easily cause problems if their ion intensities reach beyond the limits of the detection system, leading to distorted and non-ideal detector response (e.g. saturation), and largely precluding the calculation of accurate m/z and intensity values. Here we present an open source computational method to correct peaks above a defined intensity (saturated) threshold determined by the MS instrumentation such as the analog-to-digital converters or time-to-digital converters used in conjunction with time-of-flight MS. In this method, the isotopic envelope for each observed ion above the saturation threshold is compared to its expected theoretical isotopic distribution. The most intense isotopic peak for which saturation does not occur is then utilized to re-calculate the precursor m/z and correct the intensity, resulting in both higher mass accuracy and greater dynamic range. The benefits of this approach were evaluated with proteomic and lipidomic datasets of varying complexities. After correcting the high concentration species, reduced mass errors and enhanced dynamic range were observed for both simple and complex omic samples. Specifically, the mass error dropped by more than 50% in most cases with highly saturated species and dynamic range increased by 1-2 orders of magnitude for peptides in a blood serum sample.

Observation of transient lattice vacancies produced during high-energy ion irradiation of Ni foils

International Nuclear Information System (INIS)

Tsuchida, Hidetsugu; Iwai, Takeo; Awano, Misa; Kishida, Mutsumi; Katayama, Ichiro; Jeong, Sun-Chang; Ogawa, Hidemi; Sakamoto, Naoki; Komatsu, Masao; Itoh, Akio

2007-01-01

Real-time positron annihilation spectroscopy has been applied for the first time for the investigation of lattice vacancies produced during ion irradiation. Measurements were performed for thin nickel foils irradiated with 2.5 MeV C ions. Doppler broadenings of positron annihilation γ-rays were measured alternately during beam-on and beam-off conditions. It was found that the Doppler broadening line-shape parameter measured during irradiation is larger than those obtained before and after irradiation. This evidently implies that transient or non-survivable vacancy defects are produced during ion irradiation. On the other hand, no such significant change in the line-shape parameter was observed for other face-centred-cubic metal forms of aluminium

Relationships between protein-encoding gene abundance and corresponding process are commonly assumed yet rarely observed

Science.gov (United States)

Rocca, Jennifer D.; Hall, Edward K.; Lennon, Jay T.; Evans, Sarah E.; Waldrop, Mark P.; Cotner, James B.; Nemergut, Diana R.; Graham, Emily B.; Wallenstein, Matthew D.

2015-01-01

For any enzyme-catalyzed reaction to occur, the corresponding protein-encoding genes and transcripts are necessary prerequisites. Thus, a positive relationship between the abundance of gene or transcripts and corresponding process rates is often assumed. To test this assumption, we conducted a meta-analysis of the relationships between gene and/or transcript abundances and corresponding process rates. We identified 415 studies that quantified the abundance of genes or transcripts for enzymes involved in carbon or nitrogen cycling. However, in only 59 of these manuscripts did the authors report both gene or transcript abundance and rates of the appropriate process. We found that within studies there was a significant but weak positive relationship between gene abundance and the corresponding process. Correlations were not strengthened by accounting for habitat type, differences among genes or reaction products versus reactants, suggesting that other ecological and methodological factors may affect the strength of this relationship. Our findings highlight the need for fundamental research on the factors that control transcription, translation and enzyme function in natural systems to better link genomic and transcriptomic data to ecosystem processes.

Impact of energetic cosmic-ray ions on astrophysical ice grains

International Nuclear Information System (INIS)

Mainitz, Martin; Anders, Christian; Urbassek, Herbert M.

2017-01-01

Highlights: • We use the REAX potential to model dissociations and reactions. • An ice grain consisting of a mixture of small molecules is considered. • The passage of a cosmic-ray ion initiates an ion track. • The track induces a shock wave and disintegrates the grain. • Abundant fragments and reaction products are detected. - Abstract: Using molecular-dynamics simulation with REAX potentials, we study the consequences of cosmic-ray ion impact on ice grains. The grains are composed of a mixture of H_2O, CO_2, NH_3, and CH_3OH molecules. Due to the high energy deposition of the cosmic-ray ion, 5 keV/nm, a strong pressure wave runs through the grain, while the interior of the ion track gasifies. Abundant molecular dissociations occur; reactions of the fragments form a variety of novel molecular product species.

Development of a collision induced dissociation ion cyclotron resonance spectrometer

International Nuclear Information System (INIS)

Fan, Y.N.

1982-01-01

A transient analysis ion cyclotron resonance spectrometer is developed to investigate the phenomena of collision induced dissociation. The Fourier transform method and the modified maximum entropy spectral analysis or covariance least square method are implemented in measuring the mass spectrum of the ion ensemble. The Fourier transform method can be used in quantitative analysis while the maximum entropy method as developed here is useful for qualitative analysis only. The cyclotron resonance frequency, relaxation time constant, and the relative ion population are observable from the Fourier transform spectrum. These parameters are very important in investigating collision induced dissociation process and other topics in gas phase chemistry. The ion cyclotron resonance spectrometer is not only developed to study fragments and their abundance from a parent ion, but also to determine the threshold energy and reaction cross section in the collision induced dissociation process. When hard sphere model is used in the ion-molecule collision, the radius of acetone ion measured from the reactive cross section is 2.2 angstrom which is very close to the physical dimension of acetone. The threshold energy for acetone ion in collision induced dissociation process is 1.8 eV which is similar to the result obtained by the angle-resolved mass spectrometer

Ultraviolet Spectroscopic Observations of Coronal Streamers in the ...

Indian Academy of Sciences (India)

UVCS) on the Solar and Heliospheric Observatory can be used to determine physical parameters in the solar corona such as hydrogen and ion kinetic temperatures, electron densities, and absolute elemental abundances. Hydrogen and ion ...

Structure and further fragmentation of significant [a3 + Na - H]+ ions from sodium-cationized peptides.

Science.gov (United States)

Wang, Huixin; Wang, Bing; Wei, Zhonglin; Zhang, Hao; Guo, Xinhua

2015-01-01

A good understanding of gas-phase fragmentation chemistry of peptides is important for accurate protein identification. Additional product ions obtained by sodiated peptides can provide useful sequence information supplementary to protonated peptides and improve protein identification. In this work, we first demonstrate that the sodiated a3 ions are abundant in the tandem mass spectra of sodium-cationized peptides although observations of a3 ions have rarely been reported in protonated peptides. Quantum chemical calculations combined with tandem mass spectrometry are used to investigate this phenomenon by using a model tetrapeptide GGAG. Our results reveal that the most stable [a3 + Na - H](+) ion is present as a bidentate linear structure in which the sodium cation coordinates to the two backbone carbonyl oxygen atoms. Due to structural inflexibility, further fragmentation of the [a3 + Na - H](+) ion needs to overcome several relatively high energetic barriers to form [b2 + Na - H](+) ion with a diketopiperazine structure. As a result, low abundance of [b2 + Na - H](+) ion is detected at relatively high collision energy. In addition, our computational data also indicate that the common oxazolone pathway to generate [b2 + Na - H](+) from the [a3 + Na - H](+) ion is unlikely. The present work provides a mechanistic insight into how a sodium ion affects the fragmentation behaviors of peptides. Copyright © 2015 John Wiley & Sons, Ltd.

MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

Science.gov (United States)

Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

2015-04-01

The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

Direct observation of the vacancy structure of depleted zones in tungsten ion irradiated at 100K

International Nuclear Information System (INIS)

Wei, C.Y.; Seidman, D.N.

1978-12-01

The structure of depleted zones (DZs) created by the in-situ irradiation of tungsten specimens, at 10 0 K, with 30 keV W + , Mo + or Cr + ions has been studied by field-ion microscopy. As the mass of the 30 keV ion was decreased the following observations were made: (1) the spatial extent of the DZs increased; (2) the vacancy concentration within the DZs decreased; (3) the fraction of isolated monovacancies increased; and (4) subcascades formed within the DZs

Determinants of distribution, abundance and reproductive success ...

African Journals Online (AJOL)

... while local vegetation structure determines the abundance of locally established populations. The abundance of trees affects nest site availability and breeding success, based on observations at two oases. Blackbird nests were usually situated on pomegranate trees and olive trees. The Common Blackbird is a successful ...

Atmospheric structure and helium abundance on Saturn from Cassini/UVIS and CIRS observations

Science.gov (United States)

Koskinen, T. T.; Guerlet, S.

2018-06-01

We combine measurements from stellar occultations observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS) and limb scans observed by the Composite Infrared Spectrometer (CIRS) to create empirical atmospheric structure models for Saturn corresponding to the locations probed by the occultations. The results cover multiple locations at low to mid-latitudes between the spring of 2005 and the fall of 2015. We connect the temperature-pressure (T-P) profiles retrieved from the CIRS limb scans in the stratosphere to the T-P profiles in the thermosphere retrieved from the UVIS occultations. We calculate the altitudes corresponding to the pressure levels in each case based on our best fit composition model that includes H2, He, CH4 and upper limits on H. We match the altitude structure to the density profile in the thermosphere that is retrieved from the occultations. Our models depend on the abundance of helium and we derive a volume mixing ratio of 11 ± 2% for helium in the lower atmosphere based on a statistical analysis of the values derived for 32 different occultation locations. We also derive the mean temperature and methane profiles in the upper atmosphere and constrain their variability. Our results are consistent with enhanced heating at the polar auroral region and a dynamically active upper atmosphere.

The Abundance of Large Arcs From CLASH

Science.gov (United States)

Xu, Bingxiao; Postman, Marc; Meneghetti, Massimo; Coe, Dan A.; Clash Team

2015-01-01

We have developed an automated arc-finding algorithm to perform a rigorous comparison of the observed and simulated abundance of large lensed background galaxies (a.k.a arcs). We use images from the CLASH program to derive our observed arc abundance. Simulated CLASH images are created by performing ray tracing through mock clusters generated by the N-body simulation calibrated tool -- MOKA, and N-body/hydrodynamic simulations -- MUSIC, over the same mass and redshift range as the CLASH X-ray selected sample. We derive a lensing efficiency of 15 ± 3 arcs per cluster for the X-ray selected CLASH sample and 4 ± 2 arcs per cluster for the simulated sample. The marginally significant difference (3.0 σ) between the results for the observations and the simulations can be explained by the systematically smaller area with magnification larger than 3 (by a factor of ˜4) in both MOKA and MUSIC mass models relative to those derived from the CLASH data. Accounting for this difference brings the observed and simulated arc statistics into full agreement. We find that the source redshift distribution does not have big impact on the arc abundance but the arc abundance is very sensitive to the concentration of the dark matter halos. Our results suggest that the solution to the "arc statistics problem" lies primarily in matching the cluster dark matter distribution.

Deuterium abundance, from ultraviolet to visible

International Nuclear Information System (INIS)

Hebrard, Guillaume

2000-01-01

In the frame of the standard Big Bang model, the primordial abundance of deuterium is the most sensitive to the baryonic density of the Universe. It was synthesized only during the primordial nucleosynthesis few minutes after the Big Bang and no other standard mechanism is able to produce any further significant amount. On the contrary, since deuterium is burned up within stars, its abundance D/H decreases along cosmic evolution. Thus, D/H measurements constrain Big Bang and galactic chemical evolution models. There are three samples of deuterium abundances: primordial, proto-solar and interstellar. Each of them is representative of a given epoch, respectively about 15 Gyrs past, 4.5 Gyrs past and present epoch. Although the evolution of the deuterium abundance seems to be qualitatively understood, the measurements show some dispersion. Present thesis works are linked to deuterium interstellar abundance measurements. Such measurements are classically obtained from spectroscopic observations of the hydrogen and deuterium Lyman series in absorption in the ultraviolet spectral range, using space observatories. Results presented here were obtained with the Hubble Space Telescope and FUSE, which has recently been launched. Simultaneously, a new way to observe deuterium has been proposed, in the visible spectral range from ground-based telescopes. This has led to the first detections and the identification of the deuterium Balmer series, in emission in HII regions, using CFHT and VLT telescopes. (author) [fr

Low planktic foraminiferal diversity and abundance observed in a spring 2013 west-east Mediterranean Sea plankton tow transect

Science.gov (United States)

Mallo, Miguel; Ziveri, Patrizia; Mortyn, P. Graham; Schiebel, Ralf; Grelaud, Michael

2017-05-01

Planktic foraminifera were collected with 150 µm BONGO nets from the upper 200 m water depth at 20 stations across the Mediterranean Sea between 2 May and 2 June 2013. The main aim is to characterize the species distribution and test the covariance between foraminiferal area density (ρA) and seawater carbonate chemistry in a biogeochemical gradient including ultraoligotrophic conditions. Average foraminifera abundances are 1.42 ± 1.43 ind. 10 m-3 (ranging from 0.11 to 5.20 ind. 10 m-3), including 12 morphospecies. Large differences in species assemblages and total abundances are observed between the different Mediterranean sub-basins, with an overall dominance of spinose, symbiont-bearing species indicating oligotrophic conditions. The highest values in absolute abundance are found in the Strait of Gibraltar and the Alboran Sea. The western basin is dominated by Globorotalia inflata and Globigerina bulloides at slightly lower standing stocks than in the eastern basin. In contrast, the planktic foraminiferal assemblage in the warmer, saltier, and more nutrient-limited eastern basin is dominated by Globigerinoides ruber (white). These new results, when combined with previous findings, suggest that temperature-induced surface water stratification and food availability are the main factors controlling foraminiferal distribution. In the oligotrophic and highly alkaline and supersaturated with respect to calcite and aragonite Mediterranean surface water, standing stocks and ρA of G. ruber (white) and G. bulloides are affected by both food availability and seawater carbonate chemistry. Rapid warming increased surface ocean stratification impacting food availability and changes in trophic conditions could be the causes of reduced foraminiferal abundance, diversity, and species-specific changes in planktic foraminiferal calcification.

Observation of String Ion Cloud in a Linear RF Trap

International Nuclear Information System (INIS)

Aramaki, M.; Kameyama, S.; Kono, A.; Sakawa, Y.; Shoji, T.

2009-01-01

We aim to study the effect of the long-range correlation among ions on their statistical characteristics using ion clouds confined in a linear rf ion trap. It is important to keep the ion cloud in one dimension, where the influence of the rf heating is negligible, for the detailed research on the effect of the Coulomb interaction on the statistical characteristics of the ion cloud. In this paper, the method of the generation of an ideal ion string is proposed. We also briefly report the performances of our experimental equipment and the preliminary results of generation of ideal 1D ion cloud.

Observation of refraction and convergence of ion acoustic waves in a plasma with a temperature gradient

International Nuclear Information System (INIS)

Nishida, Y.; Hirose, A.

1977-01-01

The refraction and convergence of ion acoustic waves are experimentally investigated in a magnetized plasma with an electron temperature gradient. When ion acoustic waves are launched parallel to the field lines the waves converge toward the interior of the plasma column where the electron temperature is lower, in good agreement with theoretical prediction. Wave interference is also observed. (author)

Experimental observations on long pulse intense ion diode operation

International Nuclear Information System (INIS)

Prono, D.S.; Clark, R.; Prestwich, K.

1976-01-01

An experiment in which a long pulse electron beam diode is converted to a reflex ion diode is reported. The results further substantiate the model of reflex ion diode behavior as well as extend the duration of ion mode operation to greater than 500 nsec

Ion-Beam-Excited Electrostatic Ion Cyclotron Waves

DEFF Research Database (Denmark)

Michelsen, Poul; Pécseli, Hans; Juul Rasmussen, Jens

1976-01-01

Self-excited electrostatic ion cyclotron waves were observed in an ion-beam-plasma system produced in a DP-operated Q-machine. The frequency of the waves showed the theoretically predicted variation with the magnetic field.......Self-excited electrostatic ion cyclotron waves were observed in an ion-beam-plasma system produced in a DP-operated Q-machine. The frequency of the waves showed the theoretically predicted variation with the magnetic field....

The Origin of Solar Filament Plasma Inferred from In Situ Observations of Elemental Abundances

Energy Technology Data Exchange (ETDEWEB)

Song, H. Q.; Chen, Y.; Li, B. [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Li, L. P. [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Zhao, L. [Department of Climate and Space sciences and Engineering, University of Michigan, Ann Arbor, MI 48105 (United States); He, J. S.; Duan, D. [School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Cheng, X. [School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210093 (China); Zhang, J., E-mail: hqsong@sdu.edu.cn [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States)

2017-02-10

Solar filaments/prominences are one of the most common features in the corona, which may lead to energetic coronal mass ejections (CMEs) and flares when they erupt. Filaments are about 100 times cooler and denser than the coronal material, and physical understanding of their material origin remains controversial. Two types of scenarios have been proposed: one argues that the filament plasma is brought into the corona from photosphere or chromosphere through a siphon or evaporation/injection process, while the other suggests that the material condenses from the surrounding coronal plasma due to thermal instability. The elemental abundance analysis is a reasonable clue to constrain the models, as the siphon or evaporation/injection model would predict that the filament material abundances are close to the photospheric or chromospheric ones, while the condensation model should have coronal abundances. In this Letter, we analyze the elemental abundances of a magnetic cloud that contains the ejected filament material. The corresponding filament eruption occurred on 1998 April 29, accompanying an M6.8 class soft X-ray flare located at the heliographic coordinates S18E20 (NOAA 08210) and a fast halo CME with the linear velocity of 1374 km s{sup −1} near the Sun. We find that the abundance ratios of elements with low and high first ionization potential such as Fe/O, Mg/O, and Si/O are 0.150, 0.050, and 0.070, respectively, approaching their corresponding photospheric values 0.065, 0.081, and 0.066, which does not support the coronal origin of the filament plasma.

Impact of energetic cosmic-ray ions on astrophysical ice grains

Energy Technology Data Exchange (ETDEWEB)

Mainitz, Martin; Anders, Christian; Urbassek, Herbert M., E-mail: urbassek@rhrk.uni-kl.de

2017-02-15

Highlights: • We use the REAX potential to model dissociations and reactions. • An ice grain consisting of a mixture of small molecules is considered. • The passage of a cosmic-ray ion initiates an ion track. • The track induces a shock wave and disintegrates the grain. • Abundant fragments and reaction products are detected. - Abstract: Using molecular-dynamics simulation with REAX potentials, we study the consequences of cosmic-ray ion impact on ice grains. The grains are composed of a mixture of H{sub 2}O, CO{sub 2}, NH{sub 3}, and CH{sub 3}OH molecules. Due to the high energy deposition of the cosmic-ray ion, 5 keV/nm, a strong pressure wave runs through the grain, while the interior of the ion track gasifies. Abundant molecular dissociations occur; reactions of the fragments form a variety of novel molecular product species.

Understanding and reducing statistical uncertainties in nebular abundance determinations

Science.gov (United States)

Wesson, R.; Stock, D. J.; Scicluna, P.

2012-06-01

Whenever observations are compared to theories, an estimate of the uncertainties associated with the observations is vital if the comparison is to be meaningful. However, many or even most determinations of temperatures, densities and abundances in photoionized nebulae do not quote the associated uncertainty. Those that do typically propagate the uncertainties using analytical techniques which rely on assumptions that generally do not hold. Motivated by this issue, we have developed Nebular Empirical Analysis Tool (NEAT), a new code for calculating chemical abundances in photoionized nebulae. The code carries out a standard analysis of lists of emission lines using long-established techniques to estimate the amount of interstellar extinction, calculate representative temperatures and densities, compute ionic abundances from both collisionally excited lines and recombination lines, and finally to estimate total elemental abundances using an ionization correction scheme. NEATuses a Monte Carlo technique to robustly propagate uncertainties from line flux measurements through to the derived abundances. We show that, for typical observational data, this approach is superior to analytic estimates of uncertainties. NEAT also accounts for the effect of upward biasing on measurements of lines with low signal-to-noise ratio, allowing us to accurately quantify the effect of this bias on abundance determinations. We find not only that the effect can result in significant overestimates of heavy element abundances derived from weak lines, but also that taking it into account reduces the uncertainty of these abundance determinations. Finally, we investigate the effect of possible uncertainties in R, the ratio of selective-to-total extinction, on abundance determinations. We find that the uncertainty due to this parameter is negligible compared to the statistical uncertainties due to typical line flux measurement uncertainties.

Diffusion and mobility of positive ions in sulphur hexafluoride

International Nuclear Information System (INIS)

Urquijo, J. de; Alvarez, I.; Cisneros, C.; Martinez, H.

1988-01-01

It is presented some recent results on the measurements of longitudinal difusion and mobility of positive ions in SF 6 . The experimental technique employed could determine the most abundant positive ion under electric discharge conditions. (A.C.A.S.) [pt

Monitoring waterbird abundance in wetlands: The importance of controlling results for variation in water depth

Science.gov (United States)

Bolduc, F.; Afton, A.D.

2008-01-01

Wetland use by waterbirds is highly dependent on water depth, and depth requirements generally vary among species. Furthermore, water depth within wetlands often varies greatly over time due to unpredictable hydrological events, making comparisons of waterbird abundance among wetlands difficult as effects of habitat variables and water depth are confounded. Species-specific relationships between bird abundance and water depth necessarily are non-linear; thus, we developed a methodology to correct waterbird abundance for variation in water depth, based on the non-parametric regression of these two variables. Accordingly, we used the difference between observed and predicted abundances from non-parametric regression (analogous to parametric residuals) as an estimate of bird abundance at equivalent water depths. We scaled this difference to levels of observed and predicted abundances using the formula: ((observed - predicted abundance)/(observed + predicted abundance)) ?? 100. This estimate also corresponds to the observed:predicted abundance ratio, which allows easy interpretation of results. We illustrated this methodology using two hypothetical species that differed in water depth and wetland preferences. Comparisons of wetlands, using both observed and relative corrected abundances, indicated that relative corrected abundance adequately separates the effect of water depth from the effect of wetlands. ?? 2008 Elsevier B.V.

The ISO spectrum of the planetary nebula NGC 6302 - II. Nebular abundances

NARCIS (Netherlands)

Pottasch, [No Value; Beintema, DA

The ISO spectrum of NGC 6302 is used, in conjunction with the visible and ultraviolet spectrum, to determine the nebular composition. In addition to being considerably more accurate than previous determinations, the abundances of many more elements (and ions) can be found. A discussion of the

MMS Observations of the Evolution of Ion-Scale Flux Transfer Events

Science.gov (United States)

Zhao, C.; Russell, C. T.; Strangeway, R. J.; Paterson, W.; Petrinec, S.; Zhou, M.; Anderson, B. J.; Baumjohann, W.; Bromund, K. R.; Chutter, M.; Fischer, D.; Gershman, D. J.; Giles, B. L.; Le, G.; Nakamura, R.; Plaschke, F.; Slavin, J. A.; Torbert, R. B.

2017-12-01

Flux transfer events are key processes in the solar wind-magnetosphere interaction. Previously, the observed flux transfer events have had scale sizes of 10,000 km radius in the cross-section and connect about 2 MWb magnetic flux from solar wind to the terrestrial magnetosphere. Recently, from the high-temporal resolution MMS magnetic field data, many ion-scale FTEs have been found. These FTEs contains only about 2 kWb magnetic flux and are believed to be in an early stage of FTE evolution. With the help of the well-calibrated MMS data, we are also able to determine the velocity profile and forces within the FTE events. We find that some ion-scale FTEs are expanding as we expect, but there are also contracting FTEs. We examine the differences between the two classes of FTEs and their differences with the larger previously studied class of FTE.

Threshold for ion movements in wood cell walls below fiber saturation observed by X-ray fluorescence microscopy (XFM)

Energy Technology Data Exchange (ETDEWEB)

Zelinka, Samuel L.; Gleber, Sophie-Charlotte; Vogt, Stefan; Rodriguez Lopez, Gabriela M.; Jakes, Joseph E.

2015-05-01

Diffusion of chemicals and ions through the wood cell wall plays an important role in wood damage mechanisms. In the present work, free diffusion of ions through wood secondary walls and middle lamellae has been investigated as a function of moisture content (MC) and anatomical direction. Various ions (K, Cl, Zn, Cu) were injected into selected regions of 2 mu m thick wood sections with a microinjector and then the ion distribution was mapped by means of X-ray fluorescence microscopy with submicron spatial resolution. The MC of the wood was controlled in situ by means of climatic chamber with controlled relative humidity (RH). For all ions investigated, there was a threshold RH below which the concentration profiles did not change. The threshold RH depended upon ionic species, cell wall layer, and wood anatomical orientation. Above the threshold RH, differences in mobility among ions were observed and the mobility depended upon anatomical direction and cell wall layer. These observations support a recently proposed percolation model of electrical conduction in wood. The results contribute to understanding the mechanisms of fungal decay and fastener corrosion that occur below the fiber saturation point.

Estimating Lion Abundance using N-mixture Models for Social Species.

Science.gov (United States)

Belant, Jerrold L; Bled, Florent; Wilton, Clay M; Fyumagwa, Robert; Mwampeta, Stanslaus B; Beyer, Dean E

2016-10-27

Declining populations of large carnivores worldwide, and the complexities of managing human-carnivore conflicts, require accurate population estimates of large carnivores to promote their long-term persistence through well-informed management We used N-mixture models to estimate lion (Panthera leo) abundance from call-in and track surveys in southeastern Serengeti National Park, Tanzania. Because of potential habituation to broadcasted calls and social behavior, we developed a hierarchical observation process within the N-mixture model conditioning lion detectability on their group response to call-ins and individual detection probabilities. We estimated 270 lions (95% credible interval = 170-551) using call-ins but were unable to estimate lion abundance from track data. We found a weak negative relationship between predicted track density and predicted lion abundance from the call-in surveys. Luminosity was negatively correlated with individual detection probability during call-in surveys. Lion abundance and track density were influenced by landcover, but direction of the corresponding effects were undetermined. N-mixture models allowed us to incorporate multiple parameters (e.g., landcover, luminosity, observer effect) influencing lion abundance and probability of detection directly into abundance estimates. We suggest that N-mixture models employing a hierarchical observation process can be used to estimate abundance of other social, herding, and grouping species.

Stellar pulsation and the abundance of helium

International Nuclear Information System (INIS)

Schmidt, E.G.

1978-01-01

It has been suggested that the appearance of nonvariable stars within the Cepheid strip could be explained by a range in the helium abundance of Population I stars. In order to study this possibility, spectra were obtained of the main-sequence B stars in the galactic cluster NGC 129, which contains a nonvariable Cepheid-strip star, and M25, which contains a relatively hot Cepheid. Unfortunately, several of the stars in these clusters turn out to be helium-weak stars. In NGC 129 two stars which appear normal give a normal abundance, while in M25 all of the observed stars have abnormally low abundances. The significance of the low abundance in M25 is not clear. The abundance in NGC 129 is not low enough to support the above suggestion. 4 figures, 2 tables

Origin of Stellar Abundances in the early Galaxy

International Nuclear Information System (INIS)

Montes, F.; Beers, T. C.; Cowan, J.; Elliot, T.; Schatz, H.; Farouqi, K.; Gallino, R.; Heil, M.; Kratz, K.-L.; Pfeiffer, B.; Pignatari, M.

2007-01-01

Observations of metal-poor stars in the last decade have revealed an abundance pattern that have recently been explained as the result of two nucleosynthesis processes, a strong r-process that creates most of the Z≥56 and some 38≤Z≤47 abundances and a light element primary process (LEPP) responsible for creating the remaining 38≤Z≤47 abundances and some small contribution to heavier elements. We review some of the current literature on the LEPP and show a derived abundance pattern as a function of mass number

Stellar abundances in the solar neighborhood: The Hypatia Catalog

Energy Technology Data Exchange (ETDEWEB)

Hinkel, Natalie R.; Timmes, F.X.; Young, Patrick A.; Pagano, Michael D. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Turnbull, Margaret C. [Global Science Institute, P.O. Box 252, Antigo, WI 54409 (United States)

2014-09-01

We compile spectroscopic abundance data from 84 literature sources for 50 elements across 3058 stars in the solar neighborhood, within 150 pc of the Sun, to produce the Hypatia Catalog. We evaluate the variability of the spread in abundance measurements reported for the same star by different surveys. We also explore the likely association of the star within the Galactic disk, the corresponding observation and abundance determination methods for all catalogs in Hypatia, the influence of specific catalogs on the overall abundance trends, and the effect of normalizing all abundances to the same solar scale. The resulting stellar abundance determinations in the Hypatia Catalog are analyzed only for thin-disk stars with observations that are consistent between literature sources. As a result of our large data set, we find that the stars in the solar neighborhood may reveal an asymmetric abundance distribution, such that a [Fe/H]-rich group near the midplane is deficient in Mg, Si, S, Ca, Sc II, Cr II, and Ni as compared to stars farther from the plane. The Hypatia Catalog has a wide number of applications, including exoplanet hosts, thick- and thin-disk stars, and stars with different kinematic properties.

Relative ion yields in mammalian cell components using C60 SIMS

Science.gov (United States)

Keskin, Selda; Piwowar, Alan; Hue, Jonathan; Shen, Kan; Winograd, Nicholas

2013-01-01

Time of flight secondary ion mass spectrometry has been used to better understand the influence of molecular environment on the relative ion yields of membrane lipid molecules found in high abundance in a model mammalian cell line, RAW264.7. Control lipid mixtures were prepared to simulate lipid–lipid interactions in the inner and outer leaflet of cell membranes. Compared with its pure film, the molecular ion yields of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine are suppressed when mixed with 2-dipalmitoyl-sn-glycero-3-phosphocholine. In the mixture, proton competition between 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 2-dipalmitoyl-sn-glycero-3-phosphocholine led to lower ionization efficiency. The possible mechanism for ion suppression was also investigated with 1H and 13C nuclear magnetic resonance spectroscopy. The formation of a hydroxyl bond in lipid mixtures confirms the mechanism involving proton exchange with the surrounding environment. Similar effects were observed for lipid mixtures mimicking the composition of the inner leaflet of cell membranes. The secondary molecular ion yield of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine was observed to be enhanced in the presence of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine. PMID:25140069

Negative ions in the auroral mesosphere during a PCA event around sunset

Directory of Open Access Journals (Sweden)

C. F. del Pozo

Full Text Available This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.

Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation.

ENERGETIC NEUTRAL ATOMS: AN ADDITIONAL SOURCE FOR HELIOSPHERIC PICKUP IONS

International Nuclear Information System (INIS)

Bochsler, Peter; Moebius, Eberhard

2010-01-01

Recently, Schwadron and McComas discussed the possibility of inner source pickup particles originating from the ionization of energetic neutral atoms (ENAs), based on new data from the IBEX mission. This proposition has some interesting features, namely, it might be able to explain why inner source pickup ions (PUIs) have a composition resembling solar abundances and show no indication of overabundance of refractory elements, although this should be expected, if the conventional explanation of solar wind-dust interaction for the origin of this heliospheric component were correct. In this Letter, we explore further consequences for ENA-related PUIs and investigate their velocity distributions. We conclude that this model will not reproduce the observed velocity distributions of inner source PUIs and point out a substantial deviation in their composition. However, it seems likely that the ionization of ENAs as observed with IBEX could contribute a significant amount of heliospheric suprathermal tail ions. Some possible consequences of our investigation for heliospheric particle populations are briefly discussed.

Anti-baryon puzzle in ultra-relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Rapp, R.; Shuryak, E.V.

2002-01-01

The evolution of (non-strange) antibaryon abundances in the hadronic phase of central heavy-ion collisions is studied within a thermal equilibrium framework, based on the well-established picture of subsequent chemical and thermal freezeout. Due to large annihilation cross sections, antiprotons are, a priori, not expected to comply with this scheme. However, we show that a significant regeneration of their abundance occurs upon inclusion of the inverse reaction of multipion fusion, n π π → p anti p (with n π =5-6), necessary to ensure detailed balance. Especially at SPS energies, the build-up of large pion-chemical potentials between chemical and thermal freezeout reinforces this mechanism, rendering the p/p ratio in reasonable agreement with the observed one (reflecting chemical freezeout). Explicit solutions of the pertinent rate equation, which account for chemical off-equilibrium effects, corroborate this explanation. (orig.)

Ion-microprobe measurements of Mg, Ca, Ti and Fe isotopic ratios and trace element abundance in hibonite-bearing inclusions in primitive meteorites

International Nuclear Information System (INIS)

Fahey, A.J.

1988-01-01

This thesis reports the isotopic abundances of Mg, Ca, and Ti and rare earth element (REE) abundances in 19 hibonite-bearing inclusions from primative meteorites. The isotopic ratios of Fe were measured in one of the samples, Lance HH-1. These measurements were made by means of secondary ion mass spectrometry (CAMECA IMS-3f). The novel hardware and software developments that made this work possible are described in detail. The samples were studied in thin section in order to investigate the relationship between the inclusions and their mineralogical environments. Inclusions from a number of different meteorites, specifically, Mighei, Murray, Murchison, Lance, Efremovka, Vigarano, Qingzhen, Dhajala, and Semarkona, were studied. The isotopes of Ca and Ti show large and correlated abundance anomalies in their most neutron-rich isotopes, 48 Ca and 50 Ti. The largest anomalies among the samples studied here are in the Murray inclusion MY-F6, with a 4.6% deficit in 48 Ca and a 5.2% deficit in 50 Ti, and Lance HH-1, with 3.3% and 6.0% deficits in 48 Ca and 50 Ti respectively. Correlated excesses of 48 Ca and 50 Ti, up to 2.4% and 1.4% respectively, are found in some other samples studied here. The fact that there is a correlation of isotopic anomalies in two different elements is clear evidence for a nucleosynthetic origin of these effects. Various possibilities for the origin of these isotopic anomalies are discussed and it is shown that a Cosmic Chemical Memory-like model of the incomplete mixing of dust grains from one or several supernovae is sufficient to explain the data. Magnesium isotopes show excesses of 26 Mg, attributable to the in-situ decay of 26 Al, in 7 of these inclusions

Geotail observations of plasma sheet ion composition over 16 years: On variations of average plasma ion mass and O+ triggering substorm model

Science.gov (United States)

Nosé, M.; Ieda, A.; Christon, S. P.

2009-07-01

We examined long-term variations of ion composition in the plasma sheet, using energetic (9.4-212.1 keV/e) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. EPIC/STICS observations are available from 17 October 1992 for more than 16 years, covering the declining phase of solar cycle 22, all of solar cycle 23, and the early phase of solar cycle 24. This unprecedented long-term data set revealed that (1) the He+/H+ and O+/H+ flux ratios in the plasma sheet were dependent on the F10.7 index; (2) the F10.7 index dependence is stronger for O+/H+ than He+/H+; (3) the O+/H+ flux ratio is also weakly correlated with the ΣKp index; and (4) the He2+/H+ flux ratio in the plasma sheet appeared to show no long-term trend. From these results, we derived empirical equations related to plasma sheet ion composition and the F10.7 index and estimated that the average plasma ion mass changes from ˜1.1 amu during solar minimum to ˜2.8 amu during solar maximum. In such a case, the Alfvén velocity during solar maximum decreases to ˜60% of the solar minimum value. Thus, physical processes in the plasma sheet are considered to be much different between solar minimum and solar maximum. We also compared long-term variation of the plasma sheet ion composition with that of the substorm occurrence rate, which is evaluated by the number of Pi2 pulsations. No correlation or negative correlation was found between them. This result contradicts the O+ triggering substorm model, in which heavy ions in the plasma sheet increase the growth rate of the linear ion tearing mode and play an important role in localization and initiation of substorms. In contrast, O+ ions in the plasma sheet may prevent occurrence of substorms.

Observations of energetic helium ions in the Earth's radiation belts during a sequence of geomagnetic storms

International Nuclear Information System (INIS)

Spjeldvik, W.N.; Fritz, T.A.

1981-01-01

Every year a significant number of magnetic storms disturb the earth's magnetosphere and the trapped particle populations. In this paper, we present observations of energetic (MeV) helium ions made with Explorer 45 during a sequence of magnetic storms during June through December of 1972. The first of these storms started on June 17 and had a Dst index excursion to approx.190 gamma, and the MeV helium ions were perturbed primarily beyond 3 earth radii in the equatorial radiation belts with a typical flux increase of an order of magnitude at L = 4. The second storm period took place during August and was associated with very major solar flare activity. Although the Dst extremum was at best 35 gamma less than the June storm, this period can be characterized as irregular (or multi-storm) with strong compression of the magnetosphere and very large (order of magnitude) MeV helium ion flux enhancements down to Lapprox.2. Following this injection the trapped helium ion fluxes showed positive spectral slope with the peak beyond 3.15 MeV at L = 2.5; and at the lowest observable L shells (Lapprox.2--3) little flux decay (tau>100 days) was seen during the rest of the year. Any effects of two subsequent major magnetic storms in September and November were essentially undetectable in the prolonged after-effect of the August solar flare associated MeV helium ion injection. The helium ion radial profile of the phase space density showed a significant negative slope during this period, and we infer that radial diffusion constitutes a significant loss of helium ions on L shells above Lapprox. =4 during the aftermath of the August 1972 magnetic storm

LITERATURE SURVEY ON ISOTOPIC ABUNDANCE RATIO MEASUREMENTS - 2001-2005

International Nuclear Information System (INIS)

HOLDEN, N.E.

2005-01-01

Along with my usual weekly review of the published literature for new nuclear data, I also search for new candidates for best measurements of isotopic abundances from a single source. Most of the published articles, that I previously had found in the Research Library at the Brookhaven Lab, have already been sent to the members of the Atomic Weights Commission, by either Michael Berglund or Thomas Walczyk. In the last few days, I checked the published literature for any other articles in the areas of natural variations in isotopic abundance ratios, measurements of isotopic abundance ratios on samples of extra-terrestrial material and isotopic abundance ratio measurements performed using ICPMS instruments. Hopefully this information will be of interest to members of the Commission, the sub-committee on isotopic abundance measurements (SIAM), members of the former sub-committee on natural isotopic fractionation (SNIF), the sub-committee on extra-terrestrial isotope ratios (SETIR), the RTCE Task Group and the Guidelines Task Group, who are dealing with ICPMS and TIMS comparisons. In the following report, I categorize the publications in one of four areas. Measurements performed using either positive or negative ions with Thermal Ionization Mass Spectrometer, TIMS, instruments; measurements performed on Inductively Coupled Plasma Mass Spectrometer, ICPMS, instruments; measurements of natural variations of the isotopic abundance ratios; and finally measurements on extra-terrestrial samples with instrumentation of either type. There is overlap in these areas. I selected out variations and ET results first and then categorized the rest of the papers by TIMS and ICPMS

Solvent Composition-Dependent Signal-Reduction of Molecular Ions Generated from Aromatic Compounds in (+) Atmospheric Pressure Photo Ionization Mass Spectrometry.

Science.gov (United States)

Lee, Seulgidaun; Ahmed, Arif; Kim, Sunghwan

2018-03-30

The ionization process is essential for successful mass spectrometry (MS) analysis because of its influence on selectivity and sensitivity. In particular, certain solvents reduce the ionization of the analyte, thereby reducing the overall sensitivity in APPI. Since the sensitivity varies greatly depending on the solvents, a fundamental understanding of the mechanism is required. Standard solutions were analyzed by (+) Atmospheric pressure photo ionization (APPI) QExactive ion trap mass spectrometer (Thermo Scientific). Each solution was infused directly to the APPI source at a flow rate 100 μl/min and the APPI source temperature was 300 °C. Other operating mass spectrometric parameters were maintained under the same conditions. Quantum mechanical calculations were carried out using the Gaussian 09 suite program. Density functional theory was used to calculate the reaction enthalpies (∆H) of reaction between toluene and other solvents. The experimental and theoretical results showed good agreement. The abundances of analyte ions were well correlated with the calculated ∆H values. Therefore, the results strongly support the suggested signal reduction mechanism. In addition, linear correlations between the abundance of toluene and analyte molecular ions were observed, which also supports the suggested mechanism. A solvent composition-dependent signal reduction mechanism was suggested and evaluated for the (+) atmospheric pressure photo ionization (APPI) mass spectrometry analysis of poly-aromatic hydrocarbons (PAHs) generating mainly molecular ions. Overall, the evidence provided in this work suggests that reactions between solvent cluster(s) and toluene molecular ions are responsible for the observed signal reductions. This article is protected by copyright. All rights reserved.

ON THE ORIGIN OF THE SLOW SPEED SOLAR WIND: HELIUM ABUNDANCE VARIATIONS

Energy Technology Data Exchange (ETDEWEB)

Rakowski, Cara E.; Laming, J. Martin [Space Science Division, Naval Research Laboratory Code 7674L, Washington, DC 20375 (United States)

2012-07-20

The first ionization potential (FIP) effect is the by now well-known enhancement in abundance over photospheric values of Fe and other elements with FIP below about 10 eV observed in the solar corona and slow speed solar wind. In our model, this fractionation is achieved by means of the ponderomotive force, arising as Alfven waves propagate through or reflect from steep density gradients in the solar chromosphere. This is also the region where low FIP elements are ionized, and high FIP elements are largely neutral leading to the fractionation as ions interact with the waves but neutrals do not. Helium, the element with the highest FIP and consequently the last to remain neutral as one moves upward, can be depleted in such models. Here, we investigate this depletion for varying loop lengths and magnetic field strengths. Variations in this depletion arise as the concentration of the ponderomotive force at the top of the chromosphere varies in response to Alfven wave frequency with respect to the resonant frequency of the overlying coronal loop, the magnetic field, and possibly also the loop length. We find that stronger depletions of He are obtained for weaker magnetic field, at frequencies close to or just above the loop resonance. These results may have relevance to observed variations of the slow wind solar He abundance with wind speed, with slower slow speed solar wind having a stronger depletion of He.

Direct observations of the charge states of low energy solar particles

Science.gov (United States)

Gloeckler, G.; Fan, C. Y.; Hovestadt, D.

1974-01-01

The charge states of carbon and oxygen of solar origin have been measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6, respectively. Abundance ratios of low energy heavy nuclei to He are found which are significantly larger than the corresponding photospheric values. The enhancement of O/He is 35, and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Distribution and abundance of diatom species from coastal waters of Karachi, Pakistan

International Nuclear Information System (INIS)

Khokhar, F. N.; Burhan, Z.; Iqbal, P.; Abbasi, J.; Siddiqui, P.

2016-01-01

This is the first comprehensive study on the distribution and abundance of diatom species from the coastal and nearshore waters of Karachi, Pakistan, bordering northern Arabian Sea. A total of 20 genera are recorded in high abundance (Cerataulina, Chaetoceros, Coscinodiscus, Cylindrotheca, Eucampia, Guinardia, Haslea, Hemiaulus, Lauderia, Lennoxia, Leptocylindrus, Navicula, Nitzschia, Trieres, Planktoniella, Pleurosigma, Pseudo-nitzschia, Rhizosolenia, Thalassionema and Thalassiosira). The most abundant genera were observed Guinardia, Chaetoceros, Leptocylindrus, Nitzschia and Lennoxia at all stations. Manora coastal station (MI-1) had high abundance corresponding with high Chlorophyll a (130 meu gL- l) values. Minimum abundance and low chlorophyll a value (0.05μgL-l) were observed at Mubarak Village coastal station (MV-1). Diatom abundance showed significant correlation with Chlorophyll a. In present study 12 centric and 8 pennate forms were recorded and similarly high diversity of centric taxa was observed compared to pennate forms. A total of 134 species are recorded of which 40 species were observed at four stations, 31species at three stations, 23 at two stations and 40 species only at one station. The total phytoplankton and diatom peak abundance was observed during NE monsoon (winter season) associated with nutrient loading through up-sloping of nutrient rich water upwelled off of Oman during South West monsoon. Overall higher diversity was observed at Manora coastal and nearshore stations (MI-1, MI-2) indicating the influence of organic pollution loading from Layari and Malir rivers. (author)

A collaborative approach for estimating terrestrial wildlife abundance

Science.gov (United States)

Ransom, Jason I.; Kaczensky, Petra; Lubow, Bruce C.; Ganbaatar, Oyunsaikhan; Altansukh, Nanjid

2012-01-01

Accurately estimating abundance of wildlife is critical for establishing effective conservation and management strategies. Aerial methodologies for estimating abundance are common in developed countries, but they are often impractical for remote areas of developing countries where many of the world's endangered and threatened fauna exist. The alternative terrestrial methodologies can be constrained by limitations on access, technology, and human resources, and have rarely been comprehensively conducted for large terrestrial mammals at landscape scales. We attempted to overcome these problems by incorporating local peoples into a simultaneous point count of Asiatic wild ass (Equus hemionus) and goitered gazelle (Gazella subgutturosa) across the Great Gobi B Strictly Protected Area, Mongolia. Paired observers collected abundance and covariate metrics at 50 observation points and we estimated population sizes using distance sampling theory, but also assessed individual observer error to examine potential bias introduced by the large number of minimally trained observers. We estimated 5671 (95% CI = 3611–8907) wild asses and 5909 (95% CI = 3762–9279) gazelle inhabited the 11,027 km2 study area at the time of our survey and found that the methodology developed was robust at absorbing the logistical challenges and wide range of observer abilities. This initiative serves as a functional model for estimating terrestrial wildlife abundance while integrating local people into scientific and conservation projects. This, in turn, creates vested interest in conservation by the people who are most influential in, and most affected by, the outcomes.

Hydrocarbons and fuels analyses with the supersonic gas chromatography mass spectrometry--the novel concept of isomer abundance analysis.

Science.gov (United States)

Fialkov, Alexander B; Gordin, Alexander; Amirav, Aviv

2008-06-27

Hydrocarbon analysis with standard GC-MS is confronted by the limited range of volatile compounds amenable for analysis and by the similarity of electron ionization mass spectra for many compounds which show weak or no molecular ions for heavy hydrocarbons. The use of GC-MS with supersonic molecular beams (Supersonic GC-MS) significantly extends the range of heavy hydrocarbons that can be analyzed, and provides trustworthy enhanced molecular ion to all hydrocarbons. In addition, unique isomer mass spectral features are obtained in the ionization of vibrationally cold hydrocarbons. The availability of molecular ions for all hydrocarbons results in the ability to obtain unique chromatographic isomer distribution patterns that can serve as a new method for fuel characterization and identification. Examples of the applicability and use of this novel isomer abundance analysis (IAA) method to diesel fuel, kerosene and oil analyses are shown. It is suggested that in similarity to the "three ions method" for identification purposes, three isomer abundance patterns can serve for fuel characterization. The applications of the Supersonic GC-MS for engine motor oil analysis and transformer oil analysis are also demonstrated and discussed, including the capability to achieve fast 1-2s sampling without separation for oil and fuel fingerprinting. The relatively fast analysis of biodiesel is described, demonstrating the provision of molecular ions to heavy triglycerides. Isomer abundance analysis with the Supersonic GC-MS could find broad range of applications including petrochemicals and fuel analysis, arson analysis, environmental oil/fuel spill analysis, fuel adulteration analysis and motor oil analysis.

Enhanced ion acoustic fluctuations and ion outflows

Directory of Open Access Journals (Sweden)

F. R. E. Forme

1999-02-01

Full Text Available A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear spectral signature, the analysis is unable to fit the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT observations of large ion outflows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014 m-2 s-1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric field and can account for the observed ion outflows.Key words. Ionosphere (auroral ionosphere; ionosphere · magnetosphere interactions; plasma waves and instabilities.

Analysing destruction channels of interstellar hydrocarbon anions with a 22pol ion-trap

Energy Technology Data Exchange (ETDEWEB)

Endres, Eric; Lakhmanskaya, Olga; Best, Thorsten; Hauser, Daniel; Kumar, Sunil; Wester, Roland [Universitaet Innsbruck, Institut fuer Ionenphysik und Angewandte Physik (Austria)

2014-07-01

In the interstellar medium (ISM), ion-molecule reactions are considered to play a key role in the formation of complex molecules. The detection of the first interstellar anions, which happen to be carbon chain anions, has raised new interest in the quantitative composition of the ISM and the underlying reaction network. To understand the observed abundance of these carbon chain anions, a detailed analysis of the possible destruction channels is indispensable. A cryogenic 22-pol radio frequency ion trap is an ideal tool to observe reactions that take place slowly, such as carbon chain anions with molecular hydrogen. Furthermore, measurements over a large temperature scale are feasible. Longitudinal optical access to the trap also provides the possibility to make precise photodetachment measurements. Temperature dependent measurements of the reaction rates for the reaction between hydrocarbon chain anions and H{sub 2} are presented.

Observations of field-aligned energetic electron and ion distributions near the magnetopause at geosynchronous orbit

International Nuclear Information System (INIS)

Korth, A.; Kremser, G.; Daly, P.W.; Amata, E.

1982-01-01

On August 28, 1978, the dayside magnetopause crossed the geosynchronous satellite GEOS 2 several times during a geomagnetically disturbed period, and clear signatures of the interconnection of field lines through the magnetopause were observed. The MPAE particle spectrometer provided high time resolution observations of the distribution of energetic electrons (E>22 keV) and ions (E>27 keV). Magnetometer data were used to determine the location of GEOS 2 relative to the magnetopause. The pitch angle distributions of ions and electrons were found to be strongly asymmetric with respect to 90 0 , and the asymmetries have been interpreted in terms of field-aligned particle streaming. Evidence is provided for the first time for electron streaming inside the magnetopause which continues for many bounce periods. It is concluded that magnetospheric field lines opened, at least for brief time intervals, as a consequence of interconnection with magnetosheath field lines. Comparisons of electron spectra provide evidence that the streaming electrons observed in the magnetosheath originate in the magnetosphere

Estimation of State of Charge of a Lithium-Ion Battery Pack for Electric Vehicles Using an Adaptive Luenberger Observer

Directory of Open Access Journals (Sweden)

Yuan Zou

2010-09-01

Full Text Available In order to safely and efficiently use the power as well as to extend the lifetime of the traction battery pack, accurate estimation of State of Charge (SoC is very important and necessary. This paper presents an adaptive observer-based technique for estimating SoC of a lithium-ion battery pack used in an electric vehicle (EV. The RC equivalent circuit model in ADVISOR is applied to simulate the lithium-ion battery pack. The parameters of the battery model as a function of SoC, are identified and optimized using the numerically nonlinear least squares algorithm, based on an experimental data set. By means of the optimized model, an adaptive Luenberger observer is built to estimate online the SoC of the lithium-ion battery pack. The observer gain is adaptively adjusted using a stochastic gradient approach so as to reduce the error between the estimated battery output voltage and the filtered battery terminal voltage measurement. Validation results show that the proposed technique can accurately estimate SoC of the lithium-ion battery pack without a heavy computational load.

Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

Energy Technology Data Exchange (ETDEWEB)

Filwett, R. J.; Desai, M. I. [University of Texas at San Antonio, San Antonio, TX (United States); Dayeh, M. A.; Broiles, T. W. [Southwest Research Institute, San Antonio, TX (United States)

2017-03-20

We have analyzed the ∼20–320 keV nucleon{sup −1} suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon{sup −1} Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon{sup −1} Fe/CNO and the ∼20–320 keV nucleon{sup −1} Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

Challenges of transferring models of fish abundance between coral reefs.

Science.gov (United States)

Sequeira, Ana M M; Mellin, Camille; Lozano-Montes, Hector M; Meeuwig, Jessica J; Vanderklift, Mathew A; Haywood, Michael D E; Babcock, Russell C; Caley, M Julian

2018-01-01

Reliable abundance estimates for species are fundamental in ecology, fisheries, and conservation. Consequently, predictive models able to provide reliable estimates for un- or poorly-surveyed locations would prove a valuable tool for management. Based on commonly used environmental and physical predictors, we developed predictive models of total fish abundance and of abundance by fish family for ten representative taxonomic families for the Great Barrier Reef (GBR) using multiple temporal scenarios. We then tested if models developed for the GBR (reference system) could predict fish abundances at Ningaloo Reef (NR; target system), i.e., if these GBR models could be successfully transferred to NR. Models of abundance by fish family resulted in improved performance (e.g., 44.1% fish abundance (9% fish species richness from the GBR to NR, transferability for these fish abundance models was poor. When compared with observations of fish abundance collected in NR, our transferability results had low validation scores ( R 2   0.05). High spatio-temporal variability of patterns in fish abundance at the family and population levels in both reef systems likely affected the transferability of these models. Inclusion of additional predictors with potential direct effects on abundance, such as local fishing effort or topographic complexity, may improve transferability of fish abundance models. However, observations of these local-scale predictors are often not available, and might thereby hinder studies on model transferability and its usefulness for conservation planning and management.

CHLORINE ABUNDANCES IN COOL STARS

Energy Technology Data Exchange (ETDEWEB)

Maas, Z. G.; Pilachowski, C. A. [Indiana University Bloomington, Astronomy Department, Swain West 319, 727 East Third Street, Bloomington, IN 47405-7105 (United States); Hinkle, K., E-mail: zmaas@indiana.edu, E-mail: cpilacho@indiana.edu, E-mail: hinkle@noao.edu [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States)

2016-12-01

Chlorine abundances are reported in 15 evolved giants and 1 M dwarf in the solar neighborhood. The Cl abundance was measured using the vibration-rotation 1-0 P8 line of H{sup 35}Cl at 3.69851 μ m. The high-resolution L -band spectra were observed using the Phoenix infrared spectrometer on the Kitt Peak Mayall 4 m telescope. The average [{sup 35}Cl/Fe] abundance in stars with −0.72 < [Fe/H] < 0.20 is [{sup 35}Cl/Fe] = (−0.10 ± 0.15) dex. The mean difference between the [{sup 35}Cl/Fe] ratios measured in our stars and chemical evolution model values is (0.16 ± 0.15) dex. The [{sup 35}Cl/Ca] ratio has an offset of ∼0.35 dex above model predictions, suggesting that chemical evolution models are underproducing Cl at the high metallicity range. Abundances of C, N, O, Si, and Ca were also measured in our spectral region and are consistent with F and G dwarfs. The Cl versus O abundances from our sample match Cl abundances measured in planetary nebula and H ii regions. In one star where both H{sup 35}Cl and H{sup 37}Cl could be measured, a {sup 35}Cl/{sup 37}Cl isotope ratio of 2.2 ± 0.4 was found, consistent with values found in the Galactic ISM and predicted chemical evolution models.

Observation of the charge neutrality of the ions from target short-pulse laser interaction experiments

International Nuclear Information System (INIS)

Yasuike, Kazuhito

2003-01-01

Intended to simulate the early stage of the plasma (preformed plasma) formation in the higher (10 20 W cm -2 ) intensity experiments (in which the plasma density profile rules laser absorption thus conversion efficiency from laser into hot electrons, ions and x-rays) experiments using solid target were done under a peak intensity (main laser pulse) of up to ∼10 15 W cm -2 and pre-pulse and pedestal intensity of ∼10 3 times lower than main pulse. With pedestal, significant enhancement of laser absorption was observed with pedestal condition. Charge neutralization of the ions from the plasma was measured by biased charge collectors. Earlier part of the ion were almost un-neutralized in with or without pedestal condition, and the later part of the ions (≤ few keV) were partially neutralized (≥40%). These not-perfect charge neutralization results is different from the longer nano-seconds pulse experimental results. (author)

Probing AGB nucleosynthesis via accurate Planetary Nebula abundances

NARCIS (Netherlands)

Marigo, P; Bernard-Salas, J; Pottasch, S. R.; Tielens, A. G. G. M.; Wesselius, P. R.

2003-01-01

The elemental abundances of ten planetary nebulae, derived with high accuracy including ISO and IUE spectra, are analysed with the aid of synthetic evolutionary models for the TP-AGB phase. The accuracy on the observed abundances is essential in order to make a reliable comparison with the models.

Fast ion behavior during neutral beam injection in ATF

International Nuclear Information System (INIS)

Wade, M.R.; Thomas, C.E.; Colchin, R.J.; Rome, J.A.; England, A.C.; Fowler, R.H.; Aceto, S.C.

1993-01-01

In stellarators, single-particle confinement properties can be more complex than in their tokamak counterparts. Fast-ion behavior in tokamaks has been well characterized through an abundance of measurements on various devices and in general has been shown to be consistent with classical slowing-down theory, although anomalous ion behavior has been observed during intense beam injection in ISX-B, during fishbone instabilities in PDX, and in experiments on TFR. In contrast, fast ion behavior in stellarators is not as wel established experimentally with the primary experiments to date focusing o near-perpendicular or perpendicular neutral beam injection (NBI) on the Wendelstein 7-A stellarator (91 and Heliotron-E. This paper addresses fast-ion confinement properties in a large-aspect-ratio, moderate-shear stellarator, the Advanced Toroidal Facility, during tangential NBI. The primary data used in this study are the experimentally measured energy spectra of charge-exchange neutrals escaping from the plasma, using a two-dimensional scanning neutral particle analyzer. This diagnostic method is well established, having been used on several devices since the early 1970's. Various aspects of fast-ion behavior are investigated by comparing these data with computed theoretical spectra based on energeticion distributions derived from the fastion Fokker-Planck equation. Ion orbits are studied by computer orbit following, by the computation of J* surfaces, and by Monte Carlo calculations

On acceleration of <1 MeV/n He ions in the corotating compression regions near 1 AU: STEREO observations

Directory of Open Access Journals (Sweden)

R. Bučík

2009-09-01

Full Text Available Observations of multi-MeV corotating interaction region (CIR ions are in general consistent with models of CIR shock acceleration and transport. The presence of suprathermal particles near 1 AU in unshocked compression regions is not adequately explained. Nonetheless, more recent works demonstrate that unshocked compression regions associated with CIRs near 1 AU could energize particles. In the energy range from ~0.1 to ~1 MeV/n we investigate CIR events observed in 2007–2008 by the STEREO A and B spacecraft. We treat the predictions of compression acceleration by comparing the observed ion intensities with the model parameters. These observations show that the ion intensity in CIR events with in-situ reverse shock is well organized by the parameters which characterize the compression region itself, like compression width, solar wind speed gradients and the total pressure. In turn, for CIR events with the absence of the shocks the model predictions are not fulfilled.

Shell-like configuration in O+ ion velocity distribution at high altitudes in the dayside magnetosphere observed by Cluster/CIS

Directory of Open Access Journals (Sweden)

S. Joko

2004-07-01

Full Text Available We report shell-like configurations seen in O+ ion velocity distributions. One case was observed above 8RE in radial distance in the dayside magnetosphere, presumably in the mantle region, during the observation period of 09:30-10:00 UT on 12 April 2001 by the CIS instrument on board the Cluster satellite. This shell-like configuration was different from so-called "conics" or "beams": the lower energy (cold population and the higher energy partial shell part were seen together, but there was no obvious signature of heating process. With respect to H+ ion velocity distributions observed simultaneously, transverse heating (so-called in "pan-cake" shape or field-aligned energisation configurations were seen as the result of heating/energisation processes and the upward-going part of the distribution also formed a half spherical thick shell configuration. Concerning O+ ion heating in the case of 12 April 2001, it was obviously observed when the spacecraft passed through the mantle region close to the poleward cusp. As the spacecraft moved toward the dayside cusp shell-like (or dome shape velocity distributions appeared apparently and continued to be observed until the spacecraft reached the magnetopause according to two other different cases (13 February 2001 and 14 April 2001. Two other cases were observed in the Southern Hemisphere and the spacecraft was supposed to pass through the dayside cusp toward the mantle region at higher altitudes (9-11RE. O+ ion velocity distributions in these cases show pre-/post-structured shell-like configurations, depending on the observation sites (mantle or dayside cusp.

ICP-oa TOFMS utilisation to determine the Gd isotopic abundance in gadolinium nitrate

International Nuclear Information System (INIS)

Dragomir, M.; Ohai, D.; Dumitrescu, I.; Furtuna, I.

2010-01-01

This paper is describes the development of a method that should permit the determination of isotope abundance of gadolinium in gadolinium nitrate, used as burnable poison at Cernavoda NPP. To determine the isotopic abundance of gadolinium the inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer (ICP-oa TOFMS) was used. The ICP-oa TOFMS allows the elimination of noise associated with instrumental drift and instability (flicker noise). The absence of flicker noise in the ICP-oa TOFMS means that the isotope ratios can be measured up to the statistical limit of ion counting. With TOFMS, each spectrum acquired represents signals from ions extracted from the plasma during the same time interval, formed from identical plasma and sample introduction events. Therefore, the ICP-oa TOFMS, Optimass 8000, has been successfully used for isotope ratio measurements of Gd in gadolinium nitrate [Gd (NO 3 ) 3 x 6H 2 O] sample solutions. (authors)

Dielectronic and radiative recombination of Si- to N-like tungsten ions

International Nuclear Information System (INIS)

Biedermann, C; Radtke, R; Seidel, R; Behar, E

2009-01-01

We have performed x-ray spectroscopic measurements of the dielectronic recombination resonance strength for the LMn (n = 3, ..., 10) series of Si-like W 60+ to N-like W 67+ tungsten ions. Highly charged tungsten ions were produced, stored and excited with the Berlin electron beam ion trap and the emitted radiation was analyzed with a solid state detector. Information on the charge state abundance in the trap was extracted from a fit of the theoretical radiative recombination intensity to measured values. The fit procedure was only feasible when the fine structure, angular momentum of the recombination channels is taken into account. Our measurement of x-rays from n = 2-3, 2-4 and higher DR resonance transitions was compared to relativistic calculations of the DR cross sections and rate coefficients calculated with the Hebrew University Lawrence Livermore Atomic Code (HULLAC). The previous theoretical predictions for Ne-like tungsten (W 64+ ) were extended with calculations for ions in adjacent charge states and compare well with the observed DR resonance structure.

Millimeter observations of CS, HCO{sup +}, and CO toward five planetary nebulae: following molecular abundances with nebular age

Energy Technology Data Exchange (ETDEWEB)

Edwards, J. L.; Ziurys, L. M. [Department of Chemistry, The University of Arizona, P.O. Box 210041, Tucson, AZ 85721 (United States); Cox, E. G., E-mail: lziurys@email.arizona.edu [Department of Astronomy and Steward Observatory, Arizona Radio Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2014-08-20

Millimeter and sub-millimeter observations of CO, CS, and HCO{sup +} have been conducted toward five planetary nebulae (PNe: K4-47, NGC 6537 (Red Spider), M2-48, NGC 6720 (Ring), and NGC 6853 (Dumbbell)), spanning an age range of 900-10,000 yr, using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. The J = 5 → 4, J = 3 → 2, and J = 2 → 1 transitions of CS at 245, 147, and 98 GHz, as well as the J = 3 → 2 and J = 1 → 0 lines of HCO{sup +} at 268 and 89 GHz, were detected toward each source. At least three rotational transitions of CO have also been observed, including the J = 6 → 5 and J = 4 → 3 lines at 691 and 461 GHz. CS had not been definitively identified previously in PNe, and new detections of HCO{sup +} were made in four of the five nebulae. From a radiative transfer analysis of the CO and CS data, kinetic temperatures of T {sub K} ∼ 10-80 K and gas densities of n(H{sub 2}) ∼ 0.1-1 × 10{sup 6} cm{sup –3} were determined for the molecular material in these sources. Column densities for CO, CS, and HCO{sup +} were N {sub tot} ∼ 0.2-5 × 10{sup 16} cm{sup –2}, N {sub tot} ∼ 0.4-9 × 10{sup 12} cm{sup –2}, and N {sub tot} ∼ 0.3-5 × 10{sup 12} cm{sup –2}, respectively, with fractional abundances, relative to H{sub 2}, of f ∼ 0.4-2 × 10{sup –4}, f ∼ 1-4 × 10{sup –8}, and f ∼ 1 × 10{sup –8}, with the exception of M2-48, which had f(HCO{sup +}) ∼ 10{sup –7}. Overall, the molecular abundances do not significantly vary over a duration of 10,000 yr, in contrast to predictions of chemical models. The abundances reflect the remnant asymptotic giant branch shell material, coupled with photochemistry in the early PN phase. These observations also suggest that PNe eject substantial amounts of molecular material into the diffuse interstellar medium.

Transport, charge exchange and loss of energetic heavy ions in the earth's radiation belts - Applicability and limitations of theory

Science.gov (United States)

Spjeldvik, W. N.

1981-01-01

Computer simulations of processes which control the relative abundances of ions in the trapping regions of geospace are compared with observations from discriminating ion detectors. Energy losses due to Coulomb collisions between ions and exospheric neutrals are considered, along with charge exchange losses and internal charge exchanges. The time evolution of energetic ion fluxes of equatorially mirroring ions under radial diffusion is modelled to include geomagnetic and geoelectric fluctutations. Limits to the validity of diffusion transport theory are discussed, and the simulation is noted to contain provisions for six ionic charge states and the source effect on the radiation belt oxygen ion distributions. Comparisons are made with ion flux data gathered on Explorer 45 and ISEE-1 spacecraft and results indicate that internal charge exchanges cause the radiation belt ion charge state to be independent of source charge rate characteristics, and relative charge state distribution is independent of the radially diffusive transport rate below the charge state redistribution zone.

Observations of thermal and suprathermal tail ions from WIND

Science.gov (United States)

Randol, B. M.; Christian, E. R.; Wilson, L. B., III

2016-12-01

The velocity distribution function (VDF) of solar wind protons (as well as other ion populations) is comprised of a thermal Maxwellian core and an accelerated suprathermal tail, beginning at around 1 keV in the frame co-moving with solar wind bulk velocity. The form of the suprathermal tail is a power law in phase space density, f, vs. speed, v, such that f / vγ, where γ is the power law index. This commonly observed index is of particular interest because no traditional theory predicts its existence. We need more data in order to test these theories. The general shape is of interest because it is kappa-like. We show combined observations from three different instruments on the WIND spacecraft: 3DP/PLSP, STICS, and 3DP/SST/Open. These data stretch from 102 to 107 eV in energy, encompassing both the thermal and suprathermal proton populations. We show further evidence for this kappa-like distribution and report on our progress on fitting of empirical functions to these data.

RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES: KMOS OBSERVATIONS IN NGC 6822

International Nuclear Information System (INIS)

Patrick, L. R.; Evans, C. J.; Ferguson, A. M. N.; Davies, B.; Kudritzki, R-P.; Gazak, J. Z.; Bergemann, M.; Plez, B.

2015-01-01

We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new K-band Multi-Object Spectrograph Very Large Telescope, Chile. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = −0.52 ± 0.21, which agrees well with previous abundance studies of young stars and H ii regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast to recent evolutionary models

Beam-beam observations in the Relativistic Heavy Ion Collider

Energy Technology Data Exchange (ETDEWEB)

Luo, Y. [Brookhaven National Laboratory (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Laboratory (BNL), Upton, NY (United States); White, S. [Brookhaven National Laboratory (BNL), Upton, NY (United States)

2015-06-24

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has been operating since 2000. Over the past decade, thanks to the continuously increased bunch intensity and reduced β*s at the interaction points, the maximum peak luminosity in the polarized proton operation has been increased by more than two orders of magnitude. In this article, we first present the beam-beam observations in the previous RHIC polarized proton runs. Then we analyze the mechanisms for the beam loss and emittance growth in the presence of beam-beam interaction. The operational challenges and limitations imposed by beam-beam interaction and their remedies are also presented. In the end, we briefly introduce head-on beam-beam compensation with electron lenses in RHIC.

Microscopic observation of pattern attack by aggressive ions on finished surface of aluminium alloy sacrificial anode

International Nuclear Information System (INIS)

Zaifol Samsu; Muhammad Daud; Siti Radiah Mohd Kamarudin; Nur Ubaidah Saidin; Azali Muhammad; Mohd Shaari Ripin; Rusni Rejab; Mohd Shariff Sattar

2010-01-01

This paper presents the results of a microscopic observation on submerged finished surface of aluminium alloy sacrificial anode. Experimental tests were carried out on polished surface aluminium anode exposed to seawater containing aggressive ions in order to observe of pattern corrosion attack on corroding surface of anode. Results have shown, at least under the present testing condition, that surface of sacrificial anode were attack by an aggressive ion such as chloride along grain boundaries. In addition, results of microanalysis showed that the corrosion products on surface of aluminium alloy have Al, Zn and O element for all sample and within the pit was consists of Al, Zn, O and Cl element. (author)

SnSe2 Two Dimensional Anodes for Advanced Sodium Ion Batteries

KAUST Repository

Zhang, Fan

2017-01-01

Sodium-ion batteries (SIBs) are considered as a promising alternative to lithium-ion batteries (LIBs) for large-scale renewable energy storage units due to the abundance of sodium resource and its low cost. However, the development of anode

IUE observations of Si and C lines and comparison with non-LTE models

Science.gov (United States)

Kamp, L. W.

1982-01-01

Classical model atmosphere techniques are applied to analyze IUE spectra, and to determine abundances, effective temperatures and gravities. Measurements of the equivalent widths and other properties of the line profiles of 24 photospheric lines of Si II, Si III, Si IV, C II, C III and C IV are presented in the range of 1175-1725 A for seven B and two O stars. Observed line profiles are compared with theoretical profiles computed using non-LTE theory and models, and using line-blanketed model atmospheres. Agreement is reasonably good, although strong lines are calculated to be systematically stronger than those observed, while the reverse occurs for weak lines, and empirical profiles have smaller wings than theoretical profiles. It is concluded that the present theory of line formation when used with solar abundances, represents fairly well observed UV photospheric lines of silicon and carbon ions in the atmospheres of main sequence stars of types B5-O9.

Formation of the high-energy ion population in the earth's magnetotail: spacecraft observations and theoretical models

Directory of Open Access Journals (Sweden)

A. V. Artemyev

2014-10-01

Full Text Available We investigate the formation of the high-energy (E ∈ [20,600] keV ion population in the earth's magnetotail. We collect statistics of 4 years of Interball / Tail observations (1995–1998 in the vicinity of the neutral plane in the magnetotail region (X RE, |Y| ≤ 20 RE in geocentric solar magnetospheric (GSM system. We study the dependence of high-energy ion spectra on the thermal-plasma parameters (the temperature Ti and the amplitude of bulk velocity vi and on the magnetic-field component Bz. The ion population in the energy range E ∈ [20,600] keV can be separated in the thermal core and the power-law tail with the slope (index ~ −4.5. Fluxes of the high-energy ion population increase with the growth of Bz, vi and especially Ti, but spectrum index seems to be independent on these parameters. We have suggested that the high-energy ion population is generated by small scale transient processes, rather than by the global reconfiguration of the magnetotail. We have proposed the relatively simple and general model of ion acceleration by transient bursts of the electric field. This model describes the power-law energy spectra and predicts typical energies of accelerated ions.

THE MYSTERIOUS CASE OF THE SOLAR ARGON ABUNDANCE NEAR SUNSPOTS IN FLARES

International Nuclear Information System (INIS)

Doschek, G. A.; Warren, H. P.

2016-01-01

Recently we discussed an enhancement of the abundance of Ar xiv relative to Ca xiv near a sunspot during a flare, observed in spectra recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The observed Ar xiv/Ca xiv ratio yields an argon/calcium abundance ratio seven times greater than expected from the photospheric abundance. Such a large abundance anomaly is unprecedented in the solar atmosphere. We interpreted this result as being due to an inverse first ionization potential (FIP) effect. In the published work, two lines of Ar xiv were observed, and one line was tentatively identified as an Ar xi line. In this paper, we report observing a similar enhancement in a full-CCD EIS flare spectrum in 13 argon lines that lie within the EIS wavelength ranges. The observed lines include two Ar xi lines, four Ar xiii lines, six Ar xiv lines, and one Ar xv line. The enhancement is far less than reported in Doschek et al. but exhibits similar morphology. The argon abundance is close to a photospheric abundance in the enhanced area, and the abundance could be photospheric. This enhancement occurs in association with a sunspot in a small area only a few arcseconds (1″ = about 700 km) in size. There is no enhancement effect observed in the normally high-FIP sulfur and oxygen line ratios relative to lines of low-FIP elements available to EIS. Calculations of path lengths in the strongest enhanced area in Doschek et al. indicate a depletion of low-FIP elements.

Characterization of microdose damage caused by single heavy ion observed in trench type power MOSFETs

International Nuclear Information System (INIS)

Ikeda, Naomi; Kuboyama, Satoshi; Maru, Akifumi; Tamura, Takashi; Hirao, Toshio; Abe, Hiroshi

2010-01-01

It was demonstrated that anomalously large degradation observed in power MOSFETs was caused by a single heavy ion. It was identified as a microdose effect and successfully characterized by several parameters extracted from experimental data. (author)

Turbulence and the Li abundance in main sequence and giant stars

International Nuclear Information System (INIS)

Charbonneau, P.; Michaud, G.

1990-01-01

Calculations of Li burning via turbulent transport are conducted to determine the extent to which observed Li abundances in first ascent giants constrain the various turbulence parameterizations used to model the main-sequence surface Li abundance evolution. A full time-dependent solution to the transport equation is performed, including nuclear reaction terms and evolutionary effects. It is found that turbulence can lead to the extreme Li underabundances observed in giants of M67 and NGC 752. Consideration is given to the possibility of using observations of Li abundances to discriminate between turbulent particle transport and meridional circulation transport. Numerical solutions of the turbulent diffusion coefficient of Vauclair (1988) is used to model the Hyades Li abundance gap. The astrophysical implications of the results for main-sequence and giant stars are discussed. 36 refs

The ion population of the magnetotail during the 17 April 2002 magnetic storm: Large-scale kinetic simulations and IMAGE/HENA observations

Science.gov (United States)

Peroomian, Vahé; El-Alaoui, Mostafa; Brandt, Pontus C.:son

2011-05-01

The contribution of solar wind and ionospheric ions to the ion population of the magnetotail during the 17 April 2002 geomagnetic storm was investigated by using large-scale kinetic (LSK) particle tracing calculations. We began our investigation by carrying out a global magnetohydrodynamic simulation of the storm event by using upstream solar wind and interplanetary magnetic field data from the ACE spacecraft. We launched solar wind H+ ions and ionospheric O+ ions beginning at 0900 UT, ˜2 h prior to the sudden storm commencement (SSC), until 2000 UT. We found that during this Dst ˜ -98 nT storm, solar wind ions carried the bulk of the density and energy density in the nightside ring current and plasma sheet, with the notable exception of the 90 min immediately after the SSC when O+ densities in the ring current exceeded those of H+ ions. The LSK simulation did a very good job of reproducing ion densities observed by the Los Alamos National Laboratory spacecraft at geosynchronous orbit and reproduced the changes in the inner magnetosphere and the injection of ions observed by the IMAGE spacecraft during a substorm that occurred at 1900 UT. These comparisons with observations serve to validate our results throughout the magnetotail and allow us to obtain time-dependent maps of H+ and O+ density and energy density where IMAGE cannot make measurements. In essence, this work extends the viewing window of the IMAGE spacecraft far downtail.

Chemical abundances of globular clusters in NGC 5128 (Centaurus A)

Science.gov (United States)

Hernandez, Svea; Larsen, Søren; Trager, Scott; Kaper, Lex; Groot, Paul

2018-06-01

We perform a detailed abundance analysis on integrated-light spectra of 20 globular clusters (GCs) in the early-type galaxy NGC 5128 (Centaurus A). The GCs were observed with X-Shooter on the Very Large Telescope (VLT). The cluster sample spans a metallicity range of -1.92 poor GCs in NGC 5128 is genuine, it could hint at a chemical enrichment history different than that experienced by the MW. We also measure Na abundances in 9 out of 20 GCs. We find evidence for intracluster abundance variations in six of these clusters where we see enhanced [Na/Fe] > +0.25 dex. We obtain the first abundance measurements of Cr, Mn, and Ni for a sample of the GC population in NGC 5128 and find consistency with the overall trends observed in the MW, with a slight enhancement (<0.1 dex) in the Fe-peak abundances measured in the NGC 5128.

Theory and observation of electromagnetic ion cyclotron triggered emissions in the magnetosphere

Science.gov (United States)

Omura, Yoshiharu; Pickett, Jolene; Grison, Benjamin; Santolik, Ondrej; Dandouras, Iannis; Engebretson, Mark; Décréau, Pierrette M. E.; Masson, Arnaud

2010-07-01

We develop a nonlinear wave growth theory of electromagnetic ion cyclotron (EMIC) triggered emissions observed in the inner magnetosphere. We first derive the basic wave equations from Maxwell's equations and the momentum equations for the electrons and ions. We then obtain equations that describe the nonlinear dynamics of resonant protons interacting with an EMIC wave. The frequency sweep rate of the wave plays an important role in forming the resonant current that controls the wave growth. Assuming an optimum condition for the maximum growth rate as an absolute instability at the magnetic equator and a self-sustaining growth condition for the wave propagating from the magnetic equator, we obtain a set of ordinary differential equations that describe the nonlinear evolution of a rising tone emission generated at the magnetic equator. Using the physical parameters inferred from the wave, particle, and magnetic field data measured by the Cluster spacecraft, we determine the dispersion relation for the EMIC waves. Integrating the differential equations numerically, we obtain a solution for the time variation of the amplitude and frequency of a rising tone emission at the equator. Assuming saturation of the wave amplitude, as is found in the observations, we find good agreement between the numerical solutions and the wave spectrum of the EMIC triggered emissions.

Large Abundances of Polycyclic Aromatic Hydrocarbons in Titan's Upper Atmosphere

Science.gov (United States)

Lopez-Puertas, M.; Dinelli, B. M.; Adriani, A.; Funke, B.; Garcia-Comas, M.; Moriconi, M. L.; D'Aversa, E.; Boersma, C.; Allamandola, L. J.

2013-01-01

In this paper, we analyze the strong unidentified emission near 3.28 micron in Titan's upper daytime atmosphere recently discovered by Dinelli et al.We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 micron. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 10(exp 4) particles / cubic cm. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is approx 430 u; the mean area is about 0.53 sq. nm; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

Ion-Exchange Sample Displacement Chromatography as a Method for Fast and Simple Isolation of Low- and High-Abundance Proteins from Complex Biological Mixtures

Directory of Open Access Journals (Sweden)

Martina Srajer Gajdosik

2014-01-01

Full Text Available Sample displacement chromatography (SDC in reversed phase and ion-exchange modes was introduced at the end of 1980s. This chromatographic method was first used for preparative purification of synthetic peptides, and subsequently adapted for protein fractionation, mainly in anion-exchange mode. In the past few years, SDC has been successfully used for enrichment of low- and medium-abundance proteins from complex biological fluids on both monolithic and bulk chromatographic supports. If aqueous mobile phase is used with the application of mild chromatographic conditions, isolated proteins are not denatured and can also keep their biological activity. In this paper, the use of SDC in anion-exchange mode on a high-capacity chromatographic resin for separation of proteins from complex biological mixtures such as human plasma is demonstrated. By use of three and more columns coupled in series during sample application, and subsequent parallel elution of detached columns, additional separation of bound proteins was achieved. Highly enriched human serum albumin fraction and a number of physiologically active medium- and low-abundance proteins could be fractionated and detected by electrospray ionization tandem mass spectrometry (ESI-MS/MS and matrix assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS. The use of the aforementioned columns that can be sanitized with 1 M sodium hydroxide for further application of SDC in biotechnology and food technology was discussed.

Silicene for Na-ion battery applications

KAUST Repository

Zhu, Jiajie

2016-08-19

Na-ion batteries are promising candidates to replace Li-ion batteries in large scale applications because of the advantages in natural abundance and cost of Na. Silicene has potential as the anode in Li-ion batteries but so far has not received attention with respect to Na-ion batteries. In this context, freestanding silicene, a graphene-silicene-graphene heterostructure, and a graphene-silicene superlattice are investigated for possible application in Na-ion batteries, using first-principles calculations. The calculated Na capacities of 954mAh/g for freestanding silicene and 730mAh/g for the graphenesilicene superlattice (10% biaxial tensile strain) are highly competitive and potentials of >0.3 V against the Na/Na potential exceed the corresponding value of graphite. In addition, the diffusion barriers are predicted to be <0.3 eV.

Ammonia abundances in comets

Science.gov (United States)

Wyckoff, S.; Tegler, S.; Engel, L.

The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

Acceleration of H, He, and heavy ions observed in the magnetosheath, magnetotail, and near-by interplanetary space

International Nuclear Information System (INIS)

Fan, C.Y.; Gloeckler, G.; Hovestadt, D.

1975-01-01

Pulses of electrons and ions composed of H, He, and heavier elements were observed in the magnetosheath, magnetotail, and near-by interplanetary space. From the spatial positions where these particles were detected and the ion flow directions we conclude that they were accelerated at the bow shock near the sub-solar point and in the near-earth region of the neutral sheet of the magnetotail. (orig.) [de

In-situ observations of a bi-modal ion distribution in the outer coma of comet P/Halley

Science.gov (United States)

Thomsen, M. F.; Feldman, W. C.; Wilken, B.; Jockers, K.; Stuedemann, W.

1987-01-01

Observations obtained by the Johnstone Plasma Analyzer on the Giotto fly-by of comet Halley showed a fairly sudden decrease in the count rate of energetic (about 30 KeV) water-group ions inside about 500,000 km from the nucleus. This decrease was accompanied by the appearance of a new water-group ion population at slightly lower energies (less than 10 KeV). Close inspection reveals that this lower-energy peak was also present somewhat earlier in the postshock flow but only became prominent near the sudden transition just described. It is shown that the observed bimodal ion distribution is well explained in terms of the velocity history of the accreting solar wind flow in the outer coma. The decline in count rate of the energetic pick-up distribution is due to a relatively sudden slowing of the bulk flow there and not to a loss of particles. Hence, charge-exchange cooling of the flow is probably not important at these distances from the nucleus. The observations suggest that pitch-angle scattering is fairly efficient at least after the bow shock, but that energy diffusion is probably not very efficient.

MESSENGER Observations of the Spatial Distribution of Planetary Ions Near Mercury

Science.gov (United States)

Zurbuchen, Thomas H.; Raines, Jim M.; Slavin, James A.; Gershman, Daniel J.; Gilbert, Jason A.; Gloeckler, George; Anderson, Brian J.; Baker, Daniel N.; Korth, Haje; Krimigis, Stamatios M.;

Dissociation mechanism of HNIW ions investigated by chemical ionization and electron impact mass spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Yang, Rongjie; Xiao, Hemiao [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

2006-04-15

Chemical Ionization (CI) with Collision-Induced Dissociation (CID) spectroscopy and Electron Impacting (EI) with metastable Mass analyzed Ion Kinetic Energy (MIKE) spectroscopy have been applied to study ionic dissociations of Hexanitrohexaazaisowurtzitane (HNIW). Similarities and differences between EI/MIKE and CI/CID mass spectra of HNIW were analyzed. In EI mass spectra, the ions [HNIW-n NO{sub 2}]{sup +} (n=2-5), such as the ion at m/z 347, were less frequent (1-2% relative abundance), but in CI mass spectra, these ions were very abundant. For some ions of large molar mass from HNIW, their dissociations pathways from parent ions to daughter ions were built according to CID and MIKE spectra. Molecular ions of HNIW with a protonated nitro group at five-member ring seem more stable than at six-member ring. The HNIW ions losing five of six nitro groups are very stable based on CID spectra, which agrees with some research results for thermal decomposition of HNIW in literature. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances

Science.gov (United States)

Henry, R. B. C.; Stephenson, B. G.; Miller Bertolami, M. M.; Kwitter, K. B.; Balick, B.

2018-01-01

The primary goal of this paper is to make a direct comparison between the measured and model-predicted abundances of He, C, and N in a sample of 35 well-observed Galactic planetary nebulae (PNe). All observations, data reductions, and abundance determinations were performed in house to ensure maximum homogeneity. Progenitor star masses (M ≤ 4 M⊙) were inferred using two published sets of post-asymptotic giant branch model tracks and L and Teff values. We conclude the following: (1) the mean values of N/O across the progenitor mass range exceeds the solar value, indicating significant N enrichment in the majority of our objects; (2) the onset of hot bottom burning appears to begin around 2 M⊙, i.e. lower than ∼5 M⊙ implied by theory; (3) most of our objects show a clear He enrichment, as expected from dredge-up episodes; (4) the average sample C/O value is 1.23, consistent with the effects of third dredge up; and (5) model grids used to compare to observations successfully span the distribution over metallicity space of all C/O and many He/H data points but mostly fail to do so in the case of N/O. The evident enrichment of N in PN and the general discrepancy between the observed and model-predicted N/O abundance ratios signal the need for extra mixing as an effect of rotation and/or thermohaline mixing in the models. The unexpectedly high N enrichment that is implied here for low-mass stars, if confirmed, will likely impact our conclusions about the source of N in the Universe.

TV observations of the Barium-GEOS ion jet experiment

International Nuclear Information System (INIS)

Hapgood, M.A.; Collin, H.L.; Rothwell, P.

1980-01-01

The barium jet released by the Barium-GEOS rocket was observed by low light television cameras at Skibotn, Norway and Esrange, Sweden. The release produced a single well-defined jet containing barium ions with initial velocities between 7 and 12 km s -1 systematically slower than the velocities reported in previous experiments. Accurate data on the motion of the jet has been obtained for the first two minutes after release (up to a height of 2000 km). The orientation of the jet was close to that of an IGRF1975 model field line but was significantly different from that predicted by the Barraclough and Olson field model. The motion of the jet across the field lines was southwards with a velocity of about 150 m s -1 . (Auth.)

Limitations of Electromagnetic Ion Cyclotron Wave Observations in Low Earth Orbit

Directory of Open Access Journals (Sweden)

Junga Hwang

2018-03-01

Full Text Available Pc1 pulsations are geomagnetic fluctuations in the frequency range of 0.2 to 5 Hz. There have been several observations of Pc1 pulsations in low earth orbit by MAGSAT, DE-2, Viking, Freja, CHAMP, and SWARM satellites. However, there has been a clear limitation in resolving the spatial and temporal variations of the pulsation by using a single-point observation by a single satellite. To overcome such limitations of previous observations, a new space mission was recently initiated, using the concept of multi-satellites, named the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE. The SNIPE mission consists of four nanosatellites (~10 kg, which will be launched into a polar orbit at an altitude of 600 km (TBD in 2020. Four satellites will be deployed in orbit, and the distances between each satellite will be controlled from 10 to 1,000 km by a high-end formation-flying algorithm. One of the possible science targets of the SNIPE mission is observing electromagnetic ion cyclotron (EMIC waves. In this paper, we report on examples of observations, showing the limitations of previous EMIC observations in low earth orbit, and suggest possibilities to overcome those limitations through a new mission.

SIMS analysis of isotopic impurities in ion implants

International Nuclear Information System (INIS)

Sykes, D.E.; Blunt, R.T.

1986-01-01

The n-type dopant species Si and Se used for ion implantation in GaAs are multi-isotopic with the most abundant isotope not chosen because of potential interferences with residual gases. SIMS analysis of a range of 29 Si implants produced by several designs of ion implanter all showed significant 28 Si impurity with a different depth distribution from that of the deliberately implanted 29 Si isotope. This effect was observed to varying degrees with all fifteen implanters examined and in every 29 Si implant analysed to date 29 Si + , 29 Si ++ and 30 Si implants all show the same effect. In the case of Se implantation, poor mass resolution results in the implantation of all isotopes with the same implant distribution (i.e. energy), whilst implants carried out with good mass resolution show the implantation of all isotopes with the characteristic lower depth distribution of the impurity isotopes as found in the Si implants. This effect has also been observed in p-type implants into GaAs (Mg) and for Ga implanted in Si. A tentative explanation of the effect is proposed. (author)

Use of abundance of one species as a surrogate for abundance of others

Science.gov (United States)

Samuel A. Cushman; Kevin S. McKelvey; Barry R. Noon; Kevin McGarigal

2010-01-01

Indicator species concepts have a long history in conservation biology. Arguments in favor of these approaches generally stress expediency and assume efficacy. We tested the premise that the abundance patterns of one species can be used to infer those of other species. Our data consisted of 72,495 bird observations on 55 species across 1046 plots distributed across 30...

Observation of visible emission from the molecular helium ion in the afterglow of a dense helium Z-pinch plasma

International Nuclear Information System (INIS)

Tucker, J.E.; Brake, M.L.; Gilgenbach, R.M.

1986-01-01

The authors present the results of axial and radial time resolved visible emission spectroscopy from the afterglow of a dense helium Z-pinch. These results show that the visible emissions in the pinch afterglow are dominated by line emissions from molecular helium and He II. Axial spectroscopy measurements show the occurrence of several absorption bands which cannot be identified as molecular or atomic helium nor impurities from the discharge chamber materials. The authors believe that these absorption bands are attributable to the molecular helium ion which is present in the discharge. The molecular ion has been observed by others in low pressure and temperature helium discharges directly by means of mass spectrometry and indirectly by the presence of helium atoms in the 2/sup 3/S state, (the He 2/sup 3/S state is believed to result from molecular helium ion recombination). However, the molecular helium ion has not previously been observed spectroscopically

Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

Digital Repository Service at National Institute of Oceanography (India)

Gaonkar, C.A.; Samiksha S.V.; George, G.; Aboobacker V.M.; Vethamony, P.; Anil, A.C.

Observations were carried out to monitor the larval abundance, settlement and recruitment of barnacles on a regular basis for a period of two years. The results were then compared with the numerical modelling studies carried out along the west coast...

Auroral ion beams and ion acoustic wave generation by fan instability

Energy Technology Data Exchange (ETDEWEB)

Vaivads, A

1996-04-01

Satellite observations indicate that efficient energy transport among various plasma particles and between plasma waves and plasma particles is taking place in auroral ion beam regions. These observations show that two characteristic wave types are associated with the auroral ion beam regions: electrostatic hydrogen cyclotron waves with frequencies above hydrogen gyrofrequency, and low frequency waves with frequencies below hydrogen gyrofrequency. We speculate that the low frequency waves can be ion acoustic waves generated through the fan instability. The presence of a cold background ion component is necessary for the onset of this instability. A cold ion component has been directly observed and has been indirectly suggested from observations of solitary wave structures. The wave-particle interaction during the development of the fan instability results in an efficient ion beam heating in the direction perpendicular to the ambient magnetic field. The fan instability development and the ion beam heating is demonstrated in a numerical particle simulation. 23 refs, 16 figs.

Experimental results concerning global observables from the CERN SPS heavy ion program

International Nuclear Information System (INIS)

Young, G.R.

1990-06-01

A brief overview is given of experimental results obtained during the initial operation of the heavy-ion program at the CERN SPS during the period 1986--1988. This paper confines itself to a presentation of results on so-called global observables, such as energy flow and multiplicity distributions, and on information extracted from them. Of particular interest among the latter are an estimate of the magnitude and spatial distribution of the energy density attained. 3 refs., 27 figs

An alkali ion source based on graphite intercalation compounds for ion mobility spectrometry

International Nuclear Information System (INIS)

Tabrizchi, Mahmoud; Hosseini, Zahra S

2008-01-01

A variety of alkali cation emitters were developed as the ion source for ion mobility spectrometry. The cation emitters were constructed based on alkali ion graphite intercalation compounds (GICs). The compounds were prepared by fusing alkali salts with ground graphite. In order to produce alkali ions, the compounds were loaded on a filament and heated to red. Reactant ions of the form alk + ions were observed for the alkali salts NaCl, KCl.LiCl, CsCl and SrCl. In addition to Na + ions, K + ions were observed at the beginning of thermionic emission from Na-GIC. This is due to the low ionization potential of potassium that exists in trace amounts in sodium salts. In addition to the potassium ion, Na + was observed in the case of LiCl salt. The Na + and K + peaks originating from impurities totally disappeared after about 40 min. However, the thermionic emission of the main ion of the corresponding salt lasted for several days. No negative ions were observed upon reversing the drift field. Selected organic compounds (methyl isobutyl ketone, dimethyl sulfoxide, acetone and tetrahydrofuran) were also ionized via alkali cation attachment reaction. Distinct ion mobility patterns were observed for different substances using one type of alkali reactant ion. However, the ion mobility pattern for a given substance changed when a different alkali reactant ion was used. Ammonia and amines were not ionized when this source was used

A search for stars of very low metal abundance. VI. Detailed abundances of 313 metal-poor stars

International Nuclear Information System (INIS)

Roederer, Ian U.; Preston, George W.; Thompson, Ian B.; Shectman, Stephen A.; Burley, Gregory S.; Kelson, Daniel D.; Sneden, Christopher

2014-01-01

We present radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars. A majority of these stars were selected from the metal-poor candidates of the HK Survey of Beers, Preston, and Shectman. We derive detailed abundances for 61% of these stars for the first time. Spectra were obtained during a 10 yr observing campaign using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coudé Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, and the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We perform a standard LTE abundance analysis using MARCS model atmospheres, and we apply line-by-line statistical corrections to minimize systematic abundance differences arising when different sets of lines are available for analysis. We identify several abundance correlations with effective temperature. A comparison with previous abundance analyses reveals significant differences in stellar parameters, which we investigate in detail. Our metallicities are, on average, lower by ≈0.25 dex for red giants and ≈0.04 dex for subgiants. Our sample contains 19 stars with [Fe/H] ≤–3.5, 84 stars with [Fe/H] ≤–3.0, and 210 stars with [Fe/H] ≤–2.5. Detailed abundances are presented here or elsewhere for 91% of the 209 stars with [Fe/H] ≤–2.5 as estimated from medium resolution spectroscopy by Beers, Preston, and Shectman. We will discuss the interpretation of these abundances in subsequent papers.

Pregalactic helium abundance and abundance gradients across our galaxy from planetary nebulae

Energy Technology Data Exchange (ETDEWEB)

D' Odorico, S; Peimbert, M [Universidad Nacional Autonoma de Mexico, Mexico City. Instituto de Astronomia; Sabbadin, F [Padua Univ. (Italy). Istituto di Astronomia

1976-03-01

From the observations of planetary nebulae by Peimbert and Torres-Peimbert we have studied the radial gradients across our galaxy of the helium, oxygen and nitrogen abundance relative to hydrogen. The increase of the oxygen to hydrogen abundance ratio from a radial distance to the galactic center of 14 to 8 kpc is about a factor of 3 while that of the nitrogen to hydrogen ratio is about twice as large. By adopting oxygen as representative of the heavy elements it is found that the helium enrichment is coupled to the heavy metal enrichment by ..delta..Y/..delta..Zapproximately2.9 in close agreement with the value derived from H II regions. The pregalactic N(He)/N(H) value derived from planetary nebulae is 0.073+-0.008 also in agreement with the value derived from H II regions.

Electromagnetic ion cyclotron waves observed near the oxygen cyclotron frequency by ISEE 1 and 2

Science.gov (United States)

Fraser, B. J.; Samson, J. C.; Hu, Y. D.; Mcpherron, R. L.; Russell, C. T.

1992-01-01

The first results of observations of ion cyclotron waves by the elliptically orbiting ISEE 1 and 2 pair of spacecraft are reported. The most intense waves (8 nT) were observed in the outer plasmasphere where convection drift velocities were largest and the Alfven velocity was a minimum. Wave polarization is predominantly left-handed with propagation almost parallel to the ambient magnetic field, and the spectral slot and polarization reversal predicted by cold plasma propagation theory are identified in the wave data. Computations of the experimental wave spectra during the passage through the plasmapause show that the spectral slots relate to the local plasma parameters, possibly suggesting an ion cyclotron wave growth source near the spacecraft. A regular wave packet structure seen over the first 30 min of the event is attributed to the modulation of this energy source by the Pc 5 waves seen at the same time.

Superconductivity observed in platinum-silicon interface

Energy Technology Data Exchange (ETDEWEB)

Kuo, Pai-Chia, E-mail: paichia@phys.sinica.edu.tw [Research Program on Nanoscience and Nanotechnology, Academia Sinica, Taipei 11529, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Chen, Chun-Wei [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Lee, Ku-Pin; Shiue, Jessie, E-mail: yshiue@phys.sinica.edu.tw [Research Program on Nanoscience and Nanotechnology, Academia Sinica, Taipei 11529, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China)

2014-05-26

We report the discovery of superconductivity with an onset temperature of ∼0.6 K in a platinum-silicon interface. The interface was formed by using a unique focused ion beam sputtering micro-deposition method in which the energies of most sputtered Pt atoms are ∼2.5 eV. Structural and elemental analysis by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy reveal a ∼ 7 nm interface layer with abundant Pt, which is the layer likely responsible for the superconducting transport behavior. Similar transport behavior was also observed in a gold-silicon interface prepared by the same technique, indicating the possible generality of this phenomenon.

Investigation of Uranyl Nitrate Ion Pairs Complexed with Amide Ligands using Electrospray Ionization Ion Trap Mass Spectrometry and Density Functional Theory

International Nuclear Information System (INIS)

Groenewold, Gary S.; Dinescu, Adriana; Benson, Michael T.; Gresham, Garold L.; van Stipdonk, Michael J.

2011-01-01

Ion populations formed from electrospray of uranyl nitrate solutions containing different amides vary depending on ligand nucleophilicity and steric crowding at the metal center. The most abundant species were ion pair complexes having the general formula (UO2(NO3)(amide)n=2,3)+, and complexes containing the amide conjugate base, reduced uranyl UO2+, and a 2+ charge were also formed. The formamide experiment produced the greatest diversity of species that stems from weaker amide binding leading to dissociation and subsequent solvent coordination or metal reduction. Experiments using methyl formamide, dimethyl formamide, acetamide, and methyl acetamide produced ion pair and doubly charged complexes that were more abundant, and less abundant complexes containing solvent or reduced uranyl. This pattern is reversed in the dimethylacetamide experiment, which displayed reduced doubly charged complexes and augmented reduced uranyl complexes. DFT investigations of the tris-amide ion pair complexes showed that inter-ligand repulsion distorts the amide ligands out of the uranyl equatorial plane, and that complex stabilities do not increase with increasing amide nucleophilicity. Elimination of an amide ligand largely relieves the interligand repulsion, and the remaining amide ligands become closely aligned with the equatorial plane in the structures of the bis-amide ligands. The studies show that the phenomenological distribution of coordination complexes in a metal-ligand electrospray experiment is a function of both ligand nucleophilicity and interligand repulsion, and that the latter factor begins exerting influence even in the case of relatively small ligands like the substituted methyl-formamide and methyl-acetamide ligands.

Production of highly ionized recoil ions in heavy ion impact

International Nuclear Information System (INIS)

Tawara, H.; Tonuma, T.; Be, S.H.; Shibata, H.; Kase, M.; Kambara, T.; Kumagai, H.; Kohno, I.

1985-01-01

The production mechanisms of highly ionized recoil ions in energetic, highly charged heavy ion impact are compared with those in photon and electron impact. In addition to the innershell ionization processes which are important in photon and electron impact, the electron transfer processes are found to play a key role in heavy ion impact. In molecular targets are also observed highly ionized monoatomic ions which are believed to be produced through production of highly ionized molecular ions followed by prompt dissociation. The observed N 6+ ions produced in 1.05MeV/amu Ar 12+ ions on N 2 molecules are produced through, for example, N 2 12+ *→N 6+ +N 6+ process. (author)

A Model for Negative Ion Chemistry in Titan’s Ionosphere

Science.gov (United States)

Mukundan, Vrinda; Bhardwaj, Anil

2018-04-01

We developed a one-dimensional photochemical model for the dayside ionosphere of Titan for calculating the density profiles of negative ions under steady-state photochemical equilibrium condition. We concentrated on the T40 flyby of the Cassini orbiter and used the in situ measurements from instruments on board Cassini as input to the model. Using the latest available reaction rate coefficients and dissociative electron attachment cross sections, the densities of 10 anions are calculated. Our study shows CN‑ as the dominant anion, followed by C3N‑, which agrees with the results of previous calculations. We suggest that H‑ could be an important anion in Titan’s ionosphere and is the second most abundant anion at altitudes greater than 1200 km. The main production channel of the major ion CN‑ is the reaction of H‑ with HCN. The H‑ also play a major role in the production of anions C2H‑, C6H‑, and OH‑. We present a comparison of the calculated ion density profiles with the relative density profiles derived using recently reported Cassini CAPS/ELS observations.

Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period

Science.gov (United States)

Berčič, L.; Behar, E.; Nilsson, H.; Nicolaou, G.; Wieser, G. Stenberg; Wieser, M.; Goetz, C.

2018-06-01

Aims: Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods: We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results: On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions: Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov-Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

CHROMOSPHERIC MODELS AND THE OXYGEN ABUNDANCE IN GIANT STARS

Energy Technology Data Exchange (ETDEWEB)

Dupree, A. K.; Avrett, E. H.; Kurucz, R. L., E-mail: dupree@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2016-04-10

Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri, which include a chromosphere (CHR), influence the formation of optical lines of O i: the forbidden lines (λ6300, λ6363) and the infrared triplet (λλ7771−7775). One-dimensional semi-empirical non-local thermodynamic equilibrium (LTE) models are constructed based on observed Balmer lines. A full non-LTE formulation is applied for evaluating the line strengths of O i, including photoionization by the Lyman continuum and photoexcitation by Lyα and Lyβ. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than those in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than those produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors of ∼3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate-mass AGB stars contribute to the observed abundance pattern in globular clusters. A change in the oxygen abundance of metal-poor field giants could affect models of deep mixing episodes on the red giant branch. Changes in the oxygen abundance can impact other abundance determinations that are critical to astrophysics, including chemical tagging techniques and galactic chemical evolution.

Application of ion scattering spectrometers for the observation of process of cleaning of surfaces of materials for vacuum vessel

International Nuclear Information System (INIS)

Akashi, Ken-ya; Miyahara, Akira; Sagara, Akio.

1978-01-01

The impurity gas emitted from the surfaces of vacuum vessels was investigated by using the shadowing effect of the covering atoms. The ion scattering spectrometer used for the experiment consists of an ion source, a test sample, an energy analyzer and an ion detector. The evacuation system comprises a turbomolecular pump, a Ti-sublimation pump and an ion pump. The achieved final gas pressure is 5 x 10 -10 Torr. The ion beam intensity to a sample is 10 micro ampere/cm 2 , and the ion energy is about 1 to 1.5 keV. The quantity of oxygen on the surface of a sample molybdenum was measured in the process of evacuation. The concentration of surface oxygen decreased with the gas pressure of the system. It was found that residual oxygen was observed after the sputter etching with Ar ion impact on the surface. The reason of this residual oxygen was considered. (Kato, T.)

Juno/JEDI observations of 0.01 to >10 MeV energetic ions in the Jovian auroral regions: Anticipating a source for polar X-ray emission

Science.gov (United States)

Haggerty, D. K.; Mauk, B. H.; Paranicas, C. P.; Clark, G.; Kollmann, P.; Rymer, A. M.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.

2017-07-01

After a successful orbit insertion, the Juno spacecraft completed its first 53.5 day orbit and entered a very low altitude perijove with the full scientific payload operational for the first time on 27 August 2016. The Jupiter Energetic particle Detector Instrument measured ions and electrons over the auroral regions and through closest approach, with ions measured from 0.01 to >10 MeV, depending on species. This report focuses on the composition of the energetic ions observed during the first perijove of the Juno mission. Of particular interest are the ions that precipitate from the magnetosphere onto the polar atmosphere and ions that are accelerated locally by Jupiter's powerful auroral processes. We report preliminary findings on the spatial variations, species, including energy and pitch angle distributions throughout the prime science region during the first orbit of the Juno mission. The prime motivation for this work was to examine the heavy ions that are thought to be responsible for the observed polar X-rays. Jupiter Energetic particle Detector Instrument (JEDI) did observe precipitating heavy ions with energies >10 MeV, but for this perijove the intensities were far below those needed to account for previously observed polar X-ray emissions. During this survey we also found an unusual signal of ions between oxygen and sulfur. We include here a report on what appears to be a transitory observation of magnesium, or possibly sodium, at MeV energies through closest approach.

Dust formation in a galaxy with primitive abundances.

Science.gov (United States)

Sloan, G C; Matsuura, M; Zijlstra, A A; Lagadec, E; Groenewegen, M A T; Wood, P R; Szyszka, C; Bernard-Salas, J; van Loon, J Th

2009-01-16

Interstellar dust plays a crucial role in the evolution of galaxies. It governs the chemistry and physics of the interstellar medium. In the local universe, dust forms primarily in the ejecta from stars, but its composition and origin in galaxies at very early times remain controversial. We report observational evidence of dust forming around a carbon star in a nearby galaxy with a low abundance of heavy elements, 25 times lower than the solar abundance. The production of dust by a carbon star in a galaxy with such primitive abundances raises the possibility that carbon stars contributed carbonaceous dust in the early universe.

ACE/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Weberg, Micah J. [PhD Candidate in Space and Planetary Physics, 2435 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States); Zurbuchen, Thomas H. [Professor, Space Science and Aerospace Engineering, Associate Dean for Entrepreneurship, 2429 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States); Lepri, Susan T., E-mail: mjweberg@umich.edu, E-mail: thomasz@umich.edu, E-mail: slepri@umich.edu [Associate Research Scientist, 2417 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States)

2012-11-20

We present the first in situ observations of heavy ion dropouts within the slow solar wind, observed for select elements ranging from helium to iron. For iron, these dropouts manifest themselves as depletions of the Fe/H ratio by factors up to {approx}25. The events often exhibit mass-dependent fractionation and are contained in slow, unsteady wind found within a few days from known stream interfaces. We propose that such dropouts are evidence of gravitational settling within large coronal loops, which later undergo interchange reconnection and become source regions of slow, unsteady wind. Previously, spectroscopic studies by Raymond et al. in 1997 (and later Feldman et al. in 1999) have yielded strong evidence for gravitational settling within these loops. However, their expected in situ signature plasma with heavy elements fractionated by mass was not observed prior to this study. Using data from the SWICS instrument on board the Advanced Composition Explorer (ACE), we investigate the composition of the solar wind within these dropouts and explore long term trends over most of a solar cycle.

ACE/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

International Nuclear Information System (INIS)

Weberg, Micah J.; Zurbuchen, Thomas H.; Lepri, Susan T.

2012-01-01

We present the first in situ observations of heavy ion dropouts within the slow solar wind, observed for select elements ranging from helium to iron. For iron, these dropouts manifest themselves as depletions of the Fe/H ratio by factors up to ∼25. The events often exhibit mass-dependent fractionation and are contained in slow, unsteady wind found within a few days from known stream interfaces. We propose that such dropouts are evidence of gravitational settling within large coronal loops, which later undergo interchange reconnection and become source regions of slow, unsteady wind. Previously, spectroscopic studies by Raymond et al. in 1997 (and later Feldman et al. in 1999) have yielded strong evidence for gravitational settling within these loops. However, their expected in situ signature plasma with heavy elements fractionated by mass was not observed prior to this study. Using data from the SWICS instrument on board the Advanced Composition Explorer (ACE), we investigate the composition of the solar wind within these dropouts and explore long term trends over most of a solar cycle.

Heavy ion physics at CERN

International Nuclear Information System (INIS)

Vesztergombi, G.

1991-01-01

A summary of the present status and future plans for heavy ion experiments at CERN-SPS and CERN-LHC accelerators is given. The planned three phases give possibilities to study the properties of the quark-gluon-plasma (QGP). At the present stage the feasibility of high energy ion-ion experiments with their very abundant secondary hadron production, shows that there is a chance to obtain high densities, and to look for the onset of new, collective phenomena. In a second phase, there should be a chance to obtain more conclusive evidence for the onset of quark deconfinement. In the third stage, the average energy densities rise above the deconfinement threshold, so that a study of the properties of QGP should become possible. (G.P.)

Charge-sign-clustering observed in high-multiplicity, high-energy heavy-ion collisions

International Nuclear Information System (INIS)

Takahashi, Y.; Gregory, J.C.; Hayashi, T.

1989-01-01

Charge-sign distribution in 200 GeV/amu heavy-ion collisions is studied with the Magnetic-Interferometric-Emulsion-Chamber (MAGIC) for central collision events in 16 O + Pb and 32 S + Pb interactions. Charge-sign clustering is observed in most of the fully-analyzed events. A statistical 'run-test' is performed for each measured event, which shows significant deviation from a Gaussian distribution (0,1) expected for random-charge distribution. Candidates of charge clusters have 5 - 10 multiplicity of like-sign particles, and are often accompanied by opposite-sign clusters. Observed clustering of identical charges is more significant in the fragmentation region than in the central region. Two-particle Bose-Einstein interference and other effects are discussed for the run-test examination. (author)

Gas Chromatographic-Ion Trap Mass Spectrometric Analysis of Volatile Organic Compounds by Ion-Molecule Reactions Using the Electron-Deficient Reagent Ion CCl{3/+}

Science.gov (United States)

Wang, Cheng-Zhong; Su, Yue; Wang, Hao-Yang; Guo, Yin-Long

2011-10-01

When using tetrachloromethane as the reagent gas in gas chromatography-ion trap mass spectrometry equipped with hybrid ionization source, the cation CCl{3/+} was generated in high abundance and further gas-phase experiments showed that such an electron-deficient reagent ion CCl{3/+} could undergo interesting ion-molecule reactions with various volatile organic compounds, which not only present some informative gas-phase reactions, but also facilitate qualitative analysis of diverse volatile compounds by providing unique mass spectral data that are characteristic of particular chemical structures. The ion-molecule reactions of the reagent ion CCl{3/+} with different types of compounds were studied, and results showed that such reactions could give rise to structurally diagnostic ions, such as [M + CCl3 - HCl]+ for aromatic hydrocarbons, [M - OH]+ for saturated cyclic ether, ketone, and alcoholic compounds, [M - H]+ ion for monoterpenes, M·+ for sesquiterpenes, [M - CH3CO]+ for esters, as well as the further fragment ions. The mechanisms of ion-molecule reactions of aromatic hydrocarbons, aliphatic ketones and alcoholic compounds with the reagent ion CCl{3/+} were investigated and proposed according to the information provided by MS/MS experiments and theoretical calculations. Then, this method was applied to study volatile organic compounds in Dendranthema indicum var. aromaticum and 20 compounds, including monoterpenes and their oxygen-containing derivatives, aromatic hydrocarbon and sesquiterpenes were identified using such ion-molecule reactions. This study offers a perspective and an alternative tool for the analysis and identification of various volatile compounds.

THE VARIABILITY OF HCN IN TITAN’S UPPER ATMOSPHERE AS IMPLIED BY THE CASSINI ION-NEUTRAL MASS SPECTROMETER MEASUREMENTS

Energy Technology Data Exchange (ETDEWEB)

Cui, J.; Cao, Y.-T. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Lavvas, P. P. [Groupe de Spectroscopie Moleculaire et Atmospherique, Universite de Reims, Champagne-Ardenne, CNRS UMR F-7331 (France); Koskinen, T. T. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

2016-07-20

HCN is an important constituent in Titan’s upper atmosphere, serving as the main coolant in the local energy budget. In this study, we derive the HCN abundance at the altitude range of 960–1400 km, combining the Ion-Neutral Mass Spectrometer data acquired during a large number of Cassini flybys with Titan. Typically, the HCN abundance declines modestly with increasing altitude and flattens to a near constant level above 1200 km. The data reveal a tendency for dayside depletion of HCN, which is clearly visible below 1000 km but weakens with increasing altitude. Despite the absence of convincing anti-correlation between HCN volume mixing ratio and neutral temperature, we argue that the variability in HCN abundance makes an important contribution to the large temperature variability observed in Titan’s upper atmosphere.

Observation of reduction of secondary electron emission from helium ion impact due to plasma-generated nanostructured tungsten fuzz

International Nuclear Information System (INIS)

Hollmann, E M; Doerner, R P; Nishijima, D; Pigarov, A Yu

2017-01-01

Growth of nanostructured fuzz on a tungsten target in a helium plasma is found to cause a significant (∼3×) reduction in ion impact secondary electron emission in a linear plasma device. The ion impact secondary electron emission is separated from the electron impact secondary electron emission by varying the target bias voltage and fitting to expected contributions from electron impact, both thermal and non-thermal; with the non-thermal electron contribution being modeled using Monte-Carlo simulations. The observed (∼3×) reduction is similar in magnitude to the (∼2×) reduction observed in previous work for the effect of tungsten fuzz formation on secondary electron emission due to electron impact. It is hypothesized that the observed reduction results from re-absorption of secondary electrons in the tungsten fuzz. (paper)

Matrix effects in ion-induced emission as observed in Ne collisions with Cu-Mg and Cu-Al alloys

Science.gov (United States)

Ferrante, J.; Pepper, S. V.

1983-01-01

Ion induced Auger electron emission is used to study the surfaces of Al, Mg, Cu - 10 at. % Al, Cu - 19.6 at. % Al, and Cu - 7.4 at. % Mg. A neon (Ne) ion beam whose energy is varied from 0.5 to 3 keV is directed at the surface. Excitation of the lighter Ne occurs by the promotion mechanism of Barat and Lichten in asymmetric collisions with Al or Mg atoms. Two principal Auger peaks are observed in the Ne spectrum: one at 22 eV and one at 25 eV. Strong matrix effects are observed in the alloys as a function of energy in which the population of the second peak is greatly enhanced relative to the first over the pure materials. For the pure material over this energy range this ratio is 1.0. For the alloys it can rise to the electronic structure of alloys and to other surface tools such as secondary ion mass spectroscopy.

Study of ion exchange equilibrium and determination of heat of ion exchange by ion chromatography

International Nuclear Information System (INIS)

Liu Kailu; Yang Wenying

1996-01-01

Ion chromatography using pellicularia ion exchange resins and dilute solution can be devoted to the study of ion exchange thermodynamics and kinetics. Ion exchange equilibrium equation was obtained, and examined by the experiments. Based on ion exchange equilibrium, the influence of eluent concentration and resin capacity on adjusted retention volumes was examined. The effect of temperature on adjusted retention volumes was investigated and heats of ion exchange of seven anions were determined by ion chromatography. The interaction between anions and skeleton structure of resins were observed

Spectroscopic observations of ion line-emission from a magnetically insulated ion diode

International Nuclear Information System (INIS)

Maron, Y.; Peng, H.S.; Rondeau, G.D.; Hammer, D.A.

1984-01-01

Excited ions, produced in the surface-flashover plasma in a magnetically insulated diode, spontaneously emit light from the anode plasma region as well as (if the life time of the excited level is at least a few ns) from the diode acceleration gap. The emission lines of the ions traversing the gap are shifted from their natural wavelength because of the Stark effect due to the diode electric field. If the light is viewed transverse to the acceleration direction, the line width will be mostly determined by Doppler broadening due to ion transverse velocities. The authors use the OMNI II diode (up to 500 kV, 25 kA, 80 ns) with an insulating B field of ≅12 kG and an A-K gap of ≅7mm. The light emission from the entire 6.5 x 12 cm area in front of the anode is viewed parallel to the applied B field. A spectral resolution of 0.5 A is obtained by dispersing the light using a spectrometer followed by 6 optical fibers attached to PM-tubes. Each channel output is calibrated in situ. The spatial resolution across the gap could be made as small as 0.3 mm and the temporal resolution was varied between a few to a few tens of ns. The line spectral profile is obtained at a single discharge for a given distance from the anode surface

Preliminary observation on coordination of pellet injection and ion Bernstein wave on a HT-7 tokamak

International Nuclear Information System (INIS)

Yang Yu; Zhao Yanping; Li Jiangang; Wan Baonian; Luo Jiarong; Gu Xuemao

2002-01-01

A pellet injection (PI) experiment was performed during the application of the ion Bernstein wave on a HT-7 tokamak. A preliminary coordination effect was observed. With a lower wave power, shortly after PI, the coupling of the wave was enhanced, and the particle confinement was improved. With higher power, off-axis heating for 15% at about α/3 in the low field side was observed

Hydrogen and oxygen behaviors on Porous-Si surfaces observed using a scanning ESD ion microscope

International Nuclear Information System (INIS)

Itoh, Yuki; Ueda, Kazuyuki

2004-01-01

A scanning electron-stimulated desorption (ESD) ion microscope (SESDIM) measured the 2-D images of hydrogen and oxygen distribution on solid surfaces. A primary electron beam at 600 eV, with a pulse width of 220 ns, resulted in ion yields of H + and O + . This SESDIM is applied to the surface analysis of Porous-Si (Po-Si) partially covered with SiN films. During the heating of a specimen of the Po-Si at 800 deg. C under ultra-high-vacuum (UHV) conditions, the components of the surface materials were moved or diffused by thermal decomposition accompanied by a redistribution of hydrogen and oxygen. After cyclic heating of above 800 deg. C, the dynamic behaviors of H + and O + accompanied by the movements of the SiN layers were observed as images of H + and O + . This was because the H + and O + ions have been identified as composite materials by their kinetic energies

Decay properties of exotic N ≅ 28 S and Cl nuclei and the 48Ca/46Ca abundance ratio

International Nuclear Information System (INIS)

Sorlin, O.; Guillemaud-Mueller, D.; Mueller, A.C.; Borrel, V.; Dogny, S.; Pougheon, F.; Anne, R.; Lewitowicz, M.; Saint-Laurent, M.G.; Borcea, C.; Fifield, L.K.; Bazin, D.; Thielemann, F.K.; Hillebrandt, W.

1992-01-01

Beta-decay half-lives and β-delayed neutron-emission probabilities of the very neutron-rich nuclei 44 S and 45-47 Cl have been measured. These isotopes, which lie at or close to the N=28 magic shell were produced in interactions of a 60 MeV/u 48 Ca beam from GANIL (Grand Accelerateur National d'Ions Lourds) with a 64 Ni target and were separated by the doubly achromatic spectrometer LISE (Ligne d'Ions Super Epluches). Their decay was studied by a β-n time correlation measurement. The results are compared to recent model predictions and indicate a rapid weakening of the N=28 shell effect below 48 20 Ca 28 . The nuclear structure effects reflected in the decay properties of the exotic S and Cl isotopes may be the clue for the astrophysical understanding of the unusual 48 Ca/ 46 Ca abundance ratio measured in the solar system as well as the Ca-Ti-Cr anomalies observed in EK-inclusions of the Allende meteorite

Martian Ionospheric Observation and Modeling

Science.gov (United States)

González-Galindo, Francisco

2018-02-01

The Martian ionosphere is a plasma embedded within the neutral upper atmosphere of the planet. Its main source is the ionization of the CO2-dominated Martian mesosphere and thermosphere by the energetic EUV solar radiation. The ionosphere of Mars is subject to an important variability induced by changes in its forcing mechanisms (e.g., the UV solar flux) and by variations in the neutral atmosphere (e.g., the presence of global dust storms, atmospheric waves and tides, changes in atmospheric composition, etc.). Its vertical structure is dominated by a maximum in the electron concentration placed at about 120–140 km of altitude, coincident with the peak of the ionization rate. Below, a secondary peak produced by solar X-rays and photoelectron-impact ionization is observed. A sporadic third layer, possibly of meteoric origin, has been also detected below. The most abundant ion in the Martian ionosphere is O2+, although O+ can become more abundant in the upper ionospheric layers. While below about 180–200 km the Martian ionosphere is dominated by photochemical processes, above those altitudes the dynamics of the plasma become more important. The ionosphere is also an important source of escaping particles via processes such as dissociative recombination of ions or ion pickup. So, characterization of the ionosphere provides or can provide information about such disparate systems and processes as the solar radiation getting to the planet, the neutral atmosphere, the meteoric influx, the atmospheric escape to space, or the interaction of the planet with the solar wind. It is thus not surprising that the interest about this region dates from the beginning of the space era. From the first measurements provided by the Mariner 4 mission in the 1960s to the contemporaneous observations, still ongoing, by the Mars Express and MAVEN orbiters, our current knowledge of this atmospheric region is the consequence of the accumulation of more than 50 years of discontinuous

Study of heliumlike neon using an electron beam ion trap

International Nuclear Information System (INIS)

Wargelin, B.J.; Kahn, S.M.; Beiersdorfer, P.

1992-01-01

The 2-to-1 spectra of several astrophysically abundant He-like ions are being studied using the Electron Beam Ion Trap (EBIT) at Lawrence Livermore National Laboratory. Spectra are recorded for a broad range of plasma parameters, including electron density, energy, and ionization balance. We describe the experimental equipment and procedure and present some typical data

Ion source operating at the Unilac injector

International Nuclear Information System (INIS)

Mueller, M.; Jacoby, W.

1977-01-01

The Unilac injection velocity (v = 0.005 X c) and the maximum potential difference between ion source and ground (320 kV) limit positive ion acceleration to a specific charge of not less than 0.0336 (corresponding to 238 U 8+ ). Ion sources qualified for the Unilac must be able to produce a charge spectrum with high intensities in the required charge states (1 - 10 particle μA). This requirement is satisfied for all elements by the Dubna type heated cathode penning ion source. Obviously, for isotopes of low natural abundance high beam currents can only be produced by employing enriched isotopes as feeding materials. Presently the injector is equipped with one penning ion source and one duoplasmatron ion source. 90% of the noble gas ions are provided by the duoplasmatron ion source, whereas ion beams of solids are exclusively furnished by the penning source. In particular, this latter source is well suited and highly developped for producing ion beams from solids by means of the sputtering process. In the future, however, we intend to produce metal ions up to a mass of 100 by a sputter version of the duoplasmatron. (orig.) [de

Observation of water separated ion-pairs between cations and phospholipid headgroups.

Science.gov (United States)

van der Post, Sietse T; Hunger, Johannes; Bonn, Mischa; Bakker, Huib J

2014-04-24

In this work, we present evidence for ion pair formation of cations with a high surface charge density (Na(+) and Ca(2+)) and phosphate groups of phospholipids. We used femto-second infrared pump-probe and dielectric spectroscopy to probe the dynamics of water molecules in solutions of phosphorylethanolamine and different types of cations. We find that sodium and calcium cooperatively retard the dynamics of water in solutions of phosphorylethanolamine, implying the formation of solvent separated ion pairs. This ion-specific interaction is absent for potassium, cesium and ammonium. We compare our results to dielectric spectroscopy experiments, which probes the rotation of all dipolar molecules and ions in solution. The rotation of the dipolar phosphorylethanolamine ion shows that long-lived ion-pairs are only formed with calcium and not with ammonium, cesium, potassium, and sodium. This finding implies that the association between calcium and the phosphate is strong with lifetimes exceeding 200 ps, while the interaction with sodium is relatively short-lived (∼20-100 ps).

Dynamical explanation for the high water abundance detected in Orion

International Nuclear Information System (INIS)

Elitzur, M.

1979-01-01

Shock wave chemistry is suggested as the likely explanation for the high water abundance which has been recently detected in Orion by Phyllips et al. The existence of such a shock and its inferred properties are in agreement with other observations of Orion such as the broad velocity feature and H 2 vibration emission. Shock waves are proposed as the likely explanation for high water abundances observed in other sources such as the strong H 2 O masers

Abundance of introduced species at home predicts abundance away in herbaceous communities

Science.gov (United States)

Firn, Jennifer; Moore, Joslin L.; MacDougall, Andrew S.; Borer, Elizabeth T.; Seabloom, Eric W.; HilleRisLambers, Janneke; Harpole, W. Stanley; Cleland, Elsa E.; Brown, Cynthia S.; Knops, Johannes M.H.; Prober, Suzanne M.; Pyke, David A.; Farrell, Kelly A.; Bakker, John D.; O'Halloran, Lydia R.; Adler, Peter B.; Collins, Scott L.; D'Antonio, Carla M.; Crawley, Michael J.; Wolkovich, Elizabeth M.; La Pierre, Kimberly J.; Melbourne, Brett A.; Hautier, Yann; Morgan, John W.; Leakey, Andrew D.B.; Kay, Adam; McCulley, Rebecca; Davies, Kendi F.; Stevens, Carly J.; Chu, Cheng-Jin; Holl, Karen D.; Klein, Julia A.; Fay, Phillip A.; Hagenah, Nicole; Kirkman, Kevin P.; Buckley, Yvonne M.

2011-01-01

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.

Ulysses observations of magnetic waves due to newborn interstellar pickup ions. I. New observations and linear analysis

Energy Technology Data Exchange (ETDEWEB)

Cannon, Bradford E. [Physics Department, Florida State University, Tallahassee, FL (United States); Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Murphy, Neil [Jet Propulsion Laboratory, Mail Stop 180-600, 4800 Oak Grove Drive, Pasadena, CA (United States); Nuno, Raquel G., E-mail: bc13h@my.fsu.edu, E-mail: Charles.Smith@unh.edu, E-mail: Phil.Isenberg@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Neil.Murphy@jpl.nasa.gov, E-mail: raquel.nuno@asu.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States)

2014-04-01

We have examined Ulysses magnetic field data using dynamic spectrogram techniques that compute wave amplitude, polarization, and direction of propagation over a broad range of frequencies and time. Events were identified that showed a strong polarization signature and an enhancement of power above the local proton gyrofrequency. We perform a statistical study of 502 wave events in an effort to determine when, where, and why they are observed. Most notably, we find that waves arising from newborn interstellar pickup ions are relatively rare and difficult to find. The quantities normally employed in theories of wave growth are neutral atom density and quantities related to their ionization and the subsequent dynamics such as wind speed, solar wind flux, and magnetic field orientation. We find the observations of waves to be largely uncorrelated to these quantities except for mean field direction where quasi-radial magnetic fields are favored and solar wind proton flux where wave observations appear to be favored by low flux conditions which runs contrary to theoretical expectations of wave generation. It would appear that an explanation based on source physics and instability growth rates alone is not adequate to account for the times when these waves are seen.

Discussing the possibility of observation of parity violation in heavy ion collisions

International Nuclear Information System (INIS)

Voloshin, Sergei A.

2000-01-01

It was recently argued that in heavy ion collisions the parity could be broken. This paper addresses the question of the possibility of the experimental detection of the effect. We discuss how parity violating effects would modify the final particle distributions and how one could construct variables sensitive to the effect, and which measurement would be the (most) conclusive. Discussing different observables we also discuss the question of whether the ''signals'' can be faked by ''conventional'' effects (such as anisotropic flow, etc.) and make estimates of the signals

Electromagnetic ion cyclotron waves observed near the oxygen cyclotron frequency by ISEE 1 and 2

International Nuclear Information System (INIS)

Fraser, B.J.; Samson, J.C.; Hu, Y.D.; McPherron, R.L.; Russell, C.T.

1992-01-01

Pc 2 electromagnetic ion cyclotron waves at 0.1 waves at 0.1 Hz, near the oxygen cyclotron frequency, have been observed by ISEE 1 and 2 between L = 7.6 and 5.8 on an inbound near-equatorial pass in the dusk sector. The waves occurred in a thick plasmapause of width ∼ 1.5 R E and penetrated ∼1 R E into the plasmasphere. Wave onset was accompanied by significant increases in the thermal (0-100 eV) He + and the warm (0.1-16 keV/e) O + and He + heavy ion populations. The most intense waves (8 nT) were observed in the outer plasmasphere where convection drift velocities (E x B)/B 2 were largest and the Alfven velocity was a minimum. Wave polarization is predominantly left-handed with propagation almost parallel to the ambient magnetic field, and the spectral slot and polarization reversal predicted by cold plasma propagation theory are identified in the wave data. Poynting fluxes calculated during the first 15 min of the event show wave energy propagation directions both parallel and antiparallel to the field. Computations of the experimental wave spectra during the passage through the plasmapause show that the spectral slots relate to local plasma parameters, possibly suggesting an ion cyclotron wave growth source near the spacecraft. A regular wave packet structure seen over the first 30 min of the event may be attributed to the modulation of this energy source by the Pc 5 waves seen at the same time. Overall, the results are considered an example of an electromagnetic ion cyclotron wave-particle interaction occurring during the outer plasmasphere refilling process at the time of the substorm recovery phase

Diffuse ions produced by electromagnetic ion beam instabilities

International Nuclear Information System (INIS)

Winske, D.; Leroy, M.M.

1984-01-01

The evolution of the electromagnetic ions beam instability driven by the reflected ion component backstreaming away from the earth's how shock into the foreshock region is studied by means computer simulation. The linear the quasi-linear states of the instability are found to be in good agreement with known results for the resonant model propagating parallel to the beam along the magnetic field and with theory developed in this paper for the nonresonant mode, which propagates antiparallel to the beam direction. The quasi-linear stage, which produces large amplitude 8Bapprox.B, sinusoidal transverse waves and ''intermediate'' ion distribution, is terminated by a nonlinear phase in which strongly nonlinear, compressive waves and ''diffuse'' ion distributions are produced. Additional processes by which the diffuse ions are accelerated to observed high energies are not addressed. The results are discussed in terms of the ion distributions and hydromagnetic waves observed in the foreshock of the earth's bow shock and of interplanetary shocks

Elemental abundances in nature - fortuity or conformity to natural laws?

International Nuclear Information System (INIS)

Kist, A.A.

1995-01-01

Nuclear analytical methods during the last decades have given a lot of new data on elemental composition of various natural materials. These data allow a return to the question of the regularities of element abundance. This question seems to be important from the point view of basic science as well as analytical chemistry (analytical procedure planning, expected element concentrations, choice of sufficient sensitivity and reproducibility, etc.). The most fruitful approach in this connection is the comparison of the elemental composition of some generalized systems with an element's fundamental characteristics and/or its position in the Periodical System. Stronger correlations can be found when the elemental characteristic (its position in the Periodic Table) versus abundance is considered within separate groups of elements. This idea is illustrated by considering elements' abundance in the Universe, Solar Systems, Earth crust, sea water, soils, plants, etc. Simple equations describe these function with acceptable agreement of tabular and calculated data. The coefficients of these equations in many cases were also connected with some fundamental characteristics such as ionization potential, ion potential, melting and boiling point, etc. (author) 9 refs.; 7 figs

Auroral ion acoustic wave enhancement observed with a radar interferometer system

Directory of Open Access Journals (Sweden)

N. M. Schlatter

2015-07-01

Full Text Available Measurements of naturally enhanced ion acoustic line (NEIAL echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EISCAT radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI installed at the radar site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements, we show that the enhanced backscattering region is of limited extent in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size; however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900 × 500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar look direction, our observations are consistent with the NEIAL echo occurring on field lines with particle precipitation.

Abundance of carbon and magnesium in the Orion nebula

International Nuclear Information System (INIS)

Perinotto, M.; Patriarchi, P.

1980-01-01

The Orion nebula has been observed in two positions with IUE (International Ultraviolet Explorer) in the low-resolution mode (approx.7 A) and in the spectral range 1150--3200 A. Emission lines of C II], C III], [O II], and He I have been measured and used to determine what is probably the first reliable abundance of carbon in H II regions. The logarithmic total abundance of carbon is found to be 8.4 close to the solar value. In contrast with the situation in the planetary nebula of similar excitation, IC 418, where the resonance Mg II lambda2800 line is observed to be relatively strong, in the Orion nebula the lambda2800 line is not detectable. an upper limit for the magnesium abundance of the order of 10 times smaller than in the Sun is suggested

Lower Hybrid Frequency Range Waves Generated by Ion Polarization Drift Due to Electromagnetic Ion Cyclotron Waves: Analysis of an Event Observed by the Van Allen Probe B

Science.gov (United States)

Khazanov, G. V.; Boardsen, S.; Krivorutsky, E. N.; Engebretson, M. J.; Sibeck, D.; Chen, S.; Breneman, A.

2017-01-01

We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of approximately 0.86. We assume that the correlation is the result of LHFR wave generation by the ions polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD)parallel and perpendicular to the ambient magnetic eld to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions polarization drift in the electric field of an EMIC wave.

Determination of the Deuterium Abundances in Water from 156 to 10,000 ppm by SIFT-MS

Czech Academy of Sciences Publication Activity Database

Španěl, Patrik; Shestivska, Violetta; Chippendale, T. W. E.; Smith, D.

2011-01-01

Roč. 22, č. 1 (2011), s. 179-186 ISSN 1044-0305 Institutional research plan: CEZ:AV0Z40400503 Keywords : deuterium abundance * total body water * selected ion flow tube mass spectrometry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.002, year: 2011

Chemical composition of waterfall-induced air ions: Spectrometry vs. simulations

Energy Technology Data Exchange (ETDEWEB)

Parts, T.-E.; Luts, A. [Tartu Univ. (Estonia). Dept. of Environmental Physics; Laakso, L.; Hirsikko, A.; Groenholm, T.; Kulmala, M. [Helsinki Univ. (Finland). Dept. of Physical Sciences

2007-07-01

Our measurements of ion size distributions near a waterfall provided new evidence for a waterfall-induced modification of air ion sizes. The ion size spectrum near a waterfall permanently differs from that in ordinary tropospheric air. In this paper we investigated the near-waterfall air ions chemical nature in detail. We carried out a simulation series of air small negative ion evolution, proposing that falling water, as a new environmental component, increases the concentration of OH{sup -} cluster ions. The produced OH{sup -} ions were employed as an extra input for our ion evolution model. The presence of additional OH{sup -} ions resulted in a decrease of typically model-provided NO{sub 3}{sup -} and/or HSO{sub 4}{sup -} cluster ion concentrations and an increase of the abundance of HCO{sub 3}{sup -} cluster ions. Near the waterfall the latter ions became dominant in our simulations. (orig.)

MMS observations of magnetic reconnection signatures of dissipating ion inertial-scale flux ropes associated with dipolarization events

Science.gov (United States)

Poh, G.; Slavin, J. A.; Lu, S.; Le, G.; Cassak, P.; Eastwood, J. P.; Ozturk, D. S.; Zou, S.; Nakamura, R.; Baumjohann, W.; Russell, C. T.; Gershman, D. J.; Giles, B. L.; Pollock, C.; Moore, T. E.; Torbert, R. B.; Burch, J. L.

2017-12-01

The formation of flux ropes is thought to be an integral part of the process that may have important consequences for the onset and subsequent rate of reconnection in the tail. Earthward flows, i.e. bursty bulk flows (BBFs), generate dipolarization fronts (DFs) as they interact with the closed magnetic flux in their path. Global hybrid simulations and THEMIS observations have shown that earthward-moving flux ropes can undergo magnetic reconnection with the near-Earth dipole field in the downtail region between the Near Earth Neutral Line and the near-Earth dipole field to create DFs-like signatures. In this study, we analyzed sequential "chains" of earthward-moving, ion-scale flux ropes embedded within DFs observed during MMS first tail season. MMS high-resolution plasma measurements indicate that these earthward flux ropes embedded in DFs have a mean bulk flow velocity and diameter of 250 km/s and 1000 km ( 2‒3 ion inertial length λi), respectively. Magnetic reconnection signatures preceding the flux rope/DF encounter were also observed. As the southward-pointing magnetic field in the leading edge of the flux rope reconnects with the northward-pointing geomagnetic field, the characteristic quadrupolar Hall magnetic field in the ion diffusion region and electron outflow jets in the north-south direction are observed. Our results strongly suggest that the earthward moving flux ropes brake and gradually dissipate due to magnetic reconnection with the near Earth magnetic field. We have also examined the occurrence rate of these dissipating flux ropes/DF events as a function of downtail distances.

X-Ray Photoabsorption in Magnesium Ions

Science.gov (United States)

Abdel-Naby, Sh. A.; Hasoglu, M. F.; Nicolić, D.; Gorczyca, T. W.

2009-05-01

K-shell photoabsorption cross sections are necessary for determining elemental abundances of the interstellar medium (ISM) from observed X-ray spectra. Over the past few years, our group has computed reliable K-shell photoabsorption calculations for oxygen [1-3], neon [4,5], and carbon [6] ions. We extend our calculations to magnesium ions using a state-of-the-art R-matrix method that incorporates the important Auger broadening and pseudoresonanace-elimination effects. Comparisons with available independent-particle (IP) results and other available data will also be presented. This work was supported in part by NASA's Astronomy Physics Research and Analysis (APRA) and Solar and Heliospheric Physics (SHP) Supporting Research and Technology (SR&T) programs. [1] T. W. Gorczyca and B. M. McLaughlin. J Phys. B. 33, L859 (2000). [2] A. M. Juett, et al., Astrophys. J. 612, 308 (2004). [3] J. Garcia et al, Astrophys. J. Supp. S. 158, 68 (2005). [4] T. W. Gorczyca., Phys. Rev. A. 61, 024702 (2000). [5] A. M. Juett, et al, Astrophys. J. 648, 1066 (2006). [6] M. F. Hasoglu, et al, Astrophys. J., (in preparation)

Origin of the solar system s-process abundances

International Nuclear Information System (INIS)

Malaney, R.A.; Boothroyd, A.I.

1987-01-01

In the search for the origin of the solar system s-process abundances much attention has been focused on the intershell zones of thermally pulsing asymptotic giant branch (AGB) stars. It has recently been suggested that, relative to the poor fits obtained from intermediate-mass AGB models, low-mass AGB models may result in much better fits to the observed solar system abundances. This suggestion was motivated by the high intershell base temperatures indicated by recent low-mass AGB calculations. Using new data, presented for the peak intershell base temperature in such stars, the s-process enhancements occurring in the intershell zones of low-mass AGB stars are calculated. A nonsolar distribution of s-process abundances is reported for all realistic AGB models studied. Other possible astrophysical sites for the origin of the solar system s-process abundances are discussed. 35 references

Why abundant tropical tree species are phylogenetically old.

Science.gov (United States)

Wang, Shaopeng; Chen, Anping; Fang, Jingyun; Pacala, Stephen W

2013-10-01

Neutral models of species diversity predict patterns of abundance for communities in which all individuals are ecologically equivalent. These models were originally developed for Panamanian trees and successfully reproduce observed distributions of abundance. Neutral models also make macroevolutionary predictions that have rarely been evaluated or tested. Here we show that neutral models predict a humped or flat relationship between species age and population size. In contrast, ages and abundances of tree species in the Panamanian Canal watershed are found to be positively correlated, which falsifies the models. Speciation rates vary among phylogenetic lineages and are partially heritable from mother to daughter species. Variable speciation rates in an otherwise neutral model lead to a demographic advantage for species with low speciation rate. This demographic advantage results in a positive correlation between species age and abundance, as found in the Panamanian tropical forest community.

Fluoride ions vs removal technologies: A study

OpenAIRE

Singh, Jagvir; Singh, Prashant; Singh, Anuradha

2016-01-01

Literature reported that drinking water is a precious and scarce resource and it has to be protected and kept free from any kind of contamination. Further, it has to be used carefully without wasting. Literature also reported that fluoride bearing rocks are abundant in India, as a result, fluoride leaches out and contaminates the adjacent water and soil resources. A high concentration of fluoride ions in ground water increases up to more than 30 mg/L. This high concentration of fluoride ions ...

Structures of butyl ions formed by electron impact ionization of isomeric butyl halides and alkanes

International Nuclear Information System (INIS)

Shold, D.M.; Ausloos, P.

1978-01-01

Using a pulsed ion cyclotron resonance (ICR) spectrometer, it is demonstrated that at pressures of about 10 -6 Torr and at observation times ranging from 10 -3 to 0.5 s, isobutane, neopentane, 2,2-dimethylbutane, isobutyl halides, and tert-butyl halides form C 4 H 9 + ions having the tertiary structure. In n-alkanes, 2-methylbutane, 3-methylpentane, n-butyl halides, and sec-butyl halides, both sec-C 4 H 9 + and t-C 4 H 9 + ions are observed, the sec-C 4 H 9 + ions surviving without rearrangement for at least 0.1 s. However, in the case of the halides, a collision-induced isomerization of the sec-C 4 H 9 + to the t-C 4 H 9 + ions occurs. The efficiency of this process increases with the basicity of the alkyl halide. Radiolysis experiments carried out at atmospheric pressures indicate, in agreement with ICR and solution experiments, that at times as short as 10 -10 s the majority of the i-C 4 H 9 + ions from isobutyl bromide rearrange to the t-C 4 H 9 + structure. On the other hand, in the radiolysis of both n-hexane and 3-methylpentane, the abundance of t-C 4 H 9 + relative to sec-C 4 H 9 + is substantially smaller than that observed in the ICR experiments, and decreases with decreasing collision interval. It is suggested that about 90% of the i-C 4 H 9 + can rearrange to t-C 4 H 9 + by simple 1,2-hydride shift without involving secondary or protonated methylcyclopropane structures as intermediates. 4 figures, 2 tables

STEREO/SEPT observations of upstream particle events: almost monoenergetic ion beams

Directory of Open Access Journals (Sweden)

A. Klassen

2009-05-01

Full Text Available We present observations of Almost Monoenergetic Ion (AMI events in the energy range of 100–1200 keV detected with the Solar Electron and Proton Telescope (SEPT onboard both STEREO spacecraft. The energy spectrum of AMI events contain 1, 2, or 3 narrow peaks with the relative width at half maximum of 0.1–0.7 and their energy maxima varies for different events from 120 to 1200 keV. These events were detected close to the bow-shock (STEREO-A&B and to the magnetopause at STEREO-B as well as unexpectedly far upstream of the bow-shock and far away from the magnetotail at distances up to 1100 R_E (STEREO-B and 1900 R_E (STEREO-A. We discuss the origin of AMI events, the connection to the Earth's bow-shock and to the magnetosphere, and the conditions of the interplanetary medium and magnetosphere under which these AMI bursts occur. Evidence that the detected spectral peaks were caused by quasi-monoenergetic beams of protons, helium, and heavier ions are given. Furthermore, we present the spatial distribution of all AMI events from December 2006 until August 2007.

Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates

KAUST Repository

Naganuma, Tamaki

2014-01-01

Abundant oxygen vacancies coexisting with Ce3+ ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce3+ ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce3+ ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce3+ and Ce4+ ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce3+ ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce 3+ ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce3+ ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce 3+ to Ce4+ occurred at 350 °C in air. Highly concentrated Ce3+ ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce 3+ stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce3+ sites. This study also illuminates the potential interaction mechanisms of stable Ce3+ ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments. © The Royal Society of Chemistry 2014.

Calcium isotope effects in ion exchange electromigration and calcium isotope analysis by thermo-ionization mass spectrometry

International Nuclear Information System (INIS)

Fujii, Y.; Hoshi, J.; Iwamoto, H.; Okamoto, M.; Kakihana, H.

1985-01-01

Calcium ions were made to electromigrate along a cation exchange membrane. The abundance ratios of the calcium isotopes (Ca-40, 42, 43, 44, 48) in the migrated bands were measured by thermo-ionization mass spectrometry. The lighter isotopes were enriched in the front part of the migrated band. The increments in the isotope abundance ratios were found to be proportional to the mass difference of the isotopes. The observed epsilon-values per unit mass difference (epsilon/ΔM) were 1.26 x 10 -4 (at 20 0 C), 1.85 x 10 -4 (at 25 0 C) and 2.4 x 10 -4 (at 40 0 C). The mass spectrometry was improved by using a low temperature for the evaporation of CaI 2 . (orig.)

Observation of Global Hyperon Polarization in Ultrarelativistic Heavy-Ion Collisions

Science.gov (United States)

Upsal, Isaac; STAR Collaboration

2017-11-01

Collisions between heavy nuclei at ultra-relativistic energies form a color-deconfined state of matter known as the quark-gluon plasma. This state is well described by hydrodynamics, and non-central collisions are expected to produce a fluid characterized by strong vorticity in the presence of strong external magnetic fields. The STAR Collaboration at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) has measured collisions between gold nuclei at center of mass energies √{sNN} = 7.7- 200 GeV. We report the first observation of globally polarized Λ and Λ bar hyperons, aligned with the angular momentum of the colliding system. These measurements provide important information on partonic spin-orbit coupling, the vorticity of the quark-gluon plasma, and the magnetic field generated in the collision.

Ecological interactions and the distribution, abundance, and diversity of sponges.

Science.gov (United States)

Wulff, Janie

2012-01-01

Although abiotic factors may be important first-order filters dictating which sponge species can thrive at a particular site, ecological interactions can play substantial roles influencing distribution and abundance, and thus diversity. Ecological interactions can modify the influences of abiotic factors both by further constraining distribution and abundance due to competitive or predatory interactions and by expanding habitat distribution or abundance due to beneficial interactions that ameliorate otherwise limiting circumstances. It is likely that the importance of ecological interactions has been greatly underestimated because they tend to only be revealed by experiments and time-series observations in the field. Experiments have revealed opportunistic predation to be a primary enforcer of sponge distribution boundaries that coincide with habitat boundaries in several systems. Within habitats, by contrast, dramatic effects of predators on sponge populations seem to occur primarily in cases of unusually high recruitment rates or unusually low mortality rates for the predators, which are often specialists on the sponge species affected. Competitive interactions have been demonstrated to diminish populations or exclude sponge species from a habitat in only a few cases. Cases in which competitive interactions have appeared obvious have often turned out to be neutral or even beneficial interactions when observed over time. Especially striking in this regard are sponge-sponge interactions in dense sponge-dominated communities, which may promote the continued coexistence of all participating species. Mutualistic symbioses of sponges with other animals, plants, or macroalgae have been demonstrated to increase abundance, habitat distribution, and diversity of all participants. Symbiotic microbes can enhance sponge distribution and abundance but also render their hosts more vulnerable to environmental changes. And while photosynthetic symbionts can boost growth and

Abundances and Excitation of H2, H3+ & CO in Star-Forming Regions

Science.gov (United States)

Kulesa, Craig A.

Although most of the 123 reported interstellar molecules to date have been detected through millimeter-wave emission-line spectroscopy, this technique is inapplicable to non-polar molecules like H2 and H3+, which are central to our understanding of interstellar chemistry. Thus high resolution infrared absorption-line spectroscopy bears an important role in interstellar studies: chemically important non-polar molecules can be observed, and their abundances and excitation conditions can be referred to the same ``pencil beam'' absorbing column. In particular, through a weak quadrupole absorption line spectrum at near-infrared wavelengths, the abundance of cold H2 in dark molecular clouds and star forming regions can now be accurately measured and compared along the same ``pencil beam'' line of sight with the abundance of its most commonly cited surrogate, CO, and its rare isotopomers. Also detected via infrared line absorption is the pivotal molecular ion H3+, whose abundance provides the most direct measurement of the cosmic ray ionization rate in dark molecular clouds, a process that initiates the formation of many other observed molecules there. Our growing sample of H2 and CO detections now includes detailed multi-beam studies of the ρ Ophiuchi molecular cloud and NGC 2024 in Orion. We explore the excitation and degree of ortho- and para-H2 thermalization in dark clouds, variation of the CO abundance over a cloud, and the relation of H2 column density to infrared extinction mapping, far-infrared/submillimeter dust continuum emission, and large scale submillimeter CO, [C I] and HCO+ line emission -- all commonly invoked to indirectly trace H2 during the past 30+ years. For each of the distinct velocity components seen toward some embedded young stellar objects, we are also able to determine the temperature, density, and a CO/H2 abundance ratio, thus unraveling some of the internal structure of a star-forming cloud. H2 and H3+ continue to surprise and delight us

reSpect: Software for Identification of High and Low Abundance Ion Species in Chimeric Tandem Mass Spectra

Science.gov (United States)

Shteynberg, David; Mendoza, Luis; Hoopmann, Michael R.; Sun, Zhi; Schmidt, Frank; Deutsch, Eric W.; Moritz, Robert L.

2015-11-01

Most shotgun proteomics data analysis workflows are based on the assumption that each fragment ion spectrum is explained by a single species of peptide ion isolated by the mass spectrometer; however, in reality mass spectrometers often isolate more than one peptide ion within the window of isolation that contribute to additional peptide fragment peaks in many spectra. We present a new tool called reSpect, implemented in the Trans-Proteomic Pipeline (TPP), which enables an iterative workflow whereby fragment ion peaks explained by a peptide ion identified in one round of sequence searching or spectral library search are attenuated based on the confidence of the identification, and then the altered spectrum is subjected to further rounds of searching. The reSpect tool is not implemented as a search engine, but rather as a post-search engine processing step where only fragment ion intensities are altered. This enables the application of any search engine combination in the iterations that follow. Thus, reSpect is compatible with all other protein sequence database search engines as well as peptide spectral library search engines that are supported by the TPP. We show that while some datasets are highly amenable to chimeric spectrum identification and lead to additional peptide identification boosts of over 30% with as many as four different peptide ions identified per spectrum, datasets with narrow precursor ion selection only benefit from such processing at the level of a few percent. We demonstrate a technique that facilitates the determination of the degree to which a dataset would benefit from chimeric spectrum analysis. The reSpect tool is free and open source, provided within the TPP and available at the TPP website.

Modelling tick abundance using machine learning techniques and satellite imagery

DEFF Research Database (Denmark)

Kjær, Lene Jung; Korslund, L.; Kjelland, V.

satellite images to run Boosted Regression Tree machine learning algorithms to predict overall distribution (presence/absence of ticks) and relative tick abundance of nymphs and larvae in southern Scandinavia. For nymphs, the predicted abundance had a positive correlation with observed abundance...... the predicted distribution of larvae was mostly even throughout Denmark, it was primarily around the coastlines in Norway and Sweden. Abundance was fairly low overall except in some fragmented patches corresponding to forested habitats in the region. Machine learning techniques allow us to predict for larger...... the collected ticks for pathogens and using the same machine learning techniques to develop prevalence maps of the ScandTick region....

Observation of energy-time dispersed ion structures in the magnetosheath by CLUSTER: possible signatures of transient acceleration processes at shock

Directory of Open Access Journals (Sweden)

P. Louarn

Full Text Available We analyse energy-time dispersed ion signatures that have been observed by CLUSTER in the dayside magnetosheath. These events are characterized by sudden increases in the ion flux at energies larger than 10 keV. The high energy ions (30 keV are first detected, with the transition to the low energy ions (5 keV lasting about 100 s. These injections are often associated with transient plasma structures of a few minutes in duration, characterized by a hotter, less dense plasma and a diverted flow velocity, thus presenting similarities with "hot flow anomalies". They also involve modifications of the magnetic field direction, suggesting that the shock interacts with a solar wind discontinuity at the time of the event. The injections can originate from the magnetosphere or the shock region. Studying in detail a particular event, we discuss this last hypothesis. We show that the observed energy/time dispersion can be explained by combining a time-of-flight effect with a drift of the source of energetic particles along the shock. We propose that the acceleration results from a Fermi process linked to the interaction of the discontinuity with a quasi-perpendicular shock. This model explains the observed pitch-angle selection of the accelerated particles. The Fermi process acting on the beam of ions reflected from the shock appears to be sufficiently efficient to accelerate over short time scales (less than 30 s particles at energies above 30 keV.

Key words. Magnetospheric physics (solar-wind-magnetosphere interaction; magnetosheath – Space plasma physics (shock waves

Characterization of a Distributed Plasma Ionization Source (DPIS) for Ion Mobility Spectrometry and Mass Spectrometry

International Nuclear Information System (INIS)

Waltman, Melanie J.; Dwivedi, Prabha; Hill, Herbert; Blanchard, William C.; Ewing, Robert G.

2008-01-01

A recently developed atmospheric pressure ionization source, a distributed plasma ionization source (DPIS), was characterized and compared to commonly used atmospheric pressure ionization sources with both mass spectrometry and ion mobility spectrometry. The source consisted of two electrodes of different sizes separated by a thin dielectric. Application of a high RF voltage across the electrodes generated plasma in air yielding both positive and negative ions depending on the polarity of the applied potential. These reactant ions subsequently ionized the analyte vapors. The reactant ions generated were similar to those created in a conventional point-to-plane corona discharge ion source. The positive reactant ions generated by the source were mass identified as being solvated protons of general formula (H2O)nH+ with (H2O)2H+ as the most abundant reactant ion. The negative reactant ions produced were mass identified primarily as CO3-, NO3-, NO2-, O3- and O2- of various relative intensities. The predominant ion and relative ion ratios varied depending upon source construction and supporting gas flow rates. A few compounds including drugs, explosives and environmental pollutants were selected to evaluate the new ionization source. The source was operated continuously for several months and although deterioration was observed visually, the source continued to produce ions at a rate similar that of the initial conditions. The results indicated that the DPIS may have a longer operating life than a conventional corona discharge.

CNO abundances in Cepheids and supergiants: theoretical implications

International Nuclear Information System (INIS)

Becker, S.A.; Cox, A.N.

1982-01-01

Models of a 9 M/sub sun/ star have been evolved to see if the observed nitrogen enhancement and the carbon and oxygen depletions in yellow supergiants and Cepheids can be explained. In the standard (first dredge-up phase) evolutionary picture, the normal or near normal CNO abundances for the envelopes of stars on the main sequence are altered when such stars become red giants with deeply mixed convective envelopes prior to core He ignition. While this process does result in a noticeable nitrogen enhancement and a carbon reduction (oxygen is only slightly reduced), the observed changes in the CNO abundances are reported to be much larger. Consequently, other additional mechanisms need to be considered. The effects of primordial abundances, mass loss and transfer, convective overshoot, rotation, and magnetic fields are discussed. It is found that in order to explain the observed O depletion, there must be some form of mixing between the convective hydrogen-burning core and the inner part of the radiative envelope. This additional mixed material is then latter dredged up during the red giant phase. A simplified three-zone model is proposed. Finally, as a consequence of this additional mixing, longer main-sequence lifetimes and more luminous blue loops in the Cepheid region are predicted

Nitrogen Abundances and the Distance Moduli of the Pleiades and Hyades

OpenAIRE

Miller, Blake; King, Jeremy R.; Chen, Yu; Boesgaard, Ann M.

2013-01-01

Recent reanalyses of HIPPARCOS parallax data confirm a previously noted discrepancy with the Pleiades distance modulus estimated from main-sequence fitting in the color-magnitude diagram. One proposed explanation of this distance modulus discrepancy is a Pleiades He abundance that is significantly larger than the Hyades value. We suggest that, based on our theoretical and observational understanding of Galactic chemical evolution, nitrogen abundances may serve as a proxy for helium abundances...

X-Ray Absorption in Carbon Ions Near the K-Edge

Science.gov (United States)

Hasoglu, M. F.; Abdel-Naby, Sh. A.; Nikolic, D.; Gorczyca, T. W.; McLaughlin, B. M.

2007-06-01

K-shell photoabsorption calculations are important for determining the elemental abundances of the interstellar medium (ISM) from observed X-ray absorption spectra. Previously, we performed reliable K-shell photoabsorption calculations for oxygen [1-3] and neon [4,5] ions. We have executed detailed R-matrix calculations for carbon ions, including Auger broadening, by using an optical potential, and relaxation effects, by using pseudoorbitals with the necessary pseudoresonance elimination. This work was funded by NASA's Astronomy Physics Research and Analysis (APRA) and Solar and Heliospheric Physics (SHP) Supporting Research and Technology (SR&T) programs. References: [1] T. W. Gorczyca and B. M. McLaughlin. J Phys. B. 33 L859 (2000) [2] A. M. Juett, et al., Astrophys. J. 612, 308 (2004) [3] J. Garcia et al., Astrophys. J. Supp. S. 158, 68 (2005) [4] T. W. Gorczyca., Phys. Rev. A. 61, 024702 (2000) [5] A. M. Juett, et al., Astrophys. J. 648, 1066 (2006)

Abundance of sea kraits correlates with precipitation.

Directory of Open Access Journals (Sweden)

Harvey B Lillywhite

Full Text Available Recent studies have shown that sea kraits (Laticauda spp.--amphibious sea snakes--dehydrate without a source of fresh water, drink only fresh water or very dilute brackish water, and have a spatial distribution of abundance that correlates with freshwater sites in Taiwan. The spatial distribution correlates with sites where there is a source of fresh water in addition to local precipitation. Here we report six years of longitudinal data on the abundance of sea kraits related to precipitation at sites where these snakes are normally abundant in the coastal waters of Lanyu (Orchid Island, Taiwan. The number of observed sea kraits varies from year-to-year and correlates positively with previous 6-mo cumulative rainfall, which serves as an inverse index of drought. Grouped data for snake counts indicate that mean abundance in wet years is nearly 3-fold greater than in dry years, and this difference is significant. These data corroborate previous findings and suggest that freshwater dependence influences the abundance or activity of sea kraits on both spatial and temporal scales. The increasing evidence for freshwater dependence in these and other marine species have important implications for the possible impact of climate change on sea snake distributions.

reSpect: software for identification of high and low abundance ion species in chimeric tandem mass spectra.

Science.gov (United States)

Shteynberg, David; Mendoza, Luis; Hoopmann, Michael R; Sun, Zhi; Schmidt, Frank; Deutsch, Eric W; Moritz, Robert L

2015-11-01

Most shotgun proteomics data analysis workflows are based on the assumption that each fragment ion spectrum is explained by a single species of peptide ion isolated by the mass spectrometer; however, in reality mass spectrometers often isolate more than one peptide ion within the window of isolation that contribute to additional peptide fragment peaks in many spectra. We present a new tool called reSpect, implemented in the Trans-Proteomic Pipeline (TPP), which enables an iterative workflow whereby fragment ion peaks explained by a peptide ion identified in one round of sequence searching or spectral library search are attenuated based on the confidence of the identification, and then the altered spectrum is subjected to further rounds of searching. The reSpect tool is not implemented as a search engine, but rather as a post-search engine processing step where only fragment ion intensities are altered. This enables the application of any search engine combination in the iterations that follow. Thus, reSpect is compatible with all other protein sequence database search engines as well as peptide spectral library search engines that are supported by the TPP. We show that while some datasets are highly amenable to chimeric spectrum identification and lead to additional peptide identification boosts of over 30% with as many as four different peptide ions identified per spectrum, datasets with narrow precursor ion selection only benefit from such processing at the level of a few percent. We demonstrate a technique that facilitates the determination of the degree to which a dataset would benefit from chimeric spectrum analysis. The reSpect tool is free and open source, provided within the TPP and available at the TPP website. Graphical Abstract ᅟ.

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

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Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

2002-01-01

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization. c. 2002 American Society for Mass Spectrometry.

INTERBALL-Auroral observations of 0.1-12 keV ion gaps in the diffuse auroral zone

Directory of Open Access Journals (Sweden)

R. A. Kovrazhkin

1999-06-01

Full Text Available We examine ion flux dropouts detected by INTERBALL-Auroral upon traversal of the auroral zone at altitudes of \\sim13 000 up to 20 000 km. These dropouts which we refer to as "gaps", are frequently observed irrespectively of longitudinal sector and appear characteristic of INTERBALL-Auroral ion spectrograms. Whereas some of these gaps display a nearly monoenergetic character (~12 keV, others occur at energies of a few hundreds of eV up to several keV. INTERBALL-Auroral data exhibit the former monoenergetic gap variety essentially in the evening sector. As examined in previous studies, these gaps appear related to transition from particle orbits that are connected with the magnetotail plasma source to closed orbits encircling the Earth. The latter gap variety, which spreads over several hundreds of eV to a few keV is often observed in the dayside magnetosphere. It is argued that such gaps are due to magnetospheric residence times well above the ion lifetime. This interpretation is supported by numerical orbit calculations which reveal extremely large (up to several tens of hours times of flight in a limited energy range as a result of conflicting E × B and gradient-curvature drifts. The characteristic energies obtained numerically depend upon both longitude and latitude and are quite consistent with those measured in-situ.Key words. Magnetospheric physics (auroral phenomena; plasma convection

Proton-bound cluster ions in ion mobility spectrometry

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Ewing, R. G.; Eiceman, G. A.; Stone, J. A.

1999-01-01

Gaseous oxygen and nitrogen bases, both singly and as binary mixtures, have been introduced into ion mobility spectrometers to study the appearance of protonated molecules, and proton-bound dimers and trimers. At ambient temperature it was possible to simultaneously observe, following the introduction of molecule A, comparable intensities of peaks ascribable to the reactant ion (H2O)nH+, the protonated molecule AH+ and AH+ H2O, and the symmetrical proton bound dimer A2H+. Mass spectral identification confirmed the identifications and also showed that the majority of the protonated molecules were hydrated and that the proton-bound dimers were hydrated to a much lesser extent. No significant peaks ascribable to proton-bound trimers were obtained no matter how high the sample concentration. Binary mixtures containing molecules A and B, in some cases gave not only the peaks unique to the individual compounds but also peaks due to asymmetrical proton bound dimers AHB+. Such ions were always present in the spectra of mixtures of oxygen bases but were not observed for several mixtures of oxygen and nitrogen bases. The dimers, which were not observable, notable for their low hydrogen bond strengths, must have decomposed in their passage from the ion source to the detector, i.e. in a time less than approximately 5 ms. When the temperature was lowered to -20 degrees C, trimers, both homogeneous and mixed, were observed with mixtures of alcohols. The importance of hydrogen bond energy, and hence operating temperature, in determining the degree of solvation of the ions that will be observed in an ion mobility spectrometer is stressed. The possibility is discussed that a displacement reaction involving ambient water plays a role in the dissociation.

Multi-point observations of Ion Dispersions near the Exterior Cusp with Cluster

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Escoubet, C.-Philippe; Grison, Benjamin; Berchem, Jean; Trattner, Kralheinz; Pitout, Frederic; Richard, Robert; Taylor, Matt; Soucek, Jan; Laakso, Harri; Masson, Arnaud; Dunlop, Malcolm; Dandouras, Iannis; Reme, Henri; Fazakerley, Andrew; Daly, Patrick

2014-05-01

The exterior cusp is the most external region of the polar magnetosphere in direct contact with the plasma and the magnetic field from the solar wind. Unlike the rest of the magnetopause surface, the exterior cusp is a singular region with small and turbulent magnetic field and where large entry of plasma from solar origin takes place. The main process that injects solar wind plasma into the polar cusp is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process will take place equatorward (for IMF southward), poleward (for IMF northward) or on the dusk or dawn sides (for IMF azimuthal) of the cusp. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s and the density around 5 cm-3. The four Cluster spacecraft were still in the "magnetotail" configuration with two perfect tetrahedra of 2000 km around apogee and turning into an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions in the dispersions, we obtain an altitude of the sources of these ions between 14 and 20 RE. Using Tsyganenko model, these sources are located on the dusk flank, past the terminator. In addition, before entering the cusp, the magnetopause crossing was characterized by a large shear in By and bipolar plasma flows, suggesting that reconnection was taking place near the exterior cusp. We will discuss the extent of the reconnection line along the flank of the magnetopause based on these observations.

Effect of upstream ULF waves on the energetic ion diffusion at the earth's foreshock: Theory, Simulation, and Observations

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Otsuka, F.; Matsukiyo, S.; Kis, A.; Hada, T.

2017-12-01

Spatial diffusion of energetic particles is an important problem not only from a fundamental physics point of view but also for its application to particle acceleration processes at astrophysical shocks. Quasi-linear theory can provide the spatial diffusion coefficient as a function of the wave turbulence spectrum. By assuming a simple power-law spectrum for the turbulence, the theory has been successfully applied to diffusion and acceleration of cosmic rays in the interplanetary and interstellar medium. Near the earth's foreshock, however, the wave spectrum often has an intense peak, presumably corresponding to the upstream ULF waves generated by the field-aligned beam (FAB). In this presentation, we numerically and theoretically discuss how the intense ULF peak in the wave spectrum modifies the spatial parallel diffusion of energetic ions. The turbulence is given as a superposition of non-propagating transverse MHD waves in the solar wind rest frame, and its spectrum is composed of a piecewise power-law spectrum with different power-law indices. The diffusion coefficients are then estimated by using the quasi-linear theory and test particle simulations. We find that the presence of the ULF peak produces a concave shape of the diffusion coefficient when it is plotted versus the ion energy. The results above are used to discuss the Cluster observations of the diffuse ions at the Earth's foreshock. Using the density gradients of the energetic ions detected by the Cluster spacecraft, we determine the e-folding distances, equivalently, the spatial diffusion coefficients, of ions with their energies from 10 to 32 keV. The observed e-folding distances are significantly smaller than those estimated in the past statistical studies. This suggests that the particle acceleration at the foreshock can be more efficient than considered before. Our test particle simulation explains well the small estimate of the e-folding distances, by using the observed wave turbulence spectrum

Novel product ions of 2-aminoanilide and benzimidazole Ag(I) complexes using electrospray ionization with multi-stage tandem mass spectrometry.

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Johnson, Byron S; Burinsky, David J; Burova, Svetlana A; Davis, Roman; Fitzgerald, Russ N; Matsuoka, Richard T

2012-05-15

The 2-aminoaniline scaffold is of significant value to the pharmaceutical industry and is embedded in a number of pharmacophores including 2-aminoanilides and benzimidazoles. A novel application of coordination ion spray mass spectrometry (CIS-MS) for interrogating the silver ion (Ag(+)) complexes of a homologous series of these compounds using multi-stage tandem mass spectrometry is described. Unlike the ubiquitous alkali metal ion complexes, Ag(+) complexes of 2-aminoanilides and benzimidazoles were found to yield [M - H](+) ions in significant abundance via gas-phase elimination of the metal hydride (AgH) resulting in unique product ion cascades. Sample introduction was by liquid chromatography with mass spectrometry analysis performed on a hybrid linear ion trap/orbitrap instrument capable of high-resolution measurements. Rigorous structural characterization by multi-stage tandem mass spectrometry using [M +  H](+), [M - H](-) and [M - H](+) precursor ions derived from ESI and CIS experiments was performed for the homologous series of 2-aminoanilide and benzimidazole compounds. A full tabular comparison of structural information resulting from these product ion cascades was produced. Multi-stage tandem mass spectrometry of [M - H](+) ions resulting from Ag(+) complexes of 2-aminoanilides and benzimidazoles in CIS-MS experiments produced unique product ion cascades that exhibited complementary structural information to that obtained from tandem mass spectrometry of [M  +  H](+) and [M - H](-) ions by electrospray ionization (ESI). These observations may be broadly applicable to other compounds that are observed to form Ag(+) complexes and eliminate AgH. Copyright © 2012 John Wiley & Sons, Ltd.

Some remarks on the statistical model of heavy ion collisions

International Nuclear Information System (INIS)

Koch, V.

2003-01-01

This contribution is an attempt to assess what can be learned from the remarkable success of this statistical model in describing ratios of particle abundances in ultra-relativistic heavy ion collisions

Ion Acceleration by Double Layers with Multi-Component Ion Species

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Good, Timothy; Aguirre, Evan; Scime, Earl; West Virginia University Team

2017-10-01

Current-free double layers (CFDL) models have been proposed to explain observations of magnetic field-aligned ion acceleration in plasmas expanding into divergent magnetic field regions. More recently, experimental studies of the Bohm sheath criterion in multiple ion species plasma reveal an equilibration of Bohm speeds at the sheath-presheath boundary for a grounded plate in a multipole-confined filament discharge. We aim to test this ion velocity effect for CFDL acceleration. We report high resolution ion velocity distribution function (IVDF) measurements using laser induced fluorescence downstream of a CFDL in a helicon plasma. Combinations of argon-helium, argon-krypton, and argon-xenon gases are ionized and measurements of argon or xenon IVDFs are investigated to determine whether ion acceleration is enhanced (or diminished) by the presence of lighter (or heavier) ions in the mix. We find that the predominant effect is a reduction of ion acceleration consistent with increased drag arising from increased gas pressure under all conditions, including constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible for acceleration of multiple ion species in simple sheaths is not responsible for the ion acceleration observed in these expanding plasmas. Department of Physics, Gettysburg College.

Electromagnetic ion cyclotron waves observed in the plasma depletion layer

Science.gov (United States)

Anderson, B. J.; Fuselier, S. A.; Murr, D.

1991-01-01

Observations from AMPTE/CCE in the earth's magnetosheath on October 5, 1984 are presented to illustrate 0.1 - 4.0 Hz magnetic field pulsations in the subsolar plasma depletion layer (PDL) for northward sheath field during a magnetospheric compression. The PDL is unambiguously identified by comparing CCE data with data from IRM in the upstream solar wind. Pulsations in the PDL are dominated by transverse waves with F/F(H+) 1.0 or less and a slot in spectral power at F/F(H+) = 0.5. The upper branch is left hand polarized while the lower branch is linearly polarized. In the sheath the proton temperature anisotropy is about 0.6 but it is about 1.7 in the PDL during wave occurrence. The properties and correlation of waves with increased anisotropy indicate that they are electromagnetic ion cyclotron waves.

Chemical Abundance Measurements of Ultra-Faint Dwarf Galaxies Discovered by the Dark Energy Survey

Science.gov (United States)

Nagasawa, Daniel; Marshall, Jennifer L.; Simon, Joshua D.; Hansen, Terese; Li, Ting; Bernstein, Rebecca; Balbinot, Eduardo; Drlica-Wagner, Alex; Pace, Andrew; Strigari, Louis; Pellegrino, Craig; DePoy, Darren L.; Suntzeff, Nicholas; Bechtol, Keith; Dark Energy Suvey

2018-01-01

We present chemical abundance analysis results derived from high-resolution spectroscopy of ultra-faint dwarfs discovered by the Dark Energy Survey. Ultra-faint dwarf galaxies preserve a fossil record of the chemical abundance patterns imprinted by the first stars in the Universe. High-resolution spectroscopic observations of member stars in several recently discovered Milky Way satellites reveal a range of abundance patterns among ultra-faint dwarfs suggesting that star formation processes in the early Universe were quite diverse. The chemical content provides a glimpse not only of the varied nucleosynthetic processes and chemical history of the dwarfs themselves, but also the environment in which they were formed. We present the chemical abundance analysis of these objects and discuss possible explanations for the observed abundance patterns.

Observation of large-amplitude ion acoustic solitary waves in a plasma

International Nuclear Information System (INIS)

Nakamura, Yoshiharu

1987-01-01

Propagation of nonlinear ion acoustic waves in a multi-component plasma with negative ions is investigated in a double-plasma device. When the density of negative ions is larger than a critical value, a broad negative pulse evolves to rarefactive solitons, and a positive pulse whose amplitude is less than a certain threshold value becomes a subsonic wave train. In the same plasma, a positive pulse whose amplitude is larger than the threshold develops into a solitary wave. The critical amplitude is measured as a function of the density of negative ions and compared with predictions of the pseudo-potential method. The energy distribution of electrons in the solitary wave is also measured. (author)

Elemental abundances of intermediate-age open cluster NGC 3680

Science.gov (United States)

Mitschang, A. W.; De Silva, G. M.; Zucker, D. B.

2012-06-01

We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.

Turbulent ion heating in TCV Tokamak plasmas

International Nuclear Information System (INIS)

Schlatter, Ch.

2009-08-01

charge exchange measurements, by doping the plasma with ion neutralisation targets injected with the diagnostic neutral beam (DNBI), were used to absolutely calibrate the NPA. Advanced modelling of the measured hydrogenic charge exchange spectra with the neutralisation and neutral transport codes KN1D and DOUBLE-TCV permitted a calculation of the absolute neutral density profiles of the plasma species.The energisation and the properties of fast ions were studied in dedicated, low density, cold ion, hot electron plasmas, resonantly heated at the second harmonic of the electron cyclotron frequency. The ion acceleration occurs on a characteristic timescale in the sub-millisecond range and comprises up to 20 % of the plasma ions. The number of fast ions n i s and their effective temperature T i s are found to depend strongly on the bulk and suprathermal electron parameters, in particular T i s ≥ T e b (electron bulk) and n i s ∼ v de (toroidal electron drift speed). The suprathermal electrons, abundantly generated in plasmas subjected to ECCD, are diagnosed with perpendicular and oblique viewing electron cyclotron emission (ECE) antennas and the measured frequency spectra are reconstructed with the relativistic ECE radiation balance code NOTEC-TCV. With steady-state ECRH and ECCD, the fast ion population reaches an equilibrium state. The spatial fast ion temperature profile is broad, of similar shape compared to the bulk ion temperature profile. The hottest suprathermal temperature observed is T i s ≥ 6 keV. Various potential ion acceleration mechanisms were examined for relevance in the TCV parameter range. The simultaneous wave-electron and wave-ion resonances of ion acoustic turbulence (IAT) show the best correlation with the available experimental knowledge. Ion acoustic waves are emitted by the weakly relativistic circulating electrons and are mainly Landau damped onto the ions. Destabilisation of IAT is markedly facilitated by the important degree of

An Analysis of Ionospheric Thermal Ions Using a SIMION-based Forward Instrument Model: In Situ Observations of Vertical Thermal Ion Flows as Measured by the MICA Sounding Rocket

Science.gov (United States)

Fernandes, P. A.; Lynch, K. A.; Zettergren, M. D.; Hampton, D. L.; Fisher, L. E.; Powell, S. P.

2013-12-01

The MICA sounding rocket launched on 19 Feb. 2012 into several discrete, localized arcs in the wake of a westward traveling surge. In situ and ground-based observations provide a measured response of the ionosphere to preflight and localized auroral drivers. In this presentation we focus on in situ measurements of the thermal ion distribution. We observe thermal ions flowing both up and down the auroral field line, with upflows concentrated in Alfvénic and downward current regions. The in situ data are compared with recent ionospheric modeling efforts (Zettergren et al., this session) which show structured patterns of ion upflow and downflow consistent with these observations. In the low-energy thermal plasma regime, instrument response to the measured thermal ion population is very sensitive to the presence of the instrument. The plasma is shifted and accelerated in the frame of the instrument due to flows, ram, and acceleration through the payload sheath. The energies associated with these processes are large compared to the thermal energy. Rigorous quantitative analysis of the instrument response is necessary to extract the plasma properties which describe the full 3D distribution function at the instrument aperture. We introduce an instrument model, developed in the commercial software package SIMION, to characterize instrument response at low energies. The instrument model provides important insight into how we would modify our instrument for future missions, including fine-tuning parameters such as the analyzer sweep curve, the geometry factor, and the aperture size. We use the results from the instrument model to develop a forward model, from which we can extract anisotropic ion temperatures, flows, and density of the thermal plasma at the aperture. Because this plasma has transited a sheath to reach the aperture, we must account for the acceleration due to the sheath. Modeling of this complex sheath is being conducted by co-author Fisher, using a PIC code

Observation of self-sputtering in energetic condensation of metal ions

International Nuclear Information System (INIS)

Anders, Andre

2004-01-01

The condensation of energetic metal ions on a surface may cause self-sputtering even in the absence of substrate bias. Charge-state-averaged self-sputtering yields were determined for both zirconium and gold ions generated by a cathodic vacuum arc. Films were deposited on differently biased substrates exposed to streaming Zr and Au vacuum arc plasma. The self-sputtering yields for both metals were estimated to be about 0.05 in the absence of bias, and exceeding 0.5 when bias reached-50 V. These surprisingly high values can be reconciled with binary collision theory and molecular dynamics calculations taking high the kinetic and potential energy of vacuum arc ions into account

INTERPLANETARY PROPAGATION OF SOLAR ENERGETIC PARTICLE HEAVY IONS OBSERVED AT 1 AU AND THE ROLE OF ENERGY SCALING

International Nuclear Information System (INIS)

Mason, G. M.; Haggerty, D. K.; Li, G.; Zank, G. P.; Cohen, C. M. S.; Leske, R. A.; Mewaldt, R. A.; Desai, M. I.

2012-01-01

We have studied ∼0.3 to >100 MeV nucleon –1 H, He, O, and Fe in 17 large western hemisphere solar energetic particle events (SEP) to examine whether the often observed decrease of Fe/O during the rise phase is due to mixing of separate SEP particle populations, or is an interplanetary transport effect. Our earlier study showed that the decrease in Fe/O nearly disappeared if Fe and O were compared at energies where the two species interplanetary diffusion coefficient were equal, and therefore their kinetic energy nucleon –1 was different by typically a factor ∼2 ( e nergy scaling ) . Using an interplanetary transport model that includes effects of focusing, convection, adiabatic deceleration, and pitch angle scattering we have fit the particle spectral forms and intensity profiles over a broad range of conditions where the 1 AU intensities were reasonably well connected to the source and not obviously dominated by local shock effects. The transport parameters we derive are similar to earlier studies. Our model follows individual particles with a Monte Carlo calculation, making it possible to determine many properties and effects of the transport. We find that the energy scaling feature is preserved, and that the model is reasonably successful at fitting the magnitude and duration of the Fe/O ratio decrease. This along with successfully fitting the observed decrease of the O/He ratio leads us to conclude that this feature is best understood as a transport effect. Although the effects of transport, in particular adiabatic deceleration, are very significant below a few MeV nucleon –1 , the spectral break observed in these events at 1 AU is only somewhat modified by transport, and so the commonly observed spectral breaks must be present at injection. For scattering mean free paths of the order of 0.1 AU adiabatic deceleration is so large below ∼200 keV nucleon –1 that ions starting with such energies at injection are cooled sufficiently as to be

Chempy: A flexible chemical evolution model for abundance fitting. Do the Sun's abundances alone constrain chemical evolution models?

Science.gov (United States)

Rybizki, Jan; Just, Andreas; Rix, Hans-Walter

2017-09-01

Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of five to ten parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: for example, the star-formation history (SFH), the feedback efficiency, the stellar initial mass function (IMF), and the incidence of supernova of type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. It is essentially a chemical evolution fitting tool. We straightforwardly extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of the Sun, Arcturus, and the present-day interstellar medium (ISM). For the first time, we use such information to infer the IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that 11.6+ 2.1-1.6% of the IMF explodes as core-collapse supernova (CC-SN), compatible with Salpeter (1955, ApJ, 121, 161). We also constrain the incidence of SN Ia per 103M⊙ to 0.5-1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication of missing nucleosynthetic channels. Chempy could be a powerful tool to confront predictions from stellar

Observation of dielectronic satellites in the K-spectrum of argon ions in plasma produced by femtosecond laser pulses

International Nuclear Information System (INIS)

Magunov, A.I.; Faenov, A.Ya.; Skobelev, I.Yu.; Pikuz, T.A.; Biemont, E.; Quinet, P.; Blasco, F.; Bonte, C.; Dorchies, F.; Caillaud, T.; Salin, F.; Stenz, C.

2002-01-01

The satellite structure of 1s2p 1,3 P 1 -1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters

Kaguya observations of the lunar wake in the terrestrial foreshock: Surface potential change by bow-shock reflected ions

Science.gov (United States)

Nishino, Masaki N.; Harada, Yuki; Saito, Yoshifumi; Tsunakawa, Hideo; Takahashi, Futoshi; Yokota, Shoichiro; Matsushima, Masaki; Shibuya, Hidetoshi; Shimizu, Hisayoshi

2017-09-01

There forms a tenuous region called the wake behind the Moon in the solar wind, and plasma entry/refilling into the wake is a fundamental problem of the lunar plasma science. High-energy ions and electrons in the foreshock of the Earth's magnetosphere were detected at the lunar surface in the Apollo era, but their effects on the lunar night-side environment have never been studied. Here we show the first observation of bow-shock reflected protons by Kaguya (SELENE) spacecraft in orbit around the Moon, confirming that solar wind plasma reflected at the terrestrial bow shock can easily access the deepest lunar wake when the Moon stays in the foreshock (We name this mechanism 'type-3 entry'). In a continuous type-3 event, low-energy electron beams from the lunar night-side surface are not obvious even though the spacecraft location is magnetically connected to the lunar surface. On the other hand, in an intermittent type-3 entry event, the kinetic energy of upward-going field-aligned electron beams decreases from ∼ 80 eV to ∼ 20 eV or electron beams disappear as the bow-shock reflected ions come accompanied by enhanced downward electrons. According to theoretical treatment based on electric current balance at the lunar surface including secondary electron emission by incident electron and ion impact, we deduce that incident ions would be accompanied by a few to several times higher flux of an incident electron flux, which well fits observed downward fluxes. We conclude that impact by the bow-shock reflected ions and electrons raises the electrostatic potential of the lunar night-side surface.

Voyager observations of O(+6) and other minor ions in the solar wind

Science.gov (United States)

Villanueva, Louis; Mcnutt, Ralph L., Jr.; Lazarus, Alan J.; Steinberg, John T.

1994-01-01

The plasma science (PLS) experiments on the Voyager 1 and 2 spacecraft began making measurements of the solar wind shortly after the two launches in the fall of 1977. In reviewing the data obtained prior to the Jupiter encounters in 1979, we have found that the large dynamic range of the PLS instrument generally allows a clean separation of signatures of minor ions (about 2.5% of the time) during a single instrument scan in energy per charge. The minor ions, most notably O(+6), are well separated from the protons and alpha particles during times when the solar wind Mach number (ratio of streaming speed to thermal speed) is greater than approximately 15. During the Earth to Jupiter cruise we find that the average ratio of alpha particle number density to that of oxygen is 66 +/- 7 (Voyager 1) and 71 +/- 17 (Voyager 2). These values are consistent with the value 75 +/- 20 inferred from the Ion Composition Instrument on ISEE 3 during the period spanning 1978 and 1982. We have inferred an average coronal temperature of (1.7 +/- 0.1) x 10(exp 6) K based on the ratio of O(+7) to O(+6) number densities. Our observations cover a period of increasing solar activity. During this time we have found that the alpha particle to proton number density ratio is increasing with the solar cycle, the oxygen to proton ratio increases, and the alpha particle to oxygen ratio remains relatively constant in time.

Carbon and oxygen abundances across the Hertzsprung gap

International Nuclear Information System (INIS)

Adamczak, Jens; Lambert, David L.

2014-01-01

We derived atmospheric parameters and spectroscopic abundances for C and O for a large sample of stars located in the Hertzsprung gap in the Hertzsprung-Russell diagram in order to detect chemical peculiarities and get a comprehensive overview of the population of stars in this evolutionary state. We have observed and analyzed high-resolution spectra (R = 60,000) of 188 stars in the mass range 2-5 M ☉ with the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory including 28 stars previously identified as Am/Ap stars. We find that the C and O abundances of the majority of stars in the Hertzsprung gap are in accordance with abundances derived for local lower-mass dwarfs but detect expected peculiarities for the Am/Ap stars. The C and O abundances of stars with T eff < 6500 K are slightly lower than for the hotter objects but the C/O ratio is constant in the analyzed temperature domain. No indication of an alteration of the C and O abundances of the stars by mixing during the evolution across the Hertzsprung gap could be found before the homogenization of their atmospheres by the first dredge-up.

Secondary ions produced from condensed rare gas targets under highly charged MeV/amu heavy ion bombardment

International Nuclear Information System (INIS)

Tawara, H.; Tonuma, T.; Kumagai, H.; Matsuo, T.

1994-01-01

Secondary ions produced from condensed rare gas targets are observed under MeV/amu, highly charged, heavy ion impact. The intensities of the observed cluster ions decrease smoothly as the cluster sizes become large but show some discontinuities at particular sizes of cluster ions. This seems to be closely related to the stabilities of cluster ion structures. It is also noted that very few doubly charged or practically no triply/higher charged ions have been observed, in sharp contrast to that of some condensed molecular targets. (orig.)

Some peculiarities of fish abundance, species and sizes distribution, and spacing

International Nuclear Information System (INIS)

Astrauskas, A.; Bernotas, E.; Jovaisha, R.

1995-01-01

During the construction and exploitation process of Ignalina NPP the abundance of fishes has dropped, and especially stenothermic species (smelt and vendace). The general increase of fish abundance is observed in recent years (1992-1994). This is linked with changes of fish species and their adaptation to the new environmental conditions. Now the partial renovation of vendace abundance is observed, too. It is a result of free feeding recess coming out as the smelt dramatically decreased. Before now the ecosystem of the lake is greatly disbalanced due to antropogenetic impact of the NPP. It's partial stabilisation (but on the essentially high level) is possible only in some generations of fish living in the lake. (author). 18 refs., 1 tab., 11 figs

Mass Spectrum Analysis of CO2 and N2 Using Ion Beam Separator System

International Nuclear Information System (INIS)

Tjipto-Sujitno, BA; Darsono; Agus-Santoso

2000-01-01

The main purpose of this research is to study investigate the massspectrum profile of CO 2 and N 2 emitted from Penning ion source using ionbeam separator. Besides that, it is also identified the compositions of CO 2 and N 2 ion gas and their abundances through their mass spectrum profile,because as we know that these ions are consist of ion of atom or molecule aswell as the their abundances. To get these profiles, the ion beam acceleratedin accelerating tube are passed through magnet separator. After passing themagnet separator, the ion current beam was detected using microampere meter.By scanning the strength of magnetic field, it will be found the currentspectrum profile as a function of magnetic field. From this current spectrum,we can make a mass spectrum profile. From experiment done, it was found thatthe mass spectrum peak of CO 2 and N 2 were C + with m/z = (12.00 ± 0.10)amu, O 2 + = (31.96 ± 0.29) amu, CO 2 + = (43.93 ± 0.31) amu, N + (13.97 ± 0.33) amu, and N 2 + = (28.05 ± 0.18) amu. (author)

Observation of a shift of multicharged silicon ion recombination radiation jumps in a laser plasma

International Nuclear Information System (INIS)

Basov, N.G.; Kalashnikov, M.P.; Mikhajlov, Yu.A.; Rode, A.V.; Sklizkov, G.V.; Fedotov, S.I.

1984-01-01

In experiments on heating and compression of shell targets for the case of three-fold magnification of the laser radiation flux density on a target a shift in the recombination Si +13 ion radiation jump of 46+-8 eV has been observed, which corresponds to ionic density (1.3+-1)x10 20 cm -3 . To explain the mechanism of the jump shift, a scheme of potential energy and energy levels of two hydrogen-like ions are presented. It is shown that recording of the recombination radiation intensity jump enables one to determine the electron temperature of a plasma Tsub(e)sub(e). T value determined from the ratio of the intensity of continuous radiation before and after the recombination jump is 0.95+-0.1 keV

Free ion yield observed in liquid isooctane irradiated by γ rays. Comparison with the Onsager theory

International Nuclear Information System (INIS)

Pardo, J; Franco, L; Gomez, F; Iglesias, A; Lobato, R; Mosquera, J; Pazos, A; Pena, J; Pombar, M; RodrIguez, A; Sendon, J

2004-01-01

We have analysed data on the free ion yield observed in liquid isooctane irradiated by 60 Co γ rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian-type function and an exponential function. A linear dependence between the free ion yield and the external electric field has been found at low-electric-field values (E ≤ 1.2 x 10 3 V mm -1 ) in excellent agreement with the Onsager theory. At higher electric field values, we obtain a solution in power series of the external field using the Onsager theory

Free ion yield observed in liquid isooctane irradiated by {gamma} rays. Comparison with the Onsager theory

Energy Technology Data Exchange (ETDEWEB)

Pardo, J [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Franco, L [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Gomez, F [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Iglesias, A [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Lobato, R [Hospital ClInico Universitario de Santiago, Santiago de Compostela (Spain); Mosquera, J [Hospital ClInico Universitario de Santiago, Santiago de Compostela (Spain); Pazos, A [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Pena, J [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Pombar, M [Hospital ClInico Universitario de Santiago, Santiago de Compostela (Spain); RodrIguez, A [Departamento de FIsica de PartIculas, Facultade de FIsica, 15782 Santiago de Compostela (Spain); Sendon, J [Hospital ClInico Universitario de Santiago, Santiago de Compostela (Spain)

2004-05-21

We have analysed data on the free ion yield observed in liquid isooctane irradiated by {sup 60}Co {gamma} rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian-type function and an exponential function. A linear dependence between the free ion yield and the external electric field has been found at low-electric-field values (E {<=} 1.2 x 10{sup 3} V mm{sup -1}) in excellent agreement with the Onsager theory. At higher electric field values, we obtain a solution in power series of the external field using the Onsager theory.

Spatially resolved images of reactive ions in the Orion Bar,★★.

Science.gov (United States)

Goicoechea, Javier R; Cuadrado, Sara; Pety, Jérôme; Bron, Emeric; Black, John H; Cernicharo, José; Chapillon, Edwige; Fuente, Asunción; Gerin, Maryvonne

2017-05-01

We report high angular resolution (4.9″×3.0″) images of reactive ions SH + , HOC + , and SO + toward the Orion Bar photodissociation region (PDR). We used ALMA-ACA to map several rotational lines at 0.8 mm, complemented with multi-line observations obtained with the IRAM 30 m telescope. The SH + and HOC + emission is restricted to a narrow layer of 2″- to 10″-width (≈800 to 4000 AU depending on the assumed PDR geometry) that follows the vibrationally excited [Formula: see text] emission. Both ions efficiently form very close to the H/H 2 transition zone, at a depth of A v ≲1 mag into the neutral cloud, where abundant C + , S + , and [Formula: see text] coexist. SO + peaks slightly deeper into the cloud. The observed ions have low rotational temperatures ( T rot ≈10-30 K≪ T k ) and narrow line-widths (~2-3 km s -1 ), a factor of ≃2 narrower that those of the lighter reactive ion CH + . This is consistent with the higher reactivity and faster radiative pumping rates of CH + compared to the heavier ions, which are driven relatively faster toward smaller velocity dispersion by elastic collisions and toward lower T rot by inelastic collisions. We estimate column densities and average physical conditions from an excitation model ( n (H 2 )≈10 5 -10 6 cm -3 , n ( e - )≈10 cm -3 , and T k ≈200 K). Regardless of the excitation details, SH + and HOC + clearly trace the most exposed layers of the UV-irradiated molecular cloud surface, whereas SO + arises from slightly more shielded layers.

The Effect of Solar Wind Variations on the Escape of Oxygen Ions From Mars Through Different Channels: MAVEN Observations

Science.gov (United States)

Dubinin, E.; Fraenz, M.; Pätzold, M.; McFadden, J.; Halekas, J. S.; DiBraccio, G. A.; Connerney, J. E. P.; Eparvier, F.; Brain, D.; Jakosky, B. M.; Vaisberg, O.; Zelenyi, L.

2017-11-01

We present multi-instrument observations of the effects of solar wind on ion escape fluxes on Mars based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) data from 1 November 2014 to 15 May 2016. Losses of oxygen ions through different channels (plasma sheet, magnetic lobes, boundary layer, and ion plume) as a function of the solar wind and the interplanetary magnetic field variations were studied. We have utilized the modified Mars Solar Electric (MSE) coordinate system for separation of the different escape routes. Fluxes of the low-energy (≤30 eV) and high-energy (≥30 eV) ions reveal different trends with changes in the solar wind dynamic pressure, the solar wind flux, and the motional electric field. Major oxygen fluxes occur through the tail of the induced magnetosphere. The solar wind motional electric field produces an asymmetry in the ion fluxes and leads to different relations between ion fluxes supplying the tail from the different hemispheres and the solar wind dynamic pressure (or flux) and the motional electric field. The main driver for escape of the high-energy oxygen ions is the solar wind flux (or dynamic pressure). On the other hand, the low-energy ion component shows the opposite trend: ion flux decreases with increasing solar wind flux. As a result, the averaged total oxygen ion fluxes reveal a low variability with the solar wind strength. The large standard deviations from the averages values of the escape fluxes indicate the existence of mechanisms which can enhance or suppress the efficiency of the ion escape. It is shown that the Martian magnetosphere possesses the properties of a combined magnetosphere which contains different classes of field lines. The existence of the closed magnetic field lines in the near-Mars tail might be responsible for suppression of the ion escape fluxes.

Abundances of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS

Science.gov (United States)

Davidson, Jemma; Busemann, Henner; Nittler, Larry R.; Alexander, Conel M. O.'D.; Orthous-Daunay, François-Régis; Franchi, Ian A.; Hoppe, Peter

2014-08-01

It has been suggested that the matrices of all chondrites are dominated by a common material with Ivuna-like (CI) abundances of volatiles, presolar grains and insoluble organic matter (IOM) (e.g., Alexander, 2005). However, matrix-normalized abundances of presolar silicon carbide (SiC) grains estimated from their noble gas components show significant variations in even the most primitive chondrites (Huss and Lewis, 1995; Huss et al., 2003), in contradiction to there being a common chondrite matrix material. Here we report presolar SiC abundances determined by NanoSIMS raster ion imaging of IOM extracted from primitive members of different meteorite groups. We show that presolar SiC abundance determinations are comparable between NanoSIMS instruments located at three different institutes, between residues prepared by different demineralization techniques, and between microtomed and non-microtomed samples. Our derived SiC abundances in CR chondrites are comparable to those found in the CI chondrites (∼30 ppm) and are much higher than previously determined by noble gas analyses. The revised higher CR SiC abundances are consistent with the CRs being amongst the most primitive chondrites in terms of the isotopic compositions and disordered nature of their organic matter. Similar abundances between CR1, CR2, and CR3 chondrites indicate aqueous alteration on the CR chondrite parent body has not progressively destroyed SiC grains in them. A low SiC abundance for the reduced CV3 RBT 04133 can be explained by parent body thermal metamorphism at an estimated temperature of ∼440 °C. Minor differences between primitive members of other meteorite classes, which did not experience such high temperatures, may be explained by prolonged oxidation at lower temperatures under which SiC grains formed outer layers of SiO2 that were not thermodynamically stable, leading to progressive degassing/destruction of SiC.

SULFUR ABUNDANCES IN THE ORION ASSOCIATION B STARS

International Nuclear Information System (INIS)

Daflon, Simone; Cunha, Katia; De la Reza, Ramiro; Holtzman, Jon; Chiappini, Cristina

2009-01-01

Sulfur abundances are derived for a sample of 10 B main-sequence star members of the Orion association. The analysis is based on LTE plane-parallel model atmospheres and non-LTE line formation theory by means of a self-consistent spectrum synthesis analysis of lines from two ionization states of sulfur, S II and S III. The observations are high-resolution spectra obtained with the ARCES spectrograph at the Apache Point Observatory. The abundance distribution obtained for the Orion targets is homogeneous within the expected errors in the analysis: A(S) = 7.15 ± 0.05. This average abundance result is in agreement with the recommended solar value (both from modeling of the photospheres in one-dimensional and three-dimensional, and meteorites) and indicates that little, if any, chemical evolution of sulfur has taken place in the last ∼4.5 billion years. The sulfur abundances of the young stars in Orion are found to agree well with results for the Orion Nebulae, and place strong constraints on the amount of sulfur depletion onto grains as being very modest or nonexistent. The sulfur abundances for Orion are consistent with other measurements at a similar galactocentric radius: combined with previous results for other OB-type stars produce a relatively shallow sulfur abundance gradient with a slope of -0.037 ± 0.012 dex kpc -1 .

Ion-ion interaction and energy transfer of 4+ transuranium ions in cerium tetrafluoride

International Nuclear Information System (INIS)

Liu, G.K.; Beitz, J.V.

1990-01-01

Dynamics of excited 5f electron states of the transuranium ions Cm 4+ and Bk 4+ in CeF 4 are compared. Based on time- and wavelength-resolved laser-induced fluorescence, excitation energy transfer processes have been probed. Depending on concentration and electronic energy level structure of the studied 4+ transuranium ion, the dominant energy transfer mechanisms were identified as cross relaxation, exciton-exciton annihilation, and trapping. Energy transfer rates derived from the fitting of the observed fluorescence decays to theoretical models, based on electric multipolar ion-ion interactions, are contrasted with prior studies of 4f states of 3+ lanthanide and 3d states of transition metal ions. 16 refs., 1 tab

Spectra of W19 +-W32 + observed in the EUV region between 15 and 55 Å with an electron-beam ion trap

Science.gov (United States)

Sakaue, H. A.; Kato, D.; Yamamoto, N.; Nakamura, N.; Murakami, I.

2015-07-01

We present extreme ultraviolet spectra of highly charged tungsten ions (W19 +-W32 + ) in the wavelength range of 15 -55 Å obtained with a compact electron-beam ion trap (CoBIT) and a grazing-incidence spectrometer at the National Institute for Fusion Science. The electron energy dependence of the spectra was investigated for electron energies from 490 to 1320 eV . Identification of the observed lines was aided by collisional-radiative (CR) modeling of CoBIT plasma. Good quantitative agreement was obtained between the CR-modeling results and the experimental observations. The ion charge dependence of the 6 g -4 f ,5 g -4 f ,5 f -4 d ,5 p -4 d , and 4 f -4 d transition wavelengths were measured.

In-situ observation of damage evolution in TiC crystals during helium ion irradiation

International Nuclear Information System (INIS)

Hojou, K.; Otsu, H.; Furuno, S.; Izui, K.; Tsukamoto, T.

1994-01-01

In-situ observations were performed on bubble formation and growth in TiC during 20 keV helium ion irradiation over the wide range of irradiation temperatures from 12 to 1523 K. No amorphization occurred over this temperature range. The bubble densities and sizes were almost independent of irradiation temperatures from 12 to 1273 K. Remarkable growth and coalescence occurred during irradiation at high temperature above 1423 K and during annealing above 1373 K after irradiation. ((orig.))

Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Moda)

Science.gov (United States)

Lin, Y.; Rice, J. E.; Wukitch, S. J.; Greenwald, M. J.; Hubbard, A. E.; Ince-Cushman, A.; Lin, L.; Marmar, E. S.; Porkolab, M.; Reinke, M. L.; Tsujii, N.; Wright, J. C.; Alcator C-Mod Team

2009-05-01

At modest H3e levels (n3He/ne˜8%-12%), in relatively low density D(H3e) plasmas, n¯e≤1.3×1020 m-3, heated with 50 MHz rf power at Bt0˜5.1 T, strong (up to 90 km/s) toroidal rotation (Vϕ) in the cocurrent direction has been observed by high-resolution x-ray spectroscopy on Alcator C-Mod. The change in central Vϕ scales with the applied rf power (≤30 km s-1 MW-1), and is generally at least a factor of 2 higher than the empirically determined intrinsic plasma rotation scaling. The rotation in the inner plasma (r /a≤0.3) responds to the rf power more quickly than that of the outer region (r /a≥0.7), and the rotation profile is broadly peaked for r /a≤0.5. Localized poloidal rotation (0.3≤r/a≤0.6) in the ion diamagnetic drift direction (˜2 km/s at 3 MW) is also observed, and similarly increases with rf power. Changing the toroidal phase of the antenna does not affect the rotation direction, and it only weakly affects the rotation magnitude. The mode converted ion cyclotron wave (MC ICW) has been detected by a phase contrast imaging system and the MC process is confirmed by two-dimensional full wave TORIC simulations. The simulations also show that the MC ICW is strongly damped on H3e ions in the vicinity of the MC layer, approximately on the same flux surfaces where the rf driven flow is observed. The flow shear in our experiment is marginally sufficient for plasma confinement enhancement based on the comparison of the E ×B shearing rate and gyrokinetic linear stability analysis.

Latitudinal distribution of the Jovian plasma sheet ions observed by Juno JADE-I

Science.gov (United States)

Kim, T. K. H.; Valek, P. W.; McComas, D. J.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Connerney, J. E. P.; Ebert, R. W.; Levin, S.; Louarn, P.; Pollock, C. J.; Ranquist, D. A.; Szalay, J.; Thomsen, M. F.; Wilson, R. J.

2017-12-01

The Jovian plasma sheet is a region where the centrifugal force dominates the heavy ion plasma. Properties of the plasma sheet ions near the equatorial plane have been studied with in-situ measurements from the Pioneer, Voyager, and Galileo spacecraft. However, the ion properties for the off-equator regions are not well known due to the limited measurements. Juno is the first polar orbiting spacecraft that can investigate the high latitude region of the Jovian magnetosphere. With Juno's unique trajectory, we will investigate the latitudinal distribution of the Jovian plasma sheet ions using measurements from the Jovian Auroral Distributions Experiment Ion sensor (JADE-I). JADE-I measures an ion's energy-per-charge (E/Q) from 0.01 keV/q to 46.2 keV/q with an electrostatic analyzer (ESA) and a mass-per-charge (M/Q) up to 64 amu/q with a carbon-foil-based time-of-flight (TOF) mass spectrometer. We have shown that the ambiguity between and (both have M/Q of 16) can be resolved in JADE-I using a semi-empirical simulation tool based on carbon foil effects (i.e., charge state modification, angular scattering, and energy loss) from incident ions passing through the TOF mass spectrometer. Based on the simulation results, we have developed an Ion Composition Analysis Tool (ICAT) that determines ion composition at each energy step of JADE-I (total of 64 steps). The velocity distribution for each ion species can be obtained from the ion composition as a function of each energy step. Since there is an ambipolar electric field due to mobile electrons and equatorially confined heavy ions, we expect to see acceleration along the field line. This study will show the species separated velocity distribution at various latitudes to investigate how the plasma sheet ions evolve along the field line.

Laser-cooled atomic ions as probes of molecular ions

Energy Technology Data Exchange (ETDEWEB)

Brown, Kenneth R.; Viteri, C. Ricardo; Clark, Craig R.; Goeders, James E.; Khanyile, Ncamiso B.; Vittorini, Grahame D. [Schools of Chemistry and Biochemistry, Computational Science and Engineering and Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2015-01-22

Trapped laser-cooled atomic ions are a new tool for understanding cold molecular ions. The atomic ions not only sympathetically cool the molecular ions to millikelvin temperatures, but the bright atomic ion fluorescence can also serve as a detector of both molecular reactions and molecular spectra. We are working towards the detection of single molecular ion spectra by sympathetic heating spectroscopy. Sympathetic heating spectroscopy uses the coupled motion of two trapped ions to measure the spectra of one ion by observing changes in the fluorescence of the other ion. Sympathetic heating spectroscopy is a generalization of quantum logic spectroscopy, but does not require ions in the motional ground state or coherent control of the ion internal states. We have recently demonstrated this technique using two isotopes of Ca{sup +} [Phys. Rev. A, 81, 043428 (2010)]. Limits of the method and potential applications for molecular spectroscopy are discussed.

Strangeness production in proton and heavy ion collisions at 200 A GeV

International Nuclear Information System (INIS)

Amelin, N.S.; Bravina, L.V.; Csernai, L.P.; Toneev, V.D.; Gudima, K.K.; Sivoklokov, S.Y.

1992-11-01

Strangeness production at SPS-CERN energies is studied within the Quark Gluon String Model. The observed shape of rapidity and transverse mass distributions are reproduced fairly well for both peripheral and central heavy ion collisions. However, for central collisions the model underpredicts strange particle abundances by a factor of about 2:2:4 for K S 0 , Λ and antiΛ, respectively. This discrepancy can be considered as a possible manifestation of collective string-string interactions similar to the formation of a color rope. Model predictions for coming experiments with the Pb beam at CERN are given. 30 refs. 11 figs., 3 tabs

Ion Mobility Mass Spectrometry for Extracting Spectra of N-Glycans Directly from Incubation Mixtures Following Glycan Release: Application to Glycans from Engineered Glycoforms of Intact, Folded HIV gp120

Science.gov (United States)

Harvey, David J.; Sobott, Frank; Crispin, Max; Wrobel, Antoni; Bonomelli, Camille; Vasiljevic, Snezana; Scanlan, Christopher N.; Scarff, Charlotte A.; Thalassinos, Konstantinos; Scrivens, James H.

2011-03-01

The analysis of glycosylation from native biological sources is often frustrated by the low abundances of available material. Here, ion mobility combined with electrospray ionization mass spectrometry have been used to extract the spectra of N-glycans released with PNGase F from a serial titration of recombinantly expressed envelope glycoprotein, gp120, from the human immunodeficiency virus (HIV). Analysis was also performed on gp120 expressed in the α-mannosidase inhibitor, and in a matched mammalian cell line deficient in GlcNAc transferase I. Without ion mobility separation, ESI spectra frequently contained no observable ions from the glycans whereas ions from other compounds such as detergents and residual buffer salts were abundant. After ion mobility separation on a Waters T-wave ion mobility mass spectrometer, the N-glycans fell into a unique region of the ion mobility/ m/z plot allowing their profiles to be extracted with good signal:noise ratios. This method allowed N-glycan profiles to be extracted from crude incubation mixtures with no clean-up even in the presence of surfactants such as NP40. Furthermore, this technique allowed clear profiles to be obtained from sub-microgram amounts of glycoprotein. Glycan profiles were similar to those generated by MALDI-TOF MS although they were more susceptible to double charging and fragmentation. Structural analysis could be accomplished by MS/MS experiments in either positive or negative ion mode but negative ion mode gave the most informative spectra and provided a reliable approach to the analysis of glycans from small amounts of glycoprotein.

Lithium-ion Battery Charge Methodologies Observed with Portable Electronic Equipment

Science.gov (United States)

Jeevarajan, Judith

2009-01-01

Commercial lithium-ion batteries in portable electronic equipment has been used by NASA for space applications since 1999. First battery that was certified for flight and flown for Shuttle use was the Canon BP 927 (2.7 Ah) battery pack. Since then, numerous portable equipment with li-ion batteries have been certified and flown and remain on-orbit for crew usage. Laptops (two generations with third one being worked on now) Camcorder Camera PDA 2 versions (second one being li-ion polymer cells) Satellite Phone Due to expense and time, certified batteries are used with different equipment with the help of adapters or by working with the manufacturer of the equipment to build the appropriate battery compartment and connector. Certified and dedicated chargers are available on Shuttle and on the ISS for safe charging.

Good abundances from bad spectra - I. Techniques

Science.gov (United States)

Jones, J. Bryn; Gilmore, Gerard; Wyse, Rosemary F. G.

1996-01-01

Stellar spectra derived from multiple-object fibre-fed spectroscopic radial-velocity surveys, of the type feasible with, among other examples, AUTOFIB, 2dF, HYDRA, NESSIE, and the Sloan survey, differ significantly from those traditionally used for determination of stellar abundances. The spectra tend to be of moderate resolution (around 1A) and signal-to-noise ratio (around 10-20 per resolution element), and cannot usually have reliable continuum shapes determined over wavelength ranges in excess of a few tens of Angstroms. None the less, with care and a calibration of stellar effective temperature from photometry, independent of the spectroscopy, reliable iron abundances can be derived. We have developed techniques to extract true iron abundances and surface gravities from low-signal-to-noise ratio, intermediate-resolution spectra of G-type stars in the 4000-5000A wavelength region. Spectroscopic indices sensitive to iron abundance and gravity are defined from a set of narrow (few-several A wide) wavelength intervals. The indices are calibrated theoretically using synthetic spectra. Given adequate data and a photometrically determined effective temperature, one can derive estimates of the stellar iron abundance and surface gravity. We have also defined a single abundance indicator for the analysis of very low-signal-to-noise ratio spectra; with the further assumption of a value for the stellar surface gravity, this is able to provide useful iron abundance information from spectra having signal-to-noise ratios as low as 10 (1-A elements). The theoretical basis and calibration using synthetic spectra are described in this paper. The empirical calibration of these techniques by application to observational data is described in a separate paper (Jones, Wyse & Gilmore). The technique provides precise iron abundances, with zero-point correct to ~0.1 dex, and is reliable, with typical uncertainties being <~0.2 dex. A derivation of the in situ thick disc metallicity

The shape of oxygen abundance profiles explored with MUSE

Science.gov (United States)

Sánchez, S. F.; Sánchez-Menguiano, L.; Pérez, I.

2017-11-01

We characterise the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allows us to detect 14345 HII regions with the same image quality as with photometric data, avoiding any dilution effect. We develop a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10) or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence for the outer flattening. We find that the inner drop appears always around 0.5 r_e, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope of α_{O/H} = - 0.10±0.03 dex/r_e. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale (r_{O/H}) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (˜0.5 r_{O/H}) and the outer flattening (˜1.5 r_{O/H}).Finally, we find no significant dependence of the dispersion around the negative gradient with any galaxy property, with values compatible with the uncertainties of the derived abundances.

GAS-PHASE CHEMISTRY OF THE CYANATE ION, OCN−

International Nuclear Information System (INIS)

Cole, Callie A.; Wang, Zhe-Chen; Bierbaum, Veronica M.; Snow, Theodore P.

2015-01-01

Cyanate (OCN − ) is the only ion to date whose presence has been confirmed in the icy mantles that coat interstellar dust grains. Understanding the chemical behavior of cyanate at a fundamental level is therefore integral to the advancement of astrochemistry. We seek to unravel the chemistry of this intriguing anion through a combination of gas-phase experiments and theoretical explorations. Our approach is twofold: first, employing a flowing afterglow-selected ion flow tube apparatus, the reactions between OCN − and three of the most abundant atomic species in the interstellar medium, hydrogen, nitrogen, and oxygen, are examined. Hydrogen atoms readily react by associative detachment, but the remarkable stability of OCN − does not give rise to an observable reaction with either nitrogen or oxygen atoms. To explain these results, the potential energy surfaces of several reactions are investigated at the B3LYP/6-311++G(d,p) level of theory. Second, collision induced dissociation experiments involving deprotonated uracil, thymine, and cytosine in an ion trap mass spectrometer reveal an interesting connection between these pyrimidine nucleobase anions and OCN − . Theoretical calculations at the B3LYP/6-311++G(d,p) level of theory are performed to delineate the mechanisms of dissociation and explore the possible role of OCN − as a biomolecule precursor

LARGE ABUNDANCES OF POLYCYCLIC AROMATIC HYDROCARBONS IN TITAN'S UPPER ATMOSPHERE

Energy Technology Data Exchange (ETDEWEB)

Lopez-Puertas, M.; Funke, B.; Garcia-Comas, M. [Instituto de Astrofisica de Andalucia (CSIC), E-18080 Granada (Spain); Dinelli, B. M. [ISAC-CNR, I-40129 Bologna (Italy); Adriani, A.; D' Aversa, E. [IAPS-INAF, I-00133 Rome (Italy); Moriconi, M. L. [ISAC-CNR, I-00133 Rome (Italy); Boersma, C.; Allamandola, L. J., E-mail: puertas@iaa.es [NASA Ames Research Center, Moffett Field, CA 94035-1000 (United States)

2013-06-20

In this paper, we analyze the strong unidentified emission near 3.28 {mu}m in Titan's upper daytime atmosphere recently discovered by Dinelli et al. We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 {mu}m. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) Multiplication-Sign 10{sup 4} particles cm{sup -3}. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is {approx}430 u; the mean area is about 0.53 nm{sup 2}; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

A novel method for simultaneous observations of plasma ion and electron temperatures using a semiconductor-detector array

International Nuclear Information System (INIS)

Cho, T.; Numakura, T.; Kohagura, J.; Hirata, M.; Minami, R.; Watanabe, H.; Sasuga, T.; Nishizawa, Y.; Yoshida, M.; Nagashima, S.; Nakashima, Y.; Ogura, K.; Tamano, T.; Yatsu, K.; Miyoshi, S.

2002-01-01

A new method for a simultaneous observation of both plasma ion and electron temperatures is proposed using one semiconductor-detector array alone. This method will provide a new application of semiconductor-detector arrays for monitoring the key parameter set of nuclear-fusion triple product (i.e., ion temperatures, densities, and confinement time) as well as for clarifying physics mechanisms of energy transport between plasma ions and electrons under various plasma confining conditions. This method is developed on the basis of an alternative 'positive' use of a semiconductor 'dead layer'; that is, an SiO 2 layer is employed as a reliable ultra-thin energy analysis filter for low-energy charge-exchanged neutral particles from plasmas ranging in ion temperatures from 0.1 to several tens of kilo-electron-volts. Using recent fabrication techniques for the thin and uniform SiO 2 layers of the order of tens to hundreds of angstrom, our computer simulation and its experimental verification show the availability of such semiconductors for distinguishing neutral particles (for ion temperatures) from X-rays (for electron temperatures). These are simultaneously emitted from the plasmas into semiconductor detectors; however, we employ their quite different penetration lengths and the resultant different deposition depths and profiles in semiconductor materials. As a result, their output signals are distinguishable for these two different and fundamental species of plasmas

Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

Directory of Open Access Journals (Sweden)

A. B. Galvin

2009-10-01

Full Text Available STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007 which includes minor ion (He, Fe, O kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

Effects of finite coverage on global polarization observables in heavy ion collisions

Science.gov (United States)

Lan, Shaowei; Lin, Zi-Wei; Shi, Shusu; Sun, Xu

2018-05-01

In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented polarization signals for Λ hyperons and possible spin alignment signals for ϕ mesons. Here we discuss the effects of finite coverage on these observables. The results from a multi-phase transport and a toy model both indicate that a pseudorapidity coverage narrower than | η | value for the extracted ϕ-meson ρ00 parameter; thus a finite coverage can lead to an artificial deviation of ρ00 from 1/3. We also show that a finite η and pT coverage affect the extracted pH parameter for Λ hyperons when the real pH value is non-zero. Therefore proper corrections are necessary to reliably quantify the global polarization with experimental observables.

Abundances of neutron-capture elements in G 24-25

DEFF Research Database (Denmark)

Liu, S.; Nissen, Poul Erik; Schuster, W. J.

2012-01-01

for a peculiar halo star G24-25 with [Fe/H] = -1.4 in order to probe its origin. Methods. The equivalent widths of unblended lines are measured from high resolution NOT/FIES spectra and used to derive abundances based on Kurucz model atmospheres. In the case of CH, Pr, Eu, Gd, and Pb lines, the abundances...... are derived by fitting synthetic profiles to the observed spectra. Abundance analyses are performed both relative to the Sun and to a normal halo star G16-20 that has similar stellar parameters as G24-25. Results. We find that G24-25 is a halo subgiant star with an unseen component. It has large...

Observations on small anionic clusters in an electrostatic ion beam trap

International Nuclear Information System (INIS)

Eritt, Markus

2008-01-01

The term atomic cluster relates to compounds of at least two or three atoms. Thereby the physical properties are size dependent and the property transitions between single atoms and bulk material are not always smooth. Ion traps allow it to observe internal cluster properties independent from the influence of external forces. In this work the electron induced decay of singly negatively charged atomic clusters was observed. The dissociation cross section of the clusters is dominated by detachment of the only weakly bound outer electrons. For simple atoms at low electron energies a simple scaling law can be obtained that includes only the binding energies of the valence electrons. Nevertheless for larger sizes theoretical calculations predict so called ''giant resonances'' as dominant decay process in metal clusters. Due to mass limitations in storage rings exist so far only cross section measurements for simple anions and small negative molecules. In this work the electron detachment cross sections of small negatively charged carbon (C n - n=2-12), aluminium (Al n - n=2-7) and silver clusters (Ag n - n=1-11) were measured in an electrostatic ion beam trap. The classical scaling law, including only the binding energies of the valence electrons, turned out to be not sufficient, especially for larger clusters. In order to improve the correlation between measured and predicted values it was proposed to involve the influence of the cluster volume and the specific polarisability induced by long range coulomb interaction. For silver clusters the best agreement was obtained using a combination of the projected area reduced by the polarisability. The existence of ''giant resonances'' could not be confirmed. According to theory for clusters with a broad internal energy distribution, a power-law decay close to 1/time is expected. For some clusters the lifetime behaviour would be strongly quenched by photon emission. The thermionic evaporative decay of anionic aluminium and

Observation of the low-frequency ion acoustic instability in the turbulently heated TRIAM-1 tokamak plasma

Energy Technology Data Exchange (ETDEWEB)

Mitarai, O; Watanabe, T; Nakamura, Y; Nakamura, K; Hiraki, N; Toi, K; Kawai, Y; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1980-12-01

Density fluctuations in the frequency range of several MHz are observed in the turbulently heated TRIAM-1 tokamak plasma by means of a 4 mm microwave scattering method. It is found from the measurement of the dispersion relation that this instability is considered to be the low-frequency ion acoustic instability propagating nearly perpendicular to the toroidal magnetic field.

Ion Mobility Separations of Isomers based upon Long Path Length Structures for Lossless Ion Manipulations Combined with Mass Spectrometry

Energy Technology Data Exchange (ETDEWEB)

Deng, Liulin [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Ibrahim, Yehia M. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Baker, Erin S. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Aly, Noor A. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Hamid, Ahmed M. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Zhang, Xing [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Zheng, Xueyun [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Garimella, Sandilya V. B. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Webb, Ian K. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Prost, Spencer A. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Sandoval, Jeremy A. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Norheim, Randolph V. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Anderson, Gordon A. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Tolmachev, Aleksey V. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA; Smith, Richard D. [Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Blvd Richland, WA 99352 USA

2016-07-01

Mass spectrometry (MS)-based multi-omic measurements, including proteomics, metabolomics, lipidomics, and glycomics, are increasingly transforming our ability to characterize and understand biological systems, but, presently have limitations due to the chemical diversity and range of abundances of biomolecules in complex samples. Advances addressing these challenges increasingly are based upon the ability to quickly separate, react and otherwise manipulate sample components for analysis by MS. Here we report on a new approach using Structures for Lossless Ion Manipulations (SLIM) to enable long serpentine path ion mobility spectrometry (IMS) separations followed by MS analyses. This approach provides previously unachieved mobility biomolecule isomer separations for biomolecular species, in conjunction with more effective ion utilization, and producing a basis for the improved characterization of very small samples.

A high deuterium abundance at redshift z = 0.7.

Science.gov (United States)

Webb, J K; Carswell, R F; Lanzetta, K M; Ferlet, R; Lemoine, M; Vidal-Madjar, A; Bowen, D V

1997-07-17

Of the light elements, the primordial abundance of deuterium relative to hydrogen, (D/H)p, provides the most sensitive diagnostic for the cosmological mass density parameter, omegaB. Recent high-redshift D/H measurements are highly discrepant, although this may reflect observational uncertainties. The larger primordial D/H values imply a low omegaB (requiring the Universe to be dominated by non-baryonic matter), and cause problems for galactic chemical evolution models, which have difficulty in reproducing the steep decline in D/H to the present-day values. Conversely, the lower D/H values measured at high redshift imply an omegaB greater than that derived from 7Li and 4He abundance measurements, and may require a deuterium-abundance evolution that is too low to easily explain. Here we report the first measurement of D/H at intermediate redshift (z = 0.7010), in a gas cloud selected to minimize observational uncertainties. Our analysis yields a value of D/H ((2.0 +/- 0.5) x 10[-4]) which is at the upper end of the range of values measured at high redshifts. This finding, together with other independent observations, suggests that there may be inhomogeneity in (D/H)p of at least a factor of ten.

Development of ion-acoustic double layers through ion-acoustic fluctuations

International Nuclear Information System (INIS)

Sekar, A.N.; Saxena, Y.C.

1985-01-01

Experimental results on the formation of ion acoustic double layers resembling asymmetric ion-holes are presented. In a double plasma device, modified suitably to inject electron beam into the target plasma, modulation of the beam through step potential leads to excitation of ion-acoustic fluctuation. The ion-acoustic fluctuation, growing away from the grids separating source and target plasmas, developed into weak asymmetric ion-acoustic double layer. The observations are in qualitative agreement with theoretical models and computer simulations. (author)

A SOLAR SPECTROSCOPIC ABSOLUTE ABUNDANCE OF ARGON FROM RESIK

International Nuclear Information System (INIS)

Sylwester, J.; Sylwester, B.; Phillips, K. J. H.; Kuznetsov, V. D.

2010-01-01

Observations of He-like and H-like Ar (Ar XVII and Ar XVIII) lines at 3.949 A and 3.733 A, respectively, with the RESIK X-ray spectrometer on the CORONAS-F spacecraft, together with temperatures and emission measures from the two channels of GOES, have been analyzed to obtain the abundance of Ar in flare plasmas in the solar corona. The line fluxes per unit emission measure show a temperature dependence like that predicted from theory and lead to spectroscopically determined values for the absolute Ar abundance, A(Ar) = 6.44 ± 0.07 (Ar XVII) and 6.49 ± 0.16 (Ar XVIII), which are in agreement to within uncertainties. The weighted mean is 6.45 ± 0.06, which is between two recent compilations of the solar Ar abundance and suggests that the photospheric and coronal abundances of Ar are very similar.

Enhanced loss of fast ions during mode conversion ion Bernstein wave heating in TFTR

International Nuclear Information System (INIS)

Darrow, D.S.; Majeski, R.; Fisch, N.J.; Heeter, R.F.; Herrmann, H.W.; Herrmann, M.C.; Zarnstorff, M.C.; Zweben, S.J.

1995-12-01

A strong interaction of fast ions with ion Bernstein waves has been observed in TFTR. It results in a large increase in the fast ion loss rate, and heats the lost particles to several MeV. The lost ions are observed at the passing/trapped boundary and appear to be either DD fusion produced tritons or accelerated D neutral beam ions. Under some conditions, enhanced loss of DT alpha particles is also seen. The losses provide experimental support for some of the elements required for alpha energy channeling

Parameterization of ion-induced nucleation rates based on ambient observations

Directory of Open Access Journals (Sweden)

T. Nieminen

2011-04-01

Full Text Available Atmospheric ions participate in the formation of new atmospheric aerosol particles, yet their exact role in this process has remained unclear. Here we derive a new simple parameterization for ion-induced nucleation or, more precisely, for the formation rate of charged 2-nm particles. The parameterization is semi-empirical in the sense that it is based on comprehensive results of one-year-long atmospheric cluster and particle measurements in the size range ~1–42 nm within the EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions project. Data from 12 field sites across Europe measured with different types of air ion and cluster mobility spectrometers were used in our analysis, with more in-depth analysis made using data from four stations with concomitant sulphuric acid measurements. The parameterization is given in two slightly different forms: a more accurate one that requires information on sulfuric acid and nucleating organic vapor concentrations, and a simpler one in which this information is replaced with the global radiation intensity. These new parameterizations are applicable to all large-scale atmospheric models containing size-resolved aerosol microphysics, and a scheme to calculate concentrations of sulphuric acid, condensing organic vapours and cluster ions.

Calculations on Electron Capture in Low Energy Ion-Molecule Collisions

Energy Technology Data Exchange (ETDEWEB)

Stancil, P.C. [Oak Ridge National Lab., TN (United States); Zygelman, B. [W.M. Keck Lab. for Computational Physics, Univ. of Nevada, Las Vegas, NV (United States); Kirby, K. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

1997-12-31

Recent progress on the application of a quantal, molecular-orbital, close-coupling approach to the calculation of electron capture in collisions of multiply charged ions with molecules is discussed. Preliminary results for single electron capture by N{sup 2+} with H{sub 2} are presented. Electron capture by multiply charged ions colliding with H{sub 2} is an important process in laboratory and astrophysical plasmas. It provides a recombination mechanism for multiply charged ions in x-ray ionized astronomical environments which may have sparse electron and atomic hydrogen abundances. In the divertor region of a tokamak fusion device, charge exchange of impurity ions with H{sub 2} plays a role in the ionization balance and the production of radiative energy loss leading to cooling, X-ray and ultraviolet auroral emission from Jupiter is believed to be due to charge exchange of O and S ions with H{sub 2} in the Jovian atmosphere. Solar wind ions interacting with cometary molecules may have produced the x-rays observed from Comet Hyakutake. In order to model and understand the behavior of these environments, it is necessary to obtain total, electronic state-selective (ESS), and vibrational (or rotational) state-selective (VSS) capture cross sections for collision energies as low as 10 meV/amu to as high as 100 keV/amu in some instances. Fortunately, charge transfer with molecular targets has received considerable experimental attention. Numerous measurements have been made with flow tubes, ion traps, and ion beams. Flow tube and ion trap studies generally provide information on rate coefficients for temperatures between 800 K and 20,000 K. In this article, we report on the progress of our group in implementing a quantum-mechanical Molecular Orbital Close Coupling (MOCC) approach to the study of electron capture by multiply charged ions in collisions with molecules. We illustrate this with a preliminary investigation of Single Electron Capture (SEC) by N{sup 2+} with H

Abundance of boron in Vega and Sirius

International Nuclear Information System (INIS)

Praderie, F.; Boesgaard, A.M.; Milliard, B.; Pitois, M.L.

1977-01-01

High-resolution (0.05 A) observations of the region of the B II resonance line (1362 A) have been made of Vega (AO V) and Sirius (Al V) with the Copernicus satellite. A strong B II feature is present in Vega, but only a weak line, due primarily to V III, is present is Sirius. An upper limit of B/H -12 is derived for Sirius from line-profile fitting. A local thermodynamic equilibrium (LTE) synthesis of the B II blend in Vega results in an abundance ratio B/H=1 x 10 -10 . Calculations of the effects of non--LTE on the line profile show that the LTE abundance would not be increased by more than 50% (B.H=1.5 x 10 -10 ) to account for departures from LTE. The B content of Vega probably represents the cosmic B abundance. The B deficiency in Sirius could result from interaction with the white-dwarf companion at an earlier stage in its evolution or from diffusion processes in the Sirius atmosphere.Difficult observations at 0.10 A resolution of subordinate lines from multiplet (3) of B II at 1624 A show that those lines are not present in Sirius; but the identification of B in Vega appears to be confirmed by the presence of weak lines at 1624 A in this star

THE CORONAL ABUNDANCE ANOMALIES OF M DWARFS

Energy Technology Data Exchange (ETDEWEB)

Wood, Brian E.; Laming, J. Martin [Naval Research Laboratory, Space Science Division, Washington, DC 20375 (United States); Karovska, Margarita, E-mail: brian.wood@nrl.navy.mil [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)

2012-07-01

We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an 'inverse FIP effect' is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

The Coronal Abundance Anomalies of M Dwarfs

Science.gov (United States)

Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

2012-07-01

We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an "inverse FIP effect" is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

THE CORONAL ABUNDANCE ANOMALIES OF M DWARFS

International Nuclear Information System (INIS)

Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

2012-01-01

We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an 'inverse FIP effect' is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

Distribution of known macrozooplankton abundance and biomass in the global ocean

Science.gov (United States)

Moriarty, R.; Buitenhuis, E. T.; Le Quéré, C.; Gosselin, M.-P.

2013-07-01

Macrozooplankton are an important link between higher and lower trophic levels in the oceans. They serve as the primary food for fish, reptiles, birds and mammals in some regions, and play a role in the export of carbon from the surface to the intermediate and deep ocean. Little, however, is known of their global distribution and biomass. Here we compiled a dataset of macrozooplankton abundance and biomass observations for the global ocean from a collection of four datasets. We harmonise the data to common units, calculate additional carbon biomass where possible, and bin the dataset in a global 1 × 1 degree grid. This dataset is part of a wider effort to provide a global picture of carbon biomass data for key plankton functional types, in particular to support the development of marine ecosystem models. Over 387 700 abundance data and 1330 carbon biomass data have been collected from pre-existing datasets. A further 34 938 abundance data were converted to carbon biomass data using species-specific length frequencies or using species-specific abundance to carbon biomass data. Depth-integrated values are used to calculate known epipelagic macrozooplankton biomass concentrations and global biomass. Global macrozooplankton biomass, to a depth of 350 m, has a mean of 8.4 μg C L-1, median of 0.2 μg C L-1 and a standard deviation of 63.5 μg C L-1. The global annual average estimate of macrozooplankton biomass in the top 350 m, based on the median value, is 0.02 Pg C. There are, however, limitations on the dataset; abundance observations have good coverage except in the South Pacific mid-latitudes, but biomass observation coverage is only good at high latitudes. Biomass is restricted to data that is originally given in carbon or to data that can be converted from abundance to carbon. Carbon conversions from abundance are restricted by the lack of information on the size of the organism and/or the absence of taxonomic information. Distribution patterns of global