Measurements of Charging of Apollo 17 Lunar Dust Grains by Electron Impact

NASA Technical Reports Server (NTRS)

Abbas, Mian M.; Tankosic, Dragana; Spann, James F.; Dube, Michael J.

2008-01-01

It is well known since the Apollo missions that the lunar surface is covered with a thick layer of micron size dust grains with unusually high adhesive characteristics. The dust grains observed to be levitated and transported on the lunar surface are believed to have a hazardous impact on the robotic and human missions to the Moon. The observed dust phenomena are attributed to the lunar dust being charged positively during the day by UV photoelectric emissions, and negatively during the night by the solar wind electrons. The current dust charging and the levitation models, however, do not fully explain the observed phenomena, with the uncertainty of dust charging processes and the equilibrium potentials of the individual dust grains. It is well recognized that the charging properties of individual dust grains are substantially different from those determined from measurements made on bulk materials that are currently available. An experimental facility has been developed in the Dusty Plasma Laboratory at MSFC for investigating the charging and optical properties of individual micron/sub-micron size positively or negatively charged dust grains by levitating them in an electrodynamic balance in simulated space environments. In this paper, we present the laboratory measurements on charging of Apollo 17 individual lunar dust grains by a low energy electron beam. The charging rates and the equilibrium potentials produced by direct electron impact and by secondary electron emission process are discussed.

Electrostatic Charging of Lunar Dust by UV Photoelectric Emissions and Solar Wind Electrons

NASA Technical Reports Server (NTRS)

Abbas, Mian M.; Tankosic, Dragana; Spann, James f.; LeClair, Andre C.; Dube, Michael J.

2008-01-01

The ubiquitous presence of dust in the lunar environment with its high adhesive characteristics has been recognized to be a major safety issue that must be addressed in view of its hazardous effects on robotic and human exploration of the Moon. The reported observations of a horizon glow and streamers at the lunar terminator during the Apollo missions are attributed to the sunlight scattered by the levitated lunar dust. The lunar surface and the dust grains are predominantly charged positively by the incident UV solar radiation on the dayside and negatively by the solar wind electrons on the night-side. The charged dust grains are levitated and transported over long distances by the established electric fields. A quantitative understanding of the lunar dust phenomena requires development of global dust distribution models, based on an accurate knowledge of lunar dust charging properties. Currently available data of lunar dust charging is based on bulk materials, although it is well recognized that measurements on individual dust grains are expected to be substantially different from the bulk measurements. In this paper we present laboratory measurements of charging properties of Apollo 11 & 17 dust grains by UV photoelectric emissions and by electron impact. These measurements indicate substantial differences of both qualitative and quantitative nature between dust charging properties of individual micron/submicron sized dust grains and of bulk materials. In addition, there are no viable theoretical models available as yet for calculation of dust charging properties of individual dust grains for both photoelectric emissions and electron impact. It is thus of paramount importance to conduct comprehensive measurements for charging properties of individual dust grains in order to develop realistic models of dust processes in the lunar atmosphere, and address the hazardous issues of dust on lunar robotic and human missions.

Laboratory Studies of Charging Properties of Dust Grains in Astrophysical/Planetary Environments

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2012-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper we focus on charging of individual micron/submicron dust grains by processes that include: (a) UV photoelectric emissions involving incident photon energies higher than the work function of the material and b) electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). It is well accepted that the charging properties of individual micron/submicron size dust grains are expected to be substantially different from the bulk materials. However, no viable models for calculation of the charging properties of individual micron size dust grains are available at the present time. Therefore, the photoelectric yields, and secondary electron emission yields of micron-size dust grains have to be obtained by experimental methods. Currently, very limited experimental data are available for charging of individual micron-size dust grains. Our experimental results, obtained on individual, micron-size dust grains levitated in an electrodynamic balance facility (at NASA-MSFC), show that: (1) The measured photoelectric yields are substantially higher than the bulk values given in the literature and indicate a particle size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains; (2) dust charging by low energy electron impact is a complex process. Also, our measurements indicate that

Charging of dust grains in a plasma with negative ions

NASA Astrophysics Data System (ADS)

Kim, Su-Hyun; Merlino, Robert L.

2006-05-01

The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended SF6 is admitted into the vacuum system. The relatively cold (Te≈0.2eV ) readily attach to SF6 molecules to form SF6- negative ions. Calculations of the dust charge indicate that for electrons, negative ions, and positive ions of comparable temperatures, the charge (or surface potential) of the dust can be positive if the positive ion mass is smaller than the negative ion mass and if ɛ, the ratio of the electron to positive ion density, is sufficiently small. The K+ positive ions (mass 39amu) and SF6- negative ions (mass 146amu), and also utilizes a rotating cylinder to dispense dust into the plasma column. Analysis of the current-voltage characteristics of a Langmuir probe in the dusty plasma shows evidence for the reduction in the (magnitude) of the negative dust charge and the transition to positively charged dust as the relative concentration of the residual electrons is reduced. Some remarks are offered concerning experiments that could become possible in a dusty plasma with positive grains.

Image charge effects on electron capture by dust grains in dusty plasmas.

PubMed

Jung, Y D; Tawara, H

2001-07-01

Electron-capture processes by negatively charged dust grains from hydrogenic ions in dusty plasmas are investigated in accordance with the classical Bohr-Lindhard model. The attractive interaction between the electron in a hydrogenic ion and its own image charge inside the dust grain is included to obtain the total interaction energy between the electron and the dust grain. The electron-capture radius is determined by the total interaction energy and the kinetic energy of the released electron in the frame of the projectile dust grain. The classical straight-line trajectory approximation is applied to the motion of the ion in order to visualize the electron-capture cross section as a function of the impact parameter, kinetic energy of the projectile ion, and dust charge. It is found that the image charge inside the dust grain plays a significant role in the electron-capture process near the surface of the dust grain. The electron-capture cross section is found to be quite sensitive to the collision energy and dust charge.

Random dust charge fluctuations in the near-Enceladus plasma

NASA Astrophysics Data System (ADS)

Yaroshenko, V. V.; Lühr, H.

2014-08-01

Stochastic dust charge fluctuations have been studied in the light of Cassini data on the near-Enceladus plasma environment. Estimates of fluctuation time scales showed that this process can be of importance for the grains emanating from the icy moon. The analytical modeling predicts that in the dust-loaded Enceladus plasma a majority of the grains acquires fluctuating negative charges, but there might appear a minority of positively charged particles. The probability of this effect mostly depends on the ratio of the dust/plasma number densities. Our findings appear to be supported by the available Cassini Plasma Spectrometer measurements of the charged grain distributions during E3 and E5 plume flybys. The theoretical results can also provide new insights into the intricate process of particle dynamics in the inner magnetosphere.

Attraction of likely charged nano-sized grains in dust-electron plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vishnyakov, Vladimir I., E-mail: eksvar@ukr.net

2016-01-15

Dust-electron plasma, which contains only the dust grains and electrons, emitted by them, is studied. Assumption of almost uniform spatial electrons distribution, which deviates from the uniformity only near the dust grains, leads to the grain charge division into two parts: first part is the individual for each grain “visible” charge and the second part is the common charge of the neutralized background. The visible grain charge can be both negative and positive, while the total grain charge is only positive. The attraction of likely charged grains is possible, because the grain interaction is determined by the visible charges. Themore » equilibrium state between attraction and repulsion of grains is demonstrated.« less

The effect of dust charge variation, due to ion flow and electron depletion, on dust levitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Land, Victor; Douglass, Angela; Qiao Ke

2011-11-29

Using a fluid model, the plasma densities, electron temperature and ion Mach number in front of a powered electrode in different plasma discharges is computed. The dust charge is computed using OML theory for Maxwellian electrons and ions distributed according to a shifted-Maxwellian. By assuming force balance between gravity and the electrostatic force, the dust levitation height is obtained. The importance of the dust charge variation is investigated.

Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2012-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.

Saharan dust plume charging observed over the UK

NASA Astrophysics Data System (ADS)

Harrison, R. Giles; Nicoll, Keri A.; Marlton, Graeme J.; Ryder, Claire L.; Bennett, Alec J.

2018-05-01

A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s‑1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (‑8.0 ± 3.3) nC m‑2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

Reduction of airborne radioactive dust by means of a charged water spray.

PubMed

Bigu, J; Grenier, M G

1989-07-01

An electrostatic precipitator based on charged water spray technology has been used in an underground uranium mine to control long-lived radioactive dust and short-lived aerosol concentration in a mine gallery where dust from a rock breaking/ore transportation operation was discharged. Two main sampling stations were established: one upstream of the dust precipitator and one downstream. In addition, dust samplers were placed at different locations between the dust discharge and the end of the mine gallery. Long-lived radioactive dust was measured using cascade impactors and nylon cyclone dust samplers, and measurement of the radioactivity on the samples was carried out by conventional methods. Radon and thoron progeny were estimated using standard techniques. Experiments were conducted under a variety of airflow conditions. A maximum radioactive dust reduction of about 40% (approximately 20% caused by gravitational settling) at a ventilation rate of 0.61 m3/sec was obtained as a result of the combined action of water scrubbing and electrostatic precipitation by the charged water spray electrostatic precipitator. This represents the optimum efficiency attained within the range of ventilation rates investigated. The dust reduction efficiency of the charged water spray decreased with increasing ventilation rate, i.e., decreasing air residence time, and hence, reduced dust cloud/charged water droplets mixing time.

Complex Role of Secondary Electron Emissions in Dust Grain Charging in Space Environments: Measurements on Apollo 11 and 17 Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; Spann, J. F.; LeClair, A. C.

2010-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions. Knowledge of the dust grain charges and equilibrium potentials is important for understanding of a variety of physical and dynamical processes in the interstellar medium (ISM), and heliospheric, interplanetary, planetary, and lunar environments. The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. It has been well recognized that the charging properties of individual micron/submicron size dust grains are expected to be substantially different from the corresponding values for bulk materials and theoretical models. In this paper we present experimental results on charging of individual dust grains selected from Apollo 11 and Apollo 17 dust samples by exposing them to mono-energetic electron beams in the 10- 400 eV energy range. The charging rates of positively and negatively charged particles of approximately 0.2 to 13 microns diameters are discussed in terms of the secondary electron emission (SEE) process, which is found to be a complex charging process at electron energies as low as 10-25 eV, with strong particle size dependence. The measurements indicate substantial differences between dust charging properties of individual small size dust grains and of bulk materials.

Mars dust storms - Interannual variability and chaos

NASA Technical Reports Server (NTRS)

Ingersoll, Andrew P.; Lyons, James R.

1993-01-01

The hypothesis is that the global climate system, consisting of atmospheric dust interacting with the circulation, produces its own interannual variability when forced at the annual frequency. The model has two time-dependent variables representing the amount of atmospheric dust in the northern and southern hemispheres, respectively. Absorption of sunlight by the dust drives a cross-equatorial Hadley cell that brings more dust into the heated hemisphere. The circulation decays when the dust storm covers the globe. Interannual variability manifests itself either as a periodic solution in which the period is a multiple of the Martian year, or as an aperiodic (chaotic) solution that never repeats. Both kinds of solution are found in the model, lending support to the idea that interannual variability is an intrinsic property of the global climate system. The next step is to develop a hierarchy of dust-circulation models capable of being integrated for many years.

Positive column of a glow discharge in neon with charged dust grains (a review)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polyakov, D. N., E-mail: cryolab@ihed.ras.ru; Shumova, V. V.; Vasilyak, L. M.

The effect of charged micron-size dust grains (microparticles) on the electric parameters of the positive column of a low-pressure dc glow discharge in neon has been studied experimentally and numerically. Numerical analysis is carried out in the diffusion-drift approximation with allowance for the interaction of dust grains with metastable neon atoms. In a discharge with a dust grain cloud, the longitudinal electric field increases. As the number density of dust grains in an axisymmetric cylindrical dust cloud rises, the growth of the electric field saturates. It is shown that the contribution of metastable atoms to ionization is higher in amore » discharge with dust grains, in spite of the quenching of metastable atoms on dust grains. The processes of charging of dust grains and the dust cloud are considered. As the number density of dust grains rises, their charge decreases, while the space charge of the dust cloud increases. The results obtained can be used in plasma technologies involving microparticles.« less

Laboratory Measurements of Charging of Apollo 17 Lunar Dust Grains by Low Energy Electrons

NASA Technical Reports Server (NTRS)

Abbas, Mian M.; Tankosic, Dragana; Spann, James F.; Dube, Michael J.; Gaskin, Jessica

2007-01-01

It is well recognized that the charging properties of individual micron/sub-micron size dust grains by various processes are expected to be substantially different from the currently available measurements made on bulk materials. Solar UV radiation and the solar wind plasma charge micron size dust grains on the lunar surface with virtually no atmosphere. The electrostatically charged dust grains are believed to be levitated and transported long distances over the lunar terminator from the day to the night side. The current models do not fully explain the lunar dust phenomena and laboratory measurements are needed to experimentally determine the charging properties of lunar dust grains. An experimental facility has been developed in the Dusty Plasma Laboratory at NASA Marshall Space Flight Center MSFC for investigating the charging properties of individual micron/sub-micron size positively or negatively charged dust grains by levitating them in an electrodynamic balance in simulated space environments. In this paper, we present laboratory measurements on charging of Apollo 17 individual lunar dust grains by low energy electron beams in the 5-100 eV energy range. The measurements are made by levitating Apollo 17 dust grains of 0.2 to 10 micrometer diameters, in an electrodynamic balance and exposing them to mono-energetic electron beams. The charging rates and the equilibrium potentials produced by direct electron impact and by secondary electron emission processes are discussed.

The linear and non-linear characterization of dust ion acoustic mode in complex plasma in presence of dynamical charging of dust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharjee, Saurav, E-mail: sauravtsk.bhattacharjee@gmail.com; Das, Nilakshi

2015-10-15

A systematic theoretical investigation has been carried out on the role of dust charging dynamics on the nature and stability of DIA (Dust Ion Acoustic) mode in complex plasma. The study has been made for both linear and non-linear scale regime of DIA mode. The observed results have been characterized in terms of background plasma responses towards dust surface responsible for dust charge fluctuation, invoking important dusty plasma parameters, especially the ion flow speed and dust size. The linear analyses confirm the nature of instability in DIA mode in presence of dust charge fluctuation. The instability shows a damping ofmore » DIA mode in subsonic flow regime followed by a gradual growth in instability in supersonic limit of ion flow. The strength of non-linearity and their existence domain is found to be driven by different dusty plasma parameters. As dust is ubiquitous in interstellar medium with plasma background, the study also addresses the possible effect of dust charging dynamics in gravito-electrostatic characterization and the stability of dust molecular clouds especially in proto-planetary disc. The observations are influential and interesting towards the understanding of dust settling mechanism and formation of dust environments in different regions in space.« less

Possible method for diagnosing waves in dusty plasmas with magnetized charged dust particulates

NASA Astrophysics Data System (ADS)

Rosenberg, M.; Shukla, P. K.

2005-05-01

We discuss theoretically a possible method for diagnosing some features of dust wave behavior in a magnetized plasma containing small (tens of nm) charged dust grains whose motion is magnetized. It is easier to magnetize a small dust particle because its charge-to-mass ratio increases as its size decreases. However, it is more difficult to use the backscattering of light from the dust as a diagnostic as the dust size decreases below the diffraction limit. The idea proposed here is to measure the reduction in transmitted UV or optical light intensity due to enhanced extinction by small metal dust particles that have surface plasmon resonances at those wavelengths. Such measurements could indicate the spatial location of the dust density compressions or rarefactions, which may yield information on the dust wave behavior, or perhaps even charged dust transport. Parameters that may be relevant to possible laboratory dusty plasma experiments are discussed.

Secondary Electron Emission from Dust and Its Effect on Charging

NASA Astrophysics Data System (ADS)

Saikia, B. K.; Kakati, B.; Kausik, S. S.; Bandyopadhyay, M.

2011-11-01

Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungsten filaments and the permanent magnetic cage [1], which is grounded. The magnetic cage has a full line cusped magnetic field geometry used to confine the plasma elements. A cylindrical Langmuir probe is used to study the plasma parameters in various discharge conditions. The charge accumulated on the dust particles is calculated using the capacitance model and the dust current is measured by the combination of a Faraday cup and an electrometer at different discharge conditions. It is found Secondary electron emission from dust having low emission yield effects the charging of dust particles in presence of high energetic electrons.

Dust Grain Charge in the Lunar Environment

NASA Astrophysics Data System (ADS)

Vaverka, Jakub; Richterova, Ivana; Vysinka, Marek; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek

2014-05-01

Interaction of a lunar surface with solar wind and magnetosphere plasmas leads to it charging by several processes as photoemission, a collection of primary particles and secondary electron emission. Nevertheless, charging of the lunar surface is complicated by a presence of crustal magnetic anomalies with can generate a "mini-magnetosphere" capable for more or less complete shielding the surface. On the other hand, shielding of solar light and plasma particles by rocks and craters can also locally influence the surface potential as well as a presence of a plasma wake strongly changes this potential at the night side of the Moon. A typical surface potential varies from slightly positive (dayside) to negative values of the order of several hundred of volts (night side). At the night side, negative potentials can reach -4 kV during solar energetic particle (SEP) events. Recent measurements of the surface potential by Lunar Prospector and Artemis spacecraft have shown surprisingly high negative dayside surface potentials (-500 V) during the magnetotail crossings as well as the positive surface potential higher than 100 V. One possible explanation is its non-monotonic profile above a surface where the potential minimum is formed by the space charge. Dust grains presented in this complicated environment are also charged by similar processes as the lunar surface. A strong dependence of the secondary electron yield on the grain size can significantly influence dust charging mainly in the Earth's plasma sheet where an equilibrium grain potential can by different than the surface potential and can reach even the opposite sign. This process can lead to levitation of dust above a surface observed by the Surveyor spacecraft.

SEP events and wake region lunar dust charging with grain radii

NASA Astrophysics Data System (ADS)

Chandran, S. B. Rakesh; Rajesh, S. R.; Abraham, A.; Renuka, G.; Venugopal, Chandu

2017-01-01

Our lunar surface is exposed to all kinds of radiations from the Sun, since it lacks a global magnetic field. Like lunar surface, dust particles are also exposed to plasmas and UV radiation and, consequently they carry electrostatic charges. During Solar Energetic Particle events (SEPs) secondary electron emission plays a vital role in charging of lunar dusts. To study the lunar dust charging during SEPs on lunar wake region, we derived an expression for lunar dust potential and analysed how it varies with different electron temperatures and grain radii. Because of high energetic solar fluxes, secondary yield (δ) values reach up to 2.3 for 0.5 μm dust grain. We got maximum yield at an energy of 550 eV which is in well agreement with lunar sample experimental observation (Anderegg et al., 1972). It is observed that yield value increases with electron energy, reaches to a maximum value and then decreases. During SEPs heavier dust grains show larger yield values because of the geometry of the grains. On the wake region, the dust potential reaches up to -497 V for 0.5 μm dust grain. The electric field of these grains could present a significant threat to manned and unmanned missions to the Moon.

Flow stagnation at Enceladus: The effects of neutral gas and charged dust

NASA Astrophysics Data System (ADS)

Omidi, N.; Tokar, R. L.; Averkamp, T.; Gurnett, D. A.; Kurth, W. S.; Wang, Z.

2012-06-01

Enceladus is one of Saturn's most active moons. It ejects neutral gas and dust particles from its southern plumes with velocities of hundreds of meters per second. The interaction between the ejected material and the corotating plasma in Saturn's magnetosphere leads to flow deceleration in ways that remain to be understood. The most effective mechanism for the interaction between the corotating plasma and the neutral gas is charge exchange which replaces the hotter corotating ions with nearly stationary cold ions that are subsequently accelerated by the motional electric field. Dust particles in the plume can become electrically charged through electron absorption and couple to the plasma through the motional electric field. The objective of this study is to determine the level of flow deceleration associated with each of these processes using Cassini RPWS dust impact rates, Cassini Plasma Spectrometer (CAPS) plasma data, and 3-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations. Hybrid simulations show that the degree of flow deceleration by charged dust varies considerably with the spatial distribution of dust particles. Based on the RPWS observations of dust impacts during the E7 Cassini flyby of Enceladus, we have constructed a dust model consisting of multiple plumes. Using this model in the hybrid simulation shows that when the dust density is high enough for complete absorption of electrons at the point of maximum dust density, the corotating flow is decelerated by only a few km/s. This is not sufficient to account for the CAPS observation of flow stagnation in the interaction region. On the other hand, charge exchange with neutral gas plumes similar to the modeled dust plumes but with base (plume opening) densities of ˜109 cm-3 result in flow deceleration similar to that observed by CAPS. The results indicate that charge exchange with neutral gas is the dominant mechanism for flow deceleration at Enceladus.

CHARGING AND COAGULATION OF DUST IN PROTOPLANETARY PLASMA ENVIRONMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, L. S.; Land, V.; Hyde, T. W., E-mail: lorin_matthews@baylor.edu

2012-01-01

Combining a particle-particle, particle-cluster, and cluster-cluster agglomeration model with an aggregate charging model, the coagulation and charging of dust particles in plasma environments relevant for protoplanetary disks have been investigated, including the effect of electron depletion in high dust density environments. The results show that charged aggregates tend to grow by adding small particles and clusters to larger particles and clusters, and that cluster-cluster aggregation is significantly more effective than particle-cluster aggregation. Comparisons of the grain structure show that with increasing aggregate charge the compactness factor, {phi}{sub {sigma}}, decreases and has a narrower distribution, indicating a fluffier structure. Neutral aggregatesmore » are more compact, with larger {phi}{sub {sigma}}, and exhibit a larger variation in fluffiness. Overall, increased aggregate charge leads to larger, fluffier, and more massive aggregates.« less

Studies on plasma profiles and its effect on dust charging in hydrogen plasma

NASA Astrophysics Data System (ADS)

Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhay, M.

2010-02-01

Plasma profiles and its influence on dust charging are studied in hydrogen plasma. The plasma is produced in a high vacuum device by a hot cathode discharge method and is confined by a cusped magnetic field cage. A cylindrical Espion advanced Langmuir probe having 0.15 mm diameter and 10.0 mm length is used to study the plasma parameters for various discharge conditions. Optimum operational discharge parameters in terms of charging of the dust grains are studied. The charge on the surface of the dust particle is calculated from the capacitance model and the current by the dust grains is measured by the combination of a Faraday cup and an electrometer. Unlike our previous experiments in which dust grains were produced in-situ, here a dust dropper is used to drop the dust particles into the plasma.

LUNAR DUST GRAIN CHARGING BY ELECTRON IMPACT: COMPLEX ROLE OF SECONDARY ELECTRON EMISSIONS IN SPACE ENVIRONMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, M. M.; Craven, P. D.; LeClair, A. C.

2010-08-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions (SEEs). The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. Knowledge of the dust grain charges and equilibrium potentials is important for understanding a variety of physical and dynamical processes in the interstellar medium, and heliospheric, interplanetary/planetary, and lunar environments. It has been well recognized that the charging properties of individualmore » micron-/submicron-size dust grains are expected to be substantially different from the corresponding values for bulk materials. In this paper, we present experimental results on the charging of individual 0.2-13 {mu}m size dust grains selected from Apollo 11 and 17 dust samples, and spherical silica particles by exposing them to mono-energetic electron beams in the 10-200 eV energy range. The dust charging process by electron impact involving the SEEs discussed is found to be a complex charging phenomenon with strong particle size dependence. The measurements indicate substantial differences between the polarity and magnitude of the dust charging rates of individual small-size dust grains, and the measurements and model properties of corresponding bulk materials. A more comprehensive plan of measurements of the charging properties of individual dust grains for developing a database for realistic models of dust charging in astrophysical and lunar environments is in progress.« less

Lunary Dust Grain Charging by Electron Impact: Complex Role of Secondary Electron Emissions in Space Environments

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; Crave, P. D.; LeClair, A.; Spann, J. F.

2010-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions (SEES). The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. Knowledge of the dust grain charges and equilibrium potentials is important for understanding a variety of physical and dynamical processes in the interstellar medium, and heliospheric, interplanetary/ planetary, and lunar environments. It has been well recognized that the charging properties of individual micron-/submicron-size dust grains are expected to be substantially different from the corresponding values for bulk materials. In this paper, we present experimental results on the charging of individual 0.2-13 m size dust grains selected from Apollo 11 and 17 dust samples, and spherical silica particles by exposing them to mono-energetic electron beams in the 10-200 eV energy range. The dust charging process by electron impact involving the SEES discussed is found to be a complex charging phenomenon with strong particle size dependence. The measurements indicate substantial differences between the polarity and magnitude of the dust charging rates of individual small-size dust grains, and the measurements and model properties of corresponding bulk materials. A more comprehensive plan of measurements of the charging properties of individual dust grains for developing a database for realistic models of dust charging in astrophysical and lunar environments is in progress.

Laboratory Studies on the Charging of Dust Grains in a Plasma

NASA Astrophysics Data System (ADS)

Xu, Wenjun

1993-01-01

The charging of dust grains by the surrounding plasma is studied in a dusty plasma device (DPD) (Xu, W., B. Song, R. L. Merlino, and N. D'Angelo, Rev. Sci. Instrum., 63, 5266, 1992). The dusty plasma device consists of a rotating-drum dust dispersal device used in conjunction with an existing Q-machine, to produce extended, steady state, magnetized plasma columns. The dust density in the dust chamber is controlled by the drum rotation speed. The device is capable of generating a dusty plasma in which as much as about 90% of the negative charge is attached to the dust grains of 1-10mu m size. Measurements of the dust parameter eta, the percentage of negative charge on free electrons in the dusty plasma, are presented. The dust parameter eta is found to depend on the rotational speed of the dust chamber, plasma density and the type and size of different dust. The dust parameter eta is calculated from a pair of Langmuir curves taken with and without dust under the same conditions. The operation of the dust chamber as described above has been confirmed by the agreement between the measurements of eta and the direct mechanical measurements consisting of weighing dust samples collected within the rotation dust chamber, at different rotation rates. By varying the ratio d/lambda_ {rm D} between the intergrain distance and the plasma Debye length, the effects predicted by Goertz and Ip (Goertz, C. K., and W-H. Ip, Geophys. Res. Lett., 11, 349, 1984), and subsequently reanalyzed in a more general fashion by Whipple et al. (Whipple, E. C., T. G. Northrop, and D. A. Mendis, J. Geophys. Rev., 90, 7405, 1985), as "isolated" dust grains become "closely packed" grains, have been demonstrated experimentally (Xu, W., N. D'Angelo, and R. L. Merlino, J. Geophys. Rev., 98, 7843, 1993). Similar results are presented and compared for two types of dust, kaolin and Al_2O _3, which have been studied in the experiment.

Effect of energetic electrons on dust charging in hot cathode filament discharge

NASA Astrophysics Data System (ADS)

Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

2011-03-01

The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

Experimental Investigation of Charging Properties of Interstellar Type Silica Dust Grains by Secondary Electron Emissions

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2013-01-01

The dust charging by electron impact is an important dust charging processes in astrophysical and planetary environments. Incident low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grains, leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available classical theoretical models for calculations of SEE yields are generally applicable for neutral, planar, or bulk surfaces. These models, however, are not valid for calculations of the electron impact charging properties of electrostatically charged micron/submicron-size dust grains in astrophysical environments. Rigorous quantum mechanical models are not yet available, and the SEE yields have to be determined experimentally for development of more accurate models for charging of individual dust grains. At the present time, very limited experimental data are available for charging of individual micron-size dust grains, particularly for low energy electron impact. The experimental results on individual, positively charged, micron-size lunar dust grains levitated carried out by us in a unique facility at NASA-MSFC, based on an electrodynamic balance, indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (Abbas et al, 2010, 2012). In this paper, we discuss SEE charging properties of individual micron-size silica microspheres that are believed to be analogs of a class of interstellar dust grains. The measurements indicate charging of the 0.2m silica particles when exposed to 25 eV electron beams and discharging when exposed to higher energy electron beams. Relatively large size silica particles (5.2-6.82m) generally discharge to lower equilibrium potentials at both electron energies

Interannual variability of global dust storms on Mars.

PubMed

Haberle, R M

1986-10-24

Global dust storms on Mars occur in some years but not in others. If the four Mars years of Viking data are representative, some distinguishing characteristics can be inferred. In years with global dust storms, dust is raised in the southern hemisphere and spread over much of the planet by an intensified Hadley circulation. In years without global dust storms, dust is raised in the northern hemisphere by relatively active mid-latitude storm systems but does not spread globally. In both cases the dusty season is winter in the north. Assuming that the cross-equatorial Hadley circulation plays a key role in the onset of global dust storms, it is shown from numerical simulations that a northen hemisphere dust haze weakens its intensity and, hence, its contribution to the surface stress in the southern hemisphere. This, in turn, reduces the possibility of global dust storm development. The interannual variability is therefore the result either of a competition between circulations in opposite hemispheres, in which case the variability has a random component, or it is the result of the cycling of dust between hemispheres, in which case the variability is related to the characteristics of global dust storms themselves.

Child-Langmuir flow in a planar diode filled with charged dust impurities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang Xiaoyan; Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44870 Bochum; Shukla, Padma Kant

The Child-Langmuir (CL) flow in a planar diode in the presence of stationary charged dust particles is studied. The limiting electron current density and other diode properties, such as the electrostatic potential, the electron flow speed, and the electron number density, are calculated analytically. A comparison of the results with the case without dust impurities reveals that the diode parameters mentioned above decrease with the increase of the dust charge density. Furthermore, it is found that the classical scaling of D{sup -2} (the gap spacing D) for the CL current density remains exactly valid, while the scaling of V{sup 3/2}more » (the applied gap voltage V) can be a good approximation for low applied gap voltage and for low dust charge density.« less

High negative charge of a dust particle in a hot cathode discharge.

PubMed

Arnas, C; Mikikian, M; Doveil, F

1999-12-01

Dust particle levitation experiments in a plasma produced by a hot filament discharge, operating at low argon pressure, are presented. The basic characteristics of a dust grain trapped in a plate sheath edge in these experimental conditions are reported. Taking into account the sheath potential profiles measured with a differential emissive probe diagnostic, the forces applied to an isolated dust grain can be determined. Two different experimental methods yield approximately the same value for the dust charge. The observed high negative charge is mainly due to the contribution of the primary electrons emitted by the filaments as predicted by a simple model.

Laboratory Measurements on Charging of Individual Micron-Size Apollo-11 Dust Grains by Secondary Electron Emissions

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2012-01-01

Observations made during Apollo missions, as well as theoretical models indicate that the lunar surface and dust grains are electrostatically charged, levitated and transported. Lunar dust grains are charged by UV photoelectric emissions on the lunar dayside and by the impact of the solar wind electrons on the nightside. The knowledge of charging properties of individual lunar dust grains is important for developing appropriate theoretical models and mitigating strategies. Currently, very limited experimental data are available for charging of individual micron-size size lunar dust grains in particular by low energy electron impact. However, experimental results based on extensive laboratory measurements on the charging of individual 0.2-13 micron size lunar dust grains by the secondary electron emissions (SEE) have been presented in a recent publication. The SEE process of charging of micron-size dust grains, however, is found to be very complex phenomena with strong particle size dependence. In this paper we present some examples of the complex nature of the SEE properties of positively charged individual lunar dust grains levitated in an electrodynamic balance (EDB), and show that they remain unaffected by the variation of the AC field employed in the above mentioned measurements.

Charging and shielding of a non-spherical dust grain in a plasma

NASA Astrophysics Data System (ADS)

Zhao, L.; Delzanno, G.

2013-12-01

The interaction of objects with a plasma is a classic problem of plasma physics. Originally, it was investigated in the framework of probe theory but more recently its interest has grown in connection with space and complex or dusty plasmas. It is customary to assume that the dust grains are spherical, and theories such as the Orbital Motion Limited (OML) theory are usually applied to calculate the dust charge. However, in nature dust grains have a variety of sizes and shapes. It is therefore natural to ask about the influence of the dust shape on the charging and shielding process. In order to answer this question, we study the charging and shielding of a non-spherical dust grain immersed in a Maxwellian plasma at rest. We consider prolate ellipsoids, varying parametrically the aspect ratio while keeping the surface area constant. The study is conducted with CPIC [1], a newly developed Particle-In-Cell code in curvilinear geometry that conforms to objects of arbitrary shape. For a plasma with temperature ratio equal to unity and for a dust grain with characteristic size of the order of the Debye length, it is shown that the floating potential has a very weak dependence on the geometry, while the charge on the grain increases by a factor of three when the aspect ratio changes from one (a sphere) to hundred (a needle-like ellipsoid). These results are consistent with the higher capacitance of ellipsoidal dust grains, but also indicate that the screening length depends on the geometry. Scaling studies of the dependence of the charging time and screening length on the aspect ratio and plasma conditions are presented, including theoretical considerations to support the numerical results. [1] G.L. Delzanno, et al, ';CPIC: a curvilinear Particle-In-Cell code for plasma-material interaction studies', under review.

The Challenge of Incorporating Charged Dust in the Physics of Flowing Plasma Interactions

NASA Astrophysics Data System (ADS)

Jia, Y.; Russell, C. T.; Ma, Y.; Lai, H.; Jian, L.; Toth, G.

2013-12-01

The presence of two oppositely charged species with very different mass ratios leads to interesting physical processes and difficult numerical simulations. The reconnection problem is a classic example of this principle with a proton-electron mass ratio of 1836, but it is not the only example. Increasingly we are discovering situations in which heavy, electrically charged dust particles are major players in a plasma interaction. The mass of a 1mm dust particle is about 2000 proton masses and of a 10 mm dust particle about 2 million proton masses. One example comes from planetary magnetospheres. Charged dust pervades Enceladus' southern plume. The saturnian magnetospheric plasma flows through this dusty plume interacting with the charged dust and ionized plume gas. Multiple wakes are seen downstream. The flow is diverted in one direction. The field aligned-current systems are elsewhere. How can these two wake features be understood? Next we have an example from the solar wind. When asteroids collide in a disruptive collision, the solar wind strips the nano-scale charged dust from the debris forming a dusty plasma cloud that may be over 106km in extent and containing over 100 million kg of dust accelerated to the solar wind speed. How does this occur, especially as rapidly as it appears to happen? In this paper we illustrate a start on understanding these phenomena using multifluid MHD simulations but these simulations are only part of the answer to this complex problem that needs attention from a broader range of the community.

Polycyclic Aromatic Hydrocarbons in Residential Dust: Sources of Variability

PubMed Central

Metayer, Catherine; Petreas, Myrto; Does, Monique; Buffler, Patricia A.; Rappaport, Stephen M.

2013-01-01

Background: There is interest in using residential dust to estimate human exposure to environmental contaminants. Objectives: We aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential dust and provide guidance for investigators who plan to use residential dust to assess exposure to PAHs. Methods: We collected repeat dust samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography–mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four components and to identify sources of variability. Results: Median concentrations for individual PAHs ranged from 10 to 190 ng/g of dust. For each PAH, total variance was apportioned into regional variability (1–9%), intraregional between-household variability (24–48%), within-household variability over time (41–57%), and within-sample analytical variability (2–33%). Regional differences in PAH dust levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between dust sample collections was at least 6 years in duration. Conclusions: Our findings indicate that it may be feasible to use residential dust for retrospective assessment of PAH exposures in studies of health effects. PMID:23461863

The effect of the ambient plasma conditions on the variation of charge on dust grains

NASA Astrophysics Data System (ADS)

Chakraborty, M.; Kausik, S. S.; Saikia, B. K.; Kakati, M.; Bujarbarua, S.

2003-02-01

An experimental study has been performed into the variation of charge on dust grains with change in the ambient plasma conditons. A dust beam containing submicron sized silver grains was passed through plasma. The dust grains were charged by the plasma particles as well as by primary electrons from the filament. An increase in the filament current increased both the plasma density and the number density of the primary electrons. The grain charge was found out both from the deflection of the dust grains and also from the floating potential. The experimental observations shows that the secondary emission caused by the primary electrons significantly influenced and played a prominent role in the establishment of charge on the grains.

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

NASA Astrophysics Data System (ADS)

Kausik, S. S.; Kakati, B.; Saikia, B. K.

2013-05-01

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (˜pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

Modeling the total dust production of Enceladus from stochastic charge equilibrium and simulations

NASA Astrophysics Data System (ADS)

Meier, Patrick; Motschmann, Uwe; Schmidt, Jürgen; Spahn, Frank; Hill, Thomas W.; Dong, Yaxue; Jones, Geraint H.; Kriegel, Hendrik

2015-12-01

Negatively and positively charged nano-sized ice grains were detected in the Enceladus plume by the Cassini Plasma Spectrometer (CAPS). However, no data for uncharged grains, and thus for the total amount of dust, are available. In this paper we estimate this population of uncharged grains based on a model of stochastic charging in thermodynamic equilibrium and on the assumption of quasi-neutrality in the plasma-dust system. This estimation is improved upon by combining simulations of the dust component of the plume and simulations for the plasma environment into one self-consistent model. Calibration of this model with CAPS data provides a total dust production rate of about 12 kg s-1, including larger dust grains up to a few microns in size. We find that the fraction of charged grains dominates over that of the uncharged grains. Moreover, our model reproduces densities of both negatively and positively charged nanograins measured by Cassini CAPS. In Enceladus' plume ion densities up to ~104cm-3 are required by the self-consistent model, resulting in an electron depletion of about 50% in the plasma, because electrons are attached to the negatively charged nanograins. These ion densities correspond to effective ionization rates of about 10-7s-1, which are about two orders of magnitude higher than expected.

Dust Charging in Saturn's Rings: Observations and Theory

NASA Astrophysics Data System (ADS)

Horanyi, M.

2008-12-01

Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subsequent orbital dynamics of small grains can establish their size and spatial distributions, for example. Simultaneously, dust can alter the composition, density and temperature of the plasma surrounding it. The dynamics of charged dust particles can be surprisingly complex and fundamentally different from the well understood limits of gravitationally dominated motions of neutral particles or the adiabatic motion of electrons and ions in electromagnetic fields that dominate gravity. This talk will focus on recent Cassini observations at Saturn that are best explained by theories describing the effects of the magnetospheric fields and plasmas on the rings. As our best examples, we will discuss the physics describing the large-scale structure of the E-ring, and the formation of 'spokes' over the dense rings of Saturn.

Effects of nonthermal distribution of electrons and polarity of net dust-charge number density on nonplanar dust-ion-acoustic solitary waves.

PubMed

Mamun, A A; Shukla, P K

2009-09-01

Effects of the nonthermal distribution of electrons as well as the polarity of the net dust-charge number density on nonplanar (viz. cylindrical and spherical) dust-ion-acoustic solitary waves (DIASWs) are investigated by employing the reductive perturbation method. It is found that the basic features of the DIASWs are significantly modified by the effects of nonthermal electron distribution, polarity of net dust-charge number density, and nonplanar geometry. The implications of our results in some space and laboratory dusty plasma environments are briefly discussed.

Nonstationary stochastic charge fluctuations of a dust particle in plasmas.

PubMed

Shotorban, B

2011-06-01

Stochastic charge fluctuations of a dust particle that are due to discreteness of electrons and ions in plasmas can be described by a one-step process master equation [T. Matsoukas and M. Russell, J. Appl. Phys. 77, 4285 (1995)] with no exact solution. In the present work, using the system size expansion method of Van Kampen along with the linear noise approximation, a Fokker-Planck equation with an exact Gaussian solution is developed by expanding the master equation. The Gaussian solution has time-dependent mean and variance governed by two ordinary differential equations modeling the nonstationary process of dust particle charging. The model is tested via the comparison of its results to the results obtained by solving the master equation numerically. The electron and ion currents are calculated through the orbital motion limited theory. At various times of the nonstationary process of charging, the model results are in a very good agreement with the master equation results. The deviation is more significant when the standard deviation of the charge is comparable to the mean charge in magnitude.

A Laboratory Study of the Charging/Discharging Mechanisms of a Dust Particle Exposed to an Electron Beam

NASA Technical Reports Server (NTRS)

Venturini, C. C.; Spann, J. F.; Comfort, R. H.

1999-01-01

The interaction of micron sized particles or "dust particles" with different space and planetary environments has become an important area of research. One particular area of interest is how dust particles interact with plasmas. Studies have shown that charged dust particles immersed in plasmas can alter plasma characteristics, while ions and electrons in plasmas can affect a particle's potential and thereby, its interaction with other particles. The basis for understanding these phenomena is the charging mechanisms of the dust particle, specifically, how the particle's charge and characteristics are affected when exposed to ions and electrons. At NASA Marshall Space Flight Center, a laboratory experiment has been developed to study the interaction of dust particles with electrons. Using a unique laboratory technique known as electrodynamic suspension, a single charged particle is suspended in a modified quadrupole trap. Once suspended, the particle is then exposed to an electron beam to study the charging/discharging mechanisms due to collisions of energetic electrons. The change in the particle's charge, approximations of the charging/discharging currents, and the charging/discharging yield are calculated.

Photoemission Experiments for Charge Characteristics of Individual Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Craven, P. D.; Spann, J. F.; West, E.; Pratico, J.; Tankosic, D.; Venturini, C. C.; Six, N. Frank (Technical Monitor)

2001-01-01

Photoemission experiments with UV radiation have been performed to investigate the microphysics and charge characteristics of individual isolated dust grains of various compositions and sizes by using the electrodynamic balance facility at NASA Marshall Space Flight Center. Dust particles of 2-10 gm diameter are levitated in a vacuum chamber at pressures approximately 10(exp-5) torr and exposed to a collimated beam of UV radiation in the 120-200 nm spectral range from a deuterium lamp source with a MgF2 window. A monochromator is used to select the UV wavelength with a spectral resolution of 8 nm. The electrodynamic facility permits measurements of the charge and diameters of particles of known composition, and monitoring of photoemission rates with the incident UV radiation. Experiments have been conducted on test particles of silica and polystyrene to determine the photoelectric yields and surface equilibrium potentials when exposed to UV radiation. A brief description of an experimental procedure for photoemission studies is given and some preliminary laboratory measurements of the photoelectric yields of individual dust particles are presented.

Mars Dust: Characterization of Particle Size and Electrostatic Charge Distribution

NASA Technical Reports Server (NTRS)

Mazumder, M. K.; Saini, D.; Biris, A. S.; Sriama, P. K.; Calle, C.; Buhler, C.

2004-01-01

Some of the latest pictures of Mars surface sent by NASA's Spirit rover in early January, 2004, show very cohesive, "mud-like" dust layers. Significant amounts of dust clouds are present in the atmosphere of Mars [1-4]. NASA spacecraft missions to Mars confirmed hypotheses from telescopic work that changes observed in the planet's surface markings are caused by wind-driven redistribution of dust. In these dust storms, particles with a wide range of diameters (less than 1 micrometer to 50 micrometers) are a serious problem to solar cells, spacecraft, and spacesuits. Dust storms may cover the entire planet for an extended period of time [5]. It is highly probable that the particles are charged electrostatically by triboelectrification and by UV irradiation.

Numerical modelling of the Luna-Glob lander electric charging on the lunar surface with SPIS-DUST

NASA Astrophysics Data System (ADS)

Kuznetsov, I. A.; Hess, S. L. G.; Zakharov, A. V.; Cipriani, F.; Seran, E.; Popel, S. I.; Lisin, E. A.; Petrov, O. F.; Dolnikov, G. G.; Lyash, A. N.; Kopnin, S. I.

2018-07-01

One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. The upper insulating regolith layer is electrically charged by the solar ultraviolet radiation and the flow of solar wind particles. Resulted electric charge and thus surface potential depend on the lunar local time, latitude and the electrical properties of the regolith. Understanding of mechanisms of the dust electric charging, dust levitation and electric charging of a lander on the lunar surface is essential for interpretation of measurements of the instruments of the Luna-Glob lander payload, e.g. the Dust Impact sensor and the Langmuir Probe. One of the tools, which allows simulating the electric charging of the regolith and lander and also the transport and deposition of the dust particles on the lander surface, is the recently developed Spacecraft Plasma Interaction Software toolkit, called the SPIS-DUST. This paper describes the SPIS-DUST numerical simulation of the interaction between the solar wind plasma, ultraviolet radiation, regolith and a lander and presents as result qualitative and quantitative data of charging the surfaces, plasma sheath and its influence on spacecraft sensors, dust dynamics. The model takes into account the geometry of the Luna-Glob lander, the electric properties of materials used on the lander surface, as well as Luna-Glob landing place. Initial conditions are chosen using current theoretical models of formation of dusty plasma exosphere and levitating charged dust particles. Simulation for the three cases (local lunar noon, evening and sunset) showed us the surrounding plasma sheath around the spacecraft which gives a significant potential bias in the spacecraft vicinity. This bias influences on the spacecraft sensors but with SPIS software we can estimate the potential of uninfluenced plasma with the data from the plasma sensors (Langmuir probes). SPIS-DUST modification allows us to get the dust dynamics

Polybrominated Diphenyl Ethers in Residential Dust: Sources of Variability

PubMed Central

Whitehead, Todd P.; Brown, F. Reber; Metayer, Catherine; Park, June-Soo; Does, Monique; Petreas, Myrto X.; Buffler, Patricia A.; Rappaport, Stephen M.

2013-01-01

We characterized the sources of variability for polybrominated diphenyl ethers (PBDEs) in residential dust and provided guidance for investigators who plan to use residential dust to assess exposure to PBDEs. We collected repeat dust samples from 292 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001–2007 and during 2010) using household vacuum cleaners and measured 22 PBDEs using high resolution gas chromatography-high resolution mass spectrometry. Median concentrations for individual PBDEs ranged from <0.1–2,500 ng per g of dust. For each of eight representative PBDEs, we used a random-effects model to apportion total variance into regional variability (0–11%), intra-regional between-household variability (17–50%), within-household variability over time (38–74%), and within-sample variability (0–23%) and we used a mixed-effects model to identify determinants of PBDE levels. Regional differences in PBDE dust levels were associated with residential characteristics that differed by region, including the presence of furniture with exposed or crumbling foam and the recent installation of carpets in the residence. Intra-regional differences between households were associated with neighborhood urban density, racial and ethnic characteristics, and to a lesser extent, income. For some PBDEs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Our findings indicate that it may be feasible to use residential dust for retrospective assessment of PBDE exposures in studies of children’s health (e.g., the Northern California Childhood Leukemia Study). PMID:23628589

Electrostatic charging of lunar dust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walch, Bob; Horanyi, Mihaly; Robertson, Scott

1998-10-21

Transient dust clouds suspended above the lunar surface were indicated by the horizon glow observed by the Surveyor spacecrafts and the Lunar Ejecta and Meteorite Experiment (Apollo 17), for example. The theoretical models cannot fully explain these observations, but they all suggest that electrostatic charging of the lunar surface due to exposure to the solar wind plasma and UV radiation could result in levitation, transport and ejection of small grains. We report on our experimental studies of the electrostatic charging properties of an Apollo-17 soil sample and two lunar simulants MLS-1 and JSC-1. We have measured their charge after exposingmore » individual grains to a beam of fast electrons with energies in the range of 20{<=}E{<=}90 eV. Our measurements indicate that the secondary electron emission yield of the Apollo-17 sample is intermediate between MLS-1 and JSC-1, closer to that of MLS-1. We will also discuss our plans to develop a laboratory lunar surface model, where time dependent illumination and plasma bombardment will closely emulate the conditions on the surface of the Moon.« less

Effect of Stochastic Charge Fluctuations on Dust Dynamics

NASA Astrophysics Data System (ADS)

Matthews, Lorin; Shotorban, Babak; Hyde, Truell

2017-10-01

The charging of particles in a plasma environment occurs through the collection of electrons and ions on the particle surface. Depending on the particle size and the plasma density, the standard deviation of the number of collected elementary charges, which fluctuates due to the randomness in times of collisions with electrons or ions, may be a significant fraction of the equilibrium charge. We use a discrete stochastic charging model to simulate the variations in charge across the dust surface as well as in time. The resultant asymmetric particle potentials, even for spherical grains, has a significant impact on the particle coagulation rate as well as the structure of the resulting aggregates. We compare the effects on particle collisions and growth in typical laboratory and astrophysical plasma environments. This work was supported by the National Science Foundation under Grant PHY-1414523.

Photoemission Experiments for Charge Characteristics of Individual Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Spann, James F., Jr.; Craven, Paul D.; West, E.; Pratico, Jared; Scheianu, D.; Tankosic, D.; Venturini, C. C.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Photoemission experiments with UV radiation have been performed to investigate the microphysics and charge characteristics of individual isolated dust grains of various compositions and sizes by using the electrodynamic balance facility at NASA Marshall Space Flight Center. Dust particles of 1 - 100 micrometer diameter are levitated in a vacuum chamber at pressures approx. 10(exp -5) torr and exposed to a collimated beam of UV radiation in the 120-300 nanometers spectral range from a deuterium lamp source with a MgF2 window. A monochromator is used to select the UV radiation wavelength with a spectral resolution of 8 nanometers. The electrodynamic facility permits measurements of the charge and diameters of particles of known composition, and monitoring of photoemission rates with the incident UV radiation. Experiments have been conducted on Al2O3 and silicate particles, and in particular on JSC-1 Mars regolith simulants, to determine the photoelectron yields and surface equilibrium potentials of dust particles when exposed to UV radiation in the 120-250 micrometers spectral range. A brief discussion of the experimental procedure, the results of photoemission experiments, and comparisons with theoretical models will be presented.

The effects of electrostatic charging on the dust distribution at Halley's Comet

NASA Technical Reports Server (NTRS)

Horanyi, M.; Mendis, D. A.

1986-01-01

The distribution of fine dust near Comet Halley at its 1910 and 1986 apparitions is investigated by means of computer simulations, taking the effects of EM forces due to the dust electrostatic charge into account. It is found that the nucleus spin period and orbital obliquity estimated by Sekanina and Larson (1984) from the 1910 observations are unaffected by these EM forces because the 1910 dust morphology involved mainly large grains. For 1986, the orientation of the smaller dust is shown to depend on the interplanetary magnetic field, with implications for the dust distribution encountered by the Halley probes.

The Charging of Dust Grains in the Inner Heliosheath

NASA Astrophysics Data System (ADS)

Avinash, K.; Slavin, J.; Zank, G. P.; Frisch, P.

2008-12-01

Equilibrium electric charge and surface potential on a dust grain in the heliosheath are calculated. The grain is charged due to heliosheath plasma flux, photo electrons flux, secondary electron emission flux and transmission flux. Realistically, the heliosheath plasma consists of solar electrons, solar wind ions [SWI] and pick up ions [PUI]. These species interact differently with TS and thus have different characteristics down stream in the heliosheath. The PUI suffer multiple reflections at TS and are accelerated to high energies in the range of ~ 106 K. The solar electrons, on the other hand, are heated adiabatically through the TS and have temperature in the range ~ 5x105 K. The SWI may have a smaller temperature typically in the range 1-5x104 K The density of electrons could be in the range ~5 x 10-4 cm-3, while the ratio of PUI to SWI density could range from 0.1 to 0.5. Taking into account these parameters, grain charging due to different plasma species and other fluxes mentioned earlier, is calculated. Our results show that (a) surface potential is very sensitive to electron temp. It goes through a maxima and for realistic values close to or less than 5x105 K it can be as big as 26V which is twice the value calculated by Kimura and Mann1. This may have implications for electrostatic disruption and the size distribution of dust particles in the heliosheath. With PUI density the surface potential increases about 10 to 20 %. Though temperature of PUI is significantly larger than that of electrons, it is not large enough to make up for the mass ratio of electrons to protons. On account small temperature and electron/proton mass ratio, the effect of SWI on dust charge is very weak. (1) H. Kimura and I. Mann, Ap.J. 499, 454 (1998).

Interannual Modulation of Subtropical Atlantic Boreal Summer Dust Variability by ENSO

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeFlorio, Mike; Goodwin, Ian D.; Cayan, Dan

2016-01-01

Dust variability in the climate system has been studied for several decades, yet there remains an incomplete understanding of the dynamical mechanisms controlling interannual and decadal variations in dust transport. The sparseness of multi-year observational datasets has limited our understanding of the relationship between climate variations and atmospheric dust. We use available observations and a century-length fully coupled Community Earth System Model (CESM) simulation to show that the El Niño- Southern Oscillation (ENSO) exerts a control on North African dust transport during boreal summer. In CESM, this relationship is stronger over the dusty tropical North Atlantic than near Barbados, onemore » of the few sites having a multi-decadal observed record. During strong La Niña summers in CESM, a statistically significant increase in lower tropospheric easterly wind is associated with an increase in North African dust transport over the Atlantic. Barbados dust and Pacific SST variability are only weakly correlated in both observations and CESM, suggesting that other processes are controlling the crossbasin variability of dust. We also use our CESM simulation to show that the relationship between downstream North African dust transport and ENSO fluctuates on multidecadal timescales and may be modulated by the North Atlantic Oscillation (NAO). Our findings indicate that existing observations of dust over the tropical North Atlantic are not extensive enough to completely describe the variability of dust and dust transport, and demonstrate the importance of global models to supplement and interpret observational records.« less

Measurement of net electric charge and dipole moment of dust aggregates in a complex plasma.

PubMed

Yousefi, Razieh; Davis, Allen B; Carmona-Reyes, Jorge; Matthews, Lorin S; Hyde, Truell W

2014-09-01

Understanding the agglomeration of dust particles in complex plasmas requires knowledge of basic properties such as the net electrostatic charge and dipole moment of the dust. In this study, dust aggregates are formed from gold-coated mono-disperse spherical melamine-formaldehyde monomers in a radiofrequency (rf) argon discharge plasma. The behavior of observed dust aggregates is analyzed both by studying the particle trajectories and by employing computer models examining three-dimensional structures of aggregates and their interactions and rotations as induced by torques arising from their dipole moments. These allow the basic characteristics of the dust aggregates, such as the electrostatic charge and dipole moment, as well as the external electric field, to be determined. It is shown that the experimental results support the predicted values from computer models for aggregates in these environments.

Mechanisms of dust grain charging in plasma with allowance for electron emission processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mol’kov, S. I.; Savin, V. N., E-mail: moped@onego.ru

2017-02-15

The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion–atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson’s equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

Head-on collision of dust acoustic solitons in a nonextensive plasma with variable size dust grains of arbitrary charge

NASA Astrophysics Data System (ADS)

Behery, E. E.

2016-11-01

The head-on collision of two dust acoustic solitons (DASs) in a nonextensive plasma with positive or negative dust grains fluid including the effect of dust size distribution (DSD) is studied. The phase shifts for the two solitons due to the collision are derived by applying the extended Poincaré-Lighthill-Kuo (PLK) method. The influences of the power law DSD and the nonextensivity of plasma particles on the characteristic properties of the head-on collision of DASs are analyzed. It is found that the phase shifts can vanish, only for the case of positive dust grains, for certain values and ranges of the dust grain radius and the entropic index of ions (qi) . Also, they undergo a cutoff in the range of qi>1 for the subextensive distribution. A brief discussion of possible applications in laboratory and space plasmas is included.

Dust motions in quasi-statically charged binary asteroid systems

NASA Astrophysics Data System (ADS)

Maruskin, Jared M.; Bellerose, Julie; Wong, Macken; Mitchell, Lara; Richardson, David; Mathews, Douglas; Nguyen, Tri; Ganeshalingam, Usha; Ma, Gina

2013-03-01

In this paper, we discuss dust motion and investigate possible mass transfer of charged particles in a binary asteroid system, in which the asteroids are electrically charged due to solar radiation. The surface potential of the asteroids is assumed to be a piecewise function, with positive potential on the sunlit half and negative potential on the shadow half. We derive the nonautonomous equations of motion for charged particles and an analytic representation for their lofting conditions. Particle trajectories and temporary relative equilibria are examined in relation to their moving forbidden regions, a concept we define and discuss. Finally, we use a Monte Carlo simulation for a case study on mass transfer and loss rates between the asteroids.

Interannual Variability in Global Dust Storm Initiation on Mars from a GCM with Orbit-Spin Coupling and Active Dust Lifting

NASA Astrophysics Data System (ADS)

Mischna, M.; Shirley, J. H.; Newman, C. E.

2016-12-01

To first order, the occurrence and interannual variability of global dust storms (GDS) on Mars is attributable to two factors: the annual cycle of solar insolation (which delineates a specific `dust storm season'), and the changing spatial distribution and availability of dust at the surface. Recent work has now found a remarkable correspondence between the occurrence of GDS on Mars and years in which the orbital angular momentum of Mars is increasing during the dust storm season. A previously undefined acceleration term `couples' this orbital motion to the rotational motion of the planet and atmosphere, and small but persistent atmospheric accelerations (so-called `coupling term accelerations,' or CTA) change the atmospheric circulation in such a way as to seemingly be favorable to storm development. This becomes a third factor, then, that may regulate the occurrence and variability of GDS. Our prior work with the MarsWRF general circulation model (GCM) was performed either with no atmospheric dust, or with simplified, prescribed dust distributions, and illustrated the dual roles of both insolation and CTA on GDS variability. Recent advances in the MarsWRF GCM dust prescription can now tackle the remaining unaddressed factor: the role of dust availability in controlling the initiation of GDS. Simulations with both infinite and finite global sources of dust have been performed. For a prescribed dust lifting threshold, surface dust is removed from the surface, preferentially from locations with larger surface stress values, transported in the atmosphere and deposited at a later time. Compared to simulations without CTA, those with CTA show more realism in the variability of timing and magnitude of atmospheric dustiness during the dust storm season. For infinite surface dust, the primary dust lifting (peak wind stress) regions are spatially restricted, and year-to-year changes are largely due to variations in the CTA at these few locations. By contrast, in

EFFECT OF LOADING DUST TYPE ON THE FILTRATION EFFICIENCY OF ELECTROSTATICALLY CHARGED FILTERS

EPA Science Inventory

The paper gives results of an evaluation of the effect of loading dust type on the filtration efficiency of electrostatically charged filters. Three types of filters were evaluated: a rigid-cell filter charged using an electrodynamic spinning process, a pleated-panel filter cha...

Comparison of dust charging between orbital-motion-limited theory and particle-in-cell simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delzanno, Gian Luca, E-mail: delzanno@lanl.gov; Tang, Xian-Zhu, E-mail: xtang@lanl.gov

The Orbital-Motion-Limited (OML) theory has been modified to predict the dust charge and the results were contrasted with the Whipple approximation [X. Z. Tang and G. L. Delzanno, Phys. Plasmas 21, 123708 (2014)]. To further establish its regime of applicability, in this paper, the OML predictions (for a non-electron-emitting, spherical dust grain at rest in a collisionless, unmagnetized plasma) are compared with particle-in-cell simulations that retain the absorption radius effect. It is found that for large dust grain radius r{sub d} relative to the plasma Debye length λ{sub D}, the revised OML theory remains a very good approximation as, formore » the parameters considered (r{sub d}/λ{sub D} ≤ 10, equal electron and ion temperatures), it yields the dust charge to within 20% accuracy. This is a substantial improvement over the Whipple approximation. The dust collected currents and energy fluxes, which remain the same in the revised and standard OML theories, are accurate to within 15%–30%.« less

Study of the Effects of the Electric Field on Charging Measurements on Individual Micron-size Dust Grains by Secondary Electron Emissions

NASA Technical Reports Server (NTRS)

Tankosic, D.; Abbas, M. M.

2013-01-01

The dust charging by electron impact is an important dust charging process in Astrophysical, Planetary, and the Lunar environments. Low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available theoretical models for the calculation of SEE yield applicable for neutral, planar or bulk surfaces are generally based on Sternglass Equation. However, viable models for charging of individual dust grains do not exist at the present time. Therefore, the SEE yields have to be obtained by some experimental methods at the present time. We have conducted experimental studies on charging of individual micron size dust grains in simulated space environments using an electrodynamic balance (EDB) facility at NASA-MSFC. The results of our extensive laboratory study of charging of individual micron-size dust grains by low energy electron impact indicate that the SEE by electron impact is a very complex process expected to be substantially different from the bulk materials. It was found that the incident electrons may lead to positive or negative charging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration. In this paper we give a more elaborate discussion about the possible effects of the AC field in the EDB on dust charging measurements by comparing the secondary electron emission time-period (tau (sub em) (s/e)) with the time-period (tau (sub ac) (ms)) of the AC field cycle in the EDB that we have briefly addressed in our previous publication.

Nonlinear waves in viscoelastic magnetized complex astroplasmas with polarized dust-charge variations

NASA Astrophysics Data System (ADS)

Das, Papari; Karmakar, Pralay Kumar

2018-01-01

A nonextensive nonthermal magnetized viscoelastic astrofluid, compositionally containing nonthermal electrons and ions together with massive polarized dust micro-spherical grains of variable electric charge, is allowed to endure weakly nonlinear perturbation around its equilibrium. The nonextensivity originating from the large-scale non-local effects is included via the Tsallis thermo-statistical distribution laws describing the lighter species. Assuming the equilibrium as a homogeneous hydrostatic one, the dust polarization effects are incorporated via the conventional homogeneous polarization force law. The perturbed fluid model evolves as a unique conjugate pair of coupled extended Korteweg-de Vries (e-KdV) equations. A constructed numerical tapestry shows the collective excitations of a new pair of distinct classes of nonlinear mode structures in new parametric space. The first family indicates periodic electrostatic compressive eigenmodes in the form of soliton-chains. Likewise, the second one reveals gravitational rarefactive solitary patterns. Their microphysical multi-parametric dependencies of the eigen-patterns are illustratively analyzed and bolstered. The paper ends up with some promising implications and applications in the astro-cosmo-plasmic context of wave-induced accretive triggering processes responsible for gravitationally bounded (gravito-condensed) astro-structure formation, such as stellesimals, planetsimals, etc.

Dust acoustic and drift waves in a non-Maxwellian dusty plasma with dust charge fluctuation

NASA Astrophysics Data System (ADS)

Zakir, U.; Haque, Q.; Imtiaz, N.; Qamar, A.

2015-12-01

> ) on the wave dispersion and instability are presented. It is found that the presence of the non-thermal electron and ion populations reduce the growth rate of the instability which arises due to the dust charging effect. In addition, the nonlinear vortex solutions are also obtained. For illustration, the results are analysed by using the dusty plasma parameters of Saturn's magnetosphere.

A note on dust grain charging in space plasmas

NASA Technical Reports Server (NTRS)

Rosenberg, M.; Mendis, D. A.

1992-01-01

Central to the study of dust-plasma interactions in the solar system is the electrostatic charging of dust grains. While previous calculations have generally assumed that the distributions of electrons and ions in the plasma are Maxwellian, most space plasmas are observed to have non-Maxwellian tails and can often be fit by a generalized Lorentzian (kappa) distribution. Here we use such a distribution to reevaluate the grain potential, under the condition that the dominant currents to the grain are due to electron and ion collection, as is the case in certain regions of space. The magnitude of the grain potential is found to be larger than that in a Maxwellian plasma as long as the electrons are described by a kappa distribution: this enhancement increased with ion mass and decreasing electron kappa. The modification of the grain potential in generalized Lorentzian plasmas has implications for both the physics (e.g., grain growth and disruption) and the dynamics of dust in space plasmas. These are also briefly discussed.

Effect of dust charging and trapped electrons on nonlinear solitary structures in an inhomogeneous magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Ravinder; Malik, Hitendra K.; Singh, Khushvant

2012-01-15

Main concerns of the present article are to investigate the effects of dust charging and trapped electrons on the solitary structures evolved in an inhomogeneous magnetized plasma. Such a plasma is found to support two types of waves, namely, fast wave and slow wave. Slow wave propagates in the plasma only when the wave propagation angle {theta} satisfies the condition {theta}{>=}tan{sup -1}{l_brace}({radical}((1+2{sigma})-[(n{sub dlh}({gamma}{sub 1}-1))/(1+n{sub dlh}{gamma}{sub 1})])-v{sub 0}/u{sub 0}){r_brace}, where v{sub 0}(u{sub 0}) is the z- (x-) component of ion drift velocity, {sigma} = T{sub i}/T{sub eff}, n{sub dlh} = n{sub d0}/(n{sub el0} + n{sub eh0}), and {gamma}{sub 1}=-(1/{Phi}{sub i0})[(1-{Phi}{sub i0}/1+{sigma}(1-{Phi}{submore » i0}))] together with T{sub i} as ion temperature, n{sub el0}(n{sub eh0}) as the density of trapped (isothermal) electrons, {Phi}{sub i0} as the dust grain (density n{sub d0}) surface potential relative to zero plasma potential, and T{sub eff}=(n{sub elo}+n{sub eho})T{sub el}T{sub eh}/(n{sub elo}T{sub eh}+n{sub eho}T{sub el}), where T{sub el}(T{sub eh}) is the temperature of trapped (isothermal) electrons. Both the waves evolve in the form of density hill type structures in the plasma, confirming that these solitary structures are compressive in nature. These structures are found to attain higher amplitude when the charge on the dust grains is fluctuated (in comparison with the case of fixed charge) and also when the dust grains and trapped electrons are more in number; the same is the case with higher temperature of ions and electrons. Slow solitary structures show weak dependence on the dust concentration. Both types of structures are found to become narrower under the application of stronger magnetic field. With regard to the charging of dust grains, it is observed that the charge gets reduced for the higher trapped electron density and temperature of ions and electrons, and dust charging shows weak dependence on the

Plasma flow around and charge distribution of a dust cluster in a rf discharge

NASA Astrophysics Data System (ADS)

Schleede, J.; Lewerentz, L.; Bronold, F. X.; Schneider, R.; Fehske, H.

2018-04-01

We employ a particle-in-cell Monte Carlo collision/particle-particle particle-mesh simulation to study the plasma flow around and the charge distribution of a three-dimensional dust cluster in the sheath of a low-pressure rf argon discharge. The geometry of the cluster and its position in the sheath are fixed to the experimental values, prohibiting a mechanical response of the cluster. Electrically, however, the cluster and the plasma environment, mimicking also the experimental situation, are coupled self-consistently. We find a broad distribution of the charges collected by the grains. The ion flux shows on the scale of the Debye length strong focusing and shadowing inside and outside the cluster due to the attraction of the ions to the negatively charged grains, whereas the electron flux is characterized on this scale only by a weak spatial modulation of its magnitude depending on the rf phase. On the scale of the individual dust potentials, however, the electron flux deviates in the vicinity of the cluster strongly from the laminar flow associated with the plasma sheath. It develops convection patterns to compensate for the depletion of electrons inside the dust cluster.

Excitation of Kelvin Helmholtz instability by an ion beam in a plasma with negatively charged dust grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rani, Kavita; Sharma, Suresh C.

2015-02-15

An ion beam propagating through a magnetized dusty plasma drives Kelvin Helmholtz Instability (KHI) via Cerenkov interaction. The frequency of the unstable wave increases with the relative density of negatively charged dust grains. It is observed that the beam has stabilizing effect on the growth rate of KHI for low shear parameter, but for high shear parameter, the instability is destabilized with relative density of negatively charged dust grains.

A smoothed particle hydrodynamics model for electrostatic transport of charged lunar dust on the moon surface

NASA Astrophysics Data System (ADS)

Mao, Zirui; Liu, G. R.

2018-02-01

The behavior of lunar dust on the Moon surface is quite complicated compared to that on the Earth surface due to the small lunar gravity and the significant influence of the complicated electrostatic filed in the Universe. Understanding such behavior is critical for the exploration of the Moon. This work develops a smoothed particle hydrodynamics (SPH) model with the elastic-perfectly plastic constitutive equation and Drucker-Prager yield criterion to simulate the electrostatic transporting of multiple charged lunar dust particles. The initial electric field is generated based on the particle-in-cell method and then is superposed with the additional electric field from the charged dust particles to obtain the resultant electric field in the following process. Simulations of cohesive soil's natural failure and electrostatic transport of charged soil under the given electric force and gravity were carried out using the SPH model. Results obtained in this paper show that the negatively charged dust particles levitate and transport to the shadow area with a higher potential from the light area with a lower potential. The motion of soil particles finally comes to a stable state. The numerical result for final distribution of soil particles and potential profile above planar surface by the SPH method matches well with the experimental result, and the SPH solution looks sound in the maximum levitation height prediction of lunar dust under an uniform electric field compared to theoretical solution, which prove that SPH is a reliable method in describing the behavior of soil particles under a complicated electric field and small gravity field with the consideration of interactions among soil particles.

Electrostatic charge on a dust size distribution in a plasma. [in interplanetary space

NASA Technical Reports Server (NTRS)

Houpis, Harry L. F.; Whipple, Elden C., Jr.

1987-01-01

The capacitance of a grain immersed in a steady state plasma containing a size distribution of dust particles is studied. The grain charge is determined by assuming the equilibrium potential has been obtained by a simple balance of electron and ion collection currents. It is shown that the validity of the analytical treatment given here for the linearized Poisson equation is confined to a certain region of space. Within this region and starting at very small plasma Debye length lambda(D), the capacitance at first exhibits a monotonic increase with increasing lambda(D). The capacitance eventually reaches a maximum, followed by a monotonic decrease. The charge density of the dust in the plasma is found to be only a function of the lambda(D); there is no significant dependence on the interparticle spacing.

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akishev, Yu. S., E-mail: akishev@triniti.ru; Karal’nik, V. B.; Petryakov, A. V.

2017-02-15

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculatedmore » when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.« less

Charged dust dynamics - Orbital resonance due to planetary shadows

NASA Technical Reports Server (NTRS)

Horanyi, M.; Burns, J. A.

1991-01-01

The dynamics of a weakly charged dust grain orbiting in the equatorial plane of a planet surrounded by a rigidly corotating magnetospehre is examined. It is shown that an introduction of an effectilve 1D potential causes a perturbation due to electrostatic forces, which induces a motion of the pericenter, similar to the effect of the planetary oblateness. A case is examined where the charge varies periodically due to the modulation of the photoelectron current occurring as the grain enters and leaves the planetary shadow, causing the electromagnetic perturbation to resonate with the orbital period and to modify the size and eccentricity of the orbit. This effect is demonstrated both numerically and analytically for small grains comprising the Jovian ring, showing that their resulting changes are periodic, and their amplitude is much larger than that of the periodic changes due to light-pressure perturbation or the secular changes due to resonant charge variations that develop over a comparable time span.

Lunar dust simulant charging and transport under UV irradiation in vacuum: Experiments and numerical modeling

NASA Astrophysics Data System (ADS)

Champlain, A.; Matéo-Vélez, J.-C.; Roussel, J.-F.; Hess, S.; Sarrailh, P.; Murat, G.; Chardon, J.-P.; Gajan, A.

2016-01-01

Recent high-altitude observations, made by the Lunar Dust Experiment (LDEX) experiment on board LADEE orbiting the Moon, indicate that high-altitude (>10 km) dust particle densities are well correlated with interplanetary dust impacts. They show no evidence of high dust density suggested by Apollo 15 and 17 observations and possibly explained by electrostatic forces imposed by the plasma environment and photon irradiation. This paper deals with near-surface conditions below the domain of observation of LDEX where electrostatic forces could clearly be at play. The upper and lower limits of the cohesive force between dusts are obtained by comparing experiments and numerical simulations of dust charging under ultraviolet irradiation in the presence of an electric field and mechanical vibrations. It is suggested that dust ejection by electrostatic forces is made possible by microscopic-scale amplifications due to soil irregularities. At low altitude, this process may be complementary to interplanetary dust impacts.

VARIABLE CHARGE SOILS: MINERALOGY AND CHEMISTRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Ranst, Eric; Qafoku, Nikolla; Noble, Andrew

2016-09-19

Soils rich in particles with amphoteric surface properties in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders (1) are considered to be variable charge soils (2) (Table 1). The term “variable charge” is used to describe organic and inorganic soil constituents with reactive surface groups whose charge varies with pH and ionic concentration and composition of the soil solution. Such groups are the surface carboxyl, phenolic and amino functional groups of organic materials in soils, and surface hydroxyl groups of Fe and Al oxides, allophane and imogolite. The hydroxyl surface groups are also present on edges of some phyllosilicate mineralsmore » such as kaolinite, mica, and hydroxyl-interlayered vermiculite. The variable charge is developed on the surface groups as a result of adsorption or desorption of ions that are constituents of the solid phase, i.e., H+, and the adsorption or desorption of solid-unlike ions that are not constituents of the solid phase. Highly weathered soils and subsoils (e.g., Oxisols and some Ultisols, Alfisols and Andisols) may undergo isoelectric weathering and reach a “zero net charge” stage during their development. They usually have a slightly acidic to acidic soil solution pH, which is close to either the point of zero net charge (PZNC) (3) or the point of zero salt effect (PZSE) (3). They are characterized by high abundances of minerals with a point of zero net proton charge (PZNPC) (3) at neutral and slightly basic pHs; the most important being Fe and Al oxides and allophane. Under acidic conditions, the surfaces of these minerals are net positively charged. In contrast, the surfaces of permanent charge phyllosilicates are negatively charged regardless of ambient conditions. Variable charge soils therefore, are heterogeneous charge systems.« less

Stochastic charging of dust grains in planetary rings: Diffusion rates and their effects on Lorentz resonances

NASA Technical Reports Server (NTRS)

Schaffer, L.; Burns, J. A.

1995-01-01

Dust grains in planetary rings acquire stochastically fluctuating electric charges as they orbit through any corotating magnetospheric plasma. Here we investigate the nature of this stochastic charging and calculate its effect on the Lorentz resonance (LR). First we model grain charging as a Markov process, where the transition probabilities are identified as the ensemble-averaged charging fluxes due to plasma pickup and photoemission. We determine the distribution function P(t;N), giving the probability that a grain has N excess charges at time t. The autocorrelation function tau(sub q) for the strochastic charge process can be approximated by a Fokker-Planck treatment of the evolution equations for P(t; N). We calculate the mean square response to the stochastic fluctuations in the Lorentz force. We find that transport in phase space is very small compared to the resonant increase in amplitudes due to the mean charge, over the timescale that the oscillator is resonantly pumped up. Therefore the stochastic charge variations cannot break the resonant interaction; locally, the Lorentz resonance is a robust mechanism for the shaping of etheral dust ring systems. Slightly stronger bounds on plasma parameters are required when we consider the longer transit times between Lorentz resonances.

Electrostatic Characterization of Lunar Dust

NASA Technical Reports Server (NTRS)

2008-01-01

To ensure the safety and success of future lunar exploration missions, it is important to measure the toxicity of the lunar dust and its electrostatic properties. The electrostatic properties of lunar dust govern its behavior, from how the dust is deposited in an astronaut s lungs to how it contaminates equipment surfaces. NASA has identified the threat caused by lunar dust as one of the top two problems that need to be solved before returning to the Moon. To understand the electrostatic nature of lunar dust, NASA must answer the following questions: (1) how much charge can accumulate on the dust? (2) how long will the charge remain? and (3) can the dust be removed? These questions can be answered by measuring the electrostatic properties of the dust: its volume resistivity, charge decay, charge-to-mass ratio or chargeability, and dielectric properties.

Charged dust in planetary magnetospheres: Hamiltonian dynamics and numerical simulations for highly charged grains

NASA Technical Reports Server (NTRS)

Schaffer, L.; Burns, J. A.

1994-01-01

We use a combination of analytical and numerical methods to investigate the dynamics of charged dust grains in planetary magnetospheres. Our emphasis is on obtaining results valid for particles that are not necessarily dominated either by gravitational or electromagnetic forces. A Hamiltonian formulation of the problem yields exact results, for all values of charge-to-mass ratio, when we introduce two constraints: particles remain in the equatorial plane and the magnetic field is taken as axially symmetric. In particular, we obtain locations of equilibrium points, the frequencies of stable periodic orbits, the topology of separatrices in phase space, and the rate of longitudinal drift. These results are significant for specific applications: motion in the nearly aligned dipolar field of Saturn, and the trajectories of arbitrarily charged particles in complex magnetic fields for limited periods of time after ejection from parent bodies. Since the model is restrictive, we also use numerical integrations of the full three-dimensional equations of motion and illustrate under what conditions the constrained problem yields reasonable results. We show that a large fraction of the intermediately charged and highly charged (gyrating) particles will always be lost to a planet's atmosphere within a few hundred hours, for motion through tilted-dipole magnetic fields. We find that grains must have a very high charge-to-mass ratio in order to be mirrored back to the ring plane. Thus, except perhaps at Saturn where the dipole tilt is very small, the likely inhabitants of the dusty ring systems are those particles that are either nearly Keplerian (weakly charged) grains or grains whose charges place them in the lower end of the intermediate charge zone. Fianlly, we demonstrate the effect of plasma drag on the orbits of gyrating particles to be a rapid decrease in gyroradius followed by a slow radial evolution of the guiding center.

Review of Variable Generation Integration Charges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Porter, K.; Fink, S.; Buckley, M.

2013-03-01

The growth of wind and solar generation in the United States, and the expectation of continued growth of these technologies, dictates that the future power system will be operated in a somewhat different manner because of increased variability and uncertainty. A small number of balancing authorities have attempted to determine an 'integration cost' to account for these changes to their current operating practices. Some balancing authorities directly charge wind and solar generators for integration charges, whereas others add integration charges to projected costs of wind and solar in integrated resource plans or in competitive solicitations for generation. This report reviewsmore » the balancing authorities that have calculated variable generation integration charges and broadly compares and contrasts the methodologies they used to determine their specific integration charges. The report also profiles each balancing authority and how they derived wind and solar integration charges.« less

Variable Charge Soils: Mineralogy and Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qafoku, Nik; Van Ranst, Eric; Noble, Andrew

2003-11-01

Soils rich in particles with amphoteric surface properties in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders (1) are considered variable charge soils (2). The term “variable charge” is used to describe organic and inorganic soil constituents with reactive surface groups whose charge varies with pH, ionic concentration and composition of the soil solution. Such groups are the surface carboxyl, phenolic and amino functional groups of organic materials in soils, and surface hydroxyl groups of Fe and Al oxides, allophane and imogolite. The hydroxyl surface groups are also present on edges of some phyllosilicate minerals such as kaolinite, mica, andmore » hydroxyl-interlayered vermiculite. The variable charge is developed on the surface groups as a result of adsorption or desorption of ions that are constituents of the solid phase, i.e., H+, and the adsorption or desorption of solid-unlike ions that are not constituents of the solid. Highly weathered soils usually undergo isoeletric weathering and reach a “zero net charge” stage during their development. They have a slightly acidic to acidic soil solution pH, which is close to either point of zero net charge (PZNC) (3) or point of zero salt effect (PZSE) (3). They are characterized by high abundances of minerals with a point of zero net proton charge (PZNPC) (3) at neutral and slightly basic pHs; the most important being Fe and Al oxides and allophane. Under acidic conditions, the surfaces of these minerals are net positively charged. In contrast, the surfaces of permanent charge phyllosilicates are negatively charged regardless of ambient conditions. Variable charge soils therefore, are heterogeneous charge systems. The coexistence and interactions of oppositely charged surfaces or particles confers a different pattern of physical and chemical behavior on the soil, relatively to a homogeneously charged system of temperate regions. In some variable charge soils (Oxisols and some Ultisols

Study of dust particle charging in weakly ionized inert gases taking into account the nonlocality of the electron energy distribution function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippov, A. V., E-mail: fav@triniti.ru; Dyatko, N. A.; Kostenko, A. S.

2014-11-15

The charging of dust particles in weakly ionized inert gases at atmospheric pressure has been investigated. The conditions under which the gas is ionized by an external source, a beam of fast electrons, are considered. The electron energy distribution function in argon, krypton, and xenon has been calculated for three rates of gas ionization by fast electrons: 10{sup 13}, 10{sup 14}, and 10{sup 15} cm{sup −1}. A model of dust particle charging with allowance for the nonlocal formation of the electron energy distribution function in the region of strong plasma quasi-neutrality violation around the dust particle is described. The nonlocalitymore » is taken into account in an approximation where the distribution function is a function of only the total electron energy. Comparative calculations of the dust particle charge with and without allowance for the nonlocality of the electron energy distribution function have been performed. Allowance for the nonlocality is shown to lead to a noticeable increase in the dust particle charge due to the influence of the group of hot electrons from the tail of the distribution function. It has been established that the screening constant virtually coincides with the smallest screening constant determined according to the asymptotic theory of screening with the electron transport and recombination coefficients in an unperturbed plasma.« less

Systematic on-site monitoring of compliance dust samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grayson, R.L.; Gandy, J.R.

1996-12-31

Maintaining compliance with U.S. respirable coal mine dust standards can be difficult on high-productivity longwall panels. Comprehensive and systematic analysis of compliance dust sample data, coupled with access to the U.S. Bureau of Mines (USBM) DUSTPRO, can yield important information for use in maintaining compliance. The objective of this study was to develop and apply a customized software for the collection, storage, modification, and analysis of respirable dust data while providing for flexible export of data and linking with the USBM`s expert advisory system on dust control. An executable, IBM-compatible software was created and customized for use by the personmore » in charge of collecting, submitting, analyzing, and monitoring respirable dust compliance samples. Both descriptive statistics and multiple regression analysis were incorporated. The software allows ASCH files to be exported and directly links with DUSTPRO. After development and validation of the software, longwall compliance data from two different mines was analyzed to evaluate the value of the software. Data included variables on respirable dust concentration, tons produced, the existence of roof/floor rock (dummy variable), and the sampling cycle (dummy variables). Because of confidentiality, specific data will not be presented, only the equations and ANOVA tables. The final regression models explained 83.8% and 61.1% of the variation in the data for the two panels. Important correlations among variables within sampling cycles showed the value of using dummy variables for sampling cycles. The software proved flexible and fast for its intended use. The insights obtained from use improved the systematic monitoring of respirable dust compliance data, especially for pinpointing the most effective dust control methods during specific sampling cycles.« less

Particle Simulations on Plasma and Dust Environment near Lunar Vertical Holes

NASA Astrophysics Data System (ADS)

Miyake, Y.; Funaki, Y.; Nishino, M. N.

2016-12-01

The Japanese lunar orbiter KAGUYA has revealed the existence of vertical holes on the Moon, which have spatial scales of tens of meters and are possible lava tube skylights. The hole structure has recently received particular attention, because the structure is regarded as evidence for past existence of underground lava flows. Furthermore, the holes have high potential as locations for constructing future lunar bases, because of fewer extra-lunar rays/particles and micrometeorites reaching the hole bottoms. In this sense, these holes are not only of significance in selenology, but are also interesting from the viewpoint of plasma environments. The dayside electrostatic environment near the lunar surface is governed by interactions among the solar wind plasma, photoelectrons, and the charged lunar surface, providing topologically complex boundaries to the plasma. Thus we applied three-dimensional, massively-parallelized, particle-in-cell simulations to the near-hole environment on the Moon. This year we have introduced a horizontal cavern opened at the vertical wall of the hole, assuming the presence of a subsurface lave tube. We will show some preliminary results on the surface potential and its nearly plasma environments. We also started to study the dynamics of submicron-sized charged dust grains around the distinctive landscape. We particularly focus on an effect of a stochastic charging process of such small dust grains. Because of their small surface areas, the dusts will get/lose one elementary charge infrequently, and thus charge amount owned by each dust should be a stochastic variable unlike a widely-known spacecraft charging process. We develop a numerical model of such a charging process, which will be embedded into the test particle analysis of the dust dynamics. We report some results from our simulations on the dust charging process and dynamics around the lunar hole.

Dust around Mira variables: An analysis of IRAS LRS spectra

NASA Technical Reports Server (NTRS)

Slijkhuis, S.

1989-01-01

The spatial extent and spectral appearance of the thin dust shell around Mira variables is determined largely by the dust absorptivity, Q(sub abs)(lambda), and the dust condensation temperature T(sub cond). Both Q(sub abs)(lambda) and T(sub cond) are extracted from IRAS low-resolution spectra (LRS) spectra. In order to do this, the assumption that the ratio of total power in the 10 micron feature to that in the 20 micron feature should be equal to that measured in other amorphous silicates (e.g., synthesized amorphous Mg2SiO4). It was found that T(sub cond) decreases with decreasing strength of the 10 micron feature, from T(sub cond) = 1000 K to 500 K (estimated error 20 percent). A value for the near-infrared dust absorptivity could not be determined. Although this parameter strongly affects the condensation radius, it hardly affects the shape of the LRS spectrum (as long as the optically thin approximation is valid), because it scales the spatial distribution of the dust. Information on the magnitude of the near-infrared dust absorptivity may be deduced from the unique carbon star BM Gem. This star has a LRS spectrum with silicate features indication an inner dust shell temperature of at least 1000 K. However, on the basis of observations in the 1920s-30s one may infer an inner dust shell radius of at least 6x10(exp 12)m. To have this high temperature at such a large distance, the near-infrared absorptivity of the dust must be high.

The Martian Dust Devil Electron Avalanche: Laboratory Measurements of the E-Field Fortifying Effects of Dust-Electron Absorption

NASA Technical Reports Server (NTRS)

Farrell, W. M.; McLain, J. L.; Collier, M. R.; Keller, J. W.

2017-01-01

Analogous to terrestrial dust devils, charged dust in Mars dust devils should become vertically stratified in the convective features, creating large scale E-fields. This E-field in a Martian-like atmosphere has been shown to stimulate the development of a Townsend discharge (electron avalanche) that acts to dissipate charge in regions where charge build-up occurs. While the stratification of the charged dust is a source of the electrical energy, the uncharged particulates in the dust population may absorb a portion of these avalanching electrons, thereby inhibiting dissipation and leading to the development of anomalously large E-field values. We performed a laboratory study that does indeed show the presence of enhanced E-field strengths between an anode and cathode when dust-absorbing filaments (acting as particulates) are placed in the avalanching electron flow. Further, the E-field threshold condition to create an impulsive spark discharge increases to larger values as more filaments are placed between the anode and cathode. We conclude that the spatially separated charged dust creates the charge centers and E-fields in a dust devil, but the under-charged portion of the population acts to reduce Townsend electron dissipation currents, further fortifying the development of larger-than-expected E-fields.

Exact relativistic models of conformastatic charged dust thick disks

NASA Astrophysics Data System (ADS)

García-Reyes, Gonzalo

2018-04-01

We construct relativistic models of charged dust thick disks for a particular conformastatic spacetime through a Miyamoto-Nagai transformation used in Newtonian gravity to model disk like galaxies. Two simple families of thick disk models and a family of thick annular disks based on the field of an extreme Reissner-Nordström black hole and a Morgan-Morgan-like metric are considered. The electrogeodesic motion of test particles around the structures are analyzed. Also the stability of the particles against radial perturbation is studied using an extension of the Rayleigh criteria of stability of a fluid in rest in a gravitational field. The models built satisfy all the energy conditions.

Multi-decadal and seasonal variability of dust observations in West Greenland.

NASA Astrophysics Data System (ADS)

Bullard, Joanna E.; Mockford, Tom

2017-04-01

Since the early 1900s expedition records from west Greenland have reported local dust storms. The Kangerlussuaq region, near the inland ice, is dry (mean annual precipitation <160 mm) with, on average, 150 snow-free days per year. The main local dust sources are active, proglacial outwash plains although reworking of loess deposits may also be important. This paper presents an analysis of 70-years of dust storm observations (1945-2015) based on WMO weather codes 6 (dust haze), 7 (raised dust or sand) and 9 (distant or past dust storm) and associated wind data. The 70-year average number of dust observations days is 5 per year but variable ranging from 0 observations to 23 observations in 1985. Over the past 7 decades the number of dust days has increased from <30 in 1945-54 to >75 in 1995-2004 and 2005-2015. The seasonality of dust observations has remained consistent throughout most of the period. Dust days occur all year round but are most frequent in May-June and September-October and are associated with minimum snow cover and glacial meltwater-driven sediment supply to the outwash plains during spring and fall flood events. Wind regime is bimodal dominated by katabatic winds from the northeast, which are strongest and most frequent during winter months (Nov-Jan), with less frequent, southwesterly winds generated by Atlantic storms mostly confined to spring (May, June). The southwesterly winds are those most likely to transport dust onto the Greenland ice sheet.

CHARGED DUST GRAIN DYNAMICS SUBJECT TO SOLAR WIND, POYNTING–ROBERTSON DRAG, AND THE INTERPLANETARY MAGNETIC FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lhotka, Christoph; Bourdin, Philippe; Narita, Yasuhito, E-mail: christoph.lhotka@oeaw.ac.at, E-mail: philippe.bourdin@oeaw.ac.at, E-mail: yasuhito.narita@oeaw.ac.at

We investigate the combined effect of solar wind, Poynting–Robertson drag, and the frozen-in interplanetary magnetic field on the motion of charged dust grains in our solar system. For this reason, we derive a secular theory of motion by the means of an averaging method and validate it with numerical simulations of the unaveraged equations of motions. The theory predicts that the secular motion of charged particles is mainly affected by the z -component of the solar magnetic axis, or the normal component of the interplanetary magnetic field. The normal component of the interplanetary magnetic field leads to an increase ormore » decrease of semimajor axis depending on its functional form and sign of charge of the dust grain. It is generally accepted that the combined effects of solar wind and photon absorption and re-emmision (Poynting–Robertson drag) lead to a decrease in semimajor axis on secular timescales. On the contrary, we demonstrate that the interplanetary magnetic field may counteract these drag forces under certain circumstances. We derive a simple relation between the parameters of the magnetic field, the physical properties of the dust grain, as well as the shape and orientation of the orbital ellipse of the particle, which is a necessary conditions for the stabilization in semimajor axis.« less

Long-Term Variability of Airborne Asian Dust Observed from TOMS

NASA Technical Reports Server (NTRS)

Herman, J. R.; Hsu, N. C.; Seftor, C. J.; Holben, B. N.; Holben, B. N.; Einaudi, Franco (Technical Monitor)

2001-01-01

Recent studies suggest that airborne Asian dust may not only play an important role in the regional radiation budget, but also influence the air quality over North America through long-range transport. In this paper, we use satellite data to investigate the long-term variability of airborne Asian dust as well as the daily variation of the dust aerosol distribution. By combining the Total Ozone Mapping Spectrometer (TOMS) aerosol index with National Centers for Environmental Prediction (NCEP) wind data, our analysis shows a strong correlation between the generation of dust storms in the region and the passage of springtime weather fronts. This is consistent with earlier studies performed by other researchers. According to both the Nimbus-7 and Earth-Probe TOMS data the Takla Makan desert, the Gobi desert, and the and region of Inner Mongolia are major sources of the eastward-flowing airborne Asian dust. Heavily populated areas in eastern China (e.g., Beijing) are often on the primary path of the dust storms originating in these desert regions. The increasing desertification north of the Beijing region has served to exacerbate problems stemming from these storms. The time series derived from 20 years of TOMS aerosol index data shows the first significant satellite evidence of the atmospheric effect of increasing desertification, indicating that the amount of dust blown eastward has increased strongly during the past few years including the year 2000.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Astrophysics Data System (ADS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J. J.; Déprez, G.; Farrell, W. M.; Houghton, I. M. P.; Renno, N. O.; Nicoll, K. A.; Tripathi, S. N.; Zimmerman, M.

2016-11-01

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kV m-1 to 100 kV m-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)—MicroARES ( Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ electrical measurements.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Technical Reports Server (NTRS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J J.; Deprez, G.; Farrell, William M.;

The Lunar Dust Environment

NASA Astrophysics Data System (ADS)

Szalay, Jamey Robert

Planetary bodies throughout the solar system are continually bombarded by dust particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with thick atmospheres, such as Venus, Earth, Mars and Titan are mostly protected from incoming dust impacts as these particles ablate in their atmospheres as 'shooting stars'. However, the majority of bodies in the solar system have no appreciable atmosphere and their surfaces are directly exposed to the flux of high speed dust grains. Impacts onto solid surfaces in space generate charged and neutral gas clouds, as well as solid secondary ejecta dust particles. Gravitationally bound ejecta clouds forming dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter and Saturn, and had not yet been observed near bodies with refractory regolith surfaces before NASA's Lunar Dust and Environment Explorer (LADEE) mission. In this thesis, we first present the measurements taken by the Lunar Dust Explorer (LDEX), aboard LADEE, which discovered a permanently present, asymmetric dust cloud surrounding the Moon. The global characteristics of the lunar dust cloud are discussed as a function of a variety of variables such as altitude, solar longitude, local time, and lunar phase. These results are compared with models for lunar dust cloud generation. Second, we present an analysis of the groupings of impacts measured by LDEX, which represent detections of dense ejecta plumes above the lunar surface. These measurements are put in the context of understanding the response of the lunar surface to meteoroid bombardment and how to use other airless bodies in the solar system as detectors for their local meteoroid environment. Third, we present the first in-situ dust measurements taken over the lunar sunrise terminator. Having found no excess of small grains in this region, we discuss its implications for the putative population of electrostatically lofted dust.

Characteristic Features of Double Layers in Rotating, Magnetized Plasma Contaminated with Dust Grains with Varying Charges

NASA Astrophysics Data System (ADS)

Paul, Jaydeep; Nag, Apratim; Devi, Karabi; Das, Himadri Sekhar

2018-03-01

The evolution and the characteristic features of double layers in a plasma under slow rotation and contaminated with dust grains with varying charges under the effect of an external magnetic field are studied. The Coriolis force resulting from the slow rotation is responsible for the generation of an equivalent magnetic field. A comparatively new pseudopotential approach has been used to derive the small amplitude double layers. The effect of the relative electron-ion concentration, as well as the temperature ratio, on the formation of the double layers has also been investigated. The study reveals that compressive, as well as rarefactive, double layers can be made to co-exist in plasma by controlling the dust charge fluctuation effect supplemented by variations of the plasma constituents. The effectiveness of slow rotation in causing double layers to exist has also emanated from the study. The results obtained could be of interest because of their possible applications in both laboratories and space.

Electrostatic effects on dust particles in space

NASA Astrophysics Data System (ADS)

Leung, Philip; Wuerker, Ralph

1992-02-01

The star scanner of the Magellan spacecraft experienced operational anomalies continuously during Magellan's journey to Venus. These anomalies were attributed to the presence of dust particles in the vicinity of the spacecraft. The dust particles, which were originated from the surface of thermal blankets, were liberated when the electrostatic force acting on them was of sufficient magnitude. In order to verify this hypothesis, an experimental program was initiated to study the mechanisms responsible for the release of dust particles from a spacecraft surface. In the experiments, dust particles were immersed in a plasma and/or subjected to ultra-violet irradiation. Results showed that the charging state of a dust particle was strongly dependent on the environment, and the charge on a dust particle was approximately 10(exp 3) elementary charges. Consequently, in the space environment, electrostatic force could be the most dominant force acting on a dust particle.

The Lunar Dust Pendulum

NASA Technical Reports Server (NTRS)

Kuntz, Kip; Collier, Michael R.; Stubbs, Timothy J.; Farrell, William M.

2011-01-01

Shadowed regions on the lunar surface acquire a negative potential. In particular, shadowed craters can have a negative potential with respect to the surrounding lunar regolith in sunlight, especially near the terminator regions. Here we analyze the motion of a positively charged lnnar dust grain in the presence of a shadowed crater at a negative potential in vacuum. Previous models describing the transport of charged lunar dust close to the surface have typically been limited to one-dimensional motion in the vertical direction, e.g. electrostatic levitation; however. the electric fields in the vicinity of shadowed craters will also have significant components in the horizontal directions. We propose a model that includes both the horizontal and vertical motion of charged dust grains near shadowed craters. We show that the dust grains execute oscillatory trajectories and present an expression for the period of oscillation drawing an analogy to the motion of a pendulum.

The Lunar Dust Pendulum

NASA Technical Reports Server (NTRS)

Collier, Michael R.; Stubbs, Timothy J.; Farrell, William M.

2011-01-01

Shadowed regions on the lunar surface acquire a negative potential. In particular, shadowed craters can have a negative potential with respect to the surrounding lunar regolith in sunlight, especially near the terminator regions. Here we analyze the motion of a positively charged lunar dust grain in the presence of a shadowed crater at a negative potential in vacuum. Previous models describing the transport of charged lunar dust close to the surface have typically been limited to one-dimensional motion in the vertical direction, e.g. electrostatic levitation; however, the electric fields in the vicinity of shadowed craters will also have significant components in the horizontal directions. We propose a model that includes both the horizontal and vertical motion of charged dust grains near shadowed craters. We show that the dust grains execute oscillatory trajectories and present an expression for the period of oscillation drawing an analogy to the motion of a pendulum.

Observed 20th Century Desert Dust Variability: Impact on Climate and Biogeochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahowald, Natalie; Kloster, Silvia; Engelstaedter, S.

2010-01-01

Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates ofmore » desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be -0.14 {+-} 0.11 W/m{sup 2} (1990-1999 vs. 1905-1914). The estimated radiative change due to dust is especially strong between the heavily loaded 1980-1989 and the less heavily loaded 1955-1964 time periods (-0.57 {+-} 0.46 W/m{sup 2}), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our

Inertia-Centric Stability Analysis of a Planar Uniform Dust Molecular Cloud with Weak Neutral-Charged Dust Frictional Coupling

NASA Astrophysics Data System (ADS)

K. Karmakar, P.; Borah, B.

2014-05-01

This paper adopts an inertia-centric evolutionary model to study the excitation mechanism of new gravito-electrostatic eigenmode structures in a one-dimensional (1-D) planar self-gravitating dust molecular cloud (DMC) on the Jeans scale. A quasi-neutral multi-fluid consisting of warm electrons, warm ions, neutral gas and identical inertial cold dust grains with partial ionization is considered. The grain-charge is assumed not to vary at the fluctuation evolution time scale. The neutral gas particles form the background, which is weakly coupled with the collapsing grainy plasma mass. The gravitational decoupling of the background neutral particles is justifiable for a higher inertial mass of the grains with higher neutral population density so that the Jeans mode frequency becomes reasonably large. Its physical basis is the Jeans assumption of a self-gravitating uniform medium adopted for fiducially analytical simplification by neglecting the zero-order field. So, the equilibrium is justifiably treated initially as “homogeneous”. The efficacious inertial role of the thermal species amidst weak collisions of the neutral-charged grains is taken into account. A standard multiscale technique over the gravito-electrostatic equilibrium yields a unique pair of Korteweg-de Vries (KdV) equations. It is integrated numerically by the fourth-order Runge-Kutta method with multi-parameter variation for exact shape analyses. Interestingly, the model is conducive for the propagation of new conservative solitary spectral patterns. Their basic physics, parametric features and unique characteristics are discussed. The results go qualitatively in good correspondence with the earlier observations made by others. Tentative applications relevant to space and astrophysical environments are concisely highlighted.

Electron energy distribution function, effective electron temperature, and dust charge in the temporal afterglow of a plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2016-05-15

Analytical expressions describing the variation of electron energy distribution function (EEDF) in an afterglow of a plasma are obtained. Especially, the case when the electron energy loss is mainly due to momentum-transfer electron-neutral collisions is considered. The study is carried out for different EEDFs in the steady state, including Maxwellian and Druyvesteyn distributions. The analytical results are not only obtained for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy but also for the case when the collisions are a power function of electron energy. Using analytical expressions for the EEDF, the effective electron temperaturemore » and charge of the dust particles, which are assumed to be present in plasma, are calculated for different afterglow durations. An analytical expression for the rate describing collection of electrons by dust particles for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy is also derived. The EEDF profile and, as a result, the effective electron temperature and dust charge are sufficiently different in the cases when the rate for momentum-transfer electron-neutral collisions is independent on electron energy and when the rate is a power function of electron energy.« less

Electrostatic dust transport on the surfaces of airless bodies

NASA Astrophysics Data System (ADS)

Wang, X.; Schwan, J.; Hsu, H. W.; Horanyi, M.

2015-12-01

The surfaces of airless bodies are charged due to the exposure to solar wind plasma and UV radiation. Dust particles on the regolith of these surfaces can become charged, and may move and even get lofted due to electrostatic force. Electrostatic dust transport has been a long-standing problem that may be related to many observed phenomena on the surfaces of airless planetary bodies, including the lunar horizon glow, the dust ponds on asteroid Eros, the spokes in Saturn's rings, and more recently, the collection of dust particles ejected off Comet 67P, observed by Rosetta. In order to resolve these puzzles, a handful of laboratory experiments have been performed in the past and demonstrated that dust indeed moves and lifts from surfaces exposed to plasma. However, the exact mechanisms for the mobilization of dust particles still remain a mystery. Current charging models, including the so-called "shared charge model" and the charge fluctuation theory, will be discussed. It is found that neither of these models can explain the results from either laboratory experiments or in-situ observations. Recently, single dust trajectories were captured with our new dust experiments, enabling novel micro-scale investigations. The particles' initial launch speeds and size distributions are analyzed, and a new so-called "patched charge model" is proposed to explain our findings. We identify the role of plasma micro-cavities that are formed in-between neighboring dust particles. The emitted secondary or photo- electrons are proposed to be absorbed inside the micro-cavities, resulting in significant charge accumulation on the exposed patches of the surfaces of neighboring particles. The resulting enhanced Coulomb force (repulsion) between particles is likely the dominant force to mobilize and lift them off the surface. The role of other properties, including surface morphology, cohesion and photoelectron charging, will also be discussed.

Dust Dynamics Near Planetary Surfaces

NASA Astrophysics Data System (ADS)

Colwell, Joshua; Hughes, Anna; Grund, Chris

Observations of a lunar "horizon glow" by several Surveyor spacecraft in the 1960s opened the study of the dynamics of charged dust particles near planetary surfaces. The surfaces of the Moon and other airless planetary bodies in the solar system (asteroids, and other moons) are directly exposed to the solar wind and ionizing solar ultraviolet radiation, resulting in a time-dependent electric surface potential. Because these same objects are also exposed to bombardment by micrometeoroids, the surfaces are usually characterized by a power-law size distribution of dust that extends to sub-micron-sized particles. Individual particles can acquire a charge different from their surroundings leading to electrostatic levitation. Once levitated, particles may simply return to the surface on nearly ballistic trajectories, escape entirely from the moon or asteroid if the initial velocity is large, or in some cases be stably levitated for extended periods of time. All three outcomes have observable consequences. Furthermore, the behavior of charged dust near the surface has practical implications for planned future manned and unmanned activities on the lunar surface. Charged dust particles also act as sensitive probes of the near-surface plasma environment. Recent numerical modeling of dust levitation and transport show that charged micron-sized dust is likely to accumulate in topographic lows such as craters, providing a mechanism for the creation of dust "ponds" observed on the asteroid 433 Eros. Such deposition can occur when particles are supported by the photoelectron sheath above the dayside and drift over shadowed regions of craters where the surface potential is much smaller. Earlier studies of the lunar horizon glow are consistent with those particles being on simple ballistic trajectories following electrostatic launching from the surface. Smaller particles may be accelerated from the lunar surface to high altitudes consistent with observations of high altitude

Trajectories of charged dust grains in the cometary environment

NASA Astrophysics Data System (ADS)

Horanyi, M.; Mendis, D. A.

1985-07-01

Using a simple model of the particles and fields environment of a comet, the trajectories of the smallest (micron- and submicron-sized) dust grains that are expected to be released from a cometary nucleus are calculated. It is shown that electromagnetic forces play a crucial role in the dynamics of these particles. The present calculations indicate not only the asymmetry of the sunward dust envelopes that have been suggested earlier by other authors, but they also indicate the possible existence of wavy dust features far down the tail, reminiscent of the peculiar wavy dust feature observed in the dust tail of Comet Ikeya-Seki 1965f. The importance of these findings in studying the lower end of the cometary dust mass spectrum during the forthcoming fly-by missions to Comet Halley is underscored.

Jovian dust streams: A monitor of Io's volcanic plume activity

USGS Publications Warehouse

Kruger, H.; Geissler, P.; Horanyi, M.; Graps, A.L.; Kempf, S.; Srama, R.; Moragas-Klostermeyer, G.; Moissl, R.; Johnson, T.V.; Grun, E.

2003-01-01

Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s-1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10-3 and 10 kg s-1, and is typically in the range of 0.1 to 1 kg s-1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes. Copyright 2003 by the American Geophysical Union.

Seasonal radiogenic isotopic variability of the African dust outflow to the tropical Atlantic Ocean and across to the Caribbean

NASA Astrophysics Data System (ADS)

Kumar, Ashwini; Abouchami, W.; Galer, S. J. G.; Singh, Satinder Pal; Fomba, K. W.; Prospero, J. M.; Andreae, M. O.

2018-04-01

In order to assess the impact of mineral dust on climate and biogeochemistry, it is paramount to identify the sources of dust emission. In this regard, radiogenic isotopes have recently been used successfully for tracing North African dust provenance and its transport across the tropical Atlantic to the Caribbean. Here we present two time series of radiogenic isotopes (Pb, Sr and Nd) in dusts collected at the Cape Verde Islands and Barbados in order to determine the origin of the dust and examine the seasonality of westerly dust outflow from Northern Africa. Aerosol samples were collected daily during two campaigns - February 2012 (winter) and June-July 2013 (summer) - at the Cape Verde Atmospheric Observatory (CVAO) on the island of São Vicente (16.9°N, 24.9°W). A one-year-long time series of aerosols from Barbados (13.16°N, 59.43°W) - a receptor region in the Caribbean - was sampled at a lower, monthly resolution. Our results resolve a seasonal isotopic signal at Cape Verde shown by daily variations, with a larger radiogenic isotope variability in winter compared to that in summer. This summer signature is also observed over Barbados, indicating similar dust provenance at both locations, despite different sampling years. This constrains the isotope fingerprint of Saharan Air Layer (SAL) dust that is well-mixed during its transport. This result provides unequivocal evidence for a permanent, albeit of variable strength, long-range transport of African dust to the Caribbean and is in full agreement with atmospheric models of North African dust emission and transport across the tropical Atlantic in the SAL. The seasonal isotopic variability is related to changes in the dust source areas - mainly the Sahara and Sahel regions - that are active all-year-round, albeit with variable contributions in summer versus the winter months. Our results provide little support for much dust contributed from the Bodélé Depression in Chad - the "dustiest" place on Earth

Variability in Population Density of House Dust Mites of Bitlis and Muş, Turkey.

PubMed

Aykut, M; Erman, O K; Doğan, S

2016-05-01

This study was conducted to investigate the relationship between the number of house dust mites/g dust and different physical and environmental variables. A total of 1,040 house dust samples were collected from houses in Bitlis and Muş Provinces, Turkey, between May 2010 and February 2012. Overall, 751 (72.2%) of dust samples were mite positive. The number of mites/g dust varied between 20 and 1,840 in mite-positive houses. A significant correlation was detected between mean number of mites and altitude of houses, frequency of monthly vacuum cleaning, number of individuals in the household, and relative humidity. No association was found between the number of mites and temperature, type of heating, existence of allergic diseases, age and structure of houses. A maximum number of mites were detected in summer and a minimum number was detected in autumn. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Performance of Electrostatic Dust Collectors (EDCs) for Endotoxin Assessment in Homes: Effect of Mailing, Placement, Heating and Electrostatic Charge

PubMed Central

Kilburg-Basnyat, Brita; Metwali, Nervana; Thorne, Peter S.

2016-01-01

Electrostatic Dust Collectors (EDCs) are in use for passive sampling of bioaerosols, but particular aspects of their performance have not yet been evaluated. This study investigated the effect of mailing EDCs on endotoxin loading and the effect of EDC deployment in front of and away from heated ventilation on endotoxin sampling. Endotoxin sampling efficiency of heated and unheated EDC cloths was also evaluated. Cross-country express mailing of dust-spiked EDCs yielded no significant changes in endotoxin concentrations compared to dust-only samples for both high spiked-EDCs (p=0.30) and low spiked-EDCs (p=0.36). EDCs were also deployed in 20 identical apartments with one EDC placed in front of the univent heater in each apartment and contemporaneous EDC placed on the built-in bookshelf in each apartment. The endotoxin concentrations were significantly different (p=0.049) indicating that the placement of EDC does impact endotoxin sampling. Heated and unheated EDCs were deployed for 7 days in pairs in farm homes. There was a significant difference between endotoxin concentrations (p=0.027) indicating that heating EDCs may diminish their electrostatic capabilities and impact endotoxin sampling. The last study investigated the electrostatic charge of 12 heated and 12 unheated EDC cloths. There was a significant difference in charge (p=0.009) which suggests that heating EDC cloths may make them less effective for sampling. In conclusion, EDCs can be mailed to and from deployment sites, EDC placement in relationship to ventilation is crucial, and heating EDCs reduces their electrostatic charge which may diminish their endotoxin sampling capabilities. PMID:26325020

Performance of electrostatic dust collectors (EDCs) for endotoxin assessment in homes: Effect of mailing, placement, heating, and electrostatic charge.

PubMed

Kilburg-Basnyat, Brita; Metwali, Nervana; Thorne, Peter S

2016-01-01

Electrostatic Dust Collectors (EDCs) are in use for passive sampling of bioaerosols, but particular aspects of their performance have not yet been evaluated. This study investigated the effect of mailing EDCs on endotoxin loading and the effect of EDC deployment in front of, and away from, heated ventilation on endotoxin sampling. Endotoxin sampling efficiency of heated and unheated EDC cloths was also evaluated. Cross-country express mailing of dust-spiked EDCs yielded no significant changes in endotoxin concentrations compared to dust-only samples for both high-spiked EDCs (p = 0.30) and low-spiked EDCs (p = 0.36). EDCs were also deployed in 20 identical apartments with one EDC placed in front of the univent heater in each apartment and contemporaneous EDC placed on the built-in bookshelf in each apartment. The endotoxin concentrations were significantly different (p = 0.049) indicating that the placement of EDC does impact endotoxin sampling. Heated and unheated EDCs were deployed for 7 days in pairs in farm homes. There was a significant difference between endotoxin concentrations (p = 0.027) indicating that heating EDCs may diminish their electrostatic capabilities and impact endotoxin sampling. The last study investigated the electrostatic charge of 12 heated and 12 unheated EDC cloths. There was a significant difference in charge (p = 0.009) which suggests that heating EDC cloths may make them less effective for sampling. In conclusion, EDCs can be mailed to and from deployment sites, EDC placement in relationship to ventilation is crucial, and heating EDCs reduces their electrostatic charge which may diminish their endotoxin sampling capabilities.

Effect of Charged-Magnetic Grains in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Perry, Jonathan; Matthews, Lorin; Hyde, Truell

Effects of Charged-Magnetic Grains in Protoplanetary Disks Jonathan, Perry, Lorin Swint Matthews, and Truell W. Hyde Center for Astrophysics, Space Physics, and Engi-neering Research, addressPlaceNamePlaceNameplaceBaylor StreetPlaceTypeUniversity, Stree-taddressOne Bear Place 97316 Waco, TX 76798 USA The interaction and growth of dust grains is an important process in early planetesimal formation. The structure of aggregates formed from dust depend largely on the initial properties within the dust population, whether the grains are charged or uncharged, magnetic or non-magnetic. Theoretical simulations exam-ining pair-wise interactions between aggregates indicate that charged magnetic grains exhibit different growth behavior than populations consisting of exclusively charged or exclusively mag-netic grains. This study extends that work to predict how charged-magnetic grains influence grain growth within a protoplanetary disk. An N-body simulation containing various mixtures of dust materials is used to examine the differences in dust coagulation in the presence of charged magnetic aggregates. The growth of the dust aggregates is analyzed to determine the effects that charged magnetic grains contribute to the evolution of the dust cloud. Comparison of the rate of aggregation as well as the dynamic exponent relating mass of a cluster to the elapsed time will both be discussed.

Regional variability in dust-on-snow processes and impacts in the Upper Colorado River Basin

USGS Publications Warehouse

Skiles, S. McKenzie; Painter, Thomas H.; Belnap, Jayne; Holland, Lacey; Reynolds, Richard L.; Goldstein, Harland L.; Lin, J.

2015-01-01

Dust deposition onto mountain snow cover in the Upper Colorado River Basin frequently occurs in the spring when wind speeds and dust emission peaks on the nearby Colorado Plateau. Dust loading has increased since the intensive settlement in the western USA in the mid 1880s. The effects of dust-on-snow have been well studied at Senator Beck Basin Study Area (SBBSA) in the San Juan Mountains, CO, the first high-altitude area of contact for predominantly southwesterly winds transporting dust from the southern Colorado Plateau. To capture variability in dust transport from the broader Colorado Plateau and dust deposition across a larger area of the Colorado River water sources, an additional study plot was established in 2009 on Grand Mesa, 150 km to the north of SBBSA in west central, CO. Here, we compare the 4-year (2010–2013) dust source, deposition, and radiative forcing records at Grand Mesa Study Plot (GMSP) and Swamp Angel Study Plot (SASP), SBBSA's subalpine study plot. The study plots have similar site elevations/environments and differ mainly in the amount of dust deposited and ensuing impacts. At SASP, end of year dust concentrations ranged from 0.83 mg g−1 to 4.80 mg g−1, and daily mean spring dust radiative forcing ranged from 50–65 W m−2, advancing melt by 24–49 days. At GMSP, which received 1.0 mg g−1 less dust per season on average, spring radiative forcings of 32–50 W m−2 advanced melt by 15–30 days. Remote sensing imagery showed that observed dust events were frequently associated with dust emission from the southern Colorado Plateau. Dust from these sources generally passed south of GMSP, and back trajectory footprints modelled for observed dust events were commonly more westerly and northerly for GMSP relative to SASP. These factors suggest that although the southern Colorado Plateau contains important dust sources, dust contributions from other dust sources contribute to dust loading in this region

Electrostatic Levitation of Lunar Dust: Preliminary Experimental Observations

NASA Astrophysics Data System (ADS)

Marshall, J.; Davis, S.; Laub, J.

2007-12-01

A lunar dust laboratory has been established in the Space Science Division at NASA Ames to evaluate fundamental electrostatic processes at the Moon's surface. Photoelectric charging, triboelectric charging, and interactions of these processes are investigated for dust-size materials. An electric field simulating the solar- plasma induced E-field of the lunar surface has been created with parallel charged capacitance plates. The field is linear, but field-shaping to create lunar-like exponentially decaying E-fields will be conducted in the near future. Preliminary tests of dust tribocharging have been conducted using a vibrating base plate within the electric field and have produced electrostatic levitation of 1.6 micron diameter silicate particles. We were able to achieve levitation in a modest vacuum environment (1.7 Torr) with the particles charged to approximately 15 percent of the Gaussian limit (defined as 2.64 E-5 C/m-2 for atmospheric air) at a threshold field strength of 2250 V/m. This charging corresponds to only a few hundred (negative) charges per particle; the field strength drops to 375 V/m when gravitationally scaled for the Moon, while dust tribocharging to greater than 100 percent of the Gaussian limit would be possible in the ultra high vacuum environment on the Moon and result in even lower threshold field strengths. We conclude therefore, that anthropogenic disturbance of lunar dust (as a result of NASA's proposed base construction, mining, vehicle motion, etc) could potentially pollute the lunar environment with levitated dust and severely impair scientific experiments requiring a pristine lunar exosphere.

Short-term variability of mineral dust, metals and carbon emission from road dust resuspension

NASA Astrophysics Data System (ADS)

Amato, Fulvio; Schaap, Martijn; Denier van der Gon, Hugo A. C.; Pandolfi, Marco; Alastuey, Andrés; Keuken, Menno; Querol, Xavier

2013-08-01

Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well described in the air quality models, hampering a reliable description of air pollution and related health effects. In this study we experimentally show that the emission strength of resuspension varies widely among road dust components/sources. Our results offer the first experimental evidence of different emission rates for mineral dust, heavy metals and carbon fractions due to traffic-induced resuspension. Also, the same component (or source) recovers differently in a road in Barcelona (Spain) and a road in Utrecht (The Netherlands). This finding has important implications on atmospheric pollution modelling, mostly for mineral dust, heavy metals and carbon species. After rain events, recoveries were generally faster in Barcelona rather than in Utrecht. The largest difference was found for the mineral dust (Al, Si, Ca). Tyre wear particles (organic carbon and zinc) recovered faster than other road dust particles in both cities. The source apportionment of road dust mass provides useful information for air quality management.

Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study

NASA Astrophysics Data System (ADS)

Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.

2016-12-01

Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and Sahel region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the Sahel experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the Sahel. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western Sahel using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the Sahel.

The Electric Environment of Martian Dust Devils

NASA Astrophysics Data System (ADS)

Barth, E. L.; Farrell, W. M.; Rafkin, S. C.

2017-12-01

While Martian dust devils have been monitored through decades of observations, we have yet to study their possible electrical effects from in situ instrumentation. However, evidence for the existence of active electrodynamic processes on Mars is provided by laboratory studies of analog material and field campaigns of dust devils on Earth. We have enabled our Mars regional scale atmospheric model (MRAMS) to estimate an upper limit on electric fields generated through dust devil circulations by including charged particles as defined from the Macroscopic Triboelectric Simulation (MTS) code. MRAMS is used to investigate the complex physics of regional, mesoscale, and microscale atmospheric phenomena on Mars; it is a 3-D, nonhydrostatic model, which permits the simulation of atmospheric flows with large vertical accelerations, such as dust devils. MTS is a 3-D particle code which quantifies charging associated with swirling, mixing dust grains; grains of pre-defined sizes and compositions are placed in a simulation box and allowed to move under the influence of winds and gravity. Our MRAMS grid cell size makes our results most applicable to dust devils of a few hundred meters in diameter. We have run a number of simulations to understand the sensitivity of the electric field strength to the particle size and abundance and the amount of charge on each dust grain. We find that Efields can indeed develop in Martian dust convective features via dust grain filtration effects. The overall value of these E-fields is strongly dependent upon dust grain size, dust load, and lifting efficiency, and field strengths can range from 100s of mV/m to 10s of kV/m.

Dust particles investigation for future Russian lunar missions.

NASA Astrophysics Data System (ADS)

Dolnikov, Gennady; Horanyi, Mihaly; Esposito, Francesca; Zakharov, Alexander; Popel, Sergey; Afonin, Valeri; Borisov, Nikolay; Seran, Elena; Godefroy, Michel; Shashkova, Inna; Kuznetsov, Ilya; Lyash, Andrey; Vorobyova, Elena; Petrov, Oleg; Lisin, Evgeny

One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Meteorites bombardment has accompanied by shock-explosive phenomena, disintegration and mix of the lunar soil in depth and on area simultaneously. As a consequence, the lunar soil has undergone melting, physical and chemical transformations. Recently we have the some reemergence for interest of Moon investigation. The prospects in current century declare USA, China, India, and European Union. In Russia also prepare two missions: Luna-Glob and Luna-Resource. Not last part of investigation of Moon surface is reviewing the dust condition near the ground of landers. Studying the properties of lunar dust is important both for scientific purposes to investigation the lunar exosphere component and for the technical safety of lunar robotic and manned missions. The absence of an atmosphere on the Moon's surface is leading to greater compaction and sintering. Properties of regolith and dust particles (density, temperature, composition, etc.) as well as near-surface lunar exosphere depend on solar activity, lunar local time and position of the Moon relative to the Earth's magneto tail. Upper layers of regolith are an insulator, which is charging as a result of solar UV radiation and the constant bombardment of charged particles, creates a charge distribution on the surface of the moon: positive on the illuminated side and negative on the night side. Charge distribution depends on the local lunar time, latitude and the electrical properties of the regolith (the presence of water in the regolith can influence the local distribution of charge). On light side of Moon near surface layer there exists possibility formation dusty plasma system. Altitude of levitation is depending from size of dust particle and Moon latitude. The distribution dust particle by size and altitude has estimated with taking into account photoelectrons, electrons and ions of solar wind, solar

Experimental Determination of Infrared Extinction Coefficients of Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Spann, J. F., Jr.; Abbas, M. M.

1998-01-01

This technique is based on irradiating a single isolated charged dust particle suspended in balance by an electric field, and measuring the scattered radiation as a function of angle. The observed scattered intensity profile at a specific wavelength obtained for a dust particle of known composition is compared with Mie theory calculations, and the variable parameters relating to the particle size and complex refractive index are adjusted for a best fit between the two profiles. This leads to a simultaneous determination of the particle radius, the complex refractive index, and the scattering and extinction coefficients. The results of these experiments can be utilized to examine the IRAS and DIRBE (Diffuse Infrared Background Experiment) infrared data sets in order to determine the dust particle physical characteristics and distributions by using infrared models and inversion techniques. This technique may also be employed for investigation of the rotational bursting phenomena whereby large size cosmic and interplanetary particles are believed to fragment into smaller dust particles.

Dust deposition and ambient PM10 concentration in northwest China: spatial and temporal variability

NASA Astrophysics Data System (ADS)

Zhang, Xiao-Xiao; Sharratt, Brenton; Chen, Xi; Wang, Zi-Fa; Liu, Lian-You; Guo, Yu-Hong; Li, Jie; Chen, Huan-Sheng; Yang, Wen-Yi

2017-02-01

Eolian dust transport and deposition are important geophysical processes which influence global bio-geochemical cycles. Currently, reliable deposition data are scarce in central and east Asia. Located at the boundary of central and east Asia, Xinjiang Province of northwestern China has long played a strategic role in cultural and economic trade between Asia and Europe. In this paper, we investigated the spatial distribution and temporal variation in dust deposition and ambient PM10 (particulate matter in aerodynamic diameter ≤ 10 µm) concentration from 2000 to 2013 in Xinjiang Province. This variation was assessed using environmental monitoring records from 14 stations in the province. Over the 14 years, annual average dust deposition across stations in the province ranged from 255.7 to 421.4 t km-2. Annual dust deposition was greater in southern Xinjiang (663.6 t km-2) than northern (147.8 t km-2) and eastern Xinjiang (194.9 t km-2). Annual average PM10 concentration across stations in the province varied from 100 to 196 µg m-3 and was 70, 115 and 239 µg m-3 in northern, eastern and southern Xinjiang, respectively. The highest annual dust deposition (1394.1 t km-2) and ambient PM10 concentration (352 µg m-3) were observed in Hotan, which is located in southern Xinjiang and at the southern boundary of the Taklamakan Desert. Dust deposition was more intense during the spring and summer than other seasons. PM10 was the main air pollutant that significantly influenced regional air quality. Annual average dust deposition increased logarithmically with ambient PM10 concentration (R2 ≥ 0.81). While the annual average dust storm frequency remained unchanged from 2000 to 2013, there was a positive relationship between dust storm days and dust deposition and PM10 concentration across stations. This study suggests that sand storms are a major factor affecting the temporal variability and spatial distribution of dust deposition in northwest China.

Nonlinear properties of small amplitude dust ion acoustic solitary waves

NASA Astrophysics Data System (ADS)

Ghosh, Samiran; Sarkar, S.; Khan, Manoranjan; Gupta, M. R.

2000-09-01

In this paper some nonlinear characteristics of small amplitude dust ion acoustic solitary wave in three component dusty plasma consisting of electrons, ions, and dust grains have been studied. Simultaneously, the charge fluctuation dynamics of the dust grains under the assumption that the dust charging time scale is much smaller than the dust hydrodynamic time scale has been considered here. The ion dust collision has also been incorporated. It has been seen that a damped Korteweg-de Vries (KdV) equation governs the nonlinear dust ion acoustic wave. The damping arises due to ion dust collision, under the assumption that the ion hydrodynamical time scale is much smaller than that of the ion dust collision. Numerical investigations reveal that the dust ion acoustic wave admits only a positive potential, i.e., compressive soliton.

Positively charged particles in dusty plasmas.

PubMed

Samarian, A A; Vaulina, O S; Nefedov, A P; Fortov, V E; James, B W; Petrov, O F

2001-11-01

The trapping of dust particles has been observed in a dc abnormal glow discharge dominated by electron attachment. A dust cloud of several tens of positively charged particles was found to form in the anode sheath region. An analysis of the experimental conditions revealed that these particles were positively charged due to emission process, in contrast to most other experiments on the levitation of dust particles in gas-discharge plasmas where negatively charged particles are found. An estimate of the particle charge, taking into account the processes of photoelectron and secondary electron emission from the particle surface, is in agreement with the experimental measured values.

IR photometry and models for the dust shells of two oxygen Mira variables

NASA Astrophysics Data System (ADS)

Bogdanov, M. B.; Taranova, O. G.; Shenavrin, V. I.

2015-05-01

Long-term JHKLM photometric measurements of the oxygen Mira variables RU Her and RS Vir are presented. Variations of the brightnesses and colors of these stars over the observation period are analyzed, and master light curves and color indices of these stars are derived. A linear trend was present in the mean infrared brightness of RS Vir on a time scale of ˜6000 day, possibly related to changes in the dust shell of the Mira. The results of model calculations of spherically symmetric dust shells of stars based on mean-flux data supplemented by observations from the IRAS and AKARI satellites in the intermediate- and far-IR are presented. The visual optical depth of the dust shell of RU Her, which has a temperature at its inner boundary T 1 = 590 K, is quite low: τ V = 0.33. The dust shell of RS Vir is much cooler ( T 1 = 410 K), and has τ V = 0.77. The estimated mass-loss rate of RU Her is 6.2 × 10-7 M ⊙/yr, while the mass-loss rate of RS Vir is 7.1 × 10-7 M ⊙/yr.

A combined rocket-borne and ground-based study of the sodium layer and charged dust in the upper mesosphere

NASA Astrophysics Data System (ADS)

Plane, John M. C.; Saunders, Russell W.; Hedin, Jonas; Stegman, Jacek; Khaplanov, Misha; Gumbel, Jörg; Lynch, Kristina A.; Bracikowski, Phillip J.; Gelinas, Lynette J.; Friedrich, Martin; Blindheim, Sandra; Gausa, Michael; Williams, Bifford P.

2014-10-01

The Hotel Payload 2 rocket was launched on January 31st 2008 at 20.14 LT from the Andøya Rocket Range in northern Norway (69.31° N, 16.01° E). Measurements in the 75-105 km region of atomic O, negatively-charged dust, positive ions and electrons with a suite of instruments on the payload were complemented by lidar measurements of atomic Na and temperature from the nearby ALOMAR observatory. The payload passed within 2.58 km of the lidar at an altitude of 90 km. A series of coupled models is used to explore the observations, leading to two significant conclusions. First, the atomic Na layer and the vertical profiles of negatively-charged dust (assumed to be meteoric smoke particles), electrons and positive ions, can be modelled using a self-consistent meteoric input flux. Second, electronic structure calculations and Rice-Ramsperger-Kassel-Markus theory are used to show that even small Fe-Mg-silicates are able to attach electrons rapidly and form stable negatively-charged particles, compared with electron attachment to O2 and O3. This explains the substantial electron depletion between 80 and 90 km, where the presence of atomic O at concentrations in excess of 1010 cm-3 prevents the formation of stable negative ions.

Transparent self-cleaning dust shield

DOEpatents

Mazumder, Malay K.; Sims, Robert A.; Wilson, James D.

2005-06-28

A transparent electromagnetic shield to protect solar panels and the like from dust deposition. The shield is a panel of clear non-conducting (dielectric) material with embedded parallel electrodes. The panel is coated with a semiconducting film. Desirably the electrodes are transparent. The electrodes are connected to a single-phase AC signal or to a multi-phase AC signal that produces a travelling electromagnetic wave. The electromagnetic field produced by the electrodes lifts dust particles away from the shield and repels charged particles. Deposited dust particles are removed when the electrodes are activated, regardless of the resistivity of the dust. Electrostatic charges on the panel are discharged by the semiconducting film. When used in conjunction with photovoltaic cells, the power for the device may be obtained from the cells themselves. For other surfaces, such as windshields, optical windows and the like, the power must be derived from an external source. One embodiment of the invention employs monitoring and detection devices to determine when the level of obscuration of the screen by dust has reached a threshold level requiring activation of the dust removal feature.

Variability of North African hydroclimate during the last two climatic cycles: New insights from dust flux and provenance

NASA Astrophysics Data System (ADS)

Skonieczny, C.; McGee, D.; Bory, A. J. M.; Winckler, G.; Bradtmiller, L.; Bout-Roumazeilles, V.; Perala-Dewey, J.; Delattre, M.; Kinsley, C. W.; Polissar, P. J.; Malaizé, B.

2016-12-01

Every year, several hundred teragrams of dust are emitted from the Sahara and Sahel regions. These mineral particles sensitively track variations in atmospheric circulation and continental aridity. Sediments of the Northeastern Tropical Atlantic Ocean (NETAO) are fed by this intense dust supply and comprise unique long-term archives of past Saharan/Sahelian dust emissions. Past modifications of dust characteristics in these sedimentary archives can provide unique insights into changes in environmental conditions in source areas (aridity, weathering), as well as changes in atmospheric transport (wind direction and strength). Here we document changes in sediment supply to the NETAO using marine sediment core MD03-2705 (18°05N; 21°09W; 3085m water depth). This record is strategically located under the influence of seasonal dust plumes, and marine sediments of this area have revealed that past dust inputs were sensitive to global climate changes over the late Quaternary. We will focus our study on the last two climatic cycles (0-240ka), a period orbitally characterized by changes in the amplitude of both precession (MIS6-5 vs. MIS1-2) and ice volume (MIS 7 vs. MIS5). We will present, for the first time in this area, a continuous high-resolution record of dust, opal, carbonate and organic matter fluxes using 230Th-normalization. The constant flux proxy 230Thxs provides flux data that are not substantially affected by lateral advection or age model errors. These fluxes data will be complemented by grain-size, clay mineralogical and geochemical (major elements) analysis. By pairing dust flux measurements with complementary proxy data reflecting changes in aridity, wind strength and dust source, this study will provide a robust, continuous record of the magnitude and pacing of the North African hydroclimate variability through the last two climatic cycles. In particular, this long-term study will offer the opportunity to compare the well-documented North African climate

Non-monotonic spatial distribution of the interstellar dust in astrospheres: finite gyroradius effect

NASA Astrophysics Data System (ADS)

Katushkina, O. A.; Alexashov, D. B.; Izmodenov, V. V.; Gvaramadze, V. V.

2017-02-01

High-resolution mid-infrared observations of astrospheres show that many of them have filamentary (cirrus-like) structure. Using numerical models of dust dynamics in astrospheres, we suggest that their filamentary structure might be related to specific spatial distribution of the interstellar dust around the stars, caused by a gyrorotation of charged dust grains in the interstellar magnetic field. Our numerical model describes the dust dynamics in astrospheres under an influence of the Lorentz force and assumption of a constant dust charge. Calculations are performed for the dust grains with different sizes separately. It is shown that non-monotonic spatial dust distribution (viewed as filaments) appears for dust grains with the period of gyromotion comparable with the characteristic time-scale of the dust motion in the astrosphere. Numerical modelling demonstrates that the number of filaments depends on charge-to-mass ratio of dust.

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-06-01

Long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and merged with results obtained from the Northeast Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust. Including codes 04-06 into the criteria for dust observations, the frequency was 135 dust days annually. The Sea Level Pressure (SLP) oscillation controlled whether dust events occurred in NE (16.4 dust days annually) or in southern part of Iceland (about 18 dust days annually). The most dust-frequent decade in S Iceland was the 1960s while the most frequent decade in NE Iceland was the 2000s. A total of 32 severe dust storms (visibility < 500 m) was observed in Iceland with the highest frequency during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May-September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March-May). About half of dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between PM10 concentrations and visibility during dust observations at the stations Vik and Storhofdi. This study shows that Iceland is among the dustiest areas of the world and dust is emitted the year-round.

Dust-wall and dust-plasma interaction in the MIGRAINe code

NASA Astrophysics Data System (ADS)

Vignitchouk, L.; Tolias, P.; Ratynskaia, S.

2014-09-01

The physical models implemented in the recently developed dust dynamics code MIGRAINe are described. A major update of the treatment of secondary electron emission, stemming from models adapted to typical scrape-off layer temperatures, is reported. Sputtering and plasma species backscattering are introduced from fits of available experimental data and their relative importance to dust charging and heating is assessed in fusion-relevant scenarios. Moreover, the description of collisions between dust particles and plasma-facing components, based on the approximation of elastic-perfectly plastic adhesive spheres, has been upgraded to take into account the effects of particle size and temperature.

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-12-01

The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May-September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March-May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

Properties of dust particles near Saturn inferred from voltage pulses induced by dust impacts on Cassini spacecraft

NASA Astrophysics Data System (ADS)

Ye, S.-Y.; Gurnett, D. A.; Kurth, W. S.; Averkamp, T. F.; Kempf, S.; Hsu, H.-W.; Srama, R.; Grün, E.

2014-08-01

The Cassini Radio and Plasma Wave Science (RPWS) instrument can detect dust particles when voltage pulses induced by the dust impacts are observed in the wideband receiver. The size of the voltage pulse is proportional to the mass of the impacting dust particle. For the first time, the dust impacts signals measured by dipole and monopole electric antennas are compared, from which the effective impact area of the spacecraft is estimated to be 4 m2. In the monopole mode, the polarity of the dust impact signal is determined by the spacecraft potential and the location of the impact (on the spacecraft body or the antenna), which can be used to statistically infer the charge state of the spacecraft. It is shown that the differential number density of the dust particles near Saturn can be characterized as a power law dn/dr ∝ rμ, where μ ~ - 4 and r is the particle size. No peak is observed in the size distribution, contrary to the narrow size distribution found by previous studies. The RPWS cumulative dust density is compared with the Cosmic Dust Analyzer High Rate Detector measurement. The differences between the two instruments are within the range of uncertainty estimated for RPWS measurement. The RPWS onboard dust recorder and counter data are used to map the dust density and spacecraft charging state within Saturn's magnetosphere.

Indirect Charged Particle Detection: Concepts and a Classroom Demonstration

NASA Astrophysics Data System (ADS)

Childs, Nicholas B.; Horányi, Mihály; Collette, Andrew

2013-11-01

We describe the principles of macroscopic charged particle detection in the laboratory and their connections to concepts taught in the physics classroom. Electrostatic dust accelerator systems, capable of launching charged dust grains at hypervelocities (1-100 km/s), are a critical tool for space exploration. Dust grains in space typically have large speeds relative to the probes or satellites that encounter them. Development and testing of instruments that look for dust in space therefore depends critically on the availability of fast, well-characterized dust grains in the laboratory. One challenge for the experimentalist is to precisely measure the speed and mass of laboratory dust particles without disturbing them. Detection systems currently in use exploit the well-known effect of image charge to register the passage of dust grains without changing their speed or mass. We describe the principles of image charge detection and provide a simple classroom demonstration of the technique using soup cans and pith balls.

Dust Particle Dynamics in The Presence of Highly Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Lynch, Brian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene

2016-10-01

Complex plasmas are four component plasmas that contain, in addition to the usual electrons, ions, and neutral atoms, macroscopic electrically charged (nanometer to micrometer) sized ``dust'' particles. These macroscopic particles typically obtain a net negative charge due to the higher mobility of electrons compared to that of ions. Because the electrons, ions, and dust particles are charged, their dynamics may be significantly modified by the presence of electric and magnetic fields. Possible consequences of this modification may be the charging rate and the equilibrium charge. For example, in the presence of a strong horizontal magnetic field (B >1 Tesla), it may be possible to observe dust particle gx B deflection and, from that deflection, determine the dust grain charge. In this poster, we present recent data from performing multiple particle dropping experiments to characterize the g x B deflection in the Magnetized Dusty Plasma Experiment (MDPX). This work is supported by funding from the U. S. Department of Energy Grant Number DE - SC0010485 and the NASA/Jet Propulsion Laboratory, JPL-1543114.

Characterizing the Variable Dust Permeability of Planet-induced Gaps

NASA Astrophysics Data System (ADS)

Weber, Philipp; Benítez-Llambay, Pablo; Gressel, Oliver; Krapp, Leonardo; Pessah, Martin E.

2018-02-01

Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can significantly alter the dust dynamics. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle size for retention outside a gap as a function of particle size, as well as various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet’s orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains—potentially limiting the accretion of solids onto forming terrestrial planets.

Interannual variability of planet-encircling dust storms on Mars

NASA Technical Reports Server (NTRS)

Zurek, Richard W.; Martin, Leonard J.

1993-01-01

A recent review of earth-based telescopic observations of Mars together with Viking orbiter and lander data are employed to estimate the frequency of occurrence of planet-encircling dust storms over the past century and to test whether the period spanned by the Mariner 9 and Viking missions to Mars is representative of the decades prior to 1950. Both spacecraft and earth-based observations suggest that planet-encircling dust storms on Mars occur during a 'dust storm season' in southern spring and summer. Viking data show that planet-encircling dust storms could have occurred in the past on Mars without being detected from earth during years in which Mars was far from earth during the dust storm season. Planet-encircling storms were absent during the dust storm seasons monitored during several favorable oppositions prior to 1956 and after 1986. The change of a planet-encircling dust storm occurring in any arbitrary Mars year is estimated to be approximately one in three, if this occurrence is random from year to year and yet restricted seasonally to southern spring and summer.

What controls springtime fine dust variability in the western United States? Implications for air quality and public health risks under future climate change.

NASA Astrophysics Data System (ADS)

Achakulwisut, P.; Mickley, L. J.; Shen, L.; Anenberg, S.

2017-12-01

Studies suggest that deposition of atmospheric dust and its surface concentrations have recently been increasing in the Southwest, and a key concern is that climate change will impact dust mobilization and transport across the western United States. Here we diagnose the dominant meteorological factors driving observed fine dust interannual variability in the western United States during 2002-2015 in March-May, and investigate the implications of our results for future dust levels. Empirical orthogonal function analysis suggests that for each spring month, 50-61% of present-day variance in fine dust can be explained by either a coherent pattern of co-variability across the West or a dipole Northwest-Southwest pattern. We identify the key drivers of fine dust variability to be regional precipitation, temperature, and soil moisture, which in turn are influenced at least in part by large-scale changes in sea surface temperature and/or atmospheric circulation patterns. Fluctuations in the trans-Pacific transport of Asian dust also contribute to fine dust variability in March and April. We find that March fine dust concentrations have increased from 2002 to 2015 in Southwest regions (0.09 ± 0.07 μg m-3 a-1). Multiple linear regression analysis suggests that these increases are associated with: (1) regionally drier and warmer conditions driven by constructive interference between El Niño Southern-Oscillation and Pacific Decadal Oscillation; (2) soil moisture reductions in areas spanning the North American deserts; and (3) stronger trans-Pacific transport. We then use observed drought-sensitivities to project future changes in annual mean fine dust during the late-21st century (2076-2095), using bias-corrected downscaled meteorological outputs from 23 CMIP5 models following two Representative Concentration Pathways (RCP2.6 and RCP8.5). Together with projections of future population and baseline incidence rates, and results from epidemiological studies of health risks

Electrostatic Characterization of Lunar Dust Simulants

NASA Technical Reports Server (NTRS)

Calle, C. I.; Buhler, C. R.; Ritz, M. L.

2008-01-01

Lunar dust can jeopardize exploration activities due to its ability to cling to most surfaces. In this paper, we report on our measurements of the electrostatic properties of the lunar soil simulants. Methods have been developed to measure the volume resistivity, dielectric constant, chargeability, and charge decay of lunar soil. While the first two parameters have been measured in the past [Olhoeft 1974], the last two have never been measured directly on the lunar regolith or on any of the Apollo samples. Measurements of the electrical properties of the lunar samples are being performed in an attempt to answer important problems that must be solved for the development of an effective dust mitigation technology, namely, how much charge can accumulate on the dust and how long does the charge remain on surfaces. The measurements will help develop coatings that are compatible with the intrinsic electrostatic properties of the lunar regolith.

Shock structures in a strongly coupled self-gravitating opposite-polarity dust plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamun, A. A.; Schlickeiser, R.

2016-03-15

A strongly coupled, self-gravitating, opposite-polarity dust plasma (containing strongly coupled inertial positive and negative dust fluids, and inertialess weakly coupled ions) is considered. The generalized hydrodynamic model and the reductive perturbation method are employed to examine the possibility for the formation of the dust-acoustic (DA) shock structures in such an opposite-polarity dust plasma. It has been shown that the strong correlation among charged dust is a source of dissipation and is responsible for the formation of the DA shock structures in such the opposite-polarity dust plasma medium. The parametric regimes for the existence of the DA shock structures (associated withmore » electrostatic and gravitational potentials) and their basic properties (viz., polarity, amplitude, width, and speed) are found to be significantly modified by the combined effects of positively charged dust component, self-gravitational field, and strong correlation among charged dust. The implications of our results in different space plasma environments and laboratory plasma devices are briefly discussed.« less

Theory of Dust Voids in Plasmas

NASA Technical Reports Server (NTRS)

Goree, J.; Morfill, G. E.; Tsytovich, V. N.; Vladimirov, S. V.

1999-01-01

Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M = 1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

Rover wheel charging on the lunar surface

NASA Astrophysics Data System (ADS)

Jackson, Telana L.; Farrell, William M.; Zimmerman, Michael I.

2015-03-01

The environment at the Moon is dynamic, with highly variable solar wind plasma conditions at the lunar dayside, terminator, and night side regions. Moving objects such as rover wheels will charge due to contact electrification with the surface, but the degree of charging is controlled by the local plasma environment. Using a dynamic charging model of a wheel, it is demonstrated herein that moving tires will tribocharge substantially when venturing into plasma-current starved regions such as polar craters or the lunar nightside. The surface regolith distribution and the overall effect on charge accumulation of grains cohesively sticking to the rover tire has been incorporated into the model. It is shown that dust sticking can limit the overall charge accumulated on the system. However charge dissipation times are greatly increased in shadowed regions and can present a potential hazard to astronauts and electrical systems performing extra-vehicular activities. We show that dissipation times change with wheel composition and overall system tribocharging is dependent upon wheel velocity.

Photoemission of Single Dust Grains for Heliospheric Conditions

NASA Technical Reports Server (NTRS)

Spann, James F., Jr.; Venturini, Catherine C.; Abbas, Mian M.; Comfort, Richard H.

2000-01-01

Initial results of an experiment to measure the photoemission of single dust grains as a function of far ultraviolet wavelengths are presented. Coulombic forces dominate the interaction of the dust grains in the heliosphere. Knowledge of the charge state of dust grains, whether in a dusty plasma (Debye length < intergrain distance) or in the diffuse interplanetary region, is key to understanding their interaction with the solar wind and other solar system constituents. The charge state of heliospheric grains is primarily determined by primary electron and ion collisions, secondary electron emission and photoemission due to ultraviolet sunlight. We have established a unique experimental technique to measure the photoemission of individual micron-sized dust grains in vacuum. This technique resolves difficulties associated with statistical measurements of dust grain ensembles and non-static dust beams. The photoemission yield of Aluminum Oxide 3-micron grains For wavelengths from 120-300 nm with a spectral resolution of 1 nm FWHM is reported. Results are compared to interplanetary conditions.

Indirect Charged Particle Detection: Concepts and a Classroom Demonstration

ERIC Educational Resources Information Center

Childs, Nicholas B.; Horányi, Mihály; Collette, Andrew

2013-01-01

We describe the principles of macroscopic charged particle detection in the laboratory and their connections to concepts taught in the physics classroom. Electrostatic dust accelerator systems, capable of launching charged dust grains at hypervelocities (1-100 km/s), are a critical tool for space exploration. Dust grains in space typically have…

Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

NASA Astrophysics Data System (ADS)

Zhang, Kai; Zhao, Chun; Wan, Hui; Qian, Yun; Easter, Richard C.; Ghan, Steven J.; Sakaguchi, Koichi; Liu, Xiaohong

2016-02-01

This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities. In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by mesoscale systems and fine-scale topography over land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature. Wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis data set at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from 1 year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing.The wind-distribution-based emission calculations are implemented in CAM5. In terms of computational cost, the increase in total simulation time turns out to be less than 3 %. Simulations at 2° resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and mesoscale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the default model

Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

DOE PAGES

Zhang, Kai; Zhao, Chun; Wan, Hui; ...

2016-02-12

This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities. In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by mesoscale systems and fine-scale topography overmore » land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature. Wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis data set at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from 1 year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing.The wind-distribution-based emission calculations are implemented in CAM5. In terms of computational cost, the increase in total simulation time turns out to be less than 3 %. Simulations at 2° resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and mesoscale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the

Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kai; Zhao, Chun; Wan, Hui

This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities. In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by mesoscale systems and fine-scale topography overmore » land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature. Wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis data set at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from 1 year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing.The wind-distribution-based emission calculations are implemented in CAM5. In terms of computational cost, the increase in total simulation time turns out to be less than 3 %. Simulations at 2° resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and mesoscale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the

North African dust emissions and transport

NASA Astrophysics Data System (ADS)

Engelstaedter, Sebastian; Tegen, Ina; Washington, Richard

2006-11-01

The need for a better understanding of the role of atmospheric dust in the climate system and its impact on the environment has led to research of the underlying causes of dust variability in space and time in recent decades. North Africa is one of the largest dust producing regions in the world with dust emissions being highly variable on time scales ranging from diurnal to multiannual. Changes in the dust loading are expected to have an impact on regional and global climate, the biogeochemical cycle, and human environments. The development of satellite derived products of global dust distributions has improved our understanding of dust source regions and transport pathways in the recent years. Dust models are now capable of reproducing more realistic patterns of dust distributions due to an improved parameterization of land surface conditions. A recent field campaign has improved our understanding of the natural environment and emission processes of the most intense and persistent dust sources in the world, the Bodélé Depression in Chad. In situ measurements of dust properties during air craft observations in and down wind of source regions have led to new estimates of the radiative forcing effects which are crucial in predicting future climate change. With a focus on the North African desert regions, this paper provides a review of the understanding of dust source regions, the variability of dust emissions, climatic controls of dust entrainment and transport, the role of human impact on dust emission, and recent developments of global and regional dust models.

Development of Charge to Mass Ratio Microdetector for Future Mars Mission

NASA Technical Reports Server (NTRS)

Chen, Yuan-Lian Albert

2003-01-01

The Mars environment comprises a dry, cold and low air pressure atmosphere with low gravity (0.38g) and high resistivity soil. The global dust storms that cover a large portion of Mars are observed often from Earth. This environment provides an ideal condition for turboelectric charging. The extremely dry conditions on the Martian surface have raised concerns that electrostatic charge buildup will not be dissipated easily. If turboelectrically generated charge cannot be dissipated or avoided, then dust will accumulate on charged surfaces and electrostatic discharge may cause hazards for future exploration missions. The low surface on Mars helps to prolong the charge decay on the dust particles and soil. To better understanding the physics of Martian charged dust particles is essential to future Mars missions. We research and design two sensors, velocity/charge sensor and PZT momentum sensors, to measure the velocity distribution, charge distribution and mass distribution of Martian wed dust particles. These sensors are fabricated at NASA Kenney Space Center, Electrostatic and Surface Physics Laboratory. The sensors are calibrated. The momentum sensor is capable to measure 45 pan size particles. The designed detector is very simple, robust, without moving parts, and does not require a high voltage power supply. Two sensors are combined to form the Dust Microdetector - CHAL.

Ubiquitous Instabilities of Dust Moving in Magnetized Gas

NASA Astrophysics Data System (ADS)

Hopkins, Philip F.; Squire, Jonathan

2018-06-01

Squire & Hopkins (2017) showed that coupled dust-gas mixtures are generically subject to "resonant drag instabilities" (RDIs), which drive violently-growing fluctuations in both. But the role of magnetic fields and charged dust has not yet been studied. We therefore explore the RDI in gas which obeys ideal MHD and is coupled to dust via both Lorentz forces and drag, with an external acceleration (e.g., gravity, radiation) driving dust drift through gas. We show this is always unstable, at all wavelengths and non-zero values of dust-to-gas ratio, drift velocity, dust charge, "stopping time" or drag coefficient (for any drag law), or field strength; moreover growth rates depend only weakly (sub-linearly) on these parameters. Dust charge and magnetic fields do not suppress instabilities, but give rise to a large number of new instability "families," each with distinct behavior. The "MHD-wave" (magnetosonic or Alfvén) RDIs exhibit maximal growth along "resonant" angles where the modes have a phase velocity matching the corresponding MHD wave, and growth rates increase without limit with wavenumber. The "gyro" RDIs are driven by resonances between drift and Larmor frequencies, giving growth rates sharply peaked at specific wavelengths. Other instabilities include "acoustic" and "pressure-free" modes (previously studied), and a family akin to cosmic ray instabilities which appear when Lorentz forces are strong and dust streams super-Alfvénically along field lines. We discuss astrophysical applications in the warm ISM, CGM/IGM, HII regions, SNe ejecta/remnants, Solar corona, cool-star winds, GMCs, and AGN.

Orbit-spin coupling and the interannual variability of global-scale dust storm occurrence on Mars

NASA Astrophysics Data System (ADS)

Shirley, James H.; Mischna, Michael A.

2017-05-01

A new physical hypothesis predicts that a weak coupling of the orbital and rotational motions of extended bodies may give rise to a modulation of circulatory flows within their atmospheres. Driven cycles of intensification and relaxation of large-scale circulatory flows are predicted, with the phasing of these changes linked directly to the rate of change of the orbital angular momentum, dL/dt, with respect to inertial frames. We test the hypothesis that global-scale dust storms (GDS) on Mars may occur when periods of circulatory intensification (associated with positive and negative extrema of the dL/dt waveform) coincide with the southern summer dust storm season on Mars. The orbit-spin coupling hypothesis additionally predicts that the intervening 'transitional' periods, which are characterized by the disappearance and subsequent sign change of dL/dt, may be unfavorable for the occurrence of GDS, when they occur during the southern summer dust storm season. These hypotheses are strongly supported by comparisons between calculated dynamical time series of dL/dt and historic observations. All of the nine known global-scale dust storms on Mars took place during Mars years when circulatory intensification during the dust storm season is 'retrodicted' under the orbit-spin coupling hypothesis. None of the historic global-scale dust storms of our catalog occurred during transitional intervals. Orbit-spin coupling appears to play an important role in the excitation of the interannual variability of the atmospheric circulation of Mars.

Oblique Interaction of Dust-ion Acoustic Solitons with Superthermal Electrons in a Magnetized Plasma

NASA Astrophysics Data System (ADS)

Parveen, Shahida; Mahmood, Shahzad; Adnan, Muhammad; Qamar, Anisa

2018-01-01

The oblique interaction between two dust-ion acoustic (DIA) solitons travelling in the opposite direction, in a collisionless magnetized plasma composed of dynamic ions, static dust (positive/negative) charged particles and interialess kappa distributed electrons is investigated. By employing extended Poincaré-Lighthill-Kuo (PLK) method, Korteweg-de Vries (KdV) equations are derived for the right and left moving low amplitude DIA solitons. Their trajectories and corresponding phase shifts before and after their interaction are also obtained. It is found that in negatively charged dusty plasma above the critical dust charged to ion density ratio the positive polarity pulse is formed, while below the critical dust charged density ratio the negative polarity pulse of DIA soliton exist. However it is found that only positive polarity pulse of DIA solitons exist for the positively charged dust particles case in a magnetized nonthermal plasma. The nonlinearity coefficient in the KdV equation vanishes for the negatively charged dusty plasma case for a particular set of parameters. Therefore, at critical plasma density composition for negatively charged dust particles case, the modified Korteweg-de Vries (mKdV) equations having cubic nonlinearity coefficient of the DIA solitons, and their corresponding phase shifts are derived for the left and right moving solitons. The effects of the system parameters including the obliqueness of solitons propagation with respect to magnetic field direction, superthermality of electrons and concentration of positively/negatively static dust charged particles on the phase shifts of the colliding solitons are also discussed and presented numerically. The results are applicable to space magnetized dusty plasma regimes.

The Fogging Method with Variable of Nozle Diameter as the Mitigation Alternative for Spreading the Dust of Cement

NASA Astrophysics Data System (ADS)

Purwanta, J.; Marnoto, T.; Setyono, P.; Ramelan, A. H.

2018-03-01

The cement plant impacts on the lives of people around the factory site, one of them on the air quality, especially dust. Cement plant has made various efforts to mitigate dust generated, but the reality on the ground is still a lot of dust flying around either of the cement factory chimneys and transportation. The purpose of this study was to find the optimum condition of nozle diameter from the cement dust catcher, for mitigation the dust spread to around the cement plant. This study uses research methods such as collecting secondary data which includes data intensity rainfall, the average long rains, wind speed and direction as well as data quality monitoring dust around PT. Semen Gresik (Persero) Tbk. Tuban plant. To determine the wind direction propensity models, use a soft Windrose file. To determine the impact on the spread of dust into the environment using secondary data monitoring air quality. Results of the study is that the mitigation of dust around the cement plant is influenced by natural factors, namely the tendency of wind direction, rainfall and rainy days, and the rate of dust emission from the chimney. I try for operate the cement dust catcher with variable of nozle diameter. Finally, I find the optimum condition of nozle diameter for cement dust catcher is 1.40 mm, with line equation is y = 149.09.e 1.6237.x and error 5%. In that condition, nozle can make the fog with a good quality and it can catch the cement dust well.

Atmospheric Circulation and Climate Variability over the Last 200 Years from Talos Dome (East Antarctica) Dust Record

NASA Astrophysics Data System (ADS)

Sala, M.; Marino, F.; Delmonte, B.; Uglietti, C.; Maggi, V.

2004-12-01

Aeolian dust concentration and size distribution measurements performed on the first 30 m of the Talos Dome (East Antarctica, 72°48'S, 159°06'E) firn core, drilled during the 1996 PNRA-ITASE (Programma Nazionale di Ricerche in Antartide-International Trans-Antarctic Scienticic Expedition) traverse, provide a record of recent climatic and atmospheric history over the East Antarctic sector facing the Ross Sea-Oates Coast (Southern Ocean). Talos Dome (2316 m a.s.l.) is located in the Northern Victoria Land at the topoghraphic summit of a dome (Frezzotti et al., 1998). More than 500 samples analyzed from 1.5 to 30 m allowed to obtain a record of atmospheric mineral dust at high temporal resolution (sub-annual) for the last ~200 years. The average dust concentration and size distribution levels, as well as their variability, are higher from early 1800 to the mid-1900 with respect to the most recent part of the record, with a sharp decrease occurring around 1950-55. The concentration and size distribution of microparticles almost covary over the period investigated, high dust concentrations being generally associated to coarser dust and vice versa. Moreover, average modal value of the volume (mass) background dust size distribution and total dust concentration are slightly higher that typical Holocene values for other East Antarctic sites (Delmonte et al., 2004). These evidences suggest that mixing of fine-grained atmospheric dust from long-range transport with more local sources such as the rock outcrops of the Northern Victoria Land, for example, cannot be excluded. A possible local contribution for dust was also suggested by Maggi and Petit (1998) from earlier dust investigations on a firn core drilled in the Northern Victoria Land close to the Transantarctic Mountains (Hercules Nevé, 73°06'S; 165°27'E). Interestingly, the dust concentration and size distribution profiles are embedded by clear cycles having periodicity of 7-8 years on average overall the 200

The Charged Aerosol Release Experiment (CARE)

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Ganguli, G.; Lampe, M.; Scales, W. A.

2005-12-01

The physics of radar scatter from charged particulates in the upper atmosphere will be studied with the Charged Aerosol Release Experiment (CARE). In 2008, two rocket payloads are being designed for launch North America. The purpose of the CARE program is to identify the mechanisms for radar scatter from polar mesospheric clouds. Polar mesospheric summer echoes (PMSE) are observed at high latitudes when small concentrations of electrons (one-thousand per cubic cm) become attached to sub-micron dust particles. Radar in the VHF (30-300 MHz) frequency range have seen 30 dB enhancements in radar echoes coincident with formation of ice near 85 km altitude. Radar echoes from electrons in the vicinity of charged dust have been observed for frequencies exceeding 1 GHz. Some fundamental questions that remain about the scatting process are: (1) What is the relative importance of turbulent scatter versus incoherent (i.e., Thompson) scatter from individual electrons? (2) What produces the inhomogeneous electron/dust plasma? (3) How is the radar scatter influenced by the density of background electrons, plasma instabilities and turbulence, and photo detachment of electrons from the particulates? These questions will be addressed when the CARE program releases 50 kg of dust particles in an expanding shell at about 300 km altitude. The dust will be manufactured by the chemical release payload to provide particulate sizes in the 10 to 1000 nm range. The expanding dust shell will collect electrons making dense, heavy particles the move the negative charges across magnetic field lines. Plasma turbulence and electron acceleration will be formed from the charge separation between the magnetized oxygen ions in the background ionosphere and the streaming negatively charged dust. Simulations of this process provide estimates of plasma structure which can scatter radar. As the particulates settle through the lower thermosphere into the mesosphere, artificial mesospheric clouds will be

Self-confinement of finite dust clusters in isotropic plasmas.

PubMed

Miloshevsky, G V; Hassanein, A

2012-05-01

Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas.

Propagation of electromagnetic wave in dusty plasma and the influence of dust size distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; China Research Institute of Radio Wave Propagation; Wu, Jian

The effect of charged dust particle and their size distribution on the propagation of electromagnetic wave in a dusty plasma is investigated. It is shown that the additional collision mechanism provided by charged dust particles can significantly alter the electromagnetic properties of a plasma, leading to the appearance of attenuation of electromagnetic wave through dusty plasma. The attenuation coefficient mainly depends on the dust density, radius, and the charge numbers on the dust surface. The results described here will be used to enhance understanding of electromagnetic wave propagation processed in space and laboratory dusty plasma.

Development and Tests of Elements of a Dust Telescope

NASA Astrophysics Data System (ADS)

Gruen, E.; Srama, R.; Rachev, M.; Srowig, A.; Sternovsky, Z.; Horanyi, M.; Amyx, K.; Auer, S.

2005-08-01

A dust telescope is a combination of a dust trajectory sensor together with an analyzer for the chemical composition of dust particles in space. Dust particles' trajectories are determined by the measurement of the electric signals that are induced when a charged grain flies through a position sensitive electrode system. The objective of the trajectory sensor is to measure dust charges in the range 10-16 to 10-13 C and dust speeds in the range 6 to 100 km/s. The trajectory sensor has four sensor planes consisting of about 16 wire electrodes each. Two adjacent planes have orthogonal wire direction. An ASIC charge sensitive amplifier has been developed with a RMS noise of about 1.5 10-17 C. The signals from 32 electrodes are digitized and sampled at 20 MHz rate by an ASIC transient recorder. First tests with a laboratory set-up have been performed and demonstrate a charge sensitivity corresponding to 100 electrons. The dust chemical analyzers shall have sufficient mass resolution in order to resolve ions with atomic mass number up to 100. The annular impact area of the mass analyzer will be > 0.1 m2. The mass spectrometer consists of the target area with an acceleration grid and the single-stage reflectron consisting of two grids and the central ion detector. Different field configurations have been found that have a mass resolution of M/Δ M > 150 for impacts onto the annular target between 100 and 240 mm from the center. An Ion Detector of 50 to 110 mm radius is necessary to collect all generated ions. A lab model has been constructed and first dust accelerator tests demonstrate a mass resolution (FWHM) of M/Δ M 250. Acknowledgements: This research is supported by NASA grant NAG5-11782 and by DLR grant 50OO0201.

Characteristics of the Dust-Plasma Interaction Near Enceladus' South Pole

NASA Technical Reports Server (NTRS)

Shafiq, Muhammad; Wahlund, J.-E.; Morooka, M. W; Kurth, W. S.; Farrell, W. M.

2010-01-01

We present RPWS Langmuir probe data from the third Enceladus flyby (E3) showing (he presence of dusty plasma near Enceladus' South Pole. There is a sharp rise in both the electron and ion number densities when the spacecraft traverses through Enceladus plume. The ion density near Enceladus is found to increase abruptly from about 10(exp 2) cm (exp -3) before the closest approach to 10(exp 5) cm (exp -3) just 30 s after the closest approach, an amount two orders of magnitude higher than the electron density. Assuming that the inconsistency between the electron and ion number densities is due to the presence of dust particles that are collecting the missing electron charges, we present dusty plasma characteristics down to sub-micron particle sizes. By assuming a differential dust number density for a range in dust sizes and by making use of Langmuir probe data, the dust densities for certain lower limits in dust size distribution were estimated. In order to achieve the dust densities of micrometer and larger sized grains comparable to the ones reported in the literature. we show that the power law size distribution must hold down to at least 0.03 micron such that the total differential number density is dominated by the smallest sub-micron sized grains. The total dust number density in Enceladus' plume is of the order of l0(exp 2) cm(exp -3) reducing to 1 cm(exp -3) in the E- ring. The dust density for micrometer and larger sized grains is estimated to be about 10(exp -4) cm(exp -3) in the plume while it is about 10(exp -6) - 10(exp -7) cm(exp -3) in the E-ring. Dust charge for micron sized grains is estimated to be about eight thousand electron charges reducing to below one hundred electron charges for 0.03 micron sized grains. The effective dusty plasma Debye length is estimated and compared with intergrain distance as well as the electron Debye length. The maximum dust charging time of 1.4 h is found for 0.03 11mmicron sized grains just 1 min before the closest

Electrodynamic Dust Shield Demonstrator

NASA Technical Reports Server (NTRS)

Stankie, Charles G.

2013-01-01

The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid

Does the presence of cosmic dust influence the displacement of the Earth's Magnetopause?

NASA Astrophysics Data System (ADS)

Mann, I.; Hamrin, M.

2012-04-01

In a recent paper Treumann and Baumjohann propose that dust particles in interplanetary space occasionally cause large compressions of the magnetopause that, in the absence of coronal mass ejections, are difficult to explain by other mechanisms (R.A. Treumann and W. Baumjohann, Ann. Geophys. 30, 119-130, 2012). They suggest that enhanced dust number density raises the contribution of the dust component to the solar wind dynamical pressure and hence to the pressure balance that determines the extension of the magnetopause. They quantify the influence of the dust component in terms of a variation of the magnetopause stagnation point distance. As a possible event to trigger the compressions they propose the encounters with meteoroid dust streams along Earth's orbit. We investigate the conditions under which these compressions may occur. The estimate by Treumann and Baumjohann of the magnetopause variation presupposes that the dust particles have reached solar wind speed. Acceleration by electromagnetic forces is efficient in the solar wind for dust particles that have a sufficiently large ratio of surface charge to mass (Mann et al. Plasma Phys. Contr. Fusion, Vol. 52, 124012, 2010). This applies to small dust particles that contribute little to the total dust mass in meteoroid streams. The major fraction of dust particles that reach high speed in the solar wind are nanometer-sized dust particles that form and are accelerated in the inner solar system (Czechowski and Mann, ApJ, Vol. 714, 89, 2010). Observations suggest that the flux of these nanodust particles near 1 AU is highly time-variable (Meyer-Vernet, et al. Solar Physics, Vol. 256, 463, 2009). We estimate a possible variation of the magnetopause stagnation point distance caused by these nanodust fluxes and by the dust associated to meteoroid streams. We conclude that the Earth's encounters with meteoroid dust streams are not likely to strongly influence the magnetopause according to the proposed effect. We

Effect of the radio frequency discharge on the dust charging process in a weakly collisional and fully ionized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motie, Iman; Bokaeeyan, Mahyar, E-mail: Mehyar9798@gmail.com

2015-02-15

A close analysis of dust charging process in the presence of radio frequency (RF) discharge on low pressure and fully ionized plasma for both weak and strong discharge's electric field is considered. When the electromagnetic waves pass throughout fully ionized plasma, the collision frequency of the plasma is derived. Moreover, the disturbed distribution function of plasma particles in the presence of the RF discharge is obtained. In this article, by using the Krook model, we separate the distribution function in two parts, the Maxwellian part and the perturbed part. The perturbed part of distribution can make an extra current, so-calledmore » the accretion rate of electron (or ion) current, towards a dust particle as a function of the average electron-ion collision frequency. It is proven that when the potential of dust grains increases, the accretion rate of electron current experiences an exponential reduction. Furthermore, the accretion rate of electron current for a strong electric field is relatively smaller than that for a weak electric field. The reasons are elaborated.« less

Characterization of the Temporal-Spatial Variability of Trans-Atlantic Dust Transport Based on CALIPSO Lidar Measurements

NASA Technical Reports Server (NTRS)

Yu, Hongbin

2015-01-01

The trans-Atlantic dust transport has important implications for human and ecosystem health, the terrestrial and oceanic biogeochemical cycle, weather systems, and climate. A reliable assessment of these influences requires the characterization of dust distributions in three dimensions and over long time periods. We provide an observation-based multiyear estimate of trans-Atlantic dust transport by using a 7-year (2007 - 2013) lidar record from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) in both cloud-free and above-cloud conditions. We estimate that on a basis of the 7-year average and integration over 10S - 30N, 182 Tg a-1 dust leaves the coast of North Africa at 15W, of which 132 Tg a-1 and 43 Tg a-1 reaches 35W and 75W, respectively. These flux estimates have an overall known uncertainty of (45 - 70). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8 - 48) Tg a-1 or 29 (8 - 50) kg ha-1 a-1. This imported dust could provide about 0.022 (0.006 - 0.037) Tg P of phosphorus per year, equivalent to 23 (7 - 39) g P ha-1 a-1 to fertilize the Amazon rainforest, which is comparable to the loss of phosphorus to rainfall. Significant seasonal variations are observed in both the magnitude of total dust transport and its meridional and vertical distributions. The observed large interannual variability of annual dust transport is highly anti-correlated with the prior-year Sahel Precipitation Index. Comparisons of CALIPSO measurements with surface-based observations and model simulations will also be discussed.

Measurements of Photoelectric Yield and Physical Properties of Individual Lunar Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, F. A.; Taylor, L.; Hoover, R.

2005-01-01

Micron size dust grains levitated and transported on the lunar surface constitute a major problem for the robotic and human habitat missions for the Moon. It is well known since the Apollo missions that the lunar surface is covered with a thick layer of micron/sub-micron size dust grains. Transient dust clouds over the lunar horizon were observed by experiments during the Apollo 17 mission. Theoretical models suggest that the dust grains on the lunar surface are charged by the solar UV radiation as well as the solar wind. Even without any physical activity, the dust grains are levitated by electrostatic fields and transported away from the surface in the near vacuum environment of the Moon. The current dust charging and the levitation models, however, do not fully explain the observed phenomena. Since the abundance of dust on the Moon's surface with its observed adhesive characteristics is believed to have a severe impact on the human habitat and the lifetime and operations of a variety of equipment, it is necessary to investigate the phenomena and the charging properties of the lunar dust in order to develop appropriate mitigating strategies. We will present results of some recent laboratory experiments on individual micro/sub-micron size dust grains levitated in electrodynamic balance in simulated space environments. The experiments involve photoelectric emission measurements of individual micron size lunar dust grains illuminated with UV radiation in the 120-160 nm wavelength range. The photoelectric yields are required to determine the charging properties of lunar dust illuminated by solar UV radiation. We will present some recent results of laboratory measurement of the photoelectric yields and the physical properties of individual micron size dust grains from the Apollo and Luna-24 sample returns as well as the JSC-1 lunar simulants.

Investigation of Dusts Effect and Negative Ion in DC Plasmas by Electric Probes

NASA Astrophysics Data System (ADS)

Oh, Hye Taek; Kang, Inje; Bae, Min-Keun; Park, Insun; Lee, Seunghwa; Jeong, Seojin; Chung, Kyu-Sun

2017-10-01

Dust is typically negatively charged by electron attachment whose thermal velocities are fast compared to that of the heavier ions. The negatively charged particles can play a role of negative ions which affect the quasi-neutrality of background plasma. To investigate effect of metal dusts and negative ion on plasma and materials, metal dusts are injected into background Ar plasma which is generated by tungsten filament using dust dispenser on Cubical Plasma Device (CPD). The CPD has following conditions: size =24x24x24cm3, plasma source =DC filament plasma (ne 1x10x1010, Te 2eV), background gas =Ar, dusts =tungsten powder (diameter 1.89micron). The dust dispenser is developed to quantitate of metal dust by ultrasonic transducer. Electronegative plasmas are generated by adding O2 + Ar plasma to compare negative ion and dust effect. A few grams of micron-sized dusts are placed in the dust dispenser which is located at the upper side of the Cubical Plasma Device. The falling particles by dust dispenser are mainly charged up by the collection of the background plasma. The change in parameters due to negative ion production are characterized by measuring the floating and plasma potential, electron temperature and negative ion density using electric probes.

Laboratory Measurements of Optical and Physical Properties of Individual Lunar Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; Craven, P. D.; Hoover, R. B.

2006-01-01

The lunar surface is covered with a thick layer of sub-micron/micron size dust grains formed by meteoritic impact over billions of years. The fine dust grains are levitated and transported on the lunar surface, and transient dust clouds over the lunar horizon were observed by experiments during the Apollo 17 mission. Theoretical models suggest that the dust grains on the lunar surface are charged by the solar UV radiation as well as the solar wind. Even without any physical activity, the dust grains are levitated by electrostatic fields and transported away from the surface in the near vacuum environment of the Moon. The current dust charging and levitation models, however, do not fully explain the observed phenomena. Since the abundance of dust on the Moon's surface with its observed adhesive characteristics has the potential of severe impact on human habitat and operations and lifetime of a variety of equipment, it is necessary to investigate the charging properties and the lunar dust phenomena in order to develop appropriate mitigating strategies. Photoelectric emission induced by the solar UV radiation with photon energies higher than the work function of the grain materials is recognized to be the dominant process for charging of the lunar dust, and requires measurements of the photoelectric yields to determine the charging and equilibrium potentials of individual dust grains. In this paper, we present the first laboratory measurements of the photoelectric yields of individual sub-micron/micron size dust grains selected from sample returns of Apollo 17, and Luna 24 missions, as well as similar size dust grains from the JSC-1 simulants. The experimental results were obtained on a laboratory facility based on an electrodynamic balance that permits a variety of experiments to be conducted on individual sub-micron/micron size dust grains in simulated space environments. The photoelectric emission measurements indicate grain size dependence with the yield

Galileo dust data from the jovian system: 2000 to 2003

NASA Astrophysics Data System (ADS)

Krüger, H.; Bindschadler, D.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Moissl, R.; Morfill, G. E.; Polanskey, C.; Roy, M.; Schwehm, G.; Srama, R.

2010-06-01

The Galileo spacecraft was the first man-made satellite of Jupiter, orbiting the planet between December 1995 and September 2003. The spacecraft was equipped with a highly sensitive dust detector that monitored the jovian dust environment between approximately 2 and 370 RJ (jovian radius RJ=71 492 km). The Galileo dust detector was a twin of the one flying on board the Ulysses spacecraft. This is the tenth in a series of papers dedicated to presenting Galileo and Ulysses dust data. Here we present data from the Galileo dust instrument for the period January 2000 to September 2003 until Galileo was destroyed in a planned impact with Jupiter. The previous Galileo dust data set contains data of 2883 particles detected during Galileo's interplanetary cruise and 12 978 particles detected in the jovian system between 1996 and 1999. In this paper we report on the data of additional 5389 particles measured between 2000 and the end of the mission in 2003. The majority of the 21 250 particles for which the full set of measured impact parameters (impact time, impact direction, charge rise times, charge amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the impact rates frequently exceeded 10 min -1. Surprisingly large impact rates up to 100 min -1 occurred in August/September 2000 when Galileo was far away (≈280RJ) from Jupiter, implying dust ejection rates in excess of 100 kg s -1. This peak in dust emission appears to coincide with strong changes in the release of neutral gas from the Io torus. Strong variability in the Io dust flux was measured on timescales of days to weeks, indicating large variations in the dust release from Io or the Io torus or both on such short timescales. Galileo has detected a large number of bigger micron-sized particles mostly in the region between the Galilean moons. A surprisingly large

Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

NASA Technical Reports Server (NTRS)

Pankine, A. A.; Ingersoll, Andrew P.

2002-01-01

We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

LADEE Search for a Dust Exosphere: A Historical Perspective

NASA Technical Reports Server (NTRS)

Glenar, D. A.; Stubbs, T. J.; Elphic, R.

2014-01-01

The LADEE search for exospheric dust is strongly motivated by putative detections of forward-scattered sunlight from exospheric dust grains which were observed during the Apollo era. This dust population, if it exists, has been associated with charging and transport of dust near the terminators. It is likely that the concentration of these dust grains is governed by a saltation mechanism originated by micrometeoroid impacts, which are the source of the more tenuous ejecta cloud.

Nonlinear dust-acoustic structures in space plasmas with superthermal electrons, positrons, and ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saberian, E., E-mail: e.saberian@neyshabur.ac.ir; Esfandyari-Kalejahi, A.; Afsari-Ghazi, M.

Some features of nonlinear dust-acoustic (DA) structures are investigated in a space plasma consisting of superthermal electrons, positrons, and positive ions in the presence of negatively charged dust grains with finite-temperature by employing a pseudo-potential technique in a hydrodynamic model. For this purpose, it is assumed that the electrons, positrons, and ions obey a kappa-like (κ) distribution in the background of adiabatic dust population. In the linear analysis, it is found that the dispersion relation yield two positive DA branches, i.e., the slow and fast DA waves. The upper branch (fast DA waves) corresponds to the case in which bothmore » (negatively charged) dust particles and (positively charged) ion species oscillate in phase with electrons and positrons. On the other hand, the lower branch (slow DA waves) corresponds to the case in which only dust particles oscillate in phase with electrons and positrons, while ion species are in antiphase with them. On the other hand, the fully nonlinear analysis shows that the existence domain of solitons and their characteristics depend strongly on the dust charge, ion charge, dust temperature, and the spectral index κ. It is found that the minimum/maximum Mach number increases as the spectral index κ increases. Also, it is found that only solitons with negative polarity can propagate and that their amplitudes increase as the parameter κ increases. Furthermore, the domain of Mach number shifts to the lower values, when the value of the dust charge Z{sub d} increases. Moreover, it is found that the Mach number increases with an increase in the dust temperature. Our analysis confirms that, in space plasmas with highly charged dusts, the presence of superthermal particles (electrons, positrons, and ions) may facilitate the formation of DA solitary waves. Particularly, in two cases of hydrogen ions H{sup +} (Z{sub i} = 1) and doubly ionized Helium atoms He{sup 2+} (Z{sub i} = 2), the mentioned results are

Dust Mitigation for Martian Exploration

NASA Technical Reports Server (NTRS)

Williams, Blakeley Shay

2011-01-01

One of the efforts of the In-Situ Resource Utilization project is to extract oxygen, fuel, and water from the Martian air. However, the surface of Mars is covered in a layer of dust, which is uploaded into the atmosphere by dust devils and dust storms. This atmospheric dust would be collected along with the air during the conversion process. Thus, it is essential to extract the dust from the air prior to commencing the conversion. An electrostatic precipitator is a commonly used dust removal technology on earth. Using this technology, dust particles that pass through receive an electrostatic charge by means of a corona discharge. The particles are then driven to a collector in a region of high electric field at the center of the precipitator. Experiments were conducted to develop a precipitator that will function properly in the Martian atmosphere, which has a very low pressure and is made up . of primarily carbon dioxide.

The Lunar Environment: Determining the Health Effects of Exposure to Moon Dusts

NASA Technical Reports Server (NTRS)

Khan-Mayberry, Noreen

2007-01-01

The moon's surface is covered with a thin layer of fine, charged, reactive dust capable of layer of fine, charged, reactive dust capable of capable of entering habitats and vehicle compartments, where it can result in crewmember health problems. NASA formed the Lunar Airborne Dust Toxicity Advisory Group (LADTAG) to study the effects of exposure to Lunar Dust on human health. To date, no scientifically defensible toxicological studies have been performed on lunar dusts, specifically the determination of exposure limits and their affect on human health. The multi-center LADTAG (Lunar Airborne Dust Toxicology center LADTAG (Lunar Airborne Dust Toxicology Advisory Group) was formed in response to the Office of the Chief Health and Medical Office s (OCHMO) request to develop recommendations for defining risk (OCHMO) request to develop recommendations for defining risk defining risk criteria for human lunar dust exposure.

Tropical Atlantic Dust and Smoke Aerosol Variabilities Related to the Madden-Julian Oscillation in MODIS and MISR Observations

NASA Technical Reports Server (NTRS)

Guo, Yanjuan; Tian, Baijun; Kahn, Ralph A.; Kalashnikova, Olga; Wong, Sun; Waliser, Duane E.

2012-01-01

In this study, MODIS fine mode fraction and MISR non-spherical fraction are 2used to derive dust and smoke AOT components (tau(sub dust) and tau(sub smoke)) over the tropical Atlantic, and their variabilities related to the Madden-Julian Oscillation (MJO) are then investigated. Both MODIS and MISR show a very similar dust and smoke winter climatology. tau(sub dust) is found to be the dominant aerosol component over the tropical Atlantic while tau(sub smoke) is significantly smaller than tau(sub dust). The daily MODIS and MISR tau(sub dust) are overall highly correlated, with the correlation coefficients typically about 0.7 over the North Atlantic. The consistency between the MODIS and MISR dust and smoke aerosol climatology and daily variations give us confidence to use these two data sets to investigate their relative contributions to the total AOT variation associated with the MJO. However, unlike the MISR dust discrimination, which is based on particle shape retrievals, the smoke discrimination is less certain, based on assumed partitioning of maritime aerosol for both MISR and MODIS. The temporal evolution and spatial patterns of the tau(sub dust) anomalies associated with the MJO are consistent between MODIS and MISR. The tau(sub dust) anomalies are very similar to those of tau anomalies, and are of comparable magnitude. In contrast, the MJO-related tau(sub smoke) anomalies are rather small, and the tau(sub mar) anomalies are negligible. The consistency between the MODIS and MISR results suggests that dust aerosol is the dominant component on the intra-seasonal time scale over the tropical Atlantic Ocean.

Dust in magnetised plasmas - Basic theory and some applications. [to planetary rings

NASA Technical Reports Server (NTRS)

Northrop, T. G.; Morfill, G. E.

1984-01-01

In this paper the theory of charged test particle motion in magnetic fields is reviewed. This theory is then extended to charged dust particles, for which gravity and charge fluctuations play an important role. It is shown that systematic drifts perpendicular to the magnetic field and stochastic transport effects may then have to be considered none of which occur in the case of atomic particles (with the exception of charge exchange reactions). Some applications of charged dust particle transport theory to planetary rings are then briefly discussed.

Spatial inhomogeneities in ionic liquids, charged proteins, and charge stabilized colloids from collective variables theory.

PubMed

Patsahan, O; Ciach, A

2012-09-01

Effects of size and charge asymmetry between oppositely charged ions or particles on spatial inhomogeneities are studied for a large range of charge and size ratios. We perform a stability analysis of the primitive model of ionic systems with respect to periodic ordering using the collective variables-based theory. We extend previous studies [Ciach et al., Phys. Rev. E 75, 051505 (2007)] in several ways. First, we employ a nonlocal approximation for the reference hard-sphere fluid which leads to the Percus-Yevick pair direct correlation functions for the uniform case. Second, we use the Weeks-Chandler-Anderson regularization scheme for the Coulomb potential inside the hard core. We determine the relevant order parameter connected with the periodic ordering and analyze the character of the dominant fluctuations along the λ lines. We show that the above-mentioned modifications produce large quantitative and partly qualitative changes in the phase diagrams obtained previously. We discuss possible scenarios of the periodic ordering for the whole range of size and charge ratios of the two ionic species, covering electrolytes, ionic liquids, charged globular proteins or nanoparticles in aqueous solutions, and charge-stabilized colloids.

Spatial variability of excess mortality during prolonged dust events in a high-density city: a time-stratified spatial regression approach.

PubMed

Wong, Man Sing; Ho, Hung Chak; Yang, Lin; Shi, Wenzhong; Yang, Jinxin; Chan, Ta-Chien

2017-07-24

Dust events have long been recognized to be associated with a higher mortality risk. However, no study has investigated how prolonged dust events affect the spatial variability of mortality across districts in a downwind city. In this study, we applied a spatial regression approach to estimate the district-level mortality during two extreme dust events in Hong Kong. We compared spatial and non-spatial models to evaluate the ability of each regression to estimate mortality. We also compared prolonged dust events with non-dust events to determine the influences of community factors on mortality across the city. The density of a built environment (estimated by the sky view factor) had positive association with excess mortality in each district, while socioeconomic deprivation contributed by lower income and lower education induced higher mortality impact in each territory planning unit during a prolonged dust event. Based on the model comparison, spatial error modelling with the 1st order of queen contiguity consistently outperformed other models. The high-risk areas with higher increase in mortality were located in an urban high-density environment with higher socioeconomic deprivation. Our model design shows the ability to predict spatial variability of mortality risk during an extreme weather event that is not able to be estimated based on traditional time-series analysis or ecological studies. Our spatial protocol can be used for public health surveillance, sustainable planning and disaster preparation when relevant data are available.

Adhesion of Lunar Dust

NASA Astrophysics Data System (ADS)

Walton, Otis R.

2007-04-01

This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

Adhesion of Lunar Dust

NASA Technical Reports Server (NTRS)

Walton, Otis R.

2007-01-01

This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

GEO Debris and Interplanetary Dust: Fluxes and Charging Behavior

NASA Astrophysics Data System (ADS)

Graps, A. L.; Green, S. F.; McBride, N. M.; McDonnell, J. A. M.; Drolshagen, G.; Svedhem, H.; Bunte, K. D.

2005-08-01

A population of cosmic dust mixed with a population of man-made debris exists within the Earth's magnetosphere. Measurements of these provide the data samples for studies of the interplanetary dust particles that travel through our magnetosphere from the outside and for studies of the local byproducts of our space endeavours. Even though instruments to detect natural meteoroids and space debris particles have been flown in Low Earth Orbits (LEO) and on interplanetary missions, very little information on the particle environment for Earth orbits above about 600 km altitude have been available. In particular, knowledge about particles smaller than 1 m in the geostationary (GEO) region was largely unknown before GORID. In September 1996, a dust/debris detector: GORID was launched into GEO as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris from the interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. Here we present some results of that study. We give GORID flux distributions for debris and IDPs and then present intriguing debris clustering features that might be the result of electrostatic fragmentation of the rocket slag particles.

Dust composition and mass-loss return from the luminous blue variable R71 in the LMC

NASA Astrophysics Data System (ADS)

Guha Niyogi, S.; Min, M.; Meixner, M.; Waters, L. B. F. M.; Seale, J.; Tielens, A. G. G. M.

2014-09-01

Context. We present an analysis of mid- and far-infrared (IR) spectrum and spectral energy distribution (SED) of the luminous blue variable (LBV) R71 in the Large Magellanic Cloud (LMC). Aims: This work aims to understand the overall contribution of high-mass LBVs to the total dust-mass budget of the interstellar medium (ISM) of the LMC and compare this with the contribution from low-mass asymptotic giant branch (AGB) stars. As a case study, we analyze the SED of R71. Methods: We compiled all the available photometric and spectroscopic observational fluxes from various telescopes for a wide wavelength range (0.36-250 μm). We determined the dust composition from the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate, and other dust shell properties by modeling the SED of R71. We noted nine spectral features in the dust shell of R71 by analyzing Spitzer Space Telescope spectroscopic data. Among these, we identified three new crystalline silicate features. We computed our model spectrum by using 3D radiative transfer code MCMax. Results: Our model calculation shows that dust is dominated by amorphous silicates, with some crystalline silicates, metallic iron, and a very tiny amount of polycyclic aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01 M⊙, from which we arrive at a total ejected mass of ≈5 M⊙. This implies a time-averaged dust mass-loss rate of 2.5 × 10-6 M⊙ yr-1 with an explosion about 4000 years ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass at a similar rate, and estimate the total contribution to the mass budget of the LMC to be ≈10-5 M⊙ yr-1, which is comparable to the contribution by all the AGB stars in the LMC. Conclusions: Based on our analysis on R71, we speculate that LBVs as a class may be an important dust source in the ISM of the LMC.

Properties of Arizona Dust Devils: a Martian Analog

NASA Astrophysics Data System (ADS)

Smith, P. H.; Renno, N.; MATADOR Team

2001-11-01

During the week of June 4-8, 2001, the MATADOR team instrumented a truck to study the properties of dust devils at a Martian analog site in Eloy, AZ. MATADOR consists of a group of instruments operated by a science team of about 20 members originally selected by the HEDS program for a 2003 lander mission to Mars. Currently deselected with the loss of the mission, the team has continued studying the optimum means for measuring dust devil properties. With an eye for remotely sensing and identifying potential hazards to humans and their equipment, MATADOR can eventually act as an early warning system much like tornedo and hurricane watches on the Earth. Key questions that the MATADOR group is addressing concern the ability of LIDAR (provided by Optech in Canada) to scan dust devils, the strength of electrical charging and the associated E-fields that are created, the oxidation of the local soil from ionized species, and the best ways to measure the quixotic meteorological properties that define dust devils. Dozens of dust devils were monitored during the field test both remotely and in situ, the results of our study will be presented in detail. One thing is clear though, dust devils maintain a tremendous charge separation such that E-fields approach the breakdown potential of the Earth's atmosphere. Equivalent dust devils on Mars would be 100 times larger than their small Earth cousins; despite the much reduced breakdown potential of the Martian atmosphere, charge separations are likely to occur on Mars. The discharging of these dust events would create electrical signals that can be studied remotely. We would like to thank NASA's HEDS division for their support of these investigations.

Circumstellar dust in symbiotic novae

NASA Astrophysics Data System (ADS)

Jurkic, Tomislav; Kotnik-Karuza, Dubravka

2015-08-01

Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use

Variability in the correlation between Asian dust storms and chlorophyll a concentration from the North to Equatorial Pacific.

PubMed

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997-2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54-0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32-0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas.

Simulation of Martian surface conditions and dust transport

NASA Astrophysics Data System (ADS)

Nørnberg, P.; Merrison, J. P.; Finster, K.; Folkmann, F.; Gunnlaugsson, H. P.; Hansen, A.; Jensen, J.; Kinch, K.; Lomstein, B. Aa.; Mugford, R.

2002-11-01

The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid water to be stable close to the surface (less than 10 cm). This is being investigated in an environment simulator where heat and moisture transport can be studied through layers of Mars analogue dust.

Escape mechanisms of dust in Io

NASA Astrophysics Data System (ADS)

Flandes, A.

The injection of material into the jovian magnetosphere through Io's volcanic activity makes possible the formation of structures such as the plasma torus and the dust ballerina skirt. Io's high temperature volcanism produces spectacular plumes, but even the tallest plumes, as those of Pelen Patera, will not produce enough energy to defeat the gravitational attraction of Io. The fact is that dust escapes from Io, which implies that a second mechanism is acting on the grains. Grains brought to the top of the highest plumes by the volcanic forces are still under Io's gravitational pull, but need only a minimum charge (~10-1 4 C) so that the Lorentz force due to the Jovian magnetic field equilibrates this attraction. In the volcanic vents, the escape velocity of the ejected material and its own density produces enough collisions to create charges. On top of the highest plumes (~500km) charged grains are exposed to the plasma torus that co-rotates rigidly with Jupiter and, due to the relative velocity among Io and the torus, the grains will be dragged away from Io. As it is well known, these dust grains will also be dragged away from Jupiter.

Interaction force in a vertical dust chain inside a glass box.

PubMed

Kong, Jie; Qiao, Ke; Matthews, Lorin S; Hyde, Truell W

2014-07-01

Small number dust particle clusters can be used as probes for plasma diagnostics. The number of dust particles as well as cluster size and shape can be easily controlled employing a glass box placed within a Gaseous Electronics Conference (GEC) rf reference chamber to provide confinement of the dust. The plasma parameters inside this box and within the larger plasma chamber have not yet been adequately defined. Adjusting the rf power alters the plasma conditions causing structural changes of the cluster. This effect can be used to probe the relationship between the rf power and other plasma parameters. This experiment employs the sloshing and breathing modes of small cluster oscillations to examine the relationship between system rf power and the particle charge and plasma screening length inside the glass box. The experimental results provided indicate that both the screening length and dust charge decrease as rf power inside the box increases. The decrease in dust charge as power increases may indicate that ion trapping plays a significant role in the sheath.

Seasonal, Spatial, and Long-term Variability of Fine Mineral Dust in the United States

NASA Astrophysics Data System (ADS)

Hand, J. L.; White, W. H.; Gebhart, K. A.; Hyslop, N. P.; Gill, T. E.; Schichtel, B. A.

2017-12-01

Characterizing the seasonal, spatial, and long-term variability of fine mineral dust (FD) is important to assess its environmental and climate impacts. FD concentrations (mineral particles with aerodynamic diameters less than 2.5 µm) were estimated using ambient, ground-based PM2.5 elemental chemistry data from over 160 remote and rural Interagency Monitoring of Protected Visual Environments (IMPROVE) sites from 2011 through 2015. FD concentrations were highest and contributed over 50% of PM2.5 mass at southwestern sites in spring and across the central and southeastern United States in summer (20-30% of PM2.5). The highest seasonal variability in FD occurred at sites in the Southeast during summer, likely associated with impacts from North African transport, which was also evidenced in the elemental ratios of calcium, iron, and aluminum. Long-term trend analyses (2000-2015) indicated widespread, regional increases in FD concentrations during spring in the West, especially in March in the Southwest. This increase was associated with an early onset of the spring dust season and correlated with the Pacific Decadal Oscillation and the El Niño Southern Oscillation. The Southeast and central United States also experienced increased FD concentrations during summer and fall, respectively. Contributions of FD to PM2.5 mass have increased in regions across the United States during all seasons, in part due to increased FD concentrations but also as a result of reductions in secondary aerosols (e.g., sulfates, nitrates, and organic carbon). Increased levels of FD have important implications for its environmental and climate impacts; mitigating these impacts will require identifying and characterizing source regions and underlying mechanisms for dust episodes.

Dust-Particle Transport in Tokamak Edge Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K

2005-09-12

Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensivemore » dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.« less

The Dust Ring of Luminous Blue Variable Candidate HD 168625: Infrared Observations and Model Calculations

NASA Astrophysics Data System (ADS)

O'Hara, Timothy B.; Meixner, Margaret; Speck, Angela K.; Ueta, Toshiya; Bobrowsky, Matthew

2003-12-01

We present a 2.218 μm image from the Hubble Space Telescope/Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and a 55 μm image from ISOPHOT of the dust ring surrounding the luminous blue variable (LBV) candidate HD 168625, together with new temperature and optical depth maps derived from mid-IR images. The shell is detached from the star in the near-IR, and substructure in the overall toroidal shell is visible. The far-IR image constrains the extent of the dust shell to ~25" in diameter, providing an upper radius limit for modeling. The temperature maps and the NICMOS image show evidence for very small transiently heated dust grains in the shell. The opacity maps show higher optical depth in the limbs, consistent with interpretation of the dust shell as an equatorially enhanced torus inclined ~60° with respect to the observer. An overall trend in the dust emission location with wavelength is observed and interpreted as a variation with respect to location in the nebula of either the dust grain size distribution or gas-to-dust mass ratio. Radiative transfer calculations using 2-DUST indicate that a mass-loss event occurred ~5700 yr ago with a rate of (1.9+/-0.1)×10-4Msolaryr-1, creating a dust torus that currently has a τV~0.22 in the equatorial plane and a dust mass of (2.5+/-0.1)×10-3Msolar. Using published values for the gas mass, we find a gas-to-dust mass ratio of 840, which is ~4 times higher than current estimates for the interstellar medium. In addition to a high equator-to-pole density ratio (~31) torus, an elliptical midshell is needed to reproduce the appearance and spectral energy distribution of the dust. Therefore, HD 168625 is an excellent example of proposed models of LBV nebulae in which a stellar wind interacts with a preexisting density contrast and creates a blowout in the polar direction perpendicular to the equatorial ring. The circumstellar shell is much lower in mass than that of LBV η Carinae, suggesting that HD 168625 had

Characteristic study of head-on collision of dust-ion acoustic solitons of opposite polarity with kappa distributed electrons

NASA Astrophysics Data System (ADS)

Parveen, Shahida; Mahmood, Shahzad; Adnan, Muhammad; Qamar, Anisa

2016-09-01

The head on collision between two dust ion acoustic (DIA) solitary waves, propagating in opposite directions, is studied in an unmagnetized plasma constituting adiabatic ions, static dust charged (positively/negatively) grains, and non-inertial kappa distributed electrons. In the linear limit, the dispersion relation of the dust ion acoustic (DIA) solitary wave is obtained using the Fourier analysis. For studying characteristic head-on collision of DIA solitons, the extended Poincaré-Lighthill-Kuo method is employed to obtain Korteweg-de Vries (KdV) equations with quadratic nonlinearities and investigated the phase shifts in their trajectories after the interaction. It is revealed that only compressive solitary waves can exist for the positive dust charged concentrations while for negative dust charge concentrations both the compressive and rarefactive solitons can propagate in such dusty plasma. It is found that for specific sets of plasma parameters, the coefficient of nonlinearity disappears in the KdV equation for the negative dust charged grains. Therefore, the modified Korteweg-de Vries (mKdV) equations with cubic nonlinearity coefficient, and their corresponding phase shift and trajectories, are also derived for negative dust charged grains plasma at critical composition. The effects of different plasma parameters such as superthermality, concentration of positively/negatively static dust charged grains, and ion to electron temperature ratio on the colliding soliton profiles and their corresponding phase shifts are parametrically examined.

Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

PubMed Central

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997–2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32–0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas. PMID:23460892

Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps

NASA Astrophysics Data System (ADS)

Huang, Po-Chieh; Chen, Wen-Ping; Hu, Chia-Ling; Burkhonov, Otabek; Ehgamberdiev, Shuhrat; Liu, Jinzhong; Naito, Hiroyuki; Pakstiene, Erika; Qvam, Jan Kare Trandem; Rätz, Stefanie; Semkov, Evgeni

2018-04-01

UX Orionis stars are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such an UX Orionis star in the young (∼ 4 Myr) open cluster Trumpler 37 at ∼ 900 pc, showing a prominent infrared access, H-alpha emission, and flare activity. Our multi-color photometric monitoring from 2009 to 2016 showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) cyclic, but not strictly periodical, occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual "blueing" phenomena near the brightness minima, during which the star appeared bluer when dimmer, and (v) a noticeable polarization, from 3 to 9 percent in g', r', and i' -bands. The occultation events may be caused by dust clumps, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. The level of polarization was anti-correlated with the brightness in the bright state, when the dust clump backscattered stellar light. We discussed two potential hypotheses: orbiting dust clumps versus dust clumps along a spiral arm structure.

Anomalous transport of charged dust grains in a magnetized collisional plasma: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bezbaruah, Pratikshya; Das, Nilakshi

2018-05-01

Anomalous diffusion of charged dust grains immersed in a plasma in the presence of strong ion-neutral collision, flowing ions, and a magnetic field has been observed. Molecular Dynamics simulation confirms the deviation from normal diffusion in an ensemble of dust grains probed in laboratory plasma chambers. Collisional effects are significant in governing the nature of diffusion. In order to have a clear idea on the transport of particles in a real experimental situation, the contribution of streaming ions and the magnetic field along with collision is considered through the relevant interaction potential. The nonlinear evolution of Mean Square Displacement is an indication of the modification in particle trajectories due to several effects as mentioned above. It is found that strong collision and ion flow significantly affect the interparticle interaction potential in the presence of the magnetic field and lead to the appearance of the asymmetric type of Debye Hückel (D H) potential. Due to the combined effect of the magnetic field, ion flow, and collision, dusty plasma exhibits a completely novel behavior. The coupling parameter Γ enhances the asymmetric D H type potential arising due to ion flow, and this may drive the system to a disordered state.

Charging of Interstellar Dust Grains in the out-of-equilibrium Heliosheath Plasma traced by IBEX ENAs

NASA Astrophysics Data System (ADS)

Frisch, P. C.; Ogasawara, K.; Livadiotis, G.; Slavin, J. D.; McComas, D. J.; Funsten, H. O.; Schwadron, N.; Heerikhuisen, J.

2017-12-01

Dusty bow waves are common around stars and anticipated around the heliosphere due to the deficit of low-mass interstellar dust grains in the inner heliosphere. Interstellar grains entering the heliosphere must first cross barriers of non-Maxwellian plasma in the heliosheath regions where collisional charging of grains is highly effective. IBEX measures 0.1-6 keV ENAs in the heliosheath plasma, providing an in situ sample of the heliosheath plasma thermodynamics that can be used for grain-charging calculations. Plasma in three-quarters of the sky can be described with a stationary state kappa-distribution, giving predictions for kappa, kappa-distribution temperature, and plasma density [1]. This thermodynamic description allows a more realistic evaluation of the dominant heliosheath electron and ion currents, and hence also grain gyroradii and exclusion from the heliosphere. At the highest temperatures ion collisional currents dominate grain charging; at lower temperatures collisional electron currents are more important together with the photoelectric ejection of electrons. An absence of data on the thermodynamical state of heliosheath electrons has led to the assumption of similar thermodynamic parameters for the electron and ion populations. The balance between electron, proton and photoionization currents on the grains then yield the equilibrium grain charges. Grain gyroradii calculated based on these charging currents differentiate between interstellar grains able to penetrate the heliosphere, versus those that are excluded, and allow predictions of properties of the dusty bow wave likely to be present around the heliosphere. The smallest grains are excluded and grains at the high latitude edges of the described regions tend to have systematically lower grain potentials. Grain charging calculations utilize the modeling of [2]. [1] Livadiotis et al., ApJ 734, 1 (2011). [2] Weingartner Draine, ApJSS 263 (2001)

Palaeo-dust records: A window to understanding past environments

NASA Astrophysics Data System (ADS)

Marx, Samuel K.; Kamber, Balz S.; McGowan, Hamish A.; Petherick, Lynda M.; McTainsh, Grant H.; Stromsoe, Nicola; Hooper, James N.; May, Jan-Hendrik

2018-06-01

Dust entrainment, transport over vast distances and subsequent deposition is a fundamental part of the Earth system. Yet the role and importance of dust has been underappreciated, due largely to challenges associated with recognising dust in the landscape and interpreting its depositional history. Despite these challenges, interest in dust is growing. Technical advances in remote sensing and modelling have improved understanding of dust sources and production, while advances in sedimentology, mineralogy and geochemistry (in particular) have allowed dust to be more easily distinguished within sedimentary deposits. This has facilitated the reconstruction of records of dust emissions through time. A key advance in our understanding of dust has occurred following the development of methods to geochemically provenance (fingerprint) dust to its source region. This ability has provided new information on dust transport pathways, as well as the reach and impact of dust. It has also expanded our understanding of the processes driving dust emissions over decadal to millennial timescales through linking dust deposits directly to source area conditions. Dust provenance studies have shown that dust emission, transport and deposition are highly sensitive to variability in climate. They also imply that dust emissions are not simply a function of the degree of aridity in source areas, but respond to a more complex array of conditions, including sediment availability. As well as recording natural variability, dust records are also shown to sensitively track the impact of human activity. This is reflected by both changing dust emission rates and changing dust chemistry. Specific examples of how dust responds to, and records change, are provided with our work on dust emissions from Australia, the most arid inhabited continent and the largest dust source in the Southern Hemisphere. These case studies show that Australian dust emissions reflect hydro-climate variability, with

Effect of dust on tilted electrostatic resistive instability in a Hall thruster

NASA Astrophysics Data System (ADS)

Tyagi, Jasvendra; Singh, Sukhmander; Malik, Hitendra K.

2018-03-01

Effect of negatively charged dust on resistive instability corresponding to the electrostatic wave is investigated in a Hall thruster plasma when this purely azimuthal wave is tilted and strong axial component of wave vector is developed. Analytical calculations are done to obtain the relevant dispersion equation, which is solved numerically to investigate the growth rate of the instability. The magnitude of the growth rate in the plasma having dust particles is found to be much smaller than the case of pure plasma. However, the instability grows faster for the increasing dust density and the higher charge on the dust particles. The higher magnetic field is also found to support the instability.

Lunar Dust and Dusty Plasma Physics

NASA Technical Reports Server (NTRS)

Wilson, Thomas L.

2009-01-01

In the plasma and radiation environment of space, small dust grains from the Moon s surface can become charged. This has the consequence that their motion is determined by electromagnetic as well as gravitational forces. The result is a plasma-like condition known as "dusty plasmas" with the consequence that lunar dust can migrate and be transported by magnetic, electric, and gravitational fields into places where heavier, neutral debris cannot. Dust on the Moon can exhibit unusual behavior, being accelerated into orbit by electrostatic surface potentials as blow-off dust, or being swept away by moving magnetic fields like the solar wind as pick-up dust. Hence, lunar dust must necessarily be treated as a dusty plasma subject to the physics of magnetohydrodynamics (MHD). A review of this subject has been given before [1], but a synopsis will be presented here to make it more readily available for lunar scientists.

Kuiper Belt Dust Grains as a Source of Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Zook, Herbert A.; Dermott, Stanley F.

1996-01-01

The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar

Long-term Satellite Observations of Asian Dust Storm: Source, Pathway, and Interannual Variability

NASA Technical Reports Server (NTRS)

Hsu, N. Christina

2008-01-01

between Deep Blue retrievals of aerosol optical thickness and those directly from AERONET sunphotometers over desert and semi-desert regions. New Deep Blue products will allow scientists to determine quantitatively the aerosol properties near sources using high spatial resolution measurements from SeaWiFS and MODIS-like instruments. Long-term satellite measurements (1998 - 2007) from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with the Asian dust storm outbreaks. In addition, monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

VISTA variables in the Sagittarius dwarf spheroidal galaxy: pulsation-versus dust-driven winds on the giant branches

NASA Astrophysics Data System (ADS)

McDonald, I.; Zijlstra, A. A.; Sloan, G. C.; Kerins, E.; Lagadec, E.; Minniti, D.

2014-04-01

Variability is examined in over 2.6 million stars covering 11 square degrees of the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) from Visible and Infrared Survey Telescope for Astronomy Z-band observations. Generally, pulsation on the Sgr dSph giant branches appears to be excited by the internal κ mechanism. Pulsation amplitudes appear identical between red and asymptotic (red giant branch/asymptotic giant branch) giant stars, and between unreddened carbon and oxygen-rich stars at the same luminosity. The lack of correlation between infrared excess and variability among oxygen-rich stars indicates that pulsations do not contribute significantly to wind driving in oxygen-rich stars in the Sgr dSph, though the low amplitudes of these stars mean this may not apply elsewhere. The dust-enshrouded carbon stars have the highest amplitudes of the stars we observe. Only in these stars does an external κ-mechanism-driven pulsation seem likely, caused by variations in their more opaque carbon-rich molecules or dust. This may allow pulsation driving of winds to be effective in carbon stars. Variability can be simplified to a power law (A ∝ L/T2), as in other systems. In total, we identify 3026 variable stars (with rms variability of δZ ≳ 0.015 mag), of which 176 are long-period variables associable with the upper giant branches of the Sgr dSph. We also identify 324 candidate RR Lyrae variables in the Sgr dSph and 340 in the outer Galactic bulge.

Effect of anisotropic dust pressure and superthermal electrons on propagation and stability of dust acoustic solitary waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bashir, M. F., E-mail: frazbashir@yahoo.com; Behery, E. E., E-mail: eebehery@gmail.com; Department of Physics, Faculty of Science, Damietta University, P.O. 34517, New Damietta

2015-06-15

Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary waves in a magnetized plasma which consists the effects of dust anisotropic pressure, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary wave solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary waves is also discussed. The effects of the dust pressure anisotropy and the electron superthermality on the basic characteristics of DA waves as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary wave is rarefactivemore » (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.« less

Beyond Orbital-Motion-Limited theory effects for dust transport in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delzanno, Gian Luca; Tang, Xianzhu

Dust transport in tokamaks is very important for ITER. Can many kilograms of dust really accumulate in the device? Can the dust survive? The conventional dust transport model is based on Orbital-Motion-Limited theory (OML). But OML can break in the limit where the dust grain becomes positively charged due to electron emission processes because it overestimates the dust collected power. An OML + approximation of the emitted electrons trapped/passing boundary is shown to be in good agreement with PIC simulations.

Tentative explanatory variable of lung dust concentration in gold miners exposed to crystalline silica.

PubMed

Dufresne, A; Loosereewanich, P; Bégin, R; Dion, C; Ecobichon, D; Muir, D C; Ritchie, A C; Perrault, G

1998-01-01

The first objective of the study was to investigate the relationships between quantitative lung mineral dust burdens, dust exposure history, and pathological fibrosis grading in silicotic workers. The second objective was to evaluate the association between particle size parameters, concentration of retained silica particles and the severity of the silicosis. Sixty-seven paraffin-embedded lung tissue samples of silicotic patients were analyzed. The cases of silicosis included 39 non-lung cancer patients and 28 patients with lung cancer. All of the cases were gold miners in the Province of Ontario, Canada. Particles, both angular and fibrous, were extracted from lung parenchyma by a bleach digestion method, mounted on copper microscopic grids by a carbon replica technique, and analyzed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Quartz concentration was also determined by X-ray diffraction (XRD) on a silver membrane filter after the extraction from the lung parenchyma. Total particles, silica, clay, and quartz also increase in concentration with increased age at death, although the trends are not statistically significant. Quartz concentration has a statistically significant correlation with the silicosis severity score (r = +0.45, p < 0.001), with the geometric mean concentration increasing from 2.24 micrograms/mg in the group having silicosis severity score less than 1 to 4.80 micrograms/mg in group with highest score. Quartz concentration is the only significant explanatory variable of the silicosis severity with a regression coefficient of +0.41 (p < 0.001). Among several dust exposure variables extracted from the work history of the miners, the calendar year of first exposure was the primary significant determinant of lung retained total particles, silica, and clay minerals, except for quartz. A statistically significant linear relationship between lung quartz concentration and silicosis severity in the gold miners was

A Mid-Infrared Study of the Circumstellar Dust Composition and Phase Behavior of Oxygen-rich Mira Variables

NASA Astrophysics Data System (ADS)

Guth, Tina

2017-08-01

The elements essential as building blocks of life, such as carbon and oxygen, have long been considered to come from exploding stars, known as supernovae. However, in the last several years, observations obtained with improved telescopes and instruments have shown that these heavier elements, i.e. elements beyond helium, are readily found in mass-loss products of stars called Asymptotic Giant Branch (AGB) stars. The sub-category of AGB stars that have regular pulsation periods of 200 - 500 days, called Mira variables, are of particular interest. These regular pulsators are quite bright in both the optical and infrared wavelengths, and exhibit large changes in magnitude that are easily observable. Studying their circumstellar dust environment allows astronomers to determine the presence of compounds, such as silicates and oxides, which are indicative of common elements found on Earth - oxygen, carbon, and silicon. Mira variables are dynamic stars, which implies that the circumstellar dust composition should change as the star goes through its pulsation cycle. In order to study the dust behavior with pulsational phase, repeated infrared observations were obtained with the Spitzer Space Telescope. This infrared, space-based telescope was launched in 2003 and carries the Infrared Spectrograph (IRS) instrument, which produces brightness versus wavelength, i.e. a spectrum (Houck et al., 2004). Due to the pulsation period of these stars, they were observed approximately monthly during the campaign run in 2008-9. This work focuses on the high-resolution data over a wavelength range of 9.8 - 40 microns because it provides a high signal-to-noise ratio and examines the part of the spectrum where dust features are most apparent. The full dataset obtained with Spitzer consists of 25 stars and covers nearly 100 spectra spanning all three chemical subclasses, however the focus of this dissertation is on investigating the dusty environment of oxygen-rich Mira variables. First, an

The Martian Dust Cycle: Observations and Modeling

NASA Technical Reports Server (NTRS)

Kahre, Melinda A.

2013-01-01

The dust cycle is critically important for Mars' current climate system. Suspended atmospheric dust affects the radiative balance of the atmosphere, and thus greatly influences the thermal and dynamical state of the atmosphere. Evidence for the presence of dust in the Martian atmosphere can be traced back to yellow clouds telescopically observed as early as the early 19th century. The Mariner 9 orbiter arrived at Mars in November of 1971 to find a planet completely enshrouded in airborne dust. Since that time, the exchange of dust between the planet's surface and atmosphere and the role of airborne dust on Mars' weather and climate has been studied using observations and numerical models. The goal of this talk is to give an overview of the observations and to discuss the successes and challenges associated with modeling the dust cycle. Dust raising events on Mars range in size from meters to hundreds of kilometers. During some years, regional storms merge to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by tens of kelvin. The interannual variability of planet encircling dust storms is poorly understood. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. A low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading are generally observed: one peak occurs before northern winter solstice and one peak occurs after northern winter solstice. Numerical modeling studies attempting to interactively simulate the Martian dust cycle with general circulation models (GCMs) include the lifting, transport, and sedimentation of radiatively active dust. Two dust lifting processes are commonly represented in

LUNAR SURFACE AND DUST GRAIN POTENTIALS DURING THE EARTH’S MAGNETOSPHERE CROSSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaverka, J.; Richterová, I.; Pavlu, J.

2016-07-10

Interaction between the lunar surface and the solar UV radiation and surrounding plasma environment leads to its charging by different processes like photoemission, collection of charged particles, or secondary electron emission (SEE). Whereas the photoemission depends only on the angle between the surface and direction to the Sun and varies only slowly, plasma parameters can change rapidly as the Moon orbits around the Earth. This paper presents numerical simulations of one Moon pass through the magnetospheric tail including the real plasma parameters measured by THEMIS as an input. The calculations are concentrated on different charges of the lunar surface itselfmore » and a dust grain lifted above this surface. Our estimations show that (1) the SEE leads to a positive charging of parts of the lunar surface even in the magnetosphere, where a high negative potential is expected; (2) the SEE is generally more important for isolated dust grains than for the lunar surface covered by these grains; and (3) the time constant of charging of dust grains depends on their diameter being of the order of hours for sub-micrometer grains. In view of these results, we discuss the conditions under which and the areas where a levitation of the lifted dust grains could be observed.« less

The Cosmic Dust Analyzer for Cassini

NASA Technical Reports Server (NTRS)

Bradley, James G.; Gruen, Eberhard; Srama, Ralf

1996-01-01

The Cosmic Dust Analyzer (CDA) is designed to characterize the dust environment in interplanetary space, in the Jovian and in the Saturnian systems. The instrument consists of two major components, the Dust Analyzer (DA) and the High Rate Detector (HRD). The DA has a large aperture to provide a large cross section for detection in low flux environments. The DA has the capability of determining dust particle mass, velocity, flight direction, charge, and chemical composition. The chemical composition is determined by the Chemical Analyzer system based on a time-of-flight mass spectrometer. The DA is capable of making full measurements up to one impact/second. The HRD contains two smaller PVDF detectors and electronics designed to characterize dust particle masses at impact rates up to 10(exp 4) impacts/second. These high impact rates are expected during Saturn ring, plane crossings.

Electrostatic Power Generation from Negatively Charged, Simulated Lunar Regolith

NASA Technical Reports Server (NTRS)

Choi, Sang H.; King, Glen C.; Kim, Hyun-Jung; Park, Yeonjoon

2010-01-01

Research was conducted to develop an electrostatic power generator for future lunar missions that facilitate the utilization of lunar resources. The lunar surface is known to be negatively charged from the constant bombardment of electrons and protons from the solar wind. The resulting negative electrostatic charge on the dust particles, in the lunar vacuum, causes them to repel each other minimizing the potential. The result is a layer of suspended dust about one meter above the lunar surface. This phenomenon was observed by both Clementine and Surveyor spacecrafts. During the Apollo 17 lunar landing, the charged dust was a major hindrance, as it was attracted to the astronauts' spacesuits, equipment, and the lunar buggies. The dust accumulated on the spacesuits caused reduced visibility for the astronauts, and was unavoidably transported inside the spacecraft where it caused breathing irritation [1]. In the lunar vacuum, the maximum charge on the particles can be extremely high. An article in the journal "Nature", titled "Moon too static for astronauts?" (Feb 2, 2007) estimates that the lunar surface is charged with up to several thousand volts [2]. The electrostatic power generator was devised to alleviate the hazardous effects of negatively charged lunar soil by neutralizing the charged particles through capacitive coupling and thereby simultaneously harnessing power through electric charging [3]. The amount of power generated or collected is dependent on the areal coverage of the device and hovering speed over the lunar soil surface. A thin-film array of capacitors can be continuously charged and sequentially discharged using a time-differentiated trigger discharge process to produce a pulse train of discharge for DC mode output. By controlling the pulse interval, the DC mode power can be modulated for powering devices and equipment. In conjunction with a power storage system, the electrostatic power generator can be a power source for a lunar rover or other

Discrete stochastic charging of aggregate grains

NASA Astrophysics Data System (ADS)

Matthews, Lorin S.; Shotorban, Babak; Hyde, Truell W.

2018-05-01

Dust particles immersed in a plasma environment become charged through the collection of electrons and ions at random times, causing the dust charge to fluctuate about an equilibrium value. Small grains (with radii less than 1 μm) or grains in a tenuous plasma environment are sensitive to single additions of electrons or ions. Here we present a numerical model that allows examination of discrete stochastic charge fluctuations on the surface of aggregate grains and determines the effect of these fluctuations on the dynamics of grain aggregation. We show that the mean and standard deviation of charge on aggregate grains follow the same trends as those predicted for spheres having an equivalent radius, though aggregates exhibit larger variations from the predicted values. In some plasma environments, these charge fluctuations occur on timescales which are relevant for dynamics of aggregate growth. Coupled dynamics and charging models show that charge fluctuations tend to produce aggregates which are much more linear or filamentary than aggregates formed in an environment where the charge is stationary.

Controlling dust from concrete saw cutting.

PubMed

Shepherd, Susan; Woskie, Susan

2013-01-01

Cutting concrete with gas-powered saws is ubiquitous in the construction industry and a source of exposure to respirable crystalline silica. Volunteers from the New England Laborers Training Center were recruited to participate in a field experiment examining dust reductions through the use of water, from a hose and from a sprayer, as a dust control. In four series of tests, reinforced concrete pipe was cut under both "dry" and "wet" control conditions. Overall, the geometric mean respirable dust concentration for "dry" cutting (14.396 mg/m³) exceeded both types of water-based controls by more than tenfold. Wet cutting reduced the respirable dust concentration by 85% compared with dry cutting when comparing tests paired by person and saw blade (n = 79 pairs). Using a respirable cyclone, a total of 178 samples were taken. Due to the high variability in dust exposure found in this and other studies of saw cutting, the data were examined for potential exposure determinants that contribute to that variability. Using mixed models, three fixed effects were statistically significant: control condition, worker experience, and location. A random effect for subject was included in the model to account for repeated measures. When each of the significant fixed effects was included with the random effect, it was apparent that inclusion of worker experience or location reduced the between-worker component of exposure variability, while inclusion of control condition (wet vs. dry) explained a large portion of the within-subject variability. Overall, the fixed effect variable for control condition explained the largest fraction of the total exposure variability.

Model of the dust-loaded ionospheres of Mars and Titan

NASA Astrophysics Data System (ADS)

Witasse, Olivier; Cardnell, Sandy; Molina-Cuberos, Gregorio; Michael, Mary; Tripathi, Sachi; Deprez, Gregoire; Montmessin, Franck; O'Brien, Keran

2016-10-01

The ionization of lower atmospheres of celestial bodies and the presence of charged species are fundamental in the understanding of atmospheric electricity phenomena, such as electric discharges, large scale electric currents and Schumann resonances. On January 14, 2005, the Huygens Probe measured the electric conductivity of Titan's atmosphere from 140 km down to the surface. Micro-ARES, the electric field and conductivity sensor on board the ExoMars 2016 Schiaparelli lander, will conduct the very first measurement and characterization of Martian atmospheric electricity. The landing is scheduled for October 19, 2016 and the measurements will be performed over 2-4 sols.The present photochemical model is developed to compute the concentration of the most abundant charged species (cluster-ions, electrons and charged aerosols) and electric conductivity in the lower atmospheres of Mars (0-70 km) and Titan (0-145 km). For both cases, the main source of ionization is galactic cosmic rays. In addition, during daytime, photoionization of aerosols due to solar UV radiation is important at Mars. Ion and electron attachment to aerosols is another major source of aerosol charging, which can vary between -50 and +200 elementary charges for Mars and -55 and -25 for Titan. The steady state concentration of charged species is computed by solving the respective balance equations, which include the source and sink terms of the photochemical reactions. Since the amount of suspended dust in the Martian atmosphere can vary considerably and it has an important effect on the atmospheric properties, several dust scenarios, in addition to the day-night variations, are considered to characterize the variability of the concentration of charged species.The agreement between with the results of the model for Titan and the Huygens data suggests an improvement with respect to previous models. This gives confidence in the results of the model for Mars, which characterize the predicted electric

Dust models post-Planck: constraining the far-infrared opacity of dust in the diffuse interstellar medium

NASA Astrophysics Data System (ADS)

Fanciullo, L.; Guillet, V.; Aniano, G.; Jones, A. P.; Ysard, N.; Miville-Deschênes, M.-A.; Boulanger, F.; Köhler, M.

2015-08-01

Aims: We compare the performance of several dust models in reproducing the dust spectral energy distribution (SED) per unit extinction in the diffuse interstellar medium (ISM). We use our results to constrain the variability of the optical properties of big grains in the diffuse ISM, as published by the Planck collaboration. Methods: We use two different techniques to compare the predictions of dust models to data from the Planck HFI, IRAS, and SDSS surveys. First, we fit the far-infrared emission spectrum to recover the dust extinction and the intensity of the interstellar radiation field (ISRF). Second, we infer the ISRF intensity from the total power emitted by dust per unit extinction, and then predict the emission spectrum. In both cases, we test the ability of the models to reproduce dust emission and extinction at the same time. Results: We identify two issues. Not all models can reproduce the average dust emission per unit extinction: there are differences of up to a factor ~2 between models, and the best accord between model and observation is obtained with the more emissive grains derived from recent laboratory data on silicates and amorphous carbons. All models fail to reproduce the variations in the emission per unit extinction if the only variable parameter is the ISRF intensity: this confirms that the optical properties of dust are indeed variable in the diffuse ISM. Conclusions: Diffuse ISM observations are consistent with a scenario where both ISRF intensity and dust optical properties vary. The ratio of the far-infrared opacity to the V band extinction cross-section presents variations of the order of ~20% (40-50% in extreme cases), while ISRF intensity varies by ~30% (~60% in extreme cases). This must be accounted for in future modelling. Appendices are available in electronic form at http://www.aanda.org

Solitary wave solutions of two-dimensional nonlinear Kadomtsev-Petviashvili dynamic equation in dust-acoustic plasmas

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.

2017-09-01

Nonlinear two-dimensional Kadomtsev-Petviashvili (KP) equation governs the behaviour of nonlinear waves in dusty plasmas with variable dust charge and two temperature ions. By using the reductive perturbation method, the two-dimensional dust-acoustic solitary waves (DASWs) in unmagnetized cold plasma consisting of dust fluid, ions and electrons lead to a KP equation. We derived the solitary travelling wave solutions of the two-dimensional nonlinear KP equation by implementing sech-tanh, sinh-cosh, extended direct algebraic and fraction direct algebraic methods. We found the electrostatic field potential and electric field in the form travelling wave solutions for two-dimensional nonlinear KP equation. The solutions for the KP equation obtained by using these methods can be demonstrated precisely and efficiency. As an illustration, we used the readymade package of Mathematica program 10.1 to solve the original problem. These solutions are in good agreement with the analytical one.

On the Role of Dust in the Lunar Ionosphere

NASA Technical Reports Server (NTRS)

Stubbs, Timothy J.; Glenar, D. A.; Collier, M. R.; Farrell, W. M.; Halekas, J S.; Delory, G. T.; Vondrak, R. R.

2011-01-01

Evidence suggests that electron concentrations above the dayside lunar surface can be significantly higher than expected from either the photo-ionization of exospheric neutrals or any other well-known process. The Luna 19 mission performed dual-frequency radio occultation experiments in order to determine electron column concentrations above the lunar limb as a function of tangent height (shown in the figure below), The resulting electron concentration profiles surprisingly indicated a peak of approx.500-1000/cu cm and scale heights of approx. 10-30 km. It has been suggested that electrically charged exospheric dust could contribute to these electron cnhancemcnts2 , Here we describe how to estimate the electrons produced by photo-charged dust, which is then used to predict electron concentrations from exospheric dust distribution models that are based on the "excess brightness" observed in Apollo 15 coronal photographs. The results indicate that radio occultation measurements likely provide a valuable perspective on the role of dust in the lunar environment.

Nonplanar dust-ion acoustic shock waves with transverse perturbation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue Jukui

2005-01-01

The nonlinear dust-ion acoustic shock waves in dusty plasmas with the combined effects of bounded cylindrical/spherical geometry, the transverse perturbation, the dust charge fluctuation, and the nonthermal electrons are studied. Using the perturbation method, a cylindrical/spherical Kadomtsev-Petviashvili Burgers equation that describes the dust-ion acoustic shock waves is deduced. A particular solution of the cylindrical/spherical Kadomtsev-Petviashvili Burgers equation is also obtained. It is shown that the dust-ion acoustic shock wave propagating in cylindrical/spherical geometry with transverse perturbation will be slightly deformed as time goes on.

Laboratory investigation of dust impacts on antennas in space

NASA Astrophysics Data System (ADS)

Drake, K.; Gruen, E.; Malaspina, D.; Sternovsky, Z.

2013-12-01

We are performing calibration measurements in our laboratory using a dust accelerator to understand the mechanisms how dust impact generated plasma clouds couple into electric field antennas on spacecraft. The S/WAVES electric field instruments on board the twin STEREO spacecraft observed short duration (milliseconds), large amplitude (> 15 mV) voltage spikes associated with the impact of high velocity dust particles on the spacecraft [St. Cyr et al., 2009, MeyerVernet et al, 2009a, Zaslavsky et al., 2012]. These sharp spikes have been attributed to plasma clouds generated by the impact ionization of high velocity dust particles. The high count rate has lead to the interpretation that S/WAVES is detecting nanometer sized dust particles (nano-dust) generated in the inner solar system and accelerated to close to solar wind velocities before impacting the spacecraft at 1 AU. The S/WAVES nano-dust interpretation is currently based on an incomplete understanding of the charge generated from relevant materials and the coupling mechanism between the plasma cloud and the electric field instrument. Calibration measurements are performed at the dust accelerator facility at the University of Colorado to investigate the effect of various impact parameters on the signals measured by the electric field instrument. The dust accelerator facility allows experimental control over target materials, size (micron to sub-micron), and velocity (1-60 km/s) of impacting dust particles, geometry of the impact, the ';spacecraft' potential, and the presence or absence of photoelectrons, allowing each coupling factor to be isolated and quantified. As the first step in this effort, we measure the impact charge generation for materials relevant for the STEREO spacecraft.

Climatic controls of the interannual to decadal variability in Saudi Arabian dust activity: Towards the development of a seasonal prediction tool

NASA Astrophysics Data System (ADS)

Yu, Y.; Notaro, M.; Liu, Z.; Alkolibi, F.; Fadda, E.; Bakhrjy, F.

2013-12-01

Atmospheric dust significantly influences the climate system, as well as human life in Saudi Arabia. Skillful seasonal prediction of dust activity with climatic variables will help prevent some negative social impacts of dust storms. Yet, the climatic regulators on Saudi Arabian dust activity remain largely unaddressed. Remote sensing and station observations show consistent seasonal cycles in Saudi Arabian dust activity, which peaks in spring and summer. The climatic controls on springtime and summertime Saudi Arabian dust activity during 1975-2010 are studied using observational and reanalysis data. Empirical Orthogonal Function (EOF) of the observed Saudi Arabian dust storm frequency shows a dominant homogeneous pattern across the country, which has distinct interannual and decadal variations, as revealed by the power spectrum. Regression and correlation analyses reveal that Saudi Arabian dust activity is largely tied to precipitation on the Arabian Peninsula in spring and northwesterly (Shamal) wind in summer. On the seasonal-interannual time scale, warm El Niño-Southern Oscillation (ENSO) phase (El Niño) in winter-to-spring inhibits spring dust activity by increasing the precipitation over the Rub'al Khali Desert, a major dust source region on the southern Arabian Peninsula; warm ENSO and warm Indian Ocean Basin Mode (IOBM) in winter-to-spring favor less summer dust activity by producing anomalously low sea-level pressure over eastern north Africa and Arabian Peninsula, which leads to the reduced Shamal wind speed. The decadal variation in dust activity is likely associated with the Atlantic Multidecadal Oscillation (AMO), which impacts Sahel rainfall and North African dust, and likely dust transport to Saudi Arabia. The Pacific Decadal Oscillation (PDO) and tropical Indian Ocean SST also have influence on the decadal variation in Saudi Arabian dust activity, by altering precipitation over the Arabian Peninsula and summer Shamal wind speed. Using eastern

Effects of granular charge on flow and mixing

NASA Astrophysics Data System (ADS)

Shinbrot, T.; Herrmann, H. J.

2008-12-01

Sandstorms in the desert have long been reported to produce sparks and other electrical disturbances - indeed as long ago as 1850, Faraday commented on the peculiarities of granular charging during desert sandstorms. Similarly, lightning strikes within volcanic dust plumes have been repeatedly reported for over half a century, but remain unexplained. The problem of granular charging has applied, as well as natural, implications, for charged particle clouds frequently generate spectacularly devastating dust explosions in granular processing plants, and sand becomes strongly electrified by helicopters traveling in desert environments. The issue even has implications for missions to the Moon and to Mars, where charged dust degrades solar cells viability and clings to spacesuits, limiting the lifetime of their joints. Despite the wide-ranging importance of granular charging, even the simplest aspects of its causes remain elusive. To take one example, sand grains in the desert manage to charge one another despite having only similar materials to rub against over expanses of many miles - thus existing theories of charging due to material differences fail entirely to account for the observed charging of desert sands. In this talk, we describe recent progress made in identifying underlying causes of granular charging, both in desert-like environments and in industrial applications, and we examine effects of granular charging on flow, mixing and separation of common granular materials. We find that charging of identical grains can occur under simple laboratory conditions, and we make new predictions for the effects of this charging on granular behaviours.

Electron density modification in ionospheric E layer by inserting fine dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Misra, Shikha, E-mail: shikhamish@gmail.com; Mishra, S. K.

2015-02-15

In this paper, we have developed the kinetics of E-region ionospheric plasma comprising of fine dust grains and shown that the electron density in E-layer can purposely be reduced/enhanced up to desired level by inserting fine dust particles of appropriate physical/material properties; this may certainly be promising for preferred rf-signal processing through these layers. The analytical formulation is based on average charge theory and includes the number and energy balance of the plasma constituents along with charge balance over dust particles. The effect of varying number density, work function, and photo-efficiency of dust particles on ionospheric plasma density at differentmore » altitude in E-layer has been critically examined and presented graphically.« less

Dust Removal Technolgy for a Mars In Situ Resource Utilization System

NASA Technical Reports Server (NTRS)

Calle, C. I.; Johansen, M. R.; Williams, B. S.; Hogue, M. D.; Mackey, P. J.; Clements, J. S.

2011-01-01

Several In Situ Resource Utilization (lSRU) systems being considered to enable future manned exploration of Mars require capture of Martian atmospheric gas to extract oxygen and other commodities. However, the Martian atmosphere contains relatively large amounts of dust which must be removed in tbe collection systems of the ISRU chambers. The amount of atmospheric dust varies largely with the presence of daily dust devils and the less frequent but much more powerful global dust storms. A common and mature dust removal technology for terrestrial systems is the electrostatic precipitator. With this technology, dust particles being captured are imparted an electrostatic charge by means of a corona discharge. Charged dust particles are then driven to a region of high electric field which forces the particles onto a collector for capture. Several difficulties appear when this technology is adapted to the Martian atmospheric environment At the low atmospheric pressure of Mars, electrical breakdown occurs at much lower voltages than on Earth and corona discharge is difficult to sustain. In this paper, we report on our efforts to obtain a steady corona/glow discharge in a simulated Martian atmosphere of carbon dioxide at 9 millibars of pressure. We also present results on the design of a dust capture system under these atmospheric conditions.

Dust Ion-Acoustic Shock Waves in a Multicomponent Magnetorotating Plasma

NASA Astrophysics Data System (ADS)

Kaur, Barjinder; Saini, N. S.

2018-02-01

The nonlinear properties of dust ion-acoustic (DIA) shock waves in a magnetorotating plasma consisting of inertial ions, nonextensive electrons and positrons, and immobile negatively charged dust are examined. The effects of dust charge fluctuations are not included in the present investigation, but the ion kinematic viscosity (collisions) is a source of dissipation, leading to the formation of stable shock structures. The Zakharov-Kuznetsov-Burgers (ZKB) equation is derived using the reductive perturbation technique, and from its solution the effects of different physical parameters, i.e. nonextensivity of electrons and positrons, kinematic viscosity, rotational frequency, and positron and dust concentrations, on the characteristics of shock waves are examined. It is observed that physical parameters play a very crucial role in the formation of DIA shocks. This study could be useful in understanding the electrostatic excitations in dusty plasmas in space (e.g. interstellar medium).

Laboratory investigation of antenna signals from dust impacts on spacecraft

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Collette, Andrew; Malaspina, David M.; Thayer, Frederick

2016-04-01

Electric field and plasma wave instruments act as dust detectors picking up voltage pulses induced by impacts of particulates on the spacecraft body. These signals enable the characterization of cosmic dust environments even with missions without dedicated dust instruments. For example, the Voyager 1 and 2 spacecraft performed the first detection of dust particles near Uranus, Neptune, and in the outer solar system [Gurnett et al., 1987, 1991, 1997]. The two STEREO spacecraft observed distinct signals at high rate that were interpreted as nano-sized particles originating from near the Sun and accelerated to high velocities by the solar wind [MeyerVernet et al, 2009a, Zaslavsky et al., 2012]. The MAVEN spacecraft is using the antennas onboard to characterize the dust environment of Mars [Andersson et al., 2014] and Solar Probe Plus will do the same in the inner heliosphere. The challenge, however, is the correct interpretation of the impact signals and calculating the mass of the dust particles. The uncertainties result from the incomplete understanding of the signal pickup mechanisms, and the variation of the signal amplitude with impact location, the ambient plasma environment, and impact speed. A comprehensive laboratory study of impact generated antenna signals has been performed recently using the IMPACT dust accelerator facility operated at the University of Colorado. Dust particles of micron and submicron sizes with velocities of tens of km/s are generated using a 3 MV electrostatic analyzer. A scaled down model spacecraft is exposed to the dust impacts and one or more antennas, connected to sensitive electronics, are used to detect the impact signals. The measurements showed that there are three clearly distinct signal pickup mechanisms due to spacecraft charging, antenna charging and antenna pickup sensing space charge from the expanding plasma cloud. All mechanisms vary with the spacecraft and antenna bias voltages and, furthermore, the latter two

Frontiers in In-Situ Cosmic Dust Detection and Analysis

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltán; Auer, Siegfried; Drake, Keith; Grün, Eberhard; Horányi, Mihály; Le, Huy; Srama, Ralf; Xie, Jianfeng

2011-11-01

In-situ cosmic dust instruments and measurements played a critical role in the emergence of the field of dusty plasmas. The major breakthroughs included the discovery of β-meteoroids, interstellar dust particles within the solar system, Jovian stream particles, and the detection and analysis of Enceladus's plumes. The science goals of cosmic dust research require the measurements of the charge, the spatial, size and velocity distributions, and the chemical and isotopic compositions of individual dust particles. In-situ dust instrument technology has improved significantly in the last decade. Modern dust instruments with high sensitivity can detect submicron-sized particles even at low impact velocities. Innovative ion optics methods deliver high mass resolution, m/dm>100, for chemical and isotopic analysis. The accurate trajectory measurement of cosmic dust is made possible even for submicron-sized grains using the Dust Trajectory Sensor (DTS). This article is a brief review of the current capabilities of modern dust instruments, future challenges and opportunities in cosmic dust research.

ISM DUST GRAINS AND N-BAND SPECTRAL VARIABILITY IN THE SPATIALLY RESOLVED SUBARCSECOND BINARY UY Aur

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skemer, Andrew J.; Close, Laird M.; Hinz, Philip M.

2010-03-10

The 10 {mu}m silicate feature is an essential diagnostic of dust-grain growth and planet formation in young circumstellar disks. The Spitzer Space Telescope has revolutionized the study of this feature, but due to its small (85 cm) aperture, it cannot spatially resolve small/medium-separation binaries ({approx}<3''; {approx}< 420 AU) at the distances of the nearest star-forming regions ({approx}140 pc). Large, 6-10 m ground-based telescopes with mid-infrared instruments can resolve these systems. In this paper, we spatially resolve the 0.''88 binary, UY Aur, with MMTAO/BLINC-MIRAC4 mid-infrared spectroscopy. We then compare our spectra to Spitzer/IRS (unresolved) spectroscopy, and resolved images from IRTF/MIRAC2, Keck/OSCIR,more » and Gemini/Michelle, which were taken over the past decade. We find that UY Aur A has extremely pristine, interstellar medium (ISM)-like grains and that UY Aur B has an unusually shaped silicate feature, which is probably the result of blended emission and absorption from foreground extinction in its disk. We also find evidence for variability in both UY Aur A and UY Aur B by comparing synthetic photometry from our spectra with resolved imaging from previous epochs. The photometric variability of UY Aur A could be an indication that the silicate emission itself is variable, as was recently found in EX Lupi. Otherwise, the thermal continuum is variable, and either the ISM-like dust has never evolved, or it is being replenished, perhaps by UY Aur's circumbinary disk.« less

Studies on Charge Variation and Waves in Dusty Plasmas

NASA Astrophysics Data System (ADS)

Kausik, Siddhartha Sankar

Plasma and dust grains are both ubiquitous ingredients of the universe. The interplay between them has opened up a new and fascinating research domain, that of dusty plasmas, which contain macroscopic particles of solid matter besides the usual plasma constituents. The research in dusty plasmas received a major boost in the early eighties with Voyager spacecraft observation on the formation of Saturn rings. Dusty plasmas are defined as partially or fully-ionized gases that contain micron-sized particles of electrically charged solid material, either dielectric or conducting. The physics of dusty plasmas has recently been studied intensively because of its importance for a number of applications in space and laboratory plasmas. This thesis presents the experimental studies on charge variation and waves in dusty plasmas. The experimental observations are carried out in two different experimental devices. Three different sets of experiments are carried out in two different experimental devices. Three different sets of experiments are carried out to study the dust charge variation in a filament discharge argon plasma. The dust grains used in these experiments are grains of silver. In another get of experiment, dust acoustic waves are studied in a de glow discharge argon plasma. Alumina dust grains are sprinkled in this experiment. The diagnostic tools used in these experiments are Langmuir probe and Faraday cup. The instruments used in these experiments are electrometer, He-Ne laser and charge coupled device (CCD) camera. Langmuir probe is used to measure plasma parameters, while Faraday cup and electrometer are used to measure very low current (~pA) carried by a collimated dust beam. He-Ne laser illuminates the dust grains and CCD camera is used to capture the images of dust acoustic waves. Silver dust grains are produced in the dust chamber by gas-evaporation technique. Due to differential pressure maintained between the dust and plasma chambers, the dust grains move

Nonlinear dust-lattice waves: a modified Toda lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cramer, N. F.

Charged dust grains in a plasma interact with a Coulomb potential, but also with an exponential component to the potential, due to Debye shielding in the background plasma. Here we investigate large-amplitude oscillations and waves in dust-lattices, employing techniques used in Toda lattice analysis. The lattice consists of a linear chain of particles, or a periodic ring as occurs in experimentally observed dust particle clusters. The particle motion has a triangular waveform, and chaotic motion for large amplitude motion of a grain.

3D dust clouds (Yukawa Balls) in strongly coupled dusty plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melzer, A.; Passvogel, M.; Miksch, T.

2010-06-16

Three-dimensional finite systems of charged dust particles confined to concentric spherical shells in a dusty plasma, so-called 'Yukawa balls', have been studied with respect to their static and dynamic properties. Here, we review the charging of particles in a dusty plasma discharge by computer simulations and the respective particle arrangements. The normal mode spectrum of Yukawa balls is measured from the 3D thermal Brownian motion of the dust particles around their equilibrium positions.

Instrument study of the Lunar Dust eXplorer (LDX) for a lunar lander mission

NASA Astrophysics Data System (ADS)

Li, Yanwei; Srama, Ralf; Henkel, Hartmut; Sternovsky, Zoltan; Kempf, Sascha; Wu, Yiyong; Grün, Eberhard

2014-11-01

One of the highest-priority issues for a future human or robotic lunar exploration is the lunar dust. This problem should be studied in depth in order to develop an environment model for a future lunar exploration. A future ESA lunar lander mission requires the measurement of dust transport phenomena above the lunar surface. Here, we describe an instrument design concept to measure slow and fast moving charged lunar dust which is based on the principle of charge induction. LDX has a low mass and measures the speed and trajectory of individual dust particles with sizes below one micrometer. Furthermore, LDX has an impact ionization target to monitor the interplanetary dust background. The sensor consists of three planes of segmented grid electrodes and each electrode is connected to an individual charge sensitive amplifier. Numerical signals were computed using the Coulomb software package. The LDX sensitive area is approximately 400 cm2. Our simulations reveal trajectory uncertainties of better than 2° with an absolute position accuracy of better than 2 mm.

Method and apparatus for smart battery charging including a plurality of controllers each monitoring input variables

DOEpatents

Hammerstrom, Donald J.

2013-10-15

A method for managing the charging and discharging of batteries wherein at least one battery is connected to a battery charger, the battery charger is connected to a power supply. A plurality of controllers in communication with one and another are provided, each of the controllers monitoring a subset of input variables. A set of charging constraints may then generated for each controller as a function of the subset of input variables. A set of objectives for each controller may also be generated. A preferred charge rate for each controller is generated as a function of either the set of objectives, the charging constraints, or both, using an algorithm that accounts for each of the preferred charge rates for each of the controllers and/or that does not violate any of the charging constraints. A current flow between the battery and the battery charger is then provided at the actual charge rate.

Characterization of Defects in Scaled Mis Dielectrics with Variable Frequency Charge Pumping

NASA Astrophysics Data System (ADS)

Paulsen, Ronald Eugene

1995-01-01

Historically, the interface trap has been extensively investigated to determine the effects on device performance. Recently, much attention has been paid to trapping in near-interface oxide traps. Performance of high precision analog circuitry is affected by charge trapping in near-interface oxide traps which produces hysteresis, charge redistribution errors, and dielectric relaxation effects. In addition, the performance of low power digital circuitry, with reduced noise margins, may be drastically affected by the threshold voltage shifts associated with charge trapping in near -interface oxide traps. Since near-interface oxide traps may substantially alter the performance of devices, complete characterization of these defects is necessary. In this dissertation a new characterization technique, variable frequency charge pumping, is introduced which allows charge trapped at the interface to be distinguished from the charge trapped within the oxide. The new experimental technique is an extension of the charge pumping technique to low frequencies such that tunneling may occur from interface traps to near-interface oxide traps. A generalized charge pumping model, based on Shockley-Read-Hall statistics and trap-to-trap tunneling theory, has been developed which allows a more complete characterization of near-interface oxide traps. A pair of coupled differential equations governing the rate of change of occupied interface and near-interface oxide traps have been developed. Due to the experimental conditions in the charge pumping technique the equations may be decoupled, leading to an equation governing the rate of change of occupied interface traps and an equation governing the rate of change of occcupied near-interface oxide traps. Solving the interface trap equation and applying non-steady state charge dynamics leads to an interface trap component of the charge pumping current. In addition, solution to the near-interface oxide trap equation leads to an additional

On the sizes and observable effects of dust particles in polar mesospheric winter echoes

NASA Astrophysics Data System (ADS)

Havnes, O.; Kassa, M.

2009-05-01

In the present paper, recent radar and heating experiments on the polar mesospheric winter echoes (PMWE) are analyzed with the radar overshoot model. The PMWE dust particles that influence the radar backscatter most likely have sizes around 3 nm. For dust to influence the electrons in the PMWE layers, it must be charged; therefore, we have discussed the charging of nanometer-sized particles and found that the photodetachment effect, where photons of energy less than the work function of the dust material can remove excess electrons, probably is dominant at sunlit conditions. For moderate and low electron densities, very few of the dust smaller than ˜3 nm will be charged. We suggest that the normal requirement that disturbed magnetospheric conditions with ionizing precipitation must be present to create observable PMWE is needed mainly to create sufficiently high electron densities to overcome the photodetachment effect and charge the PMWE dust particles. We have also suggested other possible effects of the photodetachment on the occurrence rate of the PMWE. We attribute the lack of PMWE-like radar scattering layers in the lower mesosphere during the summer not only to a lower level of turbulence than in winter but also to that dust particles are removed from these layers due to the upward wind draught in the summer mesospheric circulation system. It is likely that this last effect will completely shut off the PMWE-like radar layers in the lower parts of the mesosphere.

Laboratory investigation of dust impacts induced signals on antennas in space

NASA Astrophysics Data System (ADS)

Rocha, J. R.; Collette, A.; Malaspina, D.; Gruen, E.; Sternovsky, Z.

2014-12-01

Recent observations of sharp voltage spikes by the WAVES electric field experiments onboard the twin STEREO spacecraft have been attributed to plasma clouds generated by the impact ionization of high velocity dust particles. The reported dust fluxes are much higher than those measured by dedicated dust detectors at 1 AU, which leads to the interpretation that the STEREO observations are due to nanometer-sized dust particles originating from the inner solar system and accelerated to high velocities by the solar wind magnetic field. However, this interpretation is based on a simplified model of coupling between the expanding plasma cloud from the dust impact and the WAVES electric field instrument. A series of laboratory measurements are performed to validate this model and to calibrate/investigate the effect of various impact parameters on the signals measured by the electric field instrument. The dust accelerator facility operating at the University of Colorado is used for the measurement with micron and submicron sized particles accelerated to 50 km/s. The first set of measurements was aimed at the understanding of the charge yield of impact-generated plasmas from common materials used on spacecraft, i.e. BeCu, germanium coated black Kapton, MLI, and solar cells. The measurements show that at 10 km/s these materials yield similar charge signals. At higher speeds (~50 km/s) the variation is with material increases. The impact charge is also found to depend on angle of incidence; the data suggest a maximum at 45 degrees. The second set of measurements investigates the variation of the induced dust signal with bias potential applied on the simulated spacecraft.

Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

NASA Astrophysics Data System (ADS)

Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

2009-04-01

Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

Composition of Plasma Formed from Hypervelocity Dust Impacts

NASA Astrophysics Data System (ADS)

Lee, N.; Close, S.; Rymer, A. M.; Mocker, A.

2012-12-01

Dust impacts can occur on all solar system bodies but are especially prevalent in the case of the Saturnian moons that are near or within the dust torus produced by Enceladus's plumes. Depending on the mass and charge on these plume particles, they will be influenced by both gravitational and electrodynamic forces, resulting in a range of possible impact speeds on the moons. The plasma formed upon impact can have very different characteristics depending on impact speed and on the electric field due to surface charging at the impact point. Through recent tests conducted at the Max Planck Institute for Nuclear Physics using a Van de Graaff dust accelerator, iron dust particles were electrostatically accelerated to speeds of 3-65 km/s and impacted on a variety of target materials including metallic and glassy surfaces. The target surfaces were connected to a biasing supply to represent surface charging effects. Because of the high specific kinetic energy of the dust particles, upon impact they vaporize along with part of the target surface and a fraction of this material is ionized forming a dense plasma. The impacts produced both positive and negative ions. We made measurements of the net current imparted by this expanding plasma at a distance of several centimeters from the impact point. By setting the bias of the target, we impose an electric field on the charge population, allowing a measurement of plasma composition through time of flight analysis. The figure shows representative measurements of the net current measured by a retarding potential analyzer (RPA) from separate 18 and 19 km/s impacts of 7 fg particles on a glassy surface that was negatively and positively biased, respectively. This target was an optical solar reflector donated by J. Likar of Lockheed Martin for these experiments. These results show that ions of both positive and negative charge can be formed through the mechanism of dust impacts, and has implications on the surface plasma environment

Interannual Variability of Dust and Ice in the Mars Atmosphere: Comparison of MRO Mars Climate Sounder Retrievals with MGS-TES Limb Sounding Retrievals

NASA Technical Reports Server (NTRS)

Shirley, J. H.; McConnochie, T. H.; Kleinbohl, A.; Schofield, J. T.; Kass, D.; Heavens, N. G.; Benson, J.; McCleese, D. J.

2011-01-01

Dust and ice play important roles in Martian atmospheric dynamics on all time scales. Dust loading in particular exerts an important control on atmospheric temperatures and thereby on the strength of the atmospheric circulation in any given year. We present the first comparisons of MGS-TES aerosol opacity profiles with MRO-MCS aerosol opacity profiles. While the differences in vertical resolution are significant (a factor of 2), we find good agreement at particular seasons between nightside zonal average dust opacity profiles from the two instruments. Derived water ice opacities are likewise similar but show greater variability.

Adsorption properties of subtropical and tropical variable charge soils: Implications from climate change and biochar amendment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Ren-Kou; Qafoku, Nikolla; Van Ranst, Eric

2016-01-25

This review paper attempts to summarize the progress made in research efforts conducted over the last years to study the surface chemical properties of the tropical and subtropical soils, usually called variable charge soils, and the way they response to different management practices. The paper is composed of an introductory section that provides a brief discussion on the surface chemical properties of these soils, and five other review sections. The focus of these sections is on the evolution of surface chemical properties during the development of the variable charge properties (second section), interactions between oppositely charged particles and the resultingmore » effects on the soil properties and especially on soil acidity (third section), the surface effects of low molecular weight organic acids sorbed to mineral surfaces and the chemical behavior of aluminum (fourth section), and the crop straw derived biochar induced changes of the surface chemical properties of these soils (fifth section). A discussion on the effect of climate change variables on the properties of the variable charge soils is included at the end of this review paper (sixth section).« less

The Cassini Cosmic Dust Analyser CDA - A 10 year exploration of Saturn's dust environment

NASA Astrophysics Data System (ADS)

Srama, Ralf

2014-05-01

The interplanetary space probe Cassini/Huygens reached Saturn in July 2004 after seven years of cruise phase. Since then, the German-lead Cosmic Dust Analyser (CDA) was operated continuously for 10 years in orbit around Saturn. The first discovery of CDA related to Saturn was the measurement of nanometer sized dust particles ejected by its magnetosphere to interplanetary space with speeds higher than 100 km/s. Their origin and composition was analysed and an their dynamical studies showed a strong link to the conditions of the solar wind plasma flow. A recent surprising result was, that stream particles stem from the interior of Enceladus. Since 2004 CDA measured millions of dust impacts characterizing the dust environment of Saturn. The instrument showed strong evidence for ice geysers located at the south pole of Saturn's moon Enceladus in 2005. Later, a detailed compositional analysis of the salt-rich water ice grains in Saturn's E ring system lead to the discovery of liquid water below the crust connected to an ocean at depth feeding the icy jets. CDA was even capable to derive a spatially resolved compositional profile of the plume during close Enceladus flybys. A determination of the dust-magnetosphere interaction and the discovery of the extended E ring (at least twice as large as previously known) allowed the definition of a dynamical dust model of Saturns E ring describing the observed properties. Cassini performed shadow crossings in the ring plane and dust grain charges were measured in shadow regions delivering important data for dust-plasma interaction studies. In the last years, dedicated measurement campaigns were executed by CDA to monitor the flux of interplanetary and interstellar dust particles reaching Saturn.

A planetary dust ring generated by impact-ejection from the Galilean satellites

NASA Astrophysics Data System (ADS)

Sachse, Manuel

2018-03-01

All outer planets in the Solar System are surrounded by a ring system. Many of these rings are dust rings or they contain at least a high proportion of dust. They are often formed by impacts of micro-meteoroids onto embedded bodies. The ejected material typically consists of micron-sized charged particles, which are susceptible to gravitational and non-gravitational forces. Generally, detailed information on the dynamics and distribution of the dust requires expensive numerical simulations of a large number of particles. Here we develop a relatively simple and fast, semi-analytical model for an impact-generated planetary dust ring governed by the planet's gravity and the relevant perturbation forces for the dynamics of small charged particles. The most important parameter of the model is the dust production rate, which is a linear factor in the calculation of the dust densities. We apply our model to dust ejected from the Galilean satellites using production rates obtained from flybys of the dust sources. The dust densities predicted by our model are in good agreement with numerical simulations and with in situ measurements by the Galileo spacecraft. The lifetimes of large particles are about two orders of magnitude greater than those of small ones, which implies a flattening of the size distribution in circumplanetary space. Information about the distribution of circumplanetary dust is also important for the risk assessment of spacecraft orbits in the respective regions.

Dust in Jupiter's magnetosphere. I - Physical processes. II - Origin of the ring. III - Time variations. IV - Effect on magnetospheric electrons and ions

NASA Technical Reports Server (NTRS)

Morfill, G. E.; Gruen, E.; Johnson, T. V.

1980-01-01

The physical processes acting on charged microscopic dust grains in the Jovian atmosphere involve electromagnetic forces which dominate dust particle dynamics and diffusion across field lines resulting from random charge fluctuations of the dust grains. A model of the Jovian ring hypothesizes that the 'visible' ring particles are produced by erosive collisions between an assumed population of kilometer-sized parent bodies and submicron-sized magnetospheric dust particles. Fluctuations in the ring topology and intensity are determined over various time scales, showing that the ring is a quasipermanent and quasistable characteristic of the Jovian system. Finally, the interaction of the Jovian energetic belt electrons and the Jovian plasma with an ambient dust population is examined; the distribution of dust ejected from Io in the inner magnetosphere and losses of magnetospheric ions and electrons due to direct collisions with charged dust particles are calculated.

Atmospheric transport of mineral dust from the Indo-Gangetic Plain: Temporal variability, acid processing, and iron solubility

NASA Astrophysics Data System (ADS)

Srinivas, Bikkina; Sarin, M. M.; Rengarajan, R.

2014-08-01

transport of chemical constituents from the Indo-Gangetic Plain (IGP) to the Bay of Bengal is a conspicuous seasonal feature that occurs during the late NE-monsoon (December-March). With this perspective, aerosol composition and abundance of mineral dust have been studied during November 2009 to March 2010 from a sampling site (Kharagpur: 22.3°N, 87.3°E) in the IGP, representing the atmospheric outflow to the Bay of Bengal. The chemical composition of PM2.5 suggests the dominance of nss-SO42- (6.9-24.3 µg m-3); whereas the abundance of mineral dust varied from 3 to 18 µg m-3. The concentration of aerosol iron (FeTot) and its fractional solubility (Fews % = Fews/FeTot *100, where Fews is the water-soluble fraction of FeTot) varied from 60 to 1144 ng m-3 and from 6.7 to 26.5%, respectively. A striking similarity in the temporal variability of total inorganic acidity (TIA = NO3- + nss-SO42-) and Fews (%) provides evidence for acid processing of mineral dust (alluvium) during atmospheric transport from the IGP. The contribution of TIA to water-soluble inorganic species [(nss-SO42- + NO3-)/ΣWSIS], mass ratios of Ca/Al and Fe/Al, and abundance of dust (%) and Fews (%) in the IGP-outflow are similar to the aerosol composition over the Bay of Bengal. With the rapid increase in anthropogenic activities over south and south-east Asia, the enhanced fractional solubility of aerosol iron (attributed to acid processing of mineral dust) has implications to further increase in the air-sea deposition of Fe to the Ocean surface.

Two-dimensional positive column structure with dust cloud: Experiment and nonlocal kinetic simulation

NASA Astrophysics Data System (ADS)

Zobnin, A. V.; Usachev, A. D.; Petrov, O. F.; Fortov, V. E.; Thoma, M. H.; Fink, M. A.

2018-03-01

The influence of a dust cloud on the structure of the positive column of a direct current gas discharge in a cylindrical glass tube under milligravity conditions has been studied both experimentally and numerically. The discharge was produced in neon at 60 Pa in a glass tube with a diameter of 30 mm at a discharge current 1 mA. Spherical monodisperse melamine formaldehyde dust particles with a diameter of 6.86 μm were injected into the positive column and formed there a uniform dust cloud with a maximum diameter of 14.4 mm. The shape of the cloud and the dust particle number density were measured. The cloud was stationary in the radial direction and slowly drifted in the axial direction. It was found that in the presence of the dust cloud, the intensity of the neon spectral line with a wavelength by 585.25 nm emitted by the discharge plasma increased by 2.3 times and 2 striations appeared on the anode side of the cloud. A numerical simulation of the discharge was performed using the 2D (quasi-3D) nonlocal self-consistent kinetic model of a longitudinally inhomogeneous axially symmetric positive column [Zobnin et al., Phys. Plasmas 21, 113503 (2014)], which was supplemented by a program module performing a self-consistent calculation of dust particle charges, the plasma recombination rate on dust particles, and ion scattering on dust particles. A new approach to the calculation of particle charges and the screening radius in dense dust clouds is proposed. The results of the simulation are presented, compared with experimental data and discussed. It is demonstrated that for the best agreement between simulated and experimental data, it is necessary to take into account the reflection of electrons from the dust particle surface in order to correctly describe the recombination rate in the cloud, its radial stability, and the dust particle charges.

Anomalous diffusion due to the non-Markovian process of the dust particle velocity in complex plasmas

NASA Astrophysics Data System (ADS)

Ghannad, Z.; Hakimi Pajouh, H.

2017-12-01

In this work, the motion of a dust particle under the influence of the random force due to dust charge fluctuations is considered as a non-Markovian stochastic process. Memory effects in the velocity process of the dust particle are studied. A model is developed based on the fractional Langevin equation for the motion of the dust grain. The fluctuation-dissipation theorem for the dust grain is derived from this equation. The mean-square displacement and the velocity autocorrelation function of the dust particle are obtained in terms of the Mittag-Leffler functions. Their asymptotic behavior and the dust particle temperature due to charge fluctuations are studied in the long-time limit. As an interesting result, it is found that the presence of memory effects in the velocity process of the dust particle as a non-Markovian process can cause an anomalous diffusion in dusty plasmas. In this case, the velocity autocorrelation function of the dust particle has a power-law decay like t - α - 2, where the exponent α take values 0 < α < 1.

VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clayton, Geoffrey C.; Zhang Wanshu; Geballe, T. R., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wzhan21@lsu.edu, E-mail: tgeballe@gemini.edu

2013-08-01

We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I {lambda}10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities {approx}400 km s{sup -1} appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the declinemore » and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.« less

How Much Dust Does Enceladus eject?

NASA Astrophysics Data System (ADS)

Kempf, S.; Southworth, B.; Srama, R.; Schmidt, J.; Postberg, F.

2016-12-01

There is an ongoing argument how much dust per second the ice volcanoes on Saturn's ice moon eject. By adjusting their plume model to the dust flux measured by the Cassini dust detector during the close Enceladus flyby in 2005, Schmidt et al. (2008) obtained a total dust production rate in the plumes of about 􏱱5 kg/s. On the other hand, Ingersoll and Ewald (2005) derived a dust production rate of 51 kg/s from the total plume brightness. Knowledge of the production rate is essential for estimating the dust to gas mass ratio, which in turn is an important constraint for finding the plume source mechanism. Here we report on measurements of the plume dust density during the last close Cassini flyby at Enceladus in October 2015. The data match our numerical model for the Enceladus plume. The model is based on a large number of dynamical simulations including gravity and Lorentz force to investigate the earliest phase of the ring particle life span. The evolution of the electrostatic charge carried by the initially uncharged grains is treated self-consistently. Our numerical simulations reproduce all Enceladus data sets obtained by Cassini's Cosmic Dust Analyzer (CDA). Our model calculations together with the new density data constrain the Enceladus dust source rate to < 5 kg/s. Based on our simulation results we are able to draw conclusions about the emission of plume particles along the fractures in the south polar terrain.

Mesospheric dust observations during the MAXIDUSTY campaign

NASA Astrophysics Data System (ADS)

Antonsen, Tarjei; Havnes, Ove; Fredriksen, Åshild; Friedrich, Martin; Sternovsky, Zoltan; Plane, John; Hartquist, Tom; Olsen, Sveinung; Eilertsen, Yngve; Trondsen, Espen; Mann, Ingrid; Hedin, Jonas; Gumbel, Jörg; Moen, Jøran; Latteck, Ralph; Baumgarten, Gerd; Höffner, Josef; Williams, Bifford; Hoppe, Ulf-Peter; Karlberg, Jan-Ove

2017-04-01

The MAXIDUSTY rocket payloads, launched from Andøya June 30 and July 8 2016, were equipped with dust impact detectors aiming to characterize mesospheric dust charge state, mass distribution of impact fragments and NLC/PMSE structure. One of the main scientific objectives for the campaign was to confirm that material of meteoric origin is abundant inside the icy mesospheric dust particles. The rockets were launched simultaneously with PMSE and NLC (MAXIDUSTY-1) and PMSE (MAXIDUSTY-1B) respectively, and radar measurements were made coincident with the rocket flight path. We report here on the initial results from the rocket probes and remote soundings, with emphasis on the dust impact detector results. Results from the Multiple Dust Detector (MUDD) confirm that NLC ice particles probably have a relatively high content of meteoric smoke particles with a filling factor of up to several percent. Comparisons of the DUSTY faraday bucket and PMSE show that there is no simple correlation between the two.

Reversed Hall effect and plasma conductivity in the presence of charged impurities

NASA Astrophysics Data System (ADS)

Yaroshenko, V. V.; Lühr, H.

2018-01-01

The Hall conductivity of magnetized plasma can be strongly suppressed by the contribution of negatively charged particulates (referred further as "dust"). Once the charge density accumulated by the dust exceeds a certain threshold, the Hall component becomes negative, providing a reversal in the Hall current. Such an effect is unique for dust-loaded plasmas, and it can hardly be achieved in electronegative plasmas. Further growth of the dust density leads to an increase in both the absolute value of the Hall and Pedersen conductivities, while the field-aligned component is decreased. These modifications enhance the role of transverse electric currents and reduce the anisotropy of a magnetized plasma when loaded with charged impurities. The findings provide an important basis for studying the generation of electric currents and transport phenomena in magnetized plasma systems containing small charged particulates. They can be relevant for a wide range of applications from naturally occurring space plasmas in planetary magnetospheres and astrophysical objects to laboratory dusty plasmas (Magnetized Dusty Plasma Experiment) and to technological and fusion plasmas.

Electrodynamic Dust Shield for Solar Panels on Mars

NASA Technical Reports Server (NTRS)

Calle, C. I.; Buhler, C. R.; Mantovani, J. G.; Clements S.; Chen, A.; Mazumder, M. K.; Biris, A. S.; Nowicki, A. W.

2004-01-01

The Materials Adherence Experiment on the Mars Pathfinder mission measured an obscuration of the solar arrays due to dust deposition at a rate of about 0.2 8% per day. It was estimated that settling dust may cause degradation in performance of a solar panel of between 22% and 89% over the course of two years [1, 2]. These results were obtained without the presence of a global dust storm. Several types of adherence forces keep dust particles attached to surfaces. The most widely discussed adherence force is the electrostatic force. Laboratory experiments [3] as well as indirect evidence from the Wheel Abrasion Experiment on Pathfinder [4] indicate that it is very likely that the particles suspended in the Martian atmosphere are electrostatically charged.

Experiments to trap dust particles by a wire simulating an electron beam

NASA Astrophysics Data System (ADS)

Saeki, Hiroshi; Momose, Takashi; Ishimaru, Hajime

1991-11-01

Motion of trapped dust particles has been previously analyzed using high-energy bremsstrahlung data obtained during dust trapping in the TRISTAN accumulation ring. Because it is difficult to observe the actual motions of dust particles trapped in an electron beam due to the strong synchrotron light background, we carried out experiments to trap sample dust particles with a Cu wire simulating an electron beam. A negative potential was slowly applied to the wire using a high voltage dc power supply. Motions of dust particles trapped by the wire were recorded with a video camera system. In an experiment using a Cu wire (1.5 mm in diameter) with no magnetic field, the charged dust particle made vertical oscillation about the wire. In another experiment using the same wire but with a vertical magnetic field (0.135 T) simulating a bending magnetic field, both vertical and horizontal oscillating motions perpendicular to the wire were observed. Furthermore, it was found that the dust particle moved in the longitudinal direction of the wire in the bending magnetic field. Therefore, it is expected that charged dust particles trapped by the electric field of the electron beam oscillate vertically where there is no magnetic field in the TRISTAN accumulation ring. It is also expected that trapped dust particles where there is a bending magnetic field oscillate horizontally and vertically as the particle drifts in a longitudinal direction along the ring.

ISM Dust Grains and N-band Spectral Variability in the Spatially Resolved Subarcsecond Binary UY Aur

NASA Astrophysics Data System (ADS)

Skemer, Andrew J.; Close, Laird M.; Hinz, Philip M.; Hoffmann, William F.; Greene, Thomas P.; Males, Jared R.; Beck, Tracy L.

2010-03-01

The 10 μm silicate feature is an essential diagnostic of dust-grain growth and planet formation in young circumstellar disks. The Spitzer Space Telescope has revolutionized the study of this feature, but due to its small (85 cm) aperture, it cannot spatially resolve small/medium-separation binaries (lsim3''; <~ 420 AU) at the distances of the nearest star-forming regions (~140 pc). Large, 6-10 m ground-based telescopes with mid-infrared instruments can resolve these systems. In this paper, we spatially resolve the 0farcs88 binary, UY Aur, with MMTAO/BLINC-MIRAC4 mid-infrared spectroscopy. We then compare our spectra to Spitzer/IRS (unresolved) spectroscopy, and resolved images from IRTF/MIRAC2, Keck/OSCIR, and Gemini/Michelle, which were taken over the past decade. We find that UY Aur A has extremely pristine, interstellar medium (ISM)-like grains and that UY Aur B has an unusually shaped silicate feature, which is probably the result of blended emission and absorption from foreground extinction in its disk. We also find evidence for variability in both UY Aur A and UY Aur B by comparing synthetic photometry from our spectra with resolved imaging from previous epochs. The photometric variability of UY Aur A could be an indication that the silicate emission itself is variable, as was recently found in EX Lupi. Otherwise, the thermal continuum is variable, and either the ISM-like dust has never evolved, or it is being replenished, perhaps by UY Aur's circumbinary disk. The observations reported here were partially obtained at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program.

How much dust does Enceladus eject?

NASA Astrophysics Data System (ADS)

Kempf, Sascha; Horanyi, Mihaly; Schmidt, Jürgen; Southworth, Ben

2015-04-01

There is an ongoing argument how much dust per second the ice volcanoes on Saturn's ice moon Enceladus eject. By adjusting their plume model to the dust flux measured by the Cassini dust detector during the close Enceladus flyby in 2005, as well as to the plume brightness in Cassini imaging, Schmidt et al. (2008) obtained a total dust production rate in the plumes of about 5 kg/s. On the other hand, Ingersoll and Ewald (2011) derived a dust production rate of 51 kg/s from photometry of very high phase-angle images of the plume, a method that is sensitive also to particles in the size range of microns and larger. Knowledge of the production rate is essential for estimating the dust to gas mass ratio, which in turn is an important constraint for finding the plume source mechanism. Here we report on numerical simulations of the Enceladus dust plume. We run a large number of dynamical simulations including gravity and Lorentz force to investigate the earliest phase of the ring particle life span. The magnetic field in the vicinity of Enceladus is based on the model by Simon et al. (2012). The evolution of the electrostatic charge carried by the initially uncharged grains is treated self-consistently. Our numerical simulations reproduce dust measurements by the Cassini Cosmic Dust Analyzer (CDA) during Cassini plume traversals as well as the snowfall pattern derived from ISS observations of the Enceladus surface (Schenk et al, 2011, EPSC abstract). Based on our simulation results we are able to draw conclusions about the dust production rate as well as wether the Enceladus dust plume constitutes a dusty plasma.

A NOVEL DEVICE FOR CHARGING HIGH RESISTIVITY DUST

EPA Science Inventory

The paper describes an aerosol precharger that can provide a charging environment with relatively high unipolar ion density for particulate matter having high electrical resistivity. The result is a much higher level of charge on the particles than can be achieved by a convention...

Black Carbon, Dust and Organic Matter at South Cascade Glacier in Washington State, USA: A Comprehensive Characterization of Temporal (1865-2014) and Spatial Variability

NASA Astrophysics Data System (ADS)

Kaspari, S.; Pittenger, D.; Swick, M.; Skiles, M.; Perez, A.; Sethi, H.; Sevier, E.

2017-12-01

Rising temperatures are a widely recognized cause of glacial retreat in Washington, however light absorbing aerosols (LAA, including black carbon (BC), dust and organic matter) can also contribute to increased melt by reducing snow albedo. We present updated results of BC and dust variability at South Cascade (SOCAS) glacier spanning 1865-1994 using a 158 m ice core. Peak BC deposition occurred between 1940-1958, when median BC concentrations were 25 times higher than background levels. Post 1958 BC concentrations decrease, followed by an increase post 1980 associated with melt consolidation and/or trans-Pacific aerosol transport. Dust deposition at SOCAS is dominated by local sources. Albedo reductions from LAA are dominated by dust deposition, except during high BC deposition events from wildfires, and during the 1940-1958 period when BC contributes equally to albedo reductions. Results from a 2014 field campaign that included collection of 3 shallow ice cores, surface snow, and snow albedo measurements allow the 1865-1994 ice core record to be extended toward present, and spatial variability in LAA to be characterized. Snow albedo transects were measured using a spectrometer. BC concentrations were measured using a Single Particle Soot Photometer (SP2). Gravimetric filtration was used to determine the total LAA, and a thermal gravimetric technique was used to partition the LAA between dust and organic matter. The organic matter was partitioned into organic and elemental carbon using a thermal optical method. These methods allow LAA abundances be measured, but to partition the contribution of the LAA to albedo reductions requires characterization of LAA optical properties. This was accomplished using a Hyperspectral Imaging Microscope Spectrometer method that allows particle reflectance to be measured at 138 nm2 pixel resolution. By combining these methods, we provide a comprehensive characterization of spatial and temporal LAA variability at SOCAS.

Results From Mars Show Electrostatic Charging of the Mars Pathfinder Sojourner Rover

NASA Technical Reports Server (NTRS)

Kolecki, Joseph C.; Siebert, Mark W.

1998-01-01

Indirect evidence (dust accumulation) has been obtained indicating that the Mars Pathfinder rover, Sojourner, experienced electrostatic charging on Mars. Lander camera images of the Sojourner rover provide distinctive evidence of dust accumulation on rover wheels during traverses, turns, and crabbing maneuvers. The sol 22 (22nd Martian "day" after Pathfinder landed) end-of-day image clearly shows fine red dust concentrated around the wheel edges with additional accumulation in the wheel hubs. A sol 41 image of the rover near the rock "Wedge" (see the next image) shows a more uniform coating of dust on the wheel drive surfaces with accumulation in the hubs similar to that in the previous image. In the sol 41 image, note particularly the loss of black-white contrast on the Wheel Abrasion Experiment strips (center wheel). This loss of contrast was also seen when dust accumulated on test wheels in the laboratory. We believe that this accumulation occurred because the Martian surface dust consists of clay-sized particles, similar to those detected by Viking, which have become electrically charged. By adhering to the wheels, the charged dust carries a net nonzero charge to the rover, raising its electrical potential relative to its surroundings. Similar charging behavior was routinely observed in an experimental facility at the NASA Lewis Research Center, where a Sojourner wheel was driven in a simulated Martian surface environment. There, as the wheel moved and accumulated dust (see the following image), electrical potentials in excess of 100 V (relative to the chamber ground) were detected by a capacitively coupled electrostatic probe located 4 mm from the wheel surface. The measured wheel capacitance was approximately 80 picofarads (pF), and the calculated charge, 8 x 10(exp -9) coulombs (C). Voltage differences of 100 V and greater are believed sufficient to produce Paschen electrical discharge in the Martian atmosphere. With an accumulated net charge of 8 x 10(exp

THERMODYNAMICS AND CHARGING OF INTERSTELLAR IRON NANOPARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hensley, Brandon S.; Draine, B. T., E-mail: brandon.s.hensley@jpl.nasa.gov

Interstellar iron in the form of metallic iron nanoparticles may constitute a component of the interstellar dust. We compute the stability of iron nanoparticles to sublimation in the interstellar radiation field, finding that iron clusters can persist down to a radius of ≃4.5 Å, and perhaps smaller. We employ laboratory data on small iron clusters to compute the photoelectric yields as a function of grain size and the resulting grain charge distribution in various interstellar environments, finding that iron nanoparticles can acquire negative charges, particularly in regions with high gas temperatures and ionization fractions. If ≳10% of the interstellar ironmore » is in the form of ultrasmall iron clusters, the photoelectric heating rate from dust may be increased by up to tens of percent relative to dust models with only carbonaceous and silicate grains.« less

Thermodynamics and Charging of Interstellar Iron Nanoparticles

NASA Astrophysics Data System (ADS)

Hensley, Brandon S.; Draine, B. T.

2017-01-01

Interstellar iron in the form of metallic iron nanoparticles may constitute a component of the interstellar dust. We compute the stability of iron nanoparticles to sublimation in the interstellar radiation field, finding that iron clusters can persist down to a radius of ≃4.5 Å, and perhaps smaller. We employ laboratory data on small iron clusters to compute the photoelectric yields as a function of grain size and the resulting grain charge distribution in various interstellar environments, finding that iron nanoparticles can acquire negative charges, particularly in regions with high gas temperatures and ionization fractions. If ≳10% of the interstellar iron is in the form of ultrasmall iron clusters, the photoelectric heating rate from dust may be increased by up to tens of percent relative to dust models with only carbonaceous and silicate grains.

Atmospheric Electricity Effects of Eastern Mediterranean Dust Storms

NASA Astrophysics Data System (ADS)

Katz, Shai; Yair, Yoav; Yaniv, Roy; Price, Colin

2016-04-01

We present atmospheric electrical measurements conducted at the Wise Observatory (WO) in Mizpe-Ramon (30035'N, 34045'E) and Mt. Hermon (30024'N, 35051'E), Israel, during two massive and unique dust storms that occurred over the Eastern Mediterranean region on February 10-11 and September 08-12, 2015. The first event transported Saharan dust from Egypt and the Sinai Peninsula in advance of a warm front of a Cyprus low pressure system. In the second event, dust particles were transported from the Syrian desert, which dominates the north-east border with Iraq, through flow associated with a shallow Persian trough system. In both events the concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 2200 μg m-3. Aerosol Optical Thickness (AOT) obtained from the AERONET station in Sde-Boker reached values up to 4.0. The gradual intensification of the first event reached peak values on the February 11th > 1200 μg m-3 and an AOT ~ 1.8, while the second dust storm commenced on September 8th with a sharp increase reaching peak values of 2225 μg m-3 and AOT of 4.0. Measurements of the fair weather vertical electric field (Ez) and of the vertical current density (Jz) were conducted continuously with a 1 minute temporal resolution. During the February event, very large fluctuations in the electrical parameters were measured at the WO. The Ez values changed between +1000 and +8000 V m-1 while the Jz fluctuated between -10 and +20 pA m-2 (this is an order of magnitude larger compared to the fair weather current density of ~2 pA m-2. In contrast, during the September event, Ez values registered at WO were between -430 and +10 V m-1 while the Jz fluctuated between -6 and +3 pA m2. For the September event the Hermon site showed Ez and Jz values fluctuating between -460 and +570 V m-1 and -14.5 and +18 pA m-2 respectively. The electric field and current variability, amplitude and the

The past, present and future of African dust.

PubMed

Evan, Amato T; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

2016-03-24

African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations--in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and

A Cosmic Dust Sensor Based on an Array of Grid Electrodes

NASA Astrophysics Data System (ADS)

Li, Y. W.; Bugiel, S.; Strack, H.; Srama, R.

2014-04-01

We described a low mass and high sensitivity cosmic dust trajectory sensor using a array of grid segments[1]. the sensor determines the particle velocity vector and the particle mass. An impact target is used for the detection of the impact plasma of high speed particles like interplanetary dust grains or high speed ejecta. Slower particles are measured by three planes of grid electrodes using charge induction. In contrast to conventional Dust Trajectory Sensor based on wire electrodes, grid electrodes a robust and sensitive design with a trajectory resolution of a few degree. Coulomb simulation and laboratory tests were performed in order to verify the instrument design. The signal shapes are used to derive the particle plane intersection points and to derive the exact particle trajectory. The accuracy of the instrument for the incident angle depends on the particle charge, the position of the intersection point and the signal-to-noise of the charge sensitive amplifier (CSA). There are some advantages of this grid-electrodes based design with respect to conventional trajectory sensor using individual wire electrodes: the grid segment electrodes show higher amplitudes (close to 100%induced charge) and the overall number of measurement channels can be reduced. This allows a compact instrument with low power and mass requirements.

Electrical Charging Hazards Originating from the Surface (ECHOS): Understanding the Martian Electro-Meteorological Environment

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Desch, M. D.; Marshall, J. R.; Delory, G. T.; Kolecki, J. C.; Hillard, G. B.; Kaiser, M. L.; Haberle, R. M.; Zent, A. P.; Luhmann, J. G.

2000-01-01

In 1999, the NASA/Human Exploration and Development of Space (HEDS) enterprise selected a number of payloads to fly to the Martian surface in an 03 opportunity (prior to the MPL loss). Part of a proposed experiment, ECHOS, was selected to specifically understand the electrical charging hazards from tribocharged dust in the ambient atmosphere, in dust devils, and in larger storms. It is expected that Martian dust storms become tribocharged much like terrestrial dust devils which can possess almost a million elementary charges per cubic centimeter. The ECHOS package features a set of instruments for measuring electric effects: a radio to detect AC electric fields radiating from discharges in the storm,a DC electric field system for sensing electrostatic fields from concentrations of charged dust grains, and a lander electrometer chain for determining the induced potential on its body and MAV (Mars Ascent Vehicle) during the passages of a charged dust storm. Given that electricity is a systemic process originating from wind-blown dust, we also proposed to correlate the electrical measurements with fundamental fluid/meteorological observations, including wind velocity and vorticity, temperature, and pressure. Triboelectricity will also affect local chemistry, and chemical-sensing devices were also considered a feature of the package. The primary HEDS objectives of the ECHOS sensing suite is to discover and monitor the natural electrical hazards associated with dust devils and storms, and determine their enviro-effectiveness on human systems. However, ECHOS also has a strong footprint in the overarching science objectives of the Mars Surveyor Program.

On the injection of fine dust from the Jovian magnetosphere

NASA Technical Reports Server (NTRS)

Maravilla, D.; Flammer, K. R.; Mendis, D. A.

1995-01-01

Using a simple aligned dipole model of the Jovian magnetic field, and exploiting integrals of the gravito-electrodynamic equation of motion of charged dust, we obtain an analytic result which characterizes the nature of the orbits of grains of different (fixed) charge-to-mass ratios launched at different velocities from different radial distances from Jupiter. This enables us to consider various possible sources of the dust-streams emanating from Jupiter which have been observed by the Ulysses spacecraft. We conclude that Jupiter's volcanically active satellite Io is the likely source, in agreement with the earlier calculations and simulations of Horanyi et al. using a detailed three-dimensional model of the Jovian magnetosphere. Our estimates of the size range and the velocity range of these dust grains are also in good agreement with those of the above authors and are within the error bars of the observations.

Trajectories and distribution of interstellar dust grains in the heliosphere

DOE PAGES

Slavin, Jonathan D.; Frisch, Priscilla C.; Müller, Hans-Reinhard; ...

2012-11-01

The solar wind carves a bubble in the surrounding interstellar medium (ISM) known as the heliosphere. Charged interstellar dust grains (ISDG) encountering the heliosphere may be diverted around the heliopause or penetrate it depending on their charge-to-mass ratio. Here, we present new calculations of trajectories of ISDG in the heliosphere, and the dust density distributions that result. We include up-to-date grain charging calculations using a realistic UV radiation field and full three-dimensional magnetohydrodynamic fluid + kinetic models for the heliosphere. Models with two different (constant) polarities for the solar wind magnetic field (SWMF) are used, with the grain trajectory calculationsmore » done separately for each polarity. Small grains a gr ≲ 0.01 μm are completely excluded from the inner heliosphere. Large grains, a gr ≳ 1.0 μm, pass into the inner solar system and are concentrated near the Sun by its gravity. Trajectories of intermediate size grains depend strongly on the SWMF polarity. When the field has magnetic north pointing to ecliptic north, the field de-focuses the grains resulting in low densities in the inner heliosphere, while for the opposite polarity the dust is focused near the Sun. The ISDG density outside the heliosphere inferred from applying the model results to in situ dust measurements is inconsistent with local ISM depletion data for both SWMF polarities but is bracketed by them. Our result points to the need to include the time variation in the SWMF polarity during grain propagation. This provides valuable insights for interpretation of the in situ dust observations from Ulysses.« less

Charging of interplanetary grains

NASA Technical Reports Server (NTRS)

Baragiola, R. A.; Johnson, R. E.; Newcomb, John L.

1995-01-01

The objective of this program is to quantify, by laboratory experiments, the charging of ices and other insulators subject to irradiation with electrons, ions and ultraviolet photons and to model special conditions based on the data. The system and conditions to be studied are those relevant for charging of dust in magnetospheric plasmas. The measurements are supplemented by computer simulations of charging or grains under a variety of conditions. Our work for this period involved experiments on water ice, improved models of charging of ice grains for Saturn's E-ring, and the construction of apparatus for electron impact studies and measurements of electron energy distributions.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES Dust Acoustic Solitary Waves in Saturn F-ring's Region

NASA Astrophysics Data System (ADS)

E. K., El-Shewy; M. I. Abo el, Maaty; H. G., Abdelwahed; M. A., Elmessary

2011-01-01

Effect of hot and cold dust charge on the propagation of dust-acoustic waves (DAWs) in unmagnetized plasma having electrons, singly charged ions, hot and cold dust grains has been investigated. The reductive perturbation method is employed to reduce the basic set of fluid equations to the Kortewege-de Vries (KdV) equation. At the critical hot dusty plasma density Nh0, the KdV equation is not appropriate for describing the system. Hence, a set of stretched coordinates is considered to derive the modified KdV equation. It is found that the presence of hot and cold dust charge grains not only significantly modifies the basic properties of solitary structure, but also changes the polarity of the solitary profiles. In the vicinity of the critical hot dusty plasma density Nh0, neither KdV nor mKdV equation is appropriate for describing the DAWs. Therefore, a further modified KdV (fmKdV) equation is derived, which admits both soliton and double layer solutions.

Dust, Climate, and Human Health

NASA Technical Reports Server (NTRS)

Maynard, Nancy G.

2003-01-01

Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. Ths paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health.

Dust, Climate, and Human Health

NASA Technical Reports Server (NTRS)

Maynard, Nancy G.

2003-01-01

Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. This paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health.

Dust, Climate, and Human Health

NASA Astrophysics Data System (ADS)

Maynard, N. G.

2003-12-01

Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. This paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health

An electrified dust storm over the Negev desert, Israel

NASA Astrophysics Data System (ADS)

Yair, Y.; Price, C. G.; Yaniv, R.; Katz, S.

2015-12-01

We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30035'N, 34045'E) during a massive dust storm that occurred over the Eastern Mediterranean region on 10-11 February 2015. The event transported Saharan dust from Egypt and the Sinai Peninsula in advance of the warm front of a Cyprus low pressure system. Satellite images show the dust plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m-3 and AOT from the AERONET station in Sde-Boker was 1.5 on the 10th. The gradual intensification of the event reached peak values on February 11th of over 1200 μg m-3 and AOT of 1.8. This was the most severe dust event in a decade. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the dust was advected over the observation site, we noted very large fluctuations in the electrical parameters. Since the onset of the dust storm, the Ez values changed between +1000 and +8000 V m-1 while the Jz fluctuated between -10 pA m2 and +20 pA m2, both on time-scales of a few minutes. These values are a significant departures from the mean fair-weather values measured at the site, which are -~200 V m-1 and ~2 pA m2. The disturbed episodes lasted for several hours on the 10th and 11th and coincided with local meteorological conditions related to the wind direction, which carried large amounts of dust particles. We interpret the rapid changes as caused by the transport of electrically charged dust. Calculation of the total electrical charge during the dust storm will be presented.

Dust on Mars: An Aeolian Threat to Human Exploration?

NASA Technical Reports Server (NTRS)

Marshall, J.

1999-01-01

The NASA HEDS Program is duly concerned for human explorers regarding the potential hazard posed by the ubiquitous dust mantle on Mars. To evaluate properties of dust that could be hazardous to humans, the NMS 2001 Lander payload will include the Mars Environmental Compatibility Assessment (MECA) experiment. This includes optical and atomic-force microscopy to evaluate soil grains for shape and size, wet chemistry to evaluate toxic substances, electrometry to evaluate triboelectric charging, and test-material palets to evaluate electrostatic and magnetic adhesion, and the hardness/abrasiveness of soil grains; these experimental subcomponents are delivered samples by the camera-equipped robotic arm of the lander which will acquire material from depths of 0.5 to 1.0 m in the soil. Data returned by MECA will be of value to both the hEDS and planetary/astrobiology communities. Dust poses a threat to human exploration because the martian system does not hydrologically or chemically remove fine particles that are being continuously generated by thermal, aeolian, and colluvial weathering, and by volcanism and impact over billions of years. The dust is extremely fine-grained, in copious quantities, ubiquitous in distribution, continually mobile, and a source of poorly-grounded static charges -- a suite of characteristics posing a particulate and electrical threat to explorers and their equipment. Dust is mobilized on global and regional scales, but probably also unpredictably and violently at local scales by dust devils. The latter might be expected in great abundance owing to near surface atmospheric instability (dust devils were detected by Pathfinder during its brief lifetime). Preliminary laboratory experiments suggest that space-suit materials subjected to windblown dust may acquire a uniform, highly adhesive dust layer that is also highly cohesive laterally owing to electrostatic forces. This layer will obscure visibility through the helmet visor, penetrate joints

Dust on Mars: An Aeolian Threat to Human Exploration?

NASA Technical Reports Server (NTRS)

Marshall, J.

1999-01-01

The NASA HEDS Program is duly concerned for human explorers regarding the potential hazard posed by the ubiquitous dust mantle on Mars. To evaluate properties of dust that could be hazardous to humans, the MPS 2001 Lander payload will include the Mars Environmental Compatibility Assessment (MECA) experiment. This includes optical and atomic-force microscopy to evaluate soil grains for shape and size, wet chemistry to evaluate toxic substances, electrometry to evaluate triboelectric charging, and test-material palets to evaluate electrostatic and magnetic adhesion, and the hardness/abrasiveness of soil grains; these experimental subcomponents are delivered samples by the camera-equipped robotic arm of the lander which will acquire material from depths of 0.5 to 1.0 m in the soil. Data returned by MECA will be of value to both the BEDS and planetary/astrobiology communities. Dust poses a threat to human exploration because the martian system does not hydrologically or chemically remove fine particles that are being continuously generated by thermal, aeolian, and colluvial weathering, and by volcanism and impact over billions of years. The dust is extremely fine-grained, in copious quantities, ubiquitous in distribution, continually mobile, and a source of poorly-grounded static charges -- a suite of characteristics posing a particulate and electrical threat to explorers and their equipment. Dust is mobilized on global and regional scales, but probably also unpredictably and violently at local scales by dust devils. The latter might be expected in great abundance owing to near surface atmospheric instability (dust devils were detected by Pathfinder during its brief lifetime). Preliminary laboratory experiments suggest that space-suit materials subjected to windblown dust may acquire a uniform, highly adhesive dust layer that is also highly cohesive laterally owing to electrostatic forces. This layer will obscure visibility through the helmet visor, penetrate joints

Reducing Demand Charges and Onsite Generation Variability Using Behind-the-Meter Energy Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattarai, Bishnu P.; Myers, Kurt S.; Bush, Jason W.

Electric utilities in the United States are increasingly employing demand charges and/or real-time pricing. This directive is bringing potential opportunities in deploying behindthe-meter energy storage (BMES) systems for various grid functionalities. This study quantifies techno-economic benefits of BMES in reducing demand charge and smoothing load/generation intermittencies, and determines how those benefits vary with onsite distributed photovoltaic. We proposed a two-stage control algorithm, whereby the first stage proactively determines costoptimal BMES configuration for reducing peak-demands and demand charges, and the second stage adaptively compensates intermittent generations and short load spikes that may otherwise increase the demand charges. The performance of themore » proposed algorithm is evaluated through a 24 hours time sweep simulation performed using data from smart microgrid testbed at Idaho National Laboratory (INL). The simulation results demonstrated that this research provides a simple but effective solution for peak shaving, demand charge reductions, and smoothing onsite PV variability.« less

Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, Kathleen E.; Goebel, J. H.; Price, Stephan D.

2003-09-01

A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 μm dust feature. These correlated features include dust features at 19.8 and 28.1 μm and the bands produced by warm carbon dioxide molecules (the strongest of which are at 13.9, 15.0, and 16.2 μm). The database does not provide any evidence for a correlation of the 13 μm feature with a dust feature at 32 μm, and it is more likely that a weak emission feature at 16.8 μm arises from carbon dioxide gas rather than dust. The correlated dust features at 13, 20, and 28 μm tend to be stronger with respect to the total dust emission in semiregular and irregular variables associated with the asymptotic giant branch than in Mira variables or supergiants. This family of dust features also tends to be stronger in systems with lower infrared excesses and thus lower mass-loss rates. We hypothesize that the dust features arise from crystalline forms of alumina (13 μm) and silicates (20 and 28 μm). Based on observations with the ISO, a European Space Agency (ESA) project with instruments funded by ESA member states (especially the Principal Investigator countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of the Institute of Space and Astronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA).

Flue Dust Agglomeration in the Secondary Lead Industry

NASA Astrophysics Data System (ADS)

Schwitzgebel, Klaus

1981-01-01

A secondary lead smelter produces several tons of bag-house dust a day. Appropriate handling of this dust is mandatory to meet the proposed OSHA and EPA workroom and ambient standards. Dust agglomeration proved a successful approach. Dusts with a high concentration of PbCl2, or compounds containing PbCl2 can be agglomerated at much lower temperatures than samples with low PbCl2 concentrations. The chlorine sources are polyvinyl chloride (PVC) battery plate separators. Since PVC is used in Europe to a much greater extent than in the U.S., the composition of feedstock must be considered in equipment selection at U.S. secondary smelters. The vapor pressure characteristics of PbCl2 favor its evaporation at blast furnace temperatures. Condensation occurs in the gas cooling system. Recycling of baghouse dust leads to a buildup of PbCl2 in the smelter. Its removal from the system is eventually necessary through leaching, if charges with a high PVC content are processed.

Defining an Abrasion Index for Lunar Surface Systems as a Function of Dust Interaction Modes and Variable Concentration Zones

NASA Technical Reports Server (NTRS)

Kobrick, Ryan L.; Klaus, David M.; Street, Kenneth W., Jr.

2010-01-01

Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental abrasion of materials upon exposure to the fine-grained, irregular shaped dust on the surface of the Moon. For critical design features involving contact with the lunar surface and for astronaut safety concerns, operational concepts and dust tolerance must be considered in the early phases of mission planning. To systematically define material selection criteria, dust interaction can be characterized by two-body or three-body abrasion testing, and subcategorically by physical interactions of compression, rolling, sliding and bending representing specific applications within the system. Two-body abrasion occurs when a single particle or asperity slides across a given surface removing or displacing material. Three-body abrasion occurs when multiple particles interact with a solid surface, or in between two surfaces, allowing the abrasives to freely rotate and interact with the material(s), leading to removal or displacement of mass. Different modes of interaction are described in this paper along with corresponding types of tests that can be utilized to evaluate each configuration. In addition to differential modes of abrasion, variable concentrations of dust in different zones can also be considered for a given system design and operational protocol. These zones include: (1) outside the habitat where extensive dust exposure occurs, (2) in a transitional zone such as an airlock or suitport, and (3) inside the habitat or spacesuit with a low particle count. These zones can be used to help define dust interaction frequencies, and corresponding risks to the systems and/or crew can be addressed by appropriate mitigation strategies. An abrasion index is introduced that includes the level of risk, R, the hardness of the mineralogy, H, the severity of the abrasion mode, S, and the frequency of particle interactions, F.

Phthalate concentrations in house dust in relation to autism spectrum disorder and developmental delay in the CHildhood Autism Risks from Genetics and the Environment (CHARGE) study.

PubMed

Philippat, Claire; Bennett, Deborah H; Krakowiak, Paula; Rose, Melissa; Hwang, Hyun-Min; Hertz-Picciotto, Irva

2015-06-26

Phthalates are endocrine-disrupting chemicals that influence thyroid hormones and sex steroids, both critical for brain development. We studied phthalate concentrations in house dust in relation to the risks of developing autism spectrum disorder (ASD) or developmental delay (DD). Participants were a subset of children from the CHARGE (CHildhood Autism Risks from Genetics and the Environment) case-control study. ASD and DD cases were identified through the California Department of Developmental Services system or referrals; general population controls were randomly sampled from state birth files and frequency-matched on age, sex, and broad geographic region to ASD cases. All children (50 ASD, 27 DD, 68 typically developing (TD)) were assessed with Mullen Scales of Early Learning, Vineland Adaptive Behavior Scales (VABS) and Aberrant Behavior Checklist. We measured 5 phthalates in dust collected in the child's home using a high volume small surface sampler. None of the phthalates measured in dust was associated with ASD. After adjustment, we observed greater di(2-ethylhexyl) phthalate (DEHP) and butylbenzyl phthalate (BBzP) concentrations in indoor dust from homes of DD children: Odds ratios (OR) were 2.10 (95% confidence interval (CI); 1.10; 4.09) and 1.40 (95% CI; 0.97; 2.04) for a one-unit increase in the ln-transformed DEHP and BBzP concentrations, respectively. Among TD children, VABS communication, daily living, and adaptive composite standard scores were lower, in association with increased diethyl phthalate (DEP) concentrations in dust. Participants with higher dibutyl phthalate (DBP) concentrations in house dust also trended toward reduced performance on these subscales. Among ASD and DD boys, higher indoor dust concentrations of DEP and DBP were associated with greater hyperactivity-impulsivity and inattention. House dust levels of phthalates were not associated with ASD. The inability to distinguish past from recent exposures in house dust and the fact

Hypervelocity Dust Impacts in Space and the Laboratory

NASA Astrophysics Data System (ADS)

Horanyi, Mihaly; Colorado CenterLunar Dust; Atmospheric Studies (CCLDAS) Team

2013-10-01

Interplanetary dust particles continually bombard all objects in the solar system, leading to the excavation of material from the target surfaces, the production of secondary ejecta particles, plasma, neutral gas, and electromagnetic radiation. These processes are of interest to basic plasma science, planetary and space physics, and engineering to protect humans and instruments against impact damages. The Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) has recently completed a 3 MV dust accelerator, and this talk will summarize our initial science results. The 3 MV Pelletron contains a dust source, feeding positively charged micron and sub-micron sized particles into the accelerator. We will present the technical details of the facility and its capabilities, as well as the results of our initial experiments for damage assessment of optical devices, and penetration studies of thin films. We will also report on the completion of our dust impact detector, the Lunar Dust Experiment (LDEX), is expected to be flying onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission by the time of this presentation. LDEX was tested, and calibrated at our dust accelerator. We will close by offering the opportunity to use this facility by the planetary, space and plasma physics communities.

The Spatial and Seasonal Variability in Fine Mineral Dust and Coarse Mass Concentrations at Remote Sites across the United States

NASA Astrophysics Data System (ADS)

Hand, J. L.; White, W. H.; Hyslop, N. P.; Schichtel, B. A.; Gill, T. E.

2016-12-01

Mineral dust influences air quality, visibility, health, hydrology, heterogeneous chemistry, biogeochemistry, ecology, and climate. The spatial and seasonal variability of fine (PM2.5) mineral dust (FD, mineral particles with diameters less than 2.5 µm) and coarse mass (CM, mass of particles with diameters between 2.5 and 10 µm) were characterized at over 160 rural and remote sites in the United States from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. Monthly, seasonal, and annual means were computed for 2011 through 2014 to investigate the spatial and seasonal variability of FD and CM. Regions with significant FD included the Southwest in spring (≥ 50% contributions to PM2.5 mass) and in the Midwest, Midsouth, and Southeast regions in summer (20-30% of PM2.5 mass). The seasonality of FD and CM decoupled farther from local source regions suggesting long-range transport of FD or non-dust related CM. FD mineralogy was also explored and confirmed the seasonal and regional impacts of long-range transport. Temporal trends in FD from 2000-2014 revealed regions and seasons with significantly increased FD, especially the Southwest during spring months, the central United States during summer and fall, and the Southeast in summer—all regions that were associated with significant contributions of FD to PM2.5 mass. Positive trends in FD contrast negative trends in other major aerosol species over the same time periods, further enhancing the relative importance of FD to PM2.5 mass. Increased levels of FD have important implications for its environmental and climate impacts; mitigating these impacts will require identifying and characterizing source regions and causal mechanisms for dust episodes in order to better inform resource management decisions.

The effect of radiation pressure on spatial distribution of dust inside H II regions

NASA Astrophysics Data System (ADS)

Ishiki, Shohei; Okamoto, Takashi; Inoue, Akio K.

2018-02-01

We investigate the impact of radiation pressure on spatial dust distribution inside H II regions using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. In order to investigate grain-size effects as well, we introduce two additional fluid components describing large and small dust grains in the simulations. Relative velocity between dust and gas strongly depends on the drag force. We include collisional drag force and coulomb drag force. We find that, in a compact H II region, a dust cavity region is formed by radiation pressure. Resulting dust cavity sizes (˜0.2 pc) agree with observational estimates reasonably well. Since dust inside an H II region is strongly charged, relative velocity between dust and gas is mainly determined by the coulomb drag force. Strength of the coulomb drag force is about 2 order of magnitude larger than that of the collisional drag force. In addition, in a cloud of mass 105 M⊙, we find that the radiation pressure changes the grain-size distribution inside H II regions. Since large (0.1 μm) dust grains are accelerated more efficiently than small (0.01 μm) grains, the large-to-small grain mass ratio becomes smaller by an order of magnitude compared with the initial one. Resulting dust-size distributions depend on the luminosity of the radiation source. The large and small grain segregation becomes weaker when we assume stronger radiation source, since dust grain charges become larger under stronger radiation and hence coulomb drag force becomes stronger.

Electrical Characteristics of Simulated Tornadoes and Dust Devils

NASA Technical Reports Server (NTRS)

Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.

2012-01-01

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado.

Remote sensing of mesospheric dust layers using active modulation of PMWE by high-power radio-waves

NASA Astrophysics Data System (ADS)

Cohen, M.; Zhang, X.; Cohen, M.; Mahmoudian, A.; Scales, W.; Kosch, M. J.; M Farahani, M.; Mohebalhojeh, A.

2016-12-01

So-called polar mesospheric winter echoes (PMWE) are radar echoes observed during winter at altitudes around 50-80 km and are much weaker than their PMSE (Polar Mesospheric Summer Echoes) counterpart. Unlike PMSE, PMWE are less studied and understood. Breaking of gravity waves and the associated turbulence are proposed as the major source for PMWE echoes. The action of neutral turbulence alone does not appear to give a good explanation for PMWE. PMWE is also attributed to Bragg scatter from electron irregularities which result from charging of free electrons onto sub-visible particles. The temporal behavior of PMWE response to HF pump heating can be employed to diagnose the charged dust layer. Specifically, the rise and fall time of radar echo strength as well as relaxation and recovery time after heater turn-on and off are distinct parameters that are a function of radar frequency. This work presents the first study of the modulation of PMWE by artificial radiowave heating using computational modeling and experimental observation in different radar frequency bands. Variation of dust plasma parameters associated with PMWE such as dust radius, dust density, recombination rate, electron- and dust-neutral collision frequencies, photo-detachment current and electron temperature enhancement ratio are included. Computational results derived from different sets of parameters are considered and compared with recent observations at EISCAT using 224 MHz and 56 MHz radars. The agreement between the model results and the observations show the high potential of remote sensing of dust and plasma parameters associated with PMWE. Measurement of Te/Ti using ISR and simultaneous observations in two frequency bands may lead to a more accurate estimation of dust density and radius. The enhancement of backscattered signal in the HF band during PMWE heating is predicted for the first time. The required background dust-plasma parameters as well as heater power (Te/Ti) for the observation

Dust Analyzer Instrument (DANTE) for the detection and elemental analysis of dust particles originating from the inner heliosphere

NASA Astrophysics Data System (ADS)

Sternovsky, Z.; O'brien, L.; Gruen, E.; Horanyi, M.; Malaspina, D.; Moebius, E.; Rocha, J. R. R.

2016-12-01

Nano- to sub-micron-size dust particles generated by the collisional breakup of interplanetary dust particles (IDPs) in the inner solar system can be accelerated away from the Sun and are available for detection and analysis near 1 AU. Beta-meteoroids are sub-micron sized particles for which the radiation pressure dominates over gravity and have already been detected by dedicated dust instrument. Charged nano-sized dust particles are picked up by the expanding solar wind and arrive to 1 AU with high velocity. The recent observations by the WAVE instrument on the two STEREO spacecraft indicated that these particles may exist in large numbers. The Dust Analyzer Instrument (DANTE) is specifically developed to detect and analyze these two populations of dust particles arriving from a direction close to the Sun. DANTE is a linear time-of-flight (ToF) mass spectrometer analyzing the ions generated by the dust impact on a target surface. DANTE is derived from the Cosmic Dust Analyzer instrument operating on Cassini. DANTE has a 300 cm2 target area and a mass resolution of approximately m/dm = 50. The instrument performance has been verified using the dust accelerator facility operating at the University of Colorado. A light trap system, consisting of optical baffles, is designed and optimized in terms of geometry and surface optical properties. A solar wind ion repeller system is included to prevent solar wind from entering the sensor. Both measures facilitate the detection with the instrument pointing close to the Sun's direction. The DANTE measurements will help to understand the sources, sinks and distribution of dust between the Sun and 1 AU, and, when combined with solar wind ion analyzer instrument, they will provide insight on the suspected link between dust particles and pickup ions, and how the massive particles affect the dynamics and energetics of the solar wind.

Investigation of dust transport on the lunar surface in laboratory plasmas

NASA Astrophysics Data System (ADS)

Wang, X.; Horanyi, M.; Robertson, S. H.

2009-12-01

There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. To learn about the basic physical process, we investigated the dynamics of dust grains on a conducting surface in laboratory plasmas. The first experiment was conducted with a dust pile (JSC-Mars-1) sitting on a negatively biased surface in plasma. The dust pile spread and formed a diffusing dust ring. Dust hopping was confirmed by noticing grains on protruding surfaces. The electrostatic potential distributions measured above the dust pile show an outward pointing electrostatic force and a non-monotonic sheath above the dust pile, indicating a localized upward electrostatic force responsible for lifting dust off the surface. The second experiment was conducted with a dust pile sitting on an electrically floating conducting surface in plasma with an electron beam. Potential measurements show a horizontal electric field at the dust/surface boundary and an enhanced vertical electric field in the sheath above the dust pile when the electron beam current is set to be comparable to the Bohm ion current. Secondary electrons emitted from the surfaces play an important role in this case.

Modelling of Lunar Dust and Electrical Field for Future Lunar Surface Measurements

NASA Astrophysics Data System (ADS)

Lin, Yunlong

Modelling of the lunar dust and electrical field is important to future human and robotic activities on the surface of the moon. Apollo astronauts had witnessed the maintaining of micron- and millimeter sized moon dust up to meters level while walked on the surface of the moon. The characterizations of the moon dust would enhance not only the scientific understanding of the history of the moon but also the future technology development for the surface operations on the moon. It has been proposed that the maintaining and/or settlement of the small-sized dry dust are related to the size and weight of the dust particles, the level of the surface electrical fields on the moon, and the impaction and interaction between lunar regolith and the solar particles. The moon dust distributions and settlements obviously affected the safety of long term operations of future lunar facilities. For the modelling of the lunar dust and the electrical field, we analyzed the imaging of the legs of the moon lander, the cover and the footwear of the space suits, and the envelope of the lunar mobiles, and estimated the size and charges associated with the small moon dust particles, the gravity and charging effects to them along with the lunar surface environment. We also did numerical simulation of the surface electrical fields due to the impaction of the solar winds in several conditions. The results showed that the maintaining of meters height of the micron size of moon dust is well related to the electrical field and the solar angle variations, as expected. These results could be verified and validated through future on site and/or remote sensing measurements and observations of the moon dust and the surface electrical field.

Hypervelocity Dust Injection for Plasma Diagnostic Applications

NASA Astrophysics Data System (ADS)

Ticos, Catalin

2005-10-01

Hypervelocity micron-size dust grain injection was proposed for high-temperature magnetized plasma diagnosis. Multiple dust grains are launched simultaneously into high temperature plasmas at several km/s or more. The hypervelocity dust grains are ablated by the electron and ion fluxes. Fast imaging of the resulting luminous plumes attached to each grain is expected to yield local magnetic field vectors. Combination of multiple local magnetic field vectors reproduces 2D or even 3D maps of the internal magnetic field topology. Key features of HDI are: (1) a high spatial resolution, due to a relatively small transverse size of the elongated tail, and (2) a small perturbation level, as the dust grains introduce negligible number of particles compared to the plasma particle inventory. The latter advantage, however, could be seriously compromised if the gas load from the accelerator has an unobstructed access to the diagnosed plasma. Construction of a HDI diagnostic for National Spherical Torus Experiment (NSTX), which includes a coaxial plasma gun for dust grain acceleration, is underway. Hydrogen and deuterium gas discharges inside accelerator are created by a ˜ 1 mF capacitor bank pre-charged up to 10 kV. The diagnostic apparatus also comprises a dust dispenser for pre-loading the accelerator with dust grains, and an imaging system that has a high spatial and temporal resolution.

Determinants of wood dust exposure in the Danish furniture industry.

PubMed

Mikkelsen, Anders B; Schlunssen, Vivi; Sigsgaard, Torben; Schaumburg, Inger

2002-11-01

This paper investigates the relation between wood dust exposure in the furniture industry and occupational hygiene variables. During the winter 1997-98 54 factories were visited and 2362 personal, passive inhalable dust samples were obtained; the geometric mean was 0.95 mg/m(3) and the geometric standard deviation was 2.08. In a first measuring round 1685 dust concentrations were obtained. For some of the workers repeated measurements were carried out 1 (351) and 2 weeks (326) after the first measurement. Hygiene variables like job, exhaust ventilation, cleaning procedures, etc., were documented. A multivariate analysis based on mixed effects models was used with hygiene variables being fixed effects and worker, machine, department and factory being random effects. A modified stepwise strategy of model making was adopted taking into account the hierarchically structured variables and making possible the exclusion of non-influential random as well as fixed effects. For woodworking, the following determinants of exposure increase the dust concentration: manual and automatic sanding and use of compressed air with fully automatic and semi-automatic machines and for cleaning of work pieces. Decreased dust exposure resulted from the use of compressed air with manual machines, working at fully automatic or semi-automatic machines, functioning exhaust ventilation, work on the night shift, daily cleaning of rooms, cleaning of work pieces with a brush, vacuum cleaning of machines, supplementary fresh air intake and safety representative elected within the last 2 yr. For handling and assembling, increased exposure results from work at automatic machines and presence of wood dust on the workpieces. Work on the evening shift, supplementary fresh air intake, work in a chair factory and special cleaning staff produced decreased exposure to wood dust. The implications of the results for the prevention of wood dust exposure are discussed.

3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies.

PubMed

Shu, Anthony; Collette, Andrew; Drake, Keith; Grün, Eberhard; Horányi, Mihály; Kempf, Sascha; Mocker, Anna; Munsat, Tobin; Northway, Paige; Srama, Ralf; Sternovsky, Zoltán; Thomas, Evan

2012-07-01

A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10(-7) torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10(-10) torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

Cloud Ozone Dust Imager (CODI)

NASA Astrophysics Data System (ADS)

Clancy, R. Todd; Dusenbery, Paul; Wolff, Michael; James, Phil; Allen, Mark; Goguen, Jay; Kahn, Ralph; Gladstone, Rany; Murphy, Jim

1995-01-01

The Cloud Ozone Dust Imager (CODI) is proposed to investigate the current climatic balance of the Mars atmosphere, with particular emphasis on the important but poorly understood roles which dust and water ice aerosols play in this balance. The large atmospheric heating (20-50 K) resulting from global dust storms around Mars perihelion is well recognized. However, groundbased observations of Mars atmospheric temperatures, water vapor, and clouds since the Viking missions have identified a much colder, cloudier atmosphere around Mars aphelion that may prove as important as global dust storms in determining the interannual and long-term behavior of the Mars climate. The key climate issues CODI is designed to investigate are: 1) the degree to which non-linear interactions between atmospheric dust heating, water vapor saturation, and cloud nucleation influence the seasonal and interannual variability of the Mars atmosphere, and 2) whether the strong orbital forcing of atmospheric dust loading, temperatures and water vapor saturation determines the long-term balance of Mars water, as reflected in the north-south hemispheric asymmetries of atmospheric water vapor and polar water ice abundances. The CODI experiment will measure the daily, seasonal and (potentially) interannual variability of atmospheric dust and cloud opacities, and the key physical properties of these aerosols which determine their role in the climate cycles of Mars. CODI is a small (1.2 kg), fixed pointing camera, in which four wide-angle (+/- 70 deg) lenses illuminate fixed filters and CCD arrays. Simultaneous sky/surface imaging of Mars is obtained at an angular resolution of 0.28 deg/pixel for wavelengths of 255, 336, 502, and 673 nm (similar to Hubble Space Telescope filters). These wavelengths serve to measure atmospheric ozone (255 and 336 nm), discriminate ice and dust aerosols (336 and 673 nm), and construct color images (336, 502, and 673 nm). The CODI images are detected on four 512 x 512

Improving dust emission characterization in dust models using dynamic high-resolution geomorphic erodibility map

NASA Astrophysics Data System (ADS)

Parajuli, S. P.; Yang, Z.; Kocurek, G.

2013-12-01

Dust is known to affect the earth radiation budget, biogeochemical cycle, precipitation, human health and visibility. Despite the increased research effort, dust emission modeling remains challenging because dust emission is affected by complex geomorphological processes. Existing dust models overestimate dust emission and rely on tuning and a static erodibility factor in order to make simulated results comparable to remote sensing and ground-based observations. In most of current models, dust emission is expressed in terms of threshold friction speed, which ultimately depends mainly upon the percentage clay content and soil moisture. Unfortunately, due to the unavailability of accurate and high resolution input data of the clay content and soil moisture, estimated threshold friction speed commonly does not represent the variability in field condition. In this work, we attempt to improve dust emission characterization by developing a high resolution geomorphic map of the Middle East and North Africa (MENA), which is responsible for more than 50% of global dust emission. We develop this geomorphic map by visually examining high resolution satellite images obtained from Google Earth Pro and ESRI base map. Albeit subjective, our technique is more reliable compared to automatic image classification technique because we incorporate knowledge of geological/geographical setting in identifying dust sources. We hypothesize that the erodibility is unique for different geomorphic landforms and that it can be quantified by the correlation between observed wind speed and satellite retrieved aerosol optical depth (AOD). We classify the study area into several key geomorphological categories with respect to their dust emission potential. Then we quantify their dust emission potential using the correlation between observed wind speed and satellite retrieved AOD. The dynamic, high-resolution geomorphic erodibility map thus prepared will help to reduce the uncertainty in current

Comet Gas and Dust Dynamics Modeling

NASA Technical Reports Server (NTRS)

Von Allmen, Paul A.; Lee, Seungwon

2010-01-01

This software models the gas and dust dynamics of comet coma (the head region of a comet) in order to support the Microwave Instrument for Rosetta Orbiter (MIRO) project. MIRO will study the evolution of the comet 67P/Churyumov-Gerasimenko's coma system. The instrument will measure surface temperature, gas-production rates and relative abundances, and velocity and excitation temperatures of each species along with their spatial temporal variability. This software will use these measurements to improve the understanding of coma dynamics. The modeling tool solves the equation of motion of a dust particle, the energy balance equation of the dust particle, the continuity equation for the dust and gas flow, and the dust and gas mixture energy equation. By solving these equations numerically, the software calculates the temperature and velocity of gas and dust as a function of time for a given initial gas and dust production rate, and a dust characteristic parameter that measures the ability of a dust particle to adjust its velocity to the local gas velocity. The software is written in a modular manner, thereby allowing the addition of more dynamics equations as needed. All of the numerical algorithms are added in-house and no third-party libraries are used.

Solar Spectral Radiative Forcing Due to Dust Aerosol During the Puerto Rico Dust Experiment

NASA Technical Reports Server (NTRS)

Pilewskie, P.; Bergstrom, R.; Rabbette, M.; Livingston, J.; Russell, P.; Gore, Warren J. (Technical Monitor)

2000-01-01

During the Puerto Rico Dust Experiment (PRIDE) upwelling and downwelling solar spectral irradiance was measured on board the SPAWAR Navajo and downwelling solar spectral flux was measured at a surface site using the NASA Ames Solar Spectral Flux Radiometer. These data will be used to determine the net solar radiative forcing of dust aerosol and to quantify the solar spectral radiative energy budget in the presence of elevated aerosol loading. We will assess the variability in spectral irradiance using formal principal component analysis procedures and relate the radiative variability to aerosol microphysical properties. Finally, we will characterize the sea surface reflectance to improve aerosol optical depth retrievals from the AVHRR satellite and to validate SeaWiFS ocean color products.

Dust Acoustic Solitary Waves in Dusty Plasma with Trapped Electrons Having Different Temperature Nonthermal Ions

NASA Astrophysics Data System (ADS)

Deka, Manoj Kr.

2016-12-01

In this report, a detailed investigation on the study of dust acoustics solitary waves solution with negatively dust charge fluctuation in dusty plasma corresponding to lower and higher temperature nonthermal ions with trapped electrons is presented. We consider temporal variation of dust charge as a source of dissipation term to derive the lower order modified Kadomtsev-Petviashvili equation by using the reductive perturbation technique. Solitary wave solution is obtained with the help of sech method in presence of trapped electrons and low (and high) temperature nonthermal ions. Both nonthermality of ions and trapped state of the electrons are found to have an imperative control on the nonlinear coefficient, dissipative coefficient as well as height of the wave potential.

Identification of Dust Source Regions at High-Resolution and Dynamics of Dust Source Mask over Southwest United States Using Remote Sensing Data

NASA Astrophysics Data System (ADS)

Sprigg, W. A.; Sahoo, S.; Prasad, A. K.; Venkatesh, A. S.; Vukovic, A.; Nickovic, S.

2015-12-01

Identification and evaluation of sources of aeolian mineral dust is a critical task in the simulation of dust. Recently, time series of space based multi-sensor satellite images have been used to identify and monitor changes in the land surface characteristics. Modeling of windblown dust requires precise delineation of mineral dust source and its strength that varies over a region as well as seasonal and inter-annual variability due to changes in land use and land cover. Southwest USA is one of the major dust emission prone zone in North American continent where dust is generated from low lying dried-up areas with bare ground surface and they may be scattered or appear as point sources on high resolution satellite images. In the current research, various satellite derived variables have been integrated to produce a high-resolution dust source mask, at grid size of 250 m, using data such as digital elevation model, surface reflectance, vegetation cover, land cover class, and surface wetness. Previous dust source models have been adopted to produce a multi-parameter dust source mask using data from satellites such as Terra (Moderate Resolution Imaging Spectroradiometer - MODIS), and Landsat. The dust source mask model captures the topographically low regions with bare soil surface, dried-up river plains, and lakes which form important source of dust in southwest USA. The study region is also one of the hottest regions of USA where surface dryness, land use (agricultural use), and vegetation cover changes significantly leading to major changes in the areal coverage of potential dust source regions. A dynamic high resolution dust source mask have been produced to address intra-annual change in the aerial extent of bare dry surfaces. Time series of satellite derived data have been used to create dynamic dust source masks. A new dust source mask at 16 day interval allows enhanced detection of potential dust source regions that can be employed in the dust emission and

The role of water content in triboelectric charging of wind-blown sand.

PubMed

Gu, Zhaolin; Wei, Wei; Su, Junwei; Yu, Chuck Wah

2013-01-01

Triboelectric charging is common in desert sandstorms and dust devils on Earth; however, it remains poorly understood. Here we show a charging mechanism of sands with the adsorbed water on micro-porous surface in wind-blown sand based on the fact that water content is universal but usually a minor component in most particle systems. The triboelectric charging could be resulted due to the different mobility of H(+)/OH(-) between the contacting sands with a temperature difference. Computational fluid dynamics (CFD) and discrete element method (DEM) were used to demonstrate the dynamics of the sand charging. The numerically simulated charge-to-mass ratios of sands and electric field strength established in wind tunnel agreed well with the experimental data. The charging mechanism could provide an explanation for the charging process of all identical granular systems with water content, including Martian dust devils, wind-blown snow, even powder electrification in industrial processes.

SPARCLE: Electrostatic Dust Control Tool Proof of Concept

NASA Technical Reports Server (NTRS)

Clark, P. E.; Curtis, S. A.; Minetto, F.; Marshall, J.; Nuth, J.; Calle, C.

2010-01-01

Successful exploration of most planetary surfaces, with their impact-generated dusty regoliths, will depend on the capabilities to keep surfaces free of the performance-compromising dust. Once in contact with surfaces, whether set in motion by natural or mechanical means, regolith fines, or dust, behave like abrasive Velcro, coating surfaces, clogging mechanisms, making movement progressively more difticult, and being almost impossible to remove by mechanical mcans (brushing). The successful dust removal strategy will deal with dust dynamics resulting from interaction between Van der Waals and Coulombic forces. Here, proof of concept for an electrostatically-based concept for dust control tool is described and demonstrated. A low power focused electron beam is used in the presence of a small electrical field to increase the negative charge to mass ratio of a dusty surface until dust repulsion and attraction to a lower potential surface, acting as a dust collector, occurred. Our goal is a compact device of less than 5 kg mass and using less than 5 watts of power to be operational in less than 5 years with heritage from ionic sweepers for active spacecraft potential control (e.g ., on POLAR). Rovers could be fitted with devices that could hamess the removal of dust for sampling as part of the extended exploration process on Mercury, Mars, asteroids or outer solar system satellites, as well as the Moon.

Secondary emission from dust grains: Comparison of experimental and model results

NASA Astrophysics Data System (ADS)

Richterova, I.; Pavlu, J.; Nemecek, Z.; Safrankova, J.; Zilavy, P.

The motion, coalescence, and other processes in dust clouds are determined by the dust charge. Since dust grains in the space are bombarded by energetic electrons, the secondary emission is an important process contributing to their charge. It is generally expected that the secondary emission yield is related to surface properties of the bombarded body. However, it is well known that secondary emission from small bodies is determined not only by their composition but an effect of dimension can be very important when the penetration depth of primary electrons is comparable with the grain size. It implies that the secondary emission yield can be influenced by the substrate material if the surface layer is thin enough. We have developed a simple Monte Carlo model of secondary emission that was successfully applied on the dust simulants from glass and melanine formaldehyd (MF) resin and matched very well experimental results. In order to check the influence of surface layers, we have modified the model for spheres covered by a layer with different material properties. The results of model simulations are compared with measurements on MF spheres covered by different metals.

Photoelectric Emission Measurements on the Analogs of Individual Cosmic Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.; Weingartner, J. C.; Tielens, A. G. G. M.; Nuth, J. a.; Camata, R. P.

2006-01-01

The photoelectric emission process is considered to be the dominant mechanism for charging of cosmic dust grains in many astrophysical environments. The grain charge and equilibrium potentials play an important role in the dynamical and physical processes that include heating of the neutral gas in the interstellar medium, coagulation processes in the dust clouds, and levitation and dynamical processes in the interplanetary medium and planetary surfaces and rings. An accurate evaluation of photoelectric emission processes requires knowledge of the photoelectric yields of individual dust grains of astrophysical composition as opposed to the values obtained from measurements on flat surfaces of bulk materials, as it is generally assumed on theoretical considerations that the yields for the small grains are much different from the bulk values. We present laboratory measurements of the photoelectric yields of individual dust grains of silica, olivine, and graphite of approx. 0.09-5 micrometer radii levitated in an electrodynamic balance and illuminated with ultraviolet radiation at 120-160 nm wavelengths. The measured yields are found to be substantially higher than the bulk values given in the literature and indicate a size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains.

Phototelectric Emission Measurements on the Analogs of Individual Cosmic Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, Mian M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.; Weingartner, J. C.; Tielens, A. G. G. M.; Nuth, J. A.; Camata, R. P.;

Variability of Disk Emission in Pre-Main Sequence and Related Stars. II. Variability in the Gas and Dust Emission of the Herbig Fe Star SAO 206462

NASA Technical Reports Server (NTRS)

Sitko, Michael L.; Day, Amanda N.; Kimes, Robin L.; Beerman, Lori C.; Martus, Cameron; Lynch, David K.; Russell, Ray W.; Grady, Carol A.; Schneider, Glenn; Lisse, Carey M.;

VARIABILITY OF DISK EMISSION IN PRE-MAIN SEQUENCE AND RELATED STARS. II. VARIABILITY IN THE GAS AND DUST EMISSION OF THE HERBIG Fe STAR SAO 206462

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sitko, Michael L.; Day, Amanda N.; Kimes, Robin L.

2012-01-20

We present 13 epochs of near-infrared (0.8-5 {mu}m) spectroscopic observations of the pre-transitional, 'gapped' disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (Br{alpha}, Br{gamma}, Pa{beta}, Pa{gamma}, Pa{delta}, Pa{epsilon}, and the 0.8446 {mu}m line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 Multiplication-Sign 10{sup -8} M{sub Sun} yr{sup -1} was derived from the Br{gamma} and Pa{beta} lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months.more » The continuum also varied, but by only {approx}30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 {mu}m was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on timescales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magnetorotational) would operate there on longer timescales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on timescales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer timescales that have been sampled so far.« less

Dust particle radial confinement in a dc glow discharge.

PubMed

Sukhinin, G I; Fedoseev, A V; Antipov, S N; Petrov, O F; Fortov, V E

2013-01-01

A self-consistent nonlocal model of the positive column of a dc glow discharge with dust particles is presented. Radial distributions of plasma parameters and the dust component in an axially homogeneous glow discharge are considered. The model is based on the solution of a nonlocal Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particle density in a dust cloud was fixed as a given steplike function or was chosen according to an equilibrium Boltzmann distribution. The balance of electron and ion production in argon ionization by an electron impact and their losses on the dust particle surface and on the discharge tube walls is taken into account. The interrelation of discharge plasma and the dust cloud is studied in a self-consistent way, and the radial distributions of the discharge plasma and dust particle parameters are obtained. It is shown that the influence of the dust cloud on the discharge plasma has a nonlocal behavior, e.g., density and charge distributions in the dust cloud substantially depend on the plasma parameters outside the dust cloud. As a result of a self-consistent evolution of plasma parameters to equilibrium steady-state conditions, ionization and recombination rates become equal to each other, electron and ion radial fluxes become equal to zero, and the radial component of electric field is expelled from the dust cloud.

The flow of a dust particle by highly collisional drifting plasma

NASA Astrophysics Data System (ADS)

Grach, Veronika; Semenov, Vladimir; Trakhtengerts, Victor

We present the study of the flow of a dust particle by a weakly ionized highly collisional drifting plasma. The charging of a conductive sphere and wake formation downstream and upstream of it is analyzed in the case of a strong external field l0 = E0 /(4πen0 ) λD a (E0 is the magnitude of the external field, n0 is plasma density, λD is Debye length and a is a radius of the sphere). Under such conditions, the effects of the space charge field and ionization-recombination processes play crucial role. The sphere charge and the spatial distributions of plasma ions and electrons are calculated nu-merically; analytical expressions are obtained for some limiting cases. We obtain that the size of the wake is determined by the external field and the recombination rate. At low recombination rates (α/(4πµ+,- ) 1, where α is the recombination coefficient, µ+,- are mobilities of positive and negative plasma particles) the longitudinal scale of wake is about 20l0 , at high recombina-tion rates the longitudinal scale is about l0 . The transverse scale of the wake is determined by the ratio of the mobilities and can reach several dust particle radii. It was also shown that the absolute value of the dust particle charge decreases with increasing recombination rate. The total electric charge (the sphere charge plus the plasma space charge) is shown to be zero in accordance with predictions of the theory of static currents in a conducting medium. On the basis of the obtained spatial distributions of charged plasma particles, the electrostatic potential around the sphere is calculated numerically. The interaction potential between two systems "particle+wake" is analyzed for arbitrary locations of such systems. We obtain that the potential can be attractive at moderate and large distances, if the particles are not aligned in the direction perpendicular to the external electric field. The results can be important in understanding intergrain interactions in weakly ionized highly

Lighthouse in the dust: infrared echoes of periodic emission from massive black hole binaries★

NASA Astrophysics Data System (ADS)

D'Orazio, Daniel J.; Haiman, Zoltán

2017-09-01

The optical and UV emission from sub-parsec massive black hole binaries (MBHBs) in active galactic nuclei (AGNs) is believed to vary periodically, on time-scales comparable to the binary's orbital time. If driven by accretion rate fluctuations, the variability could be isotropic. If dominated by relativistic Doppler modulation, the variability should instead be anisotropic, resembling a rotating forward-beamed lighthouse. We consider the infrared (IR) reverberation of either type of periodic emission by pc-scale circumbinary dust tori. We predict the phase and amplitude of IR variability as a function of the ratio of dust light crossing time to the source variability period, and of the torus inclination and opening angle. We enumerate several differences between the isotropic and anisotropic cases. Interestingly, for a nearly face-on binary with an inclined dust torus, the Doppler boost can produce IR variability without any observable optical/UV variability. Such orphan-IR variability would have been missed in optical searches for periodic AGNs. We apply our models to time-domain WISE IR data from the MBHB candidate PG 1302-102 and find consistency with dust reverberation by both isotropically emitting and Doppler-boosted sources in the shorter wavelength W1-W2 (2.8 → 5.3 μm) bands. We constrain the dust torus to be thin (aspect ratio ˜ 0.1), with an inner radius at 1-5 pc. More generally, our dust-echo models will aid in identifying new MBHB candidates, determining their nature and constraining the physical properties of MBHBs and their dust tori.

Observation of dust acoustic shock wave in a strongly coupled dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sumita K., E-mail: sumita-sharma82@yahoo.com; Boruah, A.; Nakamura, Y.

2016-05-15

Dust acoustic shock wave is observed in a strongly coupled laboratory dusty plasma. A supersonic flow of charged microparticles is allowed to perturb a stationary dust fluid to excite dust acoustic shock wave. The evolution process beginning with steepening of initial wave front and then formation of a stable shock structure is similar to the numerical results of the Korteweg-de Vries-Burgers equation. The measured Mach number of the observed shock wave agrees with the theoretical results. Reduction of shock amplitude at large distances is also observed due to the dust neutral collision and viscosity effects. The dispersion relation and themore » spatial damping of a linear dust acoustic wave are also measured and compared with the relevant theory.« less

Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

2012-01-01

The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

The role of water content in triboelectric charging of wind-blown sand

PubMed Central

Gu, Zhaolin; Wei, Wei; Su, Junwei; Yu, Chuck Wah

2013-01-01

Triboelectric charging is common in desert sandstorms and dust devils on Earth; however, it remains poorly understood. Here we show a charging mechanism of sands with the adsorbed water on micro-porous surface in wind-blown sand based on the fact that water content is universal but usually a minor component in most particle systems. The triboelectric charging could be resulted due to the different mobility of H+/OH− between the contacting sands with a temperature difference. Computational fluid dynamics (CFD) and discrete element method (DEM) were used to demonstrate the dynamics of the sand charging. The numerically simulated charge-to-mass ratios of sands and electric field strength established in wind tunnel agreed well with the experimental data. The charging mechanism could provide an explanation for the charging process of all identical granular systems with water content, including Martian dust devils, wind-blown snow, even powder electrification in industrial processes. PMID:23434920

An electrified dust storm over the Negev desert, Israel

NASA Astrophysics Data System (ADS)

Yair, Yoav; Katz, Shai; Yaniv, Roy; Ziv, Baruch; Price, Colin

2016-11-01

We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30°35‧N, 34°45‧E) during a large dust storm that occurred over the Eastern Mediterranean region on 10-11 February 2015. The dust was transported from the Sahara, Egypt and the Sinai Peninsula ahead of an approaching Cyprus low. Satellite images show the dust plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m- 3 and the AOT from the AERONET station in Sde-Boker was 1.5 on February 10th. The gradual intensification of the event reached peak concentrations on February 11th of over 1200 μg m- 3 and an AOT of 1.8. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted at the Wise Observatory with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the dust was advected over the observatory, very large fluctuations in the electrical parameters were registered. From the onset of the dust storm, the Ez values changed between + 1000 and + 8000 V m- 1 while the current density fluctuated between - 10 pA m2 and + 20 pA m2, both on time-scales of a few minutes. These values are significant departures from the average fair-weather values measured at the site, which are ~- 200 V m- 1 and ~ 2 pA m2. The disturbed episodes lasted for several hours on February 10th and the 11th and coincided with local meteorological conditions related to the wind speed and direction, which carried large amounts of dust particles over our observation station. We interpret the rapid changes as caused by the transport of electrically charged dust, carrying an excess of negative charge at lower altitudes.

Cassini RPWS Measurement of Dust Particles in Saturn's Magnetosphere

NASA Astrophysics Data System (ADS)

Ye, S.; Gurnett, D. A.; Kurth, W. S.; Averkamp, T. F.; Kempf, S.; Hsu, S.; Sakai, S.; Morooka, M.; Wahlund, J.

2013-12-01

The Cassini Radio and Plasma Wave Science (RPWS) instrument can detect dust impacts when voltage pulses induced by the impact charges are observed in the wideband receiver. The size of the voltage pulse is proportional to the mass of the impacting dust particle. Based on the data collected during the E-ring crossings and Enceladus flybys, we show that the size distribution of the dust particles can be characterized as dn/dr ∝ rμ, where μ~-4. We compare the density of dust particles above a certain size threshold calculated from the impact rate with the Cosmic Dust Analyzer (CDA) High Rate Detector (HRD) data. When the monopole antenna is connected to the wideband receiver, the polarity of the dust impact signal is determined by the spacecraft potential and the location of the impact (on the spacecraft body or the antenna). Because the effective area of the antenna is relatively easy to estimate, we use the polarity ratio of the dust impacts to infer the effective area of the spacecraft body. RPWS onboard dust detection data is analyzed, from which we infer the sign of the spacecraft potential and the dust density within Saturn's magnetosphere. A new phenomenon called dust ringing has been found to reveal the electron density inside the Enceladus plume. The ringing frequencies, interpreted as the local plasma frequencies, are consistent with the values measured by other methods, i.e., Langmuir probe and upper hybrid resonance.

The effects of dust on Colorado mountain snow cover albedo and compositional links to dust-source areas

NASA Astrophysics Data System (ADS)

Goldstein, H. L.; Reynolds, R. L.; Landry, C.; Derry, J. E.; Kokaly, R. F.; Breit, G. N.

2016-12-01

Dust deposited on mountain snow cover (DOS) changes snow albedo, enhances absorption of solar radiation, and effectively increases rates of snow melt, leading to earlier-than-normal runoff and overall smaller late-season water supplies for tens of millions of people and industries in the American West. Visible-spectrum reflectance of DOS samples is on the order of 0.2 (80% absorption), in stark contrast to the high reflectivity of pure snow which approaches 1.0. Samples of DOS were collected from 12 high-elevation Colorado mountain sites near the end of spring from 2013 through 2016 prior to complete snow melt, when most dust layers had merged into one layer. These samples were analyzed to measure dust properties that affect snow albedo and to link DOS to dust-source areas. Dust mass loadings to snow during water year 2014 varied from 5 to 30 g/m2. Median particle sizes centered around 20 micrometers with more than 80% of the dust <63 micrometers. Dark minerals, carbonaceous matter, and iron oxides, including nano-sized hematite and goethite, together diminished reflectance according to their variable concentrations. Documenting variations in dust-particle masses, sizes, and compositions helps determine their influences on snow-melt and may be useful for modeling snow-melt effects from future dust. Furthermore, variations in dust components and particle sizes lead to new ways to recognize sources of dust by comparison with properties of fine-grained sediments in dust-source areas. Much of the DOS in the San Juan Mountains, Colorado can be linked to southern Colorado Plateau source areas by compositional similarities and satellite imagery. Understanding dust properties that affect snow albedo and recognizing the sources of dust deposited on snow cover may guide mitigation of dust emission that affects water resources of the Colorado River basin.

Satellite Monitoring of Asian Dust Storms from SeaWiFS and MODIS: Source, Pathway, and Interannual Variability

NASA Astrophysics Data System (ADS)

Hsu, N.; Tsay, S.; Jeong, M.; Holben, B.

2006-12-01

MODIS-like instruments. The multiyear satellite measurements since 1998 from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with these dust outbreaks in East Asia. The monthly av-eraged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

Satellite Monitoring of Asian Dust Storms from SeaWiFS and MODIS: Source, pathway and Interannual Variability

NASA Technical Reports Server (NTRS)

Hsu, N. Christina

2007-01-01

-like instruments. The multiyear satellite measurements since 1998 from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with these dust outbreaks in East Asia. The monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

Satellite Monitoring of Asian Dust Storms from SeaWiFS and MODIS: Source, Pathway, and Interannual Variability

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Tsay, S.-C.; Bettenhausen, C.; Salustro, C.; Jeong, M. J.

2010-01-01

-like instruments. The multiyear satellite measurements since 1998 from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with these dust outbreaks in East Asia. The monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

Satellite Monitoring of Asian Dust Storms from SeaWiFS and MODIS: Source, Pathway, and Interannual Variability

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Tsay, S.-C.; Bettenhausen, C.; Sayer, A.

2011-01-01

MODISlike instruments. The multiyear satellite measurements since 1998 from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with these dust outbreaks in East Asia. The monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

Dust Around Herbig Ae Stars: Additional Constraints from their Photometric and Polarimetric Variability

NASA Technical Reports Server (NTRS)

Krivova, N. A.; Ilin, V. B.; Fischer, O.

1996-01-01

For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul, etc), the effects of circumstellar dust include: excess infrared emission, anomalous ultraviolet extinction, the 'blueing' of the stars in minima accompanying by an increase of intrinsic polarization. Using a Monte-Carlo code for polarized radiation transfer we have simulated these effects and compared the results obtained for different models with the observational data available. We found that the photometric and polarimetric behavior of the stars provided essential additional constraints on the circumstellar dust models. The models with spheroidal shell geometry and compact (non-fluffy) dust grains do not appear to be able to explain all the data.

Laboratory investigation of dust impacts on antennas in space

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Malaspina, D.; Gruen, E.; Drake, K.

2013-10-01

Recent observations of sharp voltage spikes by the WAVES electric field experiments onboard the twin STEREO spacecraft have been attributed to plasma clouds generated by the impact ionization of high velocity dust particles. The reported dust fluxes are much higher than those measured by dedicated dust detectors at 1 AU, which leads to the interpretation that the STEREO observations are due to nanometer-sized dust particles originating from the inner solar system and accelerated to high velocities by the solar wind magnetic field. However, this interpretation is based on a simplified model of coupling between the expanding plasma cloud from the dust impact and the WAVES electric field instrument. A series of laboratory measurements are performed to validate this model and to calibrate/investigate the effect of various impact parameters on the signals measured by the electric field instrument. The dust accelerator facility operating at the University of Colorado is used for the measurement with micron and submicron sized particles accelerated to 50 km/s. The first set of measurements is performed to calibrate the impact charge generated from materials specific the STEREO spacecraft and will help to interpret electric field data.

Identification of dust source regions and dust emission trends across North Africa and the Middle East using MISR satellite observations

NASA Astrophysics Data System (ADS)

Yu, Y.; Kalashnikova, O. V.; Garay, M. J.; Notaro, M.

2017-12-01

Global arid and semi-arid regions supply 1100 to 5000 Tg of Aeolian dust to the atmosphere each year, primarily from North Africa and secondarily from the Middle East. Previous dust source identification methods, based on either remotely-sensed aerosol optical depth (AOD) or dust activity, yield distinct dust source maps, largely due to the limitations in each method and remote-sensing product. Here we apply a novel motion-based method for dust source identification. Dust plume thickness and motion vectors from Multi-angle Imaging SpectroRadiometer (MISR) Cloud Motion Vector Product (CMVP) are examined to identify the regions with high frequency of fast moving-dust plumes, by season. According to MISR CMVP, Bodele depression is the most important dust source across North Africa, consistent with previous studies. Seasonal variability of dust emission across the North Africa is largely driven by climatology of wind and precipitation, featuring the influence of Sharav Cyclone and western African monsoon. In the Middle East, Iraq, Kuwait, and eastern Saudi Arabia are identified as dust source regions, especially during summer months, when the Middle Eastern Shamal wind is active. Furthermore, dust emission trend at each dust source are diagnosed from the motion-based dust source dataset. Increase in dust emission from the Fertile Crescent, Sahel, and eastern African dust sources are identified from MISR CMVP, implying potential contribution from these dust sources to the upward trend in AOD and dust AOD over the Middle East in the 21st century. By comparing with various dust source identification studies, we conclude that the motion-based identification of dust sources is an encouraging alternative and compliment to the AOD-only source identification method.

Global scale variability of the mineral dust longwave refractive index from laboratory chamber experiments: re‒evaluation of its direct radiative effect

NASA Astrophysics Data System (ADS)

Di Biagio, C.; Formenti, P.; Balkanski, Y.; Caponi, L.; Cazaunau, M.; Pangui, E.; Journet, E.; Nowak, S.; Caquineau, S.; Andreae, M. O.; Kandler, K.; Saeed, T.; Piketh, S.; Seibert, D.; Williams, E.; Boucher, O.; Doussin, J. F.

2017-12-01

New measurements of the longwave complex refractive index (LW CRI) of mineral dust and its global variability were obtained in situ in the 4.2 m3CESAM simulation chamber at LISA (Laboratoire Interuniversitaire des Systemes Atmospheriques) in Créteil, France. Aerosols generated by mechanical shaking from nineteen natural soils with contrasted mineralogical composition were suspended in the chamber, where their LW extinction spectra (2-16 μm), size distribution, and mineralogical composition were measured. The CRI of the dust aerosol was obtained by optical calculations based upon the measured extinction spectrum and size distribution. Laboratory results indicate that the LW refractive index of dust strongly varies with the source region of emission in link with the changes of its mineralogy. In the 2-16 μm spectral range, the imaginary refractive index (k) is between 0.001 and 0.92, and the real part (n) in the range 0.84-1.94. The strength of the dust absorption at 7 and 11.4 µm depends on the amount of calcite within the samples, while the absorption between 8 and 14 µm is determined by the relative abundance of quartz and clays. A linear relationship between the magnitude of k at 7, 9.2, and 11.4 µm and the mass concentration of calcite and quartz absorbing at these wavelengths was found, which suggests that predictive rules could be established to estimate the LW refractive index of dust in specific bands based on an assumed or predicted mineralogical composition. Our observations also suggest that the LW CRI of dust does not change as a result of the loss of coarse particles by gravitational settling, so that a constant value can be assumed close to sources and following transport. This unprecedented dataset of refractive indices was used as input into the LMDZORINCA model coupled with the RRTM radiative transfer module in order to re‒evaluate the direct dust LW radiative effect. This represents a first attempt to use regional‒dependent values of the

Is dust acoustic wave a new plasma acoustic mode?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwivedi, C.B.

1997-09-01

In this Brief Communication, the claim of the novelty of the dust acoustic wave in a dusty plasma within the constant dust charge model is questioned. Conceptual lacunas behind the claim have been highlighted and appropriate physical arguments have been forwarded against the claim. It is demonstrated that the so-called dust acoustic wave could better be termed as a general acoustic fluctuation response with a dominant characteristic feature of the acoustic-like mode (ALM) fluctuation response reported by Dwivedi {ital et al.} [J. Plasma Phys. {bold 41}, 219 (1989)]. It is suggested that both correct and more usable nomenclature of themore » ALM should be the so-called acoustic mode. {copyright} {ital 1997 American Institute of Physics.}« less

ELECTROSTATIC BARRIER AGAINST DUST GROWTH IN PROTOPLANETARY DISKS. II. MEASURING THE SIZE OF THE 'FROZEN' ZONE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okuzumi, Satoshi; Sakagami, Masa-aki; Tanaka, Hidekazu

2011-04-20

Coagulation of submicron-sized dust grains into porous aggregates is the initial step of dust evolution in protoplanetary disks. Recently, it has been pointed out that negative charging of dust in the weakly ionized disks could significantly slow down the coagulation process. In this paper, we apply the growth criteria obtained in Paper I to finding out a location ('frozen' zone) where the charging stalls dust growth at the fractal growth stage. For low-turbulence disks, we find that the frozen zone can cover a major part of the disks at a few to 100 AU from the central star. The maximummore » mass of the aggregates is approximately 10{sup -7}g at 1 AU and as small as a few monomer masses at 100 AU. Strong turbulence can significantly reduce the size of the frozen zone, but such turbulence will cause the fragmentation of macroscopic aggregates at later stages. We examine a possibility that complete freezeout of dust evolution in low-turbulence disks could be prevented by global transport of dust in the disks. Our simple estimation shows that global dust transport can lead to the supply of macroscopic aggregates and the removal of frozen aggregates on a timescale of 10{sup 6} yr. This overturns the usual understanding that tiny dust particles get depleted on much shorter timescales unless collisional fragmentation is effective. The frozen zone together with global dust transport might explain 'slow' ({approx}10{sup 6} yr) dust evolution suggested by infrared observation of T Tauri stars and by radioactive dating of chondrites.« less

Perturbed soliton excitations of Rao-dust Alfvén waves in magnetized dusty plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kavitha, L., E-mail: louiskavitha@yahoo.co.in; The Abdus Salam International Centre for Theoretical Physics, Trieste; Lavanya, C.

We investigate the propagation dynamics of the perturbed soliton excitations in a three component fully ionized dusty magnetoplasma consisting of electrons, ions, and heavy charged dust particulates. We derive the governing equation of motion for the two dimensional Rao-dust magnetohydrodynamic (R-D-MHD) wave by employing the inertialess electron equation of motion, inertial ion equation of motion, the continuity equations in a plasma with immobile charged dust grains, together with the Maxwell's equations, by assuming quasi neutrality and neglecting the displacement current in Ampere's law. Furthermore, we assume the massive dust particles are practically immobile since we are interested in timescales muchmore » shorter than the dusty plasma period, thereby neglecting any damping of the modes due to the grain charge fluctuations. We invoke the reductive perturbation method to represent the governing dynamics by a perturbed cubic nonlinear Schrödinger (pCNLS) equation. We solve the pCNLS, along the lines of Kodama-Ablowitz multiple scale nonlinear perturbation technique and explored the R-D-MHD waves as solitary wave excitations in a magnetized dusty plasma. Since Alfvén waves play an important role in energy transport in driving field-aligned currents, particle acceleration and heating, solar flares, and the solar wind, this representation of R-D-MHD waves as soliton excitations may have extensive applications to study the lower part of the earth's ionosphere.« less

Dust acoustic solitary and shock excitations in a Thomas-Fermi magnetoplasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahim, Z.; Qamar, A.; National Center for Physics

The linear and nonlinear properties of dust-acoustic waves are investigated in a collisionless Thomas-Fermi magnetoplasma, whose constituents are electrons, ions, and negatively charged dust particles. At dust time scale, the electron and ion number densities follow the Thomas-Fermi distribution, whereas the dust component is described by the classical fluid equations. A linear dispersion relation is analyzed to show that the wave frequencies associated with the upper and lower modes are enhanced with the variation of dust concentration. The effect of the latter is seen more strongly on the upper mode as compared to the lower mode. For nonlinear analysis, wemore » obtain magnetized Korteweg-de Vries (KdV) and Zakharov-Kuznetsov (ZK) equations involving the dust-acoustic solitary waves in the framework of reductive perturbation technique. Furthermore, the shock wave excitations are also studied by allowing dissipation effects in the model, leading to the Korteweg-de Vries-Burgers (KdVB) and ZKB equations. The analysis reveals that the dust-acoustic solitary and shock excitations in a Thomas-Fermi plasma are strongly influenced by the plasma parameters, e.g., dust concentration, dust temperature, obliqueness, magnetic field strength, and dust fluid viscosity. The present results should be important for understanding the solitary and shock excitations in the environments of white dwarfs or supernova, where dust particles can exist.« less

Dust environment of an airless object: A phase space study with kinetic models

NASA Astrophysics Data System (ADS)

Kallio, E.; Dyadechkin, S.; Fatemi, S.; Holmström, M.; Futaana, Y.; Wurz, P.; Fernandes, V. A.; Álvarez, F.; Heilimo, J.; Jarvinen, R.; Schmidt, W.; Harri, A.-M.; Barabash, S.; Mäkelä, J.; Porjo, N.; Alho, M.

2016-01-01

The study of dust above the lunar surface is important for both science and technology. Dust particles are electrically charged due to impact of the solar radiation and the solar wind plasma and, therefore, they affect the plasma above the lunar surface. Dust is also a health hazard for crewed missions because micron and sub-micron sized dust particles can be toxic and harmful to the human body. Dust also causes malfunctions in mechanical devices and is therefore a risk for spacecraft and instruments on the lunar surface. Properties of dust particles above the lunar surface are not fully known. However, it can be stated that their large surface area to volume ratio due to their irregular shape, broken chemical bonds on the surface of each dust particle, together with the reduced lunar environment cause the dust particles to be chemically very reactive. One critical unknown factor is the electric field and the electric potential near the lunar surface. We have developed a modelling suite, Dusty Plasma Environments: near-surface characterisation and Modelling (DPEM), to study globally and locally dust environments of the Moon and other airless bodies. The DPEM model combines three independent kinetic models: (1) a 3D hybrid model, where ions are modelled as particles and electrons are modelled as a charged neutralising fluid, (2) a 2D electrostatic Particle-in-Cell (PIC) model where both ions and electrons are treated as particles, and (3) a 3D Monte Carlo (MC) model where dust particles are modelled as test particles. The three models are linked to each other unidirectionally; the hybrid model provides upstream plasma parameters to be used as boundary conditions for the PIC model which generates the surface potential for the MC model. We have used the DPEM model to study properties of dust particles injected from the surface of airless objects such as the Moon, the Martian moon Phobos and the asteroid RQ36. We have performed a (v0, m/q)-phase space study where the

Coagulation of dust grains in the plasma of an RF discharge in argon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mankelevich, Yu. A.; Olevanov, M. A.; Pal', A. F.

2009-03-15

Results are presented from experimental studies of coagulation of dust grains of different sizes injected into a low-temperature plasma of an RF discharge in argon. A theoretical model describing the formation of dust clusters in a low-temperature plasma is developed and applied to interpret the results of experiments on the coagulation of dust grains having large negative charges. The grain size at which coagulation under the given plasma conditions is possible is estimated using the developed theory. The theoretical results are compared with the experimental data.

Relativistic dust accretion of charged particles in Kerr-Newman spacetime

NASA Astrophysics Data System (ADS)

Schroven, Kris; Hackmann, Eva; Lämmerzahl, Claus

2017-09-01

We describe a new analytical model for the accretion of particles from a rotating and charged spherical shell of dilute collisionless plasma onto a rotating and charged black hole. By assuming a continuous injection of particles at the spherical shell and by treating the black hole and a featureless accretion disk located in the equatorial plane as passive sinks of particles, we build a stationary accretion model. This may then serve as a toy model for plasma feeding an accretion disk around a charged and rotating black hole. Therefore, our new model is a direct generalization of the analytical accretion model introduced by E. Tejeda, P. A. Taylor, and J. C. Miller [Mon. Not. R. Astron. Soc. 429, 925 (2013), 10.1093/mnras/sts316]. We use our generalized model to analyze the influence of a net charge of the black hole, which will in general be very small, on the accretion of plasma. Within the assumptions of our model we demonstrate that already a vanishingly small charge of the black hole may in general still have a non-negligible effect on the motion of the plasma, as long as the electromagnetic field of the plasma is still negligible. Furthermore, we argue that the inner and outer edges of the forming accretion disk strongly depend on the charge of the accreted plasma. The resulting possible configurations of accretion disks are analyzed in detail.

A new approach developed to study variability in North African dust transport routes over the Atlantic during 2001-2015

NASA Astrophysics Data System (ADS)

Meng, L.; Gao, H. W.; Yu, Y.; Yao, X. H.; Gao, Y.; Zhang, C.; Fan, Lei

2017-10-01

We investigated the variability in the North African dust transport routes over the Atlantic (NAD routes) by extracting the dust transport central axis using Moderate Resolution Imaging Spectroradiometer aerosol data for 2001-2015. The results showed that the NAD routes can be classified into two regimes, a southern route centered at the southernmost position of 6.08 ± 1.12°N during November to March and a northern route centered at the northernmost position of 18.21 ± 1.04°N during April to October. In the southern route, large intervariation was correlated with the Intertropical Convergence Zone (ITCZ) and North Atlantic Oscillation (NAO), but the ITCZ and NAO jointly explained only 38% of the variation. In the northern route, the ITCZ alone explained 67% of the intervariation. The extracted trends during 2001-2015 exhibited a northward shift of 1.68° for the southern route and of 0.52° for the northern route. The causes for the shift were also examined.

Charge control experiments on a CH-53E helicopter in a dusty environment

NASA Technical Reports Server (NTRS)

Moore, C. B.; Jones, J. J.; Hunyady, S. J.

1991-01-01

Charge control tests were carried out on a ground based, Marine Corps helicopter to determine if control of the electric fields acting on the engine exhaust gases could be used to reduce the electrification of the helicopter when it operated in a dusty atmosphere. The test aircraft was flown to a dusty, unpaved area and was then isolated electrically from the earth. When the helicopter engines were operated at ground idle with the rotor locked, the isolated aircraft charged positively, as had been observed previously. However, when the rotor brake was released and the turning rotor created a downdraft that raised dust clouds, the aircraft always became charged more positively, to potentials ranging form +30 to +45 kV. The dust clouds raised by the rotor downwash invariably carried negative space charges with concentrations of up to -100 nC/cu m and caused surface electric fields with strengths of up to 10 kV/m immediately down wind of the aircraft. The natural charging of the helicopter operating in these dust clouds was successfully opposed by control of the electric fields acting on the hot, electrically conductive exhaust gases. The control was achieved by placing electrostatic shield around the exhausts.

Large-Eddy Simulations of Dust Devils and Convective Vortices

NASA Astrophysics Data System (ADS)

Spiga, Aymeric; Barth, Erika; Gu, Zhaolin; Hoffmann, Fabian; Ito, Junshi; Jemmett-Smith, Bradley; Klose, Martina; Nishizawa, Seiya; Raasch, Siegfried; Rafkin, Scot; Takemi, Tetsuya; Tyler, Daniel; Wei, Wei

2016-11-01

In this review, we address the use of numerical computations called Large-Eddy Simulations (LES) to study dust devils, and the more general class of atmospheric phenomena they belong to (convective vortices). We describe the main elements of the LES methodology. We review the properties, statistics, and variability of dust devils and convective vortices resolved by LES in both terrestrial and Martian environments. The current challenges faced by modelers using LES for dust devils are also discussed in detail.

Calibration of impact ionization cosmic dust detectors: first tests to investigate how the dust density influences the signal

NASA Astrophysics Data System (ADS)

Jasmin Sterken, Veerle; Moragas-Klostermeyer, Georg; Hillier, Jon; Fielding, Lee; Lovett, Joseph; Armes, Steven; Fechler, Nina; Srama, Ralf; Bugiel, Sebastian; Hornung, Klaus

2016-10-01

Impact ionization experiments have been performed since more than 40 years for calibrating cosmic dust detectors. A linear Van de Graaff dust accelerator was used to accelerate the cosmic dust analogues of submicron to micron-size to speeds up to 80 km s^-1. Different materials have been used for calibration: iron, carbon, metal-coated minerals and most recently, minerals coated with conductive polymers. While different materials with different densities have been used for instrument calibration, a comparative analysis of dust impacts of equal material but different density is necessary: porous or aggregate-like particles are increasingly found to be present in the solar system: e.g. dust from comet 67P Churyumov-Gerasimenko [Fulle et al 2015], aggregate particles from the plumes of Enceladus [Gao et al 2016], and low-density interstellar dust [Westphal 2014 et al, Sterken et al 2015]. These recalibrations are relevant for measuring the size distributions of interplanetary and interstellar dust and thus mass budgets like the gas-to-dust mass ratio in the local interstellar cloud.We report about the calibrations that have been performed at the Heidelberg dust accelerator facility for investigating the influence of particle density on the impact ionization charge. We used the Cassini Cosmic Dust Analyzer for the target, and compared hollow versus compact silica particles in our study as a first attempt to investigate experimentally the influence of dust density on the signals obtained. Also, preliminary tests with carbon aerogel were performed, and (unsuccessful) attempts to accelerate silica aerogel. In this talk we explain the motivation of the study, the experiment set-up, the preparation of — and the materials used, the results and plans and recommendations for future tests.Fulle, M. et al 2015, The Astrophysical Journal Letters, Volume 802, Issue 1, article id. L12, 5 pp. (2015)Gao, P. et al 2016, Icarus, Volume 264, p. 227-238Westphal, A. et al 2014, Science

The Enigma of Lunar Dust Transport

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Stubbs, T. J.; Vondrak, R. R.; Delory, G. T.; Halekas, J. S.

2011-01-01

We will review the highly contrasting points of view regarding the ability of fine dust grains to become transported in the near-space lunar environment. While Surveyor and Apollo camera images suggest the presence of a horizon glow that has been provocatively interpreted as levitated and/or lofted dust, there is contrasting geological evidence to indicate that surface regolith has not been moved in a substantial way. While electric forces have been suggested as a driver for grain dynamics, recent detailed modeling of near-surface non-monotonic potentials would suggest grains could not get to large heights. While lofting models require submicron grains to hold/contain 100's of elementary charges, it can be shown analytical1y that a grain residing on a flat surface would have an extremely low probability of having even a single electron on its surface, Can these diametrically opposing viewpoints be reconciled? We will review the pros and cons on both sides. and suggest that the UVS and LDEX instrument on LADEE will provide key new insights on dust transport at the Moon.

Summary of the results from the Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment (LADEE) Mission

NASA Astrophysics Data System (ADS)

Horanyi, Mihaly

2016-07-01

The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission (9/2013 - 4/2014) discovered a permanently present dust cloud engulfing the Moon. The size, velocity, and density distributions of the dust particles are consistent with ejecta clouds generated from the continual bombardment of the lunar surface by sporadic interplanetary dust particles. Intermittent density enhancements were observed during several of the annual meteoroid streams, especially during the Geminids. LDEX found no evidence of the expected density enhancements over the terminators where electrostatic processes were predicted to efficiently loft small grains. LDEX is an impact ionization dust detector, it captures coincident signals and full waveforms to reliably identify dust impacts. LDEX recorded average impact rates of approximately 1 and 0.1 hits/minute of particles with impact charges of q > 0.5 and q > 5 fC, corresponding to particles with radii of a > 0.3 and a> 0.7~μm, respectively. Several of the yearly meteor showers generated sustained elevated levels of impact rates, especially if their radiant direction intersected the lunar surface near the equatorial plane, greatly enhancing the probability of crossing their ejecta plumes. The characteristic velocities of dust particles in the cloud are on the order of ~100 m/s which we neglect compared to the typical spacecraft speeds of 1.6 km/s. Hence, with the knowledge of the spacecraft orbit and attitude, impact rates can be directly turned into particle densities as functions of time and position. LDEX observations are the first to identify the ejecta clouds around the Moon sustained by the continual bombardment of interplanetary dust particles. Most of the dust particles generated in impacts have insufficient energy to escape and follow ballistic orbits, returning to the surface, 'gardening' the regolith. Similar ejecta clouds are expected to engulf all airless planetary objects, including

Effects of dust polarity and nonextensive electrons on the dust-ion acoustic solitons and double layers in earth atmosphere

NASA Astrophysics Data System (ADS)

Ghobakhloo, Marzieh; Zomorrodian, Mohammad Ebrahim; Javidan, Kurosh

2018-05-01

Propagation of dustion acoustic solitary waves (DIASWs) and double layers is discussed in earth atmosphere, using the Sagdeev potential method. The best model for distribution function of electrons in earth atmosphere is found by fitting available data on different distribution functions. The nonextensive function with parameter q = 0.58 provides the best fit on observations. Thus we analyze the propagation of localized waves in an unmagnetized plasma containing nonextensive electrons, inertial ions, and negatively/positively charged stationary dust. It is found that both compressive and rarefactive solitons as well as double layers exist depending on the sign (and the value) of dust polarity. Characters of propagated waves are described using the presented model.

Temperature measurement of a dust particle in a RF plasma GEC reference cell

NASA Astrophysics Data System (ADS)

Kong, Jie; Qiao, Ke; Matthews, Lorin S.; Hyde, Truell W.

2016-10-01

The thermal motion of a dust particle levitated in a plasma chamber is similar to that described by Brownian motion in many ways. The primary difference between a dust particle in a plasma system and a free Brownian particle is that in addition to the random collisions between the dust particle and the neutral gas atoms, there are electric field fluctuations, dust charge fluctuations, and correlated motions from the unwanted continuous signals originating within the plasma system itself. This last contribution does not include random motion and is therefore separable from the random motion in a `normal' temperature measurement. In this paper, we discuss how to separate random and coherent motions of a dust particle confined in a glass box in a Gaseous Electronic Conference (GEC) radio-frequency (RF) reference cell employing experimentally determined dust particle fluctuation data analysed using the mean square displacement technique.

Global trends in visibility: Implications for dust sources

USGS Publications Warehouse

Mahowald, N.M.; Ballantine, J.A.; Feddema, J.; Ramankutty, N.

2007-01-01

There is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. We did this by looking at time series of visibility derived variables and their correlations with precipitation, drought, winds, land use and grazing. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 357 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility-derived variables and AERONET optical depths indicate a moderate correlation (0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility-derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the Palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not

Lunar and Planetary Science XXXV: Mars: Wind, Dust Sand, and Debris

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Mars: Wind, Dust Sand, and Debris" included: Mars Exploration Rovers: Laboratory Simulations of Aeolian Interactions; Thermal and Spectral Analysis of an Intracrater Dune Field in Amazonis Planitia; How High is that Dune? A Comparison of Methods Used to Constrain the Morphometry of Aeolian Bedforms on Mars; Dust Devils on Mars: Scaling of Dust Flux Based on Laboratory Simulations; A Close Encounter with a Terrestrial Dust Devil; Interpretation of Wind Direction from Eolian Features: Herschel Crater, Mars Erosion Rates at the Viking 2 Landing Site; Mars Dust: Characterization of Particle Size and Electrostatic Charge Distributions; Simple Non-fluvial Models of Planetary Surface Modification, with Application to Mars; Comparison of Geomorphically Determined Winds with a General Circulation Model: Herschel Crater, Mars; Analysis of Martian Debris Aprons in Eastern Hellas Using THEMIS; Origin of Martian Northern Hemisphere Mid-Latitude Lobate Debris Aprons; Debris Aprons in the Tempe/Mareotis Region of Mars;and Constraining Flow Dynamics of Mass Movements on Earth and Mars.

Nonlinear Dust Acoustic Waves in a Magnetized Dusty Plasma with Trapped and Superthermal Electrons

NASA Astrophysics Data System (ADS)

Ahmadi, Abrishami S.; Nouri, Kadijani M.

2014-06-01

In this work, the effects of superthermal and trapped electrons on the oblique propagation of nonlinear dust-acoustic waves in a magnetized dusty (complex) plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique (RPT) a nonlinear modified Korteweg-de Vries (mKdV) equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively (or positively) charged. The properties of dust acoustic solitons (DASs) are also investigated numerically.

Transverse Motion of a Particle with an Oscillating Charge and Variable Mass in a Magnetic Field

NASA Astrophysics Data System (ADS)

Alisultanov, Z. Z.; Ragimkhanov, G. B.

2018-03-01

The problem of motion of a particle with an oscillating electric charge and variable mass in an uniform magnetic field has been solved. Three laws of mass variation have been considered: linear growth, oscillations, and stepwise growth. Analytical expressions for the particle velocity at different time dependences of the particle mass are obtained. It is established that simultaneous consideration of changes in the mass and charge leads to a significant change in the particle trajectory.

Lunar Surface Charging during Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Halekas, Jasper S.; Delory, G. T.; Mewaldt, R. A.; Lin, R. P.; Fillingim, M. O.; Brain, D. A.; Lee, C. O.; Stubbs, T. J.; Farrell, W. M.; Hudson, M. K.

2006-09-01

The surface of the Moon, not protected by any substantial atmosphere, is directly exposed to the impact of both solar UV and solar wind plasma and energetic particles. This creates a complex lunar electrostatic environment, with the surface typically charging slightly positive in sunlight, and negative in shadow. Observations from the Apollo era and theoretical considerations strongly suggest that surface charging leads to dust electrification and transport, posing a potentially significant hazard for exploration. The most significant charging effects should occur when the Moon is exposed to high-temperature plasmas like those encountered in the terrestrial plasmasheet or in solar storms. We now present evidence for kilovolt-scale negative charging of the shadowed lunar surface during solar energetic particle (SEP) events, utilizing data from the Lunar Prospector Electron Reflectometer (LP ER). We find that SEP events are associated with the most extreme lunar surface charging observed during the LP mission - rivaled only by previously reported charging during traversals of the terrestrial plasmasheet. The largest charging event observed by LP is a 4 kV negative surface potential (as compared to typical values of V) during a SEP event in May 1998. We characterize lunar surface charging during several SEP events, and compare to energetic particle measurements from ACE, Wind, and SOHO in order to determine the relationship between SEP events and extreme lunar surface charging. Space weather events are already considered by NASA to be a significant hazard to lunar exploration, due to high-energy ionizing radiation. Our observations demonstrate that plasma interactions with the lunar surface during SEP events, causing extreme surface charging and potentially significant dust electrification and transport, represent an additional hazard associated with space weather.

Simulation of dust voids in complex plasmas

NASA Astrophysics Data System (ADS)

Goedheer, W. J.; Land, V.

2008-12-01

In dusty radio-frequency (RF) discharges under micro-gravity conditions often a void is observed, a dust free region in the discharge center. This void is generated by the drag of the positive ions pulled out of the discharge by the electric field. We have developed a hydrodynamic model for dusty RF discharges in argon to study the behaviour of the void and the interaction between the dust and the plasma background. The model is based on a recently developed theory for the ion drag force and the charging of the dust. With this model, we studied the plasma inside the void and obtained an understanding of the way it is sustained by heat generated in the surrounding dust cloud. When this heating mechanism is suppressed by lowering the RF power, the plasma density inside the void decreases, even below the level where the void collapses, as was recently shown in experiments on board the International Space Station. In this paper we present results of simulations of this collapse. At reduced power levels the collapsed central cloud behaves as an electronegative plasma with corresponding low time-averaged electric fields. This enables the creation of relatively homogeneous Yukawa balls, containing more than 100 000 particles. On earth, thermophoresis can be used to balance gravity and obtain similar dust distributions.

A new dust source map of Central Asia derived from MODIS Terra/Aqua data using dust enhancement techniques

NASA Astrophysics Data System (ADS)

Nobakht, Mohamad; Shahgedanova, Maria; White, Kevin

2017-04-01

Central Asian deserts are a significant source of dust in the middle latitudes, where economic activity and health of millions of people are affected by dust storms. Detailed knowledge of sources of dust, controls over their activity, seasonality and atmospheric pathways are of crucial importance but to date, these data are limited. This paper presents a detailed database of sources of dust emissions in Central Asia, from western China to the Caspian Sea, obtained from the analysis of the Moderate Resolution Imaging Spectroradiometer (MODIS) data between 2003 and 2012. A dust enhancement algorithm was employed to obtain two composite images per day at 1 km resolution from MODIS Terra/Aqua acquisitions, from which dust point sources (DPS) were detected by visual analysis and recorded in a database together with meteorological variables at each DPS location. Spatial analysis of DPS has revealed several active source regions, including some which were not widely discussed in literature before (e.g. Northern Afghanistan sources, Betpak-Dala region in western Kazakhstan). Investigation of land surface characteristics and meteorological conditions at each source region revealed mechanisms for the formation of dust sources, including post-fire wind erosion (e.g. Lake Balkhash basin) and rapid desertification (e.g. the Aral Sea). Different seasonal patterns of dust emissions were observed as well as inter-annual trends. The most notable feature was an increase in dust activity in the Aral Kum.

Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing

NASA Astrophysics Data System (ADS)

Di Biagio, Claudia; Formenti, Paola; Balkanski, Yves; Caponi, Lorenzo; Cazaunau, Mathieu; Pangui, Edouard; Journet, Emilie; Nowak, Sophie; Caquineau, Sandrine; Andreae, Meinrat O.; Kandler, Konrad; Saeed, Thuraya; Piketh, Stuart; Seibert, David; Williams, Earle; Doussin, Jean-François

2017-02-01

Modeling the interaction of dust with long-wave (LW) radiation is still a challenge because of the scarcity of information on the complex refractive index of dust from different source regions. In particular, little is known about the variability of the refractive index as a function of the dust mineralogical composition, which depends on the specific emission source, and its size distribution, which is modified during transport. As a consequence, to date, climate models and remote sensing retrievals generally use a spatially invariant and time-constant value for the dust LW refractive index. In this paper, the variability of the mineral dust LW refractive index as a function of its mineralogical composition and size distribution is explored by in situ measurements in a large smog chamber. Mineral dust aerosols were generated from 19 natural soils from 8 regions: northern Africa, the Sahel, eastern Africa and the Middle East, eastern Asia, North and South America, southern Africa, and Australia. Soil samples were selected from a total of 137 available samples in order to represent the diversity of sources from arid and semi-arid areas worldwide and to account for the heterogeneity of the soil composition at the global scale. Aerosol samples generated from soils were re-suspended in the chamber, where their LW extinction spectra (3-15 µm), size distribution, and mineralogical composition were measured. The generated aerosol exhibits a realistic size distribution and mineralogy, including both the sub- and super-micron fractions, and represents in typical atmospheric proportions the main LW-active minerals, such as clays, quartz, and calcite. The complex refractive index of the aerosol is obtained by an optical inversion based upon the measured extinction spectrum and size distribution. Results from the present study show that the imaginary LW refractive index (k) of dust varies greatly both in magnitude and spectral shape from sample to sample, reflecting the

Magnitude and Variability of Controllable Charge Capacity Provided by Grid Connected Plug-in Electric Vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scoffield, Don R; Smart, John; Salisbury, Shawn

2015-03-01

As market penetration of plug-in electric vehicles (PEV) increases over time, the number of PEVs charging on the electric grid will also increase. As the number of PEVs increases, their ability to collectively impact the grid increases. The idea of a large body of PEVs connected to the grid presents an intriguing possibility. If utilities can control PEV charging, it is possible that PEVs could act as a distributed resource to provide grid services. The technology required to control charging is available for modern PEVs. However, a system for wide-spread implementation of controllable charging, including robust communication between vehicles andmore » utilities, is not currently present. Therefore, the value of controllable charging must be assessed and weighed against the cost of building and operating such as system. In order to grasp the value of PEV charge control to the utility, the following must be understood: 1. The amount of controllable energy and power capacity available to the utility 2. The variability of the controllable capacity from day to day and as the number of PEVs in the market increases.« less

Dust Devil Tracks

NASA Astrophysics Data System (ADS)

Reiss, Dennis; Fenton, Lori; Neakrase, Lynn; Zimmerman, Michael; Statella, Thiago; Whelley, Patrick; Rossi, Angelo Pio; Balme, Matthew

2016-11-01

-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic

Highlights and discoveries of the Cosmic Dust Analyser (CDA) during its 15 years of exploration

NASA Astrophysics Data System (ADS)

Srama, R.; Moragas-Klostermeyer, G.; Kempf, S.; Postberg, F.; Albin, T.; Auer, S.; Altobelli, N.; Beckmann, U.; Bugiel, S.; Burton, M.; Economou, T.; Fliege, K.; Grande, M.; Gruen, E.; Guglielmino, M.; Hillier, J. K.; Schilling, A.; Schmidt, J.; Seiss, M.; Spahn, F.; Sterken, V.; Trieloff, M.

2014-04-01

The interplanetary space probe Cassini/Huygens reached Saturn in July 2004 after seven years of cruise phase. Today, the German-lead Cosmic Dust Analyser (CDA) is operated continuously for 10 years in orbit around Saturn. During the cruise phase CDA measured the interstellar dust flux at one AU distance from the Sun, the charge and composition of interplanetary dust grains and the composition of the Jovian nanodust streams. The first discovery of CDA related to Saturn was the measurement of nanometer sized dust particles ejected by its magnetosphere to interplanetary space with speeds higher than 100 km/s. Their origin and composition was analysed and an their dynamical studies showed a strong link to the conditions of the solar wind plasma flow. A recent surprising result was, that stream particles stem from the interior of Enceladus. Since 2004 CDA measured millions of dust impacts characterizing the dust environment of Saturn. The instrument showed strong evidence for ice geysers located at the south pole of Saturn's moon Enceladus in 2005. Later, a detailed compositional analysis of the salt-rich water ice grains in Saturn's E ring system lead to the discovery of liquid water below the icy crust connected to an ocean at depth feeding the icy jets. CDA was even capable to derive a spatially resolved compositional profile of the plume during close Enceladus flybys. A determination of the dust-magnetosphere interaction and the discovery of the extended E ring allowed the definition of a dynamical dust model of Saturn's E ring describing the observed properties. The measured dust density profiles in the dense E ring revealed geometric asymmetries. Cassini performed shadow crossings in the ring plane and dust grain charges were measured in shadow regions delivering important data for dust-plasma interaction studies. In the last years, dedicated measurement campaigns were executed by CDA to monitor the flux of interplanetary and interstellar dust particles reaching

Investigation of dust particles with future Russian lunar missions: achievements of further development of PmL instrument.

NASA Astrophysics Data System (ADS)

Kuznetsov, Ilya; Zakharov, Alexander; Afonin, Valeri; Seran, Elena; Godefroy, Michel; Shashkova, Inna; Lyash, Andrey; Dolnikov, Gennady; Popel, Sergey; Lisin, Evgeny

2016-07-01

One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Meteorites bombardment has accompanied by shock-explosive phenomena, disintegration and mix of the lunar soil in depth and on area simultaneously. As a consequence, the lunar soil has undergone melting, physical and chemical transformations. Recently we have the some reemergence for interest of Moon investigation. The prospects in current century declare USA, China, India, and European Union. In Russia also prepare two missions: Luna-Glob and Luna-Resource. Not last part of investigation of Moon surface is reviewing the dust condition near the ground of landers. Studying the properties of lunar dust is important both for scientific purposes to investigation the lunar exosphere component and for the technical safety of lunar robotic and manned missions. The absence of an atmosphere on the Moon's surface is leading to greater compaction and sintering. Properties of regolith and dust particles (density, temperature, composition, etc.) as well as near-surface lunar exosphere depend on solar activity, lunar local time and position of the Moon relative to the Earth's magneto tail. Upper layers of regolith are an insulator, which is charging as a result of solar UV radiation and the constant bombardment of charged particles, creates a charge distribution on the surface of the moon: positive on the illuminated side and negative on the night side. Charge distribution depends on the local lunar time, latitude and the electrical properties of the regolith (the presence of water in the regolith can influence the local distribution of charge). On the day side of Moon near surface layer there exists possibility formation dusty plasma system. Altitude of levitation is depending from size of dust particle and Moon latitude. The distribution of dust particles by size and altitude has estimated with taking into account photoelectrons, electrons and ions of solar wind

Modified jeans instability for dust grains in a plasma.

PubMed

Delzanno, G L; Lapenta, G

2005-05-06

An investigation of the properties of linear stability is conducted for a system consisting of particles having mass m and charge q, interacting through the gravitational and electrostatic force (Jeans instability). However, in light of recent works showing that dust particles in a plasma can have a Lennard-Jones-like shielding potential, a new set of equations has been derived, where the electrostatic interaction among the dust particles is Lennard-Jones-like instead of Coulomb-like. A new condition for the gravitational instability is derived, showing a broader spectrum of unstable modes with faster growth rates.

Mechanism for the acceleration and ejection of dust grains from Jupiter's magnetosphere

NASA Technical Reports Server (NTRS)

Horanyi, M.; Morfill, G.; Gruen, E.

1993-01-01

The Ulysses mission detected quasi-periodic streams of high-velocity submicron-sized dust particles during its encounter with Jupiter. It is shown here how the dust events could result from the acceleration and subsequent ejection of small grains by Jupiter's magnetosphere. Dust grains entering the plasma environment of the magnetosphere become charged, with the result that their motion is then determined by both electromagnetic and gravitational forces. This process is modeled, and it is found that only those particles in a certain size range gain sufficient energy to escape the Jovian system. Moreover, if Io is assumed to be the source of the dust grains, its location in geographic and geomagnetic coordinates determines the exit direction of the escaping particles, providing a possible explanation for the observed periodicities. The calculated mass and velocity range of the escaping dust gains are consistent with the Ulysses findings.

Measurements Required to Understand the Lunar Dust Environment and Transport Mechanism

NASA Technical Reports Server (NTRS)

Spann, James F., Jr.; Abbas, Mian

2006-01-01

Going back to the lunar surface offers an opportunity to understand the dust environment and associated transport mechanisms. This talk will explore what measurements are required to understand and characterize the dust-plasma environment in which robotic and human activities will be conducted. The understanding gained with the measurements can be used to make informed decisions on engineering solutions and follow-on investigations. Particular focus will be placed on required measurements of the size, spatial and charge distribution of the suspended lunar regolith.

A decade of infrared versus visible AOD analysis within the dust belt

NASA Astrophysics Data System (ADS)

Capelle, Virginie; Chédin, Alain; Pondrom, Marc; Crevoisier, Cyril; Armante, Raymond; Crépeau, Laurent; Scott, Noëlle

2017-04-01

Aerosols represent one of the dominant uncertainties in radiative forcing, partly because of their very high spatiotemporal variability, a still insufficient knowledge of their microphysical and optical properties, or of their vertical distribution. A better understanding and forecasting of their impact on climate therefore requires precise observations of dust emission and transport. Observations from space offer a good opportunity to follow, day by day and at high spatial resolution, dust evolution at global scale and over long time series. In this context, infrared observations, by allowing retrieving simultaneously dust optical depth (AOD) as well as the mean dust layer altitude, daytime and nighttime, over oceans and over continents, in particular over desert, appears highly complementary to observations in the visible. In this study, a decade of infrared observations (Metop-A/IASI and AIRS/AQUA) has been processed pixel by pixel, using a "Look-Up-Table" (LUT) physical approach. The retrieved infrared 10µm coarse-mode AOD is compared with the Spectral Deconvolution Algorithm (SDA) 500nm coarse mode AOD observed at 50 ground-based Aerosol RObotic NETwork (AERONET) sites located within the dust belt. Analyzing their brings into evidence an important geographical variability. Lowest values are found close to dust sources ( 0.45 for the Sahel or Arabian Peninsula, 0.6-0.7 for the Northern part of Africa or India), whereas the ratio increases for transported dust with values of 0.9-1 for the Caribbean and for the Mediterranean basin. This variability is interpreted as a marker of clays abundance, and might be linked to the dust particle illite to kaolinite ratio, a recognized tracer of dust sources and transport. More generally, it suggests that the difference between the radiative impact of dust aerosols in the visible and in the infrared depends on the type of particles observed. This highlights the importance of taking into account the specificity of the

Characteristics of mineral dust impacting the Persian Gulf

NASA Astrophysics Data System (ADS)

Ahmady-Birgani, Hesam; McQueen, Kenneth G.; Mirnejad, Hassan

2018-02-01

It is generally assumed that severe dust events in western Iran could be responsible for elevated levels of toxic and radioactive elements in the region. Over a period of 5 months, from January 2012 to May 2012, dust particles in the size range PM10 (i.e. <10 μm) were collected at Abadan, a site beside the Persian Gulf. The research aim was to compare chemical compositions of dust and aerosol samples collected during the non-dusty periods and during two severe dust events. Results of ICP-MS analysis of components indicate that during dust events the concentrations of major elements such as Ca, Mg, Al and K increase relative to ambient conditions when Fe and trace elements such as Cu, Cr, Ni, Pb and Zn are in higher proportions. Toxic trace elements that are generally ascribed to human activities, including industrial and urban pollution, are thus proportionately more abundant in the dust under calm conditions than during dust events, when their concentration is diluted by more abundant mineral particles of quartz, calcite and clay. The variability of chemical species during two dust events, noted by tracking the dust plumes in satellite images, was also assessed and the results relate to two different source areas, namely northern Iraq and northwestern Syria.

A Study of Mars Dust Environment Simulation at NASA Johnson Space Center Energy Systems Test Area Resource Conversion Test Facility

NASA Technical Reports Server (NTRS)

Chen, Yuan-Liang Albert

1999-01-01

The dust environment on Mars is planned to be simulated in a 20 foot thermal-vacuum chamber at the Johnson Space Center, Energy Systems Test Area Resource Conversion Test Facility in Houston, Texas. This vacuum chamber will be used to perform tests and study the interactions between the dust in Martian air and ISPP hardware. This project is to research, theorize, quantify, and document the Mars dust/wind environment needed for the 20 foot simulation chamber. This simulation work is to support the safety, endurance, and cost reduction of the hardware for the future missions. The Martian dust environment conditions is discussed. Two issues of Martian dust, (1) Dust Contamination related hazards, and (2) Dust Charging caused electrical hazards, are of our interest. The different methods of dust particles measurement are given. The design trade off and feasibility were studied. A glass bell jar system is used to evaluate various concepts for the Mars dust/wind environment simulation. It was observed that the external dust source injection is the best method to introduce the dust into the simulation system. The dust concentration of 30 Mg/M3 should be employed for preparing for the worst possible Martian atmosphere condition in the future. Two approaches thermal-panel shroud for the hardware conditioning are discussed. It is suggested the wind tunnel approach be used to study the dust charging characteristics then to be apply to the close-system cyclone approach. For the operation cost reduction purpose, a dehumidified ambient air could be used to replace the expensive CO2 mixture for some tests.

Coulomb scatter of diamagnetic dust particles in a cusp magnetic trap under microgravity conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myasnikov, M. I., E-mail: miasnikovmi@mail.ru; D’yachkov, L. G.; Petrov, O. F.

2017-02-15

The effect of a dc electric field on strongly nonideal Coulomb systems consisting of a large number (~10{sup 4}) of charged diamagnetic dust particles in a cusp magnetic trap are carried out aboard the Russian segment of the International Space Station (ISS) within the Coulomb Crystal experiment. Graphite particles of 100–400 μm in size are used in the experiments. Coulomb scatter of a dust cluster and the formation of threadlike chains of dust particles are observed experimentally. The processes observed are simulated by the molecular dynamics (MD) method.