scholarly journals Glow and Dust in Plasma Boundaries

2013 ◽  
Vol 41 (4) ◽  
pp. 799-803 ◽  
Author(s):  
Victor Land ◽  
Angela Douglass ◽  
Ke Qiao ◽  
Zhuanhao Zhang ◽  
Lorin Matthews ◽  
...  
Keyword(s):  
Dust Particle ◽  
Local Maximum ◽  
Optical Emission ◽  
Dust Particles ◽  
Vertical Force ◽  
Dust Density ◽  
Sheath Region ◽  
Complex Plasma ◽  
Dust Clouds ◽  
Force Profile

The sheath region is probed in different complex plasma experiments using dust particles in addition to the measurement of the optical emission originating from the plasma. The local maximum in the optical emission coincides with the breaking of quasi-neutrality at the sheath boundary, as indicated by the vertical-force profile reconstructed from dust-particle trajectories as well as by the local onset of dust-density waves in high-density dust clouds suspended in a dielectric box.

scholarly journals Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

2011 ◽  
Vol 11 (2) ◽  
pp. 723-740 ◽  
Author(s):  
G. Chen ◽  
L. D. Ziemba ◽  
D. A. Chu ◽  
K. L. Thornhill ◽  
G. L. Schuster ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Dust Particle ◽  
Saharan Dust ◽  
Dust Particles ◽  
Small Range ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Field Campaign ◽  
Sahara Dust

Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in-situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, a nephelometer, and a Particle Soot Absorption Photometer. The NAAMA sampling inlet has a size cut (i.e., 50% transmission efficiency size) of approximately 4 μm in diameter for dust particles, which limits the representativeness of the NAMMA observational findings. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions can be well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The Ångström Exponent assessments exhibited strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97 ± 0.02. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. Closure analysis showed that observed scattering coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. These values are generally consistent with literature values reported from studies with similar particle sampling size range.

scholarly journals Charting nearby dust clouds using Gaia data only

2019 ◽  
Vol 631 ◽  
pp. A32 ◽  
Author(s):  
R. H. Leike ◽  
T. A. Enßlin
Keyword(s):  
Power Spectrum ◽  
Spatial Correlation ◽  
Electromagnetic Spectrum ◽  
Normal Process ◽  
Dust Density ◽  
Dust Clouds ◽  
Correlation Spectrum ◽  
Log Normal ◽  
Local Dust ◽  
The Impact

Aims. Highly resolved maps of the local Galactic dust are an important ingredient for sky emission models. Over almost the whole electromagnetic spectrum one can see imprints of dust, many of which originate from dust clouds within 300 pc. Having a detailed 3D reconstruction of these local dust clouds enables detailed studies, helps to quantify the impact on other observables, and is a necessary milestone of larger reconstructions, as every sightline for more distant objects will pass through the local dust. Methods. To infer the dust density we use parallax and extinction estimates published by the Gaia collaboration in their second data release (DR2). We model the dust as a log-normal process using a hierarchical Bayesian model. We also nonparametrically infer the kernel of the log-normal process, which corresponds to the physical spatial correlation power spectrum of the log-density. Results. Using only data from Gaia DR2, we reconstruct the 3D dust density and its spatial correlation spectrum in a 600 pc cube centered on the Sun. We report a spectral index of the logarithmic dust density of 3.1 on Fourier scales with wavelengths between 2 and 125 pc. The resulting 3D dust map as well as the power spectrum and posterior samples are publicly available for download.

Ion transport in electrode sheath with non-uniform dusts

2002 ◽  
Vol 68 (4) ◽  
pp. 249-255
Author(s):  
A. P. SUN ◽  
X. M. QIU ◽  
H. H. TONG ◽  
Q. C. CHEN
Keyword(s):  
Ion Transport ◽  
Dust Particles ◽  
Uniform Density ◽  
Key Factors ◽  
Ion Density ◽  
Factors Affecting ◽  
Dust Density ◽  
Dust Charge ◽  
The Monte Carlo Method ◽  
Electrode Sheath

The Monte Carlo method is used to simulate ion transport in an Ar plasma electrode sheath with a non-uniform dust. Charge exchange and elastic collisions between ions and neutral atoms and also the collection and Coulomb scattering of ions on the dust particles are examined during the motion of ions in the sheath. In order to study the effect of the non-uniform dust density and size on ion transport, we choose an exponent dust density distribution with a uniform dust size and a normal dust radius distribution with a uniform density and compare the simulation results with those for a uniform dust. It is found that both a non-uniform and a uniform dust density affect the ion density arriving at the electrode significantly and to the same degree. At the same time, it is also found that a non-uniform and uniform dust size influence the ion density arriving at the electrode greatly, but with a slight difference. Therefore, although the dust content is very low in most processing plasmas, its influence becomes evident whether its content is uniform or non-uniform in content and size. So, we can come to the conclusion that the key factors affecting the influence of dust particles on plasma behaviour are the linear density and the average radius of dust particles rather than their distribution.

scholarly journals Dust Particle Size Distributions during Spring in Yinchuan, China

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Jiangfeng Shao ◽  
Jiandong Mao
Keyword(s):  
Particle Size ◽  
Wind Speed ◽  
Dust Particle ◽  
Dust Storm ◽  
Fine Particles ◽  
Dust Particles ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Mass Distributions ◽  
Mass Size

Dust particle size distributions in Yinchuan, China, were measured during March and April 2014, using APS-3321 sampler. The distributions were measured under different dust conditions (background, floating dust, blowing dust, and dust storm) and statistical analyses were performed. The results showed that, under different dust conditions, the instantaneous number concentrations of dust particles differed widely. For example, during blowing sand and dust storm conditions, instantaneous dust particles concentrations varied substantially, while, under floating dust conditions, concentration differences were relatively small. The average dust particles size distributions were unimodal under all dust conditions, but the average surface area and mass size distributions were all bimodal. These distributions had peaks in different locations under different dust conditions. Under different dust conditions, wind speed and humidity were very important factors for particles size distributions. With increasing wind speed and decreasing humidity, fine particles were dominant in the atmosphere and the number and mass distributions of the coarse particles were indicative of long-range transport from surrounding deserts. Different dust conditions had different influences on PM1, PM2.5, and PM10concentrations.

Long-range attraction of negatively charged dust particles in weakly ionized dense dust clouds

2010 ◽  
Vol 17 (4) ◽  
pp. 043702 ◽  
Author(s):  
U. de Angelis ◽  
G. Regnoli ◽  
S. Ratynskaia
Keyword(s):  
Long Range ◽  
Dust Particles ◽  
Charged Dust ◽  
Dust Clouds ◽  
Weakly Ionized

ERE from Graphene Oxide in the ISM. A possible link to IOM?

2020 ◽  
Author(s):  
Peter Sarre
Keyword(s):  
Graphene Oxide ◽  
Organic Material ◽  
Interstellar Dust ◽  
Emission Spectra ◽  
Optical Emission ◽  
Interplanetary Dust ◽  
Infrared Emission ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Infrared Space Observatory

<p>Dust particles play a major role in the formation, evolution and chemistry of interstellar clouds, stars, and planetary systems. Commonly identified forms include amorphous and crystalline carbon-rich particles and silicates. Also present in many astrophysical environments are polycyclic aromatic hydrocarbons (PAHs), detected through their infrared emission, and which are essentially small flakes of graphene. Astronomical observations over the past four decades have revealed a widespread unassigned ‘extended red emission’ (ERE) feature which is attributed to luminescence of dust grains. A luminescence feature with similar characteristics to ERE has been found in organic material in interplanetary dust particles and carbonaceous chondrites.  </p> <p>There is a strong similarity between laboratory optical emission spectra of graphene oxide (GO) and ERE, leading to this proposal that emission from GO nanoparticles is the origin of ERE and that heteroatom-containing PAH structures are a significant component of interstellar dust. The proposal is supported by infrared emission features detected by the <em>Infrared Space Observatory (ISO)</em> and the <em>Spitzer Space Telescope</em>.  </p> <p>Insoluble Organic Material (IOM) has a chemical structure with some similarities to graphene oxide.  It is suggested this may contribute to the discussion as to whether IOM has an origin in the interstellar medium or the solar nebula, or some combination.</p>

Tempest in a glass tube: A helical vortex formation in a complex plasma

2014 ◽  
Vol 80 (6) ◽  
pp. 869-876 ◽  
Author(s):  
Yoshifumi Saitou ◽  
Osamu Ishihara
Keyword(s):  
Horizontal Plane ◽  
Vortex Formation ◽  
Vertical Plane ◽  
Glass Tube ◽  
Disk Center ◽  
Dust Particles ◽  
Experimental Conditions ◽  
Complex Plasma ◽  
Dust Disk ◽  
Helical Vortex

A collective behavior of dust particles in a complex plasma with a magnetic field (up to 4 kG) is investigated. Dust particles form a dust disk which is rotating in a horizontal plane pushed by ions rotating with the E × B drift as a trigger force. The thickness of the disk is determined by controlling the experimental conditions. The disk rotates in a horizontal plane and forms a two-dimensional thin structure when the pressure pAr is relatively high. The dust particles are ejected from near the disk center and form a rotation in the vertical plane and, hence, forms a helical vortex when the disk is thick for relatively low pAr. The reason the dust disk has the different thickness is due to the neutral pressure. Under a higher (lower) neutral gas pressure, the disk becomes two (three) dimensional due to the influence of the neutral drag force.

scholarly journals Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

2012 ◽  
Vol 19 (1) ◽  
pp. 013707 ◽  
Author(s):  
Angela Douglass ◽  
Victor Land ◽  
Ke Qiao ◽  
Lorin Matthews ◽  
Truell Hyde
Keyword(s):  
Dust Particles ◽  
Complex Plasma
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