scholarly journals The Role of Particle Size in Producing the F- Coronal Scattered Brightness

1996 ◽  
Vol 150 ◽  
pp. 349-352
Author(s):  
R.M. MacQueen ◽  
W.C. Davidson ◽  
I. Mann
Keyword(s):  
Particle Size ◽  
Mie Theory ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Interplanetary Dust Particles ◽  
Infrared Observations ◽  
Flux Measurements

AbstractMotivated by new infrared observations, we examine the contribution of various size intervals of interplanetary dust particles to visible and infrared scattered radiances of the solar F-corona, employing Mie theory and particle size distributions based upon differing interpretations of lunar microcrater evidence and interplanetary flux measurements.

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 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.

Textural properties of regoliths on vegetated steep slopes in upland regions, Scotland

1986 ◽  
Vol 77 (3) ◽  
pp. 241-250 ◽  
Author(s):  
J. L. Innes
Keyword(s):  
Particle Size ◽  
Early Stage ◽  
Probability Distributions ◽  
Textural Properties ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Normal Probability ◽  
Log Normal ◽  
Steep Slopes

ABSTRACTThe textural properties of many sediments provide a good indication of their provenance, but surprisingly little information is available on the transitional stages between the breakdown of a rock and the incorporation of the material into a fluvial sediment. These transitional stages are important as certain fractions (particularly the finer ones) may be selectively removed. Regoliths developed on steep slopes represent an early stage in the debris cascade and they are here examined in detail to assess the role of parent lithology on the textural properties of the regolith. There are substantial variations between lithologies, although the majority of regoliths are dominated by coarser fractions and are poorly sorted. Most particle size distributions show some degree of fit to both log-normal probability distributions and Rosin distributions. Differences from these can be ascribed to the processes operating on steep slopes, particularly the influx of sand- and silt-sized material by colluvial processes and the removal of clay-sized material by leaching. The regoliths form a distinct facies type which may be recognisable in the geological record.

scholarly journals Applicability of A1-term Method to the Scattering by Irregularly Shaped Interplanetary Dust Grains

1996 ◽  
Vol 150 ◽  
pp. 423-426 ◽  
Author(s):  
Hajime Okamoto
Keyword(s):  
Incident Wave ◽  
Mie Theory ◽  
Interplanetary Dust ◽  
Dipole Approximation ◽  
Dust Particles ◽  
Dipole Polarizability ◽  
Size Parameter ◽  
Interplanetary Dust Particles ◽  
Equivalent Radius ◽  
Single Dipole

AbstractThe first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the discrete dipole approximation (DDA) to calculate the scattering properties of the cluster of spheres in order to improve our understanding of interplanetary dust particles. In this method, each sphere in a cluster is replaced by a single dipole. The accuracy of this method is tested for a few spheres in contact. It is confirmed that the a1-term method is superior to other types of DDA and is particularly suitable for the case when the particles are placed randomly. By using this method, it becomes possible to treat large cluster of spheres, i.e., a size parameter of the target X(≡ 2πreq/λ) ∽ 50, where req is a volume equivalent radius of the target, and λ is the wavelength of incident wave.

scholarly journals 2.1.1 In-Situ Records of Interplanetary Dust Particles - Methods and Results

1976 ◽  
Vol 31 ◽  
pp. 143-158 ◽  
Author(s):  
H. Fechtig
Keyword(s):  
Interplanetary Dust ◽  
Space Missions ◽  
Dust Particles ◽  
Measure Data ◽  
Interplanetary Dust Particles ◽  
Detection Techniques ◽  
The Earth ◽  
Future Space

AbstractA review is given on the techniques used to record and to quantitatively measure data of individual interplanetary dust particles. New developments in detection techniques are briefly discussed.The main results from recent space missions at about 1 AU and in the earth-moon neighborhood are discussed and compared with the flux results from lunar microcrater studies. Spatial anisotropies and time fluctuations are found indicating that the earth is exposed to two main micrometeoroid dust populations: the “apex”-population and the B-meteoroids. The near planet-dust enrichments measured by HEOS 2 near the earth and by the Pioneer 10/11 near Jupiter are emphasized. The experimental data strongly suggest a fragmentation process associated with the earth. The role of the moon as a dust source is discussed. The important problems in the dust field for future space missions are summarized.

scholarly journals Impact of optical indices on particle size distribution of activated sludge measured by laser diffraction method

2014 ◽  
Vol 21 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Agata Sochan ◽  
Cezary Polakowski ◽  
Grzegorz Łagód
Keyword(s):  
Particle Size ◽  
Refractive Index ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Mie Theory ◽  
Diffraction Method ◽  
Laser Diffraction ◽  
Optical Parameters ◽  
Size Distributions ◽  
Particle Size Distributions

Abstract The important factors that strongly influence the particle size distributions measured by the laser diffraction method are the optical parameters of the suspension (refractive index and absorption coefficient). Knowledge of the values of these parameters is necessary for Mie theory. Mie theory is applied for conversion of the intensity of light recorded on detectors into particle size distribution (PSD) of tested material. Both wastewater and activated sludge are mixtures of a variety of elements (mineral or organic, including living organisms). In practice, it is not possible to define clearly the values of the optical parameters, as the composition of the suspension changes over time. The aim of the study was to estimate the impact of assumed values of the optical parameters on particle size distributions obtained. The PSDs of suspensions sampled in different stages of wastewater treatment are the most reproducible when the following optical parameters are defined: absorption coefficients - 1.0 and the refractive index - 1.52.

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