共查询到20条相似文献,搜索用时 15 毫秒
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Radiophysics and Quantum Electronics - We consider the dust charging processes in protoplanetary disks. It is shown that in the atmosphere of a disk, grains can acquire anomalously high positive... 相似文献
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研究月尘颗粒在电子束环境下以及紫外源辐照下的带电机理,利用数值方法模拟月尘颗粒在不同背景环境下的充电过程,以探索月表尘埃颗粒的带电机理,进而便于地面月尘环境模拟装置选择合适的月尘带电方式进行空间模拟实验.给出了尘埃在电子束环境下的充电方程,并将紫外辐射带电与具体应用相结合.通过模拟结果可知,在电子束环境下,月尘表面的电荷数随粒径尺寸增大,随电子枪辐照束斑半径减少,随电子枪流强的增加而增多;在紫外源的辐照下,月尘表面电荷数随颗粒尺寸的增大以及紫外线辐照度的增加而增多.由月尘颗粒受太阳紫外辐照带电的数值模拟结果可知,月尘需要在太阳长时间的辐照下才可以带上可观的电荷数,地面模拟该过程需增加辐照源来加速实验.通过模拟结果的分析比较并结合"空间环境模拟装置"中对月尘舱的设计要求,最终优选紫外源辐照带电方式作为月尘颗粒的带电方案. 相似文献
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We study characteristics of a single dust particle in a duai-frequency capacitively coupled plasma sheath, such as charging and suspending processes, using a collisionless self-consistent model. Also, the movement of the dust grain with time is investigated for the various radii and initial velocities. The numerical results show that, after several microseconds, the charging process of the dust particle reaches equilibrium, and the grain obtains its equilibrium position, In addition, it is found that the parameters of the low-frequency source impact on the charging and suspending processes of the dust grain significantly. 相似文献
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B. A. Klumov G. E. Morfill S. I. Popel 《Journal of Experimental and Theoretical Physics》2005,100(1):152-164
An analysis of the evolution of microscopic particles (dust grains) in the Earth’s ionosphere and their effect on ionization in the middle atmosphere is presented. It is shown that summer conditions in the polar ionosphere, which are characterized by an ambient air temperature below 150 K and presence of supersaturated water vapor, facilitate the formation of dust structures in the middle atmosphere, such as noctilucent clouds and polar mesospheric summer echoes. The ionospheric plasma composition can change significantly in the regions occupied by these structures. Depending on photoelectric properties of the grains, their presence may lead to excess, or decrease in, electron concentration and complex behavior of ion concentration. The proposed self-consistent model of the ionosphere allows for grain growth, sedimentation, and charging and can be used to explain the behavior of ionization under summer conditions in the polar ionosphere. 相似文献
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I. Mann T. Gunnarsdottir I. Hggstrm S. Eren A. Tjulin M. Myrvang M. Rietveld P. Dalin D. Jozwicki H. Trollvik 《等离子体物理论文集》2019,59(6)
We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of dust plasma interactions observed with radar. The mesosphere is a region where atmospheric temperature decreases with altitude and can reach frost point temperature. The formation of the polar mesospheric radar echoes involves neutral atmosphere dynamics, which is latitude dependent and it involves charged dust particles, especially icy dust that forms in the polar summer mesosphere. Charged dust can also influence incoherent scatter that results from electromagnetic waves scattering off electrons, where the electrons are coupled to other charged components. Observers rarely report charged dust signatures in the incoherent scatter spectra; we show that there is a good chance for doing so with improved observations. The incoherent scatter can possibly also be used to estimate the amount of charged dust in the direct vicinity of a meteor, as we show based on the order of magnitude considerations. This prospect of new observational results makes theoretical investigations of radio‐wave scattering in the presence of charged dust with size distributions worthwhile. 相似文献
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WU Hai-Cheng XIE Bai-Song 《理论物理通讯》2005,44(3):547-550
By taking into account thermic emission current from hot dust surface, the problem involved in dust charging and levitation of dust grains in plasma sheath has been researched. The results are compared to that without including thermal emission current while the system parameters are same. It is found that the thermal emission current has played a significant role on modifying the dust charging and balance levitations. Both of the charging numbers of dust and the dust radius in balance are dramatically reduced. The stability of dust levitation is also analyzed and discussed. 相似文献
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WU Hai-Cheng XIE Bai-Song 《理论物理通讯》2005,44(9)
By taking into account thermic emission current from hot dust surface, the problem involved in dust charging and levitation of dust grains in plasma sheath has been researched. The results are compared to that without including thermal emission current while the system parameters are same. It is found that the thermal emission current has played a significant role on modifying the dust charging and balance levitations. Both of the charging numbers of dust and the dust radius in balance are dramatically reduced. The stability of dust levitation is also analyzed and discussed. 相似文献
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A. V. Filippov V. N. Babichev V. E. Fortov A. V. Gavrikov A. F. Pal’ O. F. Petrov A. N. Starostin N. E. Sarkarov 《Journal of Experimental and Theoretical Physics》2011,112(5):884-895
The photoemission charging of dust particles under ultraviolet radiation from a xenon lamp has been investigated. The velocities
of yttrium dust particles with a work function of 3.3 eV and their charges have been determined experimentally; the latter
are about 400–500 and about 100 elementary charges per micron of radius for the positively and negatively charged fractions,
respectively. The dust particle charging and the dust cloud evolution in a photoemission cell after exposure to an ultraviolet
radiation source under the applied voltage have been simulated numerically. The photoemission charging of dust particles has
been calculated on the basis of nonlocal and local charging models. Only unipolar particle charging is shown to take place
in a system of polydisperse dust particles with the same photoemission efficiency. It has been established that bipolar charging
is possible in the case of monodisperse particles with different quantum efficiencies. Polydispersity in this case facilitates
the appearance of oppositely charged particles in a photoemission plasma. 相似文献
9.
Features of dusty structures in the upper Earth’s atmosphere 总被引:1,自引:0,他引:1
The features of the Earth’s dusty ionosphere are considered using as an example the summer polar mesosphere. The effect of the optical properties of microparticles on their heating and photoelectron emission under the action of solar radiation is analyzed in detail. Certain photochemical consequences of the presence of dust in the upper atmosphere are studied. In particular, it is shown that microparticles can noticeably reduce the concentration of water vapor in the upper atmosphere and this decrease in turn limits the particle sizes. The influence of the effect under consideration on the behavior of the charged component of the upper atmosphere is discussed. 相似文献
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采用轨道受限运动方法研究了极区夏季中层顶区域的尘埃粒子电荷数与尘埃粒子半径。利用尘埃等离子体充电理论,建立了尘埃粒子充电方程模型,得到尘埃粒子充电时尘埃电荷数和半径的比值。然后结合ECT02实验数据,分析了发生极区中层夏季回波现象时极区中层顶区域尘埃粒子电荷数和半径的比值,并得到尘埃粒子的半径以及尘埃粒子所带电荷量。结果表明,极区中层顶区域的尘埃粒子平均所带电荷不到一个,它的半径约为20nm。 相似文献
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采用轨道受限运动方法研究了极区夏季中层顶区域的尘埃粒子电荷数与尘埃粒子半径。利用尘埃等离子体充电理论,建立了尘埃粒子充电方程模型,得到尘埃粒子充电时尘埃电荷数和半径的比值。然后结合ECT02实验数据,分析了发生极区中层夏季回波现象时极区中层顶区域尘埃粒子电荷数和半径的比值,并得到尘埃粒子的半径以及尘埃粒子所带电荷量。结果表明,极区中层顶区域的尘埃粒子平均所带电荷不到一个,它的半径约为20nm。 相似文献
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Nonlinear electrostatic wave structures in plasmas containing variable-charge dust grains, Boltz-mann electrons, and inertial ions are investigated. The charge variation is assumed to be caused by electron and ion currents at the grains. It is found that intense shock waves can exist. The dissipation in such shock waves originate from the process of dust charging. 相似文献
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Nejoh Y.N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(3):492-498
The dust grain charging effect on large amplitude ion-acoustic double layers in a dusty plasma are investigated by the numerical calculation. The nonlinear structures of ion-acoustic double layers are examined, showing that the characteristics of the double layer sensitively depend on the dust charging effect, the influence of the ion temperature, the electrostatic potential, and the Mach number. The flow of the plasma current to the surface of dust particles increases the dust charge numbers. The effect of the ion temperature decreases the propagation speed of the ion-acoustic double layers and decreases the dust charge numbers. It is found that rarefactive double layers can propagate in this system. New findings of large amplitude ion-acoustic double layers with the dust charging effect and finite ion temperature in a dusty plasma are predicted 相似文献
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The mechanized harvesting of tree nuts relies upon mechanically collecting and aerodynamically separating the nuts from extraneous vegetative and soil matter within the orchard using mobile power equipment. Typically the associated high-volume, high-velocity exhaust air disperses into the ambient atmosphere excessive concentrations of respirable-size particulate matter in the PM10 and PM2.5 micrometer realm creating a significant community air-quality problem. Our work developed a cyclonic-separation process for removing the PM10 dust and several candidate electrostatic-abatement processes for the smaller PM2.5 dust. We present the theoretical basis, including relevant mass- and charge-balances, for electrostatically abating the PM2.5 airborne dust via: (a) Ionized-field charging of the dust plume and its space-charge deposition within adjacent grounded tree-leaf canopies as air velocity subsides; (b) Injection of induction-charged spray of like polarity into the ion-charged-dust plume for space-charge-field enhancement; (c) Injection of charged spray alone into the dust plume; and (d) Injection of (+) polarity charged spray into the (?) polarity ionized-field-charged plume for electrostatic wet scrubbing of the dust. In addition to the theoretical basis, we report the technical development of a full-scale prototype to implement these electrostatic-abatement approaches on a mechanical harvester having ~10 g/s PM2.5 dust emission at ~27 m/s in an ~7 m3/s exhaust plume. 相似文献
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C.I. Calle P.J. Mackey M.D. Hogue M.R. Johansen J.D. Kelley J.R. Phillips J.S. Clements 《Journal of Electrostatics》2013,71(3):254-256
Human exploration missions to Mars will require the development of technologies for the utilization of the planet's own resources for the production of commodities. However, the Martian atmosphere contains large amounts of dust. The extraction of commodities from this atmosphere requires prior removal of this dust. We report on our development of an electrostatic precipitator able to collect Martian simulated dust particles in atmospheric conditions approaching those of Mars. Extensive experiments with an initial prototype in a simulated Martian atmosphere showed efficiencies of 99%. The design of a second prototype with aerosolized Martian simulated dust in a flow-through is described. 相似文献
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We present a simulation study of the charging of a dust grain immersed in a plasma, considering the effect of thermionic electron emission from the grain. It is shown that the orbit motion limited theory is no longer reliable when electron emission becomes large: screening can no longer be treated within the Debye-Huckel approach and an attractive potential well can form, leading to the possibility of attractive forces on other grains with the same polarity. We suggest to perform laboratory experiments where emitting dust grains could be used to create nonconventional dust crystals or macromolecules. 相似文献
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