To determine the nucleation region location of Si nano-crystal grains, pulsed laser ablation of Si target is performed in Ar gas of 10 Pa at room temperature with laser fluence of 4 J/cm2, the substrates are located h...To determine the nucleation region location of Si nano-crystal grains, pulsed laser ablation of Si target is performed in Ar gas of 10 Pa at room temperature with laser fluence of 4 J/cm2, the substrates are located horizontal under ablation spot with different vertical distance. Characteristics of deposited grains are described by scanning electron microscopy, Raman scattering and X-ray diffraction spectra, the results indicate that deposition position on substrates in a certain range is relative to target surface, which changes according to different vertical distance of substrates to ablation spot. Grain size increased?at first and then decreased with addition of lateral distances to target in the range, but the integral distribution rule was independent of position of substrates. Combining with hydrodynamics model, nucleation division model, thermokinetic equation and flat parabolic motion, spatial nucleation region location of grains is obtained through numerical calculations, which is 2.7 mm-43.2 mm to target surface along the plume axis.展开更多
Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based o...Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.展开更多
文摘To determine the nucleation region location of Si nano-crystal grains, pulsed laser ablation of Si target is performed in Ar gas of 10 Pa at room temperature with laser fluence of 4 J/cm2, the substrates are located horizontal under ablation spot with different vertical distance. Characteristics of deposited grains are described by scanning electron microscopy, Raman scattering and X-ray diffraction spectra, the results indicate that deposition position on substrates in a certain range is relative to target surface, which changes according to different vertical distance of substrates to ablation spot. Grain size increased?at first and then decreased with addition of lateral distances to target in the range, but the integral distribution rule was independent of position of substrates. Combining with hydrodynamics model, nucleation division model, thermokinetic equation and flat parabolic motion, spatial nucleation region location of grains is obtained through numerical calculations, which is 2.7 mm-43.2 mm to target surface along the plume axis.
基金supported by the National Natural Science Foundation of China(Grant No.12375250)。
文摘Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.
