Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field

The characteristics of the blue core phenomenon observed in a divergent magnetic field helicon plasma are investigated using two different helical antennas, namely right-handed and lefthanded helical antennas. The mode transition, discharge image, spatial profiles of plasma density and electron temperature are diagnosed using a Langmuir probe, a Nikon D90 camera,an intensified charge-coupled device camera and an optical emission spectrometer, respectively.The results demonstrated that the blue core phenomenon appeared in the upstream region of the discharge tube at a fixed magnetic field under both helical antennas. However, it is more likely to appear in a right-handed helical antenna, in which the plasma density and ionization rate of the helicon plasma are higher. The spatial profiles of the plasma density and electron temperature are also different in both axial and radial directions for these two kinds of helical antenna. The wavelength calculated based on the dispersion relation of the bounded whistler wave is consistent with the order of magnitude of plasma length. It is proved that the helicon plasma is part of the wave mode discharge mechanism.

Shearing Wind Helicity and Thermal Wind Helicity

Helicity is defined as H ： V ω, where V and ω are the velocity and vorticity vectors, respectively. Many works have pointed out that the larger the helicity is, the longer the life cycle of the weather system is. However, the direct relationship of the helicity to the evolution of the weather system is not quite clear. In this paper, the concept of helicity is generalized as shearing wind helicity （SWH）. Dynamically, it is found that the average SWH is directly related to the increase of the average cyclonic rotation of the weather system. Physically, it is also pointed out that the SWH, as a matter of fact, is the sum of the torsion terms and the divergence term in the vorticity equation. Thermal wind helicity （TWH）, as a derivative of SWH, is also discussed here because it links the temperature field and the vertical wind field. These two quantities may be effective for diagnosing a weather system. This paper applies these two quantities in cylindrical coordinates to study the development of Hurricane Andrew to validate their practical use. Through analyzing the hurricane, it is found that TWH can well describe the characteristics of the hurricane such as the strong convection and release of latent heat. SWH is not only a good quantity for diagnosing the weather system, but also an effective one for diagnosing the development of the hurricane.

On the Helicity Dynamics of Severe Convective Storms

A well-documented supercell thunderstorm occurred in Del City, Oklahoma, on 20 May 1977 is successfully simulated by a three-dimensional, nonhydrostatic storm-scale numerical model ARPS. With the numerical simulated data of the storm, the structure and evolution of the helicity, superhelicity and their dynamical influences on the development of the storm are investigated. The initial helical structure of environmental flow is favorable to the development of storm. In the developing stage of storm, low helicity is beneficial to the nonlinear energy cascade. However, the high helicity is of help to maintain the energy of convection cell at the mature stage of storm, and lead to a long life cycle of convective cell. Rotating thunderstorm has a tendency of adjusting to the Beltrami flow structure and tends to a higher helicity of flow. The negative superhelicity could lead to an increase of helicity. Superhelicity is negative in the initial developing process of storm however the superhelicity is positive in the mature stage of storm. Therefore, the superhelicity can be used as an indicator of the mature degree of convective storm.

On the physical significance and use of a set of horizontal and vertical helicity budget equations

For better understanding the variation of helicity and its governing mechanisms,based on the primary momentum equation under the local Cartesian coordinate,a set of horizontal and vertical helicity equations are derived in this study.On this basis,a storm-relative helicity budget equation is derived,the main factors that govern the variation of helicity are discussed,and the key mechanisms underlying the helicity variation are illustrated by using schematic images.Both scale analysis and real case diagnosis are used to compare the relative importance of di erent factors on the variation of helicity.For a meso-α system,it is found that:(i)horizontal helicity is much larger than vertical helicity,and they show signi cantly di erent variation mechanisms;(ii)for the vertical helicity,the vertical perturbation pressure gradient force,buoyancy,the diver-gence-related e ect,and the conversion between vertical and horizontal helicity govern its variation(whereas,the conversion is negligible for the evolution of horizontal helicity);and(iii)baroclinity is crucial for the variation of horizontal helicity,but it is only of secondary importance for the vertical helicity variation.

正负电子对湮灭过程中发生的真实过程——helicity守恒

基于正负电子对湮灭过程中的helicity守恒假设和已经知道的其它的守恒量,可以得出正负电子对湮灭过程中不仅产生纠缠同态双光子对,还会在产物中出现零动量零静质量的真实的引力子,即自旋和动量反向的正负纠缠电子对湮灭生成处于纠缠态的由引力子和双光子构成的3个粒子。这个结论将被未来的实验结果所证实。

Vertical Helicity Analysis of First Rainstorm at the Beginning of Meiyu in Hubei in 2009

By using the data in Hubei automatic rainfall station and NCEP 1°×1° global reanalysis data,the vertical helicity analysis on the rainstorm weather process which happened in Hubei Province during June 28-30 in 2009 was done.The results showed that the spatial and temporal evolution characteristic of vertical helicity could reflect well the occurrence time and the falling zone of strong precipitation in the situation that the strong vertical ascent movement in the whole layer stably maintained.The distribution of 700 hPa vertical helicity gradient big value area which was 6 h interval and the ∑θse(500+700+850) horizontal energy frontal zone superposition area both had the good directive significance for the falling zone of 6 h heavy precipitation.The zone where the heavy precipitation appeared had the configuration of positive vertical helicity in the low layer and the negative vertical helicity in the high layer.When the positive vertical helicity in the low layer was slightly higher than the negative vertical helicity in the high layer,it favored the generation of heavy rainstorm center.

The Conservation of Helicity in Hurricane Andrew(1992)and the Formation of the Spiral Rainband

The characteristics of helicity in a hurricane are presented by calculating the MM5 model output in addition to theoretical analysis. It is found that helicity in a hurricane mainly depends on its horizontal component, whose magnitude is about 100 to 1000 times larger than its vertical component. It is also found that helicity is approximately conserved in the hurricane. Since the fluid has the intention to adjust the wind shear to satisfy the conservation of helicity, the horizontal vorticity is even larger than the vertical vorticity, and the three-dimensional vortices slant to the horizontal plane except in the inner eye. There are significant horizontal vortices and inhomogeneous helical flows in the hurricane. The formation of the spiral rainband is discussed by using the law of horizontal helical flows. It is closely related to the horizontal strong vortices and inhomogeneous helical flows.

Helicity Dynamics of Atmospheric Flow

Helicity is an important physical variable which is similar to the energy and enstrophy in three-dimensional fluid. It can be used to describe the motion in the direction of fluid rotation and also can be regarded as a new physical variable ill turbulence theory. In recent years, it has been used in atmospheric dynamics. In this paper, helicity of atmospheric flow, especially helicity in the boundary layer and in the vicinity of front was discussed. These results show that helicity is usually positive in the boundary layer due to the effect of friction. The helicity of boundary layer flow is larger in anticyclone than that in cyclone, resulting from the different wind structures of boundary layers in anticyclone and cyclone under the geostrophic momentum approximation. It is possible that the helicity is negative at certain height in the baroclinic boundary layer. The influences of nonlinearity and baroclinity on the helicity are important. The so called 'Cloud Street' in the boundary layer is related to the dynamics of helicity. Helicity in the atmosphere can be expressed as the temperature advection under some conditions, so helicity would be allowed to describe the frontogenesis and development of frontal structure. The amplitude of helicity increases with time in the frontogenesis. A large gradient of helicity is generated in the region located to the northeast of the surface low and in which the front is formed. In warm frontal region, as well as behind the trough of temperature, the felicity is positive, while the helicity is negative in cold frontal sector and in the ahead ridge of temperature. The largest helicity occurs in the boundary.

On the relationship between tropical cyclone size and environmental helicity in the South China Sea

In this study,the impact of environmental factors on tropical cyclone(TC)outer-core size was investigated for both migrating and local TCs in the South China Sea during the period 2001–2019.Among all the thermodynamic and dynamic factors,the low-level environmental helicity showed the strongest positive correlation with TC outer-core size.Large helicity favors the development and organization of convection in TCs,and the corresponding strong inflow and large angular momentum fluxes into the system is beneficial for the maintenance and enlargement of TC outer-core size.Besides,the asymmetric distribution of helicity may account for the asymmetry of TC outer-core size.Therefore,the environmental helicity,as an integrated dynamic factor,can provide an alternative view on TC outer-core size.

Relations Between Helicity Coupling Amplitude and L—S Coupling Amplitude

Relations between helicity coupling amplitude and L-S coupling amplitude are discussed. The equivalence condition for these two kinematic analysis methods and the limitations of the L-S coupling amplitude are also studied in this paper.

Study of Helicity in Typhoon Rainfall Regions——A Case Study of Typhoon "Muifa"

Using the center of figure method and center of mass method, precipitation and heavy precipitation processes caused by No. 9 typhoon ＂ Muifa＂ in 2011 were analyzed based on helicity, and the mechanism of typhoon rainfall was interpreted from the relation between helicity and ener- gy. The results showed that horizontal helicity checked the diffusion of nonlinear energy and maintained the development of the system. Precipitati- on mainly appeared on the southeast of vertical helicity, while heavy precipitation mainly occurred on its southwest. Compared with the center of fig- ure method, the center of mass method had good results, especially for heavy precipitation. Vertical helicity at 700 hPa reflected system deviation in rainfall regions well and had the best correction effect on rainfall intensity and regions

Coronal Magnetic Flux Rope Equilibria and Magnetic Helicity

Using a 2.5-dimensional (2.5-D) ideal MHD model, this paper analyzes the equilibrium properties of coronal magnetic flux ropes in a bipolar ambient magnetic field. It is found that the geometrical features of the magnetic flux rope, including the height of the rope axis, the half-width of the ropes and the length of the vertical current sheet below the ropes are determined by a single magnetic parameter, the magnetic helicity, which is the sum of the self-helicity of the rope and the mutual helicity between the rope field and the ambient magnetic field. All the geometrical parameters increase monotonically with increasing magnetic helicity. The implication of this result in solar active phenomena is briefly discussed.

Helicity Amplitude Analysis of Z_c(3900)~± in e^+e^- →π^+π^-J/ψ

It is crucial to determine the spin and parity （jR） of Zc（3900）＋ for understanding its structure. We perform a helicity amplitude analysis on Zc（3900）＋ in the process e＋e- →π＋π-J/φ＊ with the hypotheses JP = 0-, 1＋, 1-, 2＋ and 2-. To estimate the significance of JP = 1＋ over other hypotheses, we perform a Monte Carlo simulation study, and we also discuss the prospect of measuring the spin parity in the future experiment with a large data sample.

SYNTHESIS,HELICITY,AND BIOLOGICAL PROPERTIES OF MONOSACCHARIDE-CONTAININGPOLY(PHENYLACETYLENE)S

Poly（phenylacetylene）s beating monosaccharide pendant groups are synthesized in high yields by [Rh（nbd）Cl]2 catalyst. The polymers have high molecular weights and give satisfactory spectroscopic data corresponding to their molecular structures. They are thermally quite stable （≥ 300℃） and show strong circular dichroism signals in the visible spectral region owing to the helicity of the polyene backbone. The monosaccharide-containing polyacetylenes are cytophilic and can stimulate the growth of living cells.

Helicity as a Method for Forecasting Severe Weather Events

This paper introduces a method for forecasting severe weather which is yieded by integrating helicity as a dynamical parameter with K and TOT indexes as thermal parameters.The results of operational tests for two years ure detailed.And the seasonal suitability of the method applications is discussed as well.

Helicity Amplitude Analysis of η_c Decays into Hyperon-Antihyperon Pairs

The helicity amplitudes for the processes of e^＋e^- →J/ψ→γηc→γYY（Y： hyperon） are presented, together with the joint angular distributions for ηc decays into ∧∧,∑^0 ∑^0, and [1]-[1]＋. The sensitivities to measure the hyperon decay parameters in these decays are evaluated based on the helicity amplitudes. The prospects to test the Bell inequality in experiment using the decay of ηc→∧∧ are discussed.

Formalism of Helicity Coupling Amplitudes for J/ψ→π^＋π^-π^0

The formalisms of helicity coupling amplitudes for J/ψ→π^＋π^-π^0 are presented. A detailed discussion is also given on the barrier factor, Breit Wigner, and density matrix. A Monte Carlo simulation of J/ψ→ρ（770）π→π^＋π^-π^0 is carried out. The results show that the p（770） resonance is well reproduced compared with experimental data.

HELICITY ANALYSIS FOR HIGH-WIND AND UNCOMMON RAINSTORM PROCESSES OVER YUNNAN IN EARLY SUMMER

Helicity was applied to analyze several high-wind and rainstorm processes, which occurred from May to June, 2001 over Yunnan in early summer. The results of diagnostic analyses show that the rainstorm occurs in the area in which hp is positive at 700 hPa and energy is unstable. The change of helicity can reflect the movement and development of synoptic system and the position and intensity of the rainstorm. The value of hp is a negative center at the upper level and a positive at the lower level over the rainstorm position; moreover it can reflect the characteristics of vertical distribution and rotational motion.

Analysis on the TBB Bright Temperature and Vertical Helicity in a Heavy Rain at Anqiu in 2010

In order to get insight into the mechanism of summer rainstorm occurred in central Shandong Province and further improve the prediction accuracy,the FY-2E satellite TBB data and 6 h of NCEP/NCAR 1°×1° reanalysis data were used to carry out the weather dynamics diagnosis and TBB cloud image analysis of a heavy rain happened in Anqiu City on July 18,2010.The results showed that the Anqiu torrential rain was caused by common effects of the subtropical high and upper trough and ground cyclone system;TBB strong low clouds moved with cloud band along the low level jet direction,and closely associated with water vapor and energy belt,while the heavy rain occurred in the north of TBB light in low temperature zone,making the unstable energy release above the Anqiu area;the changes of the vertical spiral degrees at center could well guide the movement of the ground cyclonic center.

Quantum Theory Explanation of Helicity Inversion of Laser(Photons) During Reflection

Theretical analysis of the helicity inversion of laser （photons） during reflection is made by quantum theory for laser （photons） through an optical helix. The result reveals that the helicity inversion of the laser （photons） occurs when the wave vector of the laser （photon） rotates at an extremely high angular velocity. The dynamic factor that dominates the process is the Coriolis coupling between the spin of the photon and the rotation of the wave vector. This non-intertial effect is treated successfully by simplification of the Maxwell equation in the rotational frame. In addition, the implication of the helicity inversion in information theory is discussed.