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.

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.

Magnetic Helical Micro-and Nanorobots:Toward Their Biomedical Applications

Magnetic helical micro- and nanorobots can perform 3D navigation in various liquids with a sub- micrometer precision under low-strength rotating magnetic fields （〈 10 rer）. Since magnetic fields with low strengths are harmless to cells and tissues, magnetic helical micro/ nanorobots are promising tools for biomedical applications, such as minimally invasive surgery, cell manipulation and analysis, and targeted therapy. This review provides general information on magnetic helical micro/nanorobots, including their fabrication, motion control, and further functionalization for biomedical applications.

Synthesis, Crystal Structure and Magnetic Properties of a Coordination Polymer Based on Iron(Ⅱ) Carboxylate Helical Chains [Fe(bpdc)(H_2O)_2]n

A coordination polymer based on iron（II） carboxylate helical chains [Fe（bpdc）（H2O）2]n 1 has been constructed hydrothermally using H2bpdc （H2bpdc = 2,2＇-bipyridine-4,4＇-dicarboxylic acid）, pyridine and FeSO4·7H2O. Its crystal structure reveals that the Fe（Ⅱ） ion adopts a slightly distorted octahedron. The carboxylates of bpdc ligands alternately bridge the Fe（Ⅱ） cations to form 1D infinite helical chains. The Fe···Fe intrachain distance is 4.8246（6） . The adjacent chains are further interlinked by the coordination of bpdc ligands and hydrogen bonding to form a 3D framework. Magnetic studies for complex 1 show weak antiferromagnetic coupling between the Fe（Ⅱ） ions. The best-fit for χM T vs. T with a Hamiltonian∑∑==iBiiHJSi SigHS11 leadsto g = 2.314（4） and J = –0.68（1） cm-1.

Influence of magnetic field on power deposition in high magnetic field helicon experiment

Based on high magnetic field helicon experiment(HMHX), HELIC code was used to study the effect of different magnetic fields on the power deposition under parabolic distribution. This paper is divided into three parts: preliminary calculation, actual discharge experiment and calculation. The results of preliminary calculation show that a magnetic field that is too small or too large cannot produce a good power deposition effect. When the magnetic field strength is 1200 Gs,a better power deposition can be obtained. The actual discharge experiment illustrates that the change of the magnetic field will have a certain influence on the discharge phenomenon. Finally, the results of verification calculation successfully verify the accuracy of the results of preliminary simulation. The results show that in the actual discharge experiment, it can achieve the best deposition effect when the magnetic field is 1185 Gs.

The Influence of Magnetic Field on Antenna Performance in Plasma

A spacecraft loses all forms of communication, including global positioning system signals, data telemetry, voice communication and so on, when it enters the communication blackout phase. This becomes more and more critical with the development of reentry vehicle missions since radio blackout brings about many serious issues related to vehicle safety. This paper studies the influence of magnetic field on antenna performance in plasma. The results indicate that the effect of plasma on the antenna performance can be negligible when the magnetic field reaches a certain strength. This provides another way to solve the reentry blackout problem.

Wave-vector filtering effect of the electric-magnetic barrier in HgTe quantum wells

Because of the helicity of electrons in HgTe quantum wells（QWs） with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.

Quantum control of ultrafast magnetic field in H_(3)^(2+)molecules by tricircular polarized laser pulses

We present a scheme to control the generated ultrafast magnetic field in H_(3)^(2+)molecules using multi-frequency tricircular pulses composed of co-and counter-rotating bicircular pulses.Simulations show that the field amplitude and the wavelength are two significant factors for magnetic field generation by tricircular pulses.Specifically,the strength of the magnetic field is linearly related to the field amplitude atλ_(0)=50 nm,while atλ_(0)=70 nm,the strength first increases and then decreases with the amplitude,this can be attributed to the resonance between the ground and excited states.Moreover,the phase and helicity of bicircular pulses are shown to have important effects on the magnetic field.The dependence of the magnetic field on the phase arises from the interference effect between multiple ionization pathways.These findings illustrate a guiding principle for controlling the magnetic field in molecular systems for future research in ultrafast magneto-optics.

Solar Flare Activity and Variability of Electric Current Helicity

Recent study using Huairou vector magnetograph data shows that durlug flare activity, the current helicity exhibits rapid and substantial variations and, in some cases, a recovering phase. We considered various representative the magnetic configurations. First, interacting twisted magnetic flux tubes are analyzed separately for positive, negative and mixed-sign helicity regions. The results show that the helicity during flares decreases in positive-sign, and increases in negative-sign regions. Then, flaring arcade also shows that the magnitude of the helicity decreases after flares. We also investigated current sheets formed by sheared magnetic field and showed that the current helicity (with either positive and negative signs) vanishes after reconnection. The emergence of twisted flux tubes which can trigger flares may be another source of flare-associated variability of current helicity. We demonstrate the relevance of current helicity to the description of flare activity by comparing its variation with that of shear angle in the active region AR 6891.

From polarimetry to helicity: Studies of solar magnetic fields at the Huairou Solar Observing Station

In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the solar atmosphere. We introduce some basic research progress in magnetic field measurement at Huairou Solar Observing Station of National Astronomical Observatories,Chinese Academy of Sciences, especially concerning the non-potentiality in solar active regions, such as the magnetic shear,current and helicity. We also discuss some basic questions for the measurements of the magnetic fields and corresponding challenges for the future studies.

Current helicity pattern of large-scale magnetic field on the photosphere

Following Pevtsov and Latushko, we study the current helicity pattern of the large-scale magnetic field on the photosphere. We use the same technique as theirs to derive the vector magnetic field (Br,Bθ,Bφ) from full-disk longitudinal magnetograms based on the assumption that large-scale magnetic fields evolve rather slowly and the variations of the longitudinal magnetic fields within certain time duration are caused by the changing position angles only. Different from their study, we have calculated the current helicity maps directly from the derived vector magnetograms, rather than from obtaining the latitudinal variation of hc by ignoring the role of Bθ component and averaging Br and Bφ over all solar longitudes. This approach significantly strengthens the evidence of the hemispheric rule presented in the reconstructed vector magnetic field. Our study shows that the established hemispheric sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere, is applicable everywhere in the global magnetic field, namely, also evident in weak fields outside active regions, and that the obtained sign pattern is independent of the longitudinal magnetograms and the parameters that we have used.

Helicity conservation in magnetic reconnection

TAYLOR postulated that the total magnetic helicity is approximately conserved in a highly conductive plasma for resistive dissipation is limited to local regions in it. Using such a postu-

Scale Effects on Magnet Systems of Heliotron-Type Reactors

For power plants heliotron-type reactors have attractive advantages, such asno current-disruptions, no current-drive, and wide space between helical coils for the maintenanceof in-vessel components. However, one disadvantage is that a major radius has to be large enough toobtain large Q-value or to produce sufficient space for blankets. Although the larger radius isconsidered to increase the construction cost, the influence has not been understood clearly, yet.Scale effects on superconducting magnet systems have been estimated under the conditions of aconstant energy confinement time and similar geometrical parameters. Since the necessary magneticfield with a larger radius becomes lower, the increase rate of the weight of the coil support to themajor radius is less than the square root. The necessary major radius will be determined mainly bythe blanket space. The appropriate major radius will be around 13 m for a reactor similar to theLarge Helical Device (LHD).

Law of Universal Magnetism, <i>F</i>= <i>k_e</i>×<i>H</i>

A new universal equation using planet magnetic pole strength is presented and given reasoning for its assemblage. Coulomb’s Constant, normally used in calculating electrostatic force is utilized in a new magnetic dipole equation for the first time, along with specific orbital energy. Results were generated for five planets that give insight into specific orbital energy as an energy constant for differing planets based on gravitational potential at the surface of a planet. Specific energy can be evaluated as both energy per unit volume (J/kg) and/or specific orbital energy (m2/s2). Due to a multitude of terms that lead to confusion it is recommended that the IEEE standards committee review specific orbital energy SI units for m2/s2. The magic number for cyclonic “lift off”, or anti-gravity, is calculated to be ∈ = 148 m2/s2 the value at which a classical law of magnetism appears as F = ke × H.

Theory of Electromagnetism and Gravity —Modeling Earth as a Rotating Solenoid Coil

Presented in this manuscript are conventional electrical engineering tools to model the earth as a rotating electrical machine. Calculations using known parameters of the earth and measured field data has resulted in new understanding of the earth’s electrical system and gyroscopic rotation. The material makeup of the inner earth is better understood based on derived permeability and permittivity constants. The planet has been modeled as simple coils and then as a parallel impedance circuit which has led to fundamental insight into planetary speed control and RLC combination for Schumann Resonance of 7.83 Hz. Torque and Voltage Constants and the inverse Speed Constant are calculated using three methods and all compare favorably with Newton’s Gravitational Constant. A helical resonator is referenced and Schumann’s Resonant ideal frequency is calculated and compared with others idealism. A new theory of gravity based on particle velocity selector at the poles is postulated. Two equations are presented as the needed links between Faraday’s electromagnetism and Newtonian physics. Acceleration and Deceleration of earth is explained as a centripetal governor. A new equation for planetary attraction and the attraction of atomic matter is theorized. Rotation of the earth’s electrical coil is explained in terms of the Richardson effect. Electric power transfer from the sun to the planets is proposed via Flux Transfer Events. The impact of this evolving science of electromagnetic modeling of planets will be magnified as the theory is proven, and found to be useful for future generations of engineers and scientists who seek to discover our world and other planets.

A Three-dimensional Network Topology in 〔Mn(N_3)_2(4,4'-bipy)〕_n,Generated by Self-assembly of ‘Helical-shaped’ Building Block

Compound Mn(N 3) 2(4, 4’ bipy) n having three dimensional structure was obtained with crystallographic data: C 10 H 8N 8Mn ( M r =295.16), tetragonal, space group P4 12 12 1(#99), a=8.220(2), c=16.918(5) , V=1143.1(5) 3, Z=4, D c =1.715 g/cm -3 , μ =11.07 cm -1 , F(000)=596, R=0.042, R w =0.051, for 590 observable reflections. The special topology structure in the compound occurs from the helical chain consisting of the -Mn-N-N-N-Mn’ unit. The value of χ mT decreases with the decreasing of temperature

锥形螺旋微机器人的结构设计与三维运动控制

为模拟微机器人在生物体内执行靶向给药、血管疏通等复杂操作,设计了锥形螺旋微机器人。锥形螺旋微机器人主要由圆柱体头部、锥形螺旋尾部和钕铁硼永磁铁组成。针对锥形螺旋微机器人在低雷诺数液体环境中的三维运动控制需求,基于空间矢量叠加原理设计万向旋转磁场发生装置,通过有限元分析方法对万向旋转磁场发生装置的磁场强度及磁场均匀性进行优化。制作锥形螺旋微机器人,并搭建磁驱动系统,进行锥形螺旋微机器人三维运动控制操控实验,实验结果表明,锥形螺旋微机器人在甘油中的最大运动速度为1 mm/s,能够实现稳定的二维及三维运动控制,并完成穿越迷宫的复杂操作。

Some basic questions on helicity inferred from vector magnetograms

This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magnetographs through two solar cycles, but there is a large dispersion of the fraction of ARs following the HSR. In our sample, there are 50%-78% ARs in solar cycle 22 and 44%-79% ARs in cycle 23 following the HSR. A variation is also found in the fraction of the ARs following the HSR between different instruments even when the same ARs are selected. The difference also exists for the same instrument when the selected ARs are different. There are some differences in the variation of HSR with solar cycle for the individual helicity parameter inferred from different instruments. Factors which influence the correlation of different data sets are analyzed.

Design and Characterization of Magnetically Actuated Helical Swimmers at Submillimeter-scale

Bacteria with helical flagella show an ideal mechanism to swim at low Reynolds number. For application of artificial mi- croswimmers, it is desirable to identify effects of structural and geometrical parameters on the swimming performance. In this study, a double-end helical swimmer is proposed based on the usual single-end helical one to improve the forward-backward motion symmetry, The propulsion model of the artificial helical microswimmer is described. Influences of each helix parameter on the swimming velocity and propulsion efficiency are further analyzed. The optimal design for achieving a maximum propulsion velocity of submillimeter scale swimmers is performed based on some constraints. An experimental setup consisting of three-pair of Helmholtz coils is built for the helical microswimmers. Experiments of microswimmers with several groups of parameters were performed, and the results show the validity of the analysis and design.

Magnetic Actuated Shape-memory Helical Microswimmers with Programmable Recovery Behaviors

Inspired by bacterial flagella in nature,magnetic helical microswimmer is an ideal model to perform complex task in a low Reynolds number environments.Shape Memory Polymers(SMPs)with desirable properties are considered as one of the most preferred options for the development of small-scale robots.However,fabricating and programming strategies are still challenging.Here,we report an approach to fabricate helical microswimmers based on thermoplastic SMP(polylactic acid).Melt-spun polylactic acid fibers containing magnetic particles were enwound to form helical microstructures.Their shape recovery behaviors were programmed by annealing and pre-deformation.Three forms of helical microswimmers(constant-helix-angle conical helix,constant-pitch conical helix,and straight helix)with controlled morphological parameters were tailored.The obtained microswimmers showed 3D locomotion capability under rotating magnetic fields.The maximum swimming velocity of microswimmers was nearly six body lengths per second,and the near-wall swimming of conical helixes along their sharp end exhibited a smaller drift.Moreover,we demonstrated programmed shape-switching processes(spring-like contraction and elongation,coiling and uncoiling)and self-repairing of the microswimmers.As demonstrations of potential applications,tasks of mobile microstent,cargo delivery,and minimally invasive injection were carried out.The multifunctional shape-memory microswimmers have immense potential in a variety of applications.