Zonal flows have been measured with several novel Langmuir probe array on the HT-7 tokamak since 2002. The forked probe and its improved generation, the farmer forked probe were designed based on the original idea of ...Zonal flows have been measured with several novel Langmuir probe array on the HT-7 tokamak since 2002. The forked probe and its improved generation, the farmer forked probe were designed based on the original idea of the Reynolds stress triple tips array. In order to measure the radial shearing rate of zonal flows, the pyramid probe was also designed. This paper addresses the technical aspects regarding this new application. Since the zonal flows dynamics is now widely believed crucial to plasma confinement physics, an important application field of Langmuir probe was opened up.展开更多
We will give an overview of results obtained by our reactive fluid model. It is characterised as a fluid model where all moments with sources in the experiment are kept. Furthermore, full account is taken for the high...We will give an overview of results obtained by our reactive fluid model. It is characterised as a fluid model where all moments with sources in the experiment are kept. Furthermore, full account is taken for the highest moments appearing in unexpanded denominators also including full toroidicity. It has been demonstrated that the strength of zonal flows is dramatically larger in reactive fluid closures than in those which involve dissipation. This gives a direct connection between the fluid closure and the level of excitation of turbulence. This is because zonal flows are needed to absorb the inverse cascade in quasi 2D turbulence. This also explains the similarity in structure of the transport coefficients in our model with a reactive closure in the energy equation and models which have a reactive closure because of zero ion temperature such as the Hasegawa-Wakatani model. Our exact reactive closure unifies several well-known features of tokamak experiments such as the L-H transition, internal transport barriers and the nonlinear Dimits upshift of the critical gradient for onset of transport. It also gives transport of the same level as that in nonlinear gyrokinetic codes. Since these include the kinetic resonance this confirms the validity of the thermodynamic properties of our model. Furthermore, we can show that while a strongly nonlinear model is needed in kinetic theory a quasilinear model is sufficient in the fluid description. Thus our quasilinear fluid model will be adequate for treating all relevant problems in bulk transport. This is finally confirmed by the reproduction by the model of the experimental power scaling of the confinement time Te ~ P-2/3. This confirms the validity of our reactive fluid model. This also gives credibility to our ITER simulations including the H-mode barrier. A new result is here, that alpha heating strongly reduces the slope of the H-mode barrier. This should significantly reduce the effects of ELM＇s.展开更多
We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flo...We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.展开更多
An attempt has been made to apply Arnold type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, ...An attempt has been made to apply Arnold type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, the cut-off low and the zonal flow, the relationships of the geostrophic stream function versus the potential vorticity of the observed atmosphere are analyzed, which indicates that Arnold second type nonlinear stability theorem is more relevant to the observed atmosphere than the first one. For both the stable and unstable zonal flows, Arnold second type nonlinear stability criteria are applied to the diagnosis. The primary results show that our analyses correspond well to the evolution of the atmospheric motions. The synoptically stable zonal flows satisfy Arnol′d second type nonlinear stability criteria; while the synoptically unstable ones violate the nonlinear stability criteria.展开更多
Generation of zonal flows by small-scale drift-Alfven modes is investigated by adopting the approach of parametric instability with the electron polarization drift included. The zonal mode can be excited by primary mo...Generation of zonal flows by small-scale drift-Alfven modes is investigated by adopting the approach of parametric instability with the electron polarization drift included. The zonal mode can be excited by primary modes propagating at both electron and ion diamagnetic drift directions in contrast to the assertion in previous studies that only primary modes propagating in the ion diamagnetic drift directions can drive zonal instabilities. Generally, the growth rate of the driven zonal mode is in the same order as that in previous study. However, different from the previous work, the growth rate is no longer proportional to the difference between the diamagnetic drift frequencies of electrons and ions.展开更多
This paper reviews the theoretical foundations of zonal flow, putting emphasis on the linear response function of plasma to the external flow drive. An extension of the theory is made in order to apply it to helical s...This paper reviews the theoretical foundations of zonal flow, putting emphasis on the linear response function of plasma to the external flow drive. An extension of the theory is made in order to apply it to helical systems and to study the properties of the zonal flow in the low frequency range. Further refinement of the theory is made incorporating the orbital effects of particles more precisely, and the role of neoclassical polarization current is identified.展开更多
A linear response function for zonal flows is obtained by solving the gyro-kinetic equation. This is an extension of a previous work which adopted the method of ＂integrating along particle orbit＂ to solve the drift ...A linear response function for zonal flows is obtained by solving the gyro-kinetic equation. This is an extension of a previous work which adopted the method of ＂integrating along particle orbit＂ to solve the drift kinetic equation. The formula derived in this paper is used to calculate the dispersion relation of geodesic acoustic mode, which is then compared with that of the gyro-kinetic analytic formula.展开更多
Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelm...Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This vertical shear of mean flow is to some extent weakened by thermal forcing.展开更多
Inertia-gravity waves play an increasingly important role in the middle atmosphere dynamics. As a result, more attention has been paid to the study of inertia-gravity waves, especially to the middle atmosphere gravity...Inertia-gravity waves play an increasingly important role in the middle atmosphere dynamics. As a result, more attention has been paid to the study of inertia-gravity waves, especially to the middle atmosphere gravity waves. This paper presents some aspects of inertia-gravity waves with emphasis on the propagation. Two methods are used here, namely, geometric optical method and physical optical method. We can see from the study that inertia-gravity waves are similar to planetary waves in some respects and they are different from planetary waves in others.展开更多
The gravity wave breaking is crucial to the large-scale circulation of middle atmosphere. In this paper, we follow Lindzen (1981) to draw out the parameterization of two-dimensional gravity wave breaking including ine...The gravity wave breaking is crucial to the large-scale circulation of middle atmosphere. In this paper, we follow Lindzen (1981) to draw out the parameterization of two-dimensional gravity wave breaking including inertial effect. Also we present some properties of critical levels and inertial critical levels.展开更多
The nonlinear interactions between zonal flow and Rossby waves are studied by numerical simulations with focus on the effects of scalar nonlinearity. The numerical results show that the scalar nonlinearity has an appr...The nonlinear interactions between zonal flow and Rossby waves are studied by numerical simulations with focus on the effects of scalar nonlinearity. The numerical results show that the scalar nonlinearity has an appreciable influence on the Rossby dipole evolution and can reduce the threshold of the disturbance energy increase.展开更多
The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized p...The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition.The energy ratio of the low frequency zonal flow to the total drift wave turbulence is calculated.During ELM-free H mode,the energy ratio is higher than that in L mode,which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.展开更多
Residual zonal flow level is calculated for tokamak plasmas in the neax-separatrix region of a diverted tokamak. A recently developed method is used to construct an analytic divertor tokamak configuration. It is shown...Residual zonal flow level is calculated for tokamak plasmas in the neax-separatrix region of a diverted tokamak. A recently developed method is used to construct an analytic divertor tokamak configuration. It is shown that the residual zonal flow level becomes smaller but still keeps finite near the separatrix because the neoclassical polarisation mostly due to the trapped particles goes larger in this region.展开更多
In this paper, we using phase plane method have derived the stability criteria of linear and nonlinear Rossby waves under the conditions of semi-geostrophic approximation and have gotten the solutions and geostrophic ...In this paper, we using phase plane method have derived the stability criteria of linear and nonlinear Rossby waves under the conditions of semi-geostrophic approximation and have gotten the solutions and geostrophic vorticity of corresponding solitary Rossby waves. It is pointed out that the wave stability is connected with the distribution of zonal flow and when the zonal flow is different the solitary wave trough or ridge is formed.展开更多
Possibility of generation of large-scale sheared zonal flow and magnetic field by coupled under the typical ionospheric conditions short-scale planetary low-frequency waves is shown. Propagation of coupled internal-gr...Possibility of generation of large-scale sheared zonal flow and magnetic field by coupled under the typical ionospheric conditions short-scale planetary low-frequency waves is shown. Propagation of coupled internal-gravity-Alfven, Rossby-Khantadze, Rossby-Alfven-Khantadze and collision-less electron skin depth order drift-Alfven waves is revealed and investigated in detail. To describe the nonlinear interaction of such coupled waves with sheared zonal flow the corresponding nonlinear equations are deduced. The instability mechanism is based on the nonlinear parametric triple interaction of the finite amplitude short-scale planetary waves leading to the inverse energy cascade toward the longer wavelengths. It is shown that under such interaction intense sheared magnetic fields can be generated. Appropriate growth rates are discussed in detail.展开更多
This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions ...This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions where the fluid depth increases or decreases with radius.Three different regimes are found:inertial wave attractor,global oscillations(the cavity’s resonant modes)and regime of symmetric reflection of wave beams.In linear wave regimes,a steady single vortex elongated along the rotation axis is generated.The location of the wave’s interaction with the sloping ends determines the vortex position and the vorticity sign.In non-linear regimes several pairs of the triadic resonance subharmonics are detected simultaneously.The instability of triadic resonance is accompanied by the periodic generation of mean vortices drifting in the azimuthal direction.Moreover,the appearance frequency of the vortices is consistent with the low-frequency subharmonic of the triadic resonance.The experimental results shed light on the mechanisms of the inertial wave interaction with zonal flow and may be useful for the development of new methods of mixing.展开更多
The impact of the mass isotope on plasma conflnement and transport properties has been investigated in Ohmically-heated hydrogen and deuterium plasmas in the HL-2 A tokamak.Experimental results show that under similar...The impact of the mass isotope on plasma conflnement and transport properties has been investigated in Ohmically-heated hydrogen and deuterium plasmas in the HL-2 A tokamak.Experimental results show that under similar discharge parameters the deuterium plasma has better conflnement and lower turbulent transport than the hydrogen one,and concomitantly,it is found that the magnitude of geodesic acoustic mode zonal flows,the tilting angle of the Reynolds stress tensor and the turbulence correlation lengths are all larger in the edge region of the deuterium plasma.The results provide direct experimental evidence on the importance of the nonlinear energy coupling between ambient turbulence and zonal flows for governing the isotope effects in fusion plasmas.展开更多
The isotope effect on zonal flows(ZFs)and turbulence remains a key issue that is not completely solved in fusion plasmas.This paper presents the first experimental results of the ab initio prediction of causal relatio...The isotope effect on zonal flows(ZFs)and turbulence remains a key issue that is not completely solved in fusion plasmas.This paper presents the first experimental results of the ab initio prediction of causal relation between geodesic acoustic mode(GAM)and ambient turbulence at different isotope masses in the edge of HL-2A tokamak,where transfer entropy method based on information-theoretical approach is utilized as a quantified indicator of causality.Analysis shows that GAM is more pronounced in deuterium plasmas than in hydrogen,leading to a lower heat transport as well as more peaked profiles in the former situation.The causal impact of GAM on conductive heat flux component is stronger than on the convective component,which is resulted from a larger causal influence of zonal flow on temperature fluctuation.While a stronger GAM in deuterium plasmas has larger influence on all flux components,the relative change in temperature fluctuation and coefficient is more obvious when the ion mass varies.These findings not only offer an in-depth understanding of the real causality between zonal flow and turbulence in the present isotope experiments,but also provide useful ways for the physical understandings of transport and zonal flow dynamics in future deuterium-tritium fusion plasmas.展开更多
This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transitio...This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transition; （b） the mechanism for subsequent generation of sheared flow. We briefly review recent advances in the understanding of the fast suppression of edge turbulence across the L-H transition. We uncover a comprehensive physical picture of the L-H transition by piecing together a number of recent experimental observations and insights obtained from 1D and 2D simulation models. Different roles played by diamagnetic mean flow, neoclassical-driven mean flow, turbulence-driven mean flow, and turbulence-driven zonal flows are discussed and clarified. It is found that the L-H transition occurs spontaneously mediated by a shift in the radial wavenumber spectrum of edge turbulence, which provides a critical evidence for the theory of turbulence quench by the flow shear. Remaining questions and some key directions for future investigations are proposed.展开更多
Wave-number spectral characteristics of drift wave micro-turbulence with large-scale structures （LSSs） including zonal flows （ZFs） and Kelvin-Holmheltz （KH） mode are investigated based on three dimensional gyrof...Wave-number spectral characteristics of drift wave micro-turbulence with large-scale structures （LSSs） including zonal flows （ZFs） and Kelvin-Holmheltz （KH） mode are investigated based on three dimensional gyrofluid simulations in a slab geometry. The focus is on the property of the wave-number spectral scaling law of the ambient turbulence under the back reaction of the self-generated LSSs. A comparison of the spectral scaling laws between ion/electron temperature gradient （ITG/ETG） driven turbulences is presented. It is shown that the spectral scaling of the ITG turbulence with robust ZFs is fitted well by an exponential-law function （Φ^2/2）E∝e^-λkx in kx and a power-law one in （Φ^2/2）p∝ky^-β in ky. However, the ETG turbulence is characterized by a mixing Kolmogorov-like power-law and exponential-law （Φ^2/2）E∝e-λkx＇yk^-3x,y/（1 ＋ k^2x,y）^2 scaling for both kx and ky spectra due to the ZFs and KH mode dynamics, with λ and β the slope index factors. The underlying physical mechanism is understood as the spectral scattering caused by the back-reaction of the LSSs on the ambient turbulence. These findings may provide helpful guideline to diagnose the plasma fluctuations and flow structures in experiments.展开更多
基金supported by National Natural Science Foundation of China(No.10235010)
文摘Zonal flows have been measured with several novel Langmuir probe array on the HT-7 tokamak since 2002. The forked probe and its improved generation, the farmer forked probe were designed based on the original idea of the Reynolds stress triple tips array. In order to measure the radial shearing rate of zonal flows, the pyramid probe was also designed. This paper addresses the technical aspects regarding this new application. Since the zonal flows dynamics is now widely believed crucial to plasma confinement physics, an important application field of Langmuir probe was opened up.
文摘We will give an overview of results obtained by our reactive fluid model. It is characterised as a fluid model where all moments with sources in the experiment are kept. Furthermore, full account is taken for the highest moments appearing in unexpanded denominators also including full toroidicity. It has been demonstrated that the strength of zonal flows is dramatically larger in reactive fluid closures than in those which involve dissipation. This gives a direct connection between the fluid closure and the level of excitation of turbulence. This is because zonal flows are needed to absorb the inverse cascade in quasi 2D turbulence. This also explains the similarity in structure of the transport coefficients in our model with a reactive closure in the energy equation and models which have a reactive closure because of zero ion temperature such as the Hasegawa-Wakatani model. Our exact reactive closure unifies several well-known features of tokamak experiments such as the L-H transition, internal transport barriers and the nonlinear Dimits upshift of the critical gradient for onset of transport. It also gives transport of the same level as that in nonlinear gyrokinetic codes. Since these include the kinetic resonance this confirms the validity of the thermodynamic properties of our model. Furthermore, we can show that while a strongly nonlinear model is needed in kinetic theory a quasilinear model is sufficient in the fluid description. Thus our quasilinear fluid model will be adequate for treating all relevant problems in bulk transport. This is finally confirmed by the reproduction by the model of the experimental power scaling of the confinement time Te ~ P-2/3. This confirms the validity of our reactive fluid model. This also gives credibility to our ITER simulations including the H-mode barrier. A new result is here, that alpha heating strongly reduces the slope of the H-mode barrier. This should significantly reduce the effects of ELM＇s.
基金Supported by the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics under Grant Nos 11261140328 and 2012K2A2A6000443the ’Thirteenth Five-Year’ Strategic Planning of Chinathe Funds of the Chinese Academy of Sciences and ASIPP
文摘We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.
文摘An attempt has been made to apply Arnold type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, the cut-off low and the zonal flow, the relationships of the geostrophic stream function versus the potential vorticity of the observed atmosphere are analyzed, which indicates that Arnold second type nonlinear stability theorem is more relevant to the observed atmosphere than the first one. For both the stable and unstable zonal flows, Arnold second type nonlinear stability criteria are applied to the diagnosis. The primary results show that our analyses correspond well to the evolution of the atmospheric motions. The synoptically stable zonal flows satisfy Arnol′d second type nonlinear stability criteria; while the synoptically unstable ones violate the nonlinear stability criteria.
基金supported by National Natural Science Foundation of China (No. 10775137)by the Ministry of Science and Technology of China (No. 2009CB105001)partly by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘Generation of zonal flows by small-scale drift-Alfven modes is investigated by adopting the approach of parametric instability with the electron polarization drift included. The zonal mode can be excited by primary modes propagating at both electron and ion diamagnetic drift directions in contrast to the assertion in previous studies that only primary modes propagating in the ion diamagnetic drift directions can drive zonal instabilities. Generally, the growth rate of the driven zonal mode is in the same order as that in previous study. However, different from the previous work, the growth rate is no longer proportional to the difference between the diamagnetic drift frequencies of electrons and ions.
基金supported in part by the JSPS-CAS Core University Program in the field of plasma and nuclear fusion
文摘This paper reviews the theoretical foundations of zonal flow, putting emphasis on the linear response function of plasma to the external flow drive. An extension of the theory is made in order to apply it to helical systems and to study the properties of the zonal flow in the low frequency range. Further refinement of the theory is made incorporating the orbital effects of particles more precisely, and the role of neoclassical polarization current is identified.
基金partially supported by the JSPS-CAS Core-University program in the field of 'Plasma and Nuclear Fusion'
文摘A linear response function for zonal flows is obtained by solving the gyro-kinetic equation. This is an extension of a previous work which adopted the method of ＂integrating along particle orbit＂ to solve the drift kinetic equation. The formula derived in this paper is used to calculate the dispersion relation of geodesic acoustic mode, which is then compared with that of the gyro-kinetic analytic formula.
基金Research Project No.[75-09-01] on medium-range numerical weather forecasts.
文摘Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This vertical shear of mean flow is to some extent weakened by thermal forcing.
文摘Inertia-gravity waves play an increasingly important role in the middle atmosphere dynamics. As a result, more attention has been paid to the study of inertia-gravity waves, especially to the middle atmosphere gravity waves. This paper presents some aspects of inertia-gravity waves with emphasis on the propagation. Two methods are used here, namely, geometric optical method and physical optical method. We can see from the study that inertia-gravity waves are similar to planetary waves in some respects and they are different from planetary waves in others.
文摘The gravity wave breaking is crucial to the large-scale circulation of middle atmosphere. In this paper, we follow Lindzen (1981) to draw out the parameterization of two-dimensional gravity wave breaking including inertial effect. Also we present some properties of critical levels and inertial critical levels.
基金supported by the National Natural Science Foundation of China(Grant No.41175052)
文摘The nonlinear interactions between zonal flow and Rossby waves are studied by numerical simulations with focus on the effects of scalar nonlinearity. The numerical results show that the scalar nonlinearity has an appreciable influence on the Rossby dipole evolution and can reduce the threshold of the disturbance energy increase.
基金the EAST team for their support during the experimentssupported by the National Natural Science Foundation of China with Grant Nos.10990210,10990211,11375188,11105144,and 11375053+1 种基金the National Magnetic Confinement Fusion Science Program of China under Contracts Nos.2013GB106002, 2013GB106003the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology with Grant No.2014FXCX003
文摘The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition.The energy ratio of the low frequency zonal flow to the total drift wave turbulence is calculated.During ELM-free H mode,the energy ratio is higher than that in L mode,which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.
基金supported by the National Natural Science Foundation of China (Grant No.10575037)
文摘Residual zonal flow level is calculated for tokamak plasmas in the neax-separatrix region of a diverted tokamak. A recently developed method is used to construct an analytic divertor tokamak configuration. It is shown that the residual zonal flow level becomes smaller but still keeps finite near the separatrix because the neoclassical polarisation mostly due to the trapped particles goes larger in this region.
文摘In this paper, we using phase plane method have derived the stability criteria of linear and nonlinear Rossby waves under the conditions of semi-geostrophic approximation and have gotten the solutions and geostrophic vorticity of corresponding solitary Rossby waves. It is pointed out that the wave stability is connected with the distribution of zonal flow and when the zonal flow is different the solitary wave trough or ridge is formed.
文摘Possibility of generation of large-scale sheared zonal flow and magnetic field by coupled under the typical ionospheric conditions short-scale planetary low-frequency waves is shown. Propagation of coupled internal-gravity-Alfven, Rossby-Khantadze, Rossby-Alfven-Khantadze and collision-less electron skin depth order drift-Alfven waves is revealed and investigated in detail. To describe the nonlinear interaction of such coupled waves with sheared zonal flow the corresponding nonlinear equations are deduced. The instability mechanism is based on the nonlinear parametric triple interaction of the finite amplitude short-scale planetary waves leading to the inverse energy cascade toward the longer wavelengths. It is shown that under such interaction intense sheared magnetic fields can be generated. Appropriate growth rates are discussed in detail.
基金supported by the Ministry of Education of the Russian Federation(Project KPZU-2023-0002).
文摘This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions where the fluid depth increases or decreases with radius.Three different regimes are found:inertial wave attractor,global oscillations(the cavity’s resonant modes)and regime of symmetric reflection of wave beams.In linear wave regimes,a steady single vortex elongated along the rotation axis is generated.The location of the wave’s interaction with the sloping ends determines the vortex position and the vorticity sign.In non-linear regimes several pairs of the triadic resonance subharmonics are detected simultaneously.The instability of triadic resonance is accompanied by the periodic generation of mean vortices drifting in the azimuthal direction.Moreover,the appearance frequency of the vortices is consistent with the low-frequency subharmonic of the triadic resonance.The experimental results shed light on the mechanisms of the inertial wave interaction with zonal flow and may be useful for the development of new methods of mixing.
基金partially supported by National Natural Science Foundation of China(Nos.11820101004,11875017,12075079 and 51821005)partially supported by the National Key R&D Program of China(No.2019YFE03020000)+2 种基金the National Magnetic Conflnement Fusion Science Program of China(No.2018YFE0310300)the Science and Technology Plan Project in Sichuan Province of China(No.2020YFSY0047)Sichuan International Science and Technology Innovation Cooperation Project(No.2021YFH0066)。
文摘The impact of the mass isotope on plasma conflnement and transport properties has been investigated in Ohmically-heated hydrogen and deuterium plasmas in the HL-2 A tokamak.Experimental results show that under similar discharge parameters the deuterium plasma has better conflnement and lower turbulent transport than the hydrogen one,and concomitantly,it is found that the magnitude of geodesic acoustic mode zonal flows,the tilting angle of the Reynolds stress tensor and the turbulence correlation lengths are all larger in the edge region of the deuterium plasma.The results provide direct experimental evidence on the importance of the nonlinear energy coupling between ambient turbulence and zonal flows for governing the isotope effects in fusion plasmas.
基金supported by the National MCF Energy Research and Development Program(Grant Nos.2024YFE03190001,2024YFE03190004,2022YFE03030001,and 2019YFE03030002)the National Natural Science Foundation of China(Grant Nos.12405257,12475215,and 12475219)+2 种基金the Natural Science Foundation of Sichuan Province,China(Grant Nos.2023NSFSC1289 and 2025ZNSFSC0066)the Nuclear Technology Research and Development Program(Grant No.HJSYF2024(02))the Innovation Program of Southwestern Institute of Physics(Grant No.202301XWCX001)。
文摘The isotope effect on zonal flows(ZFs)and turbulence remains a key issue that is not completely solved in fusion plasmas.This paper presents the first experimental results of the ab initio prediction of causal relation between geodesic acoustic mode(GAM)and ambient turbulence at different isotope masses in the edge of HL-2A tokamak,where transfer entropy method based on information-theoretical approach is utilized as a quantified indicator of causality.Analysis shows that GAM is more pronounced in deuterium plasmas than in hydrogen,leading to a lower heat transport as well as more peaked profiles in the former situation.The causal impact of GAM on conductive heat flux component is stronger than on the convective component,which is resulted from a larger causal influence of zonal flow on temperature fluctuation.While a stronger GAM in deuterium plasmas has larger influence on all flux components,the relative change in temperature fluctuation and coefficient is more obvious when the ion mass varies.These findings not only offer an in-depth understanding of the real causality between zonal flow and turbulence in the present isotope experiments,but also provide useful ways for the physical understandings of transport and zonal flow dynamics in future deuterium-tritium fusion plasmas.
文摘This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transition; （b） the mechanism for subsequent generation of sheared flow. We briefly review recent advances in the understanding of the fast suppression of edge turbulence across the L-H transition. We uncover a comprehensive physical picture of the L-H transition by piecing together a number of recent experimental observations and insights obtained from 1D and 2D simulation models. Different roles played by diamagnetic mean flow, neoclassical-driven mean flow, turbulence-driven mean flow, and turbulence-driven zonal flows are discussed and clarified. It is found that the L-H transition occurs spontaneously mediated by a shift in the radial wavenumber spectrum of edge turbulence, which provides a critical evidence for the theory of turbulence quench by the flow shear. Remaining questions and some key directions for future investigations are proposed.
文摘Wave-number spectral characteristics of drift wave micro-turbulence with large-scale structures （LSSs） including zonal flows （ZFs） and Kelvin-Holmheltz （KH） mode are investigated based on three dimensional gyrofluid simulations in a slab geometry. The focus is on the property of the wave-number spectral scaling law of the ambient turbulence under the back reaction of the self-generated LSSs. A comparison of the spectral scaling laws between ion/electron temperature gradient （ITG/ETG） driven turbulences is presented. It is shown that the spectral scaling of the ITG turbulence with robust ZFs is fitted well by an exponential-law function （Φ^2/2）E∝e^-λkx in kx and a power-law one in （Φ^2/2）p∝ky^-β in ky. However, the ETG turbulence is characterized by a mixing Kolmogorov-like power-law and exponential-law （Φ^2/2）E∝e-λkx＇yk^-3x,y/（1 ＋ k^2x,y）^2 scaling for both kx and ky spectra due to the ZFs and KH mode dynamics, with λ and β the slope index factors. The underlying physical mechanism is understood as the spectral scattering caused by the back-reaction of the LSSs on the ambient turbulence. These findings may provide helpful guideline to diagnose the plasma fluctuations and flow structures in experiments.
