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Experimental measurements of the propagation of large-amplitude shear Alfven waves

机译：大振幅剪切阿尔夫文波传播的实验测量

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Experiments on the edge plasma of tokamaks have discovered magnetic fluctuations which are highly correlated along the magnetic field, and are correlated with scale size of the electron inertial length (delta = c/omega (pe)) across the field. They are, in all probability, shear Alfven waves. The FREJA, FAST, and Interball satellites have frequently encountered density striations in the auroral ionosphere. These can be narrow, also of the order of delta. Intense wave activity has been measured within these structures and tentatively identified as shear inertial (V-A > V-the) Alfven waves. These waves have been studied in great derail in the Large Plasma Device at UCLA. The plasma, which is 10 m in length and 500 ion Larmor radii in diameter (He (lambda (parallel to) approximate to 2 m), Ar (lambda (parallel to) approximate to 10 m, 1.5 kG, 40 cm plasma diameter, n = 1.0-4.0 x 10(12) cm(-3), fully ionized) supports Alfven waves. Our initial investigations, which will be briefly reviewed, involved low-amplitude (deltaB(wave)/B-0 approximate to 10(-4)) shear waves launched by modulating a skin depth size current channel, and have examined the wave characteristics in the kinetic (V-A < V-the) and inertial regimes and in magnetic field gradients. Launching higher-power waves (B-wave/B-0 greater than or equal to 10(-3)) waves with the use of a helical antenna has extended these studies. Both shear Alfven waves (omega < (ci)) and compressional Alfven waves have been investigated. Below f(cl) the wave fields slowly spread across the background magnetic field and the current associated with it forms a rotating spiral. The higher-power wave causes a localized density perturbation when deltaB(wave)/B-0 exceeds 10(-3) even when the wave propagates below the cyclotron frequency. The perturbation is measured using Langmuir probes as well as laser-induced fluorescence (LIF) signal from Ar II ions. We present data of the wave propagation in which the temporal history of the vector magnetic field was acquired at 20 000 spatial locations. The data is used to calculate 3D wave currents, wave phase fronts and energy propagation. In helium the wave pattern is more complex than in argon. We also present the space and time evolution of the density perturbations associated with the wave in an Ar plasma. LIF data was used to directly measure the ion motion in the electric field of the wave, ion polarization currents and the motion of the ions as they form the density non-uniformities. [References: 28]
机译：在托卡马克的边缘等离子体上进行的实验发现，磁波动沿磁场高度相关，并且与整个场的电子惯性长度的尺度大小有关（δ= c /Ω（pe））。它们很可能是剪切阿尔夫文波。 FREJA，FAST和Interball卫星在极光电离层中经常遇到密度条纹。这些可以很窄，也可以是三角形。已在这些结构中测量了强波活动，并初步确定为剪切惯性（V-A> V-the）Alfven波。在加州大学洛杉矶分校的大型等离子设备中，对这些波进行了大的脱轨研究。等离子体，其长度为10 m，直径为500离子拉莫尔半径（He（λ（平行））约2 m），Ar（lambda（平行）约10 m，1.5 kG，40 cm等离子体直径， n = 1.0-4.0 x 10（12）cm（-3），完全电离）支持Alfven波，我们的初步研究将简要回顾，涉及低振幅（deltaB（wave）/ B-0大约为10（ -4））通过调制趋肤深度大小的电流通道发射的剪切波，并检查了动力学（VA 使用螺旋天线的B波/ B-0大于或等于10（-3）波扩展了这些研究，剪切Alfven波（omega

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