阿尔文波

阿尔文波，又称剪切阿尔文波，是等离子体中的一种沿磁场方向传播的波，这种波的频率远低于等离子体的回旋频率，是一种线偏振的低频横波。处在磁场中的导电流体在垂直于磁场的方向上受到局部扰动时，沿着磁感线方向的磁张力提供恢复力，就会激发阿尔文波。阿尔文波是由瑞典物理学家汉尼斯·阿尔文首先预言的，因此得名。后来隆德奎斯特（Lundquist）使用1特斯拉左右的磁场在水银中观察到了阿尔文波，列纳尔特（Lehnert）使用液态钠也证实了阿尔文波的存在。

运动的阿尔文波。

A cluster of double layers forming in an Alfvén wave, about a sixth of the distance from the left.
图例:
红色=electrons
绿色=ions
黄色=electric potential
橙色=parallel electric field
粉色=charge density
蓝色=magnetic field

阿尔文波的色散关系为：

${\displaystyle \omega ^{2}=k^{2}v_{A}^{2}\cos ^{2}\theta }$

这样的波称为斜阿尔文波。θ=0时是沿着磁感线的方向传播的，称为阿尔文波。此时阿尔文波的相速度为：

${\displaystyle v_{A}={\frac {B}{\sqrt {\mu _{0}\rho _{0}}}}}$

称为阿尔文速度，其中μ₀是等离子体的磁导率，ρ₀是离子的密度。在垂直于磁感线的方向上阿尔文波不能传播。

阿尔文时间

在等离子体物理中, 阿尔文时间${\displaystyle \tau _{A}}$ 是波动现象的一个重要时标。它和阿尔文速度的关系为：

${\displaystyle \tau _{A}={\frac {a}{v_{A}}}}$ 

式中${\displaystyle a}$  代表了系统的特征尺度。例如，${\displaystyle a}$  是托卡马克中较小的环的半径。

参见

• 压缩阿尔文波

延伸阅读

• Alfvén, H., Existence of electromagnetic-hydrodynamic waves, Nature, 1942, 150 (3805): 405–406, Bibcode:1942Natur.150..405A, doi:10.1038/150405d0 
• Alfvén, H., Cosmic Plasma, Holland: Reidel, 1981, ISBN 90-277-1151-8 
• Aschwanden, M. J.; Fletcher, L.; Schrijver, C. J.; Alexander, D., Coronal Loop Oscillations Observed with the Transition Region and Coronal Explorer, The Astrophysical Journal, 1999, 520 (2): 880–894, Bibcode:1999ApJ...520..880A, doi:10.1086/307502 
• Berthold, W. K.; Harris, A. K.; Hope, H. J., World-Wide Effects of Hydromagnetic Waves Due to Argus, Journal of Geophysical Research, 1960, 65 (8): 2233–2239, Bibcode:1960JGR....65.2233B, doi:10.1029/JZ065i008p02233 
• Bostick, Winston H.; Levine, Morton A., Experimental Demonstration in the Laboratory of the Existence of Magneto-Hydrodynamic Waves in Ionized Helium, Physical Review, 1952, 87 (4): 671, Bibcode:1952PhRv...87..671B, doi:10.1103/PhysRev.87.671 
• Coleman, P. J., Jr.; Sonett, C. P.; Judge, D. L.; Smith, E. J., Some Preliminary Results of the Pioneer V Magnetometer Experiment, Journal of Geophysical Research, 1960, 65 (6): 1856–1857, Bibcode:1960JGR....65.1856C, doi:10.1029/JZ065i006p01856 
• Cramer, N. F.; Vladimirov, S. V., Alfvén Waves in Dusty Interstellar Clouds, Publications of the Astronomical Society of Australia, 1997, 14 (2): 170–178 [2018-01-05], Bibcode:1997PASA...14..170C, doi:10.1071/AS97170, （原始内容于2008-08-19） 
• Dessler, A. J., Swedish iconoclast recognized after many years of rejection and obscurity, Science, 1970, 170 (3958): 604–606, Bibcode:1970Sci...170..604D, PMID 17799293, doi:10.1126/science.170.3958.604 
• Falceta-Gonçalves, D.; Jatenco-Pereira, V., The Effects of Alfvén Waves and Radiation Pressure in Dust Winds of Late-Type Stars, Astrophysical Journal, 2002, 576 (2): 976–981, Bibcode:2002ApJ...576..976F, arXiv:astro-ph/0207342  , doi:10.1086/341794 
• Fermi, E., On the Origin of the Cosmic Radiation, Physical Review, 1949, 75 (8): 1169–1174, Bibcode:1949PhRv...75.1169F, doi:10.1103/PhysRev.75.1169 
• Galtier, S., A weak turbulence theory for incompressible magnetohydrodynamics, J. Plasma Physics, 2000, 63 (5): 447–488, Bibcode:2000JPlPh..63..447G, arXiv:astro-ph/0008148  , doi:10.1017/S0022377899008284 
• Hollweg, J. V., Hydromagnetic waves in interplanetary space, Publications of the Astronomical Society of the Pacific, 1974, 86 (October 1974): 561–594, Bibcode:1974PASP...86..561H, doi:10.1086/129646 
• Ip, W.-H.; Mendis, D. A., The cometary magnetic field and its associated electric currents, Icarus, 1975, 26 (4): 457–461, Bibcode:1975Icar...26..457I, doi:10.1016/0019-1035(75)90115-3 
• Jephcott, D. F., Alfvén waves in a gas discharge, Nature, 1959, 183 (4676): 1652–1654, Bibcode:1959Natur.183.1652J, doi:10.1038/1831652a0 
• Lehnert, Bo, Magneto-Hydrodynamic Waves in Liquid Sodium, Physical Review, 1954, 94 (4): 815–824, Bibcode:1954PhRv...94..815L, doi:10.1103/PhysRev.94.815 
• Lundquist, S., Experimental Investigations of Magneto-Hydrodynamic Waves, Physical Review, 1949, 76 (12): 1805–1809, Bibcode:1949PhRv...76.1805L, doi:10.1103/PhysRev.76.1805 
• Mancuso, S.; Spangler, S. R., Coronal Faraday Rotation Observations: Measurements and Limits on Plasma Inhomogeneities, The Astrophysical Journal, 1999, 525 (1): 195–208, Bibcode:1999ApJ...525..195M, doi:10.1086/307896 
• Motz, R. O., Alfven Wave Generation in a Spherical System, Physics of Fluids, 1966, 9 (2): 411–412, Bibcode:1966PhFl....9..411M, doi:10.1063/1.1761687 
• Nakariakov, V. M.; Ofman, L.; Deluca, E. E.; Roberts, B.; Davila, J. M., TRACE observation of damped coronal loop oscillations: Implications for coronal heating, Science, 1999, 285 (5429): 862–864, Bibcode:1999Sci...285..862N, PMID 10436148, doi:10.1126/science.285.5429.862 
• Ofman, L.; Wang, T. J., Hinode observations of transverse waves with flows in coronal loops, Astronomy and Astrophysics, 2008, 482 (2): L9–L12, Bibcode:2008A&A...482L...9O, doi:10.1051/0004-6361:20079340 
• Otani, N. F., The Alfvén ion-cyclotron instability, simulation theory and techniques, Journal of Computational Physics, 1988a, 78 (2): 251–277, Bibcode:1988JCoPh..78..251O, doi:10.1016/0021-9991(88)90049-6 
• Otani, N. F., Application of Nonlinear Dynamical Invariants in a Single Electromagnetic Wave to the Study of the Alfvén-Ion-Cyclotron Instability, Physics of Fluids, 1988b, 31 (6): 1456–1464, Bibcode:1988PhFl...31.1456O, doi:10.1063/1.866736 
• Parker, E. N., Hydromagnetic Waves and the Acceleration of Cosmic Rays, Physical Review, 1955, 99 (1): 241–253, Bibcode:1955PhRv...99..241P, doi:10.1103/PhysRev.99.241 
• Parker, E. N., Suprathermal Particle Generation in the Solar Corona, Astrophysical Journal, 1958, 128: 677, Bibcode:1958ApJ...128..677P, doi:10.1086/146580 
• Parker, E. N., Extragalactic Cosmic Rays and the Galactic Magnetic Field, Astrophysics and Space Science, 1973, 24 (1): 279–288, Bibcode:1973Ap&SS..24..279P, doi:10.1007/BF00648691 
• Silberstein, M.; Otani, N. F., Computer simulation of Alfvén waves and double layers along auroral magnetic field lines (PDF), Journal of Geophysical Research, 1994, 99 (A4): 6351–6365 [2018-01-05], Bibcode:1994JGR....99.6351S, doi:10.1029/93JA02963, （原始内容 (PDF)于2005-05-09） 
• Sugiura, Masahisa, Some Evidence of Hydromagnetic Waves in the Earth's Magnetic Field, Physical Review Letters, 1961, 6 (6): 255–257, Bibcode:1961PhRvL...6..255S, doi:10.1103/PhysRevLett.6.255 
• Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.; Schad, T.; Seeley, D. H.; Edmondson, J., Waves in the Solar Corona, Science, 2007, 317 (5842): 1192–1196, Bibcode:2007Sci...317.1192T, doi:10.1126/science.1143304 
• Van Doorsselaere, T.; Nakariakov, V. M.; Verwichte, E., Detection of Waves in the Solar Corona: Kink or Alfvén?, The Astrophysical Journal, 2008, 676 (1): L73–L75, Bibcode:2008ApJ...676L..73V, doi:10.1086/587029 
• Vasheghani Farahani, S.; Van Doorsselaere, T.; Verwichte, E.; Nakariakov, V. M., Propagating transverse waves in soft X-ray coronal jets, Astronomy and Astrophysics, 2009, 498 (2): L29–L32, Bibcode:2009A&A...498L..29V, doi:10.1051/0004-6361/200911840 
• Jess, David B.; Mathioudakis, Mihalis; Erdélyi, Robert; Crockett, Philip J.; Keenan, Francis P.; Christian, Damian J., Alfvén Waves in the Lower Solar Atmosphere, Science, 2009, 323: 1582, Bibcode:2009Sci...323.1582J, arXiv:0903.3546  , doi:10.1126/science.1168680 
• Srivastava, Abhishek K.; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N., High-frequency torsional Alfvén waves as an energy source for coronal heating, Nature Scientific Reports, 2017, 7: id.43147, Bibcode:2017NatSR...743147S, doi:10.1038/srep43147