Bale S D, Kellogg P J, Mozer F S, Horbury T S, Reme H
Department of Physics and Space Sciences Laboratory, University of California, Berkeley, California 94720, USA.
Phys Rev Lett. 2005 Jun 3;94(21):215002. doi: 10.1103/PhysRevLett.94.215002. Epub 2005 Jun 2.
Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show the spectral behavior of classical Kolmogorov fluid turbulence over an inertial subrange and departures from this at short wavelengths, where energy should be dissipated. Here we present the first measurements of the electric field fluctuation spectrum over the inertial and dissipative wave number ranges in a Beta > or approximately = 1 plasma. The k(-5/3) inertial subrange is observed and agrees strikingly with the magnetic fluctuation spectrum; the wave phase speed in this regime is shown to be consistent with the Alfvén speed. At smaller wavelengths krho(i) > or = 1 the electric spectrum is enhanced and is consistent with the expected dispersion relation of short-wavelength kinetic Alfvén waves. Kinetic Alfvén waves damp on the solar wind ions and electrons and may act to isotropize them. This effect may explain the fluidlike nature of the solar wind.
观测发现，太阳风中的磁流体动力学（MHD）湍流在惯性子范围内呈现出经典柯尔莫哥洛夫流体湍流的频谱特性，而在能量应耗散的短波长处则偏离了这一特性。本文首次给出了在β≥1等离子体中，电场涨落频谱在惯性波数范围和耗散波数范围的测量结果。观测到了k^(-5/3)惯性子范围，且与磁涨落频谱惊人地一致；该区域的波相速度与阿尔文速度相符。在较小波长krho(i)≥1时，电频谱增强，与短波长动力学阿尔文波的预期色散关系一致。动力学阿尔文波在太阳风离子和电子上发生阻尼，可能会使其各向同性化。这种效应或许可以解释太阳风的类流体性质。
