Institute of Geophysics and Meteorology, University of Cologne, Albertus-Magnus-Platz 1, 50923, Cologne, Germany.
Phys Rev Lett. 2009 Oct 16;103(16):165003. doi: 10.1103/PhysRevLett.103.165003. Epub 2009 Oct 14.
To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorov's law approximately k(-5/3) at MHD scales, a approximately k(-2.8) power law at ion scales, and an exponential approximately exp[-sqrt[k(rho)e]] at scales k(rho)e approximately [0.1,1], where rho(e) is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence.
为了研究空间等离子体中磁湍流的普遍性，我们分析了自由太阳风中七个不同等离子体条件下的时间段。在不同频率范围内运行的“Cluster”号飞船上的三台仪器使我们有可能解析高达 300 Hz 的谱。我们表明，谱在 MHD 尺度上大致遵循 Kolmogorov 定律为 k(-5/3)，在离子尺度上为 a 约为 k(-2.8)幂律，在尺度 k(rho)e 约为 [0.1,1]上为指数 exp[-sqrt[k(rho)e]]，其中 rho(e)是电子回旋半径。这是首次在空间等离子体中观测到的指数磁谱，可能表明耗散的开始。我们首次区分了不同空间动力学等离子体尺度的作用，并表明电子拉莫半径在空间等离子体湍流中起着耗散尺度的作用。
