Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas

被引:288
作者
Karimabadi, H. [1 ]
Roytershteyn, V. [1 ]
Wan, M. [2 ]
Matthaeus, W. H. [2 ]
Daughton, W. [3 ]
Wu, P. [2 ]
Shay, M. [2 ]
Loring, B. [4 ]
Borovsky, J. [5 ]
Leonardis, E. [6 ]
Chapman, S. C. [6 ,7 ]
Nakamura, T. K. M. [3 ]
机构
[1] Univ Calif San Diego, Dept Elect & Comp Engn, La Jolla, CA 92093 USA
[2] Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA
[3] Los Alamos Natl Lab, Los Alamos, NM 87545 USA
[4] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA
[5] Space Sci Inst, Boulder, CO 80301 USA
[6] Univ Warwick, Ctr Fus Space & Astrophys, Coventry CV4 7AL, W Midlands, England
[7] Univ Tromso, Dept Math & Stat, Tomso, Norway
基金
英国工程与自然科学研究理事会; 美国国家科学基金会;
关键词
KELVIN-HELMHOLTZ INSTABILITY; SOLAR-WIND; FIELDS; FLUID; POWER;
D O I
10.1063/1.4773205
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
An unsolved problem in plasma turbulence is how energy is dissipated at small scales. Particle collisions are too infrequent in hot plasmas to provide the necessary dissipation. Simulations either treat the fluid scales and impose an ad hoc form of dissipation (e. g., resistivity) or consider dissipation arising from resonant damping of small amplitude disturbances where damping rates are found to be comparable to that predicted from linear theory. Here, we report kinetic simulations that span the macroscopic fluid scales down to the motion of electrons. We find that turbulent cascade leads to generation of coherent structures in the form of current sheets that steepen to electron scales, triggering strong localized heating of the plasma. The dominant heating mechanism is due to parallel electric fields associated with the current sheets, leading to anisotropic electron and ion distributions which can be measured with NASA's upcoming Magnetospheric Multiscale mission. The motion of coherent structures also generates waves that are emitted into the ambient plasma in form of highly oblique compressional and shear Alfven modes. In 3D, modes propagating at other angles can also be generated. This indicates that intermittent plasma turbulence will in general consist of both coherent structures and waves. However, the current sheet heating is found to be locally several orders of magnitude more efficient than wave damping and is sufficient to explain the observed heating rates in the solar wind. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773205]
引用
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页数:15
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