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

Abstract

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, themore » 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.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [2];  [2];  [4];  [5];  [6];  [6];  [3]
  1. Univ. of California, San Diego, CA (United States)
  2. Univ. of Delaware, Newark, DE (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  5. Space Science Inst., Boulder, CO (United States)
  6. Univ. of Warwick, Coventry (United Kingdom)
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1564998
Grant/Contract Number:  
AC05-00OR22725; SC0004662
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 20; Journal Issue: 1; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Physics

Citation Formats

Karimabadi, H., Roytershteyn, V., Wan, M., Matthaeus, W. H., Daughton, W., Wu, P., Shay, M., Loring, B., Borovsky, J., Leonardis, E., Chapman, S. C., and Nakamura, T. K. M. Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas. United States: N. p., 2013. Web. doi:10.1063/1.4773205.
Karimabadi, H., Roytershteyn, V., Wan, M., Matthaeus, W. H., Daughton, W., Wu, P., Shay, M., Loring, B., Borovsky, J., Leonardis, E., Chapman, S. C., & Nakamura, T. K. M. Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas. United States. doi:10.1063/1.4773205.
Karimabadi, H., Roytershteyn, V., Wan, M., Matthaeus, W. H., Daughton, W., Wu, P., Shay, M., Loring, B., Borovsky, J., Leonardis, E., Chapman, S. C., and Nakamura, T. K. M. Wed . "Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas". United States. doi:10.1063/1.4773205. https://www.osti.gov/servlets/purl/1564998.
@article{osti_1564998,
title = {Coherent structures, intermittent turbulence, and dissipation in high-temperature plasmas},
author = {Karimabadi, H. and Roytershteyn, V. and Wan, M. and Matthaeus, W. H. and Daughton, W. and Wu, P. and Shay, M. and Loring, B. and Borovsky, J. and Leonardis, E. and Chapman, S. C. and Nakamura, T. K. M.},
abstractNote = {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.},
doi = {10.1063/1.4773205},
journal = {Physics of Plasmas},
number = 1,
volume = 20,
place = {United States},
year = {2013},
month = {1}
}

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