Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Suppressed effective viscosity in the bulk intergalactic plasma


Transport properties, such as viscosity and thermal conduction, of the hot intergalactic plasma in clusters of galaxies are largely unknown. Whereas for laboratory plasmas these characteristics are derived from the gas density and temperature1, such recipes can be fundamentally different for the intergalactic plasma2 owing to a low rate of particle collisions and a weak magnetic field3. In numerical simulations, these unknowns can often be avoided by modelling these plasmas as hydrodynamic fluids4,5,6, even though local, non-hydrodynamic features observed in clusters contradict this assumption7,8,9. Using deep Chandra observations of the Coma Cluster10,11, we probe gas fluctuations in intergalactic medium down to spatial scales where the transport processes should prominently manifest themselves—provided that hydrodynamic models12 with pure Coulomb collision rates are indeed adequate. We do not find evidence of such transport processes, implying that the effective isotropic viscosity is orders of magnitude smaller than naively expected. This indicates either an enhanced collision rate in the plasma due to particle scattering off microfluctuations caused by plasma instabilities2,13,14 or that the transport processes are anisotropic with respect to the local magnetic field15. This also means that numerical models with high Reynolds number appear more consistent with observations. Our results demonstrate that observations of turbulence in clusters16,17 are giving rise to a branch of astrophysics that can sharpen theoretical views on galactic plasmas.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: X-ray image of the Coma Cluster.
Fig. 2: Scale-by-scale comparison of the amplitude of density fluctuations in the Coma Cluster and DNS of hydrodynamic turbulence.
Fig. 3: Constraints on gas viscosity in the Coma Cluster.
Fig. 4: Comparison between velocity amplitudes measured in a sample of galaxy clusters and DNS.

Similar content being viewed by others

Data availability

The observational data analysed in this study are available in NASA’s HEASARC repository ( The analysed and plotted data of this study are available from the corresponding author upon reasonable request.


  1. Spitzer, L. & Härm, R. Transport phenomena in a completely ionized gas. Phys. Rev. 89, 977–981 (1953).

    Article  ADS  Google Scholar 

  2. Schekochihin, A. A. & Cowley, S. C. Turbulence, magnetic fields and plasma physics in clusters of galaxies. Phys. Plasmas 13, 056501 (2006).

    Article  ADS  Google Scholar 

  3. Schekochihin, A. A., Cowley, S. C., Rincon, F. & Rosin, M. S. Magnetofluid dynamics of magnetized cosmic plasma: firehose and gyrothermal instabilities. Mon. Not. R. Astron. Soc. 405, 291–300 (2010).

    ADS  Google Scholar 

  4. Bryan, G. L. & Norman, M. L. Statistical properties of X-ray clusters: analytic and numerical comparisons. Astrophys. J. 495, 80–99 (1998).

    Article  ADS  Google Scholar 

  5. Kravtsov, A. V., Klypin, A. & Hoffman, Y. Constrained simulations of the real universe. II. Observational signatures of intergalactic gas in the local supercluster region. Astrophys. J. 571, 563–575 (2002).

    Article  ADS  Google Scholar 

  6. Dolag, K., Vazza, F., Brunetti, G. & Tormen, G. Turbulent gas motions in galaxy cluster simulations: the role of smoothed particle hydrodynamics viscosity. Mon. Not. R. Astron. Soc. 364, 753–772 (2005).

    Article  ADS  Google Scholar 

  7. Markevitch, M. & Vikhlinin, A. Shocks and cold fronts in galaxy clusters. Phys. Rep. 443, 1–53 (2007).

    Article  ADS  Google Scholar 

  8. Fabian, A. C., Johnstone, R. M. & Sanders, J. S. Magnetic support of the optical emission line filaments in NGC 1275. Nature 454, 968–970 (2008).

    Article  ADS  Google Scholar 

  9. Roediger, E. et al. Stripped elliptical galaxies as probes of ICM physics. I. Tails, wakes, and flow patterns in and around stripped ellipticals. Astrophys. J. 806, 103–121 (2015).

    Article  ADS  Google Scholar 

  10. Churazov, E. et al. X-ray surface brightness and gas density fluctuations in the Coma cluster. Mon. Not. R. Astron. Soc. 421, 1123–1135 (2012).

    Article  ADS  Google Scholar 

  11. Sanders, J. S. et al. Linear structures in the core of the Coma cluster of galaxies. Science 341, 1365–1368 (2013).

    Article  ADS  Google Scholar 

  12. Ishihara, T., Morishita, K., Yokokawa, M., Uno, A. & Kaneda, Y. Energy spectrum in high-resolution direct numerical simulations of turbulence. Phys. Rev. Fluids 1, 082403 (2016).

    Article  ADS  Google Scholar 

  13. Melville, S., Schekochihin, A. A. & Kunz, M. W. Pressure-anisotropy-driven microturbulence and magnetic-field evolution in shearing, collisionless plasma. Mon. Not. R. Astron. Soc. 459, 2701–2720 (2016).

    Article  ADS  Google Scholar 

  14. Kunz, M. W., Schekochihin, A. A. & Stone, J. M. Firehose and mirror instabilities in a collisionless shearing plasma. Phys. Rev. Lett. 112, 205003 (2014).

    Article  ADS  Google Scholar 

  15. Squire, J., Schekochihin, A. A., Quataert, E. & Kunz, M. W. Magneto-immutable turbulence in weakly collisional plasmas. J. Plasma Phys. 85, 905850114 (2019).

    Article  Google Scholar 

  16. Zhuravleva, I. et al. Turbulent heating in galaxy clusters brightest in X-rays. Nature 515, 85–87 (2014).

    Article  ADS  Google Scholar 

  17. Hitomi Collaboration. The quiescent intracluster medium in the core of the Perseus cluster. Nature 535, 117–121 (2016).

    Article  ADS  Google Scholar 

  18. Vikhlinin, A., Forman, W. & Jones, C. Another collision for the Coma cluster. Astrophys. J. 474, L4–L10 (1997).

    Article  ADS  Google Scholar 

  19. Schuecker, P., Finoguenov, A., Miniati, F., Böhringer, H. & Briel, U. G. Probing turbulence in the Coma galaxy cluster. Astron. Astrophys. 426, 387–397 (2004).

    Article  ADS  Google Scholar 

  20. Bonafede, A. et al. The Coma cluster magnetic field from Faraday rotation measures. Astron. Astrophys. 513, A30 (2010).

    Article  Google Scholar 

  21. Arévalo, P., Churazov, E., Zhuravleva, I., Hernández-Monteagudo, C. & Revnivtsev, M. A Mexican hat with holes: calculating low-resolution power spectra from data with gaps. Mon. Not. R. Astron. Soc. 426, 1793–1807 (2012).

    Article  ADS  Google Scholar 

  22. Zhuravleva, I. et al. The relation between gas density and velocity power spectra in galaxy clusters: qualitative treatment and cosmological simulations. Astrophys. J. 788, L13–L18 (2014).

    Article  ADS  Google Scholar 

  23. Gaspari, M. & Churazov, E. Constraining turbulence and conduction in the hot ICM through density perturbations. Astron. Astrophys. 559, A78–A96 (2013).

    Article  ADS  Google Scholar 

  24. Gauding, M., Wick, A., Pitsch, H. & Peters, N. Generalized scale-by-scale energy-budget equations and large-eddy simulations of anisotropic scalar turbulence at various Schmidt numbers. J. Turbul. 15, 857–882 (2014).

    Article  ADS  MathSciNet  Google Scholar 

  25. Sarazin, C. L X-ray Emissions from Clusters of Galaxies (Cambridge Astrophysics Series, Cambridge Univ. Press, 1988).

  26. Zhuravleva, I., Allen, S. W., Mantz, A. & Werner, N. Gas perturbations in the cool cores of galaxy clusters: effective equation of state, velocity power spectra, and turbulent heating. Astrophys. J. 865, 53–68 (2018).

    Article  ADS  Google Scholar 

  27. Riquelme, M. A., Quataert, E. & Verscharen, D. PIC simulations of the effect of velocity space instabilities on electron viscosity and thermal conduction. Astrophys. J. 824, 123–134 (2016).

    Article  ADS  Google Scholar 

  28. Komarov, S., Schekochihin, A. A., Churazov, E. & Spitkovsky, A. Self-inhibiting thermal conduction in a high-β, whistler-unstable plasma. J. Plasma Phys. 84, 905840305 (2018).

    Article  Google Scholar 

  29. Braginskii, S. I. Transport processes in a plasma. Rev. Plasma Phys. 1, 205 (1965).

    ADS  Google Scholar 

  30. Vikhlinin, A., Forman, W. & Jones, C. Mass concentrations associated with extended X-ray sources in the core of the Coma cluster. Astrophys. J. 435, 162–170 (1994).

    Article  ADS  Google Scholar 

  31. Batchelor, G. K. Small-scale variation of convected quantities like temperature in turbulent fluid. Part 1. General discussion and the case of small conductivity. J. Fluid Mech. 5, 113–133 (1959).

    Article  ADS  MathSciNet  Google Scholar 

  32. Finoguenov, A. et al. The X-ray luminosity function of galaxies in the Coma cluster. Astron. Astrophys. 419, 47–61 (2004).

    Article  ADS  Google Scholar 

  33. Yagi, M., Koda, J., Komiyama, Y. & Yamanoi, H. Catalog of ultra-diffuse galaxies in the Coma clusters from Subaru imaging data. Astrophys. J. Suppl. Ser. 225, 11–34 (2016).

    Article  ADS  Google Scholar 

  34. Vikhlinin, A., Markevitch, M., Forman, W. & Jones, C. Zooming in on the Coma cluster with Chandra: compressed warm gas in the brightest cluster galaxies. Astrophys. J. 555, L87–L90 (2001).

    Article  ADS  Google Scholar 

  35. Planck Collaboration. Planck intermediate results. X. Physics of the hot gas in the Coma cluster. Astron. Astrophys. 554, 1–19 (2013).

    Google Scholar 

  36. Zhuravleva, I. et al. Gas density fluctuations in the Perseus cluster: clumping factor and velocity power spectrum. Mon. Not. R. Astron. Soc. 450, 4184–4197 (2015).

    Article  ADS  Google Scholar 

Download references


Support for this work was provided by NASA through Chandra Award Number GO6-17123×, issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. E.C. acknowledges partial support by the Russian Science Foundation grant 19-12-00369. A.A.S. acknowledges partial support by grants from UK STFC and EPSRC and by the Simons Foundation via a Visiting Professorship at NBIA. N.W. is supported by the Lendület LP2016-11 grant awarded by the Hungarian Academy of Sciences.

Author information

Authors and Affiliations



I.Z.: data analysis, interpretation, manuscript preparation, principal investigator of the offset Coma Cluster observations; E.C.: data analysis, interpretation, discussions, manuscript preparation; A.A.S.: interpretation, discussions, manuscript preparation; S.W.A., A.V., N.W.: discussions and manuscript review.

Corresponding author

Correspondence to I. Zhuravleva.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–16 and refs 1–4.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Zhuravleva, I., Churazov, E., Schekochihin, A.A. et al. Suppressed effective viscosity in the bulk intergalactic plasma. Nat Astron 3, 832–837 (2019).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing