Abstract
Dynamo action refers to energy exchange processes through which magnetic fields are generated at the expense of kinetic energy of the plasma flows. Dynamos can generate magnetic fields across scales larger or smaller than the flows themselves. Multi-scale dynamo processes underpin magnetic phenomena from planetary cores to stellar and galactic environments, while also shaping turbulent magnetic fields at smaller scales. Yet, experimental validation of dynamo action has remained largely confined to laboratories. Here we report evidence for a turbulent dynamo in the terrestrial magnetosheath. Observations reveal the predicted spatial topology of stretched and folded magnetic fields, compressive effects, and pressure anisotropy instabilities essential for magnetic field amplification. Our findings also highlight the central role of turbulent dynamos in energy conversion and structure formation within collisionless plasma turbulence. The observed energy exchange signatures indicate that the magnetosheath may serve as a natural testbed for validating dynamo theories and simulations.
Similar content being viewed by others
Data availability
MMS data are publicly available at https://lasp.colorado.edu/mms/sdc/public/about/browse-wrapper/, where in the folders mms1-4, the magnetic field data are under /fgm/brst/l2/2015/11/30/, and the ion moments data, including velocity, pressure, and temperature, are under fpi/brst/l2/dis-moms/2015/11/30/, and pitch angle data are under fpi/brst/l2/dis-dist/2015/11/30/. Source data are provided with this paper.
Code availability
The estimation of spatial gradients from multi-spacecraft tetrahedron measurements is described in ref. 53 implemented in the software package irfu-matlab, https://github.com/irfu/irfu-matlab. Irfu MATLAB can also be downloaded from Zenodo56. The following functions were applied: c_4_grad.m for calculating divergences, gradients, and curls; mms.rotate_tensor.m for calculating parallel and perpendicular components of the temperature tensor; irf_resamp.m for resampling a quantity onto a timeline of another quantity. The scripts for reproducing the figures are uploaded to Zenodo https://doi.org/10.5281/zenodo.1778077057.
References
Schekochihin, A. A. & Cowley, S. C. Turbulence and magnetic fields in astrophysical plasmas. in Fluid Mechanics and Its Applications: Magnetohydrodynamics—Historical Evolution and Trends (eds Molokov, S., Moreau, R. & Moffatt, H.) Vol. 80, 85–115. https://doi.org/10.1007/978-1-4020-4833-3_6 (Springer, 2007).
Verhille, G., Plihon, N., Bourgoin, M., Odier, P. & Pinton, J.-F. Laboratory dynamo experiments. Space Sci. Rev. 152, 543–564 (2010).
Tzeferacos, P. et al. Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma. Nat. Commun. 9, 591 (2018).
Bott, A. F. A. et al. Time-resolved turbulent dynamo in a laser plasma. Proc. Natl. Acad. Sci. USA. 118, e2015729118 (2021).
Tobias, S. M., Cattaneo, F. & Boldyrev, S. MHD dynamos and turbulence. in Ten Chapters in Turbulence (eds Davidson, P., Kaneda, Y. & Sreenivasan, K.) 351–404 (Cambridge University Press, 2013).
Rincon, F. Dynamo theories. J. Plasma Phys. 85, 855850501 (2019).
Moffatt, K. & Dormy, E. Self-exciting Fluid Dynamos (Cambridge University Press, 2019).
St-Onge, D. & Kunz, M. W. Fluctuation dynamo in a collisionless, weakly magnetized plasma. Astrophys. J. Lett. 863, L25 (2018).
Narita, Y. & Vörös, Z. Evaluation of electromotive force in interplanetary space. Ann. Geophys. 36, 101–106 (2018).
Bourdin, P.-A., Hofer, B. & Narita, Y. Inner structure of CME shock fronts revealed by the electromotive force and turbulent transport coefficients in Helios-2 observations. Astrophys. J. 855, 111 (2018).
Bourdin, P.-A. & Narita, Y. Electromotive field in space and astrophysical plasmas. Rev. Mod. Plasma Phys. 9, 3 (2025).
Narita, Y., Plaschke, F. & Vörös, Z. The magnetosheath. in Space Physics and Aeronomy Collection Volume 2: Magnetospheres in the Solar System (eds Maggiolo, R., André, N., Hasegawa, H. & Welling, D.) Vol. 259, 137–152. AGU Geophysical Monograph. https://doi.org/10.1002/9781119815624.ch9 (John Wiley & Sons, Inc., 2021).
Burch, J. L., Moore, T. E., Torbert, R. B. & Giles, B. L. Magnetospheric multiscale overview and science objectives. Space Sci. Rev. 199, 5–21 (2016).
Mininni, P. D., Gómez, D. O. & Mahajan, S. M. Dynamo action in magnetohydrodynamics and Hall-magnetohydrodynamics. Astrophys. J. 587, 472–481 (2003).
Ryu, C.-M. Turbulence-induced transport dynamo mechanism. Plasma Res. Expr. 3, 035002 (2021).
Meneguzzi, M., Frisch, U. & Pouquet, A. Helical and nonhelical turbulent dynamos. Phys. Rev. Lett. 47, 1060–1064 (1981).
Zeldovich, Y. B., Ruzmaikin, A. A., Molchanov, S. A. & Sokolov, D. D. Kinematic dynamo problem in a linear velocity field. J. Fluid Mech. 144, 1–11 (1984).
Schekochihin, A. A., Cowley, S. C., Taylor, S. F., Maron, J. L. & McWilliams, J. C. Simulations of the small-scale turbulent dynamo. Astrophys. J. 612, 276–307 (2004).
St-Onge, D. A., Kunz, M. W., Squire, J. & Schekochihin, A. A. Fluctuation dynamo in a weakly collisional plasma. J. Plasma Phys. 86, 905860503 (2020).
Tobias, S. M. The turbulent dynamo. J. Fluid Mech. 912, P1 (2021).
Schekochihin, A. A., Maron, J. L., Cowley, S. C. & McWilliams, J. C. The small-scale structure of magnetohydrodynamic turbulence with large magnetic Prandtl numbers. Astrophys. J. 576, 806–813 (2002).
Kulsrud, R. M., Cowley, S. C., Gruzinov, A. V. & Sudan, R. N. Dynamos and cosmic magnetic fields. Phys. Rep. 283, 213–226 (1997).
Santos-Lima, R. et al. Magnetic field amplification and evolution in turbulent collisionless magnetohydrodynamics: an application to the intracluster medium. Astrophys. J. 781, 84 (2014).
Helander, P., Strumik, M. & Schekochihin, A. A. Constraints on dynamo action in plasmas. J. Plasma Phys. 82, 905820601 (2016).
Chew, G. F., Goldberger, M. L. & Low, F. E. The Boltzmann equation and the one-fluid hydromagnetic equations in the absence of particle collisions. Proc. R. Soc. A 236, 112–118 (1956).
Arzamasskiy, L., Kunz, M. W., Squire, J., Quataert, E. & Schekochihin, A. A. Kinetic turbulence in collisionless high-β plasmas. Phys. Rev. X 13, 021014 (2023).
Rincon, F., Califano, F., Schekochihin, A. A. & Valentini, F. Turbulent dynamo in a collisionless plasma. Proc. Natl. Acad. Sci. USA. 113, 3950–3953 (2016).
Vörös, Z., Yordanova, E., Khotyaintsev, Y. V., Varsani, A. & Narita, Y. Energy conversion at kinetic scales in the turbulent magnetosheath. Front. Astron. Space Sci. 6, 60 (2019).
Yordanova, E. et al. Electron scale structures and magnetic reconnection signatures in the turbulent magnetosheath. Geophys. Res. Lett. 43, 5969–5978 (2016).
Vörös, Z. et al. MMS observations of magnetic reconnection in the turbulent magnetosheath. J. Geophys. Res. Space Phys. 122, 11442–11467 (2017).
Yang, Y. et al. Role of magnetic field curvature in magnetohydrodynamic turbulence. Phys. Plasmas 26, 072306 (2019).
Bandyopadhyay, R. et al. In situ measurement of curvature of magnetic field in turbulent space plasmas: a statistical study. Astrophys. J. Lett. 893, L25 (2020).
Hellinger, P., Trávníček, P. M., Kasper, J. C. & Lazarus, A. J. Solar wind proton temperature anisotropy: linear theory and WIND/SWE observations. Geophys. Res. Lett. 33, L09101 (2006).
Samsonov, A. A., Alexandrova, O., Lacombe, C., Maksimovic, M. & Gary, S. P. Proton temperature anisotropy in the magnetosheath: comparison of 3-D MHD modelling with Cluster data. Ann. Geophys. 25, 1157–1173 (2007).
Gary, S. P., Li, H., O’Rourke, S. & Winske, D. Proton resonant firehose instability: temperature anisotropy and fluctuating field constraints. J. Geophys. Res. Space Phys. 103, 14567–14574 (1998).
Galishnikova, A. K., Kunz, M. W. & Schekochihin, A. A. Tearing instability and current sheet disruption in the turbulent dynamo. Phys. Rev. X 12, 041027 (2022).
Hellinger, P. & Trávníček, P. M. Oblique proton fire hose instability in the expanding solar wind: hybrid simulations. J. Geophys. Res. Space Phys. 113, A10109 (2008).
Hasegawa, A. Drift mirror instability in the magnetosphere. Phys. Fluids 12, 2642–2650 (1969).
Yang, Y. et al. Effective viscosity, resistivity and Reynolds number in weakly collisional plasma turbulence. Mon. Not. R. Astron. Soc. 528, 6119–6128 (2024).
Stawarz, J. E. et al. Turbulence-driven magnetic reconnection and the magnetic correlation length: observations from Magnetospheric Multiscale in Earth’s magnetosheath. Phys. Plasmas 29, 012302 (2022).
Yordanova, E., Vaivads, A., André, M., Buchert, S. & Vörös, Z. Magnetosheath plasma turbulence and its spatiotemporal evolution as observed by the Cluster spacecraft. Phys. Rev. Lett. 100, 205003 (2008).
Vörös, Z. et al. How to improve our understanding of solar wind–magnetosphere interactions on the basis of the statistical evaluation of the energy budget in the magnetosheath? Front. Astron. Space Sci. 10, 1163139 (2023).
Svenningsson, I., Yordanova, E., Khotyaintsev, Y., André, M. & Cozzani, G. Classifying the magnetosheath using local measurements from MMS. J. Geophys. Res. Space Phys. 130, e2024JA033272 (2024).
Hadid, L. Z., Sahraoui, F., Galtier, S. & Huang, S. Y. Compressible magnetohydrodynamic turbulence in the Earth’s magnetosheath: estimation of the energy cascade rate using in situ spacecraft data. Phys. Rev. Lett. 120, 055102 (2018).
Sahraoui, F., Hadid, L. & Huang, S. Magnetohydrodynamic and kinetic scale turbulence in the near-Earth space plasmas: a (short) biased review. Rev. Mod. Plasma Phys. 4, 4 (2020).
Koller, F. et al. Stability of the Earth’s dayside magnetosheath: effects of upstream solar wind structures and downstream jets. J. Geophys. Res. Space Phys. 130, e2025JA034098 (2025).
Rakhmanova, L. S., Riazantseva, M. O., Zastenker, G. N. & Yermolaev, Y. I. Large-scale solar wind phenomena affecting the turbulent cascade evolution behind the quasi-perpendicular bow shock. Universe 8, 611 (2022).
Yordanova, E., Vörös, Z., Raptis, S. & Karlsson, T. Current sheet statistics in the magnetosheath. Front. Astron. Space Sci. 7, 2 (2020).
Winarto, H. & Kunz, M. W. Triggering tearing in a forming current sheet with the mirror instability. J. Plasma Phys. 88, 905880210 (2022).
Stawarz, J. E. et al. The interplay between collisionless magnetic reconnection and turbulence. Space Sci. Rev. 220, ARTN 90 (2024).
Matthaeus, W. H. Turbulence in space plasmas: Who needs it? Phys. Plasmas 28, 032306 (2021).
Cassak, P. A., Barbhuiya, M. H. & Weldon, H. A. Pressure–strain interaction. II. Decomposition in magnetic field-aligned coordinates. Phys. Plasmas 29, 122307 (2022).
Chanteur, G. Spatial interpolation for four spacecraft: theory. in Analysis Methods for Multi-Spacecraft Data (eds Paschmann, G. & Daly, P.) 349–370 (ISSI/ESA, 1998).
Roberts, O. W. et al. Estimation of the error in the calculation of the pressure-strain term: application in the terrestrial magnetosphere. J. Geophys. Res. Space Phys. 128, e2023JA031565 (2023).
Yordanova, E., Vörös, Z., Sorriso-Valvo, L., Dimmock, A. P. & Kilpua, E. K. J. A possible link between turbulence and plasma heating. Astrophys. J. 921, 65 (2021).
Khotyaintsev, Y. et al. IRFU-Matlab. Zenodo, https://doi.org/10.5281/zenodo.14525047 (2024).
Vörös, Z. et al. Turbulent dynamo in the terrestrial magnetosheath, ncomms-25-30764a. Zenodo, https://doi.org/10.5281/zenodo.17780770 (2025).
Acknowledgements
The authors thank the MMS team and the MMS Science Data Center for providing high-quality data for this study. This research was funded in part by the Austrian Science Fund (FWF) under 10.55776/PAT9232923. For the purpose of Open-Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission; Z.V. and P.A.B. were also funded by the Austrian Science Fund (FWF) P 37265-N; Y.N. was funded by the German Science Foundation under project number 535057280; E.Y. was funded by the Swedish National Space Agency (SNSA) under grant 2020-00192. The work of C.S.W. was funded by the Austrian Science Fund (FWF) 10.55776/P35954. L.S.-V. was supported by the Swedish Research Council (VR) Research Grant N. 2022-03352, by the project 2022KL38BK. L.S.-V. also acknowledges the projects PRIN/PNRR-H53D23011020001 and PRIN-2022KL38BK, supported by the Italian Ministry of University and Research.
Author information
Authors and Affiliations
Contributions
Z.V. initiated this study, did the analysis, and wrote the paper. O.W.R., Y.N., and P.A.B. gave the initial idea of the LSD in the turbulent solar wind; E.Y. contributed to data preparation and analysis, writing and editing the manuscript. R.N., A.S., D.S., M.W., C.L.S.W., and A.V. contributed to the analysis methods and helped to edit the paper. L.S.V. contributed to the idea of SSD in a turbulent plasma environment. Á.K. contributed conceptual guidance on the turbulent magnetosheath that strengthened the framing of the study.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Consent to publish
All authors give permission to publish the work.
Peer review
Peer review information
Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Source data
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Vörös, Z., Roberts, O.W., Narita, Y. et al. Turbulent dynamo in the terrestrial magnetosheath. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69469-y
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41467-026-69469-y
