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Birkeland currents in Jupiter’s magnetosphere observed by the polar-orbiting Juno spacecraft

Abstract

The exchange of energy and momentum between the Earth’s upper atmosphere and ionosphere, and its space environment (magnetosphere) is regulated by electric currents (called Birkeland currents) flowing along magnetic field lines that connect these two regions of space1. The associated electric currents flow towards and away from each pole primarily in two concentric conical sheets2. It has been expected that powerful sheets of magnetic-field-aligned electric currents would be found in association with the bright Jovian auroras3. The Juno spacecraft is well positioned to explore Jupiter’s polar magnetosphere and sample Birkeland or field-aligned currents and particle distributions. Since July 2016, Juno has maintained a near-polar orbit, passing over both polar regions every 53 days. From this vantage point, Juno’s complement of science instruments gathers in situ observations of magnetospheric particles and fields while its remote-sensing infrared and ultraviolet spectrographs and imagers map auroral emissions4. Here we present an extensive analysis of magnetic field perturbations measured during Juno’s transits of Jupiter’s polar regions, and thereby demonstrate Birkeland currents associated with Jupiter’s auroral emissions. We characterize the magnitude and spatial extent of the currents and we find that they are weaker than anticipated and filamentary in nature. A significant asymmetry is observed between the field perturbations and the current associated with the northern and the southern auroras.

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Data availability

The Juno magnetometer data used in this study will be made available through the NASA Planetary Data System (https://pds.nasa.gov) in accordance with NASA policy.

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The authors declare no competing interests.

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References

  1. 1.

    Birkeland, K. The Norwegian Aurora Polaris Expedition 1902–1903 Vol. 1 (H. Aschelhoug & Co., 1908).

  2. 2.

    Potemra, T. A. Birkeland currents in the Earth’s magnetosphere. Astrophys. Space Sci. 144, 155–169 (1988).

  3. 3.

    Connerney, J. E. P. et al. Jupiter’s magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits. Science 356, 826–832 (2017).

  4. 4.

    Bagenal, F. et al. Magnetospheric science objectives of the Juno mission. Space Sci. Rev. 213, 219–287 (2017).

  5. 5.

    Gladstone, G. R. et al. The ultraviolet spectrograph on NASA’s Juno mission. Space Sci. Rev. 213, 447–473 (2017).

  6. 6.

    Bonfond, B. et al. Morphology of the UV aurorae Jupiter during Juno’s first perijove observations. Geophys. Res. Lett. 44, 4463–4471 (2017).

  7. 7.

    Connerney, J. E. P. et al. A new model of Jupiter’s magnetic field from Juno’s first nine orbits. Geophys. Res. Lett. 45, 2590–2596 (2018).

  8. 8.

    Connerney, J. E. P., Acua, M. H. & Ness, N. F. Modeling the Jovian current sheet and inner magnetosphere. J. Geophys. Res. Space Phys. 86, 8370–8384 (1981).

  9. 9.

    Lühr, H., Warnecke, F., Jórg, K. A. & Rother, M. An algorithm for estimating field-aligned currents from single spacecraft magnetic field measurements: a diagnostic tool applied to Freja satellite data. IEEE Trans. Geosci. Remote Sens. 34, 1369–1376 (1996).

  10. 10.

    Hoffman, R. A., Fujii, R. & Sugiura, M. Characteristics of the field-aligned current system in the nighttime sector during auroral substorms. J. Geophys. Res. Space Phys. 99, 21303–21325 (1994).

  11. 11.

    Kurth, W. S. et al. The Juno waves investigation. Space Sci. Rev. 213, 347–392 (2017).

  12. 12.

    McComas, D. J. et al. The Jovian Auroral Distributions Experiment (JADE) on the Juno mission to Jupiter. Space Sci. Rev. 213, 547–643 (2017).

  13. 13.

    Mauk, B. H. et al. The Jupiter Energetic Particle Detector Instrument (JEDI) investigation for the Juno mission. Space Sci. Rev. 213, 289–346 (2017).

  14. 14.

    Chaston, C. C. et al. The turbulent Alfvénic aurora. Phys. Rev. Lett. 100, 175003 (2008).

  15. 15.

    Mauk, B. H. et al. Discrete and broadband electron acceleration in Jupiter’s powerful aurora. Nature 549, 66–69 (2017).

  16. 16.

    Saur, J., Annick, P. & William, M. H. An acceleration mechanism for the generation of the main auroral oval on Jupiter. Geophys. Res. Lett. 30, 1260 (2003).

  17. 17.

    Saur, J. et al. Wave-particle interaction of Alfvén waves in Jupiter’s magnetosphere: auroral and magnetospheric particle acceleration: wave-particle interaction in Jupiter’s magnetosphere. J. Geophys. Res. Space Phys. 123, 9560–9573 (2018).

  18. 18.

    Mauk, B. H. et al. Diverse electron and ion acceleration characteristics observed over Jupiter’s main aurora. Geophys. Res. Lett. 45, 1277–1285 (2018).

  19. 19.

    Chaston, C. et al. Turbulent heating and cross-field transport near the magnetopause from THEMIS. Geophys. Res. Lett. 35, L17S08 (2008).

  20. 20.

    Moore, K. M. et al. A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field. Nature 561, 76–78 (2018).

  21. 21.

    Parish, J. L., Goertz, C. K. & Thomsen, M. F. Azimuthal magnetic field at Jupiter. J. Geophys. Res. 85, 4152–4156 (1980).

  22. 22.

    Connerney, J. E. P. Comment on ‘Azimuthal magnetic field at Jupiter’ by J. L. Parish, C. K. Goertz, and M. F. Thomsen. J. Geophys. Res. Space Phys. 86, 7796–7797 (1981).

  23. 23.

    Khurana, K. K. Influence of solar wind on Jupiter’s magnetosphere deduced from currents in the equatorial plane. J. Geophys. Res. Space Phys. 106, 25999–26016 (2001).

  24. 24.

    Cowley, S. & Bunce, E. Origin of the main auroral oval in Jupiter’s coupled magnetosphere–ionosphere system. Planet. Space Sci. 49, 1067–1088 (2001).

  25. 25.

    Ray, L. C., Ergun, R. E., Delamere, P. A. & Bagenal, F. Magnetosphere–ionosphere coupling at Jupiter: effect of field-aligned potentials on angular momentum transport. J. Geophys. Res. Space Phys. 115, A09211 (2010).

  26. 26.

    Tao, C., Fujiwara, H. & Kasaba, Y. Neutral wind control of the Jovian magnetosphere–ionosphere current system. J. Geophys. Res. Space Phys. 114, A08307 (2009).

  27. 27.

    Iijima, T. & Potemra, T. A. Large-scale characteristics of field-aligned currents associated with substorms. J. Geophys. Res. Space Phys. 83, 599–615 (1978).

  28. 28.

    Moen, J. & Brekke, A. On the importance of ion composition to conductivities in the auroral ionosphere. J. Geophys. Res. Space Phys. 95, 10687–10693 (1990).

  29. 29.

    Garcia, D. Robust smoothing of gridded data in one and higher dimensions with missing values. Comput. Stat. Data Anal. 54, 1167–1178 (2010).

  30. 30.

    Connerney, J. E. P. et al. The Juno magnetic field investigation. Space Sci. Rev. 213, 39–138 (2017).

  31. 31.

    Lam, H. A. et al. A baseline spectroscopic study of the infrared auroras of Jupiter. Icarus 127, 379–393 (1997).

  32. 32.

    Hinson, D. P. et al. Jupiter’s ionosphere: results from the first Galileo radio occultation experiment. Geophys. Res. Lett. 24, 2107–2110 (1997).

  33. 33.

    Ridley, A. J. Effects of seasonal changes in the ionospheric conductances on magnetospheric field-aligned currents. Geophys. Res. Lett. 34, L05101 (2007).

  34. 34.

    Dessler, A. J. in Physics Of The Jovian Magnetosphere (ed. Dessler, A. J.) 498–504 (Cambridge Planetary Science Old, 1983).

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Acknowledgements

S.K. thanks F. Bagenal for the motivation and valuable scientific discussions in relation to this paper. All authors acknowledge support from the Juno project. E.J.B. was supported by STFC grant ST/N000749/1 and a Royal Society Wolfson Research Merit Award.

Author information

S.K. wrote the manuscript and performed the magnetic field data analysis. J.E.P.C. contributed to the discussions of the data analysis and assisted with the writing of the manuscript. G.C. and F.A. performed the data analysis of the JEDI and JADE instruments and contributed to Fig. 3 of the manuscript. G.R.G. performed the data analysis of the UVS instrument and contributed to Fig. 1 of the manuscript. W.S.K. performed the data analysis of the Waves instrument and contributed to Supplementary Fig. 2 of the manuscript. D.J.G. contributed to the magnetic field data calibration and the discussions of the data analysis. B.H.M., T.K.G and Y.M.M. contributed to the discussions of the data analysis. J.S. and E.J.B. contributed to the discussions of the physics of the Birkeland currents and the data analysis. S.J.B. is the principal investigator of the mission and S.M.L. is the project scientist of the mission.

Competing interests

The authors declare no competing interests.

Correspondence to Stavros Kotsiaros.

Supplementary information

Supplementary Information

Supplementary Figs. 1–3 and Supplementary reference 1.

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Fig. 1: Magnetic field perturbations associated with Jupiter’s aurora.
Fig. 2: Models of Birkeland currents.
Fig. 3: Magnetic field perturbations and electron observations.
Fig. 4: Birkeland current system and current intensities.