Skip to main content

Thank you for visiting nature.com. 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:

Observation and origin of non-thermal hard X-rays from Jupiter

A Publisher Correction to this article was published on 15 March 2022

This article has been updated

Abstract

Electrons accelerated on Earth by a rich variety of wave-scattering or stochastic processes1,2 generate hard, non-thermal X-ray bremsstrahlung up to ~1 MeV (refs. 3,4) and power Earth’s various types of aurorae. Although Jupiter’s magnetic field is an order of magnitude larger than Earth’s, space-based telescopes have previously detected X-rays only up to ~7 keV (ref. 5). On the basis of theoretical models of the Jovian auroral X-ray production6,7,8, X-ray emission in the ~2–7 keV band has been interpreted as thermal (arising from electrons characterized by a Maxwell–Boltzmann distribution) bremsstrahlung5,9. Here we report the observation of hard X-rays in the 8–20 keV band from the Jovian aurorae, obtained with the NuSTAR X-ray observatory. The X-rays fit to a flat power-law model with slope of 0.60 ± 0.22—a spectral signature of non-thermal, hard X-ray bremsstrahlung. We determine the electron flux and spectral shape in the kiloelectronvolt to megaelectronvolt energy range using coeval in situ measurements taken by the Juno spacecraft’s JADE and JEDI instruments. Jovian electron spectra of the form we observe have previously been interpreted as arising in stochastic acceleration, rather than coherent acceleration by electric fields10. We reproduce the X-ray spectral shape and approximate flux observed by NuSTAR, and explain the non-detection of hard X-rays by Ulysses11, by simulating the non-thermal population of electrons undergoing precipitating electron energy loss, secondary electron generation and bremsstrahlung emission in a model Jovian atmosphere. The results highlight the similarities between the processes generating hard X-ray aurorae on Earth and Jupiter, which may be occurring on Saturn, too.

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

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

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

Fig. 1: NuSTAR 8–20 keV image of Jupiter overlaid on a graticule.
Fig. 2: XMM-Newton-EPIC and NuSTAR flux spectra of Jupiter with the simulated spectrum and best-fit thermal bremsstrahlung model.
Fig. 3: JADE and JEDI energy spectra of precipitating electrons for PJ6, PJ7 and PJ12.
Fig. 4: Simulated spectra of X-ray photons escaping from the model atmosphere for three different electron spectra.

Similar content being viewed by others

Data availability

The NuSTAR and XMM-Newton data are archived at NASA’s HEASARC website (https://heasarc.gsfc.nasa.gov). The JEDI, JADE and MAG data are available at the Planetary Data System(https://pds-ppi.igpp.ucla.edu). The magnetic footprint of JUNO is available through the LASP MOP group’s website (https://lasp.colorado.edu/home/mop/missions/juno/trajectory-information/).

Code availability

NuSTAR and XMM-Newton data were analysed by HEASOFT version 6.28 and SAS analysis software version 16.1.0, respectively. GEANT4 is publicly available at https://geant4.web.cern.ch. The simulation and data reduction code is available from the corresponding author upon request.

Change history

References

  1. Li, Z. et al. Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: a quantitative comparison of simulation with observations. Geophys. Res. Lett. 41, 8722–8729 (2014).

    Article  ADS  Google Scholar 

  2. Lorentzen, K. R. et al. Precipitation of relativistic electrons by interaction with electromagnetic ion cyclotron waves. J. Geophys. Res. 105, 5381–5390 (2000).

    Article  ADS  Google Scholar 

  3. Millan, R. M., Lin, R. P., Smith, D. M., Lorentzen, K. R. & McCarthy, M. P. X-ray observations of MeV electron precipitation with a balloon-borne germanium spectrometer. Geophys. Res. Lett. 29, 2194 (2002).

    Article  ADS  Google Scholar 

  4. Foat, J. E. et al. First detection of a terrestrial MeV X-ray burst. Geophys. Res. Lett. 25, 4109–4112 (1998).

    Article  ADS  Google Scholar 

  5. Branduardi-Raymont, G. et al. A study of Jupiter’s aurorae with XMM-Newton. Astron. Astrophys. 463, 761–774 (2007).

    Article  ADS  Google Scholar 

  6. Barbosa, D. D. Bremsstrahlung X rays from Jovian auroral electrons. J. Geophys. Res. 95, 14969–14976 (1990).

    Article  ADS  Google Scholar 

  7. Waite, J. J. H., Boice, D. C., Hurley, K. C., Stern, S. A. & Sommer, M. Jovian Bremsstrahlung X rays: a Ulysses prediction. Geophys. Res. Lett. 19, 83–86 (1992).

    Article  ADS  Google Scholar 

  8. Singhal, R. P., Chakravarty, S. C., Bhardwaj, A. & Prasad, B. Energetic electron precipitation in Jupiter’s upper atmosphere. J. Geophys. Res. 97, 18245–18256 (1992).

    Article  ADS  Google Scholar 

  9. Wibisono, A. D. et al. Temporal and spectral studies by XMM-Newton of Jupiter’s X-ray auroras during a compression event. J. Geophys. Res. Space Phys. 125, e27676 (2020).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  11. Hurley, K., Sommer, M. & Waite, J. H. Upper limits to Jovian hard X radiation from the Ulysses gamma ray burst experiment. J. Geophys. Res. 98, 21217–21220 (1993).

    Article  ADS  Google Scholar 

  12. Harrison, F. A. et al. The Nuclear Spectroscopic Telescope Array (NuSTAR) high-energy X-ray mission. Astrophys. J. 770, 103 (2013). 1301.7307.

    Article  ADS  Google Scholar 

  13. Dunn, W. R. et al. The impact of an ICME on the Jovian X-ray aurora. J. Geophys. Res. Space Phys. 121, 2274–2307 (2016).

    Article  ADS  Google Scholar 

  14. Jackman, C. M. et al. Assessing quasi-periodicities in Jovian X-ray emissions: techniques and heritage survey. J. Geophys. Res. Space Phys. 123, 9204–9221 (2018).

    Article  ADS  MathSciNet  Google Scholar 

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

    Article  ADS  Google Scholar 

  16. Dunn, W. R. et al. The independent pulsations of Jupiter’s northern and southern X-ray auroras. Nat. Astron. 1, 758–764 (2017).

    Article  ADS  Google Scholar 

  17. Kotsiaros, S. et al. Birkeland currents in Jupiter’s magnetosphere observed by the polar-orbiting Juno spacecraft. Nat. Astron. 3, 904–909 (2019).

    Article  ADS  Google Scholar 

  18. Clark, G. et al. Energetic particle signatures of magnetic field-aligned potentials over Jupiter’s polar regions. Geophys. Res. Lett. 44, 8703–8711 (2017).

    Article  ADS  Google Scholar 

  19. Allegrini, F. et al. Electron beams and loss cones in the auroral regions of Jupiter. Geophys. Res. Lett 44, 7131–7139 (2017).

    Article  ADS  Google Scholar 

  20. 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).

    Article  ADS  Google Scholar 

  21. Clark, G. et al. Precipitating electron energy flux and characteristic energies in Jupiter’s main auroral region as measured by Juno/JEDI. J. Geophys. Res. Space Phys. 123, 7554–7567 (2018).

    Article  ADS  Google Scholar 

  22. Agostinelli, S. et al. GEANT4—a simulation toolkit. Nucl. Instrum. Methods Phys. Res. Sect. A 506, 250–303 (2003).

    Article  ADS  Google Scholar 

  23. Atreya, S., Mahaffy, P., Niemann, H., Wong, M. & Owen, T. Composition and origin of the atmosphere of Jupiter—an update, and implications for the extrasolar giant planets. Planet. Space Sci. 51, 105–112 (2003).

    Article  Google Scholar 

  24. Atreya, S. K., Donahue, T. M. & Festou, M. Jupiter: structure and composition of the upper atmosphere. Astrophys. J. Lett. 247, L43–L47 (1981).

    Article  ADS  Google Scholar 

  25. Woodger, L. A. et al. A summary of the BARREL campaigns: technique for studying electron precipitation. J. Geophys. Res. Space Phys. 120, 4922–4935 (2015).

    Article  ADS  Google Scholar 

  26. Saur, J. et al. Anti-planetward auroral electron beams at Saturn. Nature 439, 699–702 (2006).

    Article  ADS  Google Scholar 

  27. Giorgini, J.D. et al. JPL’s On-Line Solar System Data Service. AAS 28, 1158 (1996).

    ADS  Google Scholar 

  28. Abazajian, K. N. et al. The seventh data release of the Sloan Digital Sky Survey. Astrophys. J. Suppl. Ser. 182, 543–558 (2009).

    Article  ADS  Google Scholar 

  29. Wik, D. R. et al. NuSTAR observations of the Bullet Cluster: constraints on inverse Compton emission. Astrophys. J. 792, 48 (2014).

    Article  ADS  Google Scholar 

  30. Scargle, J. D., Norris, J. P., Jackson, B. & Chiang, J. Studies in astronomical time series analysis. VI. Bayesian block representations. Astrophys. J. 764, 167 (2013).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  32. Mauk, B. et al. The Jupiter Energetic Particle Detector Instrument (JEDI) investigation for the Juno mission. Space Sci. Rev. 98, 98– (2013).

    Google Scholar 

  33. Allegrini, F., Wilson, R., Ebert, R. & Loeffler, C. JUNO JADE Calibrated Science Data (NASA Planetary Data System, 2019); https://pds-ppi.igpp.ucla.edu/data/JNO-J_SW-JAD-3-CALIBRATED-V1.0/

  34. JUNO JEDI Jupiter Standard Calibrated Products (NASA Planetary Data System, 2020); https://pds-ppi.igpp.ucla.edu/data/JNO-J-JED-3-CDR-V1.0/

  35. Connerney, J. JUNO Magnetometer Jupiter Archive (NASA Planetary Data System, 2020); https://pds-ppi.igpp.ucla.edu/data/JNO-J-3-FGM-CAL-V1.0/

  36. Acton, C., Bachman, N., Semenov, B. & Wright, E. A look towards the future in the handling of space science mission geometry. Planet. Space Sci. 150, 9–12 (2018).

    Article  Google Scholar 

  37. Allegrini, F. et al. Energy flux and characteristic energy of electrons over Jupiter’s main auroral emission. J. Geophys. Res. Space Phys 125, e2019JA027693 (2020).

    Article  ADS  Google Scholar 

  38. Bonfond, B. et al. Auroral evidence of Io’s control over the magnetosphere of Jupiter. Geophys. Res. Lett 39, L01105 (2012).

    Article  ADS  Google Scholar 

  39. Allison, J. et al. Geant4 developments and applications. IEEE Trans. Nucl. Sci. 53, 270–278 (2006).

    Article  ADS  Google Scholar 

  40. Pandola, L., Andenna, C. & Caccia, B. Validation of the GEANT4 simulation of bremsstrahlung from thick targets below 3 MeV. Nucl. Instrum. Methods Phys. Res B 350, 41–48 (2015).

    Article  Google Scholar 

  41. Livengood, T. A., Strobel, D. F. & Moos, H. W. Long-term study of longitudinal dependence in primary particle precipitation in the north Jovian aurora. J. Geophys. Res. Space Phys 95, 10375–10388 (1990).

    Article  ADS  Google Scholar 

  42. Valek, P. W. et al. Jovian high-latitude ionospheric ions: Juno in situ observations. Geophys. Res. Lett 46, 8663–8670 (2019).

    Article  ADS  Google Scholar 

  43. Ozak, N., Schultz, D. R., Cravens, T. E., Kharchenko, V. & Hui, Y. W. Auroral X-ray emission at Jupiter: depth effects. J. Geophys. Res. Space Phys. 115, A11306 (2010).

    Article  ADS  Google Scholar 

  44. Branduardi-Raymont, G. et al. Spectral morphology of the X-ray emission from Jupiter’s aurorae. J. Geophys. Res. Space Phys. 113, A02202 (2008).

    Article  ADS  Google Scholar 

  45. Paranicas, C. et al. Intervals of intense energetic electron beams over Jupiter’s poles. J. Geophys. Res. Space Phys. 123, 1989–1999 (2018).

    ADS  Google Scholar 

Download references

Acknowledgements

We thank R. Wilson for his help in analysing JADE data. We also thank the MOP group of LASP for their work on Juno’s trajectory and magnetic footprint. We acknowledge D. Wik for his help in analysing NuSTAR background data. Support for this work by K.M. was provided by NASA through NuSTAR Cycle 3 Guest Observer Program grant number NNH16ZDA001N. Support for this work by C.J. at DIAS was supported by the Science Foundation Ireland grant number 18/FRL/6199.

Author information

Authors and Affiliations

Authors

Contributions

K.M., C.H., G.B. and S.M. wrote the manuscript and made large contributions to data analysis and interpretation. G.B. performed the JADE/JEDI data analysis and GEANT4 simulations. S.M. and B.J.H. analysed NuSTAR data. B.G. contributed to NuSTAR data analysis and interpretation. A.G. and W.D. were involved with XMM-Newton data analysis. J.C. and M.N. conducted a feasibility study of NuSTAR observations of Jupiter. G.B.-R., C.J. and L.R. interpreted the analysis results and provided insights into Jovian aurora physics. All authors contributed to discussing the results and commented on the manuscript.

Corresponding author

Correspondence to Kaya Mori.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Astronomy thanks Tomoki Kimura and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

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

Extended data

Extended Data Fig. 1 Altitude Distribution of Escaping X-Rays.

Counts of escaping X-rays as a function of the altitude [km] (which is measured from 1 Rj). The counts drop sharply below h ~ 200 [km] as X-rays are heavily absorbed. The altitude range shown in the plot cover Region 1 and 2 described in the Method. Note that most of escaping X-rays are from Region 1 (h < 430 km).

Extended Data Fig. 2 Magnetic Footprint of Juno for the 12th Peri-jove.

Magnetic footprint of Juno as viewed from above the north (left) and south (right) poles in PJ12. Black ovals represent the UV ovals39. The color bar indicates the net electron counts obtained by JADE across all energy channels and look directions (in logarithmic scale). A region in the Juno orbit (indicated by black), where background counts exceeded signal counts, was removed from our analysis. We obtained coordinates for the auroral ovals and JRM09 magnetic footprint20 from the MOP LASP website. All coordinates are SYS III.

Extended Data Table 1 NuSTAR observations of Jupiter.

NuSTAR observations of Jupiter. aNet count rates in the 3–20 keV band. Both FPMA and FPMB counts are combined. Source and background counts were extracted from an r = 45” circle and an r = 60–75” annular region around the Jovian center, respectively.

Extended Data Table 2 Juno orbits coincident with NuSTAR observations and electron spectral parameters.

Juno orbits coincident with NuSTAR observations and electron spectral parameters. Note: αe is the best-fit spectral index of JADE + JEDI electron spectra in each Juno passage. The last column lists the downward electron flux in the 3keV – 1 MeV band.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Mori, K., Hailey, C., Bridges, G. et al. Observation and origin of non-thermal hard X-rays from Jupiter. Nat Astron 6, 442–448 (2022). https://doi.org/10.1038/s41550-021-01594-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41550-021-01594-8

Search

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