Auroral hot spots are observed across the Universe at different scales1 and mark the coupling between a surrounding plasma environment and an atmosphere. Within our own Solar System, Jupiter possesses the only resolvable example of this large-scale energy transfer. Jupiter’s northern X-ray aurora is concentrated into a hot spot, which is located at the most poleward regions of the planet’s aurora and pulses either periodically2,3 or irregularly4,5. X-ray emission line spectra demonstrate that Jupiter’s northern hot spot is produced by high charge-state oxygen, sulfur and/or carbon ions with an energy of tens of MeV (refs 4,5,6) that are undergoing charge exchange. Observations instead failed to reveal a similar feature in the south2,3,7,8. Here, we report the existence of a persistent southern X-ray hot spot. Surprisingly, this large-scale southern auroral structure behaves independently of its northern counterpart. Using XMM-Newton and Chandra X-ray campaigns, performed in May–June 2016 and March 2007, we show that Jupiter’s northern and southern spots each exhibit different characteristics, such as different periodic pulsations and uncorrelated changes in brightness. These observations imply that highly energetic, non-conjugate magnetospheric processes sometimes drive the polar regions of Jupiter’s dayside magnetosphere. This is in contrast to current models of X-ray generation for Jupiter9,10. Understanding the behaviour and drivers of Jupiter’s pair of hot spots is critical to the use of X-rays as diagnostics of the wide range of rapidly rotating celestial bodies that exhibit these auroral phenomena.
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W.R.D. thanks N. Achilleos and R. Gray for discussions on Jovian X-rays, J.-U. Ness and R. Gonzalez-Riestra for extensive help with XMM-Newton observations, and particularly P. Rodriguez for assistance in re-framing them to Jupiter-centred coordinates. We also thank S. Badman, B. Bonfond, E. Chané, G. Clark, P. Delamere, R. Ebert, H. Hasegawa, S. Imber, E. Kronberg, P. Lourn, W. Kurth, A. Masters, J. Nichols, A. Otto, C. Paranicas, A. Radioti, J. Reed, E. Roussos, A. Smith and C. Tao for conversations on Jupiter’s aurora at the Vogt/Masters and Jackman/Paranicas ISSI team meetings. W.R.D. is supported by a Science and Technology Facilities Council (STFC) research grant to University College London (UCL), an SAO fellowship to Harvard-Smithsonian Centre for Astrophysics and by European Space Agency (ESA) contract no. 4000120752/17/NL/MH. I.J.R., G.H.J., G.B.-R. and A.J.C. are supported by STFC Consolidated Grant ST/N000722/1 to the Mullard Space Science Laboratory (MSSL). I.J.R. is supported by NERC grants NE/L007495/1, NE/P017150/1 and NE/P017185/1. G.A.G. is supported by a UCL IMPACT studentship and ESA. C.M.J. is supported by a STFC Ernest Rutherford Fellowship ST/L004399/1. M.F.V. is supported by the US National Science Foundation under Award No. 1524651. Z.Y. is a Marie-Curie COFUND postdoctoral fellow at the University of Liege, co-funded by the European Union. G.R.G. thanks Smithsonian Astrophysical Observatory for award GO6-17001A to the Southwest Research Institute. J.A.S. and G.S.O. acknowledge support from NASA to the Jet Propulsion Laboratory, California Institute of Technology. R.C.-C. acknowledges support from Universidad Pontificia Comillas de Madrid-ICAI and Universidad Complutense de Madrid-Facultad de Informática This work is based on observations from the NASA Chandra X-ray Observatory (Observations 18608, 18609 and archival observation 8219) made possible through the HRC grant (NAS8-03060) and observations from the XMM-Newton Observatory (Observations 0781830301 and 0781830601). We thank the Chandra and XMM-Newton Projects for their support in setting up the observations
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Nature Astronomy (2017)