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Observation and Origin of the Hard Non-thermal X-ray Emission from Jupiter's Aurorae

Presentation #110.67 in the session “Stellar/Compact (Poster)”.

Published onApr 01, 2022
Observation and Origin of the Hard Non-thermal X-ray Emission from Jupiter's Aurorae

We report the detection of hard (> 10 keV) X-ray emission from Jupiter with the Nuclear Spectroscopic Telescope Array (NuSTAR). NuSTAR is the first and only hard X-ray telescope with sufficient angular resolution to resolve the northern and southern auroral regions of the giant planet. Our NuSTAR observation campaign was conducted from 2015 to 2018 and included a total exposure of 600 ksec. These observations coincided with several Juno perijoves, and were coordinated with the Chandra and XMM-Newton X-ray telescopes, as well as HST. NuSTAR detected hard X-ray emission from both the north and south aurorae, an extension — and confirmation — of the non-thermal spectral component that had earlier been detected up to 7 keV in XMM-Newton data. Previous observations with the Ulysses spacecraft had only produced an upper limit on the hard X-ray emission. Our broad-band (3-20 keV) X-ray continuum spectra of the Jovian aurorae from NuSTAR, supplemented by the coeval XMM-Newton observations, are well characterized by a power-law model with a very hard photon index (Γ ~0.6) and a spectral cutoff above ~20 keV, consistent with the Ulysses upper limits. Intriguingly, NuSTAR observed brighter hard X-ray emission from the south aurora compared to its counterpart in the north, in contrast to the soft (< 2 keV) X-ray emission, which is brighter in the north aurora. We investigate whether bremsstrahlung emission from the electrons measured in-situ by Juno’s JADE/JEDI instruments can account for the X-ray spectra observed by NuSTAR and XMM-Newton.

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