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Jupiter's X‐rays 2007 Part 1: Jupiter's X‐ray Emission During Solar Minimum

Dunn, WR; Branduardi-Raymont, G; Carter-Cortez, V; Campbell, A; Elsner, R; Ness, J-U; Gladstone, GR; ... Achilleos, N; + view all (2020) Jupiter's X‐rays 2007 Part 1: Jupiter's X‐ray Emission During Solar Minimum. Journal of Geophysical Research: Space Physics , 125 (6) , Article e2019JA027219. 10.1029/2019ja027219. Green open access

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Abstract

The 2007‐2009 solar minimum was the longest of the space age. We present the first of two companion papers on Chandra and XMM‐Newton X‐ray campaigns of Jupiter through February‐March 2007. We find that low solar X‐ray flux during solar minimum causes Jupiter's equatorial regions to be exceptionally X‐ray dim (0.21GW at minimum; 0.76GW at maximum). While the Jovian equatorial emission varies with solar cycle, the aurorae have comparably bright intervals at solar minimum and maximum. We apply atomic charge exchange models to auroral spectra and find that iogenic plasma of sulphur and oxygen ions provides excellent fits for XMM‐Newton observations. The fitted spectral S:O ratios of 0.4‐1.3 are in good agreement with in‐situ magnetospheric S:O measurements of 0.3‐1.5, suggesting that the ions that produce Jupiter's X‐ray aurora predominantly originate inside the magnetosphere. The aurorae were particularly bright on Feb 24‐25 and March 8‐9, but these two observations exhibit very different spatial, spectral and temporal behaviour. 24‐25 Feb was the only observation in this campaign with significant hard X‐ray bremsstrahlung from precipitating electrons, suggesting this may be rare. For 8‐9 March, a bremsstrahlung component was absent, but bright oxygen O6+ lines and best‐fit models containing carbon, point to contributions from solar wind ions. This contribution is absent in the other observations. Comparing simultaneous Chandra ACIS and XMM‐Newton EPIC spectra showed that ACIS systematically under‐reported 0.45‐0.6keV Jovian emission, suggesting quenching may be less important for Jupiter's atmosphere than previously thought. We therefore recommend XMM‐Newton for spectral analyses and quantifying opacity/quenching effects.

Type: Article
Title: Jupiter's X‐rays 2007 Part 1: Jupiter's X‐ray Emission During Solar Minimum
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2019ja027219
Publisher version: https://doi.org/10.1029/2019ja027219
Language: English
Additional information: Copyright ©2020. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Keywords: Jupiter, X‐ray, Aurora, Charge Exchange, Solar Cycle, XMM‐Newton
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10094909
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