Jupiter's X-ray aurora during UV dawn storms and injections as observed by XMM-Newton, Hubble, and Hisaki

TL;DR

This study uses multiwavelength observations to analyze Jupiter's aurorae, revealing how magnetic reconnection and plasma injections influence X-ray and UV emissions, with implications for understanding magnetospheric dynamics.

Contribution

It provides new insights into the connection between dawn storms, plasma injections, and auroral X-ray and UV emissions through simultaneous multi-instrument observations.

Findings

Dawn storms and injections correlate with increased hard X-ray aurora counts.

Impulsive brightening in the Io plasma torus indicates large-scale plasma injections.

Spectral analysis shows precipitating ions are iogenic, with complex powerlaw continua needed for hard X-ray spectra.

Abstract

We present results from a multiwavelength observation of Jupiter's northern aurorae, carried out simultaneously by XMM-Newton, the Hubble Space Telescope (HST), and the Hisaki satellite in September 2019. HST images captured dawn storms and injection events in the far ultraviolet aurora several times during the observation period. Magnetic reconnection occurring in the middle magnetosphere caused by internal drivers is thought to start the production of those features. The field lines then dipolarize which injects hot magnetospheric plasma from the reconnection site to enter the inner magnetosphere. Hisaki observed an impulsive brightening in the dawnside Io plasma torus (IPT) during the final appearance of the dawn storms and injection events which is evidence that a large-scale plasma injection penetrated the central IPT between 6-9 RJ (Jupiter radii). The extreme ultraviolet aurora brightened and XMM-Newton detected an increase in the hard X-ray aurora count rate, suggesting an increase in electron precipitation. The dawn storms and injections did not change the brightness of the soft X-ray aurora and they did not "switch-on" its commonly observed quasi-periodic pulsations. Spectral analysis of the X-ray aurora suggests that the precipitating ions responsible for the soft X-ray aurora were iogenic and that a powerlaw continuum was needed to fit the hard X-ray part of the spectra. The spectra coincident with the dawn storms and injections required two powerlaw continua to get good fits.