Jupiter’s X-ray aurora during UV dawn storms and injections as observed byXMM–Newton, Hubble, andHisaki

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.

Identifying the Variety of Jovian X‐Ray Auroral Structures: Tying the Morphology of X‐Ray Emissions to Associated Magnetospheric Dynamics

“…Such dipolarizations of the field in the middle magnetosphere have been found to be associated with injection events found from HST UV observations and can be accompanied by bright dawn storm emissions (Yao et al., 2020). These bright dawn storm emissions have been found to be correlated with a brightening of HXR intensity in the Jovian aurora (Wibisono et al., 2021), likely linked to similar regions of electron bremsstrahlung activity (e.g., Branduardi‐Raymont et al., 2008). However, we note that the CXO interval was 2–3 Jovian rotations after the reconfiguration of the field and showed no concentrated X‐ray emissions in expected the dawn or LLE regions.…”

“…The X-ray dawn region is found to coincide with a portion of the ME and the Io footprint suggesting an association between dawn storms, injections of hot plasma from the middle magnetosphere (e.g., Gerard et al, 1994;Kimura et al, 2017) and bright X-ray populations. Recent work by Wibisono et al (2021) found the intensity of the HXRs to increase during the presence of a dawn storm with reduced activity from the more poleward SXRs, utilizing the energy resolution of XMM-Newton. Dawn storms typically have a duration of at least 1-2 hr (e.g., Ballester et al, 1996), therefore our CML thresholding (spanning an interval of 2.5-3 hr during each Chandra observation) will be sufficient to detect the brightest signatures associated with these events, if any.…”

“…(2021). Other studies have looked at how the HXR are correlated with the more intense UV auroral emissions (Wibisono et al., 2021), such as dawn storms—major enhancements of the UV ME along the dawn arc with a broadening in latitude (Bonfond et al., 2021; Yao et al., 2020).…”

Jupiter's X‐Ray and UV Dark Polar Region

“…Jupiter generates bright and dynamic ultraviolet (UV) and X‐ray aurorae at its poles. Jupiter's UV aurora are typically grouped into four components: (a) footprints of the Galilean satellites (e.g., Bhattacharyya et al., 2018 ; Bonfond et al., 2009 , 2013 ; Hue et al., 2019 ; Szalay et al., 2018 ), (b) the main emission (e.g., Grodent et al., 2008 ), (c) emissions between the satellite footprints and main emission (e.g., Kimura et al., 2015 ; Mauk et al., 2002 ; Wibisono et al., 2021 ; Yao et al., 2020 ), and (d) emissions poleward of the main emissions (e.g., Grodent, 2015 , and references therein). The main focus of this study is those emissions poleward of the main emission.…”

“…This joint observation revealed two key connections between the wavebands: (a) X‐ray bremsstrahlung emissions from precipitating electrons coincide with the UV main emission (Branduardi‐Raymont et al., 2008 ) and (b) X‐ray emissions from precipitating ions coincide with UV flares in the active region (Elsner et al., 2005 ). A recent spectral and timing study of the X‐ray and UV aurora (Wibisono et al., 2021 ) suggested that auroral injection events and dawn storms (Yao et al., 2020 ) may also coincide with an X‐ray bremsstrahlung component. In analyzing the X‐ray, UV, and radio observations from 2007, there was found to be a difference between pulsed/flared X‐ray emissions and a steady “flickering” X‐ray aurorae, with both distinct aurorae produced by precipitating ions (Dunn, Gray, et al., 2020 ).…”