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

any planets in our Solar System produce auroral emissions, but none are as large or as powerful as Jupiter’s. The morphology of the gas giant planet’s aurora consists of the bright main UV emission that is produced by atmospheric hydrogen atoms and molecules after they are excited by precipitating electrons. The same population of energetic electrons are also responsible for the hard X-ray (energy > 2 keV) emissions that are found along this main emission (Branduardi-Raymont et al., 2008). Diffuse UV and soft X-ray (energy < 2 keV) auroral emissions are located at higher latitudes. The low energy X-ray aurora arise from high charge state ions charge exchanging with native neutrals and often pulse quasi-periodically with periods of tens of minutes (Gladstone et al., 2002; Jackman et al., 2018; Dunn et al., 2016; Weigt et al., 2020; Wibisono et al., 2020).
Dawn storms appear in the UV aurora as brightenings in the dawn sector main emission that tend to last no longer than one Jupiter rotation. They may be accompanied by enhancements in the dusk sector found in between the main emission and Io footprint which are known as injection events. Previous studies show that magnetic reconnection in Jupiter’s middle magnetosphere results in the dawn storms, while the injection events are a consequence of hot magnetospheric plasma being injected from the middle to the inner magnetosphere (Mauk et al., 2002; Dumont et al., 2018; Haggerty et al., 2019; Yao et al., 2020). Bonfond et al., 2021 demonstrate how dawn storms at Jupiter and substorms at the Earth share similar characteristics.
Here, we report our results from a multiwavelength observation of Jupiter’s northern aurora using data from the Hubble Space Telescope, Hisaki satellite and XMM-Newton to determine how the X-ray aurora responds to the processes that produce dawn storms and injection events. We found that the hard X-ray and UV aurorae brightened when dawn storms were present leading us to the conclusion that more electrons precipitated into Jupiter’s atmosphere, or that those that did precipitate were more energetic when compared to times when the aurora did not have these transient features. The soft X-ray aurora did not follow this behaviour indicating that there is an independency between ion and electron precipitation. We also found that the dawn storms did not ’switch on’ the quasi- periodic pulsations of the ion emissions. Spectral analysis of the X-ray aurora agreed with previous observational and theoretical work that the precipitating ions that produced the soft X-ray aurora throughout the observation period were predominantly from the local environment rather than the solar wind (e.g. Cravens et al., 1995; Dunn et al., 2016; Houston et al., 2020). However, spectra extracted while dawn storms and injection events were present had enhanced bremsstrahlung tails, suggesting that there was a second population of electrons precipitating into Jupiter’s atmosphere at these times.