Events in Physics

Planetary X-ray astronomy provides an insight into the high energy processes that are present in the solar system. While visible light shows us surface topographies and clouds, X-rays reveal where matter is being violently accelerated, heated to millions of degrees, or bombarded by high-energy radiation. Applications of X-ray astronomy in the solar system include studying planetary magnetospheres, probing solar wind interactions, and analysing surface composition analysis. The seminar will provide a summary of how X-rays are used to study these applications and the challenges of using the current generation of X-ray instruments.

Jupiter provides a natural laboratory for the study of charge exchange (CX) processes. The X-ray aurorae have been found to be dominated by ion CX spectral lines from energetic particle precipitation from the outer magnetosphere into the auroral regions of Jupiter (Branduardi-Raymont et al. 2007). Jupiter provides a unique opportunity to study the observed CX spectra and the ion population and conditions that produce them. For example, ion populations have been studied using the Juno Jupiter Energetic Particle Detector (JEDI) instrument (e.g. Haggerty et al. 2017; Clark et al. 2020), along with spectral analysis of the aurora in the X-ray waveband (e.g. Elsner et al. 2005). These CX spectra have rarely been directly compared with the ion populations that produce them.

The study investigates a high signal X-ray spectra from the northern auroral regions of Jupiter using the XMM-Newton X-ray telescope in the energy range 0.24 to 7.00 keV. The spectra are created from fourteen co-added observations of Jupiter taken over a five-year period, giving ~660 ks of reliable observation time. The results show that a good fit is obtained with the ion species and abundances observed by JEDI on the first perijove of the Juno mission. The study investigates potential CX emission lines in the high energy X-ray (1.60 keV – 7.00 keV) range confirming the detection of high charge states of sulphur (S XV) with greater than 5  significance for S XV. This result shows that sulphur ions are precipitating into Jupiter’s northern auroral region with energies up to 30 MeV which aligns well with the presence of megavolt potential drops previously reported (Clarke et al. 2020).