The impact of an ICME on the Jovian Xâ ray aurora

We report the first Jupiter Xâ ray observations planned to coincide with an interplanetary coronal mass ejection (ICME). At the predicted ICME arrival time, we observed a factor of â ¼8 enhancement in Jupiter’s Xâ ray aurora. Within 1.5Â h of this enhancement, intense bursts of nonâ Io decametric radio emission occurred. Spatial, spectral, and temporal characteristics also varied between ICME arrival and another Xâ ray observation two days later. Gladstone et al. (2002) discovered the polar Xâ ray hot spot and found it pulsed with 45Â min quasiperiodicity. During the ICME arrival, the hot spot expanded and exhibited two periods: 26Â min periodicity from sulfur ions and 12Â min periodicity from a mixture of carbon/sulfur and oxygen ions. After the ICME, the dominant period became 42Â min. By comparing Vogt et al. (2011) Jovian mapping models with spectral analysis, we found that during ICME arrival at least two distinct ion populations, from Jupiter’s dayside, produced the Xâ ray aurora. Auroras mapping to magnetospheric field lines between 50 and 70Â RJ were dominated by emission from precipitating sulfur ions (S7+,â ¦,14+). Emissions mapping to closed field lines between 70 and 120Â RJ and to open field lines were generated by a mixture of precipitating oxygen (O7+,8+) and sulfur/carbon ions, possibly implying some solar wind precipitation. We suggest that the best explanation for the Xâ ray hot spot is pulsed dayside reconnection perturbing magnetospheric downward currents, as proposed by Bunce et al. (2004). The auroral enhancement has different spectral, spatial, and temporal characteristics to the hot spot. By analyzing these characteristics and coincident radio emissions, we propose that the enhancement is driven directly by the ICME through Jovian magnetosphere compression and/or a largeâ scale dayside reconnection event.Key PointsThe arrival of an ICME changes Jupiter’s Xâ ray auroral spectra, spatial, and temporal characteristicsJupiter’s Xâ ray aurora maps to sources in the outer magnetosphere and also to open field linesJupiter’s Xâ ray aurora is produced by two distinct ion populations during the ICMEPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134147/1/jgra52419.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134147/2/jgra52419-sup-0001-supplementary.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134147/3/jgra52419_am.pd