The impact of an ICME on the Jovian X‐ray aurora

Abstract

We report the first Jupiter X‐ray observations planned to coincide with an interplanetary coronal mass ejection (ICME). At the predicted ICME arrival time, we observed a factor of ∼8 enhancement in Jupiter's X‐ray aurora. Within 1.5 h of this enhancement, intense bursts of non‐Io decametric radio emission occurred. Spatial, spectral, and temporal characteristics also varied between ICME arrival and another X‐ray observation two days later. Gladstone et al. (2002) discovered the polar X‐ray hot spot and found it pulsed with 45 min quasiperiodicity. During the ICME arrival, the hot spot expanded and exhibited two periods: 26 min periodicity from sulfur ions and 12 min periodicity from a mixture of carbon/sulfur and oxygen ions. After the ICME, the dominant period became 42 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 X‐ray aurora. Auroras mapping to magnetospheric field lines between 50 and 70 RJ were dominated by emission from precipitating sulfur ions (S7+,…,14+). Emissions mapping to closed field lines between 70 and 120 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 X‐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 large‐scale dayside reconnection event.

Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation

“…We took the simulated X‐ray photon fluxes emitted from the in situ ion flux measurements at a 60° viewing angle to represent the latitudinal location of the observed northern X‐ray emissions (e.g., see Dunn et al, ; Gladstone et al, ). We multiplied these photon fluxes per cm by the area of a typical dim X‐ray auroral region (e.g., time‐binned X‐ray projections in Dunn et al, ) to attain a total flux of photons from the aurora. We then scaled these auroral photon fluxes by 4 r to account for their dispersion between Jupiter and XMM‐Newton.…”

“…The observed X‐ray aurora has shown a strange complexity. For example, in 30% of observations, the X‐ray aurora pulses with a regular period on the order of tens of minutes as reported by Dunn et al (; ), Gladstone et al (), and Jackman et al (); however, during other observations, the emission is either continuous or the pulses are erratic, with no clear periodic signature (Branduardi‐Raymont et al, ; Elsner et al, ). Therefore, when analyzing heavy ion measurements made by JEDI, it is important to consider that this emission is highly temporally and spatially variable and that the associated ion precipitation may also vary with time.…”

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

“…26, a comparison with magnetic field models (Vogt et al 2011) indicates that these emissions tend to cluster at the footprints of open magnetic field lines that map to the outer magnetosphere. This led Dunn et al (2016) to associate the origin of at least some of the X-ray emissions with possible direct solar wind O and C precipitation.…”

Jovian Auroral Ion Precipitation: Field‐Aligned Currents and Ultraviolet Emissions

“…Recently, Dunn et al () analyzed the consequences for the X‐ray aurora due to an interplanetary coronal mass ejection at Jupiter. They mapped the observed emissions from the outer magnetosphere to the polar ionosphere using the Vogt et al () field.…”

“…We use the most current and complete set of updated oxygen ion‐neutral collision cross sections recently published by Schultz et al (). The following analysis only accounts for oxygen collisions although sulfur and/or carbon line emission is observed in the lower‐energy X‐ray spectral regions (Dunn et al, ; Elsner et al, ). For comparison, we also model auroral electron precipitation.…”