Long Exposure Chandra X‐Ray Observation of Jupiter's Auroral Emissions During Juno Plasmasheet Encounters in September 2021

On 15 September 2021, Chandra carried out a 40‐hr (∼4 jovian rotations) observation as part of its longest planetary campaign to study the drivers of jovian X‐ray aurora that may be linked to ultra‐low frequency (ULF) wave activity. During this time, Juno's orbit had taken the spacecraft into Jupiter's dusk magnetosphere. Here is believed to be the most probable location of ULF waves propagating along jovian magnetic field lines that drive the X‐ray auroral emissions. This is the first time that this region has been observed by an orbiter since Galileo >20 years ago, and never before has there been contemporaneous in situ and X‐ray observations. A 1D solar wind propagation model identifies a compression event near the midpoint of the 40‐hr observation window. The influence of a compression is confirmed when comparing the measured magnetic field in the dusk lobes of the magnetotail from Juno MAG data against a baseline lobe field model. Data from the Juno Waves instrument also show activation of broadband kilometric (bKOM) emissions during the arrival of the shock, a feature that has previously been observed during compression events. Therefore this is the first time we can fully analyze the morphological variability during the evolution of a shock. Wavelet transforms and Rayleigh testing are used to search for statistically significant quasi‐periodic pulsations (QPPs) of the X‐ray emissions in the data set, and find significant QPPs with periods of 25–26 min for the northern auroral X‐rays. Key Points We compare a 40‐hr Chandra observation of Jupiter's X‐ray aurora with in situ Juno measurements and a 1‐D solar wind propagation model We find statistically significant quasi‐periodic pulsation with a ∼25 min period likely linked to the arrival of a solar wind compression Using Juno MAG data form the dusk tail lobes, we infer the state of compression/loading of the magnetosphere