Abstract
AbstractWe compare Chandra and XMM‐Newton X‐ray observations of Jupiter during 2007 with a rich multi‐instrument data set including upstream in situ solar wind measurements from the New Horizons spacecraft, radio emissions from the Nançay Decametric Array and Wind/Waves, and ultraviolet (UV) observations from the Hubble Space Telescope. New Horizons data revealed two corotating interaction regions (CIRs) impacted Jupiter during these observations. Non‐Io decametric bursts and UV emissions brightened together and varied in phase with the CIRs. We characterize three types of X‐ray aurorae: hard X‐ray bremsstrahlung main emission, pulsed/flared soft X‐ray emissions, and a newly identified dim flickering (varying on short time scales, but quasi‐continuously present) aurora. For most observations, the X‐ray aurorae were dominated by pulsed/flaring emissions, with ion spectral lines that were best fit by iogenic plasma. However, the brightest X‐ray aurora was coincident with a magnetosphere expansion. For this observation, the aurorae were produced by both flickering emission and erratic pulses/flares. Auroral spectral models for this observation required the addition of solar wind ions to attain good fits, suggesting solar wind entry into the outer magnetosphere or directly into the pole for this particularly bright observation. X‐ray bremsstrahlung from high energy electrons was only bright for one observation, which was during a forward shock. This bremsstrahlung was spatially coincident with bright UV main emission (power > 1 TW) and X‐ray ion spectral line dusk emission, suggesting closening of upward and downward current systems during the shock. Otherwise, the bremsstrahlung was dim, and UV main emission power was also lower (<700 GW), suggesting their power scaled together.
Highlights
Jupiter produces diverse and dynamic multiwaveband auroral emissions
2002) are observed in many wavebands, they are yet to be observed in the X-rays, so we focus on Jupiter's auroral main emission and the regions poleward of this
By examining how X-ray counts are distributed across time bins and through fast Fourier transforms (FFTs) of the lightcurves, we identify three types of temporal behavior exhibited by Jupiter's X-ray aurora during 2007: regular pulsed behavior, irregular pulsed behavior, and “flickering” emission
Summary
Jupiter produces diverse and dynamic multiwaveband auroral emissions. Radio, infrared, visible, ultraviolet (UV), and X-ray auroral emissions have all been observed from the planet (e.g., Badman et al, 2015, and Bagenal et al, 2014, and references therein). Jupiter's dominant aurora is its “main emission,” which is a near-continuous auroral emission that occurs near the footprints of Ganymede and Callisto (e.g., Grodent et al, 2008) This bright emission is produced by an upward current system that transfers angular momentum from the planet to plasma in the middle magnetosphere (15–40 Jupiter radii [RJ]) in order to enforce corotation (e.g., Cowley & Bunce, 2001; Hill, 2001). These propagation models had large timing uncertainties (±10–15 hr in Dunn et al, 2016, and ±48 hr in Kimura et al, 2016), and this may have at least partially lead to the two works contradictory results, in which the former suggests a connection with solar wind density but not velocity and the latter with velocity, but not density This present study provides a rare opportunity to examine contemporaneous auroral data with solar wind information from an upstream monitor. We present the New Horizons solar wind measurements (section 3) and the more thoroughly studied UV (section 4) and radio (section 5) wavebands to provide further context for the X-ray
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