Comparisons Between Jupiter's X‐ray, UV and Radio Emissions and In‐Situ Solar Wind Measurements During 2007

Abstract

We 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.

Characteristics of Jupiter's X‐Ray Auroral Hot Spot Emissions Using Chandra

“…The flux within this region however may change due to the changing dynamic pressure caused by the solar wind's effect on the magnetosphere as opposed to a direct effect on the X-ray emission itself. Therefore, the variable morphologies we see in the northern X-ray aurora (as classified by (Dunn, Gray, et al, 2020)) may be a result of changing dynamic pressure and reflect the jovian magnetosphere's sensitivity to such changes.…”

Reconnection and Dipolarization Driven Auroral Dawn Storms and Injections

“…Breakdown of corotation is the predominant physical interpretation for the driver of Jupiter's main auroral emission (Cowley & Bunce, 2001;Hill, 1979Hill, , 2001Southwood & Kivelson, 2001), which is generally believed to result in a reduction of the auroral main emission under enhanced solar wind dynamic ram pressure. However, studies have shown that instead the Jovian aurora appears to enhance during solar wind compressions (Connerney & Satoh, 2000;Dunn et al, 2016Dunn et al, , 2020Nichols et al, 2007Nichols et al, , 2017. This leads to the proposal of a time-varying model involving transient super-corotation of the plasma in the outer magnetosphere in order to mitigate the conflict between the classical model's prediction and the observations (Cowley et al, 2007).…”

Morphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno-UVS Observations

“…As shown in Figure 3, the positions of the bright spots, except for PJ8 data (marked as a green cross), are located within 60-70°N planetocentric latitude and 160-190°W (SIII). Incidentally, this region is also the X-ray hot spot region (Dunn et al, 2016(Dunn et al, , 2017(Dunn et al, , 2020Gladstone et al, 2002;Weigt et al, 2020). One notable exception is found during PJ8, where the bright spot is located at ∼ 82°N and 216.5°W (SIII).…”