Auroral evidence of radial transport at Jupiter during January 2014

Abstract

We present Jovian auroral observations from the 2014 January Hubble Space Telescope (HST) campaign and investigate the auroral signatures of radial transport in the magnetosphere alongside contemporaneous radio and Hisaki EUV data. HST FUV auroral observations on day 11 show, for the first time, a significantly superrotating polar spot poleward of the main emission on the dawnside. The spot transitions from the polar to main emission region in the presence of a locally broad, bright dawnside main emission feature and two large equatorward emission features. Such a configuration of the main emission region is also unreported to date. We interpret the signatures as part of a sequence of inward radial transport processes. Hot plasma inflows from tail reconnection are thought to flow planetward and could generate the superrotating spot. The main emission feature could be the result of flow shears from prior hot inflows. Equatorward emissions are observed. These are evidence of hot plasma injections in the inner magnetosphere. The images are thought to be part of a prolonged period of reconnection. Radio emissions measured by Wind suggest that hectometric (HOM) and non‐Io decametric (DAM) signatures are associated with the sequence of auroral signatures, which implies a global magnetospheric disturbance. The reconnection and injection interval can continue for several hours.

Transient brightening of Jupiter's aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft

“…With reference to previous works, this torus variability is likely associated with some combination of the following processes: energetic particle injection [e.g., Mauk et al , ], adiabatic heating by the dawn‐to‐dusk electric field [ Barbosa and Kivelson , ; Murakami et al , ], and/or heating by electromagnetic waves originally proposed for Io's downstream region [ Hess et al , ; Tsuchiya et al , ]. Although it is still unclear which process is the most feasible, the appearance of outer auroral emission at dusk after the declining phase of the transient aurora (Figure f) suggests that the energetic electron injection occurred after the transient aurora onset as reported from previous HST observations [ Gray et al , ]. Therefore, the transient dusk torus brightening on DOY142.50–142.65 is presumably associated with the injection.…”

“…The image taken on DOY140 is shown as a representative for the quiet period (Figure b). Between 02:17:42 and 03:02:12 (DOY142.10–142.13) on DOY142 (Figures c–e), a dawn storm, which is suggestive of dawnside tail reconnection and planetward return flow [ Cowley et al , ; Clarke et al , ], was evident at System III longitude of 180°–260° less than in the main oval (Figures c–e) as observed during the 2014 HST campaign [ Kimura et al , ; Badman et al , ; Gray et al , ]. This exposure time corresponds to the onset timing of the transient aurora in the Hisaki data.…”

“…The simultaneous imaging by the Hubble Space Telescope (HST) with Hisaki indicated that the three structures introduced above, the main oval, poleward emissions, and outer emission, were enhanced simultaneously around the transient aurora [ Kimura et al , ; Badman et al , ; Gray et al , ]. However, the temporal and spatial evolutions of the transient aurora and energetic events were not resolved by these previous observations because of the lack of continuous monitoring that spans the typical duration of the transient aurora.…”

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

“…The Vasyliūnas reconnection is the most plausible candidate for the initiation of the transient aurora, as suggested by the energetic event. Gray et al () actually indicated that during the transient aurora, an auroral spot merged into the dawn storm from high latitudes, which is suggestive of the reconnection return flow in the outer magnetosphere.…”

Dynamics of the flares in the active polar region of Jupiter

“…The auroral signature of this current system generally looks like a partially complete ring, called the main emission [ Ballester et al , ; Grodent et al , ], which only accounts for about half of the total emitted power in the UV [e.g., Nichols et al , ]. Equatorward of the main oval are diffuse, arc‐shaped, or compact emissions associated with pitch angle diffusion [ Radioti et al , ] and/or hot plasma injections in the inner/middle magnetosphere [ Mauk et al , ; Bonfond et al , ; Dumont et al , ; Gray et al , ]. In the same region, the electromagnetic interaction between the moons Io, Europa, and Ganymede produces auroral footprints in the form of localized spots sometimes followed by a tail (see review by Bonfond []).…”