Jupiter's X‐Ray and UV Dark Polar Region

Abstract

We present 14 simultaneous Chandra X‐ray Observatory (CXO)‐Hubble Space Telescope (HST) observations of Jupiter's Northern X‐ray and ultraviolet (UV) aurorae from 2016 to 2019. Despite the variety of dynamic UV and X‐ray auroral structures, one region is conspicuous by its persistent absence of emission: the dark polar region (DPR). Previous HST observations have shown that very little UV emission is produced by the DPR. We find that the DPR also produces very few X‐ray photons. For all 14 observations, the low level of X‐ray emission from the DPR is consistent (within 2‐standard deviations) with scattered solar emission and/or photons spread by Chandra's Point Spread Function from known X‐ray‐bright regions. We therefore conclude that for these 14 observations the DPR produced no statistically significant detectable X‐ray signature.

Identifying the Variety of Jovian X‐Ray Auroral Structures: Tying the Morphology of X‐Ray Emissions to Associated Magnetospheric Dynamics

“…The SXRs are produced from precipitating MeV ions originating in the outer magnetosphere and are sometimes observed to be coincident with flaring ultraviolet (UV) emissions within the UV active polar region as observed by Dunn et al. (2022) (herein refereed to as D22). The auroral hard X‐rays (HXR: >2 keV) result from bremsstrahlung emissions from precipitating electrons, with the auroral emissions observed to sometimes coincide with the UV main emission (ME: e.g., Branduardi‐Raymont et al., 2008; Dunn et al., 2016).…”

“…understand the highly sophisticated magnetospheric driver(s) capable of energizing the ions to MeV energies that allow charge stripping and charge exchange to take place in the Jovian ionosphere for soft X-ray (SXR: <1 keV) production (e.g., Dunn et al, 2020aDunn et al, , 2020bHouston et al, 2020). The SXRs are produced from precipitating MeV ions originating in the outer magnetosphere and are sometimes observed to be coincident with flaring ultraviolet (UV) emissions within the UV active polar region as observed by Dunn et al (2022) (herein refereed to as D22). The auroral hard X-rays (HXR: >2 keV) result from bremsstrahlung emissions from precipitating electrons, with the auroral emissions observed to sometimes coincide with the UV main emission (ME: e.g., Branduardi-Raymont et al, 2008;Dunn et al, 2016).…”

Capabilities of a lobster eye telescope in the outer solar system

“…Measurements have been made by Earth-orbiting X-ray telescopes that include detections of X-rays from Jupiter, the Io torus, the Galilean Satellites, Jupiter's radiation belts, Saturn, Uranus and the rings of Saturn. [19][20][21][22][23][24][25] For most of these objects the fluxes are too low for detailed characterisation of the signal from Earth orbit.…”

“…Recent measurements of the plasma population at the torus by the Juno spacecraft, suggest that charge exchange emissions may be the source, although further work is required to explore this. 25 Observations of the Io torus by the Jupiter-orbiting SXI would provide sufficient signal to conclusively address the source processes, but then would also allow us to use these as a natural laboratory for neutral-plasma interactions across the Universe, where it is common place for hot plasmas such as stellar winds or supernovae to collide with neutral clouds.…”

Signatures of Open Magnetic Flux in Jupiter's Dawnside Magnetotail

“…The high‐latitude “swirl” region exhibits a high color ratio and is circumscribed by a “polar collar” with significant local time asymmetry (Greathouse et al., 2021). The dusk side (11–22 LT) manifests as a bright “active region” and the dawn collar is the “dark region” (0–11 LT) (Dunn et al., 2022; Stallard et al., 2003).…”