arXiv subjects

Emma J. Bunce

Publications and source records attributed to Emma J. Bunce.

4 recordsLinked to original sources

arXiv2026

The Ultraviolet Spectrograph on ESA's Jupiter Icy Moons Explorer Mission (JUICE-UVS)

The Jupiter Icy Moons Explorer (JUICE) mission, led by ESA, has an Ultraviolet Spectrograph (JUICE-UVS) contributed by NASA and built at Southwest Research Institute. JUICE-UVS is designed to provide a diversity of measurements to further our understanding of the potential habitability of icy ocean worlds at Jupiter and to study Jupiter and the Jovian system as an archetype for gas giants. JUICE-UVS observes photons in the 50-204 nm wavelength range at moderate spectral and spatial resolution along a 7.5 deg slit composed of 7.3 deg x 0.1 deg and 0.2 deg x 0.2 deg contiguous sections. JUICE-UVS performs a comprehensive study of icy satellite atmospheres, plumes, surfaces, and local space environments; Jupiter's atmosphere and aurora; Io and its Io Plasma Torus; and other Jupiter system targets (rings, small moons, etc.) as available. The variety of observational techniques employed include: nadir push-broom imaging, disk scans, limb stares, stellar and solar occultations, Jupiter transit observations, and neutral cloud/plasma torus stares and scans. This paper describes the UVS investigation's science plans, instrument details, concept of operations, and data formats in the context of the JUICE mission's habitability and Jupiter system goals.

astro-ph.EP↗

arXiv2023

Saturn's Magnetic Field at Unprecedented Detail Achieved by Cassini's Close Encounters

The last 22.5 orbits of the Cassini mission brought the spacecraft to less than 3000 km from Saturn's 1-bar surface. These close encounters offered an unprecedented view of Saturn's magnetic field, including contributions from the internal dynamo, the ionosphere, and the magnetosphere. In this chapter, we highlight the new picture of Saturn's magnetic field from the Cassini mission including the persistent yet time-varying low-latitude field-aligned currents, Alfvén waves planet-ward of the D-ring, extreme axisymmetry, and high-degree magnetic moments. We then discuss the implications and new questions raised for Saturn's innermost magnetosphere, equatorial ionosphere, and interior. We conclude this chapter with an outlook for the future exploration of Saturn and other giant planets.

astro-ph.EP↗

arXiv2019

The landscape of Saturn's internal magnetic field from the Cassini Grand Finale

The Cassini mission entered the Grand Finale phase in April 2017 and executed 22.5 highly inclined, close-in orbits around Saturn before diving into the planet on September 15th 2017. Here we present our analysis of the Cassini Grand Finale magnetometer (MAG) dataset, focusing on Saturn's internal magnetic field. These measurements demonstrate that Saturn's internal magnetic field is exceptionally axisymmetric, with a dipole tilt less than 0.007 degrees (25.2 arcsecs). Saturn's magnetic equator was directly measured to be shifted northward by ~ 0.0468 +/- 0.00043 (1-sigma) $R_S$, 2820 +/- 26 km, at cylindrical radial distances between 1.034 and 1.069 $R_S$ from the spin-axis. Although almost perfectly axisymmetric, Saturn's internal magnetic field exhibits features on many characteristic length scales in the latitudinal direction. Examining Br at the a=0.75 $R_S$, c=0.6993 $R_S$ isobaric surface, the degrees 4 to 11 contributions correspond to latitudinally banded magnetic perturbations with characteristic width similar to that of the off-equatorial zonal jets observed in the atmosphere of Saturn. Saturn's internal magnetic field beyond 60 degrees latitude, in particular the small-scale features, are less well constrained by the available measurements, mainly due to incomplete spatial coverage in the polar region. A stably stratified layer thicker than 2500 km likely exists above Saturn's deep dynamo to filter out the non-axisymmetric internal magnetic field. A heat transport mechanism other than pure conduction, e.g. double diffusive convection, must be operating within this layer to be compatible with Saturn's observed luminosity. The latitudinally banded magnetic perturbations likely arise from a shallow secondary dynamo action with latitudinally banded differential rotation in the semi-conducting layer.

astro-ph.EP↗

arXiv2019

X-rays Studies of the Solar System

X-ray observatories contribute fundamental advances in Solar System studies by probing Sun-object interactions, developing planet and satellite surface composition maps, probing global magnetospheric dynamics, and tracking astrochemical reactions. Despite these crucial results, the technological limitations of current X-ray instruments hinder the overall scope and impact for broader scientific application of X-ray observations both now and in the coming decade. Implementation of modern advances in X-ray optics will provide improvements in effective area, spatial resolution, and spectral resolution for future instruments. These improvements will usher in a truly transformative era of Solar System science through the study of X-ray emission.

astro-ph.HE↗