Charles Michael Haynes
(Advisor: Prof. Simon)
will defend a doctoral thesis entitled,
Emission of Energetic Neutral Atoms from Magnetosphere-Atmosphere Interactions at Jupiter's Icy Galilean Satellites
On
Friday, November 06 at 3:00 p.m.
Ford ES&T Room L1205
311 Ferst Dr NW, Atlanta, GA 30332
Abstract
Jupiter's icy Galilean satellites--Europa, Ganymede, and Callisto--represent critical targets for space exploration. These moons are constantly exposed to the (sub)corotating plasma occupying the Jovian magnetosphere as it overtakes their orbital motion. Jupiter's dipolar and spin axes are offset by 9.6º so the ambient plasma properties and magnetic fields at the moons oscillate with the Jovian synodic period (≈11 hr). The time-variable magnetic field drives an observable inductive response in the putative saline subsurface ocean inside each moon. Ganymede also boasts a permanent, dynamo-driven dipole field that locally dominates Jupiter's field, constructing a mini-magnetosphere. These objects' tenuous atmospheres and internal fields interact with Jupiter's magnetosphere, generating perturbations in the electromagnetic fields and plasma flow. Atmospheric inhomogeneities and induction signatures affect the morphology of these perturbations, providing a glimpse into moon properties. However, three-dimensional characterization of the moon-plasma interaction regions requires information assembled from many spacecraft flybys under similar ambient conditions. Fortunately, there exists another avenue to characterize plasma interactions using the energetic ion population of Jupiter's magnetosphere. Charge exchange between such ions and atmospheric neutrals generates energetic neutral atoms (ENAs), which travel away along straight lines due to their high inertia. The Jupiter Icy Moons Explorer (JUICE) mission will arrive at Jupiter in 2031 and capture ENA images of the icy Galilean satellites using a detector analogous to a camera for ENAs. Since the energetic ions are guided into the moons' atmospheres by the locally deformed electromagnetic fields, ENA emissions are encoded with information on the structure of the fields as well as the atmospheres and ambient energetic ion populations. Hence, ENA images are two-dimensional “snapshots” of a moon's interaction region that complement magnetometer and plasma data collected in situ. However, this information is intertwined within the images in a complex way. Therefore, we develop a theoretical framework to facilitate the planning and analysis of upcoming ENA observations by JUICE. We present a suite of models that determines the ENA emissions for a given set of ambient magnetospheric parameters and configurations of each moon's atmosphere. First, we calculate global maps of the ENA flux through a sphere encapsulating the atmosphere. Next, we emulate the detector aboard JUICE to produce synthetic ENA images for a variety of vantages. We demonstrate that ENA emissions at Europa and Callisto are observable in a band oriented perpendicular to the ambient field direction, while the closed dipolar field lines at Ganymede reduce the ENA emissions emanating from this moon's equatorial regions. Analysis of hundreds of synthetic ENA images indicates that, for certain detector vantages, each moon's plasma interaction leaves unique signatures in the emissions.
Committee
• Prof. Sven Simon – School of Earth and Atmospheric Sciences and School of Physics (advisor)
• Dr. Lucas Liuzzo – Space Sciences Laboratory, University of California, Berkeley
• Prof. Samer Naif – School of Earth and Atmospheric Sciences
• Prof. A. Nepomuk Otte – School of Physics
• Prof. James Wray – School of Earth and Atmospheric Sciences