Congratulations to Simon Mendenhall on successfully passing his qualifying exam today!

His research, “From Atmosphere to Plasma: Observational Constraints on Mass Supply to Io’s Neutral Cloud and Plasma Torus,” explores how material escapes from Io’s atmosphere and ultimately supplies plasma to Jupiter’s magnetosphere.

ABSTRACT

Io is the primary source of plasma in Jupiter’s magnetosphere, supplying material through the interaction of its SO2 atmosphere with the surrounding plasma environment. Atmospheric escape from Io forms extended neutral clouds, where neutral species are gradually ionized to form the Io plasma torus. However, the physical coupling between Io’s atmosphere, volcanism, neutral clouds, and torus remains poorly understood due to the complex interactions between each component. Atmospheric loss is essential for providing material to Io’s neutral clouds, whose spatial distribution remains uncertain due to the faint brightness of far-ultraviolet (FUV) emissions from oxygen and sulfur atoms orbiting around Jupiter. This poses challenges when deriving neutral source rates from Io’s atmosphere, which are crucial for initializing models of the torus to estimate the production and outward transport of plasma. To address these gaps in our understanding of the Jovian plasma environment, we will implement an observational approach, combining FUV measurements of Io’s neutral cloud and plasma torus from the Hubble Space Telescope’s (HST) Cosmic Origins Spectrograph (COS) with spatially resolved infrared observations of Io’s atmosphere from the James Webb Space Telescope’s (JWST) Mid-Infrared Instrument (MIRI). By linking atmospheric loss to neutral cloud formation and plasma production, we will place observational constraints on mass loading into the torus and improve our understanding of the processes that control the dynamics of Jupiter’s magnetosphere.