When
Student: Eonho Chang, Program in Applied Mathematics
Title: Dust Drift, Trapping, and Accretion: From Protoplanetary Disks to Mature Planets
Advisors: Andrew Youdin (Department of Astronomy and Steward Observatory)
Location: Steward Observatory, Room 550 | Zoom https://arizona.zoom.us/j/87479752031 (password: rossby)
Abstract: Solid particles in planetary systems tend to lose angular momentum and drift inward. In protoplanetary disks, pebbles experience a headwind from sub-Keplerian gas and migrate toward the star. In gas-poor environments, micron size dust spirals inward due to the Poynting-Robertson drag. Such drifting particles can be intercepted by disk structures and planets, leading to dust concentrations that affect planet formation, evolution, and observable properties.
In this dissertation, I investigate the stability and evolution of dust-trapping gas structures, and the consequences of dust accretion onto planetary atmospheres.
First, I use linear stability analysis to determine when axisymmetric pressure bumps can simultaneously trap dust and remain stable to the Rossby wave instability (RWI). I find isothermal dust traps to be RWI-stable for one to several gas scaleheights. On the other hand, I show temperature bumps without surface density component are less likely to be long-lived dust traps.
I then develop a theoretical framework for studying the RWI. Using incompressible and compressible shearing sheets, I analyze the linear modes and derive analytic stability boundaries and growth rates for disk features defined by enthalpy amplitude and width. I demonstrate that the ``halfway to Rayleigh'' criterion serves as an approximate necessary and sufficient condition for the RWI. These results extend robustly in global disk models.
Next, I show that migrating planets can generate a large number of vortices driven by linear instabilities. Similar to the RWI, these unstable modes arise from phase locking of counter-propagating Rossby waves. Low azimuthal wavenumber modes follow the classical RWI dispersion relation, whereas high azimuthal wavenumber modes do not. I speculate that this mismatch reflects differences in the overreflection configuration.
Finally, I explore accretion of exozodiacal dust onto planetary atmospheres and its impact on cloud distribution. Combining radiative-convective and microphysical models, I show that such infall can lead to the formation of high-altitude clouds in hot Jupiter atmospheres. These clouds can mute transmission spectral features, particularly in cases of high infall rates and weak vertical mixing.