Research

Publications

Chang, E., and Youdin, A. N., 2024,``Halfway to Rayleigh'' and Other Insights into the Rossby Wave Instability, ApJ, 976, 100
Chang, E., Youdin, A. N., and Krapp, L., 2023, On the Origin of Dust Structures in Protoplanetary Disks: Constraints from the Rossby Wave Instability, ApJL, 946, L1
Chang, E., and Garaud, P., 2021, Modelling coexisting GSF and shear instabilities in rotating stars, MNRAS, 506, 4914-4932
Rosenthal, M. et al. (including Chang, E.), 2019, Measuring the Orbital Parameters of Radial Velocity Systems in Mean Motion Resonance---a Case Study of HD 200964, AJ, 158, 136
Choi, J., Chang, E. et al., 2017, Effects of exchange-correlation potentials on the density-functional description of C60 versus C240 photoionization, Phys. Rev. A, 95, 023404

Theses

M.S. thesis, ``Stratified rotational instabilities at low Péclet number'' link (eScholarship)
B.S. thesis, ``Resonance Capture Scenarios of HD 200964 System via Convergent Migration'' pdf (Google Drive)

Videos

When do vortices form in protoplanetary disks?

torq_rwi_vortices_H2R.mp4

In this simulation, a disk is continuously torqued to slowly reduce its stability at a specific location. Classical stability criteria provide useful references: the necessary condition for instability (potential vorticity minimum, known as the Lovelace criterion or the Rayleigh-Fjortoft theorem), and the sufficient condition for instability (kappa^2<0, known as the Rayleigh centrifugal criterion).

However, as this simulation demonstrates, neither of these conditions reliably predict when vortices form. Instead, the vortices emerge somewhere in between. In our paper Chang & Youdin 2024, we quantify the necessary-and-sufficient criterion using linear stability analysis and introduce the "halfway-to-Rayleigh" criterion.

shearbucket.mov

Fun: shear instability in a bucket

In this experiment, a bucket is filled with about an inch of water, with some used tea added as tracer to visualize the flow. A string is tied to bucket handle, twisted tightly, and then released. At the same time, the bucket is gently dropped onto a towel. While the bucket comes to a stop, the water inside keeps moving, creating vortices near the walls due to strong shear.

This experiment, based on T. Howard & A. Aguilar 2020, illustrates the essence of radial shear instability, which includes the Rossby Wave Instability.

...more to come (hopefully)

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