Title：Protoplanetary disk substructures and planet formation

Speaker：Xuening Bai，Tsinghua University

Time：3:00 pm July 11th (Thursday)

Tencent Meeting：42915400486 password: 6360

Location: Lecture Hall, 3rd floor

Abstract：

The prevalence of substructures has been established as the new observational paradigm for protoplanetary disks (PPDs), but it remains largely elusive to what extent such substructures are related to planet formation. I will discuss disk substructures and planet formation from the perspective of realistic gas dynamics in protoplanetary disks. It has been established that magnetized disk winds largely govern disk evolution, and within this framework, the disk can be divided into three regions depending on the microphysics involved. The outer disk (beyond 10 AU or so) is subject to modest level of turbulence by the magneto-rotational instability (MRI) and potentially also the vertical shear instability (VSI). The system can spontaneously form ring-like pressure bumps and/or vortices, which become favorable locations to concentrate dust and form planetesimals. The inner disk (about 1-10AU) is subject to the Hall effect, and generically develops asymmetric flow structures. There is also paleomagnetic evidence for the presence of substructures in the solar system. The disk innermost region (<1AU) is more distinct in that thermal-ionization of Alkali species can make the disk fully MRI-active, sustained by viscous heating. This region is also thermally unstable and may lead to mass pile-up and limiting cycle behaviors. Altogether, the richness of physical processes in PPDs calls for a closer look into planet formation in disk substructures across different disk regions.

CV：Dr. Xuening Bai is a professor at the Institute for Advanced Study, Tsinghua University, and is jointly affiliated with department of astronomy. He graduated from Tsinghua University with a B.S. in mathematics and physics in 2007, and obtained his PhD in astrophysics from Princeton University in 2012. He was a Hubble Fellow and Institute for Theory and Computation (ITC) fellow at the Harvard-Smithsonian Center for Astrophysics from 2012-2017. He joined Tsinghua University as a research professor in 2017, and became a full professor in 2023. He is a theoretical and computational astrophysicist. His research group studies protoplanetary disks and planet formation, as well as several aspects of plasma astrophysics especially on cosmic-ray acceleration and transport, and develops computational tools for related applications.