Speaker: Dr. Chen Wang (王辰博士)

Time: 10:00-11:00, 8 May 2025 (Thursday) (Beijing time)

Venue: A103, Lijiao Building

Abstract

For magnetohydrodynamic (MHD) flow on a sphere, a `clamshell instability’ exists: field lines on two hemispheres tilt in opposite directions and finally overturn (Cally, Sol. Phys., vol. 199, 2001, pp. 231–249), and this instability has important implications to the magnetic field of the sun. We undertake an analytical study to understand this instability via the method of matched asymptotic expansions. It is shown that when the zonal flow is solid body rotation, there exists a neutral mode that tilts the magnetic field lines, referred to as the ‘tilting mode’. A shear of the zonal flow excites the critical layer of the tilting mode, which reverses the tilting direction to form a clamshell pattern and induces the instability. The asymptotic solution concisely reveals the instability properties for a wide range of flow and field profiles.

About the Speaker

王辰博士于2020年在英属哥伦比亚大学获得应用数学博士学位，指导教师为 Neil Balmforth 教授。随后在英国埃克塞特大学从事博士后研究，博士后导师为Andrew Gilbert 教授，于2023年9月加入北京师范大学数学研究中心和北师香港浸会大学应用数学系。王辰博士的研究方向包括应用分析方法和流体力学。具体包括地球、天文物理中的流体力学，流动中的波动和稳定性，以及渐进分析方法在其中的应用， 研究成果发表在 Journal of Fluid Mechanics 等著名流体力学期刊。