报告题目：Onset of thermal instabilities in rapidly rotating oblate-spheroidal planets and stars

报告人：孔大力 研究员

报告人单位：中国科学院上海天文台

报告语言：中文

报告时间：2023年2月28日（星期二）上午 10: 00-11: 30

报告地点：主楼427会议室

报告摘要：The problem of thermal instability in rapidly rotating, self-gravitating fluid bodies has been widely modeled in spheres or spherical shells, which implicitly neglects the flattening effect due to the centrifugal force. However, the fast rotation of gaseous giant planets and some of Be stars makes them bulge out enough that they can’t be treated as spheres. As a result, investigating the thermal instabilities in oblate spheroids will help researchers better understand the convection processes in these planets and stars or even very flattened systems like accretion disks. In this work, we first derive a nonspherical reference state model in oblate spheroidal geometry whose shape should be determined by the theory of figure (ToF). A closed-form solution is obtained for gravity and temperature. Based on this nonspherical model of the conduction state, the problem of thermal instability is formulated in the regime of inertial convection that is typical in stellar interiors. The critical properties of inertial modes are explicitly derived. The dependence of the onset of thermal inertial convection on the oblateness of the spheroid is systematically explored. A significant discovery is that the globally most unstable mode could switch from a non-axisymmetric quasi-geostrophic wave to an equatorially symmetric zonal oscillation when the rotational flattening effect gets very strong. This was the only form of global convection not found so far.

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2月23日