Academic Seminars 2022 No.125 – 陈昊天

==== Seville ====

时间：2022年4月12日 周二14:00

方式：腾讯会议（会议号343 850 721）

报告人：陈昊天 博士后研究员

邀请人：郭伟欣 讲师

题目：Does Streamer Exist in Electron Temperature Gradient Turbulence?

摘要：Electron temperature gradient (ETG) turbulence is a candidate for electron heat transport in tokamaks. Since observed numerically in early 2000s, radially elongated streamers have been proposed to significantly enhance the electron heat transport driven by ETG turbulence. Zonal flow (ZF) generation, meanwhile, is thought to be weak. To the best of our knowledge, however, there is no experimental evidence as yet for the existence of streamers. Here, we develop for the first time the nonlinear gyrokinetic theory of ZF generation in intermediate-scale (shorter than ion gyroradius but longer than electron gyroradius) ETG turbulence, which is connected with long-time saturation. Both plasma nonuniformity and continuous radial spectrum effects are properly included. The resultant Schr¨odinger equation for ETG amplitude is characterized by a Navier-Stokes type nonlinearity, which is typically stronger than the Hasegawa-Mima type nonlinearity in fluid limit. Therefore, ZFs can be more easily excited in intermediate-scale than in short wavelength regime. A novel ETG saturation picture is proposed that, in the early nonlinear phase, strongly unstable short wavelength ETGs are saturated by inverse cascading, with streamers being well preserved; as spectrum downshifts, the ZF generation becomes more important, and will ultimately break up streamers, leading to isotropic eddies. Therefore, streamers cannot exist in realistic experimental devices. Gyrokinetic simulations are applied to verify theoretical predictions.

报告人简介：陈昊天，博士后研究员，2018年博士毕业于浙江大学，2018年8月-2019年3月入职南昌大学，2019年-2020年在美国科罗拉多大学博尔德分校做博士后研究员。2020年至今在西班牙塞维利亚大学做博士后研究员。主要从事聚变与空间等离子体中电磁湍流的回旋动理学研究，以第一或通讯作者在Phys. Rev. Lett., Nucl. Fusion等国际主流期刊发表论文9篇，EPS邀请报告一次。自2018年起担任Nat. Commun. NF, PPCF, PoP, PST杂志审稿人