题目：Nonlinear wave-particle dynamics in chorus excitation

报告人：Fulvio Zonca^1,2

¹ENEAFusion and Nuclear Safety Dept., C.R. Frascati, Via E. Fermi 45, 00044 Frascati(Roma), Italy

²IFTS and Department ofPhysics, Zhejiang University, Hangzhou, 310027 P.R. China

地点： 教十二―201

时间： 5月31日，周五，15:00-17:00

Abstract：

The Earth’sradiation belts’ plasma, under certain conditions, can amplify specific typesof electromagnetic waves. In particular, the whistler waves, which areelectromagnetic fluctuations propagating at less than the non-relativisticelectron cyclotron frequency, can occur in ~0.1s bursts with either rising orfalling tones and are known as chorus because of their characteristic chirping.Chorus excitation and nonlinear dynamics is one of the long-studied physicsproblems of Earth’s magnetosphere due to its implications for particleacceleration and distribution in the radiation belts.

Nonlinear waveparticle interaction during chorus wave generation has been recently shown tobe a non-adiabatic process; that is, the wave-particle trapping time in theresonant phase-space structures, t_tr, is typically ofthe same order as the characteristic nonlinear time scale, t_NL. Theseresults shed new light on the physical processes underlying wave-particleresonance and nonlinear mode evolution with respect to previous analysesassuming t_NL >>t_tr. Inthis work, we present an analytical study of nonlinear evolution of phase-phasespace structures in support of our earlier numerical simulation results, basedon a hybrid MHD-fully kinetic description.

We adopt a nonlinear description of the phase-space structures due to theinteraction of supra-thermal electrons with the fluctuating fields produced bya quasi-periodic chorus wave. This allows us to derive the renormalizedexpression of supra-thermal electron distribution function in the form of aDyson-like equation, which illuminates the self-consistent nonlinear evolutionof resonance structures in the phase-space. In particular, we demonstrate thatfrequency sweeping of chorus fluctuations occurs as consequence of maximizationof wave-particle power transfer; and discuss the consequence of this on thespatiotemporal features of the fluctuation spectrum.

FulvioZonca Brief Bio

FulvioZonca is ResearchDirector at the ENEA Research Centre, Frascati, Italy, and Adjunct Professor atthe Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou,China since 2009. At present, he is Principal Investigator of the project Multi-scale Energetic particle Transport in fusion devices (MET), an EnablingResearch Project for the implementation of the fusion roadmap by the Consortium EUROfusion. He is Author of more than 150 papers in majorinternational journals and has recently published an extended Reviews of Modern Physics work, togetherwith Professor Liu Chen, on the Physics of Alfvénwaves and energetic particles in burning plasmas (RMP 88, 015008, 2016). Fulvio Zonca received hisPh.D. degree in Astrophysical Sciences from Princeton University in 1993 andwas employed as Researcher at ENEA-Frascati Research Centre from 1993 till 1997. From 1997 till2015 he was the Head of the Plasma Physics Theory Group in the Magnetic FusionDivision of the same Institute. He is Fellow of the American Physical Societysince 2005 and Member of the Editorial Board of Physics of Plasmas (since2019), and of Annals of Mathematical Sciences and Applications (since 2015). Heis former member of the Editorial Board of Plasma Physics and Controlled Fusion(from 2006 till 2018), and of the EFDA Science and Technology AdvisoryCommittee (from 2007 till 2014). He is also present or former member of anumber of University and National Laboratory International Advisory Committees.