[IGPP Everyone] Space Physics Seminar, Fri. 1/11, 3:30pm: "Properties of intense field-aligned lower-band chorus waves: implications for nonlinear wave-particle interaction" (X. Zhang, EPSS)

[Emmanuel V. Masongsong]

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SPACE PHYSICS SEMINAR 
DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 


DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 

UNIVERSITY OF CALIFORNIA, LOS ANGELES 
(AOS M275C, EPSS M288C) 




Properties of intense field-aligned lower-band chorus waves: implications for nonlinear wave-particle interaction 



Xiaojia Zhang 
UCLA EPSS 



AResonant interactions between electrons and chorus waves are responsible for a wide range of phenomena in the near-Earth space (e.g., diffuse aurora and acceleration of > 1 MeV electrons). Although quasi-linear diffusion is believed to be the primary paradigm for describing such interactions, an increasing number of investigations suggest that nonlinear effects are also important in controlling the rapid dynamics of energetic electron fluxes. This presentation addresses the relative contribution of nonlinear resonant processes to the radiation belt dynamics, which includes three topics: (1) What is the distribution of intense chorus wave characteristics that are important for nonlinear wave-particle interaction? (2) How can the observed wave characteristics influence the nonlinear wave-particle interaction? (3) What is the cumulative effect of nonlinear wave-particle interaction on electron distribution functions? 

We show that while as many as 10–15% of chorus wave packets are sufficiently intense to interact nonlinearly with relativistic electrons, most of them are short (include less than 10 wave periods), reducing the efficacy of such interactions. We construct the kinetic equation to describe the nonlinear resonant interaction of radiation belt electrons with such short, intense wave packets, and demonstrate that this peculiar type of nonlinear interaction produces similar effects as the quasi-linear diffusion. To investigate effects of sufficiently long (large) wave-packets, we introduce a method to incorporate these effects (namely, phase trapping and nonlinear scattering) into the kinetic equation describing the evolution of the electron distribution function. Solutions of this equation indicates that nonlinear resonant effects should lead to electron distributions similar to results of quasi-linear diffusion, but the electron distribution evolution driven by nonlinear resonances is much quicker than the quasi-linear diffusion. . 



Friday, January 11, 2019 

Room 6704 Geology 

3:30 - 5:00 PM 



In Charge: 

V. Angelopoulos 



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