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Area-Preserving Maps Models of the Electric Drift Motion with Finite Larmor Radius Effects

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Author(s):
Júlio César David da Fonseca
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
Defense date:
Examining board members:
Ibere Luiz Caldas; Ricardo Egydio de Carvalho; Edson Denis Leonel; Roberto Venegeroles Nascimento; Ricardo Luiz Viana
Advisor: Ibere Luiz Caldas
Abstract

Area-preserving maps have been extensively used to model chaotic transport in plasmas and fluids. In this work we propose three types of maps describing electric drift motion in magnetized plasmas. Finite Larmor radius effects are included in all maps. In the limit of zero Larmor radius, the monotonic frequency map reduces to the Chirikov-Taylor map, and, in cases with non-monotonic frequencies, the maps reduce to the standard nontwist map. We show how the finite Larmor radius can lead to chaos suppression, modify the phase space topology and the robustness of transport barriers. A method based on counting the number of recurrence times is used to quantify the dependence on the Larmor radius of the threshold for the breakup of transport barriers. We also study a model for a system of particles where the electric drift is described by the monotonic frequency map, and the Larmor radius is a random variable that takes a specific value for each particle of the system. The Larmor radius\' probability density function is obtained from the Maxwell-Boltzmann distribution, which characterizes plasmas in thermal equilibrium. An important parameter in this model is the random variable gamma, defined by the zero-order Bessel function evaluated at the Larmor radius\'particle. We show analytical and numerical computations related to the statistics of gamma. The set of analytical results obtained here is then applied to the study of two numerical transport measures: the escape rate and the rate of trapping by period-one islands. (AU)

FAPESP's process: 12/10240-6 - Particle Transport in Magnetically Confined Plasmas
Grantee:Julio César David da Fonseca
Support type: Scholarships in Brazil - Doctorate