Transport Properties, Pattern Dynamics and Self-Organized States in Magnetized Plasmas

磁化等离子体存在于各种空间和天体物理环境中，在用于核聚变的磁约束装置以及其他技术上重要的装置中发挥着重要作用。等离子体在密度、温度和电流等方面的空间不均匀性会驱动小尺度的不稳定波，这些波将非线性饱和并导致涉及多个自由度的准平稳湍流状态。这些湍流起伏可以诱导粒子、能量和动量输运，通常称为“异常输运”，以区别于等离子体带电粒子之间的经典库仑碰撞产生的碰撞输运。

Magnetized plasmas are present in a variety of space and astrophysical environments and play an important role in magnetic confinement devices for fusion as well as other technologically important devices. Plasmas are generally far from equilibrium and spatial inhomogeneities in the density, temperature and current can drive small-scale unstable waves that will saturate nonlinearly and lead to a quasi-stationary turbulent state involving many degrees of freedom. These turbulent fluctuations can induce particle, energy and momentum transport which is generally termed “anomalous transport” to distinguish it from collisional transport that arises from classical Coulombic collisions among the plasma charged particle species. In anomalous transport there are different mechanisms involved in the transport processes ranging from diffusion to advection and mixing in the case of turbulent or chaotic motions. Recently a new concept in the study of transport processes in complex fluid flows has been introduced by G. Haller, termed Lagrangian Coherent Structures (LCS) and naturally form a skeleton of the transport dynamics. The LCS can separate the flow domain into macro-regions inside which fast mixing phenomena will take place. Over the finite time span of the LCS macro-regions do not exchange fluid elements and thus may act as transport barriers. The LCS concept has wide applicability and the analysis techniques that have been developed were used in pollutant transport on ocean surfaces, spreading of plankton blooms, blood flow, solar photospheric flows and atmospheric dataset analysis. It has only recently been introduced into plasma physics and one of the main objectives of the proposal is to fully characterize the LCS in magnetized plasmas where transport arises from a combination of charged particle drifts in crossed electric and magnetic fields and along confining magnetic field which are regular or stochastic. In this work we propose to investigate Lagrangian Coherent Structures in two magnetized plasma systems in 3D cylindrical geometry. The first consists of several mutually interacting magnetic flux ropes and the second is a configuration with multiple magnetized thermal filaments in close proximity. These systems will be first be modeled using gyrokinetic particle-in-cell simulations with proper boundary conditions so that they can be compared with measurements in a linear plasma device. The tools for analysis of LCS will be applied to the simulation data and compared to results from experiments in a large linear plasma device. A major outcome of this project will be the first detailed characterization of the LCS in magnetized plasma where transport arises from ExB drifts and stochastization of the magnetic field.