Sherwood 2015

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A Hamiltonian Five Field Gyrofluid Model

Author: Ioannis Keramidas Charidakos
Requested Type: Poster Only
Submitted: 2015-01-19 20:35:18

Co-authors: F.L.Waelbroeck

Contact Info:
University of Texas at Austin, Institute for Fusio
620 W.51st Street
Austin, Texas   78751

Abstract Text:
Reduced electromagnetic fluid models constitute versatile tools for the study of multi-scale phenomena including in particular the interaction of turbulence with magnetohydrodynamic perturbations exhibiting meso-scale structures. Examples include magnetic islands,[1] edge localized modes,[2] resonant magnetic perturbations,[3] and fishbone [4] and Alfven modes.[5] Gyrofluid models improve over Braginskii-type models by accounting for the nonlocal response due to particle orbits. A desirable property for all models is that they not only have a conserved energy, but also that they be Hamiltonian in the ideal limit. By ideal limit, we mean the limit obtained by neglecting dissipative terms such as those related to collisions and Landau damping. Hamiltonian systems enjoy well-posed equilibrium equations and possess families of invariants, called Casimirs.

Here we propose a five-field gyrofluid model describing the evolution of ion and electron density, parallel momenta and ion parallel temperature. The model includes field curvature and compressibility and is capable of describing ITG, KBM, drift waves, and tearing modes. We show that our model is Hamiltonian by finding a Lie-Poisson bracket that satisfies the Jacobi identity. The corresponding Casimir invariants are presented, and shown to be associated to five Lagrangian invariants advected by distinct velocity fields. Linear dispersion and stability criteria for the electrostatic and the electromagnetic cases are derived and shown to provide improved fidelity compared to the corresponding Braginskii models.

This work was funded by U.S. DOE Contract No. DE-FG03-96ER-54346.

[1] A. Ishizawa and F. L. Waelbroeck, Phys. Plasmas 20, 122301 (2013).

[2] P. W. Xi, X. Q. Xu, and P. H. Diamond, Phys. Rev. Lett. 112, 085001 (2014).

[3] F. Militello and F. L. Waelbroeck, Nucl. Fusion 49, 065018 (2009)

[4] A. Odblom et al., Phys. Plasmas 9, 155 (2002).

[5] B. J. Tobias et al., Phys. Rev. Lett. 106, 075003 (2011).


March 16-18, 2015
The Courant Institute, New York University