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Starting from the complete short mean-free path fluid equations describing magnetized plasmas, assuming that plasma pressure is small compared to magnetic pressure, considering field-aligned plasma fluctuations, and adopting an ordering in which the plasma species flow velocities are much smaller than the ion thermal speed, a system of non-linear equations… (More)

- K D Marr, B Lipschultz, P J Catto, R M McDermott, M L Reinke, A N Simakov
- 2010

The study and prediction of velocities in the pedestal region of Alcator C-Mod are important for understanding plasma confinement and transport. In this study we examine the simplified neoclassical predictions for impurity flows using equations developed for plasmas with background ions in the Pfirsch-Schlüter (high collisionality) and banana (low… (More)

The neoclassical electric field in a tokamak is determined by the conservation of toroidal angular momentum. In the steady state in the absence of momentum sources and sinks it is explicitly evaluated by the condition that radial flux of toroidal angular momentum vanishes. For a collisional or Pfirsch-Schlüter short mean-free path ordering with sub-sonic… (More)

Short mean free path descriptions of magnetized plasmas have existed for almost 50 years so it is surprising to find that further modifications are necessary. The earliest work adopted an ordering in which the flow velocity was assumed to be comparable to the ion thermal speed. Later, less well known studies extended the short mean free path treatment to… (More)

Simulating electrostatic turbulence in tokamaks on transport time scales requires retaining and evolving a complete turbulence modified neoclassical transport description, including all the axisymmetric neoclassical and zonal flow radial electric field effects, as well as the turbulent transport normally associated with drift instabilities. Neoclassical… (More)

The drift kinetic equation of Hazeltine [R. for a magnetized plasma of arbitrary collisionality is widely believed to be exact through the second order in the gyro-radius expansion. We demonstrate that this equation is only exact through the first order. The reason is that when evaluating the second order gyro-phase dependent distribution function,… (More)

- William T. Taitano, Luis Chacón, A. N. Simakov
- J. Comput. Physics
- 2016

- William T. Taitano, Luis Chacón, A. N. Simakov, K. Molvig
- J. Comput. Physics
- 2015

For a tokamak, we consider gyrokinetic quasineutrality limitations when evaluating the axisymmetric radial electric field; provide an insight by considering the gyrokinetic entropy production restriction on an ion temperature pedestal like that of ITER; and an present an improved hybrid gyrokinetic-fluid treatment valid on slowly evolving transport time… (More)

- Andrei N Simakov, L Chacón
- Physical review letters
- 2008

Dissipation-independent, or "fast", magnetic reconnection has been observed computationally in Hall magnetohydrodynamics (MHD) and predicted analytically in electron MHD. However, a quantitative analytical theory of reconnection valid for arbitrary ion inertial lengths, d{i}, has been lacking and is proposed here for the first time. The theory describes a… (More)