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- J J Ramos
- 2005

Assuming only small gyromotion periods and Larmor radii compared to any other time and length scales, and retaining the lowest significant order in δ = ρ i /L 1, the general expression of the ion gyroviscous stress tensor is presented. This expression covers both the " fast dynamics " (or " magne-tohydrodynamic ") ordering, where the time derivative and ion… (More)

- J A Snipes, J E Rice, J J Ramos, D Schmittdiel, G Taylor, S M Wolfe
- 2001

When operating at low collisionality and high input power (P ICRF ≤ 5 MW), large amplitude (5 × 10-5 < [ ~ / B B θ θ ] wall ≤ 5 × 10-3) low frequency (f MHD < 50 kHz) MHD modes appear to limit the achievable β in Alcator C-Mod. Modes with m/n = 5/4, 4/3, 3/2, and 2/1 were destabilized when β p > 0.52 and increased in amplitude with increasing β until a… (More)

- J. J. Ramos
- 2006

Finite Larmor radius (FLR) fluid equations for magnetized plasmas evolving on either sonic or diamagnetic drift time scales are derived consistent with a broad low-collisionality hypothesis. The fundamental expansion parameter is the ratio δ between the ion Larmor radius and the shortest macro-scopic length scale (including fluctuation wavelengths in the… (More)

- D T Garnier, E S Marmar, +14 authors A Martynov
- 2014

Central fueling of Alcator C-Mod plasmas with lithium and deuterium pellets often leads to a strong reduction of core energy and particle transport. These transient modes, which typically persist for a few energy confinement times, are characterized by the development, during the post-pellet reheat, of a very steep pressure gradient (scale length l, ; a/5)… (More)

- J J Ramos
- 2008

A straightforward operator method is used to derive a form of the drift-kinetic equation for a col-lisionless plasma species in the moving reference frame of its macroscopic flow. This equation is valid for sonic time scales and flow velocities, with first-order finite-Larmor-radius (FLR) effects included. It applies rigorously to far-from-Maxwellian… (More)

- J. J. Ramos
- 2004

A comprehensive analysis of the finite-Larmor-radius (FLR) fluid moment equations for collision-less magnetized plasmas is presented. It is based on perturbative but otherwise general solutions for the second and third rank fluid moments (the stress and stress flux tensors) with closure conditions on the fourth rank moment. The single expansion parameter is… (More)

- A D Haschick, J A Garcia-Barreto, +46 authors Electron Cyclotron
- 2009

- J J Ramos, F Porcelli, R Verástegui
- Physical review letters
- 2002

A two-dimensional, two-fluid model is used to investigate driven magnetic reconnection in collisionless or semicollisional plasmas. The reconnection is driven by externally induced plasma flows in a background magnetic configuration that has a hyperbolic null component in the reconnection plane and a strong component, the so-called guide component,… (More)

The stability of axisymmetric plasmas confined by a closed poloidal magnetic field is investigated using magnetohydrodynamic equations with anisotropic resistivity and sound waves retained. It is shown that when the system is axially and up-down symmetric and the plasma beta = (plasma pressure/magnetic pressure) is finite, a resistive instability with a… (More)

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