Jesus J. Ramos

Learn More
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)
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)
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)
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)
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)
  • 1