#### E. Tassi F. Militello F. Porcelli R. J. Hastie

A simple formula for predicting the width of a saturated island, formed as a consequence of tearing perturbation of linear force-free fields in cylindrical geometry, is derived. The formula makes it possible to calculate the saturated island width in terms of the values of parameters characterizing the initial force-free equilibrium and can be appl…

Published#### P. Helander D. Grasso R. J. Hastie A. Perona

In tokamak disruptions the Ohmic current is often replaced by a current of runaway electrons, which is likely to be more peaked in the center of the discharge than the predisruption current. This raises the question of the resistive stability of the postdisruption plasma, where the equilibrium current is entirely carried by the runaway electrons wh…

Published#### E. Tassi R. J. Hastie F. Porcelli

The linear stability of a class of force-free equilibria in cylindrical geometry is investigated. The class consists of cylindrically symmetric force-free equilibria for which the ratio between the parallel current density and the magnetic field is a step function of the radius. It is suggested that plasmas in reversed field pinches could be roughl…

Published#### I. T. Chapman S. D. Pinches L. C. Appel R. J. Hastie T. C. Hender S. Saarelma S. E. Sharapov I. Voitsekhovitch J. P. Graves

Recent advances in modeling the effects of anisotropic energetic ion distributions have enabled the development of a complete coherent physics explanation of sawtooth stabilization in both conventional and spherical tokamaks. As an example, a complete model has been developed to explain the asymmetric stabilization of sawteeth with respect to neutr…

Published#### J. W. Connor R. J. Hastie A. J. Webster

The destabilization of ideal magnetohydrodynamic ballooning modes at finite rotation shear is demonstrated for the model s - equilibrium by exploiting low magnetic shear, s , to simplify the two-dimensional stability problem to a one-dimensional eigenvalue problem. This simpler calculation captures the same features as exhibited by a full two-dimen…

Published#### C. G. Gimblett R. J. Hastie P. Helander

Edge-localized modes (ELMs) are cyclic disturbances in the outer region of tokamak plasmas that are influential in determining present and future tokamak performance. In this Letter, we outline an approach to modeling ELMs in which we envisage toroidal peeling modes initiating a Taylor relaxation [Phys. Rev. Lett. 33 , 1139 (1974)] of a tokamak out…

Published#### P. Sandquist S. E. Sharapov P. Helander M. Lisak

A corrected relativistic collision operator is used to derive a Fokker-Planck equation for the distribution function of relativistic suprathermal electrons in a weakly relativistic plasma, which is then solved by a procedure similar to that employed in Connor and Hastie [Nucl. Fusion 15 , 415 (1975)]. Analytical expressions are derived for the elec…

Published#### C.G. Gimblett R.J. Hastie

An investigation is presented of the effect of an error field on the growth of a resistive wall mode (RWM). This issue is of importance to many toroidal confinement devices, but particularly to the proposed International Thermonuclear Experimental Reactor (ITER) [ITER Physics Basis, Nucl. Fusion 39 , 2175 (1999)], where if advanced tokamak performa…

Published#### R. J. Hastie J. J. Ramos F. Porcelli

The linear stability of high-toroidal-number drift-ballooning modes in tokamaks is investigated with a model that includes resistive and viscous dissipation, and assumes the mode frequency to be comparable to both the sound and diamagnetic frequencies. The coupled effect of ion drift waves and electron drift-acoustic waves is shown to be important,…

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