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Resistive magnetohydrodynamic equilibrium and stability of a rotating plasma with particle sources
| Author: | Huang Y. M. |
| Coauthor: | A. B. Hassam |
| Institution : | University of Maryland |
| Abstract text: | Within the framework of resistive MHD, particle sources are shown
to be necessary in order to have a well confined steady state of
azimuthally rotating axially magnetized plasma. In the absence of particle sources
density profiles relax under resistive diffusion to pile up to the outside of the system,
consistent with the outward centrifugal forces. Particle sources and resulting density profiles
are shown to play an important role in the MHD stability of the system; therefore, tailoring of
the density profiles could be used to achieve control over MHD stability. Long wavelength
Kelvin-Helmholtz modes as
well as short wavelength interchange modes are studied in relation to
profile tailoring and efficacy of velocity shear. Through a series of simulations we
establish general understandings and \"rules of thumb\" for stability. In particular, completely
laminar steady states could be achieved if (1) the density stratification is stabilizing at
the weakest point where the flow shear vanishes, and (2) the generalized Rayleigh\'s criterion
is satisfied. If (1) is violated, localized interchanges emerge around the weakest point and the
density profile there is fattened. On the other hand, if (2) is violated, the characteristic
Kelvin cat\'s eye can form. In either case, the instability does not flatten the whole
profile; rather, it brings the profile close to marginal stability, with some residual wobbles or
convection cells. We conclude that judiciously placed particle sources could be used to
enhance stability.
Work supported by DOE.
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