Interchange instabilities in a partially ionized plasma
- Massachusetts Institute of Technology, Cambridge, Massachusetts02139 (United States)
In a partially ionized plasma, the charged particle population is coupled to the neutrals through charge exchange, ionization and recombination. An interchange instability is identified in which the driving factor is the neutral pressure gradient and the dominant collisional process is charge exchange. Regimes are considered in which the mean free path for neutral collisions with ions {lambda}{sub ni} is small in comparison to the macroscopic length scales. The instability is analogous to a gravitational interchange mode with an effective gravity g{sub eff}={nu}{sub in}V{sub n} where {nu}{sub in} is the collision frequency of ions with neutrals. The neutral flow V{sub n}={minus}(Mn{sub i}{nu}{sub in}){sup {minus}1}dp{sub n}/dx results from a balance between the neutral pressure gradient and collisional friction with the ions. An arbitrary k{sub y}{lambda}{sub ni} dispersion relation is derived using fluid equations to describe the ions and the Boltzmann equation to describe the neutrals. This dispersion relation contains viscous and inertial effects and is substantially altered in the presence of realistic parallel wavelength due to a coupling between the unstable interchange mode and a stabilizing shear Alfv{acute e}n mode. Reasonable conditions under which the modes may exist are examined and the possible relevance to divertor plasmas is considered. {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 624853
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 5; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Fluctuations associated with sheared velocity regions near auroral arcs
Velocity shear and fluctuations in the auroral regions of the ionosphere