When one deals with a plasma column whose radius a is much smaller than its length L, one can think of it as of a thin filament whose kink instability can be adequately described simply by a 2D displacement vector, ξ x =ξ x (z,t); ξ y =ξ y (z,t). Details of the internal structure of the column such as the current, density, and axial flow velocity distribution would be lumped into some phenomenological parameters. This approach is particularly efficient in the problems with non-ideal (sheath) boundary conditions (BC) at the end electrodes, with the finite plasma resistivity, and with a substantial axial flow. With the sheath BC imposed at one of the end-plates, we find instability in the domain well below the classical Kruskal-Shafranov limit. The presence of an axial flow causes the onset of rotation of the kink and strong axial "skewness" of the eigenfunction, with the perturbation amplitude increasing in the flow direction. We consider the limitations of the phenomenological approach and find that they are related to the steepness with which the plasma resistivity increases at the plasma boundary with vacuum.

No abstract

No abstract

The reconnection scaling experiment ͑RSX͒, a linear device for studying three-dimensional magnetic reconnection in both collisional and collisionless laboratory plasmas, has been constructed at Los Alamos National Laboratory. Advanced experimental features of the RSX that lead to scientific advantages include the use of simple technology ͑commercial plasma guns͒ to create plasma and current channels. Physics motivations, design and construction features of the RSX, are presented. Basic plasma parameters that characterize the RSX are shown together with preliminary measurements of visible light emission during the merging of two parallel current channels.

An electron-free plasma consisting of negative ions (SF6−) and positive ions (Ar+), and negligible neutral-ion collision frequencies has been created in the laboratory. This plasma has a mass ratio of approximately 3.5-similar to many computer particle-in-cell simulated systems. A fluid description of this positive and negative ion confinement (PANIC) plasma is given and compared to experimental measurements of a beam–plasma instability for both beam species and a wide range of beam energies. The fluid dispersion relation and most growing modes are predicted to be insensitive to many parameters of the PANIC beam–plasma system, and found to the consistent with the data.