Negative magnetic viscosity in two dimensions

The occurrence of “negative viscosities” is studied within the framework of two-dimensional magnetohydrodynamics MHD. We use assumptions which are typical when studying the effects of smaller-scale fields on larger-scale ones, namely, the small-scale MHD fields are assumed to be sufficiently weak, jointly stationary, homogeneous, and maintained by external sources. The criteria of large-scale field generation due to negative viscosities are derived for various special forms of isotropic small-scale fields as well as anisotropic ones; the latter can be regarded as MHD stochastic analogs of the known Kolmogorov flow. Zh. éksp. Teor. Fiz. 116, 1264–1286 (October 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.