Representing a large heat flow in a plasma as a flow of hot relatively collisionless electrons balanced by an opposing current of cold collisional electrons, it can be shown that an electrothermal instability can be induced in the cold resistive plasma when the heat flow exceeds about 3% of the free-streaming limit. This is nonconvective if the temperature of the cold plasma is less than $0.2{n_e}^{\frac{1}{4}}{Z}^{\frac{1}{2}}$°K, with $n_e$ in ${\mathrm{m}}^{-3\mathrm{}}$. The instability will lead to filamentary magentic structures with a typical growth time of a few picoseconds and wavelength about 10 μm.

• Received 5 March 1981

DOI:https://doi.org/10.1103/PhysRevLett.47.917