Field compressing magnetothermal instability in laser plasmas

The mechanism for a new instability in magnetized plasmas is presented and a dispersion relation derived. Unstable behavior is shown to result purely from transport processes-feedback between the Nernst effect and the Righi-Leduc heat-flow phenomena in particular-neither hydrodynamic motion nor density gradients are required. Calculations based on a recent nanosecond laser gas-jet experiment D. H. Froula, Phys. Rev. Lett. 98, 135001 (2007)] predict growth of magnetic field and temperature perturbations with typical wavelengths of order 50 μm and characteristic growth times of ～0.1 ns. The instability yields propagating magnetothermal waves whose direction depends on the magnitude of the Hall parameter.