Drift-Alfvén fluctuations associated with a narrow pressure striation

This analytical and numerical study illustrates the linear stability properties of low frequency electromagnetic eigenmodes driven by field-aligned pressure striations whose scale transverse to the confining magnetic field is on the order of the electron skin-depth. A full electromagnetic formulation is given in terms of the coupling of the fluctuating axial fields (Ẽz,B̃z) and incorporates shear and compressional Alfvén waves, drift waves, and ion acoustic waves. The kinetic response of the electrons includes pitch-angle scattering (Lorentz model) and the ions are treated as a magnetized, cold fluid. Detailed quantitative comparisons of the theoretical predictions are made with laboratory observations of fluctuations generated in controlled pressure depletions [J. E. Maggs and G. J. Morales, Phys. Plasmas 4, 290 (1997)] and in narrow temperature plumes [A. T. Burke, J. E. Maggs, and G. J. Morales, Phys. Rev. Lett. 81, 3659 (1998)].