Stability theory of driftlike electromagnetic waves in two‐dimensional magnetic fields

A two‐component (hot and cold) magnetospheric plasma, with spatially varying densities and temperatures, is considered for the case where the equilibrium magnetic field is two‐dimensional: B=êzBz(x, z) + êxBx(x, z). Such a slab geometry includes the effects of field line bending, to first order. A linear theory of low‐frequency electromagnetic perturbations is developed, for long perpendicular wavelength modes (|▽ 1n n|−1 ∼λy ≲λx). We consider modes that are driven unstable by internal sources of free energy: the spatial gradients in density, temperature, and B field. The electrons of the cold component determine the polarization of the perturbed field (Bly