Electromagnetic ion acoustic perturbations in spatially varying plasma

It is pointed out that an ion acoustic wave in an inhomogeneous plasma naturally couples with a transverse (with respect to the direction of the wave vector) electromagnetic perturbation. Due to this coupling, the ion acoustic mode becomes essentially electromagnetic. In addition, there appears to be a lower frequency cutoff of the ion acoustic wave. The wave becomes dispersive and backward, i.e., with a negative group velocity. The presented coupling mechanism should play a role in the magnetic field generation in spatially inhomogeneous plasmas at the ion acoustic time scale. © 2007 American Institute of Physics.status: publishe