Improved basis set for low frequency plasma waves 

Paul Bellan Submitted: 20121025 16:38
It is shown that the low frequency plasma wave equation [Stringer, Plasma Physics 5, 89(1963)] can be obtained much more directly than by the previously used method of solving for the determinant of a matrix involving the three components of the electric field vector. The more direct method uses a twodimensional current density vector space that is precisely equivalent to the previously used threedimensional electric field vector space. Unlike the electric field, the current density is restricted by the quasineutrality condition to a twodimensional vector space. Comparison with previously obtained dispersion relations is provided and a method is presented for obtaining exact analytic solutions for the three roots of the cubic dispersion relation. The commonly used kinetic Alfvén dispersion relation is shown to be valid only for nearperpendicular propagation in a low beta plasma. It is shown that at a crossover point where the perpendicular wave phase velocity equals the ion acoustic velocity, the coupling between Alfvén and fast modes vanishes and the Alfvén mode reverts to its cold form even in situations where the Alfvén velocity is smaller than the electron thermal velocity. A method is prescribed by which measurement of wave electric current density completely eliminates the spacetime ambiguity previously believed to be an unavoidable shortcoming of singlespacecraft frequency measurements.
Authors: P. M. Bellan
Projects: None

Publication Status: accepted for publication in JGRSpace Physics
Last Modified: 20121026 14:54


