Plasma wave propagation in the neighborhood of a magnetic neutral point |
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| Authors: | Richard L Harkness Jr |
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| Institution: | (1) Harvard College Observatory, U.S.A.;(2) Present address: University of Massachusetts, Amherst, Mass., U.S.A. |
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| Abstract: | A linearized magnetohydrodynamic formalism is used to examine the propagation in two dimensions of transverse waves in a plasma in which is embedded a curl-free magnetic field. Only waves of frequency less than the ion cyclotron frequency are considered. The behavior of a wave packet near the magnetic neutral point is deduced from the general solution to the problem, which is found in terms of Bessel functions whose order is frequency dependent. It is shown that a disturbance propagates through the medium with a group velocity that decreases from the speed of light at large distances from the neutral point to zero at the neutral point, and that the amplitudes of the velocities associated with the disturbance diverge there. It is suggested that the  stagnation of waves near the origin and the deformation of the magnetic field resulting from the large plasma-flow velocities may provide a clue to the formation of the magnetic neutral sheet required by several flare theories and a theory of the acceleration of cosmic rays. |
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