a1 Department of Aerospace and Atmospheric Sciences, The Catholic University of America, Washington, D.C. 20017
A study of the compressive magneto-acoustic waves in a guiding centre plasma shows that the wave-front that emerges from a point disturbance after a finite time is a simple oblate spheroid with the axis of revolution parallel to the field lines. Thus, in a steady three-dimensional supersonic flow of guiding centre plasma a simple analytic expression can be obtained to represent the characteristic surfaces. From a proper linear combination of the governing macroscopic equations, the characteristic equation is obtained. It represents the propagation of disturbances on the characteristic surface. The characteristic theory can be used to study the interaction of the solar wind with the moon and possibly with other planetary bodies.
(Received August 16 1971)