Observations of plasma waves during a traversal of the Moon's wake

The Wind satellite passed through the solar wind wake of the moon at a distance of about 8 lunar radii on 27 Dec. 1994. Several different wave modes were observed, which we describe. Some of these modes are not certainly identifiable with modes of a uniform plasma, and are probably associated with the density discontinuity, and possibly with a velocity shear, at the boundary of the wake. Modes which are identifiable, at least tentatively, include electromagnetic waves at both fp and 2 fp from outside the wake, and a mode at the local plasma frequency of the wake.