SIMILARITY OF WAVES IN DISPERSIVE MEDIA

In a previous letter, D.A.Gurnert [1995] discussed the remarkable fact that atmospheric whistlers propagate under, the same emission cone re lative to the earth's magnetic field as bow waves do with respect to t he ship's velocity - namely under 19 degrees 28'. The present contribu tion is a comment on Gurnett's letter and considers a prerequisite for the occurence of the similarity of both phenomena: the independence o f the wave features of parameters such as the ship's speed or the eart h's magnetic field. It is found that media with dispersion relations o f the form omega similar to k(alpha) show such independence; a more ge neral solution is also given.