The dispersion relation for the electron cyclotron mode propagating parallel to the magnetic field is calculated for a Maxwellian plasma by using various densities and temperatures appropriate to the magnetosphere. In addition to the phenomenon of cyclotron damping it is noted that the inclusion of temperature effects markedly changes the wavelength for frequencies above 0.9 &ohgr;ce. A similar result is obtained in the case of the ion cyclotron mode. The altered &ohgr;-k diagrams have significant impact on proposed three-wave interaction mechanisms.