Electromagnetic radiation from sources immersed in a cold magnetoplasma is analyzed by the use of 'principal-polarized' wave coordinates; and the wave fields, the mean complex radiated power, and the Poynting vector are systematically expressed in terms of 'polarized' wave modes. For each polarized wave mode, the medium is effectively isotropic, since the Fourier-transformed wave equation for each principal mode is decoupled and is similar to the one obtained from the usual scalar Helmholtz operator. In application of the theory, consideration is made of the radiation resistance of a linear electric antenna of moderate length oriented both parallel and perpendicular to the static magnetic field. Approximate closed form expressions for the radiation resistance are obtained for the VLF frequency range by using a plasma model appropriate to the magnetosphere. These approximate closedform expressions are compared with the results obtained previously by other workers using a quasi-static approximation, and it is shown that excellent agreement exists between the two methods of analysis. It is concluded that the quasi-static approximation can accurately predict the radiation resistance of a linear antenna in the magnetosphere, given certain moderate restrictions on the antenna length.

By using full‐wave theory, an analysis is made of the radiation resistance of a short filamentary electric dipole, oriented with an arbitrary angle with respect to the static magnetic field, in a cold, uniform magnetoplasma. The frequency range considered lies below the local lower hybrid resonance frequency and above the proton gyrofrequency, and in this range approximate closed‐form expressions for the radiation resistance are obtained by using a plasma model appropriate to the magnetosphere. These closed‐form expressions are valid for dipoles of moderately restricted length, and the physical implications of this length restriction are discussed. It is found that the radiation resistance R increases rapidly as ф0, the angle of dipole orientation with respect to the magnetic field, varies from 0° to 30° but only gradually as ф0 varies from 30° up to 90°. The ratio of R(ф0 = 90°)/R(ф0= 0°) is approximately equal to (ƒHe/ƒ)2. Except for the case of parallel orientation and ƒ < 10−2 ƒHe, the radiation resistance of an electric dipole in the magnetoplasma is ∼ 102 to 105 times larger than that in free space. Thus, for the low frequency range considered, an electric dipole in the magnetoplasma is generally much more efficient that it would be in free space.