The antenna impedance of a small VLF loop antenna carrying a uniform current in a warm Collisionless, uniform multicomponent magnetoplasma is investigated. Integral expressions are derived for the antenna impedance when the loop is oriented with its axis either parallel or perpendicular to the static magnetic field B0. These integral expressions for impedance are then applied to plasmas typical of the upper ionosphere and inner magnetosphere. Numerical values of the loop radiation resistance corresponding to the whistler mode and the thermal modes are derived and used to estimate the whistler mode radiation efficiency. This efficiency is usually larger than 80% but may be as low as 60% for frequencies close to the lower hybrid resonance frequency if the plasma density is relatively low.

Linear electromagnetic theory is used to find the VLF‐ELF radiation characteristics of a quadrature‐phased crossed‐dipole array in a cold multicomponent magnetoplasma. Each dipole is perpendicular to the static magnetic field B0, and the current on each is assumed to have a skin‐triangular distribution. Formal solutions valid throughout the VLF and ELF ranges are derived for the total radiated complex power and mutual coupling power. These solutions are used to obtain both numerical results and approximate closed‐form expressions for mutual input impedance ΔZ applicable to the driving terminals of either dipole of the array. Approximate closed‐form expressions for the power fluxes parallel and perpendicular to B0 are also derived. When a right‐circularly phased dipole array is used as a radiating source in the VLF range, the total power radiated into the whistler mode is increased, and the power flux along the field line is enhanced by a factor of 4 compared to that from a single dipole carrying the same current. In the ELF range, the effects are similar but more complicated. The mutual input reactance due to the effects of medium anisotropy and circular phasing of the dipole array are found to be negligible. It is shown that the power flux along B0 from a right‐circularly phased dipole array peaks by at least 1 order of magnitude at approximately half the electron gyrofrequency. This result suggests a possible use of the proposed array as a radiating source to trigger artificially stimulated VLF emissions.