Whistler Mode Radiation From a Dipole Antenna in Cold Magnetized Plasma

Abstract:

We treat whistler mode radiation from a dipole antenna based on the Fresnel zone construction theory. Radiated waves with different propagation directions interfere in space. Strong waves are observed when the interference is predominantly constructive at the observation point. The observed coherent wave propagates at the group velocity. If the antenna is perpendicular to the background magnetic field, the regions of strong waves form a parabolic-shaped cone of the Fresnel zone along the background magnetic field with a power drop-off rate of 1/r. The derived radiation resistance from the total energy flux integrated over the Fresnel zone is proportional to 1/f². A longer antenna length squarely increases the radiation resistance from that of a shorter antenna. The model predictions are compared with the Demonstration and Science Experiments (DSX) measurements of antenna resistance and the observation of the size of the Fresnel zone and amplitude of the electric field by the Arase satellite.