Comparison of calculated and measured height profiles of transverse electric VLF signals across the daytime earth-ionosphere waveguide

Airborne VLF antennas radiate energy that propagates via both transverse electric (TE) and transverse magnetic (TM) modes in the earth-ionosphere waveguide. In order to compare the structure of such signals, measurements were made using rocket probes launched from Wallops Island, Virginia. The probes measured TE and TM fields at all altitudes between the ground and the base of the ionosphere. The nearly horizontal airborne transmitting antenna radiated a TE signal that was stronger than its TM signal at altitudes above about 10 km. The signals comprised one or more well-defined TE or TM waveguide modes. Calculated height profiles agree well with the measured ones and correctly reproduce details of profile structure caused by interaction between two or more modes.