Very Low Frequency (VLF) radio phenomena (on the ground or in space) has been an interesting field of research. This area has rapidly gained immense importance in the diagnostic study of navigation, frequency, time standards and observations of naturally occurring VLF waves as a remote sensing technique for the earth’s upper atmosphere. The VLF technique also has the ability to measure very low electron density, which cannot be sensed by the satellite.

The present volume, which is one step towards achieving the above mentioned goals, covers the most important topic of the generation and propagation of the VLF waves along with some important results through VLF radio experiments like Trimpi effect and absorption of VLF radio waves under the polar cap of earth’s upper atmosphere. Recent observation of VLF waves through direction finding experiment at Antarctica that revealed some important aspects on the above subject and related theories on generation and propagation of the VLF waves have also been discussed by the experts.