Ray propagation of VLF waves beyond about 1000 km breaks down, because, and ther sum of thses waves succesive multihop sky waves are involved, and it becomes necessary to take into account the spherical Earth.
Ray propagation of VLF waves beyond about 1000 km breaks down. This is because. Ther sum of thses waves succesive. Multihop sky waves are involved. It becomes necessary to take into account the spherical Earth.