Radio atmospheric km. For ELF waves (< 3 kHz), ray theory becomes invalid, and only mode theory is appropriate. Here, the zeroth mode begins to dominate and is responsible for the second window at greater distances. Resonant waves of this zeroth mode can be excited in the Earth–ionosphere waveguide cavity, mainly by the continuing current components of lightning flowing between two return strokes. Their wavelengths are integral fractions of the Earth's circumference, and their resonance frequencies can thus be approximately determined by "f" ≃ "mc"/(2π"a") ≃ 7.5 "m" Hz (with "m" = 1, 2, ...; "a" the Earth's radius and "c" the
Waves Radio Waves Radio Waves Radio is a local radio station based in Peterhead, North East Scotland. The station is on air 24 hours a day with live shows from 6am till 10pm (apart from "a wave of hits" from 6pm-7pm on weekdays which is automated). Waves Radio was born in 1990 after its founder and owner known as Kenny King applied to the then Radio Authority for an RSL licence. The station in the early years was known as Waves AM broadcasting by means of Restricted Service Licences from a studio at the Lido beach area in Peterhead, during the towns