Some automatic records of wireless waves reflected from the ionosphere

Some automatic records of wireless waves reflected from the ionosphere are discussed. The records extend over a period of fourteen months. They indicate that the region below the F region may be triply stratified and consist of the intermediate region (effective height approximately 120 to 180 km.), the E region (effective height approximately 100 to 120 km.) and the e region with an effective height which is always nearly 105 km., within ± 5 km. The e region is shown to be intermittent in its occurrence, and is identified with the "nocturnal E region" mentioned in previous papers. The temporal variation of the ionization in these three regions is discussed. A statistical investigation is made to see whether the occurrence of the nocturnal ionization in region e is associated with the occurrence of magnetic disturbances or of thunderstorms. It is shown that if the nocturnal ionization was unrelated to magnetic disturbances the probability of the observed coincidences between the occurrence of the two phenomena would be 0.01, and if thunderstorms and the nocturnal ionization were unrelated the corresponding probability would be 0.0015.