R&D Report 1956-10 : Reception disturbances over North Atlantic paths during the years 1947 to 1954. T.W. Bennington The records of reception conditions over North Atlantic paths which are regularly made at Tatsfield have been examined for the eight years 1947 to 1954, with a view to learning something about the effects of ionospheric disturbances upon reception over these paths. The nature of the long-period and seasonal variations in the incidence of such disturbances has been investigated. The mean duration of the 250 reception disturbances examined was found to be 3.1 days, with a maximum duration of 17 days. Using the superposed epoch method for studying the average conditions during disturbances the relation between the time of start of a magnetic and of a reception disturbances was ascertained, and the variation of fÂ° f2, may have some warning value of the onset of disturbed reception conditions.