Double?Layer Phenomena in the Es Region

Abstract

At Brisbane, ionospheric records are frequently made which show the simultaneous presence of two types of Es ionization, one at greater virtual range than the other; these have been classified by McNicol and Gipps (1951) as "sequential" type (Ess), and "constant-height" type (Esc), respectively. Such records occur most frequently in the late afternoon and early evening, particularly in summer, when Ess is in its last stages and Esc is building up to its maximum intensity (Thomas 1956).