Spectral widths and shapes and other characteristics of incoherent backscatter from the ionosphere observed at 440 megacycles per second during a 24-hour period in May 1961

Abstract

Characteristics of radar signals backscattered incoherently from the F region of the ionosphere were observed during a 24-hour period from May 9 to 10, 1961. Samples of the frequency spectrums and of the electron density distributions deduced from backscatter power measurements were taken at various times during the period. Objective of the experiment was threefold: (1) to determine the spectral characteristics as functions of height and time of day; (2) to observe any diurnal variations in the scale height on the topside of the F region; and (3) to observe any diurnal variation in , the radar cross section of the scatterers. Changes observed in the spectral width are interpreted as indicating that the ion temperature is lower at night than during the day. The height of the wings observed in the frequency spectrums was greater in the day than at night, indicating an increase in the electron-to-ion temperature ratio. Topside scale heights were larger in the day than at night. Values of calculated from nearly simultaneous measurements of backscattered power and the F2 critical frequency varied by a factor of about two to one, the smallest value occurring near sunrise.