Topside Scale Height Research Articles

Atmospheric sodium measurements at 23°S

Measurements of the nighttime atmospheric sodium layer have been made over a period of 4 months at São José dos Campos (23°S, 46°W), using the laser radar technique. Peak sodium concentration is found at a height of 95 km and the topside scale height of the layer is usually less than 2 km. On six occasions a secondary peak has been observed at heights between 100 and 105 km. Detailed structure in the layer is frequently conserved from night to night and it is suggested that such structure may be the result of atmospheric tidal oscillations. Comparison with twilight measurements indicates that the average total abundance of sodium shortly after sunset is between 0.38 and 1.25 of the twilight value.

Shallow-Solar-Zenith-Angle Control of Topside Ionospheric Parameters

STRONG latitudinal variations in topside ionospheric electron densities and scale heights occurred during the overall sunrise period October 28, 1963, to November 21, 1963 (ref. 1). The raw data of ref. 1 were some 600 ionograms obtained by the Alouette I topside sounder as it traversed above regions near and over the North American continent which was experiencing local sunrise at ionospheric heights. Here I report variations in topside electron densities, scale heights and related parameters at fixed latitudes (45° N, 55° N, 60° N geomagnetic latitude) with solar zenith angle at local sunrise during the time period mentioned

Sunrise Effects on the Latitudinal Variations of Topside Ionospheric Densities and Scale Heights

IONOSPHERIC sunrise represents the transition period between quasi-equilibrium conditions attained during the night and those attained during the day. The arrival of sunrise is manifested by a rapid increase in electron temperatures and a less rapid increase in ion temperatures at all altitudes1. In a plasma distribution that tends towards equilibrium, a sharp increase in particle temperature results in a redistribution of the plasma. In the topside ionosphere, this is manifested by a diffusive flux of ions and electrons.

Mariner 9 ultraviolet spectrometer experiment: Structure of Mars' upper atmosphere

Analysis of 18 observations of the limb intensity profile of the CO Cameron bands in the Martian airglow shows that the equivalent subsolar zenith intensity, ICAM, is related to the Ottawa 10.7 cm radio flux index, F10.7, by the expression ICAM = 0.062(74 + F10.7)kR, with a correlation coefficient of 0.80. Comparison of averaged limb intensities of the CO2+ doublet and the Cameron bands on four favorable occasions is consistent with the intensities being directly proportional, in the ratio 0.24:1. The mean of 18 Cameron band topside scale heights is 17.8 km, corresponding to an exospheric temperature of 325°K, and the largest and smallest values observed differ by 9.5 km. These observations are in accord with theoretical predictions within the uncertainties in the latter. However, the solar EUV flux used in these predictions is a factor of at least two too weak to produce the electron densities measured by the S-band occultation experiment.

Laser radar measurements of the atmospheric sodium layer

Regular measurements of the sodium layer at 90 km height, during twilight and throughout the night, by means of a laser radar are reported. The main features observed are night-time abundances similar to those at twilight, topside scale heights of 2–3 km and fluctuations corresponding to patches of sodium extending over horizontal distances of 10–200 km. The observations are discussed in relation to theories of the sodium layer and suggestions for future experiments are made.

Twilight observations of upper atmospheric sodium, potassium, and lithium

Twilight resonance emissions due to atmospheric sodium, lithium, and potassium have been measured for over one year. The existence of the potassium resonance line was verified by using an absorption cell.Several problems of measuring the emissions and of subsequently calculating a density distribution are discussed. The widths of about 13 km and the topside scale heights of about 4.5 km obtained for the sodium layer are significantly less than obtained at Saskatoon in previous measurements. Atmospheric transmission functions have been recalculated with the results that the sodium and lithium layers are both at about the same height of around 90 km. A lower height of about 85 km was obtained for the potassium layer.The seasonal variations of sodium and lithium twilight abundances are shown to be similar with additional sharp enhancements of lithium abundances thought to be due to natural and man-made injections of lithium. Any seasonal variations of the potassium abundances in the lower layer were masked by large day-to-day fluctuations.

Rocket measurements of the sodium dayglow

Sodium dayglow photometers were flown on Aerobee rockets on the mornings of April 7 and June 19, 1964. Good profiles of the emission were obtained for comparison with twilight measurements. In June, the twilight and daytime abundances were the same; the vertical distributions agreed fairly well. In April, the daytime abundance was greater by a factor of about 1.45; the heights were again nearly the same. The top of the day layer had the remarkably small scale height of 3 km. Photochemical theory, including the recent version by Blamont and Donahue, predicts a topside scale height of 7 or 8 km and a considerable lowering of the daytime layer. It is suggested that a new factor must be introduced, consisting of an equilibrium between sodium atoms and a distribution of dust particles. Under some conditions, atoms may evaporate from these particles in the daytime and return to them at night. Another photometer on the June flight was unable to detect any lithium emission. The upper limit thus set to the lithium abundance is consistent with the low part of the range observed in twilight.

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

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 σ¯, 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 σ¯ 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.