Total Density Profile Research Articles

The quiet midlatitude D-region: a comparison between modeling efforts and experimental measurements

Two long-standing problems in the atmospheric sciences have been the correct modeling of the ion chemistry in the earth's atmosphere and the proper determination of the ion species and densities through in situ measurements. Comparison between experimental data and simulations of the data by computer modeling of atmospheric chemistry is a means of validating the model as well as indicating which processes are in need of further study. The DAIRCHEM computer code is used here to simulate data taken in the midlatitude D-region during quiet conditions. On the one hand, comparison between the total positive ion density profile derived from rocket measurements and the one computed by the code shows very good agreement in the 30–90 km range, with the exception that the simulated ion profile is somewhat smaller than the experimental one in the 60–75 km region. Such discrepancy is only partially explained by the inherent uncertainties in the NO density profile or the total ionization rate profile. On the other hand, comparison between the measured and the computed electron density profiles shows that the measured profile is consistently smaller than the computed profile in the 65–85 km range. We interpret this discrepancy as a deficiency in the modeling of the negative ion chemistry. Also, this deficiency is probably the main cause of the disparity between the total positive ion density profiles in the corresponding altitude range. It is felt that the positive ion chemistry of the D-region is reasonably well understood. However, the negative ion chemistry is in need of further study. Specifically, alternate electron attachment/detachment processes should be considered, as well as an as yet undetermined, possibly very massive, negative species which may affect the ion recombination rates.

Theory of Surface Tension in Liquid Mixtures

Abstract Equations determining the density profiles of a multicomponent liquid are first given in terms of the partial direct correlation functions in the presence of the surface. The fluctuation theory of surface tension is also generalized to liquid mixtures. The density gradient procedure simplifies the above problem to knowledge of direct correlation functions in the bulk mixture. For the binary case, the density profile equations are then usefully written in terms of number-concentration correlation functions. The total density and surface segregation profiles are finally considered in a simplified model by utilizing the theory of conformal solutions. Such a model, though limited in practice, should apply, for example, to the Na-K alloy system.

Changes in water level at Lake Vanda, Antarctica

Summary Work already done and that proposed at Lake Vandia is outlined. Water‐level measurements are not indicative of total river inflow, as summer saturation of grounded porous ice temporarily lowers the lake level; for accurate inflow measurements, construction of a weir at the river mouth is planned. To calculate the total lake budget, density and temperature profiles of the ice cover and knowledge of evaporation rates are needed.