Barbara K. Ching

A phenomenological model of global ionospheric electron density in the E-, F1- and F2-regions

Abstract A global phenomenological model of the large scale variations of ionospheric electron density with the annual, diurnal and solar activity cycles has been constructed from monthly-averaged hourly ionospheric sounding data from some 50 stations spanning the years 1957–1970 as provided by World Data Center (A), Boulder, Colorado. The model, summarizing the data in simple empirical formulae and thus requiring little computer storage, is specifically designed for global thermospheric and ionospheric dynamical calculations such as ion drag, Joule heating and atmospheric dynamo effects which require electron or ion densities as essential inputs. Extensive comparison of the model with data and with other models is discussed.

Effects of heating at high latitudes on global thermospheric dynamics

Abstract Three dimensional numerical calculations of thermospheric wind, density and temperature fields generated by solar EuV heating were described in a recent paper by Straus et al. (1975). These model calculations indicated that many of the global characteristics of the thermosphere are generated by EUV heating alone. However, several observed features were found to be poorly represented by the model results. These include the amplitude of the diurnal temperature variation and properties of the diurnal variations of the meridional wind and pressure gradient fields. The present paper describes investigation of the extent to which heating of the thermosphere at high latitudes would contribute to the resolution of these difficulties. This heating lowers the day to night temperature ratio, since it provides a heat source at night. It brings calculated meridional winds and pressure gradients into better agreement with observations, since it raises isobaric surfaces at high latitudes. The amount of heating at high latitudes required to make these modifications is consistent with that due to quiet time joule heating.

A global model of thermospheric dynamics—II. Wind, density, and temperature fields generated by EUV heating

Abstract This paper discusses the extension of the numerical model of the Earths upper atmosphere described by Creekmore et al. (1975) to treat global wind, density and temperature fields generated by absorption of solar extreme ultraviolet (EUV) radiation. The equations of mass, momentum and energy conservation are solved in a spherical shell between the altitudes of 120 and 500 km. Comparisons of the calculated wind, density and temperature fields with those resulting from previous theoretical and observational studies are made. The phases of the density and temperature fields agree quite well with those given by empirical models. However, further comparisons indicate the necessity of a heat source at high latitudes, even during geomagnetically quiet times.

A Global Model of Thermospheric Dynamics, I. Wind and Density Fields Derived from a Phenomenological Temperature.

Abstract This paper describes the mathematical formulation and implementation of a numerical model of the neutral upper atmosphere based on the equations of conservation of mass, momentum and energy in the altitude range 120–500 km. The model is three-dimensional and includes the effects of viscosity, ion drag, the Coriolis force and the nonlinear terms in the equations of motion. The Galerkin method is used as an efficient alternative to finite-difference approaches for the solution of three-dimensional partial differential equations. In the preliminary computations discussed here, the upper atmosphere is represented by a single fluid with molecular weight and temperature fields taken from the phenomenological model of Jacchia (1971). The horizontal and vertical wind fields and the density of the thermosphere are discussed, with particular attention to the diurnally averaged wind fields. Comparisions with previous theoretical and observational investigations are made.