Ionospheric Modeling

Published by the American Geophysical Union as part of theGeophysical Monograph Series, Volume 201. Modeling the Ionosphere-Thermosphere System bringstogether for the first time a detailed description of the physicsof the IT system in conjunction with numerical techniques to solvethe complex system of equations that describe the system, as wellas issues of current interest. Volume highlights includediscussions of: Physics of the ionosphere and thermosphere IT system, and thenumerical methods to solve the basic equations of the ITsystem The physics and numerical methods to determine the globalelectrodynamics of the IT system The response of the IT system to forcings from below (i.e., thelower atmosphere) and from above (i.e., the magnetosphere) The physics and numerical methods to model ionosphericirregularities Data assimilation techniques, comparison of model results todata, climate variability studies, and applications to spaceweather Providing a clear description of the physics of this system inseveral tutorial-like articles, Modeling theIonosphere-Thermosphere System is of value to the upperatmosphere science community in general. Chapters describingdetails of the numerical methods used to solve the equations thatdescribe the IT system make the volume useful to both activeresearchers in the field and students.

An electron density model, which permits a three-dimensional specification of the ionospheric structure, has been developed. The model generates realistic electron density profiles in the altitude range from 100 to 800 km by making use of selected ionospheric parameters that are routinely observed. The model also allows for the calculation of the electron distribution over the entire path of propagation of a radio signal by employing a synoptic mapping technique. The mapping technique enagles ionospheric parameters observed at specific locations to be extended and extrapolated to regions where data are not normally accessible. The electron densities that are computed are done in a manner that is totally consistent with the observed parameters needed to generate the profiles. (Author).

The purpose of this report is to familiarize a user of ionospheric models with the options presently available for ionospheric prediction and specification. Two types of ionospheric models are available: the numerical-phenomenological and theoretical models. From the numerical type, the ITS-78, IONCAP, and Bent models have been discussed. In the theoretical models the main concern is the number of parameters included in the model. Nine ionospheric models available have been summarized. The differences and limitations of these models are compared and tabulated. This information will help a user make a judicious selection of an ionospheric model to satisfy his specific needs. The sources for obtaining the programs for these models have been listed for ready references.

The results of a study undertaken to determine the feasibility of employing synoptic mapping to improve ionospheric forecasting capabilities are presented. Using electron density data obtained from 16 ionosonde stations located in North America and Greenland during the time period mid-April through July 1970, the temporal and spatial variability of the ionosphere was assessed. (Author).

A model describing the mid-latitude bottomside electron density profile is presented. The only geophysical input parameters required for the model are critical frequency, M-factor, planetary index (Ap), and 2800 MHz solar radio flux. An empirically-determined formula for calculating H(m)F2 is derived and used in the model. This formula is a function of the M-factor, local time, day number and magnetic activity. The results obtained by comparing predicted profiles to observed electron density profiles are presented in the form of mean percentage errors as a function of height and local time. The New Model IS COMPARED TO A MODEL CURRENTLY IN OPERATIONAL USE AND IS SHOWN TO BE A 10 TO 20 PERCENT IMPROVEMENT. (Author)