A computer simulation of the midlatitude plasmasphere and ionosphere

Abstract

The main objective of this paper is to report the development of a new computer model to simulate species density, temperature and plasma flow in the ionosphere and plasmasphere. The paper provides a general description of the code for potential users. The model incorporates the attractive features of previous models reported in the literature. In addition significant improvements have been made, which render the code a comprehensive tool for studying the ionosphere-plasmasphere environment. For example, the calculations are carried out across an entire field tube extending from the E region in one hemisphere to the E region in the conjugate ionosphere. The coupled continuity, momentum, energy, heat flow and photoelectron equations are solved in a quasi-simultaneous manner. The efficiency of the numerical solution was much improved by using an integral form of the continuity and momentum equations which resembles the form used in the shooting method at high altitudes, and the conventional parabolic solution in the F region and topside ionosphere below 2000 km. The equations are formulated to facilitate linking the plasmasphere and ionosphere. The equations have been expressed in a new way which we have called "flux preserving," and solved using a Newton iteration. The speed of convergence of the solution procedure is further improved by the use of predictive techniques.The results reported in the paper are the product of numerical tests that were carried out to assess the performance of the code. The choice of material for analysis therefore was not determined by geophysical criteria. However, several interesting results were obtained which warrant reporting. These include (1) the discovery that counterstreaming of H+ and O+ ions occurs under steady state conditions; (2) that our theoretical results agree with recent measurements of electron temperature in the plasmasphere, which are significantly lower than previous measurements. However, there is an indication that a magnetospheric source of heat may nevertheless be required for precise agreement.