MODELING HIGH-LATITUDE ELECTRON-DENSITIES WITH A COUPLED THERMOSPHERE-IONOSPHERE MODEL

A few of the difficulties in accurately modelling high-latitude electr on densities with a large-scale numerical model of the thermosphere an d ionosphere are addressed by comparing electron densities calculated with the Coupled Thermosphere-Ionosphere Model (CTIM) to EISCAT data. Two types of simulations are presented. The first set of simulations c onsists of four diurnally reproducible model runs for a Kp index of 40 which differ only in the placement of the energetic-particle distribu tion and convection pattern input at high latitudes. These simulations predict varying amounts of agreement with the EISCAT data and illustr ate that for a given Kp there is no unique solution at high-latitudes. Small changes in the high-latitude inputs cause dramatic changes in t he high-latitude modelled densities. The second type of simulation con sists of inputting statistical convection and particle precipitation p atterns which shrink or grow as a function of Kp throughout a 3-day pe riod 21-23 February 1990. Comparisons with the EISCAT data for the 3 d ays indicate that equatorward of the particle precipitation the model accurately simulates the data, while in the auroral zone there is more variability in the data than the model. Changing the high-latitude fo rcing as a function of Kp allows the CTIM to model the average behavio r of the electron densities; however at auroral latitudes model spatia l and temporal scales are too large to simulate the detailed variation seen in individual nights of data.