A high-resolution, three-dimensional, time dependent, nested grid model ofthe coupled thermosphere-ionosphere

First results are presented from a 3-D, time dependent, high resolution, ne sted grid model that has been developed to study mesoscale processes in the global, coupled thermosphere-ionosphere system. This new Thermosphere-Iono sphere Nested Grid (TING) model, which is an extension of the National Cent er for Atmospheric Research's thermosphere-ionosphere general circulation m odel (NCAR-TIGCM), runs on a UNIX workstation. The TING model simultaneousl y calculates global (coarse resolution) and local (high resolution) distrib utions of:neutral and plasma winds, temperature and composition. It is comp rised of two coupled codes-a global TIGCM and an adjustable nested grid cod e which uses the same solvers as the TIGCM, but has higher spatial and temp oral resolution. The size, location and level of nesting of the high resolu tion grid(s) are adjustable to suit the specific application. The coupling between the coarse (TIGCM) grid and the nested interior grids is via a 'one -way interaction' scheme. In this Scheme, the TIGCM output influences the n ested grid model by providing initial conditions and temporally evolving bo undary conditions, but the outputs from the nested grid are not permitted t o influence the TIGCM. Diurnally-reproducible results of the TING model are presented for solar-maximum, winter solstice, geomagnetically-quiet condit ions. The TING model successfully simulates well-known thermosphere-ionosph ere features that are smeared or not modeled at the spatial resolutions use d in standard TIGCM's. These include the sub-auroral electron density troug h, the polar cap 'hole' and the polar cap 'tongue of ionization'. (C) 1999 Elsevier Science Ltd. All rights reserved.