An investigation of high-latitude ionosphere -thermosphere dynamics and electrodynamics.

Abstract

Results of an investigation of the spatial and temporal effects of mesoscale processes and different model inputs on the simulations of the high-latitude dynamics and electrodynamics are presented. This work is undertaken by using both theoretical and experimental tools. The small-scale, local ion-neutral coupling processes were studied with measurements obtained from ground-based instruments (Thule FPI, <italic>Q&acirc;n&acirc;q</italic> digisonde and Sondrestrom radar and FPI), which built up a base line for the later modeling efforts. The global morphological structures of high-latitude electrodynamics were simulated by using the Thermosphere-Ionosphere Nested Grid (TING) model with both fine grid (1.67&deg; x 1.67&deg;) and coarse grid (5&deg; x 5&deg;), the diagnostic packages of the TING model were modified to enable the capability. The spatial resolution effects on the modeling of various high-latitude electrodynamic features have been thoroughly investigated under both geomagnetic storm and quiet conditions. The study shows that a higher spatial resolution and realistic auroral inputs are essential in describing the mesoscale processes, such as Joule heating and field-aligned currents. To extend the model predictability to Interplanetary Magnetic Field (IMF) B_z northward and close to zero (nT) conditions, Weimer-grid TING model has been developed, which incorporates the Weimer convection model and the Air Force precipitation models into the TING model and is able to simulate some typical phenomena under IMF northward conditions. Validation work has been made using measurements from the DE-2 satellite, observational data from an Incoherent Scatter radar over Sondrestrom, calculations from the one-dimensional satellite track model, and the Heelis-grid TING model results, good agreements were found between the Weimer-grid TING model results and the observational data as well as other model results during IMF B_z close to zero (nT) and southward conditions.