From Ionospheric Weather Nowcast to Forecast: 1. Choice of IRTAM Basis

Assimilative empirical models use available geospace observations to transform, on local or global scales, the underlying climatological model, such as International Reference Ionosphere (IRI), into a better match with the observations. Provided with near real-time sensor data, AEMs become useful in applications that rely on an accurate ionospheric weather nowcast. We make another step towards extending the AEM scope to the forecast applications that require knowledge of the ionospheric conditions over next several days. Development of such forecast capability has to emphasize processes that are not local and rethink the reference frame and coordinate system for its representations of the ionospheric dynamics from corotating to solar synchronous frame. We discuss details of the proposed expansion basis functions for implementation in forecasting AEMs.