A Global Data Assimilation Study of Substorms

Study of substorms and their ionospheric effects has its fundamental importance for understanding the Sun-Earth interactions. In the past, numerous model studies of the ionospheric electrodynamics and plasma dynamics during substorms have been performed, but very few studies have been done by using a data assimilation model with the ingestion of observational measurements. Due to their internal consistency and the completeness of descriptions on the status of global systems, the physics-based data assimilation models have their unique strength in discovering the important physical processes that are inadequately observed or missed by measurements due to observational limitations. In this study, an Ionospheric Dynamics and Electrodynamics Data Assimilation Model (IDED-DA) is used to perform a series of studies of substorms in order to get a more self-consistent global dynamic picture of the ionospheric electrodynamics and plasma dynamics during substorms. Specifically, we first identify a number of substorm periods with various substorm characteristics and a wide range of geo-conditions. Then, the IDED-DA model is run for these periods with the ingestions of multiple observational measurements, including the magnetometer data from more than 40 ground stations and SuperDARN line-of-sight velocity measurements. The model outputs are the time-dependent 3-dimensional representations of the ionospheric dynamics and electrodynamics during the substorms, including the plasma density, ion and electron temperatures, convection electric field, horizontal and field-aligned currents, conductivity, as well as a complete set of the auxiliary ionospheric plasma parameters. The initial results from these runs are presented in this presentation with the focus on the development of small-scale substorm structures.