Inter-hemispheric asymmetries of high-latitude electrodynamic forcing and their impacts on the I-T system: GITM simulations

Most empirical models for the high-latitude electrodynamic forcing are developed assuming the forcing is inter-hemispheric symmetric, which might not be the case under certain conditions. Quantifying the inter-hemispheric asymmetries in the high-latitude electrodynamic forcing and their influences on the ionosphere-thermosphere (I-T) system is an important subject of the Magnetosphere-Ionosphere (M-I) coupling. The major mechanisms contributing to these asymmetries include: (1) different displacements between the Earth's geomagnetic pole and geographic pole at different hemispheres, (2) asymmetric solar EUV irradiations in different hemispheres, and (3) asymmetric high-latitude geomagnetic energy dissipations, including Joule heating and particle precipitation, which vary strongly under the influence of the IMF orientation, especially the effect of B_y. In this study, the effects of these mechanisms on the I-T system have been estimated by comparing several groups of simulations using the Global Ionosphere and Thermosphere Model (GITM), which is a global non-hydrostatic physics-based model. For example, in order to examine the impacts associated with the geomagnetic configuration, three GITM simulations with the pure dipole, tilt dipole and International Geomagnetic Reference Field (IGRF) configurations are compared while keeping other parameters (season, particle precipitation and polar cap potential pattern) the same. The inter-hemispheric asymmetries of the I-T parameters (e.g., the electron density, neutral density and hemispheric integrated Joule heating) associated with different parameters are quantified among the different GITM simulations. Meanwhile, specifications of multi-scale field-aligned currents (FACs) data (e.g., those obtained from the Swarm satellites or the AMPERE patterns) will be used to drive the GITM through a recently coupled NCAR 3D electrodynamo module for real event studies. Our studies will help understand the relative significance of inter-hemispheric asymmetries in the high-latitude electrodynamic forcing and their effects on I-T system, which can be further used to improve the coupled General Circulation Model-Magnetohydrodynamics (GCM-MHD) simulations for the M-I-T system.