Our understanding of geospace often assumes the northern and southern hemispheres respond symmetrically to Sun–Earth interactions—but this is not the case. Our studies investigate inter-hemispheric asymmetries (IHAs) in the high-latitude electrodynamics and their impacts on the coupled magnetosphere-ionosphere-thermosphere (M-I-T) system, using multi-satellite observations and advanced numerical model simulations. The work addresses three key questions: (1) Why are the ionosphere and thermosphere different between hemispheres? (2) How do these differences influence the geospace environment? and (3) How can we better detect and quantify these asymmetries across scales? Our results show that the IHA is not a minor phenomenon but has important implications for understanding the coupled magnetosphere-ionosphere-thermosphere.