We study the Earth’s variable space environment, from the middle atmosphere to the outer boundaries of the magnetosphere, including the shocked solar wind and the bow shock. Our group leads critical data analysis and theoretical studies, and designs and operates in-situ space science instruments and missions, whose data we share with the world. These efforts provide new understanding of the fundamental physical processes governing conditions in our local cosmos as they change in response to highly variable solar and terrestrial forcing. These processes are universal in nature and our work is also relevant to astrophysical environments and planetary atmospheres. Understanding our Geospace and how it responds to changes in solar activity is also crucial for space weather predictions, which is becoming increasingly important with current and future technological advances including human space flights. The SSL Geospace group has in recent years led highly successful NASA Explorer missions to study the magnetosphere and ionosphere, and in developing new understanding of how they are physically coupled.