Journal ArticleThe Significance of Magnetospheric Precipitation for the Coupling of Magnetosphere-Ionosphere-Thermosphere Systems: Sources and PropertiesOzturk, Dogacan; Lin, Dong; Gabrielse, Christine; Chen, Margaret; Grandin, Maxime; Sivadas, Nithin; Robinson, Robert; Garcia-Sage, Katherine; Damiano, Peter; Blum, Lauren; Yu, Yiqun; Liu, Jiang; Varney, Roger; Sarris, Theodoros; Zhan, Weijia; Vines, Sarah; Jaynes, Allison; Lin, Yu; Ridley, Aaron; Kaeppler, Stephen RMagnetospheric precipitation plays an important role for the coupling of Magnetosphere, Ionosphere, and Thermosphere (M-I-T) systems. Particles from different origins could be energized through various physical mechanisms and in turn disturb the Ionosphere, the ionized region of the Earth’s atmosphere that is important for telecommunication and spacecraft operations. Known to cause aurora, bright displays of light across the night sky, magnetospheric particle precipitation, modifies ionospheric conductance further affecting the plasma convection, field-aligned (FAC) and ionospheric currents, and ionospheric/thermospheric temperature and densities. Therefore, understanding the properties of different sources of magnetospheric precipitation and their relative roles on electrodynamic coupling of M-I across a broad range of spatiotemporal scales is crucial. In this paper, we detail some of the important open questions regarding the origins of magnetospheric particle precipitation and how precipitation affects ionospheric conductance. In a companion paper titled “The Significance of Magnetospheric Precipitation for the Coupling of Magnetosphere-Ionosphere-Thermosphere Systems: Effects on Ionospheric Conductance”, we describe how particle precipitation affects the vertical structure of the ionospheric conductivity and provide recommendations to improve its modelling.Bulletin of the American Astronomical Society2023-08-2310516085Bulletin of the AAS0002-7537https://doi.org/10.3847/25c2cfeb.be32d93d2225405National Science Foundation