Feedback of Ionospheric D Region to the Coupled Geospace System

Abstract

Understanding and predicting geospace dynamics is critical for safeguarding space infrastructure. For decades, geospace models have ignored the electrical influence of the lower atmosphere below 95 km, presuming low ionization. Since high‐energy particle precipitation reaches these altitudes and triggers intense ionization, this omission may bias our understanding of geospace dynamics. Here we show that the ionospheric D region, a thin chemically active layer at the lower boundary of geospace near 80 km altitude, exerts electrical influences that actively regulate system‐scale dynamics, with consequences extending to 200,000 km away from Earth. Poker Flat Incoherent Scatter Radar observations show that a significant fraction of Hall current flows in the D region during storm‐time precipitation. By analyzing coupled geospace simulations, we found that particle precipitation‐driven, chemistry‐modulated D‐region conductivity instantly reorganizes high‐latitude current closure. In hours, it shifts the magnetotail reconnection site by several Earth radii, and alters thermospheric mass density, thus satellite drag, by . These results establish a novel coupling between atmospheric chemistry and space physics, with implications for satellite orbital prediction.