Electrodynamic Reconfiguration of the Polar Ionosphere During the 2021 Antarctic Solar Eclipse

Abstract. The 4 December 2021 Antarctic total solar eclipse enhanced anti-sunward polar cap plasma flow, as directly and independently observed by the SuperDARN McMurdo (MCM) radar and the Jang Bogo VIPIR, modulated by eclipse obscuration. AMPERE field-aligned currents (FACs) over the same interval likewise increased with eclipse obscuration, together indicating a possibility of eclipse-driven reconfiguration of polar cap electrodynamics. As supporting, model-dependent context, we combine GITM-derived ionospheric conductance with the AMPERE FACs in a pyMIX potential solver, which shows a loosely corresponding increase in cross-polar-cap potential - consistent with, though not independent confirmation of, the electrodynamic changes observed directly. Separately, the SuperDARN Falkland Islands (FIR) radar observed the sudden emergence of a new 1.5-hop HF propagation mode near the auroral oval boundary during totality and its location of appearance modulated by eclipse obscuration. We examine possible sources of this mode using ray-tracing simulations driven by the same eclipse-modified GITM electron density fields. Together, these multi-instrument observations show that eclipse-driven reduction in ionospheric conductance may drive the coupled magnetosphere--ionosphere (M--I) system through complex, nonlinear adjustment of currents and plasma flow, and that the accompanying changes in ionospheric density can also alter HF propagation conditions.