EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-5257 Electrodynamic Reconfiguration of the Polar Ionosphere During the 2021 Antarctic Solar Eclipse Chakraborty Shibaji https://orcid.org/0000-0001-6792-0037 1 Mrak Sebastijan 2 Chartier Alex https://orcid.org/0000-0002-4215-031X 2 Thomas Evan G. https://orcid.org/0000-0001-8036-8793 3 Chisham Gareth https://orcid.org/0000-0003-1151-5934 4 Bristow William 5 Barjatya Aroh 1 Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA Dartmouth College, Hanover, NH, USA British Antarctic Survey, Cambridge CB3 0ET, UK Department of Meteorology and Atmospheric Science, Pennsylvania State University, PA, USA 14 09 2026 2026 1 20 Copyright: © 2026 Shibaji Chakraborty et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5257/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5257/egusphere-2026-5257.pdf

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

 National Science Foundation 2512183 2412295 1934997 2426199 National Aeronautics and Space Administration 80NSSC19K0773 80NSSC24K1268 80NSSC19K0773 Air Force Office of Scientific Research FA9550-24-1-0013 Office of Naval Research N000142312109