Frissell, N. A.Katz, J. D.Gunning, S. W.Vega, J. S.Gerrard, Andrew J.Earle, Gregory D.Moses, M. L.West, M. L.Huba, J. D.Erickson, P. J.Miller, E. S.Gerzoff, R. B.Liles, W.Silver, H. W.2019-09-052019-09-052018-05-280094-8276http://hdl.handle.net/10919/93402On 21 August 2017, a total solar eclipse traversed the continental United States and caused large-scale changes in ionospheric densities. These were detected as changes in medium-and high-frequency radio propagation by the Solar Eclipse QSO Party citizen science experiment organized by the Ham Radio Science Citizen Investigation (hamsci.org). This is the first eclipse-ionospheric study to make use of measurements from a citizen-operated, global-scale HF propagation network and develop tools for comparison to a physics-based model ionosphere. Eclipse effects were observed +/- 0.3 hr on 1.8 MHz, +/- 0.75 hr on 3.5 and 7 MHz, and +/- 1 hr on 14 MHz and are consistent with eclipse-induced ionospheric densities. Observations were simulated using the PHaRLAP raytracing toolkit in conjunction with the eclipsed SAMI3 ionospheric model. Model results suggest 1.8, 3.5, and 7 MHz refracted at h >= 125 km altitude with elevation angles theta >= 22 degrees, while 14 MHz signals refracted at h < 125 km with elevation angles theta < 10 degrees.application/pdfenCreative Commons Attribution-NonCommercial-NoDerivatives 4.0 Internationalsolar eclipseionosphereamateur radiocitizen scienceham radioHF propagationArticle - Refereedhttps://doi.org/10.1029/2018GL07732445101944-8007