Sophier's Law of Synchrony: A Physical Framework for the Earth Flyby Anomaly with a Dated Prediction for Europa Clipper, December 3, 2026

The Earth flyby anomaly — an unexplained residual velocity change measured in spacecraft during close Earth flybys — has resisted physical explanation since its identification in the Galileo-1 encounter of 1990. We present Sophier's Law of Synchrony, a first-principles framework deriving the anomaly from two coupled mechanisms: (1) a centrifugal resonance term driven by Earth's rotational medium, and (2) a magnetic field-line coupling term using the full IGRF-13 multipole structure. The framework introduces a dimensionless orbital phase function f_soft = 1 − exp(−k_239 × frac_N), where k_239 = ln(239)/ln(ρ_p) = 19.4754 is derived from the Plastic Ratio ρ_p = 1.324718 and the twin prime pair (239, 241). Applied to all nine reliably measured Earth flybys using verified Jouannic 2015 parameters, the formula (v22b) achieves RMS = 0.753 mm/s — a 51.5% improvement over the Anderson 2008 empirical formula. Seven of nine flybys are predicted within ±1.0 mm/s and all nine within ±2.0 mm/s, with all six non-zero signs correct. A specific, dated, falsifiable prediction is registered: the Europa Clipper Earth flyby of December 3, 2026 will exhibit a positive velocity anomaly in the range +0.578 to +1.736 mm/s. Registered publicly September 3, 2026 — 91 days before the flyby. U.S. Provisional Patent Application No. 64/144,548, filed August 30, 2026.