Tidal–Magnetic Coupling in the Early Earth–Moon System

This work presents a conceptual model describing the coupled tidal and magnetic evolution of the early Earth–Moon system. Following the lunar-forming giant impact, the Moon likely formed at an orbital distance of approximately 25,000–35,000 km from Earth while the terrestrial rotation period may have been between 3.5 and 5 hours. Under these conditions tidal forces and energy dissipation would have been dramatically stronger than in the present system. The model explores the hypothesis that strong tidal interaction and rapid planetary rotation may have temporarily enhanced Earth’s magnetic field during the earliest stage of the Earth–Moon system. A simplified scaling relation is introduced to represent tidal–magnetic coupling: B(D)=5 \times S(D) \times B_{today} with S(D)=1+0.4\left(\frac{D_0}{D}\right)^3 This formulation suggests that Earth’s magnetic field could have been several times stronger than today when the Moon was much closer to Earth. The analysis further indicates that the early terrestrial magnetosphere may have extended beyond ~100,000 km. Given an estimated early lunar distance of about 30,000 km, the Moon may have remained inside Earth’s magnetosphere for a period of roughly 1–10 million years. The work integrates tidal dissipation, angular momentum transfer, planetary rotation, and magnetic field evolution into a unified conceptual framework describing the earliest phase of the Earth–Moon system. Future work will explore a differential dynamical system describing the coupled evolution of Earth–Moon distance, planetary rotation, and magnetic field intensity.