Formation of the Moon by secession of a collective flow from the intertropical belt. Fully fluid regime, Λ ∗ criterion, hydrodynamic phase transition, bifurcation, collective mode and coherent ejection dynamics

Formation of the Moon by intertropical secession of a collective flow: fully fluid regime, Λ criterion, hydrodynamic phase transition, bifurcation, collective mode, and coherent ejection dynamics This work proposes a physically autonomous alternative to the Giant Impact hypothesis for the formation of the Moon. It is set in the tumultuous context of the early Solar System (~4.55–4.50 Ga), characterized by a high density of unaccreted objects, an active T-Tauri Sun, and a fully fluid proto-Earth with a torrid silicate atmosphere (T ~ 2,000–4,000 K), maintained by the absence of an insulating crust. The mechanism relies on a supercritical pitchfork bifurcation governed by the dimensionless control parameter Λ* = α₀ Ω τν(T), which compares rotational power injection to viscous dissipation. When Λ* exceeds unity, the tropical band (±15–30° latitude) becomes unstable. Taylor–Proudman columns focus the flow, and the dominant global azimuthal mode (m = 1, ℓ = 1) emerges. The flow accelerates exponentially toward a critical velocity U_crit ≈ 11.3 km/s. Each secession episode ejects a mass M_ej ≈ 10²² kg (≈ M_Moon/7), with kinetic energy E_k ≈ 7.4 |E_orb|, forming a debris disk at r ≈ 2.0 R_⊕, inside the Roche limit. Accretion onto a seed core ≲200 km builds the Moon over 5–14 episodes, spanning ~40 Myr. The lunar iron deficit and near-isotopic identity (O, W, Ti, Cr, Si) arise naturally: the ejected material originates from the silicate mantle already depleted by rapid core segregation (<30 Myr, Hf–W chronology), with no ad hoc adjustment. The process self-extinguishes as cooling increases viscosity, reducing Re_rot below a critical threshold. Falsifiable predictions include: M_Moon ∝ Ω² (testable on exoplanets), a T-Tauri solar wind signature in primitive lunar materials, a radial Fe/Si lunar gradient, a small out-of-plane velocity component v_z ≈ 17 m/s, and zonally structured mantle heterogeneities on Earth. This work is explicitly submitted to the simulation community (SPH, GFD, N-body) for testing, validation, or refutation. It is an open theoretical proposal, not a definitive demonstration.