The Origin of the Hot Plasma in the Galactic Halo: A Proton-Sea Model and Jet-Termination Nucleosynthesis

The precise origin of the high-temperature plasma (~10⁷ K) and heavy-element content (C, Si, O) of the galactic halo is not fully explained by standard models. This paper proposes a complementary mechanism: relativistic AGN jets arrive at a "proton sea" of previously deposited protons in the halo. At the collision zone, the Maxwell–Boltzmann tail exceeds the 1.293 MeV neutron-formation threshold, initiating heavy-element synthesis. Consistent with Hubble Project AMIGA, XMM-Newton, Suzaku, and eROSITA observations. Three falsifiable predictions are presented. This is Paper 3 in the Scale-Invariant Vortex Dynamics series (Joó, 2026).