Abstract We compute the electromagnetic structure of the proton within the topological soliton framework developed in Papers I and III. The proton is identified with the lightest $H=1$ configuration of the $F_2 = \text{SU}(3)/[\text{U}(1)\times\text{U}(1)]$ flag manifold sigma model, whose three topological sectors carry the quantum numbers of two up quarks and one down quark. Adapting the Adkins-Nappi-Witten collective coordinate quantization to the flag manifold target space, we derive the proton mass, electromagnetic form factors $G_E(Q^2)$ and $G_M(Q^2)$, charge radius (fitted as a single scale parameter), magnetic moment, and the parameter-free ratio $\mu_p/\mu_n$. The sector energy distribution — with $u$-type sectors concentrated inside the torus and the $d$-type sector on the periphery — naturally reproduces the qualitative features of parton distribution functions measured at Jefferson Lab. We compare all results to the classic SU(2) Skyrmion benchmark of Adkins, Nappi, and Witten, finding that the three-sector structure provides additional predictive content absent in the standard Skyrme model. The proton radius puzzle is addressed through the connection to Paper XVI's $\kappa$-suppression mechanism. Although the $F_2$ soliton is a classical saddle point, five independent cross-checks — including a rigorous variational bound ($\Delta E = -391$ soliton units, Eq. 14.13) — establish that the quantum ground state of the geometrically bounded fiber has lower energy than the trivial CP$^1$ configuration. Quantitative predictions remain conditional on a fully self-consistent Born-Oppenheimer minimum. Keywords physics proton quarks charge radius confinement form factors skyrmion Type Preprint License CC BY 4.0 Date 2026-03-25 Subject Theoretical Physics DOI 10.5281/zenodo.19163268 Paper Series: Topological Soliton Theory The Toroidal Electron (Paper I) Fine Structure Constant as Soliton Aspect Ratio (Paper II) Quarks and Confinement from Multi-Sector Hopf Solitons (Paper III) Neutrinos as SU(2) Skyrmions (Paper IV) Entanglement as Topology (Paper V) Dark Matter as Topological EM Structures (Paper VI) Topological Solitons vs. the Standard Model (Paper VII) Strong CP Problem Dissolved (Paper VIII) Topological Baryogenesis (Paper IX) From the Hopf Bundle to the Standard Model (Paper X) Dark Energy from Topological Vacuum Constraints (Paper XI) Speed of Light from Vacuum Topology (Paper XII) Antenna Impedance and Topological Mode Conversion (Paper XIII) Two Roads to 137 (Paper XIV) Quantum Foam from Hopf-Linked Fluctuations (Paper XV) Detecting Electron Topology via Precision Spectroscopy (Paper XVI) Proton Structure from Three-Sector Hopf Solitons (Paper XIX) © 2026 Alexander Novickis. Licensed under Creative Commons Attribution 4.0 International.