We consider relativistic plasma particles subjected to an external gravitation force in a 3D half space whose boundary is a perfect conductor. When the mean free path is much bigger than the variation of electromagnetic fields, the collision effect is negligible. As an effective PDE, we study the relativistic Vlasov-Maxwell system and its local-in-time unique solvability in the space-time locally Lipschitz space, for several basic mesoscopic (kinetic) boundary conditions: the inflow, diffuse, and specular reflection boundary conditions. We construct weak solutions to these initial-boundary value problems and study their locally Lipschitz continuity with the aid of a weight function depending on the solutions themselves. Finally, we prove the uniqueness of a solution, by using regularity estimate and realizing the Gauss's law at the boundary within Lipschitz continuous space.Introduction. Plasma is the most abundant form of ordinary matter in universe, being mostly associated with stars. The Sun, our nearest star, is composed of 92.1% hydrogen and 7.8% helium by number, and 0.1% of heavier elements. At the central core, hydrogen burns into helium (so-called the p-p chain of reactions starting from the fusion of two protons into a nucleus of deuterium), which is the major reaction that drives the sun's radiance (see the famous B 2 FH paper [2] for details).