(a) Temporal evolution of the kinetic energy distribution for protons. (b) Kinetic energy distribution at t = 0 and t = 1 s (steady state) for the protons remaining inside the box with size L = 10⁹ cm, together with a Maxwellian fit at low energies and a power-law fit at high energies. (c) Escape time distribution for the protons. (d) Escape energy distribution for the protons, along with a power-law fit and a Maxwellian fit yielding a temperature T = 205 eV.