Depiction of the 1D simulation model geometry in HTF. The singular spatial dimension of the model is along the shock normal, denoted as x. A finite-thickness shock is set at x = 0, with the upstream and downstream of the shock modeled with free-escape boundaries far from the shock. Particles travel along the magnetic field lines and particles’ position is tracked along x. Particle speed, v, pitch-angle cosine, μ, and residence time, t − t₀, within the simulation box are also tracked.