Electron acceleration in the quasi-steady loop-top configuration at t = 130 s. This figure shows the trajectories and energy evolution for two selected electrons. (a) Overview of electron trajectories with magnetic field lines. (b), (f) Trajectories on the magnetic field strength (B) map. (c), (g) Time evolution of kinetic energy (black), cumulative Fermi reflection energy gain (orange), and cumulative betatron energy gain (green). (d), (h) Trajectories overlaid on the rate of energy gain from Fermi reflection, u_E · [(b · ∇ )b]. (e), (i) Trajectories overlaid on the betatron acceleration rate, (u_E · ∇ B)/(2B). In all panels, squares (■) and circles (•) denote the initial (t = 0 s) and final (t = 1 s) positions, respectively. Triangles (▴) in the spatial maps (b), (d), (e), (f), (h), (i) and dashed lines in the time plots (c), (g) mark the onset of particle trapping at the loop-top edge. In this state, betatron cooling (negative contribution) largely counteracts Fermi reflection, resulting in inefficient net energy gain.