Simulated distribution of the log-mean energy of primary CRs as a function of ﹩\sum {\rho }_{\mathrm{FT}}﹩ and zenith angle. The y-axis is ﹩\sum {\rho }_{\mathrm{FT}}﹩; the x-axis is sec θ, where θ is the reconstructed zenith angle; and the color scale represents the reconstructed log-mean energy in units of TeV. Dashed lines mark out the borders of events with different energies (15, 50, 100, 300, and 1000 TeV).