y, proton flux observations (normalized to the equatorial flux intensity of the shell), as a function of $x=(H_{\min }-50)/(H_{\min ,\mathrm{eq}}\left(L\right)-50)$in four L shells. Discrete data points: based on observations within the L-shell interval by RPS-b in year 2013 (red: >192 MeV; green: >300 MeV); Solid line: g_h function for the shell (see Equation (8), with the value of η indicated; Vertical dashed line: $H_{\min }\left( B/B_0\right)$ = 1000 km, separating the high-altitude region and the low-altitude region of the environment.