Schematic slices of the accretion disk in radial direction at different accretion luminosities. Different zones are named and the corotation radius for GRO J1744−28 is shown with the dashed line. Here we have assumed m = 1.4, R_*, 6 = 1.2, α = 0.1 and B = 5 × 10¹¹ G. The observed magnetospheric truncation radii in the RPD region for GRO J1744−28 are shown with the black circles (see Sects. 3.2 and 4.1). The truncation radius depends on luminosity as ∝L^−0.1 (the boundary between blue and gray regions). The dotted line shows the model truncation radius computed using Eq. (5). The parameter ξ is taken to be 0.05 to smoothen the transition from the observed truncation radius in the RPD region.