Timescales for nonthermal electrons in the various scenarios. Different rows show different scenarios (accretion rate increases downward), and each column shows different regions in the RIAF; left column: inner regions (∼5R_S), right column: outer regions (∼200R_S). Plain solid lines show acceleration timescales, where a proper flag indicates the value of the acceleration efficiency η_acc; dotted lines shows acceleration timescales for SDA (see Sect. 3.1). Dashed lines show the diffusion timescale, dash-dotted lines show the advection timescale. Solid lines with markers show cooling timescales for the relevant processes; with triangles: synchrotron, with stars: inverse Compton.