TGCC mode temperature oscillation power spectra for Region IIb (Fig. 2): (a) Rc/Rsc = 4.0, Grx = 8.24 × 106; (b) Rc/Rsc = 3.33, Grx = 2.0 × 105; (c) Rc/Rsc = 2.76, Grx = 2.47 × 104; (d) Rc/Rsc = 7.43, Grx = 7.43 × 104.