Radial profile of the density, temperature, and helium mass fraction in an interval of 3−5.5 × 10⁸ cm of the initial setup and at helium ignition of Model M2a; the black solid, green dotted, and blue dashed lines represent the core-shell transition, base of the helium shell, and outer edge of the transition region, respectively; the cells with temperatures higher than 7 × 10⁸ K in the profile at He ignition represent the detonating cells of the He detonation.