A flame between heavy fuel and light ash is gravitationally unstable. The heavy fuel sits above the light combustion products, and Rayleigh-Taylor instability crumples the flame front into turbulent fingers. The instability is intrinsic — the flame generates its own turbulence through the density difference it creates.
These self-turbulized flames are thickened by the turbulence they produce, but their internal structure differs from conventional turbulent flames (arXiv:2603.11406). In a standard turbulent flame, external turbulence wrinkles and thickens the flame zone. The turbulence comes from the flow; the flame responds to it. In a Rayleigh-Taylor flame, the turbulence comes from the flame itself. The density jump across the flame drives the instability that wrinkles the flame that maintains the density jump.
The self-referential loop changes the internal structure. Conventional models for turbulent flames assume the turbulence is imposed externally and decorrelated from the flame's local state. When the turbulence is self-generated, it correlates with the flame's structure — the regions of strongest turbulence are the regions where the flame has the steepest density gradients, which are the regions where the Rayleigh-Taylor drive is strongest. The flame and its turbulence are coupled, not independent.
The applications span scales: scramjet engines (where fuel-air mixing occurs across density-stratified interfaces) and Type Ia supernovae (where thermonuclear flames propagate through density-stratified stellar interiors). The same instability, the same self-thickening, at scales differing by fifteen orders of magnitude.