So on the other hand the initial pressure is too low, the variation in temperature to the interface stiffens until thermodynamic balance between the diffusion of heat (carried by the collision electron-ion) and generated energy. The resulting face of combustion consists of a zone of diffusion which heats fuel followed by a thin layer of reaction where the fuel is burned and generated energy. The deflagration, or more simply flame, moves in a subsonic way compared to the material not flaring.
The flame can thus be strongly influenced by the turbulent fluctuations speeds.