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A convection zone, convective zone or convective region of a star is a layer which is unstable due to convection. Energy is primarily or partially transported by convection in such a region. In a radiation zone , energy is transported by radiation and conduction .
The convection zone of a star is the range of radii in which energy is transported outward from the core region primarily by convection rather than radiation. This occurs at radii which are sufficiently opaque that convection is more efficient than radiation at transporting energy.
For example, in the Sun the convection at the base of the convection zone, near the core, is adiabatic but that near the surface is not. The mixing length theory contains two free parameters which must be set to make the model fit observations, so it is a phenomenological theory rather than a rigorous mathematical formulation.
Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method ...
By definition, during a dredge-up, a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, the fusion products are mixed into the outer layers of the star's atmosphere, where they can be seen in stellar spectra .
The buoyancy generated turbulence peaks in the afternoon, hence the boundary layer flow is in free convection during most of the afternoon. The up and downdrafts of boundary layer convection is the primary way in which the atmosphere moves heat, momentum, moisture, and pollutants between the Earth's surface and the atmosphere.
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The radius of the radiative zone increases monotonically with mass, with stars around 1.2 solar masses being almost entirely radiative. Above 1.2 solar masses, the core region becomes a convection zone and the overlying region is a radiative zone, with the amount of mass within the convective zone increasing with the mass of the star. [7]