Convective Zone

This is the area that we consider to form the outer shell of the Sun.  The atoms in this layer of the Sun have electrons because the temperature is not hot enough to strip them away like it is in the core (15.6X 10⁶ K as opposed to 2 million K).  Atoms with electrons are able to absorb and emit radiation, making this region more opaque, like a thick fog.

In the convective zone, the energy is transferred much faster than it is in the radiative zone.  This is because it is transferred through the process of convection.  Hotter gas coming from the radiative zone expands and rises through the convective zone.  It can do this because the convective zone is cooler than the radiative zone and therefore less dense.  As the gas rises, it cools and begins to sink again.  As it falls down to the top of the radiative zone, it heats up and starts to rise.  This process repeats, creating convection currents and the visual effect of boiling on the Sun's surface.  This is called granulation, as seen in the picture below.

How does this transfer energy?  Heat is released to the outside when the material reaches the top of the convective zone and cools.  In this way, energy is transferred into the next layer of the sun, the photosphere.

The combination of what takes place in the convection zone and the differential rotation of the Sun creates something called the solar dynamo.  This phenomenon is the true origin of solar activity.  Solar dynamo causes the changes that occur in the magnetic field of the Sun, and these changes are what cause solar activity.  (For an explanation of the different kinds of solar activity, check out the Solar Activity page in the Virtual Tour.)